A Novel Construction Technology for Self-Anchored Suspension Bridge Considering Safety and Sustainability Performance

sustainability

Article A Novel Construction Technology for Self-Anchored Suspension Bridge Considering Safety and Sustainability Performance

Xiaoming Wang 1 , Xudong Wang 2, You Dong 3,* and Chengshu Wang 4 1 Key Laboratory for Bridge and Tunnel of Shannxi Province, Chang’an University, Xi’an 710064, China 2 Key Laboratory of Concrete and Prestressed Concrete Structures of Ministry of Education, Southeast University, Nanjing 210000, China 3 Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong 999077, China 4 Zhejiang Provincial Transport Planning, Design and Research Institute, Hangzhou 310000, China * Correspondence: [email protected]

Received: 20 March 2020; Accepted: 6 April 2020; Published: 8 April 2020

Abstract: To promote sustainable development of civil infrastructures, minimizing environmental impact and mobility disruptions have been elevated to a higher priority during decision-making for bridge construction scheme. This study presents a novel temporary pylon-anchor (TPA) technology for construction of self-anchored suspension bridges by considering not only safety performance, but also environmental impacts. A practical assessment method and index of sustainability associated with bridge construction technology are established to facilitate the selection of construction schemes. The sustainability index takes the environmental impact, traffic disruption, onsite construction materials and equipment, onsite construction cost, and onsite construction risk into consideration. The sustainability index associated with both conventional and novel construction methods is assessed and compared in this paper. Specifically, a novel girder-pylon antithrust system (GPAS) is proposed, which is the crucial component of the TPA technology in engineering application. In addition, an analytical approach is developed, considering both global load-carrying capacity and local stress distribution within the design and construction of the GPAS. The applicability and rationality of the proposed construction technology are illustrated by the successful application in real-world engineering. The field tests and sustainability assessment during the construction stage reveal that the proposed sustainability assessment method and analytical approach can facilitate the implementation of sustainable construction for self-anchored suspension bridges by considering both construction safety and sustainability.

Keywords: Sustainable construction; environmental impact and traﬃc disruptions; self-anchored suspension bridge; design-oriented analytical approach

1. Introduction The onsite bridge construction activities can have significant impacts on environment, mobility, and safety [1,2]. The direct and indirect loss of environment and traffic disruptions resulting from the bridge construction can exceed the actual cost of the structure itself [3]. For instance, full-lane closures in large urban centers, or on highways or waterways with heavy traffic volumes, can have a significant economic impact on commercial and industrial activities in the region [4,5]; partial lane closures that occur alongside adjacent traffic can also lead to safety and environmental issues (e.g., extra CO2 emissions due to traffic detour) [6]. Sustainable construction emphasizes an efficient use of natural resources to minimize the impacts of the built environment on the Earth and enhancing

Sustainability 2020, 12, 2973; doi:10.3390/su12072973 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 2973 2 of 23 the quality of surrounding environment [7,8]. Because of the potential economic and safety impacts, minimizing environment and traffic disruptions is a goal that has been elevated to a higher priority when determining bridge sustainable construction scheme [9,10]. Self-anchored suspension bridges have found increasingly wide applications in urban bridge engineering as a landmark, due to its attractive architectural appearance and lightweight configuration [11–13]. Due to being anchored to the girder, the main cables could not be erected until the girder has been built on lots of temporary supports, which inevitably causes serious impacts on environment and traffic. This issue has emerged during the erection of several typical self-anchored suspension bridges, such as the Yongjong Bridge in Korea [13], San Francisco–Oakland Bay Bridge in the States [14], and Qingdao Bay Bridge in China [15]. Several new technologies were developed on the basis of the concept of sustainable construction to solve these issues [16,17], such as temporary earth-anchor method [18], temporary stayed cables method [19,20], and temporary compressive strut method [21]. Although these technologies could reduce mobility impacts, the use of expensive temporary structures (e.g., stayed cables, earth anchor, and compressive strut) increases environmental impact and onsite construction cost. Hence, to promote the construction sustainability for self-anchored suspension bridge, further research needs to focus on the development of the sustainable construction through new technology and new design-oriented analytical approaches. A practice-oriented assessment method and index of sustainability on bridge construction technology are essential for selection of sustainable bridge construction schemes [22]. Penadés-Plà et al. [23] analyzed the life-cycle environmental impact of a prestressed concrete precast bridge from the economic point of view, and proposed an optimization-life-cycle assessment method. Chang et al. [24] established an index system and evaluated the sustainability of high-speed railway construction projects. Seo et al. [25] analyzed the economic impacts of three sustainable vertical extension methods for existing underground spaces. Although these methods could assess the construction sustainability, the real-world application of decision making for bridge construction schemes by considering sustainability is relatively scarce, and more studies are needed on this aspect. Therefore, it is urgent to establish a practical assessment method and index of sustainability on construction technology for urban bridge construction, which is addressed in this paper. On the basis of the aforementioned studies, this study presents a novel temporary pylon-anchor (TPA) technology to promote sustainable construction, which is suited for self-anchored suspension bridges with the mid-span less than 300 m, three spans and two pylons. A practical assessment method and index of sustainability on construction technologies are established to facilitate making decisions for sustainable construction scheme. A novel girder-pylon antithrust system (GPAS) is proposed, which is the crucial component of the TPA technology in engineering application. For the reliable and cost-effective design of GPAS, a design-oriented two-phase framework is developed considering global load-carrying capacity and local stress distribution. In phase I, the global shear capacity and stiffness are designed through a set of specially derived practical formulas, which capture the main characteristics of the slip and uplift behavior at steel-concrete joint surface within an antithrust system. In phase II, the local stress distribution is improved based on the effects of different parameters induced by grouped parametric analyses using 3D elaborate finite element analysis. The applicability and rationality of the sustainable construction new technology are illustrated by the first successful application in real-world engineering. The field tests and construction sustainability assessment show that the proposed sustainability assessment method and design-oriented analytical approach facilitate the implementation of sustainable construction for self-anchored suspension bridge.

2. Sustainability Assessment on Construction Technologies for Self-Anchored Suspension Bridge

2.1. Environmental Impact and Traﬃc Disruption Caused by Traditional Construction Technologies As shown in Figure1a, the traditional construction technology needs lots of temporary supports to build girders, which inevitably causes serious environmental impact and traﬃc disruption. Sustainability 2020, 12, x FOR PEER REVIEW 3 of 23

2.1. Environmental Impact and Traffic Disruption Caused by Traditional Construction Technologies As shown in Figure 1(a), the traditional construction technology needs lots of temporary supports to build girders, which inevitably causes serious environmental impact and traffic disruption. As shown in Figure 1(b), for reducing traffic disruptions, the temporary earth-anchor method builds temporary earth anchor blocks to enable a construction sequence that is similar to a conventional suspension bridge. The technology has been applied in the Zhuyuan Bridge (33 m + 90 m + 33 m) in China [18]. However, the building of earth-anchor also damages the surrounding environment and produces pollution. As shown in Figure 1(c), to avoid traffic disruptions, the temporary stayed cables technology uses temporary stayed-cables to erect girder segments, just as a cable-stayed bridge, and these stayed-cables aren’t removed until the main cables and hangers are erected. The technology has been applied in the E’gongyan Rail Bridge (210 m + 600 m + 210 m) in China [19], and the Duisburg Bridge [20]. Although the technology reduces both environmental impact and traffic disruption, the use of Sustainability 2020, 12, 2973 3 of 23 expensive temporary structures (lots of stayed cables and heightened segments of the pylon) increases onsite construction cost and time.

Bracing force of the support

Traffic disruption ★Temporary support

(a)

Vertical force of anchor

Horizontal force of anchor Undisturbed traffic under mid-span ★Temporary earth anchor

(b) Tension of the ★temporary heightened ★temporary stayed cable segments of pylon stayed cable

Undisturbed traffic under mid-span

(c)

FigureFigure 1. 1.Traditional Traditional construction construction technologiestechnologies for self-anchored self-anchored suspension suspension bridge: bridge: (a) (aTemporary) Temporary supportssupports technology technology [13[13,26];,26]; ((bb)) temporarytemporary earth-anchor earth-anchor technology technology [18]; [18 ];and and (c) ( ctemporary) temporary stayed-cablesstayed-cables technology technology [ 19[19,20].,20].

2.2.As Novel shown TPA in Technology Figure1b, to for Impr reducingove Construction tra ffic disruptions, Sustainability the temporary earth-anchor method builds temporaryIn this earth study, anchor a novel blocks temporary to enable pylon-anchor a construction (TPA) sequencetechnology that is proposed is similar to to solve a conventional the issue suspensionin a safe and bridge. cost-effective The technology manner for has minimizing been applied environment in the Zhuyuan and traffic Bridge disruptions. (33 m + 90 As m shown+ 33 m)in in ChinaFigure [18 2,]. the However, horizontal the cable building force of is earth-anchor transferred to also the damagespylon through the surrounding the side span environment girder and is and produces pollution. As shown in Figure1c, to avoid tra ffic disruptions, the temporary stayed cables technology uses temporary stayed-cables to erect girder segments, just as a cable-stayed bridge, and these stayed-cables aren’t removed until the main cables and hangers are erected. The technology has been applied in the E’gongyan Rail Bridge (210 m + 600 m + 210 m) in China [19], and the Duisburg Bridge [20]. Although the technology reduces both environmental impact and traffic disruption, the use of expensive temporary structures (lots of stayed cables and heightened segments of the pylon) increases onsite construction cost and time.

2.2. Novel TPA Technology to Improve Construction Sustainability In this study, a novel temporary pylon-anchor (TPA) technology is proposed to solve the issue in a safe and cost-eﬀective manner for minimizing environment and traﬃc disruptions. As shown in Figure2, the horizontal cable force is transferred to the pylon through the side span girder and is resisted by means of the bending bearing capacity of the pylon. Thus, the mid-span girder is lifted in sections and connected to the hangers. After the entire girder is erected, the horizontal cable force is transferred from the pylon to the girder, and the structure is transformed into a permanent self-balanced Sustainability 2020, 12, x FOR PEER REVIEW 4 of 23

Sustainability 2020, 12, 2973 4 of 23 resisted by means of the bending bearing capacity of the pylon. Thus, the mid-span girder is lifted in sections and connected to the hangers. After the entire girder is erected, the horizontal cable force is system.transferred In this way, from the the permanent pylon to environmentalthe girder, and impact the structure and traﬃ cis disruption transformed are into eliminated a permanent during construction,self-balanced and system. the onsite In constructionthis way, the cost,permanent time, and environmental risk are minimized. impact and traffic disruption are eliminated during construction, and the onsite construction cost, time, and risk are minimized.

Self-weight of Thrust force of girder segments the side-span

Temporary Horizontal thrust force Undisturbed traffic under mid-span supports of tower foundation ★Girder-pylon antithrust system (b) Girder Pylon

(a)

Figure 2. Temporary pylon-anchorFigure 2. Temporary technology: pylon-anchor (a) Construction technology. process; (b) Gider-pylon antithrust system. 2.3. Primary Sustainability Performance of Construction Technologies 2.3. Primary Sustainability Performance of Construction Technologies As shown in Table 1, the traditional temporary supports technology results in not only serious environmentalAs shown in Table impact1, theand traditional traffic disruption, temporary but supportsalso high technologyonsite construction results incost, not time, only and serious risk. environmentalEven if the impact temporary and tra earth-anchorffic disruption, technology but also and high stayed-cables onsite construction technology cost, time,reduce and traffic risk. Evendisruption, if the temporary the other earth-anchor important sustainable technology pe andrformance stayed-cables still needs technology further reduceimprovement. traffic disruption, the other important sustainable performance still needs further improvement. Table 1. Construction sustainability evaluation of construction technologies for self-anchored Tablesuspension 1. Construction bridge. sustainability evaluation of construction technologies for self-anchored suspension bridge. Technology Temporary The proposed Temporary supports Temporary Technology stayed-cables temporary [13,26] earth-anchor [18] Performance Temporary Supports Temporary Temporary[19,20] Thepylon-anchor Proposed Serious[13,26: ] Earth-AnchorSerious [18: ] Stayed-Cables [19,20] Temporary Pylon-Anchor Performance environmental environmental Environmental Serious: damage Serious:caused by damage caused by Almost none Almost none impact environmental environmental damage Environmental impact temporary supports' damagetemporary caused by Almost none Almost none caused by temporary foundation earth-anchoragetemporary supports’ foundation Serious: earth-anchorage traffic underSerious: the traffic under the bridge TrafficTraffic disruption disruption AlmostAlmost none none Almost Almost none none AlmostAlmost none none bridge is blockedblocked by by temporarytemporary supports supports High: High: High: High: High: lots of temporary Low:Low: Onsite construction materials expensive Onsite construction lotsHigh of temporary: stayed-cables,lots of temporary cheap girder–pylon and equipment temporaryexpensive cheap girder– materials and lots of temporarysupports heightenedstayed-cables, segments antithrust system earth-anchoragetemporary pylon antithrust equipment supports of pylonheightened earth-anchorage system segments of pylon Onsite construction Long: Long: Long: Short: time lots of lots of lots of Fast erection and SustainabilitySustainability 2020, 122020, x ,FOR12, 2973 PEER REVIEW 5 of 23 5 of 23

time-consuming for time-consumingTable 1. Cont. for time-consuming for removal of erection and removal erection and erection and girder–pylon Technology of supports removal of removal of antithrust Temporary Supports Temporary Temporary The Proposed [13,26] earth-anchorageEarth-Anchor [18] Stayed-Cables stay-cables [19,20] andTemporary system Pylon-Anchor Performance heightened Long: Long: Long: lots of lots of time-consumingsegments of pylonShort: lots of time-consuming time-consuming for erection and Fast erection and Onsite construction time Highfor: erection and for erection and removal of stay-cables removal of girder–pylon Onsite construction temporaryremoval supports of supports removal of and heightened antithrust system earth-anchorageLow segments of pylonLow Low risk subjected to floodHigh: and temporary supports Onsite constructioncollision risk of vehicles Low Low Low subjected to ﬂood and collision of vehicles 2.4. Assessment Method and Index Considering Construction Sustainability 2.4. Assessment Method and Index Considering Construction Sustainability In orderIn orderto facilitate to facilitate decision-making decision-making forfor sustainablesustainable bridge bridge construction construction scheme, scheme, a practical a practical assessmentassessment procedure procedure is isproposed proposed asas shown shown in Figure in Figu3. There detailed 3. The procedure detailed is explainedprocedure as follows:is explained as follows: Start

Construction Technologies Structural reliability • Temporary supports (TS) analysis during • Temporary earth-anchor (TEA) construction processes by • Temporary stayed-cables (TSC) FEA • Temporary pylon-anchor (TPA)

Index system • Environmental impact Construction sustainability • Traffic disruption assessment • Onsite construction materials and equipment • Onsite construction time • Onsite construction risk

Construction economic Evaluation index evaluation • Comprehensive onsite construction cost

End

Figure Figure3. Practice-oriented 3. Practice-oriented assessment assessment procedure procedure of sust ofainability sustainability assessment assessment of bridge of bridge construction technology.construction technology.

(1) Structural safety analysis （1）Structural safety analysis To ensure the structural safety during the entire construction processes, the global step-by-step Toforward ensure model the structural and local 3D safety solid elaborate during model the entire should construction be analyzed for processes, each construction the global technology, step-by-step forwardrespectively. model and The analyticallocal 3D approach solid elaborate proposed in model Section 3should presents thebe detailedanalyzed analysis for procedureeach construction technology,and mechanical respectively. performance. The analytical The structural approach analysis proposed performance in includes Section the 3 strength, presents rigidity, the detailed stability, etc. analysis procedureThrough thisand step, mechanical those construction performance. technologies The structural that cannot analysis meet the performance safety requirement includes the strength,are rigidity, excluded. stability, etc. Through this step, those construction technologies that cannot meet the safety requirement are excluded.

(2）Construction sustainability assessment

Considering the various influencing factors on construction sustainability, this paper uses an index system by considering the following aspects: Environmental impact, traffic disruption, onsite construction materials and equipment, onsite construction cost, and onsite construction risk. Then, the hierarchical evaluation method based on a rose chart is employed to compare sustainability associated with different construction schemes. As shown in Figure 4, the area Si enclosed by connecting lines is taken as analysis index of the sustainability associated with the construction Sustainability 2020, 12, 2973 6 of 23

(2) Construction sustainability assessment Considering the various influencing factors on construction sustainability, this paper uses an index system by considering the following aspects: Environmental impact, traffic disruption, onsite constructionSustainability materials 2020, 12, x andFOR PEER equipment, REVIEW onsite construction cost, and onsite construction risk.6 Then,of 23 the hierarchical evaluation method based on a rose chart is employed to compare sustainability associated withtechnology. different construction As indicated, schemes. the indices As of shown four techno in Figurelogies4, theare areaindicatedSi enclosed in Figure by 4 connectingfor illustrative lines is takenpurpose, as analysis and indexthe TPA of technology the sustainability has comprehensiv associatede performance with the construction on construction technology. sustainability. As indicated, the indicesThrough of four technologiesstep 2, the construction are indicated technology in Figure with4 for the illustrative best sustainability purpose, is and efficiently the TPA screened technology out. has comprehensive performance on construction sustainability.

Onsite construction risk TS Temporary supports (TS) 5 Temporary earth-anchor (TEA) 4 Temporary stayed-cables (TSC) Temporary pylon-anchor (TPA) 3 Traffic 2 Environmental TEA disruption impact 1 0

TSC

Onsite costruction2 Onsite construction time materials and equipment

FigureFigure 4. 4.Construction Construction sustainability assessment. assessment.

Through（3）Construction step 2, the economic construction evaluation technology with the best sustainability is eﬃciently screened out.

(3) ConstructionIn this step, economic the direct evaluation and indirect construction cost of the most sustainable construction technology is assessed. The comprehensive onsite construction cost is the sum of C1, C2, C3, C4, and In this step, the direct and indirect construction cost of the most sustainable construction technology C5. C1 is direct and indirect losses due to environmental impact; C2 is the direct and indirect losses is assessed. The comprehensive onsite construction cost is the sum of C1, C2, C3, C4, and C5. C1 is caused by traffic disruption; C3 is the cost of materials and equipment in onsite construction; C4 is directthe and cost indirect of onsite losses construction due to time, environmental which is obtained impact; by multiplyingC2 is the direct labor andcost (per indirect day) and losses days; caused by traandffic C disruption;5 represents theC3 costis the of costonsite of construction materials and risks, equipment which is quantified in onsite by construction; multiplying insuranceC4 is the cost of onsiteamount construction and failure time,probability. which is obtained by multiplying labor cost (per day) and days; and C5 represents the cost of onsite construction risks, which is quantified by multiplying insurance amount and failure3. Design-Oriented probability. Analytical Approach for Novel Antithrust System As shown in Figure 2, the GPAS is the crucial component of the proposed TPA technology. In 3. Design-Orientedthe GPAS, the horizontal Analytical cable Approach force is smoothly for Novel transferred Antithrust from System the side span girder to the pylon Asthrough shown the in thrust Figure shoulder.2, the GPAS The isshear the crucialcapacity component and stiffness of of the the proposed thrust shoulder TPA technology. need to be In the designed to meet the construction performance requirements, and the girder and pylon should be GPAS, the horizontal cable force is smoothly transferred from the side span girder to the pylon through nondestructive. the thrust shoulder. The shear capacity and stiffness of the thrust shoulder need to be designed to meet the construction3.1. Novel Girder–Pylon performance Antithrust requirements, System and the girder and pylon should be nondestructive.

3.1. NovelThe Girder–Pylon GPAS can be Antithrust classified System on the basis of the gap width between the side span girder and the pylon as follows: Type I (Figure 5a) for the wide gap, and Type II (Figure 5b) for the narrow gap. A Theconcrete GPAS side can span be girder classiﬁed is usually on the installed basis ofin a the self-anchored gap width suspension between thebridge side to span balance girder the and the pylonuplift ascomponent follows: of Type cable I (Figureforce. Hence,5a) for groupe the wided perfobond gap, and rib Typeconnectors II (Figure [Perfobond5b) for Leiste the narrow in gap.German A concrete (PBL)] side and span U-shaped girder anchor is usually rebars installed are used in to a self-anchoredfasten the antithrust suspension system bridgeto the lateral to balance the upliftside of component the side span of girder. cable force. Hence, grouped perfobond rib connectors [Perfobond Leiste in

(1) Type I Sustainability 2020, 12, 2973 7 of 23

German (PBL)] and U-shaped anchor rebars are used to fasten the antithrust system to the lateral side of the side span girder. (1)Sustainability Type I 2020, 12, x FOR PEER REVIEW 7 of 23

FigureFigure5a 5(a) shows shows the the Type Type I antithrust I antithrust system, system, consisting consisting of of a a girder-side girder-side thrust thrust shoulder, shoulder, a a pylon-side thrustthrust shoulder,shoulder, andand aa forceforce transmissiontransmission bracebrace located located between between the the set set of of thrust thrust shoulders.shoulders. Each Each thrust thrust shoulder shoulder is is composed composed of of a grillea grille frame, frame, grouped grouped PBLs, PBLs, and and U-shaped U-shaped anchor anchor rebarsrebars that that are are welded welded to to the the two two sides sides of of the the wallboard. wallboard. The The grille grille frame frame comprises comprises longitudinal, longitudinal, vertical,vertical, and and transverse transverse plates. plates. The The thrust thrust shoulder shoulder is fastened is fastened to the lateralto the sidelateral of theside side of the span side girder span andgirder pylon and with pylon the aidwith of the grouped aid of PBLs grouped and U-shapedPBLs and anchorU-shaped rebars anchor that preventrebars that the thrustprevent shoulders the thrust fromshoulders slip and from uplift. slip and uplift. (2) Type II (2) Type II The only diﬀerence between Types II (Figure5b) and I is that the pylon-side thrust shoulder is The only difference between Types II (Figure 5(b)) and I is that the pylon-side thrust shoulder is replaced by the foot brace to eﬀectively transfer the thrust force and disperse the narrow gap stress. replaced by the foot brace to effectively transfer the thrust force and disperse the narrow gap stress.

Thrust Pylon shoulder Pylon U-shaped anchor rebar Force transmission brace Force transmission PBL shear brace Girder Girder connector

U-shaped anchor rebar Transverse plate Vertical plate Grille frame Longitudinal plate Wallboard (a) (b)

FigureFigure 5. Schematic5. Schematic diagram diagram of of GPAS GPAS (Girder-Pylon (Girder-Pylon Antithrust Antithrust System): System): (a )(a Type) Type I antithrust I antithrust system system and (b) Type II antithrust system. and (b) Type II antithrust system.

3.2.3.2. Failure Failure Modes Modes and and Mechanism Mechanism of Forceof Force Transmission Transmission TheThe three three failure failure modes modes of of the the thrust thrust are are considered considered to to meet meet the the construction construction performance performance requirements.requirements. (I) (I) Shear Shear slip slip of of PBL PBL shear shear connector connector [27 [27–29]:–29]: The The shear shear slip slip deformation deformation of of PBL PBL connectorconnector is is limited limited to to ensure ensure that that the the girder girder and an pylond pylon are are nondestructive. nondestructive. The The increase increase in in shear shear capacitycapacity after after sliding sliding is excludedis excluded in in the the design; design; (II) (II) uplift uplift of of wallboard: wallboard: Under Under the the strong strong thrust thrust force, force, thethe out-of-plane out-of-plane deformation deformation of the of wallboard the wallboard at the headat the position head position must be avoided;must be andavoided; (III) buckling and (III) failurebuckling of grille failure frame: of Thegrille grille frame: frame The must grille have frame suﬃ mustcient rigidityhave sufficient in the 3D rigidity space. Thein the overall 3D space. or local The bucklingoverall ofor thelocal grille buckling frame of must the begrille avoided. frame Nomust cyclic be avoided. loading occursNo cyclic although loading the occurs structural although stress the variesstructural seriously stress during varies construction. seriously Hence,during theconstruc fatiguetion. failure Hence, of the the thrust fatigue shoulder failure can of be the ignored. thrust shoulderAs shown can inbe Figure ignored.6, the horizontal cable force is transmitted to the wallboard, U-shaped anchor rebars,As and shown PBL shear in Figure connectors 6, the through horizontal the grillecable frameforce tois achievetransmitted the force to the transmission wallboard, betweenU-shaped theanchor girder rebars, and pylon. and PBL The shearshear capacityconnectors of PBLthrough shear th connectorse grille frame is the to chiefachieve resistance the force for transmission the thrust force.between The eccentricthe girder e ﬀandect pylon. of the grilleThe shear frame capacity would causeof PBL the shear wallboard connectors uplift is atthe the chief head resistance position, for enablingthe thrust the force. U-shaped The eccentric anchor rebars effect and of the PBL grille shear frame connectors would tocause withstand the wallboard the transverse uplift at pull-out the head forceposition, for resisting enabling the the out-of-plane U-shaped deformation.anchor rebars and PBL shear connectors to withstand the transverse pull-out force for resisting the out-of-plane deformation. Sustainability 2020, 12, 2973 8 of 23 Sustainability 2020, 12, x FOR PEER REVIEW 8 of 23

Figure 6. MechanismFigure diagram 6. Mechanism of force diagram transmission of force of transmission thrust shoulder: of thrust (a) shoulder. Calculation scheme; (b) Simpliﬁed calculation scheme. The equilibrium formula is established on the basis of the calculation scheme (Figure 6(a)) as follows:The equilibrium formula is established on the basis of the calculation scheme (Figure6a) as follows:

n nmm   = P FV=++++ P + VVV+  F VUi UPFViiPi VF V   i=1 ii==i=111   n nmm  P P   T = TUTTi =+++ TPi + T TTF   (1)(1) i= i= UPFii  1 ii==111  n n m m   P nnmmP P P   F D = HU ⋅=TUi ⋅DU −VU ⋅i + HP +T ⋅Pi D −P ⋅VPi + +HF ⋅−TF DF ⋅VF  · FD· i=1 HUUUUPPPPFFFF− T·iiiii=1 D V· i H=1 − T D· i=1 V H· T− D· V iiii====1111  where F is the longitudinal thrust force, D is the distance of the longitudinal thrust force from the center where F is the longitudinal thrust force, D is the distance of the longitudinal thrust force from the Pn Pn of rotation in the X direction, VUi is then total force of U-shaped rebars in the Y direction, TUi is i=1 i=1 center of rotation in the X direction, VUi is the total force of U-shaped rebars in the Y direction, the transverse (X-direction) pull-out forcei=1 of U-shaped rebars, n is the number of U-shaped rebars, m m P n P VPTi and is theT transversePi are the total (X-direction) forces of penetrating pull-out force rebar of inU-shaped the Y and rebars, X directions, n is the mnumberis the numberof U-shaped of i=1  Ui i=1 i=1 penetrating rebars, VF and TF are the friction between the steel and concrete in the Y and X directions, m m V and T are the reactions at the end of the wallboard in the Y and X directions, HU and DU are the rebars, VPi and TPi are the total forces of penetrating rebar in the Y and X directions, m is the distances ofi=1 the total forcei=1 of U-shaped rebars from the center of rotation in the Y and X directions, HPnumberand DP ofare penetrating the distances rebars, of the VF total and forceTF are of the penetrating friction between rebar from the steel the center and concrete of rotation in the in Y the and Y X anddirections, X directions, V and and T HareF and the DreactionsF are the at distances the end of the friction wallboard from the in centerthe Y and of rotation X directions, in the H YU and and X DU directions,are the distances respectively. of the total force of U-shaped rebars from the center of rotation in the Y and X directions,The following HP and simplifications DP are the distances are adopted of tothe ensure total designforce of reliability penetrating and rebar improve from practicability: the center of Therotation thrust forcein the is Y only and borne X directions, by PBL shearand H connectors.F and DF are The the internal distances force of redistributionfriction from the caused center by of sliprotation deformation in the isY ignored,and X directions, indicating respectively. that the relative increase in shear capacity after sliding can be ignoredThe [30]; following the friction andsimplifications embedment eareffects adopted of the wallboard to ensure on sheardesign resistance reliability are ignored;and improve and thepracticability: out-of-plane upliftThe ofthrust the wallboard force is isonly significant borne atby the PBL head shear zone, makingconnectors. it reasonable The internal to assume force redistribution caused by slip deformation is ignored, indicating that the relative increase in shear capacity after sliding can be ignored [30]; the friction and embedment effects of the wallboard on shear resistance are ignored; and the out-of-plane uplift of the wallboard is significant at the head zone, making it reasonable to assume that the transverse pull-out force is only borne by the U-shaped anchor rebars. Based on the above simplifications (Figure 6(b)), Formula (1) can be simplified to Formula (2). Sustainability 2020, 12, 2973 9 of 23 that the transverse pull-out force is only borne by the U-shaped anchor rebars. Based on the above simplifications (Figure6b), Formula (1) can be simplified to Formula (2).

m  P  F = VPi   i=1  Pn  T = V  (2) Ui  i=1  n m  P P  F D = HU TUi DP VPi  · · i=1 − · i=1

3.3. Global Design Formulas

The calculation formula of PBL bearing capacity (Vpud) provided by the design code [31] is adopted to improve the applicability of design formula. The shear heterogeneity coeﬃcient of PBL shear connector α = 0.4 is considered for security redundancy [32]. The formula to estimate the number of PBL shear connectors is derived as follows: F F N = (3) P 2 2 ≥ α Vpud 0.4 (1.4 (d2 d ) f + 1.2d f ) · · · − s cd s sd where NP is the number of PBL shear connectors, F is the longitudinal thrust force in Formula (1), α is the shear heterogeneity coeﬃcient, Vpud is the shear capacity of PBL shear connector under the ultimate limit state, d is the diameter of circular hole in the steel plate, ds is the diameter of penetrating rebar, fcd is the design value of concrete axial compressive strength, and fsd is the design value of penetrating rebar tensile strength. The anchorage length of U-shaped anchor rebar must reach the yield strength before anchorage failure to meet the construction performance requirements. The design code [33] indicates that the minimum anchorage length of HRB400 rebar adopted in this paper should be greater than 25 times the rebar diameter. The formula to estimate the number of U-shaped anchor rebars is derived as follows:

Pm F D + (DPi Vpud) · i=1 · NU (4) ≥ 2 H As f · U · · sd where NU is the number of U-shaped anchor rebars, DPi is the distance of the ith penetrating rebar from the center of rotation in the X direction, and As is the cross-sectional area of U-shaped anchor rebar. The longitudinal plate of the grille frame is designed considering the rigidity criterion. The thickness and number of longitudinal plates must ensure that the structural deformation meets the construction requirements. The transverse and vertical plates of the grille frame are designed on the basis of stability control criterion, and their thickness and spacing are set in accordance with the code [34] to avoid buckling.

3.4. Design-Oriented Two-Phase Analytical Framework As indicated in Figure7, the design-oriented analytical framework of the girder-pylon thrust shoulder is constructed. The detailed steps are provided as follows: 1. Lectotype The type of antithrust system is selected on the basis of speciﬁc structural parameters, such as the conﬁguration and material of the side span girder and bridge pylon and the gap width between the girder and pylon. Sustainability 2020, 12, 2973 10 of 23

2. Determination of unfavorable construction state Global geometric nonlinear analysis of the entire construction process is conducted through the spatial cable and beam element ﬁnite element (FE) simulation, and the maximum design load of the GPASSustainability is determined. 2020, 12, x FOR PEER REVIEW 10 of 23

Style selection Lectotype According to gap width, configuration and material of pylon and girder

Determination of the Beam&cable element-based FEA most unfavorable for entire construction process construction state

Dimension determination Phase Ⅰ: Global design for grille frame, PBL and U-shaped anchor rebar by formula(3)&(4)

Solid FEA for thrust shoulder Ⅱ Phase : Parameter Parameter analysis study Performance improvement Design revision Performance Check

Mises stress: σs≤[σs] No Exceed Principal tensile stress: σc≤[σc] limitation? PBL slip: spmax≤slim Yes Grille frame disp. : ∆≤l/4000

END Wallboard relative disp. : D=0

FigureFigure 7. 7.Design-oriented Design-oriented analytical analytical framework framework for for girder-pylon girder-pylon thrust thrust shoulder. shoulder.

3.1. Phase Lectotype I: Global design TheThe numbers type of antithrust of PBL shear system connectors is selected and on U-shapedthe basis of anchor specific rebars structural are determinedparameters, usingsuch as Formulasthe configuration (3) and (4) and on thematerial basis of of the the side design span criterion girder and in Section bridge 3.3 pylon. The and grille the frame gap width is designed between consideringthe girder rigidityand pylon. and stability control criteria.

4.2. Phase Determination II: Parametric of study unfavorable construction state GroupedGlobal geometric parametric nonlinear analyses analysis are performed of the entire to reveal construction the effects process of parameter is conducted variation through on the structuralspatial cable performance and beam and element to improve finite element the local (FE) performance. simulation, Aand high-fidelity the maximum 3D design solid FE load model of the is establishedGPAS is determined. to analyze the local effect and avoid stress distortion and size disturbance effect. The nonlinear surface contact behavior is simulated to consider the friction effect between the steel and3. concrete. Phase I: Global design 5. PerformanceThe numbers check of PBL shear connectors and U-shaped anchor rebars are determined using Formulas (3) and (4) on the basis of the design criterion in Section 3.3. The grille frame is designed The performance of the parametric study in step 4 is verified using the performance indicators. considering rigidity and stability control criteria. The design procedure is completed when the performance is verified, otherwise, the design is updated using steps 3-5. The performance indicators and relative thresholds are provided as follows: 4. Phase II: Parametric study (1) The principal tensile stress of concrete σc and Mises stress of steel σs must not exceed the Grouped parametric analyses are performed to reveal the effects of parameter variation on limit value. ( structural performance and to improve the localσc [performance.σc] A high-fidelity 3D solid FE model is ≤ (5) established to analyze the local effect and avoidσs [ σstresss] distortion and size disturbance effect. The ≤ nonlinear surface contact behavior is simulated to consider the friction effect between the steel and where [σc] is the allowable tensile stress of concrete, and [σs] is the allowable yield stress of steel (Detailedconcrete. reference values are shown in Table2).

5. Performance check The performance of the parametric study in step 4 is verified using the performance indicators. The design procedure is completed when the performance is verified, otherwise, the design is updated using steps 3-5. The performance indicators and relative thresholds are provided as follows: σ σ (1) The principal tensile stress of concrete c and Mises stress of steel s must not exceed the limit value. Sustainability 2020, 12, x FOR PEER REVIEW 11 of 23

σσ≤   cc  (5) σσ≤   ss Sustainability 2020, 12, 2973 11 of 23 σ σ where c is the allowable tensile stress of concrete, and s is the allowable yield stress of steel (Detailed reference values are shown in Table 2). (2) The slip of PBL shear connectors must not exceed the limit value [31]. (2) The slip of PBL shear connectors must not exceed the limit value [31]. 0.6V 06pud. V Spmax = pud s = 0.2 mm (6) Ss=≤=p ≤ lim 02.mm pmax29 (d ds−)ds fckEc lim (6) 29−()dddfEssckc where Spmax is the maximum slip of the joint surface, slim is the slip limit, fck is the standard value of where Spmax is the maximum slip of the joint surface, slim is the slip limit, fck is the standard value concrete axial compressive strength, and Ec is the Young’s modulus of concrete. of concrete(3) The deformation axial compressive of grille strength, frame must and notEc is exceed the Young’s the limit modulus value [of34 ].concrete. (3) The deformation of grille frame must not exceed the limit value[34]. ∆ l/4000 mm (7) ≤Δ≤l /mm4000 (7) wherewhere∆ andΔ andl arel are the the longitudinal longitudinal displacement displacement and and design design length length of theof the grille grille frame, frame, respectively. respectively. (4)(4) No No relative relative deformation deformation is is found found between between the the wallboard wallboard and and the the girder, girder, that that is, is, relative relative deformationdeformationD =D=0. 0.

4.4. Design Design and and Engineering Engineering Implementation Implementation TheThe Dongtiao Dongtiao River River Bridge Bridge in in Huzhou, Huzhou, China, China, which which is is a self-anchoreda self-anchored cable-stayed-suspension cable-stayed-suspension bridgebridge with with a spana span of of 75 75 m m+ +228 228 m m+ +75 75 m m and and a a semi-ﬂoating semi-floating structural structural system system (Figure (Figure8), 8), is usedis used as as thethe illustrative illustrative example. example. The The bridge bridge tower tower is is a steela stee structure.l structure. The The steel-concrete steel-concrete composite composite girder girder is is usedused in in the the mid-span mid-span to reduceto reduce the the self-weight, self-weight, and and the staythe stay cable cable and prestressedand prestressed concrete concrete girder girder are usedare inused the in side the span side to span balance to balance the thrust the forcethrust transmitted force transmitted from the from main the cable main to cable the bridge to the tower. bridge Fourtower. sets Four of GPAS sets of are GPAS used inare the used bridge in the to bridge balance to the balance thrust the force thrust of the force side of span the side generated span generated during theduring construction the construction process using process the proposedusing the TPA proposed technology. TPA technology. The type I GPAS The type is selected I GPAS because is selected the gapbecause between the thegap girder between and the the girder pylon and is approximately the pylon is approximately 1 m. 1 m.

Note: DY-Single movable support

Basin type rubber support (DY)

PBL shear Grille frame connector Pylon

Z Y X Girder Basin type rubber Wallboard support (DY)

Jack

U-shaped anchor rebar Reaction frames (a) (b)

Figure 8. The global FE model of Dongtiao river bridge and the layout of GPAS: (a) Girder-pylon antithrust system and (b) force transmission brace. Sustainability 2020, 12, x FOR PEER REVIEW 12 of 23

SustainabilityFigure2020 8., 12The, 2973 global FE model of Dongtiao river bridge and the layout of GPAS: (a) Girder-pylon12 of 23 antithrust system and (b) force transmission brace. 4.1. Determination of Unfavorable Construction State 4.1. Determination of Unfavorable Construction State A temporary GPAS for the Dongtiao River Bridge is designed on the basis of the design procedure A temporary GPAS for the Dongtiao River Bridge is designed on the basis of the design in Section 3.4. A 3D beam-link-cable FE model (Figure8) is presented for the entire construction procedure in Section 3.4. A 3D beam-link-cable FE model (Figure 8) is presented for the entire analysis of the structural system. Then, the construction stage analysis is conducted to obtain the construction analysis of the structural system. Then, the construction stage analysis is conducted to maximum thrust force of the side span girder during construction, as shown in Figure9. With the obtain the maximum thrust force of the side span girder during construction, as shown in Figure 9. progress of construction, the maximum thrust force on the GPAS is 17,400 kN. The antithrust system is With the progress of construction, the maximum thrust force on the GPAS is 17,400 kN. The installed at the two sides of pylons, and a load safety factor of 1.4 [35] is considered on the basis of antithrust system is installed at the two sides of pylons, and a load safety factor of 1.4 [35] is construction experience. The maximum thrust force on the unilateral antithrust system is 17,400/2 considered on the basis of construction experience. The maximum thrust force on the unilateral× 1.4 = 12,180 kN, which is deﬁned as the most unfavorable thrust force. antithrust system is 17,400/2×1.4=12,180 kN, which is defined as the most unfavorable thrust force. 5.0k Thrust force of girder-pylon antithrust system 0.0

-5.0k

-10.0k Thrust force(kN) -15.0k Z Y Thrust force Girder-pylon antithrust system 17400kN -20.0k 0 3 6 9 12 15 18 21 24 27 30 33 Construction step Figure 9. Thrust force variation of GPAS during the construction process. Figure 9. Thrust force variation of GPAS during the construction process. 4.2. Phase I: Global Design 4.2. Phase I: Global Design The test results [36] indicated that the rebar diameter in PBL shear connectors ranges from 10 mm to 25 mm.The Thetest PBLresults shear [36] connectors, indicated that with the a 60 rebar mm diameter diameter in hole PBL and shear 25 mm connectors diameter ranges penetrating from 10 rebarmm in to the 25 hole, mm. are The arranged PBL shear in 200 connectors, mm spacing with along a 60 with mm longitudinal diameter hole and transverseand 25 mm directions diameter onpenetrating the basis of rebar the constructionin the hole, code are requirementsarranged in 200 [31]. mm The spacing number along of PBL with shear longitudinal connectors and is preliminarilytransverse directions calculated on using theFormula basis of (8).the Theconstruc Twin-PBLtion code shear requirements connector [37 [31].] is adopted The number to increase of PBL theshear torsional connectors resistance is preliminarily and overall calculated stiﬀness of using PBL shear Formula connectors. (8). The ConsideringTwin-PBL shear that connector the Twin-PBL [37] is shearadopted connector to increase is arranged the intorsional two-holes, resistance 45-holes areand arranged overall instiffness 15-rows forof eachPBL perforatedshear connectors. rib, as shownConsidering in Figure that 10a. the Twin-PBL shear connector is arranged in two-holes, 45-holes are arranged in 15-rows for each perforated rib, as shown in Figure 10(a). F F 12180 kN N = = 12180 90 (8) P ≥=FF2 2 kN ≈ ≥ α NVpud 0.4 (1.4 (d2 d ) f + 1.2d f ) = 136 kN ≈90 · P α ⋅ ⋅⋅−22s cd +s sd2 136 (8) Vpud · 04.(.(· 14−ddfscd ) 12 . df ssd ) kN On the basis of the aforementioned design principle, the anchorage length of U-shaped anchor On the basis of the aforementioned design principle, the anchorage length of U-shaped anchor rebar should be longer than 25 du, where du is the U-shaped anchor rebar diameter, and the number of U-shapedrebar should anchor be rebars longer should than 25 be d calculatedu, where d usingu is the Formula U-shaped (9). anchor As shown rebar in diameter, Figure 10 a,and three the groups number ofof six U-shaped U-shaped anchor anchor rebars rebars should with 25 be mm calculated diameter using and 1.8Formula m length (9). areAs initiallyshown in designed Figure 10a, to meet three safetygroups redundancy. of six U-shaped As shown anchor in Figure rebars 10 withb, the 25 preliminary mm diameter size and of grille1.8 m framelength is are proposed. initially designed to meet safety redundancy. As shown in Figure 10(b), the preliminary size of grille frame is proposed. Pm F D + (D V ) Pi pud 3 6 · i=1 · 12180 10 0.615 + 6.885 10 N m = × × × 11 (9) U FD⋅+() D ⋅ V 2 ≥ 2 HU As fsd Ppudi 2 4.2××364.9 330 +10 × ≈ · · ·=1 12180× 10× 0..× 615 6× 885 10 (9) N ≥=i ≈11 U ⋅⋅⋅ ××× ×2 2 HAfUssd 2424933010.. Sustainability 2020, 12, 2973 13 of 23 Sustainability 2020, 12, x FOR PEER REVIEW 13 of 23

(a) (b)

FigureFigure 10. 10.The The layout layout of theof the thrust thrust shoulder: shoulder: (a) Grouped (a) Grouped PBL shear PBL connectorsshear connectors and U-shaped and U-shaped anchor rebars,anchor and rebars, (b) grilleand ( frame.b) grille frame.

4.3.4.3. PhasePhase II:II: ParametricParametric StudyStudy

4.3.1. FEA 4.3.1. FEA The general software package ANSYS is used to simulate the behavior of the thrust shoulder The general software package ANSYS is used to simulate the behavior of the thrust shoulder (Figure 11). After considering the size eﬀect and the stress distortion on the coupling nodes of diﬀerent (Figure 11). After considering the size effect and the stress distortion on the coupling nodes of elements [38,39], the concrete in the anchorage zone is simulated by solid element SOLID65 [40]. The different elements [38,39], the concrete in the anchorage zone is simulated by solid element SOLID65 solid[40]. elementThe solid SOLID92 element is SOLID92 used to simulate is used theto grillesimulate frame the and grille PBL frame shear and connectors, PBL shear (including connectors, the perforated(including rib the and perforated penetrating rib rebar), and penetrating and the beam re elementbar), and BEAM4 the beam is used element to simulate BEAM4 the U-shapedis used to anchorsimulateSustainability rebars. the 2020U-shaped, 12, x FOR anchor PEER REVIEWrebars. 14 of 23 In order to simulate the friction between the steel and concrete (Figure 11), the nonlinear surface-to-surface contactUX,UY,UZ elements CONTA174Penetrating anrebard TARGE170Concrete dowel are used to simulate three contract Grille frame CP 3 Dowel pairs (CPs), namely, CP1 between the wallboard and concrete, CP2 betweenhoels the perforated4.7m ribs and concrete, and CP3 between the penetrating rebar and concrete dowel. CONTA174 element is adopted to the concrete surface, whereas TARGE170 element is used to the steel plate surface. The Perforated ribs 2m tangential behavior is assumed via= a penalty friction formulation+ with a friction coefficient of 0.35 Perforated [38]. 3m Z CP 2 rib hoels Y Pressure X U-shaped loads=36.7MPa anchor rebar CP 1

Stress,σs

CP1 is the contact pairs of c f

Tension t

wallboard and adjacent f concrete; CP2 is the contact pairs of perforated ribs and adjacent Strain, εs concrete; Compression Tensile stress, CP3 is the contact pairs of Compressive stress, Tensile strain, ε penetrating rebar and concrete Compressive strain, εc t Stress -strain dowel; Stress -strain relationship of concrete relationship of steel

Figure 11. The high-ﬁdelity 3D solid ﬁnite element model. Figure 11. The high-fidelity 3D solid finite element model. In order to simulate the friction between the steel and concrete (Figure 11), the nonlinear The displacements in X, Y, and Z directions of the concrete anchorage zone are constrained in surface-to-surface contact elements CONTA174 and TARGE170 are used to simulate three contract the model calculation. The unfavorable thrust force is 12,180 kN, and the direction is Y-axis. The thrust force is applied in the form of surface load to ensure the model load accuracy. The material properties are shown in Table 2. The material of the grille frame, wallboard, and perforated rib is Q345C. The material of the penetrating and U-shaped anchor rebars is HRB400, and that of the concrete is C50. The nonlinear behavior of materials is considered to increase the accuracy of FE simulation. The uniaxial stress–strain relationship of concrete in compression is obtained using the Hongnestad model, and incorporated into the FE model with Multi-linear Isotropic Hardening (MISO) option. The linear model of concrete in tension is adopted for the relationship between stress and strain. After crack resistance strength, the tensile stress linearly reduces to zero toward the ultimate strain because of the softening of concrete in tension (Figure 11) [41]. The stress–strain relationship of steel components is regarded as elastic-perfectly-plastic, and incorporated into the FE model with Bilinear Kinematic Hardening (BKIN) option. The assumed stress–strain curve of steel is shown in Figure 11, which is assumed to be a bilinear curve, including the strain hardening effect on the tension and compression sides [41].

Table 2. Material properties.

Compressive Tensile Yield Young’s Material Grade strength/MPa strength/MPa strength/MPa modulus/GPa Structural steel Q345C 270 270 345 210 Rebar HRB400 330 330 400 200 Concrete C50 22.4 1.83 - 34.5

4.3.2. Parametric Analysis Various FE models are used in the parametric analysis to examine the effects of penetrating rebar diameter (PD), hole space on the perforated rib (PS), diameter (UD) and length (UL) of the U-shaped anchor rebar, number of longitudinal plates (NL), and number of transverse plates (NT) of the grille frame. The test model T1 is established on the basis of the preliminary design, and all model parameters are listed in Table 3.

Table 3. Grouped models for parametric analyses.

Specimens PS (mm) PD (mm) UL (mm) UD (mm) NL NT T1 200 25 1800 25 2 5 T1-PD-20 200 20 1800 25 2 5 Sustainability 2020, 12, 2973 14 of 23 pairs (CPs), namely, CP1 between the wallboard and concrete, CP2 between the perforated ribs and concrete, and CP3 between the penetrating rebar and concrete dowel. CONTA174 element is adopted to the concrete surface, whereas TARGE170 element is used to the steel plate surface. The tangential behavior is assumed via a penalty friction formulation with a friction coeﬃcient of 0.35 [38]. The displacements in X, Y, and Z directions of the concrete anchorage zone are constrained in the model calculation. The unfavorable thrust force is 12,180 kN, and the direction is Y-axis. The thrust force is applied in the form of surface load to ensure the model load accuracy. The material properties are shown in Table2. The material of the grille frame, wallboard, and perforated rib is Q345C. The material of the penetrating and U-shaped anchor rebars is HRB400, and that of the concrete is C50. The nonlinear behavior of materials is considered to increase the accuracy of FE simulation. The uniaxial stress–strain relationship of concrete in compression is obtained using the Hongnestad model, and incorporated into the FE model with Multi-linear Isotropic Hardening (MISO) option. The linear model of concrete in tension is adopted for the relationship between stress and strain. After crack resistance strength, the tensile stress linearly reduces to zero toward the ultimate strain because of the softening of concrete in tension (Figure 11)[41]. The stress–strain relationship of steel components is regarded as elastic-perfectly-plastic, and incorporated into the FE model with Bilinear Kinematic Hardening (BKIN) option. The assumed stress–strain curve of steel is shown in Figure 11, which is assumed to be a bilinear curve, including the strain hardening eﬀect on the tension and compression sides [41].

Table 2. Material properties.

Compressive Tensile Yield Young’s Material Grade Strength/MPa Strength/MPa Strength/MPa Modulus/GPa Structural steel Q345C 270 270 345 210 Rebar HRB400 330 330 400 200 Concrete C50 22.4 1.83 - 34.5

4.3.2. Parametric Analysis Various FE models are used in the parametric analysis to examine the eﬀects of penetrating rebar diameter (PD), hole space on the perforated rib (PS), diameter (UD) and length (UL) of the U-shaped anchor rebar, number of longitudinal plates (NL), and number of transverse plates (NT) of the grille frame. The test model T1 is established on the basis of the preliminary design, and all model parameters are listed in Table3.

Table 3. Grouped models for parametric analyses.

Specimens PS (mm) PD (mm) UL (mm) UD (mm) NL NT T1 200 25 1800 25 2 5 T1-PD-20 200 20 1800 25 2 5 T1-PD-22 200 22 1800 25 2 5 T1-PD-28 200 28 1800 25 2 5 T1-PD-32 200 32 1800 25 2 5 T1-PS-100 100 25 1800 25 2 5 T1-PS-150 150 25 1800 25 2 5 T1-PS-250 250 25 1800 25 2 5 T1-PS-300 300 25 1800 25 2 5 T1-UD-20 200 25 1800 20 2 5 T1-UD-22 200 25 1800 22 2 5 T1-UD-28 200 25 1800 28 2 5 T1-UD-32 200 25 1800 32 2 5 T1-UL-1600 200 25 1600 25 2 5 Sustainability 2020, 12, x FOR PEER REVIEW 15 of 23

T1-PD-22 200 22 1800 25 2 5 T1-PD-28 200 28 1800 25 2 5 T1-PD-32 200 32 1800 25 2 5 T1-PS-100 100 25 1800 25 2 5 T1-PS-150 150 25 1800 25 2 5 T1-PS-250 250 25 1800 25 2 5 T1-PS-300 300 25 1800 25 2 5 Sustainability 2020T1-,U12D,-20 2973 200 25 1800 20 2 155 of 23 T1-UD-22 200 25 1800 22 2 5 T1-UD-28 200 25 1800 28 2 5 Table 3. Cont. T1-UD-32 200 25 1800 32 2 5 T1-UL-1600 200 25 1600 25 2 5 Specimens PS (mm) PD (mm) UL (mm) UD (mm) NL NT T1-UL-2000 200 25 2000 25 2 5 T1-T1-UL-2000UL-2200 200200 25 25 2000 2200 2525 22 5 5 T1-U -2200 200 25 2200 25 2 5 T1-L UL-2400 200 25 2400 25 2 5 T1-UL-2400 200 25 2400 25 2 5 T1-NL(3)-NT(5) 200 25 1800 25 3 5 T1-NL(3)-NT(5) 200 25 1800 25 3 5 T1-NL(4)-NT(5) 200 25 1800 25 4 5 T1-NL(4)-NT(5) 200 25 1800 25 4 5 T1-NL(5)-NT(5) 200 25 1800 25 5 5 T1-NL(5)-NT(5) 200 25 1800 25 5 5 T1-NL(2)-NT(4) 200 25 1800 25 2 4 T1-NL(2)-NT(4) 200 25 1800 25 2 4 T1-NL(2)-NT(6) 200 25 1800 25 2 6 T1-NL(2)-NT(6) 200 25 1800 25 2 6 T1-NT1-L(2)-NL(2)-NT(7)NT(7) 200200 25 25 1800 1800 25 25 2 2 7 7

Eff4.3.2.1.ects of Effects Penetrating of Penetrating Rebar Diameter Rebar Diameter and Perforated and Perforated Rib Hole Rib Spacing Hole Spacing ToTo investigate investigate the the e ffeffectect of of penetrating penetrating rebar rebar diameter diameter and and perforated perforated rib rib hole hole spacing spacing on on the the yield stress of the penetrating rebar, five types of penetrating rebar diameter PD and hole spacing PS, yield stress of the penetrating rebar, five types of penetrating rebar diameter PD and hole spacing PS, asas shown shown in in Table Table3, are3, are considered, considered, respectively. respectively. FigureFigures 12 a,b12(a), illustrate (b) illustrate the effects the of effects diameter of anddiameter hole spacingand hole on spacing Mises stress on Mises of the penetratingstress of the rebarpenetrating at the first rebar column, at the respectively.first column, As respectively. shown in Figure As shown 12a, thein Figure peak Mises 12(a), stressthe peak appears Mises in stress the 12thappears row position,in the 12th thereby row indicatingposition, thereby that the indicati middleng PBL that shear the connectorsmiddle PBL bear shear a large connectors thrust force.bear a Aslarge shown thrust in Figure force. 12Asb, shown the maximum in Figure stress 12(b), value the maximum of the penetrating stress value rebar of is the less penetrating than that of rebar other is spacingless than when that theof other hole spacing when is 100 the mm, hole indicating spacing is that 100 the mm, spacing indicating between that the holes spacing is extremely between short,holes and is extremely the PBL shear short, connectors and the PBL do shear not exert connectors the maximum do not eexertffect. the The maximum peak stress effect. appears The andpeak movesstress to appears the loading and sidemoves when to thethe hole loading spacing side is greaterwhen the than hole 200 mm,spacing indicating is greater that thethan PBL 200 shear mm, connectorsindicating exert that the the maximum PBL shear effect connectors under the structuralexert the sizemaximum constraint. effect The under results the of FEstructural analysis aresize consistentconstraint. with The the results design of formulasFE analysis deduced are consistent in phase with I, and the the design reliability formulas of Formula deduced (3) in isphase verified. I, and the reliability of Formula (3) is verified.

(a) (b)

FigureFigure 12. 12.Comparison Comparison of PBLof PBL performance performance with with different different parameters: parameters: (a)Eff ect(a) ofEffect diameter of diameter on Mises on stressMises of penetratingstress of penetrating rebar at 1st rebarcolumn; at (1stb) effcolumn;ect of hole (b) spacing effect of on Miseshole spacing stress of on penetrating Mises stress rebar of atpenetrating 1st column. rebar at 1st column.

Eﬀ4.3.2.2.ects of Effects the Diameter of the Diameter and Length and of Length U-Shaped of U-Shaped Anchor Rebar Anchor Rebar

Five types of diameter UD and length UL are considered to investigate the effects of the diameter and length of U-shaped anchor rebar on tensile stress, as shown in Table3. Figure 13a shows the effect of diameter on the tensile stress of U-shaped anchor rebar. The maximum stress of the U-shaped anchor rebar gradually decreases with the increase in diameter. Figure 13b shows the effect of length on the tensile stress of U-shaped anchor rebar. The maximum tensile stress of the U-shaped anchor rebar slowly decreases with the increase in length. The maximum stress decreases 84 and 42 MPa when the diameter and length of U-shaped anchor rebar vary from 22 mm to 32 mm and from 1.6 m to 2.4 m, respectively, indicating that diameter plays a great role in the tension capacity of the U-shaped anchor Sustainability 2020, 12, x FOR PEER REVIEW 16 of 23 Sustainability 2020, 12, x FOR PEER REVIEW 16 of 23

Five types of diameter UD and length UL are considered to investigate the effects of the diameter Five types of diameter UD and length UL are considered to investigate the effects of the diameter and length of U-shaped anchor rebar on tensile stress, as shown in Table 3. Figure 13(a) shows the and length of U-shaped anchor rebar on tensile stress, as shown in Table 3. Figure 13(a) shows the effect of diameter on the tensile stress of U-shaped anchor rebar. The maximum stress of the effect of diameter on the tensile stress of U-shaped anchor rebar. The maximum stress of the U-shaped anchor rebar gradually decreases with the increase in diameter. Figure 13(b) shows the U-shaped anchor rebar gradually decreases with the increase in diameter. Figure 13(b) shows the effect of length on the tensile stress of U-shaped anchor rebar. The maximum tensile stress of the effect of length on the tensile stress of U-shaped anchor rebar. The maximum tensile stress of the U-shapedSustainability anchor2020, 12, rebar 2973 slowly decreases with the increase in length. The maximum stress decreases16 of 23 U-shaped anchor rebar slowly decreases with the increase in length. The maximum stress decreases 84 and 42 MPa when the diameter and length of U-shaped anchor rebar vary from 22 mm to 32 mm 84 and 42 MPa when the diameter and length of U-shaped anchor rebar vary from 22 mm to 32 mm and from 1.6 m to 2.4 m, respectively, indicating that diameter plays a great role in the tension rebar.and from This 1.6 condition m to 2.4 is mainlym, respectively, due to the indicating fact that thethat maximum diameter tensileplays a stress great appears role in inthe the tension weld capacity of the U-shaped anchor rebar. This condition is mainly due to the fact that the maximum betweencapacity theof the U-shaped U-shaped anchor anchor rebar rebar. and theThis wallboard, condition andis mainly the increase due to in the the fact diameter that the of maximum U-shaped tensile stress appears in the weld between the U-shaped anchor rebar and the wallboard, and the anchortensile rebarstress leadsappears to the in increasethe weld in between the butt the weld U-shaped area. anchor rebar and the wallboard, and the increase in the diameter of U-shaped anchor rebar leads to the increase in the butt weld area. increase in the diameter of U-shaped anchor rebar leads to the increase in the butt weld area. 300 260 3rd group 300 rd 260 rd 3 group 3nd group rd 2 group 275 3nd group 240 nd 2 group 2st group 275 nd 240 1 group 2 group st 250 1st group 220 1 group 250 1st group 220 225 200 225 200 200 180 200 180 175 160 st 175 1st group 1 group Tensile stress(MPa) st Tensile stress(MPa) Tensile st 160 150 1nd group 1nd group

Tensile stress(MPa) 2 group

Tensile stress(MPa) Tensile 2 group 140 nd 150 2rdnd group 2rd group F 3 group 140 F 3 group 125 rd rd 125 F 3 group F 3 group 20 22 24 26 28 30 32 1.6 1.8 2.0 2.2 2.4 1.6 1.8 2.0 2.2 2.4 Diameter20 of 22 the U-shaped 24 26 anchor 28 30 rebar(mm) 32 Length of the U-shaped anchor rebar (m) Diameter of the U-shaped anchor rebar(mm) Length of the U-shaped anchor rebar (m) (a) (b) (a) (b) Figure 13. ComparisonComparison of of tensile tensile stress stress of ofU-shaped U-shaped anchor anchor bars bars in different in different (a) (diametersa) diameters and and(b) Figure 13. Comparison of tensile stress of U-shaped anchor bars in different (a) diameters and (b) lengths.(b) lengths. lengths. 4.3.2.3.Effects ofEffects the Number of the Number of Grille of Plates Grille Plates 4.3.2.3. Effects of the Number of Grille Plates The grille frame transmits the thrust force to the wallboard through several soldering seams The grille frame transmits the thrust force to the wallboard through several soldering seams connected between the longitudinal plates, transver transversese plates, and the wallboard.wallboard. The The effect effect of the connected between the longitudinal plates, transverse plates, and the wallboard. The effect of the number of different different kinds of plates on the thrust-sharingthrust-sharing proportion of the gr grilleille frame, as shown in number of different kinds of plates on the thrust-sharing proportion of the grille frame, as shown in Table3 3,, areare considered considered to to investigate investigate the the optimal optimal number number of of each each kind kind of of plates. plates. Table 3, are considered to investigate the optimal number of each kind of plates. The thrust-sharing proportion of the longitudin longitudinalal plate exceeds 80%, and the transverse plates The thrust-sharing proportion of the longitudinal plate exceeds 80%, and the transverse plates do not exceed 20%, as shown in Figure 1414,, indicating that the longitudinal plate is the important do not exceed 20%, as shown in Figure 14, indicating that the longitudinal plate is the important force transfertransfer component.component. TheThe thrust-sharing thrust-sharing proportion proportion transmitted transmitted by by the the two two components components does does not force transfer component. The thrust-sharing proportion transmitted by the two components does notsignificantly significantly vary vary with with the increasethe increase in the in numberthe number of longitudinal of longitudinal and and transverse transverse plates. plates. not significantly vary with the increase in the number of longitudinal and transverse plates.

Figure 14. Effect of number of plates on thrust-sharing proportion. FigureFigure 14.14. EEffectffect ofof numbernumber ofof platesplates onon thrust-sharingthrust-sharing proportion.proportion. 4.3.3. Performance Performance Improvement Improvement 4.3.3. Performance Improvement In this section, the the global design design of of phase I is improved on the basis of the aforementioned In this section, the global design of phase I is improved on the basis of the aforementioned parametric analyses. The The design design of of PBL PBL and and U-shaped U-shaped anchor anchor rebar rebar is is the the key factor affecting affecting the parametric analyses. The design of PBL and U-shaped anchor rebar is the key factor affecting the thrust shoulder performance. The stress is more sensitive to the change of hole spacing and diameter of U-shaped anchor rebar, so special attention should be paid to the selection of their sizes. However, the number of grille plates is not a key factor, and the change of the number has little effect on the thrust-sharing proportion of each component. Therefore, according to the results of parameter analysis and considering the safety redundancy of the structure, the improved parameters are as follows: (1) The penetrating rebar diameter is 25 mm, and the hole spacing is 200 mm; (2) the diameter of U-shaped Sustainability 2020, 12, x FOR PEER REVIEW 17 of 23

thrust shoulder performance. The stress is more sensitive to the change of hole spacing and diameter of U-shaped anchor rebar, so special attention should be paid to the selection of their sizes. However, the number of grille plates is not a key factor, and the change of the number has little effect on the thrust-sharing proportion of each component. Therefore, according to the results of parameter analysis and considering the safety redundancy of the structure, the improved parameters are as follows: (1) The penetrating rebar diameter is 25 mm, and the hole spacing is 200 mm; (2) the diameter of U-shaped anchor rebar is 28 mm, and the length is 2 m; and (3) the number Sustainability 2020, 12, 2973 of plates in each component of grilles frame is consistent with the 17global of 23 design of phase I. The improved structural performance analysis is provided as follows:

anchor rebar is 28 mm, and4.3.3.1. the length PBL Shear is 2 m; Connectors and (3) the number of plates in each component of grilles frame is consistent with the global design of phase I. The improved structural performance analysis is provided as follows: Figure 15 shows the Mises stress distribution of the PBL shear connectors. The Mises stress of the PBL shear connectors is less than that of the yield strength, and the maximum stress is 28 MPa, PBL Shear Connectors which occurs at the 12th row of the first column. For the PBL shear connectors in the same row, the stress on the side close to the wallboard is greater than that on the side far from the wallboard, and Figure 15 shows the Mises stress distribution of the PBL shear connectors. The Mises stress of the Sustainability 2020, 12, x FOR PEER REVIEW shear of the first row is the most disadvantageous. 17 of 23 PBL shear connectors is less than that of the yield strength, and the maximum stress is 28 MPa, which Figure 16 shows the shear force and slip of PBL shear connectors at the first column. The shear occurs at the 12th row of the ﬁrst column. For the PBL shear connectors in the same row, the stress on thrust shoulder performance. The stress is more sensforceitive toof thePBL change connectors of hole is spacingfirst increased, and diameter and then decreased with the increase in the row number. the side close to the wallboard is greater than that on the side far from the wallboard, and shear of the of U-shaped anchor rebar, so special attention shTheould maximum be paid slippingto the selection value is 0.of05 their mm, sizes. thereby showing a gradually decreasing trend. The slip ﬁrst row is the most disadvantageous. However, the number of grille plates is not a key factor,value is and less the than change 0.2 mm, of therebythe number meeting has thelittle design requirements of Formula (6). effect on the thrust-sharing proportion of each component. Therefore, according to the results of 30 120 0.06 parameter analysis and considering the safety redundancy of the1st column structure, the improved Shear force 102 2nd column parameters are as follows: (1) The penetrating rebar diameter25 is 25 mm, and the hole spacing is 200 100 Slip 92 91 0.05 3rd column 8183 80 mm; (2) the diameter of U-shaped anchor rebar is 28 mm, and the length is 2 m; and (3) the number 80 7478 74 20 71 of plates in each component of grilles frame is consistent with the global design of phase I. The 62636466 0.04 60 59 improved structural performance analysis is provided as follows:15 0.03

40 Slip (mm) Shear Shear (kN)force Mises stress (MPa) 10 4.3.3.1. PBL Shear Connectors 20 0.02 Figure 15 shows the Mises stress distribution of the PBL5 shear connectors. The Mises stress of 0 0.01 123456789101112131415 123456789101112131415 the PBL shear connectors is less than that of the yield strength, and the maximumRow number stress is 28 MPa, Row number which occurs at the 12th row of the first column. For the PBL shear connectors in the same row, the Figure 15. Mises stress distribution of the PBL shear connectors (unit: Pa). stress on the side close to the wallboard is greater than thatFigure on the15. sideMises far stress from distribution the wallboard, of the and Figure 16. Shear force and slip of PBL shear shear of the first row is the most disadvantageous. Figure 16 shows the shearPBL force shear and connectors slip of PBL (unit: shear Pa). connectors at the first column.connectors The at 1st shear column. Figure 16 shows the shear force and slip of PBL shear connectors at the first column. The shear force of PBL connectors is first increased, and then decreased with the increase in the row number. force of PBL connectors is first increased, and then decreased with the increase in the row number. The maximum slipping value is 0.05 mm, thereby showing a gradually decreasing trend. The slip The maximum slipping value is 0.05 mm, thereby showing4.3.3.2. U-Shaped a gradually Anchor decreasing Rebar trend. The slip value is less than 0.2 mm, thereby meeting the design requirements of Formula (6). value is less than 0.2 mm, thereby meeting the design requirements of Formula (6). Three sets of anchor rebars are found on the inner side of the wallboard, where each set has six 30 120 0.06 1st column rebars for a total of 18 U-shaped anchor rebars. The stress value and group-sharing proportion of Shear force 102 2nd column U-shaped anchor rebar are shown in Figure 17(a), (b). 25 100 Slip 92 91 0.05 3rd column As shown in Figure 8117(a),83 the maximum80 tensile stress of U-shaped anchor rebar is 228 MPa, 80 7478 74 20 6671 0.04 which is 59less62 63than64 the threshold value of 330 MPa. The maximum tensile stress appears at the first group60 of U-shaped anchor rebar near the loading side. The tensile stress gradually decreases because 15 0.03 the U-shaped40 anchor rebar position is far from Slip (mm) the loading side. The group-sharing proportion of Shear Shear (kN)force Mises stress (MPa) 10 U-shaped20 anchor rebar is uniform, indicating0.02 that all U-shaped anchor rebars undertake the out-of-plane deformation of the wallboard. 5 0 0.01 123456789101112131415 As indicated123456789101112131415 in Figure 17(b), the maximum shear stress at the weld of U-shaped anchor rebar is Row number 107 MPa, which is Rowless numberthan the limit value of 175 MPa and meets the safety requirements. The Figuremaximum 16. Shear force shear and stress slip of at PBL the shear weld connectors appears at at 1st the column. first group of U-shaped anchor rebar near the Figure 15. Mises stress distribution of the loadingFigure side. 16. TheShear maximum force and slipshear of PBLstress shear significan tly decreases with the U-shaped anchor rebar PBL shear connectors (unit:U-Shaped Pa). Anchor Rebar positionconnectors away atfrom 1st column.the loading side. At the same time, the group-sharing proportion among the Three sets of anchorgroups rebars areis uneven. found on The the group-sharing inner side of theproportion wallboard, am whereong the each first set group has six is more than 50%, and the 4.3.3.2. U-Shaped Anchor Rebarrebars for a total of 18 U-shaped anchor rebars. The stress value and group-sharing proportion of U-shaped anchor rebar are shown in Figure 17a,b. Three sets of anchor rebars Asare shown found inon Figure the in ner17a, side the maximumof the wallboard, tensile stresswhere of each U-shaped set has anchor six rebar is 228 MPa, which rebars for a total of 18 U-shapedis less thananchor the rebars threshold. The valuestressof value 330 MPa.and grou Thep-sharing maximum proportion tensile stress of appears at the first group U-shaped anchor rebar are ofshown U-shaped in Figure anchor 17(a), rebar (b). near the loading side. The tensile stress gradually decreases because the As shown in Figure 17(a),U-shaped the maximum anchor rebar tensile position stress is farof fromU-shaped the loading anchor side. rebar The is group-sharing228 MPa, proportion of U-shaped which is less than the thresholdanchor value rebar of is330 uniform, MPa. The indicating maximum that tensile all U-shaped stress appears anchor at rebarsthe first undertake the out-of-plane group of U-shaped anchor rebardeformation near the of loading the wallboard. side. The tensile stress gradually decreases because the U-shaped anchor rebar position is far from the loading side. The group-sharing proportion of U-shaped anchor rebar is uniform, indicating that all U-shaped anchor rebars undertake the out-of-plane deformation of the wallboard. As indicated in Figure 17(b), the maximum shear stress at the weld of U-shaped anchor rebar is 107 MPa, which is less than the limit value of 175 MPa and meets the safety requirements. The maximum shear stress at the weld appears at the first group of U-shaped anchor rebar near the loading side. The maximum shear stress significantly decreases with the U-shaped anchor rebar position away from the loading side. At the same time, the group-sharing proportion among the groups is uneven. The group-sharing proportion among the first group is more than 50%, and the Sustainability 2020, 12, x FOR PEER REVIEW 18 of 23

Sustainability 2020, 12, 2973 18 of 23 proportion of the third group is only 10%, thereby indicating that the U-shaped anchor rebars Sustainability 2020, 12, x FOR PEER REVIEW 18 of 23 provide shear bearing reserve.

240 proportion Proportion of the40% third group 150is only 10%, thereby indicating 60%that the U-shaped anchor rebars 36.60% Tensile stress 53.41% Proportion 33.94%provide shear bearing35% reserve. 125 Shear stress 50% 220 29.45% 30% 150 60% 240 Proportion100 40% 40% 36.60%25% Tensile stress 36.21% 53.41% Proportion 33.94% 35% 125 Shear stress 50% 200 75 30% 220 20% 29.45% 30% 100 40% 15% 50 25% 20% 36.21% 180 200 10% 10.38%75 30%

Shear stress (MPa) 20% Tensile stress Tensile (MPa) 5% 25 10% Group-sharing proportion Group-sharing 15% 50 Group-sharing proportion 20% 160 0% 0 0% 123180 10% 10.38% Shear stress (MPa)

Tensile stress Tensile (MPa) 123 Group number 5% 25 10%

Group proportion Group-sharing number Group-sharing proportion 160 0% 0 0% (a) 123 (b) 123 Group number Group number FigureFigure 17.17. StressStress and and group-sharing group-sharing proportion proportion of U-shaped of U-shaped anchor anchor rebar: rebar: (a) Tensile (a) Tensile stress and stress (b) and (bshear) shear stress. stress. (a) (b) Figure 17. Stress and group-sharing proportion of U-shaped anchor rebar: (a) Tensile stress and (b) 4.3.3.3. Grille Frame As indicated in Figure 17shearb, the stress. maximum shear stress at the weld of U-shaped anchor rebar is 107Figure MPa, which18 shows is lessthe maximum than the limit Mises value stress of change 175 MPa in the and grid meets frame the during safety construction. requirements. TheThe maximumMises stress shear of the stress grille at the frame4.3.3.3. weld under Grille appears thrust Frame at theforce first is groupless than of U-shaped the yield anchorstrength rebar of 345 near MPa. the loadingThe side.maximum The maximum Mises stress shear is stress 201Figure significantlyMPa, 18 which shows decreasesappears the maximum withat the the Misesweld U-shaped stressbetween change anchor the in rebartransverse the positiongrid frame and away during construction. The fromlongitudinal the loading plates side. near At the theMises loading same stress time, side. of thetheThis group-sharinggrille condition frame is under mainly proportion thrust because force among the is longitudinal less the than groups the plateis yield uneven. is strength of 345 MPa. The Thebent group-sharing and deformed, proportion resultingmaximum in among the stress Mises the concentr first stress groupation is is201 morecaused MPa, than by whichthe 50%, limited andappears the internal proportion at thedisplacement. weld of the between third the transverse and groupMeanwhile, is only the 10%, Mises thereby stresslongitudinal indicating in the rest that platesof the the neargrille U-shaped the frame loading anchoris significantly side. rebars Thisprovide conditionreduced. shear Theis mainly plates bearing becauseof reserve.the the longitudinal plate is entire grille frame have bentlow andstress, deformed, thereby resultingmeeting inthe the criterion stress concentr in Tableation 2. caused Meanwhile, by the limitedthe internal displacement. Grille Frame maximum displacement ofMeanwhile, the grille frame the Misesin the stressY direction in the is rest 0.365 of mm,the grille which frame is less is thansignificantly the limit reduced. The plates of the valueFigure calculated 18 shows using theFormulaentire maximum (7). grille Misesframe stresshave low change stress, in thethereby grid me frameeting duringthe criterion construction. in Table 2. Meanwhile, the The Mises stress of the grillemaximum frame displacement under thrust of force the grille is less frame than in thethe yieldY direction strength is 0.365 of 345mm, MPa. which is less than the limit 4.3.3.4. Concrete Anchorage Zone The maximum Mises stressvalue is 201calculated MPa, using which Formula appears (7). at the weld between the transverse and longitudinalAs shown plates in Figure near the19, the loading maximum side. principal This condition tensile isand mainly compress becauseive stresses the longitudinal in the concrete plate is 4.3.3.4. Concrete Anchorage Zone bentanchorage and deformed, zone are resulting1.46 and in17.4 the MPa, stress which concentration are less than caused the limit by the values limited of 1.86 internal and displacement.22.4 MPa, Meanwhile,respectively. the The Mises maximum stress tensile inAs the shown and rest compressive of in the Figure grille 19, framestresses the maxi is occur significantlymum at principal the joint reduced. oftensile the wallboard and The compress plates and ofive the stresses in the concrete entireconcrete, grille where frame havean obvious lowanchorage stress, stress thereby zone concentrat are meeting 1.46ion and the phenomenon criterion17.4 MPa, in which Tableoccurs, 2are. Meanwhile, lessand thanthe thetensile the limit maximum and values of 1.86 and 22.4 MPa, compressive stresses of concrete far from this area significantly decrease. displacement of the grillerespectively. frame in the The Y directionmaximum is tensile 0.365 and mm, compressive which is less stresses than occur the limit at the value joint of the wallboard and calculated using Formula (7).concrete, where an obvious stress concentration phenomenon occurs, and the tensile and compressive stresses of concrete far from this area significantly decrease.

MAX MAX

MAX MAX MAX

MAX

Figure 19. Stress in anchorage zone of Figure 18. Mises stress of the grille frame. concrete side span beam. Figure 18. Mises stress of the grille frame. Figure 19. Stress in anchorage zone of Figure 18. Mises stress of the grille frame. concrete side span beam. Concrete4.4. Field AnchorageTest and Verification Zone As shown in Figure 19, the maximum principal tensile and compressive stresses in the concrete anchorage zone are 1.46 and4.4. 17.4Field MPa,Test and which Verification are less than the limit values of 1.86 and 22.4 MPa, respectively. The maximum tensile and compressive stresses occur at the joint of the wallboard and Sustainability 2020, 12, x FOR PEER REVIEW 18 of 23 proportion of the third group is only 10%, thereby indicating that the U-shaped anchor rebars provide shear bearing reserve.

240 Proportion 40% 150 60% 36.60% Tensile stress 53.41% Proportion 33.94% 35% 125 Shear stress 50% 220 29.45% 30% 100 40% 25% 36.21% 200 20% 75 30% 15% 50 20% 180 10% 10.38% Shear stress (MPa) Tensile stress Tensile (MPa) 5% 25 10% Group-sharing proportion Group-sharing Group-sharing proportion 160 0% 0 0% 123 123 Group number Group number (a) (b)

Figure 17. Stress and group-sharing proportion of U-shaped anchor rebar: (a) Tensile stress and (b) shear stress.

4.3.3.3. Grille Frame Figure 18 shows the maximum Mises stress change in the grid frame during construction. The Mises stress of the grille frame under thrust force is less than the yield strength of 345 MPa. The maximum Mises stress is 201 MPa, which appears at the weld between the transverse and longitudinal plates near the loading side. This condition is mainly because the longitudinal plate is bent and deformed, resulting in the stress concentration caused by the limited internal displacement. Meanwhile, the Mises stress in the rest of the grille frame is significantly reduced. The plates of the entire grille frame have low stress, thereby meeting the criterion in Table 2. Meanwhile, the maximum displacement of the grille frame in the Y direction is 0.365 mm, which is less than the limit value calculated using Formula (7).

4.3.3.4. Concrete Anchorage Zone Sustainability 2020, 12, 2973 19 of 23 As shown in Figure 19, the maximum principal tensile and compressive stresses in the concrete anchorage zone are 1.46 and 17.4 MPa, which are less than the limit values of 1.86 and 22.4 MPa, respectively. The maximumconcrete, tensile where and ancompressive obvious stress stresses concentration occur at the phenomenon joint of the wallboard occurs, and and the tensile and compressive concrete, where an obviousstresses ofstress concrete concentrat far fromion thisphenomenon area signiﬁcantly occurs, decrease. and the tensile and compressive stresses of concrete far from this area significantly decrease.

MAX MAX

MAX

Figure 19. FigureStress in19. anchorage Stress in zone anchorage of concrete zone side of span beam. Figure 18. Mises stress of the grille frame. concrete side span beam. 4.4. Field Test and Veriﬁcation SustainabilityAs shown 2020 in, 12 Figure, x FOR PEER20a,b, REVIEW the designed girder–pylon thrust shoulders have been successfully 19 of 23 4.4. Field Test and Verification appliedAs to helpshown facilitate in Figures the implementation 20(a), (b), the ofdesigned sustainable girder–pylon construction thrust of the shoulders Dongtiao have River been Bridge. Forsuccessfully ﬁeld tests, applied three stress to help measuring facilitate the points implementation are arranged of onsustainable the grille construction frame to monitor of the Dongtiao the stress changesRiver duringBridge. theFor construction.field tests, three Figure stress 20c,d measuring shows the points comparison are arranged of the measuredon the grille and frame calculated to stressmonitor values the atstress points changes 1, 2, andduring 3. the The construction grille frame. Figures stress is20(c), constantly (d) shows in thethe comparison safe range, of and the the variationmeasured tendencies and calculated of the stress measured values and at points calculated 1, 2, and values 3. The are grille the frame same. stress The measuredis constantly values in the are slightlysafe range, larger and than the the variation calculated tendencies values becauseof the measured of the measurement and calculated errors values and are construction the same. The load uncertainty.measured values The errors are slightly of the calculatedlarger than andthe calc measuredulated values values because are within of the 10 measurement MPa and are errors in good agreement,and construction verifying load the uncertainty. accuracy of The the proposederrors of the analytical calculated framework. and measured values are within 10 MPa and are in good agreement, verifying the accuracy of the proposed analytical framework.

Pylon

Grille frame Girder Reaction frames Pylon

Girder Grille frame

(a) (b)

0 Calculated values 0 Calculated values Measured values Measured values -20 Point 1 -20 Point 3 Point 2 -40 -40

1# Vertical plate 300mm 3# Vertical plate 300mm -60 165mm -60 1 3 165mm 635mm -80 2 -80 Longitudinal stress (MPa) stress Longitudinal Longitudinal stress (MPa) Strain Gauge Strain Gauge -100 -100 0 3 6 9 12 15 18 21 24 27 30 33 0 3 6 9 12 15 18 21 24 27 30 Construction step Construction step (c) (d)

FigureFigure 20. 20.Field Field tests: tests: ((aa)) Girder-pylon antithrust antithrust system; system; (b () bforce) force transmission transmission brace; brace; and and(c)-(d (c), d) calculatedcalculated and and measured measured results results of of the the longitudinal longitudinal stressesstresses of the grille grille frame. frame.

5. Result Discussion on Construction Sustainability The proposed TPA technology enables a construction sequence that is similar to the construction of conventional suspension bridge, where the main cable is first erected, and the mid-span girder is lifted in sections and connected to the hangers (Figure 21(a)). In this way, the ship navigation during the construction period avoids interruptions (Figure 21(b)). Without the need for temporary supports, the TPA technology enables to minimize environmental impact and traffic disruption during the construction stage. A comprehensive onsite construction cost is evaluated for the engineering practice. As shown in Table 4, the traffic disruption has been minimized to 76 hours during the entire 4 months period of girder erection. The environmental impact on the navigation channel can be eliminated. The total onsite construction time is significantly reduced to 21 days. In Table 4, materials for the GPAS include steel (ton) and reinforced bar (ton), and the equipment for erection and removal of GPAS includes arc welder (set) and plasma cutting machine (set).

Table 4. Comprehensive onsite construction cost of TPA technology.

Unit price Cost Sum Division of Construction Unit Quantity (USD) (USD) (USD)

Environmental impact (C1) 56,838 56,838 Sustainability 2020, 12, x FOR PEER REVIEW 20 of 23

Traffic disruption (C2) Hour 76 412 31,312 31,312 GPAS Steel ton 7.87 584 4,596 Materials Reinforcing bars ton 0.8 541 433 Onsite construction Arc welder Set 2 5,870 11,740 materials and equipment 80,400 Plasma cutting (C3) Equipment Set 2 21,428 42,856 machine Sustainability 2020, 12, 2973 Other Set 15 1,385 20,775 20 of 23

Onsite construction time (C4) Day 21 8,405 176,505 176,505

Onsite construction risk (C5) 22,600 22,600 5. Result Discussion onTPGA Construction Sustainability Total (C) 367,655 The proposed TPA technology enables a construction sequence that is similar to the construction To compare sustainability among four construction technologies, the comprehensive onsite of conventional suspension bridge, where the main cable is ﬁrst erected, and the mid-span girder is construction costs are calculated. As shown in Figure 21(c), the total cost of TPA technology is the liftedleast, in which sections accounts and connected for 27%, to28%, the and hangers 34% (Figureof the total 21a). cost In thisof TS, way, TEA, the and ship TSC navigation technology, during therespectively. construction In periodparticular, avoids the interruptionsTPA technology (Figure significa 21b).ntly Without reduces the the need cost of for environmental temporary supports, and thetraffic TPA impact technology compared enables with to other minimize technologies, environmental indicating impact that andthe impact traﬃc disruptionon the environment during the constructionand stage.

Hoisting girder segments Normal navigation of the ship

(a) (b) 1.50M 1.35M TS TEA 1.20M TSC 1.05M TPA 900.00k 750.00k 600.00k Cost (USD) 450.00k 300.00k 150.00k 0.00 Environmental Traffic Onsit construction Onsit Onsit Total impact disruption materials and construction construction equipment time risk

(c)

FigureFigure 21. 21.Construction Construction sustainability sustainability evaluation: evaluation: (a) Hoisting(a) Hoisting girder girder segments; segments; (b) channel (b) channel operation duringoperation construction; during construction; and (c) economic and (c) evaluationeconomic evaluation for construction. for construction.

6. ConclusionsA comprehensive onsite construction cost is evaluated for the engineering practice. As shown in Table4,To the promote tra ffic disruptionsustainable hasconstruction been minimized within real-world to 76 hours application, during the a comprehensive entire 4 months research period of girderis studied erection. in the The paper environmental on sustainable impact construction on the navigation by using channelnovel technology can be eliminated. for self-anchored The total onsitesuspension construction bridge. time The ismain significantly conclusions reduced and innovation to 21 days. points In Table are summarized4, materials foras follows: the GPAS include steel (ton)1. A and novel reinforced temporary bar pylon-anch (ton), andor the (TPA) equipment technology for erection is proposed and removalto minimize of GPAS environmental includes arc welderimpact (set) and and traffic plasma disruption. cutting machineA novel (set).girder-pylon antithrust system (GPAS) is developed to achieveTo compare the engineering sustainability application among for fourthe TPA construction technology. technologies, The new TPA the and comprehensive GPAS technology onsite constructioncould efficiently costs improve are calculated. the construction As shown sustainability. in Figure 21c, the total cost of TPA technology is the least, which accounts for 27%, 28%, and 34% of the total cost of TS, TEA, and TSC technology, respectively. In particular, the TPA technology significantly reduces the cost of environmental and traffic impact compared with other technologies, indicating that the impact on the environment and traffic is relatively small. Meanwhile, in terms of onsite materials and equipment, construction time and risk, TPA technology also offers obvious economic advantages. Sustainability 2020, 12, 2973 21 of 23

Table 4. Comprehensive onsite construction cost of TPA technology.

Unit price Cost Sum Division of Construction Unit Quantity (USD) (USD) (USD)

Environmental impact (C1) 56,838 56,838

Traﬃc disruption (C2) Hour 76 412 31,312 31,312 Steel ton 7.87 584 4596 Onsite GPAS Reinforcing bars ton 0.8 541 433 construction Materials Arc welder Set 2 5870 11,740 80,400 materials and Equipment Plasma cutting equipment (C ) Set 2 21,428 42,856 3 machine Other Set 15 1385 20,775

Onsite construction time (C4) Day 21 8405 176,505 176,505 Onsite construction risk (C ) 5 22,600 22,600 TPGA Total (C) 367,655

6. Conclusions To promote sustainable construction within real-world application, a comprehensive research is studied in the paper on sustainable construction by using novel technology for self-anchored suspension bridge. The main conclusions and innovation points are summarized as follows: 1. A novel temporary pylon-anchor (TPA) technology is proposed to minimize environmental impact and traffic disruption. A novel girder-pylon antithrust system (GPAS) is developed to achieve the engineering application for the TPA technology. The new TPA and GPAS technology could efficiently improve the construction sustainability. 2. A practical assessment method and index of sustainability on bridge construction technology are established to facilitate decision making for sustainable construction scheme. This paper creates an evaluation index system by considering different aspects: Environmental impact, traffic disruption, onsite construction materials and equipment, time, and risk. 3. A two-phase analytical approach for the GPAS is proposed by considering the global design and parametric study. In phase I, the global design of thrust shoulder is performed using a set of specially derived practical formulas. Various performance indicators are established to ensure the applicability and global reliability of the thrust shoulder. In phase II, the local stress distribution is improved based on effects of different parameters induced by grouped parametric analyses using 3D elaborate finite element analysis, which simulates the nonlinear surface contact behavior to consider the friction effect between the steel and the concrete. 4. The applicability and rationality of the proposed novel construction technology are illustrated by the successful application in real-world engineering. The field tests and sustainability assessment show that the proposed sustainability assessment method and analytical approach can facilitate the implementation of sustainable construction for self-anchored suspension bridge. All in all, this research lays a solid and comprehensive basis to promote construction sustainability for self-anchored suspension bridge.

Author Contributions: X.W. (Xiaoming Wang) conceived and wrote the paper; X.W. (Xudong Wang) wrote the paper; Y.D. edited and improve the paper; C.W. provided the project data. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by the Natural Science Foundation of Shannxi Province, grant number 2020JM-219, the China Postdoctoral Science Foundation, grant number 2019M653519, and the National Key Research and Development Project of China, grant number 2018YFB1600300. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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