cm TG 16, Sustainable , Tampa, Florida, USA, November 6-9, 1994.

DEVELOPMENT OF COMPUTER INTEGRATED CONSTRUCTION TECHNIQUES FOR REINFORCED MASONRY BY CASTING JOINT METHOD TO IMPROVE CONSTRUCTION SUST AINABILITY

Takayuki Fukushima and Takaaki Nishi Technical Research Institute, HASEKO Corporation 1063 Kaneda, Atsugi, Kanagawa, 243, Japan Akio Baba Research Institute, Ministry of Construction I Tatehara, Tsukuba, Ibaraki, 305, Japan Naoji Hasegawa Minister's Secrctariat, Ministry of Construction 2-1-3 Kasumigaseki, Chiyoda-ku, Tokyo, 100, Japan

Introduction

In constructing buildings, there may be five goals to be achieved, namely, high performance, high durability, high productivity, manifold beauty and ecological balance. One of the most important problems the construction industry faces today is disposal of for protecting the global environment. In reinforced concrete (RC hereafter) construction, a large amount of plywood panel is used that have to be cast away after several uses. In achieving the five goals, thercfore, it is of primary importance to find ways that may substitute for the RC construction method. A solution to this problem of RC construction, the authors consider, is the reduced use of plywood panels and more effective use of materials through I) development of substitute materials for casting panels and 2) devclopment of a new method replacing the RC construction method. From this viewpoint, we have bcen conducting research and development of computer integrated construction techniques for reinforced masonry (RM hereafter) buildings by casting joint method using RM units as an automated RC construction system. In this paper, the authors outline the development of a casting joint method of reinforced masonry construction that excels in earthquake resistance and is capable of realizing the five above-mentioned goals. The paper will present RM construction as a sustainable method of construction by showing construction efficiency, construction accuracy and quality control demonstrated in an experiment.

Development of RM Structure

1) Background

Masonry has long been known around the world as a representative traditional architectural method that can flexibly meet diverse design requirements, such as durability, fire resistance, sound insulation and heat insulation. However, because of its limited resistance to earthquakes, a great number of cases have been reported of damage from earthquakes in various parts of the world. Accordingly, there are great hopes for the development of RM construction method that provides resistance against earthquakes.

725 The development of RM structure has been conducted in a 5-year project starting in 1984 as the third phase of the V.S.-Japan Coordinated Earthquake Research Program. The researchers on the Japanese team came from the govemment, universities and industry with the Ministry of Construction Building Research Institute coordinating their activities. The targets of Japanese side for this project was the compilation of the Design and Construction Guidelines for Medium-Rise RM Buildings.

2) Features

In the RM structure, the and girders are composed of members, each of which is a combination of mass-produced high-quality, high-strength ceramic or concrete units (RM units hereafter) reinforced with steel bars and grout, and the and slabs are made of reinforced concrete. Therefore this structure has a strong resemblance to that of box frame type reinforced concrete structure. The RM structure features: I) A seismic performance almost equivalent to that of box frame type reinforced concrete structures 2) High durability comparable to that oftraditional brick or stone structure 3) Construction system capable of coping with all sorts of site conditions with satisfactory construction efficiency 4) Beautiful exterior and maintenance-free finish at the same time as skeleton forming thanks to the imprcved construction accuracy 5) Excellent residential performance, such as adequate heat insulation and resistance to condensation 6) Reduction in construction waste resulting from the reduced use of plywood panels

3) Seismic Safety

The RM units, which are the basic structural material, are designed to work in unison with grout to ensure structural safety. The basic strength of the material and the elastic modules necessary for structural design can therefore be obtained by the combination of both materials. Hence, the material strength (prism strength) can be evaluated using a prism which is a composite of these materials. The exterior of an RM building resembles that of ceramic tile facing or stone facing. The finishing, however, occurs simultaneously with the framework forming, so that there is no fear of surface peeling du ring earthquakes or under normal conditions. .

4) DurabiIity

The RM units, whose module is adjusted three-dimensionally, can completely cover any complex form that is often found in . Furthennore, the great slrength of RM units markedly slo\Vs the neutralization of grout. Also, the manufacturing accuracy of RM units has been drastically improved by standardization of reinforcing steel and mass production. The most serious problem of concrete buildings is drying shrinkage and cracking. In the RM construction, the RM units are used only after their shrinkage has stopped. In addition, the RM units are made of material with no or minimal shrinkage. It is therefore considered that the walls created by this method will not develop an)' cracking even with the contraction of the grout.

726 5) Construction Efficiency and Reliability

The RM construction inco'1'orates the following designs to improve the construction efficiency and reliability: I) The RM units, grout andjoint material are mass-produced to stabilize the quality. 2) The dimensional accuracy of RM units has been improved to realize thin joints and casting joints. 3) Grouting is performed in one operation from floor to floor, so that mass-produced grout can be used. 4) A exclusive chemical admixture has been developed to cancei out the defects of the grout and prevent segregation. 5) Methods of checking grout filling and nonrestrictive inspection methods to be used after the filling havc been dcveloped and standardized. 6) The RM units ofpcrfectly adjusted module and the bonding patterns have been developed, and the arrangement ofreinforcement standardized, for smooth construction works. 7) An RM simulator and RMCAD have been developed to make possible the prior simulation of masonry works and coping with sudden design changes.

6) Improved Body Forming Accuracy and Beautiful Exterior

The RM construction accomplishes the finishing, which resembles stonework or ceramic tile finish, at the same time as the forming of the building frame. Further, it does not use plY'wood panels such as in the building of reinforced concrete structures. As a result, the RM structure easily provides high construction accuracy and is maintenance-free.

7) RM Units

The RM units are classified basically by material, strength, shape and size. By application, they can also be classified into those for mortar joints, those for thin joints and those for casting joints. The RM units are not only made of material that excels dynamically, but they are standardized for low permeability of water, carbon dioxide and saJinity. Another important property of the RM units is the small movement that accompanies drying. That is, the concrete RM units are made of concrete with small water cement ratio that gives zero slump, and the ceramic RM units are made of material that has no drying shrinkage. Hence, the RM units have minimized the drying shrinkage that occurs frequently with reinforced concn~te. As shown in Figure I., the cross section of RM units is such that reinforcing steel can be arranged at equal intervals within the AAl wall, and the design forms hollows for easier filling of grout.

Figure 1. RM unit for castirg joint method

727 8) Bonding Pattern

The RM structure displays its designed performance by dynamically combining the masonry part of the RM urnts and the internal grout. Hence, the bonding pattern, which is an assembly method of RM units, is particularly important. The bonding pattern is determined by the following seven rules: I) Basically open-end unit 2) Breaking joint 3) Horizontal dimensions of the structure, the members of framework and the openings are integral multiples ofthe basic horiwntal module 4) Vertical dimensions of the structure, the members of framework and the openings are integral multiples of the basic vertical module 5) Reinforcement interval is determined by the basic reinforcement arrangement module 6) The number of special form units is minimized . 7) Combination masonrJ in the intcrsection of walls facilitates the filling of grout and arrangement of reinforcement. According to these rules, we have proposed the dimensional types 1-2 and 2-3 for the RM unit as shown in Figure 2, and have comprehensively evaluated their proof strength by structural experiments.

9) Our Activities

At HASEKO Corporation, with its technical research institute playing a central role, the authors and others have engaged in the development and generalization of the RM construction method characterized by the al ready mentioned features with a view to solving problems of the global environment, construction waste and tropical rain forests and to develop small precast concrete members of framework . As part of the efforts, wc participated in the U.S.-Japan research program and attended the Council for Reinforced Masonry Buildings, which started on the heels of the joint research project, in order to gencralize RM buildings with the aforementioned features. To demonstrate the above-mcntioned system by confirming the construction efficiency, construction accuracy, possibility of automated construction, quality control, etc., wc conducted an experiment by constructing a 3-story office building . As a result, we found that I) the RM construction is a sustainable construction, 2) more than 90 percent of plywood panel can be eliminated with the result of drastically reducing construction waste, and 3) the construction efficiency and accuracy of RM structures are satisfactory. We will outline the findings in the following.

1-2 type 2-3 type Figure 2. Bonding pattern

728 Experimental Construction of the RM Building

1) Outline ofthe RM Building

Table I shows the outline specifications of the building, Photo 1 shows how the building looks extemally, and Figure 3. shows a distribution drawing of the units . In order to secure relatively wide spaces in a box frame type office building, the cross-shaped bearing walls are arranged on the plan as shown in Figure 3 and the arrangement is identical for aB the floars . Table 1. Outline specifications of the building Construction period from Sept. 1992 to Mar. 1993 Use Office Building area 177.44 m' Total floor space 489 .66 m' Structure 3-story RM struclure by casting joint method RMunit Dimensions 400x200x200 mm Compressive strength 300 kgflcm' RM masonry prism Design strength Fm = 240 kgflcm'

Photo 1. Thc extcrior of RM building.

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Figure 3. Distribution drawing of RM unit.

729 2) Outline of Construction

Figure 4 shows the schedule of work for a f1oor . The schedule of work for a floor was about two weeks including holidays. The were built by HASEKO's original RMSS method using the steel deck as shown in Photo 2. This method not only shortened the construction period, but reduced by 90 percent the use of plywood panel for walls and floors as compared with the conventional method. Consequently, a substantial reduction ofconstruction waste was achieved. Table 2 shows the mix proportion ofthe concrete used for the construction ofthis building. The grout concrete was made on site by adding the super plasticizer and expansive admixture (600g/mJ) to base concrete (ready-mixed concrete) in order to achieve better workability of grout concrete and preventsettling shrinkage crack of the concrete. The grout concrete was placed in the wall areas, and the concrete with only the super plasticizer added was deposited in the beam and floor members.

- I 2 3 4 5 6 7 8 9 I 0 I I I 2 I 3

Marlring Steel deck

Figure 4. Schedule of work for a noor

Photo 2. RMSS method Table 2. Mix proportion of grout concrete

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730 3) Casting Joint and Mortar Joint

The casting joint method is a technique designed to further enhance the advantage of RM construction. In masonry works using the conventional mortar joint method, construction accuracy is assured by the experience and perception of masons who adjust the thickness of joint mortar. The casting joint method, on the other hand, rehes on the high-accuracy RM units coming with improved forms for the joint area. Accordingly, the construction accuracy is achieved simply by laying the units one atop another. This improves the work efficiency drastically without depending on the professional skill ofthe workers . (See Table 3 and Figure 5.)

4) Construction Experiment

The masonry work efficiency was determined by measuring the masonry area per day and labor (man-days) in all the masonry processes. Figure 6 shows the relationship between masonry area and labor on each floor . The total amount of labor required for masonry was 44 man-days for the Ist floor, 41 man-days for the 2nd floor and 22 man-days for the 3rd floor. The low masonry efficiency for the first three days on the Ist floor is attributable to the laying-out of vertical batter boards, the masonry using mortar on the root tier and bad weather. The slow progress on the 2nd floor was due to changing material in the batter boards and the buried electrical piping (additional shaping of RM units). The masonry performance also dropped on the final day because of the beam construction and finishing works. The outstanding masonry efficiency on the 3rd floor was due to the acquired skill ofmasonry. The masonry efficiency on the middle day was 6-8 m'/man-day fur the Ist and the 2nd floor and about 10 m'/man-day for the 3rd floor as indicated by a thin line in Figure 6. This represents a marked improvement over 3-5 m2/man-day, which is said to be the average efficiency ofthe mortar joint method . The results were thus favorable for a building whose walls were all of relatively small width. Table 3. DifTerences between casting joint and mortar joint Joint material Mason efficienc 'oint Mortar 3-5 m'/man*da Castin 'oint Adhesive 9-15 m'/man*da

Unit of Unit of mortal joint method casting joint method

Figure 5. Differences between casting joint and mortar joint.

731 It has been said that the construction accuracy of the RM building by casting joint method is better than that of ordinary Re construction methods. Therefore we measured the dimensional accuracy ofthe building frame. As shown in Figure 7, measurements were taken ofthe cross walls of X2-Y2 and X3-Y2 on each floor. The horizontal accuracy in the X and Y directions at the wall ends of the cross walls were measured vertically. Transits and measuring tapes were used to measure in units ofO.5 nun. Figure 8 shows the frequency distribution of vertical accuracy at aB the measuring points. As is evident, the vertical construction accuracy of the RM building by casting joint method was 0.4 nun on the average \\~th the standard deviation being 3.3. nun and the dispersion being nearly within ~ 5 nun.

o~~~--~------~ o 20 40 Labor

B 1si - 2nd <> 3rd Figure 6. Efficieney of masonry \\'ork

4' l' , 1 , I I X2 X3 Figure 7. Measuring point of eonstruetion aeeuraey 100 .. . . . • ::>..:.: .:.:. : Average=OAmm ++ tandard deviation=3.3mm " ., i i ­ . ~ .•. ~ . •• _~.L:. ~_ : :_:). 50 ~~~~~~~~~.~. ~I

o +10 [mm] Error Figure 8. Frequeney distribution of vertical aeeuraey

732 The filling of grout concrete was checked by a nonrestrictive inspection using a transmission technique (measurement of ultrasonic speeds). The ultrasonic speeds were measured near the bottom ofthe walls where the grout might not fill easily. As shown in Figure 9, the centers of the RM units on the Ist, 3rd and 5th tier from the floar were located 70 and 270 mm respectively inward from the wall side. The measurement was performed on all the walls for each floar. The measuring points totaled 848, that is, 282 points on eachfloar. Figure 10 shows the frequency distribution of ultrasonie speeds at all the measuring points. The average value was 3.9 kmls, and the standard deviation 0.19 kmls. When the measurement results were assumed to be in a normal distribution in consideration of the dispersion in strength of the RM units and grout concrete, and when the measurement results beyond the dispersion range of filling performance (defective filling points) were assumed to be of a probability below 5 percent, the ultrasonie speed was 3.6 kmls or below as indicated in Figure 10. Also, the ultrasonic speed through the walls was estimated from those of the RM units and grout concrete alone. The result was 3.9 kmls, which equaled the above-mentioned average value. The ultrasonic speeds measured in the honeycomb, or rock pocket, that actually impairs the yield strength of the concrete are said to be 0.5 to I kmls slower than those in the sound part of the concrete. Hence, if we consider the speeds of 3.4 kmls or above to represent satisfactory filling and the probability to be below 5 percent as mentioned above, the graut filling in our building is concluded to have been satisfactory.

• Measuring Point

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Figure 9. Measuring point of filling for grout concrete of wall

100

O~~~~~~~~~~~~~ iniovJs ' i7 . da ' ~ , ~ ,iI ' tr Ultrasonic Speed (km!sec.) Figure 10. Frequency distribution of ullrasonic speeds

733 ConcIusions

The RM structure by casting joint method has been developed in an effort to modemize the traditional RC construction method. It uses ready-made RM Uluts as precast concrete parts. Through a building experiment using the RM construction method, the authors have confinned: I)Use of plywood panels for walls and floors is reduced by about 90 percent as compared with RC construction, and consequently construction waste is reduced drasticaJly. 2)High-accuracy building frame can be constructed by use of high-quality RM units and proper design and construction works (especially grout works). 3)The construction efficiency can be raised by improving the joint method. From these observations, we conc1ude that the RM structure by casting joint method can reduce the use of panel material and thus rcduce construction waste, conserve labor and enhance the durability of the structure. The RM structure by casting joint method is therefore considered to be a sustainable mode of architecture that can contribute to the protection of the global environment.

References

Akio Baba, et al., 1988: Guidelines to Construction Methods of Reinforced Masonry Buildings, 8/h ln/erna/ional BrieklBloek Masonry Con(erenee, Dublin, Ireland. Shin Okamoto and 1.Noland, 1986: U.S.-Japan Coordinated Program on Masonry Research, Proeeedings of/he FOllr/h Canadian Masonry Symposium, Fredericton, Canada. Shin Okamoto, et al., 1988: Development of Medium-Rise Reinforced Masonry System, Nin/h World Conforenee on Ear/hquake Engineering, Tokyo-Kyoto, Japan. Takaaki Nishi, et al., 1988: Seismic Behavior ofThree Story Full Scale Clay Block Planar Frame Under Cyclic Lateral Loading, Nin/h World Conferenee on Ear/hquake Engineering, Tokyo-Kyoto, Japan. Yutaka Yamazaki, and Masaomi Teshigawara, 1986: Earthquake Response of Five Story Reinforced Concrete Masonry Test Building, Third ASCE Engineering Meehanies Speeialty Con(erenee on Dynamies ofS/nie/ures, Los Angeles, US o

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