Paper #103 FDOT Experience with PBES for Small
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FDOT Experience with PBES for Small-Medium Span Bridges Steven Nolan, P.E, Florida Dept. of Transportation (1), (850) 414-4272, [email protected] Sam Fallaha, P.E, Florida Dept. of Transportation (1), (850) 414-4296, [email protected] Vickie Young, P.E, Florida Dept. of Transportation (1), (850) 414-4301, [email protected] (1) State Structures Design Office, 605 Suwannee St, Tallahassee FL. 32399 ABSTRACT In the last quarter century, some elaborate methods of accelerated bridge construction (ABC) have been explored and executed in Florida, predominately though necessity in the segmental construction. ABC techniques have also been applied to more traditional flat-slab and slab-on-girder bridges including: Prefabricated Bridge Elements and Systems (PBES), full size bridge moves, top down construction, and other efforts to minimize road user delays and environmental impacts. This paper focuses on four modest structural systems which were successfully implemented on FDOT construction projects since the initiation of FHWA’s Every Day Counts program. This discussion focuses on ABC structural systems for: Precast Intermediate Bent Caps, Precast Full-Depth Bridge Deck Panels, Prestressed Concrete Florida-Slab Beams, and Geosynthetic Reinforced Soil Integrated Bridge Systems. INTRODUCTION Florida has been heavily involved in accelerated bridge construction activities (ABC) since the middle of the last century, primarily driven for economic advantage, with efforts predominantly led by the precast concrete industry. In the last quarter century, some elaborate methods of accelerated bridge construction have been explored and executed in Florida, predominately though necessity in the post-tensioned (PT) segmental construction to provide economy through speed of fabrication and erection, to offset significant mobilization and setup cost, specialized PT subcontractors and equipment. ABC techniques have also been applied to more traditional flat-slab and slab-on-girder bridges including: Prefabricated Bridge Elements and Systems (PBES), full size bridge moves, top down construction, and other efforts to minimize road user delays and environmental impacts. There have been some lessons learned on the quest for more rapid and economical construction, however the predominance of successful projects should encourage further ABC innovation and application. This paper focuses on four practical structural systems which where demonstrated on several FDOT construction projects since the initiation of FHWA’s Every Day Counts program. These ABC structural systems include: 1. Precast Pile Bent Caps; 2. Precast Full-Depth Bridge Deck Panels; 3. Prestressed Concrete Florida-Slab Beams; 4. Geosynthetic Reinforced Soil Integrated Bridge Systems. These systems represent a narrow but potentially prolific scope of the ABC initiative and reflect some of the structural priorities of the FDOT, and lessons learned during the period of 2010 to 2018. BEFORE “EDC” Long before the FHWA’s “Every Day Counts” programs formalized the term Prefabricated Bridge Elements and Systems (PBES) under the ABC initiative in 2011 & 2013, this concept had been used since the 1950’s in Florida at various scales and complexity, especially with precast/prestressed components. One of the first and largest prestressed beam bridge project began in 1951, shortly after the successful Walnut Lane demonstration in Pennsylvania (1). The first Sunshine Skyway crossing involved production, delivery and erection of 2,178 prestressed beams of 48-feet for the 3 miles of the approach trestle spans (2) at the mouth of Tampa Bay. A similar parallel bridge was completed in 1971 to bring it to Interstate standards as a dual carriageway. This feat was later rapidly repeated with the upgraded replacement crossing in 1986 after the tragic MV Summit Venture bridge collision (3). 1,300 longer AASHTO Type IV prestressed beams were used for the trestle approaches (and the longest segmental box cable-stay bridge in the US at the time (4). Prior to the new Skyway, replacement of the Seven Mile Bridge (35,867 ft. long) in the Florida Keys saw the construction of the longest precast concrete bridge in the world completed at the time (1982), with a maximum of five spans erected in one week (5). Sixteen years later the 18,425-ft. Garcon Point Bridge achieved a world record “seven [140 ft.] spans erected in seven consecutive days” (6) in May 1998, with the 19,265-ft. Mid-Bay Bridge completed five years earlier in just 25 months (7), all using span-by-span segmental construction as a proof points for ABC. There were some connection integrity issues that arose from the early effort in the “need for speed” in construction. Match-cast dry-joint segmental box connections did not provide the desired water tightness needed for low-maintenance highly durable structures (Long Key Bridge, 1978) (8). Requirements for pre- package post-tensioning grout, to improve the flowability and subsequent quality of duct filling, did not provide the desired elimination of voids or complete protection of the steel-strands as hoped (Sunshine Skyway and Wonderwood Bridges) (9) (10). Accelerated schedules for design, review, and construction activities on design-build projects resulted in undesirable effects including: plunging of a complete pier foundation during segmental span erection (Selmon Expressway, 2004), warping of split-box segments (Ringling Causeway, 2002), segment box joint opening under traffic (Hathaway, 2012), and the collapse of a partially completed bridge over traffic discussed by Zhou et al. (2019) (11) and Cao et al. 2019 (12). PRECAST PILE BENT CAPS Precast pile bent caps were used on several Florida bridge projects since the 1990’s (Edison Bridge 1993), sometimes at the initiative of the contractor (Buckman Bridge, 1997), inspiring initiatives for standardization in the late 1990’s by LoBruono, et al. (1996) (13) that were never fully realized. Design-Build project such as St. George Island bridge replacement (2004); and I-10 over Escambia Bay (2007), both utilized precast bent caps but with different precast piling systems. After the rollout of the Every Day Counts initiative and completion of the NCHRP Report 681 (14), there was renewed interest in standardizing due to improved design provisions for the connections of PBES. The FDOT 2013-2014 demonstration project on US90 over Little River (15) provided positive performance of the grouted duct connection details on multi-column bents and further developments for standardization of these elements. Subsequent research project BDV30 977- 16 investigated grouted pile pocket connections Kampmann et al. (2017) (16). The results provided recommendations and additional confidence in the constructability of this type of connection for typical driven-concrete pile construction tolerances and hot weather grouting. In 2015, FDOT developed a Mathcad worksheet design tool (17) for precast pile-bent cap analysis. In 2018 the program was updated to include a glass fiber-reinforced polymer (FRP) reinforcing option and published to the FDOT website. Efforts to integrate the output with a future FDOT Standard Plan parametric configuration as discussed in Nolan et al. (2015) (18) are still under consideration. Also, the discussed Standard Plan development in (18) has been delayed in favor of contractor initiated and design-build options, such as the recently completed 2.3- mile SR-90/Tamiami Trail bridge in the Everglades National Park shown in Figure 1. Figure 1: SR-90/Tamiami Trail bridge with 90 precast intermediate pile-bent caps completed in May 2019. As the most recent example, the SR-90/Tamiami Trail bridge included more than 90 precast pile-bent caps to accelerate the construction schedule for critical path activities of two bridges. The first bridge (7675-ft.) with 56 spans and the second bridge (4650-ft.) with 34 spans. Discussions with the design-build team list several reasons for using precast bent caps including cost and compressing the time for critical path schedule items. Ongoing FDOT sponsored research related to precast pile connections includes testing and further evaluation of socketed connections in bent caps and footings under research project BDV29 977-51 by Garber (2019) (19). Other FDOT sponsored research is improving the economy of corrosion-resistant precast/prestressed piles using GFRP spiral reinforcing under BDV30 977-27 by Sungmoon et al. (2017) (20), and GFRP pile splicing under BDV29 977-52 by Melarbi and Farhangdoust (2019) (21). PRECAST FULL-DEPTH DECK PANELS These elements typically are intended for slab-on-girder bridges with either: full-width transverse deck panels with transverse CIP joints; or between-girder spans with longitudinal joints and transverse joints. FDOT has used both systems in recent years, with another novel system implemented at the contractor’s request using a full-length bridge span and longitudinal ultra-high performance concrete (UHPC) joint as shown in Figure 2 (US-441 over Taylor Creek) (22). The same principal has also been applied for two rapid replacements of deteriorated approach slabs on Interstate I-10: Between-Girder Longitudinal Deck Panels Typically, the between-girder span deck slabs have been proposed for rapid replacement of deteriorated decks supported on precast partial-depth stay-in-place forms from 1980-90’s era bridge construction or widening projects, such as I-95 Northbound over CR 5A (Fast-Facts, 2018) (23). This typically allows overnight replacement of damaged deck