Alternative Deck System for Moveable Bridges

2010 Structures Congress © 2010 ASCE

Alternative Deck System for Moveable Bridges M.A. Saleem1, A. Mirmiran2, J. Xia3 and K. Mackie4 1

PhD Candidate, Department of Civil and Environmental Engineering, Florida International University, Miami, FL 33174, E-mail: [email protected] 2 Corresponding author, Professor and Dean, College of Engineering and Computing, Florida International University, Miami, FL 33174, E-mail: [email protected] 3 PhD Candidate, Department of Civil, Environmental, and Construction Engineering, University of Central Florida, Orlando, FL 32816, E-mail: [email protected] 4 Assistant Professor, Department of Civil, Environmental, and Construction Engineering, University of Central Florida, Orlando, FL 32816, E-mail: [email protected]

ABSTRACT Florida has the largest stock of moveable bridges in the United States. More than half of these bridges are located along the inter-coastal waterways in Miami and Ft Lauderdale. Most of the moveable bridges use open grid steel decks. These open grid decks have several disadvantages, including poor skid resistance, high maintenance costs, high noise levels, and susceptibility to vibrations. It is therefore desirable to find alternative deck systems with better performance. Three potential deck systems: a lightweight aluminum bridge deck system made by SAPA Group (Sweden), a waffle shape reinforced ultra-high performance concrete (UHPC) deck system, and a fiber-reinforced polymer tube-UHPC composite deck system were selected for further development and experimental testing. The first system is currently commercially available while the latter two systems are newly proposed composite systems. The component-level tests on all three systems and system-level tests on the first two systems are presented in this paper. Results confirm that the first system is a feasible alternative (already available) to the open grid steel decks from a strength and serviceability point of view. The proposed UHPC composite systems are promising alternatives based on preliminary results. INTRODUCTION According to the national bridge inventory (2008), Florida has a total of 148 moveable bridges, of which 90% are bascule, 7% swing and 3% lift. In addition, 72 moveable bridges in Florida are either structurally deficient or functionally obsolete. Therefore, there is an urgent need to develop new techniques, materials, and systems for rehabilitation and replacement of these deteriorated structures (Vyas et al. 2009). Most of the moveable bridges currently use open grid steel decks. These decks have several problems including poor skid resistance and rideability, costly maintenance, high noise levels and susceptibility to vibrations (Mirmiran et al. 2009). In the context of addressing the aforementioned issues and to rehabilitate the structurally deficient bridges, development of innovative lightweight bridge deck systems is one of the active areas of research. Over the last decade, several researchers have carried out significant work to develop bridge decks using fiber reinforced polymers (FRPs),

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aluminum alloys and ultra high performance concrete (UHPC) (Robinson 2008; Zhenhua 2004; Alagusundaramoorthy 2006; Dobmeier 1999; Graybeal 2006). The focus of the research presented in this paper is on the experimental (both static and dynamic) and analytical evaluation of three lightweight bridge deck systems. The requirements of each system are x, y, and z (insert info about selfweight here). System One is a low-profile aluminum deck system that has been used in Europe, mainly Sweden, but has never been implemented in the United States. System Two is a generic ultra-high performance concrete and high strength steel composite deck system that was proposed, designed, and tested specifically for this project. System Three is an FRP tube and ultra-high performance concrete composite system that is still an exploratory deck concept that is currently undergoing further design refinements and testing. REVIEW OF CURRENTLY AVAILABLE DECK SYSTEMS Open Grid Steel Decks: Most of the movable bridges use open grid steel decks because these are light-weight and quite easy to install. These decks can weigh as little as 0.67 kN/m2, with an average weight of 1.2 kN/m2 (Tyuryayeva 2006). First time used in 1920, open grid steel decks became more popular in 1950’s and were redesigned and reintroduced in 1980’s (Huang 2002). Three types of open grid steel decks are in use: Unfilled system, concrete filled system, and unfilled composite system (ExodermicTM). Unfilled system is used with or without roughened surface. Filled system is either filled with concrete to the full depth of the grid or partial depth (ASTM D 5484-99). Unfilled composite system consists of reinforced concrete slab composite with an unfilled grid (ExodermicTM brochure). Sandwiched Plate System: The sandwiched plate system (SPS) is developed by Intelligent Engineering Limited of Buckinghamshire, U.K. It consists of two metal plates and an elastomeric core, which is sandwiched between the plates (Kennedy et al. 2002). SPS has improved fatigue and corrosion resistance because most of the fatigue and corrosion prone details are removed from it (www.ie-sps.com). SPS is compatible with all type wearing surfaces. With the first application on Shenley Bridge in Quebec, Canada, SPS has been implemented in U.S., U.K. and Germany (Tyuryayeva 2006). Florida department of transportation considered SPS for the Mathews Bridge in Jacksonville. Fiber Reinforced Polymer (FRP) Bridge Decks: An FRP bridge deck weighs approximately 80% less than a concrete deck (Mu et al. 2006). Therefore, FRP decks can be extremely advantageous for movable bridges, in which self-weight is most of the times governing design criterion. During the last fifteen years, several old bridge decks have been replaced by FRP decks. At present, a total of nine state DOTs are using FRP decks including Illinois, Maryland, North Carolina, Delaware, Kansas, New York, Ohio, Oregon. An existing timber bridge deck of a moveable bridge in Oregon has been replaced by and FRP deck (Hong and Hastak 2006). Recently developed FRP decks include DuraSpan® Bridge Deck, ZellComp® Decking System,

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Strongwell® FRP Bride Deck, Honeycomb Sandwich Panels and KSCI® FRP Composite Bridge Deck. ALTERNATIVE DECK SYSTEMS INVESTIGATED Use of aluminum in bridge decks started as early as 1933, when the timber and steel floor system of Smithfield Street Bridge in Pittsburg, PA, was replaced by an aluminum deck (Growdon et al. 1934; Arrien et al. 2001). The first all-aluminum railway bridge in the U.S. was constructed in 1946 near Massena, NY. The first allaluminum high bridge was constructed in 1950 in Arvida, Canada, over the Sayuenay River (Das and Kaufman 2007). Aluminum bridge decks are lightweight, corrosion resistant, have short installation time and low maintenance cost (Mirmiran et al. 2009). Two recently developed aluminum decks include one by Reynolds Metals Company of Richmond, VA, and the other by SAPA Group of Sweden. The Virginia Department of Transportation has used Reynolds aluminum decks on a simple-span bridge located on U.S. route 58 (Dobmeier 1999). The Florida Department of Transportation has interest in evaluation of the SAPA aluminum deck and may apply it to a bridge in future. The aluminum deck system that was investigated in this research study (identified as System 1) is composed of five voided individual panels made of 6063F25-T6 alloy. These panels can be mechanically fastened with the girders and are connected to each other by a tongue and groove connection. The self-weight of the deck panels is around 0.67 kN/m2, which satisfies the self-weight limit (1.2 kN/m2). This system is developed in Sweden and deployed in Sweden and other European countries. However, it has not seen any application in the United States. An acrylic-based material (Acrydur®) and hot asphalt mix have been the most commonly used wearing surfaces with this system. The approximate cost of the system is $485 per m2, excluding the connectors, wearing surface, and shipping. Figure 1 shows the size and shape of the individual deck panel along with the geometrical properties.

Figure 1. Cross Section and Properties of Deck Panel (SAPA Building Systems)

System Two takes advantage of two recently developed construction materials: ultra-high performance concrete (Ductal) with a compressive strength up to 220 MPa, and high strength MMFX2 steel rebar with a yielding stress of 690 MPa. The schematic of the proposed waffle deck system is shown in Figure 3. A transverse strip of the deck transfers the wheel load to steel girders. The reinforced longitudinal webs help distribute the wheel load to the adjacent transverse deck units. The waffle

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shape helps make full use of the materials thus achieving high strength with light weight.

Figure 2. Schematics of System 2

System Three is a Ductal®-fiber reinforced polymer (FRP) tube hollow core deck system. The FRP tubes serve as tensile reinforcement both in the positive and negative moment regions, and help reduce the selfweight of the deck. Several different design realizations were considered, including full embedment of the FRP tube in UHPC and a more efficient section that uses UHPC only the compressive region of each section along the length. EXPERIMENTAL WORK: COMPONENT LEVEL The major objectives of the experimental work on the component level are to investigate the ultimate load capacity and mode of failure of the typical deck strips that transfer the wheel load as a beam to the supporting girders. Flexural tests were conducted with the AASHTO prescribed footprint of an HS 20 truck dual tire wheel (508 mm x 254 mm). The panels were subjected to a single load at the mid-span with the displacement control procedure. For System One, a single deck profile was tested as a simply supported beam over the steel stingers that were 1219 mm apart. For System Two, the typical 305 mm wide, 127 mm high T-beam reinforced with one No 7 MMFX2 rebar and with 180 degree hook anchorage at both supports was tested. For System Three, two 305 mm wide composite UHPC-tube beams were tested under the same loading configuration as what?. One of them has uniform UHPC layers that fully surrounded the FRP tube and the other has a tapered UHPC layer that only covered the top portion of the tube. The load versus displacement results of the four selected component-level specimens from the three systems are shown in Figure 3. The test setup and the loading configuration for each of specimens is shown in Figure 4.

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The deck panel of System One demonstrated a stiffness of 16.8 kN/m up to the load of 200 kN, and then began softening gradually. The panel was loaded up to 280 kN, where signs of yielding were clearly visible from the load-deflection response. The panel was unloaded to zero load level and then reloaded to the failure load of 312 kN with a maximum deflection of 46.7 mm. The deck panel had a residual tensile strain of around 0.009 at mid-span when completely unloaded. The test was stopped because of safety concerns over excessive deflection. The specimen of System Two failed in shear at 209 kN; however was not sudden in the traditional sense of a brittle shear failure. The first shear crack appeared


at 115.6 kN. There were very small flexural cracks, which damaged the bottom concrete strain gauge at around 133.4 kN. For the uniform System Three specimen, the first flexural crack appeared at 45.8 kN at the mid-span. The specimen failed at 165kN. Two more flexural cracks appeared at a later stage, and kept on growing until failure. The three FRP tubes failed suddenly in compression one after the other. There was no slippage in the tubes up to 89 kN, after which the tubes started slipping inwards because of the opening of flexural cracks at the mid-span. For the tapered section, the deck failed suddenly in compression at 120 kN. The failure initiated on the compression side of concrete, and then cracks penetrated into FRP tubes leading to a sudden compressive bursting failure. It is evident from the load versus displacement curve that the deck component from System One has the highest stiffness and the highest ultimate load capacity. Both specimens of System One and Two exceeded the required load capacity of 166 kN based on the AASHTO LRFD code, while the capacity of specimens of System Three were lower but close to that range. Both System One and Two show promising results from component-level tests and thus system-level performance was further investigated. For System Three, the effect of prestressing the tube or increasing the bond between the tube and UHPC layer are worth further investigation because this system is the most corrosion resist option of the three proposed systems. EXPERIMENTAL WORK: SYSTEM LEVEL SYSTEM ONE Fatigue is a major design consideration for metal structures under repeated load cycles. Most failures of metal structures in the field are by fatigue. Fatigue testing on SAPA aluminum bridge deck panels was performed at the FDOT Structures Lab in Tallahassee. Deck panels were subjected to two million cycles of a sinusoidal load (2.2-80 kN) with a frequency of 4 Hz. The load level followed AASHTO requirements. The test was run continuously for almost six days. Load, displacement, and strain data were recorded after every 1,000 cycles up to 10,000 cycles, and then after every 10,000 cycles up to 2 million cycles. At each interval, eight sinusoidal cycles were continuously recorded for all channels. During and after the test, the deck panels were monitored for cracks in the panels or connections. After the fatigue test, two static tests were performed on the panels to determine their residual strengths. Figure 5 shows the instrumentation plan, loading configurations, and test setup for the fatigue test. Figure 6 shows the fatigue load-deflection responses for both Spans 1 and 2. The bolt of the clamp holding the center panel on the interior support failed at about 200,000 cycles, and was replaced with a new one. Installation of the new bolt increased the stiffness of the system, as evident in Figure 6. There was only one clamp, instead of two, for each panel on every support because the top flanges of the supporting stingers were only 114 mm wide and could only accommodate one clamp. Had there been two clamps on each support, as per the manufacturer’s recommendation, this failure would not have occurred. All other bolts performed well throughout the fatigue test, but bolted connections have a tendency to loosen over time and therefore need routine inspection. Figure 6 also shows the load-strain responses of deck panels. Strains at all locations remained within the elastic range

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throughout the fatigue test. The effect of bolt failure is again quite clear in the response curves.

Figure 5. Fatigue test configuration 60

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Figure 7 shows the setup for the two loading configurations in the residual strength tests. Figure 8Figure 8 shows the load-deflection and load-strain responses. The diagrams for both loading configurations show that deck panels remained within the linear elastic range. In both cases, the deck panels were loaded up to a level of 444.8 kN, which is nearly three times the target load of 166 kN. The panels and the connections remained intact and did not show any sign of failure. However, some local buckling was observed in the inclined webs. Deflections and strains in the panels adjacent to the loading panels prove that the system is able to develop adequate panel action. This is by the virtue of the tongue and groove connection, which helps to carry the loads in the lateral direction.

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EXPERIMENTAL WORK: SYSTEM LEVEL SYSTEM TWO The final system-level experimental investigation of System Two was performed on a three-T two-span (3T2S) deck specimen as shown in Figure 10. The instrumentation plan was shown in Figure 11. At the load of 218 kN, a flexural crack appeared in the top flange at the interior support section

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Figure 12 a), followed by the shear cracks on the two interior ribs near the interior

support ( Figure 12 b). These cracks kept on growing, which led to the punching of the neoprene pad into the flange

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Figure 12 c). As the punching shear began, the top flexural crack at the support section closed. Punching was more prominent in the north span than the south span

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Figure 12 d). Load-deflection curves in Figure 13 show that the majority of the load was taken by the two interior ribs. Figure 14 shown that the top concrete strain at mid-span (S22, S23) did not reach its ultimate value of 0.0035 at ultimate load. However, the bottom compressive strain at the interior support section (S37, S38) was very high (0.016), indicating the crushing of concrete. The transverse steel strain (S15, S16) was high in this specimen and reached 0.027. The total failure load was 654 kN, i.e., 327 kN for each span. This is almost twice the target load of 166 kN.

Figure 10. Test Setup for Specimen 3T2S

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CONCLUSIONS Based on the component-level and system-level tests, several conclusions were made regarding each deck system. System One is a feasible alternative to the open grid steel decks from both the strength and serviceably points of view. Two million cycles of AASHTO-specified fatigue loading on deck panels did not show any sign of global or local failure in the deck panels and the residual strength exceed the AASHTO load requirement. System Two has great potential to serve as an alternative to the open grid steel decks. The ultimate load capacity and behavior of the tested specimens make this system an appropriate choice to replace the conventional system. Use of standard 180° hooks at both ends of flexural reinforcement helped effectively avoid bond failure. For the multi-T simple-span and two-span specimens, most of the load was taken by the ribs present either under or near the loading pad, which ultimately led to punching through the slab. System Three has shown good promise to replace the conventional open steel grid decks if prestressing the tube or improving bond between UHPC and FRP tube were proved to enhance the load capacity. ACKNOWLEDGEMENTS This study was sponsored by Florida Department of Transportation (FDOT) under the contract No. BD015 RPWO #22. Authors are pleased to acknowledge the support of Lafarge North America who provided the UHPC (Ductal®) materials.


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