Ultrahigh performance concrete (UHPC) is increasingly making its way into the construction field. Characterization of UHPC has therefore received much-needed attention in the research arena. One effective application of UHPC is in combination with high-strength steel (HSS) reinforcing rebar in shallow beams or slabs. However, bond and development characteristics of HSS rebar in UHPC have not yet been investigated. This paper presents the experimental results of the pullout and flexure tests conducted with HSS rebar in UHPC. This work was a part of a larger project to develop a new light-weight UHPC-HSS bridge deck system for a moveable bridge. Because the bridge deck was designed with #10 and #22 rebar as the main reinforcement, only these two rebar sizes were used in the experiments. First, pullout specimens were tested with three different embedment lengths of 8, 10, and 12 times the rebar diameter. Then, from the results of pullout specimens, beam specimens were tested with embedment lengths of...

MATEC Web of Conferences, open access proceedings in Materials science, Engineering and Chemistry

Most of the movable bridges in the United States have open grid steel decks, primarily because they are factory assembled, lightweight, and easy to install. Open grid steel decks, however, are not as skid resistant as solid decks. Costly maintenance, high noise levels, poor riding comfort, and susceptibility to vibrations are among the other disadvantages of these decks. The objective of the research presented in this paper is to evaluate an alternative lightweight extruded aluminum deck system that has a solid surface and meets the loading requirements as well as weight and thickness limits for movable bridge decks. These aluminum deck panels with their tongue and groove connections have previously been used in Europe, mainly in Sweden. A detailed experimental evaluation of the aluminum deck system has been carried out, including static and fatigue load testing on the deck panels, as well as ancillary tests on the connections with the girders. On the basis of the in-depth experimental evaluation and the subsequent finite-element (FE) modeling and predictions, the extruded aluminum deck is shown to be a feasible alternative to the open grid steel deck and ready for implementation on movable bridges as well as bridges that require a lightweight deck.

Among the states, Florida has the largest stock of moveable bridges, most of which with open grid steel decks. These decks are often associated with poor rideability, high noise levels, susceptibility to fatigue damage, and high maintenance costs. To address these issues, two alternative lightweight shallow deck systems are proposed. One with a thin flange, narrow ribs across the deck span, and short transverse ribs, made with ultra high performance concrete (UHPC) and high-strength MMFX steel (HSS). Another one is a hollow core deck made with UHPC and fiber reinforced polymer (FRP) tubes. A large number of experiments, both static and fatigue, were conducted on simple and continuous two-span models of the UHPC-HSS deck system with single and multiple ribs in the cross section. Limited tests were carried out on the UHPC-FRP deck system. The UHPC-HSS deck system was shown to satisfy the strength serviceability requirements, whereas the UHPC-FRP deck system required additional stiffness. In addition, a series of pullout and beam tests were conducted to determine the bond and development for high-strength MMFX steel in UHPC. A detailed comparison between experimental results and the code recommendations showed that ACI 408R-03 compares more favorably than the ACI 318-08 for the development lengths of MMFX in UHPC.

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.

Selection of wind force resisting system is an important decision in the design of tall buildings, especially for those located in hurricane prone regions. Rigid frames, shear walls, braced frames, framed tube, bundled tube and hybrid system are the common structural forms used to resist lateral forces produced due to wind. Cables have a great potential to be used as a structural element. Cable stayed and hanging bridges and guyed towers are the common structural applications of cables. Not much work has been done to use cables for bracing tall buildings against the lateral movement produced by natural forces like wind and earthquakes. This research work proposes an external cable bracing system for tall buildings which may be used in the future for high-rise structures. A sixty story tall building has been analyzed for the wind speed recommended for Miami, FL., USA., using a shear wall bracing system and the proposed cable bracing system. Comparison of structural performance of the two systems is presented to establish the suitability of the cable bracing system as a part of the wind force resisting system.