Il-Sang Ahn

Cyclic Performance of Precast Concrete Segmental Bridge Columns: Simplified Analytical and Finite Element Studies

The cyclic performance of an unbonded precast concrete segmental bridge column system is examined in this paper. This system uses unbonded posttensioning to enhance the self-centering capability and mild steel reinforcement extended across the segment joints to enhance the energy dissipation capability. A simplified analytical method for the system under lateral load is established, and the simplified analytical results are compared with those obtained from the three-dimensional (3-D) finite element method (FEM). On the basis of the simplified analytical method, suggestions are made about both the height of the column to which the mild steel should be continued from the foundation and the limitation of the steel ratio to minimize residual displacement. With the steel ratio varied, the correlation between the energy dissipation capability and the self-centering capability of this system is investigated by means of the 3-D FEM. From simulation results, it was found that both the energy dissipation and the r...

Live Load Distribution of Hybrid Fiber-Reinforced Polymer Composite Superstructure on the Basis of Field Test

Transverse live load distribution in a concrete–fiber-reinforced polymer (FRP) composite hybrid bridge was investigated both experimentally and analytically. The subject bridge was a concrete–FRP composite hybrid bridge, constructed with four 31-ft (9.4-m) long, prefabricated superstructure panels, which were joined along longitudinal field joints made of steel-reinforced grout. The live load distribution factors (DFs) of this bridge were evaluated with strain values measured in field tests and produced from finite element analysis. Design documents and load rating reports showed that a simplified method on the basis of beam-bending could be used in the design process, which required live load DFs. From strain values measured during load tests, the DFs were inferred to be 0.35 and 0.49 for interior and exterior panels, respectively. The comparison of load tests done 6 years apart indicated no significant change in the structural performance of the bridge. Although the design of this structure was unique, the evaluation showed that other hybrid structural members also could achieve good load distribution. The investigation indicated that composite structures could be durable with little maintenance required.

Accelerated bridge pier construction in the U.S.: Seismic implications

In several successful accelerated bridge construction projects in Florida and Texas, prefabricated bridge pier components have been utilized, which result in significant reduction of the construction schedule. This paper summarizes major accelerated bridge construction projects through adopting pre-fabricated bridge pier components, which shows its popularity in recent years. In particular, details in geometry, reinforcement, and connections from several projects are compared, focusing on their applicability in seismic regions. Systems in seismic regions investigated recently by several research groups are also summarized and compared. As concluding remarks, issues and recommendations regarding connections and reinforcement detailing are summarized.

Part 1: General Structures: Experimental Study on Ultimate Behavior at Negative Moment Regions of Composite Bridges

This paper presents experimental results of the ultimate behavior of the negative moment region of a quarter-scale full model and a half-scale subassemblage model of a two-span continuous composite bridge of concrete deck slab on steel girder. The two specimens are based on a prototype bridge that has a large girder spacing [3,800 mm (13 ft)]. At the ultimate state, it is shown that a larger portion of the deck is activated to resist tensile stress compared with the effective width specified in the AASHTO load and resistance factor design bridge specifications. Also, a plastic hinge that forms at the internal support has enough rotational capacity (ductility) to enable development of a second plastic hinge within the span. Experimental results show a reasonably good match with accompanying finite element method analyses.