A number of older bridges were constructed with floor systems consisting of a noncomposite concrete slab over steel girders. A potentially economical means of strengthening these floor systems is to connect the existing concrete slab and steel girders with postinstalled shear connectors to permit the development of composite action. This paper presents the results of an experimental investigation of this concept. Five large-scale noncomposite beams were constructed, and four of these were retrofitted with postinstalled shear connectors and tested under static load. The retrofitted composite beams were designed as partially composite with a 30% shear connection ratio. A noncomposite beam was also tested as a baseline specimen. Test results showed that the strength and stiffness of existing noncomposite bridge girders can be increased significantly. Further, excellent ductility of the strengthened partially composite girders was achieved by placing the postinstalled shear connectors near zero-moment regions...

This paper is a continuation of research on strengthening the load-carrying capacity of existing noncomposite bridge girders by postinstalling shear connectors. In this study, finite element models were developed to evaluate the behavior of composite beams retrofitted with postinstalled shear connectors over a wide range of variables with an objective of providing preliminary design recommendations. Variables considered in the parametric studies included beam depth, span length, and shear-connection ratio. The parametric studies showed that current simplified design approaches commonly used for partially composite beams in buildings provide good predictions of the strength and stiffness of partially composite bridge girders strengthened using postinstalled shear connectors. Use of a shear-connection ratio of less than 30% is not recommended to avoid nonductile behavior of the strengthened girder.

Fiber-reinforced polymers offer several advantages over conventional construction materials but are also faced with several challenges. These include increased first cost, relatively low stiffness, and a lack of field experience. To address these challenges and to advance the state of the art, a hybrid fiber reinforced polymer/reinforced concrete bridge was designed and constructed in Texas. The bridge design and field evaluation are unique in several respects. Design considerations, the bid process, and the results of intermittent live load evaluations that have been conducted over a period of approximately 2 years are presented. Recommendations for the design of future similar bridges are provided.

As demonstrated by terrorist attacks against the Murrah Building in Oklahoma City and a U.S. Embassy building in Nairobi, Kenya, some structures may be vulnerable to progressive collapse. Previous computational studies have shown that floor systems play a key role in redistributing loads during progressive collapse events, but only a few experimental studies support these results. The aim of the current research is to experimentally characterize the behavior of steel-concrete composite floor slabs under column loss scenarios. Two large-scale tests on isolated sections of a steel-framed building were conducted until complete collapse. The two specimens were designed and detailed according to commonly used practices found in buildings in the United States. No special provisions to mitigate progressive collapse were included in the design. The first specimen was an interior $2\text{-}\times 2$ -bay section, and the second specimen was an exterior $2\text{-}\times 1$ -bay section. Both specimens were tested under a center column loss scenario. The column was statically removed while the floor slab was uniformly loaded under service load conditions. Because both specimens survived the column removal stage, the slab was subsequently loaded with a uniformly distributed load until total collapse was achieved. Observations from the test program indicate the potential for significant capacity of composite floor systems following column loss.

Over the past decade, much research has focused on the behaviour of structures following the failure of a key structural component. Particular attention has been given to sudden column loss, though questions remain as to whether this event-independent scenario is relevant to actual extreme events such as explosion. Few studies have been conducted to assess the performance of floor slabs above a failed column, and the computational tools used have not been validated against experimental results. The research program presented in this paper investigates the adequacy of sudden column loss as an idealisation of local damage caused by realistic explosion events, and extends prior work by combining the development of accurate computational models with large-scale testing of a typical floor system in a prototypical steel-framed structure. The floor system consists of corrugated decking topped by a lightly reinforced concrete slab that is connected to the floor beams through shear studs. The design is consistent with typical building practices in the US. The first test has been completed, and subsequent tests are currently being planned. This paper addresses the importance of robustness design for localized damage and includes a detailed description regarding how the research program advances the current state of knowledge for assessing robustness of compositely constructed steel-framed buildings.