| Thousands of buildings throughout the United States were designed and constructed prior to the implementation of formal seismic design standards. These buildings have an increased risk of collapse if an earthquake event were to occur. Many seismic retrofit techniques are currently used to improve the structural performance of these buildings during earthquake events. The aim of this study is to determine if the use of Fiber Reinforced Polymer (FRP) tubes as diagonal bracing members is a viable option for the seismic retrofit of existing buildings.;A parametric analytical study has been conducted to predict the performance of axially loaded FRP bracing members within a representative building structure, subjected to simulated seismic loads. 23 unique models were developed and tested using the structural analysis software SAP2000. Various combinations of structural parameters such as bracing configuration, material properties, and loading type were evaluated to obtain an understanding of their effect on the structure's ability to resist seismic load. Bracing materials used include hollow structural steel tubes, hollow FRP tubes, and FPR confined concrete tubes, with the hollow structural steel tubes being included as a control case. Hollow FRP tubes were found to perform poorly under seismic loading, primarily due to their very brittle failure mode -- remaining linear elastic until ultimate rupture. The ductility ratios of the FRP confined concrete tubes were found to be 40 to 50 percent less than those of the hollow structural steel tubes. However, FRP confined concrete tubes performed sufficiently enough to warrant continuing research efforts regarding their use for seismic bracing applications. |
