| High strength concrete is a new construction material with enormous potential. Structures using high strength concrete are becoming more and more popular. However, the application of high strength concrete to structures, especially in seismic regions, is questioned as the ductility of the material is poor under unconfined conditions. The ductile performance of reinforced concrete columns can be improved if provided with sufficient transverse reinforcement.;The mechanical properties of three high strength concretes containing silica fume are investigated. The test results are used to modify and calibrate a fracture energy-based non-associated plasticity model for high strength concrete. The model is verified by analyzing four tied high-strength concrete columns tested by Ibrahim and MacGregor at University of Alberta. The finite element analysis has successfully captured the load-deformation response, along with important information such as the strain softening and spalling of the cover, the development of a triaxial stress state of concrete in the column core, and the yielding of ties.;A parametric study of tied high strength concrete columns subjected to eccentric loading is conducted. Twenty-one specimens forming nine series are analyzed. The parameters involved in the analysis are the configuration, size and yield strength of ties, concrete strength, depth of cover, and amount of longitudinal reinforcement. The behavior of these specimens in both pre-peak and post-peak regimes is discussed.;Results of the parametric study are used to examine the performance of ACI Code sections related to tied concrete members. It is found that the ACI Code seismic design requirement of minimum transverse reinforcement is sufficient and necessary for tied high strength concrete columns. On the other hand, the ACI Code rectangular stress block over-estimates the moment capacity of high strength concrete columns. Modifications of related parameters in the ACI Code are suggested. |
