Determination of the seismic performance factors for post-tensioned rocking timber wall systems

Post-tensioned technologies for concrete seismic resistant buildings were first developed in the 1990s during the PREcast Seismic Structural Systems program. Among different solutions, the hybrid system proved to be the most resilient solution providing a combination of re-centering and energy dissipative contributions respectively by using post-tensioned tendons and mild steel reinforcement. The system, while providing significant strength and energy dissipation, reduces structural element damage and limits post-earthquake residual displacements. More recently, the technology was extended to laminated veneer lumber (LVL) structural members, and extensive experimental and numerical work was carried out and allowed the development of reliable analytical and numerical models as well as design guidelines. On the basis of the experimental and numerical outcomes, this paper presents the evaluation of the seismic performance factors for post-tensioned rocking LVL walls using the FEMA P-695 procedure. Several archetype buildings were designed considering different parameters such as the building and story height, the type of seismic resistant system, the magnitude of gravity loads and the seismic design category. Lumped plasticity models were developed for each index archetype to simulate the behavioral aspects and collapse mechanisms. Non-linear quasi-static analyses were carried out to evaluate the system over-strength factor; moreover, non-linear time history analyses were performed using the incremental dynamic analysis concept to assess the collapse of each building. From the results of quasi-static and dynamic analyses the response modification factor, R, system over-strength factor, (0), and deflection amplification factor, C-d, values of, respectively, 7, 3.5 and 7.5 are recommended. Copyright (c) 2016 John Wiley & Sons, Ltd.