Seismic vulnerability of precast reinforced concrete structures

In the Ph.D. thesis, the seismic vulnerability and seismic collapse risk of precast reinforced concrete structures, typical for the building practice in Slovenia and Europe, are discussed. Full-scale pseudo- dynamic and cyclic tests of some precast structures have confirmed the assumption of the large strength of connections, and have provided important information about the behaviour of very slender cantilever columns when subjected to large deformations, as the structure approaches collapse. Based on the experimental results obtained, an improved numerical model capable of modelling global collapse was formulated for such columns with large shear spans. The model was applied to the seismic risk assessment of precast structures. Seismic risk was evaluated by means of probabilistic analysis, taking into account the randomness in seismic excitations and other sources of uncertainty. A solution strategy, which is based on an intensity measure rather than a damage measure, has been suggested. A special study focused on the variance related to the uncertainty in the numerical modelling of the structure. A verified probabilistic method was used to assess the seismic risk of the whole range of the analyzed precast structures, as built in practice. It was found that the minimum detailing requirements according to Eurocode 8 usually provide such structures with sufficient overstrength so that the seismic risk is acceptably low (the probability of collapse is 0.1–1.2 % in 50 years). However, if only design reinforcement is provided in the structures, the seismic risk is rather high (the probability of collapse is 1.0–8.5 % in 50 years). The results have been used to obtain a quantitative evaluation of the force reduction factor used in Eurocode 8.