The role of non-structural components in the seismic reliability of concrete tunnel-form building structures: Multi-level and multi-objective approaches

Abstract

Concluding from a review of the existing technical literature, the tunnel-form system exhibits desirable seismic performance from a structural standpoint. However, effects of non-structural components on the overall system reliability have not been investigated in any study to date. Furthermore, the level of coordination between the damage states of structural and non-structural components in this system is not well understood. With the aim of eliminating potential ambiguities, the present study evaluates the seismic reliability of such system by considering both acceleration- and displacement-sensitive non-structural elements. By dividing input earthquakes into two categories of demand and capacity and simulating the building using the classical block diagram method, prerequisites are created for multi-level and multi-objective assessments. In this study, a relationship for estimating the seismic demand of acceleration-sensitive non-structural components under the desired hazard level for tunnel-form systems is proposed. Based on the results obtained from the analysis of 5- and 10-story models, non-structural components significantly affect the overall system reliability. In the demand approach, when the moderate damage state for non-structural components is considered, the reliability of immediate occupancy performance level decreases by 100 % in the system. In the capacity approach, considering the same level of damage in non-structural components, the reliability for life safety and collapse prevention performance levels in the system decreases by 100 %. The investigations indicate that there is insufficient coordination between damage states of structural and non-structural components in this system, and in achieving the target reliability, acceleration-sensitive non-structural components are among the main weaknesses of the system. In estimating the distribution of acceleration demand along the height of structures, the proposed relationship underestimates the actual values by at most 3 %, which provides a significantly better safety margin compared to the relationships currently specified in the seismic design code (which underestimate the actual demand by more than 50 %).