Upgrading of isolated bridges with space-bar energy-dissipation devices: Shaking table test

The results of the experimental research program realized on a bridge model constructed by using the seismically isolated system upgraded with space-bar devices (USI-SB) are presented in the paper. The installed adaptable system for seismic protection of bridges utilizes double spherical rolling seismic bearings (DSRSB) as seismic isolators, while the qualitative improvement of seismic performances is achieved through the use of novel adjustable multi-directional space-bar energy dissipation (SB-ED) devices. The experimental program consisted of quasi-static testing of isolation and energy dissipation devices under the cyclic loading and extensive shaking-table testing of a large-scale bridge model with installed USI-SB system. For both types of devices, a very stable all-directional response during cycling tests, as well as the favorable hysteretic behavior of the energy dissipation devices along the entire range of applied large displacements were registered. In the dynamic testing, the system showed high seismic response modification performances needed for the efficient protection, exhibiting its large potential in the qualitative improvement of seismic performances of isolated bridges.

Seismic Reliability Assessment of Base-Isolated Bridges in Quebec

The aim of this work is to estimate the seismic reliability of a simple typical two span lifeline base-isolated bridge designed to behave essentially elastic or as per the Canadian Highway Bridge Design Code, for seven localities in Quebec. Two limit states are considered for possible failure due to unacceptable damage: by flexure at pier-base and by displacement within the SIS. Main problem random variables (RVs) considered and modeled are: Seismic hazard, temperature, pier base dimensions and material mechanical properties. The Monte-Carlo method is used to evaluate each limit state reliability and probability of failure. Preliminary results reveal that notwithstanding the large temperature and seismic hazard variabilities between the seven sites in Quebec, the global reliability indices are almost uniform, around 3.45±0.02. Furthermore, security factor (i.e.1.25) on SIS displacement capacity results in reliability indices for SIS displacement are not levelled with the flexural reliability indices and needs further exam and consideration.