Seismic performance improvement of elevated highway bridges using high energy dissipation materials

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In order to improve the seismic performance, an energy absorption strategy which localizes damage in structural systems is proposed : intentionally localizing damage in specially designed weak structural elements, with which energy is dissipated during earthquake. The weak elements are so designed that they yield prior to the main structure to avoid damage in the main gravity supporting element. This treatment will also reduce the repair works after seismic events considerably, because only the added weak elements which do not support gravity yield. To achieve this structural design concept to control damage, energy dissipation strategy is studied in three steps. At the first step, optimal design method of energy dissipation devices is constructed and distribution of damage is studied using simplified lumped mass model of elevated highway bridges. At the second step, low yield point steel (LYPS) is introduced as an example of the weak element, and damage control strategy is constructed for bridge piers. Analytical, and experimental studies revealed that LYPS is high energy absorbing ductile material suitable for the designated weak element. At the third step, real elevated highway bridges where seismic accelerograms or damage records during 1995 Kobe earthquake are studied to show the feasibility of damage control. The distribution of damage in three span continuous bridges is found to be predicted with precise evaluatoin of damage in bearing. Localization of response is also observed in base-isolated bridges. These evidence show the possible application of damage control. Three dimensional finite element analysis is also conducted for sontinuous span bridges to compare the performance of several damage control design. Although practical aspects, such as construction details needs to be considered before its application, this research work shows that the proposed design concept is promising alternative to improve seismic performance of elevated highway bridges.