Analytical Study of Steel Accordion Metal Dampers in Seismic Retrofitting of Bridges

Experiencing earthquakes with different magnitude scales every few years, Iran is one of the most seismically active countries in the world. Therefore, it is very important to do research studies in terms of seismology before construction of bridges. Without considering seismic parameters, it would not be possible to design earthquake resistant bridges. Earth`s natural structure in different areas varies in relation with factors including kinetic energy at faults, global plate movements, velocity and maximum acceleration of plate displacements as well as the frequency and oscillation time.As mentioned before, demolition of an important structure like bridges,which is one of the basic elements in communication system among different areas leads to both heavy losses of life, and economic, social, hygienic and political losses. While a close and exact searching look at real seismic conditions of design site makes engineers able not only to prevent heavy costs of design and construction of bridges and to decrease earthquake losses significantly, but also to hold the communication system in service for the purpose of providing passages for firefighters to make all losses minimum.Studying occurred earthquakes such as Northridge and Kobe, which caused a lot of losses to different structures especially bridges contribute to feel the need of considering and studying available bridges in Iran under earthquake.Accordingto the increasing growth of studies in field of vulnerability assessment and earthquake-resistant construction, this need was felt that a damper tested in building structures would be used as an option to make bridges earthquake-resistant.In this article, analytical studies have been done on an available concrete bridge, which is common in Iran based on structure types and its elements arrangement.This bridge was modeled in SAP 2000, and the model was run based on four earthquake records including Tabas,Kobe, Northridge and El Centro applying four different PGAs and nonlinear dynamic time-history analysis were carried out, then the steel accordion damper was installed in order to compare analysis results of model before and after the damper installation.The result showed a decrease in seismic response of bridge structure after damper installation and acceptable amount of energy absorption and losses by dampers, which contribute to energy-loss increment in different elements of the main structure. These results lead to the conclusion that steel accordion dampers are a suitable solution in earthquake-resistant design of bridges.