A new high performance semi-active bracing system

Abstract

Structural control under seismic excitation is becoming an important problem in earthquake engineering. Among several control systems, semi-active control is usually possible and efficient. In the conventional bracing systems it is assumed that the braces buckle under little compressive forces. In this research a semi-active on–off brace strategy is implemented to improve the conventional braces performance. A new completely tensile ribbed bracing system (RBS) has been developed to use the whole capacity of the member. In the proposed system the buckling of compressive member is prevented using a ribbed shape cylinder. RBS causes a permanent-stiffness-presence system that leads to less structural responses. The permanent deflections are removed at the end of excitations by a length correction control system. In this mechanism there is no need for any actuator and large power supply, but just a battery-sized power supply to switch the ribbed mechanical system on or off. The developed mechanism is composed of a ribbed supplemental part and a normal wind-bracing on each floor. Despite the fact that this system does not get control command from outside, it is called a semi-active control system. The hysteresis loop of the braces is similar to ductile tensile steel members. Therefore the system is full capacity design. Nonlinear dynamic analysis of the system has been carried out and its structural behaviour has been investigated. Also damage indices are determined in order to compare the RBS with the conventional bracing systems.