بررسی تأثیر میراگر اصطکاکی سیلندری بر پاسخ لرزه ای سازه های فلزی

In this investigation, seismic response of steel structures utilizing Cylindrical Frictional Dampers (CFD) is studied. CFD is an innovative frictional damper which comprises two principal elements, the shaft and the hollow cylinder. These two elements are assembled such that one is shrink-fitted inside the other. If the damper’s axial force overcomes the static friction load, the shaft inside the cylinder will move and results in considerable mechanical energy absorption. To assess the efficacy of CFD, various steel frames are constructed and analyzed . Nonlinear time history analyses and Incremental Dynamic Analysis (IDA) are applied to the frames and clear distinction has been drawn between the frames comprising CFD and the counterparts without CFD to emphasize the effectiveness of CFD in altering seismic responses. The results show that CFD extremely improves the seismic response of the structure. Frictional devices dissipate energy through friction caused by two solid bodies sliding relative to each other. The idea of using frictional dampers was first proposed by Pall (1979). Pall and Marsh (1982) proposed frictional dampers installed at the crossing joint of the X-brace. Tension in one of the braces forces the joint to slip thus activating four links, which in turn force the joint in the other brace to slip. This device is usually called the Pall frictional damper (PFD). B. Wu et al. (2005) introduced improved Pall frictional damper (IPFD) which replicates the mechanical properties of the PFD, but offers some advantages in terms of ease of manufacture and assembly. Sumitomo friction damper (1990) utilizes a more complicated design. The pre-compressed internal spring exert a force that is converted through the action of inner and outer wedges into a normal force on the friction pads. Fluor Daniel Inc., has developed and tested other type of friction device which is called Energy Dissipating Restraint (EDR) (1994). The design of this friction damper is similar to Sumitomo friction damper since this device also includes an internal spring and wedges encased in a steel cylinder. The EDR utilizes steel and bronze friction wedges to convert the axial spring force into normal pressure on the cylinder. Constantine et al. (1990) proposed frictional dampers composed of a sliding steel shaft and two frictional pads clamped by high strength bolts. Grigorian et al. (1998) studied the energy dissipation effect of a joint with slotted holes both analytically and experimentally. Mualla and Belev (2002) proposed a friction damping device and carried out tests for assessing the friction pad material. Cho and Kwon (2004) proposed a wall-type friction damper in order to improve the seismic performance of the reinforced concrete structures. Recently Mirtaheri et.al. (2011) proposed an innovative type of frictional damper called cylindrical friction damper (CFD). In contrast with other frictional dampers the CFDs do not use high-strength bolts to induce friction between contact surfaces. This reduces construction costs, simplifies design computations and increase reliability in comparison with other types of frictional dampers.