Civil structures are subjected to various types of loading, which induce severe damage to the structures. Many techniques have been developed for structural rehabilitation; one of the emerging technologies is the use of energy dissipation systems such as fluid viscous dampers (referred to hereafter by FVD). In this chapter, the effect of these devices on the dynamic behavior of an RC building is investigated, with an optimal choice of the linear FVD parameter (i.e., damping coefficient), using a simplified and effective approach. It was found that the maximum inter-story drift of the analyzed retrofitted structures can be significantly reduced compared to the original ones.
TopDiffrence Between Active And Passive Control Systems
Active control systems are considered as a more advanced technology, their concept is based on a real time processing that allows them to act accordingly to the excitation, thanks to the sensors integrated within the device. These sensors collect information about the excitation and the structural response, then adapts the device’s behavior based on the collected data (Saaed & Nikolakopoulos, 2015, Soong & Spencer, 2002).
Passive control systems consists in materials and devices that enhance damping, strength and stiffness, the most common devices of this class operate generally on principles such as deformation of fluids and fluid orificing (the case of this chapter), deformation of viscoelastic solids, frictional sliding and yielding of metals (Soong & Spencer, 2002). A passive dissipation device utilizes the motion of the structure to generate the control force (no external power source needed). In the following, it will be mainly focused on fluid viscous dampers i.e. FVD, and their design optimization, which is seen as intensive task, all illustrated with an example. Figure 1 shows some of the passive dissipation devices followed by a brief definition and a summary of their advantages and disadvantages.
Figure 1. Passive energy dissipation systems.
Friction damper consists of four links located at the intersection of cross bracings (tension brace and compression brace) (Canstantinou & Spencer, 1992). A slippage is permitted for one of the braces then the other slips, which allow the device to dissipate energy in both braces. Filiatrault & Cherry (1990) tested and confirmed that this type of devices can increase substantially the capacity of dissipation in one cycle and reduce the amount of drifts. However Symans & al (2008), cited some reliability issues that concerns this sliding option, which can change the interface condition with time, and since their behavior is highly nonlinear, it may provoke undesirable structural behavior by exciting higher modes.
Metallic damper or also called yielding steel elements, many concepts are proposed, it can consist on round steel bar integrated in the bracing frame (Canstantinou & Symans, 1992, Tyler, 1985 and Whittaker & al, 1991), with their stable hysteretic behavior and reliability for long periods, they also present an insensitivity to temperature. One must mention that after a severe excitation, this device may be severely damaged and must be replaced.