Experimental Response of HPFRCC Dampers for Structural Control

Abstract

Structural performance of a cementitious damper made of HPFRCC and steel bar was experimentally observed. These dampers will be applied for reducing seismic damage as well as seismic response of RC structures under performance-based engineering. Since the stiffness of RC structures is higher than that of steel structures, dampers that are stiffer than the conventional ones mainly applied for steel structures are required for drastically reducing the seismic response of RC structures. The advantage of HPFRCC dampers is selective structural performance, strength, stiffness, and ductility, obtained by varying the configuration, bar arrangements and types of materials used. Compressive resistance, which is never a feature of conventional response control dampers, is also a unique advantage of HPFRCC dampers. Thus optimum dampers that meet high performance requirements such as damage reduction for buildings in the event of large-scale earthquakes, can be easily obtained in order to minimize the reconstruction burden. The experimental results indicate that when HPFRCC is used, an extremely large capacity of more than 6N/mm² in average shear stress and large deflection capacity of more than 10% in deflection angle can be achieved since HPFRCC contribute to the prevention of shear failure and compression failure. HPFRCC can remarkably reduce structural damage by initiating multiple fine cracks. Thus HPFRCC can be used to create small, stiffer dampers capable of high energy absorption due to large capacities in lateral resistance and lateral deflection, as well as high compressive resistance. However, the bending capacity of dampers is drastically increased by increases in axial compression force due to restriction of their elongation. Standard methods of calculating bending and shear capacities of RC columns are inadequate for predicting the capacity and failure modes of these HPFRCC dampers. Therefore, it is recommended that further investigation on evaluation methods for lateral resistance capacity, ductility, fluctuation of axial force, and hysteresis of HPFRCC dampers is essential to develop a performance-based-design method.