ABSTRACT
Engineers around the world are now often required to design for the effects of rare and potentially disastrous events such as earthquakes and blast effects. To meet the demands during these events, engineers are seeking to utilize the advantages of innovative materials to ensure not only that a structure can survive without collapse, but also to provide some minimum level of service and intended performance objective following the event. One such innovative solution is the use of advanced composite materials such as FiberReinforced Polymer (FRP) sheets. The use of FRP as a structural material gives engineers an effective tool to enhance the performance of new and existing structures to meet the severe demands during blast and earthquake events. The advantages of FRP composites include its ease of application, high strengthto-weight ratio and resistance to environmental degradation. In Reinforced Concrete (RC) structures, FRP sheets can easily be applied to a wide range of structural members including beams, columns, slabs, or walls. In such cases, the optimal mode of failure for the FRP strengthened element is controlled by crushing of the concrete and/or rupture of the FRP laminate after yielding of the steel reinforcement. However, it is commonly recognized that in many cases the failure of the FRP strengthening system is controlled by separation or delamination of the FRP material from the concrete substrate. This phenomenon is referred to as debonding and occurs before the FRP composite reaches its ultimate tensile strength, lowering the strength of the retrofitted member (Teng et al., 2002). Design standards for the application
for a RC column flexurally strengthened with vertically oriented FRP sheets on opposite faces of the column. Both IC and CDC debonding mechanisms initiate at the location of a flexural or shear cracks in the concrete. After IC or CDC debonding is initiated it propagates towards the ends of the FRP sheet. Alternatively, end interfacial delamination results from normal stresses at or near the termination of the FRP sheet. When anchorage is not provided, these normal stresses result in debonding or separation of the FRP sheets from the concrete substrate. End delamination is the most commonly observed failure mode in experimental tests on FRP-strengthened RC members (Pham & Al-Mahaidi, 2004). However, through the implementation of an effective anchor system, end delamination can be prevented, allowing the FRP sheet to reach beyond the strain limits prescribed by design standards and utilize a larger portion of the entire strength of the FRP composite material.
