Numerical Modeling of RC and ECC encased RC columns subjected to close-in explosion

Abstract

New structures could have been designed to withstand blast loads. However, in the case of existing structures, ways to address this problem have to be found through studying the response of such structures to blast loads.

In a typical existing apartment block in Singapore, the ground floor, located close to car parks, is generally vacant comprising a void deck used to hold social functions for the residents. Bearing in mind that Singapore is not within any earthquake zones, therefore the design and the detailing of the structural elements based on Singapore's building code CP65 only considered axial imposed loads and lateral wind loads. Another characteristic of such structure is that the ground floor RC columns as used in a typical apartment block generally have breadth to depth ratio (B/H) greater than two. As a result, the ground floor columns in existing void deck may be vulnerable when subjected to close-in blast loads arising from vehicular bombs m typical of those used in the terrorist attack. The columns, the ground, and the 1st storey slabs may present channeling to the blast wave as it propagates from the source of explosion. Thus, with the prevalence of apartment blocks and the heavily built up environment, this research is intentionally done to shed light on the performance of existing apartment blocks when subjected to blast loads arising from close-in explosions, particularly to understand the behavior of critical RC columns located at ground floor.

The methodology of the present study consists of numerical, theoretical and experimental analyses of blast wave propagation through the ground floor void deck and the dynamic response of structural elements, particularly critical ground floor columns, of typical existing RC apartment blocks in Singapore. The study starts with the dynamic response analysis of standalone RC cantilever columns when subjected to blast loads. The study is carried out further on the effects of the close-in blast loads acting on the critical exterior columns nearest to the explosion charge. Moreover, to prevent such critical RC columns from failure by enhancing the resistance against close-in blast loads, Engineered Cementitious Composite (ECC) material is proposed as encasement layer.

It is expected that this research will contribute to the existing literature and hopefully lead to the recommendation of design guidelines for newly built apartment blocks in Singapore as well as guidelines for strengthening typical existing apartment blocks.