Assessment of Reinforced Concrete and Composite Steel-Concrete Columns to Resist the Effects of Suitcase Bombs
Date Issued
2009
Date
2009
Author(s)
Wu, Ke-Chiang
Abstract
The risks represented by suitcase bombs are of particular concern in the modern context because they can be transported by hand and placed almost anywhere in close proximity with key structural components. Although suitcase bombs are relatively small in size, ranging from to , their effect on structural components may be severe. The most common failure mode of blast loads is progressive collapse. As such, one of the most useful information that can aid in assessing if a structure would collapse is the residual axial strength of its columns. In this study, a high-fidelity physics based computer program, LS-DYNA is utilized to provide numerical simulations of the dynamic response and residual axial strength. There are three column specimens experimented with contact explosive tests out in the field, one being a composite steel-concrete column and the other two being reinforced concrete columns. The analytical results were compared with the test results for validation. The strain rate effects are important to the accuracy of simulations. The dynamic increase factor is used to describe this phenomenon. The models based on these three column specimens produced similar damage profiles when subjected to blast loads as applied to the actual specimens during the blast tests conducted in the field. An extensive parametric study utilized the validated finite element models to investigate the relationship with residual axial strength and other parameters, such as material strength, column details and blast conditions. Two types of columns were considered in the parametric study. One is the reinforced concrete column and the other is the composite steel-concrete column. TNT explosive, of weight between and , was used and located at either the bottom of columns or a height of from the footing of columns. Four analytical formulae were derived through multivariable regression analysis in terms of various parameters to predict the residual capacity index based on the non-dimensional column dimension parameter. According to the proposed formulae, the residual capacity index can be determined and compared with service axial load index. In general, a larger value of residual capacity index indicates a greater column resistance to the blast loads. A column whose service axial load index is greater than its residual capacity index is said to have failed or collapsed. Otherwise, the column has sufficient strength for the threat considered.
Subjects
contact explosive test
reinforced concrete column
composite steel-concrete column
analytical formulae
residual capacity index
Type
thesis
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