Investigation on Relations Available for Residual Axial Resistance Estimation of Reinforced Concrete Columns under Blast Loading

Reinforced concrete structures may be affected by different blast loadings during their service life. External columns are the key load bearing structural elements in those structures. Under the effect of external blast loading, external columns of the ground and first floors may experience severe damage which can cause progressive collapse of the whole building frame. Among the variety of different factors that can affect blast response of structural components, residual resistance of the component is an important factor. Residual axial load bearing capacity of the reinforced concrete (RC) columns after the effect of lateral blast loading, could be a suitable criterion for damage assessment of columns. It is essential to determine whether the column has to be replaced or repaired after the blast event near the building. Therefore, residual axial capacity of the column could be very helpful. In this paper, residual axial strength of some square RC columns under the effect of constant initial axial force and lateral blast loading is studied. Explicit finite element hydro-code LS-DYNA is used to analyze the considered RC column models and determine their residual strength after the experience of blast loading. In current literature, there are some suggested equations for estimating residual axial capacity of blast damaged RC columns which have been introduced by executing experimental blast tests. With respect to complexity, limitations and high costs of laboratory and experimental researches in this field, analytical studies and software simulations can be good alternatives to experimental methods. Accordingly, in this paper, some of available equations are used to predict residual strength of the considered RC columns. Afterward, FEM results are compared to the estimations of these equations for RC columns with different levels of initial axial force under different range of lateral blast loading. Residual axial strength of the damaged column is compared to an undamaged one and estimated residual axial capacities are compared.