Analysis of direct shear failure mode for RC slabs under external explosive loading

• A new Single-Degree-of-Freedom (SDOF) system is developed for predict direct shear response of RC slab against blast loading.
• Three different direct shear resistance models are proposed for evaluating slabs have different material properties.
• Pressure–impulse diagrams are generated for assess the direct shear failure of RC slab under explosion.
• Simplified functions are generated for quickly determine the direct shear pressure–impulse diagrams of a given RC slab.

The single degree of freedom system (SDOF) is used to predict the shear responses of RC (reinforced concrete) members under external blast loading in the present study. An RC member suffering a blast may experience both flexural and shear failure modes. Under very high amplitude short duration shock, structural failure is usually governed by direct shear loading, whereas under low amplitude long duration shock, the structural failure is most likely governed by flexural damage. However, most previous studies are based on the assumption that flexural response dominates the failure mode without taking shear failure into consideration. In the present study, dynamic response equations of a structural member experiencing direct shear failure are derived for elastic, plastic and elasto-plastic shear resistance–slip models. With these equations the P–I curves of both flexural and direct shear failure modes are generated for an RC slab. Furthermore, a parametric study is conducted to investigate the effect of different parameters of RC slabs on the pressure–impulse (P–I) diagrams based on the elasto-plastic model. Finally, based on the results from the parametric studies, curve fitting technique is used to generate the P–I curves for RC slabs in a simplified way.