Numerical study on the ballistic performance of prestressed concrete slabs subjected to hard missile impact

Prestressed concrete (PC) structure has been extensively used in civil engineering like nuclear and protective structures. But systematic studies on its ballistic performance are still inadequate, hindering its ballistic design and applications. In this paper, the ballistic performance of PC slabs subjected to hard missile impact is numerically investigated through finite element (FE) modeling. The method to introduce prestressing force is specially investigated and the feasibility of the established models is verified against existing experimental results. The models are then employed to conduct a comparative study between PC and reinforced concrete (RC) slabs, in which the influences of the prestress and prestressing bars are decoupled. The variations of concrete tensile strain and energy dissipation capacities of PC slabs with different failure modes are analyzed to understand the mechanism of the ballistic resistance. It is revealed that the prestress is the main reason for the enhancement of ballistic resistance of PC slabs, while the increase of reinforcement ratio due to prestressing bars is the secondary reason. It is also proved that the confinement effect applied to the concrete is the major reason for the increase in ballistic resistance. Based on the mechanism, by using mechanical and regression analysis, a semi-empirical formula for the critical perforation velocity of the PC slabs is proposed, which gives better predictions compared to existing formulas. The proposed formula also allows a straightforward parametric study, the results of which could be used for simplified estimations in the ballistic design of PC slabs.