Calculation of Dynamic Load Factor for Reinforced Concrete Slabs Subjected to Above Ground Explosion

One of the common methods for structural design against explosive loads is the static linear equivalent analysis. Multiplying the maximum value of the explosive load by the dynamic load factor (DLF), the method would yield a static load equivalent to the explosive load. With this, the dynamic analysis can be transformed into an equivalent static analysis which, in turn, can be carried out using the current codes and standards. The lack of a complete and comprehensive study for computing the DLF means that the engineers carry out their design based on approximation by applying the coefficient diagrams obtained for beams and considering the ratio of the explosive load run-time to the main period of the member vibration (td/T). The purpose of this paper is to present the dynamic coefficient (d) of concrete slabs with different ratios of vibration periods, different boundary conditions, and different aspect ratios to be used as a basis of design against explosive load on structures. In this regard, a range of concrete slabs were modelled with a maximum measuring unit of dynamic load (using Single-Degree-of-Freedom (SDOF) models under triangular load) and consequently, before a static load was applied. Then, by considering the maximum bending moments obtained from static and dynamic analyses, the dynamic coefficient (d) or DLF was derived for each structure. For this purpose, 1680 model runs, including both dynamic and static cases, were carried out. The findings from these were plotted and analysed in terms of the dynamic coefficient (d) vs. (td/T), for a range of boundary conditions. The results revealed variation trends in the value of the dynamic coefficient (d) for each slab under different boundary conditions and can be used in the development of enhanced and more realistic procedures for structural design against explosive loads.

Keywords: Explosive loads; Dynamic load factor (dlf); Concrete slab; Sdof model; Vibration