DefinePK

Abstract

In a typical developing country like India where urbanization is taking place at a rapid pace, multistory parking structures have started mushrooming in almost every city landscape. Firstly, the structure has to be made earthquake resistant. Secondly, the parked vehicles have also to be protected from damage during an earthquake. The safety of parked vehicles is seldom factored into the design. During extreme lateral loading the vehicles themselves will be subjected to excessive displacements which will make them collide with each other leading to considerable damage especially to sensitive electronic / digital controls. Normally the parked vehicles are modelled as mass objects in a structure. However, if one has to understand the behaviour of parked vehicles, the same have to be modelled as dynamic objects with mass and stiffness. This work has precisely considered this important aspect, which is rarely addressed, and herein lies the uniqueness of this research work. This work envisages analysis of a G+11 car parking structure with moment resistant frame as the structural system. The analyses consisted of essentially two procedures; one to model the parked cars as mass objects, treating them as point loads; second, to treat them as dynamic objects, treating each car as single storey portal frame with mass, stiffness and supports. In order to model the car as dynamic object, a typical automobile was considered and its mass and stiffness were found out and from these values, an equivalent frame model was arrived at. Further the analyses included considering mass regularities vertically across the floors as well as horizontally within the floors. Overall 11 models were analyzed five with cars as mass objects and five with cars as dynamic objects. The results studied were base shear, time period, displacement of structure as a whole and displacement of individual cars. It is seen that modelling of the parked vehicles as dynamic objects increases the rigidity of the structure resulting in higher base shear with the percentage difference ranging from 4.58% to 4.75% in comparison with the structures in which parked objects are treated as mass objects. Therefore, from safety point of view modelling of parked vehicles as dynamic objects is required. Car displacement varies from 3.48 mm in ground floor for model Ms2 to 24.74 mm in 11th floor for model Ms5 whereas corresponding floor displacements varies from 2.81 mm to 23.84 mm, indicating the cars do not collide during an earthquake.