Pounding of a modular building unit during road transportation

Abstract

A modular building unit (MBU) is a volumetric box-like structure that is manufactured in the factory and transported to the building site. Damage to internal components of an MBU during transportation is widely reported. The accidental uplifting behaviour of the MBU on the trailer riding over road bumps has been studied and published. What ensues from the uplifting of the MBU is pounding on the trailer bed. Mounts/pallets used for transporting MBU would cushion the impact to an extent determined by its material properties. The first half of the work presents a methodology to quantify the impact acceleration resulting from a steel MBU to wooden mount impact. Authors have employed dynamic scaling and numerical modelling in LS Dyna along with established quasi-static testing technique to predict the dynamic contact properties of steel-wood impact. Hunt's – Crossley contact force model was then deployed to quantify the impact acceleration pulse analytically. A 10-tonne steel module impacting on pinewood pallet with 1 m/s velocity was found to generate an impact accelerations pulse of up to 25–35 g's using experimental, numerical and analytic techniques. The second part of the work predicted the response accelerations in the components attached to the MBU at midspan location. Vertical plane stiffness of an MBU structure was shown to affect the component response accelerations significantly. Typical steel MBU was found to amplify the component acceleration to up to 3-times the impact pulse generated during pounding. The highlight of the work is its ability to employ simplistic quasi-static testing on the choice of mounts (cushions) and predict its dynamic contact properties which in turn facilitates contact force equations (H&C) in predicting impact pulse on the prototype MBU.