Slippage of thermal insulation under foundation slab subjected to seismic load

The main goal of the study was to determine and predict the possibility of the slippage of thermal insulation when subjected to the seismic load. The research was focused on the behaviour of insulation under the foundation slab. The experimental study of the coefficient of friction between different layers was performed at the Faculty of Civil and Geodetic Engineering. Two types of insulation were studied: a) the insulations with smooth surface, and b) with grooves on the upper side, which provided better connection between the foundation slab and insulation. We also evaluated the design formula for coefficient of slippage, which was defined for one-storey buildings and compared with the friction coefficient defined by an experimental study. The base-shear stresses were compared with the available friction stresses. It was found that the slippage of thermal insulation could occur especially when a structure has a fundamental period of vibration, which is in the resonant area of the acceleration spectrum, and the building responds essentially elastic to an earthquake load. The formula was evaluated for two examples: a) a RC wall structure, which can be considered as an infinity rigid, and b) a frame structure, whose fundamental period is in the resonant area. The simplified method is based only on the first mode of vibration. For the most common structures (wall structural systems – infinity rigid), the results, especially in a resonant area, can also be generalised and shown in a simple table, which makes them easier to use. The final equation to evaluate the coefficient of slippage represents a quick and simple tool, useful for designers in order to check a possible slippage of thermal insulation subjected to the seismic load. At the end we designed two typical construction systems (wall and frame system) by the Eurocode 8 standard. With the pushover analysis in SAP2000 and N2 method we evaluated target displacements for the insulation system with smooth upper surface. By using insulation system with grooves, total base shear of the structure does not even reach nonlinear\ud behaviour