Punching failure of car park ceilings - An analysis using GPR

“Punching” describes a mode of failure where a pile remains standing upright but the ceiling carried by the pile collapses. Punching failures of car park ceilings have occurred several times in recent years, sometimes with disastrous results. In order to avoid punching failure, several systems of punching shear reinforcement are available that can be placed during construction in the concrete ceiling in the vicinity of piles. For an evaluation of the risk of punching failure the details of the structure have to be known. In particular, the presence or absence of punching shear reinforcement has to be known. If this is not the case, for example because plans of the building are unavailable, non-destructive testing may be an option. This paper presents a series of experiments carried out in car parks, where the presence or absence of punching shear reinforcement was known. GPR data were acquired around piles and processed subsequently. It can be shown that a range of punching shear reinforcement can be clearly identified.