Measurement of temporary prop loads at Mayfair car park

The construction of an underground car park in Park Lane, London using diaphragm walls has provided a further opportunity to investigate the development of loads in temporary props during construction of a braced excavation. Two transverse and two corner props in one half of the symmetrical excavation were monitored using vibrating wire strain gauges incorporating thermistors. The prop temperatures were also monitored independently using an additional set of thermistors attached directly onto the steel prop. The prop loads are presented both with and without correction for temperature effects and are compared with the design loads, which significantly underestimated the effects of temperature on prop loads. The horizontal force parallel to the wall generated by the corner props is assessed and its implications for the design of waling systems are discussed.