Formwork Design

A contractor is to construct a reinforced concrete retaining wall 3.5m in height having a stem thickness of 250mm. The works specification requires the concrete to be 40N20 with a slump of 75mm. Average site temperature has been measured at 10oC. The wall has a total length of 60m and contractor is working in bays 7.5m in length. The contractor’s ready mix concrete supplier has indicated a supply rate to site of 6m3/hr. The wall is to be constructed in horizontal bay lengths and owing to the lack of available cranage the formwork must be manhandled into position therefore construction must take place in a minimum of 2no. vertical lifts. The formwork is to be made using Cofiform Douglas fir plywood strengthened with rough sawn timber strength class SC3 vertical studs. The formwork is to be tied together using a minimum of 3no divi bars per vertical lift. The divi bar loadings are to be transferred to twin pairs of horizontal walings also made from rough sawn timber. (divi bars to be MS tie rods with an allowable axial tensile stress of 130N/mm2) Select a suitable arrangement of the formwork for 1 vertical lift of wall bay. Calculate the design pressures and hence produce the design for the selected arrangement.