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In this study, well-instrumented field tests on bored piles were conducted at two construction sites in Zhejiang, China. At the first site, three bored piles in clay deposits overlying rock were load-tested to investigate the load transfer and deformation behaviour of a single pile. The lengths of the 1·1 m diameter test piles ranged from 88 m to 120 m, allowing particular insight into the in situ performance of long piles. In addition, the load–settlement behaviour of these piles within a piled raft group was observed during and after construction of the building they supported. At the second site, four bored piles 32 m long and 0·6 m in diameter were observed during single-pile static load tests, and during and after construction of the overlying building. The pile-head settlement was observed to be due mainly to the compression of the pile shaft for the long pile at the first site. The threshold of slip displacement for fully mobilising the shaft resistance was found to be 15–20 mm and 10–15 mm in clayey and silty deposits respectively. The measured load–deformation behaviour at the pile base demonstrates that the base resistance of single piles in a piled raft system is greater than that in the single-pile condition, and the pile-group settlement ratio is related to the applied pile-head load. The bearing pressure under the perimeter of the raft was measured and found to be greater than the bearing pressure beneath the central part of the raft, although the ratio between these values was found to vary with the applied structural load. In the cases studied, approximately 80% of the applied structural load was carried by the piles; the remainder was carried by the raft in bearing against the soil.

For large-span retractable roof structures, the mechanism should be simple and efficient for the convenience of motion control. The kinematic characteristics of parallelogram closed-loop chain linkages (PCCL) show that a set of the angulated beams of PCCL rotates around the fixed points, which is suitable for retractable structures. This paper focuses on the geometrical design of the rotary retractable plate structures (RRPS), which evolves from PCCL by replacing the rotation angulated beams with cover plates. Each plate of RRPS has a fixed support and all the plates rotate simultaneously with a single DOF. The fixed points used as supports for cover plates to improve the stability and simplify the motion control of the system restrict the open area of the RRPS. By adjusting the contact boundaries of the cover plates, an optimisation method is proposed to increase the open area of the RRPS after fully deployed. The design approach is successfully extended to both symmetrical and asymmetrical RRPS. An example is carried out to demonstrate the feasibility of the approach and a simple physical model is manufactured to validate the design result in the example.