PFA Concrete: Strength Development of RHPC/PFA Blends

Partial underpinning of semidetached houses In our column for February, Mr V. T. Brierley invited comments on a situation in which the local authority was threatening action against a client for contravention of Building Regulation requirement A.1 para. (b) because her house-one of a semidetached pair on a raft foundation - had been repaired by being piled. A number of readers have responded, including Eric Skilton of Waltham Abbey, Essex: The question of foundation repair to half of a pair of semidetached houses is one which has, in the past, raised a wealth of issues and opinions. The DOE determination to which Mr Brierley refers was by no means the first on this issue; they invariably stem from an objection from the Building Control Department under Regulation A.l (1) (b). Verulam

The behaviour of beam-column joints is discussed in the context of current design procedures for reinforced concrete ductile frames subjected to severe earthquake motions. As plastic hinges are expected to develop in beams, the beamcolumn joints must be capable of transferring large shear forces across the joint cores. The mechanisms of shear resistance of joint cores comprise a diagonal concrete strut mechanism and a truss mechanism. A considerable amount of joint core shear reinforcement is necessary to sustain the truss mechanism if bond failure of longitudinal bars is avoided. The diameter of longitudinal beam reinforcement in joint cores needs to be restricted to ensure adequate anchorage in joint cores. The significant differences in detailing requirements of beam-column joints that exist between various concrete design Codes led to an international collaborative research project involving the testing of full-scale beam-column-slab joint subassemblages under quasi-static cyclic loading. The three subassemblages designed to New Zealand practice performed very well. P.C. Cheung, Professor T. Paulay and Professor R. Park