Issue 12

The Christmas period 2004 was a busy time for the team working on the Holmethorpe Underbridge, near Redhill in Surrey. After 4 months of hectic preparation the portal structure was inserted into a railway embankment over a 101h possession period which started late on Christmas Eve 2004. The complete 1700t structure, including the wing walls and foundations, was cast offline during the run up to Christmas, but this still left removal of the track and embankment, the moving of the underbridge into position, the backfilling and the reinstatement of the permanent way to be completed in the short time available. The construction was undertaken by Hochtief (UK) Construction Ltd on behalf of Linden Homes, with the completed structure becoming a Network Rail asset. The design of the underbridge structure, in its permanent condition and during transportation, was done by Tony Gee and Partners from its Cobham office in Surrey. Nigel R. Hewson, BSc, CEng, FIStructE, FICE Tony Gee and Partners Andrew W. Richards, BSc, DipArb, CEng, FICE, FCIArb, FIHT Director – Rail & Marine, Hochtief (UK) Construction Ltd

The events in recent years of total or partial destruction of large buildings as a result of accidental abnormal loadings have created a new challenge for the structural engineering community. The challenge is to ensure that catastrophic collapse of structures can be avoided while designing the structure primarily for normal loadings and economy. The principle is based on utilising the ultimate strength of the structure and its ability in redistributing abnormal loads so that any accidental damage will not be disproportionate to the cause. This paper examines the current design approaches available to the designers, principally the recent Building Regulations in UK and in particular elaborating the mechanism of tying approach in fulfilling this goal. Also common approaches found in the US are briefly reviewed. Medhi M. Khabbazan, BSc, MSc, PhD, CEng, MIStructE, FASCE Kellogg Brown & Root UK Ltd. (KBR)

The transverse lateral load capacity of masonry built using solid dense concrete blocks with thin joint mortar is up to 4.0 times that of similar blockwork constructed using conventional mortar. Both the mortar properties and the constituents of the parent material forming the block alter the joint strength resulting in enhancements to tensile flexural bond strength. Testing on two block types and one mortar has been undertaken and verifies the trend. Essentially when thin joint technology is employed, in conjunction with solid dense concrete blocks, the masonry behaves more as a concrete plate than conventional blockwork. A. N. Fried, BSc (Civ) Eng, MSc, PhD, CEng, MICE, FBMS School of Engineering, Kingston University, London E. Marrocchino, PhD Dept. of Earth Sciences, University of Ferrara, Italy C. Bradsell, BSc (Hons) School of Engineering, Kingston University, London Prof. John J. Roberts, BSc(Eng), PhD, CEng, FIStructE, FICE, FBMS, FIMgt, MICT Faculty of Technology, Kingston University, London