Issue 16

The equivalent load method is a technique for replacing a prestressing tendon by a system of external, statically equivalent loads. Bending moments induced in the member under the latter system of loads will represent the total prestressing effect and can be determined by any of the existing techniques for analysing indeterminate structures. Consequently, the method is useful because derived equivalent loads may be employed as input data to computer programs for direct evaluation of the total prestress moments (including secondary moments) for a continuous beam.

Until the introduction of Amendment AMD l787 in July 1975, BS 449 gave the steelwork designer no guidance concerning the ultimate or design load of a black bolt, when it is subjected to the combined effect of tension and shear forces. It was therefore unavoidable that different designers had their own 'design methods' for the purpose of checking such bolts. The work described in this paper was carried out with a view to providing the designer with information regarding the behaviour, response, and ultimate carrying capacity of black bolts subjected to varying tension-shear ratios. H. Shakir-Khalil and C.M. Ho

A beam-rotational spring model is presented for nonlinear analysis of reinforced concrete structures subjected to monotonically increased or reversed static loading. A beam or frame is treated as an assembly of beam elements. Each beam element has a bilinear hysteretic rotary spring at each end. The beam elements are assumed to remain elastic in bending along their length, but may undergo inelastic bilinear hysteretic axial deformation. M. Seniwongse

A simplified dynamic model of a marine crane is used to calculate the magnitude of dynamic loads arising from lifting cargoes from the deck of a moving supply boat. Typical results show that the maximum dynamic loads acting on the crane system are, in general, much greater than is commonly believed. For North Sea applications, it is suggested that dynamic factors of at least 5 should be used in design. Although motion compensators can be used to minimise system loads, it is maintained that a marine crane should be safe in terms of allowable stresses and fatigue life in the absence of such aids. D.G. Owen