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Definition of New Techniques
For the purpose of this paper new techniques are defined as methods of construction, materials and processes differing fundamentally from what was regarded as the normal practice between the wars. Thus a steel frame would not be regarded as a new technique for an office building, but it could be so regarded for a house.
THE USUAL THEORY.-It is usual to estimate the moment of resistance of the lateral pressure of earth against sheet piling and footings by calculation of the passive pressures on each side of the member according to Rankine’s Formula. The full value of passive pressure given by this formula is known to require very considerable movement and only a fraction (n) of it can be allowed.* Fig. 1 shows this method of treatment
of the problem in its simple form applied to a square section pile or pole, where a centre of rotation A is found so as to provide a balance of moments and of horizontal forces. The method suffers from two defects. In the first place it is assumed that the pressure distribution on a tilting surface is the same as it would be on the same surface moving horizontally, whilst in the second place the fraction (n) of Rankine’s value for maximum pressure is a matter of judgment or ignorance.
Arthur A. Fordham
IT has been generally considered that, as the standard theory does not give the ultimate load at which a reinforced concrete beam fails, it must be discarded. In consequence of this, a number of attempts have been made in recent years to predict the ultimate strength of R.C. beams by different methods, notably by Dr. Glanville (*), Professor Saliger, and C.S. Whitney. The theories advanced by these writers are purely empirical and do not give any idea of the stresses at loads other than the ultimate. This paper is intended to show how the standard theory, which is useful in giving an idea of the stresses at working loads, can alsoobe extended to predict the ultimate loads.