THE use of focal points in the analysis of continuous beams is not new, but the construction given below is quicker and simpler than those in general use; it is applicable to a uniform* continuous beam of any number of equal or unequal spans. The method will first be demonstrated by an example of a three-span beam (Fig. 1.) The beam is simply supported at A, B and C, and built in horizontally at D. R.E. Bowles and R.J. Cornish
Whilst engaged on a problem here it became necessary to check the usual assumption in beam analysis, viz. that plane sections remain plain after bending (Bernouillis' assumption). This is obviously inaccurate and the following analysis is offered in case the point is novel and of interest.
REINFORCED Concrete is finding increasing application in Cooling Towers and in pipe lines, pump houses, etc., which go with them. Great attention is being given to the design of Cooling Towers for maximum efficiency and for the reduction of the nuisance of precipitation. An increase in the first cost is often more than justified by fuel saving in the Power Station and a large size of tower giving a low range of cooling is a factor in reducing the deposition of moisture on surrounding areas. Uniform distribution of the Water over the interior stack at all variations of loading and the minimum impediment to the inflow of air is also necessary. The first slides show a modern interior stack of timber construction having small laths in continuous circles held in notched bearer boards. This stack occurs in the lower portion of the concrete tower, which may rise for 200 ft. above the stack. The water is sprayed over the stack from brass sprayers mounted on the top of asbestos cement pipes from a main Conduit of Reinforced Concrete passing diametrically across the centre line of the Reinforced Concrete Tower. Wartime scarcity of timber made it necessary to attempt to save some or all of the timber entailed in the stack and further slides illustrate two Cooling Tower stacks built entirely of Reinforced Concrete and one stack built with Reinforced Concrete main members but having timber laths. H.E. Manning
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. R. Fitzmaurice
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
INTRODUCTION 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. K.L. Rao