SECTIONAL TRANSACTIONS.— G. 355 



(a) Agricultural machinery of many kinds. 



(6) Examples of the new McLaren-Benz high-speed heavy oil engine. 

 (t>) Sun Foundry. — Messrs. Hathom Davey. 



(a) Water pumping plant for Ahmedabad. 



(6) Sewage pumping plant for Karachi. 



(c) Large irrigation screw pumps for fen drainage. 

 (vi) Leeds Meadow Lane Gasworks. 



Inspection of the old Middleton viaduct, by invitation of the Superintendent. 

 The first steam locomotive ran on this viaduct in 1812. 



Wednesday, September 7. 



Mr. J. Gilchrist. — Strength of Reinforced Concrete Beams in Shear. 



1. Results of compressive and tensile tests of concretes used in the beams tested : 

 between 1000 and 5000 lbs. per square inch the compressive strength can be expressed 

 in terms of the tensile strength by the following formula : — 



C=12(T— 100) 

 where C is the compressive strength of the concrete and T its tensile strength, both 

 in lbs. per square inch. Above a compressive strength of 5000 lbs. per square inch 

 there is not the same increase in the tensile strength for this particular kind of concrete, 

 which was made of varying mixtures of cement fondu and crushed millstone grit to 

 pass through a quarter-inch riddle. 



2. Shearing strength of beams of T section, with straight tension reinforcement 

 bars hooked at the ends, with no verticals or shear reinforcement whatever. The 

 following table gives the practical minimum values of the shearing stress at the neutral 

 axis near the end of the beam calculated on the ordinary beam theory from the results 

 of the tests. 



C.S.D.C. C.S.B.L. 



C. T. 1% steel. 1£% steel. 1% steel. 1£% steel. 



C and T are the compressive and tensile strengths of the concrete, C.S.D.C. is the 

 calculated shear stress under the load at which the first crack was seen in the region 

 of greatest shear ; while C.S.B.L. is the calculated shearing stress at the breaking load. 

 All the figures are in lbs. per square inch. 



The author had previously stated in a paper published in Engineering in 1915 that, 

 for a concrete of about 3000 lbs. per square inch compressive strength, the failing 

 shear stress of a beam would be 275 lbs. per square inch, this being a conclusion from 

 published tests. In the above table the corresponding figure would be the mean of 

 290 and 350, that is 320 lbs. per square inch. 



Mr. H. H. Burness. — Large Low Head Conduits. 



Mr. T. M. Naylor.— The Whirling of Shafts. 



Some years ago a discussion took place as to whether there was a disturbance 

 before the whirling speed proper. A further discussion followed as to whether the 



disturbance occurred at or of the whirling speed proper. 



Before describing his experiments, the author gives a brief summary of the matter 

 published on this point. Then he describes his experiments and gives photographs of 

 the disturbances which occurred when experimenting with an overhung shaft loaded 

 at the end. 



The conclusion arrived at is that there is a disturbance at \ the whirling speed 

 proper. 



Report of the Earth Pressure Committee. 



•a a 2 



