282 Lateral Stability of the Victoria-street Bridge. 



which happened to be the production of two young and 

 comparatively inexperienced men; and the subsequent troubles 

 have given rise to various remarks as to the un desirability 

 of entrusting important designs to inexperienced persons. 

 In reply to these remarks, it is to be pointed out that the 

 choice of the design from a considerable number of competi- 

 tors was made by experienced practical engineers, and the 

 execution of the work supervised by a gentleman of high 

 standing in the profession, and thus the responsibility 

 was entirely removed from the shoulders of the original 

 designers. 



The engineer in charge of the execution of the work 

 departed from the original design as far as the construction 

 of the abutments was concerned, and a partial failure took 

 place in this part of the structure. With the question of the 

 desirability of this departure I do not propose at present to 

 deal, but would merely say that the failure does not appear 

 to me to be by any means as serious as it has been repre- 

 sented, or as similar movements in other structures with 

 regard to which the public mind is at rest. 



Before the failure took place the bridge was subjected to 

 an unusually severe test by being traversed by the heavily- 

 loaded drays carrying earth and rock from the cutting on the 

 high side to the bank on the low side of the stream. Under 

 this ordeal no sign of weakness appeared in the iron columns 

 or girders. 



On the occurrence of the partial failure of the abutments 

 considerable alarm arose, and a Government engineer of 

 high standing was called in to advise as to the remedy. 

 This gentleman not only proposed a most complicated and 

 costly reconstruction of the abutments, but went further, 

 and condemned the rest of the bridge as unsafe under wind 

 pressure, and insisted upon the width of the base of the 

 taller piers being increased threefold. The arguments used 

 in favour of this startling proposal were as follows : — 



1. It was ascertained that on one occasion a wind pressure 

 of 35 lbs. had been registered at the Observatory. 



2. This pressure was multiplied by 3, giving 105 lbs. to 

 the square foot as the extreme pressure the structure ought 

 to be able to endure. 



3. The moment of stability of the highest pier and corre- 

 sponding portion of the superstructure was computed, and 

 the ultimate overturning wind pressure determined as only 

 56 lbs. per square foot. 



