A Continuous The common form of construction in strictly fireproof buildings is as per sketch. Occur- 



Beam or a ring in adjoining spans, it has the appearance of continuous beam construction. Text books, as 



Flat Arch? ' 'Well as building laws, err in computing them as such. In the absence of a proper formula for 

 computing a flat arch,, engineers have been forced to use continuous or fixed beam formulae, 

 which, however fallacious their application, to this case may be, possess the redeeming feature of 

 erring on the side of safety. The discrepancy between theory and tests is too great 'to be ignored. 

 That this construction does not behave like a beam, but -rather as an arch; can be noted by any 

 casual observer of a test. This fact is now generally recognized and admitted by even the warm- 

 est advocates of the continuous bond. 



Fig. (4) This sketch shows a common method of reinforcing in fireproof buildings. It has 

 the appearance ,of continuous beam construction. Under tests its behavior is more like the arch 

 construction shown in the next sketch. The sustaining powers of the construction shown in this 

 sketch is three or four times greater than the loads calculated by the ordinary continuous beam 

 formulae. 



.''.i ' ' v Fig.- (5) A -flat segmental arch showing ;he similarity between it and the flat arch above. 



Has an Arch ^ vital difference exists between these two types of structures, namely, the continuous 



Tension at the beam and the arch. The continuous beam implies a high tensile stress .-.in the upper part of the 

 Abutment? . slab over the support. The arch implies-only a thrust or compression .at. the support. This dif- 

 ference is of the highest importance. If it could be demonstrated that an. arch exists in the 

 form of construction under discussion, instead of a continuous beam, it would follow with indis- 

 putable logic that little tensile .stress could, then be transmitted from arch to arch any more 



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