CONSTRUCTIOJST AND FiRE PEOTECTION OE COTTON WAREHOUSES. 35 



most severo fires — the conflagration of Salem, Mass, — ir> shown in 

 Plate XIX, figure 1. This view shows the exterior of the building 

 practically undamaged after the surrounding buildings had been 

 destroyed. The interior ^iew (fig. 2 of the same plate) shows 

 the complete protection aiJorded by the tin-clad fire shutter. The 

 interior of another building which withstood the test, though the 

 contents were entirely consumed, is shown in Plate XX, figure 1. 

 Some idea of the eiTect of fire on hollow clay tile may be gained Ijy 

 an examination of Plate XX, figure 2. Here the fire wall is of 

 the panel-wall type previously described, the tile panels being carried 

 in a frame of reinforced concrete. The timber and plank floors 

 of this building were only slightly charred by the fire which shat- 

 tered the tile as illustrated. 



SOME DETAILS OF CONSTRUCTION. 



Emphasis should be given to the previous statement that the de- 

 signing should be done by a competent engineer. Eeliable engineer- 

 ing service is frequently supplied by proprietors of the patented 

 systems, but it is best to have the services of a disinterested engi- 

 neer who is familiar with the character and cost of the local materials 

 to be used.^ 



while entirely satisfactory for exterior use, as for platforms, is not the 

 most tiesirable for use inside as the corners are readily damaged by severe 

 fire or broken by truclcs. 



While concrete properly reinforced with steel is the best material for 

 fire-resistance floors and roofs, it is true that there have been cases of poor 

 design and workmanship which failed utterly, and there are isolated instances 

 of substantial reinforced concrete structures being damaged hy extremely 

 severe and prolonged fire. These fires have shown that concrete should be 

 cast solidly in place in such manner as to make the building, or large sections 

 of it, one solid whole, or monolithic, structure. These tests have further demon- 

 strated the necessity of so placing the steel that it will be well protected from 

 heat by the surrounding concrete. Such observations have indicated that con- 

 crete floor slabs should have a protecting thickness of concrete for the steel 

 of 1 inch, while this thickness should be li inch for walls and beams and 2 

 inches for very heavy beams, or girders, and columns. If such protection is 

 not provided, a severe fire is lil^ely to result in the steel reinforcement be- 

 coming so heated a"?; to stretch, causing serious damage to the structure. 



Floors may extend through division fire walls provided the mechanical de- 

 sign is such as to make the floor on either side independently self-sustaining 

 in case the floor on the other side of the wall is destroyed. The same con- 

 struction may be applied to tlie roof slab. This involves some modification in 

 arrangement of reinforcement, and in some cases additional material. These 

 stresses which would arise only in an emergency may be computed on the 

 basis of the elastic limit of the materials rather than with reference to the 

 usual allowable stresses which should bej.ised in computing the normal working 

 load. 



1 Materials for concrete permit of wide variation. The proportions for 

 concrete reinforced should usually be 1 part Portland cement. 2 parts sand, 

 4 parts stone, and water as required. The stoue should be iu small pieces 



