Constructional Lesson from San Francisco.

Progress, Volume II, Issue 5, 1 March 1907, Page 181

Constructional Lesson from San Francisco.

In the January number of Concrete and Constructiona 1 Engineering, Captain Sewell has a valuable article on reinforced concrete as a fire-resistant. The article was partly written before tin catastrophe at San Francisco occurred, but its publication was deferred until the author had an opportunity of incorporating some additional matter suggested by the results of the catastrophe on concrete buildings. The article is illustrated by some striking photographs showing the effects of the earthquake and fire on buildings of various types. The author thus summarises his conclusions — In general, the San Francisco fire brought out nothing new relative to the value of the various materials used for fire-resisting purposes. It de monstrated beyond question that the commercial .york in the United States, both reinforced concrete and hollow tiles, have been applied in a flimsy and inadequate way. Both the San Francisco fire and the Baltimore fire demonstrated that commercial hollow tile work is very apt to fail by expansion stresses in the exposed webs, and that reinforced concrete was likely to be seriously damaged by the dehydration of the cement. Both fires indicated clearly, however, that both of these materials can be used so as to secure adequate and satisfactory results, and, in the writer's opinion, when so used, the cost will be about the same in both cases.

While this is an article especially on remfoiced concrete, the writer would point out that the serious problem in congested districts of large cities is not so much the securing of a fireproof covering for the street frame or a fireproof construction which will have such resistance that it will come through a fierce fire undamaged, as the devising of means of excluding an external fire. The question of window protection is by all odds the most important one at the present time. Had the fire been kept out of the fireproof buildings in San Francisco, none of the weakness in either concrete or hollow tiles would have been developed, and even the flimsy commercial type would have been, on the whole good enough. However even a fire ouginating within would have done serious struct ural damage to the fire proof construction in San Francisco ; so that, after the question of window protection is properly attended to the interior fireresisting features should al*.o be improved. So far as the concrete itself is concerned, that which was used in San Francisco for fire-resisting purposes was so poor to begin with that the writer had great difficulty in many cases in determining whether its unsatisfactory condition at the time he examined it was due to the fire or to carelessness or neglect in its original installation Careful examination, however, indicated that the surfaces exposed to the fire were manifestly in worse condition than the portion which had been protected from the fire, although it was all so inferior that there was not very much room for a different quality.

In order to determine the leal lelative efficiencies of the different types of flooring construction, those of each type that had evidently been subjected to the worst heat in a place like San Fiansi^co ought to be tested to destruction by superimposed loads Of course, it is not at all piobable that any such tests will be made It seems more than probablp that the better appeal ance of the reinforced concrete floots will cause a great many people to ascribe a fictitious value to the fire-resisting qualities of reinforced conciete , as a matter of fact if both the tile floors and the concrete- floois were tested, as above indicated, it is moie than probable that it would be discovered that all the lioors of both types that had been exposed to a really severe fire test ought to be taken out and renewed, in which case the floor loss would be total for both types