A portion of the girder covering consisted of mackite blocks plastered, another portion consisting of 2-inch cinder concrete, the latter being the regular construction. There were also two 8-inch I-beams set up, one covered with cinder concrete to 9 inches X 13 inches ; the other covered with hollow bricks to 12 inches X 16 inches, giving 4 inches covering.
The floor was first loaded with 1,000 lbs. per square foot, under which it deflected inch. The load was then reduced to 400 lbs. per square foot, and the fire test commenced. This lasted for two and one-quarter hours at a maximum temperature of 1,700°. A stream of water was then applied for 41- minutes, and afterwards another fire test given of 38 minutes and a second stream of water applied. The floor, at the end of the test, showed a deflection of 11 inches. The cinder concrete beam and column coverings were not materially damaged. The mackite covering was entirely stripped off, and the hollow brick column covering badly damaged. No apparent injury occurred in the floor slab. After this test the floor was loaded up to 1,650 lbs. per square foot, at which point the walls of the test house made it necessary to stop. The net deflection under this load was 14 inches. A few cracks appeared in the ceiling under this load, most of them being parallel to the bars.* Numerous other tests of expanded metal floors on shorter spans have shown satisfactory results. For spans up to 8 feet and loads under 2)0 lb;. per square foot, which are the ordinary condi tions, the cinder concrete shows safe results. Beyond these limits special tests should be made in each case.
A valuable review of the effects of a practical fire test on terra cotta and concrete floor construction, is given in the discussion bearing on the fire that occurred in the Horne Building, Pittsburg, Penn., May 3, 1897, which was published in Engineering News,
May 20 and 27, and .Tuly 1 and 15, in that year. An account of a second fire which occurred on April 7, 1900, is published in the same periodical under dates of April 12 and April 1900.
The New York Building Department conducted a test on three arches of the Guastavino type, each 3 feet in length. The spans were 6 feet, 10 feet, and 12 feet. The 6-foot span was composed of 2 courses of tile, making a thickness of 2:;- inches; the 10-foot span, of four courses, giving 5 inches thickness ; and the 12-foot span, of three courses, with a total thickness of 3:1 inches. All were leveled up with concrete. The 6-foot span carried 2,500 lbs. per square foot, and showed a maximum deflec tion of .13 inch. The 10-foot span carried 3,600 lbs. per square foot, with a deflection of .19 inch. The 12-foot span carried 3,125 lbs.,per square foot, with a maximum deflection of .32 inch.
This was a simple loading test with no application of fire and water.
Tests of porous terra cotta hollow tile arches have not been so numerous, especially under fire exposure. Table XIII gives the results of a series of tests to determine breaking loads of differ ent arches, and is taken from the " Transactions " of the American Society of Civil Engineers, Nos. XXX IV and XXXV, of 1895 and 1896.
In terra cotta arches as in concrete arches, great variations in strength will result from varying degrees of thoroughness in con struction. These arches should always be set in cement and care fully keyed, and the use of broken blocks should be avoided. Settlement in arches of this type often results in cracks in tile or mosaic floors.