Tintern Abbey. Repairs Executed Since 1913 Under the Direction of H.M. Office of Works. Part III.-Co

IN the design of steel frame buildings it is usual to adopt a “factor of safety” of four, and many people think that this means that four times the ordinary load upon the building would cause failure. This is, however, by no means the case, and it is very difficult to say how many times the ordinary load upon the building would cause failure. Fortunately failures in practice are extremely rare-the author does not remember seeing particulars of a single failure during the past twenty years-and we therefore are unable to learn much as to the actual strength of steel frame buildings from an analysis of the loads and stresses in a building that has failed. Ewart S. Andrews

Colonel J. Mitchell Moncrieff, C.B.E., M.INST.C.E.(Association of Consulting Engineers) agreed with M. Forchhammer. Before the war, he said, Messrs. Redpath Brown & Co., through their chairman, Sir John Cowan, had approached him with regard to a testing machine they had given to the National Physical Laboratory, and, with regard to certain tests they wished to make, they had this type of construction in their minds. Owing to the war the tests were held up. Tests had been carried out on a few structures, however, and although they were necessarily incomplete, they indicated that there was something to be done in the future in the way of what Mr. Andrews called steelwork reinforced with concrete. To illustrate that, Colonel Moncrieff referred to a test made at the National Physical Laboratory on a 4 in. by 3 in. steel joist covered all round with at least 2 in. of concrete. That made a column something like 7 in. by 6 in., and the column was 16 ft. long, between the points of bearing, including the universal joints at each end. A similar steel joist, without concrete on it, was also tested. The naked joist, which was also 16 ft. long, failed at about 4 tons. The joist coated with concrete carried from 45 to 50 tons. That was worth thinking about. If they could put up the framework of a building, sufficient to carry the mere weight of the structure itself, in concrete, with the addition of tension members, as M. Forchhammer had said, think of the saving in staging! If they could make the bones of the structure carry the flesh until that flesh had sufficient strength in it to act, there was something to be thought about.

The Board of the Swedish Concrete Association has commissioned the author to work out a method of testing plain cement on the building site without adding of aggregates, as sand or gravel, and to conduct research work into thc possibilities of a short period test. The following is a preliminary report of the tests carried out during 1921-1922. Robert Mossberg