Knickerbocker Theatre.

Progress, Volume XVIII, Issue 1, 1 September 1922, Page 16

Knickerbocker Theatre.

CAUSES OF THE DISASTER.

Two committees have already reported on the collapse of the Knickerbocker Theatre, Washington, and while there is some difference of opinion as to where the responsibility should be placed, the two committees agree practically on the cause of the failure.

The two committees which have already reported are a committee of the Washington Chapter of the American Association of Engineers and a board appointed by the Associated General Contractors. The board of engineers of the War and Navy Departments has not made public its report. According to a review of the many weaknesses and defects of the structure given by the committee of the American Association of Engineers mentioned in the Engineering News Record , no evidence was found in the wreckage that the roof slabs failed until after the failure had started elsewhere. The committee finds that the roof slab, with a working stress of 16,000 lbs. per sq. in., had a total capacity of dead and live load of only 23 lbs. per sq. ft., while the actual .load was about 75 lbs. The reinforcement had a yield point of 73,000 lbs. per sq. in. r*

While inadequate strength of roof slab is listed among the principal defects, it is cited that a breaking of the roof slab could not have pulled the beams

toward each other, since in the south-east corner of the building a large slab of the roof is still holding together unsupported, making the action suggested by one army officer appear unlikely. Other principal defects listed by the American Association of Engineers’ Committee as most deserving criticism are: support of main truss on a thin wall, lacking solidity and mass. Support of main truss on a skew bearing, combined with lack of stiffness in the gusset between the end post and the lower chord of the truss. ■ Failure to anchor trusses and heavy beams into walls.

Scant bearing at walls. Insufficient section area and inadequate details of truss members.

Inadequate column bracing. Absence of lateral support at intermediate panels of the main truss.

Absence of diagonal bracing between other trusses. The English technical journal Concrete declares that the failure was entirely due to the bad design of the steelwork. The failure, nevertheless it adds, has a moral for architects and engineers, for it appears that considerable variations from the engineer’s design for the steelwork were authorised by the architect on the suggestion of the contractor, and were allowed to be carried into execution without being examined by either the architect or the engineer in conjunction with whom he was working. Without casting any reflection on steel erectors, it cannot be too strongly emphasised that the architect or designing engineer is primarily responsible for the soundness and stability of a building carried out to his designs, and it is unfair to the client to allow the work to be done by a contractor without thorough examination.

Edward I. was probably responsible for the origination of vertical iron palisading or railing in England, for, by his patronage of metal and smith crafts, he revived an art which had languished since the early mediaeval days, when it had been the relaxation of kings; and it became necessary to protect the gilded and enamelled bronze effigies of royalty introduced by him along with their complement of precious helmets, gauntlets, weapons and insignia, with palisading. * * *

In level, treeless places groups of flat-roofed houses are usually monotonous and, therefore, to be avoided, although an occasional flat-roofed house in the midst of structures with pitched roofs is likely to prove interesting. In hilly or wooded locations particularly where the streets are winding or run up and down steep grades, groups of flatroofs are frequently acceptable and occasionally can be made to possess great charm. Given a mountain for a background and some terraces or woodlands to work with, fiat roofs, the handiest type to build of reinforced concrete, can be designed with great’ success.