Determination of Influence Lines and Surfaces by Electronic Computer

Introducing the paper, Mr. Needham said that a testing rig had been evolved capable of taking beams up to 25 ft span and 2 ft 6 in. deep with two 20-ton loads, hydraulically applied at the quarter-points. It had been intended for testing a wide range of prestressed girder designs. The loads needed to impart a load factor of two, on a quarter-scale model of the girder tested at MEXE, amounted to approximately 7 tons per jack; thus the capacity of the rig would enable much stronger models to be tested.

The problems of wind loads on high buildings of unconventional shape are discussed as a function of building shape and characteristics of the natural wind. The new Toronto City Hall is used to demonstrate how wind loads, their distribution and fluctuation can create critical structural problems. The natural wind loads were obtained from wind tunnel tests on a City Hall model. These tests are described in enough detail to familiarize the structural engineer with the value and potential as well as the shortcomings of wind tunnel testing of buildings. G.K. Korbacher and N. Seethaler

This month's letters cover legislation for design checks, embodied carbon of modular construction approaches, and assessment of masonry buildings for earthquake resilience in New Zealand.