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The Structural Engineer

Mr D. Beckett (Sir Frederick Snow & Partners): The design objective was to utilise the potential of automated fabrication techniques applied to non-prismatic frames to dgvelop a profile that broadly follows the form of the bending moment diagram and thus achieve significant weight reduction. An initial study of 21 span frames indicated that a weight saving of upwards of 250 kg could be achieved by using a tapered plated frame as an alternative to a plastically designed prismatic frame. This weight saving could be achieved only by adopting an unstiffened webdepth- to-thickness ratio of about 2.5 times the limit in the current edition of BS449. A departure of this magnitude from a current design standard obviously requires detailed theoretical and experimental investigations, but the precedent was set with the extensive use of tapered frames in the USA with a limiting web-depth-to-thickness ratio of 240 for grade 50 steel. The development of the design method progressed simultaneously with the test programme and the first step was to examine the elastic interaction of bending, shear and axial load effects on web plates, using the interaction formula shown in Fig Dl. The results were not encouraging but the first series of tests on frames fabricated in the USA revealed that the most significant design criterion was the stability of the compression flange. In spite of initial web distortions, web instability was not apparent. There was a subsequent shift in emphasis from considerations of web stability to the containment of lateral torsional instability of the compression flange. To achieve this, the following assumptions were made for a bending strength check.

The Structural Engineer

How does a young engineer tackle the Institution’s examination if he has always produced drawings on a computer and calculations by editing standard formats on a word processor? Edmund C. Hambly

The Structural Engineer

Like previous Presidents, I an honoured at being elected to be the President of this, to me, very special Institution. Unlike most of them, I am twice honoured by being concurrently President during the 75th Anniversary of its foundation and also the 50th Anniversary of the receipt of its Royal Charter. Hence I follow in the distinguished footsteps of Sir Alfred Pugsley, President during the 50th and 25th Anniversaries. I also take some pleasure in remembering that, in its original form, the Institution was the Concrete Institute-my affinity with, and penchant for, concrete being reasonably well known! However, although being honoured by, and taking much pleasure in, being President, there are certain feelings of trepidation caused by the extensive list of distinguished Past Presidents and their contributions to the Institution-I will endeavour to emulate them to the best of my ability. R.E. Rowe

The Structural Engineer

Investigation into recent failures of steel chimneys has revealed that there is a need for greater awareness of factors that can endanger structural performance. A widespread failure to monitor structural conditions has also been evident. D. McQuillan

The Structural Engineer

The heavy lifting industry has recently been required to develop extra capabilities to deal with the ever-increasing sizes of vessels and structures being fabricated for the petrochemical, energy, and construction industries. The complexity of lifting operations has also required a greater emphasis on the control and accuracy with which lifting is carried out. This paper describes some recent projects that have been successfully completed using developments devised to meet these increasing requirements. David J. Rolton

The Structural Engineer

Echoes of Ronan Point A letter from Mr Jan Korff, concerning the safety of structures and the scope of building controls, continues last month's debate on health and safety: I make no apologies for returning to the vexed subject of progressive collapse or, as it is known in modern parlance, disproportionate collapse. Verulam