Issue 21

The recently completed Greenside Place Bridge Link is a steel structure of innovative helical form designed in response to a challenging architectural brief and difficult site conditions. This paper describes the design development process, including an explanation of the structural concept and how this unusual bridge was analysed from first principles. Interesting geotechnical considerations that arose during the design of the bridge are described. Details of the fabrication and erection process, which demanded high standards of workmanship and dimensional control, are also given. The project provides a useful case study for the design and construction of link bridges between buildings in a typical urban setting. Simon Fryer, MEng, CEng, MIStructE, MICE Associate, Buro Happold Ltd.

Simple design rules are proposed that will enable engineers to take into account in-plane stability when designing single-storey steel portal frames plastically to Eurocode 3, without the need to resort to second-order elastic-plastic analysis software. The proposed design rules, developed from the results of a parametric study of different types of frame, are based on the Merchant-Rankine reduction method and take into account a modest amount of benefit from strain-hardening. A simple hand method for estimating the elastic critical load, required for calculating the Merchant-Rankine reduction, is also presented. From the results of the parametric study, the proposed design rules place frames into one of two categories: • Category A: Regular, symmetric and mono-pitched frames • Category B: Frames that fall outside of Category A but excluding tied portals For each category of frame, a reduction factor based on the Merchant-Rankine reduction method is proposed. J. B. P. Lim, BEng, PhD, CEng, MICE The Steel Construction Institute C. M. King, BSc, MSc, DIC, CEng, MIStructE The Steel Construction Institute A. J. Rathbone, BEng, CEng, FICE CSC (UK) Ltd. J. M. Davies, BSc, PhD, DSc, FREng, FIStructE, FICE The University of Manchester V. Edmondson, BSc, MEng, CEng, MICE The University of Manchester