Is Your Non-Building Structure Suitably Braced: A Third Case Study in a Series

There are instances during complex construction projects when temporary work platforms are needed to assist in the timely installation of supplemental structural steel, mechanical and electrical equipment, etc., at various floor elevations. The structural system designed by the subcontractor was a freestanding structure with chevron braced frame in one direction and an x-braced frame in the other to provide for minimum headroom clearance under the platforms. In all cases the bracing members were composed of double-angle members.

The issue that arose during the erection of these temporary work platforms was, simply, that the intermediate connectors that should have been designed, detailed, fabricated, and installed prior to or during erection to have the double angle bracing act as a double-angle cross section in accordance with the AISC 360-10 Specification for Structural Steel Buildings were not provided causing great concern as to the viability of the structures to perform properly without being retrofitted. A study was then undertaken to look at the behavior of the temporary work platforms if the structural deficiency had not been discovered as well as the platform's behavior to the performance based loading conditions provided in the contract documents to which they were supposedly designed. In addition to the stability analysis conducted the paper will also address the following four fundamental areas:

• Understanding today's process of design and analysis
• Understanding today's process of detailing for fabrication
• Understanding today's procurement, subcontract contractual process
• Understanding today's work process and relying on commercially available software approved for project use

Learning Objectives:
According to the AISC 360-10 Specification, a built-up member is composed of two shapes that may be interconnected by (a) bolts or (b) welds.

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