![]() ![]() Planning must include appropriate anchorages for temporary bracing cables. PEMB clear spans need to be braced sufficiently before being released, either with temporary cables or by tying into the existing braced erection with beams, girts or purlins. “Spreader bars and/or chainfalls may be necessary to provide enough support. If a rafter spans over 80 feet, Joseph Allen, project manager, and safety and training manager at Thomas Phoenix International Inc., East Hampton, N.J., agrees the erector must study the shop and erection drawings carefully to make sure the span will be rigid enough to fly with standard rigging. Joseph Allen, project manager, and safety and training manager at Thomas Phoenix International Inc., East Hampton, N.J. Never be too proud to reach out to fellow MBCEA members for advice and support, especially if attempting a large clear-span build for the first time.The surface area and weight of long clear-span rafters can act like a sail in even moderate wind, and this can cause them to fly out beyond the planned lift radius. ![]() Dynamic loading can cause crane and structural collapses.Side-loading clear-span rafters is a recipe for collapse. Do not use a crane to pull on the existing structure.Columns should be plumbed within tolerance before the rafters are flown. ![]() Fill purlins should be installed staring at the low eaves and worked up toward the peak.
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