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One of many designs we undertook for Cowley Timberwork. The Structural Engineer for the project as a whole was Buro Happold. Our role has been to design the timber connection joints, steel and concrete to timber interfaces and alternative timber raking columns to take the place of the original steel columns. We also, as always, provided advice on all structural and construction problems encountered by Cowleys. The roof consists of 360x76 mm laminated veneer lumbar (LVL) ribs, 2.4m long, laid out in a diagonal grid. The ribs are arranged in a lamella pattern, with the end of each rib meeting the midpoint of the next. In this manner short sections can be used to make up large spans, without the need to carry large bending moments at the joints. Structural boarding braced the cells and distributed lateral forces back to the braced bays and shear walls. The high shear forces generated at the internal joints (up to 30 kN) were carried by "Shearlock" connectors, illustrated above and below. These were developed by Cowleys and part of our brief has been to develop design rules and procedures for their use. The shearlocks consist of a high stength (Grade 12.8) steel bolt embedded into the timber end grain, inside a steel tube. A steel cup, filled with glue is then pressed inover the end of the bolt. This cup gives the bolt its shear strength. A large diameter threaded steel coupler is used in the receiving timber. The result is an exceptionally high capacity joint compared to other available connectors. Connectors fabricated from steel plate were used for the interfaces with the steel and concrete supports. Because of the curved geometry these wer often very involved, with little repetition. In order to reduce the number of variables, a "gate hinge" joint was used around the perimeter, allowing free rotation about one plane.
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