A Finite Element Study of Steel Rafter to Concrete Ring Beam Connections Used in Trinidad and Tobago

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Rafter to ring beam connections are the most critical connections in a roof as their failure can result in dislodgement of the entire roof along with its framing and covering. The aim of this study was to conduct a finite element analysis study on the performance of some of the non-coded steel rafter to concrete ring beam connections used in Trinidad and Tobago. The most popular of these connections involve using steel rebars that are cast into the ring beam and subsequently welded to the rafter. Nine versions of this connection were identified and categorized as Type 2 & Type 3. The Type 2 Connections are those in which the rebars are welded to the top flange of the rafter and the Type 3 Connections are those in which the rebars are welded to the bottom flange of the rafter. The Type 2 and Type 3 connections consisted of several variations including mechanically anchoring the rebar to the rafter without welds, using one and two rebars, varying of the rebar embedment depth and using 90 degree and straight rebars. A Type 1 standard, code-compliant, bolted-endplate connection was used as the control for the investigation. The connections were analysed using “ABAQUS” and the maximum load resistances were compared with computed category 1 hurricane loads for this region. The load capacities of all the connections were found to be lower than the control connection but were still adequate for hurricane category 1 loads, with the exception of the connection in which the rebars were mechanically anchored to the rafter without welds. The Type 2 connections were less stiff, experienced larger rafter displacements, inflicted less damage on the concrete ring beam, and required less rebar embedment to prevent pull-out failure than the Type 3 connections


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Rafter gages -- Design and construction, Roofing, Iron and steel -- Design and construction