PurposeThis paper aims to investigate the fire performance of composite beams when considering the hogging moment resistance of the fin-plate beam-to-girder joints including the effect of continuity of reinforcements.Design/methodology/approachExperiments on composite beams with fin-plate joints protected only at the beam ends are conducted. The test parameter is the specification of reinforcement, which affects the rotational restraint of the beam ends. In addition, a simple method for predicting the failure time of the beam using an evaluation model based on the bending moment resistance of the beam considering the hogging moment resistance of the fin-plate joint and the reinforcement is also presented.FindingsThe test results indicate that the failure time of the beam is extended by the hogging moment resistance of the joints. This is particularly noticeable when using a reinforcing bar with a large plastic deformation capability. The predicted failure times based on the evaluation method corresponded well with the test results.Originality/valueRecent studies have proposed large deformation analysis methods using FEM that can be used for fire-resistant design of beams including joints, but these cannot always be applicable in practice due to the cost and its complexity. Our method can consider the hogging moment resistance of the joint and the temperature distribution in the axial direction using a simple method without requirement of FEM.
In this study, load-heating tests were conducted on glued laminated timber frames to investigate the temperature and charring behavior of columnbeam connections of dowels under standard fire heating for more than 1 hour. This paper reported on these results and discussed on the required covering thickness to control the temperature and charring. Wood plugs with 40 mm thickness at the dowel connections prevented that the charring reaches to head of the dowels during 4 hours (heating for 1 hour and decay for 3 hours) for Japanese larch. Partial wood-covering at the beam ends decreased temperatures of the steel connectors.
PurposeThe main purpose of this study was to propose theoretical calculation models to evaluate the theoretical bending strengths of welded wide-flange section steel beams with local buckling at elevated temperatures.Design/methodology/approachSteady-state tests using various test parameters, including width-thickness ratios (Class 2–4) and specimen temperatures (ambient temperature, 400, 500, 600, 700, and 800°C), were performed on 18 steel beam specimens using roller supports to examine the maximum bending moment and bending strength after local buckling. A detailed calculation model (DCM) based on the equilibrium of the axial force in the cross-section and a simple calculation model (SCM) for a practical fire-resistant design were proposed. The validity of the calculation models was verified using the bending test results.FindingsThe strain concentration at the local buckling cross-section was mitigated in the elevated-temperature region, resulting in a small bending moment degradation after local buckling. The theoretical bending strengths after local buckling, evaluated from the calculation models, were in good agreement with the test results at elevated temperatures.Originality/valueThe effect of local buckling on the bending behaviour after the maximum bending strength in high-temperature regions was quantified. Two types of calculation models were proposed to evaluate the theoretical bending strength after local buckling.
This paper discusses, based on the results of load-bearing fire tests, bending moment resistance of unprotected composite beams in fire including hogging moment resistance at pin joints. In particular, the influence of the specifications of rebars in concrete slab on hogging moment resistance at pin joints is focused on. The test results indicated that hogging moment resistance at pin joints is greatly improved by the effect of rebars, but the effect cannot be expected if rebars fracture prematurely. In this study, the effect of suppressing temperature rise of joints when protected only at joints is also discussed.
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