| The laminated slab composite beams have been widely used in the field of construction engineering by virtue of their outstanding performance in terms of convenient construction,energy saving and emission reduction,and better overall force and so on.The side of the prefabricated base plate will generally protrude bearded bars,but the existence of bearded bars is likely to cause transportation difficulties and construction inconveniences,Therefore,this topic proposes a structure of close-packed steel joist laminated plate with pre-buried angle connections in the bottom slab,which can avoid the problems of safety and construction inconvenience caused by the bearded bars.Since the combination beam has a concrete slab in tension and a steel beam in compression in the negative moment zone so that the cross-section is in an unfavorable condition,it is tested with a laminated slab combination beam with conventional precast bottom slab out of reinforcement in a static loading test in the negative moment zone in the span,and the characteristics and differences of failure pattern and the crack development,section strain distribution,interface slip curve and load-deflection curve in the section of the two composite beams with different structural forms are analyzed.ABAQUS finite element software is used to simulate and analyze the laminated plate composite beam.Furthermore,the influence of different parameters on the bending property of the compact laminated plate composite beam in the negative moment region are studied.At the same time,based on the test and numerical simulation analysis results,the formula of the load carrying capacity in the negative moment zone of this type of combined beam and the calculation and analysis of its deflection is established.The main conclusions of this paper are as follows:(1)Under the action of negative moment loading,the damage patterns of the two types of dense laminated plate composite beams with different bottom plate configurations made in this paper are similar,showing that the specimens are obviously bent,the bottom of the plate is severely cracked and the crack width in the span develops quickly,and there is obvious slippage and misalignment between the laminated layers.And both cracks are similar in distribution and appear first near the mid-span section.The crack development rate of the combination beam with angle bars is lower than that of the combination beam with extended bearded bars,which is due to the fact that the installation of angle connections increases the shear stiffness of the combination beam and effectively suppresses the crack development rate.(2)The difference in load carrying capacity between the two configurations is not significant,and the deflection of the joint with angles is reduced by 32.1% and the slip is reduced by 43.6% compared with the deflection of the combined beam in the form of outgoing bars.The deflection and slip of the specimen are significantly reduced due to the shear stiffness of the specimen being improved by the setting of angles.(3)The finite element model of dense laminated composite beam is verified to be correct by numerical simulation method,and the influence of different parameters on the flexural load capacity of the composite beam is investigated,and it is found that the flexural load capacity of the composite beam is insensitive to the changes of the thickness of the cast-in-place layer and the angle of the angle,and when the force ratio is increased from 0.18 to 0.36,the ultimate load capacity of the composite beam was increased by 10.2%,and increasing the force ratio could improve the composite beam.When the strength grade of steel beam is increased from Q235 to Q390,the flexural load is increased by 41.9% and the limit load is increased by 36.6%,which indicates that increasing the strength of steel beam within a certain range effectively improves the yield load and ultimate load of the specimen.(4)The deviation between the flexural bearing capacity of the laminated plate combined beam calculated by the plastic theory analysis method and the actual bearing capacity is small,the error is within 10%,but the calculated value is generally smaller than the measured value,mainly because the role of stiffening ribs is ignored in the calculation of the formula.In the calculation of deflection,the conversion section method does not take into account the effect of slip,resulting in a small deflection;while the discounted stiffness method,which takes into account the effect of slip,calculates the deflection of the laminated plate combination beam to match the measured value,and the calculation is more accurate.Figure [48] table [13] reference [82]... |
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