| The composite beam formed by the web-opened steel beam and the concrete slab connected by bolts is a new type that uses the characteristics of steel that is suitable for tension and concrete that is suitable for compression.The two materials are combined to form a whole through the connector and work together.structure.With the development of China's economy in recent years,steel-concrete composite beams have been widely used in domestic high-rise buildings,industrial plants and bridges,especially in the construction of large-span interchanges in large and medium-sized cities in China.Many applications,due to the frequent effects of vehicle loads,its fatigue problem is increasingly prominent.At present,there are relatively few studies on the fatigue of composite beams.The fatigue performance of composite beams is mainly studied by experimental methods and rarely by numerical analysis methods.Based on the consideration of the above problems,this paper analyzes and analyzes the fatigue performance of rigid-concrete composite circular-hole simply-supported honeycomb beams.The finite element software abaqus is used for different opening ratios,number of openings,web height-thickness ratio,and web between holes.Stiffeners and other parameters were numerically calculated and analyzed,and their fatigue properties were studied.First,the fatigue life of a solid-web composite beam under mid-span loading was analyzed,and the normal stress,shear stress,and beam end shear stress were compared.The fatigue life calculated from the shear stress of bolts and studs was found to be safer based on the span-to-mid-span normal stress amplitude.It can be seen that the fatigue design of a composite beam structure is more suitable for selecting the mid-span normal stress as the control parameter for fatigue life analysis.Furthermore,the effect of initial defects on the fatigue performance of composite honeycomb beams was analyzed,and the location of the most unfavorable initial cracks and the way of adding initial defects were determined.The combined circular holes with the number of openings of 3,5,and 10 were established taking the initial defects into consideration The finite element model of a simple supported honeycomb beam is studied by changing the opening ratio of the web.The results show that with the increase of the open porosity,although the stress redistribution occurs occasionally,the fatigue strength of the composite honeycomb beam as a whole shows a downward trend,especially when the open porosity is greater than 50%,the fatigue life decreases significantly.By analyzing the effect of different opening numbers on the fatigue performance of composite honeycomb beams,as the number of openings increases,the fatigue life of composite honeycomb beams will be controlled by the mid-span normal stress,the mid-span shear stress,and the stud shear stress in order.In the process of increasing the number of holes in a composite honeycomb beam,the fatigue life does not decrease blindly.Although the number of openings is large,the distribution of the holes is reasonable to avoid stress concentration,and the fatigue life is increased.Pay attention to the reasonable distribution of the holes.The study found that with the increase of the height-to-thickness ratio of the web,the mechanical properties of the web of the composite honeycomb beam decreased.When the web-to-thickness ratio was greater than 105,the fatigue life obtained by each stress decreased significantly.Adding stiffeners between holes in the web can effectively improve the stress level across the middle section and increase the fatigue strength and fatigue life of the structure. |
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