Study on stress properties of steel-concrete composite beams with web openings in negative bending moment zone
In order to understand the mechanical properties of the internal stressed reinforcement of the steel-concrete composite beam with openings in the web in the negative bending moment area,experimental research and finite element analysis were carried out on a number of composite beam specimens with openings in the web.The research focused on the stress characteristics and laws of the steel bars in the concrete slab in the opening area.The test and analysis results show that,under the action of negative bending moment,the failure of composite beams with web openings occurs in the opening area,not at the place with the maximum bending moment.The cracks in the concrete slab in the opening area develop rapidly and eventually break,with obvious hollow damage occurring at the opening and secondary bending moments appearing at the four corners of the opening.Under the action of the secondary bending moment,part of the stressed reinforcement in the concrete slab in the opening area are compressed and part are strained,and the tensile effect of the reinforcement is not fully exerted,among which the upper reinforcement at the left end of the opening is most obviously strained and the tensile effect is better.Adding additional steel bars in appropriate positions can limit the development of cracks in the concrete slab above the opening,and effectively improve the bearing capacity and deformation capacity of the specimen.Among them,the addition of additional steel bars with a diameter of 8 mm at 65 mm from the central axis has the best improvement effect on the bearing capacity and deformation capacity of the specimen.
composite beamweb openingnegative moment regionin-plate reinforcementadditional reinforce-ment
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