Wide Box Beam Wet Seam Analysis Of The Causes Of Early Cracks

With the development of computer technology and the needs of the country,hybrid cable-stayed Bridges with large spans are also developing rapidly.More and more wide-width box girders were applied in hybrid beam cable-stayed Bridges.However,due to the large overall width of the wide box beam and the small amount of bridges in the world,furthermore the hybrid beam cable-stayed bridge,there was not much research on the corresponding wet joints.Therefore,based on the actual engineering background,this paper analyzes the causes of the early crack formation of the wet joints of wide-width box girder.Exploring the effects of various parameters on early cracks in wet joints of wide box girder.Propose corresponding crack prevention and treatment measures,provide construction experience for the same type of wide box girder in the future.The main research contents and related conclusions of this paper are as follows:(1)Introduce the cast-in-place construction method of the wide-frame box girder and the concrete to match your design process,and carefully observe the various parts of the wet joint beam section to obtain the development law of the wet joint crack.It was found through observation that the crack was concentrated at the junction between the web and the top and bottom plates.The farther away from this,the crack distribution is relatively short and short.In addition,since the construction time is in the summer,the cracks are relatively sparse due to the influence of temperature and better health measures.(2)Based on the relevant calculation theory of early shrinkage of concrete,the finite element software Midas FEA was used to establish a three-dimensional finite element solid model of wide box girder wet joint.The comparison between measured data and finite element theory shows that the two have higher Consistency.In addition,the shrinkage of the wet joints were studied by changing the parameters of the wet joint beam section,such as the length of the wet joint beam section,the section size and the degree of constraint of the joint surface.The results show that the above parameters have a greater impact on the early shrinkage of concrete.(3)According to the field measured data and theoretical analysis results,combined with the construction characteristics of wide-width box girder and on-site construction technology,the corresponding crack prevention measures were proposed.First of all,in the concrete mix design,by adding an appropriate amount of expansion agent to offset the early shrinkage of the concrete.Secondly,according to the local winter and summer climate characteristics,different conservation methods were adopted,and through finite element simulation calculation and analysis,it was found that demolition template after 4 days of wet joint casting was beneficial to reduce cracks.Finally,the more mature crack treatment method been used,the existing cracks are treated in time to avoid the cracks from continuing to expand,providing experience for the crack prevention of wet joints in the same type of engineering in the future.