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| Calculation and Analysis of Impact of Prestress Tension on Cast － in － place Falsework |
| WAN Cheng － gang，YAO Fa － hai |
| China Zhongtie Major Bridge Engineering Group，Wuhan，Hubei 430050，China |
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Abstract Research purposes: When the prestress is in tensile state，the concrete beam and cast － in － place falsework will interact． The load on the falsework will redistribute because of the deformation of the concrete beam． Only a little calculation is made for such working condition in actual project． Therefore，as the calculation is incomplete，the safety factor of the designed falsework structure is insufficient and it may cause the safety accident because the load on some parts of the cast － in － place falsework is insufficient． In this paper，taking the cast － in － place falsework of one cable stayed bridge as an example，the research is done on the calculation method for the impact of the tension of lateral and vertical prestress on the load bearing of the cast － in － place and the analysis is made for the causes for the load redistribution of the cast － in － place falsework caused by the prestress tension for the purpose of providing theory evidence to construction of prestress concrete beam．
Research conclusions: By establishing the finite element model for the prestress concrete beam and the cast － in － place falsework，the analysis and calculation are made for the changes of the load bearing of the cast － in － place falsework under conditions of the concrete casting，designed strength，tensile vertical prestress and tensile lateral prestress in each construction stage． The calculation results show when the vertical and lateral prestress is in tensile state，the the concretebeam will deform to cause transmission of the load on the cast － in － place falsework into the two sides of the falsework． The more tensile prestress there is，the more obvious the load redistribution sign is． The load redistribution will produce the big negative impact on the local structure of the falsework．
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Received: 09 March 2012
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［1］ 张伟民，毛志鑫，陈衡治． 预应力混凝土箱梁结构三维实体有限元计算方法研究［J］． 现代交通技术，2006( 4) :29 － 33．
Zhang Weiming，Mao Zhixin，Chen Hengzhi． Study of Calculation of PC Box Girder Structure with 3D － FEM ［J］． Modern Transportation Technology，2006 ( 4) : 29 － 33．
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Liu Jingmian． Research on the Pre － stressed Tendon Arrangement and Stress Calculation of Pre － stressed Concrete Continuous Girder with Segmental Construction ［J］． Journal of Railway Engineering Society，2008( 12) : 61 － 65．
［3］ 高安荣，张建军，李 松，等． 鄂东长江大桥超宽箱梁现浇支架设计与施工［J］． 桥梁建设，2009( 12) : 23 －26．
Gao Anrong，Zhang Jianjun，Li Song，etc． Design and Construction of Scaffolding for Cast － in － situ Concreting of Very Wide Box Girders of EdongChangjiang River Bridge ［J］． Bridge Construction，2009( 12) : 23 － 26．
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2012, Vol. 29 
