课程（毕业）论文-体内体外混合配束节段预制箱梁体外束极限应力增量计算方法

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1、体内体外混合配束节段预制箱梁体外束极限1!应力增量计算方法摘要：节段预制箱梁在我国桥梁设计中使用渐多，其体外预应力筋的极限应力的计算是计算梁体极限承载力的关键问题。节段预制箱梁与整体式箱梁的变形特点、破坏形式有较人的秀别，目前的体外筋计算公式不再适用于节段预制箱梁体外筋应力增量的计算。在考虑混合配朿节段预制箱梁变形和破坏特征的基础上,提出推导节段预制箱梁体外筋应力增量的基本假设，建立节段箱梁梁体变形前后的儿何关系，分三阶段详细揭示节段预制箱梁的受力机理，给出了每阶段体外筋氏度的变化量，最终推导了双转向块、3分点加载情况下的节段预制箱梁体外预应力筋极限应力坍量的计算公

2、式。公式反映了节段箱梁张开角度，体外束“二次效应”对体外筋应力增量变化规律的影响。最后根据三根不同配束比的体内外混合配束节段式预制箱梁试验体外束应力增量测试数据，对本文公式和其它儿种典型体外筋计算公式进行了验证，结果农明建议公式的计算结果与试验屮实测数据吻合较好。关键词：体外预应力筋；节段预制箱梁；双转向块；塑性区长度；应力增量StressincrementofexternaltendonscalculationmethodofsegmentalboxbeamswithinternalandexternaltendonsYuanAiminDongHuanengWuW

3、enxiuChengHongbin(HohaiUniversity,Nanjing,210098)AbstractInrecentyears,precastsegmentalbridgeswithintemalandexternaltendonshavebecomethepreferredconstruction.Todeterminethestressincrementofexternaltendonsisthekeyissueinevaluatingultimatebearingcapacityofbeams・Thedeformationcharacterist

4、icsandmajorfailuremodeofprecastsegmentalprestressedconcreteboxbeamsaredifferentfromthecommonreinforcedconcretewholebeams・Thepresentcalculationmethodsforstressincrementofexternaltendonsarenotsuitableforsegmentalbeams.Basedonthedeformationcharacteristicsoftheprecastsegmentalboxbeamsandit

5、sfailuremode,severalbasichypothesesareputforwardandthegeometricalrelationshipisestablishedbeforeandafterdeformationofprecastsegmentalboxbeams.Theload-carryingmechanismofprecastsegmentalboxbeamsarcrevealedindetailbythreesteps・Ateachstcp.thcchangedlengthofexternaltendonsaregiven.Thenthes

6、tressincrementofexternaltendonscalculationformulaisobtainedforprecastsegmentalboxbeamwithloadactingonthelocationof1/3spanandtwodeviators・Thededucedcalculationformulashowstheaffectofjointsopeningangleandsecond-ordereflect.Finally,basedonthetestdataofthreeprecastsegmentalboxbeamswithdiff

7、erentratioofexternaltointernaltendons,ourproposedmethodandotherformulasarcvalidated.Theresultsshowthattheproposedalgorithmhasagoodaccuracyandinaccordancewiththeexperimentalresults・Keywordsexternaltendons;precastsegmentalboxesbeam;towdeviators;thelengthoftheplasticzone;stressincrement