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1、保证箱梁桥竖向预应力筋有效预应力的探讨2010年3月第3期(总138)铁道工程JOURNALOFRAILWAYENGINEERINGSOCIETYMar20l0NO.3(Ser.138)文章编号:1006—2106(2010)03—0052—05保证箱梁桥竖向预应力筋有效预应力的探徐华轩(中铁十六局集团有限公司,北京100018)讨摘要:研究目的:通过理论分析,试验,实践,研究混凝土箱梁腹板内竖向预应力筋预应力损失大,作用效果差的成因,提出对策与措施,以保证竖向预应力作用效果,避免腹板出现主拉应力裂纹.研究结论:设计中,对竖向筋控制应力与屈服强度的比值进行控制;计算由锚具变形和缝隙压缩等引起的
2、预应力损失时,取1.65mro的回缩值;增加由锚垫板安装误差引起的预应力损失,并取3.3mm的回缩值;考虑混凝土和水泥浆水化热引起的预应力损失,施工中重视施工工艺的改进和完善;控制锚垫板安装倾角误差,做到"两平一直",控制锚垫板与螺帽的夹角在1.以内;使用扭矩扳手拧紧螺帽,对632和币25竖向筋的锚固扭矩分别取1200N?m和600N?m;采取二次张拉和超张拉工艺;前段梁与后段梁连接处的4组竖向筋与后段梁的竖向筋同步张拉.关键词:预应力混凝土;箱梁;竖向预应力;预应力损失;控制中图分类号:U445.4文献标识码:ADiscussionontheMeasuresforGuaranteeingEf
3、fectivePrestressofVerticalPrestressedReinforcementofBoxGirderBridgeXUHna—xuan(ChinaRailway16thGroupCo.Ltd.,Beijing100018,China)Abstract:Researchpurposes:Basedonthetheoreticanalysis,testandpractice,theresearchisdoneonthereasonsf0rthebigpretresslossandpooreffectofprestressedreinforcementofthewebplateo
4、fconcreteboxgirder,andthemeasuresforthemarepresentedtoguaranteetheeffectoftheve~iealprestressandavoidtheappearanceofstresscrackonthewebplate.Researchconclusions:Indesign,theratiobetweenthestressandyielddegreeofverticalreinforcementshouldbecontrolled.Thereboundvalueof1.65mmshouldbeadoptedwhencalculat
5、ingthestresslOSScausedbyanchordeformationandgapcompression.Thestresslosscausedbyinstallationerrorofanchorbackershouldbeaddedandthereboundof3.3mmshouldbeused.ThestresslOSScausedbywaterthermalizationofconcreteandeementgroutshouldbeconsideredandtheattentionshouldbepaidtoimprovementoftheconstructiontech
6、niqueinconstruction.Theerrorofinclineangleshouldbecontrolledtomaketwoflatandonestraightandmaketheincludedanglewithin1.wheninstallingtheanchorbacker.Theanchortorqueof1200N?mand600N?mwithtorquespannershouldbeusedto632reinforcementand+25reinforcement.Thetensionandsupertensiontechniquesshouldbeused.Thef
7、ourgroupsofverticalreinforcementsonthejointplaceofthefrontpartandtherearpartofthegirderandthereinforcementsontherearpartofthegirdershouldbetensedatthesametime.Keywords:prestressedconcrete;boxgirder;ve
