夹片咬合力测试方法
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摘要
为研究采用拉脱法检测预应力钢绞线受力时,张拉力荷载测试曲线突变段和夹片咬合力的关系,在夹片脱开时,采用电阻式压力传感器高频采集技术测试了预应力混凝土梁锚具下方和锚具外侧钢绞线的受力,共测试了20个样本;设计了夹片咬合力测试方案,共测试了326个样本,并进行了统计分析,建立了考虑张拉力的夹片咬合力计算公式;通过37个样本的验证性测试,研究了咬合力修正结果的测试精度;在实际工程中检测了257个样本,并将实测结果与提出的公式计算结果进行对比。研究结果表明:当钢绞线伸长超过4.5 mm时,夹片会脱离原有咬痕,而实际测试中夹片脱开时会及时停止张拉,因此,拉脱法测试不会改变预应力钢绞线锚下有效预应力,不会影响工程质量;夹片安装时,若夹片与锚杯锥孔不完全贴合,会使夹片在横向产生较大的弹性挤压力,形成附加摩擦力,该摩擦力需要在夹片退出至与锚杯分开时才能完全消失,此时锚外张拉力变化不明显,因此,拉脱法测试所得张拉力曲线中峰值拉力后的下降段斜率存在离散性,与夹片安装精度有关;拉脱法测试中夹片与锚杯的咬合力由锚下和锚外瞬态内力重分布累加组成,提出的夹片咬合力计算公式能剔除由夹片与锚杯间咬合力产生的测试误差,可使测试精度提高6.78%;实际工程现场实测夹片咬合力大于拉脱法测试所得张拉力曲线突变段,因此,采用拉脱法检测预应力钢绞线时,锚下有效预应力为拉脱法测试所得张拉力曲线峰值与咬合力的差值。
To study the relationship between the mutation segment of tension test curve and the clip bite force when using the lift-off method to test the force of prestressed steel strand, the high-frequency acquisition technique in the resistive pressure sensor was used to test the prestressed steel strand forces of a prestressed concrete beam under and outside the anchorage when the clip disengages. A total of 20 samples were tested. The clip bite force test scheme was designed. A total of 326 samples were tested and the statistical analysis was performed. The calculation formula for the clip bite force considering the tension was established. Through the verification test of 37 samples, the test accuracy of bite force correction results was studied. 257 samples were tested in the actual project, and the test results were compared with the proposed calculated formula results. Research result shows that the clip will break away from the original bite mark when the steel strand extends more than 4.5 mm. However, when the clip disengages during the actual test, the tension will be stopped in time, so the lift-off test will not change the effective prestress of prestressed steel strand under the anchorage and affect the project quality. When installing the clip, if the clip does not completely fit the taper hole of socket, the clip will have a large elastic pressing force in the lateral direction to form an additional friction force. The friction force will completely disappear when the clip is separated from the socket. The change of tension outside the anchorage is not obvious at this moment, so the slope of descending segment of tension test curve obtained by the lift-off method has a dispersion after the peak tension, and it is related to the clip installation precision. The bite force of socket in the lift-off test consists of the transient internal force redistributions under and outside the anchorage. The proposed calculation formula for clip bite force can eliminate the test error caused by the bite force between the clip and the socket, and improve the test accuracy by 6.78%. The test bite force in the actual project is larger than the mutation segment of tension test curve obtained by the lift-off method. Therefore, when using the lift-off method to test the prestressed steel strand, the effective prestress under the anchorage is the difference between the peak value of tension test curve obtained by the lift-off method and the bite force. 1 tab, 18 figs, 32 refs.
To study the relationship between the mutation segment of tension test curve and the clip bite force when using the lift-off method to test the force of prestressed steel strand, the high-frequency acquisition technique in the resistive pressure sensor was used to test the prestressed steel strand forces of a prestressed concrete beam under and outside the anchorage when the clip disengages. A total of 20 samples were tested. The clip bite force test scheme was designed. A total of 326 samples were tested and the statistical analysis was performed. The calculation formula for the clip bite force considering the tension was established. Through the verification test of 37 samples, the test accuracy of bite force correction results was studied. 257 samples were tested in the actual project, and the test results were compared with the proposed calculated formula results. Research result shows that the clip will break away from the original bite mark when the steel strand extends more than 4.5 mm. However, when the clip disengages during the actual test, the tension will be stopped in time, so the lift-off test will not change the effective prestress of prestressed steel strand under the anchorage and affect the project quality. When installing the clip, if the clip does not completely fit the taper hole of socket, the clip will have a large elastic pressing force in the lateral direction to form an additional friction force. The friction force will completely disappear when the clip is separated from the socket. The change of tension outside the anchorage is not obvious at this moment, so the slope of descending segment of tension test curve obtained by the lift-off method has a dispersion after the peak tension, and it is related to the clip installation precision. The bite force of socket in the lift-off test consists of the transient internal force redistributions under and outside the anchorage. The proposed calculation formula for clip bite force can eliminate the test error caused by the bite force between the clip and the socket, and improve the test accuracy by 6.78%. The test bite force in the actual project is larger than the mutation segment of tension test curve obtained by the lift-off method. Therefore, when using the lift-off method to test the prestressed steel strand, the effective prestress under the anchorage is the difference between the peak value of tension test curve obtained by the lift-off method and the bite force. 1 tab, 18 figs, 32 refs.
引文
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[20] 钟正强,戴典,袁建伟.基于虎克定理的预应力检测系统开发及应用[J].中南大学学报(自然科学版),2018,49(3):725-731.ZHONG Zheng-qiang,DAI Dian,YUAN Jian-wei.Development and application of prestress testing system based on Hooke theorem[J].Journal of Central South University (Science and Technology),2018,49(3):725-731.(in Chinese)
[21] 董雁,刘佳琪,张峰.锚下有效预应力检测仪器研发及工程应用[J].中外公路,2017,37(5):117-120.DONG Yan,LIU Jia-qi,ZHANG Feng.Instrument development and engineering application of effective prestressing test under anchor[J].Journal of China and Foreign Highway,2017,37(5):117-120.(in Chinese)
[22] 罗斌,唐树名,程晓辉,等.锚下预应力反拉检测技术[J].公路交通技术,2012(1):12-14,22.LUO Bin,TANG Shu-ming,CHENG Xiao-hui,et al.Techniques of reverse drawing detection for prestress under anchor[J].Technology of Highway and Transport,2012(1):12-14,22.(in Chinese)
[23] 夏静,袁建伟.反拉法锚下有效预应力检测方法研究[J].公路与汽运,2016(6):210-212.XIA Jing,YUAN Jian-wei.Research on detection method of effective prestress under anchor by lift-off method[J].Highways and Automotive Applications,2016(6):210-212.(in Chinese)
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[2] ROBERTSON I N.Prediction of vertical deflections for a long-span prestressed concrete bridge structure[J].Engineering Structures,2005,27(12):1820-1827.
[3] TAKáCS P F.Deformations in concrete cantilever bridges:observations and theoretical modeling[D].Trondheim:The Norwegian University of Science and Technology,2002.
[4] 付丹.预应力锚索工作应力的检测方法研究[D].北京:清华大学,2010.FU Dan.Working stress tests of prestressed tendons in ground anchorage[D].Beijing:Tsinghua University,2010.(in Chinese)
[5] 付丹,郭红仙,程晓辉,等.预应力锚索工作应力的检测方法——拉脱法的检测机制和试验研究[J].岩土力学,2012,33(8):2247-2252.FU Dan,GUO Hong-xian,CHENG Xiao-hui,et al.Working stress measurement of prestressed anchor cables:detection mechanism and experimental study of lift-off test[J].Rock and Soil Mechanics,2012,33(8):2247-2252.(in Chinese)
[6] 詹桂超,刘冠之.基于拉脱法的预应力钢绞线张拉力测试分析[J].公路与汽运,2016(3):191-193.ZHAN Gui-chao,LIU Guan-zhi.Test and analysis on prestressed steel strand tension test based on lift-off method[J].Highways and Automotive Applications,2016(3):191-193.(in Chinese)
[7] 赵煜,洪路加,周勇军.基于钢束应力测试的预应力混凝土箱梁承载力评估方法[J].长安大学学报(自然科学版),2019,39(1):61-69.ZHAO Yu,HONG Lu-jia,ZHOU Yong-jun.Bearing capacity assessment method for PC box girder by testing stress of tendon[J] Journal of Chang'an University (Natural Science Edition),2019,39(1):61-69.(in Chinese)
[8] 李瑞鸽.全预应力梁预应力损失的动力检测研究[D].武汉:华中科技大学,2005.LI Rui-ge.Prestress loss of full prestressed concrete beams by dynamic technology[D].Wuhan:Huazhong University of Science and Technology,2015.(in Chinese)
[9] 艾辉林,陈朝慰,戴文达.预应力梁锚下有效预应力的快速检测方法研究[J].世界桥梁,2015,43(4):42-46.AI Hui-lin,CHEN Chao-wei,DAI Wen-da.Study of rapid inspection method for under-anchorage effective prestress in prestressed beams[J].World Bridges,2015,43(4):42-46.(in Chinese)
[10] 喻国强.预应力混凝土桥梁有效预应力测试技术应用[D].西安:长安大学,2013.YU Guo-qiang.The application of prestressed concrete bridge effective prestressed testing technology[J].Xi’an:Chang’an University,2013.(in Chinese)
[11] 杨国立,李瑞鸽.预应力混凝土梁中预应力损失检测方法的发展与展望[J].四川建筑科学研究,2008,34(4):113-116.YANG Guo-li,LI Rui-ge.Development and prospect of prestress loss detection in prestressed concrete beams[J].Sichuan Building Science,2008,34(4):113-116.(in Chinese)
[12] 郭琦.复杂预应力体系梁式结构有效预应力预测理论与方法研究[D].西安:长安大学,2008.GUO Qi.Theory and method of effective prestress prediction of beam prestressed composite prestressed system[D].Xi’an:Chang’an University,2008.(in Chinese)
[13] XU Jiang,WU Xin-jun,SUN Peng-fei.Detecting broken-wire flaws at multiple locations in the same wire of prestressing strands using guided waves[J].Ultrasonics,2013,53(1):150-156.
[14] CHEN R H L,WISSAWAPAISAL K.An ultrasonic method for measuring tensile forces in a seven-wire prestressing strand[J].AIP Conference Proceedings,2002,615(1):1295-1302.
[15] 张奔牛,袁灿,陈卓敏,等.基于LC振荡的钢绞线应力测量研究[J].重庆交通大学学报(自然科学版),2017,36(3):8-12.ZHANG Ben-niu,YUAN Can,CHEN Zhuo-min,et al.Stress measurement of steel strands based on LC oscillation[J].Journal of Chongqing Jiaotong University (Natural Science),2017,36(3):8-12.(in Chinese)
[16] 贾巧燕.基于应力释放法的在役混凝土结构现存预应力确定研究[D].武汉:武汉理工大学,2008.JIA Qiao-yan.Study on the extant pre-stressed force of the concrete structure in service based on the stress release method[D].Wuhan:Wuhan University of Technology,2008.(in Chinese)
[17] 欧进萍,周智,王勃.FRP-OFBG智能复合筋及其在加筋混凝土梁中的应用[J].高技术通讯,2005,15(4):23-28.OU Jin-ping,ZHOU Zhi,WANG Bo.Smart FRP-OFBG bars and their application in reinforced concrete beams[J].Chinese High Technology Letters,2005,15(4):23-28.(in Chinese)
[18] 周智,武湛君,赵雪峰,等.混凝土结构的光纤光栅智能监测技术[J].功能材料,2003,34(3):344-348.ZHOU Zhi,WU Zhan-jun,ZHAO Xue-feng,et al.Smart monitoring technique of concrete structures based on optical fiber Bragg grating sensors[J].Journal of Functional Materials,2003,34(3):344-348.(in Chinese)
[19] 贺拴海,赵祥模,马建,等.公路桥梁检测及评价技术综述[J].中国公路学报,2017,30(11):63-80.HE Shuan-hai,ZHAO Xiang-mo,MA Jian,et al.Review of highway bridge inspection and condition assessment[J].China Journal of Highway and Transport,2017,30(11):63-80.(in Chinese)
[20] 钟正强,戴典,袁建伟.基于虎克定理的预应力检测系统开发及应用[J].中南大学学报(自然科学版),2018,49(3):725-731.ZHONG Zheng-qiang,DAI Dian,YUAN Jian-wei.Development and application of prestress testing system based on Hooke theorem[J].Journal of Central South University (Science and Technology),2018,49(3):725-731.(in Chinese)
[21] 董雁,刘佳琪,张峰.锚下有效预应力检测仪器研发及工程应用[J].中外公路,2017,37(5):117-120.DONG Yan,LIU Jia-qi,ZHANG Feng.Instrument development and engineering application of effective prestressing test under anchor[J].Journal of China and Foreign Highway,2017,37(5):117-120.(in Chinese)
[22] 罗斌,唐树名,程晓辉,等.锚下预应力反拉检测技术[J].公路交通技术,2012(1):12-14,22.LUO Bin,TANG Shu-ming,CHENG Xiao-hui,et al.Techniques of reverse drawing detection for prestress under anchor[J].Technology of Highway and Transport,2012(1):12-14,22.(in Chinese)
[23] 夏静,袁建伟.反拉法锚下有效预应力检测方法研究[J].公路与汽运,2016(6):210-212.XIA Jing,YUAN Jian-wei.Research on detection method of effective prestress under anchor by lift-off method[J].Highways and Automotive Applications,2016(6):210-212.(in Chinese)
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