预应力法加固混凝土轴心受压构件试验研究
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摘要
目前对轴心受压混凝土构件而言，常用的加固方法有混凝土加大截面法、外包钢加固法、碳纤维布加固法等。而这些方法各有其缺陷，如现场湿作业问题、养护及外观问题、灌浆材料或粘接剂的老化问题等。
加固结构属二次受力结构，加固前原结构已经承载受力产生应力、应变，而新加部分只有在新增荷载下，才开始受力。这样整个结构在二次荷载下，新加部分的应变将滞后于原构件总的应变水平。破坏时，新加部分将可能达不到自身的极限状态，其潜力得不到发挥。
预应力法加固可以使上述问题得到较好解决，它可以实现卸载和加固同步进行，部分或全部消除二次受力所引起的应变滞后现象。但这种方法对于受压构件难度较大，国内使用不多。本试验中采用专用螺栓千斤顶在恒定荷载水平下对混凝土柱角钢撑杆施加预压应力，使外包角钢在二次受力前即分担部分荷载，使混凝土应力水平和应变水平降低，达到卸载与加固同步进行的目的。
通过试验数据分析可见，预应力法加固轴心受压构件可以达到加固与卸载同步进行，使新加部分在二次受力相对于原混凝土的应变滞后现象得到较好的消除，加固后组合构件整体承载力得到显著提高，新加部分与原构件材料的承载潜力可以达到最大的发挥。预应力加固过程是干作业，施工速度快，不使用有机粘结剂，加固后占用空间小，加固效率高，适用于要求大幅度提高承载力及加固后占用空间小的混凝土结构，也适用于要求施工速度快，加固后使用年限长，工作环境温度高的结构。
合理控制预应力的大小，是发挥预应力加固法优势的一个关键。为此，需要估算原结构构件混凝土的应力应变水平。由于混凝土应力应变关系的非线性性质及其材性指标的离散性，如何比较准确地估算结构构件的原有应力应变水平是一个尚待进一步研究的问题。
试验中，还采用电阻应变计和光纤布喇格光栅传感器在加载过程中对加固构件进行同步测量，结果表明光纤布喇格光栅传感器是应用于土木工程检测的很有前途的新技术，有着广泛的应用前景。
Enlarging concrete section, enveloping iron and strengthening with carbon fiber sheet are the widely-used methods to strengthen concrete column under axial compression, although these methods have their respective defects: wet-work in construction sit, long time for curing and deformation of appearance, the aging of pouring compounds and so on.
The strengthened structure is the structure subjected to twice-loading. The old structures have worked and produced stress and strain before strengthening; the new parts just begin to work only under new loading. When the whole structure is loaded twice, the strain of new parts lag behind that of the old, so that the new parts cannot reach ultimate state when damaged.
The strengthening by prestressing may resolve the above-mentioned problems. In this way, unloading and strengthening can be achieved synchronously and strain lagging can be cleared up partly or fully. But the method for structure under axial compression is rarely used in our country because of its difficult manipulation. In this test, a special bolt-jack is used to exent of prestressing force to brace angles as the whole structure is under dead-load. In this state brace angles withstand partly load before twice-load and the stress and strain of concrete are decreased. In this way the aim of removal of load and strengthening can be reached.
The test data demonstrate that the column strengthening by the prestressing force can be removed load and strengthened synchronously and the lagging of strain of the new parts compared that of the old can be cleared up when twice-loaded. The bearing capacity of whole construction is increased remarkably and the material of both the new parts and the old reach ultimate states. The construction execution of prestressing work has many advantages such as: dry-work, rapidity, no organic adhesion agent, small space to be taken, the high efficiency of strengthening, so this way can be applied in the structures which request to improve bearing capacity largely and take small space after
strengthening as well as other structures which will work in long time and in high temperature.
The key making full use of strengthening by prestressing is to control prestressing. So estimation of stress and strain of the old structure is necessary and to estimate accurately the stress and strain of the old structure should be researched furtherly.
In this test a new method was adopted to check and test the behaviors of structures by using optical fiber Bragg grating sensors which realize the synchronous measurements with electricity-resistance gauges. The results show that optical fiber Bragg grating sensors has boundless prospects for checking in Civil Engineering.
加固结构属二次受力结构，加固前原结构已经承载受力产生应力、应变，而新加部分只有在新增荷载下，才开始受力。这样整个结构在二次荷载下，新加部分的应变将滞后于原构件总的应变水平。破坏时，新加部分将可能达不到自身的极限状态，其潜力得不到发挥。
预应力法加固可以使上述问题得到较好解决，它可以实现卸载和加固同步进行，部分或全部消除二次受力所引起的应变滞后现象。但这种方法对于受压构件难度较大，国内使用不多。本试验中采用专用螺栓千斤顶在恒定荷载水平下对混凝土柱角钢撑杆施加预压应力，使外包角钢在二次受力前即分担部分荷载，使混凝土应力水平和应变水平降低，达到卸载与加固同步进行的目的。
通过试验数据分析可见，预应力法加固轴心受压构件可以达到加固与卸载同步进行，使新加部分在二次受力相对于原混凝土的应变滞后现象得到较好的消除，加固后组合构件整体承载力得到显著提高，新加部分与原构件材料的承载潜力可以达到最大的发挥。预应力加固过程是干作业，施工速度快，不使用有机粘结剂，加固后占用空间小，加固效率高，适用于要求大幅度提高承载力及加固后占用空间小的混凝土结构，也适用于要求施工速度快，加固后使用年限长，工作环境温度高的结构。
合理控制预应力的大小，是发挥预应力加固法优势的一个关键。为此，需要估算原结构构件混凝土的应力应变水平。由于混凝土应力应变关系的非线性性质及其材性指标的离散性，如何比较准确地估算结构构件的原有应力应变水平是一个尚待进一步研究的问题。
试验中，还采用电阻应变计和光纤布喇格光栅传感器在加载过程中对加固构件进行同步测量，结果表明光纤布喇格光栅传感器是应用于土木工程检测的很有前途的新技术，有着广泛的应用前景。
Enlarging concrete section, enveloping iron and strengthening with carbon fiber sheet are the widely-used methods to strengthen concrete column under axial compression, although these methods have their respective defects: wet-work in construction sit, long time for curing and deformation of appearance, the aging of pouring compounds and so on.
The strengthened structure is the structure subjected to twice-loading. The old structures have worked and produced stress and strain before strengthening; the new parts just begin to work only under new loading. When the whole structure is loaded twice, the strain of new parts lag behind that of the old, so that the new parts cannot reach ultimate state when damaged.
The strengthening by prestressing may resolve the above-mentioned problems. In this way, unloading and strengthening can be achieved synchronously and strain lagging can be cleared up partly or fully. But the method for structure under axial compression is rarely used in our country because of its difficult manipulation. In this test, a special bolt-jack is used to exent of prestressing force to brace angles as the whole structure is under dead-load. In this state brace angles withstand partly load before twice-load and the stress and strain of concrete are decreased. In this way the aim of removal of load and strengthening can be reached.
The test data demonstrate that the column strengthening by the prestressing force can be removed load and strengthened synchronously and the lagging of strain of the new parts compared that of the old can be cleared up when twice-loaded. The bearing capacity of whole construction is increased remarkably and the material of both the new parts and the old reach ultimate states. The construction execution of prestressing work has many advantages such as: dry-work, rapidity, no organic adhesion agent, small space to be taken, the high efficiency of strengthening, so this way can be applied in the structures which request to improve bearing capacity largely and take small space after
strengthening as well as other structures which will work in long time and in high temperature.
The key making full use of strengthening by prestressing is to control prestressing. So estimation of stress and strain of the old structure is necessary and to estimate accurately the stress and strain of the old structure should be researched furtherly.
In this test a new method was adopted to check and test the behaviors of structures by using optical fiber Bragg grating sensors which realize the synchronous measurements with electricity-resistance gauges. The results show that optical fiber Bragg grating sensors has boundless prospects for checking in Civil Engineering.
引文
[1]中国工程建设标准化协会标准．混凝土结构加固技术规范CECS25：90．北京：中国计划出版社，1992
[2]葛培中．对预应力撑杆加固柱的探讨．建筑结构，2000年11月，第30卷第11期
[3]卓尚木，季直仓，卓昌志．钢筋混凝土结构事故分析与加固．北京：中国建筑工业出版社，2000．
[4]徐薇，朱华．采用体外预应力方法进行工程加固．安徽建筑，1999年6月．
[6]袁广林，吴庆安．钢筋混凝土结构的加固与修复．混凝土与水泥制品，1997年8月．
[7]S.K. Solomon, D.W. Smith and A.R. Cusens. Flexural tests of steel-concrete-steel Sandwiches.Magazine of Concrete Research. vol.28.No.94. March 1976.pp13-20.
[8]R. Jones, R. N.Swamy and T.H.Ang.Under and over reinforced concrete beams with glued steel plates.The international Journal of cerment composites and light weight concrete. Vol. 4. No.1 February 1982.pp19-32.
[9]R.N. Swamg, R. Jones. and J.W. Bloxham."Structural behavior of reinforced concrete beams strengthened by epoxy-bonded steel plates".The structural Engineer. Vol. 65A. No. 2. Feb. 1987.
[1O]R.N. Swamg et al.. The effects of external plate reinforcement on the strengthening of structurally by damaged RC beams.The Structural Engineer.Vol.67.No.3.Feb.1989.pp45-54
[11]R. Jones, R.N. Swamy. Plate separation and anchorage of reinforced concrete beams strengthened by epoxy-bonded steel plates. The Structural Engineer Vol. 66. No. 5/1. March. 1988.
[12]T.M. Robert. Approximate Analysis of shear and Normal stress concentrations in the Adhesive layer of plated RC beams.The Structural Engineer.Vol.67.No. 12 June. 1989. pp229-233.
[13]I.A. Basumbul, A.A. Gubati, G.T. AL-Sulaimani. and M.H. Baluch. "Repaired Reinforced Concrete Beams" ACI Materials Journal. July-August 1990
[14]R.N. Swamy et al.Strengthening for shear of RC beams by external plate bonding. The Structural Engineer. Vol.77.NO. 12. June.1999
[15]朱聘儒．混凝土框架外包钢节点的试验研究．苏州城建环保学院学报1994年02期
[16]田传谦，廖绍怀．高配筋外包钢高强混凝土小偏压柱试验研究．武汉水利电力大学学报1995年02期
[17]姜绍飞，张淑清，刘之洋，刘德清．外包钢轴压短柱的试验研究与性能分析．实验力学1997年02期
[18]刘匀，张林绪，姜维山，林冰．外包钢新材料灌浆加固钢筋混凝土的研究与实践．西安建筑科技大学学报(自然科学版)1997年04期
[19]万墨林，韩继云．混凝土结构加固技术．中国建筑工业出版社．1995．3
[20]张淑琴．外包钢混凝土使用阶段抗扭性能的试验研究．电力建设1998年11期
[21]廖绍怀，郝中原．外包钢高强混凝土小偏压中长柱试验研究．武汉城市建设学院学报1999年02期
[22]余有龙，刘治国等．基于悬臂梁的光纤光栅线性调谐．光学学报，1999年05期
[23]赵玉成，陈根祥等．Bragg光纤光栅．光通信技术，1995年04期
[24]刘志国，张艺兵等．光纤光栅技术及其发展．光通信技术，1996年02期
[25]廖绍怀，谢海滢，姜华．外包钢高强混凝土小偏压柱承载力直接计算法．武汉水利电力大学学报1999年03期
[26]栾天胜，许剑明．长兴桥加固试验研究简介．黑龙江交通科技1994年01期
[27]王天威．利用碳纤维材料加固结构物的现状．铁道建筑1994年03期
[28]杨延寿．微型管柱桩加固塌裂桥台的实践．结构工程师．1991．3
[29]张绍河．环氧树脂在粘钢加固钢筋砼构件中的应用．烟台大学学报(自然科学与工程版)1999年02期
[30]任玉贺．粘钢加固砼框架节点的抗震性能研究．同济大学硕士学位论文．1996．3
[31]孙耀东．纵向钢板粘钢加固钢筋混凝土受力机理研究．同济大学硕士学位论文．1997．4
[31]陈生汉．外包钢法对框架柱的加固．筑技术开发2001年04期
[32]符晶华，袁内镇，童金章．高层建筑框架柱加固计算原理及实例．建筑技术．第30卷第6期．1999年
[33]碳纤维加固混凝土技术性能评价．碳纤维加固混凝土技术性能评价．土木工程学报．建筑技术开发2001年11期
[34]李荣，佟晓利，颜子涵．碳纤维材料加固混凝土结构技术应用实践．建筑结构．工业建筑1998年11期
[35]蔡光汀，邹越，侯云芬．碳纤维加固混凝土结构的性能及应用技术．混凝土2001年10期
[2]葛培中．对预应力撑杆加固柱的探讨．建筑结构，2000年11月，第30卷第11期
[3]卓尚木，季直仓，卓昌志．钢筋混凝土结构事故分析与加固．北京：中国建筑工业出版社，2000．
[4]徐薇，朱华．采用体外预应力方法进行工程加固．安徽建筑，1999年6月．
[6]袁广林，吴庆安．钢筋混凝土结构的加固与修复．混凝土与水泥制品，1997年8月．
[7]S.K. Solomon, D.W. Smith and A.R. Cusens. Flexural tests of steel-concrete-steel Sandwiches.Magazine of Concrete Research. vol.28.No.94. March 1976.pp13-20.
[8]R. Jones, R. N.Swamy and T.H.Ang.Under and over reinforced concrete beams with glued steel plates.The international Journal of cerment composites and light weight concrete. Vol. 4. No.1 February 1982.pp19-32.
[9]R.N. Swamg, R. Jones. and J.W. Bloxham."Structural behavior of reinforced concrete beams strengthened by epoxy-bonded steel plates".The structural Engineer. Vol. 65A. No. 2. Feb. 1987.
[1O]R.N. Swamg et al.. The effects of external plate reinforcement on the strengthening of structurally by damaged RC beams.The Structural Engineer.Vol.67.No.3.Feb.1989.pp45-54
[11]R. Jones, R.N. Swamy. Plate separation and anchorage of reinforced concrete beams strengthened by epoxy-bonded steel plates. The Structural Engineer Vol. 66. No. 5/1. March. 1988.
[12]T.M. Robert. Approximate Analysis of shear and Normal stress concentrations in the Adhesive layer of plated RC beams.The Structural Engineer.Vol.67.No. 12 June. 1989. pp229-233.
[13]I.A. Basumbul, A.A. Gubati, G.T. AL-Sulaimani. and M.H. Baluch. "Repaired Reinforced Concrete Beams" ACI Materials Journal. July-August 1990
[14]R.N. Swamy et al.Strengthening for shear of RC beams by external plate bonding. The Structural Engineer. Vol.77.NO. 12. June.1999
[15]朱聘儒．混凝土框架外包钢节点的试验研究．苏州城建环保学院学报1994年02期
[16]田传谦，廖绍怀．高配筋外包钢高强混凝土小偏压柱试验研究．武汉水利电力大学学报1995年02期
[17]姜绍飞，张淑清，刘之洋，刘德清．外包钢轴压短柱的试验研究与性能分析．实验力学1997年02期
[18]刘匀，张林绪，姜维山，林冰．外包钢新材料灌浆加固钢筋混凝土的研究与实践．西安建筑科技大学学报(自然科学版)1997年04期
[19]万墨林，韩继云．混凝土结构加固技术．中国建筑工业出版社．1995．3
[20]张淑琴．外包钢混凝土使用阶段抗扭性能的试验研究．电力建设1998年11期
[21]廖绍怀，郝中原．外包钢高强混凝土小偏压中长柱试验研究．武汉城市建设学院学报1999年02期
[22]余有龙，刘治国等．基于悬臂梁的光纤光栅线性调谐．光学学报，1999年05期
[23]赵玉成，陈根祥等．Bragg光纤光栅．光通信技术，1995年04期
[24]刘志国，张艺兵等．光纤光栅技术及其发展．光通信技术，1996年02期
[25]廖绍怀，谢海滢，姜华．外包钢高强混凝土小偏压柱承载力直接计算法．武汉水利电力大学学报1999年03期
[26]栾天胜，许剑明．长兴桥加固试验研究简介．黑龙江交通科技1994年01期
[27]王天威．利用碳纤维材料加固结构物的现状．铁道建筑1994年03期
[28]杨延寿．微型管柱桩加固塌裂桥台的实践．结构工程师．1991．3
[29]张绍河．环氧树脂在粘钢加固钢筋砼构件中的应用．烟台大学学报(自然科学与工程版)1999年02期
[30]任玉贺．粘钢加固砼框架节点的抗震性能研究．同济大学硕士学位论文．1996．3
[31]孙耀东．纵向钢板粘钢加固钢筋混凝土受力机理研究．同济大学硕士学位论文．1997．4
[31]陈生汉．外包钢法对框架柱的加固．筑技术开发2001年04期
[32]符晶华，袁内镇，童金章．高层建筑框架柱加固计算原理及实例．建筑技术．第30卷第6期．1999年
[33]碳纤维加固混凝土技术性能评价．碳纤维加固混凝土技术性能评价．土木工程学报．建筑技术开发2001年11期
[34]李荣，佟晓利，颜子涵．碳纤维材料加固混凝土结构技术应用实践．建筑结构．工业建筑1998年11期
[35]蔡光汀，邹越，侯云芬．碳纤维加固混凝土结构的性能及应用技术．混凝土2001年10期