共查询到20条相似文献，搜索用时 31 毫秒
1.
苏州胥江桥为预应力桥梁 ,桥型由预制梁形成连续梁和组合梁 ,本文主要介绍预应力铺束、张拉工艺、灌浆工艺。 相似文献
2.
宗长江 《石家庄铁路工程职业技术学院学报》2013,(4):37-41
红柳河特大桥48m简支箱梁预应力质量控制的关键是节段箱梁预制过程中的预应力孔道位置控制和节段拼装过程中的湿接缝预应力孔道位置控制。由于48m箱梁节段拼装预应力筋过长、弯曲较多都会加大预应力筋的孔道摩阻损失,因此,后张法在张拉前测试预应力孔道的摩阻力是确保施工质量的有效措施。预应力孔道的摩阻测试有效验证了孔道位置施工质量,给预应力张拉提供准确的施工参数,确保预应力张拉施工质量。 相似文献
3.
The anchor stress extent of a prestress anchor cable project has a direct relation with the project safety and performance. Prestressed tensioning method is a kind of nondestructive testing method, by which a reverse stretching load is applied on the external exposure section of anchor cable under construction or in service, and then the elongation variation of stress bars is measured to determine the anchor stress. We elaborated the theory and testing mechanism of prestressed tensioning method, and systematically studied key issues during the prestressed tensioning process of anchor cable by using physical model test, including the composition of tension stress-elongation curve, the variation of anchor stress, the compensation of locked anchor stress, and the judgment of anchor stress, and verified the theory feasibility of prestressed tensioning method. A case study on slope anchor cable of one highway project was conducted to further discuss on the test method, operation procedures and judgment of prestressed tensioning method on obtaining anchor stress, and then the test data of three situations were analyzed. The result provides a theoretical basis and technical base for the application of prestressed tensioning method to the evaluation of construction quality and operation conditions of anchor cable project. 相似文献
4.
杨关锋 《杨凌职业技术学院学报》2008,7(3):18-20
钢绞线预应力混凝土在桥梁工程中已普遍使用,作为质量控制双控指标的钢绞线张拉伸长值及锚固张拉力的确定,是大梁张拉成功的关键。本文着重概述了预制大梁施工工艺及过程质量控制的主要环节,供从事钢绞线预应力张拉人员参考。 相似文献
5.
INTRODUCTION The aging or deterioration of existing R. C.(reinforced concrete) or P. C. (prestressed concrete)structures is one of the major problems that modernengineers have to face. If the flexural or shear strengthof R. C. or P. C. structures is not sufficient to maintaintheir service functions, strengthening of these struc-tures becomes necessary. To date, steel plates havebeen used to strengthen concrete members. Usingcomposite plates to strengthen R.C. or P.C. structures… 相似文献
6.
Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part Ⅰ: Experimental study 总被引：2，自引：0，他引：2
This work is aimed at studying the strengthening of reinforced concrete (R. C.) beams using prestressed glass fiber-reinforced polymer (PGFRP). Carbon fiber-reinforced polymer (CFRP) has recently become popular for use as repair or rehabilitation material for deteriorated R. C. structures, but because CFRP material is very stiff, the difference in CFRP sheet and concrete material properties is not favorable for transferring the prestress from CFRP sheets to R. C. members. Glass fiber-reinforced polymer (GFRP) sheets with Modulus of Elasticity quite close to that of concrete was chosen in this study. The load-carrying capacities (ultimate loads) and the deflections of strengthened R. C. beams using GFRP and PGFRP sheets were tested and compared. T- and ⊥-shaped beams were used as the under-strengthened and over-strengthened beams. The GFRP sheets were prestressed to one-half their tensile capacities before being bonded to the T- and l-shaped R. C. beams. The prestressed tension in the PGFRP sheets caused cambers in the R. C. beams without cracks on the tensile faces. The PGFRP sheets also enhanced the load-carrying capacity. The test results indicated that T-shaped beams with GFRP sheets increased in load-carrying capacity by 55% while the same beams with PGFRP sheets could increase load-carrying capacity by 100%. The ⊥-shaped beams with GFRP sheets could increase load-carrying capacity by 97% while the same beams with PGFRP sheets could increase the loading-carrying capacity by 117%. Under the same external loads, beams with GFRP sheets underwent larger deflections than beams with PGFRP sheets. While GFRP sheets strengthen R. C. beams, PGFRP sheets decrease the beams' ductility, especially for the over-strengthened beams (⊥-shaped beams). 相似文献
7.
冉康 《淮南职业技术学院学报》2004,4(1):53-55
通过11根无粘结部分预应力高强混凝土梁，研究了影响裂缝闭合的主要因素；预应力筋配筋率、非预应力筋配筋率、跨高比、荷载作用方式，用无粘结配筋指标βpe和换算配筋率αpp这两个参数来反映对裂缝闭合弯矩的影响，应用名义拉应力建立了闭合弯矩计算公式；计算结果与试验结果吻合较好。 相似文献
8.
在总结已有预应力砼技术优缺点的基础上，提出横张预应力砼技术的基本概念与设计。它的使用能明显节约钢材、简化工艺、提高工效，具有很好的技术经济效益。 相似文献
9.
通过对配置HRB600非预应力钢筋的预应力混凝土梁进行受弯试验,分析了混凝土及非预应力钢筋应变的发展规律,研究了预应力筋预应力损失的计算方法,提出了试验梁短期抗弯刚度的计算修正公式。研究结果表明:试验梁跨中截面平均应变符合平截面假定,HRB600钢筋的受力过程呈现显著的三阶段发展规律;计算预应力筋的预应力损失σ_4和σ_5时,引入时间影响系数可以有效提高准确性;通过引入综合配筋率影响系数,可以有效提升试验梁的短期刚度计算精度,配置HRB600非预应力钢筋的预应力混凝土梁在正常使用阶段满足挠度限值要求。 相似文献
10.
Prestressed steel ultrahigh-strength reinforced concrete (PSURC) beam is a new type of prestressed concrete beam, which not only has a considerable compressive strength attributed to the ultrahigh strength concrete, but also ensures a certain degree of ductility at failure due to the existence of structural steel. Five of these beams were monotonically tested until shear failure to investigate the static shear performance including the failure pattern, load-deflection behavior, shear capacity, shear crack width and shear ductility. The experimental results show that these beams have superior shear capacity, crack control ability and shear ductility. To study the shear performance under repeated overloading, seven PSURC beams were loaded in cyclic test simultaneously. The overall shear performance of cycled beams is similar to that of uncycled beams at low load level but different at high load level. The shear capacity and crack control ability of cycled beams at high load level are reduced, whereas the shear ductility is improved. In addition, the influences of variables including the degree of prestress, stirrup ratio and load level on the shear performance of both uncycled and cycled beams were also discussed and compared, respectively. 相似文献
11.
结合工程实例介绍了无粘结预应力结构层施工过程及模板支撑、预应力钢筋的安装、张拉、封锚保护和砼的浇筑等方面的施工工艺,从施工技术和管理上有效地控制了工程质量。 相似文献
12.
The strain monitoring and stress analysis of a new type of post-prestressed tunnel liner were carried out. The instrumentation block of the tunnel liner, with the dimensions of 12.06 m in length, 6 500 mm in diameter, and 650 mm in thickness, was post-prestressed with the unbonded tendons, each of which consists of 8 pieces of double-looped strands and the axial spacing of the tendons is 500 mm. Concrete strain meters, rebar meters, load cell and zero-stress meters were installed for the strain monitoring. The tensioning loads were applied incrementally in three cycles (50%, 77% and 100%) at the concrete age of 28 d and the tensioning work lasted for 187.1 h. Strain readings were taken before and after each cycle during tensioning period and at the specified time interval after tensioning period. It is found that concrete creep developed over tensioning period is 30% of total strain and 41.5% of elastic strain respectively. Prestress force in the unbonded tendon and concrete stress in the liner were evaluated according to the observed strain variations. Both of them are time-dependent, and about 5.3%, 8.3% and 9.0% of the prestress losses are observed at the age of 1 d, 30 d and 60 d respectively after stressing. The distribution of prestress in the liner is relatively uniform and meets the design requirement. 相似文献
13.
Carbon fiber reinforced polymer(CFRP)bars were prestressed for the structural strengthening of 8 T-shaped rein-forced concrete (RC)beams of a 21-year-old bridge in China.The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory.The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit.The field construction processes of strengthening with CFRP bars-including grouting cracks,cutting groove,grouting epoxy and embedding CFRP bars,surface treating,banding with the U-type CFRP sheets,releasing external prestressed steel tendons-were introduced in detail.In order to evaluate the effectiveness of this strengthening method,field tests using vehicles as live load were applied before and after the retrofit.The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge,including the bending strength and stiffness,is enhanced.The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges.Therefore,the proposed strengthening technology is feasible and effective. 相似文献
14.
以一根预应力钢筋混凝土梁为例,利用MIDAS/FEA和ANSYS建立有限元模型,MIDAS/FEA模型中的预应力采用桁架单元法和钢筋单元法模拟,ANSYS模型中的预应力采用实体切分法、约束方程法以及节点耦合法模拟。分析结果表明,MIDAS/FEA和ANSYS在预应力作用下的计算结果相近,在静力学领域都能得到较为精确的结果;从建模的难易程度上说,MIDAS/FEA的钢筋单元法最为方便,而ANSYS通常需要运用APDL语言辅助建模,难度相对较大;ANSYS采用节点耦合法模拟预应力时,混凝土实体的网格需要划分较密才能取得较为精确的结果。 相似文献
15.
从我国预应力混凝土发展的角度,以某学校餐厅兼礼堂预应力框架梁为例,浅谈预应力混凝土的特性,介绍其材料选用、土建施工工艺及张拉施工工艺等,并对其今后发展进行了分析。. 相似文献
16.
Dynamic tests of three bonded and two unbonded full-prestressed concrete beams were carried out.The purpose was to seek the relation between prestressing force and natural frequency.Test results indicate that the frequency of prestressed concrete(PSC)beam increases with the increase in prestressing force approximately.The results are different from the dynamic characteristics of isotropic material beam subjected to compressive axial force which were put forward by Clough et al.The reason is that the beams were considered as isotropic,homogeneous,linear elastic material in the traditional analysis method.However,more accurate results are required in the analysis of frequency of PSC beam.The constitutive mode of PSC member is analyzed based on microstructure of concrete in this paper.The orthotropic linear elastic mode is used to analyze the relation between dynamic frequency and prestressing force of concrete beam,at the same time the equivalent stiffness of prestressed tendon relating to the prestressing force is added to the bending deformation stiffness of the beam.The analytical value agrees well with the test result,indicating that the current analysis method in this paper is feasible to full-prestressed concrete beam. 相似文献
17.
大跨预应力混凝土连续刚构桥墩梁结合部位受力复杂,且布置数量较多的预应力钢束,是刚构桥中的关键部位。结合昆明市城市三环路东段工程预应力混凝土连续刚构桥的设计方案,利用有限元分析软件ANSYS对墩梁固接区进行精细有限元局部分析,得到施工阶段及运营阶段墩梁固结区的应力分布。结果表明该结构预应力配束合理,施工阶段及运营阶段应力均满足设计规范要求。 相似文献
18.
Carbon fiber reinforced polymer （CFRP） bars were prestressed for the structural strengthening of 8 T-shaped reinforced concrete （RC） beams of a 21-year-old bridge in China. The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory. The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit. The field construction processes of strengthening with CFRP bars including grouting cracks, cutting groove, grouting epoxy and embedding CFRP bars, surface treating, banding with the U-type CFRP sheets, releasing external prestressed steel tendons-were introduced in detail. In order to evaluate the effectiveness of this strengthening method, field tests using vehicles as live load were applied before and after the retrofit. The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge, including the bending strength and stiffness, is enhanced. The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges. Therefore, the proposed strengthening technology is feasible and effective. 相似文献
19.
Analyses and computations of the natural frequencies of external prestressed concrete structures are the bases for studying the dynamic properties of such structures. We carded out dynamic tests on three types of external simply supported beams, pulling the beams gradually. Then vertical loads were applied to the beams while the frequencies and related coefficients were measured at every step. We calculated natural frequencies and the results indicate that natural frequencies increase as the prestressing force rises in the pre-crack stage, and decrease significantly during the post-crack stage. Substantial incoincidences exist between the calculated and experimental results for the frequency and its tendency to changel Based on the experimental results, we modified the stiffness and other parameters in the equations. The results calculated using the modified equations agree with experimental results well, so the modified eauations can be used nractically. 相似文献
20.
安阳某多层厂房的框架梁采用了后张曲线预应力混凝土结构,本文介绍了波纹管曲线放样、钢绞线编束、波纹管就位固定、钢绞线束张拉等工序的施工工艺,同时对曲线预应力选材进行了对比分析. 相似文献