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1.
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   

2.
Fibre-reinforced polymer （FRP） composites were widely utilized in civil engineering structures as the retrofit of reinforced concrete （RC） columns. To design FRP jackets safely and economically, the behaviour of such columns should be predicted first. This paper is concerned with the analysis and behaviour of FRP-confined RC circular and rectangular short columns subjected to eccentric loading. A simple design-oriented stress-strain model for FRP-confined concrete in a section analysis was first proposed. The accuracy was then proved by two test data. Following that, a parametric study including amount of FRP confinement, FRP strain capacity, unconfined concrete strength and shape of column section is provided. Some conclusions were obtained at the end of the paper. The work here will provide a comprehensive understanding of the behaviour of FRP-confined concrete columns. The simplicity of the model also enables a simple equivalent stress block to be developed for direct use in practical design.  相似文献   

3.
The earthquake-resistant property of reinforced concrete members depends on the interaction between reinforcing bars and surrounding concrete through bond to a large degree,In this paper a general system aimed at dealing with the failure analysis of reinforced concrete columns strengthened with carbon-fiber-reinforced plastic(CFRP) sheets including bond-slip of the anchored reinforcing bars at the foot of the columns is presented.It is based on the yield design theory with a mixed modeling of the structue,according to which the concrete material is treated as a classical two-dimensional continuum ,whereas the longitudinal reinfocing bars are regarded as one-dimensional rods including bond-slip at the foot of the columns,In shear reinforced zones both the shear CFRP sheets and transvers reinforcing bars are incorporated in the analysis throuth a homogenization procedure and they are only in tesion ,The approach is then implemented numerically by means of the finite-element formulation,The numerical procedure produces accurate estimates for the loading-carrying capactiy of the shear members taken as an illustrative application by correlation with the experimental results,so the proposed approach is valid.  相似文献   

4.
Retrofitting of RC Slabs Against Explosive Loads   总被引：1，自引：0，他引：1  
With the increase of terrorist bomb attacks on buildings, there is a need to develop advanced retrofitting techniques to strengthen structures against blast loads. Currently, several guidelines including an Australian version for retrofitting reinforced concrete (RC) structures are available for the design of retrofitting systems against seismic and monotonic loads using steel or fibre reinforced polymer (FRP) plates that can be either adhesively bonded to the surface or near surface mounted to the concrete cover. However, none of these guidelines provide advice suitable for retrofitting structures subjected to blast loads. In this paper, numerical models are used to simulate the performance of retrofitted RC slabs subjected to blast loads. Airblast pressure distributions on the surface of the slabs estimated in a previous study are used as input in the analysis. A material damage model developed previously for concrete and an elastoplastic model for steel bars are employed in this research for modelling reinforced concrete behaviour due to explosive loads. The material models and blast loading are coded into a finite element computer program LS-DYNA3D to do the analysis. With the numerical model, parametric studies are conducted to investigate RC slabs retrofitted by either externally bonded or near-surface mounted plates or GFRP sheets subjected to blast loads. Discussion is made on the effectiveness of the retrofitting system for RC slabs against blast loads.  相似文献   

5.
The Australian love of ＂heritage＂ buildings （most of them are unreinforced masonry （URM） ） means that greater attention is required to secure their performance under seismic or impact loading in the future. A research project has been carried out to develop a new, economic and high strength retrofitting technique for masonry structures. A series of experimental testing on URM walls retrofitted with an innovative technique by cable system have been conducted. In this paper, an analytical model which is based on distinct element method（DEM） is developed to simulate the behaviour of retrofitted walls, in DEM, a solid is represented as an assembly of discrete blocks. Joints are modelled as interface between distinct bodies. It is a dynamic process and specially designed to model the behaviour of discontinuities. In order to assist the practising engineers to design this new retrofitted wall system, a simple mechanical model was also developed to predict the strength of the retrofitted walls. The results obtained from this simple mechanical model are compared with those from both experiments and distinct element model.  相似文献   

6.
Strengthening reinforced concrete （R. C.） beams using prestressed glass fiber-reinforced polymer （PGFRP） was studied experimentally as described in Part I of this paper （Huang et al., 2005）. In that paper, R. C. beams, R. C. beams with GFRP （glass fiber-reinforced polymer） sheets, and R. C. beams with PGFRP sheets were tested in both under-strengthened and over-strengthened cases. The test results showed that the load-carrying capacities （ultimate loads） of the beams with GFRP sheets were greater than those of the beams without polymer sheets. The load-carrying capacities of beams with PGFRP sheets were greater than those of beams with GFRP sheets. The objective of this work is to develop an analytical method to compute all of these load-carrying capacities. This analytical method is independent of the experiments and based only on the traditional R. C. and P. C. （prestressed concrete） theory. The analytical results accorded with the test results. It is suggested that this analytical method be used for analyzing and designing R. C. beams strengthened using GFRP or PGFRP sheets.  相似文献   

7.
In order to design and retrofit a subway station to resist an internal blast, the distribution of blast loading and its effects on structures should be investigated firstly. In this paper, the behav-ior of a typical subway station subjected to different internal blast loadings was analyzed. It briefly introduced the geometric characteristics and material constitutive model of an existing two-layer and three-span frame subway station. Then three cases of different explosive charges were consid-ered to analyze the dynamic responses of the structure. Finally, the maximum principal stress, dis-placement and velocity of the columns in the three cases were obtained and discussed. It con-cluded that the responses of the columns are sensitive to the charge of explosive and the distance from the detonation. It’s also found that the stairs between the two layers have significant effects on the distribution of the maximum principal stress of the columns in the upper layer. The explicit dynamic nonlinear finite element software——ANSYS/LS-DYNA was used in this study.  相似文献   

8.
The Australian love of "heritage" buildings (most of them are unreinforced masonry (URM)) means that greater attention is required to secure their performance under seismic or impact loading in the future. A research project has been carried out to develop a new, economic and high strength retrofitting technique for masonry structures. A series of experimental testing on URM walls retrofitted with an innovative technique by cable system have been conducted. In this paper, an analytical model which is based on distinct element method (DEM) is developed to simulate the behaviour of retrofitted walls. In DEM, a solid is represented as an assembly of discrete blocks. Joints are modelled as interface between distinct bodies. It is a dynamic process and specially designed to model the behaviour of discontinuities. In order to assist the practising engineers to design this new retrofitted wall system, a simple mechanical model was also developed to predict the strength of the retrofitted walls. The results obtained from this simple mechanical model are compared with those from both experiments and distinct element model.  相似文献   

9.
OpenSees is a well-recognized open source platform with high compatibility, and it has a well-developed fiber ele- ment method to cope with nonlinear structural analysis. Fiber reinforced polymer （FRP） confined concrete can effectively improve the seismic performance of concrete structures. However, sophisticated constitutive models for FRP confined concrete are not available in the current version of OpenSees. In this paper, after reviewing several typical FRP confined concrete constitutive models, a modified constitutive model for FRP confined concrete in circular sections was proposed based on Lain and Teng （2003）＇s model with four main modifications including the determination of FRP rupture strain, ultimate condition, envelope shape, and hysteretic rules. To embed the proposed constitutive model into OpenSees is a practical solution for engineering simulation. Hence, the secondary development of OpenSees New UserMat was briefly demonstrated and a set of critical steps were depicted in a flow chart. Finally, with the numerical implementations of a series of FRP confined concrete members covering a wide range of load cases, FRP confinement types and geometric properties, the utility and accuracy of the proposed model compared with Lam and Teng （2003）＇s model and new material secondary development in OpenSees were well validated.  相似文献   

10.
To retrofit and strengthen existing unreinforced masonry (URM) structures to resist the potential earthquake damages has become an important issue in Australia. In order to secure the performance of URM under seismic loading in the future, a research project was carried out aimed at developing a simple and high strength seismic retrofitting technique for masonry structures. A series of experimental testing on URM walls retrofitted with an innovative technique by cable system have been conducted. The results indicated that both the strength and ductility of the tested speci-mens were significantly enhanced with the technique. An analytical model which is based on Dis-tinct Element Method (DEM) has also been developed to simulate the behaviour of URM walls be-fore and after retrofitting. The model is then further developed by applying a seismic wave to the wall to simulate the wall behavior under earthquake loads before and after retrofitting.  相似文献   

11.
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   

12.
为改善锈蚀钢筋混凝土柱的抗震性能, 利用碳纤维布与角钢对锈蚀柱进行复合抗震加固. 试验共对12根试件进行了低周反复加载试验, 研究参量包括钢筋锈蚀程度、轴向荷载、碳纤维布层数和角钢用量. 试验结果表明, 利用碳纤维布和角钢复合加固锈蚀柱可以显著改善锈蚀柱的承载能力、延性和耗能能力. 复合加固后, 加固柱的强度和延性与锈蚀柱相比, 可分别提高0.9倍和1倍以上. 基于试验结果, 提出了计算加固构件屈服荷载、最大荷载和位移延性系数的简化公式, 计算结果与试验结果极为吻合.  相似文献   

13.
INTRODUCTION There is increased need in recent years for strengthening or rehabilitation of existing reinforced concrete structures adversely affected by overloading, construction material deterioration, seismic loads, structural deformation, etc. An effective method for increasing the shear capacity of reinforced concrete columns is the use of externally bonded carbon fiber reinforced plastic (CFRP) systems (ACI, 2002). FRP systems were first applied to reinforced concrete col-umns i…  相似文献   

14.
二次受力下碳纤维布加固梁抗弯性能试验研究   总被引：1，自引：0，他引：1  
进行了4根不同二次受力条件下碳纤维布加固的钢筋混凝土梁和1根对比混凝土梁的抗弯性能试验研究。试验及分析结果表明,用粘贴碳纤维布的方法来提高梁的承载力十分有效,且预加载的存在使加固梁的极限荷载降低;碳纤维布能有效约束裂缝的开展,但裂缝的数量增加和分布区域变大,且预加载的大小会影响加固梁裂缝的开展和分布;碳纤维布加固可以增强梁的刚度,但延性有所降低。  相似文献   

15.
有粘结预应力FRP筋混凝土梁受弯有限元模拟   总被引：1，自引：0，他引：1  
采用有限元软件ABAQUS对预应力FRP筋混凝土梁受弯性能进行模拟。通过降温法施加预应力,忽略预应力筋与混凝土之间的粘结滑移。在收敛度差调整到3%、线性受拉损伤值dt的峰值取为0.9时,模拟结果与他人的试验结果比较基本吻合。  相似文献   

16.
This paper presents the results of an experimental investigation on the response of pre-damaged reinforced concrete (RC) beam strengthened in shear using applied-epoxy unidirectional carbon fiber reinforced polymer (CFRP) sheet. The reasearch included four test rectangular simply supported RC beams in shear capacity. One is the control beam, two RC beams are damaged to a predetermined degree from ultimate shear capacity of the control beam, and the last beam is left without pre-damaged and then strengthened with using externally bonded carbon fiber reinforced polymer to upgrade their shear capacity. We focused on the damage degree to beams during strengthening, therefore, only the beams with side- bonded CFRPs strips and horizontal anchored strips were used. The results show the feasibility of using CFRPs to restore or increase the load-carrying capacity in the shear of damaged RC beams. The failure mode of all the CFRP-strengthened beams is debonding of CFRP vertical strips. Two prediction available models in ACI-440 and fib European code were compared with the experimental results.  相似文献   

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