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Deflection behavior of a prestressed concrete beam reinforced with carbon fibers at elevated temperatures

Mohammed FARUQI, Mohammed Sheroz KHAN

《结构与土木工程前沿(英文)》 2019年 第13卷 第1期   页码 81-91 doi: 10.1007/s11709-018-0468-4

摘要: Fiber reinforced polymer(FRP) have unique advantages like high strength to weight ratio, excellent corrosion resistance, improving deformability and cost effectiveness. These advantages have gained wide acceptance in civil engineering applications. FRP tendons for prestressing applications are emerging as one of the most promising technologies in the civil engineering industry. However, the behavior of such members under the influence of elevated temperatures is still unknown. The knowledge and application of this could lead to a cost effective and practical considerations in fire safety design. Therefore, this study examines the deflection behavior of the carbon fiber reinforced polymer(CFRP) prestressed concrete beam at elevated temperatures. In this article, an analytical model is developed which integrates the temperature dependent changes of effective modulus of FRP in predicting the deflection behavior of CFRP prestressed concrete beams within the range of practical temperatures. This model is compared with a finite element mode (FEM) of a simply supported concrete beam prestressed with CFRP subjected to practical elevated temperatures. In addition, comparison is also made with an indirect reference to the real behavior of the material. The results of the model correlated reasonably with the finite element model and the real behavior. Finally, a practical application is provided.

关键词: FRP     CFRP     concrete     elevated temperatures     deflections     prestress    

Flexural and longitudinal shear performance of precast lightweight steel–ultra-high performance concretecomposite beam

《结构与土木工程前沿(英文)》 2023年 第17卷 第5期   页码 704-721 doi: 10.1007/s11709-023-0941-6

摘要: In this study, the flexural and longitudinal shear performances of two types of precast lightweight steel–ultra-high performance concrete (UHPC) composite beams are investigated, where a cluster UHPC slab (CUS) and a normal UHPC slab (NUS) are connected to a steel beam using headed studs through discontinuous shear pockets and full-length shear pockets, respectively. Results show that the longitudinal shear force of the CUS is greater than that of the NUS, whereas the interfacial slip of the former is smaller. Owing to its better integrity, the CUS exhibits greater flexural stiffness and a higher ultimate bearing capacity than the NUS. To further optimize the design parameters of the CUS, a parametric study is conducted to investigate their effects on the flexural and longitudinal shear performances. The square shear pocket is shown to be more applicable for the CUS, as the optimal spacing between two shear pockets is 650 mm. Moreover, a design method for transverse reinforcement is proposed; the transverse reinforcement is used to withstand the splitting force caused by studs in the shear pocket and prevent the UHPC slab from cracking. According to calculation results, the transverse reinforcement can be canceled when the compressive strength of UHPC is 150 MPa and the volume fraction of steel fiber exceeds 2.0%.

关键词: precast steel–UHPC composite beam     flexural performance     longitudinal shear performance     parametric study     transverse reinforcement ratio    

Effect of eccentricity in reinforced concrete beam-column-slab connection under cyclic loading

Rooh ULLAH, Amjad NASEER, Muhammad FAHIM, Mohammad ASHRAF, Eid BADSHAH

《结构与土木工程前沿(英文)》 2021年 第15卷 第2期   页码 390-398 doi: 10.1007/s11709-021-0690-3

摘要: Beam–column connections are one of the most critical elements of reinforced concrete structures, especially in seismically active regions, and have been extensively evaluated experimentally and numerically. However, very limited experimental studies about eccentric reinforced concrete connections including the effect of connected slabs are available. This study presents the experimental results of two half-scale eccentric beam-column-slab connections subjected to quasi-static cyclic loading. The horizontal eccentricity ( ) is maintained at 12.5% and 25% of column width ( ) for specimens 1 and 2, respectively. The damage pattern, performance levels, displacement ductility ( ), energy dissipation, and connection strength and stiffness are compared for both specimens, and the effect of eccentricity is evaluated. It is concluded that the eccentricity has no significant effect on the lateral load carrying capacity; however, the overall strength degradation increases with the increase in eccentricity. Similarly, the elastic stiffness of specimen 2 decreased by 14% as the eccentricity increased from 12.5% to 25%; however, the eccentricity had no significant effect on the overall stiffness degradation. decreased by 43%, and the energy dissipation capacity decreased by 40% in specimen 2 with higher eccentricity. The story drifts corresponding to the performance levels of the life safety (LS) and collapse prevention (CP) were found to be 28% lesser in specimen 2 than in specimen 1.

关键词: corner connection     eccentricity     strength degradation     stiffness degradation     energy dissipation     performance levels    

Cyclic behavior of stiffened joints between concrete-filled steel tubular column and steel beam with

Chunyan QUAN,Wei WANG,Jian ZHOU,Rong WANG

《结构与土木工程前沿(英文)》 2016年 第10卷 第3期   页码 333-344 doi: 10.1007/s11709-016-0357-7

摘要: This paper presented an investigation on a stiffened joint in practical engineering which was between concrete-filled steel tubular column and steel beam with narrow outer diaphragm and partial joint penetration welds. Through the low-frequency cyclic loading test, the cyclic behavior and failure mode of the specimen were investigated. The results of the test indicated the failure mode and bearing capacity of the specimen which were influenced by the axial compression ratio of the concrete-filled tubular column. On the contrary, the inner diaphragm and inner stiffeners had limited impacts on the hysteretic behavior of the joint. There was no hysteresis damage fracture on the narrow outer diaphragm connected to the concrete-filled steel tubular column with partial joint penetration welds. Due to the excellent ductility and energy dissipating capacity, the proposed joint could be applied to the seismic design of high-rise buildings in highly intensive seismic region, but axial compression ratio should be controlled to avoid unfavorable failure modes.

关键词: narrow outer diaphragm     concrete-filled tubular column     joint     inner and outer stiffening     cyclic behavior    

三峡升船机塔柱横梁混凝土施工技术

余英

《中国工程科学》 2013年 第15卷 第9期   页码 27-32

摘要:

三峡升船机船厢室段塔柱承重结构的横梁混凝土浇筑施工难度大、复杂性高、无成熟技术可供参考。本文结合三峡升船机塔柱横梁混凝土浇筑的结构特点以及施工特性,总结了三峡升船机续建工程顶部横梁混凝土的施工技术,即采用分层、分块浇筑的办法,通过科学计算后进行合理的施工机械布置和浇筑施工管理,以保证塔柱横梁混凝土的施工质量。通过对贝雷架支撑系统的监测结果分析可知,贝雷架支撑系统的应力变形、挠度变形以及排架变形均满足施工承载要求,筒体位移亦满足技术要求,贝雷架支撑系统稳定、安全。三峡升船机塔柱横梁混凝土施工实践证明了本技术方案的有效性与可靠性,亦可为类似工程的施工组织设计与现场实施工作提供一定的参考。

关键词: 升船机     横梁     混凝土     施工缝     浇筑分层     三峡工程    

Experimental and statistical investigation of a new concrete-composite beam with encased polymer tube

Abdelmadjid SI SALEM,Souad AIT TALEB,Kamal AIT TAHAR

《结构与土木工程前沿(英文)》 2015年 第9卷 第2期   页码 154-162 doi: 10.1007/s11709-015-0296-8

摘要: A new concrete-composite beam with high mechanical performances to weight ratio is developed in this study. The proposed design technique consists to embed a cylindrical polymer tube wrapped by a GFRP Jacket in the mechanically ineffective concrete tensile zone. An experimental investigation is carried out on composite beams under bending loads until failure to evaluate the flexural capacity and the corresponding failure mechanisms. Based on the experimental results, statistical and preliminary reliability analyses using the FORM method are performed to assess the safety margin of the new beam. The confrontation between test and simulation results shows a satisfactory agreement, and represents a promising revelation regarding the improvement in terms of strength and ductility of such design compared to conventional reinforced concrete beams with traditional one.

关键词: design     GFRP-Jacket     polymer tube     test     reliability analysis    

Experimental study on shear behavior of reinforced concrete beams with web horizontal reinforcement

Dong XU,Yu ZHAO,Chao LIU

《结构与土木工程前沿(英文)》 2014年 第8卷 第4期   页码 325-336 doi: 10.1007/s11709-014-0080-1

摘要: In determining the shear capacity of reinforced concrete beams, current codes do not provide any calculation method to evaluate the influence of web horizontal reinforcement, although they exist as structural reinforcements (or skin reinforcement). The present paper comprises results of 11 reinforced concrete beams in an effort to investigate the influence of web horizontal reinforcement on the shear behavior of reinforced concrete beams. The primary design variables are the shear-span-depth ratio, different reinforcement ratio of stirrups and web horizontal reinforcement. Influence of web horizontal reinforcement on crack patterns and failure mode was studied. It was found that web horizontal reinforcement can increase the shear capacity of the beams and restrain growth of inclined cracks effectively. Test results are very valuable, as very few references of shear tests can be found focusing on the effect of web horizontal reinforcement on the shear capacity of the beams.

关键词: reinforced concrete beam     shear strength     web horizontal reinforcement     experiments    

Calculation methods of the crack width and deformation for concrete beams with high-strength steel bars

Jianmin ZHOU, Shuo CHEN, Yang CHEN

《结构与土木工程前沿(英文)》 2013年 第7卷 第3期   页码 316-324 doi: 10.1007/s11709-013-0211-0

摘要: Three groups of concrete beams reinforced with high-strength steel bars were tested, and the crack width and deformation of the specimens were observed and studied. To facilitate the predictions, two simplified formulations according to a theory developed by the first author were proposed. The advantages of the formulations were verified by the test data and compared with several formulas in different codes.

关键词: concrete beam     high-strength steel bar     crack width     deformation    

Analysis of stiffness and flexural strength of a reinforced concrete beam using an invented reinforcement

Nazim Abdul NARIMAN, Martin HUSEK, Ilham Ibrahim MOHAMMAD, Kaywan Othman AHMED, Diyako DILSHAD, Ibrahim KHIDR

《结构与土木工程前沿(英文)》 2021年 第15卷 第2期   页码 378-389 doi: 10.1007/s11709-021-0706-z

摘要: In this study, we conducted experimental tests on two specimens of reinforced concrete beams using a three-point bending test to optimize the flexure and stiffness designs. The first specimen is a reinforced concrete beam with an ordinary reinforcement, and the second specimen has an invented reinforcement system that consists of an ordinary reinforcement in addition to three additional bracings using steel bars and steel plates. The results of the flexure test were collected and analyzed, and the flexural strength, the rate of damage during bending, and the stiffness were determined. Finite element modeling was applied for both specimens using the LS-DYNA program, and the simulation results of the flexure test for the same outputs were determined. The results of the experimental tests showed that the flexural strength of the invented reinforcement system was significantly enhanced by 15.5% compared to the ordinary system. Moreover, the flexural cracks decreased to a significant extent, manifesting extremely small and narrow cracks in the flexure spread along the bottom face of the concrete. In addition, the maximum deflection for the invented reinforced concrete beam decreased to 1/3 compared to that of an ordinary reinforced concrete beam. The results were verified through numerical simulations, which demonstrated excellent similarities between the flexural failure and the stiffness of the beam. The invented reinforcement system exhibited a high capability in boosting the flexure design and stiffness.

关键词: three-point flexure test     softening stage     flexural crack     flexural strain    

砼非标准三点弯曲梁试件双K断裂参数

吴智敏,徐世烺,丁一宁,卢喜经,刘佳毅,丁生根

《中国工程科学》 2001年 第3卷 第4期   页码 76-81

摘要:

采用跨高比为2.5的非标准三点弯曲梁试件,利用在试验中测得的最大荷载Pmax及对应的裂缝口张开位移CMODc,根据渐近线性叠加假设,求得了砼裂缝亚临界扩展量∆ac。在此基础上,采用虚拟裂缝模型计算了不同初始缝长、不同试件髙度的砼非标准三点弯曲梁试件的起裂断裂韧度KiniIC、失稳断裂韧度KunIC及临界裂 缝尖端张开位移CTODc。计算结果表明,砼KunIC:与试件高度及初始缝高比无关;而KiniIC在初始缝髙比a0/h = 0.3〜0.5内,也是一稳定的常数且与试件高度无关。这说明砼双K断裂参数可以作为砼的材料常数。

关键词:     三点弯曲梁     断裂参数    

element analysis on the seismic behavior of side joint of Prefabricated Cage System in prefabricated concrete

Yunlin LIU, Shitao ZHU

《结构与土木工程前沿(英文)》 2019年 第13卷 第5期   页码 1095-1104 doi: 10.1007/s11709-019-0538-2

摘要: The Prefabricated Cage System (PCS) has the advantages of high bearing capacity and good ductility. Meanwhile, it is convenient for factory production and it is beneficial to the cost savings, construction period shortening. Side joint is the weak region of PCS concrete frame and has great influence on seismic behavior of the whole structure. Thus systematically study on the seismic behavior of PCS concrete side joint is necessary. This paper presents a finite element study on behavior of the side joint under seismic loading. In the finite element model, PCS concrete and the reinforced concrete (RC) is modeled by the solid element and fiber-beam element, respectively. The numerical results is compared with the experimental results and it is found that the results of model based on fiber-beam element is in better agreement with the experimental results than solid element model. In addition, the overall seismic behavior of the side joints in PCS concrete is better than that of the RC with the same strength.

关键词: PCS concrete side joint     numerical simulation     fiber-beam element joint model     solid element joint model     seismic behavior    

钢箱-混凝土组合梁正截面强度设计理论与试验研究

钟新谷,舒小娟,沈明燕,莫时旭,谢文

《中国工程科学》 2008年 第10卷 第10期   页码 47-53

摘要:

基于钢箱-混凝土组合梁的基本特性,提出了正截面强度设计理论,并分析梁宽厚比、混凝土套箍效应对正截面强度的影响,提出了该类组合截面的合理尺寸选择原则,分析表明钢箱-混凝土组合梁较空箱的承载力有明显提高,其受力性能明显改善。同时进行3根大比例钢箱-混凝土组合梁的模型试验研究,试验研究表明:钢箱-混凝土组合梁具有良好的抗弯性能和延性,极限承载力提高显著。钢箱-混凝土组合梁通过进一步的试验与理论研究有广泛的应用前景。

关键词: 钢箱-混凝土组合梁     设计理论     试验研究    

Shear behavior of ultra-high-performance concrete beams prestressed with external carbon fiber-reinforced

《结构与土木工程前沿(英文)》 2021年 第15卷 第6期   页码 1426-1440 doi: 10.1007/s11709-021-0783-z

摘要: The ultra-high-performance concrete (UHPC) and fiber-reinforced polymer (FRP) are well-accepted high-performance materials in the field of civil engineering. The combination of these advanced materials could contribute to improvement of structural performance and corrosion resistance. Unfortunately, only limited studies are available for shear behavior of UHPC beams reinforced with FRP bars, and few suggestions exist for prediction methods for shear capacity. This paper presents an experimental investigation on the shear behavior of UHPC beams reinforced with glass FRP (GFRP) and prestressed with external carbon FRP (CFRP) tendons. The failure mode of all specimens with various shear span to depth ratios from 1.7 to 4.5 was diagonal tension failure. The shear span to depth ratio had a significant influence on the shear capacity, and the effective prestressing stress affected the crack propagation. The experimental results were then applied to evaluate the equations given in different codes/recommendations for FRP-reinforced concrete structures or UHPC structures. The comparison results indicate that NF P 18-710 and JSCE CES82 could appropriately estimate shear capacity of the slender specimens with a shear span to depth ratio of 4.5. Further, a new shear design equation was proposed to take into account the effect of the shear span to depth ratio and the steel fiber content on shear capacity.

关键词: beam     external prestressing     ultra-high-performance concrete     fiber-reinforced polymers     shear behavior     design equation    

Long term performance of recycled concrete beams with different water–cement ratio and recycled aggregate

Jingwei YING; Feiming SU; Shuangren CHEN

《结构与土木工程前沿(英文)》 2022年 第16卷 第3期   页码 302-315 doi: 10.1007/s11709-022-0803-7

摘要: The purpose of this study is to reveal the service performance of recycled aggregate concrete (RAC) components for different values of water−cement ratio and replacement rate of recycled coarse aggregate (RCA). Generally, the concrete strength decreases with the increase of the replacement rate of RCA, in order to meet the strength requirements when changing the replacement rate of RCA, it is necessary to change the water−cement ratio at the same time. Therefore, the axial compressive strengths of prism with 25 mix proportions, the short-term mechanical properties and long-term deformation properties of reinforced concrete beams were tested respectively by changing water−cement ratio and RCA replacement rate. The bearing capacity and the strain nephogram of samples under different loads were obtained using the Digital Image Correlation (DIC) method, and a self-made gravity loading experimental device was used for long-term deformation investigation. Results showed that the damage pattern of RAC was the same as that of natural aggregate concrete (NAC), but the brittleness was more pronounced. The brittleness of concrete before failure can be reduced more effectively by adjusting the replacement rate of RCA than by adjusting the water−cement ratio. The water−cement ratio has an evident influence on the axial compressive strength and early creep of concrete, while the replacement rate of RCA has a remarkable effect on the long-term deformation of the concrete beams.

关键词: recycled concrete     beam     the replacement rate of recycled coarse aggregate     water–cement ratio     digital image correlation    

Seismic retrofitting of severely damaged RC connections made with recycled concrete using CFRP sheets

Yasmin MURAD, Wassel AL BODOUR, Ahmed ASHTEYAT

《结构与土木工程前沿(英文)》 2020年 第14卷 第2期   页码 554-568 doi: 10.1007/s11709-020-0613-8

摘要: An experimental and numerical program is carried out in this research to investigate the influence of CFRP sheets on the cyclic behavior of unconfined connections made with recycled concrete. Cement is partially replaced by silica fume, iron filling and pulverised fuel ash using two different percentages: 15% and 20%. Each specimen is partially loaded at the first stage and then specimens are repaired using CFRP sheets. The repaired specimens are then laterally loaded until failure. In addition, a finite element model is built in ABAQUS and verified using the experimental results. The experimental results have shown that the repaired specimens have regained almost double the capacity of the un-repaired specimens and hence the adopted repair configuration is recommended for retrofitting seismically vulnerable RC connections. Increasing cement replacement percentage by silica fume, fuel ash or iron filling from 15% to 20% has reduced joint carrying capacity and weakened the joint. It is recommended using 15% pulverised fuel ash or silica fume as cement partial replacement to enhance the strength and ultimate drift of beam-column joints under cyclic loading. Iron filling concrete is also recommended but the enhancement is relatively less than that found with pulverised fuel ash concrete and silica fume concrete.

关键词: retrofitting     CFRP sheets     recycled concrete     pulverised fuel ash     silica fume     cyclic     beam-column connections    

标题 作者 时间 类型 操作

Deflection behavior of a prestressed concrete beam reinforced with carbon fibers at elevated temperatures

Mohammed FARUQI, Mohammed Sheroz KHAN

期刊论文

Flexural and longitudinal shear performance of precast lightweight steel–ultra-high performance concretecomposite beam

期刊论文

Effect of eccentricity in reinforced concrete beam-column-slab connection under cyclic loading

Rooh ULLAH, Amjad NASEER, Muhammad FAHIM, Mohammad ASHRAF, Eid BADSHAH

期刊论文

Cyclic behavior of stiffened joints between concrete-filled steel tubular column and steel beam with

Chunyan QUAN,Wei WANG,Jian ZHOU,Rong WANG

期刊论文

三峡升船机塔柱横梁混凝土施工技术

余英

期刊论文

Experimental and statistical investigation of a new concrete-composite beam with encased polymer tube

Abdelmadjid SI SALEM,Souad AIT TALEB,Kamal AIT TAHAR

期刊论文

Experimental study on shear behavior of reinforced concrete beams with web horizontal reinforcement

Dong XU,Yu ZHAO,Chao LIU

期刊论文

Calculation methods of the crack width and deformation for concrete beams with high-strength steel bars

Jianmin ZHOU, Shuo CHEN, Yang CHEN

期刊论文

Analysis of stiffness and flexural strength of a reinforced concrete beam using an invented reinforcement

Nazim Abdul NARIMAN, Martin HUSEK, Ilham Ibrahim MOHAMMAD, Kaywan Othman AHMED, Diyako DILSHAD, Ibrahim KHIDR

期刊论文

砼非标准三点弯曲梁试件双K断裂参数

吴智敏,徐世烺,丁一宁,卢喜经,刘佳毅,丁生根

期刊论文

element analysis on the seismic behavior of side joint of Prefabricated Cage System in prefabricated concrete

Yunlin LIU, Shitao ZHU

期刊论文

钢箱-混凝土组合梁正截面强度设计理论与试验研究

钟新谷,舒小娟,沈明燕,莫时旭,谢文

期刊论文

Shear behavior of ultra-high-performance concrete beams prestressed with external carbon fiber-reinforced

期刊论文

Long term performance of recycled concrete beams with different water–cement ratio and recycled aggregate

Jingwei YING; Feiming SU; Shuangren CHEN

期刊论文

Seismic retrofitting of severely damaged RC connections made with recycled concrete using CFRP sheets

Yasmin MURAD, Wassel AL BODOUR, Ahmed ASHTEYAT

期刊论文