This study investigates the flexural performance of ultra-high performance concrete(UHPC)in reinforced concrete T-beams,focusing on the effects of interfacial treatments.Three concrete T-beam specimens were fabricated...This study investigates the flexural performance of ultra-high performance concrete(UHPC)in reinforced concrete T-beams,focusing on the effects of interfacial treatments.Three concrete T-beam specimens were fabricated and tested:a control beam(RC-T),a UHPC-reinforced beam with a chiseled interface(UN-C-50F),and a UHPC-reinforced beam featuring both a chiseled interface and anchored steel rebars(UN-CS-50F).The test results indicated that both chiseling and the incorporation of anchored rebars effectively created a synergistic combination between the concrete T-beam and the UHPC reinforcement layer,with the UN-CS-50F exhibiting the highest flexural resistance.The cracking load and ultimate load of UN-CS-50F were 221.5%and 40.8%,respectively,higher than those of the RC-T.Finite element(FE)models were developed to provide further insights into the behavior of the UHPCreinforced T-beams,showing a maximumdeviation of just 8%when validated against experimental data.A parametric analysis varied the height,thickness,andmaterial strength of the UHPC reinforcement layer based on the validated FE model,revealing that increasing the UHPC layer thickness from 30 to 50 mm improved the ultimate resistance by 20%while reducing the UHPC reinforcement height from 440 to 300 mm led to a 10%decrease in bending resistance.The interfacial anchoring rebars significantly reduced crack propagation and enhanced stress redistribution,highlighting the importance of strengthening interfacial bonds and optimizing geometric parameters ofUHPCfor improved T-beam performance.These findings offer valuable insights for the design and retrofitting of UHPC-reinforced bridge girders.展开更多
To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concret...To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concrete T-beams,destructive tests were conducted on full-scale pre-stressed concrete beams.Based on the measurement and ana-lysis of beam deflection,strain,and crack development under various loading levels during the research tests,combined with the verification coefficient indicators specified in the codes,the verification coefficients of bridges at different stages of damage can be examined.The results indicate that the T-beams experience complete,incom-plete linear,and non-linear stages during the destructive test process.In the complete linear elastic stage,both the deflection and bottom strain verification coefficients comply with the specifications,indicating a good structural load-bearing capacity no longer adheres to the code’s requirements.In the non-linear stage,both coefficients exhi-bit a sharp increase,resulting in a further decrease in the structure’s load-bearing capacity.According to the pro-visions of the current code,the beam can be in the incomplete linear stage when both values fall within the code’s specified range.The strain verification coefficient sourced from the compression zone at the bottom of theflange is not recommended for assessing the bridge’s load-bearing capacity.展开更多
This investigation examines the shear performance of concrete T-beams reinforced with thin layers of ultra-high performance concrete(UHPC)through an approach that integrates experimental evaluation,numerical simulatio...This investigation examines the shear performance of concrete T-beams reinforced with thin layers of ultra-high performance concrete(UHPC)through an approach that integrates experimental evaluation,numerical simulation,and practical project verification.The research is based on a real bridge,and in accordance with the similarity principle,three reduced-scale T-beams with varying UHPC thicknesses were fabricated and tested to examine their failure modes and shear behaviors.A finite element model was created to enhance understanding of how UHPC reinforces these structures,while also considering the effects of material strength and arrangement.In addition to the laboratory tests,the actual bridge was analyzed to assess the effectiveness of the proposed strengthening technique.Results indicated that concrete T-beams strengthened with 30 mm-thick layers of UHPC had significant improvements,including a 491%increase in shear stiffness,a 23.15%rise in ultimate resistance,and a 155%enhancement in deformability compared to unreinforced T-beams.Furthermore,these improvements continued to increase with the application of thicker UHPC layers.Using 120MPa-grade UHPC with a thickness of 50mmand an A-type arrangement ensured that the dynamic and static performance of the T-beambridge met established code requirements.This research highlights the potential of UHPC thin layers in effectively reinforcing concrete beams for enhanced shear performance.展开更多
As an evaluation index,the natural frequency has the advantages of easy acquisition and quantitative evaluation.In this paper,the natural frequency is used to evaluate the performance of external cable reinforced brid...As an evaluation index,the natural frequency has the advantages of easy acquisition and quantitative evaluation.In this paper,the natural frequency is used to evaluate the performance of external cable reinforced bridges.Numerical examples show that compared with the natural frequencies of first-order modes,the natural frequencies of higher-order modes are more sensitive and can reflect the damage situation and external cable reinforcement effect of T-beam bridges.For damaged bridges,as the damage to the T-beam increases,the natural frequency value of the bridge gradually decreases.When the degree of local damage to the beam reaches 60%,the amplitude of natural frequency change exceeds 10%for the first time.The natural frequencies of the firstorder vibration mode and higher-order vibration mode can be selected as indexes for different degrees of the damaged T-beam bridges.For damaged bridges reinforced with external cables,the traditional natural frequency of the first-order vibration mode cannot be used as the index,which is insensitive to changes in prestress of the external cable.Some natural frequencies of higher-order vibration modes can be selected as indexes,which can reflect the reinforcement effect of externally prestressed damaged T-beam bridges,and its numerical value increases with the increase of external prestressed cable force.展开更多
The objective of this research is to assess the seismic behavior of the continuous T-beam bridge located at Kulungou in Xinjiang.In addition to traditional static and modal analyses,this study introduces a novel appro...The objective of this research is to assess the seismic behavior of the continuous T-beam bridge located at Kulungou in Xinjiang.In addition to traditional static and modal analyses,this study introduces a novel approach by comprehensively examining the performance of the bridge during construction stages,under ultimate load capacities and seismic load.Compliance with regulatory standards is verified by the static analysis,which also yields a thorough comprehension of stress distribution across various stages of construction.By unveiling the initial 100 vibration modes,the modal analysis has significantly enhanced our comprehension and established a robust basis for the ensuing seismic analysis.A distinctive aspect of this research is its comprehensive exploration of the bridge’s seismic behavior under E1 and E2 earthquake excitations.Under E1 earthquake excitation,the response spectrum analysis confirms the adequacy of the bridge piers’strength according to seismic design criteria,whereas the time-history analysis conducted under E2 ground motion reveals the bridge’s robust resistance to strong earthquakes.This study also undertakes a comparative assessment of the seismic behavior of the bridge,contrasting its performance with lead-rubber bearings against that with high-damping rubber bearings.According to the study’s findings,both types of bearings demonstrate their efficacy in mitigating seismic responses,thereby emphasizing their potential as innovative approaches to enhance the resilience of bridges.A notable contribution of this research lies in its assessment of seismic performance indicators,namely hysteresis curves,backbone curves,and ductility coefficients,utilizing Pushover analysis.By conducting a thorough evaluation,a more profound insight into the seismic performance of bridge piers is gained.In conclusion,the study explores how earthquake wave intensity and aftershocks affect the seismic response of bridge piers,showing a substantial increase in seismic response with intensifying wave magnitude and the potential for aftershocks to aggravate damage to compromised structures.The importance of incorporating these factors in the seismic design and retrofitting of bridges is underscored by these discoveries.This study,in its entirety,proposes a fresh and comprehensive methodology to assess the seismic performance of continuous T-beam bridges,furnishing valuable perspectives and innovative remedies to augment the seismic resilience of bridges in earthquake-prone zones.展开更多
The failure behavior of the precast prestressed concrete T girder was investigated by destructive test and finite-element analysis,and the mid-span deflection,girder stiffness and the variation of the cross section st...The failure behavior of the precast prestressed concrete T girder was investigated by destructive test and finite-element analysis,and the mid-span deflection,girder stiffness and the variation of the cross section strain in the loading process were obtained,and the mechanical properties,mechanical behavior,elastic and plastic behavior and ultimate bearing capacity of T girder with large span were revealed.Furthermore,the relationship between the beam stiffness degradation,the neutral axis in cross-section,steel yielding and concrete cracking are investigated and analyzed.A method was proposed to predict the residual bearing capacity of a bridge based on the variation of the position of the cross section strain distribution and the section neutral axis,which provided a theoretical basis for predicting the stiffness detection and carrying capacity assessment of prestressed concrete beam.展开更多
The shear performance, modes of failure, and strain analysis of simply supported reinforced concrete （RC） T-beams, externally strengthened in shear using epoxy bonded glass fiber reinforced polymer （GFRP） strips a...The shear performance, modes of failure, and strain analysis of simply supported reinforced concrete （RC） T-beams, externally strengthened in shear using epoxy bonded glass fiber reinforced polymer （GFRP） strips are focused in the present paper. Six RC T-beams of 2.5 m span without shear reinforcement are cast. Three beams are used as control specimens and rest three beams are strengthened in shear with GFRP strips in U-shape, side bonded at 45° and 90° to the longitudinal axis of the beam. All the beams are tested in a Universal Testing Machine. The test results demonstrate the feasibility of using an externally applied, epoxy-bonded GFRP strips to restore or increase the shear strength of RC T-beams. It is also observed that the RC T-beams strengthened by diagonal side strips outperformed those strengthened with vertical side strips.展开更多
In recent years, prestressed concrete members are widely used in bridge beam and slab members because of its advantages of good tensile properties of steel strand and scientific and reasonable stress of members.In the...In recent years, prestressed concrete members are widely used in bridge beam and slab members because of its advantages of good tensile properties of steel strand and scientific and reasonable stress of members.In the construction of small span bridges in Fujian, Chongqing, Sichuan, Yunnan and other southern provinces, post tensioned precast prestressed T-beams are widely used in engineering practice. The construction method has been very mature, with obvious economic and social benefits.Precast prestressed T-beam is to offset all or part of the tensile stress due to external load by pre stressing the flexural concrete members by tensioning steel strand, so as to enhance the bearing capacity of precast T-beam. The pre stressing is transformed into the stress under the anchor through jack, anchorage, clip, etc., and applied to the precast members, which is an important guarantee for the quality of precast members. In engineering practice, due to the deformation of anchorage, elastic compression and shrinkage creep of concrete, relaxation of prestressed tendons, construction quality defects and other factors, tensile stress loss will be caused, resulting in insufficient effective stress under the anchor. It directly affects the bearing capacity and durability of precast T-beam. Based on the construction practice of prestressed tension of precast T-beam in capacity expansion project of Chongqing Changsha expressway, this paper finds out and lists the construction quality defects that affect the effective stress under the anchor of precast T-beam, and summarizes some construction quality control measures to solve the prestress loss under the anchor.展开更多
Recently,inverted T-beams have been used in reinforced concrete(RC)bridges to support transverse precast stringers.Inverted T-beams,contrary to practice with conventional beams,are loaded on the flanges upper surface....Recently,inverted T-beams have been used in reinforced concrete(RC)bridges to support transverse precast stringers.Inverted T-beams,contrary to practice with conventional beams,are loaded on the flanges upper surface.This loading configuration causes hanger failure due to the generation of vertical tensile stresses near the bottom of the web.The key purpose of this study is to investigate the efficiency of vertical external prestressing stainless-steel bars in mitigating non-ductile hanger failure in reinforced concrete inverted T-beams.An experimental study on six inverted-T beams,including two un-strengthened specimens,was carried out.The study showed that the value of the prestressing level had a considerable impact on the performance of hanger mechanism in relation to crack pattern,ultimate loads,cracking behavior,load-deflection,strains,and ductility.The experimental results indicated that the suggested method for strengthening inverted T-beams had efficacy in reducing the seriousness of the non-ductile hanger failure and resulted in a strength increase of up to 53% when compared to that of the un-strengthened specimen.Additionally,two analytical models for estimating the hanger capacity and the average crack width of the strengthened RC inverted T-beams were proposed.The models that were proposed exhibited a high degree of agreement with the experimental results.展开更多
The provision of transverse openings in floor beams to facilitate the passage of utility pipes and service ducts not only results in a more systematic layout of pipes and ducts,it also translates into substantial econ...The provision of transverse openings in floor beams to facilitate the passage of utility pipes and service ducts not only results in a more systematic layout of pipes and ducts,it also translates into substantial economic savings in the construction of a multi-storey building.In this paper,ultimate load analysis of statically loaded simply supported pretensioned inverted T-beams with circular web openings is presented.Major findings relevant to ultimate load analysis of pretensioned beams with circular web openings are summarized.An attempt has been made to answer the frequently asked questions related to ultimate load analysis on multiple circular web open-ings.It has been shown that the analysis method for pretensioned beams with multiple large circular web openings can be further simplified without sacrificing rationality.展开更多
针对高速公路改扩建项目中既有桥梁因桥下净空不足需抬升纵断面的问题,该文以广深高速改扩建项目中32.5 m T梁桥改造为研究对象,采用碳排放因子法,测算断柱式顶升、垫石改造为桥墩、拆除重建3种改造方案在不同抬高值时的碳排放量,并对...针对高速公路改扩建项目中既有桥梁因桥下净空不足需抬升纵断面的问题,该文以广深高速改扩建项目中32.5 m T梁桥改造为研究对象,采用碳排放因子法,测算断柱式顶升、垫石改造为桥墩、拆除重建3种改造方案在不同抬高值时的碳排放量,并对比分析相应的建安费。结果表明:当桥梁纵面抬升到一定高度时,断柱式顶升和拆除重建方案经济效益基本相当,但顶升方案碳排放总量显著低于拆除重建方案;在断柱顶升方案中,材料生产碳排放占86%,场外运输占2%,施工直接碳排放占12%,表明碳排放主要来源为材料生产,其次为施工机械。该研究发现:顶升改造方案不仅符合国家“碳达峰、碳中和”战略目标,还在一定条件下与拆除重建方案经济效益相当,可为桥梁顶升工程方案比选决策提供有力参考。展开更多
基金The National Natural Science Foundation of China(Grant#52278161)the Science and Technology Project of Guangzhou(Grant#2024A04J9888)the Guangdong Basic and Applied Basic Research Foundation(Grant#2023A1515010535).
文摘This study investigates the flexural performance of ultra-high performance concrete(UHPC)in reinforced concrete T-beams,focusing on the effects of interfacial treatments.Three concrete T-beam specimens were fabricated and tested:a control beam(RC-T),a UHPC-reinforced beam with a chiseled interface(UN-C-50F),and a UHPC-reinforced beam featuring both a chiseled interface and anchored steel rebars(UN-CS-50F).The test results indicated that both chiseling and the incorporation of anchored rebars effectively created a synergistic combination between the concrete T-beam and the UHPC reinforcement layer,with the UN-CS-50F exhibiting the highest flexural resistance.The cracking load and ultimate load of UN-CS-50F were 221.5%and 40.8%,respectively,higher than those of the RC-T.Finite element(FE)models were developed to provide further insights into the behavior of the UHPCreinforced T-beams,showing a maximumdeviation of just 8%when validated against experimental data.A parametric analysis varied the height,thickness,andmaterial strength of the UHPC reinforcement layer based on the validated FE model,revealing that increasing the UHPC layer thickness from 30 to 50 mm improved the ultimate resistance by 20%while reducing the UHPC reinforcement height from 440 to 300 mm led to a 10%decrease in bending resistance.The interfacial anchoring rebars significantly reduced crack propagation and enhanced stress redistribution,highlighting the importance of strengthening interfacial bonds and optimizing geometric parameters ofUHPCfor improved T-beam performance.These findings offer valuable insights for the design and retrofitting of UHPC-reinforced bridge girders.
文摘To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concrete T-beams,destructive tests were conducted on full-scale pre-stressed concrete beams.Based on the measurement and ana-lysis of beam deflection,strain,and crack development under various loading levels during the research tests,combined with the verification coefficient indicators specified in the codes,the verification coefficients of bridges at different stages of damage can be examined.The results indicate that the T-beams experience complete,incom-plete linear,and non-linear stages during the destructive test process.In the complete linear elastic stage,both the deflection and bottom strain verification coefficients comply with the specifications,indicating a good structural load-bearing capacity no longer adheres to the code’s requirements.In the non-linear stage,both coefficients exhi-bit a sharp increase,resulting in a further decrease in the structure’s load-bearing capacity.According to the pro-visions of the current code,the beam can be in the incomplete linear stage when both values fall within the code’s specified range.The strain verification coefficient sourced from the compression zone at the bottom of theflange is not recommended for assessing the bridge’s load-bearing capacity.
基金The Science and Technology Project of Guangzhou(Grant#2024A04J9888)the National Natural Science Foundation of China(Grant#52278161)the Guangdong Basic and Applied Basic Research Foundation(Grant#2023A1515010535).
文摘This investigation examines the shear performance of concrete T-beams reinforced with thin layers of ultra-high performance concrete(UHPC)through an approach that integrates experimental evaluation,numerical simulation,and practical project verification.The research is based on a real bridge,and in accordance with the similarity principle,three reduced-scale T-beams with varying UHPC thicknesses were fabricated and tested to examine their failure modes and shear behaviors.A finite element model was created to enhance understanding of how UHPC reinforces these structures,while also considering the effects of material strength and arrangement.In addition to the laboratory tests,the actual bridge was analyzed to assess the effectiveness of the proposed strengthening technique.Results indicated that concrete T-beams strengthened with 30 mm-thick layers of UHPC had significant improvements,including a 491%increase in shear stiffness,a 23.15%rise in ultimate resistance,and a 155%enhancement in deformability compared to unreinforced T-beams.Furthermore,these improvements continued to increase with the application of thicker UHPC layers.Using 120MPa-grade UHPC with a thickness of 50mmand an A-type arrangement ensured that the dynamic and static performance of the T-beambridge met established code requirements.This research highlights the potential of UHPC thin layers in effectively reinforcing concrete beams for enhanced shear performance.
基金supported by Henan Province Science and Technology Research Funding Project(No.222102320129)the Key Research Project of Henan Higher Education Institutions(Grant Nos.22A560004,22A56005).
文摘As an evaluation index,the natural frequency has the advantages of easy acquisition and quantitative evaluation.In this paper,the natural frequency is used to evaluate the performance of external cable reinforced bridges.Numerical examples show that compared with the natural frequencies of first-order modes,the natural frequencies of higher-order modes are more sensitive and can reflect the damage situation and external cable reinforcement effect of T-beam bridges.For damaged bridges,as the damage to the T-beam increases,the natural frequency value of the bridge gradually decreases.When the degree of local damage to the beam reaches 60%,the amplitude of natural frequency change exceeds 10%for the first time.The natural frequencies of the firstorder vibration mode and higher-order vibration mode can be selected as indexes for different degrees of the damaged T-beam bridges.For damaged bridges reinforced with external cables,the traditional natural frequency of the first-order vibration mode cannot be used as the index,which is insensitive to changes in prestress of the external cable.Some natural frequencies of higher-order vibration modes can be selected as indexes,which can reflect the reinforcement effect of externally prestressed damaged T-beam bridges,and its numerical value increases with the increase of external prestressed cable force.
基金Supported by the Scientific and Technological Research and Development Program of Xinjiang Transportation Investment(Group)Co.,Ltd.:XJJTZKX-FWCG-202312-0456。
文摘The objective of this research is to assess the seismic behavior of the continuous T-beam bridge located at Kulungou in Xinjiang.In addition to traditional static and modal analyses,this study introduces a novel approach by comprehensively examining the performance of the bridge during construction stages,under ultimate load capacities and seismic load.Compliance with regulatory standards is verified by the static analysis,which also yields a thorough comprehension of stress distribution across various stages of construction.By unveiling the initial 100 vibration modes,the modal analysis has significantly enhanced our comprehension and established a robust basis for the ensuing seismic analysis.A distinctive aspect of this research is its comprehensive exploration of the bridge’s seismic behavior under E1 and E2 earthquake excitations.Under E1 earthquake excitation,the response spectrum analysis confirms the adequacy of the bridge piers’strength according to seismic design criteria,whereas the time-history analysis conducted under E2 ground motion reveals the bridge’s robust resistance to strong earthquakes.This study also undertakes a comparative assessment of the seismic behavior of the bridge,contrasting its performance with lead-rubber bearings against that with high-damping rubber bearings.According to the study’s findings,both types of bearings demonstrate their efficacy in mitigating seismic responses,thereby emphasizing their potential as innovative approaches to enhance the resilience of bridges.A notable contribution of this research lies in its assessment of seismic performance indicators,namely hysteresis curves,backbone curves,and ductility coefficients,utilizing Pushover analysis.By conducting a thorough evaluation,a more profound insight into the seismic performance of bridge piers is gained.In conclusion,the study explores how earthquake wave intensity and aftershocks affect the seismic response of bridge piers,showing a substantial increase in seismic response with intensifying wave magnitude and the potential for aftershocks to aggravate damage to compromised structures.The importance of incorporating these factors in the seismic design and retrofitting of bridges is underscored by these discoveries.This study,in its entirety,proposes a fresh and comprehensive methodology to assess the seismic performance of continuous T-beam bridges,furnishing valuable perspectives and innovative remedies to augment the seismic resilience of bridges in earthquake-prone zones.
基金the support from the Program for Natural Science Foundation of Zhejiang Province(LY16E080006)National Natural Science Foundation of China(51378240)+1 种基金2015 Jiangsu provincial building energy saving and construction industry science and technology project2016 Jiangsu provincial construction industry modernization base project.
文摘The failure behavior of the precast prestressed concrete T girder was investigated by destructive test and finite-element analysis,and the mid-span deflection,girder stiffness and the variation of the cross section strain in the loading process were obtained,and the mechanical properties,mechanical behavior,elastic and plastic behavior and ultimate bearing capacity of T girder with large span were revealed.Furthermore,the relationship between the beam stiffness degradation,the neutral axis in cross-section,steel yielding and concrete cracking are investigated and analyzed.A method was proposed to predict the residual bearing capacity of a bridge based on the variation of the position of the cross section strain distribution and the section neutral axis,which provided a theoretical basis for predicting the stiffness detection and carrying capacity assessment of prestressed concrete beam.
文摘The shear performance, modes of failure, and strain analysis of simply supported reinforced concrete （RC） T-beams, externally strengthened in shear using epoxy bonded glass fiber reinforced polymer （GFRP） strips are focused in the present paper. Six RC T-beams of 2.5 m span without shear reinforcement are cast. Three beams are used as control specimens and rest three beams are strengthened in shear with GFRP strips in U-shape, side bonded at 45° and 90° to the longitudinal axis of the beam. All the beams are tested in a Universal Testing Machine. The test results demonstrate the feasibility of using an externally applied, epoxy-bonded GFRP strips to restore or increase the shear strength of RC T-beams. It is also observed that the RC T-beams strengthened by diagonal side strips outperformed those strengthened with vertical side strips.
文摘In recent years, prestressed concrete members are widely used in bridge beam and slab members because of its advantages of good tensile properties of steel strand and scientific and reasonable stress of members.In the construction of small span bridges in Fujian, Chongqing, Sichuan, Yunnan and other southern provinces, post tensioned precast prestressed T-beams are widely used in engineering practice. The construction method has been very mature, with obvious economic and social benefits.Precast prestressed T-beam is to offset all or part of the tensile stress due to external load by pre stressing the flexural concrete members by tensioning steel strand, so as to enhance the bearing capacity of precast T-beam. The pre stressing is transformed into the stress under the anchor through jack, anchorage, clip, etc., and applied to the precast members, which is an important guarantee for the quality of precast members. In engineering practice, due to the deformation of anchorage, elastic compression and shrinkage creep of concrete, relaxation of prestressed tendons, construction quality defects and other factors, tensile stress loss will be caused, resulting in insufficient effective stress under the anchor. It directly affects the bearing capacity and durability of precast T-beam. Based on the construction practice of prestressed tension of precast T-beam in capacity expansion project of Chongqing Changsha expressway, this paper finds out and lists the construction quality defects that affect the effective stress under the anchor of precast T-beam, and summarizes some construction quality control measures to solve the prestress loss under the anchor.
文摘Recently,inverted T-beams have been used in reinforced concrete(RC)bridges to support transverse precast stringers.Inverted T-beams,contrary to practice with conventional beams,are loaded on the flanges upper surface.This loading configuration causes hanger failure due to the generation of vertical tensile stresses near the bottom of the web.The key purpose of this study is to investigate the efficiency of vertical external prestressing stainless-steel bars in mitigating non-ductile hanger failure in reinforced concrete inverted T-beams.An experimental study on six inverted-T beams,including two un-strengthened specimens,was carried out.The study showed that the value of the prestressing level had a considerable impact on the performance of hanger mechanism in relation to crack pattern,ultimate loads,cracking behavior,load-deflection,strains,and ductility.The experimental results indicated that the suggested method for strengthening inverted T-beams had efficacy in reducing the seriousness of the non-ductile hanger failure and resulted in a strength increase of up to 53% when compared to that of the un-strengthened specimen.Additionally,two analytical models for estimating the hanger capacity and the average crack width of the strengthened RC inverted T-beams were proposed.The models that were proposed exhibited a high degree of agreement with the experimental results.
基金The authors gratefully acknowledge the financial support from the Universiti Malaysia Pahang(UMP)through a short-term grant(Grant No.FR56398)from the Ministry of Science,Technology and Innovation(MOSTI)through an e-science fund(Grant No.03-02-03 SF0115).
文摘The provision of transverse openings in floor beams to facilitate the passage of utility pipes and service ducts not only results in a more systematic layout of pipes and ducts,it also translates into substantial economic savings in the construction of a multi-storey building.In this paper,ultimate load analysis of statically loaded simply supported pretensioned inverted T-beams with circular web openings is presented.Major findings relevant to ultimate load analysis of pretensioned beams with circular web openings are summarized.An attempt has been made to answer the frequently asked questions related to ultimate load analysis on multiple circular web open-ings.It has been shown that the analysis method for pretensioned beams with multiple large circular web openings can be further simplified without sacrificing rationality.
文摘针对高速公路改扩建项目中既有桥梁因桥下净空不足需抬升纵断面的问题,该文以广深高速改扩建项目中32.5 m T梁桥改造为研究对象,采用碳排放因子法,测算断柱式顶升、垫石改造为桥墩、拆除重建3种改造方案在不同抬高值时的碳排放量,并对比分析相应的建安费。结果表明:当桥梁纵面抬升到一定高度时,断柱式顶升和拆除重建方案经济效益基本相当,但顶升方案碳排放总量显著低于拆除重建方案;在断柱顶升方案中,材料生产碳排放占86%,场外运输占2%,施工直接碳排放占12%,表明碳排放主要来源为材料生产,其次为施工机械。该研究发现:顶升改造方案不仅符合国家“碳达峰、碳中和”战略目标,还在一定条件下与拆除重建方案经济效益相当,可为桥梁顶升工程方案比选决策提供有力参考。
文摘预制装配式先张折线预应力T梁因具有承载能力高、抗裂性能好、施工速度快等优点,在中小跨径桥梁结构中具有广泛的应用前景。设计了一种新型30 m,跨先张折线预应力T型梁,并通过足尺静力试验研究了其在扭转作用下的性能,包括变形能力、应变分布、抗裂性能和裂缝发展规律等。试验结果表明:试验梁在扭转作用下的受力过程分为弹性阶段和裂缝开展阶段。裂缝优先出现在端部上翼缘与腹板交界处和加载截面底部下翼缘处,随后试件腹板立面出现较多斜裂缝和弯剪裂缝,同时顶面开始出现斜裂缝,裂缝位置也逐渐向支座截面扩展;弯曲裂缝的出现会使底部纵筋的应变发生突变,腹板混凝土出现斜裂缝后箍筋应变和混凝土应变发生突变,箍筋上部相比中下部应变峰值更大,加载底部与支座上部连线附近的主应变峰值较大;根据ACI 318—19规范计算的开裂扭矩为777 k N·m,与测试值的比例系数为1.16,表明先张折线预应力混凝土T型梁具有良好的抗裂性能。为先张折线预应力T梁在扭转作用下的损伤过程与结构优化提供了重要参考。
