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
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
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
桥梁工程是公路建设碳排放的主要环节,T梁桥作为公路项目标准化制造的重要结构形式,掌握其碳排放特征和规律,有助于公路低碳建设和管理。研究采用排放因子法对23座典型T梁桥进行碳排放测算,划定了公路T梁桥建设边界范围,确定了碳排放测...桥梁工程是公路建设碳排放的主要环节,T梁桥作为公路项目标准化制造的重要结构形式,掌握其碳排放特征和规律,有助于公路低碳建设和管理。研究采用排放因子法对23座典型T梁桥进行碳排放测算,划定了公路T梁桥建设边界范围,确定了碳排放测算功能单位,测算了各工程部位的碳排放强度,开展了参数敏感性分析和相关性分析,并提出了基于桥梁长度的桥梁主要结构碳排放估算模型。通过测算结果可知,公路T梁桥建设碳排放强度为8927.13 t CO_(2)e/(km·lane),变化区间为4002.64~9871.74 t CO_(2)e/(km·lane),其中间接碳排放占比为98.28%~99.13%,而直接碳排放为6820.99 t CO_(2)e。桥梁建设约86%碳排放主要集中在预应力T梁和桩基础,碳排放强度分别为1.23 t CO_(2)e/m^(3)、0.68 t CO_(2)e/m^(3);约95%来源于水泥、钢材、回旋钻机和交流电弧焊机。敏感性分析表明,当水泥、钢材、电力、化石燃料碳排放因子变化±(10%~30%)时,碳排放变化分别为±(4.77%~14.32%)、±(4.24%~12.74%)、±(0.57%~1.72%)、±(0.14%~0.43%)。相关性分析表明,桥梁主要工程部位的碳排放受桥梁规模影响较大,可基于桥梁长度快速估算T梁桥整体和各工程部位的碳排放。对此,项目管理者可通过低碳采购等方式降低间接碳排放;可通过优化加工工艺和施工方案等方式,在工程活动中节约材料、降低能耗;可通过降低用量和碳排放因子多种组合方式,对主要材料和能源进行综合减碳。相关结果可为公路建设项目的低碳管理及相关研究提供详实的数据支持和节能降碳措施建议。展开更多
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 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.
文摘桥梁工程是公路建设碳排放的主要环节,T梁桥作为公路项目标准化制造的重要结构形式,掌握其碳排放特征和规律,有助于公路低碳建设和管理。研究采用排放因子法对23座典型T梁桥进行碳排放测算,划定了公路T梁桥建设边界范围,确定了碳排放测算功能单位,测算了各工程部位的碳排放强度,开展了参数敏感性分析和相关性分析,并提出了基于桥梁长度的桥梁主要结构碳排放估算模型。通过测算结果可知,公路T梁桥建设碳排放强度为8927.13 t CO_(2)e/(km·lane),变化区间为4002.64~9871.74 t CO_(2)e/(km·lane),其中间接碳排放占比为98.28%~99.13%,而直接碳排放为6820.99 t CO_(2)e。桥梁建设约86%碳排放主要集中在预应力T梁和桩基础,碳排放强度分别为1.23 t CO_(2)e/m^(3)、0.68 t CO_(2)e/m^(3);约95%来源于水泥、钢材、回旋钻机和交流电弧焊机。敏感性分析表明,当水泥、钢材、电力、化石燃料碳排放因子变化±(10%~30%)时,碳排放变化分别为±(4.77%~14.32%)、±(4.24%~12.74%)、±(0.57%~1.72%)、±(0.14%~0.43%)。相关性分析表明,桥梁主要工程部位的碳排放受桥梁规模影响较大,可基于桥梁长度快速估算T梁桥整体和各工程部位的碳排放。对此,项目管理者可通过低碳采购等方式降低间接碳排放;可通过优化加工工艺和施工方案等方式,在工程活动中节约材料、降低能耗;可通过降低用量和碳排放因子多种组合方式,对主要材料和能源进行综合减碳。相关结果可为公路建设项目的低碳管理及相关研究提供详实的数据支持和节能降碳措施建议。
