Investigations of the seismic behavior of steel reinforced concrete L-shaped columns under constant axial compression and cycled bending-shear-torsion load were performed.Six specimens,which considered two parameters,...Investigations of the seismic behavior of steel reinforced concrete L-shaped columns under constant axial compression and cycled bending-shear-torsion load were performed.Six specimens,which considered two parameters,i.e.,the moment ratio of torsion to bending(γ)and the aspect ratio(column length-to-depth ratio,φ),were prepared for the experiment.In this study,the failure process,torsion-displacement hysteresis curves,and flexure-displacement hysteresis curves were obtained.The failure characteristics,mechanical behavior of specimens such as the failure patterns,hysteresis curves,rigidity degradation,ductility and energy dissipation,are analyzed.The experimental research indicated that the major failures of the specimens were bending failure,bending-shear failure and bending-torsion failure as the moment ratio of torsion to bending(γ)increased.The torsion-displacement hysteresis curves were pinched in the middle,formed a slip platform,and the phenomenon of“load drop”occurred after the peak load.The bending-displacement hysteresis curves were plump,which showed that bending capacity of the specimen was better than its torsion capacity.Additionally,the energy dissipation of the specimen was dominated by torsion in the early stage and ultimately governed by the bending moment in the later phase.Test results also indicated that the displacement ductility coefficient and interstory rotation angle of the failure point were less than 3.0 and 1/50,respectively,which means the test specimen performance does not meet the requirement of the Chinese Code for Seismic Design of Buildings(GB 50011-2014)in this respect.展开更多
While modem prestressed techniques have improved the torsion properties of high-strength concrete （HSC） composite beams with prestressed steel （PS） boxes, no research has been reported in either the national or in...While modem prestressed techniques have improved the torsion properties of high-strength concrete （HSC） composite beams with prestressed steel （PS） boxes, no research has been reported in either the national or international literature on the an- ti-torque and composite torque properties of this type of beam. With the aim of understanding the torque properties of these beams, this paper presents results of ten comprehensive tests; three of these were based on stirrup spacings and prestressing levels as the main parameters, while the other seven were based on torsional rates. The torsion tests were conducted on the re- sults which established several key parameters, including curves of constant torsion, strain curves of steel torsion, strain distri- bution of steel beams and concrete, curves of bending-moment and mid-span deflection, as well as cross strain distribution.The prestressing impact-factor method was adopted to deduce semiempirical equations for cracking torque in such composite beams. Furthermore, this involves the use of the equation of ultimate torque based on tress-model-theory of the distortion an- gle, the calculated results show good agreement with the measured values. In summary, this paper offers theoretical analysis for future applications of HSC composite beams with PS boxes, and provides both validation of the methods employed and a reference point for on-going research on composite beams and related anti-torque studies.展开更多
Textile-reinforced concrete (TRC) is a new high performance cementitious composite material,which not only has superior corrosion resistance but also can effectively limit the development of concrete cracks and make t...Textile-reinforced concrete (TRC) is a new high performance cementitious composite material,which not only has superior corrosion resistance but also can effectively limit the development of concrete cracks and make the crack width and spacing of concrete become smaller.However,due to the brittle feature of fiber materials,the TRC structural member has no distinct failure symptom when it arrives at its ultimate load.At the same time,ordinary reinforced concrete (RC) elements have large dead weight and can not efficiently restrict the expansion of the main crack of structures because of the restriction of their special cover thickness.In order to overcome the disadvantages of both the TRC and the RC,a new architecture reinforced with textile-combined steel is proposed in this study,making full use of the advantages of the above two structures.The cover concrete at the tension zone of an RC element is partially replaced with TRC and thus the steel reinforcements replaced with textiles are subtracted.Compared with the old one,the new structure has less dead weight and has the merits of service safety and good durability.The flexural development process of the proper beam with this new structure is investigated in this paper and based on the plane section assumption,analytical equations are derived by using nonlinear analysis theory,including the load-carrying capacity at different stages and moment-curvature relationship and mid-span deflection during the entire loading process.Comparison between the calculated and the experimental results reveals satisfactory agreement and thus verifies the feasibility of the equations.展开更多
基金National Natural Science Foundation of China under Grant Nos.51268004 and 51578163Natural Science Foundation of Guangxi under Grant No 2016GXNSFDA380032Bagui Scholar Program of Guangxi under Grant No:[2019]79。
文摘Investigations of the seismic behavior of steel reinforced concrete L-shaped columns under constant axial compression and cycled bending-shear-torsion load were performed.Six specimens,which considered two parameters,i.e.,the moment ratio of torsion to bending(γ)and the aspect ratio(column length-to-depth ratio,φ),were prepared for the experiment.In this study,the failure process,torsion-displacement hysteresis curves,and flexure-displacement hysteresis curves were obtained.The failure characteristics,mechanical behavior of specimens such as the failure patterns,hysteresis curves,rigidity degradation,ductility and energy dissipation,are analyzed.The experimental research indicated that the major failures of the specimens were bending failure,bending-shear failure and bending-torsion failure as the moment ratio of torsion to bending(γ)increased.The torsion-displacement hysteresis curves were pinched in the middle,formed a slip platform,and the phenomenon of“load drop”occurred after the peak load.The bending-displacement hysteresis curves were plump,which showed that bending capacity of the specimen was better than its torsion capacity.Additionally,the energy dissipation of the specimen was dominated by torsion in the early stage and ultimately governed by the bending moment in the later phase.Test results also indicated that the displacement ductility coefficient and interstory rotation angle of the failure point were less than 3.0 and 1/50,respectively,which means the test specimen performance does not meet the requirement of the Chinese Code for Seismic Design of Buildings(GB 50011-2014)in this respect.
基金supported by the National Natural Science Foundation of China (Grant No. 50879048)"948" Project of the Ministry of Water Resources of China (Grant No. 201127)
文摘While modem prestressed techniques have improved the torsion properties of high-strength concrete （HSC） composite beams with prestressed steel （PS） boxes, no research has been reported in either the national or international literature on the an- ti-torque and composite torque properties of this type of beam. With the aim of understanding the torque properties of these beams, this paper presents results of ten comprehensive tests; three of these were based on stirrup spacings and prestressing levels as the main parameters, while the other seven were based on torsional rates. The torsion tests were conducted on the re- sults which established several key parameters, including curves of constant torsion, strain curves of steel torsion, strain distri- bution of steel beams and concrete, curves of bending-moment and mid-span deflection, as well as cross strain distribution.The prestressing impact-factor method was adopted to deduce semiempirical equations for cracking torque in such composite beams. Furthermore, this involves the use of the equation of ultimate torque based on tress-model-theory of the distortion an- gle, the calculated results show good agreement with the measured values. In summary, this paper offers theoretical analysis for future applications of HSC composite beams with PS boxes, and provides both validation of the methods employed and a reference point for on-going research on composite beams and related anti-torque studies.
基金support from the Key Program of the National Natural Science Foundation of China (Grant No.50438010)
文摘Textile-reinforced concrete (TRC) is a new high performance cementitious composite material,which not only has superior corrosion resistance but also can effectively limit the development of concrete cracks and make the crack width and spacing of concrete become smaller.However,due to the brittle feature of fiber materials,the TRC structural member has no distinct failure symptom when it arrives at its ultimate load.At the same time,ordinary reinforced concrete (RC) elements have large dead weight and can not efficiently restrict the expansion of the main crack of structures because of the restriction of their special cover thickness.In order to overcome the disadvantages of both the TRC and the RC,a new architecture reinforced with textile-combined steel is proposed in this study,making full use of the advantages of the above two structures.The cover concrete at the tension zone of an RC element is partially replaced with TRC and thus the steel reinforcements replaced with textiles are subtracted.Compared with the old one,the new structure has less dead weight and has the merits of service safety and good durability.The flexural development process of the proper beam with this new structure is investigated in this paper and based on the plane section assumption,analytical equations are derived by using nonlinear analysis theory,including the load-carrying capacity at different stages and moment-curvature relationship and mid-span deflection during the entire loading process.Comparison between the calculated and the experimental results reveals satisfactory agreement and thus verifies the feasibility of the equations.
