This study presents an investigation on the fatigue analysis of four types of details on orthotropic steel decks(OSDs)for a cable-stayed super-wide steel box girder bridge based on finite-element analysis(FEA)with veh...This study presents an investigation on the fatigue analysis of four types of details on orthotropic steel decks(OSDs)for a cable-stayed super-wide steel box girder bridge based on finite-element analysis(FEA)with vehicle transverse distribution model(VTDM).A high-fidelity 3D FE model verified by the static load test is established to satisfy the fatigue analysis accuracy.The stress behavior of super-wide steel box girders under the vehicle load at different lane locations is investigated.Then,considering the effect of VTDM,the fatigue life analysis of four typical details is performed using the Miner cumulative damage rule.The results show that the vehicle transverse location has a great influence on the stress behavior of details with sharp influence surface,and the stress ranges in the outermost lane are larger than those in other lanes,indicating that the details of OSD in the outermost lane are prone to fatigue.The fatigue life analysis indicates that the diaphragm cutout is more prone to fatigue than other details,which should be carefully treated in bridge maintenance.展开更多
Epoxy asphalt concrete has been one of the mainstream technology of steel deck pavement in China. But little specification about evaluation system for its distress condition has been researched and maintenance was sti...Epoxy asphalt concrete has been one of the mainstream technology of steel deck pavement in China. But little specification about evaluation system for its distress condition has been researched and maintenance was still unsystematic. The section weight coefficient of different distress is proposed by analyzing the applicability of the “Highway Performance Assessment Standards”. Indexes mainly including SDPCI PDR and PCR are presented to evaluate its distress condition. The evaluation system and maintenance plan decision tree were recommended which can assist scientific maintenance of epoxy asphalt steel deck pavement.展开更多
Fatigue has become critical issue for bridge with orthotropic steel deck.Number of stress cycle and equivalent stress amplitude were adopted as two investigated fatigue effects.As presented from fatigue monitoring com...Fatigue has become critical issue for bridge with orthotropic steel deck.Number of stress cycle and equivalent stress amplitude were adopted as two investigated fatigue effects.As presented from fatigue monitoring comparison of two series-lined bridges,three local geometric parameters of steel box girder have significant influence on fatigue performance of two welded joints.They are thickness of longitudinal ribs(Tr),longitudinal spacing of transverse floor plate(Sc)and longitudinal truss(LT).Fatigue analytical models were created for parametric study of fatigue effects under wheel load.Consequently,three local parameters have exhibited insignificant influence on number of stress cycle.Compared with Tr and Sc,configuration of LT has brought about foremost effect on the equivalent stress amplitude.For equivalent stress amplitude of rib-to-deck and rib-to-rib welded joints,the influence regions of LT are respectively longitudinal strap and quadrate with the geometric length of 600 mm.Enough attention ought to be paid for local stiffen structure on fatigue performance of orthotropic steel deck in fatigue design and monitoring.展开更多
With the development of steel deck paving technology, the associated gussasphalt pavement system also develops maturely. In this paper, the structure characteristics and performance advantages are thoroughly explained...With the development of steel deck paving technology, the associated gussasphalt pavement system also develops maturely. In this paper, the structure characteristics and performance advantages are thoroughly explained by introducing the development course of gussasphalt. The material composition, properties and application effect of three typical pavement methods are analyzed. This paper is intended to give a relatively clear understanding regarding the specific features of gussasphalt, and provide some guidance to further expansion concerning gussasphalt pavement.展开更多
In order to study the fatigue properties of rib-to-deck welded connection and rib-to-rib welded connection in orthotropic steel bridge decks,a multi-scale finite element model was set up to analyze the stress distribu...In order to study the fatigue properties of rib-to-deck welded connection and rib-to-rib welded connection in orthotropic steel bridge decks,a multi-scale finite element model was set up to analyze the stress distribution characteristics and the load test was conducted on the Taizhou Yangtze River Bridge.Comparing the vehicle test results with the muli-scale finite element model results to verify the accuracy of the finite element simulation for the stress response of two welded details.The results indicated that The stress at the rib-to-deck welded connection and the rib-to-rib welded connection are the bending stress and the membrane stress,respectively;the stress response of the two welded connection has strong local characteristics;the lateral stress influence line of the two welded connection is relatively short and the length of the lateral stress influence line is greatly affected by the longitudinal ribs;increasing the thickness of the roof and longitudinal ribs can reduce the stress response and improve the stress performance of the heavy lanes.For the two welded details,the fatigue damage increment of the ordinary lane is greater than the heavy lane.The thickened roof and longitudinal ribs at the position of the heavy lane still cannot balance the fatigue damage caused by the heavy truck.Therefore,it is necessary to strictly control the fatigue effect of overloaded vehicles on steel box girders.展开更多
As an important part of steel bridge deck,the engineering quality and service condition of steel bridge deck pavement(SBDP)directly affects the capacity and operational efficiency of the bridge.This paper reviews the ...As an important part of steel bridge deck,the engineering quality and service condition of steel bridge deck pavement(SBDP)directly affects the capacity and operational efficiency of the bridge.This paper reviews the history of the development of SBDP in China over the past 20 years from the exploration stage,rapid development stage and prosperity stage.The development and application of SBDP at different stages are discussed in terms of materials,structure,design,performance evaluation,maintenance and rehabilitation,respectively.The advantages and disadvantages of different pavement materials and structures,and the application of different research methods are summarized.The review shows that the improvement of pavement materials and structures and the development of new materials should be further studied on the multi-scale to enhance the durability of pavement materials,so as to extend the service life of pavements.The design method of SBDP related to the synergistic effect of vehicle,pavement and bridge should be established,and the design concept and method standard of rigid base pavement structure should be improved and formulate a complete design standard.In addition,multi-disease intelligent identification system and equipment should be studied to track the entire course of disease development in real time.And it is necessary to develop appropriate algorithms to select and classify the complex data of disease and maintenance history.展开更多
Fatigue has gradually become a serious issue for orthotropic steel deck used for long-span bridges. Two fatigue effects, namely number of stress cycles and equivalent stress amplitude, were introduced as investigated ...Fatigue has gradually become a serious issue for orthotropic steel deck used for long-span bridges. Two fatigue effects, namely number of stress cycles and equivalent stress amplitude, were introduced as investigated parameters in this paper. Investigation was focused on their relationships with traffic volume and ambient temperature by using 7-months fatigue monitoring data of an actual bridge. A fatigue analytical model considering temperature-induced changes in material property of asphalt pavement was established for verifying these relationships. The analysis results revealed that the number of stress cycles and equivalent stress amplitude showed a linear correlation with the traffic volume and ambient temperature, respectively, and that the rib-to-deck welded joint was much more sensitive to the traffic volume and ambient temperature than the rib-to-rib welded joint. The applicability of the code-recommended model for fatigue vehicle loading was also discussed, which revealed that the deterministic vehicle loading model requires improvement to account for significant randomness of the actual traffic conditions.展开更多
Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress grad...Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress gradient. The optimum drilling location and diameter were studied through analysis of different locations and diameters. By analyzing the effects of flank holes and an additional hole, drilling advice was proposed and fatigue testing of the cracks in a steel bridge deck with a crack stop hole was conducted. The results show that the stress at the crack tip with a crack stop hole decreased, and the major principal stress around the hole was distributed accordingly. The optimum position of the crack stop hole centre was where the centre of the crack stop hole was situated behind the crack and the hole edge coincided with the crack tip. Therefore, hole diameters larger than 8 mm, or those weakening the section by 10%, were suggested as the best diameters. In terms of multi-hole crack stopping, a flank hole was not recommended. The optimum horizontal position of flank holes was at a distance of 1/4 of a single hole diameter from, and in front of, the single hole. Besides, the experiment showed that crack stop hole could only prevent cracks from growing and had no influence on crack growth rate.展开更多
To improve the strength-toughness of traditional U-rib( TUR) and solve the problem of insufficient penetration between TUR and deckplate,a new local thickened U-rib( LTUR) has been proposed to improve the fatigue resi...To improve the strength-toughness of traditional U-rib( TUR) and solve the problem of insufficient penetration between TUR and deckplate,a new local thickened U-rib( LTUR) has been proposed to improve the fatigue resistance of the weld joint under the premise of not increasing thickness and strength of the TUR material. And a hot /warm roll-forming process( RFP) adopting partially induction heating to 700- 1 000℃ was carried out to fabricate LTUR. The deformation behaviors in the forming process and microstructure of LTUR have been investigated.Mechanical properties and fracture mechanism of the LTUR after hot / warm RFP have been systematically discussed. Moreover,the results are compared with those obtained in cold RFP. Mechanical properties of the LTUR deformed above the critical transformation temperature( A_(c3)) show high performance characteristics with marked fatigue resistance and superior toughness. Upon increasing the heating temperature from 700 to 900 ℃,the initial coarse ferrite-pearlite structure transform into equiaxed ultrafine ferrite( 1- 3 μm) and precipitates such as( Nb,Ti)( C,N) are uniformly distributed in the matrix. The average dislocation density of the specimens after hot rollforming at heating temperature of 900 ℃ decreases dramatically compared with those of the specimens subjected to the cold RFP. Furthermore,a typical characteristic of ductile fracture mechanism and the high impact energy are more convinced that the specimens deformed above 900 ℃ have obtained an optimal combination of strength and toughness.展开更多
The corrosion of the anticorrosion coating and the defects of the asphalt concrete paved layer have been investigated on long-span steel box bridge decks. The anticorrosion coating lies in the middle of two entirely d...The corrosion of the anticorrosion coating and the defects of the asphalt concrete paved layer have been investigated on long-span steel box bridge decks. The anticorrosion coating lies in the middle of two entirely different materials: a highway steel box bridge deck and a paved layer, which is used as anticorrosion and waterproof coating for the steel bridge deck. For our study, electrochemical corrosion and pull strength experiments have been selected for the investigation of the corrosion properties of inorganic zinc rich coating, epoxy zinc rich coating and arc sprayed zinc coating. The adhesive strength between the coatings and the panel, and the effect of the coating corrosion on the shear properties of the paved layers including cast asphalt, thermal asphalt mortar, epoxy asphalt and modified asphalt concrete have been investigated. The results show that the adhesive strength between the coatings and the bridge panel is controlled by the method of pre-processing rust removal. Coating by sandblasting has stronger adhesive strength than coating by shot peening. The results also reveal that shear strength of the paved layer is affected by the corrosion product of zinc coating. The arc sprayed zinc coating has stronger shear strength than zinc rich coalings.展开更多
Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure...Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure,mechanical characteristics and transmission routes of deck loads.The simplified calculation models were brought out for the stud design of the longitudinal girders and transverse girders in the composite floor system of Nanjing Dashengguan Yangtze River Bridge (NDB).Studs were designed and arranged by taking the middle panel of 336 m main span for example.The results show that under deck loads,the longitudinal girders in the composite floor system of through steel bridges are in tension-bending state,longitudinal shear force on the interface is caused by both longitudinal force of "The first mechanical system" and vertical bending of "The second mechanical system",and studs can be arranged with equal space in terms of the shear force in range of 0.2d (where d is the panel length) on the top ends.Transverse girders in steel longitudinal and transverse girders-concrete slab composite deck are in compound-bending state,and out-of-plane bending has to be taken into account in the stud design.In orthotropic integral steel deck-concrete slab composite deck,out-of-plane bending of transverse girders is very small so that it can be neglected,and studs on the orthotropic integral steel deck can be arranged according to the structural requirements.The above design methods and simplified calculation models have been applied in the stud design of NDB.展开更多
As a solution against the serviceability problem caused by the cracks occurring at the UHPC precast deck-joint interface, this study proposes a method exposing the steel fiber at the interface and evaluates the corres...As a solution against the serviceability problem caused by the cracks occurring at the UHPC precast deck-joint interface, this study proposes a method exposing the steel fiber at the interface and evaluates the corresponding flexural performance of the lap spliced construction joint. After having slowed down the strength development of the concrete placed in the joint of the precast deck by means of a curing retardant, the concrete at the interface is crushed so as to expose the steel fibers and the change in the flexural performance is observed experimentally according to the exposure of the steel fibers. The results show that, even if the ultimate strength and stiffness of the UHPC precast deck including the joint are mostly determined by the arrangement details of the rebar lap splice, the exposure of the steel fibers can secure stable ductile behavior and reduce the width of the cracks generated at the precast deck-joint interface under service load.展开更多
Along with the popularization and application of the steel bridge in China,due to the high modulus of asphalt concrete with good waterproof,anti-fatigue,anti-aging and good performance,asphalt concrete with high modul...Along with the popularization and application of the steel bridge in China,due to the high modulus of asphalt concrete with good waterproof,anti-fatigue,anti-aging and good performance,asphalt concrete with high modulus was widely used in steel bridge deck pavement,the test and comparative study of high modulus asphalt concrete were carried out based on two types of common high modulus asphalt concrete which include the casting type asphalt concrete and epoxy resin modified asphalt concrete,aims to further explore the performance features of the steel bridge deck with high modulus asphalt concrete,and provide help on the application of this asphalt concrete on the steel bridge deck.展开更多
In this paper, the seismic response of a newly designed steel jacket offshore platform with a float over deck (FOD) system in the Persian Gulf was investigated through incremental dynamic analysis. Comparison of incre...In this paper, the seismic response of a newly designed steel jacket offshore platform with a float over deck (FOD) system in the Persian Gulf was investigated through incremental dynamic analysis. Comparison of incremental dynamic analysis results for both directions of the platform shows that the lateral strength of the platform in the float over direction is less than its lateral strength in other direction. Dynamic characteristics measurement of a scale model of platform was also performed using forced vibration tests. From experimental measurement of the scaled model, it was observed that dynamic characteristic of the platform is different in the float over direction compared to the other direction. Therefore, a new offshore installed bracing system for the float over direction was proposed for improvement of seismic performance of this type of platform. Finally, the structure with the modified system was assessed using the probabilistic seismic assessment method as well as experimental measurement of its dynamic characteristics. It was observed that the proposed offshore installed bracing system improves the performance of platforms subjected to strong ground motion.展开更多
To alleviate deck fatigue failure and regular pavement damage,which are congenital deficiencies of highway steel bridge deck structure,this paper proposes a newtype of composite bridge deck,consisting of steel tubular...To alleviate deck fatigue failure and regular pavement damage,which are congenital deficiencies of highway steel bridge deck structure,this paper proposes a newtype of composite bridge deck,consisting of steel tubular connectors and steel-reactive powder concrete (RPC). Push-out tests were conducted to study the newdeck's shear performance. During the experimental process,specimens were divided into two groups which are composed of steel tubular connectors with or without penetrative bars set in. Then,researchers analyzed destroyed models and mechanisms of the composite structure under shear forces. Results showed that test models in two groups,once destroyed,displayed similar shear fracture,which appeared on the lower margin of the steel tubular wall along the welds. Meanwhile,RPC under the connector,for varied tests,was crushed at the same stage,although the large shear and bending deformation just occurred on connectors with penetrative bars. Additionally,shear capacity of specimens with penetrative bars,compared with the ones without bars,unexpectedly decreased by 20%,but the structural ductility was 1.75 times as much,and the ductility coefficients of specimens were all larger than 3.5,demonstrating certain deformation capacity.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51778135,52178119)the Distinguished Young Scientists of Jiangsu Province(Grant No.BK20190013)the National Key R&D Program Foundation of China(Grant No.2017YFC0806001).
文摘This study presents an investigation on the fatigue analysis of four types of details on orthotropic steel decks(OSDs)for a cable-stayed super-wide steel box girder bridge based on finite-element analysis(FEA)with vehicle transverse distribution model(VTDM).A high-fidelity 3D FE model verified by the static load test is established to satisfy the fatigue analysis accuracy.The stress behavior of super-wide steel box girders under the vehicle load at different lane locations is investigated.Then,considering the effect of VTDM,the fatigue life analysis of four typical details is performed using the Miner cumulative damage rule.The results show that the vehicle transverse location has a great influence on the stress behavior of details with sharp influence surface,and the stress ranges in the outermost lane are larger than those in other lanes,indicating that the details of OSD in the outermost lane are prone to fatigue.The fatigue life analysis indicates that the diaphragm cutout is more prone to fatigue than other details,which should be carefully treated in bridge maintenance.
基金Sponsored by the Major Science and Technology Special Traffic and Transportation in Jiangsu Province(Grant No.2014Y02)the Jiangsu Natural Science Foundation(Grant Nos.BK20180113 and BK20181112)
文摘Epoxy asphalt concrete has been one of the mainstream technology of steel deck pavement in China. But little specification about evaluation system for its distress condition has been researched and maintenance was still unsystematic. The section weight coefficient of different distress is proposed by analyzing the applicability of the “Highway Performance Assessment Standards”. Indexes mainly including SDPCI PDR and PCR are presented to evaluate its distress condition. The evaluation system and maintenance plan decision tree were recommended which can assist scientific maintenance of epoxy asphalt steel deck pavement.
基金Project(51178100)supported by the National Natural Science Foundation of ChinaProject(2011318223170)supported by Key Program of Ministry of Transport,China+3 种基金Project(1105007001)supported by Program of the Priority Academic Development Program of Jiangsu Higher Education Institutions,ChinaProject(3205001205)supported by Teaching and Research Foundation for Excellent Young Teacher of Southeast University,ChinaProject(CXZZ-0162)supported by Graduate Scientific Innovation Research Foundation of Jiangsu Province,ChinaProject(YBJJ1122)supported by Scientific Research Foundation of Graduate School of Southeast University,China
文摘Fatigue has become critical issue for bridge with orthotropic steel deck.Number of stress cycle and equivalent stress amplitude were adopted as two investigated fatigue effects.As presented from fatigue monitoring comparison of two series-lined bridges,three local geometric parameters of steel box girder have significant influence on fatigue performance of two welded joints.They are thickness of longitudinal ribs(Tr),longitudinal spacing of transverse floor plate(Sc)and longitudinal truss(LT).Fatigue analytical models were created for parametric study of fatigue effects under wheel load.Consequently,three local parameters have exhibited insignificant influence on number of stress cycle.Compared with Tr and Sc,configuration of LT has brought about foremost effect on the equivalent stress amplitude.For equivalent stress amplitude of rib-to-deck and rib-to-rib welded joints,the influence regions of LT are respectively longitudinal strap and quadrate with the geometric length of 600 mm.Enough attention ought to be paid for local stiffen structure on fatigue performance of orthotropic steel deck in fatigue design and monitoring.
文摘With the development of steel deck paving technology, the associated gussasphalt pavement system also develops maturely. In this paper, the structure characteristics and performance advantages are thoroughly explained by introducing the development course of gussasphalt. The material composition, properties and application effect of three typical pavement methods are analyzed. This paper is intended to give a relatively clear understanding regarding the specific features of gussasphalt, and provide some guidance to further expansion concerning gussasphalt pavement.
基金This research has been supported by the National Natural Science Foundation of China(Grant No.51778135)the National Key R&D Program Foundation of China(Grant No.2017YFC0806001)+2 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20160207)Aeronautical Science Foundation of China(Grant No.20130969010)the Fundamental Research Funds for the Central Universities and Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant Nos.KYCX18_0113 and KYLX16_0253).
文摘In order to study the fatigue properties of rib-to-deck welded connection and rib-to-rib welded connection in orthotropic steel bridge decks,a multi-scale finite element model was set up to analyze the stress distribution characteristics and the load test was conducted on the Taizhou Yangtze River Bridge.Comparing the vehicle test results with the muli-scale finite element model results to verify the accuracy of the finite element simulation for the stress response of two welded details.The results indicated that The stress at the rib-to-deck welded connection and the rib-to-rib welded connection are the bending stress and the membrane stress,respectively;the stress response of the two welded connection has strong local characteristics;the lateral stress influence line of the two welded connection is relatively short and the length of the lateral stress influence line is greatly affected by the longitudinal ribs;increasing the thickness of the roof and longitudinal ribs can reduce the stress response and improve the stress performance of the heavy lanes.For the two welded details,the fatigue damage increment of the ordinary lane is greater than the heavy lane.The thickened roof and longitudinal ribs at the position of the heavy lane still cannot balance the fatigue damage caused by the heavy truck.Therefore,it is necessary to strictly control the fatigue effect of overloaded vehicles on steel box girders.
基金The authors appreciate the financial support from the National Natural Science Foundation of China(No.51878167)Qing Lan Project of Jiangsu Province。
文摘As an important part of steel bridge deck,the engineering quality and service condition of steel bridge deck pavement(SBDP)directly affects the capacity and operational efficiency of the bridge.This paper reviews the history of the development of SBDP in China over the past 20 years from the exploration stage,rapid development stage and prosperity stage.The development and application of SBDP at different stages are discussed in terms of materials,structure,design,performance evaluation,maintenance and rehabilitation,respectively.The advantages and disadvantages of different pavement materials and structures,and the application of different research methods are summarized.The review shows that the improvement of pavement materials and structures and the development of new materials should be further studied on the multi-scale to enhance the durability of pavement materials,so as to extend the service life of pavements.The design method of SBDP related to the synergistic effect of vehicle,pavement and bridge should be established,and the design concept and method standard of rigid base pavement structure should be improved and formulate a complete design standard.In addition,multi-disease intelligent identification system and equipment should be studied to track the entire course of disease development in real time.And it is necessary to develop appropriate algorithms to select and classify the complex data of disease and maintenance history.
基金supported by the National Natural Science Foundation of China(Grant No.51178100)the Key Program of Ministry of Transport(Grant No.2011318223190)+3 种基金the Project of the Priority Academic Development Program of Jiangsu Higher Education Institutions(Grant No.1105007001)the Teaching and Research Foundation for Excellent Young Teacher of Southeast University(Grant No.3205001205)the Graduate Scientific Innovation Research Foundation of Jiangsu Province(Grant No.CXZZ-0162)the Scientific Research Foundation of Graduate School of Southeast University(Grant No.YBJJ1122)
文摘Fatigue has gradually become a serious issue for orthotropic steel deck used for long-span bridges. Two fatigue effects, namely number of stress cycles and equivalent stress amplitude, were introduced as investigated parameters in this paper. Investigation was focused on their relationships with traffic volume and ambient temperature by using 7-months fatigue monitoring data of an actual bridge. A fatigue analytical model considering temperature-induced changes in material property of asphalt pavement was established for verifying these relationships. The analysis results revealed that the number of stress cycles and equivalent stress amplitude showed a linear correlation with the traffic volume and ambient temperature, respectively, and that the rib-to-deck welded joint was much more sensitive to the traffic volume and ambient temperature than the rib-to-rib welded joint. The applicability of the code-recommended model for fatigue vehicle loading was also discussed, which revealed that the deterministic vehicle loading model requires improvement to account for significant randomness of the actual traffic conditions.
基金Projects(51278166,51478163)supported by the National Natural Science Foundation of ChinaProject(2015B17414)supported by the Fundamental Research Funds for the Central Universities,China
文摘Force analysis using a compact tension model, as recommended by ASTM, was carried out on a crack stop hole. The stress before, and after, drilling the hole was compared in terms of stress concentration and stress gradient. The optimum drilling location and diameter were studied through analysis of different locations and diameters. By analyzing the effects of flank holes and an additional hole, drilling advice was proposed and fatigue testing of the cracks in a steel bridge deck with a crack stop hole was conducted. The results show that the stress at the crack tip with a crack stop hole decreased, and the major principal stress around the hole was distributed accordingly. The optimum position of the crack stop hole centre was where the centre of the crack stop hole was situated behind the crack and the hole edge coincided with the crack tip. Therefore, hole diameters larger than 8 mm, or those weakening the section by 10%, were suggested as the best diameters. In terms of multi-hole crack stopping, a flank hole was not recommended. The optimum horizontal position of flank holes was at a distance of 1/4 of a single hole diameter from, and in front of, the single hole. Besides, the experiment showed that crack stop hole could only prevent cracks from growing and had no influence on crack growth rate.
文摘To improve the strength-toughness of traditional U-rib( TUR) and solve the problem of insufficient penetration between TUR and deckplate,a new local thickened U-rib( LTUR) has been proposed to improve the fatigue resistance of the weld joint under the premise of not increasing thickness and strength of the TUR material. And a hot /warm roll-forming process( RFP) adopting partially induction heating to 700- 1 000℃ was carried out to fabricate LTUR. The deformation behaviors in the forming process and microstructure of LTUR have been investigated.Mechanical properties and fracture mechanism of the LTUR after hot / warm RFP have been systematically discussed. Moreover,the results are compared with those obtained in cold RFP. Mechanical properties of the LTUR deformed above the critical transformation temperature( A_(c3)) show high performance characteristics with marked fatigue resistance and superior toughness. Upon increasing the heating temperature from 700 to 900 ℃,the initial coarse ferrite-pearlite structure transform into equiaxed ultrafine ferrite( 1- 3 μm) and precipitates such as( Nb,Ti)( C,N) are uniformly distributed in the matrix. The average dislocation density of the specimens after hot rollforming at heating temperature of 900 ℃ decreases dramatically compared with those of the specimens subjected to the cold RFP. Furthermore,a typical characteristic of ductile fracture mechanism and the high impact energy are more convinced that the specimens deformed above 900 ℃ have obtained an optimal combination of strength and toughness.
基金Project BK2005020 supported by the Natural Science Foundation of the Jiangsu Province
文摘The corrosion of the anticorrosion coating and the defects of the asphalt concrete paved layer have been investigated on long-span steel box bridge decks. The anticorrosion coating lies in the middle of two entirely different materials: a highway steel box bridge deck and a paved layer, which is used as anticorrosion and waterproof coating for the steel bridge deck. For our study, electrochemical corrosion and pull strength experiments have been selected for the investigation of the corrosion properties of inorganic zinc rich coating, epoxy zinc rich coating and arc sprayed zinc coating. The adhesive strength between the coatings and the panel, and the effect of the coating corrosion on the shear properties of the paved layers including cast asphalt, thermal asphalt mortar, epoxy asphalt and modified asphalt concrete have been investigated. The results show that the adhesive strength between the coatings and the bridge panel is controlled by the method of pre-processing rust removal. Coating by sandblasting has stronger adhesive strength than coating by shot peening. The results also reveal that shear strength of the paved layer is affected by the corrosion product of zinc coating. The arc sprayed zinc coating has stronger shear strength than zinc rich coalings.
基金Project(2004G016-B) supported by the Science and Technology Development Program of Railways Department,China
文摘Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure,mechanical characteristics and transmission routes of deck loads.The simplified calculation models were brought out for the stud design of the longitudinal girders and transverse girders in the composite floor system of Nanjing Dashengguan Yangtze River Bridge (NDB).Studs were designed and arranged by taking the middle panel of 336 m main span for example.The results show that under deck loads,the longitudinal girders in the composite floor system of through steel bridges are in tension-bending state,longitudinal shear force on the interface is caused by both longitudinal force of "The first mechanical system" and vertical bending of "The second mechanical system",and studs can be arranged with equal space in terms of the shear force in range of 0.2d (where d is the panel length) on the top ends.Transverse girders in steel longitudinal and transverse girders-concrete slab composite deck are in compound-bending state,and out-of-plane bending has to be taken into account in the stud design.In orthotropic integral steel deck-concrete slab composite deck,out-of-plane bending of transverse girders is very small so that it can be neglected,and studs on the orthotropic integral steel deck can be arranged according to the structural requirements.The above design methods and simplified calculation models have been applied in the stud design of NDB.
文摘As a solution against the serviceability problem caused by the cracks occurring at the UHPC precast deck-joint interface, this study proposes a method exposing the steel fiber at the interface and evaluates the corresponding flexural performance of the lap spliced construction joint. After having slowed down the strength development of the concrete placed in the joint of the precast deck by means of a curing retardant, the concrete at the interface is crushed so as to expose the steel fibers and the change in the flexural performance is observed experimentally according to the exposure of the steel fibers. The results show that, even if the ultimate strength and stiffness of the UHPC precast deck including the joint are mostly determined by the arrangement details of the rebar lap splice, the exposure of the steel fibers can secure stable ductile behavior and reduce the width of the cracks generated at the precast deck-joint interface under service load.
文摘Along with the popularization and application of the steel bridge in China,due to the high modulus of asphalt concrete with good waterproof,anti-fatigue,anti-aging and good performance,asphalt concrete with high modulus was widely used in steel bridge deck pavement,the test and comparative study of high modulus asphalt concrete were carried out based on two types of common high modulus asphalt concrete which include the casting type asphalt concrete and epoxy resin modified asphalt concrete,aims to further explore the performance features of the steel bridge deck with high modulus asphalt concrete,and provide help on the application of this asphalt concrete on the steel bridge deck.
基金sponsored by POGC (Pars Oil and Gas Company,No.132 "Investigation of Structural Health Monitoring of Steel Jacket Offshore Platforms")The financial support of POGC is gratefully acknowledged
文摘In this paper, the seismic response of a newly designed steel jacket offshore platform with a float over deck (FOD) system in the Persian Gulf was investigated through incremental dynamic analysis. Comparison of incremental dynamic analysis results for both directions of the platform shows that the lateral strength of the platform in the float over direction is less than its lateral strength in other direction. Dynamic characteristics measurement of a scale model of platform was also performed using forced vibration tests. From experimental measurement of the scaled model, it was observed that dynamic characteristic of the platform is different in the float over direction compared to the other direction. Therefore, a new offshore installed bracing system for the float over direction was proposed for improvement of seismic performance of this type of platform. Finally, the structure with the modified system was assessed using the probabilistic seismic assessment method as well as experimental measurement of its dynamic characteristics. It was observed that the proposed offshore installed bracing system improves the performance of platforms subjected to strong ground motion.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51478120)
文摘To alleviate deck fatigue failure and regular pavement damage,which are congenital deficiencies of highway steel bridge deck structure,this paper proposes a newtype of composite bridge deck,consisting of steel tubular connectors and steel-reactive powder concrete (RPC). Push-out tests were conducted to study the newdeck's shear performance. During the experimental process,specimens were divided into two groups which are composed of steel tubular connectors with or without penetrative bars set in. Then,researchers analyzed destroyed models and mechanisms of the composite structure under shear forces. Results showed that test models in two groups,once destroyed,displayed similar shear fracture,which appeared on the lower margin of the steel tubular wall along the welds. Meanwhile,RPC under the connector,for varied tests,was crushed at the same stage,although the large shear and bending deformation just occurred on connectors with penetrative bars. Additionally,shear capacity of specimens with penetrative bars,compared with the ones without bars,unexpectedly decreased by 20%,but the structural ductility was 1.75 times as much,and the ductility coefficients of specimens were all larger than 3.5,demonstrating certain deformation capacity.