The blind-hole method is the most widely used approach to experimentally determine the distribution of residual stress. This paper aims to improve test accuracy of welding residual stress and conducts an experimental ...The blind-hole method is the most widely used approach to experimentally determine the distribution of residual stress. This paper aims to improve test accuracy of welding residual stress and conducts an experimental study on the strain release factors involved when using the blind-hole method for Q235 and Q345, two steels commonly used in building structures. The ranges of strain release factors A and B in the elastic stage, the effects of strain release factors on residual stress calculated values, and the plastic corrected strain release factors are analyzed considering of the effect of plastic deformation around the blind hole on measurement accuracy. Finally, a simplified calculation formula to determine strain release factors is proposed for use with the blind-hole method. Results show that in the elastic stage, strain release factor A for Q235 and Q345 ranges from-0.399 to-0.525 and strain release factor B from-0.791 to-0.960. Changing the strain release factors A and B shows that calculated residual tensile stress varies in relation to a decrease in both factor values. However, there is a increase in calculated residual compressive stress with a decrease in the strain release factor A value, but there is an decrease with a decrease in strain release factor B value. Calculated residual stress applied to elastic strain release factors is compared with that applied to amended plastic strain release factors for Q235 steel. The maximum deviation between calculated residual stress and test stress is reduced from 21.1 to 1.0%,and for Q345 steel from 26.5 to 1.2%. It is thus evident that the plastic correction formula proposed in this paper can be used in calculations when conducting a residual stress test.展开更多
This paper summarizes the analytical and experimental dynamic analyses carried out to assess the actual dynamic behaviour of a curved cable-stayed bridge,recently erected in the commercial harbour of Porto Marghera ( ...This paper summarizes the analytical and experimental dynamic analyses carried out to assess the actual dynamic behaviour of a curved cable-stayed bridge,recently erected in the commercial harbour of Porto Marghera ( Venice,Italy). Ambient vibration tests were carried out to determine the dynamic characteristics of the bridge and more than 20 modes were identified in the frequency range 0～10Hz. In the theoretical study,a 3D FE model of the bridge was developed using an integrated CAD-FEA approach; subsequently,the information obtained from the field tests,combined with simple manual tuning,provided a linear elastic model,accurately fitting the modal parameters of the bridge in its present condition.展开更多
The authors show the results of a study conducted on a joint connecting a concrete column to a composite steel concrete floor,subjected to tension on the beams as a result of the decomposition of sagging bending momen...The authors show the results of a study conducted on a joint connecting a concrete column to a composite steel concrete floor,subjected to tension on the beams as a result of the decomposition of sagging bending moment.The beam to column connection is achieved by means of headed studs welded to the beam and embedded in the concrete cast.Five different configurations have been tested at failure and the results are compared to formulae proposed in literature.Different degrees of ductility,reliability and strength have been obtained varying geometry and reinforcement ratio on the joints tested.展开更多
Integral abutment bridges(IABs) are jointless bridges where the girder or the deck is continuous and connected monolithically to the abutments.A usual and important problem in the design of IABs is how to deal with th...Integral abutment bridges(IABs) are jointless bridges where the girder or the deck is continuous and connected monolithically to the abutments.A usual and important problem in the design of IABs is how to deal with the soil-structure interaction behind the abutments and next to the foundation piles: this can be considered as a fundamental aspect for the thorough understanding of this type of structures,which requires iterative and nonlinear analysis.In this paper,a 2D simplified finite-element model of a real 400 meters long IAB,built in the Province of Verona-Italy,is implemented and used to perform non linear analysis on the bridge,whose superstructure response is examined in details in the present paper.Then,the results obtained from a parametric study on the IAB,where the soil properties are varied behind the backwall and adjacent to the piles are varied,are described.In the end,a pushover analysis is carried out to assess the failure pattern of the bridge due to temperature change,considered as one of the key parameters in IABs design;finally,the effect of abutment stiffness is also discussed.The case study presented represents the world record for this kind of bridges.Authors believe this can be a cost effective and an efficient strategy to improve the durability and extend the life span of commonly built simply supported flyovers prone to maintenance problems due to bearings and expansion joints durability.展开更多
Condition assessment of bridges has become increasingly important. In order to accurately simulate the real bridge, finite element （FE） model updating method is often applied. This paper presents the calibration of ...Condition assessment of bridges has become increasingly important. In order to accurately simulate the real bridge, finite element （FE） model updating method is often applied. This paper presents the calibration of the FE model of a reinforced concrete tied-arch bridge using Douglas-Reid method in combination with Rosenbrock optimization algorithm. Based on original drawings and topographic survey, a FE model of the investigated bridge is created. Eight global modes of vibration of the bridge are identified by ambient vibration tests and the frequency domain decomposition technique. Then, eight structural parameters are selected for FE model updating procedure through sensitivity analysis. Finally, the optimal structural parameters are identified using Rosenbrock optimization algorithm. Results show that although the identified parameters lead to a perfect agreement between approximate and measured natural frequencies, they may not be the optimal variables which minimize the differences between numerical and experimental modal data. However, a satisfied agreement between them is still presented. Hence, FE model updating based on Douglas-Reid method and Rosenbrock optimization algorithm could be used as an alternative to other complex updating procedures.展开更多
A jointless bridge could fundamentally eliminate vulnerable deck joints, thereby meeting the need for sustainable development of bridges, especially for an expressway with highspeed traffic. In this paper, one jointle...A jointless bridge could fundamentally eliminate vulnerable deck joints, thereby meeting the need for sustainable development of bridges, especially for an expressway with highspeed traffic. In this paper, one jointless bridge(deck-extension bridge) with a small box girder in an expressway was chosen as a case study to examine the structural design,construction and field test. The field tests of the bridge indicated that the designed and constructed structures can satisfy the requirement for service performance of the deckextension bridge. Some key technologies, such as the position of longitudinal reinforcements in the superstructure-approach slab connections and the arrangement of the sliding material layers, were introduced. The longitudinal thermal movement of the superstructure in the deck-extension bridge with a small box girder could be predicted accurately by using the average temperature of the cross section of a small box girder. The finite element model, built by using the MIDAS program, was used to analyze the temperature distribution on the cross section of a small box girder, the accuracy of which could be verified by comparing with the measured values. The maximum longitudinal thermal movement of the superstructure in deck-extension bridges with a small box girder under historically extreme temperature conditions was predicted.展开更多
After Maillart's concrete curved arch bridges were built before the Second World War, in the second half of the past century and this century, many curved bridges have been built with both steel and concrete. Conv...After Maillart's concrete curved arch bridges were built before the Second World War, in the second half of the past century and this century, many curved bridges have been built with both steel and concrete. Conversely, since the construction of Musmeci's shell supported bridge in Potenza, few shell bridges have been constructed. This paper explains how to design a curved footbridge supported by an anticlastic shell by shaping the shell via a thrust network analysis(TNA). By taking advantage of the peculiar properties of anticlastic membranes, the unconventional method of shaping a shell by a TNA is illustrated. The shell top edge that supports the deck has an assigned layout, which is provided by the road curved layout. The form of the bottom edge is obtained by the form-finding procedure as a thrust line, by applying the thrust network analysis(TNA) in a non-standard manner,shaping the shell by applying the boundary conditions and allowing relaxation. The influence of the boundary conditions on the bridge shape obtained as an envelope of thrust lines is investigated. A finite element analysis was performed. The results indicate that the obtained shell form is effective in transferring deck loads to foundations via compressive stresses and taking advantage of concrete mechanical properties.展开更多
Integral abutment bridges are becoming rather common, due to the durability problems of bearings and expansion joints. At the same time, among short- and medium-span bridges, multi-beam steel-concrete composite deck w...Integral abutment bridges are becoming rather common, due to the durability problems of bearings and expansion joints. At the same time, among short- and medium-span bridges, multi-beam steel-concrete composite deck with hot-rolled girder is an economical and interesting alternative to traditional pre-stressed concrete solutions. The two concepts can be linked together to design integral steel-concrete composite bridges with the benefits of two typologies. The most critical aspect for these bridges is usually the joints between deck and piers or abutments. In this paper, an innovative beam-to-pier joint is proposed and a theoretical and experimental study is introduced and discussed. The analyzed connection is aimed at combining general ease of construction with a highly simplified assembly procedure and a good transmission of hogging and sagging moment at the supports in continuous beams. For this purpose, the traditional shear studs, used at the interface be- tween steel beam and upper concrete slab, are also used at the ends of steel profiles welded horizontally to the end plates. To better understand the behaviour of this kind of joints and the roles played by different components, three large-scale specimens were tested and an FE model was implemented. The theoretical and experimental results confirmed the po- tential of the proposed connection for practical applications and indicated the way to improve its structural behaviour.展开更多
An experiment was carried out on a set of fullscale specimens of a non-conventional connection between a concrete column and a composite steel and concrete beam defined on the basis of a number of requirements.The pro...An experiment was carried out on a set of fullscale specimens of a non-conventional connection between a concrete column and a composite steel and concrete beam defined on the basis of a number of requirements.The proposed connection,conceived in the ambit of semirigid joints,is aimed at combining general ease of construction with a highly simplified assembly procedure with a satisfying transmission of hogging moment at supports in continuous beams.For this purpose,the traditional shear studs used at the interface between the steel beam and the upper concrete slab,are also employed at the ends of the steel profiles welded horizontally to the end plates.The test is aimed at investigating the hogging moment response of the connection under incremental loads until failure.展开更多
Integral abutment bridges （IABs） can be used to avoid the durability issues associated with bearings and expansion joints. For this type of bridge, the design of the optimal pile foundation, especially with respect ...Integral abutment bridges （IABs） can be used to avoid the durability issues associated with bearings and expansion joints. For this type of bridge, the design of the optimal pile foundation, especially with respect to the horizontal stiffness, is a challenging issue. A structural optimization approach is proposed in this paper to optimize the pile foundation shape in integral abutment bridges. A procedure was implemented based on linking MATLAB, where an optimization code was developed, and OpenSees, which was used as the finite element solver. The optimization technique was compared with other techniques developed in previous researches to verify its reliability; the technique was then applied to a real 400 m-long IAB building in Verona, Italy, as a case study. The following two possi- bilities were considered and compared： （a） a pile with two different diameters along the depth and Co） a pile with a pre-hole. In fact, to increase the lateral and rotational flexibilities of the pile head, piles for an integral abutment bridge foundation are often driven into pre- deep holes filled with loose sand. Finally, the case of super-long integral abutment bridges （L = 500 m） with a corresponding displacement on one bridge end of approximately 50 mm was analysed. The following four pile design optimization eases were considered with similar study criteria as the Isola della Scala Bridge： （a） a pinned pile head for semi-integral abutment, Co） a fixed pile head without a pre-hole, （c） a fixed pile head with a pre-hole of any depth, （d） a fixed pile head of a pre-hole with a depth limit （〈 2 m） allowing for enoughembedded length for the friction pile. The case studies confirmed the potential of the proposed optimization techniques for finding the optimal shape of piles in integral abut- ment bridges.展开更多
基金supported by the National Natural Science Foundation of China (no. 51478120)
文摘The blind-hole method is the most widely used approach to experimentally determine the distribution of residual stress. This paper aims to improve test accuracy of welding residual stress and conducts an experimental study on the strain release factors involved when using the blind-hole method for Q235 and Q345, two steels commonly used in building structures. The ranges of strain release factors A and B in the elastic stage, the effects of strain release factors on residual stress calculated values, and the plastic corrected strain release factors are analyzed considering of the effect of plastic deformation around the blind hole on measurement accuracy. Finally, a simplified calculation formula to determine strain release factors is proposed for use with the blind-hole method. Results show that in the elastic stage, strain release factor A for Q235 and Q345 ranges from-0.399 to-0.525 and strain release factor B from-0.791 to-0.960. Changing the strain release factors A and B shows that calculated residual tensile stress varies in relation to a decrease in both factor values. However, there is a increase in calculated residual compressive stress with a decrease in the strain release factor A value, but there is an decrease with a decrease in strain release factor B value. Calculated residual stress applied to elastic strain release factors is compared with that applied to amended plastic strain release factors for Q235 steel. The maximum deviation between calculated residual stress and test stress is reduced from 21.1 to 1.0%,and for Q345 steel from 26.5 to 1.2%. It is thus evident that the plastic correction formula proposed in this paper can be used in calculations when conducting a residual stress test.
基金support provided by the Italian Ministry of University and Research,under the grant PRIN 2006
文摘This paper summarizes the analytical and experimental dynamic analyses carried out to assess the actual dynamic behaviour of a curved cable-stayed bridge,recently erected in the commercial harbour of Porto Marghera ( Venice,Italy). Ambient vibration tests were carried out to determine the dynamic characteristics of the bridge and more than 20 modes were identified in the frequency range 0～10Hz. In the theoretical study,a 3D FE model of the bridge was developed using an integrated CAD-FEA approach; subsequently,the information obtained from the field tests,combined with simple manual tuning,provided a linear elastic model,accurately fitting the modal parameters of the bridge in its present condition.
文摘The authors show the results of a study conducted on a joint connecting a concrete column to a composite steel concrete floor,subjected to tension on the beams as a result of the decomposition of sagging bending moment.The beam to column connection is achieved by means of headed studs welded to the beam and embedded in the concrete cast.Five different configurations have been tested at failure and the results are compared to formulae proposed in literature.Different degrees of ductility,reliability and strength have been obtained varying geometry and reinforcement ratio on the joints tested.
文摘Integral abutment bridges(IABs) are jointless bridges where the girder or the deck is continuous and connected monolithically to the abutments.A usual and important problem in the design of IABs is how to deal with the soil-structure interaction behind the abutments and next to the foundation piles: this can be considered as a fundamental aspect for the thorough understanding of this type of structures,which requires iterative and nonlinear analysis.In this paper,a 2D simplified finite-element model of a real 400 meters long IAB,built in the Province of Verona-Italy,is implemented and used to perform non linear analysis on the bridge,whose superstructure response is examined in details in the present paper.Then,the results obtained from a parametric study on the IAB,where the soil properties are varied behind the backwall and adjacent to the piles are varied,are described.In the end,a pushover analysis is carried out to assess the failure pattern of the bridge due to temperature change,considered as one of the key parameters in IABs design;finally,the effect of abutment stiffness is also discussed.The case study presented represents the world record for this kind of bridges.Authors believe this can be a cost effective and an efficient strategy to improve the durability and extend the life span of commonly built simply supported flyovers prone to maintenance problems due to bearings and expansion joints durability.
文摘Condition assessment of bridges has become increasingly important. In order to accurately simulate the real bridge, finite element （FE） model updating method is often applied. This paper presents the calibration of the FE model of a reinforced concrete tied-arch bridge using Douglas-Reid method in combination with Rosenbrock optimization algorithm. Based on original drawings and topographic survey, a FE model of the investigated bridge is created. Eight global modes of vibration of the bridge are identified by ambient vibration tests and the frequency domain decomposition technique. Then, eight structural parameters are selected for FE model updating procedure through sensitivity analysis. Finally, the optimal structural parameters are identified using Rosenbrock optimization algorithm. Results show that although the identified parameters lead to a perfect agreement between approximate and measured natural frequencies, they may not be the optimal variables which minimize the differences between numerical and experimental modal data. However, a satisfied agreement between them is still presented. Hence, FE model updating based on Douglas-Reid method and Rosenbrock optimization algorithm could be used as an alternative to other complex updating procedures.
基金supported by National Natural Science Foundation of China(grant numbers 51508103,51778148,51578161)Recruitment Program of Global Experts Foundation(grant number TM2012-27)
文摘A jointless bridge could fundamentally eliminate vulnerable deck joints, thereby meeting the need for sustainable development of bridges, especially for an expressway with highspeed traffic. In this paper, one jointless bridge(deck-extension bridge) with a small box girder in an expressway was chosen as a case study to examine the structural design,construction and field test. The field tests of the bridge indicated that the designed and constructed structures can satisfy the requirement for service performance of the deckextension bridge. Some key technologies, such as the position of longitudinal reinforcements in the superstructure-approach slab connections and the arrangement of the sliding material layers, were introduced. The longitudinal thermal movement of the superstructure in the deck-extension bridge with a small box girder could be predicted accurately by using the average temperature of the cross section of a small box girder. The finite element model, built by using the MIDAS program, was used to analyze the temperature distribution on the cross section of a small box girder, the accuracy of which could be verified by comparing with the measured values. The maximum longitudinal thermal movement of the superstructure in deck-extension bridges with a small box girder under historically extreme temperature conditions was predicted.
基金supported by the Recruitment Program of Global Experts Foundation (Grant No. TM2012-27)the National Natural Science Foundation of China (Grant No. 51778148 and 51508103)the Fujian Provincial Education Department Research Foundation for Young Teacher (Grant No. JA150743)
文摘After Maillart's concrete curved arch bridges were built before the Second World War, in the second half of the past century and this century, many curved bridges have been built with both steel and concrete. Conversely, since the construction of Musmeci's shell supported bridge in Potenza, few shell bridges have been constructed. This paper explains how to design a curved footbridge supported by an anticlastic shell by shaping the shell via a thrust network analysis(TNA). By taking advantage of the peculiar properties of anticlastic membranes, the unconventional method of shaping a shell by a TNA is illustrated. The shell top edge that supports the deck has an assigned layout, which is provided by the road curved layout. The form of the bottom edge is obtained by the form-finding procedure as a thrust line, by applying the thrust network analysis(TNA) in a non-standard manner,shaping the shell by applying the boundary conditions and allowing relaxation. The influence of the boundary conditions on the bridge shape obtained as an envelope of thrust lines is investigated. A finite element analysis was performed. The results indicate that the obtained shell form is effective in transferring deck loads to foundations via compressive stresses and taking advantage of concrete mechanical properties.
文摘Integral abutment bridges are becoming rather common, due to the durability problems of bearings and expansion joints. At the same time, among short- and medium-span bridges, multi-beam steel-concrete composite deck with hot-rolled girder is an economical and interesting alternative to traditional pre-stressed concrete solutions. The two concepts can be linked together to design integral steel-concrete composite bridges with the benefits of two typologies. The most critical aspect for these bridges is usually the joints between deck and piers or abutments. In this paper, an innovative beam-to-pier joint is proposed and a theoretical and experimental study is introduced and discussed. The analyzed connection is aimed at combining general ease of construction with a highly simplified assembly procedure and a good transmission of hogging and sagging moment at the supports in continuous beams. For this purpose, the traditional shear studs, used at the interface be- tween steel beam and upper concrete slab, are also used at the ends of steel profiles welded horizontally to the end plates. To better understand the behaviour of this kind of joints and the roles played by different components, three large-scale specimens were tested and an FE model was implemented. The theoretical and experimental results confirmed the po- tential of the proposed connection for practical applications and indicated the way to improve its structural behaviour.
文摘An experiment was carried out on a set of fullscale specimens of a non-conventional connection between a concrete column and a composite steel and concrete beam defined on the basis of a number of requirements.The proposed connection,conceived in the ambit of semirigid joints,is aimed at combining general ease of construction with a highly simplified assembly procedure with a satisfying transmission of hogging moment at supports in continuous beams.For this purpose,the traditional shear studs used at the interface between the steel beam and the upper concrete slab,are also employed at the ends of the steel profiles welded horizontally to the end plates.The test is aimed at investigating the hogging moment response of the connection under incremental loads until failure.
基金supported by the Recruitment Program of Global Experts Foundation(Grant No.TM2012-27)National Natural Science Foundation of China(Grant No.51778148 and 51508103)Fujian Provincial Education Department Research Foundation for Young Teacher(Grant No.JA150743)
文摘Integral abutment bridges （IABs） can be used to avoid the durability issues associated with bearings and expansion joints. For this type of bridge, the design of the optimal pile foundation, especially with respect to the horizontal stiffness, is a challenging issue. A structural optimization approach is proposed in this paper to optimize the pile foundation shape in integral abutment bridges. A procedure was implemented based on linking MATLAB, where an optimization code was developed, and OpenSees, which was used as the finite element solver. The optimization technique was compared with other techniques developed in previous researches to verify its reliability; the technique was then applied to a real 400 m-long IAB building in Verona, Italy, as a case study. The following two possi- bilities were considered and compared： （a） a pile with two different diameters along the depth and Co） a pile with a pre-hole. In fact, to increase the lateral and rotational flexibilities of the pile head, piles for an integral abutment bridge foundation are often driven into pre- deep holes filled with loose sand. Finally, the case of super-long integral abutment bridges （L = 500 m） with a corresponding displacement on one bridge end of approximately 50 mm was analysed. The following four pile design optimization eases were considered with similar study criteria as the Isola della Scala Bridge： （a） a pinned pile head for semi-integral abutment, Co） a fixed pile head without a pre-hole, （c） a fixed pile head with a pre-hole of any depth, （d） a fixed pile head of a pre-hole with a depth limit （〈 2 m） allowing for enoughembedded length for the friction pile. The case studies confirmed the potential of the proposed optimization techniques for finding the optimal shape of piles in integral abut- ment bridges.
