The equations of the lateral deflection curve of the short pier shear wall under a lateral concentrated load at any level are derived by employing a continuous approach. Lateral flexibility matrixes for the dynamic an...The equations of the lateral deflection curve of the short pier shear wall under a lateral concentrated load at any level are derived by employing a continuous approach. Lateral flexibility matrixes for the dynamic analysis are also obtained by repeatedly calculating the lateral unit load on the wall at each level where a lumped mass located. Dynamic analyses are implemented for short pier shear walls with different parameters, called the integrative coefficient and the pier strength coefficient related to the dimensions of walls. The influences of two coefficients on the dynamic performances of the structure are studied. Results indicate that with the increase of the integrative coefficient, the periods of top two modes apparently decrease but the other periods of higher frequency modes show little variation when the pier strength coefficient remains constant. Similarly, if the integrative coefficient is constant, the top two periods of the free vibration decrease with the increase of the integrative coefficient but the other periods of higher frequency modes show less variation.展开更多
Experimental investigations have been carried out to study morpho-hydraulic characteristics such as scour geometry and turbulent flow properties around tandem piers in alluvial channels. Experiments were carried out i...Experimental investigations have been carried out to study morpho-hydraulic characteristics such as scour geometry and turbulent flow properties around tandem piers in alluvial channels. Experiments were carried out in a plane sand bed with two circular piers of same diameter arranged in tandem manner under no seepage, 10% seepage and 20% seepage conditions. Downward seepage minimizes the scour depth around piers and restrains the development of scour depth with time. Strong reversal flow is found near the bed at upstream of piers and near free surface at downstream of piers where velocity and Reynolds shear stress are found to be negative which reduce in magnitude with downward seepage. The flow is more critical within the gap between two piers where velocity is lesser near free surface and gradually increasing towards bed. Quadrant analysis shows that contribution of each event to the total Reynolds shear stress increases with downward seepage. Sedimentation effect prevails within the scour hole whereas outside the scour hole erosive forces become more dominant. Reduced reversal flow at upstream of pier because of downward seepage results in decreasing higher order moments and turbulent kinetic energy. At downstream of piers, secondary currents are dominant due to wake vortices. Strouhal number decreases in case of seepage runs than no seepage condition.展开更多
In this work, experimental investigations have been pursued to analyse the influence of downward seepage on the turbulent characteristics of flow and corresponding changes in vortex structure around circular bridge pi...In this work, experimental investigations have been pursued to analyse the influence of downward seepage on the turbulent characteristics of flow and corresponding changes in vortex structure around circular bridge pier in alluvial channel. Experiments were conducted in sand bed channel with circular piers of different sizes for no seepage, 10% seepage and 20% seepage cases. The measurement of turbulent flow statistics such as velocity and Reynolds stresses is found to be negative within the scour hole at upstream of the pier whereas application of downward seepage retards the reversal of the flow causing a decrement in the velocity and Reynolds stresses. Higher Reynolds shear stress prevails at the downstream side because of the production of wake vortices. Contribution of all bursting events to the total Reynolds shear stress production has been observed to increase with downward seepage. The analysis of integral scale suggest that size of eddies increases with seepage, which is responsible for increase in particle mobility. Initially rate of scouring is more which abatements gradually with expanding time as well as with the increased of downward seepage. Presence of downward seepage reduces the depth and length of vortex and shifts towards downstream side of the pier.展开更多
The present study examines scour geometry and turbulent flow characteristics around circular and oblong piers in alluvial channel with downward seepage.Experiments were conducted in plane sand bed of non-uniform sand ...The present study examines scour geometry and turbulent flow characteristics around circular and oblong piers in alluvial channel with downward seepage.Experiments were conducted in plane sand bed of non-uniform sand under no seepage,10%seepage and 15%seepage conditions.Scour depth at oblong pier is significantly lesser than the scour depth at circular one.However,the scour depth at both piers reduces with downward seepage.The measurements show that the velocity and Reynolds stresses are negative near the bed at upstream of piers where the strong reversal occurs.At downstream of oblong pier near the free surface,velocity and Reynolds stresses are less positive;whereas,they are negative at downstream of circular pier.The streamline shape of oblong pier leads to reduce the strength of wake vortices and consequently reversal flow at downstream of pier.With application of downward seepage turbulent kinetic energy is decreasing.The results show that the wake vortices at oblong pier are weaker than the wake vortices at circular pier.The strength of wake vortices diminishes with downward seepage.The Strouhal number is lesser for oblong pier and decreases with downward seepage for both oblong and circular piers.展开更多
At present, the method of calculating the turbulent flow width around the bridge pier is not given in the ＂Standard for Inland River Navigation＂ （GB50139-2004） in China, and the bridge designer usually increases t...At present, the method of calculating the turbulent flow width around the bridge pier is not given in the ＂Standard for Inland River Navigation＂ （GB50139-2004） in China, and the bridge designer usually increases the bridge span in order to ensure the navigation safety, which increases both of the structural design difficulty and the project investments. Therefore, it is extremely essential to give a research on the turbulent flow width around the bridge pier. Through the experiments of the fixed bed and the mobile bed, the factors influencing the turbulent flow width around the bridge pier have been analyzed, such as the approaching flow speed, the water depth, the angles between the bridge pier and the flow direction, the sizes of bridge pier, the shapes of the bridge pier, and the scouting around the bridge pier, etc. Through applying the dimension analytic method to the measured data, the formula of calculating the turbulent flow width around the bridge pier is then inferred.展开更多
The complexity of the IH-635 Managed Lanes Project, located in Dallas County, Texas, posed several technical and constructive challenges, leading to the adoption of solutions different from the traditional. Two altern...The complexity of the IH-635 Managed Lanes Project, located in Dallas County, Texas, posed several technical and constructive challenges, leading to the adoption of solutions different from the traditional. Two alternative solutions for the pier cap on one of the bridge crossings over IH-35E in the IH-635 project were analyzed in this case study, a cast-in-place post-tensioned concrete cap and an innovative prefabricated steel-concrete com- posite cap. The approach was to use an estimation of direct costs for material and labor and consideration of con- struction time schedules. A supplementary numerical modeling confirmed that both alternatives behave elasti- cally under imposed loads. The direct cost of material and labor for the two alternatives were close. However, the composite alternative required 13 days less construction time, resulting in substantial cost savings from traffic closing in the very busy traffic corridor. Traffic closing costs were substantially higher than the direct costs, especially for the post-tensioned cap. The quantification of the benefits allows more confidence in the utilization of the composites caps, leading to faster completion of bridge projects and substantial economic savings.展开更多
Jiangyin Yangtze highway bridge is a suspension bridge with main span 1 385 m. The south tower pier is located on a 70 m bedrock slope with bedding plane of strata tipping to the river channel and several weak interca...Jiangyin Yangtze highway bridge is a suspension bridge with main span 1 385 m. The south tower pier is located on a 70 m bedrock slope with bedding plane of strata tipping to the river channel and several weak intercalated layers. The stability of the tower pier is one of the main engineering geologic problems. On the basis of investigation and survey of relevant geologic condition analyses, the geomechanical model experiments are carried out for stability study of various foundation alternatives’ advantages and disadvantages. Pile foundation has been finally adopted and constructed, and this is justified by practice.展开更多
文摘The equations of the lateral deflection curve of the short pier shear wall under a lateral concentrated load at any level are derived by employing a continuous approach. Lateral flexibility matrixes for the dynamic analysis are also obtained by repeatedly calculating the lateral unit load on the wall at each level where a lumped mass located. Dynamic analyses are implemented for short pier shear walls with different parameters, called the integrative coefficient and the pier strength coefficient related to the dimensions of walls. The influences of two coefficients on the dynamic performances of the structure are studied. Results indicate that with the increase of the integrative coefficient, the periods of top two modes apparently decrease but the other periods of higher frequency modes show little variation when the pier strength coefficient remains constant. Similarly, if the integrative coefficient is constant, the top two periods of the free vibration decrease with the increase of the integrative coefficient but the other periods of higher frequency modes show less variation.
文摘Experimental investigations have been carried out to study morpho-hydraulic characteristics such as scour geometry and turbulent flow properties around tandem piers in alluvial channels. Experiments were carried out in a plane sand bed with two circular piers of same diameter arranged in tandem manner under no seepage, 10% seepage and 20% seepage conditions. Downward seepage minimizes the scour depth around piers and restrains the development of scour depth with time. Strong reversal flow is found near the bed at upstream of piers and near free surface at downstream of piers where velocity and Reynolds shear stress are found to be negative which reduce in magnitude with downward seepage. The flow is more critical within the gap between two piers where velocity is lesser near free surface and gradually increasing towards bed. Quadrant analysis shows that contribution of each event to the total Reynolds shear stress increases with downward seepage. Sedimentation effect prevails within the scour hole whereas outside the scour hole erosive forces become more dominant. Reduced reversal flow at upstream of pier because of downward seepage results in decreasing higher order moments and turbulent kinetic energy. At downstream of piers, secondary currents are dominant due to wake vortices. Strouhal number decreases in case of seepage runs than no seepage condition.
文摘In this work, experimental investigations have been pursued to analyse the influence of downward seepage on the turbulent characteristics of flow and corresponding changes in vortex structure around circular bridge pier in alluvial channel. Experiments were conducted in sand bed channel with circular piers of different sizes for no seepage, 10% seepage and 20% seepage cases. The measurement of turbulent flow statistics such as velocity and Reynolds stresses is found to be negative within the scour hole at upstream of the pier whereas application of downward seepage retards the reversal of the flow causing a decrement in the velocity and Reynolds stresses. Higher Reynolds shear stress prevails at the downstream side because of the production of wake vortices. Contribution of all bursting events to the total Reynolds shear stress production has been observed to increase with downward seepage. The analysis of integral scale suggest that size of eddies increases with seepage, which is responsible for increase in particle mobility. Initially rate of scouring is more which abatements gradually with expanding time as well as with the increased of downward seepage. Presence of downward seepage reduces the depth and length of vortex and shifts towards downstream side of the pier.
文摘The present study examines scour geometry and turbulent flow characteristics around circular and oblong piers in alluvial channel with downward seepage.Experiments were conducted in plane sand bed of non-uniform sand under no seepage,10%seepage and 15%seepage conditions.Scour depth at oblong pier is significantly lesser than the scour depth at circular one.However,the scour depth at both piers reduces with downward seepage.The measurements show that the velocity and Reynolds stresses are negative near the bed at upstream of piers where the strong reversal occurs.At downstream of oblong pier near the free surface,velocity and Reynolds stresses are less positive;whereas,they are negative at downstream of circular pier.The streamline shape of oblong pier leads to reduce the strength of wake vortices and consequently reversal flow at downstream of pier.With application of downward seepage turbulent kinetic energy is decreasing.The results show that the wake vortices at oblong pier are weaker than the wake vortices at circular pier.The strength of wake vortices diminishes with downward seepage.The Strouhal number is lesser for oblong pier and decreases with downward seepage for both oblong and circular piers.
基金Supported by the West Waterway Transportation Construction Foundation under Grant No.2004-328-000-40.
文摘At present, the method of calculating the turbulent flow width around the bridge pier is not given in the ＂Standard for Inland River Navigation＂ （GB50139-2004） in China, and the bridge designer usually increases the bridge span in order to ensure the navigation safety, which increases both of the structural design difficulty and the project investments. Therefore, it is extremely essential to give a research on the turbulent flow width around the bridge pier. Through the experiments of the fixed bed and the mobile bed, the factors influencing the turbulent flow width around the bridge pier have been analyzed, such as the approaching flow speed, the water depth, the angles between the bridge pier and the flow direction, the sizes of bridge pier, the shapes of the bridge pier, and the scouting around the bridge pier, etc. Through applying the dimension analytic method to the measured data, the formula of calculating the turbulent flow width around the bridge pier is then inferred.
基金herein for allowing the use of various data from the LBJ Project in the development of this paper
文摘The complexity of the IH-635 Managed Lanes Project, located in Dallas County, Texas, posed several technical and constructive challenges, leading to the adoption of solutions different from the traditional. Two alternative solutions for the pier cap on one of the bridge crossings over IH-35E in the IH-635 project were analyzed in this case study, a cast-in-place post-tensioned concrete cap and an innovative prefabricated steel-concrete com- posite cap. The approach was to use an estimation of direct costs for material and labor and consideration of con- struction time schedules. A supplementary numerical modeling confirmed that both alternatives behave elasti- cally under imposed loads. The direct cost of material and labor for the two alternatives were close. However, the composite alternative required 13 days less construction time, resulting in substantial cost savings from traffic closing in the very busy traffic corridor. Traffic closing costs were substantially higher than the direct costs, especially for the post-tensioned cap. The quantification of the benefits allows more confidence in the utilization of the composites caps, leading to faster completion of bridge projects and substantial economic savings.
文摘Jiangyin Yangtze highway bridge is a suspension bridge with main span 1 385 m. The south tower pier is located on a 70 m bedrock slope with bedding plane of strata tipping to the river channel and several weak intercalated layers. The stability of the tower pier is one of the main engineering geologic problems. On the basis of investigation and survey of relevant geologic condition analyses, the geomechanical model experiments are carried out for stability study of various foundation alternatives’ advantages and disadvantages. Pile foundation has been finally adopted and constructed, and this is justified by practice.
