It is helpful to improve the seismic design theory of long-span continuous bridges for studying the seismic performance of each cantilever construction state.Taking the Bridge 1 in the north of Changbai-Mountain inter...It is helpful to improve the seismic design theory of long-span continuous bridges for studying the seismic performance of each cantilever construction state.Taking the Bridge 1 in the north of Changbai-Mountain international tourism resort as an example,the authors studied it in shutdown phase and the cantilever construction process,established the simulation model by using Midas / civil,and analyzed time-history of each construction stage for the bridge.The study shows that long-span bridge cantilever construction in northeastern China can be divided into two-year tasks for construction(suspending in winter).It is needed to think about seismic stability of the cantilever position in shut-down phase of winter.The effect of longitudinal vibration is the most disadvantageous influence to bridge,and its calculation results can provide reference for seismic design of similar bridges in the future.展开更多
The temperature change caused by hydration leads to early-age cracking in concrete box girder.The early-age cracking risk is further improved with low air temperature and large daily temperature difference,especially ...The temperature change caused by hydration leads to early-age cracking in concrete box girder.The early-age cracking risk is further improved with low air temperature and large daily temperature difference,especially in Northwest China.To fill this gap,a temperature experiment and numerical simulation were performed on an actual concrete box girder segment in Northwest China.The temperature field,thermal stress and cracking risk were analyzed using evolution curves,distribution curves and contours.The key parameters that influence the hydration heat temperature,including the cement hydration heat release,cement content,height-width ratio of web,initial temperature,convective coefficient of top plate surface,were analyzed.An anti-cracking case based on parameters analysis was put forward.The results indicated that the temperature evolution can be divided into three stages:warming,cooling and environment significantly impacting.Along the thickness of each plate,temperature distributed is single peak in the center.Along the width or height,temperature distributed is double peaks at axillary position for the top and bottom plates,and single peak in center for the web.The axillary position and web have high thermal stress and significant cracking risks.The temperature difference of each plate,and the early-age cracking risk can be reduced by effectively adjusting the key parameters.Among these,the former two parameters are the most significant factors.The maximum cracking risk can be decreased by 15.7%for every 50 kJ/kg hydration heat reduction.The maximum cracking risk can be decreased by 13.1%for every 50 kg/m^(3)cement content reduction.展开更多
文摘It is helpful to improve the seismic design theory of long-span continuous bridges for studying the seismic performance of each cantilever construction state.Taking the Bridge 1 in the north of Changbai-Mountain international tourism resort as an example,the authors studied it in shutdown phase and the cantilever construction process,established the simulation model by using Midas / civil,and analyzed time-history of each construction stage for the bridge.The study shows that long-span bridge cantilever construction in northeastern China can be divided into two-year tasks for construction(suspending in winter).It is needed to think about seismic stability of the cantilever position in shut-down phase of winter.The effect of longitudinal vibration is the most disadvantageous influence to bridge,and its calculation results can provide reference for seismic design of similar bridges in the future.
基金funded by the Key R&D Plan of Qinghai Province(2023-SF-110)the National Natural Science Foundation of China(52108111)the Special Fund for Basic Scientific Research of Central College of Chang’an University(300102212102)。
文摘The temperature change caused by hydration leads to early-age cracking in concrete box girder.The early-age cracking risk is further improved with low air temperature and large daily temperature difference,especially in Northwest China.To fill this gap,a temperature experiment and numerical simulation were performed on an actual concrete box girder segment in Northwest China.The temperature field,thermal stress and cracking risk were analyzed using evolution curves,distribution curves and contours.The key parameters that influence the hydration heat temperature,including the cement hydration heat release,cement content,height-width ratio of web,initial temperature,convective coefficient of top plate surface,were analyzed.An anti-cracking case based on parameters analysis was put forward.The results indicated that the temperature evolution can be divided into three stages:warming,cooling and environment significantly impacting.Along the thickness of each plate,temperature distributed is single peak in the center.Along the width or height,temperature distributed is double peaks at axillary position for the top and bottom plates,and single peak in center for the web.The axillary position and web have high thermal stress and significant cracking risks.The temperature difference of each plate,and the early-age cracking risk can be reduced by effectively adjusting the key parameters.Among these,the former two parameters are the most significant factors.The maximum cracking risk can be decreased by 15.7%for every 50 kJ/kg hydration heat reduction.The maximum cracking risk can be decreased by 13.1%for every 50 kg/m^(3)cement content reduction.
