Numerical Simulation Analysis of Welded Joints in Arch Ribs of Large Span Steel Pipe Arch Bridges

In order to study the residual stress distribution law of welded joints of arch ribs of large-span steel pipe concrete arch bridges,numerical simulation of temperature,stress and strain fields based on ABAQUS for welded joints of arch-ribbed steel tubes using 7-,8-and 9-layer welds is carried out and its accuracy is demonstrated.The steel pipe welding temperature changes,residual stress distribution,different processes residual stress changes in the law,the prediction of post-weld residual stress distribution and deformation are studied in this paper.The results show that the temperature field values and test results are more consistent with the accuracy of numerical simulation of welding,the welding process is mainly in the form of heat transfer;Residual high stresses are predominantly distributed in the Fusion zone(FZ)and Heat-affected zone(HAZ),with residual stress levels tending to decrease from the center of the weld along the axial path,the maximum stress appears in the FZ and HAZ junction;The number of welding layers has an effect on the residual stress distribution,the number of welding layers increases,the residual stress tends to decrease,while the FZ and HAZ high stress area range shrinks;Increasing the number of plies will increase the amount of residual distortion.

Effect of soil set-up on the capacity of jacked concrete pipe piles in mixed soils

The increase in capacity of displacement piles with time after installation is typically known as soil/pile set-up. A full-scale field test is carried out to observe the set-up effect for open-ended concrete pipe piles jacked into mixed soils. Both the total capacity and the average unit shaft resistance increase approximately linearly with logarithmic time. The average increase rate for unit shaft resistance is 44% per log cycle, while the average increase for total capacity is approximately 21%. A review on case histories for long-term set-up indicates an average set-up rate of approximately 40%. Based on this, the mechanism of pile set-up is discussed in detail and a three-phase model is suggested.

Experimental study of the separated joint of an underground pipeline rehabilitated by cured-in-place pipe

Reinforced concrete pipes(RCPs)were commonly used in older underground pipelines in Taiwan,China.However,their joints are prone to damage,including fracture and separation,from problems such as overloading,poor backfilling,and liquefaction.For the rehabilitation of such aged pipelines,trenchless methods are preferred to minimize the impact on transportation.The cured-in-place-pipe(CIPP)rehabilitation could be one of the most popular trenchless methods suitable for the cases with angular alignment and changing cross-section.However,according to the existing standards,no details are available on the performance of the rehabilitated parts of the damaged pipeline,including the effect of separated joint.This study designed and conducted laboratory testing on the composite pipe joint(the CIPP rehabilitated RCPs with a separated joint)with different scenarios,including radial and longitudinal loading tests.The radial test results indicated that,for a small separation distance,CIPP rehabilitation can restore the original function of a pipeline and improve its hoop strength.The longitudinal test revealed that the damage due to bending was controlled by the tensile strength of the liner material.The ultimate flexural strength decreased as the separation distance increased.However,pipelines may be subjected to additional loads due to flotation or subsidence,for which the longitudinal loading capacity is often the limiting parameter.For such conditions,it is necessary to confirm,by more research,whether the wall thickness is sufficient.