Seismic Performance Of Scoured Steel H-Pile To Concrete Cap Edge Connections

Steel H-pile has many advantages such as strong penetration ability, lightweight, convenient splice, good bearing capacity and seismic behavior.etc. Thus, it is more widely used in bridge pile foundation. However, present researches mainly focus on the steel H-piles or caps respectively. Research on connection of steel piles and caps is relatively less, especially on scoured steel H-pile to concrete cap connections. Research and earthquake disaster survey showed that scouring could cause more serious damage of the connections under earthquake. Based on this, this paper took the edge connections of the steel H-pile embedded in the concrete cap as the research object, and completed the following research work:(1)The 7 large scale scoured steel H-pile to concrete cap edge connections were tested under low frequency cycling loads to study the effect of the depth of H-pile in the cap, concrete strength of caps, loading around the strong axis or weak axis and loading obliquely on the experimental results. And the seismic performance indexes such as hysteretic curve, skeleton curve, energy dissipation capacity, ductility, bearing capacity and stiffness degradation h were obtained.(2)In addition to the specimen HPC4 which loaded around the weak axis, positive bearing capacity of other specimens were approximate. The cap fixed steel H-pile well in the positive direction, and H-pile was easily damaged. The positive bearing capacity was controlled by the steel H-pile. As the depth of H-pile embedded in the cap and concrete grade improved, negative capacity increased a lot. The cap fixed steel H-pile badly in the negative direction, and the edge concrete cap was easily damaged. The negative bearing capacity was controlled by the edge concrete cap. Compared with the strong axis, loaded around the weak axis was a weak direction and the bearing capacity decreased significantly; oblique axial force had little effect on the positive bearing capacity, but it influenced negative bearing capacity greatly that negative bearing capacity decreased rapidly; HPC4 damaged with the formation of plastic hinge, so it had the best energy dissipation capacity; the energy dissipation capacity of 1h depth specimen was lower than other specimens significantly while 1.5h was close to 2h; in positive oblique loading, energy dissipation capacity of HPC5 degraded significantly. Depth of H-pile embedded in the cap and concrete strength that improved would allow the specimen to get better seismic performance, but changing vertical load and loading around the weak axis bearing capacity of the specimen would decrease the bearing capacity of the specimens.(3)Based on the test, the paper summarized possible failure modes and developed the method of predicting the bearing capacity of the connection from relevant research literature at home and abroad. It is found that punching shear failure of the edge concrete was happened in the case of negative loading, but the damage of the steel piles was happened in the case of positive loading. Based on the experimental phenomena, the proposed new formula to calculate punching damage was effective to estimate the bearing capacity of the connection.(4)Pushover analysis was carried out by using ABAQUS software for 6 specimens in this experiment and compared with the experimental results. It was found that the results analyzed by finite element method were similar to those of test for specimens with smaller depth, and positive simulation accuracy was less than negative simulation. Stress cloud can simulate the development of two oblique cracks effectively. In general, the simulation had a certain sense of reference but the accuracy should be improved.