Title: Investigation on Punching Behavior of Pile Cap under Column Reinforced by Section Steel Truss
Author(s): Honglei Guo
Publication: Structural Journal
Appears on pages(s): 379-390
Keywords: bearing capacity; pile cap; punching; section steel truss; strut-and-tie
Despite many investigations on the spatial strut-and-tie mechanical mechanism on pile cap punching failure at present, little has been reported on its application. Meanwhile, compared with the steel-reinforced concrete structure extensively existing in the superstructure, that in the foundation structure is yet seldom seen. The real section steel truss of better material properties was used to replace the virtual truss originally regarded as the concrete stress flow for this reason. Aiming at the punching-force bearing behavior of this kind of the pile cap reinforced by the section steel truss, two series (the first is four six-pile caps and the second is two four-pile caps) of the full-size experimental study and the theoretical analysis have been made. Under the condition of the same reinforcing steel amount, in contrast to the ordinary reinforced pile cap, this kind of the section steel truss pile cap can increase the bearing capacity and ductility. It transfers load according to the spatial strut-and-tie. Before a definite column load, the column load is born jointly by the section steel truss and the concrete spatial strut-and-tie. Then, after the concrete strut is decomposed into the two ones coupled at the two ends, the section steel truss gradually shifts into the bearing main-body. With the total yield of the section steel strut and the complete damage to the concrete strut of the splitting in the midpart plus the shear-compression at the two ends, the punching cone is formed. The failure to the composite strut of the section steel and the concrete is an indication of the loss of the pile cap punching bearing capacity. The bearing capacity calculation formulas were deduced based on this, which agree well with the test results.