Experimental Study On Bearing Capacity Of Reinforced Concrete Members Covered With Steel Tube

Rock-socketed piles are widely used in port and bridge engineering for their high bearing capacity, low settlement and good seismic performance. Only the bearing capacity of reinforced concrete is considered in current design, while that of steel casing is neglected. It will reduce the quantity of reinforcement and decrease the project costs if the effect of steel casing is considered. The members consisting of steel casing and reinforced concrete are called reinforced concrete members covered with steel tube, whose bearing capacity calculating method is not uniform currently. The project team of "Research on Bearing Capacity of Reinforced Concrete Members Covered with Steel Tube in Rock-socketed Pile" has proposed calculating method for reinforced concrete members covered with steel tube. In order to verify the proposed method, axially and eccentrically compressed experiments were carried out on reinforced concrete specimens covered with steel tube. The main contents and conclusions are summarized as follows:(1) Experiments were conducted on 2 axially compressed specimens and 6 eccentrically compressed specimens, whose eccentricities were 50mm,100mm,150mm,200mm,250mm and 300mm respectively. Strains of the steel tube and steel bar, mid-span deformation of the specimens were measured. Load-deformation curve and N-M curve of the specimens were acquired, which were compared with the calculating results. The results show that strength of the core concrete is enhanced and the failure is postponed owing to the confinement effect of the steel tube, bearing capacity and plastic deformation capacity of the specimens are improved greatly. The bearing capacity of circular reinforced concrete members covered with steel tube can be calculated by the method proposed by the project team of "Research on Bearing Capacity of Reinforced Concrete Members Covered with Steel Tube in Rock-socketed Pile".(2) Combining with a design case for pile-supported wharf, application of bearing capacity calculating formula for reinforced concrete members covered with steel tube was discussed. In order to analyze the effect of steel tube, two conditions were conducted in the process of reinforcement calculation, respectively were considering the effect of steel tube and leaving out the effect of steel tube. The amount of reinforcement of the two conditions was compared. The results show that the quantity of reinforcement decreases largely in the condition of considering the effect of steel tube. When considering the steel tube, even constructional reinforcement can meet the demand of bearing capacity.