Study On Flexural Performance Of Pretensioned Centrifugal Spun Concrete Piles With Steel Strands

With the development of construction industrialization in China,precast prestressed concrete piles are widely used in foundation engineering with the advantages of high bearing capacity,convenient manufacture process and reliable pile quality,among which the pretensioned spun concrete piles are the most widely used piles.However,the pretensioned spun concrete pile shows the problems of insufficient lateral resistance,poor deformation ductility and low seismic performance,which limits its application in high seismic fortification intensity zones.In this paper,it is proposed to improve the material and anchorage methods of prestressing tendons in the ordinary pretensioned spun high-strength concrete piles,and the pretensioned centrifugal spun high-strength concrete piles with steel strands are developed.The traditional prestressing steel bars are replaced by prestressing steel strands with high strength and high ductility,and the prestressing steel strands are anchored on the end plates with clamp type anchorage device.In addition,the non-prestressing tendons are added in the pretensioned centrifugal spun high-strength concrete piles with steel strands to improve the ultimate bearing capacity,and the pretensioned centrifugal spun high-strength concrete piles with hybrid steel strands and reinforcing bars are also developed.The flexural performances of the two new types of piles are systematically studied in this paper.The main work can be summarized as follows(1)The material properties tests are carried out on the concrete blocks,prestressing tendons,non-prestressing tendons and spiral stirrups which are the same batch as the pile test specimens,so as to obtain the key material mechanical parameters.The material constitutive models used in the subsequent finite element analysis and theoretical calculation are also determined.(2)The full-scale bending tests of the ordinary pretensioned spun high-strength concrete piles and the pretensioned centrifugal spun high-strength concrete piles with steel strands are conducted to study the effect of material of prestressing tendons on the flexural performance of piles.The numerical model is established using the finite element analysis software,and the numerical simulation results are compared with the experimental results to verify the reliability of the model.The theoretical calculation model on section bending moment is also developed and the corresponding calculation methods are put forward.By comparing the calculation results with experimental results,the feasibility of the methods is verified.(3)The full-scale bending tests of the pretensioned centrifugal spun high-strength concrete piles with hybrid steel strands and reinforcing bars are carried out.The effect of configuration of non-prestressing tendons on the flexural performance of piles is studied by comparing with the experimental results of the pretensioned centrifugal spun high-strength concrete piles with steel strands.The established finite element model and theoretical calculation model are used to study the flexural performance of the piles.and the applicability of these models is verified by comparing with experimental results.(4)The full-scale bending tests of the pretensioned spun high-strength concrete piles with high concrete compressive pre-stress are carried out.The effect of level of concrete compressive pre-stress on the flexural performance of piles is studied by comparing with the experimental results of the pretensioned spun high-strength concrete piles with medium concrete compressive pre-stress.The established finite element model and theoretical calculation model are used to study the flexural performance of the piles,and the applicability of these models is verified by comparing with experimental results.The aforementioned work can be the important basis for the design and application of the two new types of piles.