| Ordinary prestressed concrete pipe piles are technically mature and widely used,but they have defects such as low horizontal bearing capacity and poor seismic performance,which greatly restrict their development.Precast concrete solid square piles have high horizontal bearing capacity and good ductility.The prestressed steel bars used in ordinary prestressed pipe piles have poor ductility and are easily pulled off during bending.The cracking moment of ordinary prestressed pipe is similar to the ultimate bending moment and can easily causing engineering accidents.Steel strands have high tensile strength and good ductility.By combining the advantages of ordinary prestressed pipe piles,precast concrete solid square piles and steel strands,a new precast pile is proposed which uses steel strand as prestressed reinforcement and is equipped with hot-rolled reinforcement in this present study.Hereinafter referred to as prestressed steel strand square piles with reinforcement(PRS).The mechanical properties of the PRS were studied by a combination of prototype tests and finite element numerical simulations.The bending,shear and tensile tests were carried out at full scale.The finite element model was also established for the parametric analysis and the finite element simulation study of horizontal pushover of pile-soil interaction.The main study was summarized in the following aspects.(1)Study on material mechanical properties.Material mechanical tests were conducted on concrete specimens,hot-rolled steel bars,steel strands and hoops made from the same batch as the PRS.The principal structure relationship of concrete and reinforcement was determined based on the test results.(2)Study on flexural performance of the PRS.Bending performance tests were conducted on full-scale specimens to study the differences in bending performance,deformation capacity,cracking resistance and damage pattern of the PRS with different specifications.A finite element model of the PRS flexural resistance was established.Based on the accurate and reliable finite element model,parametric analysis was carried out to derive the optimal reinforcement rate for the PRS by analyzing different prestressed reinforcement rates and nonprestressed reinforcement rates.(3)Study on sheer performance of the PRS.Shear performance tests were carried out on the full-scale specimens to study the differences in shear resistance,deformation capacity and damage pattern.A shear finite element model of the PRS was established.Based on the accurate and reliable finite element model,the bearing capacity analysis and damage process analysis of the PRS were carried out.The effects of volume hoop ratio and shear-to-span ratio on the shear bearing capacity and damage form of the PRS were studied by parametric analysis.(4)Study on tensile performance of the PRS.Full-scale tests on the tensile performance of the PRS were carried out.The differences in characteristics such as crack resistance,deformation capacity,ultimate tensile bearing capacity,and failure mode of steel strand square piles of different specifications were studied.(5)Study on seismic performance of the PRS.ABAQUS was used to simulate the existing prototype test data of pile-soil interaction in engineering to verify the reliability of the parameters of the finite element model.The load-displacement curve,skeleton curve,ductility,equivalent viscous damping coefficient and concrete stress of the PRS under horizontal pushover loads were analyzed.The seismic performance of the prestressed steel bar pile model was compared to evaluate the seismic performance of the PRS and to provide reference for the seismic design of the PRS. |
