BEARING CAPACITY EVALUATION OF BRIDGE PILES USING IMPULSE TRANSIENT RESPONSE METHOD

摘要

Bearing capacity evaluation is important for existing bridge with potential defective piles.As the pile loading test and high strain test are not allowed to perform for a long highway bridge in service,impulse transient response method is suggested.Among the measured results,dynamic stiffness is a useful index.Accordingly,an analytical model of mobility response under vertical harmonic loads was deduced and solved.In this model,two inhomogeneous cross sections are considered,to analyze the dynamic stiffness of the integrated and defective piles.In addition,a bearing capacity evaluation method for bridge piles was developed,which based on the transient response measurement and can be used for evaluating a large number of bridge piles.Then,combined with the practical engineering,dynamic measurements for 680 bridge piles were performed.The dynamic stiffness of piles was used for evaluating large quantities of piles quantitatively.With the help of assistant low strain dynamic measurements and statistical analysis of dynamic stiffness,the bearing capacities for piles were calculated and reinforcement suggestions for piles were provided.Results show that:(1)dynamic stiffness changes with the level of the pile defect;(2)for integrated piles,the obvious positive correlation can be found between dynamic stiffness and bearing capacity of piles; and(3)the values of dynamic stiffness have good effects for evaluating the bearing capacity of piles when they bear similar design engineering loads.