Study On The Behavior Of Piles Under Inclined Loads

With the high-speed development of large span bridges and high-rise buildings, analysis of piles under inclined loads (or simultaneous axial and lateral loads) is becoming increasingly important. At present, abroad studies in this field are still limited to the determination of inclined ultimate loads and discussion of Zhang Method, and more emphasis is put on laboratory model tests. Some initial theoretical work has been done at home, but relative model tests are scarcely reported. Based on a summarization of existent analytical methods and applications of inclined-loading piles and mass theoretical analysis and model tests in this paper, such important achievements associated with the home engineering have been acquired as follows: 1. Through setting up the deflection differential equation of piles under inclined loads and using the M-method in current codes as basic principles, a series of design theories and computational methods are obtained, which are applicable for engineering practice in our country. Two dimensionless parameters 2. and k are used to consider the influences of axial load on the butt and the self weight of pile, and four dimensionless coefficients D5 are also raised in the determination of the maximum bending moment. With the introduction of P L effect and the principle of equivalent conversion from structural mechanics. anal is of inner forces and deflections along the pile shaft for column piers under a synthetic action of automobile braking force.. wind force.. self weight of bridges and vehicles~ self weight and side friction of piles, and other complicated loads is successfully resolved and the corresponding calculation program is worked out. 2. By introducing the finite element-finite layer theory to the inner forces and displacement analysis of inclinedly loaded piles, stiffness matrix of pile-soil interaction is established by a semi-analytical and semi-numerical layer method. Improvements are made to the current finite element-finite layer method and a new concept of weighting foundation modulus is adopted. An analytical solution to determine the radial displacement distribution of soil behind the pile under one unit horizontal load is deduced by elastic theory, through which nonlinear character of subsoil can be easily taken into account in calculation and the results are also more agreeable with the practice. Furthermore, a finite element-finite layer program by Visual Basic 6.0 is worked out to analyze the inner forces and deflections of piles under inclined loads, in which the P effect is initially considered by adopting incremental analysis method and weighting foundation modulus. Numerical computation of typical piles by this program states that, inner forces and deflections of piles under inclined loads with many factors. such as stiffness of subsoiL free length of pile butt, angle and magnitude of inclined loads, and the variant characteristics and rules from which are summarized and can be applied to direct engineering practice qualitatively 3. As most of the soil in engineering practice is stratified, a semi-analytical power series solution for piles under inclined loads in two-layered soil system is raised in this paper. For easy application in practice. a more reasonable conversion method of equivalent m is proposed. and a modification method of the maximum bending moment in the pile and the corresponding semi-empirical formula are recommended after mass numerical calculation, which results in a more convenient use and a higher precision for rn-method of two-l...