提出了一种能考虑泊松效应影响的弹塑性荷载传递模型（t-z模型）。该模型既能反映不同材料的桩基在同一土体中抗压承载力的不同，也能反映同一材料桩基在同一土体中桩身抗压摩阻力与抗拔摩阻力的不同，同时还具备模拟循环荷载下t-z曲线滞回特性的能力。根据位移协调算法编制了可用于竖向压、拔荷载作用下单桩响应分析的Matlab程序，利用程序对模型试验进行了模拟，结果对比证明了该模型的适用性。最后分析了桩体弹性模量对压、拔极限摩阻力比值的影响，结果表明，该比值随弹性模量的减小而减小，对于混凝土桩，该值介于0.6～0.8之间，与规范建议的抗拔系数接近。

An elastic-plastic load-transfer model (t-z model), which can consider the Poisson's effect, is proposed. The model can reflect both the difference in compressive bearing capacity between the piles of different materials embedded in the same soil and the difference between the compressive friction and the tensile friction for the same pile embedded in the same soil. In addition, the model can also take into account the hysteretic characteristics of t-z curve under the cyclic load. A Matlab program, which can simulate the pile responses under both the compressive load and the tensile load, is developed based on the displacement coordination algorithm. The applicability of the model is demonstrated by comparing the measured results and the calculated results with the program. Finally, the influence of the elastic modulus of pile material on the ratio of the ultimate tensile friction to the ultimate compressive friction is studied. It is shown that the ratio decreases with the decrease of elastic modulus. The ratio is between 0.6 and 0.8 for the concrete pile, which is very close to the value proposed by the standard.