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一、引言混凝土强度等级高达C80的高强度预应力混凝土管桩(PHC桩)在我国长江三角洲、珠江三角洲等地已得到了广泛应用,并且大量出口港澳地区,在国际市场上颇具竞争力。PHC桩的类型是由混凝土有效预应力的大小确定的。A、AB、B和C型管桩的混凝土有效预应力值分别约为1.0、6.0、8.0和10.0MPa级。A型和AB型和PHC桩有效预应力值是考虑防止管桩在运输、起吊、施工时开裂及防止打桩时桩尖的反弹拉应力引起开裂等情况制定的;B型和C型PHC桩的有效预应力值则是考虑产品在承受轴向力的同时承受更高侧向力和柱子的情况制定的。 PHC桩中预应力钢筋的有效预应力取决于钢筋的张拉值及预应力的损失值,钢筋中的预应力损失值由张拉端锚具变形(σ(?))、
I. INTRODUCTION High-strength prestressed concrete pipe piles (PHC piles) with a concrete strength rating of up to C80 have been widely used in the Yangtze River Delta and the Pearl River Delta in China, and have been exported to Hong Kong and Macau in large quantities, making them competitive in the international market. The type of PHC pile is determined by the size of the effective prestress of the concrete. The concrete prestressing values of A, AB, B and C pipe piles are about 1.0, 6.0, 8.0 and 10.0 MPa respectively. The effective prestress values of A-type and AB-type and PHC piles are determined taking into account the prevention of cracks in the piles during transportation, lifting, and construction, and the prevention of cracking caused by rebounding tensile stress of the pile tip during pile driving; B-type and C-type PHC piles The effective prestress value is based on the fact that the product is subjected to higher lateral forces and columns while it is subjected to axial forces. The effective prestressing force of prestressed steel bars in PHC piles depends on the tension value of the steel bars and the loss value of the prestressing force. The prestress loss value in the steel bar is caused by deformation of the tensile anchorage (σ(?)),