一、前言预应力混凝土梁、板类构件中(如吊车梁、屋面梁、V形折板、T形板等),经常出现图1所示的端面张拉裂缝。例如河南某工程280余根12米跨度的预应力混凝土大梁,90%以上发生了上述端面裂缝(最大裂缝宽度达2毫米,长度80余厘米),影响了工程质量和施工进度。怎样防止这类裂缝的产生,或者控制裂缝的宽度和长度,使它不致 I. INTRODUCTION In prestressed concrete beams and slabs (such as crane girders, roof beams, V-shaped flaps, T-shaped plates, etc.), the tensile cracks on the face shown in Fig. 1 are often present. For example, in Henan, a project with more than 280 roots of 12-meter-span prestressed concrete girders, the above-mentioned face cracks (maximum crack width of 2 mm and length of 80 cm) occurred above 90%, affecting the project quality and construction progress. How to prevent the occurrence of such cracks, or to control the width and length of cracks so that they will not