某图书馆预应力框架梁施工裂缝评价与处理

EVALUATION AND RETROFIT OF CONSTRUCTION CRACK ON PRESTRESSED CONCRETE FRAME BEAMS FOR A LIBRARY

某图书馆局部采用了6层跨度为17.6 m的预应力混凝土框架。由于三层梁板施工时支撑紧张,在未对一、二层框架梁中预应力筋实施张拉条件下即将一层支撑移至了三层,致使一层框架梁跨中部分区域出现最大宽度达1.0 mm、延伸到板底的多条裂缝。尽管对一、二层框架梁中预应力筋进行了及时补拉,补拉后大部分裂缝已趋于闭合,但框架梁个别残余裂缝宽度仍有0.1 mm左右。分析了施工阶段预应力混凝土框架梁出现裂缝的原因,对出现裂缝的框架梁进行了评价,提出了裂缝处理方法,可供处理同类工程事故时参考。

Six-story 17.6-meter-span prestressed concrete frames were used for a library. As the formwork was rare for the construction of three floors, the formwork in the first floor was moved mistakenly into the third floor for its concrete cast before prestessing tendons in the first floor were tensioned. Thus, cracks appeared on the mid-span of the first-story beams, and their width was over 1.0 mm, and height extended to bottom of slab. Pretressing tendons in frame beams of first and second floors were pulled immediately after the accident. Although major cracks on the beams were closed, the width of partial cracks was still above 0.1 mm. The reason of appearance of construction cracks was analyzed. The frame structures with construction cracks were evaluated, and retrofit scheme was proposed. It can be served as reference for prevention of the same engineering accident.