体外预应力混凝土连续梁弯曲性能试验研究

为了研究体外预应力混凝土连续梁的弯曲性能、极限受力状态及内力重分布规律,以施工方法和体内外预应力筋配比为参数,对1根整体式(体内外配筋)和2根节段式(体内外配筋和全体外配筋)体外预应力混凝土连续梁进行了模型试验。通过试验数据分析,得到了模型梁挠度、混凝土应变、体外预应力筋应力与有效高度随荷载变化规律,以及混凝土裂缝发展与分布情况。结果表明:整体式梁的混凝土极限压应变和挠度最大、延性较好但体外预应力筋有效高度减少最大,节段式体内外预应力梁的体外预应力筋极限应力最大,节段式全体外预应力梁的混凝土极限压应变和挠度最小、延性较差、体外预应力筋极限应力及有效高度减少也最小。节段式梁的裂缝主要集中在接缝位置、无斜裂缝,接缝位置的塑性变形使内力重分布更充分。整体式梁内力重分布的区域集中而节段式全体外预应力梁的范围较大,各梁控制截面弯矩增、减幅值不超过10%。

Experimental study on the flexural behavior of externally prestressed concrete continuous beams

To study the flexural behaviour,limit bearing state and internal force redistribution of externally prestressed concrete continuous beams,a monolithic(externally and internally prestressed) and two segmental(one externally and internally prestressed and the other externally prestressed) concrete continuous model beams were tested with the construction method and the ratio of internal tendons to external tendons as the parameters.From the test results,the deflection of concrete beams,strain of concrete,stress and effective height of external tendons with variations of loading are analysed,and the development and distribution of cracks investigated.It is shown that the monolithic beam has the largest deflection and ultimate compressive strain of concrete,best ductility and the smallest effective height of external tendons;the ultimate stress of externally prestressing tendons of the segmental externally and internally prestressed beam is the largest;the segmental externally prestressed beam has the smallest deflection and ultimate compressive strain of concrete,worst ductility,smallest ultimate stress and the largest effective height of externally prestressing tendons.In addition,for the segmental beams,cracks are concentrated near the joints and no oblique cracks are detected,the internal force distribution is more sufficient due to plastic deflections at the joints.The internal force redistribution in the monolithic beam is more concentrated,whereas that in the segmental externally prestressed beams is more widely spread.The range of bending moment redistribution in critical sections of the model beams is below 10%.