Deterioration Process and Evaluation of Strengthening Methods for Reinforced Concrete Bridge Deck

随着交通的日益繁忙，桥面板损坏的案例逐年增多。阐明冲剪破坏的机理具有重要的基础意义。此外，还提出了各种损伤桥面板的加固方法，可分为两种。一种是所谓的表面强化法。SFRC堆焊和D-RAP法都属于这一类。另一种是所谓的底面强化法。在这种情况下，钢板或碳纤维板（CFRP）是由环氧树脂粘在板的下表面。通过试验研究，阐明了冲剪破坏的机理，并对上述加固方法进行了评价。主要结论如下：1)加载试验过程中，加载位置附近板的径向表面压缩应变先增大，在冲剪破坏发生前，表面压缩应变逐渐减小，最终变为拉压，但周向应变单调增大。这说明在加载过程中，靠近加载位置的板坯内部结构发生了应力流动的变化。2)冲剪开裂在末期不顾已存在的弯裂而突然扩展。3)表面加固方法的效果与同深度板的效果相当。4)底面加固时，抗弯刚度大幅度提高。增加的原因是胶合材料对裂纹重新打开的抑制作用。

The heavier the traffic becomes, the more cases of damaged bridge deck slabs are reported year by year. It is basically important to clarify the mechanism of punching shear failure. In addition, various strengthening methods for damaged bridge deck slabs have been proposed and they can be divided into two. One is so-called surface strengthening method. SFRC surfacing and D-RAP method are included in this category. The other is so-called bottom surface strengthening method. In this case, steel plates or carbon-fiber sheets (CFRP) are glued on the lower face of slab by epoxy resin. Experimental studies were made to clarify the mechanism of punching shear failure and to evaluate the strengthening methods stated the above.Principal conclusions derived are as follows ;1) During loading tests, surface compression strain of slabs in radial direction near loading position increased at first and it turned to decrease fairly before punching shear failure occurred and even became tension at final stage, though strain in circumferential direction increased monotonously. The fact suggests that the changing of stress flow occurred in the internal structure of slab near loading position during loading.2) Punching shear cracking spread abruptly irrespective to the existing bending cracks at final stage.3) The effectiveness of surface strengthening method showed just as the same level as the slabs with same depth.4) In case of bottom surface strengthening flexural rigidity increased largely. The increase is caused by the arresting effect of crack re-opening with the glued materials.