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

随着交通量的增加，桥面板损坏的案例逐年增多。弄清冲剪破坏的机理是至关重要的。此外，针对破损桥面板的加固方法也有多种，大致可分为两类。一种是所谓的表面强化法。SFRC表面和D-RAP方法包括在这一类中。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）通过环氧树脂胶合在板的下表面上。通过试验研究，阐明了冲剪破坏机理，并对上述加固方法进行了评价。1）在加载过程中，板的径向表面压应变在加载位置附近先增大，在冲剪破坏发生前逐渐减小，最后变为拉应变;尽管周向应变单调增加。结果表明，在加载过程中，板的内部结构在加载位置附近发生了应力流的变化; 2）冲切裂缝在加载后期突然扩展，而与弯曲裂缝的存在无关; 3）表面加固的效果与相同深度的板相当; 4）底面加固的抗弯刚度有较大提高。这种增加是由于粘结材料对裂纹重新张开的抑制作用。

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.