Crack reinforcement of Xiamen overpass

General situation of bridge

The bridge is a double trumpet type overpass. The bridge type includes reinforced concrete special-shaped beam, reinforced concrete simply supported box girder, prestressed hollow slab beam, prestressed box connecting beam and so on. The lower layout has cylindrical piers, T shaped piers and so on. Describe load steam over 20, hang - 120, crowd load is 3.5KN/ square meters

Disease 

In addition to the prestressed concrete beam, the large part of the reinforced concrete box girder is cracked.

Cracks in reinforced concrete beam for transverse cracks, from support to mid span scale fundamental evenly spread large local cracks extend from the base to the web width of 0.1 mm to 0.32 mm.

The crack of reinforced concrete box girder, pier pier from 1# to 6#, each beam beam has transverse cracks, most cracks from beam bottom extends to the web, the bottom flange of the first extension of small cracks, crack width of 0.2 mm to 0.25 mm. The upper end of the local pier presents vertical cracks, crack length 0.15m ~ 0.70M, width of 0.05 mm to 0.3 mm

The reason of disease

At the crack of box girder, pier, by analyzing the reason that attack crack is various, elements are very messy, but the main reason is: the effect of temperature, shorten the construction process of concrete creep effect, increased traffic jam caused by the beam lead after overload and overload vehicle bridge etc.

Treatment of cracks

Because the bridge is located southeast of the coastal city, there are many cracks in the bridge after a considerable period of time the erosion of moist air, the bearing capacity and durability of the adverse effects of bridge layout. Therefore, it is necessary to repair the cracks completely and thoroughly to reinforce the layout. In order to facilitate the repair and reinforcement, the cracks were classified, one is the stress cracks, this kind of crack is serious; another kind of fault stress cracks, crack width greater than 0.20 mm; the third category is the crack width less than 0.20 mm in the non bearing cracks.

On the first crack, after checking the layout, adopt 1~2 layers of carbon fiber cloth posted to the bearing capacity and durability to the layout of progress layout; second kinds of cracks, adopt pressure grouting reinforcement method; third kinds of cracks, the appearance of the solution adopted closed.

Crack disposal: shaped beam beam cracks are mainly distributed in the box girder side surface (WEB) and the bottom of the beam, the adoption of HM carbon fiber cloth to reinforce surface and the side surface in the lateral beam bottom (WEB) posted on the two layer of carbon fiber cloth, other local posted a layer of carbon fiber cloth.

The disposal of crack of reinforced concrete beams simply supported box beam when the crack width is relatively small, the cracks on the crack width greater than 0.20 mm, the adoption of the first pressure grouting, and then put a layer made of carbon fiber cloth reinforcement measures.

Reinforcement effect inspection

After the completion of the whole bridge, the static and dynamic load test is carried out to the bridge, and the reinforcement effect is verified. The experimental results show that the effect of the load in the experimental section, control beam strain and displacement coefficient correlation were satisfied with the standard requirement, the residual deformation is small, the dynamic characteristics and the value of similar bridge layout than in the constant scale, the bridge layout depicting load load demand satisfaction. After the completion of the reinforcement project, it has been running for nearly two years, and its operation is normal.