What Is a Plate Girder?

The upper structure of the bridge mainly includes slab beams, box beams and T-beams, which refers to the cross-section form of the main beam of the bridge. The cross-section forms of beam bridges are generally: slabs (divided into hollow slabs and solid slabs), T beams, and box girder Prefabricated and cast-in-place, small box girder and box girder), etc., which include I-shaped slab beams, hollow slab beams, etc. depending on the form.

Refers to a beam-type structural member composed of steel plates. The basic cross-sectional shape is I-shaped, up and down

The force of a single bridge beam means that the bridge beams lose their horizontal connection. The action from the vehicle cannot be distributed across the bridge, but directly acts on a certain beam of the bridge. Monolithic beams are often subjected to forces, especially direct overload forces, which cause the concrete and steel bars in the beam to enter the fatigue period in advance. Cracks first appear on both sides of the lower part of the bridge, and then the cracks develop into horizontal and vertical penetrations. The bridge appears to be deflected downward, the concrete on the upper part of the beam is broken, the beam slab loses its bearing function, breaks occur, and the vehicle cannot pass. Through the investigation of the use of the upper structure of the highway hollow slab bridge in Zhejiang Province, it is found that the main reasons for the formation of the monolithic beam are as follows.

The stress of the monolithic beam is more prominent; the main reasons for the stress of the monolithic beam are joints, bridge deck paving, bearings, and foundation. Therefore, the prevention of the monolithic beam of the hollow slab bridge must be addressed from the following aspects.

Beam hinge

After analyzing the failure mechanism of hinge joints, it is considered that the failure of hinge joints is not only a problem of strength, but also the stiffness is too small due to the limitation of its own structural size. Therefore, after the size of the hinge joint was improved, a large hinge joint form and a cast-in-place wet joint form were introduced. There are also different reinforcement schemes for hinge joint reinforcement

Slab Girder Pavement

In order to enhance the crack resistance of the bridge deck pavement, so that the bridge deck pavement layer has sufficient strength and good integrity, the bridge deck pavement reinforced mesh must be reasonably laid out in the design. For assembled hollow slab beam bridges, Reinforced mesh should also be laid in the bridge deck pavement at the hinge joints to enhance the strength of the hinge joints and avoid longitudinal cracks. During the construction process, the bonding of the pavement concrete on the bridge deck and the top surface of the precast beam and slab concrete is effectively done. Waterproofing must be done and the drainage of the bridge deck must be unobstructed.

Slab bearing

A reasonable support model must be selected when designing; a support with excellent performance should be selected; as much as possible, 4 supports should be supported at the same time during construction, and the force should be uniformly, to avoid the support from vacating before operation. For the existing bridges that have deformed and vacated bearings, they must be replaced in time to ensure that they have the normal function of loading, unloading, and unloading.

Slab foundation

In order to ensure that the foundation does not appear uneven settlement as much as possible, it is recommended to do an effective bridgehead soft foundation treatment especially in the soft soil foundation area, there is no pile-up situation in the space under the bridge, and no water accumulation in the dry bridge area. ^{[2] [1]}

Plate beam other

For bridges whose beams have been cracked, the beams and plates are reinforced with epoxy mortar pasted with a 5mm thick A3 steel plate, which can compensate for the development of beams and plates due to insufficient bearing capacity. The effect is obvious after use. For bridges with cracked beams caused by over-limiting heavy-duty vehicles, the necessary heavy-duty restrictions must also be implemented after the reinforcement treatment is completed. ^[2]