Bridge earthquake damage prevention and seismic reinforcement methods

Earthquake disasters can generate great damage energy, resulting in many buildings and infrastructure being damaged to varying degrees, so it is necessary to implement seismic treatment for structures. The causes of bridge earthquake damage and seismic reinforcement measures are introduced.

Causes of earthquake damage: 1. During strong earthquakes, the topography and landform change drastically (such as ground cracks, faults, etc.), and the strata on both sides of the river slip to the center of the river, resulting in the destruction of the bridge structure. 2. During the earthquake, the sand and sand of the riverbed liquefaction, the failure of the foundation, and the sinking of a large number or uneven subsidence of the bridge pier foundation caused by it. 3. Under the action of seismic inertial force, the internal force or displacement generated by a certain part of the bridge structure exceeds the limit that the structural structure and material strength can withstand, resulting in varying degrees of damage. 4. There are many shortcomings in the design and construction of bridge structures; The seismic intensity of the bridge is much higher than the design strength of the bridge structure, resulting in the bridge structure being unable to resist the damage caused by the earthquake.

Seismic reinforcement: 1. Maintenance of structural connectors: when on the bridge,substructureWhen the relative displacement of the supporting connector cannot be withstanded, the supporting connector may fail, resulting in the beam body crashing. The strong impact force generated by the falling beam will also damage the substructure. Coping with bridge bearings,expansion jointsand other connecting components for maintenance. The usual practice is to increase the width of the bearing surface and install a limiting device between the adjacent beams of the simple support; Measures such as stops and connecting beam devices are used at the upper joints such as expansion joints; adoptedSeismic isolationThe bearing and energy-dissipating device act on the structureSeismic energy, improve the seismic performance of the bridge.

2. Reinforcement of superstructure (1) The method of increasing the section is to increase the concrete structureCross-sectional areaand reinforcement for reinforcement. The reinforced bridge substructure is required to withstand more dead weight and provide higher bearing capacity. （2）Paste steel plate reinforcement methodWhen the bottom of the main beam of the beam plate bridge appears seriouslyTransverse cracksThis method can be used. (3) Structural systemConversion method, the beam end of the simply supported beam is set with steel bars that bear the negative bending moment, so that the adjacent two main beams are connected to form multiple spansContinuous beam。 According to the stress system of the continuous beam, its mid-span bending moment ratioSimple support beamssmall, it can achieve the purpose of improving the bearing capacity of the bridge.

3. Reinforcement of the lower structure (1) Reinforcement of the bearing. Generally, elastic rubber pad bearings are used instead of steel roller bearings. In some cases where the level of use is high, the bottom can be usedSeismic isolation supportReplace steel bearings. However, elastic bearings will increase the displacement of the bridge deck, and the solution is to useLead-core rubber bearingor used in combination with the cable and the elastic bearing. (2) Fill the wall. Not only does it improve the lateral capacity of the column, but it also limits the lateral displacement of the column. By limiting the lateral displacement of the column, the possibility of forming plastic hinges in the pier cap is eliminated. Infill walls are ineffective in terms of the longitudinal capability of slightly sloping or unsloping bridge racks. (3) Abutment. Stuffing gaps with wood, concrete or steel: Some fabricated abutments often have gaps or large gaps between the superstructure end transverse beam and the back wall. If these gaps are not filled, the columns will inevitably undergo large deformations before the soil behind the abutments is compacted. (4) Cap beam. According to the type of pier cap, the vulnerability includes support failure, shear key failure, insufficient bearing width and cap beam failure. Cap beamFailure modeIncludes bending, shearing, twisting, and node shearing. The reinforcement method to deal with insufficient bending and shear resistance is usually to add pads to the existing cap beam.

4. Prestress reinforcement

Prestress reinforcement methodIt is a method of reinforcing the structure using steel tie rods with prestress, which is suitable for improving bearing capacity, stiffness andCrack resistanceand bridges that take up less space after reinforcement. It is divided into prestressed tie rod reinforcement and prestressed strut reinforcement, which is mainly used for bending components, with the beam body as the anchor solid, and applies external force to the tensile area of the beam through prestressed tensioning to offset the weight of the structure itself and reduceVehicle loadThe stress under the action reduces the crack and crack width of the beam body. Prestressed strut reinforcement is mainly used for axial compression piers of bridge substructure.