Quality inspection and control of bridge construction?

The detection and control of bridge construction quality is very important. Only by testing the bridge before use to ensure its quality can the best effect be achieved in later use. Zhong Da Consulting will explain the quality inspection and control of bridge construction for you.

1 Introduction

In recent years, with the rapid development of China's economy, the traffic flow has greatly increased, which has greatly exceeded the design flow requirements of some bridges, and some bridges have quality problems in construction. Therefore, the quality inspection of bridges under construction should be strengthened. The direct reasons such as overload transportation and large traffic volume have led to a serious decline in the technical condition of bridges at all levels. Some bridges often have early diseases, and some bridges even have structural damage. This situation not only poses a threat to the life safety of the broad masses of people, but also causes huge property losses. Therefore, bridge safety has become the most concerned issue of the whole society.

Bridge construction refers to the completion of the construction of the bridge substructure, superstructure and bridge ancillary works according to the design content. In modern bridge construction, construction units make full use of computers for efficient and orderly management. In terms of construction technology, new technologies and efficient and high-performance mechanical equipment are constantly adopted, which greatly improves the quality, shortens the construction period and reduces the project cost. For example, laser measurement is used to control the precise positioning of structures; Using remote control equipment to excavate foundation in open caisson and caisson can reduce labor intensity and avoid personal danger. In addition, prefabricated bridges will be developed to realize the standardization of structures and components and industrial production.

2 bridge construction quality inspection

2. 1 detection of bridge superstructure

The construction inspection of bridge deck appearance can be carried out in turn according to the composition of bridge deck: bridge deck pavement, bridge deck drainage facilities, railings and handrails, sidewalks, etc. The function of bridge deck pavement is to make vehicles run safely and comfortably. As the appearance construction inspection of bridge deck pavement, the type of bridge deck pavement is first detected, and then whether there are defects in the pavement layer is detected. Defects in bridge deck drainage facilities and bridge deck pavement often lead to water accumulation on the bridge deck, causing vehicles to slip and causing traffic accidents. The defects of bridge deck drainage facilities are most obvious during rainfall and snow melting, so it is very important to detect the defects of bridge deck drainage facilities. Bridge deck water often affects the durability of the main load-bearing structural members of the bridge through defects such as cracks in bridge deck pavement. Check the condition of railings and handrails, and whether the interconnected joints fall off and whether the steel members are painted. For the sidewalk, check whether the kerb is broken, the firmness of the connection between the sidewalk and the bridge deck, etc.

The integrity of the bridge superstructure is guaranteed by the transverse connection of the basic components. In general, the construction inspection of transverse connecting members includes the inspection of their own conditions and the inspection of their connection with foundation members. Generally, the actual length and section size of basic components are measured. The integrity and linearity of component joints can be investigated by random sampling. Deformation investigation (downward deflection, lateral bending, displacement, etc.). ) and cracks in basic stress components. The detection of the longitudinal axis of the basic component refers to the measurement of the deflection of the main beam of the beam bridge; For arch bridges, it refers to the measurement of the actual arch axis shape and vault deformation of the main arch ring. The construction inspection of the longitudinal axis of the foundation member can be done by visual inspection, and when obvious deformation is found, it can be measured by precision instruments.

The superstructure of a bridge is the main load-bearing structure of the bridge, which is often composed of many basic components, such as beams, slabs, arch ribs (sheets) and so on. Therefore, the construction inspection of bridge superstructure is to detect the working conditions of these basic stress components. According to the different bridge structural forms, component types, bridge construction environment, construction quality and use conditions, the parts, types and degrees of defects in foundation components are also different. For the basic components of the superstructure of concrete highway bridges, the defects usually include concrete cracking, peeling, broken joints, steel bar leakage and corrosion, insufficient quality of concrete itself, abnormal deformation and so on. Its manifestations are surface cracks, honeycombs, pits, cavities, exposed tendons, peeling, free lime, crevice interlayer and so on.

2.2 Detection of piers and abutments

The inspection of bridge pier construction mainly includes the inspection of pier defects and cracks, and the inspection of pier displacement (settlement, displacement and inclination). For reinforced concrete piers and abutments, the common defects are concrete weathering, concrete scratches on the corner-falling surface, exposed tendons, and local compression of concrete under the bearing. The common forms of cracks are cracks along the main reinforcement direction of pier and abutment, cracks along the stirrup direction (these cracks are generally few in number) and vertical cracks perpendicular to the main reinforcement direction on the capping beam.

For brick, stone and concrete piers, the common defect is the damage caused by the void of mass concrete. The common forms of cracks are reticular cracks and vertical cracks (extending along the height of piers). The detection of bridge pier defects and cracks can be done by visual inspection or with the help of some tools (for example, using a small hammer to detect surface weathering, peeling and internal cavities, and using a reading microscope to detect the maximum width of cracks).

For the detection of settlement, displacement and inclination of piers and abutments, a preliminary judgment can generally be made by visual inspection combined with the detection of bridge superstructure. For example, for a simply supported beam bridge, when the superstructure inspection finds that the pier top of the main girder is inclined and the expansion joint is dead, it can be preliminarily determined that the pier may be inclined or unevenly settled; For a hyperbolic arch bridge, it can be preliminarily considered that there may be horizontal displacement on the abutment when it is found that the arch crown sinks more and there are more radial cracks on the main arch rib during the inspection of the main arch ring. Conduct a detailed investigation.

The detailed inspection of bridge pier settlement should be carried out in strict accordance with the national first-class and second-class leveling regulations, with a precision level, and closed on permanent leveling points on both sides. Observation points are generally selected at both ends of the top surface of the pier, and their observation marks can be used as leveling observation points, and rivet heads are embedded on the pier.

In the detailed detection of pier inclination, a fixed plumb line measuring point can be set on the pier, and the pier inclination can be measured by total station or hanging ball. The observation of horizontal displacement of pier and abutment of small-span bridge can be carried out by hanging measurement with fixed tension of special steel wire ruler, and the measurement results can be directly compared with the completion data. The steel wire ruler is preferably made of indium steel to avoid the influence of temperature change.

3 Construction quality control

Before the bridge construction, we should be familiar with and carefully study the drawings of the bridge. Because design drawings are the only basis for bridge construction and the basis for construction quality control, it is necessary to do a good job of drawing review before bridge construction. The main work of reviewing drawings includes: whether the description of drawings matched with drawings is complete, whether the design of drawings is complete, whether there are omissions or defects and contradictions, whether the representation method used in design drawings is clear and whether it meets the relevant national standards and requirements.

The construction process of a bridge includes at least hundreds of processes. Only when the quality of each process is qualified can the overall quality of the bridge be guaranteed. The quality of each process mainly depends on the professional quality, sense of responsibility, sense of mission and scientific construction management of bridge builders. Therefore, the goal of quality control in bridge construction stage should be based on the construction contract terms, construction technical specifications and design documents, and the strict control of process quality should be the core. The quality control of managers is mainly to ensure the process quality by strengthening the work quality of construction personnel, and finally to ensure that the overall project quality meets the requirements of design and construction on the premise of ensuring the quality of each process, so that the completed bridge can be put into use safely, reliably and efficiently.

Check and accept the plane position, elevation, size, treatment and drainage, geological conditions and bearing capacity of the foundation. Check and accept the basement, plane size, wall thickness, inclination and bottom elevation of open caisson blades. Acceptance of items such as inclination rate of central axis of pile sinking, pile position of single row pile and pile position of group pile. Check and accept the hole position, diameter, hole shape, hole depth and inclination, bearing capacity of bored and dug piles, compressive strength of pile concrete, etc. Acceptance of steel model, steel tensile strength, anchorage length, protective layer thickness, lap length, welding zone position, steel bending position, welding length, steel skeleton size and protective layer thickness. Template elevation, axis deviation, internal dimensions, longitudinal axis plane position of support and arch, and elevation of arc arch are qualified. Acceptance of prestressed steel bar binding, cold drawing of steel bar, prestressing, reserved holes and hole grouting in prestressed concrete.

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