Organization and management of urban overpass construction?

What are the specific contents of urban overpass construction organization and management? Zhongda Consulting will answer the questions for you below.

1. Characteristics of urban bridge construction

Only by understanding the general construction characteristics of urban bridges can the best construction organization plan be designed. Therefore, before starting construction, it is necessary to carefully review the drawings and conduct on-site inspections to understand the intentions of the construction unit. Usually urban bridge construction has the following characteristics:

(1) The construction scale is large, the area is large, and the content is complex. Usually an overpass project includes professional projects such as bridges (in addition to the main bridge, including pedestrian bridges and passage bridges), roads, water supply and drainage (water supply, rainwater and sewage), electricity, communications, gas, street lights, etc. The project volume is large and various specialties The mutual constraints and influences of the projects are relatively large, and overall arrangements and coordination must be made during the construction.

(2) Full consideration must be given to traffic organization arrangements during the construction period to avoid major impacts on traffic and pedestrians. Construction is usually carried out by repairing access roads or compressing existing motor vehicle lanes.

(3) Full consideration should be given to the demolition and relocation of the original pipelines. Existing pipelines and newly built pipelines are densely distributed vertically and horizontally, so all aspects must be considered during construction so as not to affect the normal function of the existing pipelines.

(4) Overpasses often cover a large area and have narrow red lines, so they often encounter demolition work.

(5) In order to minimize the impact on traffic and improve the surrounding environment, the construction period of urban bridges is generally very tight, the quality objectives are high, and there are many work teams participating in the construction, which requires the project management department to do Extensive and effective coordination of organizational work.

(6) Effectively handle the relationship between night construction and noise pollution, and properly handle the relationship between civilized construction and project progress.

2. Consideration of the overall construction arrangement

2.1 Division and arrangement of sections

Principles for dividing construction sections: ① It is beneficial to the integrity of the structure, and try to make use of telescopic seams or settlement seams, changes in the plane, and places where stubble remains without affecting the quality. ② The subdivision should be made so that the work volume of each section is roughly equal, so as to facilitate the smooth rhythm of construction organization and make the construction balanced. ③ The number of construction sections should be coordinated with the main construction process, and the leading construction should be the main process to form a process combination. The number of process combinations should be equal to or less than the number of construction sections. ④The size of the sections should be appropriate for the labor organization and have enough working surface. In urban interchange construction, there is usually sufficient labor, but there are often not many working surfaces being constructed at the same time.

Based on the above principles, and based on the geographical environment and project content of the overpass, and taking into account the distribution and characteristics of the project volume, the construction of each overpass is divided into 3 to 5 sections in parallel according to the professional nature and location. Although many teams are involved in construction, the construction period can be guaranteed.

The construction arrangement is based on the principle of first underground and then above ground, and focus first and then general. The pile foundation or other types of foundations and pipe networks at the lower part of the bridge are constructed first. Half-width construction can be used during road construction to ensure smooth flow of vehicles. The retaining wall can be prefabricated and then transported to the construction site for installation. The upper part of the bridge must be prefabricated or cast-in-place according to the drawing requirements. From the characteristics of urban bridge construction, the cast-in-place beam construction method is currently mostly used.

2.2 Construction preparation

2.2.1 Water and electricity supply

In urban overpass construction, it is usually easier to connect water and electricity, but the principle of proximity must be considered And do not move water and electricity connections twice. For power consumption points, the overhead lines must be overhead and the ones directly buried must be directly buried. It must be noted that the distribution boxes and distribution boards are equipped with air leakage switches and implemented multi-level protection. All power uses three-phase Five-wire system. Secondly, more than 2 50kW generators and 2 water trucks should be kept in reserve to prevent water and power outages at the construction site.

2.2.2 Construction plan layout

Principles for the layout of urban overpass construction plans: ① The principle of occupying as little land as possible and saving investment, and using the scope within the road red line; ②

Rationally arrange materials, semi-finished product warehouses, equipment storage yards and prefabricated component factories to shorten transportation distances; ③ Make full use of existing or proposed buildings and facilities to reduce the engineering costs of large temporary facilities; ④ Conducive to the work of employees and life, reducing commuting time; ⑤

Comply with labor protection, environmental protection, fire prevention and safety requirements.

3. Consideration of the construction schedule arrangement

Once the bridge construction starts, it must be completed according to the established goals, otherwise it will bring great inconvenience to people's lives and affect the surrounding environment. The following principles must be followed when arranging the construction schedule:

(1) Prioritize projects that affect traffic and people's daily travel according to the completion and delivery deadlines. For example, during the construction of an overpass, if a ramp meets the entrance of the hospital, the construction of this ramp must be prioritized. If the completion of the main bridge plays an important role in alleviating traffic pressure, priority will be given to meeting the conditions for the construction of the main bridge.

(2) Scientifically arrange the construction sequence, first underground and then above ground, first three connections and one leveling, then construction. It is necessary to queue up projects, highlight key points, and overcome difficulties. Projects with long construction periods, complex technologies, and difficult construction should be arranged early, such as the construction of public piers and columns in bridge construction or the construction of vertical and horizontal prestressed beams, which should be considered first.

(3) Adopt mechanized construction methods and improve the degree of assembly. For example, the construction of approach retaining walls in overpasses mostly uses prefabricated assembly; in road construction, from the base layer to the surface layer, large-scale mechanized construction is mostly used .

(4) A scientific network planning method should be used to determine the most reasonable construction organization so that the processes can create favorable conditions for each other, expand the working area, and speed up the construction progress.

(5) Implement seasonal construction measures to ensure continuous construction. Such as water pump drainage and concrete pouring awning during rainy season.

(6) Comprehensively balance manpower and material resources, compress construction as much as possible, achieve balanced construction, avoid starting at the beginning and ending at the end, and control the construction rhythm from beginning to end.

(7) The change factors and invisibility of urban bridge design must be fully considered. The construction of urban bridges is often started due to urgent needs, and geological data, underground pipeline locations and designs are inconsistent. Once changed, the progress may be affected.

(8) Effective measures to ensure that progress can be achieved should be considered. Such as organizational measures, technical measures, economic measures, etc.

Steps and methods for preparing the overall construction progress plan:

(1) Calculate the project quantity. Based on the approved engineering projects, the actual engineering quantity per unit project is roughly calculated.

(2) Determine the construction period of each unit project based on the total construction period.

(3) Determine the start and completion time and interrelationship of each unit's projects.

(4) Prepare a preliminary overall construction progress plan. According to the preliminary overall construction progress plan, computers are used to optimize the construction period and cost of the network. After the adjustments meet the requirements, a formal construction progress plan can be prepared.

4. Consideration of the main construction methods

4.1 Principles

The construction method is the core content of the construction plan. It plays a decisive role in the implementation of the project. It is According to the basic requirements of the construction plan, tactical measures are formulated for bridge divisions and sub-projects under specific construction conditions. Secondly, the construction method should highlight the key points. All projects that adopt new technologies and new processes and play a key role in the quality of the project, as well as projects where the workers are not skilled enough in operation, should be detailed and specific. It is necessary not only to propose the proposed process and methods for carrying out this operation, but also to propose quality requirements and technical measures to achieve these requirements. And to foresee possible problems and propose ways to prevent and solve them. For projects with conventional construction methods and skilled workers, it can be simplified appropriately.

To determine the construction method, the structure and stress characteristics of each part of the bridge should be considered, combined with other on-site construction projects and the construction inspection and equipment owned by the construction unit, and absorb successful construction methods and advanced technologies to achieve Construction is fast, economical and of high quality.

4.2 Traffic organization

In urban bridge construction, construction methods centered around traffic organization must be given priority. Usually, you can consider changing routes, hanging traffic signs and nighttime traffic lights to ensure that traffic is not greatly affected. Since urban overpasses are often the intersection of multiple intersections, with many people and vehicles, closed construction is impossible. Therefore, traffic flow in the main lane must be prioritized, and traffic flow in the main lane must be closed, restricted or diverted to secondary arterial roads. Usually, the construction of the main lane overpass generally requires the construction of 2 motor vehicle lanes and 2 pedestrian passages.

4.3 Excavating the foundation or excavating the ground

During the construction of urban overpasses, whether it is earth excavation or foundation excavation (including bored piles), exploration should be carried out before construction. Determine the exact location of underground pipelines. Although the owner may have provided the plane location and elevation of the relevant pipelines, often due to changes in urban underground pipelines, the completion drawings are different from the actual ones. Therefore, radar geodetectors must be used to measure, and then manual excavation must be carefully performed to determine the foundation. After it is confirmed that there are no pipelines or after the pipelines have been relocated, mechanical excavation will be used. During construction, underground pipelines are often dug out, causing construction delays and compensation issues. This is directly related to the hasty construction.

4.4 Selection of brackets and formwork

The appearance of urban bridges must be beautiful, both inside and outside, with no spots, honeycombs or pits on the surface. Therefore, special attention must be paid to the selection of formwork. Notice. For cylindrical piers, the formwork is usually assembled in place using prefabricated steel molds, and the square symmetry is tightened and fixed with stay wires; when the column is too high, a set of cable stays are added in the middle to ensure the sag of the column. Concrete can be poured only after the model is erected and the inspector has checked that the verticality and diameter of the pier are correct. For square piers, if wooden formwork is used, the inner mold is usually covered with iron sheets. For the beam body, the inner formwork usually uses ordinary plates, but for the outer formwork, strict requirements should be met, and 2 cm phenolic resin plywood is usually used. For those with obvious requirements on appearance, imported plates must be purchased.

For the erection of cast-in-situ beam supports, foundation treatment must be carried out first. Generally, urban bridges can use the existing road surface as the support foundation, but attention should be paid to compacting the surrounding backfill to prevent uneven settlement. Secondly, the turnover of brackets and formwork cannot be repeated too many times. The more times a bridge waits for the turnover of formwork and brackets, the longer its construction period will be. According to the calculated density and size of the door frame, lay the wooden beams so that the door frame support is laid on the wooden beams. Set up the door frame to the horizontal position of the bottom of the beam. Fix the door frame with steel pipes and fasteners, and erect scissor braces according to the design. The bottom mold is set according to the design elevation and reserved settlement amount. The bottom mold uses vertical and horizontal wooden beams, and the reserved traffic channel uses I-beams, and then nails phenolic resin plywood.

4.5 Construction of concrete

Due to site constraints and the impact of concrete mixing on surrounding residents, commercial concrete should be considered for the construction of urban overpasses. In the Shenzhen area, it is now stipulated that commercial concrete should be used in all projects with a concrete pouring volume greater than 20m3. The pouring of concrete should be considered according to the following procedures: ① Before pouring concrete, check whether the mix ratio matches the bridge concrete grade, whether the personnel are in place, whether the mechanical equipment is in good condition, and the pouring method and operating essentials should be explained to the pouring personnel. ②Concrete is poured using tank trucks, pump trucks, and plug-in vibrators for tamping and continuous pouring. ③

The pouring of concrete is carried out from the low end to the high end, and is poured in sections and in layers. Taking the box beam as an example, materials should be uniformly cut from the side molds on both sides, tamped and poured into the inner box. Since the inner box is generally wider (50cm of the upper plate of the inner box is not sealed for the time being), the material can be unloaded from the top of the inner box. There must be a dedicated person responsible for tamping so that the concrete in the inner box is tamped and leveled, and then the upper plate of the inner box is sealed after plastering. When pouring bridge deck concrete, the segment length should be adjusted according to the pouring speed to avoid excessive thickness of concrete in the inner box or excessive initial setting time or poor jointing.

4.6 Construction of the bridge deck system

As the construction of urban overpasses reaches the later stages, the construction schedule becomes tighter. Therefore, the quality of the bridge deck system often has problems in the later stages and must be paid attention to.

(1) Construction of railings and anti-collision barriers: Railings are mostly made of concrete ordered by manufacturers and shipped to the construction site for installation. During installation, the base should be leveled with dry hard mortar according to the design elevation. Then install the railings one by one, fill them with mortar after correction, install the handrail base plate in time, tie the steel bars after correction, and pour concrete. The template is required to be installed firmly to ensure straight lines, rounded curves and smooth surfaces.

The key to the construction of the anti-collision barrier is that when tying the steel bars, expansion joints should be left at the top of the bridge's piers and in the middle of the span, disconnect the steel bars, and fix the expansion joint template with foam. Usually, the anti-collision barrier is cast-in-situ using steel formwork on the construction site, and attention should be paid to the protection of embedded parts before forming.

(2) Bridge deck construction: Currently, urban overpasses use concrete bridge decks and asphalt bridge decks.

In principle, the concrete bridge deck construction should be carried out according to the concrete road construction method, but attention should be paid to the accurate position of the steel mesh to prevent the movement of personnel and small vehicles during the construction period from causing the steel mesh to sink. Secondly, the strength must reach the design requirements before opening to traffic to prevent cracks in the bridge deck concrete.

In principle, the asphalt bridge deck construction should be carried out according to the asphalt pavement construction method, but attention should be paid to the contact between the asphalt surface layer and the bridge concrete. First, the bottom surface must be clean and rough, and second, the adhesive layer oil must be sprinkled , The third is to ensure the thickness of asphalt pavement paving.

(3) Expansion joint installation: After all expansion joint embedded components are installed according to the design, choose a relatively low temperature for installation. The instructions should be strictly followed during installation to ensure the installation quality.

5. Construction organizational structure

It should be emphasized that the Coordination Department is mainly responsible for assisting government departments in land acquisition, demolition, tree removal and the relocation, protection and compensation of pipelines of relevant public utility management units. .

6. Measures to ensure the construction period and environmental protection

6.1 Measures to ensure the construction period

(1) Take planning management as the leader and set up full-time planning engineers, Fully responsible for project plan management. First of all, the overall project progress plan and sub-progress plans must be determined, that is, the unit project construction progress plan must be established until the project operation plan task order.

(2) Establish control measures ① Determine the progress coordination work system, hold regular project meetings on fixed days every week, and hold daily meetings to study the daily progress of the project and new problems that arise, feedback information in a timely manner, and implement Dynamic management; ② Analyze interference and risk factors that affect the achievement of progress goals, such as the impact of demolition, traffic, typhoon and rain, etc.; ③ Fully consider design change factors. Repeated changes in the design of urban overpasses are common and will directly have an adverse impact on the schedule. After design changes occur, the schedule will be adjusted in a timely manner according to the situation, and the overall schedule will remain unchanged; ④

Economic measures will be taken to ensure that the project The funds must be earmarked and never misappropriated, and a project progress reward and punishment system shall be implemented; ⑤ Adopt technical measures that are simple, feasible, speed up or delay the progress, and do not pursue profits one-sidedly, but also pay attention to social benefits.

(3) Personnel and mechanical equipment, small machines and professional equipment must be guaranteed. Equipment on the construction site must not be transferred out at will, and mechanical equipment must be inspected in advance and maintained in good working condition.

(4) The supply of materials should be ensured at the right time, at the right place, and according to quality and quantity.

6.2 Measures for environmental protection

(1) Strengthen civilized construction, conscientiously plan the construction site, and make the site neatly arranged, compact and orderly.

(2) The silt in the construction site, especially the drilling mud, spoil and other waste, should be removed and transported to the designated location in a timely manner to ensure that the site is clean and tidy during the construction period. When the construction tasks are completed and exited, the temporary facilities that must be dismantled shall be removed.

(3) Optimize construction methods and construction techniques to protect the surrounding environment from pollution; for noisy processes, arrange construction during the day as much as possible to reduce disturbance to nearby residents at night.

(4) Sewage discharged from the construction site must be treated before being discharged into nearby trenches. It is strictly prohibited to pollute the land and surrounding environment.

(5) Do a good job in sanitation management of the living area. The toilet must have a septic tank, domestic garbage must be piled in designated places, and domestic wastewater should be discharged into the ditch to keep the living area hygienic and tidy.

(6) Necessary temporary fences and level crossings should be set up at the construction site, and obvious signs should be set up at vehicle and pedestrian crossings to make the construction site as self-contained as possible to reduce mutual interference with the outside world.

(7) The construction access road must be well maintained, the road surface should be kept smooth, the drainage on both sides is good, and there should be no potholes and water accumulation in the rainy season; appropriate watering should be sprinkled in the dry season to prevent dust from flying.

7. Conclusion

The construction organization and management of urban overpass is a huge systematic project, which includes construction technology management and organizational management. Construction technology is to ensure that the project can be constructed according to the design, and only strict organizational management can successfully complete the project in accordance with the contract. Construction organizations must pay attention to scientific management, pay attention to economic accounting, improve efficiency, and at the same time pay attention to social benefits.

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