Repair of bridgesTighteningConstruction programme
I. Overview of the project
1. 1 project background
A bridge is located in the city of xx province and is a key node linking g320 to s203 province province, with a full length of 280 m, a 12-m width of the bridge and a design load of 20 and 100 vehicles. The bridge, which began in 1995 and has been in operation for 28 years, has grown significantly as a result of the economic development of the region and the continued increase in traffic, as the proportion of heavy-carry vehicles has increased and the bridge structure has gradually deteriorated. Regular tests conducted in 2023 revealed that the bridge had problems with the main beam cracks, concrete stripping, the ageing of branches and the deterioration of the surface of the bridge, that the carrying capacity of the local building blocks was no longer sufficient to meet the requirements of existing norms and that repairs and enhancements were urgently needed to ensure safe passage。
1. 2 status of bridges
1. 2. 1 structural form
The bridge is a 3x80m pre-resilient concrete bridge, with a pillar base for the lower structure, a rectangular cross-section of the bridge, a u-type bridge with a sheet rubber sub-branch and a asphalt concrete on the surface。
1. 2. 2 main diseases
(1) principal beam disease: multiple tilt cracks with a maximum width of 0. 3 mm across the abdomen and horizontal cracks with a width of 0. 2-0. 4 mm across the median plate; some areas of concrete protection strips are stripped, steel bands are rusty with a maximum rate of 15%。
(2) the lower structure: the bridge has a vertical crack with a width of 0. 1-0. 25 mm; the branch is aging, deformation is severe, and some of the branches are cut and deformed with a maximum shift of 30 mm。
(3) the surface of the bridge is broken: the total surface area of the puddle is about 18 per cent, and the convulsive stitches are clogged and broken, resulting in a bumping of the road。
1. 3 need for maintenance reinforcement
(1) security needs: the loss of structural capacity due to the cracks in the main beam and the rusting of the steel is a security hazard; the failure of the beams may result in the transfer of the beams and endanger the overall stability of the structure。
(2) functional needs: traffic growth of 8 per cent per year, heavy vehicles account for up to 35 per cent and the original design load is no longer sufficient to meet current traffic requirements; the breach of the bridge affects the comfort of motor vehicles and constrains regional economic development。
(3) economic demand: building bridges with improved maintenance will extend the life of the bridge by 15-20 years, saving about 60 per cent of investment compared to reconstruction, consistent with the concept of green low-carbon construction。
1. 4 project objectives
(1) structural security: restore the carrying capacity of key components, such as the main beam and the bridge to ensure that the structural safety factor is more than 1. 3。
(2) increased durability: control of crack development, repair of concrete damage, replacement of ageing substations, and improvement of structural durability up to 50 years。
(3) functional improvements: repair of bridge surfaces, replacement of stretchers, improvement of car comfort and design load up to road-i level。
(4) construction security: use of a semi-construction, semi-routing programme to minimize traffic interruption time and control within 60 days。
Ii. Construction technology programme
2. 1 strengthening method selection
2. 1. 1 main beam reinforcement technology
In response to cracks in the main beams and concrete stripping, a combination of crack slurry and carbon fibre sheeting was used. Fragmentation slurry uses epoxy resin materials to fill cracks with low pressure injection techniques to prevent water intrusion and steel rust. The construction staff first cleans the surface of the cracks, installs the plating mouths and then injects specialized resins to ensure that the cracks are completely closed. For the detachment area, first the loose concrete, out of the steel bars, and then the rust removal process, then the high-strength polymer slurry is used to repair and restore cross-section integrity. Subsequently, carbon fibre sheets were placed on the base and side of the main beam to enhance resistance. Carbon fibre sheeting uses 300g/m2 specification to paste with epoxy resin, with a connection of not less than 100 mm in length to ensure integrity. This method is easy to construct, has minor damage to the original structure and can rapidly increase the carrying capacity。
2. 1. 2 lower structural reinforcement technology
Bridge crack treatment is combined with surface closure and pressure-plugging. First, vertical cracks are cleaned, sharpened with steel wire, and epoxy resin sealants are painted to prevent their extension. For deeper cracks, pur materials are injected with pressure slurry machines to fill internal gaps. The replacement of the substations is based on the overall replacement method, which involves the removal of the aging substations, the cleaning of the substrates, the installation of new high-performance rubber substations and ensuring horizontal control within 10 mm. At the same time, the bridge is reinforced by the use of outsourced steel to weld steel plates around the body and to inflate impregnated slurry to increase the resistance to shearing. The next structure is strengthened to focus on overall stability and avoid partial failure。
2. 1. 3 bridge surface rehabilitation techniques
The break-up of the bridge is covered by a re-storage process. The surface is cleaned, the water-resistant glue layer is painted, and 4 cm thick sbs-modified asphalt concrete is laid to ensure leveling. The stretcher is replaced by a steel stretcher of the type, first cutting the old stitches, cleaning the troughs, installing new stretcher stitches, adjusting the height of the markers, fixing them with epoxy resin to ensure the comfort of the car. The repair of the bridge also included a drainage system inspection, the removal of blocked leaks and the prevention of water erosion structures. Technology choices combine durability and economy and increase useful life。
2. 2 construction process design
2. 2. 1 pre-preparation
Prior to construction, the technical team conducted site surveys and prepared detailed plans. With regard to traffic control, a semi-construction semi-routing programme was introduced, with temporary fences and signposts to ensure the safe passage of vehicles. Material preparation includes the procurement of carbon fibre sheets, epoxy resins, concrete patches, etc., all materials need to meet national standards and be sampled before entering the field. The equipment inspection involved a slurry, cutter, crane etc. To ensure performance. Staff training emphasizes safe operations, including high-altitude operations and mechanical usage norms. The advance preparation took approximately seven days to prepare the ground for subsequent construction。
2. 2. 2 implementation steps
The construction was carried out in phases, giving priority to the lower structure. The first step would be to replace the substations and reinforce the bridge, use the crane to remove the old substations, install new substations, and synchronize the outsourced steel plate to strengthen the stairwells. In the second step, the main beam will be reinforced, with a cracking injection, followed by a carbon fibre sheet, and the sequence of construction will move from the center to the sub-season to avoid concentration of stress. The third step is the restoration of the bridge's surfaces, the laying of floors, the re-painting of asphalt and the replacement of the stretching stitches. The whole process is run-off, with one module completed daily to ensure efficiency. The construction cycle was kept under control for 60 days, and weather factors such as suspension of operations during snow and rain days guaranteed quality。
2. 2. 3Quality control
Quality testing runs through the entire process, with ultrasound detection of filling rates after cracking slurry to ensure no less than 95 per cent. Carbon fibre pasting is subject to a pull test, with a bond strength of 2. 5 mpa. The surface of the bridge is tested with a flattening device and the standard deviation is controlled within 3 mm. Receiving and inspection is carried out in stages, with the supervisor signing confirmation for each process completed. Quality control of materials includes on-site sampling for screening and immediate replacement of substandard materials. The quality control system ensures that the structural safety factor is met, based on the design guidelines for road bridge strengthening。
2. 3 materials and equipment
2. 3. 1 reinforcement material
The main beam is reinforced with a carbon fibre sheet with a specification of 300g/m2, a tensile strength of 3,400 mpa, with an epoxy resin glue, and a solidification time of 24 hours. Concrete patches use polymer slurry, resistant to pressure strength of 50 mpa and have good durability. The sub-seasons are selected with natural rubber, allowing a 30 per cent cut-off to meet the load requirements. The surface-painted material is sbs-modified asphalt with a soft spot of no less than 90°c, which is highly smooth. All material vendors are required to provide certification and pre-construction sampling to ensure performance stability。
2. 3. 2 construction equipment
The main equipment consists of a slurry machine with a pressure range of 0-5 mpa, which is used to fill cracks; a cutter with a power of 3kw, which handles the surface of the bridge; a crane, weighing 10 tons and replacing the substations; and support equipment such as an air pressurizer, a mixer, etc. Pre-entry inspection maintenance of equipment, daily maintenance during construction to avoid malfunction. The operation of the equipment is the responsibility of professional certified personnel to ensure safety and efficiency。
2. 4 security measures
2. 4. 1 construction security
Safety belts and safety nets were used for high-altitude operations, and scaffolding was constructed at the bridge site, which was accepted and accepted for use. Traffic handling arrangements are staffed, speed-reducing bands and warning lights are installed to prevent accidents. The construction staff wears a helmet, a reflector, and regular security training is provided. Emergency response plans include fire and collapse exercises, equipped with fire extinguishers and first aid kits. Security measures are supervised by a dedicated security officer to ensure zero accidents。
2. 4. 2 environmental protection
Construction waste is sorted, concrete pieces are recycled and waste bags are shipped. Noise control uses low-noise equipment, which avoids night hours and reduces disturbance. Waste water collects sediment and discharges to prevent the contamination of rivers. Environmental protection measures are consistent with the environmental noise emission standards for the construction site area and protect surrounding ecology。
Construction organization and management
3. 1 project organizational structure
3. 1. 1 management team configuration
The project has a dedicated management team with a project manager, who is responsible for overall coordination and coordination; a technical manager, who leads the programme's optimization and technical interface; a security supervisor, who supervises construction safety on a full-time basis; two quality engineers, who are responsible for processing and receiving in the subregion; three construction engineers, who are managed by the bridge structure sector; and four full-time security guards, who conduct 24-hour on-site inspections. The team has more than five years of experience in the construction of bridges and holds relevant professional qualifications。
3. 1. 2 division of responsibilities
The project manager handles the owner and supervisor, approves the construction plan and changes; the technical manager resolves the technical difficulties and prepares the submission documents; the head of security develops the security system and organizes emergency drills; the quality engineer carries out the “triple inspection” (self-checking, cross-checking, hand-checking) and keeps video material; the construction manager coordinates the work of the team and implements the progress nodes; and the security officer inspects protective measures to prevent irregularities. Daily meetings are held to synchronize problems and resolve them in a time-bound manner。
3. 1. 3 coordination mechanisms
Establishment of a system of “weekly meetings + thematic meetings”: tripartite meetings on supervision, construction and design are held every friday to inform progress and quality; thematic meetings are launched whenever technical difficulties or emergencies arise. Establishment of a linkage mechanism with the traffic authorities, application for temporary traffic control programmes seven days in advance, electronic induction screens and temporary access roads to ensure smooth traffic diversion。
3. 2 schedule of progress
3. 2. 1 overall work plan
The total duration of the project was 60 days, in three phases: 7 days prior to preparation (transport control, material entry, equipment debugging); 45 days for main construction (15 days lower structure, 20 days for reinforcement of the main beam and 10 days for repair of the bridge); and 8 days after acceptance and acceptance (detection, cleaning, handover). Key pathways replace the main beams with reinforced bridge surfaces and use the “parallel operations + running water construction” model to avoid cross-processing delays。
3. 2. 2 progress control
Phase i: completion of encircling, pavement and material testing in 1-7 days; phase ii, 8-22, concentrated on replacement of substations and synchronized reinforcement of bridge pits; phase 23-42, treatment of main beam cracks and placement of carbon fibre sheets; phase 43-52, laminates, heavy asphalt; phase iii, 53-60, loading test and clean transfer. Daily progress is compared to actual deviations, with an increasing number of manpower or equipment catching up over the schedule。
3. 2. 3 assurance of contingency progress
Preparation of weather plans for rain and snow: out-of-house operations are suspended during rainfall and transferred to indoor material processing; heating cells are used to conserve concrete at temperatures below 5°c. Key process reserve spares: two units each for slurry and generators to avoid single-point malfunctions affecting the whole area. Establishment of a green corridor for the supply of materials and a three-hour emergency supply agreement with local suppliers to ensure that materials are cut off for up to four hours。
3. 3 resource allocation plan
3. 3. 1 human resources staffing
The skilled workers are divided into three groups: 12 structural reinforcements (4 for crack-containing mackerel and 8 for carbon fibre paste workers); 10 for bridge construction (3 for lumber workers and 7 for asphalt stalls); and 6 for equipment operators (2 for crane drivers and 4 for cutting machines). 8 support staff (security officers, general staff). Personnel operate on a “two shifts” basis, with a peak of 36 personnel working on a single day to ensure that work is carried out on a 24-hour basis。
3. 3. 2 material supply management
The main material is double-controlled with "entry check-in + field sampling": carbon fibre sheet checks per roll, randomly sampled for tensile strength; epoxy resin tests for solidification time and viscosity; and asphalt blends for temperature and grade matching per vehicle. Material stacks are partitioned: carbon fibre sheets are stored in dry warehouses to avoid direct sunlight; cement materials are 30 cm high to protect the tide; flammable materials are stored separately with fire extinguishers. Stock levels are set at 3-day levels to avoid secondary transport affecting efficiency。
3. 3. 3 movement control programme for equipment
Core equipment is subject to a “set-up” system: the slurry machine is headed by two professional operators who calibrate daily pressure sheets; the crane checks wires and brakes prior to the operation; and the cutter installs a splash shield. The equipment schedule was drawn up three days in advance and priority was given to securing critical processes: during the reinforcement of the main beam, 2 slurry-slurries were synchronized; and during the bridge front phase, 1 cutter worked for 12 hours. The backup equipment is activated when equipment fails and the maintenance response time does not exceed two hours。
3. 4 quality management system
3. 4. 1 decomposition of quality objectives
Overall objective: 100 per cent acceptance and acceptance and 90 per cent improvement. Decomposition indicators: fissure aluminum saturation 95 per cent; carbon fibre sheet viscosity 2. 5 mpa; bridge flatness 3 mm (3m straight-foot detection); installation level deviation 2 mm. The corresponding person for each indicator, the technical officer, may not enter the next process until his or her signature has been confirmed。
3. 4. 2 process quality control
A “triple-check” system is in place: the operator's self-inspection team leaders cross-check the quality engineers. The main process side station monitoring: the engineer records the pressure and time of the slurry at the time of the cracking of the slurry; the air drum rate is measured with a small hammer when carbon fibre is pasted; and the temperature and thickness are measured in real time at the bridge stand. Unqualified units returned to work immediately and teams with a return rate of over 3 per cent were suspended on the same day。
3. 4. 3 test acceptance and inspection process
Phased third-party testing: following the reinforcement of the lower structure, the concrete strength is measured using a back-up method; the carbon fibre of the main beam is pasted and the lifting test is performed; and the surface of the bridge is completed and tested with laser flattening. Three levels of acceptance and inspection: process handover, sub-engineering acceptance, and overall acceptance. All detection data are uploaded to the smart site platform in real time to generate quality retrospective reports。
3. 5 construction of safety civilization
3. 5. 1 site safety
High-altitude operations set up double-layered protection nets: bridge scaffolds are covered with steel jumpers, with a secure seat on the outer side; and the main beam site uses an anti-crash device and is attached to a safety line. Temporary electricity use is based on the “level iii distribution level” protection, with cable racks installed empty and distribution tanks locked and managed. The construction area is equipped with a warning belt and a flashlight at night, which prohibits the entry of unrelated persons。
3. 5. 2 transport facilitation programmes
Half of the construction section provides for conical barrel isolation, with a width of 3. 5 metres and a speed limit of 20 km/h. Four traffic wardens, four road-tracking vehicles and two additional traffic police officers during peak periods. A drainage ditch is set up in the walkway and a skating steel sheet is laid in the rain to prevent the vehicles from sliding. The construction announcement was posted through the local media three days in advance and the bypass road map was posted at the top of the bridge。
3. 5. 3 environmental protection measures
Waste sorting: concrete chips are used for road-based backfilling, steel-stretch recycling, and bags are cleared. Noise-reduction measures: the use of low-noise devices is prohibited after 22:00 at night. Waste water is collected and released once a week and the sediment ponds are cleaned up. Naked soil is covered with dust protection nets, and daily regular showers of precipitation are distributed at pm10 concentrations below 150 mg/m3。
Iv. Quality and safety control systems
4. 1 quality management system
4. 1. 1 decomposition of quality targets
The project established the core objective of "zero defects, full compliance", which was refined into three levels: the structural safety layer required a 20 per cent increase in the main beam's carrying capacity and a 98 per cent fullness of the crack-up slurry; the construction process layer provided for an error of 2 mm in the flatness of the carbon fibre sheet and 96 per cent in the solid pressure of the bridge; and the durability layer ensured that concrete restorations were resistant to seepage at the p8 level, with seats with a useful life of not less than 30 years. The target responsibility matrix is clear to the class, technicians record key parameters on a daily basis, and quality engineers summarize analyses on a weekly basis。
4. 1. 2 process quality control
Pre-construction is preceded by a "triple bottom" system, whereby technicians hand over process standards to class groups, safety officers hand over risk points and materials clerks hand over acceptance norms. The "three checks" are introduced in the construction process: the operator is reviewed by the team leader after being certified for self-inspection, and ultimately by the quality examiner using specialized instruments. Fragmentation slurry uses a "two-controlled" method to monitor both the plurry pressure (0-5-1. 0 mpa) and the spill of the plasma; carbon fibre sheet paste is double-checked with the "deeping test + empty drum test" and bond strength is measured at 110 per cent of the design value。
4. 1. 3 receiving and inspection process management
Establishment of a "third level of acceptance and inspection" mechanism: processing and acceptance are confirmed by the signature of the builder and supervisor on the site; sub-acceptance and inspection are jointly conducted by the department of quality; the overall acceptance and inspection agency is invited to conduct static testing. Receiving and inspection information is a "process one file" containing construction logs, test reports and video records. For covert processes such as the replacement of substations, the dual retroactive use of "image retention + gps positioning" ensures control at each node。
4. 2Security managementSystem
4. 2. 1 responsibility for security objectives production
Implementation of the "one job and two duties" system, whereby project managers and departments sign the safety of work liability statement, which defines the goal of "zero casualties, zero accidents". The inspector general of security conducted daily inspections of the priority areas and found that the risks were immediately addressed by issuing a rectification notice form, and that high-risk operations were managed by "work tickets". For example, high-altitude operations require advance clearances for operation in heights, with anti-crash and lifelines, and security alerts in the area of operations。
4. 2. 2 risk classification
Risk rating of construction phases: high-risk operations such as seat replacement (with cranes) with dedicated programmes with full-time commanders; medium-risk operations such as carbon fibre pasting with "two-person guardianship"; low-risk operations such as material stacking with "three-check-and-see" systems. A risk dynamic map has been created to mark 12 risk points, such as bridge crack processing and bridge plaque, on the construction plan to update the risk profile on a daily basis。
4. 2. 3 emergency response mechanisms
The integrated emergency response plan was prepared to cover six categories of accidents, including fire, collapse and electrical shocks, and was equipped with emergency stores: 20 fire extinguishers, 5 first aid kits and 2 emergency generators. Quarterly hands-on exercises were conducted to simulate the collapse of the bridge scaffolding and to train personnel in the full process from the discovery of hazards to evacuation. Establishment of a "15-minute emergency circle" and a rescue agreement with a recent hospital to ensure delivery within 30 minutes。
4. 3 environmental protection measures
4. 3. 1 dust control
The construction area was equipped with 2. 5 m high encirclement, equipped with two mist cannons to defusing operations. The bridge is covered by wet work and cutters are connected to the spray system. Transport vehicles are equipped with closed panels, vehicle wash platforms are installed at the exit and sediment pond wastewater is recycled. When the pm10 monitoring value exceeds 150 mg/m3, the sprinkler multiplier operation is immediately activated。
4. 3. 2 noise control
Select low noise equipment: hydraulic shredder instead of wind mill, silent generator power 65 db. "noise-free hours": noise-producing operations are prohibited from 22:00 to 18:00 at night. Acoustic barriers in the bridge construction area and noise monitoring points at a distance of 200 metres from sensitive areas to show deutsche numbers in real time。
4. 3. 3 wastewater waste management
The construction wastewater was discharged into the municipal pipe network after the third level of sedimentation was achieved and the sediment ponds were cleared weekly. Waste material classification storage: concrete fragments are used for road-based backfilling, steel-stretch recycling, and packaging materials are centrally cleared. Establish a system of "scrambling of waste" with a residual waste area of no more than 50 square metres and a regular daily clearance。
4. 4 oversight and continuous improvement
4. 4. 1 multilevel oversight mechanisms
Establishment of a "third-level monitoring network": daily check by teams, focusing on security protection measures; weekly check by the project department of all processes, using drone patrols to inspect high-altitude operations; monthly check by companies of randomly checked materials and processes. Introduction of "quality flight checks", with the panel checking construction records on an irregular basis, to be closed and overhauled within 48 hours of the problems identified。
4. 4. 2 pdca cycle improvements
Monthly quality analysis meetings are held to analyse the root causes of the problem using "fish bone maps". For example, in response to the problem of exceeding the level of the bridge, an infrared thermometer was added to real-time monitoring by means of a five-element check of the "mechanical lawn ring" which revealed inadequate control over the temperature of the iron tablets in the stalls. • creation of a " problem processing account " to identify those responsible, the duration of the reorganization and the criteria for certification, and to form a closed-ring management of "discovery of problems -- analysis of reasons -- development of measures -- validation of results"。
4. 4. 3 implementation of the system of rewards and penalties
Implementation of the "quality security score system", monthly selection of "safe classes" and "quality zero impairment trades and crafts" with material incentives. Violations of the rules of conduct are punishable by a fine of $500 for violation of regulations, $300 for violation of regulations and $200 for violation of labour discipline. Quality accidents impose double liability, both for direct liability and for management responsibility。
V. Progress and resources
5. 1 progress control system
5. 1. 1 overall progress plan preparation
Based on the characteristics of the bridge structure and the logic of the process, a 60-day master schedule was prepared using network planning techniques to identify key paths for the replacement of the main beams for reinforced bridge surfaces. The total was broken down into six control points: 7th day for traffic decomposition, 22nd day for reinforcement of the lower structure, 35th day for treatment of the main beam crack, 45th day for carbon fibre pasting, 52nd day for bridge work and 60th day for overall acceptance. An early warning buffer period is set for each node, with three days of mobility for critical processes。
5. 1. 2 dynamic progress monitoring
Implementation of the "three-comparison" dynamic monitoring: daily mornings compare planned progress against actual completion, weekly five-week progress analysis compares the plan with performance, and monthly milestone nodes at the end of the month. The bim technology was used to simulate the construction process and to reorder the process into a step-by-step "first through the middle and back seat" when a space conflict existed between the reinforcement of the main beam and the construction of the bridge. In the event of a deviation of more than 10 per cent, the redeployment of resources is initiated, prioritizing critical processes。
5. 1. 3 progress correction measures
Establishment of a three-tier early warning mechanism: yellow early warning (5-10 per cent deviation) coordinated by the construction staff to work overtime; orange early warning (10-20 per cent deviation) assigned back-up equipment by the project manager; red early warning (> 20 per cent deviation) initiated specialist consultations. In response to the delay in the rainy season, the pre-positioning of rain-proof materials and the use of heating sheds for concrete construction, and in response to delays in the supply of materials, the "4-hour emergency response" agreement was signed with the vendor to ensure that supplies were replenished within 24 hours。
5. 2 resource safeguard mechanisms
5. 2. 1 human resources security
Specialized teams are organized according to the complexity of the process: structural reinforcement group of 12 (comprising 4 aluminum mechanics, 8 carbon fibre stickers), bridge construction team of 10 (three handmen, seven stallors) and equipment operator group of 6 (two driver of a licence crane and four operator of a cutter). Implementation of the "2+1" standby system: each team is staffed by 2 main + 1 replacement staff, with a "two shifts" for key processes, with a maximum of 36 participants per day. Establishment of skill matrices and regular specialized training in crack-up injection, carbon fibre plaque, etc。
5. 2. 2 material security system
Implementation of the "three early" strategy: 7 days in advance, 7 days in advance, 3 days in advance, 3 days in advance, and 1 day in advance. Main material storage standards: 120 per cent of carbon fibre sheet reserves, 100 per cent of epoxy resin reserves and 150 per cent of asphalt blends. Establish a material traceability system with a 2-dimensional code for each batch of material, which allows viewing of detection reports, transport routes and storage environments. For vulnerable materials, such as plating, provision is made at a rate of 20 per cent loss。
5. 2. 3 equipment security programme
Core equipment is "one machine overload": two slurry machines (one for +1 backup), two 25-ton cranes (one for master operations + 1 emergency response), three cutters (two for bridge operations + 1 backup). Equipment management is based on a "three-set" system: man-to-man (licensed induction), man-to-man maintenance (daily cleaning and lubrication), and person-to-person inspection (weekly performance testing). Equipment movements are monitored on a real-time basis through a smart site platform, which automatically alerts and sends maintenance instructions when the plume pressure is abnormal。
5. 3 risk response scenarios
5. 3. 1 progress risk management
Specific plans are developed for three typical types of risk: traffic control extended risk, establishment of a "two team leader" coordination mechanism with traffic police in advance, daily joint patrols; extreme weather risk, establishment of a "meteorological early warning-process adjustment-material security" response chain, covering the remaining operational surfaces two hours before heavy rains; and technical change risk, setting aside a design contact group to ensure that programme adjustments are completed within 24 hours。
5. 3. 2 resource disruption response
A "level iii response" is initiated when the supply of materials is interrupted: a first-response response (a delay of < 24 hours) calls the local repository; a second-response response (24-48 hours) activates the back-up supplier; and a third-level response (> 48 hours) adjusts the construction process, such as the use of fast hard concrete instead of ordinary concrete. In the event of equipment failure, a "equipment sharing pool" was established, and equipment mutual assistance agreements were signed with three surrounding projects to ensure deployment within two hours。
5. 3. 3 force majeure disposition
In the event of force majeure such as flooding, earthquakes, the three-step process of "personnel evacuation -- equipment transfer -- structural monitoring" is immediately initiated. A three-day reserve of emergency supplies for temporary shelters, equipped with satellite telephones to ensure smooth communications. The structural security assessment was conducted by a third-party testing agency prior to the resumption of work after the disaster, which confirmed that there were no hazards and that work was resumed。
5. 4 co-management mechanisms
5. 4. 1 multi-party synergistic platforms
Establishment of a "owner-supervisor-construction-design" quadripartite platform for weekly online progress meetings to share bim models and progress data. Develop a "bridge construction" micro-intelligence program to upload real-time construction images, test reports and issue clean-up records. The design unit is represented on-site to provide technical confirmation of key elements such as the crack-up slurry process。
5. 4. 2 internal coordination mechanisms
Introduction of the "day meet + week back" system: daily morning meetings identify the tasks and risk points of the day, and weekly meetings on fridays to analyse the root causes of the problem. Establish a "problem marketing" system to refine the 32 potential risk points identified (e. G., inadequate high-altitude operational protection and irregular storage of materials) and to incorporate the completion rate into the class examination。
5. 4. 3 external linkage mechanisms
Establishment of a one-hour response link with the traffic management department, installation of an electronic induction screen in the construction area and real-time dissemination of detour information. A duster is installed in the network with the environmental services and the spray system is automatically activated when pm10 exceeds the standard. An emergency response agreement was signed with the hospital to ensure that emergency injuries were treated professionally within 15 minutes。
Vi. Receiving and inspection and delivery management
6. 1 acceptance and inspection standards and processes
6. 1. 1 basis of acceptance
Project acceptance strictly follows the road bridge reinforcement design code jttg/tj22-2008 and the road engineering quality test evaluation standard jttgf80/1-2017, and special acceptance outlines are prepared in conjunction with the design documents and construction contracts. Quantification of acceptance indicators is clear: 98 per cent saturation of the cavity of the main beam, 2. 5 mpa for carbon fibre sheet binding strength, 3 mm (3m straight-foot test) for bridge flatness, and 2 mm deviation of the installed level of the substation. 12 self-inspection reports completed prior to acceptance, including basic information such as material retesting, process parameter recording, hidden engineering images, etc。
6. 1. 2 sub-paragraph receiving and inspection
A three-tier system of acceptance and acceptance is in place. The process acceptance was confirmed by the contractor's signature with the supervisor's site, and the five sites were randomly extracted to ensure that the level of confidentiality was met, if ultrasound detection was used after the cracking slurry was completed. Design units are invited to participate in the sub-acceptance to conduct a load test simulation of the main beam reinforced area, using 200 tons of hydraulic jack scalding to measure a deviation of up to 5 per cent from the design value. Upon completion of the surface of the bridge, the 10 km continuous measurements were made using the laser flattening machine and the data were uploaded to the intelligent platform in real time。
6. 1. 3 overall acceptance
Organization of joint five-party receiving and inspection teams: owners, design, construction, supervisory and inspection bodies. The standard requirements are met by completing static tests prior to acceptance, using 6 30-ton heavy vehicle simulation loads and continuous observation for 24 hours, with a maximum of 6 mm for main beam scratches. The receiving and inspection process is divided into three stages: information verification, physical on-site testing, and functional validation. The information verification focused on the review of the construction log change records, on-site testing of the use of a full-scale drone to scan faults at the bridge, and functional validation to test the deformation of the convulsors and the fluidity of the drainage system. Conclusion of acceptance
