In the civil construction stage of the project, the structural engineer is the main executor of the design unit to cooperate with the construction. So how do structural engineers cooperate with the construction? Here are some cases to learn!
1, constructability of structural design
Coordinated construction should start from the structural design stage. The result of structural design is structural construction drawing, and the idea of structural engineer must run through the construction process, and the construction unit will build the actual building structure imagined by structural engineer. At present, the construction market in China is not completely standardized. In a certain range, there are illegal phenomena such as bidding, illegal subcontracting, dismembering and contracting, the level of construction units is uneven, and a large number of unskilled migrant workers are used in the construction site. Structural engineers need to consider these realities when designing, and the feasibility of construction should be considered in structural scheme, type selection, component design and detailed structure. The easier it is to construct, the easier it is to ensure the quality of the project and the less likely it is to go wrong. This is another example.
Example 1:
According to the structural analysis results of a concrete frame structure, most columns adopt structural reinforcement. From the economic point of view, the designer uses HRB335 steel bar as column longitudinal reinforcement and HRB400 steel bar as beam longitudinal reinforcement. In this way, two kinds of deformed steel bars with the same diameter but different strength appeared on the construction site. It is difficult to distinguish these two kinds of steel bars only from the appearance, only from the labels engraved on the steel bars and the factory nameplates. If the management of the construction site is chaotic, confusion and misuse may occur. In the design stage, the construction unit has not yet been determined, and the technical ability and management level of the construction unit are still unknown. Therefore, the author suggests that in some areas where the management level of construction units is generally low, it should not be handled easily.
2, design disclosure
According to Article 30 of the Regulations on the Administration of Survey and Design of Construction Projects, the design unit shall explain the design intent and design documents to the construction unit and supervision unit before the construction project starts. Structural design disclosure should not only write the overall description of the structure, but also explain the design intention of key parts of the structure and the construction precautions of new technologies, new materials and new processes to the construction unit.
Example 2:
The basement is 94.5 meters long and 72.5 meters wide. The floor, roof and side walls all adopt expansive concrete as technical measures to deal with shrinkage cracks of concrete in super-long basement, in which the floor adopts continuous expansion strengthening belt, but serious leakage occurs after completion. After investigation, it is found that the expansive concrete is not poured continuously according to the design requirements, but the expansion reinforcement belt is poured later: the expansion concrete outside the expansion reinforcement belt is poured first, and then the expansion reinforcement belt is poured several days later, and there is no steel plate water stop at the construction joint between them. The expansion of concrete can only produce preloading stress under limited conditions. Expansive concrete is not poured continuously according to the design requirements, and the large-area floor concrete poured first can expand freely to some extent because there is no constraint from adjacent units, which greatly reduces the role of preloading stress and leaves construction joints. When pouring the expansion reinforcement belt, we were careless and did not set the steel plate water stop according to the requirements of pouring the expansion reinforcement belt later, which eventually left the future trouble of leakage. The direct cause of the accident is that the construction unit failed to implement the design requirements, and the indirect cause may be that the structural engineer did not emphasize the importance of continuous casting in the design disclosure.
Example 3:
In the structural standard story of an engineering (Figure 1), the cantilever beam with 3C axis reaches 3.5m In order to meet the building clearance requirements, connecting columns are added at the end of the cantilever beam to form a cantilever vierendeel truss, which effectively reduces the structural height and increases the stiffness. In order to prevent the construction unit from mistakenly thinking that this part is just an ordinary frame beam and column and neglecting the control of the construction load, it is pointed out in the design disclosure that "the supporting system of the cantilever vierendeel truss must be removed only after the concrete of each layer where the truss is located meets the design strength requirements", so as to avoid the risk that the construction load of this part exceeds the design load, endangering the structural safety and causing construction safety hazards.
3, try to play (pressure, drilling, digging) pile and groove inspection.
This link is to make an overall exploration of the soil layer and special soil conditions of the BenQ Trough, verify whether the evaluation of the geological conditions of the site in the investigation report conforms to the actual situation, check whether the selection of bearing stratum is appropriate, check whether the construction method of engineering piles is feasible, and judge whether the standard of hammer collection or final hole of engineering piles is appropriate. In case of special circumstances in this process, it is necessary to make a calm analysis according to local conditions, and supplement construction survey or even modify foundation design when necessary; Don't stick to the rules and stick to your own opinions, which will only intensify contradictions.
Example 4:
There are 37 high-rise residential buildings in a residential area in Hunan province, of which 2 1# building, 22# building and 23~24# building are based on hand-dug cast-in-place piles, and the pile ends are moderately weathered limestone bearing layers. Pre-drilling supplementary survey was carried out before construction, and it was found that the detailed survey report was quite different from the description of geological conditions, so it was doubtful whether it could be implemented according to the original foundation plan. Therefore, two Ф1000 piles were selected for trial excavation in 23~24# buildings, and the excavation was more than 20 meters to the moderately weathered rock layer that still could not meet the original design requirements, so the construction encountered great difficulties. The original design unit tried to modify the foundation into a bored pile according to the design parameters of the supplementary survey report, and still used moderately weathered rock as the bearing stratum. The construction unit selected three Ф 800 piles for trial flushing in 2 1# building, and the results were unsuccessful: all three piles collapsed in different degrees during the construction process, 1 pile took 7~ 15 days to complete, and the concrete filling coefficient of cast-in-place pile body reached 2. 1~2.7. The parties concerned have great differences on the principle of pile final hole, construction progress, settlement of engineering quantity and other matters, and the project was forced to stop.
The construction unit had to consult the treatment plan. After the consultant thinks that the design parameters of the supplementary survey report are conservative, the static load test of foundation pile and shallow plate load test are supplemented accordingly, and more accurate foundation design parameters are obtained and submitted to the original design unit. However, the original design unit thinks that the construction difficulty is a problem of the construction unit and is unwilling to continue to follow up. Finally, the consultant continued to optimize the design of the foundation, and the 23~24# buildings still used manual digging cast-in-place pile foundation, considering the contribution of pile side resistance to vertical compressive bearing capacity, and changed the bearing layer at the pile end; Building 2 1# and building 22# make full use of the bearing capacity of shallow foundation soil, and optimize the original designed bored pile into raft foundation. Through the foundation optimization design, the project can resume normal construction. See [3] and [4] for more information about optimization design.
4, ` cooperate with the construction scheme
In the design stage, structural engineers often only pay attention to how to meet the stress requirements. In the construction stage, the construction unit is more concerned about how to turn the idea of construction drawing into entity. Sometimes two different starting points will inevitably conflict. For the construction scheme proposed by the construction unit, structural engineers need to evaluate its structural rationality. They can neither think that it has nothing to do with themselves, push it off, nor blindly accommodate it, leaving structural safety hazards.
Expand:
1, subject to the leadership of the manager of the engineering management department and the command of the on-site competent engineer.
2, familiar with professional construction drawings and construction technical specifications, construction process. In general, the construction should be based on water use and water use drawings. If there is any contradiction or inconsistency with the civil engineering, it shall report to the competent engineer and coordinate with the design unit to solve it.
3, the construction organization design approved by the construction unit, the unreasonable and wrong part of the organization design, must require the construction unit to organize the modification in time, and re-submit for approval.
4. Review the qualifications of supervisors, check whether the arrival of supervisors meets the contract requirements, and check with supervisors whether the materials entering the site meet the design, contract requirements and relevant technical standards. If materials that do not meet the requirements are found, the construction unit shall be required to leave within a time limit in time.
5, according to the progress of the project in a timely manner for each part of the hidden acceptance, completes the relevant hidden acceptance data visa. Part-time full-time safety management of engineering projects.
6. In the process of management and construction, check whether the pipelines and grounding devices in each part meet the requirements of drawings and other construction documents, and pay special attention to whether the embedded pipelines, reserved holes and reserved grounding electrodes in the basement meet the special requirements of important equipment such as elevators, civil air defense, weak current machine rooms and power distribution rooms, and whether the bridge and enclosed buses meet the requirements. Conflict with the elevation and position of air ducts and water pipes, and whether there are strict anti-blocking protection measures for hidden pipelines. Do not meet the requirements, should promptly notify the construction unit for rectification.
7. Check whether the test process of each test of the construction unit is true and standardized, and whether the test results meet the design and specification requirements, and make relevant records.
8. Keep a diary of construction management in charge of the project, record the weather, image progress, construction quality and rectification results in detail, and accumulate first-hand information for inspection.
9. Participate in various engineering meetings, participate in solving technical problems encountered in construction, and coordinate relevant majors to solve quality problems in engineering construction.
10, participate in the project completion acceptance, carefully review and give the strong and weak electricity completion drawings, ensure the burial and description of all hidden pipelines in the completion drawings, and provide accurate maintenance basis for property management in the future.
;