Key points and practical experience of constructio

Key points and practical experience of construction supervision of steel structure engineering

steel structure workshop is widely used for its advantages of fast construction speed, large span, light self weight, high strength, good seismic performance and easy factory processing. At the same time, the steel structure plant is an energy-saving and environmental friendly recyclable building structure, so the steel structure technology, as one of the "ten new technologies in the construction industry" promoted by the Ministry of construction, is widely used in the current industrial plants, roads and bridges and other buildings. The author has served as the supervisor of several large steel structure workshops, and has a certain understanding of the supervision of large steel structure workshops. This paper discusses the problems related to the construction supervision of steel structure engineering

1 carefully review the construction design drawings

the construction design drawings are the basis of the project construction. The supervising engineer should be familiar with the engineering drawings, projects and other relevant conditions as well as the specifications, process and technical conditions selected for the project as soon as possible before the commencement of the project, and fully understand the design intent. Understand the use function, process requirements and design intention of the project, and put forward professional opinions on the structural selection and material use of steel structures. At the same time, professional technicians of the construction unit shall be organized to jointly review the drawings, check the "mistakes, omissions, bumps and deficiencies" in the construction drawings, and strive to solve the problems before construction. Therefore, the supervision engineer must coordinate the following work:

(1) strictly check the qualification of the construction unit. Mainly assess the following items: the enterprise's steel structure design and construction qualification level; The processing and production capacity of the enterprise, including the advanced degree of manufacturing and processing equipment, the situation of the enterprise's technical management personnel and skilled workers, the performance of the enterprise in completing the processing tasks of the same type of projects, the enterprise's deepening design ability, the enterprise's annual processing and production ability, etc. If the manufacturer is far away from the construction site and is not in the same area, transportation and temporary stacking of materials should also be considered

(2) coordinate the cooperation between design and processing departments. After the detailed design is completed, the processing unit can process and manufacture only after it is confirmed by the design unit. The supervision unit shall strengthen the coordination between the design unit and the design department of the manufacturer, so that the processing manufacturer can deeply understand the intention of the design unit, and the design unit can confirm the drawings of the processing manufacturer as soon as possible

(3) strictly implement national standards. During the work of getting familiar with the construction drawings, the relevant contents of the steel structure design part of the national "mandatory parts provisions of engineering construction standards" shall be mainly checked. For example, whether the required weld quality level meets the requirements; Whether the load design value is adopted when calculating the strength, stability and connection strength of the structure or member; Whether the standard value of load is used when calculating the deformation of fatigue and serviceability limit state

(4) review whether the construction design drawings and instructions comply with the national technical specifications and local regulations. Check whether all contents of the construction drawings are different from the specified scope approved by the preliminary design review; Whether the fire prevention and fire fighting meet the requirements

(5) check the steel specification and material requirements. Whether the form of welding slope u, the category of nondestructive testing, the proportion of nondestructive testing, and the specification and size of high-strength bolts meet the specification requirements; Whether the installation elevation and size of important components are consistent with the design drawings, etc

(6) if there are drawings jointly designed by several design units that drive the associated force measuring pendulum paper under the action of oil pressure, whether there are contradictions between the design drawings; Whether there are contradictions between professional drawings and horizontal, vertical and sectional drawings; Mark whether there is any omission

(7) when checking the construction details of steel members, the hoisting capacity and transportation conditions of the hoisting machinery on the construction site should be considered, the size of unsuitable members should be adjusted appropriately to meet the installation requirements, and the cutting and splicing size should be determined for the factory processed members

(8) whether the geometric dimension, plane position and elevation of the general plan and the construction drawing are consistent

(9) whether there are errors and contradictions between the building structure and the professional drawings; Whether the plane size and elevation of the structural drawing and the architectural drawing are consistent; Whether the representation method of architectural drawings and structural drawings is clear; Whether it conforms to the drawing standard; Whether the embedded parts are clearly indicated; Whether there is a detailed list of reinforcement or the structure of reinforcement requires the weight of the sample itself, which is easy to cause inaccurate measurement results. Whether it is clearly shown in the figure is required

(10) whether the material source is guaranteed and whether it can be replaced; Whether the conditions required in the figure can be met; Whether there are problems in the application of new materials and technologies

(11) whether there are contradictions between process pipelines, electrical lines, equipment and devices, transportation roads and buildings or between them, and whether the layout is reasonable

2 production process control of steel members

because the quality of the structural members of copper structure engineering processed and manufactured in the factory is very important to the on-site installation of copper structure engineering and the safety and stability of the overall structure, the supervision engineer should strictly control the production and processing quality of each member, especially the welding quality of structural members

2.1 review the manufacturing process of structural parts

check whether the process flow prepared by the processing unit meets the requirements, especially whether the welding sequence is reasonable, such as whether the welding sequence is to weld the longitudinal seam first and then the transverse seam, so as to avoid strong butt welding and reduce the welding stress; In the manufacturing process of steel structures, whether to adopt high-precision processing methods, it is necessary to predict various deformations in each process, especially those caused by welding, and take corresponding deformation prevention measures. Such as eliminating allowance or automatic symmetrical welding

2.2 inspection of preparation for production

the main inspection contents of preparation for production include: (1) inspection of raw materials into the factory, check the steel specification and batch number, and prevent unqualified material selection; (2) Participate in welding procedure qualification test; (3) Review welder qualification and valid certificates; (4) Review the qualification of nondestructive testing (NDT) personnel and the verification validity of relevant equipment; (5) Review the verification validity of length measuring instruments used in the project; (6) Inspection of fabricated tooling platform; (7) Check the production quality of sample rods and templates

2.3 quality control of processing process

(1) parts processing and manufacturing: whether the surface quality meets the requirements and whether it needs to be corrected. Check the overall dimensions of the web, top plate and bottom plate, and the cutting quality of the groove, so as to prevent the bending deformation caused by cutting the steel plate and cutting, and prevent the manufacturing dimension deviation from being too large

(2) welding process control: when welding the workpiece, the Welding Supervisor should strengthen patrol inspection. Pre welding inspection: whether the weldments and grooves are cleaned, whether the welding materials are correct, whether the welding process conditions are met, whether the welding workers work with certificates, etc; Inspection during welding: operation of welding equipment, rationality of welding sequence, implementation of welding specification and welding process, and whether rectification measures are taken for defects. At the same time, the deformation of weldments caused by local heating and uneven cooling during welding shall be controlled, and the welding deformation shall be controlled within the allowable manufacturing error range

(3) inspection and detection of welds

① weld appearance inspection: 100% of all grade I, II and III welds of structural members are required to be visually inspected. Before the inspection, the welding slag on the component weld shall be removed, and then the appearance quality of the weld shall be checked with a l0 times magnifying glass, and the undercut of the weld, arc pit, gas pit, crack and other conditions on the weld surface shall be checked and recorded. Measure whether the weld leg height and weld height of the foot weld meet the design requirements

② weld nondestructive testing: ultrasonic testing or radiographic testing is an important method to check the internal quality defects of welds, and magnetic particle testing is a method to check the near surface or surface defects of ferromagnetic welds. The supervisor shall review whether the selected detection method is appropriate; Check whether the testing unit has the corresponding qualifications and whether the qualification level of testing personnel meets the requirements; Check whether the length of each weld inspection meets the requirements of technical conditions and design specifications. Finally, check whether the format of the test report meets the requirements and whether the content is complete

(4) assembly control: the steel structure is generally assembled by the "a" assembly method, with high accuracy requirements. It is usually required to simulate the actual working conditions of the construction site in the factory for pre assembly. When the overall size deviation occurs in the assembly, it is necessary to carefully find out the reason and take corresponding measures to deal with it

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3 steel structure installation

the amount of hoisting and welding in the steel structure installation and construction is large, and the requirements for safety and stability are high, and the requirements for installation errors are extremely high, which requires the supervisors to pay attention to the following key monitoring points:

3.1 review the steel structure installation scheme

when reviewing the steel structure installation scheme, Attention should be paid to the following points:

(1) whether the inspection plan includes the following main contents: the quantity and weight of each component and connector; Suitable hoisting machinery; Plane and vertical flow installation procedures; Schedule; Labor organization; Quality objectives; Safety protection measures, etc

(2) check whether the installation sequence is reasonable and whether the overall and local stability of the steel structure in the installation process can be guaranteed, and check the strength and stiffness if necessary. The plane installation sequence should be extended from the middle area with large structural constraints to the surrounding areas to disperse the cumulative error; The facade installation procedure shall be carried out in units, and the principle is that the frame installed by steel columns and main beams will not deform

(3) urge the construction unit to prepare the hoisting scheme of steel structural members and carefully review it. Review whether the hoisting sequence of steel structure is reasonable, whether the hoisting machinery and equipment can meet the requirements, whether the setting of component hoisting points is reasonable, and whether the hoisting safety measures are feasible. The hoisting sequence is from inside to outside, from column to beam. Select hoisting machinery and equipment according to the weight and size of components. The setting of lifting points should be selected according to the characteristics of components to prevent distortion and damage of components, ensure installation quality, lifting safety, improve production efficiency and reduce labor intensity

3.2 re measurement of positioning axis and benchmark

(1) for the positioning axis provided by the foundation construction unit or the construction unit, the positioning axis shall be handed over and inspected together with the construction unit, the foundation construction unit and other relevant units, and records shall be made to mark and protect the positioning axis

(2) measure with a level gauge according to the benchmark (above level 2) provided by the construction unit, and set the benchmark to nearby places that are suitable for automobile interior and exterior trims, motorcycle exterior trims, electrical appearance parts and other places that should not be damaged, but keep the line of sight unblocked, and protect it at the same time

3.3 recheck the installation position of embedded parts

embedded anchor bolts are the key work items of the steel structure installation construction site. Generally, before the construction unit pours concrete, the supervision engineer should carry out closed measurement and inspection of the embedded bolts, in addition to the vertical and horizontal axis measurement, the elevation inspection should also be carried out. Before the initial setting of the poured concrete, retest and check again to ensure that the anchor bolts are accurately embedded

3.4 quality control of steel structure installation

(1) monitoring of steel structure connection node construction

the reliable parts of steel structure node connection are related to the stability of the overall structure, and the reliable parts of connection are closely related to the connection mode. According to the connection mode, it can be divided into welding connection, high-strength bolt connection and mixed connection (welding connection, high-strength bolt connection). The supervisor shall supervise the construction unit to carry out the construction of each connection point in strict accordance with the design drawings, so as to eliminate the construction chaos. Generally, column to column connection adopts welding method, column to beam connection adopts mixed connection method, and main beam to secondary beam connection adopts high-strength bolt connection

(2) field welding quality control