Construction of steel structure engineering

1We should do a good job in the inspection and selection of steel structure manufacturing and installation units

As we know, the construction of steel structure engineering should go through two stages: Factory fabrication and site installation. These two stages can be completed by one construction unit, but sometimes it may be completed by two units separately (subcontracting).It is of great significance for ensuring the quality and progress of steel structure engineering to do a good job in the investigation and selection of steel structure manufacturing and installation units.The inspection contents of steel structure manufacturing and installation units mainly include: enterprise qualification, production scale, number of technical personnel, professional title and resume, number and qualification certificate of technical workers, mechanical equipment and performance level.

2Strictly review the steel structure manufacturing process and installation construction organization design submitted by the contractor

Construction organization design is an important comprehensive technical document prepared by the contractor to guide all activities in the whole process of project construction. Careful examination of construction organization design is an important content of pre control and active control of supervision work.The manufacturing process and installation construction organization design shall be prepared for the steel structure engineering at the production stage and installation stage respectively. The manufacturing process content shall include the quality standards and technical requirements of each process and sub item in the production stage, as well as the specific measures formulated to ensure the product quality, such as the processing method of key parts, the process flow and process measures of main components Processing equipment, process equipment, etc.

3We should pay full attention to the supervision work in the production stage

As mentioned above, steel structure engineering must go through two stages: Factory fabrication and site installation. Generally, the fabrication and installation are respectively undertaken by two grassroots units (production workshop and installation project department) of steel structure engineering company. Sometimes, it may be completed by two units (manufacturing plant and installation company) respectively (subcontracting).The supervision engineer should pay full attention to the supervision work in the production stage. Like the supervision work of other types of projects, the supervision engineer should do a good job of pre control and in-process control, and check each process and sub item seriously and timely, strictly and in place.To avoid that kind of relaxation of the supervision of the factory manufacturing process, only rely on the component after the completion of the site acceptance of the wrong work method.This point should be paid special attention to when the manufacturing unit is far away from the project site.

4Supervision of installation stage

The supervision work content of steel structure installation stage is mainly to supervise the operation of the internal management system and quality assurance system of the contractor, to supervise the implementation of various technical and organizational measures of the construction organization design, and to carry out the construction in strict accordance with the relevant national specifications and standards for steel structures.The supervision work of steel structure installation stage should focus on the following aspects: rationality and implementation of installation scheme, installation measurement, connection of high-strength bolts, installation welding quality, measurement of installation dimension deviation, coating, etc.The supervision work should strengthen the on-site inspection, parallel inspection and on-site supervision, especially in the current situation that the quality of some steel structure construction units is low and the construction is still not standardized, it is of practical significance to do a good job of on-site inspection and on-site supervision to ensure the construction quality of steel structure engineering.

5Test and inspection of steel structure engineering

The production and installation of steel structure engineering are not available in general civil engineering. These test and detection items mainly include: detection of steel raw materials related items (if necessary), welding procedure qualification test (if necessary), weld non-destructive testing (ultrasonic wave, X-ray, magnetic powder, etc.), torque coefficient or pretension test of high-strength bolts, and high-strength bolts.The anti slip coefficient test of bolt connection surface, bearing capacity test of steel grid joint, performance test of fire retardant coating for steel structure, etc.

The following points should be paid attention to when doing these tests and inspections well:

(1) It is necessary to supervise and entrust testing institutions with corresponding qualifications;

(2) It is necessary to adhere to the witness system of sampling and submission for inspection, and avoid the inconsistency between the specimen and the project;

(3) For some testing projects, there are few qualified testing institutions, and the distance is far away, and the cost is high. In this case, the supervision engineer must adhere to the principle, have a clear attitude and firm stand, and timely urge the contractor to implement these works. This is a necessary measure to ensure the quality of steel structure fabrication and installation and construction progress, and is also the current national steel structure project”Main control items” specified in construction quality acceptance specification.

6Other important quality control points of steel structure engineering

6.1 Foundation bolt embedment

The embedded quality of anchor bolt directly affects the installation quality of steel structure. It is of great significance to control the position, perpendicularity, length and elevation of anchor bolt (Group) to reduce reaming and adjustment workload (even avoid rework), and improve the installation quality of structure.The embedded method of anchor bolt can be direct embedding method or reserved hole method.Before the foundation concrete pouring, the supervision engineer must strictly check the rationality and reliability of the embedded bolt construction method, and whether the measured indexes are within the scope of the specification.

6.2 Welding engineering quality control

Welding engineering is one of the most important sub items of steel structure fabrication and installation engineering. Supervision engineer must be engaged in preparation, welding process and finished product inspection, and do a good job in quality control of welding engineering.At present, most of the steel structure construction units in our city have automatic submerged arc welding machines, some of them have semi-automatic gas shielded welding machines, and only manual welding is used in some parts.There are many welding quality problems existing in manual welding seam. These problems include: weld bead, slag inclusion, air hole, incomplete penetration, undercut, wrong side, large deviation of weld size, no need of arc striking plate, no correction of welding deformation, and unclean cleaning of spatter.In view of this situation, the supervision engineer must do the following work well: (1) check the factory quality certificate of welding raw materials; (2) check the welder’s qualification certificate; (3) supervise and urge the necessary welding process test; (4) strengthen the patrol inspection during the welding process and supervise the implementation of various technical measures; (5) strictly carry out the weld quality and appearance inspection and the actual measurement of weld size; (6) inspect the quality and appearance of welding seam strictly）Supervise NDT.

6.3 High strength bolt connection engineering

High strength bolt connection project is also one of the most important sub items of steel structure engineering, and is also one of the weak links of current construction quality. The main performances are as follows: (1) high strength bolts are replaced by inferior ones; (2) high strength bolt connection surface treatment can not meet the requirements of the specification, including surface treatment, flat and close adhesion(3) the tightening of high-strength bolts is not carried out according to the specifications, such as the completion at one time regardless of the initial and final tightening, no torque wrench and subjective estimation.In order to ensure the construction quality of high-strength bolt connection project, the supervision engineer must, with a high sense of responsibility, urge the contractor to improve the quality awareness, strengthen the quality management and implement the quality assurance measures, and at the same time, actively adopt the work methods such as site supervision and parallel inspection. Only in this way can the construction quality of high-strength bolt connection project be under strict control.

6.4 Rust removal and painting of steel structure

Rust removal and coating of steel structure is a work that is easy to be ignored by steel structure contractor, and it is also the weak link of steel structure engineering construction.If this phenomenon is not corrected, the construction quality of steel structure will be greatly affected, because the quality of rust removal and coating will directly affect the maintenance cost of steel structure in the future, and also affect the service life of steel structure engineering, structural safety and fire resistance time in case of fire (fireproof coating).The ideological root of this phenomenon lies in the lack of awareness of the importance of painting work by the relevant personnel of the contractor, coupled with the lack of quality responsibility and even profit-making, resulting in frequent problems in the quality of painting projects.Therefore, the supervision engineer must attach great importance to the derusting and painting work, and carry out strict inspection and acceptance of each process, which is the basis and guarantee to ensure the coating quality of steel structure.

As for the coating quality of steel structure engineering, the following work should be done well:

(1) The derusting quality of steel members shall be strictly checked and accepted according to the design requirements;

(2) Check the factory quality certificate of coating raw materials and the approval certificate of fire department for fire retardant coating;

(3) Before painting, the soil, oil and other impurities on the surface of components shall be thoroughly removed;

(4) The coating construction should be carried out in a dust-free and dry environment, and the temperature and humidity should meet the requirements of the specification;

(5) The brushing times and coating thickness shall meet the design requirements;

(6) The coating damage should be treated carefully to ensure the coating quality;

(7) Carefully check the adhesion of coating;

(8) Strictly carry out appearance inspection and acceptance to ensure that the coating quality meets the requirements of specifications and standards.

6.5 Profiled metal sheet engineering profiled metal sheet engineering is mainly color steel plate maintenance structure, which is a new type of building maintenance structure.At present, the main problems in the engineering practice are: the construction unit does not formulate the color plate (sandwich board) construction scheme, the joint of color plate, the connection between plate purlin, the fabrication and installation of color plate accessories and other node structures are not fine or reliable, the maintenance structure leakage, the appearance quality of color plate sub project is uneven, not smooth, tight, deformation, scratch, pollution, etc.

In view of the above situation, the supervision engineer should pay attention to the following points in his work:

(1) Before the fabrication and installation of color board (sandwich board), the construction unit must be urged to formulate a comprehensive and reliable construction scheme of color plate project, especially the detailed layout scheme, construction method and quality assurance measures;

(2) In the process of production and installation, patrol inspection, site supervision and parallel inspection should be strengthened to eliminate most quality problems before and during construction;

(3) The acceptance of inspection lot and sub project shall be carried out strictly to ensure that the joint structure is reasonable, reliable, no leakage, the appearance is smooth, straight, tight, uniform in color, and the board surface is free of scratch, rust and pollution.