Source: Construction of steel structure engineering of steel structure alliance 1
.
It is necessary to make a good investigation and selection of steel structure manufacturing and installation units
.
We know that the construction of steel structure engineering should go through two stages: factory manufacturing and on-site installation
.
These two stages can be completed by one construction unit, but sometimes they can be completed by two units (subcontracting)
.
The investigation and selection of steel structure manufacturing units and installation units are of great significance to ensure the quality and progress of steel structure engineering
.
The inspection contents of steel structure manufacturing and installation units mainly include: enterprise qualification, production scale, number, professional title and resume of technicians, number and qualification certificate of skilled workers, mechanical equipment and performance level
.
2
.
Strictly review the steel structure manufacturing process and installation construction organization design submitted by the contractor
.
The 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 review of the construction organization design is an important content of prior control and active control of supervision work
.
For the steel structure engineering, the manufacturing process and installation construction organization design shall be prepared respectively for the manufacturing stage and installation stage
.
The manufacturing process content shall include the quality standards and technical requirements of each process and sub item in the manufacturing stage, as well as various 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
.
3
.
Full attention shall be paid to the supervision work in the manufacturing stage
.
As mentioned above, the steel structure engineering shall go through two stages: factory manufacturing and on-site installation
.
The manufacturing and installation are generally in the charge of two grass-roots units (manufacturing workshop and installation project department) under the steel structure engineering company, and sometimes may be completed (subcontracted) by two units of the manufacturer and installation company
.
The supervision engineer shall pay full attention to the supervision work in the production stage, and earnestly carry out pre control and in-process control like the supervision work of other types of projects
.
All processes and sub items shall be carefully, timely, strictly and in place
.
It is necessary to avoid the wrong working method of relaxing the supervision of the factory manufacturing process and relying only on the mobilization acceptance after the completion of components
.
This should be paid special attention when the manufacturer is far away from the project site
.
4
.
Supervision in the installation stage supervision in the steel structure installation stage is mainly to supervise the operation of the Contractor’s internal management system and quality assurance system, supervise and urge the implementation of various technical and organizational measures in the construction organization design, and carry out the construction in strict accordance with the relevant national current specifications and standards of steel structure
.
The supervision work in the steel structure installation stage shall focus on the following links: rationality and implementation of the installation scheme, installation measurement, connection of high-strength bolts, installation and welding quality, actual measurement of installation dimension deviation, coating, etc
.
The supervision work shall strengthen on-site patrol inspection, parallel inspection and on-site supervision, especially when the quality of some steel structure construction units is low and the construction is still not standardized, it is of more practical significance to do a good job in on-site patrol and on-site supervision to ensure the construction quality of steel structure engineering
.
5
.
As for the test and inspection of steel structure engineering, a number of test and inspection work for the fabrication and installation construction of steel structure engineering are not available in general civil engineering
.
These test and inspection items mainly include: inspection of relevant items of steel raw materials (if necessary), welding procedure qualification test (if necessary), weld nondestructive testing (ultrasonic, X-ray, magnetic particle, etc.) Torque coefficient or pretension test of high-strength bolts, anti slip coefficient test of high-strength bolt connection surface, bearing capacity test of steel grid joints, performance test of fire retardant coatings for steel structures, etc
.
The following points should be paid attention to in doing these tests and inspections: (1) it is necessary to supervise and entrust testing institutions with corresponding qualifications（ 2) Adhere to the witness system of sampling and inspection, and avoid the inconsistency between the test piece and the project（ 3) For some testing items, there are few qualified testing institutions, the distance is long and the cost is high
.
In this case, the supervising engineer must adhere to the principle, have a clear attitude and firm position, and timely urge the contractor to implement these works, which is a necessary measure to ensure the quality and construction progress of steel structure fabrication and installation, It is also the “main control project” stipulated in the current national code for construction quality acceptance of steel structure engineering
.
6
.
Several other important quality control points of steel structure engineering 6.1 Embedment of anchor bolts the embedment quality of anchor bolts directly affects the installation quality of steel structure
.
Controlling the position, perpendicularity, length and elevation of anchor bolts (groups) is of great significance to reduce the workload of hole expansion and adjustment (even avoid rework) and improve the quality of structural installation
.
The embedding method of anchor bolts can be direct embedding method or reserved hole method
.
Before foundation concrete pouring, the supervision engineer must strictly check the rationality and reliability of the construction method of embedded bolts and whether all measured indexes are within the scope specified in the specification
.
6.2 quality control of welding engineering welding engineering is one of the most important subdivisions of steel structure fabrication and installation engineering
.
The supervision engineer must engage in all links of pre preparation, welding process and finished product inspection, and earnestly do a good job in the quality control of welding engineering
.
At present, most of the steel structure construction units in our city have automatic submerged arc welding machines, and some have semi-automatic gas shielded welding machines
.
Only some parts are welded manually
.
Many welding quality problems exist in manual welds
.
These problems include: weld bead, slag inclusion, air hole, incomplete penetration, undercut, wrong edge, large weld size deviation, no arc striking plate, uncorrected welding deformation, unclean cleaning of spatter, etc
.
In view of this situation, the supervising engineer must do the following work: (1) check the factory quality certificate of welding raw materials（ 2) Check the welder certificate（ 3) Supervise and urge necessary welding process test（ 4) Strengthen patrol inspection during welding and supervise the implementation of various technical measures（ 5) Strictly carry out visual inspection of weld quality and actual measurement of weld size（ 6) Supervise and urge NDT
.
6.3 high strength bolt connection engineering high strength bolt connection engineering is also one of the most important subdivisions of steel structure engineering and one of the weak links of current construction quality, which is mainly reflected in: (1) high strength bolts are shoddy, (ordinary refined bolts are used to replace high strength bolts)（ 2) The treatment of high-strength bolt connection surface fails to meet the requirements of the specification, including surface treatment, flatness and tightness, bolt hole quality, etc（ 3) The tightening of high-strength bolts is not carried out in accordance with the specifications
.
For example, it is completed at one time regardless of initial tightening and final tightening, without torque wrench, all based on subjective estimation, etc
.
In order to ensure the construction quality of high-strength bolt connection project, the supervision engineer must, with a high sense of responsibility, actively adopt working methods such as on-site supervision and parallel inspection while urging the contractor to improve quality awareness, strengthen quality management and implement quality assurance measures
.
Only in this way can the construction quality of high-strength bolt connection project be under strict control
.
6.4 derusting and coating of steel structure derusting and coating of steel structure is not only a work easily ignored by the steel structure contractor, but also a weak link in the construction of steel structure engineering
.
If this phenomenon is not corrected, it will have a great impact on the construction quality of steel structure, because whether the derusting and coating quality are qualified or not will directly affect the maintenance cost of steel structure in the future, as well as 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 insufficient understanding of the importance of coating work by the relevant personnel of the contractor, coupled with the lack of quality responsibility and even mercenary, which eventually leads to frequent problems in the quality of coating engineering.
.
