Hotline：
First, the characteristics of quality problems in steel structure engineering
(1) Complexity
The complexity of the construction quality problems of steel structure engineering projects is mainly manifested in the variety of factors that cause quality problems, and the reasons for quality problems are complex, even if it is a quality problem of the same quality, the reasons are sometimes different, so that the analysis, judgment and treatment of quality problems increase the complexity. For example, welding cracks can occur both in the weld metal and in the heat effect of the base material, either on the surface of the eld or inside the weld. The crack direction can be parallel to the weld pass or perpendicular to the weld pass. The crack may be either cold crack or hot crack. The causes also include improper selection of welding materials and improper welding preheating or post-heating.
(2) Seriousness
The seriousness of the construction quality problems of steel structure engineering projects is manifested in: general, affecting the smooth progress of construction, causing delays in construction, and increasing costs; serious, building collapse, causing personal casualties, property damage, and causing adverse social impacts.
(3) Variability
The construction quality problems of steel structure engineering will continue to develop and change with the external changes and the extension of time, and the quality defects will gradually reflect. For example, the weld of a steel member, due to the change of stress, cracks occur in the weld that originally had no cracks: delayed cracks can occur due to the activity of hydrogen in the weld after welding. If the member is subjected to overload for a long time, the steel member will have the lower arch bending deformation, resulting in hidden dangers.
(4) Frequent frequency
Since modern buildings in our country are mainly concrete structures, the management personnel and technical personnel engaged in construction are relatively unfamiliar with the production and construction technology of steel structure, and the specific construction personnel mainly by migrant workers do not understand the scientific construction method of steel structure engineering, resulting in frequent accidents in the construction process.
Second, the safety countermeasures of building steel structure engineering quality problems
(1) Quality and safety control of steel structure foundation engineering
Concrete independent column foundation is generally used in steel structure engineering, and the construction process and method of concrete, steel bar and formwork of the foundation are the same as that of other projects. The bolts embedded in the foundation independent column are the focus of quality control. The spacing and deviation between individual bolts and each group of bolts directly affect the installation quality of steel structure engineering. The construction unit shall adopt measures to ensure.
1. Create an installation template
Take three steel plates the size of the steel column bottom plate (two of which are 20mm thick, a piece of 8 ~ 20mm can be), two steel plates 20mm thick according to the position and size of the bolt hole of the steel column bottom plate, the three steel plates are assembled, a set of bolts are inserted into the screw hole, and the bolts are welded into a whole with φ144-φ16 steel bars, each of which can be reused many times. In this way, the spacing and height between individual bolts are controlled within the permissible deviation range. A: Φ14 ~ Φ16 Steel bar B: 'bolt C: Φ14 ~ Φ16 Steel bar E: 20ram steel plate F: 8-10mm steel plate G: 200 ~ 300ram H: 50mm.
2. Fixing the bolt group
Before concrete placement, the bolt group is accurately positioned with the theodolite, and the steel bars with Φ14 and Φ16 are welded to the main reinforcement of the column. The top of the fixed bolt reinforcement end is on the template spoon, and the upper and lower channels are respectively, so that the spacing and height between each group of bolts can be controlled within the allowable error range. At the same time, protect the bolt thread to prevent it from being damaged when the concrete is poured.
3. Make the transition
After the completion of the civil engineering, the spacing between the bolt groups (axis spacing), height, and the height of each column body pouring are measured with the theodolite. After the re-test and acceptance, the installation unit of civil construction and steel structure is organized to carry out the intermediate handover acceptance. After the acceptance, the installation unit of steel component is required to carry out the re-test.
(2) Quality and safety control during the installation phase
Construction and installation in strict accordance with the construction drawings, as a construction unit, after obtaining the construction drawings, we must organize experienced technical personnel to review the drawings to see if there is any problem with the application specifications: whether the node diagram is clearly stated: Whether the content required by the mandatory provisions is shown in the general design instructions, whether the specifications, models, performance, grades of various materials, quality requirements of construction and safety levels of the project are clear: whether the node design is reasonable; There is no insurmountable difficulty in the construction, etc., should be put forward to the design unit in advance. Steel component installation quality control. During column and beam installation, the main inspection is to check whether the pad iron under the bottom plate of the column is solid and flat, whether the column is vertical and displacement, the vertical, flat and lateral bending of the beam, the tightening degree of the bolt and the cleaning of the friction surface, and the acceptance is qualified before lifting. When the steel structure is installed into a space fixed unit, and after acceptance, the construction unit is required to densified the space of the column bottom plate and the top surface of the foundation with secondary pouring of expanded concrete.
Control of bolt mounting quality. In steel structure engineering, high-strength bolts and bolts are generally used for bolt connection
Common bolts, common bolt connection, each end of the bolt shall not be padded with more than 2 gaskets, the bolt hole shall not be expanded with gas cutting, the exposed thread of the bolt after tightening shall not be less than 2 screw pitch j high-strength bolts before use, we check the -G -= grid certificate of the bolt and the re-test list, during the installation process, the contact surface of the plate should be smooth, and the contact surface must be greater than 75%. The edge gap shall not be larger than 0.8mm, and the high-strength bolts shall be inserted freely without tapping or reaming: High-strength bolts shall not be used as temporary installation bolts, and the bolts shall be tightened in one direction. The screws installed on the same day shall be finally screwed, and the screws shall be checked one by one, and the underscrewed and overscrewed shall be repaired or replaced.
(3) Quality and safety control of completion acceptance
Quality acceptance of steel components. The processing of steel components has been implemented in factory production, and the quality acceptance of steel components is very important. In addition to checking the quantity of components according to the detailed list, and conducting the inspection of appearance, sensory, geometric size and qualification certificate, we also need to check the following materials: Steel material retest sheet (original) : The material certificate of the steel (the copy shall be stamped with the official seal of the production unit, and the storage place of the original shall be explained); NDT report (original). In the acceptance of completion, it should be done: the site management department should make the coordination of the construction unit and relevant departments, and determine the time, place and method of the acceptance of completion; Before the completion and acceptance, the site management department shall do the site cleaning work, collect and sort out the data of the installation project, and issue the forging report, the comprehensive assessment of the cylinder and other materials; After the completion of the acceptance, the completion data shall be sent to the construction unit and the quality supervision unit for signature to determine the grade of the project, and sent to the relevant departments for filing.
