Quality problem in steel structure engineering
The complexity of construction quality problems of steel structure engineering projects is mainly reflected in the numerous factors causing quality problems and the complicated reasons. Even if the quality problems of the same nature are caused by different reasons, the analysis, judgment and treatment of quality problems increase the complexity. For example, welding cracks can occur in both the weld metal and the base metal heat effect, both on the surface of the weld and inside the weld. The crack trend can be parallel to the weld bead or perpendicular to the weld bead. Causes also have improper selection of welding materials and welding preheating or improper heat after the points.
The severity of construction quality problems of steel structure engineering projects is shown in the following aspects: general, affecting the smooth progress of construction, causing construction delays, increasing costs, serious, building collapse, causing casualties, property damage, and causing adverse social impact.
The quality of steel structure engineering construction will continue to develop and change with the change of the outside world and the extension of time. For example, changes in stress in the welds of steel components cause cracks in welds that were previously free of cracks: delayed cracks can be generated by the activity of hydrogen in the welds after welding. If the members bear overload for a long time, then the steel members to produce under arch bending deformation, hidden dangers.
(iv) frequent occurrence
Since modern buildings in China are dominated by concrete structures, the management personnel and technical personnel engaged in construction are relatively unfamiliar with the production and construction technology of steel structures, and the concrete construction personnel mainly composed of migrant workers do not understand the scientific construction methods of steel structure engineering, which leads to frequent accidents in the construction process.
Steel structures are subject to corrosion
Steel structure must pay attention to protection, especially thin-walled members, therefore, in the more corrosive medium of the building should not use steel structure. The steel structure shall be thoroughly derusted before painting, and the paint quality and coating thickness shall meet the requirements of relevant specifications. In the design, the structure should be protected from damp and rain, and the dead Angle for inspection and maintenance should be avoided as far as possible. Newly built steel structures are usually repainted at regular intervals, with high maintenance costs. Various kinds of high performance coatings and weathering steels are being developed at home and abroad. The problem of poor corrosion resistance of steel structures is expected to be solved.
The steel structure is heat resistant and refractory
The temperature over 250 ℃, the material quality, great changes have taken place not only strength gradually reduce, also blue and creep phenomenon happens. The temperature of 600 ℃, the steel into the plastic state cannot continue to load, strength of steel is almost zero.
Fracture of steel structure
Brittle fracture of steel structures at low temperature and under certain conditions, as well as lamellar tearing of thick plates, should be paid special attention to by designers.
Steel is more expensive
After the adoption of steel structure, the construction cost will increase slightly, which often affects the choice of owners. In fact, the cost of the superstructure accounts for a small proportion of the total project investment, with an increase of about 10%. High-rise buildings, for example, increased by less than 2%. Obviously, the single factor of structure cost should not be used as the basis of deciding which material to use. If all kinds of factors are considered, especially the advantage of time limit, steel structure will be paid more and more attention.
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