The complexity of construction quality problems in steel structure engineering projects is mainly reflected in the numerous factors causing the quality problems and the complicated reasons for the quality problems. Even if the quality problems are of the same nature, the reasons are sometimes different. Therefore, the analysis, judgment and treatment of the quality problems increase the complexity. For example, welding cracks can occur in both the weld metal and the heat effect of the base metal, both on the surface of the weld and inside the weld. The crack direction can be parallel to or perpendicular to the pass, and the crack can be either cold or hot. The cause also has the welding material choice improper and the welding preheating or after the improper heat points.

(1) Seriousness

The seriousness of construction quality problems of steel structure engineering projects is as follows: in general, it affects the smooth construction, causes delay of construction period, increases the cost, and in serious cases, the buildings collapse, causing human casualties, property damage and adverse social impact.

(2) Variability

The construction quality of steel structure project will also develop and change with the change of the outside world and the extension of time, and the quality defect will gradually manifest. For example, a weld in a steel member can produce a crack in a weld that previously had no crack due to a change in stress: a delayed crack can result from the action of hydrogen in the weld after welding. If the component bears overload for a long time, the steel component should produce arch bending deformation and hidden trouble.

(3) Frequency

Since modern buildings in China are mainly 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 specific construction personnel, mainly migrant workers, do not understand the scientific construction method of steel structures, resulting in frequent accidents in the construction process.