Common quality problems of space frame engineering and its causes analysis

Common quality problems in space frame processing engineering

1. Bending deformation or partial fracture of the rod;
2. The connection of the blanking plate or the cone is damaged when welding;
3. Node deformation or fracture;
4. The welding is not full or there are bubbles, slag inclusions, and micro gaps that exceed the specified standards;
5. The high-strength bolt is broken or pulled out from the ball joint;
6. The rod collides at the connection point, and the support web collides with the support structure when the upper chord is supported;
7. Displacement of support nodes;
8. The deflection of the space frame is too large, exceeding the design requirements by 1.15 times the corresponding design value.

   

The main reason

(1) Design reasons

1. The choice of structural form is unreasonable. The rod cross-section matching is unreasonable. The effects of initial bending, initial eccentricity and secondary strain of prefabricated members are ignored. Underestimation and omission of loads or improper combination of loads during design;
2. The material selection is unreasonable;
3. The selection of calculation methods, assumptions, and calculation procedures have not been found to be wrong;
4. After the structural design calculation, material replacement is carried out without review, resulting in the appearance of strength members exceeding the design value;
5. The engineering drawings are incorrect or incomplete. If the dimensions are confused, the design description is unclear, and there are omissions in materials, process requirements, construction procedures and special requirements;
6. The node structure is wrong, and the details are not comprehensively considered.

   

(2) Reasons for the space frame processing factory

1. Management is chaotic. Mixed use of different specifications, steel grades and materials;
2. The blanking size of the prefabricated component is wrong. The slenderness ratio of prefabricated members does not meet the design requirements;
3. The cutout of the space framemembers is not cut, and the welding seam is not lined or welded according to the design requirements when connecting;
4. The connection of high-strength bolts is unqualified;
5. The processing of prefabricated components is defective, and the angle deviation of the bolt ball hole is large;
6. The quality of the welding seam is poor, and the size of the welding angle does not meet the design requirements.

(3) Reasons for space frame installation

1. When the ground is assembled, the support points are uneven, the force is unreasonable, and the error accumulates during assembly. Some rods are wrong, resulting in changes in force, resulting in deformation of the space frameor some rods;
2. The welding process and welding sequence are wrong, resulting in welding stress and deformation;
3. During the overall hoisting, the selection of the hoisting point is unreasonable, and the reaction force check, the over-stress check of the rod, the deflection check, and the necessary reinforcement measures are not carried out on the hoisting point;
4. When the whole is hoisted, the hoisting speed of each hoisting point is different. The displacement and slope exceed the allowable range, resulting in deformation and damage;
5.  The selection of the project construction plan is wrong, and the plan is not effectively selected according to the structure form of the space frame and the construction conditions on site;
6.  The pre-embedded parts, pre-embedded bolts or column tops of the space frame support are relatively large, and it is difficult to seat them. Forced seating leads to changes in the force conditions of the support and deformation of the rod;
7. The installation staff were negligent, and the position of the rod and the angle of the ball were wrong;
8.  When the upper chord is supported, the accumulation of errors is too large, resulting in the displacement of the bearing, and the web rod collides with the supporting surface.