How to deal with quality problems in grid structure engineering

1. In some projects, the phenomenon that the weld seam is not full at the steel pipe, cone head or sealing plate often occurs. Especially for some large diameter and thick wall members, it may be necessary to weld several times to obtain wide and thick weld. At this time, if the welder neglects a little, the weld will be not full. If a ruler is used to lean against the welding seam, the weld seam at the joint of welding rod will appear depression, and large continuous pit may also appear. This kind of bar has large stress, which is far from the requirements of weld code, so repair welding is needed. Repair welding should be carried out before installation in the factory or on site. It is also feasible for the installed grid under the action of self weight. For the grid structure with full roof static load, proper support or interval welding should be carried out. The high temperature state of the whole section of the members should be avoided, because the steel will lose part of the bearing capacity under high temperature.

If the steel ball is too small in the grid installation, it may easily lead to rod collision and hinder the installation work. Correspondingly, in the construction drawings of large-scale grid structure and special shaped grid structure, bolt ball with diameter greater than 100 appears in the process, which means that the steel ball is too large. Due to the influence of various factors such as market, processing and on-site installation, the installation work is blocked finally. To solve the problem that the steel ball is too small and easy to lead to rod collision, the following methods can be adopted. When the conditions are convenient, the ball can be changed and the corresponding bar can be modified. Otherwise, part of the cone head and the rod part of one of the colliding rods will be burned, and then a steel plate with thickness of 2-4mm than the pipe wall will be imitated and welded. A part of the opening edge of the taper head and rod and the steel plate for repair welding shall be beveled (with hand-held grinding wheel). After repair welding, the hand-held grinding wheel shall be used for leveling, and the rust stain shall be removed and two layers of antirust primer shall be applied. The above-mentioned treatment method should follow the following principles, that is, to check the force condition of each member in the computer calculation book. 

3. The treatment method of insufficient depth of high strength bolt into bolt ball. The main reason is that the construction sequence is unreasonable. The top chord is tightened first, and the web member is tightly connected with the bolt ball, and the bolt can not be screwed. Treatment method: operate in strict accordance with the construction process, and the operator can judge according to the number of screw thread turns, and check with torque wrench.