"How to do the grid structure in bulk"
1. When assembling the small unit or bar directly in the high altitude, the order should ensure the accuracy of assembly and reduce the accumulation error.When the suspension method is constructed, it should be put into a structural system that can bear the self-weight and then gradually expand.The network frame should check the position, elevation and deviation of the reference axis at any time during the assembly process, and correct it in time.
2. The position of the support point on the bracket shall be located at the lower chord node when assembling the mounting bracket.The support should be checked for bearing capacity and stability, and test pressure can be carried out when necessary to ensure safety and reliability.Measures should be taken under the brackets to prevent the support from sinking.
Three, in the process of demolition of stents should prevent individual support concentrated force, should be based on weight of deflection value of each point using distinguish stages in proportion to drop or not greater than 10 mm with each step step descent method to remove strong point.
"Installation points of steel structure"
: (1) the friction coefficient, in which F for slip resistance test of specimen with initial sliding force, nf of friction surface, with the corresponding F high strength bolt tightening method the sum of the measured values.
(2) torque coefficient: in which d is the nominal diameter of the high strength bolt (mm), and M is the applied torque value (N · M), and P is the bolt pre-tightening force.10.9 high-strength hexagonal bolt connection must ensure that the average of the torque coefficient K is 0.110 ~ 0.150.The standard deviation should be less than or equal to 0.010.
(3) initial torque: in order to reduce the influence of steel plate deformation during bolt tightening, it can be used to reduce the mutual influence between the bolts.The high strength bolt is screwed for the first time, and its axial force should reach 60% ~ 80% of the standard shaft force.
(4) final torque: the final tightening torque of the high-strength bolt is the final twist torque.Considering the loss of all kinds of prestress, the torque is generally 5% ~ 10% of the torque value calculated according to the theoretical calculation.
Reasons for damage of steel structure and measures for reinforcement.
When the steel structure is damaged, we should immediately find out the immediate problem. The main factors of steel structure damage are:
1) due to the change of load, the service, specification and regulation change resulted in insufficient bearing capacity of the structure;
2) due to various unexpected deformation, distortion, disability and sag, the components of the component are weakened, and the member of the member is warped, and the link is cracked, etc.
3) the deformation, cracking and warping of components or joints are caused by temperature difference;
4) corrosion and electrochemical corrosion caused by the erosion of chemical materials weaken the section of steel structure;
5) other errors in design, production and construction, improper use and operation of the service period, etc.
There are three main technical measures for reinforcing steel structure:
1) section reinforcing method: in local or along the whole length of the component, the steel reinforcement is reinforced to make the joint force together;
2) change the calculation schematic diagram: add additional support, adjust the load distribution, reduce the internal force level, and force the displacement of the super static structure support to reduce the stress peak;
3) prestressing cable method: it is used to strengthen weak links of high strength cable and improve the overall bearing capacity, stiffness and stability of the structure.