[Seat] in all types of space grid structure, the rigid system of the grid (net shell) structure as a higher statically indeterminate beam structure in space, due to the good performance of its force (theoretically limited only by the lever axial force), rigidity, good integrity and seismic performance, strong carrying capacity, by the holder uneven settlement is small, flexible and adaptable sliding seat bearer, and increasingly sophisticated computer technology and the rapid development of the theory of computation, It makes any extremely complex three-dimensional structure analysis and design as possible, and therefore grid (net shell) structure is widely used in industrial and civil fields. [Grid] but bearing grid (net shell) structure if its supporting structure, bearing type and boundary conditions would be unreasonable design grid (net shell) security and economic structure has important implications. 1. The support structure and the support carriage way [grid] present in many projects, the grid (net shell) Steel Company general by a professional design according to the boundary conditions assumed in advance, and then they figure out a seat plus a load reaction force as the lower support structure. [Grid] bearing the grid (net shell) and a lower support structure separately calculated, bearing with respect to the displacement of the lower part of the grid structure although you can simulate elastic restraint method, but is supported by the lower bearing structural deformation caused by subsidence displacement and other seat itself is difficult to estimate accurately the structure of the internal forces calculated in some cases vary greatly with the actual situation, it might give the project a security risk. [Grid] substructure bearing column may be, it may be the beam, it may be other structure, not only the stiffness is limited and specific projects can be large differences in stiffness, in this assumption, calculated rod internal forces, support reactions and the internal forces and the use of grid substructure bearing stiffness and rigidity on the actual results substructure mechanical model of the calculated work together is certainly not the same. The calculated separately also separates the upper and lower structures work together, so that the upper, cycle and shift computation substructure are not accurate. Plane friction coefficient at the design load (2MN) bearing 0.0116. According to experimental data at home and abroad, at low temperature -40 ℃ grease lubricated coefficient of friction PTFE sheet, and about three times the normal temperature. Consider a certain safety factor in the design, construction design ball bearing friction coefficient values ??as follows: room temperature (-25 ℃ above); μ = 0.03; low temperature (-25 ℃ ~ -40 ℃); μ = 0.05; when torque increased enough to overcome the friction PTFE sheet when the holder rotates occur. This torque is called the initial value of the rotational torque. After rotating bearing measuring ring after unloading and stabilizing to a smaller value, called the residual value of the rotational torque. Second load bearing from rotating so that when rotational torque was significantly lower than the initial value, and unload the remaining value of the rotational torque. After several load bearing occurs stable rotating torque required to rotate to a certain value, this value is called the rotational torque stabilized value. The above phenomenon with PTFE plate and stainless steel quality inspection of the plane sliding friction Sliding Bearings consistent, rotational resistance visible ball bearing ball by friction between the crown liner and PTFE sheet caused. Ball bearing rotation after the seismic slip grid branch seminars, measuring ring unload, but not unloaded to zero, but to unload the remaining value of the rotational torque, this value has nothing to do with the size of a large corner seat rotation sliding bearings and during the test, as far as possible bearing angle increasing, but so that the rotation of the bearing torque again, are more than the initial value of the rotational torque. The above phenomenon described ball bearing rotating torque and bearing rotation independent of the size.