When the steel is not within the refractory temperature exceeds 250 ℃, the material changed greatly, not only gradually reduce the strength, but also a blue brittle and creep phenomenon. When the temperature reaches 600 ℃, the steel into the plastic state can not continue to carry. 21 Steel Steel fracture edit certain conditions and at low temperatures, brittle fracture may occur, as well as slab lamellar tearing, special attention should designer. After the steel is more expensive steel structure will be a slight increase in the cost structure, the choice is often affected owners. In fact, the upper structure of the project cost accounting for a small proportion of the total investment increased by about 10%. The high-rise buildings, for example steel plant costs, the rate of increase is less than 2%. Obviously, the structure should be based on the cost of a single factor as the decision to adopt what material. If considering a variety of factors, especially the duration of the advantages, the steel will be more and more attention. Installation Notes (1) Friction coefficient: steel canopy, where F is the anti-slip tests to make specimen measured force to generate the initial slip steel, nf for the friction surface, and F for the corresponding high-strength bolts tightened Pretension and measured values. (2) torque coefficient:, where d is the nominal diameter high-strength bolts (mm), M for applying torque value (N.M), P for bolt preload. 10.9 high strength hex bolt connection must ensure the torque coefficient K is an average of 0.110 to 0.150. The standard deviation should be less than equal to 0.010. (3) early twist torque: To reduce the impact of bolted steel during deformation, can be tightened to reduce secondary interactions has Tighten bolts between. High-strength bolts screwed for the first time early twist to the axial force should reach 60% to 80% of the standard axial force. (4) The final twist torque: high-strength bolts fastening torque for the last final twist torque. Consider a variety of prestressing loss, according to a final twist torque than the general design of the pre-tension torque value for the theoretical calculation of the big 5% to 10%. Dongguan Jian Peng steel design _ steel (certified) _ Steel provided by Zhuhai, Dongguan City, Peng Jian Steel Limited. Steel Co., Ltd., Dongguan City, Peng Jian (dgpengjian.cn) is Dongguan, steel leader, over the years, the company is implementing the scientific management, innovation and development, the principle of honesty and trustworthiness, and satisfy customer needs. Peng leader in steel construction with the staff warmly welcome all inquiries negotiations to create Peng build a better future for steel.