Steel structure engineering can use a variety of steel, channel steel, section steel, I-beam, H-beam, C-beam and other types of steel, different materials of steel strength or performance is also different. The common steel used in steel structure engineering is Q235 steel or Q345 steel, which are also different.
I. What is the difference between Q235 steel and Q345 steel in steel structure engineering?
Q235 is a common carbon steel. At present, it is also a common steel used in steel structure workshop. Q345 is a low alloy high strength steel with slightly higher strength than Q235 steel, but the corresponding steel standards are different. One is GB700, the other is GB1591, Q345A and B do not require impact performance, Q345B requires normal temperature impact, and Q345B steel for roofing and exterior wall structure has higher strength and impact resistance. According to the actual quality requirements of steel structure engineering and the analysis of steel quality requirements, steel components of different materials can be selected.
Q235 steel in steel structure engineering
Q235 steel is widely used in factory buildings. Q235 steel is usually rolled into sections such as wire rod or round steel, square steel, flat steel, angle steel, I-beam steel, channel steel, window frame steel, medium and heavy steel plate. The steel used in steel structure factory building is also composed of these steels, but some factories with higher requirements for impact resistance will use steel such as section steel. The yield point or bending resistance are relatively high, and the safety and strength of the whole structure can also be guaranteed.
For which steel is used to build steel structure engineering, steel of different materials can be selected according to the actual situation. Most of the steel structures are semi-finished products which need to be processed into steel components for engineering. The quality of the steel components processed according to the requirements of design drawings can be guaranteed. The performance of length, width and thickness can meet the actual requirements, and will not appear inappropriate. Situation.
Second, when will Q235 be used in steel structure engineering and when will Q345 be chosen?
(1) At present, there is a price difference between Q235 and 345, but it will not be very large. When Q235 has no absolute comparative advantage, try to use Q345.
Q345 steel
(2) The bearing capacity of steel structural members is smaller in strength bearing capacity R1 and stability bearing capacity R2; stability control is the dominant factor; beam strength: calculation formula f=M/Wn (considering about 0.85 net section coefficient: stability of beam; Wx does not include stability factor, so long as the overall stability coefficient of beam is greater than 0.85, the beam is strength control; when the stability coefficient is less than 0.85, it is strength control. Look at the stability factor control formula: the higher the strength, the lower the stability factor. In fact, the key essence is that the stability bearing capacity is only related to material elastic modulus E. That is to say, the stability bearing capacity is caused by large deformation. Stability bearing capacity is only related to stiffness. The principle of bending members is the same. Let's look at the table of compression stability factor in the appendix to the code.
(3) Conclusion: Q235 is preferred for beams and columns whose stability coefficient is less than 0.5. Because there are still so many materials when using Q345. Q235 is often used in light and large space structures. The essence is that the stability coefficient is too small in component calculation. The essence behind is that the elastic modulus E of Q235 steel is the same as that of 345 steel. Stability bearing capacity; has nothing to do with material strength.