Discussion on steel structure and its application in civil engineering

The 1.1 strength in general, structural member to withstand or accommodate the effects of capacity is determined by the strength of the material to the decision.Can use the relevant national standards to determine the structure of steel component performance, these criteria are listed in the steel structure can use material.From the whole, made up of steel structure can reduce the material consumption, reduces the weight of the structure, reduce the support member and the base size, ultimately reduce the structure cost.
1.2 stiffness vibration, deformation and applicability of parameters by the member rigidity to decide, then from the structure stiffness to decide.Structure system of practical rigidity but also by its members and joints distribution to decide.However, simply put, member rigidity material from the geometric cross section characteristics and the elastic modulus of the material is to determine, structural steel elastic modulus is usually 200GPa.Average density and compressive strength in the range of 20-40Gpa concrete elastic modulus is usually in the range of 20-28GPa; even for high strength concrete, its modulus of elasticity but also in between 40-45GPa, therefore, steel structure of steel concrete is ten times and five times, so the steel structure rigidity has a significant advantage.
1.3 ductility ductility refers to some kind of material stretching process of fracture plastic deformation capacity.General ductility is structure design, especially the seismic design is an important characteristic parameter, earthquake surviving buildings depends directly on the main frame structure undergoes large inelastic deformation hysteresis energy.Steel structure can be said to be the most widely used one of the best engineering materials, toughness.However, material intrinsic ductility does not necessarily translate to building structure inherent ductility, so we need to fully understand this point, take appropriate design strategies and reliable, stable hysteresis dissipation mechanism.Usually a design with ductile response will have enough materials section, ductility and the ductility of the structure and the structural ductility.Ductility value capacity and demand to change ductility level, curvature ductility (ductility) and displacement ductility (ductility) that match.Although the steel structure strain ductility is relatively high, but because the bending force is not stable, so the members often lack the curvature ductility.
1.4 measure of material fracture toughness of energy absorption and the plastic deformation ability indicator is the toughness.It can resist a notch part of the unstable crack extension.Toughness is normally expressed in steel structure in manufacturing, installation and use of the process can bear larger industrial deformation, the steel structure is a very important characteristic.It is because the steel toughness makes the bending, shear, punching, forging, drilling and production process, reduces the possibility of crack producing.Steel structure sufficient fracture toughness is necessary, especially for the alternating load and impact load of the building structure but also to have the characteristics of.Structural steel fracture toughness for temperature condition is very sensitive, and along with the temperature and the decrease of.So in cold area of steel structure design, we must first consider the toughness.Relatively speaking, low carbon Nb steel high carbon composition can improve the toughness of steel.
1.5 overall from the result, either from the stiffness, strength and ductility, steel structure is superior to the reinforced concrete, and steel structure can be relatively easily construct exotic architecture form, usually steel structure system can provide optimum design flexibility and maximum utilization of space.Steel structure of another advantage is that: it is a ideal cantilever construction system.Appropriate application of fasting steel bracket and component web opening, for pipes and other power line channel, not only reduces the floor height, but also increase the aesthetic appeal.Steel frame like in steel structure, is used to expand the existing concrete structure or add floor.In the construction, assembling steel structure construction personnel is much less than the required number of concrete building structures; and concrete construction, steel structure installation and production quality is more reliable and simple.And modified, steel ratio concrete structure more easily, lower cost, especially to the additional support system, steel structure can accelerate the construction progress.
2 steel structure.
Of course, every kind of material are not perfect, so the application of steel structure and construction also has some disadvantages, which mainly manifested in the following aspects:
The 2.1 material disadvantages though steel structural stiffness is much larger than the concrete, but for a given load, the steel structure member section stiffness than comparable concrete structure, this is mainly because the steel strength led to its member of relatively small dimensions.In order to improve the stability of members, will increase the size of steel or concrete filled and take concrete measures to improve the stiffness of the section.And steel fire resistance and corrosion resistance are relatively deficient.Steel has long been 100 degrees of radiant heat intensity changes little, show some resistance, but when the temperature reaches 150 degrees, we must use insulation layer protection, and important parts of the steel structure must be coated with fireproof coatings.
2.2 market environment
2.2.1 design strength is weak in building structure design should pay attention to requirement of structure is it right? Belonging to the steel structure and reasonable application.In the design of high capacity usually requires the use of steel structure, should consider to use is not suitable to continue to load large deformation for the structure design of the limit state criteria.Steel structure has many nodes, to each screw, backing plate and weld of accurate calculation, and each professional to one-time reach the designated position, so the steel structure design than the design of concrete structure is more complex, and the drawings are far more than the concrete structure.
2.2.2 steel structure production has not formed the system only in the case of the mass production can reflect the superiority of steel structure.And the current steel structure production standard, standard of price and quality standards are not unified, national standards as well as regulatory mechanism also has certain shortcomings, so many designers and developers are relatively vague.
2.2.3 price problems due to steel structure production has not formed a system of steel structure, so the higher prices.Although steel production in recent years has greatly improved, but the per capita output is still relatively low, steel still is economy of our country countryman more precious materials, and concrete price advantage is reflected.
2.2.4 steel structure service life of concrete structure is never damaged, but the steel structure for general use life span of only fifty years, if the steel structure is used in residential buildings, so people think of their life savings and cost to buy the house can live in fifty years, will let many people lost the desire to buy.But with the development of the insurance industry, residential life issues should be relatively easy to solve.
3 key points for installation of steel structure construction
The whole steel structure construction process is more complex, and the construction requirement, the details will have great differences.Here are three simple description.
3.1 selection and connection of steel is usually divided into plates, profiles, and tubes of metal products four major categories.Civil engineering construction steel usually uses ordinary low-alloy steel, carbon structural steel and ordinary carbon steel, carbon steel plastic is relatively low, but the relatively high hardness and strength.In the steel structure column section, the general number of box girder with wide flange "or the" font, in addition to "ten" cross section and so on; most are welded or rolling beam "H" shaped steel, if special requirements can also be consistent with section, before the installation of the main welding joint welding technology the test set, welding materials and various parameters.Between the beams, beam and column connection between, can take the welding connection or bolt connection, to the attention of high-strength bolt connection hole position accuracy.Hole preparation mainly has two kinds, one is high precision CNC drilling, another is the relatively low accuracy of the template for the hole.In the technical conditions allow more suitable for multi axis NC drilling.Delivered to the site later to bolt parameters for inspection, installation can not use wrench to screw or forced into with a hammer, screw in steps to be after initial tightening, complex s as well as the final twist.
The 3.2 components of the stacking and choose to install mechanical locations typically installation structure of land area for structure covers an area 1.5 times.In accordance with the erection sequence from transit yard facilities, shipped to the site of steel components to the loading and unloading machinery to its placement in the installation of machinery and the radius of gyration.If because of transport caused deformation, then at the construction site will be corrected.General installation of steel structure is used in tower crane, boom length should have enough coverage, and lifting capacity should be enough, to meet a variety of different parts of components of the lifting requirements.Rope capacity to meet the hoisting height requirements; lifting speed enough grades to meet the requirements of installation.In a machine case, arm elevation difference should be enough, to avoid unsafe collision, to ensure safe operation.The tower crane should be a safe distance between, to ensure that the arm rod and the tower body do not collide.Comparison of steel structure suitable for regular, symmetry and a flat floor, so the installation of pipeline layout to suit one's measures to local conditions.
3.3 paint process
3.3.1 base treatment the metal surface is clean, and then do the cleaning.Manual processing to use wire brush repeatedly brush, then fine emery cloth polishing, the surface bright, smooth, and then use cotton or gauze to grinding of rust powder and floating dust clean.If the surface corrosion is serious, then with a wire brush blade processing, large areas of corrosion can be used to clean the sand turbine.
3.3.2 antirust paint, putty in metal surface before painting to ensure dry, if water is to immediately wipe.Applied to brush, brush, brush with fine place, and pay attention to rivet hole can be painted into the.When the antirust paint after drying, using and paint matching the putty scraping component surface defect.The putty with some red lead powder or thick paint, thereby increasing its dry hard.In the putty dry to be burnished, and clean.If the time for stack is too long, will have to do a painting.
3.3.3 coated phosphating primer phosphating primer includes primer and phosphating solution in two parts.In the coating phosphating primer two hour after they finish or painted other primer.