What Is Steel Fabrication?

Steel structure is a structure composed of steel materials, which is one of the main types of building structures. The structure is mainly composed of beams, steel columns, steel trusses and other components made of profiled steel and steel plates. Components or parts are usually connected by welding, bolts or rivets. Because of its light weight and simple construction, it is widely used in large-scale factory buildings, stadiums, and super high-rise areas.

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1.High material strength and light weight

The strength of the steel is high and the elastic modulus is also high. Compared with concrete and wood, its ratio of density to yield strength is relatively low. Therefore, under the same stress conditions, the steel structure has a small cross-section, light weight, easy transportation and installation, suitable for large spans, high heights, and heavy loads. Structure.

2, steel toughness, good plasticity, uniform material, high structural reliability

It is suitable for withstanding shock and dynamic loads and has good seismic performance. The internal structure of the steel is uniform, which is close to an isotropic homogeneous body. The actual working performance of steel structures is more in line with calculation theory. Therefore, the steel structure has high reliability.

3.Mechanization of steel structure manufacturing and installation is high

Steel structural components are easy to fabricate at the factory and assembled on site. The factory mechanized manufacturing of steel structure components has high precision, high production efficiency, fast construction site assembly, and short construction period. Steel structure is the most industrialized structure.

4. Good sealing performance of steel structure

Because the welded structure can be completely sealed, it can be made into high-pressure vessels, large oil tanks, pressure pipes, etc., which have good air tightness and water tightness.

5.Heat-resistant and fire-resistant steel structure

When the temperature is below 150 ° C, the steel properties change little. Therefore, the steel structure is suitable for thermal workshops, but when the surface of the structure is exposed to heat at about 150 ° C, it is necessary to protect it with a heat shield. When the temperature is between 300 ° C and 400 ° C, the strength and elastic modulus of the steel are significantly reduced. When the temperature is around 600 ° C, the strength of the steel tends to zero. In buildings with special fire protection requirements, steel structures must be protected with refractory materials to improve fire resistance.

6. Poor corrosion resistance of steel structures

Especially in the environment of humid and corrosive media, it is easy to rust. Generally, steel structures need to be derusted, galvanized or painted and regularly maintained. For offshore platform structures in seawater, special measures such as "zinc block anode protection" are required to prevent corrosion.

7, low carbon, energy saving, green and environmental protection, can be reused

Demolition of steel structure buildings will hardly generate construction waste, and steel can be recycled and reused.

Although China had outstanding achievements in iron structure in the early days, it stayed at the level of iron buildings for a long time. It was not until the end of the 19th century that China began to adopt modern steel structures. After the founding of the People's Republic of China, the application of steel structures has greatly developed, far exceeding the past in terms of quantity and quality. The floor of the light steel structure is composed of cold-formed thin-walled steel frames or composite beams, floor OSB structural panels, supports, connectors and so on. The materials used are oriented particle board, cement fiberboard, and plywood. These lightweight floors can withstand loads of 316 to 365 kg per square meter.

Roof system

Thermal insulation and energy-saving technology In order to ensure the thermal insulation effect, the thermal insulation materials used in the exterior walls and roofs of buildings can be used for a long time and can be thermally insulated. In general, in addition to filling glass fiber mesh between the wall and pillars of the building, the light steel structure of the house is generally covered with a layer of thermal insulation material on the outside of the wall, which effectively cuts off the thermal bridge that passes through the pillars to the outer wall panels; joists between floors Filled with fiberglass to reduce heat transfer through the floor; glass fiber is filled between the columns of all interior walls to reduce heat transfer between the walls of the house.

Fire protection technology One of the most critical issues of light steel structure is the application of fire protection technology. The fire resistance rating of light steel structure housing is Grade 4. Building light steel structure houses are covered with fire-resistant gypsum board on both sides of the wall and the ceiling of the floor. The ordinary firewall and individual wall are protected with 25.4 mm thick (1 inch) gypsum board to meet the fire protection requirement for one hour. The fiberglass filled between the wall pillars and the floor joists also plays a positive role in protecting against fire and heat transfer.

Sound insulation technology The light steel structure is filled with glass wool between the internal and external walls and the floor joist, which effectively prevents the audio part transmitted through the air. For the impact sound transmitted through the solid, the following structural treatment is used: The wall pillars form two walls with an intermediate gap; for the small keel of the fixed gypsum board for the ceiling, the elastic structure with small cutouts is used to effectively reduce the solid sound transmission between floors.

connection method

Welding connection

Bolted

Rivet connection

Heavy steel structure

1. Lifting weight of factory truss: 25 tons.

2. Steel consumption per square meter: 50KG / .

Light steel structure

Refers to light steel structures made of round steel and angle steel smaller than L45 × 4 and L56 × 36 × 4. National regulations and technical documents did not say that heavy steel.

The GBJ17-88 Code for the Design of Steel Structures has been abolished since December 1, 2003. The current practice is the GB50017-2003, the Code for Design of Steel Structures.

Equipment steel structure

Equipment steel structure refers to the steel structure part of large-scale equipment. According to the experience of technicians, the following structures should be classified into the equipment steel structure category: tower steel structure of bridge crane, crane lifting beam, crane body, large equipment Brackets, etc., belong to one of the precision steel structures that require high precision, material and connection. For the complete set of equipment, it is the most stressed part, which plays a structural role in function.

The processing and manufacturing of equipment steel structure is similar to that of precision steel structure. It is between ordinary structural parts (with low processing requirements) and precision machining (requires more precise processing), and is connected by welding or bolting.

At the same time, the main types of steel structures are: shelving structures for factory buildings, frame structures for multi-rise buildings, frame-shear wall structures, frame-tube structures, flat-panel grid structures and curved roof nets for large spaces. Structure and so on. Different building functions have different structural forms. The design of steel structures must implement national technical specifications to achieve advanced technology, economical and reasonable, safe and practical, and ensure quality. Therefore, pay attention to the following requirements when designing and manufacturing the structure:

1. First, according to the requirements of the building function, adopt a corresponding reasonable structural system. Achieve advanced technology, novel structure and perfect unification of building and structure.

2. Steel structures (except containers) are mostly rods, so the dimensions of the rods are as modular and standardized as possible, which is convenient for mechanized manufacturing, transportation, installation, and productivity improvement.

3. Use high-efficiency steel with higher economic indicators.

4. The nodes of the steel structure are critical, and appropriate connection methods should be adopted to make the node design consistent with the simplified structure calculation model. Most of the previous structural damage occurred at the nodes, so the nodes must be carefully designed and carefully constructed. Advanced and reliable connection methods are used.

The steel structure will be affected by various forms during the use (load, uneven settlement of the foundation, temperature, etc.), so it is required that the steel should have good mechanical properties (strength, plasticity, toughness) and workability (cold and hot working and welding) Performance) to ensure that the structure is safe and reliable. There are many types of steel, and only a few meet the requirements of steel structures, such as Q235 in carbon steel, 16Mn in low alloy steel, and 20 manganese vanadium steel (20MnV) for high strength bolts. ^[2]

Equipment steel structures usually have special requirements or higher requirements in the following areas:

Structural parts: material, surface roughness, tolerance, surface treatment, straightness (or radian)

Connection: hole position deviation, bolt level; welding method, welding standard, welding material; air tightness, nondestructive testing, liquid penetration testing, etc. required

Overall structure: verticality, horizontality, etc.

Packaging: packaging materials, packaging methods

Storage: ambient temperature, ambient humidity

Transportation: loading and unloading, display in a car, display in a container, etc.

Refers to the structural form capable of bearing and transmitting loads connected by steel plates and hot-rolled, cold-formed or welded profiles through connecting members. The steel structure system has the comprehensive advantages of light weight, factory-made manufacturing, fast installation, short construction cycle, good seismic performance, fast investment recovery, and less environmental pollution. Compared with reinforced concrete structures, it has more advantages in "high, large, light" The unique advantages of the three aspects of development, in the global scope, especially in developed countries and regions, steel structures have been reasonably and widely used in the field of construction engineering. The steel structure industry is usually divided into five sub-categories: light steel structure, high-rise steel structure, residential steel structure, space steel structure and bridge steel structure.

The steel structure is widely used in various engineering constructions, such as steel bridges, steel workshops, steel gates, various large pipeline containers, high-rise buildings, and tower-rail mechanisms.

1. Light weight of steel structure

2. High reliability of steel structure work

3 Good vibration (shock) and impact resistance of steel

4 The industrialization of steel structure manufacturing is relatively high

5. Steel structures can be assembled quickly and accurately

6. Large steel structure indoor space

7. Easy to make a sealed structure

8. Corrosion of steel structures

9. Poor fire resistance of steel structures

10 Recyclable steel structure

11. Short construction time for steel structures

1. Carbon structural steel: Q195, Q215, Q235, Q255, Q275, etc.

2. Low-alloy high-strength structural steel

3 High-quality carbon structural steel and alloy structural steel

4 Special Purpose Steel

There is indeed no uniform standard for judging the structure of heavy steel and light steel structures. Many experienced designers or project managers often cannot fully explain it, but we can comprehensively consider and judge with some data:

Prefabrication of steel components

Prefabrication and assembly of steel components on the steel platform according to the installation sequence and process requirements, to ensure the quality of welding production.

The distance between the splicing seam of the splicing flange plate and the splicing seam of the web should be greater than 200. Flange plate splicing length should not be less than 2 times the board width; web splicing width should not be less than 300 , and the length should not be less than 600.

In order to facilitate welding and ensure welding quality, as far as possible, the columns, beams, stiffeners, connecting plates, pads, cantilever (beam), etc. are group-welded on the ground steel platform according to the size of the construction drawing.

In addition to making and assembling the steel components prefabricated on the steel platform in accordance with the construction drawings and specifications, it is also necessary to consider the changes in the processability and installation dimensions of the on-site installation.

Steel Structure Development: Three Areas to Pay Attention to

When the steel structure is also damaged, we must immediately find out and solve the problem immediately. The main factors that the steel structure network introduces to the damage of the steel structure are:

1) Insufficient structural capacity due to load changes, extended service, and changes in codes and regulations;

2) Due to various accidental deformation, distortion, disability, depression, etc. of the component, the cross section of the component is weakened, the members are warped, and the connection is cracked;

3) Deformation, cracking and warping of components or connections caused by temperature differences;

4) Corrosion caused by the erosion of chemical substances and electrochemical corrosion causes the cross-section of steel structural members to weaken;

5) Others include errors in design, production, construction, and illegal use and operation during the service period.

There are three main technical measures for strengthening steel structures:

1) Section reinforcement method: reinforce the steel partly or along the entire length of the component, and connect them together to make them bear the common force;

2) Change the calculation diagram: add additional support, adjust the load distribution, reduce the internal force level, force the statically indeterminate structure support to reduce the peak stress;

3) Pre-stressed cable method: use high-strength cables to strengthen weak links in the structure or improve the overall bearing capacity, stiffness and stability of the structure.

Compared with other constructions, steel structures have advantages in use, design, construction and comprehensive economy. The construction cost is low and they can be moved at any time.

Quality Problems in Steel Structure Engineering

(A) complexity

The complexity of the quality problems in the construction of steel structure engineering projects is mainly manifested in the many factors that cause quality problems, and the causes of quality problems are also complicated. Even for quality problems of the same nature, the causes are sometimes different. And processing adds complexity. For example, welding cracks can occur in the weld metal or in the thermal influence of the base metal, either on the surface of the weld or inside the weld; the crack direction can be parallel to the weld bead or vertical In the weld bead, the crack may be either a cold crack or a hot crack; the causes may also be caused by improper selection of welding materials and improper pre-heating or post-heating of the welding.

(Two) seriousness

The seriousness of construction quality problems of steel structure engineering projects is as follows: general, affecting the smooth progress of construction, causing delays in construction schedules, increasing costs, serious, building collapse, causing personal injury and death, property damage, and causing adverse social impacts.

(Three) variability

The quality problems of steel structure engineering construction will continue to develop and change with external changes and prolonged time, and quality defects will gradually manifest. For example, due to the change in stress of the weld of a steel member, the weld that was originally free of cracks is cracked: delayed hydrogen cracks can occur due to the action of hydrogen in the weld after welding. If the component is subjected to overload for a long period of time, the steel component will be bent and deformed, which will cause hidden dangers.

(Four) frequency

As modern buildings in China are mainly based on concrete structures, managers and technicians engaged in building construction are relatively unfamiliar with the production and construction technology of steel structures, and concrete construction workers mainly based on migrant workers do not understand the scientific construction of steel structures. Methods, accidents often occur during construction.

Corrosion of steel structures

Steel structures must be protected, especially thin-walled components. Therefore, steel structures should not be used in buildings in strong corrosive media. The steel structure should be completely derusted before painting, and the quality of the paint and the thickness of the coating should meet the requirements of relevant specifications. In the design, the structure should be protected from moisture and rain, and the structure should be avoided as far as possible. Newly constructed steel structures generally need to be repainted after a certain period of time, resulting in higher maintenance costs. Various high-performance coatings and weathering steel that are not easy to rust are being developed at home and abroad. The problem of poor rust resistance of steel structures is expected to be solved.

Heat-resistant and fire-resistant steel structure

When the temperature exceeds 250 , the material changes greatly, not only the strength gradually decreases, but also

(1) Friction coefficient: where F is the force measured by the anti-slip test to cause the initial slip of the specimen, nf is the number of friction surfaces, and is the sum of the measured values of the pre-tension of the high-strength bolts corresponding to F.

(2) Torque coefficient: where d is the nominal diameter of the high-strength bolt (mm), M is the value of applied torque (NM), and P is the pre-tightening force of the bolt. 10.9 high-strength large hexagon bolt connections must ensure that the average value of the torque coefficient K is 0.110 to 0.150. Its standard deviation should be less than or equal to 0.010.

(3) Initial tightening torque: In order to reduce the influence of the deformation of the steel plate during the bolt tightening process, secondary tightening can be used to reduce the mutual influence of successive tightening of the bolts. High-strength bolts are first tightened for the first time, so that the axial force should reach 60% to 80% of the standard axial force.

(4) Final tightening torque: The final tightening torque of the high-strength bolt is the final tightening torque. Considering the loss of various prestresses, the final torque is generally 5% to 10% larger than the theoretically calculated torque based on the design pretension.

Cleaning of steel structures-shot blasting machine for steel structures

I. Process

During the cleaning process, the electrically controlled adjustable-speed conveyor rollers feed the steel structure or steel into the ejection area in the cleaning machine room. Each side of the body is hit and abraded by the powerful dense projectiles from different coordinate orientations. The oxide scale, rust layer and its dirt quickly fall off, and the steel surface gets a smooth surface with a certain roughness. The workpieces are loaded and unloaded at the entrance and exit rollers on both sides of the outdoor. The projectile and rust dust falling on the steel are blown by the blowing device, and the dropped dust and dust mixture is conveyed by the recovery screw to the chamber funnel. In the device, the separated pure projectiles fall into the separator hopper for the shot blasting cycle. Dust generated during shot blasting is sent to the dust removal system by the exhaust pipe, and the cleaned air is discharged into the atmosphere, and particulate dust is captured and collected.

2. The main components

Steel-based structures are one of the main types of building structures. Steel is characterized by high strength, light weight, and rigidity, so it is particularly suitable for the construction of large-span, ultra-high, and ultra-heavy buildings;

The material has good homogeneity and isotropy, and is an ideal elastomer. It is in line with the basic assumptions of general engineering mechanics. The material has good plasticity and toughness, can have large deformation, and can withstand dynamic loads well. The construction period is short; its industrialization High degree, can carry out professional production with high degree of mechanization; high processing accuracy, high efficiency and good airtightness, so it can be used to build gas tanks, oil tanks and transformers.

Its disadvantage is poor fire resistance and corrosion resistance. It is mainly used for heavy-duty workshop's load-bearing skeleton, plant structure under dynamic load, plate and shell structure, towering TV tower and mast structure, bridges and warehouses, large-span structures, high-rise and super high-rise buildings, etc.

In the future, steel structures should study high-strength steels to greatly increase their yield point strength. In addition, new types of steels, such as H-shaped steel (also known as wide-flange steel), T-shaped steel, and profiled steel plates, are rolled to adapt to large-span structures And the need for super high-rise buildings.

The steel structure is divided into light steel and heavy steel. There is no uniform standard for judgment, and many experienced designers or project managers often cannot fully explain it. They can be comprehensively considered and judged with some data.

Before installation, the construction unit shall check the product qualification certificate, design documents and pre-assembly records of the components, and re-check the size of the recorded components. When the deformation and defects of the steel structure exceed the allowable deviation, it shall be handled.

Before installation, detailed measurement and correction processes should be prepared. For welding of thick steel plates, a process test simulating the product structure should be performed before welding and installation, and corresponding construction processes should be prepared. A certain degree of arching should be preset for the assembled roof truss.

After the steel structure is hoisted in place, the control points such as the positioning axis and elevation of the component shall be measured and marked, and the quality of the hoisted butt joints shall be checked before welding. Install temporary supports and steel cables to make steel roof trusses safe and stable during construction.

During the installation of steel structures, the construction unit shall submit the elevation dimensions, welding, painting, etc. of each concrete member after being hoisted to the supervisor for acceptance.

China's steel structure industry shows a sustained and rapid growth momentum. The output of steel structures increased from 8.5 million tons in 2002 to 22.94 million tons in 2009, with an average annual compound growth rate of 15.24%. According to relevant data estimates, in 2010, the output of steel structures reached 26 million tons. In 2011, steel structure output was about 29 million tons. China's steel structure industry is in a period of rapid development.

The overall concentration of China's steel structure industry is low. The number of steel structure enterprises with an annual output of less than 10,000 tons, 1-50,000 tons, 5-30 million tons, and more than 300,000 tons is 4000-5000, 100, 20, 6-8, respectively; enterprises with special steel structure manufacturing qualifications There are 51 companies with 82 Grade A qualifications for light steel structure engineering design, and even fewer companies with the above qualifications and professional contracting qualifications. With the continuous development of the industry, mergers and acquisitions within the industry will become the norm.

1. The steel structure system has the comprehensive advantages of light weight, easy installation, short construction period, good seismic performance, fast investment recovery, less environmental pollution, good plasticity and toughness, and good impact resistance.

2. The types of steel are: according to the thickness, thin plates (thin steel plate thickness <4mm), medium plates (4-20mm thickness) and thick plates (thickness 20--60mm) greater than 60 are extra thick. Steel strips are included in the category of steel plates.

3.What is the difference between ordinary bolts and high-strength bolts?

Ordinary bolts are generally made of ordinary carbon structural steel without heat treatment. High-strength bolts are generally made of high-quality carbon structural steel or alloy structural steel, and they need to be quenched and tempered to improve comprehensive mechanical properties. High strength is divided into 8.8, 10.9, and 12.9.

From strength grade: High strength bolts are commonly used in two strength grades of 8.8S and 10.9S. Ordinary bolts are generally 4.4, 4.8, 5.6, and 8.8.

The high-strength bolts exert pretension and transmit external forces by friction, and ordinary bolts rely on the shear strength of the bolt and the bearing wall pressure to transmit the shear force.

4. According to the characteristics of force: friction type and pressure type

Friction-type high-strength bolts transmit external forces based on the friction between the connected parts. When the shear force is equal to the frictional force, the design limit load of the extremely friction-type high-strength bolt connection. At this time, the rods of Lianzhong will not be relatively slipped, the bolt rod is not sheared, and the bolt hole wall is not under pressure.

Pressure-bearing high-strength bolts are similar to ordinary bolts in that the shear force can exceed the friction force. At this time, relative sliding occurs between the connected members, and the bolt rod is in contact with the hole wall. The connection depends on the friction and the shear and pressure of the bolt rod. Joint power.

The deformation of pressure-bearing high-strength bolts is large, and it is not suitable for connection of structures that directly bear dynamic loads.

5.Several types of electrodes

There are roughly a dozen types: carbon steel electrodes, low alloy steel electrodes, molybdenum and chrome molybdenum heat resistant steel electrodes, low temperature steel electrodes, stainless steel electrodes, surfacing electrodes, cast iron electrodes, nickel and nickel alloy electrodes, copper and copper alloy electrodes, Aluminum and aluminum alloy electrodes and special purpose electrodes.

6. Weld defect:

(1) Not welded through: the blunt edges at the middle (X groove) or root (V, U groove) of the parent metal joint are not completely fused together and the remaining part is not fused. Non-penetration reduces the mechanical strength of the welded joint, stress concentration points will be formed in the not-penetrated notches and ends, and it is easy to cause cracks when the welded parts are under load.

(2) Unfused: the solid metal and the filler metal (between the weld bead and the parent metal), or the filler metal (between the weld bead or the welding layer during multi-pass welding) are not completely melted or locally, or During spot welding (resistance welding), the base material and the base material are not completely fused together, and sometimes there is slag inclusion.

(3) Porosity: During the melting and welding process, the gas in the weld metal or the outside invading gas may overflow in the future before the molten pool metal cools and solidifies, and the holes or pores formed in or on the surface of the weld metal are left as it is. The morphology can be divided into single pores, chain pores, dense pores (including honeycomb pores), etc. Especially in arc welding, because the metallurgical process takes a short time, the molten pool metal solidifies quickly, Gas absorbed by liquid metal, or the flux of the electrode is decomposed at high temperature to produce gas, even if the humidity in the welding environment is too high, gas will be decomposed at high temperature, etc. These gas will form pore defects when it is too late to precipitate. Although the porosity has less tendency to stress concentration than other defects, it destroys the compactness of the weld metal, reduces the effective cross-sectional area of the weld metal, and causes the strength of the weld to decrease.

7. Non-destructive testing is a testing method for inspecting the surface and internal quality of the component to be inspected without damaging the workpiece or the working condition of the raw material.

Common non-destructive testing methods:

Ultrasonic flaw detection: A method of inspecting part defects by using ultrasonic energy to penetrate into the depths of metal materials and from one section to another, reflecting the characteristics of the interface edge reflection. When an ultrasonic beam passes from the surface of the part to the probe, Inside the metal, when encountering a defect and the bottom surface of the part, reflected waves are generated, and a pulse waveform is formed on the fluorescent screen. The position and size of the defect are determined based on these pulse waveforms.

X-ray inspection (X-ray, -ray): An inspection method that uses rays to penetrate an object to find defects inside the object.

Magnetic particle inspection: It is a detection method used to detect surface and near surface defects of ferromagnetic materials. When the workpiece is magnetized, if there is a defect on the surface of the workpiece, magnetic leakage will occur due to the increase of the magnetic resistance at the defect, forming a local magnetic field, and the magnetic powder will show the shape and location of the defect here, thereby judging the existence of the defect.

8. Procedures for component processing: preparation, correction, stakeout, cutting, bending, hole making, assembly, welding, inspection, rust removal, painting.

9. There are four methods for removing rust on metal surfaces: manual treatment, mechanical treatment, chemical treatment and flame treatment.

(1) Manual processing

Manual processing mainly uses shovel, wire brush, abrasive cloth, hacksaw blade and other tools. Manual knocking, shovel, scraping, brushing, and sanding methods are used to remove rust. This is the traditional rust removal method of painters and the easiest method. There are no restrictions on the environment and construction conditions, but due to the poor efficiency and effectiveness, only a small range of rust removal treatment can be applied.

(2) Mechanical rust removal method

The mechanical rust removal method mainly uses some electric and pneumatic tools to achieve the purpose of removing rust. Commonly used electric tools such as electric brushes and electric grinding wheels; pneumatic tools such as pneumatic brushes. The electric brush and wind brush use the rotation of a special round wire brush to remove rust or oxide scale by impact and friction. It is especially effective for surface rust, but it is difficult to remove deep rust spots. The electric grinding wheel is actually a hand-held grinder, which can be moved freely in the hand. The high-speed rotation of the grinding wheel is used to remove rust. The effect is better, especially for deep rust spots, which has high work efficiency, good construction quality, and convenient use. More ideal tool for rust removal. However, care must be taken not to puncture the metal skin.

(3) Sand blasting and shot blasting methods

The sand blasting and shot blasting methods are the same as those used in the previous section to remove the old coating film. (4) Flame treatment method The flame treatment method is to use a gas torch to burn a small amount of deep rust spots that are difficult to remove by hand to burn red, so that high temperature can change the chemical composition of rust oxide to achieve the purpose of rust removal. When using this method, care must be taken not to allow the metal surface to burn through and prevent large areas of the surface from being deformed by heat.

(5) Chemical treatment method

The chemical treatment method is actually a pickling and rust removal method, which uses acidic solutions to chemically react with metal oxides (rust) to form salts and detach from the metal surface. Commonly used acidic solutions are: sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid. During operation, the acid solution is applied to the metal rust part to allow it to slowly react with the rust to remove it. After the rust is removed, it should be rinsed with water, and neutralized with a weak alkaline solution. After rinsing with water, it is dried and dried to prevent rusting soon.

The acid-washed metal surface needs to be roughened or phosphated, mainly to increase the adhesion of the metal surface to the primer. When diluting concentrated sulfuric acid, you should slowly pour the sulfuric acid into the water in the container and keep stirring. Do not reverse the operation to prevent the sulfuric acid solution from splashing and hurting people.

10. Common lifting equipment: gantry crane, tower crane, crawler crane, truck crane, wheel crane, mast crane, jack hoist, hoist bridge crane.

Eiffel Tower in Paris

World famous steel structure buildings (7 photos)

The Eiffel Tower is a hollow structure iron tower that was completed on the Ares Square in Paris, France in 1889. It has a height of 300 meters, an antenna height of 24 meters, and a total height of 324 meters.

The tower is a steel-framed hollow structure. There are three-level platforms for viewing at 57 meters, 115 meters, and 274 meters above sea level. The fourth-level platform has an altitude of 300 meters and a weather station. There is an antenna on the top, which is the Paris Television Center. There are elevators and stairs from the ground to the top of the tower, and 710 steps.
It is understood that the iron tower used more than 1,500 giant prefabricated beams, 1.5 million rivets, 12,000 steel castings, and a total weight of 7,000 tons. It took 17 months for 250 workers to build the tower.

Petronas Twin Towers

Kuala Lumpur Twin Towers is located in the heart of Kuala Lumpur. It is 88 stories high and is the world's top super building today. Majestic and majestic, it is Malaysia's pride. At a height of 451.9 meters, it broke the highest record of 22 years held by the Chicago Hills Building in the United States and became a unique mega building in the world today.
The project started on December 27, 1993, was officially capped on February 13, 1996, and was completed and used in 1997. It was built by Malaysian National Petroleum Corporation for RM2 billion. The world-famous master of architecture-Nishizawa Poli is the designer of this building.

Empire State Building, New York

The Empire State Building is a super high-rise modern office building, which is known as the symbol of New York along with the Statue of Liberty. There is a 381-meter-high Empire State Building on the ground. Since 1931, it has been the throne of the world's tallest building for 40 years. It was not surpassed by the World Trade Center until 1971.

In the 1930s, the architect managed to add a 200-foot-tall round tower to bring the height of the Empire State Building to 1,250 feet. The skyscraper took only 410 days to build, and it can be considered a miracle in the history of architecture. For a long time, the Empire State Building has been the tallest building in the world.

Millennium Dome in London

The Millennium Dome, located on the Greenwich Peninsula on the River Thames in eastern London, is a landmark building built by the British government to welcome the 21st century. The diameter of the bending item is 320m, the circumference is greater than 1000m, there are 12 masts that pass through the roof up to 100m, and the roof adopts a spherical tension membrane structure. The membrane surface is supported on 72 radial steel cables with a cross section of 2 × 32. These steel cables are supported by the mast through a 25m cable stayed sling and a lanyard. The sling and the lanyard simultaneously stabilize the mast. effect.

It is understood that the Millennium Dome covers a total area of 73 hectares and is a large-scale comprehensive exhibition building with a total cost of 1.25 billion US dollars, including a series of exhibition and performance venues, as well as shopping malls, restaurants, bars, etc.

San Francisco Golden Gate Bridge

The Golden Gate Bridge spans north and south, connecting the city of San Francisco to Marin County. The bridge, which took more than four years to build, is one of the most beautiful structures in the world. It is no longer the longest suspension bridge in the world, but it is the most famous. The huge tower of the Golden Gate Bridge is 227 meters high, each steel cable weighs 6,412 metric tons, and is made of 27,000 steel wires. Construction began in January 1933, and was first opened to traffic in May 1937. The steel tower stands on the north and south sides of the bridge and is 342 meters high, of which the surface above the water is divided into 227 meters, which is equivalent to a 70-story building. The top of the tower is connected by two steel cables with a diameter of 92.7 centimeters and a weight of 24,500 tons. The midpoint of the steel cable sags almost to the bridge body. The steel cable and the bridge body are connected by a thin steel rope. Data show that the bridge span between steel towers reaches 1280 meters, which is one of the rare single-hole long-span large suspension bridges in bridges built in the world.

Gateway Arch

The Gateway Arch in St. Louis, Missouri is the tallest standing monument in the United States. This shiny arc shape made of steel rises from the ground, is nearly 200 meters high, and has a span of nearly 200 meters, exactly the same height. According to records, Finnish-American and well-known architectural designer Ilo Salinen designed the Gateway Arch in a national design competition in the late 1940s. However, the project did not begin construction until February 1963 and was completed in October 1965. Later, a transport system was added to the arches, allowing people to climb up to an observation platform on the top of the arches and look out. Located on the banks of the Mississippi River, the Gateway Arch is known as the gate to the west.

Sydney Opera House

The entire building of the Sydney Opera House covers an area of 1.84 hectares, is 183 meters long, 118 meters wide, and 67 meters high, which is equivalent to a height of 20 floors. Its exterior is three huge groups of shell pieces that stand on a pedestal of cast-in-situ reinforced concrete structure that is 186 meters long from north to south and 97 meters wide from east to west. The opera house is divided into three parts: the opera hall, the concert hall, and the Benilán restaurant. The opera hall, the concert hall and the rest room stand side by side, built on a giant granite stone pedestal, each consisting of 4 towering large shell roofs.
It is said that the most special thing about the opera house's concert hall is the large pipe organ designed and built by Australian artist Ronald Sharp, located directly in front of the concert hall. This large pipe organ is composed of 10,500 ducts. It is said to be the world's largest mechanical wood link organ. In addition, the entire concert hall is made of Australian wood, faithfully presenting Australia's own style.