Problems in the design of portal steel frame structure

With the rapid development of the national economy, China's steel production has increased significantly. Welding H -shaped steel is used in large quantities, and the application of portal steel frame structure in industrial or commercial buildings is becoming more and more widely used. The SAFS steel structure discusses the problems in the design of the portal steel frame structure industrial plant through the practice and exploration of many projects, and gives corresponding solutions and suggestions on related issues.

1 Overview

With the rapid development of the economy, portal steel frame structure houses have emerged quickly in my country due to their processing system, easy installation, and fast. However, due to the late starting research on light steel structure in my country, the relevant design specifications of the "Technical Regulations for Steel Structure of Light Housing Housing Housing" in the relevant design specifications are also relatively lagging. Prior to this, you can only design the "Steel Structure Design Specifications" (GBJ17-88) and "Technical Procedures for Cold Bend Thin Wall-Wall Steel Structure" (GBJ18-87) and relevant foreign regulations. Therefore, there is a large gap with Western developed countries in terms of design level, design experience and rationality. In recent years, domestic scholars have conducted a lot of exploration and research on the design of portal frame steel structure, and have achieved fruitful results. With the implementation of the "Technical Regulations for the Steel Structure of the Steel Light House" (CECS102: 2002), the corresponding practical design software has been continuously developed. Software such as portal frame steel structure light housing design system PFCAD, steel frame light housing design CAD system PS2000, PKPM, and 3D3S developed by Tongji University can analyze and calculate the portal frame steel structure. Because the design specifications are not the same as foreign abroad, we cannot copy foreign design specifications when we design, and apply foreign design software. Therefore, it is particularly important to explore the optimization design calculation method that is in line with the domestic steel frame cross -section optimization design and reduce the construction cost of the portal frame steel structure.

In recent years, a large number of portal frame steel structure have been adopted in factory design practice. Through the practice and exploration of these projects, they have also accumulated some experience and understanding. This article discusses some problems encountered during the design of the portal frame steel structure.

2. The main problems and solutions existing in the design of the current portal frame steel structure plant

2.1 The problems and solutions existing in the structure model

In the design of light portal frame steel structure, the intermediate column is often designed as the upper and lower nodes in the form of a hinge. At this time, the middle column only plays the role of the middle support in the beam. Regardless of the bending moment, the calculation length coefficient is 1, and the cross -section is greatly reduced compared with the rigid connection. At the same time, the hinge connection structure of the column and the beam is greatly simplified compared with the rigid connection structure, and it also saves a lot of steel. If the column is high, the pillar is shifted under the influence of the wind load. The pillar's foot should be rigid, and the connection between the middle column and the beam should also be used. When the span of the beam is large, it is advisable to use a broken beam. The height of the beam should not be less than 1/35-1/40 of the span. The height of the middle section of the beam should not be less than 1/60 of the full span. The length of the cross section calculated from the end of the beam can generally be 1/5 to 1/6 of the span, and it should be coordinated with the pitch.

The anti -wind column is the main component that supports the gables in the portal frame steel structure and resist the horizontal wind load. The upper end of the anti -wind column is connected to the rigid beam, and the lower end has set the foundation separately. The design methods and structural measures of the wind column not only affect the stress characteristics of the windy column itself, but also affect the rigid shelf and basic design and force connected to it. There are two ways to connect the wind column and the foundation. When hinged, the foundation only bear a small axis and horizontal shear power. The design and structure are very simple, and the amount of engineering is small. If it is just connected, the shaft force and bending moment passed to the base are much larger. The eccentric distance is also very large, which is not conducive to basic design; therefore, the windy column should be hinged.

2.2 The problems and treatment of irregular buildings

The size of the building mainly includes the span, column distance, eaves height, and roof slope of the rigid frame. For portal frame housing steel structures, unreasonable building size often leads to a sharp rise in steel volume and increased costs. In addition, due to the flexibility of the production of steel structure components and the construction of light houses (wall) surface materials, the production and construction of portal frame steel structure houses can basically be tailored.

The "CECS102: 2002: 2002) (CECS102: 2002) (hereinafter referred to as" door -type steel frame regulations ") is recommended to use the pillar distance of 6 ~ 9m. Vertical loads (such as roof loads, hanging loads, crane loads, etc.) are the main factor affecting the pillar distance of the economic column. When the load is large, the pillar distance of the economic pillar will decrease, and the economic column distance of the load will increase. When the load conditions are the same, the economic column is not obvious by the span, that is, the economic column distance of the various span -rigid systems is basically the same. However, the larger the span, the more sensitive the amount of steel is used to the column, and the range of fluctuations is increased. The better the good economic benefits presented by the economic column distance.

The portal frame steel structure system also has economic spans, so it is not advisable to blindly pursue large spans. The main factor affecting the economic span is load. The larger the load, the more sensitive the amount of steel is used to the span. The more you should pay attention to the reasonable span. This is because the large -load -large column section is large; the economic span of the portal frame steel structure is 18-30m, the economic span is 24-30m when the tonnage of the crane is large, the tonnage without a crane or a crane is small, and the economic span is 18 ～ 21m. Therefore, the use of reasonable spans can also save steel, reduce the total cost, and economic benefits are considerable.

2.3 Solution of deformation problem

Table 3.4.2-1 from the "Portal Frame Regulations" can be found in the limit of the design value of the rigid columns. Top allows a lot of displacement. This is the difference between light steel structure and ordinary steel structure. However, among the crane factories, especially in the large tonnage crane factory building of more than 20T, when the pillar top allows deformation, the pillar height affects this factor. The absolute value of controlling its horizontal displacement is within a reasonable range to ensure the normal use of the plant.

2.4 Discussion on issues related to node design

The connection node of the portal frame steel structure beam and the rigid column, according to the "portal frame steel structure regulations", can be divided into three methods: end plate vertical, end plates, and oblique end plates. Each form can be divided into two methods: end plate flat and end plate extension. In order to reduce the thickness of the end plate, the rib should be set up between the end plate to connect the bolt, so that the support boundary form of the end plate is on both sides or three sides, thereby increasing the intensity and stiffness of the connection node. In the portal frame steel structure with cranes, its structure should conform to the principle of the beams and columns in the process of use, that is, the so -called rigid connection node. If the construction conditions permit, the beam and column nodes are best to use the bolt -welded connection node, that is, the wings are connected to the welding seam, and the web plate is connected with a high -strength bolt.

It is important to note that although the pillar and the beam are envisaged as a rigid, in fact, due to various factors, the calculation assumptions may not match the actual situation. For example, the connection between the step -shaped upper columns of the crane plant and the roof beam. Compared with the section of the beam end, the cross -section height is often smaller. Although the high -strength bolt is used to connect the node design according to the calculation of a rigid connection, it seems to be just connected, but because the cross section of the beam is far greater than the connected column section height, the two rigidity ratio is very different. The pillar rigidity is small, and the beam cannot be well -embedded, and it cannot have the ideal stiffness. This makes this node similar to the state between the fixed connection and the hinge, and the embedded solid at the end of the beam at the top of the column must be guaranteed with a sufficient stiffness of the column itself.

In addition to the connection node of the rigid beam and the rigid column, the stitching nodes of the rigid beam are selected in the small parts of the bending momentaries, and the manufacturing and transportation unit often takes 8-12m. The results of practice and experts show that the connection method of external extension and rib end plates is more reasonable. In order to reduce the difficulty of bolt arrangement during the design of the end plate, the 10.9 -level friction -type high -strength bolt should be preferred. The steel number of the bolt can also be selected with 20mntib, or No. 40 steel and 35VB steel are selected.

3. Conclusion

The portal frame steel structure houses are widely used in various buildings with large span, light weight, fast construction speed, low comprehensive economic indicators, and wide scope of application. With the extensive application, there is a certain accumulation of experience. However, there are many problems worth discussing, such as the impact of welding form on the performance of components; these problems require engineering and technical personnel and researchers to work together. The above is the summary of some design experience in the design process. I hope to get the correction of experts.

Steel structure spray technology introduction

 Nowadays, the repetitive use of steel has greatly reduced construction garbage and green and environmentally friendly. It can be said that it is widely used in industrial buildings and commercial buildings.

For traditional concrete buildings, it uses steel plates or steel to replace steel concrete, which has a higher strength and better seismic resistance. And because the component can be made in factory, it is installed on the spot. As a result, it is greatly reduced and recognized by most people. Regarding the beauty of the steel structure, the spraying method is indeed a technical work.

When using the sprayer, the iron shelf and steel structure spray are essential. First of all, we must polish the surface of the steel structure for rust removal treatment. At the same time, we must remember that the steel structure after polishing can complete the paint within 4 hours.

Basically, the polished steel structure can complete the paint in 4 hours. And many times, during use, we also need to focus on the use of ET-98 inorganic phosphate long-effect type zinc-rich coatings as primer. In most cases, it is enough to remove oil and rust, but it does not need to be polished, but use steel wire brush, polished or steel sandpaper.

It is important to note that we must first polish the surface of the steel structure. In general, in addition to debris such as rust and oxide, it is also necessary to pay more attention to its surface treatment quality control should reach the SA2.5 level specified in the "front steel surface rust level and rust level" standard specified in GB8923. And the surface roughness is 35-75um, and the sand dust is removed after polishing.

Under normal circumstances, we can use light sweep -grade grinding method to remove the gray layer with galvanized layers and have impurities such as oil pollution. During the later use, we also need to pay attention to its 70-H epoxy iron red anti-corrosion paint.

If you encounter welding parts, it is recommended not to paint within 72 hours after the candle welding.

Preparation before installation of steel structure space frame

 Preparation before installation

Before the construction of the space frame structure, all technical materials on the project should be provided in a timely manner, including: a full set of drawings, the mechanical performance test report of the space frame bolt, the mechanical performance test report of the steel pipe and the analysis report of the chemical composition of the material, the welding Certificate copy and other information. Before the installation of the space frame, the construction site should be set up on the site of the project and the life and preparation of the installation team should be set up. The processing of each component of the space frame before the space frame is completed. After the acceptance and the assembly of the small unit are completed, all enter the market.

1. Before installation, check the axis and elevation of the space frame support. The axis and elevation position of the space frame must meet the design requirements and relevant standards;

2. Check the strength of the supporting concrete before installation. The concrete strength must meet the design requirements and the current national relevant standards.

3. Put the scaffolding, and arrange the position and elevation of each fulcrum. And design the temporary fulcrum, the location and quantity of the temporary fulcrum are determined;

4. Temporary fulcrum is selected to gradually adjust the height of the space frame.

Precautions for bolt connection during steel structure building construction

      The quality of steel structure construction is related to the safety of the construction of the building afterwards, so the quality control of each construction link is very important. So what do you need to pay attention to for steel structure bolt connection? The following is introduced by SAFS Steel Structure Company.

The bolt connection is the key task of the quality control of the steel structure. We need to check each bolt after tightening to prevent the phenomenon of leakage. For those phenomena that are not tightened or twisting, we must re -tighten or replace bolts.

1. Do not use gas cutting

The bolts in the steel structure building are usually used in ordinary bolts and high -strength bolts. The connection of ordinary bolts must not be padded with more than two spacers at each end of each bolt. And if the bolts are misplaced, they cannot be expanded with gas cutting, and they must be used to use a knife or re-cutter.

2. High-strong bolt quality control

After the bolt is tightened, the exposed thread must not be less than 2 to 3 thread distance. The control of high -strength bolts is the connection of the bolt, the treatment of the friction surface, and the frictional surface anti -slip coefficient. The initial twist and final twist of the bolt connection, and the torque value, the surface of the node is damaged and deformed.

3. Installation of high -strength bolts

During the installation process of the high -strength bolt of the steel structure, the contact surface must be flat, and the area of contact must be greater than 75%, and the gap of the edges must not be greater than 0.8 mm. The high -strength bolt cannot be used as a temporary installation, and the tightness of the bolt should be performed in one direction. The bolts installed every day must complete the final tightening work and check them one by one to prevent leakage.

Different steel structures have different fire protection measures

1. Expansive material

The steel structure fireproof coating is used to protect the components. This method has the advantages of good fireproof and heat insulation performance, and the construction is not limited by the geometric shape of the steel structure. Belongs to modern advanced fire prevention technical measures.

 

2. Outer cladding

It is to add an outer cladding on the surface of the steel structure, which can be cast-in-place or sprayed. The solid concrete outer cladding of steel structure fire-proof cast-in-place is usually reinforced with steel wire mesh or steel bars to limit shrinkage cracks and ensure the strength of the shell. Spraying method can apply sand pump to the surface of the steel structure at the construction site to form a protective layer. The sand pump can be lime cement or gypsum mortar, or it can be mixed with perlite or asbestos. At the same time, the outer cladding can also be made of perlite, asbestos, gypsum or asbestos cement, and light concrete to make prefabricated panels, which are fixed on the steel structure with adhesives, nails, and bolts.

 

3. Shield

The steel structure is set in the wall or ceiling composed of refractory materials, or the components are enclosed in the gap between two walls, and the purpose of fire prevention can be achieved only by adding a little or no refractory materials. This is one of the most economical fire prevention methods.

 

4. Fill with water

Filling the hollow steel structure with water is the most effective protection measure for steel structure fire prevention. This method keeps the steel structure cool during a fire, and water circulates within the steel structure, absorbing heat from the material itself being heated. The heated water can be recirculated after being cooled, or cool water can be piped in to replace the heated water.

The difference between steel structure carport and membrane structure carport

1. The value of landscape design

The carport is a small building, and its shape has attracted people's attention. Due to the particularity of steel, the steel structure carport has a relatively simple shape. The main material of the membrane structure carport is membrane material, the curve is high, and it can be shaped at will according to the designer's imagination.

 

2. Construction management cycle

1. The membrane structure carport is smooth and simple, and can be completed in the processing plant without more processes, and the construction period is short.

2. The steel structure carport requires complex processes such as welding, and the construction period is long.

 

3. Maintenance cost

1. The membrane structure carport uses the membrane material to contact the social air pollution environment, the membrane material will not be corroded by the air, and there is no maintenance and management cost in the later period. the

2. Steel structure carport, the appearance is made of steel, generally painted to prevent corrosion temporarily. Generally, steel will rust in a large area within one or two years, requiring complicated maintenance procedures such as paint removal, rust removal, and painting, and the maintenance cost is high.

 

4. Security

1. The surface of the membrane structure carport is smooth, there will be no snow and rain in large-scale development and stagnation areas, and the weight is light, so there is no need to worry about the risk of collapse.

2. The steel carport is very heavy, and the safety risk of collapse is great.

 

5. Service life

1. Membrane structure carport can be anti-corrosion, generally can be used for 20 years. the

2. The steel structure shed can generally be used for about 10 years.

 

6. Cost

1. Membrane structure carport uses membrane as the main material, which is cost-effective and easy to maintain.

2. The steel structure carport uses steel as the main research material, the process is complicated, the labor cost is high, the maintenance management cost is high, and the comprehensive engineering cost is low.

Why do you need to use wood grain paint with steel structure

               With the rapid development of the mineral industry, the previously precious metals, such as steel and iron, are currently very favorable. Therefore, many buildings are now used in metals such as steel structures, iron pipes, such as steel structure guardrails, iron pipe guardrails, steel structure gazebo, steel structure flower stand, metal corridor and other metal structures:

Due to the characteristics of steel structures, because of its own characteristics, it is easy to be affected by the water in the air or the rain, snow and frost in the natural world, and high and low temperature, and produces rust stains. It not only affects the perception, but also affects the service life of these buildings. However, after the decoration of wood grain paint, the surface of these metals will form a protective film, which effectively isolates the water in the air and the impact of wind and frost in nature on metal.

Secondly, I have to talk about the feel of the steel structure, iron pipe and other materials. The feel of these metal itself has a little rustic feeling, and the hand feels smooth and moisturized after the wood grain paint becomes the film, and the feel is very good. If you are not making wood paint on the metal surface, it is easy to score your hands or other parts when the temperature is too high. After making wood grain paint, not only the heating of the metal, but also the metal feel.

Finally, let's talk about the appearance of the metal. The appearance of the metal, whether it is steel structure or iron pipe and other metals, the surface of the building is monochrome. In addition to inconsistency with the surrounding environment, it also does not seem to have a little natural beauty, and the overall looks full of sharp feelings. However, if the wood grain paint is made, the wood grain paint gives a more gentle and stable feeling of metal building.

Installation standards for steel structure engineering

Steel structures are widely used in the construction industry. Steel structure workshops are the first choice of many entrepreneurs because they can store a large number of products. The SAFS steel structure manufacturer will take you to understand what the engineering installation standards are.

 

1. Marks should be set at the end of the steel to indicate the specification, grade, quantity and material acceptance certificate number of the steel;

 

2. When stacking in the open air, the site should be flat, higher than the surrounding ground, and drainage ditches should be set around;

 

3. When stacking, try to make the back of the section steel face upward or outward to avoid snow and water accumulation. There should be a height difference at both ends to facilitate drainage;

 

4. Before installation, the construction unit should conduct special inspections on the product qualification certificates, design documents and pre-assembly records of the components, and review and record the dimensions of the components;

 

5. Appropriate connection methods should be adopted to make the joint design consistent with the simplified structural calculation model;

 

6. When hoisting the steel structure, appropriate measures should be taken to prevent excessive bending and torsional deformation, and heat blocks should be placed at the contact between the rope buckle and the component to prevent damage to the component;

 

7. After the steel structure is hoisted in place, the brackets and other connecting parts should be fastened in time to ensure the stability of the structure;

 

8. When using tools at high places, spare parts should be put into the tool bag, and they should not be thrown up and down;

 

9. When working in rainy days, reliable anti-skid measures should be taken, and lightning protection should be paid attention to during thunderstorm seasons;

 

10. Before construction, the weather conditions are good, and no work is allowed if the wind is above level 4.

What is the difference between multi-layer steel structure and single-layer steel structure

The characteristics of steel structure are: the heat resistance of steel structure is good, but the fire resistance is poor; the test shows that when the performance of steel changes from normal temperature to 150 ℃, the strength and plasticity of steel change greatly at 600 ℃, and the strength drops to zero , Completely lose the bearing capacity, and the fire resistance level of the steel structure is improved. When the fireproof coating thickness of the fireproof coating is 15mm, the fire resistance limit of the steel member can reach 1.5h.

 

1. Single-story: There is only one-story building on the ground, which is a single-story building, including industrial plants (single-story height above 6-8m), civil buildings (2-3m) and agricultural factory buildings (above 2.2m) and other buildings.

 

2. Multi-storey: Refers to 4-6 storey buildings.

 

3. High-rise: Refers to buildings with more than 10 floors and a total height of less than 100 meters.

 

4. Super high-rise: Refers to buildings with more than 40 floors and more than 100 meters.

 

5. High-rise buildings and super high-rise buildings mainly adopt steel-concrete structures, such as: cross columns, box columns and other structural forms.

 

The above is the introduction of SAFS steel structure to different places of multi-layer and single-layer. Steel structure is widely used today and is also loved by more builders.

Space frame manufacturer's transportation and storage requirements for craft accessories

       Before the process engineering, the space frame manufacturer will process the parts of the accessories.

After the coating of the accessory surface is dry, the space frame is checked in detail after drying the coating of the accessories. The surface coating of the packaging protection component is a complete drying state, ensuring that the components and parts are not deformed, damaged, and no loss.

The names, numbers, weights, and hanging points of the space frame of the space frame packaging, the name, number, weight, and hanging point position, etc., and fill in the packaging list.

In the installation order of the process attachment, the space frame structure accessories is assembled according to the unit, and the configuration is complete and re -supply. The stacking venue on the spot can meet the needs of the on -site installation order.

During the transportation of space frame accessories, the length and weight of the space frame craft accessories are combined with the appropriate transportation vehicles. The fulcrum of the space frame accessories on the transport vehicle, the length of the two ends, and the method of ligation must ensure that the space frame accessories do not produce deformation and not damage the coating.

The daily storage requirements of the craft accessories of the space frame to ensure that the ground floor is flat and firm. Divide and store according to the type, model, and installation order of the components; the bottom cushion should have sufficient support surface to prevent the fulcrum from sinking. When the same type of space frame accessories are stacked, the fulcrum of each layer of the space frame accessories should be kept on the same vertical line to prevent the space frame accessories from being fractured and deformed.

After the craft accessories to the construction site, the relevant personnel should check the details of the accessories, check the number of accessories entry accessories, and check the factory certificate and related information.