Introduction and installation of interval space frame structures

     The interval space frame structure is a new type of space structure system developed form the open-web space frame structure system. The structure system is composed of the open-web space frame layer and the space frame or space truss supporting the open-web space frame vertically arranged alternately. When the span of the space frame structure is large, the height of the space frame is increased accordingly. Therefore, for a large-span structure, the space of the open-web space frame layer can be used as a separate building layer. This kind of open-web space frame in not only a structural layer but also a building layer, but also has a large spanning ability. This make the new structural system have the architectural function of large and small spaces intersecting each other, which overcomes the previous large space standing at the bottom or top of the building. Some architecture limitations are particularly suitable for large span high-rise buildings.

The composition of different structures makes the structure have different stress characteristics. Based on the ordinary interval space frame structure, we analyzed and studied the addition of oblique webs around the grid, the unequal spacing of the grid grid, and the support of the grid as the space. The internal force distribution and deformation of different types of interval space frame structures such as trusses under vertical and horizontal loads. At the same time, the internal force and deformation changes of the structure when the floor is involved in work and prestressing are further analyzed, and the conclusions of the analysis and calculations It provides a theoretical reference for the selection and design of the structure in engineering design.

After studying the force characteristics of the structure under the vertical load in detail, based on the flexibility method of the cross beam system considering the shear deformation and the layering method of the multi-layer frame under the vertical load, interval vierendeel grid structures method is proposed. The simplified analysis method of the open-web grid structure has made a great improvement to the simplified method proposed by some scholars in the past. This method has higher calculation accuracy and is especially suitable for the preliminary design of the structure.

For interval space frame structures, the usual concept is that the structural system has poor collapse resistance under strong earthquakes. Through the analysis of the natural vibration characteristics of different types ofinterval space frame structures, the stiffness of the space frame and the rigidity of the supporting structure are revealed The impact of the change of the structure on the natural frequency and mode shape of the structure. The response spectrum method has studied the seismic performance of the structure under three-dimensional one-dimensional excitation and simultaneous excitation in the three directions of the earthquake. The internal force and deformation of the structure under the action of the earthquake are obtained, and the response spectrum method is used for seismic design. Type interception order. Time history analysis method is used to study the linear elastic response of jump-story grid structure under frequent earthquakes and the elastoplastic response under rare earthquakes. The elasto-plastic response of the structure under rare earthquakes shows that the structural system can meet the design principle of “no collapse in large earthquakes” under the conditions of selecting appropriate cross-sections and reinforcement ratios. The analysis results of the response spectrum method and the time history method are compared, which can guide the seismic design of this new type of structural system.

Reasons for loosening of space frame bolts in gas station

A gas station is a place where gasoline is added to motor vehicles. The appearance must be more conspicuous and appealing to consumers.Gas stations with good appeal can attract a large number of customer resources and increase profits for gas stations.The shape design of the gas station using the space frame structure is generally very neat and simple. The canopy and the column constitute the main body of the structure.The area around the canopy is usually decorated with aluminum slabs and light box cloth. The upper plan is usually covered with color steel plates, and the lower plan is set for lighting fixtures. Ceiling are not required. If suspended ceilings are required, aluminum gussets are generally used. Many gas station space frame have loosening of space frame bolts during the installation period or a period of time after installation. There are many factors that lead to this type of situation.All of us must deal with it according to specific circumstances.

Picture taken from: https://www.safsteelstructure.com/

1. Installation by non-professional staff: The space frame construction team is still not professionally trained, and feels that it is caused by tightening the sleeve. Many non-professional staff, who have not undergone professional training, seem to be tightened, but in fact they are not tightened in time. Perhaps the construction site has not been able to deal with the problem in time, but it will loosen after a period of application, which is very dangerous.

2.  After the roof installation was completed, the sleeve was loosened after delivery, the rubber support was rusted, and the components were damaged. After this problem occurs, it will seriously harm the installation of the space frame design scheme. The bearing structure is changed. It is very easy to cause safety hazards and safety accidents.

If you have any of the above problems, I suggest to stop and repair it in all directions.Each component of the space frame is carefully inspected, and repairs are carried out purposefully. In serious cases, it must be disassembled and installed again, and painted again.

The space frame structure has a small steel content, and the parts are all prefabricated components of the factory. The installation is convenient and the construction period is very short, which is more suitable for rushing to the construction period.

What is the H-beam commonly used in steel structure workshops?

Steel structure workshop H-shaped steel is a kind of economical section and high-efficiency section with more optimized cross-sectional area distribution and more reasonable strength-to-weight ratio. Because the section and the English letter "H" is the same name. H beam has been widely used for its advantages of strong bending resistance, simple construction, cost saving and light structural weight. H-shaped steel is mainly used in industrial factory, civil construction, municipal engineering, etc., and light H-shaped steel is very suitable for the manufacturing of containers, mobile houses, and various garages.

1. The expression method of hot-rolled H-beam:

H-beams are divided into three types: wide-flange H-beams (HK), narrow-flange H-beams (HZ) and H-beam piles (HU).

 

The expression method is: height H width B web thickness t1 wing plate thickness t2, such as H-beam Q235, SS400 200200812, it is expressed as a wide flange H-beam with a height of 200mm, a width of 200mm, a web thickness of 8mm, and a wing plate thickness of 12mm. The grade is Q235 or SS400.

Advantages of hot rolled H-beam:

H-shaped steel is a new type of steel for economic construction. H-shaped steel has economical and reasonable cross-section shape and good mechanical properties. During rolling, each point on the cross-section extends more uniformly and has low internal stress. Compared with ordinary I-beams, it has the advantages of large section modulus, light weight, and metal saving, which can make buildings The structure is reduced by 30-40%; because the legs are parallel inside and outside, and the ends of the legs are right-angled, they can be assembled into components, which can save welding and riveting work by up to 25%. It is often used in large buildings (such as factory buildings and high-rise buildings) that require large intercepting capacity and good cross-sectional stability, as well as bridges, equipment foundations, and supports.

The Hot-rolled H-beams can reasonably allocate the height-to-width ratio of the cross-section size according to different purposes, and have excellent mechanical properties and superior use performance.

2. Welding H-beam production process

Steel plate-automatic slitting-assembly-automatic submerged arc welding-flaw detection-flange correction-web correction-end surface processing-sand blasting and rust removal-painting. The automatic submerged arc welding production line is controlled by a microcomputer to ensure the dimensional accuracy of the H-shaped steel produced, and the quality of the welds meets the national standards. The steel structure building has a simple and lightweight structure, which expands the internal space of the building, saves steel, and has a short installation period. The roof and walls are made of color profiled steel plates, which makes the building more beautiful.

H-beam weight (2*b*t2+h*t1-2*t1*t2)*7.85*L/1000000

H-beam surface area (4*b-2*t1+2*h)*L/1000

The above is the H-beam commonly used in steel structure workshops.

Five support methods of space frame structure

The support methods of the space frame structure include peripheral support, point support, combination of peripheral support and point support, two-sided and three-sided support, etc.

As the roof of a large-span building, the space frame structure should firstly meet the requirements of the building layout and the use function of the building. This structure has greater spatial rigidity and is more sensitive to the rigidity and stability of the supporting member. From a mechanical point of view, the support of the frame structure can be divided into two types: rigid support and elastic support.The former means that there is no vertical displacement under load, there can be horizontal displacement, or no horizontal displacement. It is generally suitable for the space frame to be directly placed on a column, wall, or reinforced concrete beam with greater rigidity;The latter generally refers to the situation where the free side of the three-sided support space frame is equipped with anti-beam support, truss support, and cable support.

When it is not allowed to set up columns on one or both sides of the space frame at the expansion end of industrial plants, hangars, hull workshops, gymnasiums, etc., the space frame needs to be designed in a form that supports three sides and one side is free. Mixed support is suitable for large steel column industrial plants, warehouses, exhibition halls and other buildings.

Reasons for bolt loosening after installation of space frame structure

When the space frame structure is installed, or a period of time after installation, the high-strength bolt sleeves of the space frame structure are loosened. There are many reasons for this situation, we need to analyze and deal with the specific situation:

1. Installation by undocumented workers: space frame workers have not received professional training, and they feel that they are tightening the sleeve. Many non-professional workers have not dealt with it well, and may not find the problem in time on the spot. However, it is very dangerous to loosen after a period of use.

2. After the roof panel was installed, the sleeve was loosened, the support was rusted, and the rod was damaged during use. These will seriously affect the carrying capacity of the space frame design, change the force structure, and cause hidden danger accidents.

For the above two problems, I personally suggest to stop using it and check and repair all aspects. In particular, each component of the space frame must be carefully checked and repaired in a targeted manner. The serious problems must be disassembled and reinstalled, and then repainted.

Picture from: safsteelstructure.com

How to inspect the steel structure space frame engineering coatings

In modern society, people's living standards have been greatly improved, and their tastes are getting higher and higher. There are also certain regulations for the aesthetics of engineering buildings. There are also certain regulations for common coatings for large-scale engineering buildings. Now let’s introduce how to test the construction coatings for steel structure space frame engineering. 

Inspection quantity: 10% of the number of prefabricated components shall be sampled for inspection, and similar prefabricated components shall not be less than 3.

Inspection method: check with a gray knife.

Do not miscoating, leakage coating, coating should not molt and rust.

Inspection quantity: all

Inspection method: vision inspection

                                          Picture from: safsteelstructure.com

Steel structure space frame inspection method: check the quality standard certification materials, Chinese label and test report of the product.

The types, specifications, characteristics, and quality of raw materials such as steel structure fireproof coatings, paints, paint thinners and epoxy curing agents should comply with the current standards of our country's product implementation standards and design plans.

The anti-rust treatment of the surface of the steel frame structure before painting shall comply with the relevant laws, regulations, specifications and design plans of the current standards. The surface of the treated stainless steel plate shall not have rust, weld bead, weld slag, oil stain, dust, water and burrs, etc. When the design scheme is not specified, the derusting grade of the steel frame structure surface should meet the requirements.

The key factors and solutions that affect the success of the overall installation and construction of the space frame with soil method

The overall installation and construction of the space frame earth method requires relatively high requirements for the construction plan and the operating staff. In terms of safety management, the preparation and approval of the construction plan, safety technical disclosure, staff training and education, and safety inspection and acceptance must be done carefully. In particular, the overall improvement and installation of the grid must be refined and improved in advance from the plan, all possible problems must be considered, and corresponding preventive measures must be taken.

The unified coordinated command and the overall cooperation of all operators are critical, and targeted training and exercises are required before the process is implemented.

The overall improvement plan for space frame processing requires technically perfect measures to address the difficulties and hazards of the construction process. The main points are as follows:

(1) Choose the appropriate number of lifting brackets: According to the space frame weigh, select the appropriate number of lifting brackets to lift the space frame processing project as a whole after calculation.

(2) Fair arrangement of lifting brackets: The arrangement of lifting brackets is very important. If it’s not fair, it will cause uneven forces on the lifting brackets and cause large deformation of the space frame. By checking the overall weight of the space frame and the weight distribution, the position of the lifting bracket is determined, so that the bracket basically divides the space frame weigh. In addition, pay attention to the influence of the position of the hanging points on the force of the space frame members and nodes to avoid deformation or even damage beyond the permitted range.

(3) Correctly erect the hawser cable: the angle of hawser cable erection is controlled between 30 and 45 degrees, and it is tensioned with a 5t hand chain hoist. During the lifting process, the grid members may interfere with the hawser cable. At this time, the spare hawser cable must be erected and fastened first, and then the original cable wind rope should be loosened.

(4) Choose a suitable lifting bracket: Considering the installation height and stability of the bracket, we chose the standard section of the QTZ125 tower crane as the lifting bracket. The lifting bracket composed of the standard section of the tower crane is far more satisfactory in terms of strength and bending performance. The lifting needs of the grid. It is simple and safe to ensure the stability of the lifting bracket.

(5) The ground endurance of the foundation of the lifting bracket should meet the requirements to avoid uneven settlement after the force is applied, and the foundation should be determined by calculation.

2. The chain hoist breaks

The chain hoist is the key facility of the whole process, and it is necessary to ensure that there are no problems in the hoist during the lifting.

To this end, take the following measures:

The position of the gourd is reasonably arranged to ensure that the force of the gourd is even.

Choose an appropriate number of hoists to ensure a certain safety factor when hoisting.

Choose a gourd of fair tonnage to ensure that the gourd is not damaged when it is lifted.

The gourd should be strictly inspected and carefully maintained before use, and it has normal conditions of use.

Always check the quality changes of the gourd during the lifting process to ensure the smooth lifting.

3. Work at high altitude

Space frame installation work should be placed on the ground as much as possible to reduce high-altitude operations and increase the construction safety factor. When the space frame is lifted, the lift area should be set up to prevent unrelated staff from entering the work area.

What kind of construction works is the space frame suitable for?

   Space frame is a space structure made of multiple members connected by nodes in the form of grid, adopt the construction method of factory manufacturing and site installation, which can shorten the period, reduce cost, improve economic performance. A more professional company can supply better Space frame, and choosing better materials can reduce the cost, which will lead a more prominent performance in the durability and aesthetic. 

   Space frame company can be used in the construction of the station roof, the stadium, the stands, the gas station, the theater the exhibition hall and so on. In addition, the dome structure of Space frame company is suitable for large-span roof, because it has the advantages of space force, big stiffness, saving in material, good seismic performance, low building height, attractive appearance. At present, the roof of large stadiums, exhibition halls, cinemas, theaters, industrial factories, warehouses and other construction projects adopts dome structure.

The top chord assembly and welding steps of the space frame

The top chord assembly and electric welding of steel structure space frame work steps:

1.Put in the longitudinal bars of the upper chord plan space frame to check whether the longitudinal parts and specifications of the top chord ball are appropriate.

2.Put in the transverse bars of the top chord plan space frame to check whether the longitudinal parts and specifications of the top chord ball are appropriate.

3. According to the proper adjustment of the diagonal web member of the three-dimensional small assembly module, the longitudinal and transverse bars of the top chord and the electric welding ball are properly in place. The way to adjust the oblique web members to not only laser cut too long bars, but also to open the angle of view of the transverse bars with inverted chains, so that the rods are properly in place. Ensure the proper size of the top chord grid.

4. Adjust the gaps, and weld the upper chord members after the gap foundation reaches the standard.

5. After the upper chord is fixed, weld the lower chord ball and the transverse bar to make the connection strong.

6. Check space frame specifications and push forward gradually.

The installation of web member and upper chord should be carried out in coordination with each other.

7.After the completion of the installation of the space frame pavement, the project acceptance shall be carried out according to the general specifications of the strips or blocks for the installation of the space frame.

8. The space frame to be hoisted must be hoisted (lifted) after the welding process is finished, the welding appearance quality and the welding ultrasonic flaw detector are reported to reach the standard.

The causes of paint loss during the processing of steel space frame structure

The space frame steel structure is sanded and painted according to the requirements of anti-corrosion. The amount of paint is largely related to the thickness of the dry film, as well as the construction method and coating system.

Paint loss caused by the surface roughness of the workpiece.

When painting the spray-treated surface, the film thickness at the peak of the steel plate should be less than the waves film thickness. In order to meet the anti-corrosion thickness requirements at the peak (to avoid pitting corrosion), the paint "hidden" in the pits of the waves is equivalent to being wasted, which is the "steel plate roughness consumption loss". The following table shows the paint loss caused by different spraying methods (expressed in dry film thickness):

Paint loss caused by uneven film thickness distribution

After the film thickness reaches or exceeds the specified film thickness during the acceptance of the paint film after construction, the technical service representative, the supervisor or the owner will sign as normal, but the part that does not meet the specified film thickness will be required to recoat, so it will inevitably cause "excessive thickness" loss. The specific factors leading to uneven distribution of paint film thickness mainly include: worker proficiency, construction environment, simple or complex construction work piece (flat work piece), and construction method (no air spraying, air spraying, brushing, rolling).

Processing and construction waste

Space frame steel structure processing and construction waste refers to the waste of paint that is lost to the surrounding environment or the ground without reaching the surface of the construction workpiece. If there is no air spraying, the loss of paint is about 10-20%, if there is air spraying, the loss of paint is more than 50%, and the loss of rolling is about 5%. When the brush is well controlled, it is relatively less. Bridge spraying in high wind environment can cause more than 100% waste.

Waste of paint remaining in the container. After the paint is applied, the average loss of the paint remaining on the inner wall of the paint bucket and the rubber tube is about 5%.

In summary, the paint loss coefficient during construction is mainly caused by the loss of surface roughness of the workpiece, the loss of uneven paint film thickness, the waste of construction, and the waste of residual paint in the container.