What should be paid attention to when making and installing the space frame structure pull rod

 According to the actual situation of the ground of the space frame installation construction site, there is no need to deal with the bottom of the pull rod.

 

1. The structure of the pull rod

The single-leg pull rod consists of an independent steel pipe, a base, a pulley block and a winch. The pull rod is made of steel pipe, and the top is pulled with a wind rope, which is fixed on the frame beam and column, and all the wind ropes must be tightened. 

The top and bottom of the pull rod are respectively equipped with a pulley block and a guide pulley block, and the wringing mill is used to lift heavy objects. The cable wind rope and the steel wire rope of the pulley block shall be calculated and determined. The top of the pull rod is welded with a head steel plate with holes, and a clamping plate is set to tie the cable wind rope. A cantilever plate is set close to the top to hang a hoisting tackle. The lower part of the pull rod is supported on a square timber. To prevent displacement, it must be anchored with a rope.

 

2. Fabrication of the drawing rod of the steel space frame. The steel pipe used for the lifting and drawing rod of the space frame is transported to the construction site, the assembly site is selected, the length measurement and appearance inspection of the steel pipe are carried out, and the assembly and welding of the drawing rod is started. Use bright-colored paint to number and identify the pull rods, which is convenient for unified management. After the assembled pull rod is re-tested and calibrated, install the pulley block and the steel wire rope, pay attention to the running direction of the rope, and install and arrange the cable wind rope. After all the assembled pull rods are checked, they can be put in place.

3. For the installation of the drawing rods of the steel space frame, a square timber is placed at the bottom of the drawing rods. The pull rod can be lifted and placed in a designated position by a car crane, and at the same time, the corresponding cable wind rope is stretched and fixed. The lower end of the cable wind rope is fixed on the steel column to ensure the correct position, clear direction and firm fixation. The lower part of the pull rod is provided with a bottom tie rope corresponding to the upper part, and the outer end is tied to the surrounding steel column, and the bottom of the pull rod is firmly connected and fixed to prevent horizontal lateral movement.

 

4. Take protective measures for the connection between the steel wire rope of the space frame structure and the building. First, the section of the steel pipe with a diameter of 89mm is divided into three, and then the cut steel pipe is placed at the corners of the building to protect the building from damage and wire rope damage due to broken wires. There are no less than four fixed buckles for the steel wire rope, which are required to be firm and reliable without looseness. 

What are the characteristics of several space frame structures?

 The space frame structure is one of the new structures required for the development of today's society. Since the 1960s, China has conducted in-depth research on the space frame structure and has achieved good results in practical applications. It has also allowed China-made space frame structures to be exported overseas. In recent years, the rapid development of electronic computing technology has solved the calculation problem of the high-level statically indeterminate structure of the space frame structure, making the space frame structure have an unexpected leap in terms of type and practical engineering application. The space frame structure will usher in greater breakthroughs and create more miracles.

The space frame structure includes double-layer plate-type space frame structure, single-layer and double-layer shell-type space frame structure. The members of the plate type space frame and the double shell type space frames are divided into upper chord, lower chord and web members, which are mainly subjected to tension and pressure. The nodes of single-layer shell-type space frames are generally assumed to be rigidly connected and should be calculated according to the finite element method of rigid-connected rod systems; double-shell space frames can be calculated according to the finite element method of hinged rod systems. Both single-layer and double-layer shell space frames can also use the pseudo-shell method to simplify calculations.

The rods of the single-layer shell-type space frame does not only bear the tensile force and pressure, but also bear the bending moment and shear force. At present, most of China's space frame structure adopts plate type space frame structure. This structure is a kind of spatial space frame structure. The so-called "spatial structure" is relative to the "planar structure", which has the characteristics of a three-dimensional effect. Since the advent of the space structure, it has been welcomed by people for its efficient stress performance, novel and beautiful form and quick and convenient construction. The spatial structure can also be seen as the expansion and deepening of the planar structure. The space frame structure is a spatial rod system, which mainly bear axial force, and the cross-sectional size is relatively small. Space frames are used in stadiums, convention and exhibition centers, cultural facilities, transportation hubs and even industrial plants that require large spans and large spaces, and you can see the traces of spatial structures. The advantages of the space frame structures are small amount of steel, good integrity, quick production and installation, and can be used in complex plane forms. Suitable for structures with various spans, especially for complex plane shapes. The intersecting rods in these spaces support each other and combine the force-bearing rods with the supporting system organically, so the materials are economical.

Space frames frames are mainly used in large and medium-span public buildings, such as stadiums, hangars, clubs, exhibition halls, and waiting halls. Small and medium-sized industrial plants have also begun to be promoted and applied. The larger the span, the more significant the advantages and economic effects of adopting this structure. Space frame structure -The plate type space frame structure is divided into three types according to the form of composition: the first type is composed of a plane truss system, with two-way orthogonal orthographic space frame, two-way orthogonal diagonal space frame, and two-way oblique cross. There are four types of space frame racks and three-way space frames; the second type is composed of quadrangular pyramid units, including positive quadrangular pyramid space frames, positive evacuated quadrangular pyramid space frames, oblique quadrangular pyramid space frames, and checkerboard quadrangular pyramid space frames. There are five types of racks, and star-shaped quadrangular pyramid space frame. The third type is composed of triangular pyramid units, and has three forms: triangular pyramid space frame, evacuated triangular pyramid space frame and honeycomb triangular pyramid space frame. Shell type space frame structure is divided into cylindrical shell type space frame, spherical shell type space frame and hyperbolic parabolic surface shell type space frame according to the shell surface form. The space frame structure is divided into steel space frames, reinforced concrete space frames, and combined space frames composed of steel and reinforced concrete according to the materials used, of which steel space frames are more commonly used.

According to different shapes, the space frame structure can be divided into double-layer plate-type space frame structure, single-layer and double-layer shell-type space frame structure. The members of the plate type space frame and the double-layer shell type space frame are divided into upper chord, lower chord and web members, which mainly bear tension and pressure; the members of the single-layer shell type space frame, in addition to bear the tension and pressure, also bear Bending moment and shear force. At present, most of China's space frame structure adopts plate type space frame structure.

According to actual use: the steel structure is a spatial structure formed by connecting multiple rods in a certain space frame form through nodes. It has the advantages of space stress, light weight, high rigidity, and good seismic performance; it can be used as a house for buildings such as stadiums, theaters, exhibition halls, waiting halls, stadium stands, hangars, two-way large-pillar space frame structures, and workshops covers.

The space frame has the characteristics of light weight, high strength, good overall rigidity, and strong deformability. At present, the demand for the space frame is also increasing. The structural roof is composed of cold-formed thin-walled steel components, and the steel frame is made of super anti-corrosion and high-strength cold. Manufacture of rolled galvanized sheet, effectively avoiding the influence of corrosion of steel sheet during construction and use, and increasing the service life of light steel components. The structural life can be up to 50 years.

The thermal insulation material used in the steel structure space frame is mainly glass fiber cotton, which has a good thermal insulation effect. The use of thermal insulation boards on the outer wall effectively avoids the "cold bridge" phenomenon of the wall and achieves a better thermal insulation effect. The thermal resistance of R15 insulation wool with a thickness of about 100mm can be equivalent to that of a brick wall with a thickness of 1m. The assembly of the space frame structure is generally carried out on site. Before leaving the factory, the bolted spherical joint space frame should be pre-assembled to check the size and deviation of the parts.

The assembling of the space frame should be assembled according to the different construction and installation methods, using separate assembly, quick assembly or overall assembly. The space frame assembly should be carried out on a flat rigid platform. When assembling the space frame of welded hollow sphere nodes, the assembly sequence should be correctly selected to reduce welding deformation and welding stress. According to most domestic engineering experience, the assembly and welding sequence should develop from the middle to the two sides or all around, and it is best to go from the middle to the two sides.  when the space frame is assembled forward, the ends and the front can be freely contracted. After welding a section of steel structure products, the size and geometry can be checked once, so that the welder can make adjustments during the next tack welding. Avoid forming a closed circle during the assembling of the space frame. If welding is performed in the closed circle, the welding stress will be very large.

 

Space frame structure is the fastest growing field for the last ten years

   The development of science and technology has reaffirmed the importance of space frame steel structure. In developed regions in Europe and America, all plant constructions have adopted space frame steel structures. Buildings, bridges, and large-scale public projects also mostly use space frame steel structures. In the past 10 years, about 70% of non-residential residences and buildings with two floors or less in the United States have adopted light steel space frame systems. Countries around the world have successfully built many space frame structures in large and medium-sized roofs, such as Canada and Japan. The Expo, London, England, etc., have a large plane size, and the total steel consumption is relatively economical. The former Soviet Union also adopted prestressing in the space frame.

   In short, the space frame structure has become one of the more common new structures in the modern world. The plane shape of the space frame is flexible and can be designed into various shapes. According to the different settings of the web members, it can be divided into: cross truss system, quadrangular pyramid system, triangular pyramid system and other systems. When the chord of the space frame is perpendicular to the boundary, it is called a normal-laying space frame, and when it is diagonally intersecting with the boundary, it is called an oblique-laying space frame. China began to study and adopt it in the 1960s, and the promulgation of the "Technical Regulations for Steel Structures of High-Rise Civil Buildings" gave my country a corresponding standard for high-rise space frame steel structures. As the country further encourages the use of domestic hot-rolled "H" steel for high-rise steel structures, China's space frame steel structure system has light weight, easy installation, short construction period, good seismic performance, fast investment recovery, and less environmental pollution. Compared with the reinforced concrete structure, it has the unique advantages of developing in the three aspects of "high, large and light". Recently, product structure adjustments have appeared in the field of construction engineering in our country. For a long time, the situation of concrete and masonry structure dominating the world is changing. The space frame steel structure has attracted the attention of the industry with its own advantages. In recent years, due to the rapid development of electronic computing technology, the calculation problem of the high-level statically indeterminate structure of the space frame structure has been solved, which has promoted the development of the space frame structure in terms of type and practical engineering applications.

   The steel structure of the large-span spatial space frame is the first to let people know about the space frame engineering. Its development speed is relatively fast and the calculation is relatively mature. There are many special space frame calculation and drawing programs in China, which is an important reason for its rapid development. Reticulated shells are already in use in our country, and the completed reticulated shell projects are mostly spherical and cylindrical, as well as hyperbolic paraboloids and hyperbolic flat shells. It has many advantages over the space frame, especially when it has a large span. Suspended cables and cable-stayed structures, membranes and cable-membrane structures are also widely used in China, mainly used in large-space public buildings such as stadiums and stations. Other large-span spatial steel structures also include three-dimensional truss, prestressed arch structure, bow structure, suspension structure, space frame structure, cable and rod hybrid structure, cable dome structure, space frame processing, space frame accessories, etc., which are available all over the country. This structure has a high degree of industrialization and commercialization, fast construction, high comprehensive benefits, and great market demand, which has aroused the recognition of structural designers. The research and development of light steel housing has been piloted in various places, which is an important direction of light steel development. There are already a variety of low-rise, multi-story and high-rise design schemes and examples. Because of its large span, large space, flexible use of separation, fast construction speed, and favorable seismic resistance, it will inevitably have a greater impact on my country's traditional residential structure mode. Our company has a highly skilled, highly qualified and experienced space frame processing professional team that provides our customers with one-stop service of steel space frame design, steel space frame processing and steel space frame installation. Our company has solid capital, Intermediate and senior technical personnel, advanced space frame design technology, superb space frame processing technology, scientifically supervise the entire process of space frame processing and steel space frame construction to ensure that the products meet customer requirements.

   Our company's space frame processing components are distributed all over the world, and exported to India, Nigeria, the Middle East, South Africa and other countries and various domestic regions. Our company always adheres to the tenet of "people-oriented, customer satisfaction", anxious for customers' urgency, thinking about what customers think, our company sincerely hopes to cooperate with friends from all walks of life. 

Preventive measures and causes of space frame structure corrosion

   Because the space frame structure is made of steel, it is more susceptible to the influence of the natural environment and the paint during production and processing, which leads to corrosion of the space frame structure. The corrosion of the space frame structure first affects the use time, and secondly affects the space frame structure. The overall appearance is beautiful. If the space frame structure is severely corroded, it is likely to cause partial collapse and cause damage to life and property. Therefore, preventive measures for space frame structure corrosion are very important. The following is the editor based on years of experience, summed up several reasons and preventive measures about the corrosion of the space frame structure. 

   1. Reasons for corrosion of large space frame structure 

   The aging of the space frame structure paint is an important factor that affects the corrosion of the space frame structure. No matter what kind of material, there are basically aging characteristics, and anti-corrosion coatings will also have aging problems. 

   It is the aging problem of this kind of coating that makes the steel structure, and the failure of the anti-corrosion coating, which in turn causes the space frame structure to corrode and rust, and affect its life. It is also due to the natural environmental factors surrounding the grid structure. If the air around the grid structure is relatively humid, it will definitely cause the space frame structure to gradually rust under the erosion of water and air. Among them, the content of corrosive and harmful components such as carbides, nitrides, and sulfides in the polluted atmosphere will also affect the service time of the space frame structure.

   For the maintenance of the space frame structure, it is necessary to pay attention to it. It is best to be coated with a layer of film. At the same time, the anti-corrosion paint needs to be painted after a period of time, so that it can be used for a long time. 

   2. Anti-corrosion measures for large space frame structure 

   Space frame's structure surface treatment: the surface treatment of the space frame structure is very important, the same paint, the same corrosive environment, the use of different construction time can be extended by three to five times. The dirt and rust layer on the surface of steel should be removed, especially the black oxide scale formed when rolling steel. It is the cathode of electrochemical corrosion and the source of corrosion that must be removed. The surface treatment quality should reach the Sa2.5 level of the steel surface pretreatment specification before painting.

   Material selection: The surface coating of special steel structure anti-corrosion paint during space frame processing is still the main method of anti-corrosion of steel structure and space frame. Steel structure anticorrosive coatings can be divided into primers, middle coats and top coats according to their protective functions. Each layer of paint has its own characteristics and each has its own responsibility. Several layers are combined to form a composite coating, which improves the anticorrosion performance and prolongs the use time. 

   Coating thickness: Paint is an anti-corrosion intermediate material and must be painted to form a coating. If the thickness of the coating is uneven, the burrs on the steel surface or the peaks of anchor spinning will expose the coating. If the number of coating applications is small and the coating has pinholes, oxygen, chloride ions, and water molecules in the water will pass through these weak places, causing the steel to rust and corrode. The corrosion products expand in volume to form a rust bag, which gradually expands, and the coating blisters and falls off.

Does the space frame structure use less steel than the truss?

When the plane shape of the space frame is an ellipse, the center of the ellipse is a high point. The slope cannot be arc-shaped. Similar to four-sided sloping roof, it may be necessary to be careful about the coordinate transformation of the slope and chord. Of course, the space frame ball joints at the gutter are not equal to the elevation (draining on two slopes in the direction of the short axis): 1. The gutter can be made of sections of equal height, 2. The short axis end point is very low and gradually rises along the periphery to the long axis end point, 3. The water baffle and the drain should be set at a certain distance in the gutter, otherwise the rainwater will easily accumulate at the end of the short axis, causing poor drainage or even overflow! If the space frame ball joints at the gutter are not equal in elevation, drainage can be done on two slopes in the direction of the short axis. 1. From a very low point on the short axis, gradually rising along the periphery to the long axis, 2. The gutter can be made into a cross section of equal height, 3. The water baffle and the drain should be set at a certain distance in the gutter, otherwise the rainwater will easily accumulate at the end of the short axis, causing poor drainage or even overflow! In this way, the height of the support of the space frame is not the same, the processing and installation are relatively troublesome, or it is better to level it. space space frame is a structural form suitable for large spans and at the same time relatively economical due to its two-way space force. However, there are many applications of tubular trusses and cold-formed truss purlins at present, is it necessary to save space space frames than plane trusses? The space space frame is not necessarily less expensive than the plane truss. What is not saving is that the space space frame has many structural members and bears a small force. In order to meet the slenderness ratio, larger members are used, so how to remove some Small structural rods are one of the keys to improving the amount of steel used in space space frames Space frames with relatively large length and width are mainly subjected to unidirectional force, and removing some length-direction rods can indeed save a lot of steel consumption. If the space frame with relatively small length and width is subjected to bidirectional force, it is not suitable for drawing rods. Optimizing the amount of steel used for the space frame structure In addition to the rods mentioned earlier, there is still a key point worthy of improvement, that is, the amount of steel used in the nodes is very large, reaching about 25%-30%. Reasonable design can also reduce the amount of steel used in the space frame structure. Some improvements are made to the currently commonly used joint forms. In this way, the amount of steel used in the space frame structure will be greatly reduced. All structured products have their scope of economic application. For buildings with general light roofs: The column spacing is 6-9 meters, and the C and Z-shaped purlins of cold-formed thin-walled steel are definitely more economical; 12-20 meters, flat truss purlin has advantages; More than 24 meters in both directions, the advantage of the space frame should be greater; but the disadvantage of the space frame is that it occupies more space and the ball joint uses a larger amount of steel. It is necessary to increase the primary and secondary purlins to fix the roof panel.

Space frame structure characteristics, classification and installation methods

1. The characteristics of the space frame structure The definition of space frame structure-a spatial structure formed by connecting multiple rods through nodes in a certain space frame form. The space frame structure construction speed is fast. The space frame structure components, whose size and shape are largely the same, can be mass-produced in factories, with good quality and high efficiency, and at the same time they do not compete with civil engineering. Therefore, the on-site workload is small and the construction period is shortened. The space frame structure transfers the load by the axial force of the rods, and the material strength is fully utilized, which saves steel and reduces its own weight. A good space frame design, the amount of steel used is close to the steel content of the reinforced concrete structure under the same conditions, so that a large amount of concrete can be saved, and the self-weight can be reduced by 70-80%. Compared with ordinary steel structures, it can be Save 20-50% of steel. The seismic performance of the space frame structure is good. Due to the light weight of the space frame structure, the seismic force generated during an earthquake is small. At the same time, the steel has good extensibility and can absorb a large amount of seismic energy. The space frame has a large spatial rigidity, and the structure is stable and will not collapse. So it has excellent seismic performance. The space frame structure is light and handy. It can cover planes of various shapes, and can be designed into various body shapes with beautiful and generous appearance. The space frame structure can be used as the roof of buildings such as stadiums, theaters, exhibition halls, waiting halls, stadium stands, hangars, two-way large column space frame structures and workshops. The disadvantage of the space frame structure is that the number of rods converging on the node is large, and the production and installation are more complicated than the planar structure. 2.The space frame structure classification The first type is composed of a plane truss system. There are four types of two-way orthogonal orthographic space frames, two-way orthogonal diagonal space frames, two-way diagonal diagonal space frames and three-way space frames; The second type is composed of quadrangular pyramid unit space frame structures. There are five types of positive quadrangular pyramid space frames, positive quadrangular pyramid space frames, diagonal quadrangular pyramid space frames, checkerboard quadrangular pyramid space frames and star-shaped quadrangular pyramid space frames form; According to different shapes, the space frame structure can be divided into double-layer plate-type space frame structure, single-layer and double-layer shell-type space frame structure. The members of the plate type space frame and the double-layer shell type space frame are divided into upper chord, lower chord and web members, which mainly bear tension and pressure; the members of the single-layer shell type space frame, in addition to bear the tension and pressure, also bear Bending moment and shear force. At present, most of China's space frame structure adopts plate space frame structure. The plate space frame structure is in the form of composition.

3.the installation method of the space frame structure 1.The high-altitude bulk method is a very simple grid installation method. The space frame is directly installed on the supporting structure on the installation platform, without the need for large machinery. According to the structural characteristics and site conditions, the installation platform usually adopts full house scaffolding or mobile scaffolding. The choice of this method should fully consider the economy of scaffolding and the impact on the total construction period and construction cross-operations. 2. The sliding method is to use the traction device to pull the installed net frame on the slide rail in place and form it in place. The slip method is divided into single slip method and cumulative slip method. The choice of sliding method is usually due to site restrictions, and it is used when mobile scaffolding cannot be erected. 3. The hoisting method is to use hoisting equipment to separate or hoist the space frame into place. Different hoisting methods can be selected according to the structural characteristics, site conditions and equipment conditions. The successful implementation of the hoisting plan requires a high level of experience and skills for the hoisting operation team. For a space frame with a large volume and an irregular shape, its economic indicators are quite ideal. 4. The comprehensive installation method is to use the above three or two of the installation methods for space frame installation construction under the premise of fully analyzing the site conditions.

What is the current situation of space frame structure houses?

In the first 30 years of the 21st century, China will maintain a certain scale of new housing every year. At present, the quantity, variety and quality of construction steel in China can meet the needs of space frame steel structure residential buildings. Now, the state has strengthened its policy guidance and support for steel structure housing, and the technology of space frame steel structure housing has been developing day by day. In China, the conditions for the development of space-framed steel structure residences are already available. Although energy-saving, environmentally-friendly, and land-saving space-framed steel structure residences have received increasing attention in China, there is still a big gap in the degree of promotion compared with developed countries in the world. According to the person in charge of the relevant industry association, the current proportion of steel structure housing in China is less than 5%, while in developed countries it is generally more than 40%. More than 50% of China's steel is used in the construction industry. The total amount of steel used in construction last year reached about 170 million tons, most of which were used in traditional reinforced concrete structures, and more than 10 million tons were used in steel structure residential buildings. The space frame steel structure house with new wall materials can increase the energy saving efficiency by half, increase the effective use area by 6% to 8%, shorten the construction period, save construction water, conform to the development direction of the national industrial policy, and achieve the most energy saving and land saving. One of the best housing forms.

The support is essential for the space frame structure

The space frame structure is a kind of high-order super statically indeterminate spatial structure. According to the structure of the space frame itself, it can be divided into: single-layer space frame structure, double-layer space frame structure, and three-layer space frame structure. Single-layer spaces and three-tier space frames are respectively suitable for small spans and very large spans. According to the different composition methods, the space frames can be divided into four categories: triangular pyramid system space frames, quadrangular pyramid system space frames, Hexagonal cone system space frame, cross truss system space frame. The space frame structure has good mechanical performance, strong bearing capacity, high rigidity, good seismic resistance and overall performance, less affected by the uneven settlement of the support, and strong adaptability. The gradual improvement of calculation theory and the rapid development of computer technology make it difficult. However, the analysis and design of extremely complex three-dimensional structures becomes possible, so space frame structures are widely used in civil and industrial buildings.

Unreasonable design of the support structure, support type and boundary conditions of the space frame structure will have a very important impact on the safety and economy of the space frame structure. 1. Support structure and support method Now in many projects, the space frame structure is designed by a professional company according to the pre-assumed boundary constraints, and then the support reaction force calculated by them is applied to the lower supporting structure as an applied load. Calculate the space frame and the lower support structure separately. Although the displacement of the space frame support relative to the lower structure can be simulated by the elastic restraint method, it is difficult to estimate the displacement of the support itself such as the support subsidence caused by the deformation of the lower support structure. In some cases, the calculated internal force of the structure may be quite different from the actual situation, which may leave a safety hazard to the project. The substructure may be a column, a beam, or other structural forms. Not only is the rigidity limited, but the rigidity of the specific engineering may vary greatly. Under this assumption, the calculated internal force of the rod and the support reaction, the force and the internal force of the substructure are definitely different from the results calculated by the mechanical model that uses the rigidity of the space frame support as the actual stiffness and the upper and lower structures work together. Separate calculations also split the cooperative work of the upper and lower structures, making the period and displacement calculations of the upper and lower structures inaccurate. General space frame support can be divided into three methods: peripheral support, point support, and mixed use of point support and peripheral support. Peripheral support is to place the peripheral nodes of the space frame on beams or columns, and point support is to support the space frame. It is placed on independent beams or columns with a large spacing, and the columns have no connection with other structures. When the space frame is placed on a beam or column, it can be considered that the vertical rigidity of the beam and column is very large, and the vertical deformation of the beam and the axial deformation of the column are ignored. Therefore, the vertical displacement of the space frame support is zero, and the horizontal deformation of the space frame support should be Consider working together with substructures. In the radial direction of the peripheral support space frame support, the lower support structure should be used as the elastic constraint of the space frame structure, and the boundary conditions of the point support space frame support should consider the elastic constraints in the horizontal X and Y directions. There are several calculations for the equivalent spring stiffness of the supporting structure: 1) Support column support 　　 The equivalent spring stiffness of the column in the horizontal displacement direction is: Kc=3EcIc/H3c 　　 In the formula, Hc: column height; Ic: column section moment of inertia. 2) Simply supported beam support at both ends 　　 The equivalent spring stiffness of a simply supported beam whose length is L and the space frame support is located at a distance from the beam end is: Kb=3EbIbL/a2 (L-a) 2 　　 In the formula, a: the distance between the point of application and the end of the beam; L: the length of the beam; Ib: the moment of inertia of the beam section. 3) Rubber pad support 　　 The equivalent spring stiffness of the support supported by the rubber pad with a height of Hp is: 　　Kp=GpAp/Hp In the formula, Ap: rubber pad area; Hp: rubber pad height. In actual engineering, it is often to add elastic supports with rubber pads on the top of beams or columns, especially in large-span space frames, to meet the deformation requirements of temperature stress through rubber pads, which requires consideration of the elastic stiffness of beams or columns. Superimposed with the elastic stiffness of the rubber pad, when K1 and K2 are superimposed, the superimposed stiffness K is obtained by superimposing the displacement: 1/K=1/K1+1/K2; there is K=1/(1/K1+1/K2 ). 2. Support (support node) The connection area between the structure and the foundation is simplified as a support, which is divided into five types according to its force characteristics: living hinge support (roller support), fixed hinge support, directional support (sliding support), fixed (end) Support and elastic (spring) support. The elastic support produces a corresponding displacement while providing the reaction force, and the ratio of the reaction force to the displacement remains unchanged, which is called the stiffness coefficient of the elastic support. The elastic support can provide both movement restriction and rotation restriction. When the rigidity of the support is similar to that of the structure, it should be simplified as an elastic support. When a certain part of the structure is under load (such as studying structural stability), its adjacent part can be regarded as the elastic support of this part, and the stiffness of the support depends on the rigidity of the adjacent part (such as the cable-stayed bridge Simplified as a spring support). When the rigidity of the support is much larger or much smaller than the rigidity of this part, the elastic support transforms into the previous four ideal supports. The space frame structure is generally supported on a lower supporting structure such as column tops or ring beams, and the support node refers to the space frame node on the supporting structure. It does not only connects the rods that meet at the support of the space frame, but also supports the entire space frame, and transfers the load acting on the space frame to the lower supporting structure. The support node is the link between the space frame structure and the lower supporting structure, and is also an important part of the entire structure. A reasonable bearing node must be clear in force, simple in force transmission, safe and reliable. At the same time, it should have a simple and reasonable structure, simple and convenient production, and good economy. The support node of the space frame structure should be able to ensure the safe and reliable transmission of the supporting reaction force, and must have sufficient strength and rigidity. Under the action of vertical load, the supporting nodes are generally under compression. However, in some diagonally placed frame frames, the local supporting nodes may bear the action of tensile force, and sometimes they may also bear the action of horizontal force. The support should be designed. The structure of the seat node adapts to their force characteristics. At the same time, the structure of the bearing nodes should also conform to the calculation assumptions as much as possible, and fully reflect the design intent. Because the space frame structure is a high-order statically indeterminate member system, the constraint conditions of the support nodes have a greater impact on the node displacement of the space frame and the internal force of the members; the difference between the constraint conditions between the structure and the design will directly lead to the internal force of the members. The change of the reaction force with the support sometimes causes the internal force of the rod to change sign. Enough attention should be paid to the design of the support node of the space frame structure. Whether the space frame structure design is safe and economical, the key factor is whether the selected supporting structure, support type and boundary conditions are reasonable. Therefore, in the specific design, we try to avoid separate analysis of the upper space frame structure and the lower supporting system. Design, especially when the displacement of the space frame support relative to the lower structure is difficult to simulate by the elastic restraint method, the supporting structure and the upper space frame should be modeled and calculated together to make the calculated results more consistent actual.

The difference between space frame processing and truss processing

The space frame is a spatial structure formed by connecting multiple rods through nodes in a certain space frame form. Truss refers to a lattice structure formed by connecting round rods at the ends. Nowadays, it has a wide range of applications and is economical and practical. Such as exhibition centers, stadiums or other large public buildings have been used. Compared with the space frame structure, the truss structure saves the longitudinal members of the lower chord and the spherical joints of the space frame, which can meet the requirements of various building forms, especially the construction of round arches and arbitrary curved shapes is more advantageous than the space frame structure. It can be seen from the force characteristics of the space frame structure that when its side-length ratio is greater than 1.5, its force characteristics change from two-way to one-way force. Therefore, for most rectangular plane buildings, it is mainly one-way force. The truss structure is similar to the plane steel truss, which is a unidirectional force structure, but the upper chord of the truss increases the width, so that the stability of the upper chord member that controls the original plane truss is improved, and its stability in all directions is the same, and saves material consumption. The truss structure is developed on the basis of the space frame structure. Compared with the space frame structure, it has its unique advantages and practicability, and the amount of structural steel is also more economical. In recent years, the industry of space frame processing has continued to develop, but what is the difference between a space frame and a truss, let us understand the relevant knowledge next. With the continuous growth of my country's steel production, steel structures take up an increasing proportion of buildings with their own advantages, and steel pipe structures have also made greater breakthroughs. The biggest advantage of the steel pipe structure is that it can perfectly combine the functional requirements, sensory requirements and economic efficiency requirements of the building. The pipe truss structure in the steel pipe structure has attracted people's attention and favor with its unique advantages.

Technical analysis of space frame structure production and the meaning of main symbols

 The space frame structure is a high-order statically indeterminate structure system. In the analysis of slab space frames, it is generally assumed that the joints are hinged, and the external load is applied to the joints according to the principle of static equivalent. The calculation can be carried out according to the space truss displacement method, that is, the hinged rod system finite element method. The space frame structure can use simplified calculation methods such as the cross-beam differential analysis method and the pseudo-plate method to calculate the internal force and displacement. The nodes of single-layer shell-type space frames are generally assumed to be rigidly connected and should be calculated according to the finite element method of rigid-connected rods; double-shell space frames can be calculated according to the finite element method of hinged rods. Both single-layer and double-layer shell space frames can also use the pseudo-shell method to simplify calculations.

The bar design and node structure of the bar section of the space frame structure should be determined according to the strength and stability calculations. In order to reduce the calculated length of the compression rod and increase its stability, measures such as adding sub-rods and supporting rods can be adopted. The joints of the plate space frame and double-shell space frame made of steel mainly have three forms: cross plate joints, welded hollow spherical joints and bolted spherical joints.

The cross plate node is suitable for the space frame structure of the section steel rod. The connection of the rod and the point plate of the section space frame structure is connected by welding or high-strength bolts. Hollow ball joints and bolted ball joints are suitable for the space frame structure of steel pipe rods. The nodes of the single-layer shell-type space frame should be able to withstand bending internal forces. Generally, the steel consumption of the nodes accounts for 15-20% of the steel consumption of the entire steel space frame structure.

 

Gi——the representative value of the gravity load of the i-th node of the space frame;

Gk——the permanent load standard value of the space frame; 　

Gok——The standard value of the total dead weight of the space frame;

Gok——the standard value of the self-weight of the space frame;

He——post height;

H——the height of the space frame;

I——Simplified to the converted moment of inertia of the cross beam system;

Ke——The horizontal stiffness of the cantilever column;

Ab——the cross-sectional area of the lower chord of the space frame;

At——the cross-sectional area of ​​the upper chord of the space frame;

Am——the arithmetic mean value of the cross-sectional area of ​​the plane chord of the support (upper or lower bearing);

Aeff——the effective cross-sectional area of ​​high-strength bolts;

D——The converted bending stiffness of the space frame; the diameter of the steel ball;

D—— outer diameter of steel pipe;

D1, d2——the outer diameter of the steel pipe forming the angle θ; bolt diameter;

Ds——pin diameter;

E——The modulus of elasticity;

Ec——The elastic modulus of the column material;

FEK——the standard value of the total horizontal seismic action of the grid structure;

FEVKi——the standard value of vertical seismic action acting on the i-th node of the space frame;

Ft——Total starting traction;

Ft1, Ft2——The standard value of the pulling force of the lifting pulley block;

F——design value of steel strength; ——design value of tensile strength of high-strength bolts after heat treatment;

L1——The long span of the space frame;

L2——The short span of the space frame;

I——geometric length of rod;

M——Design value of bending moment of pseudo-sandwich plate;

Ηt——the coefficient of improving the bearing capacity of the hollow ball and ribs under tension;

Θ——The included angle between any two pipes converging on the ball joint; the small included angle between two bolts;

Μ1——The sliding friction coefficient;

μ2——Rolling friction coefficient;

ΡW——deflection coefficient; —dimensionless bending moment coefficient;

Φ——the angle between the oblique web rod and the lower chord plane;

Nb——The design value of the axial force of the lower chord of the space frame;

Nc——The design value of the axial force of the inclined rod of the space frame, the design value of the axial pressure of the compressed hollow ball;

Nt——The design value of the axial force of the upper chord of the grid, the design value of the axial tension of the hollow ball under tension; —The design value of the tension of the high-strength bolt;

NV——The design value of the axial force of the vertical rod of the space frame;

Qw——the standard value of roof load or floor load other than the self-weight of the space frame;

R1——The outer diameter of the roller;

R——The radius of the shaft;

S——the length of the upper and lower chords;

U——displacement;

Ω——Deflection;

Α——The linear expansion coefficient of the grid material;

Ηc——The coefficient of improving the bearing capacity of the ribbed hollow ball under pressure;

space frame

commonly used space frame installation methods

 There are many ways to install the space frame, among which there are six commonly used methods and applicable scopes:

1. High-altitude bulk method. The high-altitude bulk method is divided into full support method, partial movable support method and cantilever method. This method is suitable for large-scale assembling of brackets when it is difficult to lift. When using this method to install the space frame, attention should be paid to the position of the elevation and axis, and a reasonable assembly sequence is determined. 

2. Split or block space frame installation method. The welding and assembling work of the space frame installed by this method must be completed on the ground, and the equipment on the construction site is used to reduce the rental cost of the crane and greatly save the cost.

3. High-altitude sliding method. To use this kind of space frame installation method, first divide the space frame into strips of space frame units, and set slide rails in advance to slide the space frame to the pre-designed position. This kind of space frame installation method is suitable for spanning projects and situations where three-dimensional crossing construction is required.