The bending capacity of a bending member is Mx/(γx*Wx)+My/(γy*Wy)≤f, where W is the section modulus. The approximate section can be calculated manually according to the section modulus.

 

 

　　It can be joined in any way, mainly considering the transfer of bending moment and/or shear force. In addition, in places with frequent dynamic loads, extra care should be taken in designing welded joints for butt joints.

 

 

　　Polishing and tightening is a way of force transmission, often used in positions that bear dynamic loads. It is a way of force transmission to avoid fatigue cracks in the weld. Some requirements specify polishing and tightening without welding, while others require welding. Refer to the specific drawing requirements. The surface roughness of the contact surface must be no less than 12.5, and the contact area is checked with a feeler gauge. The purpose of planing and tightening is to increase the contact area of the contact surface, generally used in nodes with certain horizontal displacement and simple support, and such nodes should have other connection methods (such as flange tightening, the web may use bolting).

 

　　Generally, welding is not required for the planed and tightened parts of such nodes. If welding is required, planing and tightening is not conducive to the penetration of the molten liquid during welding, and the weld quality will be poor. Even if the welded part does not require beveling, tightening is not required. Tightening and welding are contradictory to each other, so it is inaccurate to say that welding is required after tightening. However, there is a situation where tightening and welding may occur, which is when the constraints of the tightening node on other degrees of freedom are insufficient, and no other parts provide constraints, it may be necessary to weld at the tightening part to constrain other degrees of freedom, this weld is an installation weld, it is not possible to full weld, and it is not possible to use as the main stress-bearing weld.

 

 

　　Deformation affecting normal use or appearance;

 

　　Local damage (including cracks) affecting normal use or durability;

 

　　Vibration affecting normal use;

 

　　Other specific conditions affecting normal use.

 

 

　　Henan Wanjian polyurethane composite panels are generally used as the outer wall and roof panels of buildings. The panels have good heat preservation, heat insulation, and sound insulation effects, and polyurethane is not combustible and meets fire safety requirements. The combined effect of the upper and lower plates plus polyurethane has high strength and rigidity, the lower plate is smooth and flat, the lines are clear, increasing the aesthetics and flatness of the interior. Easy installation, short construction period, beautiful appearance, is a new type of building material.

 

　　Visual effect of shifting scenery. It combines three-dimensional and elegant decorative effects, and the gloss, color, and brightness of the wall change with the angle and position of the light, creating distinct light and dark stripes.

 

 

　　Radius of gyration: square root (moment of inertia/area), Slenderness ratio = effective length/radius of gyration

 

　　The slenderness ratio of the structure λ＝μl/i, where i is the radius of gyration.

 

　　The concept can be simply seen from the calculation formula: the slenderness ratio is the ratio of the effective length of the member to its corresponding radius of gyration.

 

　　From this formula, it can be seen that the concept of slenderness ratio comprehensively considers the end constraint conditions of the member, the length of the member itself, and the section characteristics of the member. The concept of slenderness ratio has a significant impact on the stability calculation of compressed members, because members with larger slenderness ratios are more prone to instability.

 

　　You can look at the calculation formulas for axial compression and compression bending members, which all have parameters related to slenderness ratio. The code also gives slenderness ratio limit requirements for tension members, this is to ensure the stiffness of the members in the transportation and installation state. The higher the stability requirement for the member, the smaller the stability limit value given by the code.

 

 

　　When the load is small, the beam basically bends in its plane of maximum stiffness, but when the load reaches a certain value, the beam will simultaneously produce large lateral bending and torsional deformation, and quickly lose its ability to continue carrying the load. At this time, the overall instability of the beam is inevitably lateral bending-torsional bending.

 

　　There are roughly three solutions:

 

　　1. Increase the lateral support points of the beam or reduce the spacing of the lateral support points

 

　　2. Adjust the section of the beam to increase the lateral moment of inertia Iy or simply increase the width of the compressed flange (such as the upper flange of the crane girder)

 

　　3. The constraint of the support on the section, if the support can provide rotational constraint, the overall stability performance of the beam will be greatly improved

 

 

　　Generally, steel beams are open sections (except box sections), and their torsional section modulus is about an order of magnitude smaller than their bending section modulus, that is, their torsional capacity is about 1/10 of their bending capacity. Thus, it is uneconomical to use steel beams to withstand torque. Therefore, it is usually ensured that they do not undergo torsion by construction, so there is no torsional calculation for steel beams in the steel structure design code.

 

 

　　The light steel specification has indeed corrected this limit value. The main reason is that the column top displacement of 1/100 cannot guarantee that the wall will not be cracked. At the same time, if the wall is built inside the frame (such as an interior partition wall), we do not consider the embedding effect of the wall on the frame when calculating the column top displacement (a bit exaggerated to say it is a frame-shear wall structure).

 

 

　　The plane of maximum stiffness is the plane of rotation around the strong axis. Generally, a section has two axes, and the moment of inertia around one of them is large, which is called the strong axis, and the other is the weak axis.

 

 

　　Theoretically, the structural steel pipes should be the same, with little difference. Welded pipes are not as regular as seamless pipes; the centroid of the welded pipe may not be in the center, so special attention should be paid when used as compression members. Welded pipes have a relatively high probability of weld defects and cannot replace seamless pipes in important parts. Due to processing limitations, the wall thickness of seamless pipes cannot be made very thin (the average wall thickness of seamless pipes with the same diameter is thicker than that of welded pipes). In many cases, the material use efficiency of seamless pipes is not as good as that of welded pipes, especially for large-diameter pipes.

 

　　The biggest difference between seamless pipes and welded pipes is their use in the transmission of pressure gases or liquids (DN).

 

 

　　Shear lag effect is a common mechanical phenomenon in structural engineering. It exists from a small component to a super-high-rise building.

 

　　Shear lag, sometimes also called shear lag, is essentially the Saint-Venant principle. Specifically, it means that within a certain local range, the effect of shear force is limited, so the normal stress distribution is uneven. This uneven distribution of normal stress is called shear lag.

 

 

　　The axial tensile stress distribution in the anchor bolt is uneven, with an inverted triangular distribution. The axial tensile stress is the largest at the top and 0 at the bottom. As the anchorage depth increases, the stress gradually decreases, and finally reduces to 0 when it reaches 25～30 times the diameter. Therefore, further increasing the anchorage length is useless. As long as the anchorage length meets the above requirements and the end is provided with a hook or anchor plate, the foundation concrete will generally not be broken.

 

 

　　For a long time, the fatigue design of steel structures has been based on the stress ratio criterion. For a certain number of load cycles, the fatigue strength σmax of the component is closely related to the stress cycle characteristics represented by the stress ratio R. Introducing a safety factor to σmax, the allowable fatigue stress value for design can be obtained: 〔σmax〕=f(R). Limiting the stress within 〔σmax〕 is the stress ratio criterion.

 

　　Since welded structures have been used to withstand fatigue loads, the engineering community has gradually realized from practice that it is not the stress ratio R, but the stress amplitude Δσ that is closely related to the fatigue strength of such structures. The calculation formula of the stress amplitude criterion is Δσ≤〔Δσ〕, where 〔Δσ〕 is the allowable stress amplitude, which varies with structural details and also with the number of cycles before failure. Fatigue calculation of welded structures should be based on the stress amplitude criterion because of the residual stress inside the structure. For non-welded components and stress cycles with R >= 0, the stress amplitude criterion is fully applicable because the fatigue strength of components with and without residual stress is not much different. For stress cycles with R < 0, using the stress amplitude criterion is more on the safe side.

 

 

　　Hot rolling is the process of pressing steel at a temperature above 1000 degrees using rollers. Usually, the thickness of the plate is as small as 2 mm. The deformation heat during the high-speed processing of steel cannot offset the heat dissipation due to the increase in the area of the steel, which makes it difficult to maintain a temperature above 1000 degrees for processing. Therefore, the efficient and inexpensive method of hot rolling has to be sacrificed. Cold rolling is performed at room temperature, which involves re-rolling hot-rolled materials to meet the market demand for thinner thicknesses.

 

　　Of course, cold rolling brings new benefits, such as work hardening, which increases the strength of the steel, but it is not suitable for welding. At least, the work hardening at the weld is eliminated, and the high strength is gone, returning to the strength of its hot-rolled material. Cold-bent steel can use hot-rolled materials, such as steel pipes, or cold-rolled materials. Whether it is cold-rolled or hot-rolled material, 2MM thick is a criterion. Hot-rolled materials are at least 2MM thick, and cold-rolled materials are at most 3MM thick.

 

 

　　Beams only have out-of-plane buckling modes. There is never such a thing as in-plane buckling of a beam. For columns, when there is axial force, the calculation lengths for out-of-plane and in-plane are different, so there are out-of-plane and in-plane buckling checks.

 

　　For rigid frame beams, although they are called beams, there is always a part of axial force in their internal forces, so their verification should strictly use the column model, that is, the stability of both in-plane and out-of-plane should be calculated according to the compression bending member. However, when the roof slope is small, the axial force is small and can be ignored, so the beam model can be used, that is, in-plane stability calculation is not needed. The meaning in the code (P33, Clause 6.1.6-1) refers to when the roof slope is small, the inclined beam member only needs to calculate the strength in-plane but still needs to calculate the stability out-of-plane.

 

 

　　If the secondary beam is rigidly connected to the main beam, it is fine if there are secondary beams on both sides of the same position of the main beam with the same load. Otherwise, the end bending moment of the secondary beam will cause out-of-plane torsion for the main beam, and the torsional resistance needs to be calculated, involving torsional stiffness, sectional modulus, etc. In addition, rigid connection increases the construction workload and greatly increases the amount of on-site welding work. It is not worth the effort, and generally, it is unnecessary to make the secondary beam a rigid connection.

 

 

　　Length of high-strength bolt = 2 x thickness of connecting end plates + 1 x thickness of nut + 2 x thickness of washers + 3 x thread length.

 

 

　　Post-buckling capacity mainly refers to the ability of a component to continue carrying load after local buckling, mainly occurring in thin-walled components, such as cold-bent thin-walled steel sections. In calculations, the effective width method is used to consider the post-buckling capacity.

 

　　The magnitude of post-buckling capacity mainly depends on the width-to-thickness ratio of the plate and the constraint conditions of the plate edges. The larger the width-to-thickness ratio and the better the constraint, the higher the post-buckling capacity.

 

　　In terms of analysis methods, current domestic and international specifications mainly use the effective width method. However, the influencing factors considered in calculating the effective width vary among different national standards.

 

 

　　Plasticity algorithms refer to achieving the yield strength at the intended locations in hyperstatic structures through the emergence of plastic hinges, thereby achieving the purpose of plastic internal force redistribution, and ensuring that the structure does not form a variable or transient system.

 

　　Considering post-buckling strength refers to a member calculation method that utilizes the remaining load-bearing capacity of a flexural member after its web loses local stability and fully utilizes its post-buckling strength.

 

 

　　Soft hook crane: refers to lifting heavy objects using steel ropes and hooks. Hard hook crane: refers to lifting heavy objects using rigid bodies, such as clamps and material rakes. Hard hook cranes operate frequently, with high running speeds, and the rigid cantilever structure attached to the trolley prevents the load from swinging freely.

 

 

　　Rigid tie rods can withstand both compression and tension, generally using double angle steel and round tubes, while flexible tie rods can only withstand tension, generally using single angle steel or round tubes.

 

 

　　1. Deflection is the amount of deformation of a member after loading, which is its displacement value.

 

　　2. "Slenderness ratio is used to express the stiffness of axially loaded members." The slenderness ratio should be a material property. Any member has this property; the stiffness of an axially loaded member can be measured using the slenderness ratio.

 

　　3. Deflection and slenderness ratio are completely different concepts. Slenderness ratio is the ratio of the effective length of a member to its section radius of gyration. Deflection is the displacement value of a certain point of a member after loading.

 

 

　　Seismic intensity levels: Level 1, Level 2, Level 3, Level 4. Seismic fortification intensity: 6, 7, 8, 9 degrees.

 

　　Seismic fortification categories: Categories A, B, C, and D.

 

　　Earthquake levels: Frequent earthquakes, occasional earthquakes, infrequent earthquakes, rare earthquakes.

 

 

　　1. Corner braces and supports are two structural concepts. Corner braces are used to ensure the stability of the steel beam section, while supports are used to form a stable structural system with the steel frame and ensure that its deformation and load-bearing capacity meet the requirements.

 

　　2. Corner braces can serve as support points outside the plane of the compressed flange of steel beams. They are used to ensure the overall stability of steel beams.

 

 

　　1. Under the action of static loads that do not cause fatigue, residual stress has no effect on the load-bearing capacity of tie rods.

 

　　2. If a tie rod section has a sudden change, the stress distribution at the change is no longer uniform.

 

 

　　Spring stiffness is determined by considering the column as a cantilever member. A unit force is applied at the top of the column, and the resulting lateral displacement is calculated. This displacement is the spring stiffness, generally in units of KN/mm. In cases with a ring beam, in the direction without ring beam restraint, the spring stiffness calculation is the same as for a cantilever member. In the other direction, because there is a ring beam at the top of the column, the EI in the calculation formula is the sum of all columns in that direction.

 

 

　　Under vertical loads, the movement trend of the gable-frame gantry is downward at the ridge and outward at the eaves. The roof panel will work with the supporting purlins to resist this deformation trend as a deep beam. At this time, the roof panel bears shear force, acting as the web of a deep beam, while the edge purlins bear axial force, acting as the flanges of a deep beam. Obviously, the shear resistance of the roof panel is far greater than its bending resistance.

 

　　Therefore, the skin effect refers to the resisting effect of the skin plate due to its shear stiffness against loads that cause deformation in the plane of the plate. For gable-frame gantries, the skin effect resisting vertical loads depends on the roof slope; the greater the slope, the more significant the skin effect; the skin effect resisting horizontal loads increases as the slope decreases.

 

　　The skin effect of the entire structure is constituted by skin units. A skin unit consists of the skin plate between two frames, edge members and connectors, and intermediate members. Edge members refer to the adjacent frame beams and edge purlins (ridge and eaves purlins), and intermediate members refer to the purlins in the middle. The main performance indicators of the skin effect are strength and stiffness.

 

 

　　It means that the ends of the stiffener should be continuously welded, such as using corner welding or circumferential welding to prevent fatigue cracks from occurring on the web.

 

 

　　Electroslag welding is used, and the quality is easily guaranteed!

 

 

　　The calculation length coefficient for cantilever beams is 1.0, and the calculation length coefficient for cantilever columns is 2.0. Columns are compression-bending members, or simply compression members, and need to consider the stability coefficient, so 2 is taken. Beams are subjected to bending, and that should be the difference.

 

 

　　1. Structural deflection control is designed according to the normal use limit state. For steel structures, excessive deflection can easily affect roof drainage and cause fear, while for concrete structures, excessive deflection can cause local damage to durability (including concrete cracks). I believe that all the above damage caused by excessive deflection of building structures can be solved by arching.

 

　　2. Some structures are easy to arch, such as double-slope portal frame beams. If the absolute deflection exceeds the limit, the roof slope can be increased during fabrication to adjust. Some structures are not easy to arch, such as large-span beams. If the relative deflection exceeds the limit, each beam segment needs to be arched. Because the arched beams are jointed into a polyline, while the deflection deformation is a curve, the two lines are difficult to coincide, resulting in an uneven roof. It is even more difficult to arch the frame flat beams; it's impossible to make the flat beams arc-shaped.

 

　　3. If you plan to use arching to reduce the steel consumption of structures controlled by deflection, and the deflection control regulations need to be lowered, then the deflection under live load must be controlled, and the deflection generated by dead load is guaranteed by arching.

 

 

　　The central grouting base plate method for steel column installation saves labor and time, and the construction accuracy can be controlled within 2mm, and the overall efficiency can be increased by more than 20%.

 

　　The construction steps are as follows:

 

　　(1) Steel column foundation construction is carried out according to the construction drawings (same as the usual construction method). The foundation is 30~50mm lower than the installation elevation of the steel column bottom surface to prepare for placing the central grouting base plate.

 

　　(2) Calculate the minimum bearing area Amin based on the steel column self-weight Q, bolt pretightening force F, and foundation concrete compressive strength P.

 

　　(3) Use 10, 12mm thick steel plates to make square or round central grouting base plates, and their area should not be less than twice the minimum bearing area Amin.

 

　　(4) Grout and place the central grouting base plate on the completed foundation. During construction, tools such as a level and spirit level should be used for precise measurement to ensure the horizontality of the central base plate, ensure that the center of the base plate is consistent with the installation axis, and ensure that the elevation of the top surface of the base plate is consistent with the installation elevation of the bottom surface of the steel column.

 

　　(5) When the strength of the grouting layer concrete reaches more than 75% of the design strength, the steel column is hoisted. The steel column can be hoisted directly, and only the foundation bolts need to be adjusted to level and align.

 

　　(6) Carry out secondary grouting using non-shrinkage concrete or micro-expansion concrete for secondary grouting.

 

 

　　Small deformation theory means that the change in geometric dimensions after structural deformation can be ignored, and the internal force calculation is still based on the dimensions before deformation! This deformation includes all deformations: tension, compression, bending, shear, torsion, and their combinations.

 

　　Small deflection theory considers that the displacement is very small, belonging to a geometrically linear problem. It can be approximated by a deflection curve equation to establish energy, derive the stability coefficient, and the deformation curvature can be approximated by y=1/ρ! Using Y to replace the curvature is used to analyze the small deflection theory of elastic rods.

 

　　It is not the same in a rigid rod with a spring. Also, using large deflection theory for analysis does not mean that the load can still increase after buckling. For example, for a cylindrical shell under compression, after buckling, it can only maintain stability under a lower load.

 

　　In short, the small deflection theory can only obtain the critical load and cannot judge the stability at or after the critical load. Large deflection theory can solve the post-buckling performance.

 

 

　　For many structures, the undeformed structure is often used as the calculation diagram for analysis, and the results obtained are sufficiently accurate. At this time, the relationship between deformation and load is linear, and this analysis method is called geometric linear analysis, also known as first-order analysis. For some structures, however, the deformed structure must be used as the basis for internal force analysis, otherwise the results will have large errors.

 

　　At this time, the relationship between deformation and load is non-linear analysis. This analysis method is called geometric nonlinear analysis, also known as second-order analysis. Using the deformed structure as the basis for calculation and considering the elastoplasticity of the material (material nonlinearity) to perform structural analysis is second-order elastoplastic analysis.

 

 

　　The Baoshengge effect is that after the material reaches plastic deformation, after unloading, there is an irreversible deformation left, which is plastic deformation. It is conceivable that this deformation has an impact on the structure!

 

 

　　Layered tearing of steel plates usually occurs when there is a large tensile stress in the plate thickness direction. In welded joints, shrinkage deformation occurs during weld cooling. If it is very thin or there is no constraint on the deformation, the steel plate will deform and release the stress. However, if the steel plate is very thick or has stiffeners and the constraints of adjacent components, the steel plate is constrained and cannot deform freely, resulting in a large stress in the direction perpendicular to the plate surface. In areas with strong constraints, the local stress caused by weld shrinkage may be several times the yield strength of the material, causing layered tearing of the steel plate.

 

 

　　Steel structures, especially welded structures, often have crack-like defects due to the quality and structural reasons of steel, processing and manufacturing, and welding. Brittle fracture is mostly caused by the development of these defects, leading to crack instability and expansion. When the crack slowly expands to a certain extent, the fracture expands at a very high speed, and it occurs suddenly without any warning before brittle fracture.