A reinforcing structure and method for a large-span industrial steel stair

Abstract

This invention provides a reinforcement structure and method for large-span industrial steel staircases. The reinforced structure includes multiple sets of prestressed V-shaped tie rods and multiple sets of angle steel compression rods distributed alternately on the bottom surface of the staircase and horizontal transition sections, forming a mesh steel support structure that creates a V-shaped tie rod-lateral compression rod support system. Reinforcing plates are installed on the lower flange and outer side of the web connecting the staircase and horizontal transition sections. An elastic diagonal bracing mechanism is installed between the horizontal transition section and the adjacent main frame structural columns. This invention integrates a prestressed V-shaped tie rod-lateral compression rod out-of-plane support system, a node domain composite reinforcement component, and an out-of-plane spatial elastic diagonal bracing subsystem to form a collaborative structural reinforcement system. Without significantly increasing the cross-sectional dimensions of the stair beams or the amount of steel used, it systematically solves the problems of deflection control, lateral stability, key node safety, and vibration comfort in large-span, unsupported industrial steel staircases through integrated construction measures.

Description

Technical Field

[0001] This invention relates to the field of industrial building steel structure technology, and in particular to a strengthening structure and method for improving the performance of large-span, super high-rise industrial steel staircase structures without intermediate vertical supports. Background Technology

[0002] In the core production framework of heavy industries such as cement, chemicals, and metallurgy, the dense arrangement of process equipment and pipelines often presents extreme design conditions for the steel staircases connecting different platforms: large single-level lifting height (often exceeding 20 meters), large horizontal span (exceeding 10 meters), and a strict prohibition on any vertical supports in the middle. Traditional design methods for these large-span industrial steel staircases typically involve increasing the cross-section of the stair beams or adopting a space truss system. Increasing the cross-section leads to a surge in steel consumption, and due to space constraints, the beam height often fails to meet stiffness requirements. The space truss system, on the other hand, suffers from complex nodes, difficult construction, inconvenient maintenance, and high costs. Therefore, there is an urgent need for an innovative structural solution that can economically and effectively improve the overall stiffness, stability, and vibration-induced comfort of large-span steel staircases under stringent geometric and process constraints. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a reinforced structure and method for large-span industrial steel staircases. Its purpose is to systematically solve the problems of deflection control, lateral stability, key node safety, and vibration comfort of large-span, unsupported industrial steel staircases through integrated construction measures without significantly increasing the cross-sectional dimensions of the stair beams and the amount of steel used.

[0004] To achieve the above objectives, the present invention provides a reinforced structure for a large-span industrial steel staircase, comprising two inclined stair sections and a horizontal transition section between the two stair sections. Both the stair sections and the horizontal transition section include two parallel channel steel main ladder beams. Stair treads are welded between the double channel steel main ladder beams of the stair section, and a horizontal walkway slab is welded between the double channel steel main ladder beams of the horizontal transition section. The reinforced structure includes a prestressed V-shaped tie rod-lateral compression rod support system, a node composite reinforcement component, and an elastic diagonal bracing mechanism. The prestressed V-shaped tie rod-lateral compression rod support system is distributed on the bottom surface of the stair sections and the horizontal transition section, including multiple sets of prestressed V-shaped tie rods and multiple angle steel compression rods connecting the lower flanges of the two parallel double channel steel main ladder beams. The multiple sets of prestressed V-shaped tie rods and multiple sets of angle steel compression rods are staggered to form a mesh steel support structure.

[0005] The node composite reinforcement component includes a lower flange reinforcement plate and an outer web reinforcement plate welded to the connection between the stair section and the horizontal transition section; the elastic bracing mechanism includes a bracing rod, a conversion beam and movable hinge supports at both ends, the conversion beam is fixedly connected to the bottom of the horizontal transition section, and the two ends of the bracing rod are respectively connected to the conversion beam and the main frame structural column of the adjacent industrial steel staircase through hinge supports.

[0006] The preferred technical solution of the present invention is as follows: the multiple sets of prestressed V-shaped tie rods are arranged longitudinally along the stair section and the horizontal transition section, with the two open ends and the tip of each set of prestressed V-shaped tie rods respectively connected to the lower flange of the double-channel steel main ladder beam; multiple angle steel compression rods are equidistantly distributed laterally between the two double-channel steel main ladder beams in the stair section and the horizontal transition section, and an angle steel compression rod is arranged at each end of the prestressed V-shaped tie rod. The prestressed V-shaped tie rods and angle steel compression rods are arranged alternately to form a network structure connected between the lower flanges of the double-channel steel main ladder beams.

[0007] The preferred technical solution of this invention: Each end of the prestressed V-shaped tie rod is connected to a connecting lug plate welded to the lower flange of the double-channel steel main ladder beam via friction-type high-strength bolts, and pretension is applied during installation. The prestress P of each V-shaped tie rod is... max ≤7.5kN.

[0008] The preferred technical solution of the present invention is as follows: the prestressed V-shaped tie rod-lateral compression rod support system, the node composite reinforcement component and the elastic diagonal bracing mechanism work together, the diagonal bracing rod adopts a circular steel pipe, and the elastic diagonal bracing mechanism controls the overall first-order vibration frequency of the large-span industrial steel staircase to be increased to above 4.0Hz.

[0009] The preferred technical solution of the present invention is as follows: the lower flange reinforcing plate and the web reinforcing plate are both connected to the double channel steel main ladder beam through bevel penetration welds; the lower flange reinforcing plate set at the connection between the horizontal transition section and the lower stair section is a diagonal bracing plate, and the two ends of the diagonal bracing plate are respectively welded to the bottom of the horizontal transition section and the lower stair section; the lower flange reinforcing plate set at the connection between the horizontal transition section and the upper stair section is an L-shaped plate, and the L-shaped plate wraps around the outer corner of the connection between the horizontal transition section and the lower stair section and is welded and fixed.

[0010] The preferred technical solution of the present invention is as follows: the diagonal bracing rod of the elastic diagonal bracing mechanism is a round tube diagonal bracing rod, and its installation inclination angle is controlled within the range of 35° to 55°; the conversion beam is connected to the horizontal transition section by welding; and the hinge support adopts a pin hinge structure.

[0011] The preferred technical solution of the present invention is as follows: the vertical elastic support provided by the elastic bracing mechanism directly transfers part of the platform load to the main frame structural column, effectively reducing the mid-span bending moment and deflection of the main stair beam; the horizontal component force generated by the elastic bracing mechanism through its oblique arrangement, together with the horizontal transition section, forms a constraint system to resist the longitudinal displacement of the staircase.

[0012] This invention also provides a method for strengthening a large-span industrial steel staircase. The method utilizes the aforementioned strengthening structure for large-span industrial steel staircases to reinforce them, specifically including the following steps:

[0013] S1. When prefabricating the double-channel steel main ladder beam in the factory, the connecting ear plate is pre-welded to the lower flange of the double-channel steel main ladder beam;

[0014] S2. Each stair section and the horizontal transition section include two parallel double-channel steel main stair beams. Stair treads are welded between the two double-channel steel main stair beams of the stair section, and horizontal walkway plates are welded between the two double-channel steel main stair beams of the horizontal transition section. After the steel staircase is assembled and welded, the lower flange reinforcing plate and the outer web reinforcing plate are welded at the connection between the stair section and the horizontal transition section to form a node composite reinforcement component.

[0015] S3. During on-site installation of the steel staircase, a prestressed V-shaped tie rod-transverse compression rod support system is installed, and prestress is applied to the longitudinal prestressed V-shaped tie rods; the maximum value P of the prestress in a single V-shaped tie rod. max It is subject to the dual constraints of the anti-slip bearing capacity of the friction surface of the connecting bolts and the bending bearing capacity of the weak axis of the ladder beam;

[0016] S4. On-site, a transition beam is welded to the bottom of the horizontal transition section, and diagonal bracing rods of the elastic diagonal bracing mechanism are installed. One end of the diagonal bracing rod is connected to the middle of the transition beam via a pin hinge support, and the other end is connected to the adjacent main frame structural column via a pin hinge support. The equivalent vertical support stiffness of the diagonal bracing rod is calculated between the connections. To determine the angle of inclination of the diagonal brace to the horizontal plane. Ensure that the fundamental frequency f0 of the staircase structure is greater than 4.0Hz, and the tilt angle is... The range is controlled between 35° and 55°;

[0017] S5. Inspect all connection points to ensure that the high-strength bolts reach the design torque value, and complete the reinforcement work on the steel staircase.

[0018] A further technical solution of the present invention: The calculation formula for the anti-slip bearing capacity of the friction surface of the connecting bolt in step S3 is as follows:

[0019] ;

[0020] ;

[0021] in, The anti-slip coefficient of the connecting bolts is taken as 0.45; P 栓 Prestress for connecting bolts;

[0022] n is the number of connecting bolts; K is the safety factor for bolt slippage, K=1.2;

[0023] The formula for calculating the weak axis bending capacity [M] of a single ladder beam in step S3 is as follows:

[0024]

[0025]

[0026] Among them, K m For the bending safety factor, K m =1.2; M u Ultimate bending capacity of a single channel steel bar along its weak axis;

[0027] f is the design value of the flexural bearing capacity of the steel in the ladder beam; W y The bending modulus of the weak axis of the ladder beam;

[0028] The maximum allowable clamping force F of the ladder beam can be deduced from the allowable bending moment; the ladder beam subjected to bending along its weak axis is a simply supported beam with a concentrated load at mid-span, and the bending moment formula is as follows: , transform into ,

[0029] in, The distance between two adjacent V-shaped nodes;

[0030] The clamping force F is equal to the sum of the lateral components of the two legs of the V-shaped tie rod; therefore: F = 2P max ×sinβ;

[0031]

[0032] Where β is the angle between the prestressed V-shaped brace and the ladder beam.

[0033] A further technical solution of the present invention: the equivalent vertical support stiffness of the diagonal brace in step S4. The calculation formula is as follows:

[0034] Where L is the length of the diagonal brace; A is the cross-sectional area of ​​the diagonal brace; and E is the elastic modulus of the diagonal brace material. The angle between the diagonal brace and the horizontal plane;

[0035] The formula for calculating the fundamental frequency f0 of a staircase structure is as follows:

[0036] ;

[0037] ;

[0038] K 弯 is the bending stiffness of the main ladder beam; m is the equivalent mass of the structure.

[0039] This invention employs a prestressed V-shaped tie rod-lateral compression rod support system between the lower flanges of two parallel channel steel main ladder beams to enhance the overall collaborative performance and lateral stiffness of the two beams. At the connection area between the stair section and the horizontal transition section (i.e., the geometric abrupt change where the ladder beams bend horizontally to form a platform beam), a nodal domain composite reinforcement component is installed to locally strengthen this stress concentration and fatigue area. Below the horizontal transition, a transfer beam is installed; this beam is welded across the lower flanges of the two channel steel ladder beams (located at the horizontal transition) to collect the load of the two beams and is connected to the adjacent main frame column via an elastic diagonal bracing mechanism. This forms a clear force transmission path of "double main ladder beams → transfer beam → spatial diagonal bracing → main frame column," thus providing effective multi-directional elastic constraints and mid-span additional support for the ladder beam system.

[0040] The prestressed V-shaped tie rod-lateral compression rod support system of this invention mainly consists of longitudinally arranged V-shaped prestressed angle steel tie rods and laterally arranged angle steel compression rods, which together provide out-of-plane support for the ladder beams. The two ends of the V-shaped tie rods are tensioned to the ear plates welded to the lower flange of the ladder beams by high-strength bolts to coordinate the vertical deformation of the two beams; the lateral compression rods directly restrict the lateral relative displacement between the two ladder beams. The two work together to significantly improve the out-of-plane lateral stiffness, torsional stiffness and overall stability of the structural system. The composite reinforcement component of the node region mainly consists of a lower flange reinforcing plate and an outer web reinforcing plate welded to the horizontal transition section connection. These reinforcing plates are reliably connected to the base material through bevel penetration welds, aiming to optimize the stress transfer path of the bending node and reduce stress concentration, thereby significantly improving the fatigue resistance and static bearing capacity of the node. The aforementioned elastic bracing mechanism has a dual core function: firstly, as a vertical elastic support, it transfers part of the platform load to the frame columns, thereby optimizing the stress mode of the main stair beam from simply supported to continuous, significantly reducing its mid-span bending moment and deflection; secondly, its diagonal arrangement forms a longitudinal constraint projected onto the horizontal plane, which, in conjunction with the lateral constraint provided by the prestressed V-shaped tie rod-lateral compression rod out-of-plane support system, effectively suppresses the longitudinal and lateral swaying of long stair sections. These static and dynamic improvements collectively enhance the overall structural fundamental frequency, preventing it from reaching pedestrian-sensitive frequency bands, thus fundamentally improving the vibration comfort of the staircase.

[0041] The beneficial effects of this invention compared to the prior art are as follows:

[0042] 1. This invention improves the structural synergy performance: This invention uses a prestressed V-shaped tie rod-lateral compression rod out-of-plane support system to tightly combine two independent main ladder beams into a whole, which significantly improves the lateral stiffness, torsional stability and load distribution uniformity of the structure, and effectively suppresses out-of-plane swaying of the steel ladder during use.

[0043] 2. This invention strengthens weak areas at nodes: The node domain composite reinforcement component in this invention locally strengthens the weak links at the horizontal "fold" connection of the ladder beam, improves the stress state in the area, reduces stress concentration, enhances the fatigue resistance of the node, and extends the service life of the structure.

[0044] 3. The present invention optimizes the stress mode of the ladder beam: The out-of-plane spatial elastic bracing subsystem in the present invention uses non-coplanar frame columns to provide elastic intermediate support, optimizing the stress mode of the main ladder beam from an unfavorable simply supported system to a continuous stress system, effectively reducing the mid-span bending moment and deflection, and resolving the structural contradiction between large span and low beam height; at the same time, it suppresses the longitudinal sway of the long ladder segment and improves vibration comfort.

[0045] 4. This invention is both economical and practical: This invention uses conventional Q235B material and a smaller cross-sectional size to achieve structural performance superior to traditional large-section schemes; the components can be prefabricated in the factory and assembled on site, saving steel consumption, reducing costs, and facilitating construction, thus meeting the needs of large-scale construction of industrial buildings.

[0046] This invention integrates a prestressed V-shaped tie rod-lateral compression rod out-of-plane support system, a node domain composite reinforcement component, and an out-of-plane spatial elastic diagonal brace subsystem to form a collaborative structural reinforcement system. Without significantly increasing the cross-sectional dimensions of the stair beams and the amount of steel used, it systematically solves the problems of deflection control, lateral stability, key node safety, and vibration comfort of large-span, unsupported industrial steel staircases through integrated construction measures. Attached Figure Description

[0047] Figure 1 This is a three-dimensional schematic diagram of the overall structure of the present invention;

[0048] Figure 2 This is a schematic diagram of the overall structural side elevation of the present invention;

[0049] Figures 3 to 5 These are three-dimensional schematic diagrams of different states of the present invention;

[0050] Figure 6 This is a schematic plan view of the prestressed V-shaped tie rod-transverse compression rod out-of-plane support system in this invention;

[0051] Figure 7 for Figure 6 Enlarged diagram of section A in the middle;

[0052] Figure 8 for Figure 7 Enlarged view of the elevation of Section B;

[0053] Figure 9 This is an enlarged schematic diagram of the elevation structure of the node domain composite reinforcement component in this invention;

[0054] Figure 10 This is a schematic diagram of the overall out-of-plane space elastic diagonal bracing subsystem in this invention;

[0055] Figure 11 This is an enlarged schematic diagram of a partial elevation structure of the out-of-plane spatial elastic diagonal bracing subsystem in this invention;

[0056] Figure 12 This is a schematic diagram of the force distribution of the prestressed V-shaped tie rod-transverse compression rod support system in this invention;

[0057] Figure 13 This is a simplified calculation diagram of the steel ladder in an embodiment of the present invention.

[0058] In the diagram: 1-Staircase section; 2-Prestressed V-type tie rod-lateral compression member support system; 201-Prestressed V-type tie rod; 202-lateral compression member; 203-High-strength bolt; 204-Connecting ear plate; 3-Node composite reinforcement component; 301-Lower flange reinforcement plate; 302-Web reinforcement plate; 303-Bevel penetration weld; 4-Horizontal transition section; 5-Elastic diagonal bracing mechanism; 501-Diagonal brace; 502-Hinged support; 503-Transfer beam; 6-Main frame structural column. Detailed Implementation

[0059] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0060] This embodiment provides a reinforcement structure for a large-span industrial steel staircase, applied to a steel staircase with a horizontal projection span of 12.7 meters and a single-story lifting height of 26 meters within the preheater frame of a cement plant. A horizontal transition section 4 is provided between adjacent staircase sections 1 and 4. Both staircase section 1 and horizontal transition section 4 include two parallel double-channel steel main stair beams. The double-channel steel main stair beams are made of hot-rolled channel steel [28a] and bear the main vertical load. Stair treads are welded between the double-channel steel main stair beams of staircase section 1, and horizontal walkway slabs are welded between the double-channel steel main stair beams of horizontal transition section 4. The reinforcement structure includes a prestressed V-shaped tie rod-lateral compression rod support system 2, a node composite reinforcement component 3, and an elastic diagonal bracing mechanism 5. The prestressed V-shaped tie rod-lateral compression rod support system 2 is distributed at the bottom of staircase section 1 and horizontal transition section 4. The structure includes multiple sets of prestressed V-shaped tie rods 201 and multiple angle steel compression rods 202 connecting the lower flanges of two parallel double-channel steel main ladder beams. The multiple sets of prestressed V-shaped tie rods 201 are arranged longitudinally along the stair section 1 and the horizontal transition section 4, with the two open ends and the tip of each set of prestressed V-shaped tie rods 201 connected to the lower flange of the double-channel steel main ladder beams, respectively. The multiple angle steel compression rods 202 are equidistantly distributed laterally between the two double-channel steel main ladder beams of the stair section 1 and the horizontal transition section 4, with one angle steel compression rod 202 provided at each end of the prestressed V-shaped tie rods 201. The prestressed V-shaped tie rods 201 and the angle steel compression rods 202 are arranged alternately to form a stable grid. The V-shaped tie rods 201 are longitudinal prestressed angle steel tie rods (L70×5), and the angle steel compression rods 202 are transverse angle steel compression rods (L70×5). The V-shaped tie rod 201 and the angle steel compression rod 202 are connected at both ends to the connecting lug plate 204 welded to the lower flange of the main beam by 8.8 grade M16 friction type high-strength bolts 203. During installation, the V-shaped tie rod is prestressed at one end P. max ≤7.5kN, to eliminate connection gaps and establish an initial cooperative working mechanism. The bolt holes on the connecting lug 204 are designed in an elliptical shape for easy fine-tuning during on-site installation. This subsystem is crucial for ensuring the coordinated operation of the two beams and resisting lateral forces and torques.

[0061] In the embodiments, such as Figures 1 to 5 and Figure 9As shown, the node composite reinforcement component 3 includes a lower flange reinforcement plate 301 and a web outer reinforcement plate 302 welded to the connection between the stair section 1 and the horizontal transition section 4. The lower flange reinforcement plate 301 is made of 12×120mm steel plate, and the web outer reinforcement plate 302 is made of 10×100mm steel plate. All reinforcement plates are connected by bevel penetration welds 303 using CO2 gas shielded welding to ensure that they work together with the base material and effectively disperse stress concentration at complex nodes. The lower flange reinforcement plate 301 and the web reinforcement plate 302 are both connected to the double channel steel main ladder beam through bevel penetration welds 303. The lower flange reinforcement plate 301 set at the connection between the horizontal transition section 4 and the stair section 1 below it is a diagonal brace plate, with both ends of the diagonal brace plate welded to the bottom of the horizontal transition section 4 and the lower stair section, respectively. The lower flange reinforcement plate 301 set at the connection between the horizontal transition section 4 and the stair section 1 above it is an L-shaped plate, which wraps around the outer corner of the connection between the horizontal transition section 4 and the lower stair section and is welded and fixed.

[0062] In the embodiments, such as Figures 1 to 5 and Figure 11 As shown, the elastic bracing mechanism 5 includes a bracing rod 501, a transition beam 503, and movable hinge supports 502 at both ends. The transition beam 503 is fixedly connected to the lower part of the horizontal transition section 4. The two ends of the bracing rod 501 are connected to the transition beam 503 and the main frame structural column 6 adjacent to the industrial steel staircase via the hinge supports 502, respectively. The bracing rod 501 of the elastic bracing mechanism 5 is a Φ140×5.0 round tube bracing rod, and its installation inclination angle is controlled within the range of 35° to 55°. The transition beam 503 is connected to the horizontal transition section 4 by welding. The hinge supports 502 adopt a pin hinge structure. The vertical elastic support provided by the elastic bracing mechanism 5 directly transfers part of the platform load to the main frame structural column 6, effectively reducing the mid-span bending moment and deflection of the main stair beam. The horizontal component force generated by the inclined arrangement of the elastic bracing mechanism 5, together with the horizontal transition section 4, forms a constraint system to resist the longitudinal displacement of the staircase. The prestressed V-shaped tie rod-lateral compression rod support system 2, the node composite reinforcement component 3, and the elastic diagonal bracing mechanism 5 work together. The diagonal bracing rod 501 is made of circular steel pipe, and the elastic diagonal bracing mechanism 5 controls the overall first-order vibration frequency of the large-span industrial steel staircase to be increased to above 4.0Hz.

[0063] The elastic bracing mechanism 5 in the embodiment has a dual core function:

[0064] Firstly (vertical action): As an elastic vertical support, its equivalent stiffness K v The axial stiffness, length, and inclination angle of the diagonal brace determine (K) v ≈(EA / L)*sin²θ). This transfers part of the platform load to the frame columns, providing intermediate support for the main ladder beam, and significantly reducing the mid-span bending moment and deflection.

[0065] Secondly (longitudinal effect): The longitudinal force constraint provided by the projection of the diagonal brace onto the horizontal plane, together with the platform beam, resists the longitudinal displacement of the staircase, effectively suppressing low-frequency swaying of long stair sections. This effect, in conjunction with the vertical support, raises the structural fundamental frequency to above 4.0Hz, significantly improving vibration comfort.

[0066] In this embodiment, to ensure the optimal balance between the structural performance, economy, and construction feasibility of each subsystem, the following design parameter optimization methods were formulated for the core structural measures before construction and installation, providing a basis for subsequent component calculations:

[0067] 1. Determination of prestressed V-shaped tie rod pretension: The pretension value of the prestressed V-shaped tie rod is determined through theoretical calculation and finite element verification. The core objective is to ensure that the deformation of the two beams is coordinated under load, meet the requirements of collaborative work and overall stiffness, and provide a basis for the selection of tie rod prestress value.

[0068] 2. Node reinforcement plate size design: The size of the node reinforcement plate is determined based on the size of the stress concentration area at the horizontal "fold" connection. Through local finite element analysis or experimental verification, the stress is ensured to be smoothly transferred, stress abrupt changes are avoided, and the performance of weak areas of the node is strengthened.

[0069] 3. Optimization of diagonal bracing system parameters: The key stiffness parameters of the diagonal bracing system are optimized using the following formulas to ensure that the diagonal bracing plays an effective supporting role:

[0070] Equivalent vertical support stiffness:

[0071] Longitudinal constraint stiffness:

[0072] In the formula, E is the elastic modulus of the bracing material, A is the cross-sectional area of ​​the bracing, L is the length of the bracing, and θ is the angle of inclination between the bracing and the horizontal plane.

[0073] The embodiment analyzes and calculates the prestressed V-shaped tie rod to determine the maximum prestress P of a single V-shaped tie rod during the maximum installation process. max。

[0074] The structural form of continuous prestressed V-shaped tie rods + transverse compression members between the tie rods between the lower flanges of the ladder beam is as follows: Figure 12 As shown, the core purpose is to ensure that the two beams work together to provide out-of-plane horizontal support; the transverse compression bar generates a clamping force F on the ladder beam, which causes the ladder beam to bend around the weak axis (y-axis). The force calculation length is the distance between two adjacent V-shaped nodes. The ladder beam resists this bending moment by relying on its own weak axis bending bearing capacity.

[0075] The core constraints for calculation are: 8.8 grade M16 friction type high-strength bolts, single-sided slip surface, and prestress continuously transferred to the support along the axial direction of the tie rod; the prestress value is determined by the dual constraints of the anti-slip bearing capacity of the single-sided friction surface of the bolt and the bending bearing capacity of the weak axis of the ladder beam, and the stability of the transverse compression member and the strength of the V-shaped tie rod are checked simultaneously; the calculation is based on the "Steel Structure Design Standard" GB 50017-2017, and the units are uniformly mm, N, and N / mm², with engineering values ​​expressed in kN.

[0076] V-shaped tie rod analysis and calculation core design parameter table

[0077]

[0078] Step 1: Ensure the maximum prestress P on the bolt friction surface is sufficient to resist slippage. max calculate

[0079] The minimum prestress is determined by the anti-slip bearing capacity of the single-sided friction surface of the M16 friction-type high-strength bolt. The control condition is to ensure that the prestress is continuously transmitted to the support along the tie rod axis without slippage.

[0080] Standard formula for anti-slip bearing capacity: F slip =n×μ×P 栓

[0081] Substituting n=1, μ=0.45, P 栓 =80kN F slip =1×0.45×80=36kN

[0082] Introducing an anti-slip safety factor K=1.2, then: P max ≤F slip / K=36 / 1.2=30kN

[0083] Conclusion: V-shaped tie rod single-limb prestressing P is required max A torque of ≤30kN is required to ensure that there is no slippage on the bolt friction surface.

[0084] Step 2: Ensure the maximum prestress P meets the bending capacity of the weak axis of the ladder beam. max calculate

[0085] The maximum prestress is inversely derived from the bending capacity of the simply supported ladder beam with weak axis. The core logic is: the tightening force F = the sum of the transverse components of the V-shaped tie rod. The tightening force F generates a mid-span bending moment, which must not exceed the bending capacity of the ladder beam with weak axis [M] (including the safety factor).

[0086] 1) Calculation of the ultimate bending capacity of a single [28a channel steel along the weak axis (y-axis)

[0087] M u =f×W y Substituting f=215N / mm 2(Q235B material), W y =35700mm 3 ;

[0088] M u =215×35700=7675500N·mm=7.6755kN·m

[0089] 2) Maximum allowable mid-span bending moment for a single ladder beam (including bending safety factor K) m =1.2)

[0090] [M]=M u / K m =7.6755 / 1.2=6.396kN·m

[0091] 3) The maximum allowable clamping force of the ladder beam is derived from the allowable bending moment.

[0092] The ladder beam subjected to bending along its weak axis is a simply supported beam with a concentrated load at mid-span. The bending moment formula is:

[0093] , transform into Substituting [M] = 6.396 kN·m and l0 = 2400 mm, we get: F = 4 × 6.396 × 10 6 / 2400=10.66kN

[0094] 4) The maximum prestress of a single V-shaped tie rod is determined by the counter-tightening force F.

[0095] The clamping force F is equal to the sum of the lateral components of the forces in both legs of the V-shaped tie rod, that is:

[0096] F=2P max ×sinβ, sinβ=sin45°=0.707, transforming to get: P max =F / (2sin45°)=10.66 / 1.414=7.5kN

[0097] Conclusion: V-shaped tie rod single-limb prestressing P is required max Only ≤7.5kN can guarantee the bending capacity requirement of the weak axis of the ladder beam.

[0098] Step 3: Verification of the axial tensile strength of a single leg of the V-shaped tie rod

[0099] Take the maximum prestress P of the ladder beam for bending control max =7.5kN, verify the axial tensile strength of the L70×5 tie rod.

[0100] Calculation of tensile stress at the axis of the tie rod: σ 杆 =P max / A 拉 Substitute P max =7.5×103 N、

[0101] A 拉 =688mm 2 σ 杆 =7.5×10 3 / 688=11N / mm 2 <f=215N / mm 2

[0102] Conclusion: The tie rod has sufficient strength reserve and there is no risk of breakage.

[0103] Step 4: Calculation of axial compressive stability of the transverse compression bar

[0104] The transverse compression member bears the superposition of the transverse components of the two V-shaped tie members, and the total compressive load is...

[0105] F = 2 × P max ×sin45°, substitute into P max =7.5×10 3 N, F = 2 × 7.5 × 10 3 ×0.707=11kN

[0106] 1) Calculation of slenderness ratio of transverse compression members

[0107] Take the length of the transverse compression bar as the calculation length i y =13.9mm

[0108] λ = 1.0 × 1697 / 13.9 = 122 < [λ] = 200, which meets the specification requirements for slenderness ratio.

[0109] 2) Overall stability stress calculation

[0110] Stability coefficient ψ selection: The diagonal brace is a single angle steel, belonging to the a-class section. According to Appendix D, Table D.0.1 of GB 50017-2017, when λ=122, ψ≈0.481.

[0111] Substitute the values: ;

[0112] Conclusion: The overall stability stress of the transverse compression member meets the specifications and there is no risk of instability.

[0113] Combining the dual constraints, the upper limit of prestress P is controlled by the weak axis flexural bearing capacity of the ladder beam. max ≤7.5kN, this value is lower than the maximum value after anti-slip correction (P max =30kN), taking the value according to the most unfavorable working condition, determine the prestress P of a single leg of the V-shaped tie rod. max With a strength of ≤7.5kN, it can simultaneously meet the requirements for bending resistance of ladder beams, stability of lateral compression members, and strength of tie rods.

[0114] In this embodiment, the diagonal brace is a seamless circular tube with a diameter of Φ140×5.0. Therefore, the supporting force of this core component is calculated, and all parameters are consistent with the patent design. The load and geometric dimensions are taken according to the actual engineering values. The units are uniformly mm, N, and N / mm², and the stiffness results are converted to kN / m to adapt to engineering applications. The strength, stability, stiffness and structural vibration comfort of the core verification diagonal brace are calculated to ensure that the design requirements of industrial steel staircases are met.

[0115] Core design parameter table for stress calculation of diagonal brace

[0116]

[0117] The simplified calculation diagram of the steel ladder is shown in Figure 13. First, calculate the mechanical parameters of the circular tube section of the diagonal brace; then calculate the core parameters according to the geometric formula of the seamless circular tube section. Among them, the outer diameter D = 140mm, the wall thickness t = 5mm, and the inner diameter d = D - 2t = 140 - 2 × 5 = 130mm.

[0118] Cross-sectional area: A = π(D) 2 -d 2 ) / 4=π(140 2 -130 2 ) / 4=2119mm 2

[0119] The radius of gyration *i* of the circular tube cross-section is calculated using the precise formula specified in the standard:

[0120]

[0121] Verification of the strength, stability, and stiffness of the diagonal brace:

[0122] (1) Calculation of axial pressure of diagonal bracing; the diagonal bracing is an elastic intermediate support that bears the vertical component of the total design load of the rest platform. The total axial force is derived from the vertical component combined with the inclination angle. The diagonal bracing only bears the axial force and has no bending moment (hinged support at both ends).

[0123] The vertical component N borne by the diagonal brace v =ηP, where η=0.7 is the load sharing ratio. Substituting the value: N v =0.7×80×10 3 =5.6×10 4 N

[0124] Where, P = (0.9 + 6.223 + 1.2 + 6.223 + 0.9) × 1.2 × (1.3 × 2 + 1.5 × 4) / 2 = 80 kN. (The load-bearing area is considered based on the inclined length of the steel ladder.)

[0125] The total axial force N under the compression along the axis of the diagonal brace. Based on the force balance relationship between the vertical component and the angle of inclination, the axial compressive force is the reciprocal of the sine of the vertical component: N = N0 v / sinθ, look up the trigonometric function table: sin40°=0.6428, substitute the value: N=5.6×10 4 / 0.6428=87118N

[0126] (2) Strength verification; According to Clause 7.1.1 of GB 50017-2017, the strength verification of axially compressed members shall be calculated using the net cross-section, and the verification formula is: σ=N / A≤f

[0127] σ = N / A = 87118 / 2119 = 41.1 N / mm 2 < 215N / mm 2

[0128] The axial compressive strength of the diagonal brace meets the specifications and has sufficient strength reserve.

[0129] (3) Stiffness (slenderness ratio λ) verification; According to Clause 7.2.2 of GB 50017-2017, the stiffness control index of axially compressed members is the slenderness ratio λ, and the verification formula is: λ=μL2 / i

[0130] Substituting the values, μ=1.0, L2=8288mm, i=47.9mm

[0131] λ=1.0×8288 / 47.9=173<[λ]=200

[0132] The slenderness ratio of the diagonal brace meets the specification limit requirements, and the stiffness reserve is sufficient.

[0133] (4) Overall stability verification; According to Clause 7.2.1 of GB 50017-2017, the overall stability of axially compressed members is the core control index, and the verification formula is as follows: ;

[0134] Stability coefficient ψ selection: The diagonal brace is a circular tube section, belonging to the b type section. According to Appendix D, Table D.0.2 of GB 50017-2017, when λ=173, ψ≈0.241.

[0135] Substitute the values:

[0136] The overall stability stress of the diagonal brace meets the specifications and there is no risk of instability.

[0137] (5) Vibration comfort verification

[0138] Core objective: To verify that after adding diagonal bracing, the fundamental frequency of the structure avoids the pedestrian-sensitive frequency band (2.0~4.0Hz), meets the vibration comfort requirements of industrial steel stairs, and compares the two working conditions of no support and with support.

[0139] The unsupported core stiffness is determined solely by the pure bending stiffness of the two [28a] channel steel main ladder beams. When supported, the effective vertical stiffness is superimposed by Φ140×5.0 diagonal bracing. The entire process uses the International System of Units (m, N, Pa, kg), and the elastic modulus E = 2.06 × 10⁻⁶. 11 Pa, gravitational acceleration g = 9.8 m / s² 2 Core formula:

[0140] Bending stiffness of a bending member: K 弯 =48EI x / L 3

[0141] Axial stiffness of the diagonal brace: K 斜撑轴 =EA / L

[0142] Vertical effective stiffness of diagonal brace: K 斜撑竖 ≈K 斜撑轴 ×sin 2 θ

[0143] Structural fundamental frequency (core of vibration comfort): ;

[0144] The sensitive frequency band for pedestrians on industrial steel staircases is 2.0~4.0Hz. The design requirement is that the fundamental frequency is >4.0Hz to meet vibration comfort standards.

[0145] Mechanical parameters of standard cross-section of core components

[0146]

[0147] Calculation of total structural stiffness without support ( ),L 斜 =15446mm

[0148]

[0149] Calculation of total structural stiffness with supports (K) 有 =Bending stiffness of double beams + effective vertical stiffness of diagonal braces)

[0150] (1) Axial stiffness of a single diagonal brace

[0151]

[0152] (2) Vertical effective stiffness of the diagonal brace (θ=40°, sin 2 θ=sin 2 40° = 0.413

[0153]

[0154] (3) Total stiffness when supported

[0155] K 有 =K 无 +K 斜撑竖 Substitute the values:

[0156]

[0157] Structural equivalent mass m: The vibration equivalent mass is calculated according to the requirements of the "Code for Design of Building Structures" GB 50009-2012, taking the standard value of dead load + 0.5 times the standard value of live load, which is consistent with the heavy vibration condition of industrial steel staircases.

[0158] Vibration equivalent load G 振 =L 斜 ×b×(g k +0.5q k Substituting the number into 2, we get:

[0159] G 振 = (0.9+6.223+1.2+6.223+0.9)×1.2×(2+0.5×4) / 2=37kN

[0160] From G=mg, we get: m=G 振 / g=37×1000 / 9.8=3775kg

[0161] Accurate calculation of fundamental frequency with and without support (verification of vibration comfort)

[0162] The sensitive frequency band of the pedestrian industrial steel staircase is 2.0–4.0 Hz. When the fundamental frequency is >4.0 Hz, the vibration comfort requirements are met. The fundamental frequency is calculated by substituting the total stiffness into the values ​​for both unsupported and supported sections:

[0163] (1) Unsupported fundamental frequency f0

[0164]

[0165] Results analysis: Without support, the fundamental frequency is only 1.2Hz, which is far below the lower limit of the pedestrian sensitive frequency band (2.0Hz). The structure will produce a large low-frequency resonance, which not only results in extremely poor vibration comfort, but also leads to long-term fatigue of the stair beams and joints, posing a serious structural safety risk. It completely fails to meet the design and use requirements of industrial steel stairs.

[0166] (2) With support, the fundamental frequency f1

[0167] f1= =12.1Hz

[0168] Results analysis: After adding Φ140×5.0 diagonal bracing, the fundamental frequency of the structure was raised to 12.1Hz, which is much greater than 4.0Hz. This completely avoids the sensitive frequency band for pedestrians, and the vertical vibration amplitude of the structure is extremely small. This meets the vibration comfort requirements of industrial steel staircases under heavy working conditions. At the same time, it significantly reduces the risk of structural fatigue and ensures long-term safety.

[0169] Calculation conclusion of the diagonal bracing: The specifications and design parameters of the Φ140×5.0 circular tube diagonal bracing are suitable for the large-span industrial steel staircase structure system of this invention; its strength, stability and stiffness all meet the requirements of GB 50017-2017 standard. After the addition, the fundamental frequency of the structure can be significantly improved, and the vibration comfort requirements can be met without increasing the cross-sectional size of the stair beam.

[0170] The installation method of the reinforcement structure of the large-span industrial steel staircase in the embodiment includes the following steps:

[0171] Step 1: Prefabricate the double-channel steel main ladder beam in the factory, and pre-weld the connecting lugs with elliptical bolt holes to the lower flange of the double-channel steel main ladder beam;

[0172] Step 2: At the connection between the stair section and the horizontal transition section, use carbon dioxide gas shielded welding to perform bevel penetration welding, and then weld the lower flange reinforcing plate and the outer web reinforcing plate.

[0173] Step 3: Hoist the double-channel steel main ladder beam into place on site; apply 5kN pretension to the longitudinally arranged prestressed V-shaped tie rods using a torque wrench, and fasten the tie rods to the connecting ear plates using friction-type high-strength bolts;

[0174] Step 4: Install the transverse angle steel compression members, staggering them with the longitudinal V-shaped tie rods to form the out-of-plane support system of the ladder beam;

[0175] Step 5: Install the transition beam and weld it to the double-channel steel ladder beam of the horizontal transition section;

[0176] Step 6: Install the round tube diagonal brace. Its upper end is connected to the conversion beam through a movable hinge support, and its lower end is connected to the main frame column through a hinge support. The installation inclination angle of the diagonal brace is controlled within the range of 35° to 55°.

[0177] Step 7: Inspect all connection points to ensure that the high-strength bolts reach the designed torque value, and complete the installation.

[0178] The working principle of this invention is a synergistic dynamic process: under load, the prestressed V-shaped tie rod-lateral compression member out-of-plane support system first takes effect, ensuring the coordinated operation of the two stair beams and effectively resisting lateral deformation; the nodal domain composite reinforcement component ensures the safe transmission and redistribution of internal forces at key connection nodes; and the elastic diagonal bracing mechanism simultaneously performs the dual functions of vertical unloading and longitudinal support, fundamentally optimizing the static and dynamic response of the structural system. The integration of these three components ultimately achieves the high-performance design goal of ultra-high, large-span, center-support-free industrial steel staircases in a lightweight and economical manner.

Claims

1. A reinforced structure for a large-span industrial steel staircase, comprising two inclined stair sections (1) and a horizontal transition section (4) between the two stair sections (1), wherein both the stair section (1) and the horizontal transition section (4) include two parallel double-channel steel main ladder beams, stair treads are welded between the double-channel steel main ladder beams of the stair section (1), and a horizontal walkway slab is welded between the double-channel steel main ladder beams of the horizontal transition section (4), characterized in that: The strengthening structure includes a prestressed V-shaped tie rod-lateral compression rod support system (2), a node composite reinforcement component (3), and an elastic diagonal bracing mechanism (5). The prestressed V-shaped tie rod-lateral compression rod support system (2) is distributed on the bottom surface of the stair section (1) and the horizontal transition section (4), including multiple sets of prestressed V-shaped tie rods (201) and multiple angle steel compression rods (202) connecting the lower flanges of two parallel double-channel steel main ladder beams. The multiple sets of prestressed V-shaped tie rods (201) and multiple sets of angle steel compression rods (202) are staggered to form a mesh steel support structure. The node composite reinforcement component (3) includes a lower flange reinforcement plate (301) and a web outer reinforcement plate (302) welded to the connection between the stair section (1) and the horizontal transition section (4). The elastic bracing mechanism (5) includes a bracing rod (501), a conversion beam (503), and movable hinge supports (502) at both ends. The conversion beam (503) is fixedly connected to the bottom of the horizontal transition section (4). The two ends of the bracing rod (501) are connected to the conversion beam (503) and the main frame structure column (6) of the adjacent industrial steel staircase through the hinge supports (502).

2. The reinforcing structure of a large-span industrial steel staircase according to claim 1, characterized in that: The multiple sets of prestressed V-shaped tie rods (201) are arranged longitudinally along the stair section (1) and the horizontal transition section (4), with the two open ends and the tip of each set of prestressed V-shaped tie rods (201) connected to the lower flange of the double channel steel main ladder beam respectively; multiple angle steel compression rods (202) are equidistantly distributed laterally between the two double channel steel main ladder beams of the stair section (1) and the horizontal transition section (4), and an angle steel compression rod (202) is arranged at each end of the prestressed V-shaped tie rod (201). The prestressed V-shaped tie rods (201) and the angle steel compression rods (202) are arranged alternately to form a network structure connected between the lower flanges of the double channel steel main ladder beam.

3. The reinforcing structure of a large-span industrial steel staircase according to claim 1 or 2, characterized in that: Each end of the prestressed V-shaped tie rod (201) is connected to the connecting lug (204) welded to the lower flange of the double-channel steel main ladder beam by friction-type high-strength bolts (203), and pretension is applied during installation. The V-shaped tie rod is prestressed on a single leg. P max ≤7.5kN.

4. The reinforcing structure of a large-span industrial steel staircase according to claim 1 or 2, characterized in that: The prestressed V-shaped tie rod-lateral compression rod support system (2), the node composite reinforcement component (3) and the elastic diagonal bracing mechanism (5) work together. The diagonal bracing rod (501) is made of circular steel pipe. The elastic diagonal bracing mechanism (5) controls the overall first-order vibration frequency of the large-span industrial steel staircase to be increased to above 4.0Hz.

5. The reinforcing structure of a large-span industrial steel staircase according to claim 1 or 2, characterized in that: The lower flange reinforcing plate (301) and the web plate reinforcing plate (302) are both connected to the double channel steel main ladder beam through a bevel penetration weld (303); the lower flange reinforcing plate (301) set at the connection between the horizontal transition section (4) and the lower stair section (1) is a bracing plate, and the two ends of the bracing plate are welded to the bottom of the horizontal transition section (4) and the lower stair section respectively; the lower flange reinforcing plate (301) set at the connection between the horizontal transition section (4) and the upper stair section (1) is an L-shaped plate, and the L-shaped plate wraps around the outer corner of the connection between the horizontal transition section (4) and the lower stair section and is welded and fixed.

6. The reinforcing structure of a large-span industrial steel staircase according to claim 1 or 2, characterized in that: The diagonal bracing rod (501) of the elastic diagonal bracing mechanism (5) is a round tube diagonal bracing rod, and its installation tilt angle is controlled within the range of 35° to 55°. The conversion beam (503) is connected to the horizontal transition section (4) by welding. The hinge support (502) adopts a pin hinge structure.

7. The reinforcing structure of a large-span industrial steel staircase according to claim 1 or 2, characterized in that: The vertical elastic support provided by the elastic bracing mechanism (5) directly transfers part of the platform load to the main frame structural column (6), effectively reducing the mid-span bending moment and deflection of the main stair beam; the horizontal component force generated by the elastic bracing mechanism (5) through its oblique arrangement, together with the horizontal transition section (4), forms a constraint system to resist the longitudinal displacement of the staircase.

8. A method for strengthening a large-span industrial steel staircase, characterized in that: Strengthening a large-span industrial steel staircase using the reinforcing structure described in any one of claims 1 to 7 specifically includes the following steps: S1. When prefabricating the double-channel steel main ladder beam in the factory, the connecting ear plate is pre-welded to the lower flange of the double-channel steel main ladder beam; S2. Each stair section and the horizontal transition section include two parallel double-channel steel main stair beams. Stair treads are welded between the two double-channel steel main stair beams of the stair section, and horizontal walkway plates are welded between the two double-channel steel main stair beams of the horizontal transition section. After the steel staircase is assembled and welded, the lower flange reinforcing plate and the outer web reinforcing plate are welded at the connection between the stair section and the horizontal transition section to form a node composite reinforcement component. S3. During on-site installation of the steel staircase, a prestressed V-shaped tie rod-transverse compression rod support system is installed, and prestress is applied to the longitudinal prestressed V-shaped tie rods; the maximum value of the prestress in a single V-shaped tie rod. P max It is subject to the dual constraints of the anti-slip bearing capacity of the friction surface of the connecting bolts and the bending bearing capacity of the weak axis of the ladder beam; S4. On-site, a transition beam is welded to the bottom of the horizontal transition section, and diagonal bracing rods of the elastic diagonal bracing mechanism are installed. One end of the diagonal bracing rod is connected to the middle of the transition beam via a pin hinge support, and the other end is connected to the adjacent main frame structural column via a pin hinge support. The equivalent vertical support stiffness of the diagonal bracing rod is calculated between the connections. To determine the angle of inclination of the diagonal brace to the horizontal plane. Ensure that the fundamental frequency f0 of the staircase structure is greater than 4.0Hz, and the tilt angle is... The range is controlled between 35° and 55°; S5. Inspect all connection points to ensure that the high-strength bolts reach the design torque value, and complete the reinforcement work on the steel staircase.

9. A method for strengthening a large-span industrial steel staircase according to claim 8, characterized in that: The formula for calculating the anti-slip bearing capacity of the friction surface of the connecting bolts in step S3 is as follows: ； ； in, The anti-slip coefficient of the connecting bolts is taken as 0.45; P 栓 Prestress for connecting bolts; n is the number of connecting bolts; K is the safety factor for bolt slippage, K=1.2; The formula for calculating the weak axis bending capacity [M] of a single ladder beam in step S3 is as follows: ； ； Among them, K m For the bending safety factor, K m =1.2; M u Ultimate bending capacity of a single channel steel bar along its weak axis; W represents the design value of the flexural bearing capacity of the steel in the ladder beam. y The bending modulus of the weak axis of the ladder beam; The maximum allowable clamping force F of the ladder beam can be deduced from the allowable bending moment; the ladder beam subjected to bending along its weak axis is a simply supported beam with a concentrated load at mid-span, and the bending moment formula is as follows: , transform into , in, The distance between two adjacent V-shaped nodes; The clamping force F is equal to the sum of the lateral components of the two legs of the V-shaped tie rod; therefore: F = 2P max ×sinβ; ； Where β is the angle between the prestressed V-shaped brace and the ladder beam.

10. A method for strengthening a large-span industrial steel staircase according to claim 9, characterized in that, In step S4, the equivalent vertical support stiffness of the diagonal brace The calculation formula is as follows: ; Where L is the length of the diagonal brace; A is the cross-sectional area of ​​the diagonal brace; and E is the elastic modulus of the diagonal brace material. The angle between the diagonal brace and the horizontal plane; The formula for calculating the fundamental frequency f0 of a staircase structure is as follows: ； ； K 弯 is the bending stiffness of the main ladder beam; m is the structural equivalent mass.

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