A U-shaped outer steel-concrete composite beam and a simulation calculation method

Abstract

The present application relates to the technical field of simulation calculation, and particularly relates to a simulation calculation method of a U-shaped outer steel-concrete composite beam, which comprises the following steps: S1: establishing a double-parameter interface equivalent stiffness model of a U-shaped outer steel-concrete composite beam with post-anchoring bolts; S2: solving and response extraction; S3: calculating a slip residual error and interface energy, and judging whether the target slip characteristic is met according to a double-convergence criterion; if the convergence requirement is not met, the interface parameters are updated adaptively and the step S2 is repeated; if the convergence criterion is met, the converged interface stiffness parameters are used for the design feedback of post-anchoring bolt pre-tightening force selection, bolt spacing and joint construction. In the present application, the double-parameter interface equivalent stiffness model and the adaptive algorithm based on the slip residual error make the interface normal stiffness and the interface tangential stiffness automatically converge to the target slip characteristic, avoid manual parameter adjustment, improve the simulation stability and calculation accuracy, and realize the integration of the composite beam construction design and simulation analysis.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of simulation calculation, in particular to a U-shaped outer steel-concrete composite beam and a simulation calculation method. BACKGROUND

[0002] The outer steel-concrete composite beam is composed of a thick steel plate shell and internal concrete. The U-shaped steel shell serves as both a formwork and a main force component, and has the characteristics of high bearing capacity, good ductility, excellent fire resistance, etc. The construction stage can reduce the traditional formwork support and has good assembly adaptability. Existing research and engineering practice show that the U-shaped steel shell has a significant restraining effect on the concrete, and the bending performance is superior to that of conventional composite beams. The main advantages include: ① the concrete provides lateral restraint to the steel web, delaying local buckling; ② the U-shaped steel bottom plate bears the main tensile force; ③ the construction stage can reduce the formwork operation and shorten the construction period.

[0003] Key problems of existing U-shaped composite beams:

[0004] 1) Interface parameters are uncertain: Experience values are often used, which are difficult to reflect the bond degradation and nonlinear slip;

[0005] 2) Fixed stiffness model has poor stability: the interface stiffness degrades with slip and constraint conditions at the medium and high load stages, and fixed values can easily lead to overestimation of stiffness or calculation divergence;

[0006] 3) Strong dependence on manual parameter adjustment: Repeated trial and error is required, which is low in efficiency and strong in subjectivity;

[0007] 4) Design and simulation are disconnected: it is difficult to parameterize the simulation results to pre-tightening force, anchor spacing, and node structure;

[0008] 5) The stress demand difference along the span is not effectively reflected: the bending moment in the middle of the span is mainly controlled, the support shear force and the node stiffness are mainly controlled, and it is difficult to consider both in a unified structure;

[0009] 6) The welding of studs and nails is reliable but affects the reinforcement binding and vibrating, and the assembly construction is limited.

[0010] In summary, the existing U-shaped outer steel-concrete composite beam has systematic limitations in structural configuration, steel-concrete interface parameter determination, and simulation modeling accuracy. It is necessary to develop a coordinated scheme for partitioned structure, post-tensioned anchor connection based on pre-tightening force, and self-adaptive interface parameter simulation algorithm to realize stress matching, construction-friendly, and design-simulation integration. SUMMARY

[0011] In view of the above-mentioned defects of the prior art, the application provides a U-shaped outer-steel-concrete composite beam and a simulation calculation method, wherein the post-anchoring bolt pre-tightening connection is used to replace the welding bolt, the construction interference is reduced, the assembly type is friendly, the reliable anti-sliding capability is realized through mechanical locking + friction under the condition of no chemical bonding layer, the double-parameter interface equivalent stiffness model and the self-adaptive algorithm enable the interface normal stiffness and the interface tangential stiffness to automatically converge to the target sliding characteristics, the manual parameter adjustment is reduced, the calculation is stable and high in precision, the closed loop of simulation-parameter identification-design correction is established, and the simulation result can directly guide the pre-tightening force and the arrangement.

[0012] To achieve the above object, the application is implemented by the following technical solutions:

[0013] A simulation calculation method of a U-shaped outer-steel-concrete composite beam, comprising the following steps:

[0014] S1: a double-parameter interface equivalent stiffness model of the U-shaped outer-steel-concrete composite beam with post-anchoring bolts is established, the double-parameter interface equivalent stiffness model comprises interface normal equivalent stiffness and interface tangential equivalent stiffness, and the interface normal equivalent stiffness and the interface tangential equivalent stiffness are calculated by using formulas a1 and a2 respectively:

[0015] (a1), (a2);

[0016] wherein, and are the interface normal / tangential equivalent stiffness, is the elastic modulus of concrete, is the interface equivalent thickness, is the normal constraint coefficient, is the tangential flexibility coefficient;

[0017] The composite beam comprises a U-shaped outer-steel plate, post-anchoring bolts, a steel bottom plate and bolts, the inside of the U-shaped outer-steel plate is filled with concrete, the upper end of the U-shaped outer-steel plate is connected with the steel bottom plate, the two ends of the U-shaped outer-steel plate are connected with frame columns, the composite beam is divided into an A-shaped section in the middle and B-shaped sections at the two ends of the A-shaped section, the bolts are welded to the inside of the web plate of the U-shaped outer-steel plate of the A-shaped section, the inside of the lower flange plate of the U-shaped outer-steel plate of the B-shaped section and the upper part of the steel bottom plate of the A-shaped section, the post-anchoring bolts are arranged on the web plate of the U-shaped outer-steel plate of the B-shaped section and the upper part of the steel bottom plate, and the interface is formed between the U-shaped outer-steel plate and the concrete;

[0018] S2: solution and response extraction: the calculation interface slip of the target measuring point / strip area is extracted for the i th load step , and is aligned with the reference slip of the target / experiment under the same load, displacement or bending moment ;

[0019] S3: Calculate the slip residual and whether the interface energy meets the convergence criterion:

[0020] The slip residual is calculated according to formula a3:

[0021] (a3);

[0022] The convergence criterion of the slip residual is judged according to formula a4:

[0023] (a4), wherein the slip residual threshold =0.02;

[0024] The convergence criterion of the interface energy is judged according to formula a5:

[0025] (a5);

[0026] wherein the energy convergence threshold , represents the interface energy, k and k+1 represent the kth and k+1th iterations in the same load step, and the interface energy is calculated according to formula a6:

[0027] (a6), is the interface normal relative displacement, is the interface tangential relative displacement;

[0028] If the slip residual and the interface energy meet the convergence criterion, the simulation result is directly fed back to the application of the pretightening force of the post-anchoring bolt, the spacing of the post-anchoring bolt and the node structure, and if the convergence criterion is not met, the interface parameters are updated, the iteration limit is checked and returned to S2, and the subsequent steps are continued until the convergence criterion is met, and both the slip residual and the interface energy meet the convergence criterion in two consecutive iteration steps.

[0029] Optionally, in the process of calculating the interface normal equivalent stiffness and the interface tangential equivalent stiffness:

[0030] The interface normal constraint coefficient is : the upper limit is taken when the pretightening force of the post-anchoring bolt is relatively dense, and the lower limit is taken when the constraint is weak;

[0031] The interface tangential constraint coefficient is : a smaller value is taken when the friction coefficient is large and the interface is rough, and vice versa;

[0032] Optionally, in the process of calculating the interface equivalent stiffness, the pretightening force of the post-anchoring bolt needs to be corrected, and the pretightening force correction relationship is corrected according to formulas a7 and a8:

[0033] (a7), (a8);

[0034] wherein, is the basic parameter under no pre-tightening condition, is the normal stiffness enhancement coefficient, taking 0.3-0.6, is the tangential flexibility reduction coefficient, taking 0.1-0.3, is the actual applied pre-tightening force, is the pre-tightening force applied by a single post-anchoring bolt, and the normal compression force generated at the steel-concrete contact surface, a7 and a8 indicate that the greater the pre-tightening force, the greater the normal constraint enhancement, the smaller the tangential flexibility, and the overall slip resistance is inhibited, and the interface is more stable.

[0035] Optionally, the friction of the steel-concrete contact surface provides shear resistance and anti-slip ability, and the friction of the contact surface The equivalent shear bearing capacity of the post-anchoring bolt is calculated by formula a9:

[0036] (a9);

[0037] wherein, is the interface friction coefficient, which is preferably taken as 0.35-0.45 after sandblasting or tooth-shaped washer treatment, is the yield strength of the anchor bolt, is the effective sectional area of the anchor bolt.

[0038] Optionally, the equivalent stiffness of the interface in the normal and tangential directions is physically constrained, and meets the following formula (a10) under the physical upper and lower constraints:

[0039] (a10);

[0040] Optionally, after the interface parameter iteration is updated, the interface normal and tangential degrees need to meet the following formulas a11 and a12:

[0041] (a11), (a12);

[0042] wherein, is the normal stiffness correction step length coefficient, taking 0.1-0.3, is the tangential stiffness correction step length coefficient, taking 0.2-0.4, and the maximum number of iterations per step .

[0043] Optionally, when oscillation occurs and the sign repeatedly changes, the step length is adaptively reduced to .

[0044] A U-shaped outer steel-concrete composite beam, the composite beam comprises a U-shaped outer steel plate, a post-anchoring bolt, a steel bottom plate, a stud, the inside of the U-shaped outer steel plate is filled with concrete, the upper end of the U-shaped outer steel plate is connected with the steel bottom plate, the two ends of the U-shaped outer steel plate are connected with frame columns, the composite beam is divided into an A-shaped section in the middle part and a B-shaped section at the two ends of the A-shaped section, the stud is welded to the inside of the web plate of the U-shaped outer steel plate of the A-shaped section, the lower flange plate of the U-shaped outer steel plate of the B-shaped section and the upper part of the steel bottom plate of the A-shaped section, the post-anchoring bolt is arranged on the web plate of the U-shaped outer steel plate of the B-shaped section and the upper part of the steel bottom plate, and an interface is formed between the U-shaped outer steel plate and the concrete.

[0045] Optionally, a longitudinal plate upper part reinforcement, a longitudinal plate lower part reinforcement and a plate stirrup are arranged on the steel bottom plate within the range of the floor flange, the longitudinal plate upper part reinforcement is located above the longitudinal plate lower part reinforcement, and the longitudinal plate upper part reinforcement and the longitudinal plate lower part reinforcement pass through the plate stirrup; in the A-shaped section, a reverse-inserted stirrup is connected in the floor, and the reverse-inserted stirrup extends into the beam by a length not less than 35 times the diameter of the reinforcement; in the B-shaped section, a longitudinal beam lower part reinforcement and a beam stirrup are bound in the U-shaped outer steel plate, a reserved hole is arranged at the position where the post-anchoring bolt is arranged on the U-shaped outer steel plate, a nut is welded at the position of the reserved hole, and the post-anchoring bolt is connected with the nut in a matched mode.

[0046] Optionally, a T-shaped steel is further arranged in the A-shaped section and located on the inside of the reverse-inserted stirrup, the T-shaped steel is welded with the lower flange plate of the U-shaped outer steel plate, studs are welded on the two sides of the T-shaped steel, a reserved hole is arranged on the steel bottom plate, a nut is welded at the position of the reserved hole, and the post-anchoring bolt is connected with the nut in a matched mode.

[0047] Compared with the known prior art, the technical scheme provided by the present application has the following beneficial effects:

[0048] 1. The present application describes the response characteristics of the steel-concrete interface under the coupling action of normal compression, tangential slip and pre-tightening friction, establishes a two-parameter equivalent stiffness model, and based on the self-adaptive simulation calculation process of slip residual error control, the interface normal and tangential equivalent stiffness is corrected online through finite element iteration, so that the calculated slip and the target slip are consistent within the allowable error, and the interface normal and tangential equivalent stiffness is automatically converged to the target slip characteristics through the interface normal and tangential model and the self-adaptive algorithm, thereby reducing manual parameter adjustment, and the calculation is stable and high in precision; a closed loop of simulation-parameter identification-design correction is established, and the simulation results can directly guide the pre-tightening force and arrangement.

[0049] 2. The U-shaped outer steel-concrete composite beam of the present application is composed of an outer U-shaped steel shell, internal concrete, longitudinal reinforcement, stirrups and a plurality of high-strength post-anchoring bolts, and is functionally divided and transitionally designed according to the cross-sectional internal force characteristics:

[0050] A-shaped section (mid-span moment control area): a composite section composed of a U-shaped steel shell and concrete is adopted to meet the bending stiffness and normal use performance;

[0051] Type B section (shear force / joint stiffness control zone near frame columns): longitudinal reinforcement, stirrups and post-installed anchor bolts are added to the U-shaped steel shell and concrete foundation to improve shear resistance and joint restraint capacity.

[0052] The A / B type sections are reliably connected by welding or high-strength bolts, forming a smooth transition in cross-section and stiffness. This system takes into account both stress matching and construction assembly, laying the foundation for subsequent adaptive simulation-design closed loop based on adjustable interface parameters of preload.

[0053] 3. Based on the force transmission mechanism and structure of the post-installed anchor bolt with preload, high-strength post-installed anchor bolts are used to replace welded studs. Reliable anchoring is formed with concrete through an in-hole expansion mechanism or mechanical locking. Preload is applied to achieve interface anti-slip and shear bearing capacity, reduce construction interference, and is easy to assemble. Reliable anti-slip capability is achieved through mechanical locking and friction without chemical bonding layer. The preload applied by the anchor bolt generates normal clamping force at the steel-concrete contact surface. The friction force of the contact surface provides the main shear and anti-slip capabilities. In the high load stage, the anchor bolt body bears additional shear force and axial force. Roughness and clamping force jointly control the amount of micro-slip.

[0054] 4. The cross-sections and connection structures are configured according to the stress targets, taking into account both mid-span bending and support shear force / node stiffness, thus improving material utilization. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0056] Figure 1 This is a schematic diagram of the calculation process of the present invention;

[0057] Figure 2 This is a structural schematic diagram of the A-type composite beam;

[0058] Figure 3 This is a structural schematic diagram of a type B composite beam;

[0059] Figure 4 This is a schematic diagram of the structure after welding nuts to section B;

[0060] Figure 5 This is a structural diagram showing that the frame columns are made of steel profiles.

[0061] Figure 6 This is a structural diagram showing that the frame columns are concrete columns;

[0062] Figure 7 A structural diagram illustrating the joint force transfer mechanism using outer steel plates and reinforcing bars.

[0063] Figure 8 This is a structural schematic diagram of the T-shaped steel in section A;

[0064] Figure 9 This is a structural diagram of the A-section with the built-in T-shaped steel welded to the nut;

[0065] Figure 10 for Figure 9 A schematic diagram of the structure in which a post-installed anchor bolt is connected to the nut;

[0066] Figure 11 This is a schematic diagram showing the web of a U-shaped steel plate being cut off at the column edge.

[0067] Attached reference numerals: 1. U-shaped outer steel plate; 1-1. Lower flange plate; 1-2. Web plate; 2. Steel base plate; 3. Stud; 4. Upper longitudinal reinforcement of plate; 5. Lower longitudinal reinforcement of plate; 6. Plate stirrups; 7. Inverted stirrups; 8. Concrete; 9. Reserved hole; 10. Nut; 11. Post-installed anchor bolt; 12. Beam stirrups; 13. Frame column; 13-1. Steel section inside column; 13-2. Stiffening plate; 14. T-shaped steel; 14-1. Upper flange plate; 15. Ordinary concrete column; 16. Outer steel at joint; 17. Lower longitudinal reinforcement of beam. Detailed Implementation

[0068] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0069] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0070] The present invention will be further described below with reference to embodiments.

[0071] like Figure 1 As shown, a simulation calculation method for a U-shaped steel-concrete composite beam includes the following steps:

[0072] S1: Establish a two-parameter interface equivalent stiffness model for a U-shaped steel-concrete composite beam with post-installed anchor bolts 11. The two-parameter interface equivalent stiffness model includes the interface normal equivalent stiffness and the interface tangential equivalent stiffness. The interface normal equivalent stiffness and the interface tangential equivalent stiffness are calculated using formulas a1 and a2, respectively.

[0073] (a1), (a2);

[0074] in, These are the equivalent stiffness in the interface normal and tangential directions (N / mm³). This refers to the elastic modulus of concrete (MPa). The equivalent thickness of the interface (mm). Normal constraint coefficient, This is the tangential compliance coefficient;

[0075] The composite beam includes a U-shaped outer steel plate 1, post-installed anchor bolts 11, a steel base plate 2, and studs 3. The inner side of the U-shaped outer steel plate 1 is filled with concrete 8. The upper end of the U-shaped outer steel plate 1 is connected to the steel base plate 2. The two ends of the U-shaped outer steel plate 1 are connected to the frame columns 13. The composite beam is divided into an A-type section in the middle and a B-type section at both ends of the A-type section. The studs 3 are welded to the inner side of the web 1-2 of the U-shaped outer steel plate 1 in the A-type section, the inner side of the lower flange 1-1 of the U-shaped outer steel plate 1 in the B-type section, and the upper part of the steel base plate 2 in the A-type section. The post-installed anchor bolts 11 are set on the web 1-2 of the U-shaped outer steel plate 1 in the B-type section and the upper part of the steel base plate 2. The U-shaped outer steel plate 1 and the concrete 8 form an interface.

[0076] S2: Solution and Response Extraction: Solve for the i-th load step and extract the calculation interface slip of the target measurement point / strip region. and reference slip of the target / test under the same load, displacement, or bending moment level. Alignment; It is calculated directly from the displacement field in the finite element model, essentially the difference between the steel-side displacement and the concrete-side displacement. In the model, the steel-concrete interface is represented by interface elements / contact elements. Each interface element has steel-side nodal displacement and concrete-side nodal displacement. Slip is the relative displacement of the two sides of the nodes in the tangential direction. Then, at a target measuring point or along an interface strip, the interface slip can be obtained by taking the peak value or a weighted average value. . It is an external standard known value, derived from the shear force-slip curve of interface shear tests (such as pull-out tests, composite beam tests), or a pre-set target slip-load relationship. Under a given load, bending moment, or displacement level, the corresponding reference slip value is obtained by looking up a table or interpolation and used as the target quantity for adaptive correction.

[0077] S3: Calculate whether the slip residual and interface energy satisfy the convergence criterion.

[0078] The slip residual is calculated using formula a3:

[0079] (a3);

[0080] The convergence criterion for the slip residual is determined by formula a4:

[0081] (a4), where the slip residual threshold =0.02;

[0082] The convergence criterion for interface energy is determined according to formula a5:

[0083] (a5);

[0084] Among them, the energy convergence threshold , The interface energy is represented by k and k+1, which represent the k-th and k+1-th iterations within the same load step. The interface energy (Nmm) is calculated using formula a6.

[0085] (a6) The relative displacement is the interface normal. This refers to the relative tangential displacement of the interface.

[0086] In this adaptive algorithm, the process for each load step i is as follows:

[0087] Fix this load level (or displacement level);

[0088] Continuous adjustment Perform inner-layer iterations until both glide and energy converge;

[0089] At this point, we use:

[0090] k: The kth iteration within this load step (k = 0,1,2,……);

[0091] k+1: The next iteration that follows;

[0092] There is a set in the k-th iteration. Calculate a set of slip residual The k+1 iterations are obtained by updating using formulas a11 and a12. , then calculate the new , .

[0093] If the slip residual and interface energy satisfy the convergence criterion, the simulation results are directly fed back to the preload of the post-anchor 11, the spacing of the post-anchor 11, and the application of the node structure. If the convergence criterion is not satisfied, the interface parameters are updated, the iteration limit is checked, and the process returns to S2 to continue the subsequent steps until the convergence criterion is satisfied. When the slip residual and interface energy both satisfy the convergence threshold in two consecutive iteration steps, the interface stiffness is considered to have converged.

[0094] For robustness, two criteria are used to continuously satisfy ≥2 iterations. Once convergence is achieved, the convergent criterion is used. Based on the slip range: Select the preload applied by a single post-installed anchor 11 that matches the target stiffness / slip level in the standard preload level, and determine the anchor spacing and arrangement by combining the calculation method of the equivalent shear bearing capacity of the combined post-installed anchor 11 and the peak value of the interface shear flow; perform a first check analysis, and if it does not meet the requirements, prioritize adjusting the preload level and spacing until the bearing capacity and normal service performance are met.

[0095] Furthermore, during the calculation of the interface normal equivalent stiffness and tangential equivalent stiffness:

[0096] Interface normal constraint coefficient is When the preload of the post-installed anchor is close to that of the post-installed anchor, take the upper limit; when the constraint is weak, take the lower limit.

[0097] The interface tangential constraint coefficient is When the coefficient of friction is high and the interface is rough, take a smaller value; otherwise, take a larger value.

[0098] Furthermore, during the calculation of the equivalent stiffness of the interface, the preload of the post-installed anchor bolts needs to be corrected. The preload correction relationship is based on formulas a7 and a8:

[0099] (a7) (a8);

[0100] in, These are the basic parameters under no preload condition. This is the normal stiffness enhancement factor, taken as 0.3 to 0.6. The tangential compliance reduction factor is taken as 0.1 to 0.3. To apply the actual preload (kN). The preload (kN) applied to a single post-installed anchor bolt and the normal clamping force generated at the steel-concrete interface, a7 and a8 indicate that the greater the preload, the stronger the normal constraint, the smaller the tangential compliance, the more the overall slippage ability is suppressed, and the more stable the interface.

[0101] Furthermore, the friction at the steel-concrete contact surface provides shear resistance and anti-slip capability. The equivalent shear capacity of the post-installed anchor bolts is calculated using formula a9:

[0102] (a9);

[0103] in, The interfacial friction coefficient should be between 0.35 and 0.45 after sandblasting or toothed gasket treatment. The anchor bolt yield strength (MPa) is given. The effective cross-sectional area of ​​the anchor bolt is (mm²).

[0104] Furthermore, the equivalent stiffness of the interface in the normal and tangential directions is physically constrained, subject to upper and lower physical bounds, and satisfies the following formula (a10):

[0105] (a10);

[0106] Furthermore, after the interface parameters are iteratively updated, the interface normal and tangent must satisfy the following formulas a11 and a12:

[0107] (a11) (a12);

[0108] in, The normal stiffness correction step size factor is taken as 0.1 to 0.3. The step size factor for tangential stiffness correction is set to 0.2–0.4, and the maximum number of iterations per step is [not specified]. .

[0109] Furthermore, when oscillations occur Furthermore, when the sign changes repeatedly, the step size is adaptively reduced. arrive .

[0110] Specifically, k / k+1 refers to the "kth" and "k+1th" iterations within the same load step. "Repeated sign changes" means the slip residual's sign jumps back and forth between adjacent iterations, and its absolute value continues to increase; this is considered "oscillation."

[0111] if This indicates that the error not only did not decrease, but actually increased. Specifically:

[0112] Step k: ;

[0113] Step k+1: ;

[0114] Then it becomes positive again, then negative again, and so on. This is called "residual oscillation with repeated sign changes." A simple numerical example can make this clearer:

[0115] 3rd iteration: ;

[0116] 4th iteration: (Note: The absolute value increased from 0.02 to 0.03, and changed from + to -).

[0117] 5th iteration: (and then changes back to + from −).

[0118] In this embodiment, the preload coefficient of the post-installed anchor is 0.7 to 0.8; the bolt strength grade is ≥10.9; the contact surface is sandblasted or toothed washers are used to improve the friction coefficient. This structure avoids welding residual stress and chemical bonding aging problems, has reliable force transmission, strong disassembly and assembly, and high construction safety, and is suitable for prefabricated construction and quality control.

[0119] A U-shaped steel-concrete composite beam is disclosed. The composite beam includes a U-shaped steel plate 1, post-installed anchor bolts 11, a steel base plate 2, and studs 3. The inner side of the U-shaped steel plate 1 is filled with concrete 8. The upper end of the U-shaped steel plate 1 is connected to the steel base plate 2, and both ends of the U-shaped steel plate 1 are connected to frame columns 13. The composite beam is divided into an A-shaped section in the middle and B-shaped sections at both ends of the A-shaped section. The studs 3 are welded to the inner side of the web 1-2 of the U-shaped steel plate 1 in the A-shaped section, the inner side of the lower flange 1-1 of the U-shaped steel plate 1 in the B-shaped section, and the upper part of the steel base plate 2 in the A-shaped section. The post-installed anchor bolts 11 are set on the web 1-2 of the U-shaped steel plate 1 in the B-shaped section and the upper part of the steel base plate 2. An interface is formed between the U-shaped steel plate 1 and the concrete 8.

[0120] Furthermore, the steel base plate 2 is provided with upper longitudinal reinforcement 4, lower longitudinal reinforcement 5 and stirrups 6 within the flange range of the floor slab. The upper longitudinal reinforcement 4 is located above the lower longitudinal reinforcement 5, and the upper longitudinal reinforcement 4 and lower longitudinal reinforcement 5 pass through the stirrups 6. In the A-type section, inverted stirrups 7 are connected inside the floor slab, and the length of the inverted stirrups 7 extending into the beam is not less than 35 times the diameter of the steel bar. In the B-type section, the lower longitudinal reinforcement 17 and stirrups 12 of the beam are tied inside the U-shaped outer steel plate 1. A reserved hole 9 is provided at the installation position of the rear anchor bolt 11 on the U-shaped outer steel plate 1, and a nut 10 is welded at the reserved hole 9. The rear anchor bolt 11 is adapted to the nut 10 for connection.

[0121] Furthermore, the A-section is also equipped with a T-shaped steel 14 located inside the inverted stirrup 7. The T-shaped steel 14 is welded to the lower flange plate 1-1 of the U-shaped outer steel plate 1. Studs 3 are welded on both sides of the T-shaped steel 14. A reserved hole 9 is provided on the steel base plate 2. Nuts 10 are welded at the reserved hole 9. The rear anchor bolt 11 is adapted to be connected to the nut 10.

[0122] In this embodiment, as Figure 5 As shown, the beam is divided into two parts. The LB section near the frame column 13 uses a B-type composite beam, while the A-type composite beam is used in the middle of the span.

[0123] Composite beams of type A, such as Figure 2As shown, the structure includes: a U-shaped outer steel plate 1 welded to a steel base plate 2; studs 3 welded to the inner side of the U-shaped outer steel plate 1 and the upper part of the steel base plate 2; on the construction site, upper longitudinal reinforcement 4, lower longitudinal reinforcement 5, and stirrups 6 are provided within the flange range of the floor slab, along with inverted stirrups 7. The inverted stirrups 7 extend into the beam for a length not less than 35d, where d is the diameter of the reinforcing bar. The U-shaped outer steel plate 1 can also serve as a formwork for pouring concrete 8, where concrete 8 is poured last. The lower flange plate 1-1 of the U-shaped outer steel plate 1 replaces the lower tensile reinforcement of the beam, fully utilizing the advantages of the steel's good tensile strength while solving the problem of concrete 8 cracking.

[0124] Type B composite beams, such as Figure 3 As shown, it includes: a U-shaped outer steel plate 1 welded to a steel base plate 2, and studs 3 welded to the inner side of the lower flange plate 1-1 of the U-shaped outer steel plate 1, as shown. Figure 4 As shown, the web 1-2 and bottom plate 2 of the U-shaped outer steel plate 1 have pre-reserved holes 9 in the factory, and nuts 10 are welded inside the pre-reserved holes 9. At the construction site, upper longitudinal reinforcement 4, lower longitudinal reinforcement 5, and stirrups 6 are set within the flange range of the floor slab. Lower longitudinal reinforcement 17 and stirrups 12 are tied inside the beam. After the reinforcement is tied, the post-installed anchor bolts 11 are installed at the positions of the pre-reserved holes 9 and tightened. The U-shaped outer steel plate 1 can also serve as a formwork for pouring concrete 8. Finally, concrete 8 is poured.

[0125] The type B composite beam is connected to frame column 13. If frame column 13 is a steel-concrete composite column (e.g.) Figure 5 As shown), the lower flange 1-1 of the U-shaped outer steel plate 1 extends and is welded to the internal steel section 13-1 of the column, and the web 1-2 of the U-shaped outer steel plate 1 stops at the column edge. If the frame column 13 is an ordinary concrete column 15 (such as...), Figure 6 As shown), an outer steel cladding 16 is installed at the node on the outside of the column, and welded to the U-shaped outer steel plate 1 at the column edge. The outer steel cladding 16 at the node has a pre-drilled hole 9 at the factory, and a nut 10 is welded at the hole. After the reinforcement is tied on site, the post-installed anchor bolt 11 is installed at the pre-drilled hole 9 and tightened. The outer steel cladding 16 at the node also serves as a formwork for pouring concrete 8. Finally, concrete 8 is poured.

[0126] Based on the A-section composite beam, a T-shaped steel 14 is built-in. The upper end of the T-shaped steel 14 is the upper web plate 1-2. The U-shaped outer steel plate 1 is welded to the steel base plate 2. The T-shaped steel 14 is welded to the lower flange plate 1-1 of the U-shaped outer steel plate 1. Studs 3 are welded to the inside of the U-shaped outer steel plate 1 and the T-shaped steel 14 at the factory. Pre-drilled holes 9 are provided on the steel base plate 2, and nuts 10 are welded to the corresponding positions (e.g., ...). Figure 9 (As shown). At the construction site, the upper longitudinal reinforcement, lower longitudinal reinforcement 5, and slab stirrups 6 are installed within the flange area of ​​the floor slab. The lower longitudinal reinforcement 17 and beam stirrups 12 are tied within the beam. After the reinforcement is tied, as shown... Figure 10As shown, the post-installed anchor bolt 11 is installed at the reserved hole 9 and tightened. The U-shaped outer steel plate 1 can also serve as a formwork for pouring concrete 8. Finally, concrete 8 is poured (as shown). Figure 8 (As shown). When using this type of beam, frame column 13 is a steel-concrete composite column. The lower flange plate 1-1 of T-shaped steel 14 and U-shaped outer steel plate 1 is connected to the built-in steel, and stiffening plate 13-2 is provided. The web plate 1-2 of U-shaped outer steel plate 1 is cut off at the column edge (as shown). Figure 11 (As shown). This new cross-sectional form exhibits multiple advantages over reinforced concrete structures: First, it significantly improves load-bearing capacity and stiffness, thereby effectively reducing the structure's self-weight and thus mitigating seismic impact. It also allows for smaller component cross-sectional dimensions, increasing usable space. This change directly reduces foundation costs and significantly shortens the construction period by eliminating formwork and reducing formwork usage. Furthermore, the structure enhances the ductility of components and the overall structure, improving structural performance.

[0127] Compared with steel structures, the new cross-section reduces the amount of steel used while maintaining or even increasing stiffness, significantly improving the stability and integrity of the structure.

[0128] Compared with other steel-concrete composite beams, this novel cross-section exhibits higher load-bearing capacity, stiffness, and ductility. Thanks to the restraining effect of the concrete 8 on the steel beam web 1-2, the cross-section can achieve its maximum load-bearing capacity under fully plastic bending moments. Simultaneously, the concrete 8 filling the U-shaped steel beam allows most of the vertical shear force of the composite beam to be shared by the concrete 8 and the steel beam web 1-2, further enhancing its vertical shear resistance.

[0129] In particular, compared with steel-reinforced concrete composite beams under the same cross-section and steel ratio, the new type of steel-concrete composite beam exhibits superior flexural strength due to the greater distance between the steel beam bottom plate and the neutral axis. Furthermore, this structure demonstrates excellent fire resistance: the lower fire-contaminated surface is only heated on one side, and the concrete, as a good heat absorber, effectively slows down the temperature rise of the steel. The overall fire resistance can be further enhanced by incorporating internal fire-resistant longitudinal reinforcement.

[0130] Ease of construction is another highlight of this structure. During construction, the U-shaped outer steel not only serves as a supporting structure for the floor slab but also acts as formwork for the concrete inside the beam, simplifying the construction process. The subsequent anchor bolt design reduces the difficulty of on-site rebar tying, making the entire construction process more efficient. In summary, this novel steel-concrete composite beam exhibits superior performance and advantages in many aspects.

[0131] Figure 5 and Figure 6 The difference between the two is that they are both applications of composite beams. Figure 5By using steel profile columns, we can directly extend the lower flange steel plate into the column and connect it to the steel profile. Figure 6 This is for ordinary concrete columns 15, where force transfer at the joints is achieved by setting an outer steel plate and reinforcing bars (e.g. Figure 7 (As shown). The connection of nodes is only a supporting solution, while the proposed cross-sectional shape solves the problems of stiffness, bearing capacity, and difficulties in on-site construction.

[0132] Construction sequence: The A-section and B-section of the composite beam are constructed as a single unit. The steel plate portion is completed in the factory and transported to the site. Because the B-section composite beam includes stirrups 12 and longitudinal reinforcement, and considering the difficulty of rebar tying, the rebar tying is completed first, followed by the installation of post-installed anchor bolts 11. Anchor bolts and studs 3 serve the same purpose. Studs 3 need to be welded to the steel plate. However, after the rebar tying is completed, there is no space available for welding. Therefore, the post-installed anchor bolts 11 are inserted from the outside of the U-shaped outer steel plate 1 and tightened with nuts 10 to complete the connection.

[0133] The A-section composite beam lacks stirrups 12 and bottom longitudinal reinforcement 17, instead directly employing studs 3, all factory-welded, simplifying construction. Simultaneously, the bottom steel plate completely replaces the bottom longitudinal reinforcement 17, providing tensile strength and addressing the cracking issue of the steel beam. Considering the floor slab flange, the excellent compressive strength of concrete 8 is fully utilized, economically and effectively increasing the beam's load-bearing capacity. Studs 3 and post-installed anchor bolts 11 ensure the connection between concrete 8 and the steel plate, guaranteeing effective force transmission and minimizing slippage between the materials. The use of post-installed anchor bolts 3 greatly simplifies the rebar tying process; the central steel section significantly enhances the combined beam's ability to function as a composite beam through the combined action of the steel structure and concrete 8; the added steel plate at the bottom of the floor slab improves the integration of the steel and concrete 8 and facilitates the function of the floor slab flange, greatly increasing the composite beam's load-bearing capacity; replacing the bottom longitudinal reinforcement with a bottom steel plate fully utilizes the excellent tensile properties of steel, effectively solving the structural cracking problem.

[0134] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A simulation calculation method for a U-shaped steel-concrete composite beam, characterized in that, Includes the following steps: S1: Establish a two-parameter interface equivalent stiffness model for a U-shaped steel-concrete composite beam with post-installed anchor bolts (11). The two-parameter interface equivalent stiffness model includes the interface normal equivalent stiffness and the interface tangential equivalent stiffness. The interface normal equivalent stiffness and the interface tangential equivalent stiffness are calculated using formulas a1 and a2, respectively. (a1) (a2) in, These are the equivalent stiffness in the interface normal and tangential directions, respectively. The elastic modulus of concrete. For the interface equivalent thickness, For interface normal constraint coefficients, The interface tangential constraint coefficient; S2: Solution and Response Extraction: Solve for the i-th load step and extract the calculation interface slip of the target measurement point / strip region. and reference slip of the target / test under the same load, displacement, or bending moment level. Alignment; S3: Calculate whether the slip residual and interface energy satisfy the convergence criterion. The slip residual is calculated using formula a3: （a3）； The convergence criterion for the slip residual is determined by formula a4: (a4), where the slip residual threshold =0.02; The convergence criterion for interface energy is determined according to formula a5: （a5）； Among them, the energy convergence threshold , The interface energy is represented by k and k+1, which represent the k-th and k+1-th iterations within the same load step. The interface energy is calculated using formula a6. (a6) The relative displacement is the interface normal. This refers to the relative tangential displacement of the interface. If the slip residual and interface energy satisfy the convergence criterion, the simulation results are directly fed back to the preload of the post-anchor (11), the spacing of the post-anchor (11), and the application of the node structure. If the convergence criterion is not satisfied, the interface parameters are updated, the iteration limit is checked, and the process returns to S2. The subsequent steps continue until the convergence criterion is satisfied. The convergence criteria for slip residual and interface energy are satisfied in two consecutive iteration steps.

2. The simulation calculation method for a U-shaped steel-concrete composite beam according to claim 1, characterized in that, During the calculation of the interface's normal and tangential equivalent stiffness: Interface normal constraint coefficient is The interface tangential constraint coefficient is .

3. The simulation calculation method for a U-shaped steel-concrete composite beam according to claim 2, characterized in that, During the calculation of the equivalent stiffness of the interface, the preload of the post-installed anchor (11) needs to be corrected. The preload correction relationship is corrected according to formulas a7 and a8: (a7) (a8) in, These are the basic parameters under no preload condition. This is the normal stiffness enhancement factor, taken as 0.3 to 0.

6. The tangential compliance reduction factor is taken as 0.1 to 0.

3. In order to actually apply preload, The preload applied to a single post-installed anchor (11) and the normal clamping force generated at the steel-concrete interface, a7 and a8 indicate that the greater the preload, the stronger the normal constraint, the smaller the tangential compliance, the more the overall slippage ability is suppressed, and the more stable the interface.

4. The simulation calculation method for a U-shaped steel-concrete composite beam according to claim 3, characterized in that, The friction at the steel-concrete contact surface provides shear resistance and anti-slip capability. The equivalent shear capacity of the post-installed anchor (11) is calculated using formula a9: （a9）； in, The interfacial friction coefficient should be between 0.35 and 0.45 after sandblasting or toothed gasket treatment. For anchor bolt yield strength, This represents the effective cross-sectional area of ​​the anchor bolt.

5. The simulation calculation method for a U-shaped steel-concrete composite beam according to claim 4, characterized in that, The equivalent stiffness of the interface in the normal and tangential directions is physically constrained and subject to the following formula (a10) by physical upper and lower bounds: （a10）。 6. The simulation calculation method for a U-shaped steel-concrete composite beam according to claim 5, characterized in that, After the interface parameters are iteratively updated, the interface normal and tangent must satisfy the following formulas a11 and a12: (a11), (a12); in, The normal stiffness correction step size factor is taken as 0.1 to 0.

3. The step size factor for tangential stiffness correction is set to 0.2–0.4, and the maximum number of iterations per step is [not specified]. .

7. The simulation calculation method for a U-shaped steel-concrete composite beam according to claim 6, characterized in that, When oscillation occurs Furthermore, when the sign changes repeatedly, the step size is adaptively reduced. arrive .

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