U-shaped steel-encased-concrete composite beam and simulation calculation method

Abstract

The invention relates to the technical field of simulation calculation, in particular to a simulation calculation method of a U-shaped steel-encased-concrete composite beam, which comprises the following steps: S1, establishing a two-parameter interface equivalent stiffness model of the U-shaped steel-encased-concrete composite beam with a rear anchor bolt; s2, solution and response extraction; s3, calculating a slip residual error and interface energy, and judging whether a target slip feature is met or not according to a double-convergence criterion; if the convergence requirement is not met, adaptively updating the interface parameters and returning to S2 for repeated solution, and if the convergence criterion is met, applying the converged interface rigidity parameters to design feedback of pretightening force selection of the rear anchor bolts and anchor bolt spacing and node construction of the rear anchor bolts. According to the method, the two-parameter interface equivalent stiffness model and the adaptive algorithm based on the slip residual error enable the interface normal stiffness and the interface tangential stiffness to be automatically converged to the target slip characteristic, manual parameter adjustment is avoided, the simulation stability and the calculation precision are improved, and integration of composite beam structure design and simulation analysis is achieved.

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 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 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 normal and tangential 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 update, the interface normal and tangential degree 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] B-type section (shear / node stiffness control area close to frame column): longitudinal reinforcement, stirrup and post-anchoring are added to the U-shaped steel shell and concrete foundation to improve shear resistance and node constraint capacity;

[0052] A / B-type sections are reliably connected by means of splicing or high-strength bolts to form smooth transition of cross section and stiffness. This system takes into account force matching and construction assembly, and lays the foundation for subsequent interface parameter adjustment based on pre-tightening force, adaptive simulation-design closed loop.

[0053] 3. Based on the force transmission mechanism and structure of post-anchoring based on pre-tightening force, high-strength post-anchoring is used to replace welded studs, and reliable anchoring is formed with concrete through hole expansion mechanism or mechanical locking, pre-tightening force is applied to realize interface anti-slippage and shear bearing, reduce construction interference, and assembly friendly. And under the condition of no chemical bonding layer, reliable anti-slippage capacity is realized through mechanical locking + friction; the pre-tightening force applied by the anchor produces a normal compressive force on the steel-concrete contact surface, and the contact surface friction provides the main shear and anti-slippage capacity. In the high load stage, the anchor rod bears additional shear and axial force, and the roughness and compressive force jointly control the amount of micro-slippage.

[0054] 4. According to the force target, the cross section and connection structure are configured respectively, and the bending in the span and the shear / node stiffness of the support are considered, and the material utilization rate is improved. BRIEF DESCRIPTION OF DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0056] Figure 1 It is a schematic diagram of the calculation process of the present application;

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

[0058] Figure 3 It is a structural schematic diagram of the B-type section composite beam;

[0059] Figure 4 It is a structural schematic diagram of the B-type section after welding nut;

[0060] Figure 5 It is a structural schematic diagram of the frame column as a steel column;

[0061] Figure 6 It is a structural schematic diagram of the frame column as a concrete column;

[0062] Figure 7 Structure diagram of the structure of the U-shaped outer steel plate and the steel reinforcement completing the force transmission of the joint;

[0063] Figure 8 Structure diagram of the T-shaped steel in the A-shaped section;

[0064] Figure 9 Structure diagram of the A-shaped section with the T-shaped steel embedded and after the nut is welded;

[0065] Figure 10 Structure diagram of the nut in the Figure 9 connecting the post-anchoring bolt;

[0066] Figure 11 Structure diagram of the web of the U-shaped outer steel plate being truncated at the column edge.

[0067] The drawing label: 1, U-shaped outer steel plate, 1-1, lower flange plate, 1-2, web, 2, steel bottom plate, 3, stud, 4, upper plate longitudinal reinforcement, 5, lower plate longitudinal reinforcement, 6, plate stirrup, 7, inverted stirrup, 8, concrete, 9, reserved hole, 10, nut, 11, post-anchoring bolt, 12, beam stirrup, 13, frame column, 13-1, column inner section steel, 13-2, stiffened plate, 14, T-shaped steel, 14-1, upper flange plate, 15, ordinary concrete column, 16, joint outer steel, 17, beam lower longitudinal reinforcement. DETAILED DESCRIPTION

[0068] The technical solutions of the present application will be further described below in combination with the drawings and through specific embodiments.

[0069] Wherein, the drawings are only used for exemplary illustration, and the representation is only a schematic diagram, not a physical diagram, and cannot be understood as a limitation on the present application; in order to better illustrate the embodiments of the present application, some components of the drawings will be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some known structures and their descriptions in the drawings can be omitted.

[0070] The present application will be further described below in combination with the embodiments.

[0071] As Figure 1 shown, a simulation calculation method of a U-shaped outer steel-concrete composite beam, comprising the following steps:

[0072] S1: establishing a two-parameter interface equivalent stiffness model of a U-shaped outer steel-concrete composite beam with a post-anchoring bolt 11, the two-parameter interface equivalent stiffness model including interface normal equivalent stiffness and interface tangential equivalent stiffness, the interface normal equivalent stiffness and the interface tangential equivalent stiffness being calculated by formulas a1 and a2 respectively:

[0073] (a1), (a2);

[0074] wherein, are the interface normal / tangential equivalent stiffness (N / mm³) respectively, is the concrete elastic modulus (MPa), is the interface equivalent thickness (mm), is the normal constraint coefficient, is the tangential flexibility coefficient;

[0075] The composite beam comprises a U-shaped outer steel plate 1, a post-anchoring bolt 11, a steel bottom plate 2 and a stud 3, the inside 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 with the steel bottom plate 2, the two ends of the U-shaped outer steel plate 1 are connected with a frame column 13, the composite beam is divided into an A-shaped section in the middle and a B-shaped section at the two ends of the A-shaped section, the stud 3 is welded to the inside of the web plate 1-2 of the U-shaped outer steel plate 1 of the A-shaped section, the inside of the lower flange plate 1-1 of the U-shaped outer steel plate 1 of the B-shaped section and the upper part of the steel bottom plate 2 of the A-shaped section, the post-anchoring bolt 11 is arranged on the web plate 1-2 of the U-shaped outer steel plate 1 of the B-shaped section and the upper part of the steel bottom plate 2, and the interface is formed between the U-shaped outer steel plate 1 and the concrete 8;

[0076] S2: solving and response extraction: solve the i-th load step and extract the calculation interface slip of the target measuring point / band-shaped area , and align with the reference slip of the target / experiment under the same load, displacement or bending moment level ; is directly calculated from the displacement field in the finite element model, and is essentially the difference between the steel side displacement and the concrete side displacement, in the model, the steel-concrete interface is represented by an interface element / contact element; on each interface element, there are steel side node displacement and concrete side node displacement, and the slip is the relative displacement of the two sides in the tangential direction, then on a target measuring point or an interface band, the peak value or the weighted average value can be taken to obtain the interface slip . is an external standard known value, which comes from the shear-slip curve of the interface shear test (such as the push-out test, the composite beam test) or the pre-set target slip-load relationship, and the corresponding reference slip value is obtained by table lookup or interpolation under the given load, bending moment or displacement level, and is used as the target quantity for adaptive correction;

[0077] S3: whether the slip residual and the interface energy meet the convergence criterion:

[0078] The slip residual is calculated according to formula a3:

[0079] (a3);

[0080] The convergence criterion of the slip residual is judged according to formula a4:

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

[0082] The convergence criterion of the interface energy is judged according to formula a5:

[0083] (a5);

[0084] 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 (Nmm) is calculated according to formula a6:

[0085] (a6), is the interface normal relative displacement, is the interface tangential relative displacement;

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

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

[0088] constantly adjust , do inner iteration, until the slip and energy are converged;

[0089] At this time, we use:

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

[0091] k+1: the next iteration immediately after;

[0092] The kth iteration has a set of , calculate a set of slip , residual , update to get the k+1th iteration , and calculate new , .

[0093] If the slip residual and the interface energy meet the convergence criterion, the simulation results are directly fed back to the application of the pretightening force of the post-anchoring bolt 11, the spacing of the post-anchoring bolt 11 and the node structure, 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. When the slip residual and the interface energy meet the convergence threshold in two consecutive iteration steps, it is considered that the interface stiffness is converged.

[0094] For robustness, two criteria are used to meet ≥2 iteration steps continuously, and when converged, the Based on the slip interval: in the standard pre-tightening force position, the pre-tightening force of the single post anchor 11 matched with the target stiffness / slip level is selected, the calculation method of the equivalent shear bearing capacity of the post anchor 11 is combined with the interface shear flow peak to determine the anchor spacing and arrangement; a primary checking analysis is performed, and when the requirement is not met, the pre-tightening force position and the spacing are adjusted preferentially until the bearing capacity and normal use performance are met.

[0095] Further, in the process of calculating the interface normal equivalent stiffness and the tangential equivalent stiffness:

[0096] The interface normal constraint coefficient is : the upper limit is taken when the post anchor is dense, and the lower limit is taken when the constraint is weak;

[0097] The interface tangential constraint coefficient is : a smaller value is taken when the friction coefficient and the interface roughness are large, and vice versa;

[0098] Further, in the process of calculating the interface equivalent stiffness, the pre-tightening force of the post anchor needs to be corrected, and the pre-tightening force correction relationship is corrected according to formulas a7 and a8:

[0099] (a7), (a8);

[0100] Wherein, is the basis parameter under the pre-tightening force-free working condition, is the normal stiffness enhancement coefficient, taken as 0.3-0.6, is the tangential flexibility reduction coefficient, taken as 0.1-0.3, is the actual applied pre-tightening force (kN), is the pre-tightening force (kN) applied by a single post anchor and the normal compression force generated on the steel-concrete contact surface, a7 and a8 show that the greater the pre-tightening force, the greater the normal constraint enhancement, the smaller the tangential flexibility, and the overall slip ability is inhibited, and the interface is more stable.

[0101] Further, the friction force of the steel-concrete contact surface provides the shear resistance and anti-slip ability, and the friction force of the contact surface The equivalent shear bearing capacity of the post anchor is calculated by formula a9:

[0102] (a9);

[0103] Wherein, is the interface friction coefficient, preferably taken as 0.35-0.45 after sandblasting or tooth-shaped washer treatment, is the anchor yield strength (MPa), is the effective cross-sectional area of the anchor (mm²).

[0104] Further, the equivalent stiffness of the interface normal and tangential is physically constrained, and the upper and lower physical constraints satisfy the following formula (a10):

[0105] (a10);

[0106] Further, after the interface parameter iterative update, the interface normal and tangential degree need to satisfy the following formulas a11 and a12:

[0107] (a11), (a12);

[0108] 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 in a single step .

[0109] Further, when the oscillation , and the sign repeatedly changes, the step length is adaptively reduced to .

[0110] Specifically, k / k+1 is the "kth" and "k+1th" iteration in the same load step. And "sign repeatedly changes" means that the slip residual jumps back and forth between adjacent iterations, and the absolute value is also getting larger, which is judged as "oscillation".

[0111] If , it means that the error not only does not become smaller, but becomes larger, specifically:

[0112] Step k: ;

[0113] Step k+1: ;

[0114] Then it becomes positive again, and then negative, and so on, which is called "residual oscillation and sign repeatedly changes". A simple numerical example can be used to make it more intuitive:

[0115] 3rd iteration: ;

[0116] 4th iteration: , (note: the absolute value from 0.02 to 0.03 becomes larger, and from + to -);

[0117] 5th iteration: , (from - to + again).

[0118] In this embodiment, the pre-tightening force coefficient of the rear anchor bolt is 0.7-0.8, the bolt strength grade is greater than or equal to 10.9, the contact surface is sandblasted or a toothed washer is used to increase the friction coefficient, the structure avoids the problems of welding residual stress and chemical bonding aging, the force transmission is reliable, the disassembly and reassembly are easy, the construction safety is high, and the structure is suitable for assembly type construction and quality control.

[0119] A U-shaped outer steel-concrete composite beam, comprising a U-shaped outer steel plate 1, a rear anchor bolt 11, a steel bottom plate 2, and a stud 3, the inside of the U-shaped outer steel plate 1 being filled with concrete 8, the upper end of the U-shaped outer steel plate 1 being connected to the steel bottom plate 2, the two ends of the U-shaped outer steel plate 1 being connected to a frame column 13, the composite beam being divided into an A-shaped section in the middle and a B-shaped section at the two ends of the A-shaped section, the stud 3 being welded to the inside of the web plate 1-2 of the U-shaped outer steel plate 1 of the A-shaped section, the inside of the lower flange plate 1-1 of the U-shaped outer steel plate 1 of the B-shaped section, and the upper part of the steel bottom plate 2 of the A-shaped section, the rear anchor bolt 11 being arranged on the web plate 1-2 of the U-shaped outer steel plate 1 of the B-shaped section and on the upper part of the steel bottom plate 2, and an interface being formed between the U-shaped outer steel plate 1 and the concrete 8.

[0120] Further, a plate upper longitudinal reinforcement 4 and a plate lower longitudinal reinforcement 5 are arranged on the steel bottom plate 2 within the range of the floor flange, and a plate stirrup 6 is arranged above the plate upper longitudinal reinforcement 4 and the plate lower longitudinal reinforcement 5; in the A-shaped section, an inverted stirrup 7 is connected in the floor, and the length of the inverted stirrup 7 extending into the beam is not less than 35 times the diameter of the reinforcement; in the B-shaped section, a beam lower longitudinal reinforcement 17 and a beam stirrup 12 are bound in the U-shaped outer steel plate 1, a reserved hole 9 is arranged at the position where the rear anchor bolt 11 is installed on the U-shaped outer steel plate 1, a nut 10 is welded at the position of the reserved hole 9, and the rear anchor bolt 11 is connected to the nut 10.

[0121] Further, a T-shaped steel 14 is arranged inside the inverted stirrup 7 in the A-shaped section, 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 two sides of the T-shaped steel 14, a reserved hole 9 is arranged on the steel bottom plate 2, a nut 10 is welded at the position of the reserved hole 9, and the rear anchor bolt 11 is connected to the nut 10.

[0122] In this embodiment, as shown in Figure 5 , the beam is divided into two parts, the length of the LB part near the two sides of the frame column 13 adopts the B-shaped section composite beam, and the middle part adopts the A-shaped section composite beam.

[0123] The A-shaped section composite beam, as shown in 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-anchoring bolt 11 is installed at the reserved hole 9 position, tightened, and the U-shaped outer steel plate 1 can be used as a concrete 8 pouring formwork, and finally the concrete 8 is poured (as shown Figure 8 As shown). When this type of beam is used, the frame column 13 is a steel reinforced concrete column, the lower flange plate 1-1 of the T-shaped steel 14 and the U-shaped outer steel plate 1 is connected with the built-in steel, and a stiffener 13-2 is arranged, and the web plate 1-2 of the U-shaped outer steel plate 1 is truncated at the column edge (as shown Figure 11 Compared with the reinforced concrete 8 structure, the new cross section has multiple advantages: first, it significantly improves the bearing capacity and stiffness, thereby effectively reducing the structure weight, reducing the influence of earthquakes, and allowing the cross-sectional size of the component to be reduced, thereby increasing the effective use space. This change also directly reduces the foundation cost and significantly shortens the construction period by omitting the formwork process and reducing the use of formwork. In addition, the structure enhances the ductility of the component and the whole, thereby improving the structural performance.

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

[0128] In comparison with other steel-concrete composite beams, the new cross section has higher bearing capacity, stiffness and ductility. Due to the restraining effect of the concrete 8 on the steel beam web plate 1-2, the cross section can achieve the maximum bearing capacity of the full plastic bending moment. At the same time, the concrete 8 filled in the U-shaped steel beam allows the majority of the vertical shear force of the composite beam to be shared by the concrete 8 and the steel beam web plate 1-2, thereby further enhancing the vertical shear bearing capacity.

[0129] In particular, compared with a steel reinforced concrete composite beam under the same cross section and steel ratio conditions, the new outer steel-concrete composite beam has superior bending resistance due to the greater distance of the steel beam bottom plate from the neutral axis. In addition, the structure also performs well in terms of fire resistance: the lower fire exposure surface is only single-sidedly heated, and the concrete 8 acts as a good heat absorbing material to effectively slow down the temperature rise of the steel. If longitudinal fireproofing reinforcement is arranged inside, the overall fire resistance performance can be further improved.

[0130] Construction convenience is another highlight of the structure. During construction, the U-shaped outer steel not only serves as a support structure for the floor slab, but also as a formwork for the concrete 8 in the beam, thereby simplifying the construction process. The design of the post-installed anchor bolt reduces the difficulty of on-site steel bar binding, making the entire construction process more efficient. In summary, the new outer steel-concrete composite beam has excellent performance and advantages in many aspects.

[0131] Figure 5 and Figure 6 The two differ in the application mode of the composite beam Figure 5Adopting the steel column, we can directly extend the lower flange steel plate into the column to connect the steel, Figure 6 is aimed at the ordinary concrete column 15, and the joint force transmission is completed by setting the outer steel plate and the steel bar (as shown in Figure 7 ). The connection of the joint is only a supporting solution, and the proposed cross-section form is a solution to the problems of stiffness, bearing capacity and on-site construction difficulty.

[0132] Construction sequence: The A-shaped section and the B-shaped section of the composite beam are an integral whole, and the steel plate part is completed in the factory and transported to the site. The B-shaped section composite beam is provided with the beam stirrup 12 and the longitudinal reinforcement, and the difficulty of steel bar binding is considered. In the construction sequence, the steel bar binding is completed first, and then the post-anchoring bolt 11 is installed. The anchoring bolt and the dowel 3 have the same effect. The dowel 3 needs to be welded on the steel plate, and after the steel bar binding is completed, there is no welding space, so the post-anchoring bolt 11 is inserted from the outside of the U-shaped outer steel plate 1 to the inside, and the connection is completed by screwing the nut 10.

[0133] The A-shaped section composite beam is not provided with the beam stirrup 12 and the lower longitudinal reinforcement 17, so the dowel 3 is directly used, all of which are factory welded, and the construction is easy. At the same time, the bottom steel plate is completely used to replace the lower longitudinal reinforcement 17 of the beam to play a role in resisting tension, solve the cracking problem of the steel beam, consider the floor flange, fully utilize the good compression resistance of the concrete 8, economically and effectively improve the bearing capacity of the beam, the dowel 3 and the post-anchoring bolt 11 ensure the connection between the concrete 8 and the steel plate, and ensure that the force can be effectively transmitted, and there is no slip between the two materials. The post-anchoring bolt 3 technology brings great convenience to the steel bar binding process; the middle part of the steel greatly improves the ability of the steel structure and the concrete 8 to work together to play the role of the composite beam; the bottom steel plate added to the floor improves the combination of the steel and the concrete 8, and is conducive to the role of the floor flange, greatly improving the bearing capacity of the composite beam; the bottom steel plate replaces the lower longitudinal reinforcement of the beam, which can fully utilize the excellent tensile properties of steel to effectively solve the cracking problem of the structure.

[0134] The above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements will not make the essence of the corresponding technical solutions deviate from the protection scope of the technical solutions of the embodiments of the present application.

Claims

1. A simulation calculation method of a U-shaped steel-encased concrete composite beam, characterized by, Comprise the following steps: S1: Establish a double-parameter interface equivalent stiffness model of a U-shaped outer steel-concrete composite beam with a post-anchoring bolt (11), the double-parameter interface equivalent stiffness model comprising an interface normal equivalent stiffness and an interface tangential equivalent stiffness, the interface normal equivalent stiffness and the interface tangential equivalent stiffness being calculated by using formulas a1 and a2 respectively: (a1), (a2); wherein, respectively the interface normal / tangential equivalent stiffness, is the concrete elastic modulus, is the interface equivalent thickness, is the normal constraint coefficient, is the tangential compliance coefficient; S2: Solution and response extraction: solve for the ith load step, extract the calculated interface slip of the target measurement point / strip region and align with the target / test reference slip at the same load, displacement or moment level alignment; S3: Calculate whether the sliding residual and the interface energy meet the convergence criterion: The sliding residual is calculated according to formula a3: （a3）； The convergence criterion of the sliding residual is judged according to formula a4: (a4), wherein the slip residual threshold = 0.02; The convergence criterion of the interface energy is judged according to formula a5: （a5）； where the energy convergence threshold , denotes the interface energy, k, k+1 denote the kth and k+1th iteration within the same load step, the interface energy is calculated using equation a6: (a6), is the relative normal displacement of the interface, is the relative tangential displacement of the interface; If the sliding 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 (11), the spacing of the post-anchoring bolt (11) 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, the subsequent steps are continued, until the convergence criterion is met, and both the sliding residual and the interface energy meet the convergence criterion in two consecutive iteration steps.

2. The simulation calculation method of the U-shaped outer package steel-concrete composite beam according to claim 1, characterized in that, In the process of calculating the interface normal equivalent stiffness and the tangential equivalent stiffness: The interface normal constraint coefficient is ; and the interface tangential constraint coefficient is .

3. The simulation calculation method of the U-shaped outer package steel-concrete composite beam according to claim 2, characterized in that, In the process of calculating the interface equivalent stiffness, the pretightening force of the post-anchoring bolt (11) needs to be corrected, and the pretightening force correction relationship is corrected according to formulas a7 and a8: (a7) (a8) wherein, is the basic parameter under the condition of no pre-tightening force, is the normal stiffness enhancement coefficient, taken as 0.3-0.6, is the tangential flexibility reduction coefficient, taken as 0.1-0.3, is the actual pre-tightening force, is the pre-tightening force applied by a single rear anchor bolt (11) 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 capacity is inhibited, and the interface is more stable.

4. The simulation calculation method of the U-shaped outer package steel-concrete composite beam according to claim 3, characterized in that, The frictional forces of the steel-concrete interface provide the shear and anti-slipping capacity, the frictional forces of the interface The equivalent shear capacity of the post-installed anchor (11) is calculated by formula a9: （a9）； wherein, is the interface friction coefficient, which after sandblasting or toothed washer treatment should be taken as 0.35-0.45, is the yield strength of the anchor, is the effective cross-sectional area of the anchor.

5. The simulation calculation method of the U-shaped outer package steel-concrete composite beam according to claim 4, characterized in that, The interface normal and tangential equivalent stiffnesses are physically constrained and meet the following formula (a10) under the physical upper and lower bounds: （a10）。 6. The simulation calculation method of the U-shaped outer package steel-concrete composite beam according to claim 5, characterized in that, After the interface parameter iteration is updated, the interface normal and tangential degrees need to meet the following formulas a11 and a12: (a11), (a12); Wherein, is the normal stiffness correction step length coefficient, 0.1-0.3, is the tangential stiffness correction step length coefficient, 0.2-0.4, and the maximum number of iterations per step .

7. The simulation calculation method of a U-shaped outer package steel-concrete composite beam according to claim 6, characterized in that, When oscillations occur , and the sign changes repeatedly, the step size is adaptively reduced to .

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