Design method of assembly type combined cover beam and assembly type combined cover beam

Abstract

According to the design method of the assembly type combined cover beam and the assembly type combined cover beam, the material characteristics of a steel structure and a concrete structure are utilized, under the design of reasonable section layout arrangement, the beam height can be effectively reduced, the clearance under a bridge is increased, the tensile strength of steel and the compressive strength of concrete are fully exerted, transition design is avoided, and the construction cost is reduced. Meanwhile, the structural safety performance is ensured, the bearing capacity and structural rigidity of the cover beam are ensured, the material consumption of a lower structure can be properly reduced under the design effect, the anti-seismic property is improved, the method is particularly suitable for a large cantilever cover beam structure, the design process is comprehensive and concise, the size of the assembly type cover beam can be rapidly and reasonably set, the design efficiency is improved, and the cost is reduced. Meanwhile, the popularization cost and difficulty of the structure are reduced; the whole combined cover beam achieves full assembly type construction and is matched with a flange assembly to achieve force transmission between the assembly type cover beam and a pier column, construction efficiency is greatly improved, meanwhile, construction cost is reduced, the construction period is shortened, and obvious economic benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridges, and in particular to a design method for an assembled composite cap beam and the assembled composite cap beam. Background Art

[0002] Compared with traditional cast-in-place beams, prefabricated bridges have significant advantages in terms of efficiency, environmental protection, and quality controllability, and have become an important direction for the development of modern bridge engineering. At present, the superstructure, piers, and pile foundations of prefabricated bridges have a variety of relatively mature structural forms, while prefabricated cap beams are mainly reinforced concrete structures. The related art discloses an assembled bridge cap beam, which is provided with a connecting sleeve at one end or both ends of the cap beam. The prefabricated cap beams are fixedly connected by inserting the protruding steel bars reserved when the structure is segmented into the connecting sleeve and grouting the connecting sleeve. The steel bar connection construction of this technical solution is complicated, and the connection effect cannot be guaranteed, which will affect the stress and seismic performance of the node. At the same time, ordinary reinforced concrete cap beams are heavy and difficult to hoist, and cannot be applied to the large cantilever structure cap beams commonly used in urban bridges. If a prestressed system is added, the difficulty and period of construction will be further increased.

[0003] In addition, the currently available technology has proposed a composite system cap beam with steel frame reinforcement, which solves some problems of ordinary concrete structures. However, the structural form of concrete wrapped with steel frame is also not suitable for the stress mode where the negative bending moment at the top of the double-pier large cantilever cap beam is much larger than the positive bending moment between the piers, and it cannot fully utilize the material properties of steel structure under tension and concrete structure under compression.

[0004] In view of this, it is necessary to propose a design method for an assembled composite cap beam and an assembled composite cap beam to solve or at least alleviate the above-mentioned defects. Summary of the Invention

[0005] The main purpose of the present invention is to provide a design method for an assembled composite cap beam and an assembled composite cap beam, so as to solve the problem that the load-bearing system of the composite system cap beam in the prior art is not suitable for large cantilever cap beams.

[0006] To achieve the above object, the present invention provides a design method for an assembled composite cap beam, comprising the steps of: S1, formulating a size group of a composite cap beam according to material properties; wherein the composite cap beam includes a steel structure section and a reinforced concrete section; S2, determining a design value group of effects of a basic action combination according to the size group of the composite cap beam; wherein the design value group of effects of the basic action combination includes a shear design value of the basic action combination, a stress value of the steel beam of the basic action combination, and a compressive stress value of the concrete of the basic action combination; S3, based on the size group of the composite cap beam and the effect design value group of the basic action combination, verify whether the safety parameters of the composite cap beam structure meet the requirements; wherein the safety parameters of the composite cap beam structure include vertical shear bearing capacity, bending bearing capacity, fatigue strength of the steel structure, and deflection of the cantilever end of the composite cap beam; S4, determine whether all the safety parameters of the combined cap beam structure meet the requirements; if all the safety parameters of the combined cap beam structure meet the requirements, determine that the combined cap beam meets the technical requirements; if any one of the safety parameters of the combined cap beam structure does not meet the requirements, adjust the size of the combined cap beam and return to step S1.

[0007] Preferably, step S1 specifically includes the steps of: S11, obtaining the total cross-sectional height of the composite cap beam according to the application scenario; S12, obtaining the cross-sectional height of the concrete beam according to the total cross-sectional height of the composite cap beam; S13, according to the formula To determine the cross-sectional dimensions of the steel beam; is the ratio of the elastic modulus of steel to that of concrete, is the elastic modulus of steel, is the elastic modulus of concrete, is the cross-sectional area of the steel, is the cross-sectional area of concrete, is the distance between the centroid of the steel beam and the upper surface of the concrete, is the height of the concrete beam section.

[0008] Preferably, the step S12 specifically includes the steps of: Using the formula Determine the section height The value of ; among them, h is the total height of the composite cap beam section, is the height of the boundary compression zone, f sd It is the design value of tensile strength of steel.

[0009] Preferably, the verification of the vertical shear bearing capacity in step S3 specifically includes the following steps: S31, according to the formula Determine whether the design value of the vertical shear bearing capacity of the composite cap beam meets the requirements. If the design value of the vertical shear bearing capacity of the composite cap beam is greater than or equal to the shear force design value of the basic action combination, the requirements are met; if the design value of the vertical shear bearing capacity of the composite cap beam is less than the shear force design value of the basic action combination, the requirements are not met; wherein, is the structural importance coefficient, is the shear design value of the basic combination of actions, is the design value of vertical shear bearing capacity, b is the width of the concrete inclined section shear compression zone corresponding to the normal section, h 0 is the effective height of the concrete section, P is the reinforcement percentage of the longitudinal tensile steel bars in the inclined section, f cu,k is the standard value of compressive strength of a concrete cube with a side length of 150 mm, ρ sv is the reinforcement ratio of stirrups in the inclined section of concrete, f sv is the design value of the tensile strength of the stirrup, f vd is the design value of the shear strength of steel, A w is the web cross-sectional area of the steel.

[0010] Preferably, the verification of the bending bearing capacity in step S3 specifically includes the following steps: S32, according to the formula Determine whether the stress value of the steel beam under the basic combination of the above mentioned actions is less than or equal to the design value of the tensile strength of the steel material. And according to the formula Determine whether the concrete compressive stress value of the basic action combination meets the requirements. If the stress value of the steel beam of the basic action combination is less than or equal to the design value of the steel tensile strength, and the compressive stress value of the concrete of the basic action combination is less than or equal to the design value of the concrete compressive strength, then the requirements are met; if the stress value of the steel beam of the basic action combination is greater than the design value of the steel tensile strength, and / or the compressive stress value of the concrete of the basic action combination is greater than the design value of the concrete compressive strength, then the requirements are not met; wherein, is the edge stress of the steel section, is the edge stress of the concrete section, is the axial force borne by the steel section, is the bending moment borne by the steel section, is the axial force borne by the concrete section, is the bending moment borne by the concrete section, is the cross-sectional bending stiffness of the steel, is the cross-sectional flexural stiffness of concrete, f cd is the design value of concrete compressive strength.

[0011] Preferably, the fatigue strength verification of the steel structure in step S3 specifically includes the following steps: S330, establishing a composite cap beam model; S331, obtaining normal stress values and shear stress values under a limit state based on the composite cap beam model; S332, according to the formula Determine whether the ultimate normal stress difference is less than or equal to the normal stress fatigue limit, and according to the formula Determine whether the ultimate shear stress difference is less than or equal to the shear stress fatigue limit. If both are within the fatigue limit, the requirement is met; if one of them is greater than the fatigue limit, the requirement is not met. s pmax 、 s pmin are the maximum and minimum normal stresses obtained by loading the influence line under the limit condition, t pmax 、 t pmin are the maximum and minimum shear stresses obtained by loading the influence line under the limit condition, is the size effect reduction coefficient, is the normal stress constant amplitude fatigue limit, is the fatigue limit of constant shear stress.

[0012] Preferably, the verification of the deflection of the cantilever end of the composite cap beam in step S3 specifically includes the following steps: S341, obtaining the live load reaction force at each support and the distance between each support and the center of the pier column based on the composite cap beam model; S342, according to the formula Determine whether the deflection of the cantilever end of the combined cap beam meets the requirements. If the maximum deflection of the cantilever end of the combined cap beam is within the limit deflection range of the cantilever end of the combined cap beam, the requirements are met; if the maximum deflection of the cantilever end of the combined cap beam exceeds the limit deflection value of the cantilever end of the combined cap beam, the requirements are not met; wherein, d max is the maximum deflection value of the cantilever end of the composite cap beam, is the live load reaction at each support, is the distance between each support and the center of the pier, n is the number of supports in the cantilever range, L is the cantilever length, is the stiffness reduction factor.

[0013] Preferably, the step S4 of "adjusting the size of the composite cap beam" specifically includes: Adjust the total cross-sectional height of the composite cap beam; wherein the total cross-sectional height difference of a single adjustment is 5cm~10cm.

[0014] The present application also provides an assembled composite cap beam, comprising a assembled cap beam and a flange assembly, wherein the assembled cap beam comprises a steel structure section and a reinforced concrete section, wherein the steel structure section is connected to the top of the reinforced concrete section, and the reinforced concrete section is connected to the pier column through the flange assembly; wherein the size of the assembled composite cap beam is obtained based on the design method of the assembled composite cap beam as described above.

[0015] Preferably, the flange assembly includes a pier flange and a cap beam flange, the bottom end of the pier flange is used to be connected to the pier column, the top end of the cap beam flange is connected to the reinforced concrete section, and the pier flange and the cap beam flange are connected by bolts.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a design method for an assembled composite cap beam and an assembled composite cap beam. By utilizing the material properties of steel and concrete structures, and under a design in which the cross-section layout is reasonably arranged, the beam height can be effectively reduced, the clearance under the bridge can be increased, and the tensile strength of steel and the compressive strength of concrete can be fully utilized. Transitional design can be avoided while ensuring structural safety performance, ensuring the bearing capacity and structural stiffness of the cap beam. Under the design effect, the material consumption of the lower structure can be appropriately reduced, and the seismic performance can be improved. The design is particularly suitable for large cantilever cap beam structures. The design process is comprehensive, concise, and clear, and the dimensions of the assembled cap beam can be quickly and reasonably determined, thereby improving design efficiency and reducing the cost and difficulty of popularizing such structures. The entire combined cap beam is fully assembled in construction, and the flange assembly is used to realize the force transmission between the assembled cap beam and the pier, which greatly improves construction efficiency while reducing construction costs and construction period, with obvious economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of a flow chart of a method for designing an assembled composite cap beam in one embodiment of the present invention; Figure 2 A schematic elevation view of an application scenario of the overall structure in one embodiment of the present invention; Figure 3 It is a side schematic diagram of an application scenario of the overall structure in one embodiment of the present invention.

[0019] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments.

[0020] Description of Figure Numbers: 10. Composite cap beam; 110. Steel structure section; 120. Reinforced concrete section; 20. Flange assembly; 210. Cap beam flange; 220. Pier flange; 30. Pier column. DETAILED DESCRIPTION

[0021] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0024] In addition, the descriptions of "first", "second", etc. in the present invention are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0025] Please see the attached Figure 1 -Attached Figure 3 In one embodiment of the present invention, a design method for a prefabricated composite cap beam and a prefabricated composite cap beam are provided, comprising the steps of: S1. Formulate a size group of the composite cap beam 10 according to the material properties; wherein, the composite cap beam 10 includes a steel structure section 110 and a reinforced concrete section 120; it should be noted that the composite cap beam 10 mainly adopts the form of a combination of steel structure and reinforced concrete structure, and the concrete in the cross section of the composite cap beam 10 is mainly compressed, and the steel beam is tensile, so as to combine the material properties of steel's tensile resistance and concrete's compressive resistance to improve the bearing capacity of the structure. Therefore, in order to make the cross-sectional dimensions of the composite cap beam 10 better, it is necessary to design a better combination of cross-sectional dimensions so that the steel beam is basically tensile and the concrete is basically compressive, thereby giving full play to their respective material properties.

[0026] In a preferred embodiment, step S1 specifically includes the following steps: S11, obtaining the total cross-sectional height of the composite cap beam 10 according to the application scenario; S12, obtaining the cross-sectional height of the concrete beam according to the total cross-sectional height of the composite cap beam 10; S13, according to formula 1: To determine the cross-sectional dimensions of the steel beam; is the ratio of the elastic modulus of steel to that of concrete, is the elastic modulus of steel, is the elastic modulus of concrete, is the cross-sectional area of the steel, is the cross-sectional area of concrete, is the distance between the centroid of the steel beam and the upper surface of the concrete, is the height of the concrete beam section.

[0027] In specific implementation, the total cross-sectional height of the composite cap beam 10 is first defined in the application scenario where the bridge design is required. When the preliminary size is first determined, the commonly used total cross-sectional height of the composite cap beam 10 can be used as a preliminary value. Based on this preliminary value, when the total height of the composite cap beam 10 is determined, the cross-sectional height of the concrete beam can be further obtained. In a preferred embodiment, Formula 2 can be used: Determine the concrete section height The value of ; among them, h is the total height of the combined cap beam 10 sections, is the height of the boundary compression zone, f sd is the design value of the tensile strength of steel, the design value of the tensile strength of steel f sd It can be obtained according to the type of steel combined with the specification, and the steel specifications and concrete grades are usually preliminarily drawn up, so the concrete section height can be obtained according to the formula It is worth mentioning that Formula 2 is mainly applicable to scenarios with concrete grade C50 and below.

[0028] It is understandable that the total cross-sectional height of the composite cap beam 10 is h , concrete section height When all are known, since the cross section of the composite cap beam 10 is usually a regular shape, the distance between the centroid of the steel beam and the upper surface of the concrete can be easily obtained. , we will not go into details here, and the concrete section width can also be determined according to the reasonable range of conventional concrete cap beams. After preliminarily determining the conventional concrete section width and combining it with the concrete section height, the concrete cross-sectional area can be obtained. , cross-sectional area refers to the cross-sectional area; it should be noted that in formula 1 n 0 is the ratio of the elastic modulus of steel to that of concrete. The elastic modulus of steel is and the elastic modulus of concrete All of these can be obtained through the corresponding material grade and specifications. After the above data are preliminarily determined, the cross-sectional area of the steel can be determined according to formula 1. , a preliminary size group of the combined cap beam 10 is obtained, and subsequent structural safety performance verification is carried out based on this preliminary size group.

[0029] S2. Determine the effect design value group of the basic action combination according to the size group of the composite cap beam 10; wherein, the effect design value group of the basic action combination includes the shear design value of the basic action combination, the steel beam stress value of the basic action combination, and the concrete compressive stress value of the basic action combination. It should be noted that the effect design value group of the basic action combination is the basic combination and frequent combination effect design value acting on the cap beam. Specifically, the effect design value of the bridge under permanent action and variable action is determined according to the general bridge internal force calculation method, and after combining the permanent action design value and the variable action design value in accordance with the "General Code for Design of Highway Bridges and Culverts" (JTGD60-2015), the effect design value group of the basic action combination is obtained. In this application, the shear design value of the basic action combination is mainly required to verify the vertical shear bearing capacity, and the steel beam stress value of the basic action combination and the concrete compressive stress value of the basic action combination are required to verify the bending bearing capacity.

[0030] S3, based on the size group of the composite cap beam 10 and the effect design value group of the basic action combination, verify whether the structural safety parameters of the composite cap beam 10 meet the requirements; wherein the structural safety parameters of the composite cap beam 10 include vertical shear bearing capacity, bending bearing capacity, fatigue strength of the steel structure, and deflection of the cantilever end of the composite cap beam 10; S4, judging whether all the structural safety parameters of the composite cap beam 10 meet the requirements; if all the structural safety parameters of the composite cap beam 10 meet the requirements, it is determined that the composite cap beam 10 meets the technical requirements; if any one of the structural safety parameters of the composite cap beam 10 does not meet the requirements, the size of the composite cap beam 10 is adjusted, and the process returns to step S1. It is worth noting that, given the material specifications, based on the preliminarily prepared size group of the composite cap beam 10, various structural safety parameters are obtained to ensure the safety performance of the composite cap beam 10 structure, mainly including vertical shear bearing capacity, bending bearing capacity, fatigue strength of the steel structure, and deflection of the cantilever end of the composite cap beam 10. Only when all the above parameters meet the requirements can the structural safety performance of the composite cap beam 10 be guaranteed. If one of the parameters does not meet the requirements, it is necessary to adjust a certain dimension based on the preliminarily prepared dimension, and then substitute the adjusted value into the process and return to step S1. Based on the adjusted dimension and formula 1, the improved proposed dimension is re-determined, and the safety parameter verification is performed again based on the improved proposed dimension until all the above parameters meet the requirements.

[0031] Specifically, the verification of the vertical shear bearing capacity in step S3 specifically includes the following steps: S31, according to formula 3: Determine whether the design value of the vertical shear bearing capacity of the composite cap beam 10 meets the requirements. If the design value of the vertical shear bearing capacity of the composite cap beam 10 is greater than or equal to the shear force design value of the basic action combination, the requirements are met; if the design value of the vertical shear bearing capacity of the composite cap beam 10 is less than the shear force design value of the basic action combination, the requirements are not met; wherein, is the structural importance coefficient, is the shear design value of the basic combination of actions, is the design value of vertical shear bearing capacity, b is the width of the concrete inclined section shear compression zone corresponding to the normal section, h 0 is the effective height of the concrete section, P is the reinforcement percentage of the longitudinal tensile steel bars in the inclined section, f cu,k is the standard value of compressive strength of a concrete cube with a side length of 150 mm, ρ sv is the reinforcement ratio of stirrups in the inclined section of concrete, f sv is the design value of the tensile strength of the stirrup, f vd is the design value of the shear strength of steel, A w is the web cross-sectional area of the steel.

[0032] It is worth noting that according to the preliminarily proposed cap beam structure size, the design value of the vertical shear bearing capacity of the cap beam is determined by combining Formula 3. , and compared with the shear design value of the basic combination of actions calculated in S2. The shear design value of the basic combination of actions is affected by the structural safety level, so the final comparison needs to be combined with the structural importance coefficient to obtain For comparison; if , indicating that the proposed cap beam structure size is reasonable and meets the vertical shear bearing capacity verification of the cap beam structure. Otherwise, the vertical shear bearing capacity does not meet the requirements. It is worth mentioning that P is the reinforcement percentage of the longitudinal tensile steel bars in the inclined section, P = 100ρ, ρ = A sl / bh0,A sl is the area of longitudinal tensile reinforcement in the concrete section, and when P>2.5, take P=2.5; and ρ sv is the reinforcement ratio of stirrups in the inclined section of concrete, ρ sv =A sv / S v b, A sv is the total cross-sectional area of the stirrups arranged in the same cross section in the inclined section, S v is the spacing of stirrup reinforcement in the inclined section.

[0033] Furthermore, the verification of the bending bearing capacity in step S3 specifically includes the following steps: S32, according to formula 4: Determine whether the stress value of the steel beam under the basic combination of the above mentioned actions is less than or equal to the design value of the tensile strength of the steel material. And according to Formula 5: Determine whether the concrete compressive stress value of the basic action combination meets the requirements. If the stress value of the steel beam of the basic action combination is less than or equal to the design value of the steel tensile strength, and the compressive stress value of the concrete of the basic action combination is less than or equal to the design value of the concrete compressive strength, then the requirements are met; if the stress value of the steel beam of the basic action combination is greater than the design value of the steel tensile strength, and / or the compressive stress value of the concrete of the basic action combination is greater than the design value of the concrete compressive strength, then the requirements are not met; wherein, is the edge stress of the steel section, is the edge stress of the concrete section, is the axial force borne by the steel section, is the bending moment borne by the steel section, is the axial force borne by the concrete section, is the bending moment borne by the concrete section, is the cross-sectional bending stiffness of the steel, is the cross-sectional flexural stiffness of concrete, f cd is the design value of concrete compressive strength.

[0034] It is worth noting that the stress value σ of the steel beam based on the basic combination of the action under the preliminarily proposed size group can be obtained from step S2. s As shown in the equation of formula 4, the concrete compressive stress value σ of the basic combination of actions is c As shown in the equation of formula 5, the structural safety level must be combined and then compared with the strength design values of steel beams and concrete respectively; if 、 If both conditions are met at the same time, it means that the size of the proposed cap beam structure is reasonable and meets the bending bearing capacity verification of the cap beam structure. On the contrary, if both conditions are not met or one of them is not met, the bending bearing capacity does not meet the requirements.

[0035] Furthermore, the fatigue strength verification of the steel structure in step S3 specifically includes the following steps: S330, establishing a composite cap beam model; S331, obtaining normal stress values and shear stress values under a limit state based on the composite cap beam model; S332, according to formula 6: Determine whether the ultimate normal stress difference is less than or equal to the normal stress fatigue limit, and according to Formula 7: Determine whether the ultimate shear stress difference is less than or equal to the shear stress fatigue limit. If both are within the fatigue limit, the requirement is met; if one of them is greater than the fatigue limit, the requirement is not met. s pmax 、 s pmin are the maximum and minimum normal stresses obtained by loading the fatigue load model onto the influence line under the limit condition, t pmax 、 t pmin are the maximum and minimum shear stresses obtained by loading the fatigue load model onto the influence line under the limit condition, is the size effect reduction coefficient, is the normal stress constant amplitude fatigue limit, is the fatigue limit of constant shear stress.

[0036] It should be noted that a three-dimensional geometric model of the cap beam can be established in the software, and material properties (such as elastic modulus, yield strength, etc.) and boundary conditions (such as support position, fixed point, etc.) can be defined. Then, various loads can be applied, and the normal stress value and shear stress value under the limit state (most unfavorable state) can be obtained through finite element analysis. The normal stress value includes the maximum normal stress value and the minimum normal stress value, and the shear stress value includes the maximum shear stress value and the minimum shear stress value, so as to obtain their respective differences. The most unfavorable state can be combined with the design specification to add load types. This is a content well known to those skilled in the art, so it will not be described in detail here. Then, Formula 6 is used to determine whether the normal stress fatigue limit meets the requirements, and Formula 7 is used to determine whether the shear stress fatigue limit meets the requirements. If both meet the requirements at the same time (that is, the ultimate normal stress difference is less than or equal to the positive stress fatigue limit, and the ultimate shear stress difference is less than or equal to the shear stress fatigue limit), it means that the size of the proposed cap beam steel structure is reasonable and meets the fatigue strength requirements. On the contrary, if both are not met or one of them is not met, the fatigue strength does not meet the requirements.

[0037] Furthermore, the verification of the deflection of the cantilever end of the composite cap beam 10 in step S3 specifically includes the following steps: S341, based on the composite cap beam model, obtaining the live load reaction force at each support and the distance between each support and the center of the pier column 30; S342, according to Formula 8: Determine whether the deflection of the cantilever end of the composite cap beam 10 meets the requirements. If the maximum deflection of the cantilever end of the composite cap beam 10 is within the limit deflection range of the cantilever end of the composite cap beam 10, the requirements are met; if the maximum deflection of the cantilever end of the composite cap beam 10 exceeds the limit deflection value of the cantilever end of the composite cap beam 10, the requirements are not met; wherein, d max is the maximum deflection value of the cantilever end of the composite cap beam 10, is the live load reaction at each support, is the distance between each support and the center of the pier 30, n is the number of supports in the cantilever range, L is the cantilever length, is the stiffness reduction factor.

[0038] It should be understood that based on the established three-dimensional geometric model, the live load reaction at each support is obtained. The distance between each support and the center of the pier 30 , and substitute it into Formula 8 to obtain the maximum deflection value of the cantilever end of the composite cap beam 10 d max, compare it with the ultimate deflection of the cantilever end of the composite cap beam 10. If it is within the range, the requirement is met, otherwise, the structural stiffness does not meet the requirement; it can be understood that the total length of the composite cap beam 10 is matched based on the width of the bridge, and the pier center distance between the piers 30 is fixed based on the application scenario (for example, in urban viaducts, the pier center distance between the piers 30 cannot be set arbitrarily, and there are regulatory requirements). Therefore, it can be seen that the cantilever length L of the composite cap beam 10 is a clearly obtainable value.

[0039] Furthermore, the step S4 of “adjusting the size of the composite cap beam 10 ” specifically includes: The total cross-sectional height of the composite cap beam 10 is adjusted; wherein the total cross-sectional height difference of a single adjustment is 5 cm to 10 cm.

[0040] It should be noted that when any one of the structural safety parameters of the combined cap beam 10 does not meet the requirements, it is necessary to adjust the size, and after the adjustment, return to step S1 (specifically, return to step S12) to obtain the adjusted size group, and then re-check the structural safety parameters based on the adjusted size group. Specifically, adjust the total cross-sectional height of the combined cap beam 10. h , when the total cross-sectional height of the composite cap beam 10 changes, h According to Formula 2, the adjusted concrete section height can be obtained. h c ´, the concrete section width remains unchanged, so the adjusted concrete section area can be obtained A c ´, and the distance between the centroid of the steel beam and the upper surface of the concrete y s ´Also adapts to changes, when the material remains unchanged, n 0 remains unchanged, and then the adjusted cross-sectional area of the steel is obtained according to formula 1 A s ´, and perform structural safety performance verification again based on the adjusted size group obtained in this way; among them, the difference in the total height of the section for a single adjustment is 5cm~10cm, that is, the total height of the section is increased or decreased each time according to the comparison of the verification results. After the increase or decrease adjustment, a new size group is obtained for verification. If it meets the requirements, the section combination form that fully utilizes the material properties is obtained. If it does not meet the requirements, the total height of the section is increased or decreased again until it meets the requirements.

[0041] To facilitate understanding by those skilled in the art, a simple example is given below: Based on the commonly used cap beam size, the total cross-sectional height of the composite cap beam 10 is set hThe preliminary size is 2m (usually there are also applications with high requirements for underbridge clearance, which may be less than 2m. The value is determined based on the actual application scenario and the commonly used values). The steel material is Q355D and the concrete is C40. When the material specifications are determined, the various strength design values (such as the tensile strength design value of steel) can be obtained according to various specifications. f sd , design value of concrete compressive strength f cd etc.) and elastic modulus values (elastic modulus of steel and the elastic modulus of concrete ), etc., according to formula 2, the preliminary concrete section height can be obtained , the total height of the cross section of the composite cap beam 10 h and concrete section height When all are determined, the distance between the centroid of the steel beam and the upper surface of the concrete can be obtained The concrete section width can usually adopt a conventional width such as 2m (usually 1.8m~2.4m), according to the determined concrete section width and concrete section height The cross-sectional area of concrete can be obtained According to formula 1, the cross-sectional area of the steel can be determined , in order to obtain the preliminary size group of the combined cap beam 10, based on this preliminary size group of the combined cap beam 10 to verify the structural safety parameters to ensure that the structural safety performance meets the requirements; when one of the structural safety parameters does not meet the requirements, adjust the total cross-sectional height of the combined cap beam 10 h In this example, 2m is adjusted to 2.05m (a single increase of 5cm). h ´Redetermine the height of the adjusted concrete section ´、The distance between the adjusted steel beam centroid and the upper surface of the concrete ´、Adjusted concrete cross-sectional area ´、The cross-sectional area of the steel after adjustment ´, obtain the adjusted size group, and verify the adjusted structural safety parameters based on the adjusted size group. If any of the adjusted structural safety parameters still does not meet the requirements, increase the total section height by 5 cm again, and repeat the above steps until all structural safety parameters meet the requirements. It is worth mentioning that if the structural safety meets the requirements, the total section height can be appropriately reduced, which can reduce costs, thereby forming a structural form that takes into account both safety performance and economic costs, and improving economy.

[0042] It should be noted that, based on certain specific embodiments, when it is found that the value of the structural safety parameter cannot produce a significant change after adjusting the cross-sectional height of the concrete, the material strength can be adjusted and the size can be re-designed.

[0043] The present application also provides an assembled composite cap beam 10, comprising a assembled cap beam 10 and a flange assembly 20, wherein the assembled cap beam 10 comprises a steel structure section 110 and a reinforced concrete section 120, wherein the steel structure section 110 is connected to the top of the reinforced concrete section 120, and the reinforced concrete section 120 is connected to the pier 30 through the flange assembly 20; wherein the size of the assembled composite cap beam 10 is obtained based on the design method of the assembled composite cap beam 10 as described above.

[0044] It should be noted that the entire composite cap beam 10 can be fully prefabricated, which has more reliable quality and higher precision than on-site casting. The structural arrangement in which the steel structure section 110 is connected to the reinforced concrete section 120 makes full use of the tensile strength of steel and the compressive strength of concrete, avoids or reduces the use of prestress, and the use of flange assembly 20 for connection improves the convenience of installation and greatly speeds up construction efficiency.

[0045] Furthermore, the flange assembly 20 includes a pier flange 220 and a cap beam flange 210. The bottom end of the pier flange 220 is used to be connected to the pier column 30, and the top end of the cap beam flange 210 is connected to the reinforced concrete section 120. The pier flange 220 and the cap beam flange 210 are connected by bolts.

[0046] It should be noted that the cap beam flange 210 is welded and fixed to the reinforced concrete section 120 of the composite cap beam 10, and the pier flange 220 is fixedly connected to the lower pier column 30 through embedded parts. After the pier pile foundation and the pier column 30 are cast-in-place, the prefabricated cap beam can be hoisted into place, and the force transmission between the prefabricated cap beam and the pier column 30 is realized through the connection between the cap beam flange 210 and the pier flange 220.

[0047] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A design method for an assembled composite cap beam, characterized in that: Including steps: S1, formulating a size group of a composite cap beam according to material properties; wherein the composite cap beam includes a steel structure section and a reinforced concrete section; S2, determining a design value group of effects of a basic action combination according to the size group of the composite cap beam; wherein the design value group of effects of the basic action combination includes a shear design value of the basic action combination, a stress value of the steel beam of the basic action combination, and a compressive stress value of the concrete of the basic action combination; S3, based on the size group of the composite cap beam and the effect design value group of the basic action combination, verify whether the safety parameters of the composite cap beam structure meet the requirements; wherein the safety parameters of the composite cap beam structure include vertical shear bearing capacity, bending bearing capacity, fatigue strength of the steel structure, and deflection of the cantilever end of the composite cap beam; S4, determine whether all the safety parameters of the combined cap beam structure meet the requirements; if all the safety parameters of the combined cap beam structure meet the requirements, determine that the combined cap beam meets the technical requirements; if any one of the safety parameters of the combined cap beam structure does not meet the requirements, adjust the size of the combined cap beam and return to step S1.

2. The design method of the assembled composite cap beam according to claim 1, characterized in that: Step S1 specifically includes the following steps: S11, obtaining the total cross-sectional height of the composite cap beam according to the application scenario; S12, obtaining the cross-sectional height of the concrete beam according to the total cross-sectional height of the composite cap beam; S13, according to the formula To determine the cross-sectional dimensions of the steel beam; is the ratio of the elastic modulus of steel to that of concrete, is the elastic modulus of steel, is the elastic modulus of concrete, is the cross-sectional area of the steel, is the cross-sectional area of concrete, is the distance between the centroid of the steel beam and the upper surface of the concrete, is the height of the concrete beam section.

3. The design method of the assembled composite cap beam according to claim 2, characterized in that: The step S12 specifically includes the following steps: Using the formula Determine the section height The value of ; among them, h is the total height of the composite cap beam section, is the height of the boundary compression zone, f sd It is the design value of tensile strength of steel.

4. The design method of the assembled composite cap beam according to claim 2, characterized in that: The verification of the vertical shear bearing capacity in step S3 specifically includes the following steps: S31, according to the formula Determine whether the design value of the vertical shear bearing capacity of the composite cap beam meets the requirements. If the design value of the vertical shear bearing capacity of the composite cap beam is greater than or equal to the shear force design value of the basic action combination, the requirements are met; if the design value of the vertical shear bearing capacity of the composite cap beam is less than the shear force design value of the basic action combination, the requirements are not met; wherein, is the structural importance coefficient, is the shear design value of the basic combination of actions, is the design value of vertical shear bearing capacity, b is the width of the concrete inclined section shear compression zone corresponding to the normal section, h 0 is the effective height of the concrete section, P is the reinforcement percentage of the longitudinal tensile steel bars in the inclined section, f cu,k is the standard value of compressive strength of a concrete cube with a side length of 150 mm, ρ sv is the reinforcement ratio of stirrups in the inclined section of concrete, f sv is the design value of the tensile strength of the stirrup, f vd is the design value of the shear strength of steel, A w is the web cross-sectional area of the steel.

5. The design method of the assembled composite cap beam according to claim 4, characterized in that: The verification of the bending bearing capacity in step S3 specifically includes the following steps: S32, according to the formula Determine whether the stress value of the steel beam under the basic combination of the above mentioned actions is less than or equal to the design value of the tensile strength of the steel material. And according to the formula Determine whether the concrete compressive stress value of the basic action combination meets the requirements. If the stress value of the steel beam of the basic action combination is less than or equal to the design value of the steel tensile strength, and the compressive stress value of the concrete of the basic action combination is less than or equal to the design value of the concrete compressive strength, then the requirements are met; if the stress value of the steel beam of the basic action combination is greater than the design value of the steel tensile strength, and / or the compressive stress value of the concrete of the basic action combination is greater than the design value of the concrete compressive strength, then the requirements are not met; wherein, is the edge stress of the steel section, is the edge stress of the concrete section, is the axial force borne by the steel section, is the bending moment borne by the steel section, is the axial force borne by the concrete section, is the bending moment borne by the concrete section, is the cross-sectional bending stiffness of the steel, is the cross-sectional flexural stiffness of concrete, f cd is the design value of concrete compressive strength.

6. The design method of the assembled composite cap beam according to claim 5, characterized in that: The fatigue strength verification of the steel structure in step S3 specifically includes the following steps: S330, establishing a composite cap beam model; S331, obtaining normal stress values and shear stress values under a limit state based on the composite cap beam model; S332, according to the formula Determine whether the ultimate normal stress difference is less than or equal to the normal stress fatigue limit, and according to the formula Determine whether the ultimate shear stress difference is less than or equal to the shear stress fatigue limit. If both are within the fatigue limit, the requirement is met; if one of them is greater than the fatigue limit, the requirement is not met. σ pmax 、 σ pmin are the maximum and minimum normal stresses obtained by loading the influence line under the limit condition, τ pmax 、 τ pmin are the maximum and minimum shear stresses obtained by loading the influence line under the limit condition, is the size effect reduction coefficient, is the normal stress constant amplitude fatigue limit, is the fatigue limit of constant shear stress.

7. The design method of the assembled composite cap beam according to claim 6, characterized in that: The verification calculation of the deflection of the cantilever end of the composite cap beam in step S3 specifically includes the following steps: S341, obtaining the live load reaction force at each support and the distance between each support and the center of the pier column based on the composite cap beam model; S342, according to the formula Determine whether the deflection of the cantilever end of the combined cap beam meets the requirements. If the maximum deflection of the cantilever end of the combined cap beam is within the limit deflection range of the cantilever end of the combined cap beam, the requirements are met; if the maximum deflection of the cantilever end of the combined cap beam exceeds the limit deflection value of the cantilever end of the combined cap beam, the requirements are not met; wherein, δ max is the maximum deflection value of the cantilever end of the composite cap beam, is the live load reaction at each support, is the distance between each support and the center of the pier, n is the number of supports in the cantilever range, L is the cantilever length, is the stiffness reduction factor.

8. The design method of the assembled composite cap beam according to claim 1, characterized in that: The step S4 of "adjusting the size of the composite cap beam" specifically includes: Adjust the total cross-sectional height of the composite cap beam; wherein the total cross-sectional height difference of a single adjustment is 5cm~10cm.

9. An assembled composite cap beam, characterized in that: It includes a composite cap beam and a flange assembly, the composite cap beam includes a steel structure section and a reinforced concrete section, the steel structure section is connected to the top of the reinforced concrete section, and the reinforced concrete section is used to connect to the pier column through the flange assembly; wherein, the size of the composite cap beam is obtained based on the design method of the assembled composite cap beam according to any one of claims 1-8.

10. The assembled composite cap beam according to claim 9, characterized in that: The flange assembly includes a pier flange and a cap beam flange. The bottom end of the pier flange is used to be connected to the pier column, and the top end of the cap beam flange is connected to the reinforced concrete section. The pier flange and the cap beam flange are connected by bolts.

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