UHPC-T-shaped beam vertical shear capacity design method and system for external reinforcement and storage medium

Abstract

The invention provides an in-vitro reinforced UHPC-T-shaped beam vertical shear capacity design method and system and a storage medium, and the method comprises the steps: calculating a vertical shear force component and a vertical shear bearing capacity characteristic value borne by a UHPC rib plate and a vertical shear force component and a vertical shear bearing capacity characteristic value borne by a steel web plate under a planned structural size of a composite structural beam, and calculating the vertical shear force component and the vertical shear bearing capacity characteristic value of the UHPC rib plate and the vertical shear bearing capacity characteristic value of the steel web plate; respectively judging whether vertical shear force components and vertical shear bearing capacity characteristic values of the two vertical shear force components and the vertical shear bearing capacity characteristic values meet set conditions or not, if so, carrying out next calculation, and if any one of the vertical shear force components and the vertical shear bearing capacity characteristic values does not meet the set conditions, adjusting the structure size and then recalculating; and obtaining a vertical shear capacity characteristic value controlled by the horizontal shear capacity, judging whether the characteristic value and an effect design value of the vertical shear force meet a set condition or not, if so, ending the design, and if not, adjusting the structure size and recalculating. According to the design method for the vertical shear capacity of the composite structural beam, engineering technicians can judge key mechanical properties of the structure easily.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge engineering, and in particular to a method, system and storage medium for designing the vertical shear capacity of an externally reinforced UHPC-T beam. Background Art

[0002] With the increasing popularity of ultra-high performance concrete (UHPC), existing bridge technologies have attempted to replace conventional concrete (NC) with UHPC as the primary construction material in recent years to reduce deadweight and improve performance. For example, composite beams with steel beams and UHPC decks suffer from drawbacks such as insufficient material performance, high steel consumption, and high welding workload. To fully utilize the superior properties of both steel and UHPC materials and further improve the economics and applicability of steel-UHPC composite beams, several new composite beam structures have been proposed. Among the currently published technologies, Chinese patent applications with publication numbers CN112391932A and CN112342889A both propose a UHPC-T beam that utilizes steel sections as external reinforcement. Both approaches utilize UHPC to bear the high compressive stresses of the upper flange and the low tensile stresses of the composite web, while using steel sections to bear the high tensile stresses of the lower portion, fully utilizing the material's properties.

[0003] Different from traditional steel-concrete composite beams, the vertical shear bearing mechanism of externally reinforced UHPC-T beams is significantly different: First, traditional composite beams consist of a steel beam with a lower flange, a steel web, and an upper flange, and a concrete deck. Because the concrete deck accounts for a relatively small proportion of the beam's height, its vertical shear capacity is generally not considered, meaning that the steel web provides the entire vertical shear capacity. However, since the web of an externally reinforced UHPC-T beam is composed of a UHPC web and an externally reinforced steel web in comparable proportions, ignoring the shear contribution of the UHPC web would, on the one hand, necessitate oversizing the externally reinforced steel web to meet requirements, which would be uneconomical. On the other hand, the UHPC web, which bears some of the shear load, would not have been verified, potentially rendering the structure unsafe. While simply summing the two to determine the vertical shear capacity of the UHPC-T beam, while considering both the UHPC web and the externally reinforced steel web, improves the performance. However, due to the mismatch between the shear distribution ratio and the load history, there is a risk of overestimating the vertical shear capacity.

[0004] Secondly, the shear connectors of traditional composite beams are located at the interface between the upper flange of the steel beam and the concrete deck, far from the neutral axis, where horizontal shear forces are relatively low. In contrast, the shear connectors of externally reinforced UHPC-T beams are closer to the neutral axis, subjecting them to greater horizontal shear forces. The ability of the UHPC-T beam to withstand bending moments and vertical shear forces as a whole requires reliable shear connectors. Therefore, its vertical shear capacity may be limited by the horizontal shear capacity of the shear connectors. Failure to account for this issue could lead to significant structural safety risks.

[0005] Finally, when externally reinforced UHPC-T beams are used as bridge components, they are often subjected to the combined effects of bending moment and shear force. Under positive bending moment, the UHPC web may crack, entering the softening stage of the material or quitting working, causing the neutral axis of the overall interface to shift upward, increasing the static moment of the steel structure, and thus increasing the shear stress in the steel web, which in turn increases the shear force borne by the steel web, that is, the shear force is transferred from the UHPC web to the steel web. In situations where positive bending moment and shear force may be simultaneously applied, if the redistribution of shear force between the UHPC web and the steel web is not considered, the design of the steel web will be unsafe.

[0006] In summary, there is an urgent need for a vertical shear capacity design method, system and storage medium for externally reinforced UHPC-T beams to solve the problems existing in the existing technology. Summary of the Invention

[0007] The present invention aims to provide a method for designing the vertical shear capacity of externally reinforced UHPC-T beams. This method aims to address the problem in the prior art of lacking a corresponding method to guide the vertical shear design of composite structural beams of steel and UHPC to ensure bridge safety and economy. The specific technical solution is as follows: A method for designing the vertical shear capacity of externally reinforced UHPC-T beams includes: S1. Obtain the design value of the vertical shear effect of the composite structural beam under the proposed structural dimensions. and the design value of the effect of the bending moment ; S2. Design value based on the geometric parameters of the cross section of the composite structure beam and the effect of vertical shear force and the design value of the effect of the bending moment , calculate the vertical shear force component borne by the UHPC ribs and the vertical shear component borne by the steel web ; S3. Calculation of the characteristic value of vertical shear bearing capacity of UHPC ribbed plates and the characteristic value of the vertical shear bearing capacity of the steel web If it exists or , then adjust the structural dimensions of the composite structural beam and return to step S1, otherwise go to step S4; wherein, is the importance coefficient of the composite structural beam, is the material partial coefficient; S4. Calculate the horizontal shear capacity per unit length of the steel tenons and mortises alternately arranged along the longitudinal direction of the bridge on the steel web. , according to the cross-sectional shear stress distribution height z and horizontal shear capacity per unit length Obtain the characteristic value of vertical shear bearing capacity controlled by horizontal shear capacity ; S5, if Then adjust the structural dimensions of the composite structural beam and return to step S1; otherwise, end the design.

[0008] In the above technical solution, preferably, step S2 is specifically: S2.1. Convert the cross-section of the composite structural beam into a cross-section of a single material; S2.2. Divide the cross section into several unit layers in the height direction; S2.3. Design value based on the effect of bending moment The distance from the neutral axis NA to the top of the section is obtained iteratively using the cross-section layering method. , and calculate the moment of inertia of the cross section about the neutral axis NA ; S2.4, according to the moment of inertia and the design value of the effect of vertical shear Calculate the shear stress of each unit layer, and further calculate the shear force of each unit layer; S2.5. Obtain the vertical shear force component borne by the UHPC ribs and the vertical shear component borne by the steel web .

[0009] In the above technical solution, preferably, in step S2.1, the cross section of the composite structural beam is converted into a cross section of a single material, specifically: Multiply the thickness of the UHPC ribs in the cross section of the composite structural beam and the width of the UHPC bridge deck by , get the cross section of a single material; among them, the elastic modulus ratio , is the elastic modulus of the steel web, is the elastic modulus of UHPC concrete.

[0010] In the above technical solution, the first Shear stress of each unit layer for: (1), Section Shear force per unit layer for: (2), in, For the The width of the unit layer, Indicates the The static moment of the location of the unit layer, For the The area of ​​the unit layer, For the The height of each unit layer.

[0011] In the above technical solution, the vertical shear force component borne by the UHPC rib in step S2.5 is preferably for: (3), Vertical shear force component borne by the steel web for: (4), in, It is the first among UHPC ribs. The shear force of each unit layer, The first Shear force of each unit layer.

[0012] In the above technical solution, preferably, in step S4, the horizontal shear capacity per unit length of the steel tenons and mortises alternately arranged along the longitudinal bridge direction on the steel web is calculated. , specifically: Calculate the horizontal shear bearing capacity characteristic value corresponding to the shear failure of the steel tenon : (7), Calculate the characteristic value of horizontal shear bearing capacity corresponding to mortise shear failure : (8), Calculation of the characteristic value of the horizontal shear capacity between layers of composite structural beams : (9), Calculation of horizontal shear capacity per unit length : (10), in, The longitudinal arrangement spacing of the steel tenons; is the thickness of the steel web; is the yield strength of the steel web; is the shape coefficient of the mortise; is the standard value of cube compressive strength of UHPC concrete; It is the horizontal reinforcement strengthening coefficient in the mortise.

[0013] The preferred technical solution above is that the vertical shear bearing capacity characteristic value controlled by the horizontal shear capacity is for: · (11).

[0014] In the above technical solution, the vertical shear bearing capacity characteristic value of the UHPC rib plate in step S3 is preferably for: (5), Characteristic value of vertical shear capacity of steel web for: (6), in, is the yield strength of the steel web; is the thickness of the steel web; is the height of the steel web; is the thickness of the UHPC rib; is the height of the UHPC rib; is the tensile elastic ultimate strength of UHPC concrete; is the ultimate tensile strength of UHPC concrete; is the sum of the cross-sectional areas of all vertical segments of a single stirrup in the UHPC rib; is the spacing of stirrups in the UHPC ribs; is the yield strength of the stirrups in the UHPC rib.

[0015] The present invention also provides a system for designing the vertical shear capacity of an externally reinforced UHPC-T-beam. The system includes a memory and a processor. When the processor runs computer instructions stored in the memory, it executes the method for designing the vertical shear capacity of an externally reinforced UHPC-T-beam.

[0016] The present invention also provides a storage medium, in which computer instructions are stored. The computer instructions are configured to execute the vertical shear capacity design method of the externally reinforced UHPC-T beam when running.

[0017] The application of the technical solution of the present invention has the following beneficial effects: The vertical shear capacity design method of the composite structural beam in the present invention helps engineering technicians to judge the key mechanical properties of the structure. The calculation method is scientific and efficient, which helps promote the engineering application of this innovative structure (referring to the composite structural beam) and create social and economic value.

[0018] The method of the present invention avoids the insufficient shear resistance of simply superimposing UHPC ribs and steel webs, and takes into account the differences in shear force distribution ratio and load-bearing history of the two materials. It prevents over-design caused by ignoring the contribution of UHPC ribs and avoids the risk of overestimation caused by simple superposition.

[0019] The method of the present invention clearly identifies the particularity of the position of the tenon and mortise (i.e., the shear connector in the background art) being close to the neutral axis, and uses the horizontal shear resistance of the tenon and mortise as a limiting condition for the vertical shear resistance. By considering the bearing capacity of the tenon and mortise, the reliability of the structural design is improved.

[0020] The method of the present invention can take into account the influence of the change in the stress mechanism after the cracking of the UHPC rib plate. Specifically, if the design value of the bending moment effect is Small, the tensile part of UHPC is in the elastic section, as The position of the neutral axis NA will not change with the increase of is a fixed value; as With further increase, after the UHPC ribs soften or crack under tension, according to the equilibrium conditions of axial force and bending moment in the section, the neutral axis NA will move upward, that is, The static moment and inertia moment of the upper and lower parts of the neutral axis NA change continuously, which causes the bending moment to affect the shear force distribution. It is the design value based on the effect of bending moment The cross-sectional layering method is used to iteratively confirm the The method of the present invention can take into account the effect design value of the bending moment under different stress conditions. The impact of the changes is taken into account, and the redistribution of shear force between the UHPC ribs and the steel web is considered. By considering the redistribution of force, the safety of the vertical shear design is ensured.

[0021] The method proposed in the present invention can be easily compiled into an application program, which greatly facilitates use by engineering designers.

[0022] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings: Figure 1 It is an axonometric view of a composite structural beam of steel and UHPC; Figure 2 yes Figure 1 Schematic diagram of the structure of the middle vertical stirrup group; Figure 3 yes Figure 1 Schematic diagram of the structure of the steel tenon and mortise; Figure 4 It is a flow chart of the vertical shear capacity design method of the externally reinforced UHPC-T beam of the present invention; Figure 5 is a schematic cross-sectional view of the composite structural beam in Example 1; Figure 6 This is a schematic diagram of the composite structural beam cross section in Example 1 after being converted into a single material cross section; Figure 7 is a schematic diagram of shear stress distribution of the composite structural beam in Example 1; Figure 8 is a simplified calculation diagram of the shear force of the composite structural beam in Example 1; Among them, 100, composite structural beam, 110, UHPC bridge deck, 111, bridge deck transverse reinforcement, 112, bridge deck longitudinal reinforcement, 120, UHPC rib, 121, lower open stirrups, 122, upper open stirrups, 123, bottom layer longitudinal reinforcement, 124, second bottom layer longitudinal reinforcement, 125, longitudinal distribution reinforcement, 126, transverse short reinforcement, 130, T-shaped steel beam, 131, steel bottom plate, 132, steel web, 133, steel tenon, 134, mortise. DETAILED DESCRIPTION

[0024] To facilitate understanding of the present invention, the present invention will be described more fully below, along with preferred embodiments thereof. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0026] Example 1: Figure 1-Figure 3The figure shows a composite structural beam of steel and UHPC (i.e., an externally reinforced UHPC-T-beam). The composite structural beam 100 includes a UHPC bridge deck 110 and composite ribs (not shown) located on the bottom surface of the UHPC bridge deck 110. The composite ribs include UHPC ribs 120 and T-shaped steel beams 130. The UHPC ribs 120 are located between the UHPC bridge deck 110 and the T-shaped steel beams 130. That is, the UHPC ribs 120 and the UHPC bridge deck 110 are cast together to form a T-shaped structure. The upper edge of the T-shaped steel beam 130 is embedded in the lower end of the UHPC ribs 120.

[0027] Furthermore, the T-shaped steel beam 130 includes a steel bottom plate 131 and a steel web 132 disposed on the steel bottom plate 131, which together form a T-shaped structure. The upper edge of the steel web 132 (i.e., the side close to the UHPC rib 120) is alternately provided with steel tenons 133 and mortises 134 along the longitudinal bridge direction. Figure 3 As shown, Figure 3 The gray area in the figure is the mortise 134, and the distance between two adjacent tenons 133 is The height of the steel tenon (i.e. the depth of the mortise) is The steel tenon 133 and the mortise 134 are embedded in the concrete at the lower end of the UHPC rib 120. The distance between the lower edge of the UHPC rib 120 and the bottom edge of the mortise 134 is .

[0028] Furthermore, the UHPC rib 120 includes a rib concrete layer and a rib reinforcement skeleton located in the rib concrete layer. The rib reinforcement skeleton includes the bottom layer of longitudinal reinforcement 123, the second bottom layer of longitudinal reinforcement 124, longitudinal distribution reinforcement 125, transverse short reinforcement 126 and a vertical stirrup group (not shown in the figure); the vertical stirrup group includes lower open stirrups 121 and upper open stirrups 122 arranged alternately along the longitudinal bridge direction, as shown in FIG. Figure 1 and Figure 2As shown, the lower open stirrup 121 and the steel tenon 133 are arranged in a one-to-one correspondence, and the upper open stirrup 122 and the mortise 134 are arranged in a one-to-one correspondence. The steel tenon 133 is inserted into the opening at the lower end of the lower open stirrup 121, and the lower end of the upper open stirrup 122 is placed in the mortise 134. Both sides of the lower end of the upper open stirrup 122 are provided with transverse short steel bars 126, and the transverse short steel bars 126 are spaced from the lower end of the upper open stirrup 122 (that is, the two are not overlapped); the lower end of the lower open stirrup 121 is located lower than the upper open stirrup 122. At the lower end, the bottom layer of longitudinal steel bars 123 is used to connect the lower ends of the lower open stirrups 121 along the longitudinal direction, and the second bottom layer of longitudinal steel bars 124 is used to connect the lower ends of the upper open stirrups 122 along the longitudinal direction. Specifically, in this embodiment, the number of the bottom layer of longitudinal steel bars 123 and the second bottom layer of longitudinal steel bars 124 are both two, and they are symmetrically arranged on both sides of the steel web 132; a plurality of longitudinal distribution steel bars 125 are arranged inside the vertical stirrup group along the vertical direction. Specifically, a single longitudinal distribution steel bar 125 passes through the alternately arranged upper open stirrups 122 and lower open stirrups 121 along the longitudinal direction.

[0029] Furthermore, the UHPC bridge deck 110 includes a bridge deck concrete layer and a bridge deck steel bar skeleton located in the bridge deck concrete layer, the bridge deck steel bar skeleton includes an upper transverse steel bar group, a lower transverse steel bar group and a bridge deck longitudinal steel bar 112; a plurality of bridge deck longitudinal steel bars 112 are arranged at intervals along the transverse direction of the bridge, the upper transverse steel bar group is located on the upper side of the bridge deck longitudinal steel bars 112, the upper transverse steel bar group includes a plurality of bridge deck transverse steel bars 111 arranged at intervals along the longitudinal direction of the bridge, the bridge deck longitudinal steel bars 112 are overlapped with the bridge deck transverse steel bars 111 in the upper transverse steel bar group; the lower transverse steel bar group is located on the lower side of the bridge deck longitudinal steel bars 112, the lower transverse steel bar group includes a plurality of bridge deck transverse steel bars 111 arranged at intervals along the longitudinal direction of the bridge, and the bridge deck transverse steel bars 111 in the lower transverse steel bar group are not overlapped with the bridge deck longitudinal steel bars 112.

[0030] Furthermore, the upper end of the lower open stirrup 121 is connected to the bridge deck steel frame, specifically, overlapped with the bridge deck longitudinal steel bars 112.

[0031] Preferably, the bridge deck concrete layer and the rib concrete layer are both cast using UHPC concrete, and the UHPC concrete is ultra-high performance concrete with ultra-high durability and ultra-high mechanical properties.

[0032] Furthermore, the lower end of the UHPC rib 120 is thickened at the embedded steel tenon 133 and mortise 134 (i.e., a reinforced horseshoe is provided) to ensure that the transverse distance from the steel tenon to the edge of the UHPC rib 120 is not less than 5 times the height of the steel tenon, thereby improving the fault tolerance of the centering error between the steel web 132 and the UHPC rib 120. At the same time, it provides bending space for the upper and lower open stirrups and reserves sufficient protective layer thickness for the stirrups, thereby improving the bonding ability between the steel web and the UHPC rib 120.

[0033] In order to ensure the safe application of UHPC and steel composite structural beams, this embodiment provides a design method for the vertical shear capacity of an externally reinforced UHPC-T beam (i.e., a composite structural beam), such as Figure 4 As shown, the design method includes the following steps: S1. Obtain the design value of the vertical shear effect of the composite structural beam under the proposed structural dimensions. and the design value of the effect of the bending moment ; Specifically, the permanent action of the composite structural beam is determined according to the structural dimensions of the proposed composite structural beam, and the variable action is determined according to the use requirements and environmental conditions of the composite structural beam; then, based on the effect design value of the permanent action and the effect design value of the variable action, the effect design value of the vertical shear force under the basic combination of action effects is obtained. and the design value of the effect of the bending moment .

[0034] The method for determining permanent and variable actions is described in the prior art and is not further described in detail in this embodiment. Preferably, the design values ​​of the effects of the composite structural beam under permanent and variable actions are determined according to a common bridge internal force calculation method, and the design values ​​of the effects of the permanent and variable actions are combined according to the General Specification for Design of Highway Bridges and Culverts (JTG D60-2015) to obtain the design values ​​of the effects of the basic combination of actions.

[0035] S2. Design value based on the geometric parameters of the cross section of the composite structure beam and the effect of vertical shear force and the design value of the effect of the bending moment , calculate the vertical shear force component borne by the UHPC ribs and the vertical shear component borne by the steel web ; Preferably, step S2 in this embodiment is specifically as follows: S2.1. Convert the cross-section of the composite structural beam into a cross-section of a single material by: Multiply the thickness of the UHPC ribs in the cross section of the composite structural beam and the width of the UHPC bridge deck by , and obtain the cross section of a single material (i.e., steel web material), such as Figure 5 and Figure 6 As shown; Among them, the elastic modulus ratio , is the elastic modulus of the steel web, is the elastic modulus of UHPC concrete.

[0036] S2.2. Divide the cross section into several unit layers in the height direction, where the height of the cross section (i.e. the height of the composite structural beam) is h ; S2.3. Determine the distance from the neutral axis NA to the top of the section , and calculate the moment of inertia of the cross section about the neutral axis NA ; Preferably, in step S2.3, the design value is based on the effect of the bending moment The cross-section layering method is used to iteratively calculate the distance from the neutral axis NA of the overall cross-section to the top of the overall cross-section based on the cross-section axial force and bending moment equilibrium conditions. For the specific iterative method, please refer to the prior art, which will not be described in detail in this embodiment. For example, the Chinese patent application with publication number CN118965548A discloses a design method for a composite structural beam of steel and UHPC, wherein paragraphs 0039 to 0054 disclose the method of determining the composite structural beam by iterative calculation. method.

[0037] Furthermore, the moment of inertia of the cross section about the neutral axis NA is The calculation method of is referred to the prior art and will not be described in detail in this embodiment.

[0038] S2.4, according to the moment of inertia and the design value of the effect of vertical shear Calculate the shear stress of each unit layer, and further calculate the shear force of each unit layer; Specifically, the cross section Shear stress of each unit layer for: (1), in, is the design value of the vertical shear effect, For the The width of the unit layer, Indicates the The static moment of the location of the unit layer; The neutral axis NA is the boundary. The sum of the area moments of all unit layers on the side of the unit layer (i.e. The sum of the area moments of the unit layers and the The sum of the area moments of the other unit layers on the same side of the unit layer), The area moment of a unit layer is expressed as , For the The area of ​​the unit layer, , For the The distance from the unit layer to the neutral axis NA, For the The height of each unit layer; Furthermore, the cross section Shear force of each unit layer For (i.e. The shear stress acts on the force on the (2), In summary, the shear force of each unit layer in the cross section can be obtained according to formula (1) and formula (2), as follows: Figure 7 As shown in the figure, the vertical shear components of the UHPC ribs and steel webs can be calculated separately in the subsequent steps.

[0039] S2.5. Obtain the vertical shear force component borne by the UHPC ribs and the vertical shear component borne by the steel web ; Specifically, the vertical shear force component borne by the UHPC ribs is for: (3), Furthermore, the vertical shear force component borne by the steel web for: (4), in, It is the first among UHPC ribs. The shear force of each unit layer, The first Shear force of each unit layer.

[0040] It should be noted that since the shear stress borne by UHPC bridge deck and steel base plate is generally small, their contribution to shear resistance is generally not considered, that is, .

[0041] S3. Calculation of the characteristic value of vertical shear bearing capacity of UHPC ribbed plates and the characteristic value of the vertical shear bearing capacity of the steel web If it exists or , then adjust the structural dimensions of the composite structural beam and return to step S1, otherwise go to step S4; wherein, is the importance coefficient of the composite structural beam, is the material partial coefficient; Specifically, the characteristic value of the vertical shear bearing capacity of UHPC ribbed plate is for: (5), Furthermore, the characteristic value of the vertical shear bearing capacity of the steel web is for: (6), in, is the yield strength of the steel web, in MPa; is the thickness of the steel web, in mm; is the height of the steel web, in mm; is the thickness of the UHPC rib (referring to the actual thickness of the UHPC rib, i.e. the thickness before conversion), in mm; is the height of the UHPC rib, in mm; is the ultimate tensile strength of UHPC concrete, in MPa; is the ultimate tensile strength of UHPC concrete, in MPa; The sum of the cross-sectional areas of all vertical segments of a single stirrup in the UHPC rib (the stirrup here refers to the upper open stirrup or the lower open stirrup. The upper open stirrup and the lower open stirrup are generally of the same specification, so the cross-sectional areas of the upper open stirrup and the lower open stirrup are the same; the upper open stirrup and the lower open stirrup in this embodiment are both double-limbed, i.e., have two vertical segments, but in some embodiments, the stirrup may be set to a single limb, i.e., have only one vertical segment), unit is mm 2 ; is the spacing of stirrups in the UHPC rib plate, in mm; is the yield strength of the stirrups in the UHPC rib, in MPa.

[0042] Optimally, the importance coefficient of the composite structural beam is The material partial coefficients are 0.9, 1.0, and 1.1 respectively according to the importance of the bridge; Used to convert the calculated bearing capacity characteristic value into the corresponding bearing capacity design value, and the value is 1.25.

[0043] S4. Calculate the horizontal shear capacity per unit length of the steel tenons and mortises alternately arranged along the longitudinal direction of the bridge on the steel web. , according to the cross-sectional shear stress distribution height z and horizontal shear capacity per unit length Obtain the characteristic value of vertical shear bearing capacity controlled by horizontal shear capacity ; Since the position of the tenon and mortise is close to the neutral axis, the vertical shear stress at the position of the tenon and mortise is relatively large in the height direction of the composite structural beam. According to the principle of shear reciprocity, the horizontal shear capacity per unit length of the tenon and mortise in the length direction of the composite structural beam is =The maximum vertical shear force that the UHPC ribs can withstand per unit height is . Since the vertical shear stress is mainly borne by the steel web and the UHPC ribs, and the vertical shear stress of the steel web is generally greater than that of the UHPC ribs, it is safe to consider that the vertical shear stress is distributed in a height of z , with a width of On the rectangle, such as Figure 8 As shown, .

[0044] Horizontal shear capacity per unit length The calculation of the minimum value of the two failure modes of tenon failure and mortise failure should be considered, specifically: Calculate the horizontal shear bearing capacity characteristic value corresponding to the shear failure of the steel tenon , unit N: (7), Calculate the characteristic value of horizontal shear bearing capacity corresponding to mortise shear failure , unit N: (8), Calculation of the characteristic value of the horizontal shear capacity between layers of composite structural beams , unit N: (9), Calculation of horizontal shear capacity per unit length : (10), Characteristic value of vertical shear bearing capacity controlled by horizontal shear capacity for: · (11), in, The longitudinal spacing of the steel tenons, in mm; is the thickness of the steel web, in mm; is the yield strength of the steel web, in MPa; is the shape coefficient of the mortise, which is related to the shape of the steel tenon, such as the MCL type key ; is the standard value of cube compressive strength of UHPC concrete, in MPa; is the strengthening coefficient of the horizontal reinforcement in the mortise, where the horizontal reinforcement in the mortise includes the horizontal segments of the short transverse steel bars and the upper opening stirrups. , It is the sum of the cross-sectional areas of the horizontal reinforcement in the mortise, including the short transverse reinforcement and the horizontal section of the upper opening stirrup; The area of ​​the mortise, such as MCL type key ; is the elastic modulus of the steel tenon (i.e., steel web), in MPa; is the elastic modulus of UHPC concrete, in MPa.

[0045] S5, if Then adjust the structural dimensions of the composite structural beam and return to step S1; otherwise, end the design.

[0046] The method of this embodiment avoids the insufficient shear capacity of simply superimposing UHPC ribs and steel webs, and takes into account the differences in shear force distribution ratio and load-bearing history of the two materials. This prevents overdesign caused by ignoring the contribution of UHPC ribs and avoids the risk of overestimation caused by simple superposition.

[0047] The method of this embodiment clearly identifies the particularity of the position of the tenon and mortise being close to the neutral axis, and uses the horizontal shear resistance of the tenon and mortise as a limiting condition for the vertical shear resistance. By considering the bearing capacity of the tenon and mortise, the reliability of the structural design is improved.

[0048] The method of this embodiment can take into account the influence of the change in the stress mechanism after the UHPC rib cracks. Specifically: if the design value of the bending moment effect Small, the tensile part of UHPC is in the elastic section, as The position of the neutral axis NA will not change with the increase of is a fixed value; as With further increase, after the UHPC ribs soften or crack under tension, according to the equilibrium conditions of axial force and bending moment in the section, the neutral axis NA will move upward, that is, The static moment and inertia moment of the upper and lower parts of the neutral axis NA change continuously, which causes the bending moment to affect the shear force distribution. It is the design value based on the effect of bending moment The cross-sectional layering method is used to iteratively confirm the The method of this embodiment can take into account the effect design value of the bending moment under different stress conditions. The impact of the changes is taken into account, and the redistribution of shear force between the UHPC ribs and the steel web is considered. By considering the redistribution of force, the safety of the vertical shear design is ensured.

[0049] Application Cases: In this case, based on the specific structural dimensions of a composite structural beam, the above design method was used to verify the vertical shear capacity of the composite structural beam, as follows: According to the effect design value of permanent action and the effect design value of variable action, the effect design value of vertical shear force under the basic combination of action effects is obtained. , design value of the effect of bending moment .

[0050] Elastic modulus of steel web , elastic modulus of UHPC concrete , , convert UHPC material into steel and get the converted cross section. Iterative calculation based on cross section layering method mm, moment of inertia ; Calculate the vertical shear force components borne by the UHPC ribs and steel webs respectively 、 .

[0051] Get the thickness of UHPC ribs , the height of UHPC ribs =770 mm , the sum of the cross-sectional areas of all vertical segments of a single stirrup in the UHPC rib , the spacing of stirrups in UHPC ribs s= 75 mm , Yield strength of stirrups in UHPC ribs , UHPC tensile elastic ultimate strength and ultimate tensile strength They are 、 , calculate the characteristic value of vertical shear bearing capacity of UHPC rib plate according to formula (5): .

[0052] Obtaining the yield strength of the steel web , steel web height , steel web thickness =19mm, the characteristic value of the vertical shear bearing capacity of the steel web is calculated according to formula (6): ; , less than , meeting the requirements.

[0053] , less than , meeting the requirements.

[0054] Get the longitudinal spacing of the steel tenons , steel web thickness =19mm, yield strength of steel web (Q355 material) According to formula (7), the horizontal shear bearing capacity characteristic value corresponding to the shear failure of the steel tenon is calculated as follows: ; according to Get the shape coefficient of the mortise =2.17, standard value of cube compressive strength of UHPC concrete The diameter of the upper opening stirrup is 10mm, the diameter of the transverse short steel bar in the mortise is 12mm, and the sum of the cross-sectional areas of the horizontal steel bars in the mortise is ,according to Get the area of ​​the mortise , elastic modulus of the steel tenon (i.e. steel web) , elastic modulus of UHPC concrete ,according to Calculate the reinforcement ratio in the mortise According to formula (8), the horizontal shear bearing capacity characteristic value corresponding to the mortise shear failure is calculated as ; The characteristic value of the horizontal shear bearing capacity between layers of the composite structure beam is calculated according to formula (9): =252.9 Horizontal shear capacity per unit length of shear connector ; Shear stress distribution height , the characteristic value of vertical shear bearing capacity controlled by horizontal shear capacity =1686×1.2=2023kN.

[0055] =1.0×1.25×716.8=896kN, less than Satisfies the requirements. But it can be seen that Much smaller than and The sum is 3360.5 kN, which further illustrates the necessity of adopting the verification method of this embodiment.

[0056] Example 2: This embodiment provides a system for designing the vertical shear capacity of an externally reinforced UHPC-T-shaped beam. The system includes a memory (i.e., a storage medium) and a processor. The memory stores computer instructions, and the computer instructions are configured to execute the method for designing the vertical shear capacity of an externally reinforced UHPC-T-shaped beam in Example 1 when executed. When the processor executes the computer instructions stored in the memory, the method for designing the vertical shear capacity of an externally reinforced UHPC-T-shaped beam in Example 1 is executed. Through the design system of this embodiment, a designer can input proposed structural dimensions into the design system and then verify whether the current structural dimensions meet safety requirements.

[0057] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for designing the vertical shear capacity of an externally reinforced UHPC-T beam, characterized in that: include: S1. Obtain the design value of the vertical shear effect of the composite structural beam under the proposed structural size Design values ​​of the effects of bending moment ; S2. Design value based on the geometric parameters of the cross section of the composite structure beam and the effect of vertical shear force Design values ​​of the effects of bending moment , calculate the vertical shear force component borne by the UHPC rib plate and the vertical shear component borne by the steel web ; S3. Calculation of the characteristic value of vertical shear bearing capacity of UHPC ribbed slabs and the characteristic value of vertical shear bearing capacity of steel web ; if exists or , then adjust the structural dimensions of the composite structural beam and return to step S1, otherwise go to step S4; wherein, is the importance coefficient of the composite structural beam, is the material partial factor; S4. Calculate the horizontal shear capacity per unit length of the steel tenons and mortises alternately arranged along the longitudinal direction of the bridge on the steel web. , according to the cross-sectional shear stress distribution height z and horizontal shear capacity per unit length Obtain the characteristic value of vertical shear bearing capacity controlled by horizontal shear capacity ; S5. If Then adjust the structural dimensions of the composite structural beam and return to step S1, otherwise the design is terminated.

2. The vertical shear capacity design method of the externally reinforced UHPC-T beam according to claim 1 is characterized in that: The step S2 specifically comprises: S2.

1. Convert the cross section of the composite structural beam into a cross section of a single material; S2.2, divide the cross section into several unit layers in the height direction; S2.

3. Design value based on the effect of bending moment The distance from the neutral axis NA to the top of the section is obtained iteratively using the section layering method. , and calculate the moment of inertia of the cross section about the neutral axis NA ; S2.4, according to the moment of inertia and the design value of the effect of vertical shear Calculate the shear stress of each unit layer, and further calculate the shear force of each unit layer; S2.

5. Obtain the vertical shear force component borne by the UHPC ribs and the vertical shear component borne by the steel web .

3. The vertical shear capacity design method of the externally reinforced UHPC-T beam according to claim 2 is characterized in that: In step S2.1, the cross section of the composite structural beam is converted into a cross section of a single material, specifically: Multiply the thickness of the UHPC rib plate in the cross section of the composite structure beam and the width of the UHPC bridge deck by , and obtain the cross section of a single material; among them, the elastic modulus ratio , is the elastic modulus of the steel web, is the elastic modulus of UHPC concrete.

4. The vertical shear capacity design method of the externally reinforced UHPC-T beam according to claim 2 is characterized in that: In step S2.4, the Shear stress per unit layer for: （1）， Section Shear force per unit layer for: （2）， in, For the The width of the unit layer, Indicates The static moment of the location of the unit layer, For the The area of ​​the unit layer, For the The height of the unit layer.

5. The vertical shear capacity design method of externally reinforced UHPC-T beam according to claim 2 is characterized in that: Vertical shear force component borne by the UHPC ribs in step S2.5 for: （3）， Vertical shear force component borne by the steel web for: （4）， in, It is the first UHPC rib plate The shear force of each unit layer, For the steel web Shear force of each unit layer.

6. The vertical shear capacity design method of externally reinforced UHPC-T beam according to claim 1 is characterized in that: In step S4, the horizontal shear capacity per unit length of the steel tenons and mortise alternately arranged along the longitudinal bridge direction on the steel web is calculated. , specifically: Calculate the horizontal shear bearing capacity characteristic value corresponding to the shear failure of the steel tenon : （7）， Calculate the characteristic value of horizontal shear bearing capacity corresponding to the shear failure of the mortise : （8）， Calculation of the characteristic value of the horizontal shear capacity between layers of composite structural beams : （9）， Calculate the horizontal shear capacity per unit length : （10）， in, The longitudinal arrangement spacing of the steel tenons; is the thickness of the steel web; is the yield strength of the steel web; is the shape coefficient of the mortise; is the standard value of cube compressive strength of UHPC concrete; It is the horizontal reinforcement strengthening coefficient in the mortise.

7. The vertical shear capacity design method of an externally reinforced UHPC-T beam according to claim 6 is characterized in that: Characteristic value of vertical shear capacity controlled by horizontal shear capacity for: · （11）。 8. The vertical shear capacity design method of externally reinforced UHPC-T beam according to claim 1 is characterized in that: Characteristic value of vertical shear bearing capacity of UHPC rib plate in step S3 for: （5）， Characteristic value of vertical shear capacity of steel web for: （6）， in, is the yield strength of the steel web; is the thickness of the steel web; is the height of the steel web; is the thickness of the UHPC rib; is the height of the UHPC rib; is the tensile elastic ultimate strength of UHPC concrete; is the ultimate tensile strength of UHPC concrete; It is the sum of the cross-sectional areas of all vertical segments of a single stirrup in the UHPC rib plate; is the spacing of stirrups in the UHPC rib plate; is the yield strength of stirrups in UHPC ribs.

9. A vertical shear capacity design system for externally reinforced UHPC-T beams, characterized in that: The system includes a memory and a processor. When the processor runs the computer instructions stored in the memory, it executes the vertical shear capacity design method of the externally reinforced UHPC-T beam according to any one of claims 1 to 8.

10. A storage medium, characterized in that: The storage medium stores computer instructions, and the computer instructions are configured to execute the vertical shear capacity design method of the externally reinforced UHPC-T beam according to any one of claims 1 to 8 when running.

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