Method for calculating bearing capacity of UHPC (Ultra High Performance Concrete) thin-layer reinforced reinforced concrete T-beam bridge

Abstract

The invention discloses a method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge. The UHPC thin layer reinforced reinforced concrete T-beam bridge is composed of an original reinforced concrete T-beam, interface embedded steel bars, a reinforcing layer reinforcing mesh and a UHPC thin layer. The reinforcing layer reinforcing mesh is of a mesh structure composed of a plurality of U-shaped stirrups and a plurality of longitudinal bars. The bearing capacity comprises the shear bearing capacity of the reinforced concrete T-beam bridge reinforced by the UHPC thin layer and the bending bearing capacity of the reinforced concrete T-beam bridge reinforced by the UHPC thin layer. According to the method, the shear bearing capacity and the flexural bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge can be effectively calculated, and the effectiveness and feasibility of the shear bearing capacity and flexural bearing capacity calculation method are proved through finite element simulation and test verification. According to the method, the influence rule of damaged reinforced concrete, the volume mixing amount of steel fibers in UHPC, the concrete strength, the shear span ratio, the longitudinal bar rate and other factors on the shear-resisting and bending-resisting bearing capacity can be well reflected.

Description

Technical Field

[0001] The invention relates to the technical field of T-beam bridge bearing capacity calculation, and in particular to a method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge. Background Art

[0002] In the past decades of bridge construction history, reinforced concrete T-beams have been widely used in bridge engineering due to their excellent performance in construction technology and mechanical properties. However, with the passage of time and the increase in traffic loads, many T-beam bridges built in the early days have gradually exposed serious diseases such as concrete carbonization, crack expansion, steel corrosion, surface damage and rainwater intrusion, resulting in a significant decrease in bearing capacity, becoming sick bridges and dangerous bridges that are in urgent need of repair. In recent years, ultra-high performance concrete (UHPC), as a new structural material, has shown great potential in repairing and reinforcing damaged T-beam bridges due to its ultra-high strength, high durability and high toughness. It has not only significantly improved the bearing capacity and durability of bridges, but has also been favored by engineers and scholars for its simple and quick construction, providing an innovative and efficient solution for effectively solving bridge diseases and ensuring long-term safe use.

[0003] At home and abroad, engineering application examples of UHPC thin-layer reinforced T-beams are constantly emerging, and scientific research in this field is also booming. However, most previous engineering practices have followed the traditional method of increasing the cross-section of ordinary concrete for reinforcement, and in the design and calculation, the main reference is the ordinary concrete reinforcement design specification. Although there are some formulas for the bending calculation of UHPC thin-layer reinforced T-beams, these formulas are derived based on the experimental parameters of their own specific studies. Therefore, they are only applicable to the bending bearing capacity calculation of UHPC reinforced T-beams with specific parameters and lack universal applicability. More importantly, there is still a gap in the research on the calculation method of the shear bearing capacity of UHPC thin-layer reinforced T-beams in China, which seriously hinders the further promotion and popularization of UHPC thin-layer reinforcement technology.

[0004] Therefore, the systematic development of a universally applicable calculation method for the flexural and shear bearing capacity of UHPC thin-layer reinforced T-beams is of great significance for promoting the in-depth application of this technology and the sustainable development of the bridge engineering field. Summary of the invention

[0005] The purpose of the present invention is to avoid the shortcomings of the prior art and provide a method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge. The method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge can effectively calculate the shear bearing capacity and the bending bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge. At the same time, the method for calculating the shear bearing capacity and the bending bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge of the present invention is simple in form and clear in physical meaning, and can better reflect the influence of factors such as damaged reinforced concrete, steel fiber volume content in UHPC, concrete strength, shear span ratio, and longitudinal reinforcement ratio on shear and bending bearing capacity.

[0006] The above-mentioned purpose of the present invention is achieved by the following technical measures:

[0007] Provided is a method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge, wherein the UHPC thin layer reinforced reinforced concrete T-beam bridge consists of an original reinforced concrete T-beam, interface embedded reinforcement, a reinforcement layer steel mesh and a UHPC thin layer; the reinforcement layer steel mesh consists of a mesh structure composed of a plurality of U-shaped stirrups and a plurality of longitudinal bars.

[0008] The bearing capacity includes the shear bearing capacity of UHPC thin layer reinforced reinforced concrete T-beam bridge and the bending bearing capacity of UHPC thin layer reinforced reinforced concrete T-beam bridge.

[0009] Preferably, the shear bearing capacity calculation method of the UHPC thin layer reinforced reinforced concrete T-beam bridge is to calculate the shear bearing capacity V′ of the damaged reinforced concrete T-beam considering the influence of the compression flange. c +V′ sv , shear bearing capacity of UHPC thin layer v UHPC and the shear bearing capacity of the U-shaped stirrups V sw Add and calculate the shear bearing capacity V of the UHPC thin layer reinforced reinforced concrete T-beam bridge through formula (1): u :

[0010] V u =V′ c +V′ sv +V UHPC +V sw ...Formula (1).

[0011] Preferably, the method for calculating the bending bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge is as follows: first, the cross-sectional area and centroid position of the UHPC thin layer and the original reinforced concrete T-beam flange are assumed to be unchanged, and the U-shaped section of the UHPC thin layer and the polygonal section of the original reinforced concrete T-beam flange are respectively equivalent to regular rectangular sections, thereby obtaining a first rectangular section corresponding to the U-shaped section and a second rectangular section corresponding to the polygonal section; and then the bending bearing capacity M is calculated by formula (2): u :

[0012]

[0013] Where t is the distance from the centroid of the cross section of the longitudinal reinforcement to the centroid of the concrete compression zone of the flange of the original reinforced concrete T-beam, h′ u is the height of the first rectangular section; α1 is the stress pattern coefficient of the flange compression zone of the UHPC thin layer reinforced reinforced concrete T-beam bridge; A s is the longitudinal reinforcement area of ​​the web tension zone of the original reinforced concrete T-beam; f UHPC is the tensile strength of UHPC thin layer; f g A is the tensile strength of the longitudinal reinforcement in the UHPC thin layer; g is the cross-sectional area of ​​the longitudinal reinforcement in the UHPC thin layer, b' u is the bottom width of the first rectangular section; h0 is the effective height of the original reinforced concrete T-beam; h is the total height of the UHPC thin layer reinforced reinforced concrete T-beam bridge; x is the height of the compression zone of the original reinforced concrete T-beam flange; f y is the tensile strength of the longitudinal reinforcement in the original reinforced concrete T-beam, and δ is the influence coefficient of the volume content of steel fiber in the UHPC thin layer.

[0014] Preferably, the shear bearing capacity of the concrete matrix in the original reinforced concrete T-beam is V c Through formula (3), we can get:

[0015] V c =α cv f t0 b h0 ...Formula (3);

[0016] Among them, α cv f is the shear bearing capacity coefficient of the inclined section of concrete; t0 is the concrete axial tensile strength of the original reinforced concrete T-beam; b is the web width of the original reinforced concrete T-beam.

[0017] Preferably, the shear bearing capacity coefficient α of the above concrete inclined section is cv The assignment method:

[0018] When the original reinforced concrete T-beam is mainly subjected to the combined action of bending moment and shear force and the axial force is negligible, α cv is 0.7;

[0019] When the original reinforced concrete T beam is mainly subjected to the combined action of bending moment and shear force and the axial force is negligible, α cv is 0.7; when the original reinforced concrete T beam is an independent beam under concentrated load, Where λ is the assigned value of the cross-section shear span ratio;

[0020] Preferably, the assignment method of the above-mentioned section shear span ratio value λ is: when the actual section shear span ratio is less than or equal to 1.5, λ is 1.5; when the actual section shear span ratio is between 1.5 and 3, λ is the actual section shear span ratio; when the actual section shear span ratio is greater than or equal to 3, λ is 3.

[0021] Preferably, the shear bearing capacity of the stirrups in the original reinforced concrete T beam is V sv Calculated by formula (4);

[0022]

[0023] Where s0 is the spacing of the stirrups in the original reinforced concrete T-beam along the length of the member; A sv0 is the cross-sectional area of ​​the stirrups in the shear span of the original reinforced concrete T-beam; f yv0 is the tensile strength of the stirrups in the original reinforced concrete T-beam.

[0024] The present invention is based on the concrete matrix shear bearing capacity V in the original reinforced concrete T beam. c and the shear bearing capacity V of the stirrups in the original reinforced concrete T beam sv , the shear bearing capacity of the damaged reinforced concrete T beam considering the influence of the compression flange is obtained by formula (5), and the shear bearing capacity of the damaged reinforced concrete T beam considering the influence of the compression flange is the shear bearing capacity V′ of the concrete matrix in the original reinforced concrete T beam considering the influence of the compression flange and damage c Compared with the shear bearing capacity V′ of the original reinforced concrete T-beam considering the compression flange and damage sv The sum of the shear bearing capacity of the damaged reinforced concrete T beam considering the influence of the compression flange is V′ c +V′ sv ;

[0025]

[0026] Among them, α f is the compression flange influence coefficient, and α f is 1.1; ψ is the damage coefficient;

[0027] Preferably, the value of the damage coefficient ψ is selected as follows:

[0028] When no oblique cracks appeared in the original reinforced concrete T-beam before reinforcement, ψ was 1.0;

[0029] When there are oblique cracks in the original reinforced concrete T-beam before reinforcement and the crack width is greater than 0 and less than or equal to 0.2 mm, ψ is 0.835;

[0030] When there are oblique cracks in the original reinforced concrete T-beam before reinforcement and the crack width is greater than 0.2 and less than 0.4, ψ is calculated by linear interpolation, which is expressed by formula (6):

[0031] ψ=0.89-0.275τ...Equation (6);

[0032] Where, τ is the crack width;

[0033] When there are oblique cracks in the original reinforced concrete T-beam before reinforcement and the crack width is equal to 0.4 mm, ψ is 0.78.

[0034] Preferably, the shear bearing capacity of the UHPC thin layer as a whole is V UHPC Calculated by formula (7);

[0035]

[0036] Among them, α UHPC is the strength utilization coefficient of UHPC material. When the original reinforced concrete T-beam interface is smooth, α UHPC is 0.7, when the original reinforced concrete T-beam interface is roughened UHPC is 0.8; f Ulud is the elastic tensile strength of UHPC material; f Ulud is the ultimate tensile strength of UHPC material; θ is the angle between the principal compressive stress and the longitudinal axis, and θ is 45°.

[0037] Preferably, the value of the influence coefficient δ of the steel fiber volume content in the above-mentioned UHPC thin layer is as follows: when the steel fiber volume content in the UHPC thin layer is 1.5%, δ is 0.9; when the steel fiber volume content in the UHPC thin layer is 3%, δ is 1.1; when the steel fiber volume content in the UHPC thin layer is between 1.5% and 3%, the value of δ is determined by formula (8):

[0038]

[0039] Where ω is the volume content of steel fiber in the UHPC thin layer.

[0040] Preferably, the shear bearing capacity of the U-shaped stirrups in the UHPC thin layer is V sw Calculated by formula (9);

[0041]

[0042] Among them, α s is the strength utilization factor of the U-shaped stirrups in the UHPC thin layer, and α s is 0.9; f yv is the tensile strength of the U-shaped stirrups in the UHPC thin layer; s is the spacing of the U-shaped stirrups in the UHPC thin layer along the length of the member; h′ is the effective height of the cross-section of the UHPC thin layer reinforced reinforced concrete T-beam bridge.

[0043] The formula (1) is converted into formula (10) to calculate the shear bearing capacity V of the UHPC thin layer reinforced reinforced concrete T-beam bridge: u ;

[0044]

[0045] Preferably, the bending bearing capacity M u The calculation method is carried out by the following steps:

[0046] S1. In the mid-span section of the UHPC thin layer reinforced reinforced concrete T-beam bridge, take any point in the mid-span section as the origin O, the vertical direction passing through the origin O as the Y axis, and the horizontal direction passing through the origin O as the X axis to establish a YXO coordinate system;

[0047] S2. In the mid-span section, the shape of the UHPC thin layer is a U-shaped section, and the shape of the original reinforced concrete T-beam flange is a polygonal section. Assuming that the cross-sectional area and centroid position of the UHPC thin layer and the original reinforced concrete T-beam flange remain unchanged, the U-shaped section of the UHPC thin layer and the polygonal section of the original reinforced concrete T-beam flange are respectively equivalent to regular rectangular sections, thereby obtaining a first rectangular section corresponding to the U-shaped section and a second rectangular section corresponding to the flange polygonal section;

[0048] S3, calculating the distance z from the surface centroid of the first rectangular cross section to the x-axis by formula (11); calculating the distance q from the surface centroid of the second rectangular cross section to the x-axis by formula (12);

[0049]

[0050] Wherein, A1 is the area of ​​the single-sided vertical rectangle in the U-shaped section; A2 is the area of ​​the bottom rectangle in the U-shaped section, and the area of ​​the U-shaped section is 2A1+A2; Z1 is the distance from the centroid of the A1 area to the X-axis, and Z2 is the distance from the centroid of the A2 area to the X-axis;

[0051]

[0052] Among them, A3 is the area of ​​one side of the original reinforced concrete T-beam flange support, A4 is the area of ​​the rectangular area above the original reinforced concrete T-beam flange support, A5 is the area of ​​the rectangular area between the supports on both sides of the original reinforced concrete T-beam flange, Z3 is the distance from the centroid of the A3 area to the X-axis, Z4 is the distance from the centroid of the A4 area to the X-axis, and Z5 is the distance from the centroid of the A5 area to the X-axis;

[0053] S4. Calculate the height h′ of the first rectangular section according to the distance z and formula (13): u ; Calculate the height h′ of the second rectangular section according to the distance q and formula (14) f ;

[0054] h′ u =2z……Formula (13);

[0055] h′ f =2q……Formula (14);

[0056] S5. Calculate the bottom width b′ of the first rectangular cross section by formula (15): u ; Calculate the top width b′ of the second rectangular cross section by formula (16): f ;

[0057]

[0058] Among them, A sc is the area of ​​the U-shaped cross section, and A sc =2A1+A2;

[0059]

[0060] Among them, A sb is the area of ​​the second rectangular cross section, and A sb =2A3+A4+A5; b′ f is the top width of the second rectangular cross section;

[0061] S6. According to the static equilibrium relationship of the mid-span section of the UHPC thin layer reinforced reinforced concrete T-beam bridge in formula (17), the height x of the compression zone of the original reinforced concrete T-beam flange is calculated;

[0062]

[0063] Among them, f′ c is the measured value of the compressive strength of ordinary concrete in the UHPC thin layer in the bending test;

[0064] S7. The bending bearing capacity M is calculated by formula (2): u .

[0065] Preferably, the original reinforced concrete T-beam is a first type T-beam, that is, the neutral axis of the cross section of the original reinforced concrete T-beam is located inside the concrete flange.

[0066] The invention discloses a method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge. The UHPC thin layer reinforced reinforced concrete T-beam bridge is composed of an original reinforced concrete T-beam, an interface embedded steel bar, a reinforcement layer steel mesh and a UHPC thin layer; the reinforcement layer steel mesh is composed of a mesh structure of a plurality of U-shaped stirrups and a plurality of longitudinal bars; the bearing capacity includes the shear bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge and the bending bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge; the method for calculating the shear bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge is to calculate the shear bearing capacity V′ of the damaged reinforced concrete T-beam considering the influence of the compression flange c +V′ sv , shear bearing capacity of UHPC thin layer V UHPC and the shear bearing capacity of the U-shaped stirrups V sw Add the shear bearing capacity V of the reinforced concrete T-beam bridge reinforced with UHPC thin layer u The method for calculating the bending bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge is to first assume that the cross-sectional area and centroid position of the UHPC thin layer and the original reinforced concrete T-beam flange remain unchanged, and the U-shaped section of the UHPC thin layer and the polygonal section of the original reinforced concrete T-beam flange are respectively equivalent to regular rectangular sections, and then obtain the first rectangular section corresponding to the U-shaped section and the second rectangular section corresponding to the polygonal section; then calculate the bending bearing capacity M u . The bearing capacity calculation method of the UHPC thin layer reinforced reinforced concrete T-beam bridge can effectively calculate the shear bearing capacity and bending bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge, and through finite element simulation and experimental verification, the effectiveness and feasibility of the shear and bending bearing capacity calculation method are proved. The bearing capacity calculation method of the UHPC thin layer reinforced reinforced concrete T-beam bridge is simple in form and clear in physical meaning. It can better reflect the influence of factors such as damaged reinforced concrete, steel fiber volume content in UHPC, concrete strength, shear span ratio, longitudinal reinforcement ratio on shear and bending bearing capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 Front view of reinforced concrete T-beam bridge reinforced with UHPC thin layer.

[0068] Figure 2 Left view of the reinforced concrete T-beam bridge reinforced with UHPC thin layer.

[0069] Figure 3This is the layout diagram of the original reinforced concrete T-beam, interface embedded reinforcement and reinforcement layer steel mesh of the UHPC thin layer reinforced reinforced concrete T-beam bridge before the UHPC thin layer is poured.

[0070] Figure 4 for Figure 3 A three-dimensional schematic diagram of .

[0071] Figure 5 for Figure 1 A three-dimensional schematic diagram of .

[0072] Figure 6 It is a schematic diagram of the equivalent rectangular section after conversion of the U-shaped section in the mid-span section and the original reinforced concrete T-beam flange section.

[0073] Figure 7 It is a schematic diagram of the division of the first rectangular cross section and the second rectangular cross section.

[0074] Figure 8 This is the static equilibrium diagram of the beam section.

[0075] Fig. 9 The layout diagram is a perspective view of the test beam.

[0076] Fig.10 Dimensional drawing of the finite element test beam.

[0077] Fig.11 Limit load diagram for the finite element calculation of the UN-2%-J50Q-Y0 beam.

[0078] Fig.12 Limit load diagram for the finite element calculation of the UN-2%-J30Q-Y0 beam.

[0079] Fig.13 The dimensions of the actual test beam are shown in Figure 2.

[0080] Fig.14 These are experimental pictures of the actual test beam's bending bearing capacity.

[0081] exist Figures 1 to 14 Including:

[0082] Original reinforced concrete T-beam 1, reinforcement layer steel mesh 2, U-shaped stirrups 21, longitudinal reinforcement 22, UHPC thin layer 3, interface embedded reinforcement 4, distribution beam 5. DETAILED DESCRIPTION

[0083] The technical solution of the present invention is further described in conjunction with the following embodiments.

[0084] Example 1

[0085] A method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge is provided, wherein the UHPC thin layer reinforced reinforced concrete T-beam bridge is composed of an original reinforced concrete T-beam 1, an interface embedded reinforcement 4, a reinforcement layer steel mesh 2 and a UHPC thin layer 3; the reinforcement layer steel mesh 2 is composed of a plurality of U-shaped stirrups 21 and a plurality of longitudinal reinforcements 22 to form a mesh structure, such as Figure 1-Figure 5 shown.

[0086] The reinforcement layer steel mesh 2 is composed of a plurality of U-shaped stirrups 21 and a plurality of longitudinal bars 22 to form a mesh structure, wherein the U-shaped stirrups 21 are formed by bending a steel bar twice to form a U-shaped structure with one end open, and the opening of the U-shaped stirrups 21 is inserted into the web surface of the original reinforced concrete T beam 1 from the bottom end of the original reinforced concrete T beam 1.

[0087] The reinforcement method of reinforced concrete T-beam bridge reinforced with UHPC thin layer is:

[0088] Step 1, roughening the web surface and the bottom end surface of the original reinforced concrete T-beam 1;

[0089] Step 2, drilling holes on the web surface and bottom end surface of the original reinforced concrete T-beam 1 after roughening to fix the interface embedded reinforcement 4;

[0090] Step 3, fixing the reinforcement layer steel mesh 2;

[0091] Step 4: completely pour the UHPC thin layer 3 outside the interface embedded reinforcement 4 and the reinforcement layer steel mesh 2 to obtain a UHPC thin layer reinforced reinforced concrete T-beam bridge.

[0092] The bearing capacity of the present invention includes the shear bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge and the bending bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge.

[0093] It should be noted that the reinforcement method of the UHPC thin layer reinforced reinforced concrete T-beam bridge of the present invention belongs to the conventional operation in the field. The original reinforced concrete T-beam 1 of the present invention is a first type T-shaped beam, that is, the cross-sectional neutral axis of the original reinforced concrete T-beam 1 is located in the concrete flange.

[0094] The shear bearing capacity calculation method of UHPC thin layer reinforced reinforced concrete T-beam bridge is to calculate the shear bearing capacity V′ of the damaged reinforced concrete T-beam considering the influence of the compression flange. c +V′ sv 、The shear bearing capacity V of UHPC thin layer 3 UHPC and the shear bearing capacity V of the U-shaped stirrup 21 sw Add and calculate the shear bearing capacity V of the UHPC thin layer reinforced reinforced concrete T-beam bridge through formula (1): u :

[0095] V u =V′c +V′ sv +V UHPC +V sw ...Formula (1).

[0096] The shear bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge of the present invention is calculated based on the current Chinese standard "Code for Reinforcement Design of Concrete Structures" (GB50367-2013), and the shear bearing capacity of ordinary concrete of the reinforced concrete T-beam and the existing stirrups, UHPC thin layer 3 and U-shaped stirrups 21. At the same time, the influence of the shear span ratio in the "Code for Design of Concrete Structures" (GB50010-2010) is adopted, and the contribution of the newly added UHPC thin layer 3 to the shear bearing capacity, the change in the effective height of the beam section, the utilization efficiency of the UHPC thin layer 3 and the steel bars, and the influence of the damage degree of the reinforced concrete T-beam and the compression flange are considered. The calculated results are consistent with the simulation results of the finite element model. Generally speaking, it is a conservative and concise formula, and the calculation is simple and convenient.

[0097] The shear bearing capacity of the concrete matrix in the original reinforced concrete T beam 1 is V c Through formula (3), we get:

[0098] V c =α cv f t0 b h0 ...Formula (3);

[0099] Among them, α cv f is the shear bearing capacity coefficient of the inclined section of concrete; t0 is the concrete axial tensile strength of the original reinforced concrete T beam 1; b is the web width of the original reinforced concrete T beam 1.

[0100] Shear bearing capacity coefficient of inclined section concrete α cv The assignment method:

[0101] When the original reinforced concrete T beam 1 is mainly subjected to the combined action of bending moment and shear force and the axial force is negligible, α cv is 0.7; when the original reinforced concrete T beam 1 is an independent beam under concentrated load, Where λ is the assigned value of the cross-section shear span ratio;

[0102] The value λ of the section shear span ratio is assigned as follows: when the actual section shear span ratio is less than or equal to 1.5, λ is 1.5; when the actual section shear span ratio is between 1.5 and 3, λ is the actual section shear span ratio; when the actual section shear span ratio is greater than or equal to 3, λ is 3.

[0103] Shear bearing capacity of stirrups in original reinforced concrete T beam 1 V sv Calculated by formula (4);

[0104]

[0105] Where s0 is the spacing of the stirrups in the original reinforced concrete T beam 1 along the length direction of the member; A sv0 is the cross-sectional area of ​​the stirrups in the shear span of the original reinforced concrete T beam 1; f yv0 is the tensile strength of the stirrups in the original reinforced concrete T beam 1.

[0106] It should be noted that according to the current Chinese standard "Code for Design of Concrete Structures" (GB50010-2010), the shear bearing capacity of reinforced concrete T-beams mainly depends on the existing concrete tensile strength, steel bar strength, cross-sectional characteristics and shear span ratio. Formulas (3) and (4) are designed with reference to the present invention.

[0107] The present invention is based on the concrete matrix shear bearing capacity V in the original reinforced concrete T beam 1 c and the shear bearing capacity V of the stirrups in the original reinforced concrete T beam 1 sv , the shear bearing capacity of the damaged reinforced concrete T beam considering the influence of the compression flange is obtained by formula (5), and the shear bearing capacity of the damaged reinforced concrete T beam considering the influence of the compression flange is the shear bearing capacity of the concrete matrix in the original reinforced concrete T beam 1 considering the influence of the compression flange and damage V′ c Compared with the shear bearing capacity V′ of the original reinforced concrete T beam 1 considering the compression flange and damage sv The sum of the shear bearing capacity of the damaged reinforced concrete T beam considering the influence of the compression flange is V′ c +V′ sv ;

[0108]

[0109] Among them, α f is the compression flange influence coefficient, and α f is 1.1; ψ is the damage coefficient.

[0110] The value of the damage coefficient ψ of the present invention is selected as follows:

[0111] When no oblique cracks appeared in the original reinforced concrete T beam 1 before reinforcement, ψ was 1.0;

[0112] When there is an oblique crack in the original reinforced concrete T beam 1 before reinforcement and the crack width is less than or equal to 0.2 mm, ψ is 0.835;

[0113] When there is an oblique crack in the original reinforced concrete T-beam 1 before reinforcement and the crack width is greater than 0.2 and less than 0.4, ψ is calculated by linear interpolation, which is expressed by formula (6):

[0114] ψ=0.86-0.275τ...Equation (6);

[0115] Where, τ is the crack width;

[0116] When there is an oblique crack in the original reinforced concrete T-beam 1 before reinforcement and the crack width is equal to 0.4 mm, ψ is 0.78.

[0117] It should be noted that according to fracture mechanics, the concrete in the compression zone of reinforced concrete T-beam can still effectively provide shear force before the limit state. However, many existing specifications only consider the shear resistance provided by the web and ignore the influence of the flange. Therefore, the present invention introduces the compression flange influence coefficient α based on the formula used in formula (5). cv , and the value for the T-section beam is 1.1; since the components that need to be reinforced are usually damaged and cracked to produce oblique cracks, resulting in degradation of their shear performance, the present invention refers to the method of evaluating the degree of damage based on the width of oblique cracks in the "Highway Bridge Reinforcement Design Code" (JTG / T J22-2008), reduces the shear bearing capacity of the original beam, and introduces the damage coefficient ψ.

[0118] It should be noted that the current calculation method of the Swiss SIA2052 specification performs shear calculation on the UHPC thin layer 3. This method considers the entire UHPC thin layer 3 as a whole, and does not separate the steel fiber from its matrix for separate calculation. Since the influence of the steel fiber volume content on the tensile strength of the UHPC thin layer 3 cannot be ignored, the present invention introduces an empirical parameter δ for the first time, thereby introducing the steel fiber volume content ω into the calculation of shear bearing capacity and bending bearing capacity.

[0119] Among them, the overall shear bearing capacity of UHPC thin layer 3 is V UHPC Calculated by formula (7);

[0120]

[0121] Among them, α UHPC is the strength utilization coefficient of UHPC material. When the interface of the original reinforced concrete T beam 1 is smooth, α UHPC is 0.7, when the original reinforced concrete T beam 1 interface is roughened UHPC is 0.8; f Ulud is the elastic tensile strength of UHPC material; f Ulud is the ultimate tensile strength of UHPC material; θ is the angle between the principal compressive stress and the longitudinal axis, and θ is 45°.

[0122] The value of the influence coefficient δ of the steel fiber volume content in the UHPC thin layer 3 is as follows: when the steel fiber volume content in the UHPC thin layer 3 is 1.5%, δ is 0.9; when the steel fiber volume content in the UHPC thin layer 3 is 3%, δ is 1.1; when the steel fiber volume content in the UHPC thin layer 3 is between 1.5% and 3%, the value of δ is determined by formula (8):

[0123]

[0124] Wherein, ω is the volume content of steel fiber in the UHPC thin layer 3.

[0125] The present invention also considers the entire UHPC thin layer 3 as a whole, rather than separating the steel fibers from their matrix and calculating them separately.

[0126] UHPC thin layer 3 U-shaped stirrup 21 shear bearing capacity V sw Calculated by formula (9);

[0127]

[0128] Among them, α s is the strength utilization factor of the U-shaped stirrup 21 in the UHPC thin layer 3, and α s is 0.9; f yv is the tensile strength of the U-shaped stirrups 21 in the UHPC thin layer 3; s is the spacing of the U-shaped stirrups 21 in the UHPC thin layer 3 along the length direction of the member; h′ is the effective height of the cross-section of the UHPC thin layer reinforced reinforced concrete T-beam bridge.

[0129] Convert equation (1) into equation (10) to calculate the shear bearing capacity V of reinforced concrete T-beam bridge reinforced with UHPC thin layer u ;

[0130]

[0131] It should be noted that the present invention calculates the shear bearing capacity provided by the stirrups in the UHPC thin layer 3 according to the concrete structure reinforcement design specification, and the U-shaped stirrup 21 is reinforced by three-sided hoop reinforcement. In addition, the shear bearing capacity calculation formula of the UHPC thin layer reinforced reinforced concrete T-beam bridge of the present invention takes into account the influence of the compression flange and the damage of the original reinforced concrete T-beam 1, and at the same time, while drawing on the calculation method of the Swiss SIA2052 specification, takes into account the influence of the steel fiber content on the shear bearing capacity of the UHPC thin layer 3.

[0132] It should be noted that, since the UHPC thin layer reinforced reinforced concrete T-beam bridge should consider bending failure in addition to shear failure, the present invention also proposes a calculation method for bending bearing capacity. Moreover, based on model experiments and theoretical analysis, it is believed that the cross-sectional stress distribution law of the reinforced concrete T-beam after roughening and interface reinforcement 4 is still in line with the flat section assumption after being reinforced by the UHPC thin layer 3; based on the existing shear and bending bearing capacity calculation methods, it is believed that the bending bearing capacity of the reinforced concrete T-beam reinforced with the UHPC thin layer 3 is mainly composed of three parts: the UHPC thin layer 3, the longitudinal steel bars in the tension zone, and the ordinary concrete in the compression zone.

[0133] The method for calculating the bending bearing capacity of the present invention is to first assume that the cross-sectional area and centroid position of the UHPC thin layer 3 and the flange of the original reinforced concrete T beam 1 remain unchanged, and respectively equate the U-shaped section of the UHPC thin layer 3 and the polygonal section of the flange of the original reinforced concrete T beam 1 to regular rectangular sections, thereby obtaining a first rectangular section corresponding to the U-shaped section and a second rectangular section corresponding to the polygonal section; then, the bending bearing capacity M is calculated by formula (2): u :

[0134]

[0135] Where t is the distance from the centroid of the cross section of the longitudinal reinforcement 22 to the centroid of the concrete compression zone of the flange of the original reinforced concrete T beam 1, h′ u is the height of the first rectangular section; α1 is the stress pattern coefficient of the flange compression zone of the UHPC thin layer reinforced reinforced concrete T-beam bridge; A s is the longitudinal reinforcement area of ​​the web tension zone of the original reinforced concrete T beam 1; f UHPC is the tensile strength of UHPC thin layer 3; f g A is the tensile strength of the longitudinal reinforcement 22 in the UHPC thin layer 3; g is the cross-sectional area of ​​the longitudinal reinforcement 22 in the UHPC thin layer 3, b′ u is the bottom width of the first rectangular section; h0 is the effective height of the original reinforced concrete T beam 1; h is the total height of the UHPC thin layer reinforced reinforced concrete T beam bridge; x is the height of the compression zone of the flange of the original reinforced concrete T beam 1; f y is the tensile strength of the longitudinal reinforcement 22 in the original reinforced concrete T-beam 1, and δ is the influence coefficient of the steel fiber volume content in the UHPC thin layer 3.

[0136] It should be noted that the calculation of effective height is common knowledge in the field of bridges, and those skilled in the art should be aware of it, so it will not be elaborated here.

[0137] Specifically, the bending bearing capacity M of the present invention is u The calculation method is carried out by the following steps:

[0138] S1. In the mid-span section of the UHPC thin layer reinforced reinforced concrete T-beam bridge, take any point in the mid-span section as the origin O, the vertical direction passing through the origin O as the Y axis, and the horizontal direction passing through the origin O as the X axis to establish a YXO coordinate system;

[0139] S2. In the mid-span section, the shape of the UHPC thin layer 3 is a U-shaped section, and the shape of the flange of the original reinforced concrete T beam 1 is a polygonal section. Assuming that the cross-sectional area and centroid position of the UHPC thin layer 3 and the flange of the original reinforced concrete T beam 1 remain unchanged, the U-shaped section of the UHPC thin layer 3 and the polygonal section of the flange of the original reinforced concrete T beam 1 are respectively equivalent to regular rectangular sections, thereby obtaining a first rectangular section corresponding to the U-shaped section and a second rectangular section corresponding to the flange polygonal section;

[0140] S3, calculating the distance z from the centroid of the first rectangular cross section to the x-axis by using formula (11); calculating the distance q from the centroid of the second rectangular cross section to the x-axis by using formula (12);

[0141]

[0142] Among them, A1 is the area of ​​the single-sided vertical rectangle in the U-shaped section; A2 is the area of ​​the bottom rectangle in the U-shaped section, and the area of ​​the U-shaped section is 2A1+A2; Z1 is the distance from the centroid of the A1 area to the X-axis, and Z2 is the distance from the centroid of the A2 area to the X-axis;

[0143]

[0144] Among them, in the second rectangular section, A3 is the area of ​​one side of the original reinforced concrete T beam 1 flange support, A4 is the area of ​​the rectangular area above the original reinforced concrete T beam 1 flange support, A5 is the area of ​​the rectangular area between the supports on both sides of the original reinforced concrete T beam 1 flange, Z3 is the distance from the centroid of the A3 area to the X-axis, Z4 is the distance from the centroid of the A4 area to the X-axis, and Z5 is the distance from the centroid of the A5 area to the X-axis;

[0145] S4. Calculate the height h′ of the first rectangular section according to the distance z and formula (13): u ; Calculate the height h′ of the second rectangular section according to the distance q and formula (14) f ;

[0146] h′ u =2z……Formula (13);

[0147] h′ f =2q……Formula (14);

[0148] S5. Calculate the bottom width b′ of the first rectangular cross section by formula (15): u ; Calculate the top width b′ of the second rectangular cross section by formula (16)f ;

[0149]

[0150] Among them, A sc is the area of ​​the U-shaped cross section, and A sc =2A1+A2;

[0151]

[0152] Among them, A sb is the area of ​​the second rectangular cross section, and A sb =2A3+A4+A5; b′ f is the top width of the second rectangular cross section;

[0153] S6. According to the static equilibrium relationship of the mid-span section of the UHPC thin layer reinforced reinforced concrete T-beam bridge in formula (17), the height x of the compression zone of the flange of the original reinforced concrete T-beam 1 is calculated;

[0154]

[0155] Among them, f′ c is the measured value of the compressive strength of ordinary concrete in UHPC thin layer 3 in the bending test;

[0156] S7, calculated by formula (2) to obtain the bending bearing capacity M u .

[0157] The bearing capacity calculation method of the UHPC thin layer reinforced reinforced concrete T-beam bridge can effectively calculate the shear bearing capacity and bending bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge, and through finite element simulation and experimental verification, the effectiveness and feasibility of the shear and bending bearing capacity calculation method are proved. The shear bearing capacity and bending bearing capacity calculation method of the UHPC thin layer reinforced reinforced concrete T-beam bridge is simple in form and clear in physical meaning, which can better reflect the influence of damaged reinforced concrete, steel fiber volume content in UHPC, concrete strength, shear span ratio, longitudinal reinforcement ratio and other factors on shear and bending bearing capacity.

[0158] Verification Example

[0159] 1. Verification of the shear bearing capacity calculation method of the UHPC thin layer reinforced reinforced concrete T-beam bridge of the present invention

[0160] Based on the Technical Guidelines for Strengthening Highway Bridges with Ultra-High Performance Concrete, a finite element model of reinforced concrete T-beams reinforced with UHPC thin layer 3 was established, taking the thickness of UHPC thin layer 3, steel fiber, the treatment method of the interface between UHPC thin layer 3 and reinforced concrete T-beam, and the damage degree of reinforced concrete T-beam as basic parameters; for reinforced concrete T-beams reinforced with UHPC thin layer 3, the reinforced area of ​​UHPC thin layer 3 was reinforced for the full cross-section of the web in the shear span section, and part of the web of the reinforced concrete T-beam was reinforced in the mid-span.

[0161] The cross-sectional height of the original reinforced concrete T-beam 1 is 570mm, the effective height of the original reinforced concrete T-beam 1 is 456.2mm, the width of the upper flange plate is 640mm, the width of the web plate is 120mm, and the beam length is 3000mm. The concrete strength design grade is C55, and the steel bars in the original reinforced concrete T-beam 1 are all HRB400, of which 4Ф16mm tensile longitudinal bars 22 in the original reinforced concrete T-beam 1 are arranged at the bottom of the beam, 6Ф10mm compressive steel bars and 20Ф10mm transverse structural steel bars are arranged at the top, and the thickness of the concrete protective layer is set to 20mm. The stirrups in the original reinforced concrete T-beam 1 are 15 Ф8 steel bars arranged at equal intervals, with a spacing of 200mm. The thickness of the UHPC thin layer 3 is 30 and 50mm respectively; the model number and parameters of the test beam in the finite element model are shown in Table 1;

[0162] Table 1. Parameters of reinforced concrete T-beam bridge reinforced with UHPC thin layer in finite element model

[0163]

[0164] Explanation of specimen number: UN indicates reinforced concrete T-beam reinforced with UHPC thin layer 3; the first digit indicates the steel fiber content; the letter J indicates that the interface between UHPC thin layer 3 and reinforced concrete T-beam is roughened + interface rebar 4 treatment; the letter Q indicates full height reinforcement of the shear span of reinforced concrete T-beam. The second to last digit indicates the thickness of the reinforced layer UHPC thin layer 3. The last digit indicates the degree of pre-damage of reinforced concrete T-beam. UN-2-J50-Y0 indicates that the steel fiber content of the specimen is 2% for UHPC thin layer 3, the thickness of the reinforced layer UHPC thin layer 3 is 50mm, the treatment method of the interface between UHPC thin layer 3 and reinforced concrete T-beam is roughened + interface rebar 4, and the degree of pre-damage of reinforced concrete T-beam is 0.

[0165] UN-2%-J30Q-Y0 and UN-2%-J50Q-Y0 were subjected to finite element modeling, and the load was transferred to the specimen through the top distribution beam 5, as shown in Fig. 9 and Fig.10 ,exist Figure 8The middle point P is the load point, forming a pure bending section of 2240 mm, the shear span lengths on both sides are 380 mm, and the shear span ratio λ is 0.83. The internal dimensions of the original reinforced concrete T beam 1 are as follows: Fig. 9 As shown, the UHPC thin layer 3 of the original reinforced concrete T beam 1 is in the vacant area of ​​the web, as shown Fig.10 The present invention can also be applied to the UHPC thin layer 3 fully covering the web. Fig.10 The following is an example in which a portion of the web of the UHPC thin layer 3 is missing.

[0166] The shear bearing capacity V′ of the damaged reinforced concrete T-beam considering the influence of the compression flange calculated by the present invention is c +V′ sv The shear resistance of the UHPC layer 3 is V UHPC And U-shaped stirrup 21 shear bearing capacity V sw , and the shear bearing capacity V of reinforced concrete T-beam bridge reinforced with UHPC thin layer u Compared with the shear bearing capacity obtained by finite element simulation (such as Figure 11 to Figure 12 ) are compared to obtain Table 2;

[0167] Table 2. Shear bearing capacity V′ of reinforced concrete T-beams considering the influence of compression flange and damage obtained by finite element simulation and calculation of the present invention c +V′ sv The shear resistance of the UHPC layer 3 is V UHPC And U-shaped stirrup 21 shear bearing capacity V sw , and the shear bearing capacity V of reinforced concrete T-beam bridge reinforced with UHPC thin layer u The numerical value of .

[0168]

[0169] It can be seen from the above table that the calculation results of the shear bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge of the present invention are consistent with the simulation results of the finite element model. Generally speaking, it is a conservative and concise formula, and the calculation is simple and convenient.

[0170] 2. Verification of the flexural bearing capacity calculation method of the present invention

[0171] The cross-sectional height of the original reinforced concrete T-beam 1 is 570mm, the effective height of the original reinforced concrete T-beam 1 is 456.2mm, the width of the upper flange plate is 640mm, the width of the web plate is 120mm, and the beam length is 3000mm. The concrete strength design grade is C55, and the steel bars in the original reinforced concrete T-beam 1 are all HRB400, of which 4Ф16mm longitudinal bars 22 in the original reinforced concrete T-beam 1 are arranged at the bottom of the beam, 6Ф10mm compressive steel bars and 20Ф10mm transverse structural steel bars are arranged at the top, and the thickness of the concrete protective layer is set to 20mm. The stirrups in the original reinforced concrete T-beam 1 are 15 Ф8 steel bars arranged evenly with a spacing of 200mm. The thickness of the UHPC thin layer 3 is 30 and 50mm respectively. The internal dimensions of the original reinforced concrete T-beam 1 are as follows Fig. 9 As shown, the UHPC thin layer 3 of the original reinforced concrete T beam 1 is in the vacant area of ​​the web, as shown Fig.13 The present invention can also be applied to the UHPC thin layer 3 fully covering the web. Fig.10 The UHPC thin layer 3 with a part of the web plate is used as an example to illustrate. The test beam number and parameters of the actual UHPC thin layer reinforced reinforced concrete T-beam bridge are shown in Table 3;

[0172] Table 3. Parameters of the actual UHPC thin layer reinforced reinforced concrete T-beam bridge test beam

[0173]

[0174] Then a 1000t long-axis compression testing machine is used to load the specimen, and the load is transferred to the specimen through the distribution beam 5, such as Fig.14 , forming a pure bending section of 1500mm, the shear span lengths on both sides are 675mm, and the shear span ratio λ is 1.33.

[0175] The calculation method of the flexural bearing capacity according to Example 1 and the actual flexural bearing capacity data of the UN-2%-J50Q-Y0.2 test beam, the UN-3%-J50Q-Y0 test beam and the UN-2%-J30Q-Y0 test beam are shown in Table 4;

[0176] Table 4. Flexural bearing capacity and actual flexural bearing capacity data of the present invention

[0177]

[0178] According to Table 4, the error between the calculation formula for the flexural bearing capacity of reinforced concrete T-beam reinforced with UHPC thin layer 3 obtained in the present invention and the flexural bearing capacity obtained in actual tests is within 10%. It can be seen that the calculation method for flexural and shearing bearing capacity proposed in the present invention has high prediction accuracy and small discreteness, and has good reliability.

[0179] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge, characterized in that: The UHPC thin layer reinforced reinforced concrete T-beam bridge is composed of the original reinforced concrete T-beam, interface embedded reinforcement, reinforcement layer steel mesh and UHPC thin layer; the reinforcement layer steel mesh is composed of a plurality of U-shaped stirrups and a plurality of longitudinal bars to form a mesh structure; The bearing capacity includes the shear bearing capacity of UHPC thin layer reinforced reinforced concrete T-beam bridge and the bending bearing capacity of UHPC thin layer reinforced reinforced concrete T-beam bridge; The shear bearing capacity calculation method of the UHPC thin layer reinforced reinforced concrete T-beam bridge is to calculate the shear bearing capacity V′ of the damaged reinforced concrete T-beam considering the influence of the compression flange. c +V′ sv , shear bearing capacity of UHPC thin layer V UHPC and the shear bearing capacity of the U-shaped stirrups V sw Add and calculate the shear bearing capacity V of the UHPC thin layer reinforced reinforced concrete T-beam bridge through formula (1): u : V u = V' c + V' sv + V UHPC + V sw …… Equation (1); The method for calculating the bending bearing capacity of the UHPC thin layer reinforced reinforced concrete T-beam bridge is as follows: first, the cross-sectional area and centroid position of the UHPC thin layer and the original reinforced concrete T-beam flange are assumed to remain unchanged, and the U-shaped section of the UHPC thin layer and the polygonal section of the original reinforced concrete T-beam flange are respectively equivalent to regular rectangular sections, thereby obtaining a first rectangular section corresponding to the U-shaped section and a second rectangular section corresponding to the polygonal section; and then the bending bearing capacity Mu is calculated by formula (2): Where t is the distance from the centroid of the cross section of the longitudinal reinforcement to the centroid of the concrete compression zone of the flange of the original reinforced concrete T-beam, h′ u is the height of the first rectangular section; α1 is the stress pattern coefficient of the flange compression zone of the UHPC thin layer reinforced reinforced concrete T-beam bridge; A s is the longitudinal reinforcement area of ​​the web tension zone of the original reinforced concrete T-beam; f UHPC is the tensile strength of UHPC thin layer; f g A is the tensile strength of the longitudinal reinforcement in the UHPC thin layer; g is the cross-sectional area of ​​the longitudinal reinforcement in the UHPC thin layer, b′ u is the bottom width of the first rectangular section; h0 is the effective height of the original reinforced concrete T-beam; h is the total height of the UHPC thin layer reinforced reinforced concrete T-beam bridge; x is the height of the compression zone of the original reinforced concrete T-beam flange; f y is the tensile strength of the longitudinal reinforcement in the original reinforced concrete T-beam, and δ is the influence coefficient of the volume content of steel fiber in the UHPC thin layer.

2. The method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge according to claim 1 is characterized in that: The shear bearing capacity of the concrete matrix in the original reinforced concrete T beam is V c Through formula (3), we can get: V c =α cv f t0 bh0 …… Formula (3); Among them, α cv f is the shear bearing capacity coefficient of the inclined section of concrete; t0 is the concrete axial tensile strength of the original reinforced concrete T-beam; b is the web width of the original reinforced concrete T-beam.

3. The method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge according to claim 2 is characterized in that: The shear bearing capacity coefficient of the inclined section of concrete is α cv The assignment method: When the original reinforced concrete T beam is mainly subjected to the combined action of bending moment and shear force and the axial force is negligible, α cv is 0.7; when the original reinforced concrete T beam is an independent beam under concentrated load, Where λ is the assigned value of the cross-section shear span ratio; The assignment method of the section shear span ratio value λ is: when the actual section shear span ratio is less than or equal to 1.5, λ is 1.5; when the actual section shear span ratio is between 1.5 and 3, λ is the actual section shear span ratio; when the actual section shear span ratio is greater than or equal to 3, λ is 3.

4. The method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge according to claim 3 is characterized in that: The shear bearing capacity of the stirrups in the original reinforced concrete T beam is V sv Calculated by formula (4); Where s0 is the spacing of the stirrups in the original reinforced concrete T-beam along the length of the member; A sv0 is the cross-sectional area of ​​the stirrups in the shear span of the original reinforced concrete T-beam; f yv0 is the tensile strength of the stirrups in the original reinforced concrete T-beam.

5. The method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge according to claim 4 is characterized in that: According to the shear bearing capacity V of the concrete matrix in the original reinforced concrete T beam c and the shear bearing capacity V of the stirrups in the original reinforced concrete T beam sv , the shear bearing capacity of the damaged reinforced concrete T beam considering the influence of the compression flange is obtained by formula (5), and the shear bearing capacity of the damaged reinforced concrete T beam considering the influence of the compression flange is the shear bearing capacity V′ of the concrete matrix in the original reinforced concrete T beam considering the influence of the compression flange and damage c Compared with the shear bearing capacity V′ of the original reinforced concrete T-beam considering the compression flange and damage sv The sum of the shear bearing capacity of the damaged reinforced concrete T beam considering the influence of the compression flange is V′ c +V′ sv ; Among them, α f is the compression flange influence coefficient, and α f is 1.1; ψ is the damage coefficient.

6. The method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge according to claim 5 is characterized in that: The value of the damage coefficient ψ is selected as follows: When no oblique cracks appeared in the original reinforced concrete T-beam before reinforcement, ψ was 1.0; When there are oblique cracks in the original reinforced concrete T beam before reinforcement and the crack width is less than or equal to 0.2 mm, ψ is 0.835; When there are oblique cracks in the original reinforced concrete T-beam before reinforcement and the crack width is greater than 0.2 and less than 0.4, ψ is calculated by linear interpolation, which is expressed by formula (6): ψ=0.89-0.275τ...Equation (6); Where, T is the crack width; When there are oblique cracks in the original reinforced concrete T-beam before reinforcement and the crack width is equal to 0.4 mm, ψ is 0.

78.

7. The method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge according to claim 6 is characterized in that: The shear bearing capacity of the UHPC thin layer is V UHPC Calculated by formula (7); Among them, α UHPC is the strength utilization coefficient of UHPC material. When the original reinforced concrete T-beam interface is smooth, α UHPC is 0.7, when the original reinforced concrete T-beam interface is roughened UHPC is 0.8; f Ulud is the elastic tensile strength of UHPC material; f Ulud is the ultimate tensile strength of the UHPC material; θ is the angle between the principal compressive stress and the longitudinal axis, and θ is 45°; The value of the influence coefficient δ of the steel fiber volume content in the UHPC thin layer is as follows: when the steel fiber volume content in the UHPC thin layer is 1.5%, δ is 0.9; when the steel fiber volume content in the UHPC thin layer is 3%, δ is 1.1; when the steel fiber volume content in the UHPC thin layer is between 1.5% and 3%, the value of δ is determined by formula (8): Where ω is the volume content of steel fiber in the UHPC thin layer.

8. The method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge according to claim 7 is characterized in that: The shear bearing capacity of the U-shaped stirrups in the UHPC thin layer V sw Calculated by formula (9); Among them, α s is the strength utilization factor of the U-shaped stirrups in the UHPC thin layer, and α s is 0.9; f yv is the tensile strength of the U-shaped stirrups in the UHPC thin layer; s is the spacing of the U-shaped stirrups in the UHPC thin layer along the length of the member; h is the effective height of the cross section of the UHPC thin layer reinforced reinforced concrete T-beam bridge; The formula (1) is converted into formula (10) to calculate the shear bearing capacity V of the UHPC thin layer reinforced reinforced concrete T-beam bridge: u ; 9. The method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge according to any one of claims 1 to 8, characterized in that: The bending resistance M u The calculation method is carried out by the following steps: S1. In the mid-span section of the UHPC thin layer reinforced reinforced concrete T-beam bridge, take any point in the mid-span section as the origin O, the vertical direction passing through the origin O as the Y axis, and the horizontal direction passing through the origin O as the X axis to establish a YXO coordinate system; S2. In the mid-span section, the shape of the UHPC thin layer is a U-shaped section, and the shape of the original reinforced concrete T-beam flange is a polygonal section. Assuming that the cross-sectional area and centroid position of the UHPC thin layer and the original reinforced concrete T-beam flange remain unchanged, the U-shaped section of the UHPC thin layer and the polygonal section of the original reinforced concrete T-beam flange are respectively equivalent to regular rectangular sections, thereby obtaining a first rectangular section corresponding to the U-shaped section and a second rectangular section corresponding to the flange polygonal section; S3, calculating the distance z from the centroid of the first rectangular cross section to the x-axis by using formula (11); calculating the distance q from the centroid of the second rectangular cross section to the x-axis by using formula (12); Wherein, A1 is the area of ​​the single-sided vertical rectangle in the U-shaped section; A2 is the area of ​​the bottom rectangle in the U-shaped section, and the area of ​​the U-shaped section is 2A1+A2; Z1 is the distance from the centroid of the A1 area to the X-axis, and Z2 is the distance from the centroid of the A2 area to the X-axis; Among them, A3 is the area of ​​one side of the original reinforced concrete T-beam flange support, A4 is the area of ​​the rectangular area above the original reinforced concrete T-beam flange support, A5 is the area of ​​the rectangular area between the supports on both sides of the original reinforced concrete T-beam flange, Z3 is the distance from the centroid of the A3 area to the X-axis, Z4 is the distance from the centroid of the A4 area to the X-axis, and Z5 is the distance from the centroid of the A5 area to the X-axis; S4. Calculate the height h′ of the first rectangular section according to the distance z and formula (13): u ; Calculate the height h′ of the second rectangular section according to the distance q and formula (14) f ; h′ u =2z……Formula (13); h′ f =2q……Formula (14); S5. Calculate the bottom width b′ of the first rectangular cross section by formula (15): u ; Calculate the top width b' of the second rectangular cross section by formula (16): f , Among them, A sc is the area of ​​the U-shaped cross section, and A sc =2A1+A2; Among them, A sb is the area of ​​the second rectangular cross section, and A sb =2A3+A4+A5; b′ f is the top width of the second rectangular cross section; S6. According to the static equilibrium relationship of the mid-span section of the UHPC thin layer reinforced reinforced concrete T-beam bridge in formula (17), the height x of the compression zone of the original reinforced concrete T-beam flange is calculated; Among them, f′ c is the measured value of the compressive strength of ordinary concrete in the UHPC thin layer in the bending test; S7. The bending bearing capacity M is calculated by formula (2): u .

10. The method for calculating the bearing capacity of a UHPC thin layer reinforced reinforced concrete T-beam bridge according to any one of claims 1 to 8, characterized in that: The original reinforced concrete T-beam is a first type T-shaped beam, that is, the cross-sectional neutral axis of the original reinforced concrete T-beam is located inside the concrete flange.

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