Railway concrete simply supported beam bridge deck integrated three-wall stress calculation method

Abstract

The invention discloses a railway concrete simply supported beam bridge floor integrated three-wall stress calculation method. The method comprises the following steps: calculating local stress at the joint of three walls and a bridge floor considering a shear hysteresis effect under the working conditions of prestress tension and self weight; calculating the local stress at the joint of the three walls and the bridge floor under the concrete shrinkage and creep working condition; calculating local stress at the joint of the three walls and the bridge floor under the sunlight temperature difference condition; the three working conditions are combined, and local stress at the joints of the three walls and the bridge floor under the combination effect of the most unfavorable working conditions is obtained; calculating local stress at the breaking joint of the three walls by considering stress concentration at the breaking joint; providing a measure for improving local stress concentration at the breaking joint of the three walls, and calculating the local stress at the breaking joint of the three walls until the local stress at the breaking joint of the three walls is not greater than a checking calculation control index of the three walls; according to the scheme, the design efficiency and the quality consistency are greatly improved through local stress calculation and checking calculation at the breaking joints of the three walls, and technical support is provided for integrated prefabrication of the three walls and the main beam.

Description

Technical Field

[0001] This invention relates to the field of bridge stress calculation technology, specifically to a method for calculating the stress of the three walls of an integrated concrete simply supported beam bridge deck for railways. Background Technology

[0002] With the development of high-speed railways and the implementation of green and sustainable development concepts in transportation infrastructure construction, precast concrete simply supported beam bridges are the most basic and dominant bridge type in high-speed railways due to their advantages such as being suitable for standardized factory construction, high quality, shortened construction period, cost savings, and reduced impact on existing traffic and the environment. The three walls in the bridge deck ancillary structure, including the protective wall, vertical wall A, and vertical wall B, are important components of the bridge, and their load-bearing performance directly affects the overall safety and durability of the bridge.

[0003] Traditional bridge deck wall construction has long relied on pre-reserved ordinary steel bars at the beam factory, followed by on-site casting of the bridge deck after the box girder is erected on-site. This method suffers from problems such as poor casting quality, low construction efficiency, and high safety risks associated with long-distance operations. Currently, some projects have adopted an improved method of on-site assembly of the bridge deck walls, but this also presents difficulties such as cumbersome construction and challenges in maintaining long-term performance.

[0004] Currently, research on bridge deck ancillary structures is limited, and most studies focus on guardrails and steel-concrete composite beam bridge decks for highway bridges, with less research and application related to railways. To further improve the prefabrication level of high-speed railways and enhance the integrity and quality of the bridge deck's three-wall structure, a new process is proposed: prefabricate vertical walls, cable troughs, and protective walls (three walls and two troughs) simultaneously in the factory along with the main beam. However, during the simultaneous prefabrication of the three walls and the main beam, under the influence of self-weight and prestressing, and during construction processes such as hoisting, transportation, and erection, the three walls may participate in the load-bearing of the main beam, potentially exceeding the tensile strength requirements of concrete at the mid-span. Therefore, it is necessary to treat the three walls with joints to allow them to partially participate in the load-bearing of the main beam and reduce the stress on the three-wall structure. However, under the influence of prestressing tension, self-weight, shrinkage, creep, and temperature changes, stress concentration can easily occur at the joints of the three walls, leading to concrete cracking and affecting structural safety.

[0005] The systematic calculation method for local stress at the fracture joints of the three-wall structure is still imperfect. Existing designs mostly rely on experience or simplified models, lacking precise consideration of the coupled effects of multiple factors such as shear lag, shrinkage and creep, and solar thermal temperature difference. This makes it difficult to effectively guide the prestressed design and crack control of the three-wall structure. Therefore, it is urgent to propose a scientific and systematic prestressed calculation method for the three-wall structure to calculate and verify the stress at the fracture joints, providing a theoretical basis for the design and construction of the integrated three-wall structure of the bridge deck, so as to ensure the structural safety and crack prevention of the three-wall structure. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a method for calculating the stress of the integrated three-wall structure of a railway concrete simply supported beam bridge deck, offering a method for local stress calculation at the joints of the integrated three-wall structure of the bridge deck.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for calculating the stress of an integrated three-wall structure for a simply supported concrete beam bridge deck in railways is provided, comprising the following steps: S1: Determine the structural parameters and joint construction parameters of the three walls, including the width, height, joint spacing, and joint size of vertical wall A, vertical wall B, and protective wall; S2: Determine the control calculation conditions, including prestressing tension and self-weight conditions, concrete shrinkage and creep conditions, and solar radiation temperature difference conditions; S3: Calculate the local stress at the connection between the three walls and the bridge deck under the conditions of prestressing tension and self-weight, considering the shear lag effect; calculate the local stress at the connection between the three walls and the bridge deck under the conditions of concrete shrinkage and creep; calculate the local stress at the connection between the three walls and the bridge deck under the conditions of solar radiation and temperature difference; combine the three conditions and obtain the local stress at the connection between the three walls and the bridge deck under the most unfavorable combination of conditions. S4: Calculate the local stress at the fracture joint of the three walls, considering the stress concentration at the fracture joint, and compare it with the verification control index of the three walls. If the local stress at the fracture joint of the three walls is greater than the verification control index of the three walls, then proceed to step S5; otherwise, proceed to step S6. S5: Propose measures to improve the local stress concentration at the fracture joint of the three walls, and recalculate the local stress at the fracture joint of the three walls until the local stress at the fracture joint of the three walls is not greater than the verification control index of the three walls. S6: Complete the local stress calculation and verification at the fracture joint of the three walls.

[0008] Furthermore, the formula for calculating the local stress at the connection between the three walls and the bridge deck under prestressed tension and self-weight conditions in step S3, considering the shear lag effect, is as follows: ; ;

[0009] Where ξ is the most unfavorable coefficient, and λ is the shear lag coefficient at the connection between the three walls and the bridge deck that participates in the bending stress of the entire beam. c g This is the self-weight combination coefficient. c p The prestress combination coefficient is... s g The bending stress under its own weight. M s The bending moment at any section of the entire bridge under the self-weight of the precast beam. yLet be the distance from the calculation point of the three walls to the centroid of the section. I Let the moment of inertia of the cross section be... s p This represents the total stress under prestressing. s ca The stress caused by the prestressed axial force. s cb This refers to the stress caused by the prestressed eccentric bending moment.

[0010] Furthermore, the formula for calculating the shear lag coefficient at the connection between the three walls and the bridge deck, which participates in the bending stress of the entire beam, is as follows: ; ;

[0011] in, L To calculate the span, b It is half the spacing between the web plates of the box girder. I s This is the sum of the moments of inertia of the top and bottom plates about the centroid of the cross section. n and k Here are the Risner parameters, G is the shear modulus, and E is the shear modulus. c This refers to the elastic modulus of concrete.

[0012] Furthermore, the calculation method for the local stress at the connection between the three walls and the bridge deck under the concrete shrinkage and creep condition in step S3 is as follows: The formula for calculating the tensile stress at the connection between the three walls and the bridge deck caused by shrinkage is as follows: ;

[0013] in, s sh E is the tensile stress caused by contraction. c The elastic modulus of concrete. L s The spacing between the breaks, x This is the distance from the wall to the centerline of the main beam. R The constraint coefficient at the fracture joint is... H The height of the wall. e sh This represents the shrinkage strain of the concrete. e sh0 The reference shrinkage strain for concrete. β rh This is the environmental humidity correction factor. It is a time function; The formula for calculating stress relaxation caused by creep is as follows: ;

[0014] in, f 0 represents the nominal creep coefficient. This is the creep time development coefficient; The formula for calculating the local stress at the connection between the three walls and the bridge deck under concrete shrinkage and creep conditions is as follows:

[0015] in, s sc This refers to the local stress at the connection between the three walls and the bridge deck under concrete shrinkage and creep conditions.

[0016] Furthermore, the formula for calculating the local stress at the connection between the three walls and the bridge deck under the solar radiation temperature difference condition in step S3 is as follows:

[0017] in, β The constraint coefficient at the fracture joint is... α T The coefficient of linear expansion is 1 / 3. This refers to the temperature difference.

[0018] Furthermore, the formula for calculating the local stress at the connection between the three walls and the bridge deck under the most unfavorable combination of working conditions in step S3 is as follows:

[0019] in, c sh This is the concrete shrinkage combination coefficient. c cr This represents the concrete creep combination factor. c T This is the temperature combination coefficient.

[0020] Furthermore, the formula for calculating the local stress at the fracture joint of the three walls in step S4 is as follows:

[0021] in, K t For right-angle fractures, the stress concentration factor is... K t The value is 3.0; for arc-shaped fractures, , r The radius of the arc, w This refers to the width of the seam.

[0022] Furthermore, the calculation formula for the verification control index of the three walls in step S4 is as follows: s max= k [ s ] in, k For the allowable stress enhancement factor, [ s The standard design specifications for the compressive and tensile strengths of bridge deck concrete.

[0023] Furthermore, the measures to improve local stress concentration at the joint of the three walls in step S5 include: changing the right-angle joint to an arc-shaped joint and / or placing longitudinal reinforcing bars under the joint and on both sides of the joint.

[0024] Furthermore, when ordinary steel reinforcement is added below and on both sides of the fracture joint, the formula for calculating the reduction in concrete stress is as follows: ; ;

[0025] in, This represents the reduction in concrete stress. e a This represents the total strain caused by concrete shrinkage, creep, and the effect of solar thermal temperature difference. m This is the ratio of the elastic modulus of concrete to the elastic modulus of steel reinforcement. r For reinforcement ratio, A s A represents the total area of ​​the longitudinal reinforcing bars at the fracture joint. c The cross-sectional area of ​​the unbroken section of concrete 2 cm below the fracture joint; The formula for calculating the local stress at the fracture joint of the three walls after improvement is as follows: .

[0026] The beneficial effects of this invention are as follows: 1. This scheme clearly distinguishes and calculates the local stress at the connection between the three walls and the bridge deck under the conditions of prestressing tension and self-weight, concrete shrinkage and creep, and solar radiation temperature difference. It systematically combines the three conditions to obtain the local stress at the connection between the three walls and the bridge deck under the most unfavorable combination of conditions. This scheme covers the key stress stages of the entire life cycle from prefabrication and tensioning to long-term use. At the same time, considering the stress characteristics of the three walls located on the flange of the bridge deck, a modified calculation formula considering the shear lag effect of the box girder is proposed. This more realistically reflects the non-uniformity of the flange stress distribution and avoids poor stress calculation accuracy due to simplified calculation. The calculation results are more consistent with the actual working state of the structure.

[0027] 2. This solution can change the right angle at the tip of the fracture to a rounded transition, effectively reducing stress concentration by using a smooth geometric transition. At the same time, longitudinal reinforcing bars can be placed in the unbroken area below the fracture. Through the joint work of the reinforcing bars and concrete, they actively bear part of the tensile stress, reducing the stress level of the concrete. A specific calculation formula for the stress reduction value of the reinforced concrete is also provided, making the reinforcement design based on evidence. Through these two measures, the local stress at the fracture can be significantly reduced, effectively preventing non-structural cracking of concrete caused by stress concentration, and greatly improving the durability of the three walls and bridge deck structure.

[0028] 3. This solution greatly improves design efficiency and quality consistency through local stress calculation and verification at the joints of the three walls, providing technical support for the integrated prefabrication of the three walls and the main beam, thereby avoiding the traditional on-site casting construction method, improving construction efficiency, and reducing on-site operation time. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The above and other objects, features, and advantages of the present invention will become clearer through the accompanying drawings. The same reference numerals indicate the same parts in all the drawings. The drawings are not intentionally drawn to scale to actual dimensions; the focus is on illustrating the main points of the invention.

[0030] Figure 1 A flowchart illustrating the method for calculating the stress of the three walls of a railway concrete simply supported beam bridge deck.

[0031] Figure 2 This is a schematic diagram of the cross-section of a prestressed concrete bridge box girder with simple support.

[0032] Figure 3 This is a structural schematic diagram of a three-wall fracture in a prestressed concrete bridge box girder with simply supported beams.

[0033] Figure 4 This is a structural diagram of a right-angled fracture in a protective wall.

[0034] Figure 5 This is a structural diagram of a protective wall with an arc-shaped fracture.

[0035] Among them, 1. Protective wall, 2. Vertical wall A, 3. Vertical wall B, 4. Right-angle joint, 5. Arc-shaped joint, 6. Longitudinal reinforcing steel. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0038] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0039] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0040] like Figure 1 As shown, the stress calculation method for the integrated three-wall structure of the railway concrete simply supported beam bridge deck in this scheme includes the following steps: S1: Determine the structural parameters and joint construction parameters of the three walls, including the width, height, joint spacing, joint size, and bridge structure calculation parameters of vertical wall A2, vertical wall B3, and protective wall 1; S2: Determine the control calculation conditions. Based on the construction process characteristics of the whole beam including the three walls being prefabricated as a whole in the beam yard, the live load after the bridge is completed is not considered because the live load after the bridge is completed is beneficial to the stress of the three walls. The most unfavorable prestressing tension and self-weight conditions are mainly considered, followed by the effects of concrete shrinkage and creep conditions and solar radiation temperature difference conditions. S3: Calculate the local stress at the connection between the three walls and the bridge deck considering shear lag under prestressed tension and self-weight conditions; calculate the local stress at the connection between the three walls and the bridge deck under concrete shrinkage and creep conditions; calculate the local stress at the connection between the three walls and the bridge deck under solar radiation and temperature difference conditions; combine the three conditions and obtain the local stress at the connection between the three walls and the bridge deck under the most unfavorable combination of conditions; specifically including: In step S3, the local stress at the connection between the three walls and the bridge deck considering shear lag effect under prestressing tension and self-weight conditions. s m The calculation formula is: ; ;

[0041] Where ξ is the most unfavorable coefficient, which is taken as 0.6-0.8 based on the length and location of the joints in the three walls, and λ is the shear lag coefficient at the connection between the three walls and the bridge deck that participates in the bending stress of the entire beam. c g This is the self-weight combination coefficient. c p This is the prestressing combination coefficient, based on the stress combination characteristics in the actual stress distribution of the three walls, and considering the structural characteristics of the three walls. c g Take a value between 1.2 and 1.35. c p Take a value between 0.8 and 1.0; s g The bending stress under its own weight. M s The bending moment at any section of the entire bridge under the self-weight of the precast beam can be calculated as a simply supported beam bridge. y Let be the distance from the calculation point of the three walls to the centroid of the section. I Let the moment of inertia of the cross section be... s p This represents the total stress under prestressing. s ca The stress caused by the prestressed axial force. s cb This refers to the stress caused by the prestressed eccentric bending moment.

[0042] The formula for calculating the shear lag coefficient at the connection between the three walls and the bridge deck, which participates in the bending stress of the entire beam, is as follows: ; ;

[0043] in, L To calculate the span, b It is half the spacing between the web plates of the box girder. I s This is the sum of the moments of inertia of the top and bottom plates about the centroid of the cross section. n and k Here are the Risner parameters, G is the shear modulus, and E is the shear modulus. c The elastic modulus of concrete; The final formula for calculating the local stress at the connection between the three walls and the bridge deck is as follows:

[0044] The calculation method for the local stress at the connection between the three walls and the bridge deck under the concrete shrinkage and creep condition in step S3 is as follows: The formula for calculating the tensile stress at the connection between the three walls and the bridge deck caused by shrinkage is as follows: ;

[0045] in, s sh Tensile stress caused by shrinkage, L s The spacing between the breaks, x This is the distance from the wall to the centerline of the main beam. R The constraint coefficient at the fracture joint is taken as 0.2-0.4; H The height of the wall. e sh This represents the shrinkage strain of the concrete. e sh0 The reference shrinkage strain for concrete. β rh This is the environmental humidity correction factor, which is set to 1.0 when the relative humidity is 60%. It is a time function; Calculate stress relaxation caused by creep s cr The calculation formula is as follows: ;

[0046] in, f 0 represents the nominal creep coefficient. This is the creep time development factor, which is determined according to the standard. Calculate the local stress at the connection between the three walls and the bridge deck under concrete shrinkage and creep conditions. s sc The calculation formula is as follows:

[0047] Local stress at the connection between the three walls and the bridge deck under the solar radiation temperature difference condition in step S3 s T The calculation formula is:

[0048] in, β The constraint coefficient at the fracture joint is taken as 0.6-0.8; α T The coefficient of linear expansion is 1 / 3. This refers to the temperature difference.

[0049] The formula for calculating the local stress at the connection between the three walls and the bridge deck under the most unfavorable combination of working conditions in step S3 is as follows:

[0050] in, c sh This is the concrete shrinkage combination coefficient. c cr This represents the concrete creep combination factor. c T This is the temperature combination coefficient; based on the stress combination characteristics in the actual stress distribution of the three walls, and considering the structural characteristics of the three walls, c sh Take 0.4-0.5, c cr Take a value of 0.6-0.8. c T Take a value between 1.0 and 1.2.

[0051] S4: Calculate the local stress at the fracture joint of the three walls, considering the stress concentration at the fracture joint, and compare it with the verification control index of the three walls. If the local stress at the fracture joint of the three walls is greater than the verification control index of the three walls, then proceed to step S5; otherwise, proceed to step S6. S5: Propose measures to improve the local stress concentration at the fracture joint of the three walls, and recalculate the local stress at the fracture joint of the three walls until the local stress at the fracture joint of the three walls is not greater than the verification control index of the three walls. S6: Complete the local stress calculation and verification at the fracture joint of the three walls.

[0052] In step S4, the stress on the three walls is discontinuous at the fracture joint, leading to local stress concentration. Therefore, a stress concentration factor is proposed. K t The formula for calculating the local stress at the fracture joint of the three walls is:

[0053] in, K t For a right-angle fracture with a stress concentration factor of 4, K t The value is 3.0; for a circular arc-shaped fracture, when the value is 5, , r The radius of the arc, w This refers to the width of the seam.

[0054] The calculation formula for the verification control index of the three walls in step S4 is as follows: s max = k [ s ] in, k The allowable stress increase factor is determined based on the actual stress characteristics of the three walls, and is ranged from 1.2 to 2.0. s The standard design specifications for the compressive and tensile strengths of bridge deck concrete.

[0055] The measures to improve local stress concentration at the fracture joint of the three walls in step S5 include (1) changing the right-angle fracture joint 4 into an arc-shaped fracture joint 5 with an arc radius r ≥ 20 mm, which reduces the stress concentration factor. K t (2) Longitudinal reinforcing bars 6 are arranged below the fracture joint and on both sides of the fracture joint. The longitudinal reinforcing bars 6 are arranged in the unbroken part 2 cm below the fracture joint, with a length of 3-5d (d is the diameter of the longitudinal reinforcing bars 6) to enhance the local bearing capacity.

[0056] When ordinary steel reinforcement is added below and on both sides of the fracture joint, the formula for calculating the reduction in concrete stress is: ; ;

[0057] in, This represents the reduction in concrete stress. e a This represents the total strain caused by concrete shrinkage, creep, and the effect of solar thermal temperature difference. m This is the ratio of the elastic modulus of concrete to the elastic modulus of steel reinforcement. r For reinforcement ratio, A s A represents the total area of ​​the longitudinal reinforcing steel bars 6 at the fracture joint. c The cross-sectional area of ​​the unbroken section of concrete 2 cm below the fracture joint; The formula for calculating the local stress at the fracture joint of the three walls after improvement is as follows: .

[0058] The following section uses protective wall 1 as an example to verify and calculate it using this scheme. The verification and calculation of vertical wall A2 and vertical wall B3 are similar.

[0059] like Figure 2 and Figure 3 As shown, a precast ballastless track post-tensioned prestressed concrete box girder bridge for a railway has a total length of 32.6 m, a calculated span of 31.5 m, a net inner width of 9.0 m for retaining wall 1, a net inner width of 12.1 m for the pedestrian walkway railing, a bridge width of 12.2 m, and a total bridge width of 12.48 m. Retaining wall 1, vertical walls A2 and B3, the contact wire foundation, and the anchor wire foundation are all constructed with concrete of the same strength grade as the beam, specifically C40 concrete. The inner height of retaining wall 1 (both straight and curved sections) is 840 mm, vertical wall A2 is 412 mm high, and vertical wall B3 is 325 mm high. Retaining wall 1 has a 10 mm wide joint every 4 m, while vertical walls A2 and B3 have 100 mm wide joints every 2 m.

[0060] Based on the bridge's design parameters and the actual stress characteristics of the protective wall 1, here... x , c g and c p Using values ​​of 0.75, 1.35, and 1.0 respectively, the stress of protective wall 1 under prestressed tension and self-weight conditions is calculated. Substituting these values ​​into the corresponding formulas yields:

[0061] The value calculated using ANSYS software is 0.780 MPa.

[0062] Calculate the local stress at the connection between the three walls and the bridge deck under concrete shrinkage and creep conditions. Based on the actual stress characteristics of protective wall 1, the constraint coefficient at this point is... R Taking a value of 0.3, substituting it into the corresponding formula yields:

[0063]

[0064]

[0065] Calculate the local stress at the connection between the three walls and the bridge deck under the condition of solar radiation and temperature difference. Based on the actual stress characteristics of the protective wall 1, the constraint coefficient is... β The value is 0.7, representing the temperature difference due to sunlight. The calculated value is 9.85℃. Substituting this into the corresponding formula, we get:

[0066] Calculate the local stress at the connection between the three walls and the bridge deck under the most unfavorable combination of loads, based on the actual stress characteristics of protective wall 1. c sh , c cr and c T Substituting 0.5, 0.6, and 1.2 into the corresponding formulas yields:

[0067] Considering stress concentration at the fracture joint, the local stress at the fracture joint of the three walls is calculated according to the right-angle fracture joint 4. The stress concentration factor at this point is... K t The value is 3.0. Substituting it into the corresponding formula, we get:

[0068] The local stress at the fracture joint of the three walls was compared with the calculated control index of the three walls (allowable stress increase factor). k (Value 1.5):

[0069] The comparison results show that the local stress at the fracture point of the protective wall 1 exceeds the standard and does not meet the verification formula.

[0070] Calculate the reduction in concrete tensile stress after adding longitudinal reinforcing bars 6 below and on both sides of the fracture joint. Two longitudinal reinforcing bars 6 Φ8@50mm are placed below and on both sides of the fracture joint. The length of the longitudinal reinforcing bars 6 is 3~5d, taken as 0.8 m. The arrangement of the longitudinal reinforcing bars 6 is as follows... Figure 4 As shown, substituting into the corresponding formula yields:

[0071] like Figure 4 and Figure 5 As shown, the right-angle fracture 4 is changed into an arc-shaped fracture 5, where the radius of the arc is... r The width of the joint is 20 mm. w The value is 10 mm. Substituting this into the corresponding formula, we can obtain the stress concentration factor. K t Given a value of 1.5, calculate the local stress at the fracture point of the improved protective wall 1. Substituting this value into the corresponding formula yields:

[0072] Therefore, the local stress at the fracture point of the improved protective wall 1 is less than the verification control index of 3.586 (MPa) for the three walls, thus satisfying the verification formula.

[0073] In summary, this scheme establishes a multi-condition, multi-factor coupled method for calculating and verifying the stress of the three walls, systematically considering the effects of prestress, self-weight, shrinkage and creep, and temperature changes, significantly improving the accuracy and reliability of the stress analysis of the three walls; it provides a standardized and operable verification method for integrated design of the three walls; this scheme also proposes measures to improve stress concentration, significantly reducing the stress peak at the fracture joint, preventing concrete cracking, and improving structural durability; this scheme is applicable to modern construction technology where the main beam and the three walls are prefabricated simultaneously, which helps to promote the industrialization and green development of high-speed railway bridge structures.

[0074] Although the specific embodiments of the invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent; various modifications and variations that can be made by a person skilled in the art without inventive effort within the scope described in the claims are still within the scope of protection of this patent.

Claims

1. A method for calculating the stress of the three walls of an integrated concrete simply supported beam bridge deck for railways, characterized in that, Includes the following steps: S1: Determine the structural parameters and joint construction parameters of the three walls, including the width, height, joint spacing, and joint size of vertical wall A, vertical wall B, and protective wall; S2: Determine the control calculation conditions, including prestressing tension and self-weight conditions, concrete shrinkage and creep conditions, and solar radiation temperature difference conditions; S3: Calculate the local stress at the connection between the three walls and the bridge deck under the conditions of prestressing tension and self-weight, considering the shear lag effect; calculate the local stress at the connection between the three walls and the bridge deck under the conditions of concrete shrinkage and creep; calculate the local stress at the connection between the three walls and the bridge deck under the conditions of solar radiation and temperature difference; combine the three conditions and obtain the local stress at the connection between the three walls and the bridge deck under the most unfavorable combination of conditions. S4: Calculate the local stress at the fracture joint of the three walls, considering the stress concentration at the fracture joint, and compare it with the verification control index of the three walls. If the local stress at the fracture joint of the three walls is greater than the verification control index of the three walls, then proceed to step S5; otherwise, proceed to step S6. S5: Propose measures to improve the local stress concentration at the fracture joint of the three walls, and recalculate the local stress at the fracture joint of the three walls until the local stress at the fracture joint of the three walls is not greater than the verification control index of the three walls. S6: Complete the local stress calculation and verification at the fracture joint of the three walls.

2. The method for calculating the stress of the integrated three-wall structure of a simply supported concrete beam bridge deck according to claim 1, characterized in that, The formula for calculating the local stress at the connection between the three walls and the bridge deck under prestressing tension and self-weight conditions in step S3, considering the shear lag effect, is as follows: ； ； Where ξ is the most unfavorable coefficient, and λ is the shear lag coefficient at the connection between the three walls and the bridge deck that participates in the bending stress of the entire beam. γ g This is the self-weight combination coefficient. γ p The prestress combination coefficient is... σ g The bending stress under its own weight. M s The bending moment at any section of the entire bridge under the self-weight of the precast beam. y Let be the distance from the calculation point of the three walls to the centroid of the section. I Let the moment of inertia of the cross section be... σ p The total stress under prestressing is σ ca The stress caused by the prestressed axial force. σ cb This refers to the stress caused by the prestressed eccentric bending moment.

3. The method for calculating the stress of the integrated three-wall structure of a simply supported concrete beam bridge deck according to claim 2, characterized in that, The formula for calculating the shear lag coefficient at the connection between the three walls and the bridge deck, which participates in the bending stress of the entire beam, is as follows: ； ； in, L To calculate the span, b It is half the spacing between the web plates of the box girder. I s This is the sum of the moments of inertia of the top and bottom plates about the centroid of the cross section. n and k Here are the Risner parameters, G is the shear modulus, and E is the shear modulus. c This refers to the elastic modulus of concrete.

4. The method for calculating the stress of the integrated three-wall structure of a simply supported concrete beam bridge deck according to claim 3, characterized in that, The calculation method for the local stress at the connection between the three walls and the bridge deck under the concrete shrinkage and creep condition in step S3 is as follows: The formula for calculating the tensile stress at the connection between the three walls and the bridge deck caused by shrinkage is as follows: ； in, σ sh Tensile stress caused by shrinkage, L s The distance between the breaks is the joint spacing. x This is the distance from the wall to the centerline of the main beam. R The constraint coefficient at the fracture joint is... H The height of the wall. ε sh This represents the shrinkage strain of the concrete. ε sh0 The reference shrinkage strain for concrete. β rh This is the environmental humidity correction factor. It is a time function; The formula for calculating stress relaxation caused by creep is as follows: ； in, φ 0 represents the nominal creep coefficient. This is the creep time development coefficient; The formula for calculating the local stress at the connection between the three walls and the bridge deck under concrete shrinkage and creep conditions is as follows: in, σ sc This refers to the local stress at the connection between the three walls and the bridge deck under concrete shrinkage and creep conditions.

5. The method for calculating the stress of the integrated three-wall structure of a simply supported concrete beam bridge deck according to claim 4, characterized in that, The formula for calculating the local stress at the connection between the three walls and the bridge deck under the solar radiation temperature difference condition in step S3 is as follows: in, β The constraint coefficient at the fracture joint is... α T The coefficient of linear expansion is 1 / 3. This refers to the temperature difference.

6. The method for calculating the stress of the integrated three-wall structure of a simply supported concrete beam bridge deck in railway as described in claim 5, is characterized in that... The formula for calculating the local stress at the connection between the three walls and the bridge deck under the most unfavorable combination of working conditions in step S3 is as follows: in, γ sh This is the concrete shrinkage combination coefficient. γ cr This represents the concrete creep combination factor. γ T This is the temperature combination coefficient.

7. The method for calculating the stress of the integrated three-wall structure of a simply supported concrete beam bridge deck according to claim 6, characterized in that, The formula for calculating the local stress at the fracture joint of the three walls in step S4 is: in, K t For right-angle fractures, the stress concentration factor is... K t The value is 3.0; for arc-shaped fractures, , r The radius of the arc, w This refers to the width of the seam.

8. The method for calculating the stress of the integrated three-wall structure of a simply supported concrete beam bridge deck according to claim 7, characterized in that, The calculation formula for the verification control index of the three walls in step S4 is as follows: σ max = κ [ σ ] in, κ For the allowable stress enhancement factor, [ σ The standard design specifications for the compressive and tensile strengths of bridge deck concrete.

9. The method for calculating the stress of the integrated three-wall structure of a simply supported concrete beam bridge deck according to claim 8, characterized in that, The measures to improve local stress concentration at the fracture joint of the three walls in step S5 include: changing the right-angle fracture joint into an arc-shaped fracture joint and / or placing longitudinal reinforcing bars under the fracture joint and on both sides of the fracture joint.

10. The method for calculating the stress of the integrated three-wall structure of a simply supported concrete beam bridge deck according to claim 9, characterized in that, When ordinary steel reinforcement is added below and on both sides of the fracture joint, the formula for calculating the reduction in concrete stress is: ； ； in, This represents the reduction in concrete stress. ε a This represents the total strain caused by concrete shrinkage, creep, and the effect of solar thermal temperature difference. m This is the ratio of the elastic modulus of concrete to the elastic modulus of steel reinforcement. ρ For reinforcement ratio, A s A represents the total area of ​​the longitudinal reinforcing bars at the fracture joint. c The cross-sectional area of ​​the unbroken section of concrete 2 cm below the fracture joint; The formula for calculating the local stress at the fracture joint of the three walls after improvement is as follows: 。

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