Method and system for calculating shear capacity of composite beams with composite webs

Abstract

The present invention discloses a method and a computer system for calculating the shear bearing capacity of a steel-ultra-high performance concrete composite beam with a composite web. The calculation method comprises the following steps: Step 1: obtaining the shear bearing capacity V provided by the steel web; u,HRS ; Step 2: Obtain the shear bearing capacity V provided by the ultra-high performance concrete web u,UHPC , V u,UHPC =V c +V f +V s ; Step 3: Obtain the shear bearing capacity V of the steel-UHPC composite beam with composite web u , V u =V u,HRS +V u,UHPC The calculation method provided by the present invention can be well applied to steel-ultra-high performance concrete composite beams with composite webs, and has good accuracy and reliability.

Description

Technical Field

[0001] The invention belongs to the field of bridge structure design, and in particular relates to a method and a system for determining the shear bearing capacity of a composite beam. Background Art

[0002] Steel-concrete composite structures can give full play to the advantages of concrete structures and steel structures, so they are widely used in bridge construction. When the composite beam bridge adopts a continuous beam structure, it can not only effectively improve the rigidity and bearing capacity of the structure, but also save material consumption and reduce the project cost. Due to the low tensile strength and poor durability of ordinary concrete itself, the traditional steel-concrete composite beam has problems such as heavy structure and poor crack resistance. When the concrete bridge deck cracks, joint leakage, concrete carbonization, steel corrosion and other diseases will occur, which seriously affect the safety of the bridge structure. In addition, the traditional steel-concrete composite beam adopts welded steel beams, which increases the workload of steel beam welding, increases the cost, and prolongs the construction period. Welding easily introduces residual stress, reduces the fatigue life of the steel beam, and affects the service performance of the structure.

[0003] As a new type of fiber-reinforced cement-based composite material, ultra-high performance concrete has excellent mechanical properties, durability and working performance, good toughness, and can well make up for the shortcomings of ordinary concrete. Existing research and engineering applications have shown that when ultra-high performance concrete structures are used, the structural size and concrete dosage can be effectively reduced, thereby reducing the structural deadweight and carbon emissions, and significantly improving the structural crack resistance and durability, extending the service life of the structure, and saving the full life cost. As an industrialized product, hot-rolled steel has the advantages of low cost, low residual stress, and less welding workload. However, the specifications of steel are limited, and the height listed in the current specifications is 100-1200mm. For composite beam bridges with a span of 20-60m, the beam height is roughly 800-3000mm, and the steel beam height is in the range of 600-2800mm, while the existing steel is difficult to be used in composite beam bridges with a span of more than 30m.

[0004] Therefore, in response to the problems faced by traditional steel-concrete composite beam structures, a steel-ultra-high performance concrete composite beam structure with a composite web is proposed based on ultra-high performance concrete and hot-rolled steel. The composite beam is composed of ultra-high performance concrete-T beam and hot-rolled H-shaped steel (see patent document CN110331648A). Existing studies have shown that, based on a composite beam bridge with a length of 35m and a width of 16.25m, compared with the traditional steel-concrete composite beam scheme with a small main beam, the steel-ultra-high performance concrete composite beam scheme reduces the steel consumption per square meter by 30%, reduces the deadweight by 37%, and saves about 12% of the cost.

[0005] At present, the steel-concrete composite beam specifications "Design and Construction Specifications for Highway Steel-Concrete Composite Bridges" (JTG / T D64-01-2015) and "Design Specifications for Steel-Concrete Composite Bridges" (GB 50917-2013) both provide calculation methods for the shear bearing capacity of composite beams. This calculation method is applicable to traditional steel-concrete composite beam structures with only steel webs; the UHPC structure specifications "Technical Code for Ultra-High Performance Concrete Beam Bridges" (T / CCES 27-2021) and "Design Standard for Steel Fiber Concrete Structures" (JGJ / T 465-2019) provide calculation methods for the shear bearing capacity of ultra-high performance concrete components. This method is only applicable to ultra-high performance concrete structures with ultra-high performance concrete webs. If one of the calculation methods in the above specifications is directly used, it will not be able to fully reflect the shear force distribution ratio of the steel web and the ultra-high performance concrete web in the steel-UHPC composite beam, and it will be difficult to accurately evaluate the shear bearing capacity of the steel-UHPC composite beam, which will underestimate the shear bearing capacity of the steel-UHPC composite beam, resulting in material waste and increased construction costs; and if the above two methods are used in combination and the calculation results are added together, it will not be able to accurately reflect the impact of the shear span ratio on the bearing capacity and the shear force distribution mechanism, and it is very likely to overestimate the bearing capacity of the composite beam, making the designed steel-UHPC composite beam unsafe. Therefore, the method provided by the above specifications cannot be applied to the steel-UHPC composite beam structure with a composite web, which also limits the promotion and application of steel-UHPC composite beams in actual engineering.

[0006] Therefore, it is necessary to establish a method for determining the shear capacity of steel-UHPC composite beams that fully reflects the shear force distribution ratio of the composite web, considers the influence of shear span ratio and other key parameters, and has high prediction accuracy. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings and defects mentioned in the above background technology, and provide a calculation method and system for the shear bearing capacity of a steel-ultra-high performance concrete composite beam with a composite web, which is used to solve the technical problem that the method for determining the shear bearing capacity of a steel-concrete composite beam or an ultra-high performance concrete beam provided in the existing specifications cannot be applied to a steel-ultra-high performance concrete composite beam.

[0008] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0009] A method for calculating the shear bearing capacity of a steel-ultra-high performance concrete composite beam with a composite web comprises the following steps:

[0010] Step 1: Obtain the steel web yield strength f y , steel web height h ws, Steel web thickness t ws , calculate the shear span length a of the section, the total height h of the steel-UHPC composite beam and the yield shear span ratio Based on the above parameters, the shear strength V of the steel web is obtained. y and calculate the shear span ratio of the section , based on the above-obtained steel web shear strength V y and calculate the shear span ratio of the section , the shear bearing capacity V provided by the steel web is obtained u,HRS ;

[0011] Step 2: Obtain the compressive strength f of ultra-high performance concrete c , UHPCC web thickness t wc 、UHPC beam height h c Based on the above parameters, the shear bearing capacity V provided by the ultra-high performance concrete matrix is ​​calculated. c ;

[0012] Obtaining the tensile strength f of ultra-high performance concrete t , UHPCC web thickness t wc 、UHPC beam height h c , UHPCC beam flange thickness t f , the angle θ between the principal compressive stress at the calculation section and the longitudinal axis of the beam, and the partial factor of the tensile ultra-high performance concrete at the ultimate bearing capacity state and the fiber orientation coefficient K of the UHP concrete as a whole global Based on the above parameters, the post-crack tensile strength of ultra-high performance concrete f is obtained. te and the effective shear height d when calculating the contribution of steel fibers vf Based on the above parameters, the shear bearing capacity V provided by ultra-high performance concrete steel fibers is obtained. f ;

[0013] Get stirrup diameter d s , the number of stirrups n, the stirrup spacing s, and the stirrup yield strength f for the same section y,sv , UHPCC web thickness t wc 、UHPC beam height h c , UHPCC beam flange thickness t f and the angle θ between the principal compressive stress at the calculated section and the longitudinal axis of the beam. Based on the above-obtained parameters, the stirrup area A is obtained. sv and stirrup ratio , the effective shear height d when calculating the stirrup contribution is obtained vs Based on the above parameters, the shear bearing capacity V provided by the UHPCC web stirrups is obtained. s ;

[0014] Based on the shear bearing capacity V provided by the ultra-high performance concrete matrix c , shear bearing capacity provided by ultra-high performance concrete steel fibers V f and the shear capacity provided by the UHP concrete web stirrups V s , the shear bearing capacity V provided by the ultra-high performance concrete web is obtained u,UHPC , V u,UHPC =V c +V f +V s ;

[0015] Step 3: Based on the shear capacity V provided by the steel web in Step 1 u,HRS and the shear capacity V provided by the UHPC web in step 2 u,UHPC , the shear bearing capacity V of the steel-UHPC composite beam with composite web is obtained u , V u =V u,HRS +V u,UHPC .

[0016] In the above calculation method, preferably, the shear strength V y and calculate the shear span ratio of the section Calculated as follows:

[0017] ;

[0018] =a / h, a and the height h of the UHPCC beam c The ratio is not less than 1.5;

[0019] Shear resistance provided by steel web V u,HRS Calculated as follows:

[0020] For 0.7< <1.4, ;

[0021] for ≥1.4, .

[0022] In the above calculation method, preferably, the yield shear span ratio The determination includes the following steps:

[0023] Get the steel height h s , total height h of steel-UHPC composite beam, yield strength f of steel web y , Steel web thickness t ws , UHP concrete tensile strength ft , ultra-high performance concrete compressive strength f c , UHPCC web thickness t wc ;

[0024] Calculate the steel height h s Ratio to the total height h of steel-UHPC composite beam , =h s / h, and Satisfy 0.3≤ ≤0.5;

[0025] Based on the above parameters, the yield shear span ratio is calculated :

[0026] .

[0027] In the above calculation method, preferably, the shear bearing capacity V provided by the ultra-high performance concrete matrix is c Calculated as follows:

[0028] .

[0029] In the above calculation method, preferably, the post-crack tensile strength of ultra-high performance concrete f te and the effective shear height d when calculating the contribution of steel fibers vf Calculated as follows:

[0030] ;

[0031] d vf =h c -t f ;

[0032] Shear resistance provided by ultra-high performance concrete steel fibers V f Calculated as follows:

[0033] ;

[0034] Among them, θ satisfies 30°≤θ≤45°. When θ<30°, 30° is taken, and when θ>45°, 45° is taken.

[0035] In the above calculation method, preferably, the stirrup area A sv and stirrup ratio Calculated as follows:

[0036] A sv =πnd s 2 / 4;

[0037] =A sv / (t wc s);

[0038] Effective shear height d when calculating stirrup contribution vs Calculated as follows:

[0039] d vs =0.9(h c -t f ).

[0040] In the above calculation method, preferably, the shear bearing capacity V provided by the ultra-high performance concrete web stirrups is s Calculated as follows:

[0041] .

[0042] In the above calculation method, preferably, the partial coefficient of the ultra-high performance concrete under tension at the ultimate bearing capacity limit state is , when verifying the shear bearing capacity of the composite beam in the design, take 1.45, and when comparing the shear bearing capacity of the test beam or simulation model, take 1.0.

[0043] In the above calculation method, preferably, the fiber orientation coefficient K of the ultra-high performance concrete as a whole is global Take 1.25.

[0044] In the above calculation method, preferably, the steel web yield strength f y , ultra-high performance concrete compressive strength f c , UHP concrete tensile strength f t , stirrup yield strength f y,sv When verifying the shear bearing capacity of the composite beam in the design, the design value is taken; when comparing the shear bearing capacity of the test beam or simulation model, the measured value is taken.

[0045] As a general technical concept, the present invention also provides a computer system, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the computer program.

[0046] Compared with the prior art, the advantages of the present invention are:

[0047] 1. The calculation method and system of the shear bearing capacity of the steel-ultra-high performance concrete composite beam with a combined web of the present invention, compared with the calculation method provided by the current specification, the calculation method provided by the present invention can be well applied to the steel-ultra-high performance concrete composite beam with a combined web, and has good accuracy and reliability, and can be used in the field of steel-ultra-high performance concrete composite beams with a combined web, for realizing the accurate determination of the shear bearing capacity of the steel-ultra-high performance concrete composite beam.

[0048] 2. In the preferred embodiment, the calculation method and system of the shear bearing capacity of the steel-ultra-high performance concrete composite beam with a combined web of the present invention take into account the respective contributions of the steel web and the ultra-high performance concrete web to the shear bearing capacity of the steel-ultra-high performance concrete composite beam, and reflect the shear stress characteristics and shear force distribution ratio of the steel-ultra-high performance concrete composite beam with a combined web. It can more accurately evaluate the shear bearing capacity of the steel-ultra-high performance concrete composite beam, which is of great value to promoting the engineering application of steel-ultra-high performance concrete composite beams.

[0049] 3. In the preferred embodiment, the method and system for calculating the shear bearing capacity of the steel-UHPC composite beam with a composite web of the present invention introduces the calculation of the shear span ratio of the section , which reflects the influence of shear span ratio on the shear bearing capacity of steel-UHPC composite beams. In the design of actual projects, it can provide a reference for the design and shear bearing capacity detection of steel-UHPC composite beams, and has important engineering application value.

[0050] 4. In the preferred embodiment, the method and system for calculating the shear bearing capacity of the steel-UHPC composite beam with a composite web of the present invention introduces the yield shear span ratio , accurately reflects the experimental phenomenon that the steel web may not completely yield at different shear span ratios; in addition, the steel height h is also comprehensively considered. s , total height h of steel-UHPC composite beam, yield strength f of steel web y , Steel web thickness t ws , UHP concrete tensile strength f t , ultra-high performance concrete compressive strength f c , UHPCC web thickness t wc , Ratio of steel section height to total height of steel section-UHPC composite beam The different degrees of influence of these key design parameters on the shear bearing capacity provided by the steel section have important engineering application value for the design and testing of steel-UHPC composite beams. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0052] Figure 1 It is a schematic diagram of calculating the shear bearing capacity of a steel-ultra-high performance concrete composite beam with a composite web according to a preferred embodiment of the present invention.

[0053] Figure 2 yes Figure 1 Schematic cross-section of the structure shown.

[0054] Figure 3 It is a calculation flow chart of a method for calculating the shear bearing capacity of a steel-ultra-high performance concrete composite beam with a composite web according to a preferred embodiment of the present invention.

[0055] Figure 4 is a schematic diagram of the correlation between the key parameters and the yield shear span ratio of the preferred embodiment of the present invention (the ordinates in the figure are all the yield shear span ratios ).

[0056] Figure 5 It is a schematic diagram comparing the calculation method of the shear bearing capacity of the steel-ultra-high performance concrete composite beam with a composite web according to a preferred embodiment of the present invention and the sample results, and the comparison content is the shear bearing capacity provided by the steel.

[0057] Figure 6 1 is a schematic diagram comparing the calculation method of the shear bearing capacity of a steel-ultra-high performance concrete composite beam with a composite web according to a preferred embodiment of the present invention with the calculation method given in the current specification, wherein (a) is a comparison between the calculation result obtained by the calculation method of the present invention and the sample result; (b) and (c) are comparisons between the calculation result of the calculation method given in the composite beam specification and the UHPC structure specification and the sample result, respectively; (d) is a comparison between the superposition result of the shear bearing capacity of the steel web and the UHPC web calculated by the specification in (b) and (c) and the sample result. DETAILED DESCRIPTION

[0058] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0059] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0060] Example:

[0061] A method for calculating the shear bearing capacity of a steel-ultra-high performance concrete composite beam with a composite web comprises the following steps:

[0062] Step 1: Obtain the steel web yield strength f y , steel web height h ws , Steel web thickness t ws , calculate the shear span length a of the section, the total height h of the steel-UHPC composite beam and the yield shear span ratio Based on the above parameters, the shear strength V of the steel web is obtained. y and calculate the shear span ratio of the section , based on the above-obtained steel web shear strength V y and calculate the shear span ratio of the section , the shear bearing capacity V provided by the steel web is obtained u,HRS ;

[0063] Step 2: Obtain the compressive strength f of ultra-high performance concrete c , UHPCC web thickness t wc 、UHPC beam height h c Based on the above parameters, the shear bearing capacity V provided by the ultra-high performance concrete matrix is ​​calculated. c ;

[0064] Obtaining the tensile strength f of ultra-high performance concrete t , UHPCC web thickness t wc 、UHPC beam height h c , UHPCC beam flange thickness t f , the angle θ between the principal compressive stress at the calculation section and the longitudinal axis of the beam, and the partial factor of the tensile ultra-high performance concrete at the ultimate bearing capacity state and the fiber orientation coefficient K of the UHP concrete as a whole global Based on the above parameters, the post-crack tensile strength of ultra-high performance concrete f is obtained. te and the effective shear height d when calculating the contribution of steel fibers vf Based on the above parameters, the shear bearing capacity V provided by ultra-high performance concrete steel fibers is obtained. f ;

[0065] Get stirrup diameter d s, the number of stirrups n, the stirrup spacing s, and the stirrup yield strength f for the same section y,sv , UHPCC web thickness t wc 、UHPC beam height h c , UHPCC beam flange thickness t f and the angle θ between the principal compressive stress at the calculated section and the longitudinal axis of the beam. Based on the above-obtained parameters, the stirrup area A is obtained. sv and stirrup ratio , the effective shear height d when calculating the stirrup contribution is obtained vs Based on the above parameters, the shear bearing capacity V provided by the UHPCC web stirrups is obtained. s ;

[0066] Based on the shear bearing capacity V provided by the ultra-high performance concrete matrix c , shear bearing capacity provided by ultra-high performance concrete steel fibers V f and the shear capacity provided by the UHP concrete web stirrups V s , the shear bearing capacity V provided by the ultra-high performance concrete web is obtained u,UHPC , V u,UHPC =V c +V f +V s ;

[0067] Step 3: Based on the shear capacity V provided by the steel web in Step 1 u,HRS and the shear capacity V provided by the UHPC web in step 2 u,UHPC , the shear bearing capacity V of the steel-UHPC composite beam with composite web is obtained u , V u =V u,HRS +V u,UHPC .

[0068] In this embodiment, the shear strength V y and calculate the shear span ratio of the section Calculated as follows:

[0069] ;

[0070] =a / h, a and the height h of the UHPCC beam c The ratio is not less than 1.5;

[0071] Shear resistance provided by steel web V u,HRS Calculated as follows:

[0072] For 0.7< <1.4, ;

[0073] for ≥1.4, .

[0074] In this embodiment, the yield shear span ratio The determination includes the following steps:

[0075] Get the steel height h s , total height h of steel-UHPC composite beam, yield strength f of steel web y , Steel web thickness t ws , UHP concrete tensile strength f t , ultra-high performance concrete compressive strength f c , UHPCC web thickness t wc ;

[0076] Calculate the steel height h s Ratio to the total height h of steel-UHPC composite beam , =h s / h, and Satisfy 0.3≤ ≤0.5;

[0077] Based on the above parameters, the yield shear span ratio is calculated :

[0078] .

[0079] In this embodiment, the shear bearing capacity V provided by the ultra-high performance concrete matrix is c Calculated as follows:

[0080] .

[0081] In this embodiment, the post-crack tensile strength of ultra-high performance concrete is f te and the effective shear height d when calculating the contribution of steel fibers vf Calculated as follows:

[0082] ;

[0083] d vf =h c -t f ;

[0084] Shear resistance provided by ultra-high performance concrete steel fibers V f Calculated as follows:

[0085] ;

[0086] Among them, θ satisfies 30°≤θ≤45°. When θ<30°, 30° is taken, and when θ>45°, 45° is taken.

[0087] In this embodiment, the stirrup area A sv and stirrup ratio Calculated as follows:

[0088] A sv =πnd s 2 / 4;

[0089] =A sv / (t wc s);

[0090] Effective shear height d when calculating stirrup contribution vs Calculated as follows:

[0091] d vs =0.9(h c -t f ).

[0092] In this embodiment, the shear bearing capacity V provided by the UHP concrete web stirrups is s Calculated as follows:

[0093] .

[0094] In this embodiment, the tensile ultra-high performance concrete partial coefficient at the ultimate bearing capacity state is , when verifying the shear bearing capacity of the composite beam in the design, take 1.45, and when comparing the shear bearing capacity of the test beam or simulation model, take 1.0.

[0095] In this embodiment, the fiber orientation coefficient K of the ultra-high performance concrete as a whole is global Take 1.25.

[0096] In this embodiment, the steel web yield strength f y , ultra-high performance concrete compressive strength f c , UHP concrete tensile strength f t , stirrup yield strength f y,sv When verifying the shear bearing capacity of the composite beam in the design, the design value is taken; when comparing the shear bearing capacity of the test beam or simulation model, the measured value is taken.

[0097] A computer system of this embodiment includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the above method are implemented.

[0098] More specifically, Figure 1-Figure 3 As shown, this embodiment provides a method for calculating the shear bearing capacity of a steel-ultra-high performance concrete composite beam with a composite web, and the detailed method includes the following steps:

[0099] S1. Get basic parameters, such as Figure 1 and Figure 2 As shown in FIG. 1 , according to the determined steel-UHPC composite beam with composite web, the material strength parameters, section design parameters and calculation position parameters are obtained. The material strength parameters include the steel web yield strength f y , ultra-high performance concrete compressive strength f c , UHP concrete tensile strength f t , stirrup yield strength f y,sv The cross-sectional design parameters include the total height h of the steel-UHPC composite beam, the height h of the steel s , steel web height h ws , Steel web thickness t ws 、UHPC beam height h c , UHPCC web thickness t wc , UHPCC beam flange thickness t f , the angle between the principal compressive stress at the calculation section and the longitudinal axis of the beam θ, the diameter of the stirrup d s , the number of stirrups n and the stirrup spacing s of the same section, the calculation position parameter is the shear span length a of the calculation section; in addition, for the material strength parameter, that is, the yield strength f of the steel web y , ultra-high performance concrete compressive strength f c , UHP concrete tensile strength f t , stirrup yield strength f y,sv When verifying the shear bearing capacity of the composite beam in the design, the design value is taken; when comparing the shear bearing capacity of the test beam or simulation model, the measured value is taken.

[0100] S2. Determine the relevant coefficients, including the partial coefficients of the tensile ultra-high performance concrete at the ultimate bearing capacity limit state and the fiber orientation coefficient K of the UHP concrete as a whole global ; When calculating the shear capacity of composite beams in design, Take 1.45; when comparing the shear bearing capacity of the test beam or simulation model, Take 1.0; the fiber orientation coefficient K of the ultra-high performance concrete as a whole global Take 1.25.

[0101] S3. Basic assumptions are made. The basic assumptions used in the calculation method of the shear bearing capacity of steel-UHPC composite beams with composite webs include: at the ultimate bearing capacity limit state, all stirrups yield; steel and steel bars are regarded as ideal elastic-plastic materials; the mechanical bite force and friction force between the UHPC matrix on the shear oblique crack interface are ignored; the above assumptions are reasonable assumptions made for calculating the shear bearing capacity of steel-UHPC composite beams with composite webs, which can simplify the calculation, but have little effect on the calculation results of the shear bearing capacity.

[0102] S4. Based on the parameters obtained in S1, calculate the shear strength V of the steel web y ,Right now ; Calculate the ratio of the steel height to the total height of the steel-UHPC composite beam ,Right now =h s / h, and the design parameter h s and h should be such that Satisfy 0.3≤ ≤0.5, which is determined by the design concept of steel-UHPC composite beams, to ensure that the UHPC web has good crack resistance while utilizing the tensile properties of steel and the compressive properties of UHPC, so as to control the crack width and improve the durability of the structure; the shear span ratio of the calculated section is calculated ,Right now =a / h. The introduction of shear span ratio can more accurately consider the influence of shear span ratio on the shear bearing capacity of steel-UHPC composite beams, making the calculation results more accurate. The yield shear span ratio is calculated. ,Right now The introduction of the yield shear span ratio takes into account the influence of different key design parameters on the shear state of the steel section at the ultimate bearing capacity limit state, so that the calculation method of the present invention has better adaptability and higher accuracy; based on the above-obtained parameters and the basic assumptions in S3, the shear bearing capacity V provided by the steel section web can be further calculated. u,HRS :

[0103] For 0.7< <1.4, ;

[0104] for ≥1.4, .

[0105] S5. Based on the parameters obtained in S1 and S2 and the basic assumptions in S3, the shear bearing capacity V provided by the ultra-high performance concrete matrix is ​​calculated. c ,Right now .

[0106] S6. Based on the parameters obtained in S1 and S2, the post-crack tensile strength f of the ultra-high performance concrete is calculated. te ,Right now ; Calculate the effective shear height d when calculating the steel fiber contribution vf , that is, d vf =h c -t f ; Since the shear diagonal cracks of the steel-UHPC composite beam only extend in the UHPC web, the effective shear height d when calculating the contribution of steel fibers is vf It is necessary to deduct the thickness of the UHPC beam flange to better fit the actual structural failure mode; based on the above-obtained parameters and the basic assumptions in S3, the shear bearing capacity V provided by the UHPC steel fiber can be calculated. f ,Right now .

[0107] S7. Based on the parameters obtained in S1, calculate the stirrup area A sv , that is, A sv =πnd s 2 / 4; Calculate the stirrup ratio ,Right now =A sv / (t wc s); calculate the effective shear height d when calculating the stirrup contribution vs , that is, d vs =0.9(h c -t f ); Generally speaking, the failure surface of shear bearing capacity is the inclined section where the shear oblique crack is located, and according to the failure mode and test phenomena observed in the test and Figure 1 The structural diagram shows that the stirrups passing through the diagonal cracks contribute to the shear bearing capacity of the composite beam, and the effective height of the diagonal cracks in the web is (h c -t f ), and considering the effective load range of the stirrups, the effective shear height d when the stirrups contribute is calculated vs It is determined to be 0.9 times the effective height of the web inclined crack. Based on the above parameters and the basic assumptions in S3, the shear bearing capacity V provided by the UHPCC web stirrups can be obtained. s ,Right now:

[0108] ;

[0109] The above formula takes into account the influence of web stirrup ratio on the shear capacity of steel-UHPC composite beams. If the web stirrup ratio is very high, the shear capacity of the steel-UHPC composite beam is still calculated according to the actual stirrup ratio. It is easy to overestimate the contribution of stirrups to the shear capacity. Because when the stirrup ratio is too high, the stirrups do not all yield under the ultimate bearing capacity state. Therefore, according to the analysis, a stirrup ratio of 1.5% is used as the maximum stirrup ratio when calculating the contribution of stirrups to the shear capacity. When the actual stirrup ratio is greater than 1.5%, the actual stirrup ratio is replaced by 1.5%.

[0110] S8, based on the shear bearing capacity V provided by the ultra-high performance concrete matrix obtained in S5-S7 c , shear bearing capacity provided by ultra-high performance concrete steel fibers V f and the shear capacity provided by the UHP concrete web stirrups V s , the shear bearing capacity V provided by the ultra-high performance concrete web can be calculated u,UHPC , that is, V u,UHPC =V c +V f +V s .

[0111] S9, based on the shear bearing capacity V provided by the steel web obtained in S2 and S8 u,HRS and the shear resistance provided by the ultra-high performance concrete web V u,UHPC , the two are added together to finally calculate the shear bearing capacity V of the steel-UHPC composite beam. u .

[0112] In order to better illustrate the advantages of the calculation method of the shear bearing capacity of the steel-ultra-high performance concrete composite beam with a combined web in this embodiment, the following is a comparison between the calculation method of the shear bearing capacity of the steel-ultra-high performance concrete composite beam with a combined web in this embodiment and the existing calculation method as follows:

[0113] like Figure 4 As shown in the figure, the key parameters are determined by simulation analysis to determine the yield shear span ratio The analysis results show that, except for the stirrup ratio, the other key parameters have an important influence on the yield shear span ratio. Therefore, the yield shear span ratio considering the influence of each key parameter is proposed by multivariate linear fitting method. Based on this calculation method, the shear bearing capacity V provided by the steel section can be determined. u,HRS . Figure 5 is the shear bearing capacity V provided by the steel section provided by the present invention. u,HRSThe calculation results obtained by the calculation method of the present invention are compared with the samples. The average value of the ratio of the calculated value to the sample value is 0.990, the coefficient of variation is 0.0259, and the overall error is within 10%. This shows that the calculation method provided by the present invention can well evaluate the shear bearing capacity V provided by the steel section. u,HRS , high precision and reliability.

[0114] The shear bearing capacity test and simulation analysis samples of steel-UHPC composite beams were collected and compared with the calculation results obtained by the calculation method proposed in this invention. Figure 6 As shown in (a), the average value of the ratio of the calculated value to the sample value is 0.978, the coefficient of variation is 0.0295, and the overall error is within 15%, indicating that the calculation method provided by the present invention can well predict the shear bearing capacity V of the steel-ultra-high performance concrete composite beam. u . Figure 6 (b) is a comparison between the calculation results obtained by the calculation method of the shear bearing capacity of the steel web provided in the composite beam specification "Design and Construction Specification for Highway Steel-Concrete Composite Bridges" (JTG / T D64-01-2015) and "Design Specification for Steel-Concrete Composite Bridges" (GB 50917-2013) and the sample value. Figure 6 (c) is a comparison between the calculation results obtained by the calculation method of the shear bearing capacity of the UHPC web provided in the UHPC structural specification "Technical Code for Ultra-High Performance Concrete Beam Bridges" (T / CCES 27-2021) and the sample value. It can be found that the shear bearing capacity of the steel web or the UHPC web calculated by the two specifications alone obviously underestimates the shear bearing capacity of the steel-UHPC composite beam with a composite web, making the designed structure conservative, which will cause material waste and cost increase; Figure 6 (d) is the superposition of the single calculation results of the above two specifications. It can be found that most of the calculated values ​​are greater than the sample values, which overestimates the shear bearing capacity of the steel-UHPC composite beam with composite webs, making the designed structure dangerous and posing a safety hazard to the bridge. Therefore, the above specifications are not applicable to the calculation of the shear bearing capacity of the steel-UHPC composite beam with composite webs.

[0115] In summary, the calculation method of the shear bearing capacity of the steel-UHPC composite beam with a composite web of the present invention is to use the shear test sample and the simulation sample of the steel-UHPC composite beam to perform correlation analysis, and to verify the result by regression fitting and calculation, and to introduce the shear span ratio , reflecting the influence of shear span ratio on the shear bearing capacity of steel-UHPC composite beams; introducing the yield shear span ratio , reflecting the influence of different key design parameters on the shear state of steel at the ultimate bearing capacity limit state; introducing the maximum stirrup ratio to reflect the influence of the shear span ratio on the stress state of stirrups, and preventing overestimation of the contribution of stirrups to the shear bearing capacity. The calculation method of the present invention has good adaptability and accuracy for the calculation of the shear bearing capacity of steel-ultra-high performance concrete composite beams with combined webs. The prediction results are in good agreement with the test results and simulation results, and can provide a reference for the design of steel-ultra-high performance concrete composite beams and the calculation of their shear bearing capacity, which is of great value in promoting the application of steel-UHPC composite beams in practical engineering.

[0116] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the technical content disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for calculating the shear bearing capacity of a steel-ultra-high performance concrete composite beam with a composite web, characterized in that: The following steps are involved: Step 1: Obtain the steel web yield strength f y , steel web height h ws , Steel web thickness t ws , calculate the shear span length a of the section, the total height h of the steel-UHPC composite beam and the yield shear span ratio Based on the above parameters, the shear strength V of the steel web is obtained. y and calculate the shear span ratio of the section , based on the above-obtained steel web shear strength V y and calculate the shear span ratio of the section , the shear bearing capacity V provided by the steel web is obtained u,HRS ; Step 2: Obtain the compressive strength f of ultra-high performance concrete c , UHPCC web thickness t wc 、UHPC beam height h c Based on the above parameters, the shear bearing capacity V provided by the ultra-high performance concrete matrix is ​​calculated. c ; Obtaining the tensile strength f of ultra-high performance concrete t , UHPCC web thickness t wc 、UHPC beam height h c , UHPCC beam flange thickness t f , the angle θ between the principal compressive stress at the calculation section and the longitudinal axis of the beam, and the partial factor of the tensile ultra-high performance concrete at the ultimate bearing capacity state and the fiber orientation coefficient K of the UHP concrete as a whole global Based on the above parameters, the post-crack tensile strength of ultra-high performance concrete f is obtained. te and the effective shear height d when calculating the contribution of steel fibers vf Based on the above parameters, the shear bearing capacity V provided by ultra-high performance concrete steel fibers is obtained. f ; Get stirrup diameter d s , the number of stirrups n, the stirrup spacing s, and the stirrup yield strength f for the same section y,sv , UHPCC web thickness t wc 、UHPC beam height h c , UHPCC beam flange thickness t f and the angle θ between the principal compressive stress at the calculated section and the longitudinal axis of the beam. Based on the above-obtained parameters, the stirrup area A is obtained. sv and stirrup ratio , the effective shear height d when calculating the stirrup contribution is obtained vs Based on the above parameters, the shear bearing capacity V provided by the UHPCC web stirrups is obtained. s ; Based on the shear bearing capacity V provided by the ultra-high performance concrete matrix c , shear bearing capacity provided by ultra-high performance concrete steel fibers V f and the shear capacity provided by the UHP concrete web stirrups V s , the shear bearing capacity V provided by the ultra-high performance concrete web is obtained u,UHPC , V u,UHPC =V c +V f +V s ; Step 3: Based on the shear capacity V provided by the steel web in Step 1 u,HRS and the shear capacity V provided by the UHPC web in step 2 u,UHPC , the shear bearing capacity V of the steel-UHPC composite beam with composite web is obtained u , V u =V u,HRS +V u,UHPC ; The shear strength of the steel web V y and calculate the shear span ratio of the section Calculated as follows: ； =a / h, a and the height h of the UHPCC beam c The ratio is not less than 1.5; Shear resistance provided by steel web V u,HRS Calculated as follows: For 0.7< <1.4, ; for ≥1.4, ; Shear resistance provided by ultra-high performance concrete matrix V c Calculated as follows: ； Shear resistance provided by UHP concrete web stirrups V s Calculated as follows: 。 2. The calculation method according to claim 1, characterized in that: Yield shear span ratio The determination includes the following steps: Get the steel height h s , total height h of steel-UHPC composite beam, yield strength f of steel web y , Steel web thickness t ws , UHP concrete tensile strength f t , ultra-high performance concrete compressive strength f c , UHPCC web thickness t wc ; Calculate the steel height h s Ratio to the total height h of steel-UHPC composite beam , =h s / h, and Satisfy 0.3≤ ≤0.5; Based on the above parameters, the yield shear span ratio is calculated : 。 3. The calculation method according to claim 1, characterized in that: The post-crack tensile strength of ultra-high performance concrete te and the effective shear height d when calculating the contribution of steel fibers vf Calculated as follows: ； d vf =h c -t f ; Shear resistance provided by ultra-high performance concrete steel fibers V f Calculated as follows: ； Among them, θ satisfies 30°≤θ≤45°. When θ<30°, 30° is taken, and when θ>45°, 45° is taken.

4. The calculation method according to claim 1, characterized in that: The stirrup area A sv and stirrup ratio Calculated as follows: A sv =πnd s 2 / 4; =A sv / (t wc s); Effective shear height d when calculating stirrup contribution vs Calculated as follows: d vs =0.9(h c -t f )。 5. The calculation method according to claim 1, characterized in that: The partial factor of ultra-high performance concrete in tension at the ultimate bearing capacity state , when verifying the shear bearing capacity of the composite beam in the design, take 1.45, and when comparing the shear bearing capacity of the test beam or simulation model, take 1.

0.

6. The calculation method according to claim 1, characterized in that: The fiber orientation coefficient K of ultra-high performance concrete global Take 1.

25.

7. A computer system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method described in any one of claims 1 to 6 are implemented.

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