Steel-concrete composite beam with pre-embedded shear channel and shear analysis method thereof

Abstract

The present application relates to the technical field of composite beam, in particular to a steel-concrete composite beam with embedded shear groove and a shear analysis method thereof.The present application comprises a concrete layer, the concrete layer is arranged with studs and steel bars in a matrix staggered manner, the studs are used for fixing the concrete layer with the lower steel beam, and the steel bars are used for fixing the concrete layer with the upper UHPC layer;the top surface of the concrete layer is embedded with a shear groove, which is used for enhancing the shear strength with the UHPC layer.The shear bearing capacity of the steel-concrete composite beam is analyzed from three dimensions, namely: taking the steel-concrete composite beam as the object, analyzing the vertical shear bearing capacity;taking the UHPC-concrete layer interface as the object, analyzing the longitudinal shear bearing capacity;taking the UHPC-concrete layer interface as the object, analyzing the interface longitudinal shear;comprehensively analyzing the results of the three dimensions, judging whether the theoretical shear bearing capacity of the designed steel-concrete composite beam meets the actual use requirements;respectively considering the contribution of each parameter to the shear bearing capacity, optimizing the design scheme.

Description

Technical Field

[0001] This invention relates to the field of composite beam technology, specifically to a steel-concrete composite beam with pre-embedded shear grooves and its shear analysis method. Background Technology

[0002] Steel-concrete composite beams fully utilize the mechanical properties of both steel and concrete, connecting them into a unified whole through shear connectors. They offer significant technical and economic advantages and are widely used in engineering projects both domestically and internationally. However, engineering practice shows that during long-term service in complex environments and under continuous loads, the bridge deck of steel-concrete composite beams suffers cumulative deterioration damage due to the inherent cracking susceptibility, low toughness, and insufficient durability of the concrete itself. This damage jeopardizes the safety and performance of the composite beam.

[0003] Shear strength calculation and analysis is one of the most important load-bearing capacity control states in the design and analysis of steel-concrete composite beams. Accidents of severe structural failure due to insufficient shear capacity of composite beams are common. As the application scenarios of steel-concrete composite beams become more widespread, especially with the continuous development towards large spans and super high-rise buildings, the web of composite beams tends to be thinner and more flexible in design. The shear failure problem of composite beams is more prominent due to the larger height-to-thickness ratio of the web. At the same time, composite beams are accompanied by some problems of bridge deck during use, such as bending failure of the concrete layer, concrete shear-compression failure, diagonal tension failure, or diagonal compression failure in the shear span. The occurrence of these failures further reduces the shear capacity of the composite beams, making the shear problem of composite beams more severe over time.

[0004] Ultra-high performance concrete (UHPC) possesses advantages such as high strength, high toughness, high durability, high impermeability, and good economy. As a novel fiber-reinforced concrete material with excellent mechanical and durability properties, it has seen rapid development and application in the field of civil engineering in recent years. However, UHPC faces the problem of high cost in engineering applications, with its construction cost being more than ten times that of ordinary concrete. If the concrete flange of a steel-concrete composite beam is completely replaced with UHPC, although the structural mechanical performance is improved, it brings significant economic problems. To reduce the deterioration and damage of the steel-concrete composite beam bridge deck and achieve good technical and economic benefits, this invention comprehensively considers technical, economic, durability, and applicability aspects, combining UHPC with key structural load-bearing parts. The UHPC layer directly replaces the top concrete layer of the steel-concrete composite beam that directly bears the load, thereby improving the mechanical performance of the steel-concrete composite beam. To ensure reliable interfacial shear resistance between the UHPC layer and the concrete layer, this invention achieves reliable and stable interfacial performance through pre-embedded shear grooves and interfacial connecting reinforcement.

[0005] This invention discloses a steel-concrete composite beam with pre-embedded shear grooves. It leverages the ultra-high strength mechanical properties of the UHPC layer to enhance the beam's load-bearing capacity, utilizes the high durability of the UHPC layer to reduce bridge deck deterioration damage, and uses the shear grooves and interface reinforcement to ensure good shear resistance at the UHPC-concrete interface, avoiding brittle shear failure and achieving a combined effect. However, due to its novel structural form, there is limited research on this topic, and no shear analysis method considering the contributions of each component of the composite beam has been reported to date. To advance the research and application of this type of composite beam, it is crucial to propose a theoretical shear analysis method. This invention, through experimental and numerical simulation methods, proposes calculation formulas for the vertical shear capacity, longitudinal shear capacity, and longitudinal interface shear force of this novel steel-concrete composite beam. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a steel-concrete composite beam with pre-embedded shear grooves and its shear analysis method. By adding shear grooves through the concrete layer, a new type of steel-concrete composite beam is obtained by utilizing the combined action of shear grooves, studs and reinforcing bars, and a three-dimensional shear analysis is performed on the steel-concrete composite beam.

[0007] The technical solution of this invention is as follows:

[0008] A steel-concrete composite beam with pre-embedded shear grooves includes a concrete layer with studs and reinforcing bars arranged in a matrix. The studs are used to fix the concrete layer to the steel beam below, and the reinforcing bars are used to fix the concrete layer to the UHPC layer above. A shear groove is pre-embedded on the top surface of the concrete layer to enhance the shear strength of the UHPC layer.

[0009] Preferably, the steel beam includes flange I, flange II, and a web between flange I and flange II, with stiffening ribs arranged at intervals on both sides of the web; flange I is fixed to the concrete layer by studs.

[0010] Preferably, the width of the concrete layer is greater than the width of the flange I, and the coverage area of ​​the stud is the portion of the concrete layer located above the flange I.

[0011] Preferably, the width of the concrete layer is equal to the width of the UHPC layer, and the area covered by the reinforcing bars is the entire concrete layer area, including the shear groove.

[0012] Preferably, the shear groove includes the following shapes: "T" shaped groove, circular groove, rhomboid groove, oblique groove, elliptical groove, and rectangular groove.

[0013] Preferably, the reinforcing bars are arranged in a "C" shape and are all encapsulated inside the concrete layer and the UHPC layer.

[0014] Another technical solution of the present invention is as follows:

[0015] A method for shear analysis of a steel-concrete composite beam with pre-embedded shear grooves includes the following steps:

[0016] S1. Analyze the shear capacity of the steel-concrete composite beam from three dimensions:

[0017] S11: Taking a steel-concrete composite beam as the object, analyze the vertical shear bearing capacity;

[0018] S12: Taking the UHPC-concrete layer interface as the object, analyze the longitudinal shear bearing capacity;

[0019] S13: Taking the UHPC-concrete layer interface as the object, analyze the longitudinal shear force at the interface;

[0020] S2. Based on the analysis results from the three dimensions, determine whether the theoretical shear bearing capacity of the designed steel-concrete composite beam meets the actual use requirements;

[0021] S3. Consider the contribution of each parameter to the shear capacity and optimize the design scheme.

[0022] Preferably, in step S11, the vertical shear bearing capacity is analyzed using a steel-concrete composite beam as the object, and the specific calculation method is as follows:

[0023] S111. Obtain the dimensions of the concrete layer, UHPC layer and steel beam, as well as the axial compressive strength of the concrete and UHPC and the yield strength of the steel plate;

[0024] S112, Based on the shear bearing capacity V of the concrete layer c Shear bearing capacity V of UHPC layer cu Shear bearing capacity V of steel beams s Calculate the shear capacity V of the steel-concrete composite structure. u ,but:

[0025]

[0026]

[0027]

[0028] V u =V s +V c +V cu

[0029] In the formula: α is the shear capacity coefficient of the concrete layer.

[0030] f cThe axial compressive strength of concrete is given in MPa.

[0031] b c Width of the concrete layer, in mm;

[0032] h c The thickness of the concrete layer is in mm;

[0033] h s The height of the steel beam is in mm.

[0034] λ c Let λ be the shear span ratio of the concrete layer. c =a / h c ;

[0035] λ cu λ is the shear span ratio of the UHPC layer. cu =a / h cu ;

[0036] 'a' is the distance from the loading point of the test beam to the center of the support, in mm;

[0037] b cu UHPC layer width, mm;

[0038] h cu UHPC layer thickness, mm;

[0039] f cu UHPC axial compressive strength, MPa;

[0040] f y The yield strength of the steel plate is given by MPa.

[0041] A w The cross-sectional area of ​​the web of the steel beam is in mm². 2 .

[0042] Preferably, in step S12, the longitudinal shear bearing capacity is analyzed using the UHPC-concrete layer interface as the object, and the specific calculation method is as follows:

[0043] S121. Obtain the shear groove area, interfacial bond strength, interfacial friction coefficient, and interfacial reinforcement ratio ρ.

[0044] S122, based on the shear bearing capacity V provided by the interface excluding the shear groove. n1 The longitudinal shear force V provided by the shear groove at the interface n2 Calculate the longitudinal shear capacity V of the UHPC-concrete layer. n Shear bearing capacity V n1 The longitudinal shear force V provided by the shear groove at the interface n2 Calculate the longitudinal shear capacity V of the UHPC-concrete layer. n ,but:

[0045] V n1 =cA cv +μ(A vf f yv +P c And V n1 ≤min(K1f c A cv K2A cv )

[0046] And V n2 =min{γf c A K1 0.1f c A' K2 +0.15f c A” K2}

[0047] V n =V n1 +V n2

[0048] Where: c is the interfacial bond strength, MPa;

[0049] μ is the interfacial friction coefficient, which is dimensionless.

[0050] A cv The shear interface area excluding the shear groove shear surface, in mm. 2 ;

[0051] A vf The area of ​​shear reinforcement passing through the interface excluding the shear groove shear plane, in mm. 2 ;

[0052] f yv The shear strength of the reinforcing steel through the shear interface, in MPa;

[0053] P c The static pressure perpendicular to the shear interface generated under constant load, in kN;

[0054] K1 is the concrete strength coefficient, which is dimensionless, and the value is 0.3 for rough interfaces;

[0055] K2 is the interfacial resistance limiting strength, MPa, and the value for a rough interface is 12.4 MPa;

[0056] γ is the bearing capacity coefficient for shear groove verification, taken as 1.25;

[0057] A k The area of ​​the bottom surface of the shear groove is in mm. 2 ;

[0058] Asd The area of ​​shear reinforcement passing through the inner interface of the shear groove, in mm. 2 ;

[0059] A K1 This refers to the bearing area of ​​the protruding part of the shear groove;

[0060] A' K2 It is the sum of the root shear areas of the shear grooves at the top and bottom of the interface that may be subjected to tensile failure;

[0061] A” K2 It is the sum of the shear areas at the roots of the remaining shear grooves.

[0062] Preferably, in step S13, the longitudinal shear force at the UHPC-concrete layer interface is analyzed, and the specific calculation method is as follows:

[0063] S131. When the limit state control plastic neutral axis is located in the concrete layer, the criterion for determining the plastic neutral axis is as follows:

[0064] C U2 =α1β1f cu b c h cu <f y A s ≤α1β1f cu b c h cu +α2β2f c b c h c

[0065] In the formula: A s The total cross-sectional area of ​​the steel beam is in mm². 2 ;

[0066] α1 and β1 are the stress coefficient and height coefficient of the rectangular equivalent stress diagram of the UHPC layer, respectively, α1 = 0.94 and β1 = 0.74;

[0067] α2 and β2 are the stress coefficient and height coefficient of the rectangular equivalent stress diagram of the concrete layer, respectively. When the concrete strength grade does not exceed C50, the values ​​are α2 = 1.0 and β2 = 0.8. When the concrete strength grade is C80, the values ​​are α2 = 0.94 and β2 = 0.74. The values ​​are determined by linear interpolation as the concrete strength grade changes.

[0068] S132, Calculate the ultimate flexural capacity M of the steel-concrete composite beam section. u ,but:

[0069]

[0070] In the formula: x is the height from the plastic neutral axis to the compression zone at the top surface of the steel-concrete composite beam.

[0071] h、h f These are the heights of the steel beam and the concrete flange, respectively, in mm;

[0072] A sb A st These are the cross-sectional areas of wing plate II and wing plate I, respectively, in mm². 2 ;

[0073] t b t t The thicknesses of wing plate II and wing plate I are respectively, in mm;

[0074] h w The height of the steel beam web is in mm.

[0075] S133. Perform isolation analysis on the steel beam, based on the moment equilibrium equation of the composite beam shear span and the shear force V at the UHPC-concrete layer interface. h Considering the boundary conditions at the support point, calculate the longitudinal shear force V at the UHPC-concrete layer interface within the shear span length. h ,but:

[0076] M1 + VdL = M2

[0077] V h =C U2 -C U1

[0078] M1 = C U1 =C N1 =T1=0

[0079] V h =C U2

[0080] In the formula: M1 and M2 are the bending moments of the cross section; V is the vertical shear force of the cross section; dV is the increment of the vertical shear force of the cross section;

[0081] C U1 C U2 The combined pressure force provided to the UHPC; C N1 C N2 The resultant pressure force provided to the concrete;

[0082] T1 and T2 are the resultant tensile forces provided by the steel beam.

[0083] Compared with the prior art, the present invention has the following advantages:

[0084] 1. A new type of steel-concrete composite beam is obtained by directly replacing the top concrete layer of the steel-concrete composite beam that directly bears the load with a UHPC layer. Shear grooves are added to the concrete layer, and the shear resistance of the UHPC-concrete layer interface is enhanced by the combined action of shear grooves, studs and steel bars. This improves the mechanical properties of the steel-concrete composite beam and reduces the deterioration and damage of the composite beam bridge deck.

[0085] 2. By conducting shear analysis on the vertical shear capacity, longitudinal shear capacity at the UHPC-concrete layer interface, and longitudinal shear force at the UHPC-concrete layer interface of the new steel-concrete composite beam in three dimensions, a precise theoretical shear calculation analysis of the new steel-concrete composite beam is performed. Attached Figure Description

[0086] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0087] Figure 1 This is a cross-sectional view of the steel-concrete composite beam of the present invention.

[0088] Figure 2 This is an assembly drawing of the steel-concrete composite beam of the present invention.

[0089] Figure 3 This is a outline diagram of the steel-concrete composite beam of the present invention.

[0090] Figure 4 This is an elevation view of the steel-concrete composite beam of the present invention.

[0091] Figure 5 This is a cross-sectional view of the steel-concrete composite beam of the present invention.

[0092] Figure 6 It is a surface fitting diagram showing the contribution of variable UHPC compressive strength and thickness UHPC layer to shear bearing capacity.

[0093] Figure 7 This is a comparison chart of the calculation formula for vertical shear bearing capacity and the results of numerical simulation.

[0094] Figure 8 This is a stress analysis diagram of a micro-segment of a steel-concrete composite beam.

[0095] Figure 9 This is a shear stress analysis diagram of the exposed UHPC-concrete layer interface of a micro-segment of a steel-concrete composite beam.

[0096] Figure 10 This is one of the analysis diagrams of the longitudinal shear force at the UHPC-concrete layer interface.

[0097] Figure 11 This is the second diagram analyzing the longitudinal shear force at the UHPC-concrete layer interface.

[0098] In the diagram: 1. Concrete layer; 2. UHPC layer; 3. Connecting reinforcement; 4. Shear groove; 5. Stud; 6. Flange I; 7. Flange II; 8. Web; 9. Stiffening rib. Detailed Implementation

[0099] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0100] Example 1

[0101] like Figures 1 to 5 As shown, this embodiment provides a steel-concrete composite beam with pre-embedded shear grooves, including a concrete layer 1. The concrete layer 1 has studs 5 and reinforcing bars 3 arranged in a matrix of staggered patterns. The width of the concrete layer 1 is greater than the width of the flange I 6, and the studs 5 cover a portion of the concrete layer 1 above the flange I 6. The width of the concrete layer 1 is equal to the width of the UHPC layer 2, and the reinforcing bars 3 cover the entire area of ​​the concrete layer 1, including the shear grooves 4. The concrete layer 1 is made of any one of C30, C40, C50, or C60.

[0102] like Figure 1 , Figure 2 , Figure 4 and Figure 5 As shown, the stud 5 is used to fix the concrete layer 1 to the steel beam below.

[0103] like Figure 1 , Figure 2 , Figure 4 and Figure 5 As shown, the reinforcing bars 3 are used to fix the concrete layer 1 to the upper UHPC layer 2. Preferably, the reinforcing bars 3 are arranged in a "C" shape and are all enclosed inside the concrete layer and the UHPC layer 2.

[0104] like Figure 1 and Figure 2As shown, the shear groove 4 is used to enhance the shear strength of the UHPC layer 2. Preferably, the shear groove 4 includes the following shapes: "T" shaped groove, circular groove, rhomboid groove, beveled groove, elliptical groove, and rectangular groove. The shear groove 4 has a certain depth, which should not exceed 3cm, and reinforcing bars 3 can be pre-embedded at the bottom of the shear groove 4. The shear groove 4 can be integrally formed during the pouring of the concrete layer 1, or it can be formed by removing existing concrete and processing it later. The volume of the shear groove removed should not be too large, and the volume loss rate of the concrete layer 1 should be controlled within 0.06% during removal.

[0105] like Figure 1 , Figure 2 , Figure 3 As shown, the steel beam includes flange I6, flange II7, and a web 8 located between flange I6 and flange II7. Stiffening ribs 9 are spaced apart on both sides of the web 8. Flange I6 is fixed to the concrete layer 1 by studs 5. The steel beam is made of either Q235 or Q345 steel. The shear span ratio of the steel-concrete composite beam is 1.5-2.0.

[0106] Example 2

[0107] Based on Example 1, this example provides a shear analysis method for a steel-concrete composite beam with pre-embedded shear grooves, including the following steps:

[0108] S1. Analyze the shear capacity of the steel-concrete composite beam from three dimensions:

[0109] S11: Taking a steel-concrete composite beam as the object, analyze its vertical shear capacity, such as... Figure 6 , Figure 7 As shown;

[0110] S12: Taking the UHPC-concrete layer interface as the object, analyze the longitudinal shear bearing capacity;

[0111] S13: Taking the UHPC-concrete layer interface as the object, analyze the longitudinal shear force at the interface, such as... Figure 8 , Figure 9 , Figure 10 and Figure 11 As shown;

[0112] S2. Based on the analysis results from the three dimensions, determine whether the theoretical shear bearing capacity of the designed steel-concrete composite beam meets the actual use requirements;

[0113] S3. Consider the contribution of each parameter to the shear capacity and optimize the design scheme.

[0114] Example 3

[0115] Based on Example 2, in step S11, the vertical shear capacity of the steel-concrete composite beam is analyzed. The specific calculation method is as follows:

[0116] S111. Obtain the dimensions of the concrete layer, UHPC layer and steel beam, as well as the axial compressive strength of the concrete and UHPC and the yield strength of the steel plate;

[0117] S112, Based on the shear bearing capacity V of the concrete layer c Shear bearing capacity V of UHPC layer cu Shear bearing capacity V of steel beams s Calculate the shear capacity V of the steel-concrete composite structure. u ,but:

[0118]

[0119]

[0120]

[0121] V u =V s +V c +V cu

[0122] In the formula: α is the shear capacity coefficient of the concrete layer.

[0123] f c The axial compressive strength of concrete is given in MPa.

[0124] b c Width of the concrete layer, in mm;

[0125] h c The thickness of the concrete layer is in mm;

[0126] h s The height of the steel beam is in mm.

[0127] λ c Let λ be the shear span ratio of the concrete layer. c =a / h c ;

[0128] λ cu λ is the shear span ratio of the UHPC layer. cu =a / h cu ;

[0129] 'a' is the distance from the loading point of the test beam to the center of the support, in mm;

[0130] b cu UHPC layer width, mm;

[0131] h cu UHPC layer thickness, mm;

[0132] f cu UHPC axial compressive strength, MPa;

[0133] f y The yield strength of the steel plate is given by MPa.

[0134] A w The cross-sectional area of ​​the web of the steel beam is in mm². 2 .

[0135] Example 4

[0136] Based on Example 2, in step S12, the longitudinal shear capacity is analyzed using the UHPC-concrete layer interface as the object. The contribution of the steel beam flange to the shear capacity is ignored, and the contributions of the steel beam web, concrete layer, and UHPC layer to the shear capacity of the composite beam are considered separately. The specific calculation method is as follows:

[0137] S121. Obtain the shear groove area, interfacial bond strength, interfacial friction coefficient, and interfacial reinforcement ratio ρ.

[0138] S122, based on the shear bearing capacity V provided by the interface excluding the shear groove. n1 The longitudinal shear force V provided by the shear groove at the interface n2 Calculate the longitudinal shear capacity V of the UHPC-concrete layer. n ,but:

[0139] V n1 =cA cv +μ(A vf f yv +P c And V n1 ≤min(K1f c A cv K2A cv )

[0140] And V n2 =min{γf c A K1 0.1f c A' K2 +0.15f c A” K2}

[0141] V n =V n1 +V n2

[0142] Where: c is the interfacial bond strength, MPa;

[0143] μ is the interfacial friction coefficient, which is dimensionless.

[0144] A cv The shear interface area excluding the shear groove shear surface, in mm. 2 ;

[0145] A vf The area of ​​shear reinforcement passing through the interface excluding the shear groove shear plane, in mm. 2 ;

[0146] f yv The shear strength of the reinforcing steel through the shear interface, in MPa;

[0147] P c The static pressure perpendicular to the shear interface generated under constant load, in kN;

[0148] K1 is the concrete strength coefficient, which is dimensionless, and the value is 0.3 for rough interfaces;

[0149] K2 is the interfacial resistance limiting strength, MPa, and the value for a rough interface is 12.4 MPa;

[0150] γ is the bearing capacity coefficient for shear groove verification, taken as 1.25;

[0151] A k The area of ​​the bottom surface of the shear groove is in mm. 2 ;

[0152] A sd The area of ​​shear reinforcement passing through the inner interface of the shear groove, in mm. 2 ;

[0153] A K1 This refers to the bearing area of ​​the protruding part of the shear groove;

[0154] A' K2 It is the sum of the root shear areas of the shear grooves at the top and bottom of the interface that may be subjected to tensile failure;

[0155] A” K2 It is the sum of the shear areas at the roots of the remaining shear grooves.

[0156] Example 5

[0157] Based on Example 2, in step S13, as follows: Figure 8 , Figure 9 , Figure 10 and Figure 11 As shown, taking the UHPC-concrete layer interface as the object, the longitudinal shear force at the interface is analyzed. The specific calculation method is as follows:

[0158] S131. When the limit state control plastic neutral axis is located in the concrete layer, the criterion for determining the plastic neutral axis is as follows:

[0159] CU2 =α1β1f cu b c h cu <f y A s ≤α1β1f cu b c h cu +α2β2f c b c h c

[0160] In the formula: A s The total cross-sectional area of ​​the steel beam is in mm². 2 ;

[0161] α1 and β1 are the stress coefficient and height coefficient of the rectangular equivalent stress diagram of the UHPC layer, respectively, α1 = 0.94 and β1 = 0.74;

[0162] α2 and β2 are the stress coefficient and height coefficient of the rectangular equivalent stress diagram of the concrete layer, respectively. When the concrete strength grade does not exceed C50, the values ​​are α2 = 1.0 and β2 = 0.8. When the concrete strength grade is C80, the values ​​are α2 = 0.94 and β2 = 0.74. The values ​​are determined by linear interpolation as the concrete strength grade changes.

[0163] S132, Calculate the ultimate flexural capacity M of the steel-concrete composite beam section. u ,but:

[0164]

[0165] In the formula: x is the height from the plastic neutral axis to the compression zone at the top surface of the steel-concrete composite beam.

[0166] h、h f These are the heights of the steel beam and the concrete flange, respectively, in mm;

[0167] A sb A st These are the cross-sectional areas of wing plate II and wing plate I, respectively, in mm². 2 ;

[0168] t b t t The thicknesses of wing plate II and wing plate I are respectively, in mm;

[0169] h w The height of the steel beam web is in mm.

[0170] S133. Perform a body isolation analysis on the steel beam. Based on the moment equilibrium equation of the composite beam shear span and the shear force Vh at the UHPC-concrete interface, considering the boundary conditions at the supports, calculate the longitudinal shear force Vh at the UHPC-concrete interface within the length of the shear span. h ,but:

[0171] M1 + VdL = M2

[0172] V h =C U2 -C U1

[0173] M1 = C U1 =C N1 =T1=0

[0174] V h =C U2

[0175] In the formula: M1 and M2 are the bending moments of the cross section; V is the vertical shear force of the cross section; dV is the increment of the vertical shear force of the cross section;

[0176] C U1 C U2 The combined pressure force provided to the UHPC; C N1 C N2 The resultant pressure force provided to the concrete;

[0177] T1 and T2 are the resultant tensile forces provided by the steel beam.

[0178] Example 6

[0179] Numerical simulation of a steel-concrete composite beam with embedded shear grooves was performed using ABAQUS. First, a numerical model with the same dimensions and boundary conditions as the test beam was established. Specific dimensions are as follows: Figure 4 and Figure 5 As shown, the shear grooves are 150×150×30mm (length×width×depth), and five are evenly arranged along the longitudinal direction. Figure 7 As shown in the figure, the numerical simulation results show that the simulated ultimate shear capacity is 498.19 kN, while the experimental ultimate shear capacity is 495 kN, with an error of 0.6%. This demonstrates that the numerical simulation results using ABAQUS are reliable.

[0180] Based on the above numerical simulation, the present invention is subjected to parameter analysis, and the specific parameters include UHPC compressive strength, UHPC thickness, concrete compressive strength and steel beam web height.

[0181] The compressive strength parameters of UHPC were varied to 128 MPa, 133 MPa, 138 MPa, and 143 MPa, respectively, and named Comparative Examples 1-4, with other dimensions consistent with the test beam; the thickness parameters of UHPC were varied to 30 mm, 50 mm, and 60 mm, and the shear groove dimensions were varied to 130×130×30 mm, 150×150×30 mm, and 160×160×30 mm, respectively, named Comparative Examples 5-7, with other dimensions consistent with the test beam; the concrete strength was varied... Compressive strengths were set to 24 MPa, 34 MPa, and 54 MPa, respectively, and named Comparative Examples 8-10. All other dimensions remained the same as the test beam. The web height of the steel beam was varied to 274 mm, 294 mm, and 334 mm, while the shear groove dimensions were varied to 130×130×30 mm, 140×140×30 mm, and 160×160×30 mm, respectively, and named Comparative Examples 11-13. Numerical analysis was performed using ABAQUS on the above parameters to obtain the ultimate shear capacity V. u,e The calculated values ​​of the longitudinal shear capacity and longitudinal shear force at the interface are summarized in Table 1.

[0182] Table 1 Calculation results of this invention

[0183]

[0184] Note: V u,c V represents the calculation result of the vertical shear bearing capacity calculation formula in this invention. u,e V represents the ultimate shear capacity obtained from numerical simulation calculations, * represents the experimental value. n V represents the longitudinal shear capacity of the interface. h This represents the longitudinal shear force at the interface.

[0185] The present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, but the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope of the claims.

Claims

1. A steel-concrete composite beam with pre-embedded shear grooves, characterized in that, The concrete layer (1) includes a matrix of studs (5) and reinforcing bars (3). The studs (5) are used to fix the concrete layer (1) to the steel beam below, and the reinforcing bars (3) are used to fix the concrete layer (1) to the UHPC layer (2) above. A shear groove (4) is embedded in the top surface of the concrete layer (1). The shear groove (4) is used to enhance the shear strength of the UHPC layer (2). The steel beam includes flange I (6), flange II (7), and web (8) located between flange I (6) and flange II (7). Stiffening ribs (9) are arranged at intervals on both sides of the web (8). Flange I (6) is fixed to the concrete layer (1) by studs (5). The width of the concrete layer (1) is greater than the width of the flange I (6), and the coverage area of ​​the stud (5) is the part of the concrete layer (1) above the flange I (6); The width of the concrete layer (1) is equal to the width of the UHPC layer (2), and the area covered by the reinforcing bars (3) is the entire area of ​​the concrete layer (1), including the shear groove (4). The UHPC layer directly bears the load; the bottom of the shear groove (4) is pre-embedded with steel bars (3).

2. The steel-concrete composite beam with pre-embedded shear groove as described in claim 1, characterized in that, The shear groove (4) includes the following shapes: "T" shaped groove, circular groove, rhomboid groove, oblique groove, elliptical groove, and rectangular groove.

3. The steel-concrete composite beam with pre-embedded shear groove as described in claim 1, characterized in that, The steel bars (3) are arranged in a "C" shape and are all encapsulated inside the concrete layer (1) and the UHPC layer (2).

4. A method for shear analysis of a steel-concrete composite beam with pre-embedded shear grooves, using a steel-concrete composite beam with pre-embedded shear grooves as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Analyze the shear capacity of the steel-concrete composite beam from three dimensions: S11: Taking a steel-concrete composite beam as the object, analyze the vertical shear bearing capacity; S12: Taking the UHPC-concrete layer interface as the object, analyze the longitudinal shear bearing capacity; S13: Taking the UHPC-concrete layer interface as the object, analyze the longitudinal shear force at the interface; S2. Based on the analysis results from the three dimensions, determine whether the theoretical shear bearing capacity of the designed steel-concrete composite beam meets the actual use requirements; S3. Consider the contribution of each parameter to the shear capacity and optimize the design scheme.

5. The shear analysis method for steel-concrete composite beams with pre-embedded shear grooves as described in claim 4, characterized in that, In step S11, taking the steel-concrete composite beam as the object, the vertical shear bearing capacity is analyzed. The specific calculation method is as follows: S111. Obtain the dimensions of the concrete layer, UHPC layer and steel beam, as well as the axial compressive strength of the concrete and UHPC and the yield strength of the steel plate; S112. Based on the shear bearing capacity of the concrete layer V c Shear bearing capacity of UHPC layer V cu Shear bearing capacity of steel beams V s Calculate the shear bearing capacity of the steel-concrete composite structure. V u ,but: In the formula: α This is the shear capacity coefficient of the concrete layer. ; f c The axial compressive strength of concrete is given in MPa. b c Width of the concrete layer, in mm; h c The thickness of the concrete layer is in mm; h s The height of the steel beam is in mm. λ c The shear span ratio of the concrete layer. λ c = a / h c ; λ cu For the shear span ratio of the UHPC layer, λ cu = a / h cu ; a The distance from the loading point of the test beam to the center of the support is in mm; b cu UHPC layer width, mm; h cu UHPC layer thickness, mm; f cu UHPC axial compressive strength, MPa; f y The yield strength of the steel plate is given by MPa. A sw The cross-sectional area of ​​the web of the steel beam is in mm². 2 .

6. The shear analysis method for steel-concrete composite beams with pre-embedded shear grooves as described in claim 4, characterized in that, In step S12, the longitudinal shear bearing capacity is analyzed using the UHPC-concrete layer interface as the object. The specific calculation method is as follows: S121. Obtain the shear groove area, interfacial bond strength, interfacial friction coefficient, and interfacial reinforcement ratio. ρ ; S122, based on the shear bearing capacity provided by the interface excluding the shear groove. V n1 Longitudinal shear force provided by the shear groove V n2 Calculate the longitudinal shear capacity of the UHPC-concrete layer. V n ,but: and and In the formula: c The interfacial bond strength is expressed in MPa. μ Let be the interfacial friction coefficient, which is dimensionless; A cv The shear interface area excluding the shear groove shear surface, in mm. 2 ; A vf The area of ​​shear reinforcement passing through the interface excluding the shear groove shear plane, in mm. 2 ; f yv The shear strength of the reinforcing steel through the shear interface, in MPa; P c The static pressure perpendicular to the shear interface generated under constant load, in kN; K 1 represents the concrete strength coefficient, which is dimensionless, and the value for rough interfaces is 0.3; K 2 represents the interfacial resistance limiting strength, in MPa, with a rough interface value of 12.4 MPa; γ is the bearing capacity coefficient for shear groove verification, taken as 1.25; A k The area of ​​the bottom surface of the shear groove is in mm. 2 ; A sd The area of ​​shear reinforcement passing through the inner interface of the shear groove, in mm. 2 ; A K1 This refers to the bearing area of ​​the protruding part of the shear groove; It is the sum of the root shear areas of the shear grooves at the top and bottom of the interface that may be subjected to tensile failure; It is the sum of the shear areas at the roots of the remaining shear grooves.

7. The shear analysis method for steel-concrete composite beams with pre-embedded shear grooves as described in claim 4, characterized in that, In step S13, the longitudinal shear force at the UHPC-concrete layer interface is analyzed, and the specific calculation method is as follows: S131. When the limit state control plastic neutral axis is located in the concrete layer, the criterion for determining the plastic neutral axis is as follows: In the formula: The total cross-sectional area of ​​the steel beam is in mm². 2 ; , These are the stress coefficients and height coefficients of the rectangular equivalent stress diagram of the UHPC layer, respectively. , ; , These represent the stress coefficient and height coefficient of the rectangular equivalent stress diagram of the concrete layer, respectively. When the concrete strength grade does not exceed C50, the values ​​are taken as follows: =1.0, =0.8, when the concrete strength grade is C80, the value is taken as follows. =0.94, =0.74, and the value of the value varies with the concrete strength grade, which is determined by linear interpolation. S132. Calculate the ultimate flexural capacity of the normal section of a steel-concrete composite beam. M u ,but: In the formula: The height from the plastic neutral axis to the compression zone at the top surface of the steel-concrete composite beam. ; , These are the heights of the steel beam and the concrete flange, respectively, in mm; , These are the cross-sectional areas of wing plate II and wing plate I, respectively, in mm². 2 ; , The thicknesses of wing plate II and wing plate I are respectively, in mm; The height of the steel beam web is in mm. S133. Perform a body isolation analysis on the composite beam, and based on the moment equilibrium equation of the shear span of the composite beam, expose the shear force at the UHPC-concrete layer interface. Considering the boundary conditions at the support point, calculate the longitudinal shear force at the UHPC-concrete layer interface within the shear span length. ,but: In the formula: , The bending moment of the section; Vertical shear force at the cross section; This represents the increment of vertical shear force at the cross section. The length of the micro-segment; , The combined pressure force provided to the UHPC layer; , The combined pressure force provided to the concrete layer; , The resultant tensile force provided to the steel beam.

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