Method for determining the shear capacity of a combined pin connector based on shear stud reinforcement

Abstract

The application discloses a method for determining the shearing bearing capacity of a combined pin connector based on shear pin enhancement, comprising the following steps: step one, determining the basic form of the shearing bearing capacity formula of the combined pin connector based on shear pin enhancement; step two, determining the shearing bearing capacity calculation formula of the single pin of the combined pin connector; step three, establishing the shearing pin bearing capacity calculation formula considering the cross-sectional area of the shearing pin and the tensile strength of the shearing pin; step four, combining the push-out test data of the combined pin connector based on shear pin enhancement, fitting the interaction influence coefficient, and putting forward the shearing bearing capacity calculation formula, so that the shearing bearing capacity of the combined pin shearing connector based on shear pin enhancement can be determined. The application makes the determination of the shearing bearing capacity of the new combined pin connector more reasonable, accurate and convenient, and provides a theoretical basis for the application of the combined pin connector based on shear pin enhancement in the combined bridge structure.

Description

TECHNICAL FIELD

[0001] The application relates to a method for determining the shear bearing capacity of a connecting piece, in particular to a method for determining the shear bearing capacity of a combined dowel connecting piece based on shear pin enhancement, and belongs to the technical field of traffic engineering. BACKGROUND

[0002] A steel-concrete composite bridge can fully exert the compressive strength of concrete and the tensile strength of steel, reduce the self weight of the bridge structure, save engineering cost, and has a wide application prospect in bridge engineering. A shear connecting piece is an important component for connecting a bridge deck slab and a steel main beam into a whole. At present, the most important forms of the connecting piece are a shear pin connecting piece and a PBL connecting piece, which are arranged on the upper flange plate of the steel beam and connected with the bridge deck slab. In recent years, Europe has proposed a web straight insertion type improved clothoid shape composite dowel (MCL for short), which has good shear resistance and fatigue resistance and has been successfully applied in bridge engineering.

[0003] However, research shows that the MCL composite dowel connecting piece has obvious stress concentration areas, which causes the bottom of the steel pin to tear prematurely, limiting the exertion of the shear bearing capacity thereof.

[0004] Therefore, a new type of composite dowel connecting piece based on shear pin enhancement can be conceived, that is, a shear pin is arranged transversely on the MCL steel pin to improve the stress state of the steel pin, relieve the stress concentration phenomenon, and achieve the purpose of improving the shear bearing capacity. However, there is no accurate method for evaluating and determining the shear bearing capacity of the composite dowel connecting piece, which limits the application of the new type of composite dowel connecting piece in steel-concrete composite bridges and other traffic engineering. SUMMARY

[0005] The application aims to provide a method for determining the shear bearing capacity of a composite dowel connecting piece based on shear pin enhancement, which can accurately determine the shear bearing capacity of the composite dowel connecting piece based on shear pin enhancement and provide a theoretical basis for the application of the composite dowel connecting piece based on shear pin enhancement in composite bridge structures.

[0006] The application is implemented in the following manner:

[0007] The method for determining the shear bearing capacity of a composite dowel connecting piece based on shear pin enhancement comprises the following steps:

[0008] Step 1: Considering that the web straight insertion type composite dowel connecting piece and the shear pin connecting piece both provide shear bearing capacity, according to the superposition principle, the basic form of the formula for determining the shear bearing capacity of the composite dowel connecting piece based on shear pin enhancement is determined.

[0009] Step two, based on the failure mode and geometric parameters of shear pin enhanced combined pin connector, the single pin shear capacity calculation formula of combined pin connector is determined;

[0010] Step three, according to the phenomenon that the shear pin and the steel pin all occur root shear failure, the shear pin capacity calculation formula considering the cross-sectional area of shear pin and the tensile strength of shear pin is established;

[0011] Step four, combined with the push-out test data of shear pin enhanced combined pin connector, the interaction influence coefficient is fitted, and the shear capacity calculation formula is proposed, so that the shear capacity of shear pin enhanced combined pin connector can be determined.

[0012] Further scheme is:

[0013] The combined pin connector based on shear pin enhancement is a steel pin with shear pins transversely arranged on the improved spiral line combined pin connector (referred to as MCL) inserted in the web, and the thickness of the steel pin is 8-16 mm. The number of shear pins arranged on a single steel pin is 1-3 pairs to improve the stress state of the steel pin of MCL and relieve the stress concentration phenomenon, so as to improve the shear capacity of MCL.

[0014] Further scheme is:

[0015] In step one, according to the superposition principle, the shear capacity calculation formula of the combined pin connector based on shear pin enhancement is obtained as follows:

[0016] P = αP mcl + βP sd (1)

[0017] Wherein: α is the interaction influence fitting coefficient of the combined pin connector based on shear pin enhancement; β is the interaction influence fitting coefficient of the shear pin connector in the combined pin connector based on shear pin enhancement; P mcl is the single pin shear capacity of the combined pin connector; P sd is the single pin shear capacity of the shear pin connector.

[0018] Further scheme is:

[0019] In step two, the three failure modes of MCL combined pin connector are steel pin failure, concrete shear failure and concrete pry-out failure. Since the failure mode of the combined pin connector based on shear pin enhancement is steel pin failure, the failure mode of the combined pin connector is determined as steel pin failure. Since the shear capacity is linearly related to the thickness of the steel pin, the critical section width and the yield strength, and the geometric parameters are represented by the steel pin spacing e x , the single pin shear capacity calculation formula of the combined pin connector is:

[0020] Pmcl = 0.25 e x t w f yk (2)

[0021] Wherein, e x is the steel pin spacing; t w is the steel pin thickness; f yk is the steel web yield strength;

[0022] Further scheme is:

[0023] In step three, according to the 'Highway Steel-mix Combined Beam Bridge Design and Construction Specification', and the phenomenon that the steel pin shear nail is all sheared at the root and shear failure occurs, two key parameters of shear nail cross-sectional area and shear nail tensile strength are considered, and the shear nail bearing capacity calculation formula is established as:

[0024] P sd = 0.7 A n f su (3)

[0025] Wherein, A n is the shear nail cross-sectional area (mm 2 ); f su is the minimum value of the tensile strength of the welding nail material (MPa);

[0026] Further scheme is:

[0027] In step four, the differential evolution method is used to fit the coefficients alpha and beta by combining the combined pin connector push-out test data based on shear nail enhancement, alpha=1.461 and beta=0.853 are obtained. The coefficients obtained by fitting and formula (2), (3) are substituted into formula (1), and the shear bearing capacity calculation formula (4) of the combined pin shear connector based on shear nail enhancement is obtained, so that the shear bearing capacity of the combined pin shear connector based on shear nail enhancement can be determined,

[0028] P = 0.365 e x t w f yk + 0.597 n s A n f su (4)

[0029] Wherein, n s is the number of increased shear nails on a single steel pin.

[0030] The present application has at least the following outstanding beneficial effects:

[0031] 1. The application provides a new type of combined pin shear connector based on shear pin enhancement, which provides a new way for the connection of combined bridge structure and promotes the development of steel-concrete combined bridge structure.

[0032] 2. Based on the test and relevant specifications, the application provides a shear capacity determination method of the combined pin shear connector based on shear pin enhancement, so that the determination of the shear capacity of the new combined pin connector is more reasonable, accurate and convenient, and provides a theoretical basis for the application of the combined pin connector based on shear pin enhancement in the combined bridge structure. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The application provides a shear capacity determination method of the combined pin shear connector based on shear pin enhancement.

[0034] Figure 2 The application provides a new type of combined pin connector based on shear pin enhancement.

[0035] Figure 2 (a) the front view of the single steel pin with three pairs of shear pins arranged transversely;

[0036] (b) the side view of the single steel pin with three pairs of shear pins arranged transversely;

[0037] (c) the top view of the single steel pin with three pairs of shear pins arranged transversely;

[0038] (d) the side view of the single steel pin with two pairs of shear pins arranged transversely;

[0039] (e) the side view of the single steel pin with one pair of shear pins arranged transversely;

[0040] (f) the side view of the single steel pin with no shear pin arranged transversely. DETAILED DESCRIPTION

[0041] The application will be further described below in combination with the drawings and specific embodiments, but it should not be understood as a limitation of the application.

[0042] The application provides a shear capacity determination method of a combined pin connector based on shear pin enhancement, as shown in the accompanying drawings, which comprises the following steps: Figure 1 Step one, considering that the web straight insertion type combined pin connector and the shear pin connector both provide shear capacity, according to the superposition principle, the basic form of the shear capacity formula of the combined pin connector based on shear pin enhancement is determined.

[0043]

[0044] ​Step two, based on the failure mode and geometric parameters of the shear pin enhanced combined pin connector, the single pin shear capacity calculation formula of the combined pin connector is determined;

[0045] Step three, according to the phenomenon that the steel pin shear pin is sheared at the root, the shear pin capacity calculation formula considering the cross-sectional area of the shear pin and the tensile strength of the shear pin is established;

[0046] Step four, combined with the push-out test data of the shear pin enhanced combined pin connector, the interaction influence coefficient is fitted, and the shear capacity calculation formula is proposed, so that the shear capacity of the shear pin enhanced combined pin connector can be determined.

[0047] Among them, the shear pin enhanced combined pin connector is a shear pin transversely arranged on the steel pin of the web straight insertion type improved spiral line combined pin connector (referred to as MCL), as shown in the accompanying Figure 2 The steel pin thickness is 8-16mm; the number of shear pins arranged on a single steel pin is 1-3 pairs to improve the stress state of the steel pin of MCL and relieve the stress concentration phenomenon, so as to improve the shear capacity of MCL.

[0048] Therefore, the shear capacity of the shear pin enhanced combined pin connector is provided by the MCL combined pin connector and the shear pin connector, and according to the superposition principle, the basic form of the shear capacity calculation formula is obtained:

[0049] P=αP mcl +βP sd (1)

[0050] The three failure modes of MCL combined pin connector are: steel pin failure, concrete shear failure and concrete pry-out failure, and the minimum value of the shear capacity of the three is taken as the shear capacity calculation value according to the failure mode. According to the test results, the failure mode of the shear pin enhanced combined pin connector is steel pin failure, and the shear capacity is linearly related to the steel pin thickness, critical section width and yield strength, and the geometric parameters are represented by the steel pin spacing e x , then the single pin shear capacity calculation formula of the combined pin connector is:

[0051] P mcl =0.25·e x ·t w ·f yk (2)

[0052] According to the "Design and Construction Specification for Highway Steel-concrete Composite Girder Bridges", and the phenomenon that the steel pin shear pin is sheared at the root, the shear pin capacity calculation formula is established considering the cross-sectional area of the shear pin and the tensile strength of the shear pin:

[0053] Psd = 0.7A n f su (3)

[0054] By changing the thickness of different steel pins and the number of transverse shear pins, 12 groups of 24 push-out test pieces were designed and manufactured, and the specific size arrangement is shown in Figure 2 and Table 1. The label rule of the push-out test piece is the thickness of the steel pin + the number of shear pins arranged, and the test piece with strain gauges arranged on the steel pin is marked with Y. For example, 10+1Y indicates that the thickness of the steel pin is 10mm, a pair of shear pins are arranged on a single steel pin, and strain gauges are arranged on the steel pin; 10+0Y indicates that the thickness is 10mm, 0 pairs of shear pins, and strain gauges; 10+0 indicates that the thickness is 10mm, 0 pairs of shear pins, and no strain gauges; 10+1 indicates that the thickness is 10mm, 1 pair of shear pins, and no strain gauges.

[0055] Table 1 Shear capacity of combined pin push-out test pieces based on shear pin enhancement

[0056]

[0057] Based on the push-out test data of the combined pin connector based on shear pin enhancement, the differential evolution method is used to fit the coefficients α and β, and α = 1.461 and β = 0.853 are obtained. By substituting the fitted coefficients and equations (2) and (3) into equation (1), the shear capacity calculation formula (4) of the combined pin shear connector based on shear pin enhancement is obtained, so that the shear capacity of the combined pin shear connector based on shear pin enhancement can be determined,

[0058] P = 0.365e x t w f yk + 0.597n s A n f su (4)

[0059] In order to make the purpose, technical scheme and advantages of the present application more clear and obvious, the following specific application examples are provided to further illustrate the present application in detail.

[0060] Specific application examples:

[0061] It is known that 12 groups of 24 push-out test pieces, the concrete strength grade is C50, the size of the concrete slab on both sides of the test piece is: 650mmx350mmx825mm, the steel pin and the I-beam material are Q355B, the steel bar adopts HRB400 grade, the shear pin material is ML15AL, the diameter is 13mm, and the length is 100mm, see Figure 2 . The shear capacity of the combined pin shear connector based on shear pin enhancement obtained by the test is shown in Table 2.

[0062] Table 2 Comparison of the calculated and tested shear capacity of the combined pin push-out specimen based on shear pin enhancement

[0063]

[0064] As shown in Table 2, the calculated and tested shear capacity of the combined pin push-out specimen based on shear pin enhancement are in good agreement, the average of the ratio of the theoretical calculation value and the test result of the shear capacity determination method of the combined pin shear connector based on shear pin enhancement is 1.002, and the standard deviation is 0.027, so the accuracy of the shear capacity calculation formula of the combined pin connector based on shear pin enhancement is high, and the application requirements in bridge and other traffic engineering can be completely met.

[0065] Although the present application has been described with reference to the explanatory embodiments thereof, the above-described embodiments are merely preferred embodiments of the present application, and the embodiments of the present application are not limited to the above-described embodiments, and it should be understood that those skilled in the art can design many other modifications and embodiments, which will fall within the scope and spirit of the principles disclosed in the present application.

Claims

1. A method for determining the shear capacity of a combined pin connector reinforced with shear studs, characterized in that Comprising the following steps: Step one, considering that both the web straight-in combination pin connector and the shear stud connector provide shear bearing capacity, according to the superposition principle, the basic form of the shear bearing capacity formula of the combination pin connector based on shear stud enhancement is determined; Wherein, according to the superposition principle, the basic form of the shear bearing capacity calculation formula of the combination pin connector based on shear stud enhancement is obtained as: （1） wherein: is the interaction influence fitting coefficient for the combined pin connection based on shear stud reinforcement; is the interaction influence fitting coefficient for the shear stud connection in the combined pin connection based on shear stud reinforcement; is the single pin shear capacity for the combined pin connection; is the single stud shear capacity for the shear stud connection; Step two, based on the failure mode and geometric parameters of the combination pin connector based on shear stud enhancement, the shear bearing capacity calculation formula of the single pin of the combination pin connector is determined; Step three, according to the phenomenon that the steel pin shear stud is subjected to root shear failure, the shear stud bearing capacity calculation formula considering the cross-sectional area of the shear stud and the tensile strength of the shear stud is established; Step four, combined with the push-out test data of the combination pin connector based on shear stud enhancement, the interaction influence coefficient is fitted, and the shear bearing capacity calculation formula is proposed, so that the shear bearing capacity of the combination pin shear connector based on shear stud enhancement can be determined.

2. The method of claim 1, wherein: The combination pin connector based on shear stud enhancement is formed by transversely arranging shear studs on the steel pin of the web straight-in improved spiral line type combination pin connector.

3. The method of claim 2, wherein: The thickness of the steel pin is 8-16 mm.

4. The method of claim 3, wherein: The number of shear studs arranged on a single steel pin is 1-3 pairs.

5. The method of claim 1, wherein: In step two, the three failure modes of the web-inserted improved helical stud shear connector are steel stud failure, concrete shear failure and concrete pry-out failure. Since the failure mode of the combined stud connector based on shear stud enhancement is steel stud failure, the failure mode of the combined stud connector is determined to be steel stud failure. Since the shear capacity is linearly related to the steel stud thickness, the critical section width and the yield strength, and the geometric parameters are represented by the steel stud spacing , the single stud shear capacity calculation formula of the combined stud connector is: （2） wherein, is the steel pin spacing; is the steel pin thickness; is the steel web yield strength.

6. The method of claim 5, wherein: In step three, according to the "Design and Construction Specification for Highway Steel-Concrete Composite Girder Bridges", and the phenomenon that the steel pin shear stud is subjected to shear failure by being sheared at the root, two key parameters, the cross-sectional area of the shear stud and the tensile strength of the shear stud, are considered to establish the shear stud bearing capacity calculation formula as: （3） wherein A is the cross-sectional area of the shear pin, units ; σ is the minimum tensile strength of the pin material, units .

7. The method of claim 6, wherein: In step four, experimental data are derived from the combined pin connector reinforced with shear studs. The differential evolution method is then used to analyze the coefficients. α , β By fitting, we can obtain... α =1.461, β =0.853; The fitted coefficient and formulas (2) and (3) are substituted into formula (1) to obtain the shear bearing capacity calculation formula (4) of the combination pin shear connector based on shear stud enhancement, so that the shear bearing capacity of the combination pin shear connector based on shear stud enhancement can be determined, （4） wherein, is the number of additional shear pins on the single steel pin.

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