Test piece for detecting joint strength of steel-concrete combined arch bridge
By arranging pressure sensors on the nodes of the steel truss web concrete composite arch bridge and using through steel bars and nails, the problem of determining the range of the connection nodes between the overall node plate and the steel truss web and chord steel is solved, the bearing capacity and structural stability of the nodes are improved, and the damage of the weak links of welding is avoided.
Patent Information
- Application Number
- CN202411771614.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-04
- Publication Date
- 2025-07-04
AI Technical Summary
The prior art lacks the determination of the connection node range of the overall node plate and steel truss web and chord steel of the steel truss web and chord steel of the steel truss web and chord steel, resulting in weak welding strength and affecting the bearing capacity and construction safety of the arch bridge.
A test piece for node strength detection of steel concrete composite arch bridge is designed. By arranging multiple sets of pressure sensors on the node plate, chord steel and steel truss belly rod, the stress changes are monitored, the size range of the node plate is determined, and the penetrating steel bars and bolts are used as shear connections to enhance the connection strength.
The larger part of the node plate is effectively determined, the bearing capacity and structural stability of the node plate are improved, the damage of the welded parts is prevented, and the bearing capacity needs of the new arch bridge structure is met.
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Figure CN120253431A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of structural testing, and particularly relates to a specimen for detecting the strength of a joint of a steel-concrete composite arch bridge and a test method therefor. Background Art
[0002] In the field of bridge engineering, improving the spanning ability of arch bridges is an important topic. At present, for super-long-span concrete arch bridges, the stiffening skeleton method is mainly adopted for construction. The arch ring is a stiffening skeleton concrete structure, and the stiffening skeleton is generally concrete-filled steel tubes. The construction process is to erect and close the steel tube arch frame first, then pour the concrete inside the chord tubes to form a concrete-filled steel tube stiffening skeleton, and then use it as a support to wrap the concrete outside to form the arch ring. Although the use of the stiffening skeleton reduces the self-weight of the overall arch bridge, the amount of concrete used in large-span concrete arch bridges still accounts for a relatively high proportion. During the construction of large-span arch bridges, the requirements for the structural stability are extremely high. Due to the large self-weight of concrete, the structure is more likely to deform and become unstable during construction, thus affecting the construction safety and engineering quality, resulting in a long construction period and high cost for the arch ring construction. This has become the main problem restricting the development of concrete arch bridges towards super-long-span.
[0003] To effectively reduce the self-weight of the concrete arch ring, usually two methods can be adopted: one method is to use high-strength or ultra-high-strength concrete to replace ordinary-strength concrete to reduce the self-weight by reducing the cross-sectional area of the arch ring; the other method is to use steel to replace part of the concrete to form a steel-concrete composite structure to reduce the self-weight. For super-long-span concrete arch bridges, the main arch of a large-span concrete arch bridge is either a box slab or a box rib, and the top and bottom plates are its main load-bearing parts, and the webs mainly play a role in force transmission. To reduce the self-weight, the web thickness is relatively thin. However, to increase the section efficiency, the section height is relatively large, and the web is relatively high, resulting in greater difficulty in on-site concrete pouring construction. If high-strength or ultra-high-strength concrete is used, its cross-section is smaller and the construction will be more difficult. Therefore, in the construction process of a certain bridge, an H-shaped steel stiffening skeleton was innovatively used as the web to form a new arch bridge structure of a steel truss web concrete composite arch ring. Since the top and bottom plates are its main load-bearing parts and the webs mainly play a role in force transmission, a steel-concrete composite structure is adopted for the upper and lower chords of the arch bridge to ensure the structural strength, and a steel truss web is used for support in the middle. Using this kind of bridge structure can not only save the pouring work of the concrete web and facilitate construction, but also greatly reduce the self-weight of the arch ring.
[0004] At present, although some basic research has been carried out on the steel truss web-stiffening steel frame concrete composite arch, it mainly focuses on the stiffening steel frame of concrete-filled steel tube and the composite arch structure with circular steel tubes as web members. The construction method is to first construct the stiffening steel frame and then cast the outer concrete in-situ. The circular steel tube used as the web member is directly welded to the steel tube in the chord member. The joint between the web member and the concrete top and bottom plates is the weak link in the force-bearing of the overall structure, and the welding strength between the web member and the chord member becomes the main determining factor for the tensile strength of the web member. Based on this, the H-shaped steel stiffening steel frame is adopted in this bridge, and an integral joint plate is used to connect the H-shaped steel chord member in the top and bottom plate concrete and the steel truss web member, which is quite different from the existing composite arch structure. From the perspective of force analysis, the reliable force transmission performance of the integral joint is an important factor for the normal operation of the arch bridge. Therefore, how to determine the joint range of the connection joints between the integral joint plate and the steel truss web member and the chord member steel section, so that the joint can bear a large force without failure, is crucial for the bearing capacity of the new arch bridge structure. Summary of the Invention
[0005] Aiming at the deficiencies of the prior art, the technical problem solved by the present invention is to provide a specimen for detecting the joint strength of a steel-concrete composite arch bridge, aiming at the lack of technical means for determining the joint range of the connection joints between the integral joint plate and the steel truss web member and the chord member steel section in the new arch bridge structure of the steel truss web-concrete composite arch ring in the prior art.
[0006] To solve the above problems, the technical solution adopted by the present invention is: a specimen for detecting the joint strength of a steel-concrete composite arch bridge, including a joint plate, a chord member steel section, a steel truss web member, and a steel reinforcement cage. Both the chord member steel section and the steel truss web member are H-shaped steels. The joint plate includes two integrally formed wing plates and a web plate fixedly connecting the two wing plates. The wing plate includes a first connecting rod arranged linearly along the longitudinal direction and two second connecting rods arranged on one side of the first connecting rod. The first connecting rod is fixedly connected to the chord member steel section to form a chord member skeleton. Shear connectors are provided outside the chord member skeleton. The steel reinforcement cage surrounds the chord member skeleton. The chord member skeleton and the steel reinforcement cage are wrapped with concrete to form a chord member. The second connecting rod is fixedly connected to the steel truss web member to form a web member. Multiple groups of pressure sensors are detachably connected to the surface of the chord member concrete, the chord member skeleton, and the web member. The pressure sensors are electrically connected to a static strain tester. One group of pressure sensors is provided on each of the four side surfaces of the chord member concrete along the length direction of the chord member. The pressure sensor groups located in the chord member skeleton are respectively provided with one group on each of the two wing plates and the web plate along the length direction of the chord member. The pressure sensors located in the web member are provided with one on each of the two wing plates and the web plate of the web member, and one pressure sensor is provided on each of the two wing plates of the second connecting rod of the joint plate.
[0007] The beneficial effects produced by this solution are as follows: By fabricating this joint specimen and arranging multiple groups of pressure sensors on the chord truss, chord concrete, and web members respectively, the stress changes in various parts of the specimen are monitored through the pressure sensors arranged at different positions, thereby obtaining the stress change curves of various parts. Through the stress changes, the parts with larger forces in the chord and web members can be determined, and then the size range of the gusset plate can be determined; if the welded parts of the gusset plate with the chord section steel and the steel truss web members are located in the parts with larger forces, it is likely to cause damage to the welded parts. For example, in the existing concrete-filled steel tube stiffening truss, and the combined arch structure with circular steel tubes as web members, fractures usually occur at the welded joints between the circular steel tubes and the steel tubes in the chord. By controlling the size of the gusset plate, the parts with larger forces are located within the gusset plate range. Since the flange of the gusset plate is an integrally formed integral plate, it can better disperse the force, thereby making the overall bearing capacity of the joint specimen stronger.
[0008] Further, the shear connectors are through reinforcement bars. There are multiple through reinforcement bars fixedly connected between the parallel side surfaces of the steel reinforcement cage, and the through reinforcement bars penetrate through the flange of the chord section steel or the first connecting rod. By using through reinforcement bars to fixedly connect the steel reinforcement cage and the chord truss, while strengthening the connection between the concrete and the chord truss, it helps to more effectively transfer the load, improve the bearing capacity of the structure, thereby improving the stability of the chord and preventing relative slippage between the concrete and the chord truss.
[0009] Further, the shear connectors are stud bolts. There are multiple stud bolts fixedly connected to the outside of the chord truss. As shear connectors, the stud bolts can firmly connect the chord truss and the concrete together. The shear force and tensile force between the chord truss and the concrete are transmitted through the stud bolts, enabling the two to jointly bear the external load, and thus enhancing the bearing capacity of the chord structure.
[0010] Further, the shear connectors include stud bolts and through reinforcement bars. There are multiple stud bolts fixedly connected to the outside of the chord truss, and there are multiple through reinforcement bars fixedly connected between the parallel side surfaces of the steel reinforcement cage. The through reinforcement bars penetrate through the flange of the chord section steel or the first connecting rod. By using through reinforcement bars and stud bolts together as shear connectors, the shear force and tensile force between the chord truss and the concrete are effectively transmitted, improving the strength of the connection structure.
[0011] Further, the joint specimen is fabricated in a ratio of 2:1 with the actual bridge joint. Using this ratio, under the condition of meeting the laboratory test conditions, it is as close as possible to the size of the actual bridge joint, so that the test results can more truly reflect the force condition of the joint and the structural strength of the joint.
[0012] Further, strain rosettes are used for all the pressure sensors located at the gusset plate flanges. Since the stress at the gusset plate is complex during the test loading, strain rosettes can be used to measure more complex stress change data.
[0013] Further, taking the horizontal midline of the chord when placed vertically during the experiment as the reference, the upper half of the chord is above the horizontal midline, the lower half of the chord is below the horizontal midline, and the distance between multiple pressure sensors on the same side of the lower half of the chord concrete and the lower half of the chord skeleton is 140 - 160 mm, and the distance between multiple pressure sensors on the same side of the upper half of the chord concrete and the upper half of the chord skeleton is 280 - 460 mm. In an arch bridge structure, the arch design causes the upper chord to mainly bear tensile forces, while the lower chord bears greater compressive forces and bending moments. This stress characteristic leads to large stresses and deformations in the lower chord under the action of loads. By reducing the layout spacing in the lower half to set more strain gauges to monitor the stress changes, more detailed stress change data can be obtained, which is convenient for subsequent structural strength analysis of the joint specimens.
[0014] Further, 2 - 3 groups of pressure sensors are also distributed along the width direction of the side of the chord concrete close to the gusset plate. Each group has 3 - 5 pressure sensors, and the pressure sensors within each group are evenly spaced along the width direction of the chord. By setting the sensors in the width direction, that is, the horizontal sensors when the chord is placed vertically during the experiment, it is used to monitor the transverse strain of the concrete around the gusset plate flange.
[0015] Further, an integrally formed arc portion is provided at the angle between the two second connecting rods and the first connecting rod, and a strain rosette is provided at the arc portion between the two second connecting rods. By providing the arc portion, the strength of the gusset plate is further improved, which is convenient for the end of the second connecting rod to better disperse the force to the first connecting rod. At the same time, the strain rosette provided at the arc portion monitors the strain in the joint area of the gusset plate.
[0016] Further, a wax seal layer is provided outside the pressure sensors located on the chord skeleton, and epoxy resin is coated outside the wax seal layer. This can prevent damage to the strain gauges during concrete pouring. Description of the Drawings
[0017] Figure 1 It is a three - dimensional view of the specimen in Embodiment 1 of the present invention.
[0018] Figure 2 It is a front view of the specimen in Embodiment 1.
[0019] Figure 3 It is a cross - sectional view of the specimen in Embodiment 1.
[0020] Figure 4 It is a schematic diagram of the gusset plate.
[0021] Figure 5 Schematic diagram of each side of the chord member.
[0022] Figure 6 Schematic diagram of the layout of the chord member skeleton and the web member pressure sensors.
[0023] Figure 7 Layout drawing of the chord member concrete pressure sensors.
[0024] Figure 8 Layout drawing of the displacement gauges.
[0025] Figure 9 Cross-sectional view of the specimen in Example 2.
[0026] Figure 10 Cross-sectional view of the specimen in Example 3.
[0027] Figure 11 Schematic diagram of the load application.
[0028] Figure 12 Load-web member displacement curve of nodes K0 - K3. Specific implementation manners
[0029] The following is a further detailed description through specific implementation manners:
[0030] The reference numerals in the accompanying drawings of the specification include: gusset plate 1, first connecting rod 11, second connecting rod 12, arc portion 13, chord member section steel 2, connecting plate 21, stiffening rib 22, concrete 23, steel truss web member 3, steel reinforcement cage 4, penetrating reinforcement 5, stud 6, chord member jack 7, web member jack 8, pressure jack 81, tension jack 82, pressure sensor 9.
[0031] Example 1 is basically as shown in the appendix Figures 1-4As shown: A specimen for testing the strength of a steel-concrete composite arch bridge node, including a gusset plate 1, chord steel sections 2, and steel truss web members 3. The chord steel sections 2 and the steel truss web members 3 both use chord steel sections. The gusset plate includes two integrally formed wing plates and a web connecting the two wing plates. The wing plate includes a first connecting rod arranged in a straight line along the longitudinal direction and two second connecting rods provided on one side of the first connecting rod. There are two second connecting rods 12 and they are located in the middle on the same side of the first connecting rod 11. The two second connecting rods 12 are symmetric about the length center line of the first connecting rod 11; the first connecting rod 11 is welded to the chord steel section 2 to form a chord skeleton. A steel reinforcement cage 4 is provided outside the chord skeleton. A through reinforcement 5 is welded between one set of parallel sides of the steel reinforcement cage 4. The chord skeleton and the steel reinforcement cage 4 are wrapped with concrete 23 to form a chord; the second connecting rod 12 is welded to the steel truss web member 3 to form a web member. Multiple groups of pressure sensors are detachably connected to the concrete surface of the chord, the chord skeleton, and the web member. The pressure sensors are electrically connected to a static strain tester; the group of pressure sensors on the concrete surface of the chord is provided with one group on each of the four sides along the length direction of the chord. The group of pressure sensors on the chord skeleton is provided with one group on each of the two wing plates and the web along the length direction of the chord. The pressure sensors on the web member are provided with one on each of the two wing plates and the web of the web member, and one pressure sensor is provided on each of the two wing plates of the second connecting rod of the gusset plate. The pressure sensor 9 is one or several of a resistance strain gauge, a strain rosette, a piezoelectric sensor, and a capacitive strain pressure sensor.
[0032] As Figure 4 shown, the included angles between the two second connecting rods 12 and the first connecting rod 11 of the gusset plate 1 are 60°. The included angles between the two second connecting rods 12 and the first connecting rod 11 are provided with arc-shaped portions 13, and the arc-shaped portions 13 are integrally formed with the flanges of the first connecting rod 11 and the second connecting rod 12. The radius of the arc-shaped portion 13 is half of the diameter of the first connecting rod 11. If the length from the end of the first connecting rod to the connection end of the arc-shaped portion is 100 cm, then the radius of the arc-shaped plate is 50 cm.
[0033] Connection plates 21 are welded to both ends of the chord steel section 2, and stiffeners 22 are welded to the ends of the chord steel section 2. There are multiple stiffeners 22 and they are spaced circumferentially along the ends of the chord steel section 2. In this embodiment, 4 are provided. By providing the stiffeners 22, local crushing of the concrete 23 at the ends of the chord is avoided during load application.
[0034] There are multiple pressure sensors 9 on the chord. The multiple pressure sensors 9 are respectively bonded to the outer surface of the concrete 23 and the flange of the chord skeleton, so as to facilitate understanding the stress distribution on the chord skeleton and the surface of the concrete 23; a wax seal layer is provided outside the pressure sensor 9 on the chord skeleton, and epoxy resin is coated on the wax seal layer to prevent damage to the strain gauge during concrete 23 pouring; the pressure sensor 9 on the web member is bonded to the flange of the web member.
[0035] As Figure 5 shown, the side connecting the chord member and the web member is defined as surface A, and the remaining sides are sequentially defined as surfaces B, C, and D by rotating clockwise. The pressure sensors arranged on the chord member skeleton are sequentially numbered S1 - SN from top to bottom, and each surface is numbered separately; the pressure sensors on the web member are numbered F1 - FN from the 1st to the Nth. The arrangement of the pressure sensors on the chord member skeleton and on the web member is as Figure 6 shown. A total of 11 strain gauges are arranged on surface B of the chord member skeleton. Due to the complex stress of the gusset plate, strain rosettes are used for S2 - S5 and S9 - S11 at the gusset plate, and the rest are strain gauges and are arranged vertically. Among them, S9 - S11 are used to monitor the strain in the junction area of the gusset plate. Taking the horizontal midline when the chord member is placed vertically during the experiment as the reference, the upper half of the chord member is above the horizontal midline, and the lower half of the chord member is below the horizontal midline. The distances between the pressure sensors on the same surface of the upper half of the chord member skeleton that are not connected to the web member, that is, between the pressure sensors on surfaces B, C, and D, are 450 mm and 300 mm from top to bottom in sequence; the vertical strain gauges are arranged in a denser pattern on the lower half of surfaces B, C, and D of the chord member skeleton, and the spacing of the vertical strain gauges is 150 mm. In an arch bridge structure, the arch design causes the upper chord member to mainly bear tensile force, while the lower chord member bears greater pressure and bending moment. This stress characteristic causes the lower chord member to generate greater stress and deformation under load. By reducing the arrangement spacing in the lower half to set more strain gauges to monitor the stress change, it is used to explore the stress change law of the profiled steel and the influence of the through - reinforcement on the force transfer of the composite joint. S1 - S11 are arranged on surface D of the chord member skeleton, and S1 - S8 are only arranged on the web of surface C. Strain gauges F1 - F3, F4 - F6 are arranged on the three surfaces of the compression web member and the tension web member respectively.
[0036] The strain measuring points of the chord member concrete are as Figure 7 shown. A total of 8 strain gauges are arranged along the axial direction on surfaces B, C, and D of the concrete chord member corresponding to the strain measuring points of the chord member skeleton. The arrangement spacing of the strain gauges is the same as that of the chord member skeleton, which are B1 - B8, C1 - C8, and D1 - D8 respectively. Among them, the No. 1 strain gauge is used to measure the concrete strain affected only by the axial force of the chord member, and the No. 2 - 8 strain gauges are used to measure the concrete strain at different positions on the force transfer path of the profiled steel. Nine additional horizontal strain gauges are arranged on surfaces B and D. The nine horizontal strain gauges are grouped into three groups of three, and are spaced and distributed at the concrete corresponding to the gusset plate, and are used to monitor the transverse strain of the concrete in the area corresponding to the profiled steel flange of the gusset plate. Eleven strain gauges are arranged on surface A, among which A2 - A10 are bi - axial strain gauges, which are used to measure the strain of the concrete around the gusset plate, and can also timely detect the position and time of concrete cracking.
[0037] A total of 9 displacement gauges, namely D1 - D9, are arranged. The layout diagram of the displacement gauges is as Figure 8As shown in the figure. D1 and D9 arranged at the upper and lower end plates of the chord are used to measure the axial deformation of the chord; D8 is arranged at the center of the chord to measure its lateral deflection; D4 and D5 are arranged in the central region where the integral gusset plate meets the concrete to monitor the slip of the integral gusset plate; to measure the axial deformation of the steel web member, finally, two displacement gauges are arranged at the ends of the compressed web member and the tension web member respectively. The displacement gauges at the ends of the compressed web member are D2 and D3 respectively; the displacement gauges at the ends of the tension web member are D6 and D7 respectively. The displacement gauges, strain gauges, and strain rosettes are respectively connected to the static strain tester. The static strain tester uses the Yangzhou Jingming JM3813 instrument, and data is collected in combination with the static strain test system supporting this instrument.
[0038] As Figure 9 shown, the same parts of Example 2 and Example 1 will not be described in detail. The difference lies in that the shear connector is the stud 6, and multiple studs 6 are provided and welded on the outer side of the gusset plate of the chord skeleton. As the shear connector, the stud 6 can firmly connect the chord skeleton and the concrete together, transfer the shear force and tensile force between the chord skeleton and the concrete through the stud 6, so that the two can jointly bear the external load, thereby improving the bearing capacity of the chord structure.
[0039] The same parts of Example 3 and Example 1 will not be described in detail. The difference lies in that the shear connector includes the stud 6 and the through reinforcement 5. Multiple studs 6 are provided and welded on the outer side of the gusset plate of the chord skeleton, and multiple through reinforcements 5 are provided and welded between the two parallel side surfaces of the reinforcement cage. The through reinforcement 5 penetrates the flange of the chord section steel or the first connecting rod. By using the through reinforcement and the stud together as the shear connector, the shear force and tensile force between the chord skeleton and the concrete are effectively transmitted, and the strength of the connection structure is improved.
[0040] A test method for specimens used in the strength detection of joints of steel-concrete composite arch bridges. The experimental device is as Figure 11 shown. The experimental method includes the following steps;
[0041] Step 1: Hoist and fix the chord jack 7 on the frame so that the chord hydraulic jack and the chord are on the same axis; and place and fix the chord of the specimen vertically on the base;
[0042] Step 2: Connect one end of the web member jack 8 to the end of the web member through a flange, and connect the other end of the web member jack 8 to the frame through a flange, and the web member jack 8 and the web member are on the same axis; the web member jack 8 includes a pressure jack 81 at the upper end and a tension jack 82 at the lower end;
[0043] Step 3: Apply a vertically downward pressure to the chord through the chord jack 7, apply a pressure to the upper web member through the pressure jack 81, and apply a tensile force to the lower web member through the tension jack 82;
[0044] Step 4: Gradually increase the pressure of the chord jack 7 until the set value. The set value of the loading pressure this time is 3000 kN, and the load increment per step is 1000 kN; when the chord pressure reaches the set value, keep the axial pressure of the chord unchanged, and synchronously increase the loads applied by the two web member jacks. At the initial stage of loading, increase by 50 kN each time. After the web member enters the plastic range, adopt a continuous and slow loading method until the specimen fails and the load can no longer be increased.
[0045] Take the joint specimen without shear connectors as the comparative example. The comparative example joint is named Joint K0, the joint specimen of Example 1 is Joint K1, the joint of Example 2 is Joint K2, and the joint of Example 3 is Joint K3. Conduct the loading experiment according to the above steps respectively to test the joint performance;
[0046] As Figure 12 shown in the load-web member displacement curves of each composite joint. In the figure, the ordinate is the axial load of the web member, and the abscissa is the axial deformation of the loading end of the web member relative to the chord. Compression is positive and tension is negative. In the legend, "T" and "C" represent the tensile web member and the compressive web member of each composite joint respectively. Define Nu as the ultimate bearing capacity of the composite joint, and the corresponding axial deformation value of the web member is the ultimate deformation Su. The load-displacement curves of the compressive web members of each composite joint consist of two segments: among them, the OA segment is close to a straight line. At this time, the specimen is in the elastic segment, and the axial deformation of the web member is very small. As the axial load of the web member gradually increases, the compressive web member enters the elastic-plastic segment, that is, the AB segment. At this time, the deformation rate of the compressive web member increases rapidly, and the curve shows an obvious deviation until the ultimate load is reached, and the ultimate deformation Su reaches 7.29 - 9.28 mm.
[0047] The load-chord concrete strain curves of the comparative example joint KO and the joints of Examples K1 - K3. In the figure, the Y column represents the concrete measuring points on the flange side of the chord skeleton. The shear connectors act directly on the concrete on this side and the flange plate of the chord section steel. The strain value is the average value of the concrete on both sides of the flange plate.
[0048] The concrete at the Y6 measuring point of each composite joint is subjected to greater force and is located 450 mm below the center of the composite joint. During the entire loading process, the load-strain curves of the Y2, Y3, and Y4 measuring points can be divided into an elastic segment and an elastic-plastic segment, while the remaining measuring points of the chord concrete are in the elastic stage, and the strain basically increases linearly; for the comparative example K0 joint, when the load reaches 1090 kN, cracks appear in the concrete on both sides, resulting in a sudden increase in the strain values of the Y2, Y3, and Y4 measuring points and entering the elastic-plastic segment.
[0049] Load-chord concrete strain curves of each measuring point on the flange side of the composite joints. By comparing the load-concrete strain curves of each composite joint at the same measuring point during the entire loading process, the influence of shear connectors on the force transfer of composite joints is analyzed. At measuring point Y1, the load-strain curves of the chord concrete of the four composite joints basically coincide. Comparing joints K3, K2, K1, and K0, the chord concrete strain of the composite joints with shear connectors is significantly higher than that of the joints without shear connectors. Comparing joints K1 and K2, except that the concrete strains of the two joint specimens are similar at measuring points Y1 and Y6, the concrete strain of K1 is greater than that of K2 at the remaining measuring points. Comparing joints K2 and K3, the load-chord concrete strain curves of each measuring point basically coincide.
[0050] Load-chord steel strain curves of each composite joint. In the figure, the compressive strain is negative and the tensile strain is positive. The ordinate in the figure is the axial load of the web member, and the abscissa is the strain of the chord steel under the action of the axial load of the web member, and the ranges of the horizontal and vertical coordinates are the same. Here, measuring points 1, 2, 4, and 8 on the flange side are selected for analysis. The chord skeleton strains of each composite joint specimen at measuring point Y1 are basically the same. Comparing composite joints K1, K2, K3 with composite joint K0, the chord skeleton strains of the composite joints with shear connectors are significantly lower than those of the joints without shear connectors. The difference in the chord skeleton strains between joints K1 and K0 is about 130 με at measuring point Y4 and about 80 με at measuring point Y8, and the differences in the chord skeleton strains between K2, K3 and K0 are greater at measuring point Y4 than at measuring point Y8.
[0051] From the above tests, it can be seen that when the web members of the specimens of the comparative example and Examples 1-3 are loaded to 2 times the design load, there are no abnormal phenomena in each component of the composite joint, indicating that the bearing capacity of the composite joint meets the design requirements and has a high safety reserve. The final failure modes of the composite joints are all located at the steel web members and the outside of the gusset plates, meeting the design concept of "strong joints, weak members" for composite joints. From the load-strain curves, it can be obtained that the chord concrete of the specimen is subjected to greater force at 450 mm below the joint center, that is, close to the longitudinal bottom end of the gusset plate. Within the range of 1 times the web member width below the joint center, the influence of the through reinforcement on the force transfer between the steel and the concrete is more significant.
[0052] By fabricating the present joint specimen and arranging multiple groups of pressure sensors on the chord truss, chord concrete, and web members respectively, the stress changes of each part of the specimen are monitored through the pressure sensors arranged at different positions, thereby obtaining the stress change curves of each part. Through the stress changes, the parts with larger forces on the chord and web members can be determined. It is found through the fabricated joint specimen that the concrete at the Y6 measuring point of each composite joint is subjected to a larger force, which is located 450 mm below the center of the composite joint. Furthermore, the size range of the gusset plate is determined, that is, the welding position of the first connecting rod of the overall gusset plate and the chord section steel should at least cross the Y6 joint; if the welding parts of the gusset plate and the chord section steel and the steel truss web member are located at the parts with larger forces, it is easy to cause damage to the welding parts. For example, in the existing concrete-filled steel tube rigid truss with circular steel tubes as web members in a composite arch structure, fractures usually occur at the welded joints between the circular steel tubes and the steel tubes in the chord. By controlling the size of the gusset plate, the parts with larger forces are located within the gusset plate range. Since the flange of the gusset plate is an integrally formed whole plate, it can better disperse the force, thereby making the overall bearing capacity of the joint specimen stronger.
[0053] The above are only embodiments of the present invention, and common knowledge such as specific structures and characteristics well known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.
Claims
1. A specimen for testing the strength of a joint of a steel-concrete composite arch bridge, characterized in that: It includes gusset plates, chord steel sections, steel truss web members, and steel reinforcement cages. The chord steel sections and steel truss web members are both H-shaped steels. The gusset plate includes two integrally formed flange plates and a web plate fixedly connecting the two flange plates. The flange plate includes a first connecting rod arranged in a straight line along the longitudinal direction and two second connecting rods arranged on one side of the first connecting rod; the first connecting rod is fixedly connected to the chord steel section to form a chord skeleton. Shear connectors are provided outside the chord skeleton. The steel reinforcement cage surrounds the chord skeleton. The chord skeleton and the steel reinforcement cage are wrapped with concrete to form a chord; the second connecting rod is fixedly connected to the steel truss web member to form a web member. Multiple groups of pressure sensors are detachably connected to the surface of the chord concrete, the chord skeleton, and the web member. The pressure sensors are electrically connected to a static strain tester; one group of pressure sensors is provided on each of the four side surfaces of the chord concrete along the length direction of the chord. The pressure sensor groups located on the chord skeleton are provided with one group each along the length direction of the chord on the two flange plates and the web plate respectively. One pressure sensor is provided on each of the two flange plates and the web plate of the web member, and one pressure sensor is provided on each of the two flange plates of the second connecting rod of the gusset plate.
2. The test piece for detecting the strength of the joint of a steel-concrete composite arch bridge according to claim 1, wherein: The shear connector is a through-bar. There are multiple through-bars, which are fixedly connected between the parallel side surfaces of the steel reinforcement cage, and the through-bars penetrate through the flange of the chord steel section or the first connecting rod.
3. The test piece for detecting the strength of the joint of a steel-concrete composite arch bridge according to claim 1, characterized in that: The shear connector is a stud. There are multiple studs, which are fixedly connected to the outside of the chord skeleton.
4. The test piece for detecting the strength of the joint of a steel-concrete composite arch bridge according to claim 1, wherein: The shear connector includes studs and through-bars. There are multiple studs, which are fixedly connected to the outside of the chord skeleton. There are multiple through-bars, which are fixedly connected between the parallel side surfaces of the steel reinforcement cage, and the through-bars penetrate through the flange of the chord steel section or the first connecting rod.
5. A specimen for testing the strength of a joint of a steel-concrete composite arch bridge according to claim 1, characterized in that: The joint specimen is fabricated in a ratio of 2:1 with the actual bridge joint.
6. A specimen for testing the strength of a joint of a steel-concrete composite arch bridge according to claim 1, characterized in that: Based on the horizontal midline of the chord when it is vertically placed during the experiment, the upper half of the chord is above the horizontal midline, and the lower half of the chord is below the horizontal midline. The distance between multiple pressure sensors on the same side of the lower half of the chord concrete and the lower half of the chord skeleton is 140 - 160 mm, and the distance between multiple pressure sensors on the same side of the upper half of the chord concrete and the upper half of the chord skeleton is 280 - 460 mm.
7. A specimen for testing the strength of a joint of a steel-concrete composite arch bridge according to claim 6, characterized in that: The pressure sensor is a strain rosette located at the flange plate of the gusset plate.
8. A specimen for testing the strength of a joint of a steel-concrete composite arch bridge according to claim 6, characterized in that: There are also 2 - 3 groups of pressure sensors distributed along the width direction of the side surface of the chord concrete near the gusset plate. Each group has 3 - 5 pressure sensors, and the pressure sensors within each group are evenly spaced along the width direction of the chord.
9. The test piece for detecting the strength of a steel-concrete composite arch bridge node according to claim 1, characterized in that: An arc part is provided at the angle between the two second connecting rods and the first connecting rod, and a strain rosette is provided at the arc part between the two second connecting rods.
10. A test piece for detecting the strength of a joint of a steel-concrete composite arch bridge according to claim 1, characterized in that: A wax sealing layer is provided outside the pressure sensor located on the chord skeleton, and epoxy resin is coated on the outside of the wax sealing layer.