Experimental method for detecting strength of steel-concrete combined arch bridge node test piece

Abstract

The invention relates to the technical field of structure testing, and particularly discloses a steel-concrete combined arch bridge joint test piece strength detection experiment method and a test method.The test piece comprises a joint plate, chord member profile steel and a steel truss web member, the joint plate comprises a first connecting rod and two second connecting rods, and the two second connecting rods are located in the middle of the first connecting rod; the two second connecting rods are symmetrical along the length center line of the first connecting rod; the first connecting rods and the chord member profile steel are fixedly connected to form a chord member framework, a reinforcement cage is arranged outside the chord member framework, penetrating steel bars are fixedly connected between the two parallel edges of the reinforcement cage, and the chord member framework and the reinforcement cage are wrapped with concrete and form a chord member; the second connecting rods and the steel truss web members are fixedly connected to form web members, and sensors are bonded to the chord members and the web members. The objective of the invention is to solve the problem that the prior art is lack of means for testing the reliability of a novel arch bridge structure of a steel truss web member concrete combined arch ring.

Description

Technical Field

[0001] The invention relates to the technical field of structural testing, and in particular to a steel-concrete composite arch bridge node specimen strength detection experimental method and a test method thereof. Background Art

[0002] In the field of bridge engineering, improving the spanning capacity of arch bridges is an important topic. At present, super-long span concrete arch bridges are mainly constructed by the rigid skeleton method. The arch ring is a rigid skeleton concrete structure. The rigid skeleton is generally steel tube concrete. The construction process is to first erect and close the steel tube arch frame, then pour concrete in the chord tube to form a steel tube concrete rigid skeleton, and then use it as a support to wrap concrete to form an arch ring. Although the use of a rigid skeleton reduces the self-weight of the overall arch bridge, the amount of concrete used for long-span concrete arch bridges still accounts for a relatively high proportion. The stability of the structure is extremely high during the construction of long-span arch bridges. Due to the heavy weight of concrete, the structure will be more prone to deformation and instability during the construction process, which will affect the construction safety and project quality, resulting in difficult arch ring construction, long construction period and high cost. This has become the main problem restricting the development of concrete arch bridges in the direction of super-long spans.

[0003] In order to effectively reduce the deadweight of concrete arch rings, two methods can usually be used: one method is to use high-strength or ultra-high-strength concrete to replace ordinary-strength concrete, and reduce the deadweight by reducing the cross-section 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 deadweight. For ultra-large-span concrete arch bridges, the main arch of the large-span concrete arch bridge is either a box plate or a box rib. The top and bottom plates are the main force-bearing parts, and the web mainly plays a role in transmitting force. In order to reduce the deadweight, the web plate is thinner. However, in order to increase the cross-sectional efficiency, the cross-sectional height is larger and the web is higher, which makes the on-site concrete pouring construction more difficult. If high-strength or ultra-high-strength concrete is used, the cross-section will be smaller and the construction will be more difficult. Therefore, in the construction process of a certain bridge, an H-shaped steel rigid frame was innovatively used as the web to form a new type of arch bridge structure with a steel truss web-concrete composite arch ring. Since the top and bottom plates are the main stress-bearing parts and the web mainly plays a force transmission role, a steel-concrete composite structure is used in 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. The use of this bridge structure can not only save the pouring of the concrete web and facilitate construction, but also greatly reduce the deadweight of the arch ring.

[0004] At present, although some basic research has been conducted on steel truss web-rigid frame concrete composite arches, they are mainly aimed at composite arch structures with steel tube concrete rigid frames and circular steel tube web members. The construction method is to first build a rigid frame and then cast in situ concrete. The circular steel tubes used as web members are directly welded to the steel tubes in the chord. The nodes between the web members and the concrete top and bottom plates are the weak links in the overall structure. The welding strength of the web members and the chord members becomes the main determinant of the tensile strength of the web members. Based on this, the bridge adopts an H-shaped steel rigid frame, and an integral node plate is used to connect the H-shaped steel chord members in the top and bottom plate concrete with the steel truss web members, which is quite different from the existing composite arch structure. From the perspective of force analysis, the reliable force transmission performance of the integral node is an important factor in the normal operation of the arch bridge. Therefore, how to determine the node range of the connection node between the integral node plate and the steel truss web members and chord steel so that the node can withstand large forces without damage is crucial to the bearing capacity of the new arch bridge structure. The node specimen design has been completed. Figure 1 As shown, the node specimen includes chord steel, web steel and node plate composed of H-shaped steel. The node plate and chord steel are welded to form a chord skeleton. The web steel and node plate are welded to form a web. The chord skeleton is provided with a steel cage and wrapped with concrete to form a chord. It is now necessary to design a node specimen experimental method specifically to conduct strength tests on bridge node structures to determine the node range of the connection nodes of the node specimens, so as to achieve the design of strong nodes and weak components and ensure that the bearing capacity of the new arch bridge structure meets the requirements. Summary of the invention

[0005] In view of the deficiencies in the prior art, the technical problem solved by the present invention is to provide a steel-concrete composite arch bridge node specimen strength detection experimental method and test method thereof to determine the node range of the connection node of the node specimen to achieve the design goal of strong nodes and weak components.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is: a steel-concrete composite arch bridge node specimen strength detection experimental method, comprising the following steps: Step 1: A node specimen is made in proportion according to the actual bridge node, and multiple groups of pressure sensors are arranged on the chord concrete surface, chord skeleton, and web of the node specimen. The pressure sensor adopts a strain type pressure sensor, and the pressure sensor is electrically connected to the static strain tester. The node specimen includes a comparison node of the chord without a shear member and an experimental node with a shear member in the chord; a group of pressure sensors is arranged on each of the four sides of the chord concrete along the length direction of the chord, a group of pressure sensors is arranged on each of the two wing plates and the web along the length direction of the chord, a pressure sensor is arranged on each of the two wing plates and the web of the web, and a pressure sensor is arranged on each of the two wing plates of the web and the web, and a pressure sensor is arranged on each of the two wing plates of the second connecting rod of the node plate; Step 2: Continuously apply pressure to both ends of the chord of the node specimen until the set pressure is reached; Step 3: Apply tension and pressure along the axes of the two webs respectively, and record the pressure change value and stress change value at the same time; Step 4: Adjust the loads applied by the chord jack and the web jack until the specimen fails and the load can no longer be increased.

[0007] The beneficial effects of this program are: Through this experiment, stress and pressure changes are detected for comparison nodes without shear members and experimental nodes with shear members respectively. Thus, through multiple strain-type pressure sensors arranged on the chord concrete surface, chord skeleton and web of the node specimen, the strain data of the chord concrete, chord skeleton and web under load are obtained, so as to determine the maximum stress position of the node specimen; and then determine the design range of the connection node, so as to realize the design concept of "strong node, weak member", and consume energy by utilizing the plastic deformation of the member. When encountering a sudden large load, the yield and deformation of the member can play a buffering role on the whole structure. At the same time, the node can still maintain the basic connection function to avoid the instantaneous overall collapse of the structure, thereby increasing the ductility and seismic performance of the structure.

[0008] Through the strain curve measured in this experiment, it is concluded that the chord concrete of the specimen is subjected to greater stress at 450 mm below the center of the node, that is, close to the longitudinal bottom end of the node plate. Within the range of 1 times the width of the web below the center of the node, the shear connector has a more significant effect on the force transmission between the steel and concrete. When the web of the specimen is loaded to 2 times the design load, there are no abnormal phenomena in the components of the composite node, indicating that the bearing capacity of the composite node meets the design requirements and has a high safety reserve. The final failure mode of the composite node is on the outside of the steel web and the node plate, which meets the design concept of "strong node, weak component" of the composite node.

[0009] Furthermore, the node specimens are made in a ratio of 2:1 to the actual bridge nodes. This ratio is used to make the size of the actual bridge nodes as close as possible while meeting laboratory testing conditions, so that the experimental results at the test site can more truly reflect the stress conditions at the node and the structural strength of the node.

[0010] Furthermore, the shear member of the experimental node is any one or both of a through steel bar that penetrates the flange of the chord frame and a bolt that is fixedly connected to the outside of the chord frame. Through this experiment, the mechanical properties of the node specimen itself and the influence of setting various shear members on the mechanical properties of the node specimen can be obtained, so that appropriate shear members can be selected to improve the node specimen; avoiding blind improvement and adding too many shear members, which will lead to increased manufacturing costs.

[0011] Furthermore, the strain type pressure sensors located at the wing plate of the node plate all use strain gauges. Since the forces at the node plate are complex during the test loading, the strain gauges can be used to measure more complex stress change data.

[0012] Furthermore, taking the chord rod along the vertically placed transverse center line as a reference, the part above the transverse center line is the upper half of the chord rod, and the part below the transverse center line is the lower half of the chord rod. The spacing between multiple pressure sensors located on the same surface of the lower half of the chord rod concrete and the lower half of the chord rod frame is 140-160mm, and the spacing between multiple pressure sensors located on the same surface of the upper half of the chord rod concrete and the upper half of the chord rod frame is 280-460mm.

[0013] In the arch bridge structure, the arch design makes the upper chord mainly bear tension, while the lower chord bears greater pressure and bending moment. This force characteristic causes the lower chord to produce greater stress and deformation under load. By reducing the spacing in the lower half and setting more strain gauges to monitor the force changes, more detailed stress change data can be obtained, which is convenient for the subsequent structural strength analysis of the node specimens.

[0014] Furthermore, 2-3 pressure sensor groups are distributed along the width direction of the chord on the side of the chord near the node plate, each group is provided with 3-5 pressure sensors, and the pressure sensors in each group are evenly spaced along the width direction of the chord. By setting the width direction sensor, that is, the transverse sensor when the chord is placed vertically in the experiment, it is used to monitor the transverse strain of the concrete around the node plate wing.

[0015] Furthermore, the pressure sensor located on the chord frame is provided with a wax seal layer, and the wax seal layer is coated with epoxy resin, so as to prevent the strain gauge from being damaged during concrete pouring.

[0016] Furthermore, the step 5 adopts a step-by-step loading method, in which before the estimated load reaches 55%-65%, the estimated limit load is increased by 10%-15% at each stage, and after the estimated load reaches 55%-65% or when obvious deformation occurs, the estimated limit load is increased by 3%-5% at each stage.

[0017] The initial load is quickly increased to the preset starting load level, and then it is switched to a slow and fine incremental loading mechanism. This loading method not only ensures the test efficiency, but also greatly improves the control accuracy and safety of the test. The initial rapid loading helps to quickly cross the linear response area of ​​the material, while the subsequent gentle increase ensures that the change of loading force is gentle and controllable, avoiding unnecessary stress concentration or sudden damage of the specimen caused by sudden force values. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1It is a three-dimensional diagram of the node specimen of the present invention.

[0019] Figure 2 This is the front view of the K1 node.

[0020] Figure 3 This is the cross-sectional view of the K1 node.

[0021] Figure 4 Schematic diagram of the node plate.

[0022] Figure 5 Schematic diagram of each side of the chord.

[0023] Figure 6 Schematic diagram of the layout of the chord skeleton and web pressure sensors.

[0024] Figure 7 Layout diagram of the chord concrete pressure sensor.

[0025] Figure 8 This is the layout diagram of the displacement meter.

[0026] Fig. 9 This is a cross-sectional view of the specimen of Example 2.

[0027] Fig.10 This is a cross-sectional view of the specimen of Example 3.

[0028] Fig.11 Schematic diagram of load loading.

[0029] Fig.12 It is the load-web member displacement curve of K0-K3 node.

[0030] Fig.13 This is the load-chord concrete strain curve at the K0-K3 node.

[0031] Fig.14 The load-chord concrete strain curves of each measuring point on the flange side of the K0-K3 node. Fig.15 K0-K3 node load-chord steel strain curve DETAILED DESCRIPTION The following is further described in detail through specific implementation methods: The figure marks in the drawings of the specification include: node plate 1, first connecting rod 11, second connecting rod 12, arc portion 13, chord steel 2, connecting plate 21, reinforcing rib 22, concrete 23, steel truss web 3, steel cage 4, through steel bar 5, bolt 6, chord jack 7, web jack 8, pressure jack 81, tension jack 82, pressure sensor 9.

[0032] Experimental setup Fig.11As shown, the chord jack 7 is hoisted and fixed on the frame so that the chord jack 7 and the chord of the node specimen are located on the same axis; one end of the web jack 8 is connected to the end of the web of the node specimen through a flange, and the other end of the web jack is connected to the frame through a flange, and the web jack and the web are located on the same axis; the web jack includes a pressure jack 81 connected to the upper end web and a tension jack 82 connected to the lower end web.

[0033] A steel-concrete composite arch bridge node specimen strength test method comprises the following steps: Step 1: A node specimen is made in proportion according to the actual bridge node, and multiple groups of pressure sensors are arranged on the chord concrete surface, chord skeleton, and web of the node specimen. The pressure sensor adopts a strain type pressure sensor, and the pressure sensor is electrically connected to the static strain tester. The node specimen includes a comparison node of the chord without a shear member and an experimental node with a shear member in the chord; a group of pressure sensors is arranged on each of the four sides of the chord concrete along the length direction of the chord, a group of pressure sensors is arranged on each of the two wing plates and the web along the length direction of the chord, a pressure sensor is arranged on each of the two wing plates and the web of the web, and a pressure sensor is arranged on each of the two wing plates of the web and the web, and a pressure sensor is arranged on each of the two wing plates of the second connecting rod of the node plate; Step 2: Continuously apply pressure to both ends of the chord of the node specimen until the set pressure is reached; the set value of the chord pressure for this loading is 3000kN, and the load increment for each step is 1000kN; when the chord pressure reaches the set value, the axial pressure of the chord is kept unchanged; Step 3: Apply tension and pressure along the axes of the two webs respectively, and record the pressure change value and stress change value at the same time; Step 4: Adjust the load applied by the chord jack and the web jack. In the initial stage of loading, increase the load by 50KN each time. After the web enters the plastic range, use continuous slow loading until the specimen is destroyed and the load can no longer be increased.

[0034] The comparison node produced in this embodiment is named K0, and the experimental nodes produced include the K1 node with only through-steel as the shear connector, the K2 node with only stud as the shear connector, and the K3 node with stud and through-steel as the shear connector; Figure 2-3 As shown, the K1 node has multiple through-steel bars which are welded between the two parallel sides of the steel cage, and the through-steel bars penetrate the flange of the chord skeleton; Fig. 9 As shown, the K2 node has multiple bolts and is welded to the outside of the node plate of the chord frame; Fig.10As shown, a plurality of bolts are provided at the K3 node and welded to the outer side of the node plate of the chord frame, a plurality of through steel bars are provided and welded between two parallel side surfaces of the steel cage, and the through steel bars penetrate the flange of the chord frame; the height of the bolts is greater than the height of the through steel bars.

[0035] There are multiple pressure sensors 9 for the chord, which are respectively bonded to the outer surface of the concrete 23 and the flange of the chord skeleton, so as to facilitate understanding of the stress distribution of the chord skeleton and the surface of the concrete 23; the pressure sensor 9 located on the chord skeleton is provided with a wax seal layer, and the wax seal layer is coated with epoxy resin to prevent the strain gauge from being damaged during the pouring of the concrete 23; the pressure sensor 9 of the web is bonded to the flange of the web. The pressure sensor 9 uses any one or two of a resistance strain gauge, a strain rosette, and a capacitive strain pressure sensor.

[0036] like Figure 5 As shown in the figure, the side where the chord and the web are connected is defined as the A side, and the remaining sides are defined as the B, C, and D sides in a clockwise rotation. The pressure sensors arranged on the chord skeleton are numbered S1-SN from the first to the Nth from top to bottom, and each side is numbered separately; the pressure sensors on the web are numbered F1-FN from the first to the Nth. The arrangement of the pressure sensors on the chord skeleton and on the web is shown in the figure. Figure 6 As shown in the figure, 11 strain gauges are arranged on the B surface of the chord skeleton. Due to the complex stress of the node plate, strain rosettes are used at S2-S5 and S9-S11 of the node plate, and strain gauges are used for the rest. S9-S11 is used to monitor the strain of the node plate junction area. Taking the transverse midline of the chord placed vertically during the experiment as the reference, the part above the transverse midline is the upper half of the chord, and the part below the transverse midline is the lower half of the chord. The spacing between the pressure sensors located on the same surface of the upper half of the chord skeleton that is not connected to the web member, that is, on the B, C, and D surfaces, is 450mm and 300mm from top to bottom respectively; the strain gauges in the lower half of the B, C, and D surfaces of the chord skeleton are densely arranged, and the vertical strain gauge spacing is 150mm. In the arch bridge structure, the arch design makes the upper chord mainly bear tension, while the lower chord bears greater pressure and bending moment. This stress characteristic causes the lower chord to produce greater stress and deformation under load. By reducing the spacing in the lower half and setting more strain gauges to monitor the stress changes, it is used to explore the stress change law of the steel section and the influence of the penetration discipline on the force transmission of the composite node. S1-S11 is arranged on the D surface of the chord skeleton, and S1-S8 is arranged only on the web on the C surface. Strain gauges F1-F3 and F4-F6 are arranged on the three surfaces of the compression web and the tension web, respectively.

[0037] The strain measurement points of the chord concrete are as follows: Figure 7As shown in the figure, 8 strain gauges are arranged on the three surfaces of the concrete chord B, C, and D along the axial direction corresponding to the strain measurement points of the chord skeleton. The spacing of the strain gauges is consistent with the chord skeleton, which are B1-B8, C1-C8, and D1-D8 respectively. Among them, strain gauge No. 1 is used to measure the concrete strain affected only by the axial force of the chord, and strain gauges No. 2-8 are used to measure the concrete strain at different positions on the force transmission path of the steel. 9 transverse strain gauges are added on the B and D surfaces. The 9 transverse strain gauges are divided into three groups of 3 and are distributed at intervals in the concrete corresponding to the node plate to monitor the transverse strain of the concrete in the node plate area corresponding to the steel flange. 11 strain gauges are arranged on the A surface, of which A2-A10 are bidirectional strain gauges, which are used to measure the concrete strain around the node plate, and the concrete cracking position and cracking time can be discovered in time.

[0038] There are 9 displacement meters, namely D1-D9, arranged in total. The displacement meter arrangement diagram is shown in the figure below: Figure 8 As shown. 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 area of ​​the junction between the integral node plate and the concrete to monitor the slip of the integral node plate; to measure the axial deformation of the steel web, two displacement meters are arranged at the ends of the compression web and the tension web respectively, and the displacement meters at the ends of the compression web are D2 and D3 respectively; the displacement meters at the ends of the tension web are D6 and D7 respectively. The displacement meter, strain gauge, and strain rosette are connected to the static displacement tester respectively. The static strain tester uses the Yangzhou Jingming JM3813 instrument, combined with the static strain test system supporting the instrument to collect data.

[0039] like Fig.12 The load-web member displacement curves of each composite node are shown in the figure. The ordinate is the axial load of the web member, and the abscissa is the axial deformation of the loaded end of the web member relative to the chord. Compression is positive and tension is negative. "T" and "C" in the legend represent the tension web member and compression web member of each composite node respectively. Nu is defined as the ultimate bearing capacity of the composite node, and the corresponding axial deformation value of the web member is the ultimate deformation Su. Fig.13 It can be seen that the load-displacement curve of the compressed web member of each combined node consists of two sections: the OA section is close to a straight line, at this time the specimen is in the elastic section, and the axial deformation of the web member is very small. As the axial load of the web member gradually increases, the compressed web member enters the elastic-plastic section, that is, the AB section. At this time, the rate of increase of the deformation of the compressed web member accelerates, and the curve shows an obvious deviation until the ultimate load is reached, and the ultimate deformation Su reaches 7.29~9.28mm.

[0040] like Fig.13The load-chord concrete strain curves of the comparative node KO and the nodes K1-K3 of the embodiment. The Y column in the figure represents the concrete measuring point on the flange side of the chord skeleton. The shear connector directly acts on the concrete on this side and the chord steel flange plate. The strain value is the average value of the concrete on both sides of the flange plate.

[0041] The concrete at the Y6 measuring point of each combined node is subjected to greater stress and is located 450mm below the center of the combined node. During the entire loading process, the load-strain curves of the Y2, Y3 and Y4 measuring points can be divided into elastic and elastoplastic sections, while the remaining measuring points of the chord concrete are in the elastic stage, and the strain increases basically linearly; for the comparative K0 node, when the load was loaded to 1090kN, cracks appeared in the concrete on both sides, causing the strain values ​​of the Y2, Y3 and Y4 measuring points to increase sharply and enter the elastoplastic section.

[0042] Fig.14 The load-concrete strain curve of the chord rod at each measuring point on the flange side of the composite node is compared with the load-concrete strain curve of each composite node at the same measuring point during the entire loading process to analyze the influence of the shear connector on the force transmission of the composite node. Fig.14 It can be seen that at the Y1 measuring point, the load-strain curves of the chord concrete of the four combined nodes are basically the same; compared with the K3, K2, K1 and K0 nodes, the chord concrete strain of the combined node with shear connector is significantly higher than that of the node without shear connector; compared with the K1 and K2 nodes, except for the two node specimens at the Y1 and Y6 measuring points, the concrete strains of the other measuring points K1 are all greater than K2. Compared with the K2 and K3 nodes, the load-chord concrete strain curves of each measuring point are basically the same.

[0043] Fig.15 The load-chord steel strain curve of each combined node, in which the compressive strain is negative and the tensile strain is negative. 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 axial load of the web member, and the range of the abscissa and ordinate are consistent. Here, the side points 1, 2, 4, and 8 on the flange side are selected for analysis. Fig.15 It can be seen that the chord skeleton strains of each composite node specimen at the Y1 measuring point are basically the same. Comparing the K1, K2, and K3 composite nodes with the K0 composite node, the chord skeleton strains of the composite nodes with shear connectors are significantly lower than those of the nodes without shear connectors. The chord skeleton strains of the K1 and K0 composite nodes differ by about 130με at the measuring point Y4 and about 80με at the measuring point Y8, and the chord skeleton strain differences of K2, K3, and K0 at the measuring point Y4 are all greater than those at the measuring point Y8.

[0044] The above tests show that the failure mode of the composite node without shear connectors is the cracking of the concrete on the steel flange side, and finally the local buckling failure of the node plate of the compression web; the failure modes of the composite nodes K1-K3 with shear connectors are the same, all of which are the overall bending of the compression web, and the local buckling failure of the node plate and the compression web, and the ultimate bearing capacity is similar.

[0045] When the web member of the comparison node K0 and the experimental nodes K1-K3 was loaded to 2 times the design load, there was no abnormality in the components of the composite node, indicating that the bearing capacity of the composite node meets the design requirements and has a high safety reserve. The final failure mode of the composite node is on the outside of the steel web member and the node plate, which meets the design concept of "strong node, weak component" of the composite node. From the load-strain curve, it can be seen that the chord concrete of the specimen is subjected to greater force at 450mm below the center of the node, that is, close to the longitudinal bottom end of the node plate. Within the range of 1 times the width of the web member below the center of the node, the through-steel has a more significant effect on the force transmission between the steel section and the concrete.

[0046] Through this experiment, stress and pressure changes are detected for comparison nodes without shear members and experimental nodes with shear members respectively. Thus, through multiple strain-type pressure sensors arranged on the chord concrete surface, chord skeleton and web of the node specimen, the strain data of the chord concrete, chord skeleton and web under load are obtained, so as to determine the maximum stress position of the node specimen; and then determine the design range of the connection node, so as to realize the design concept of "strong node, weak member", and consume energy by utilizing the plastic deformation of the member. When encountering a sudden large load, the yield and deformation of the member can play a buffering role on the whole structure. At the same time, the node can still maintain the basic connection function to avoid the instantaneous overall collapse of the structure, thereby increasing the ductility and seismic performance of the structure.

[0047] Through this experimental method, the specimen is loaded with loads. The loaded pressure or tension is located on the same axis as the load-bearing component to ensure uniform force, and can effectively simulate the force mode of the bridge structure in the real state, thereby verifying the reliability of the structural strength. At the same time, through this experiment, the mechanical properties of the node specimen itself can be obtained, as well as the influence of setting various shear members on the mechanical properties of the node specimen, so that appropriate shear members can be selected to improve the node specimen; avoid blindly improving and adding too many shear members, which will increase the manufacturing cost.

[0048] In Example 2, the same parts as Example 1 are not described in detail. The difference is that the step-by-step loading method adopted in step 4 is to load step by step by increasing the estimated limit load by 10% at each stage before the estimated load reaches 60%. After the estimated load reaches 60% or when obvious deformation occurs, the step-by-step loading is performed by increasing the estimated limit load by 5% at each stage until the specimen node is destroyed. This loading method can increase the loading speed and load slowly in the subsequent process to avoid the specimen being destroyed due to excessive changes in the loading force, and at the same time improve the loading accuracy.

[0049] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A steel-concrete composite arch bridge node specimen strength test method, characterized in that: The steps include: Step 1: A node specimen is made in proportion according to the actual bridge node, and multiple groups of pressure sensors are arranged on the chord concrete surface, chord skeleton, and web of the node specimen. The pressure sensor adopts a strain type pressure sensor, and the pressure sensor is electrically connected to the static strain tester. The node specimen includes a comparison node of the chord without a shear member and an experimental node with a shear member in the chord; a group of pressure sensors is arranged on each of the four sides of the chord concrete along the length direction of the chord, a group of pressure sensors is arranged on each of the two wing plates and the web along the length direction of the chord, a pressure sensor is arranged on each of the two wing plates and the web of the web, and a pressure sensor is arranged on each of the two wing plates of the web and the web, and a pressure sensor is arranged on each of the two wing plates of the second connecting rod of the node plate; Step 2: Continuously apply pressure to both ends of the chord of the node specimen until the set pressure is reached; Step 3: Apply tension and pressure along the axes of the two webs respectively, and record the pressure change value and stress change value at the same time; Step 4: Adjust the loads applied by the chord jack and the web jack until the specimen fails and the load can no longer be increased.

2. The strength test method of a steel-concrete composite arch bridge node specimen according to claim 1 is characterized by: The node specimen and the actual bridge node are manufactured in a ratio of 2:

1.

3. The strength test method of a steel-concrete composite arch bridge node specimen according to claim 1 is characterized by: The shear member of the test node is any one or both of a through steel bar penetrating the flange of the chord frame and a bolt fixedly connected to the outside of the chord frame.

4. The strength test method of a steel-concrete composite arch bridge joint specimen according to claim 1 is characterized by: Taking the chord rod along the vertically placed transverse center line as a reference, the part above the transverse center line is the upper half of the chord rod, and the part below the transverse center line is the lower half of the chord rod. The spacing between the multiple pressure sensors located on the same surface of the lower half of the chord rod concrete and the lower half of the chord rod frame is 140-160mm, and the spacing between the multiple pressure sensors located on the same surface of the upper half of the chord rod concrete and the upper half of the chord rod frame is 280-460mm.

5. The strength test method of a steel-concrete composite arch bridge node specimen according to claim 4 is characterized by: The strain type pressure sensors located at the node plate wing plate all adopt strain rosettes.

6. The strength test method of a steel-concrete composite arch bridge joint specimen according to claim 4 is characterized by: The side of the chord close to the node plate is also provided with 2-3 pressure sensor groups along the length direction of the chord, each group is provided with 3-5 pressure sensors, and the pressure sensors in each group are evenly spaced along the width direction of the chord.

7. The strength test method of a steel-concrete composite arch bridge joint specimen according to claim 4 is characterized by: The pressure sensor located on the chord frame is provided with a wax sealing layer on the outside, and the wax sealing layer is coated with epoxy resin on the outside.

8. The strength test method of a steel-concrete composite arch bridge joint specimen according to claim 1 is characterized by: The step 5 adopts a step-by-step loading method. Before the estimated load reaches 55%-65%, the estimated limit load is increased by 10%-15% at each level. After the estimated load reaches 55%-65% or when obvious deformation occurs, the estimated limit load is increased by 3%-5% at each level.

Images