Method for obtaining shear resistance of hollow plate beam

Abstract

The present invention discloses a method for obtaining the shear resistance of a hollow plate beam, which includes: Step 1 of obtaining the basic parameters of the concrete and steel bars of an unreinforced hollow plate beam and calculating the shear resistance of the unreinforced hollow plate beam; Step 2 of obtaining the basic parameters of the concrete and steel bars of a hollow plate beam reinforced by a combination of web steel bar implantation and ESS-HPC filling, and calculating the shear resistance due to the filling material ESS-HPC and the additional shear resistance steel bars respectively; Step 3 of constructing a shear resistance calculation model; and Step 4 of obtaining the shear resistance of the reinforced hollow plate beam by the constructed shear resistance calculation model. The method for obtaining the shear resistance of the present invention is simple, and based on information such as the relevant dimensions, reinforcement parameters, and damage degree of the hollow plate beam, it is possible to obtain the shear resistance of the reinforced hollow plate beam without conducting a large number of tests and simulations, saving costs and also saving design time.

Description

Technical Field

[0001] The present invention relates to the technical field of hollow plate beam reinforcement, and particularly to a method for obtaining the shear resistance of a hollow plate beam reinforced by a combination of web reinforcement bar implantation and ESS-HPC filling.

Background Art

[0002] The main causes of diagonal cracks in the web of a hollow plate beam are as follows. During the design process, there is a shortage of stirrups arranged at the ends of the plate beam, there are quality problems in bridge construction, the prestress at the plate ends is insufficient, repeated load actions by vehicles occur during its service life, and also, because the web thickness of the hollow plate beam is thin, due to the action of external fatigue loads, the web concrete is prone to cracking, thereby causing problems such as insufficient shear resistance.

[0003] In order to solve the above problems, according to research, it has been discovered that the slip cast reinforcement method can increase the shear resistance of the hollow plate beam. Currently, the methods for improving the reinforcement problem of the mechanical performance of hollow plate beams mainly include the cross-section enlargement method (usually adding high-performance concrete materials at the top or bottom of the bridge), the adhesive reinforcement method, the prestress reinforcement method, the system change reinforcement method, the beam reduction rib increase method, and the slip cast reinforcement method. The main disadvantages of these reinforcement methods are as follows. 1. In the cross-section enlargement method, it significantly increases the self-weight of the bridge and is disadvantageous for the flexural rigidity. 2. The adhesive reinforcement method has an interface debonding problem. 3. In the prestress reinforcement method, the improvement of shear resistance is not obvious. 4. In the system change reinforcement method and the beam reduction rib increase method, the workload is large and the construction difficulty is high. 5. In the slip cast reinforcement method, it increases the self-weight, the interface is prone to slipping, the bottom plate is opened for slip cast reinforcement, and the interface between the new concrete and the old concrete cannot be treated, the closure technology is immature and the improvement of shear resistance is not obvious.

[0004] In order to improve the shear performance of hollow plate beams, the prior art further proposed a new reinforcement method by combining web reinforcement implantation and ESS-HPC filling (abbreviated as Early-strength Self-compacting Shrinkage-compensating High-performance Concrete, ESS-HPC), which ensures the reinforcement effect and quality. However, the corresponding shear resistance calculation method is lacking, bringing many problems to its popularization and application. Currently, the methods for obtaining the shear resistance of reinforced hollow plate beams mainly focus on the test method, the finite element simulation method, and the formula calculation method. The shear resistance calculation formulas for the hollow plate beams of the above five reinforcement methods are mature. However, for the hollow plate beams reinforced by the new reinforcement method of combining web reinforcement implantation and ESS-HPC filling, the shear resistance calculation is not sufficient. For example, if the conventional calculation method is adopted, the cost of the test method is high, and if the simulation method is adopted, it takes time and effort. In the conventional calculation methods at home and abroad, the superposition theory is used to calculate the shear resistance of the reinforced beam, and the shear resistance of the component is obtained by superimposing the shear resistance of the new material on the shear resistance of the original concrete and steel bars. However, since the influence of the reinforcement length and the damage degree is not considered, the shear resistance cannot be accurately obtained by the above acquisition method.

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method for obtaining the shear resistance of a hollow plate beam in order to solve the technical problem of the prior art that the shear resistance of a hollow plate beam reinforced by a reinforcement method combining web reinforcement implantation and ESS-HPC filling cannot be accurately obtained.

Means for Solving the Problems

[0006] The present invention is a method for obtaining the shear resistance of a hollow plate beam, comprising: Step 1 of obtaining the basic parameters of the concrete and steel bars of the unreinforced hollow plate beam and calculating the shear resistance of the unreinforced hollow plate beam; Step 2 of obtaining the basic parameters of the concrete and steel bars of the hollow plate beam reinforced by the combination of web reinforcement implantation and ESS-HPC filling, and calculating the shear resistance by the filling material ESS-HPC and the shear resistance by the additional shear resistance steel bars during reinforcement; Step 3 of constructing a shear resistance calculation model, V = V c +V sv +V ESS-HPC +V ss 、 In the formula, V c is the shear resistance by concrete, V sv is the shear resistance by stirrups, V ESS-HPC is the shear resistance by the filling material ESS-HPC, V ss is the shear resistance by the additional shear resistance steel bars, which is Step 3; Step 4 of obtaining the shear resistance of the reinforced hollow plate beam by the constructed shear resistance calculation model, and a method for obtaining the shear resistance of the hollow plate beam is provided.

[0007] Furthermore, in the above Step 1, the obtained parameters include the width of the cross-section, the effective height, the concrete cube compressive strength, the design value of the stirrup tensile strength, the stirrup arrangement ratio, and the stirrup spacing distance.

[0008] Furthermore, in the above Step 2, the obtained parameters include the cube compressive strength of ESS-HPC, the ESS-HPC strength grade, the ESS-HPC filling area, the spacing distance of the shear resistance steel bars, the diameter of the shear resistance steel bars, the design value of the tensile strength of the shear resistance steel bars, the length of the shear resistance steel bars, the steel bar arrangement ratio, and the reinforcement length.

[0009] Furthermore, in the above Step 1, the method for obtaining the width of the cross-section and the effective height is as follows: The cross-section of the hollow plate beam is made equivalent to an I-shaped cross-section, and the width and effective height of the equivalent cross-section are obtained as the width and effective height of the cross-section based on the equality of the moment of inertia and the area.

[0010] Furthermore, in the step 3, the calculation formula for the shear resistance force by the filling material ESS-HPC is as follows: V ESS-HPC =ηα ESS-HPC α cv α c f et A c In the formula, η is the influence coefficient of the reinforcement length, α cv is the shear gravity coefficient of concrete in the inclined cross-section, α c is the ESS-HPC strength utilization coefficient, α ESS-HPC is the strengthening coefficient considering the fibers of ESS-HPC, f et and A c are the tensile strength and filling area of ESS-HPC, respectively.

[0011] Furthermore, the calculation formula for the influence coefficient of the reinforcement length is as follows:

Number

[0012] Furthermore, the calculation formula for the shear gravity coefficient of concrete in the inclined cross-section is as follows:

Number

[0013] Furthermore, in the step 3, the specific formula of the shear resistance calculation model is as follows:

Number

[0014] Furthermore, the formula of the shear resistance calculation model further includes a damage coefficient, and the specific formula is as follows.

Equation

Advantages of the Invention

[0015] Beneficial effects of the present invention: In the present invention, the shear resistance of reinforcement, concrete, ESS-HPC and shear resistance reinforcement can be accurately calculated, providing a basis for engineering design and construction, and the combined reinforcement method can be popularized. The hollow plate beam reinforced based on the method of the present invention can effectively prevent the shear failure of the hollow plate beam. Compared with the experimental values, in the present invention, the calculation error can be controlled within 10%, and the accuracy is high.

[0016] The method for obtaining the shear resistance of the present invention is simple. Based on information such as the relevant dimensions of the hollow plate beam, reinforcement parameters, and degree of damage, the shear resistance of the reinforced hollow plate beam can be obtained without conducting a large number of tests and simulations, saving costs and also saving design time.

[0017] In the present invention, during the calculation process of the ESS-HPC shear resistance, the influence coefficient of the reinforcement length is introduced as the reinforcement length influence variable, which can adjust the influence of different reinforcement lengths on the shear resistance of the reinforced hollow plate beam, and the application range of the reinforcement method of the present invention becomes wider.

[0018] In the present invention, by introducing a damage coefficient during the process of obtaining the shear resistance, the calculation formula is more suitable for the actual situation and has a wider application.

[0019] The features and advantages of the present invention are more clearly understood by referring to the drawings. The drawings should not be understood as limiting the present invention and are schematic.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiment for Carrying out the Invention

[0021] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, hereinafter, while combining the drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative labor shall fall within the protection scope of the present invention.

[0022] Hereinafter, the present invention will be further described in combination with specific embodiments. These embodiments are not intended to limit the scope of the present invention, but are only for explaining the present invention. Those skilled in the art should understand that the modifications to various equivalent forms of the present invention are included in the scope defined by the claims attached to this application.

[0023] The present invention is applied to a hollow plate beam reinforcement method by combining web reinforcement implantation and ESS-HPC filling. The construction steps of this combined reinforcement method are as follows.

[0024] Step S1: In the top plate reinforcement areas at both ends of the beam, grooves are opened according to the design requirements.

[0025] The test beam is not integrally reinforced. Instead, as shown in Figure 2, the entire test beam is divided into a hollow plate beam reinforcement part 1, an interface 2, and a non-reinforced part 3. The hollow plate beam reinforcement part 1 has a length in the range of about 1 / 8 to 1 / 4 of the beam length and is blocked at the interface 2 to prevent the ESS-HPC from flowing into the non-reinforced part 3. The blocking material for the interface 2 selects a combination of a flexible material and a rigid material, with the rigid material as the matrix and the flexible material as the filler, to reduce the sudden change in rigidity at the interface and relieve stress concentration. The purpose of grooving is to facilitate the injection of ESS-HPC. The specific injection process is as follows. At the top plates at both ends of the beam, as shown by the small opening 4 and the large opening 5 in Figure 3, the number of grooves to be opened is determined based on the beam length and the reinforcement length. Usually, a small opening 4 with dimensions of 100 mm × 100 mm is opened 200 mm from the end of the beam. When the length of the test beam is small, for example, less than 8 m, a large opening 5 with dimensions of 100 mm × 200 mm is opened 200 mm from the end of the reinforcement part. When the test beam is long, for example, more than 8 m, in addition to the above two openings, one or two large openings 5 are added at equal intervals between the two openings. Also, to increase the adhesion between the ESS-HPC and the inner wall, the inner wall of the grooved hollow plate beam is rough-finished until the coarse aggregate is exposed.

[0026] Step S2: Drill holes in the top plate of the beam according to the position of the shear resistance bars. Before implanting the shear resistance bars, use an air compressor to clean the dust after drilling to enhance the adhesion performance with the concrete.

[0027] Regarding the arrangement of shear resistance reinforcement bars such as the shear resistance reinforcement bar 6 in Fig. 3, mark the corresponding positions in the beam according to the reinforcement planting position diagram. To enhance the integrity of the shear resistance reinforcement bar 6, additional horizontal and vertical reinforcement bars are added to the groove, and together with the shear resistance reinforcement bar 6, a reinforcement framework such as the reinforcement framework 7 in Fig. 3 is formed. To ensure the adhesion performance between the ESS-HPC and the inner wall of the hollow plate beam, since the length of the reinforcement planting was determined to be 280 mm, a circular handle impact drill with a length of 300 mm and a diameter of 10 mm was adopted, and the difference between the drilling position and the preset position must not be greater than 5 mm. Before drilling, mark the drilling depth on the drill to prevent over-drilling or under-drilling and reduce damage to the original structure. When drilling, keep the drill as perpendicular as possible to the test beam and avoid the force-receiving reinforcement bars and stirrups of the original structure. After drilling is completed, first remove a large amount of dust and debris inside the round hole, blow out the dust inside the hole with a compressed air compressor, blow out all the dust in the round hole with a blower, and try to insert the shear resistance reinforcement bar to ensure that it can be inserted into the position of the bottom plate of the hollow plate beam.

[0028] The process of hole cleaning is as follows. It is necessary to perform hole cleaning after the above drilling. First, conduct an insertion trial to inspect the drilling depth and diameter and try to insert the reinforcement bar or bolt to be planted. After the hole depth of the shear resistance reinforcement bar meets the design requirements, blow out the dust in the hole with compressed air, insert a brush to clean the hole wall, and then blow out the dust with compressed air. Repeat the cleaning and blowing at least three times in this way. When drilling a hole with a water drill, wait for the hole to dry before cleaning the hole by the above method to clean and dry the inside of the hole.

[0029] Step S3: Before implanting the reinforcement bar, apply a reinforcement bar planting adhesive to the bottom of the shear resistance reinforcement bar 6, insert the shear resistance reinforcement bar 6 into the bottom plate of the hollow plate beam, fill all other spaces in the hole with the reinforcement bar planting adhesive, and after the strength of the reinforcement bar planting adhesive reaches the requirement, the next construction work can be carried out. To obtain the stress variation of the shear resistance steel bars, strain gauges or sensors are arranged at the middle positions thereof. Before implanting the steel bars, the steel bar implanting adhesive is arranged in the steel bar implanting gun, and 5 mm at the discharge port of the gun is removed to expose the color of the steel bar implanting adhesive used for this construction. A certain amount of the steel bar implanting adhesive is inserted into the top plate of the hollow plate beam. Before inserting the shear resistance steel bar 6, one layer of the steel bar implanting adhesive is applied to its end, and it is slowly rotated and inserted to the bottom of the hole. Finally, the steel bar implanting adhesive in the hole of the top plate is replenished, and all other parts in the hole are filled. After the strength of the steel bar implanting adhesive reaches the requirement, the next construction work is carried out.

[0030] Step S4: Rough finish the inner wall to increase the interfacial adhesion performance between the ESS-HPC and the inner wall concrete. Maintenance of the interface connection: The new concrete should receive force together with the old concrete, and the surface of the old concrete in the cavity in the hole should be subjected to rough finishing treatment to expose the coarse aggregate. The rough finishing range is the range where the electric hammer within the hole range of the top plate contacts, and it is sufficient that the coarse aggregate is exposed and the depth is 3 mm or more. To enhance the reinforcement effect, by adding structural steel bars, they are welded to the inserted shear resistance steel bars, bound with the steel bars, and a steel bar framework is formed.

[0031] Step S5: Before injecting ESS-HPC, it is necessary to support the cavity at the end with a formwork such as the closing formwork 8 in Fig. 4, bind it with the shear resistance reinforcement bars 6, and prevent the outflow of ESS-HPC. To inspect the filling degree of ESS-HPC, for the end of the hollow plate beam, a PVC elbow such as the ESS-HPC inspection port 9 in Fig. 4 is designed at the position of the closing formwork 8 corresponding to the top of the cavity to observe whether the ESS-HPC flows out. If the ESS-HPC flows out from the groove, it proves that the cavity is already sufficiently filled. ESS-HPC is a bagged finished product. Before placing, first wet the outer wall of the mixer and the holes of the hollow plate beam with water, put the required amount of ESS-HPC into the mixer, stir it in a dry state for 1 min, add 2 / 3 of the water, stir it for 3 min, then add all of the remaining 1 / 3 of the water, stir it for another 3 min, and finally slowly and gently inject the ESS-HPC into the hollow plate beam from the holes left in a container such as the slip casting device 10 in Fig. 4. At the same time, pay attention to the closing status of the plugs on both sides and deal with any problems promptly. During the placing process, vibrate the vibrating rod against the side wall of the hollow plate beam for 2 min to ensure that the reinforcement part of the hollow plate beam is sufficiently filled. Sprinkle water for moisture conservation and curing for 24 h immediately after placing, and then cure it in the natural environment for 28 d in the later stage, and then the test can be carried out.

[0032] In the above reinforcement method, ESS-HPC corresponds to an increase in the web thickness of the hollow plate beam and reinforces the ends of the test beam as shown in Figs. 2 to 4.

[0033] In the reinforcement method, by adding shear resistance steel bars, the integrity between the ESS-HPC and the original beam is enhanced, which is equivalent to increasing the web thickness after the reinforcement and the original hollow plate beam component form a whole, and the added shear resistance steel bars are equivalent to increasing the stirrup ratio of the stirrups, thereby increasing the shear resistance of the structure. In addition, the added shear resistance steel bars improve the interfacial adhesion performance between the ESS-HPC and the original beam, and the addition of ESS-HPC improves the cracking load of diagonal cracks in the shear resistance region. The fibers contained in the ESS-HPC play a role in suppressing the deterioration of cracks, reducing the probability of stirrups being eroded, and improving the ductility of the structure.

[0034] In a specific embodiment of the present invention, in order to verify whether the shear resistance of the hollow plate beam after reinforcement meets the design requirements before the reinforcement is carried out, a method for obtaining the shear resistance of the hollow plate beam reinforcement method reinforced by the combination of the above web steel bar implantation and ESS-HPC filling is provided. Specifically, it includes the following steps.

[0035] Step 1: Obtain the basic parameters of the concrete and steel bars of the unreinforced hollow plate beam, and calculate the shear resistance V cs of the unreinforced hollow plate beam.

[0036] The parameters include the width b k of the equivalent cross-section of the hollow plate beam and the effective height h k , the width b and the effective height h0 of the cross-section of the original beam, the concrete cube compressive strength f cu,k , the design value f sv of the stirrup tensile strength, the stirrup ratio ρ sv , and the stirrup spacing s.

[0037] Most of the parameters can obtain relevant test values according to relevant specifications (GB / T50081-2019, GB / T1499.2-2018, GB / T 28900-2012).

[0038] The shear resistance V csis the shear resistance V provided by concrete c and the shear resistance V provided by steel bars sv It is composed of. To obtain it, the "nominal shear area" may be introduced to consider the effect of the flange, and it may be modified according to the JTG 3362-2018 specification. The calculation formula is as follows.

[0039]

Number

[0040] Step 2: Obtain the basic parameters of the concrete and steel bars of the hollow plate beam reinforced by the combination of web reinforcement implantation and ESS-HPC filling, and calculate the shear resistance V ESS-HPC provided by the filling material ESS-HPC and the shear resistance V ss provided by the shear resistance steel bars added during reinforcement.

[0041] The parameters include the cube compressive strength f et of ESS-HPC, the ESS-HPC strength grade, the width b ss and the height h ss to form the filling area A c , the spacing distance s ss between the shear resistance steel bars, the diameter d s , the design value of the tensile strength f ss , the length l ss , the reinforcement ratio ρ ss , and the reinforcement length l s including.

[0042] Step 3: Build a shear resistance calculation model.

[0043]

Number

[0044] The calculation formula for the shear load coefficient α cv of concrete in the inclined section is as follows:

Number

Number

[0045] Step 4: Obtain the shear resistance of the reinforced hollow plate beam by the shear resistance calculation model to be constructed.

[0046] Hereinafter, the method of the present invention will be described by way of examples.

[0047] Example 1: Taking the reinforcement of a hollow plate beam with a rectangular cross-section as an example, in the test, seven reinforced concrete hollow plate beams were designed and tested. The test beams had a length of 4000 mm, a cross-sectional dimension of 300 mm×350 mm, a cavity diameter of 200 mm, a concrete strength grade of C50, an ESS-HPC strength grade of C70, reinforcement lengths of 600 mm, 800 mm, and 1000 mm respectively, and a shear span ratio of 1.85.

[0048] Four longitudinal HRB400 threaded bars with a diameter of 22 mm were arranged at the edge of the tensile flange at the bottom of the hollow plate beam, and three longitudinal HRB400 threaded bars with a diameter of 10 mm were arranged at the edge of the compression flange at the top of the beam. The stirrups were HRB400 grade bars with a diameter of 8 mm and a spacing distance of 200 mm. The shear resistance bars 6 were HRB400 grade bars with a diameter of 8 mm and a length of 280 mm. The concrete cover thickness was 30 mm. The dimensions and steel bar arrangements of the test beams are shown in Fig. 5.

[0049] In the method for detecting the shear resistance of a hollow plate beam reinforced by a combination of web steel bar implantation and ESS-HPC filling, the support seats were simulated simple support beams. The support seat close to the load point was a fixed support seat, and the support seat away from the load point was a sliding support seat. Using the force loading mode, the test beam was loaded twice. The distance between the center of the fixed support seat and the end of the beam was 200 mm, and the distance between the sliding support seat and the end of the beam was 1500 mm.

[0050] Before conducting the destructive test, inspect all test equipment to ensure it is in a normal state. Apply a preload to the test beam, but it must not exceed 5 kN. During the test process, adopt displacement control with a displacement speed of 0.3 mm / min. To accurately obtain the initial crack load, before cracking, the displacement speed is 0.2 mm / min. After cracking until the test beam fails, the displacement speed is 0.3 mm / min. When the width of the diagonal shear crack reaches 3 mm or more, the displacement speed is corrected to 0.5 mm / min, and when the beam fails, the test ends.

[0051] During the test process, the width and development trajectory of cracks are recorded approximately every 10 kN. Displacement gauges are arranged at the positions of L / 8, 2L / 8, 3L / 8, L / 2, 5L / 8, 3L / 4, 7L / 8, L of the test beam and at the load point to measure the variation rule of the deflection of the test beam with the load. Two displacement gauges are arranged at each end of the beam to measure the displacement variation rule of the support seat before and after loading. Two displacement gauges are arranged along the transverse direction to measure the relative slip. And two displacement gauges are arranged at the position of the support seat at the top of the beam to measure the distance from the deflection of the support seat under the action of the load. The strain includes the strain of the concrete and the strain of the steel bars. The strain of the concrete includes the strain of the main beam concrete and the ESS-HPC strain. The strain of the steel bars includes the strain of the tensile steel bars, the strain of the shear resistance steel bars and the strain of the stirrups. The strain of the main beam steel bars is arranged at the mid-span and the load point respectively. The strain of the shear resistance steel bars is arranged at the centroid of the hollow plate beam. The strain of the main beam concrete is arranged at the mid-span position and along the beam height direction. The strain of the ESS-HPC in the compression zone is arranged in the groove. The strain of the plane section is arranged at the load point, the mid-span and 3L / 4. In the flexure-shear region, that is, the region between the load point and the center of the support seat, a certain number of strain gauge rosettes are arranged in the direction perpendicular to the development of the cracks. Based on different load points, the strain of the stirrups arranged on each beam is different. The number of strain gauge rosettes of the test beams with different shear span ratios is different. When the shear span ratio is less than 1.5, two strain gauge rosettes are arranged. When the shear span ratio is greater than that of the test beam with a shear span ratio of 3, five strain gauge rosettes are arranged. When the shear span ratio is greater than 1.5 and less than 3, three strain gauge rosettes are arranged. The strain gauge rosettes are arranged on the line connecting the edge of the support seat and the load point, and 45° strain gauge rosettes are adhered to the surface of the concrete outside the web. Two strain gauges are adhered to the opening at the top of the beam, and a general concrete strain gauge is arranged at 500 mm from the load point to measure the compressive strain. One strain gauge is arranged at the bottom of the beam at the load point and at 1 / 8 of the beam length respectively to measure the cracking strain of the concrete. The layout diagrams of all strains and displacements are shown in Figure 6.

[0052] As can be seen from the above, the damage coefficients Ψ = 1.000, 0.835, 0.780, the design value of the concrete compressive strength f cu = 53 MPa, the design value of the tensile strength of the ribbed bars f sv = 400 MPa, the reinforcement ratio ρ s = 2.93%, the ribbed bar arrangement ratio ρ sv = 0.003%, the width b of the original test beam is 350 mm, the width b k of the equivalent beam is 168 mm, the effective height h0 = 255 mm, the shear span ratio λ = 1.85, the design value of the tensile strength of ESS - HPC f et = 3.5 MPa, the width and height of the equivalent filling are b e = 181 mm and h e = 173 mm respectively, α ESS-HPC where the influence coefficient α ESS-HPC of the ESS - HPC fiber reinforcement is 1.1, the strength utilization coefficient α c of the ESS - HPC is 0.9, the utilization coefficient β of the shear - resisting reinforcement is 0.9, and the reinforcement ratio ρ ss of the shear - resisting reinforcement is 0.003%.

[0053] According to the method of the present invention, the following data can be obtained.

[0054] The shear resistance of the original hollow - plate beam due to concrete and ribbed bars

Number

Number

Number

Number

[0055]

Table 1

[0056] According to the method of the present invention, in the test, for the shearing resistance of 7 test beams, the average value of the ratio of the calculated value to the test value is 1.05, the standard deviation is 0.08, and the coefficient of variation is 0.07. As can be seen from Table 1, the calculation results are almost the same as the test results, and the deviation is very small. As can be seen from this, the method for obtaining the shearing resistance model of the hollow plate beam reinforced by the combination of web reinforcement implantation and ESS-HPC filling proposed in the present invention is more reasonable, the calculation results are closer to the experimental values, and it has strong practicability.

[0057] Due to the limited number of tests, tests were only conducted for a shear span ratio of 1.85 and different reinforcement lengths. In order to expand the application of hollow plate beams reinforced with the combination of this web reinforcement implantation and ESS-HPC filling, simulations were carried out by ABAQUS finite element software for different shear span ratios, ESS-HPC strength grades and damage degrees, and relevant conclusions were obtained. First, simulations were carried out according to the test beams with a shear span ratio of 1.85, compared with the test values, and the error was controlled within 10%. Then, on this basis, simulations were carried out for different shear span ratios, ESS-HPC strength grades and damage degrees. The results are shown in Figures 7 to 9. It can be seen that for different shear span ratio results, the optimal reinforcement length is about 1 / 5 of the beam length. The strength grade of ESS-HPC needs to meet the reinforcement requirements and be 1 to 2 grades higher than the concrete strength grade of the original beam. When the damage degree is smaller than the cracking load of diagonal cracks, the shear stress point cloud image basically does not change. When the damage degree is larger than the cracking load of diagonal cracks, the greater the damage degree, the greater the shear stress in the shear span area under the same load after reinforcement, and the more failure areas there are.

[0058] The embodiments of the present invention have been described in conjunction with the drawings. Those skilled in the art can make various modifications and deformations without departing from the spirit and scope of the present invention, and all such modifications and deformations fall within the scope defined by the appended claims.

Description of Symbols

[0059] 1 Reinforcement part of hollow plate beam 2 Interface 3 Unreinforced part 4 Small opening 5 Large opening 6 Shear resistance reinforcement 7 Steel skeleton 8 Plugging plate 9 ESS-HPC inspection port 10 Slip casting device

Claims

1. A method for obtaining the shear resistance of a hollow plate beam, comprising: Step 1 of obtaining the basic parameters of the concrete and steel bars of an unreinforced hollow plate beam and calculating the shear resistance of the unreinforced hollow plate beam; Step 2 of obtaining the basic parameters of the concrete and steel bars of a hollow plate beam reinforced by a combination of web steel bar implantation and ESS-HPC filling, and calculating the shear resistance due to the filling material ESS-HPC and the shear resistance due to the shear resistance steel bars added during reinforcement, wherein the calculation formula for the shear resistance due to the filling material ESS-HPC is as follows: V ＥＳＳ-ＨＰＣ = ηα ＥＳＳ-ＨＰＣ α ｃｖ α ｃ f ｅｔ A ｃ where η is the influence coefficient of the reinforcement length, and η = -4.54l １ ２ + 7.8l １ - 1.56, and l １ is the reinforcement length, and α ｃｖ is the shear load gravity coefficient of concrete in the diagonal section 【Number 13】 where λ is the shear span ratio, and α ｃ is the ESS-HPC strength utilization coefficient, and α ＥＳＳ－ＨＰＣ is the strengthening coefficient considering the fibers of ESS-HPC, f ｅｔ and A ｃ are the tensile strength and the filling area of ESS-HPC, respectively, The calculation formula for the shear resistance due to the shear resistance steel bars added during reinforcement is as follows: V ｓｓ = 4.5 × 10 －４ λβρ ｓｓ f ｓｓ b ｓｓ h ｓｓ In the formula, λ is the shear span ratio, β is the utilization coefficient of the shear reinforcement bars, and ρ ｓｓ , f ｓｓ , b ｓｓ and h ｓｓ are, respectively, the reinforcement ratio, the tensile strength, the width and height of the ESS-HPC of the shear reinforcement bars added in Step 2, and Step 3 of constructing a shear resistance calculation model; V = V ｃ + V ｓｖ + V ＥＳＳ－ＨＰＣ + V ｓｓ , In the formula, V ｃ is the shear resistance by concrete, V ｓｖ is the shear resistance by the stirrups, V ＥＳＳ－ＨＰＣ is the shear resistance by the filling material ESS-HPC, V ｓｓ is the shear resistance by the additional shear reinforcement in Step 3, and and Step 4 of obtaining the shear resistance of the reinforced hollow plate beam by using the constructed shear resistance calculation model. The method for obtaining the shear resistance of a hollow plate beam is characterized by the above.

2. In the Step 1, the obtained parameters include the width of the cross-section, the effective height, the concrete cube compressive strength, the design value of the tensile strength of the stirrup, the stirrup ratio, and the stirrup spacing distance. The method for obtaining the shear resistance of a hollow plate beam according to Claim 1 is characterized by the above.

3. In the Step 2, the obtained parameters include the cube compressive strength of ESS-HPC, the strength grade of ESS-HPC, the filling area of ESS-HPC, the spacing distance of the shear resistance steel bars, the diameter of the shear resistance steel bars, the design value of the tensile strength of the shear resistance steel bars, the length of the shear resistance steel bars, the steel bar ratio, and the reinforcement length. The method for obtaining the shear resistance of a hollow plate beam according to Claim 1 is characterized by the above.

4. In the Step 1, the method for obtaining the width and the effective height of the cross-section is as follows: Equivalent the cross-section of the hollow plate beam to an I-shaped cross-section, and obtain the width and the effective height of the equivalent cross-section as the width and the effective height of the cross-section based on the equal moment of inertia and area. The method for obtaining the shear resistance of a hollow plate beam according to Claim 2 is characterized by the above.

5. In the Step 3, the specific formula of the shear resistance calculation model is as follows: 【Number 14】 In the formula, P is the reinforcement ratio of the longitudinal reinforcement in the calculated diagonal section, b is the width of the cross-section of the original beam, and h ０ is the effective height of the original beam, f ｃｕ，ｋ is the standard value of the concrete cube compressive strength, λ is the shear span ratio, ρ ｓｖ and f ｓｖ are respectively the reinforcement ratio of the stirrups and the design value of the tensile strength of the stirrups in the diagonal section, η is the influence coefficient of the reinforcement length, α ｃｖ is the shear bearing coefficient of concrete in the diagonal section, α ｃ is the strength utilization coefficient of ESS-HPC, α ＥＳＳ－ＨＰＣ is the strengthening coefficient considering the fibers of ESS-HPC, f ｅｔ and A ｃ are respectively the tensile strength and the filling area of ESS-HPC, β is the utilization coefficient of the shear resistance reinforcement, ρ ｓｓ , f ｓｓ , b ｓｓ and h ｓｓ are respectively the reinforcement ratio, tensile strength, width and height of the ESS-HPC of the shear resistance reinforcement, and a method for obtaining the shear resistance of the hollow plate beam according to claim 1, characterized in that.

6. The formula of the shear resistance calculation model further includes a damage coefficient, and the specific formula is as follows: 【Number 15】 In the formula, Ψ is the damage coefficient. The method for obtaining the shear resistance of a hollow plate beam according to Claim 5 is characterized by the above.

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