A method for modeling a scaled-down model of a large-span prestressed concrete beam

Abstract

This invention discloses a method for modeling a scaled-down model of a large-span prestressed concrete beam. This method achieves the stress characteristics of the actual beam by establishing a scaled-down model beam. Specific operations include: proportionally reducing the geometric dimensions of the actual beam while ensuring the same reinforcement ratio for ordinary steel bars; deriving the prestressing tendon curve equation in the actual beam; determining the prestressing tendon equation in the model using the same method, without considering prestress loss, to ensure the same internal force effect of prestressing in both the actual beam and the model; determining the number of prestressing tendons and the tension control stress in the model; then, considering prestress loss analysis to determine whether the effective prestressing effect is the same in the actual beam and the model beam; if not, returning to the derivation method to re-determine the prestressing tendon equation in the model, repeating the above steps to ensure the same effective prestressing effect; after successful calculation of the scaled-down model, fabricating the scaled-down model beam. The scaled-down model of the large-span prestressed concrete beam obtained by this method facilitates relevant experimental tests on large-span prestressed concrete beams, ensuring experimental accuracy.

Description

Technical Field

[0001] This invention relates to the field of structural performance analysis technology for large-span prestressed concrete beams, specifically to a method for modeling a scaled-down model of a large-span prestressed concrete beam. Background Technology

[0002] In modern large-scale commercial buildings, factories, railway stations, spacious residential buildings, and simply supported concrete bridges, prestressed concrete beams are often used as the main load-bearing components, depending on the building's function. When the span exceeds 20m, it is called a large-span prestressed concrete beam. Generally, large-span or precast components are tensioned using the post-tensioning method. With continuous research by scientists, various methods for assessing the safety of prestressing have been established, mainly including theoretical prediction, experimental analysis, and in-situ testing. While theoretical prediction methods show good economic performance in practical applications, the accuracy of their prediction models is generally limited. In-situ testing methods show good accuracy, but their operability, practicality, economy, and time constraints are average. Experimental analysis methods show good performance in terms of accuracy, operability, and economy.

[0003] Experimental analysis, characterized by its focus on single-factor consideration of independent variables under specific environmental and experimental conditions, often has limitations for practical analysis and research, failing to accurately represent the complex stress effects within a prestressed concrete beam under a unified structural framework. Therefore, it is necessary to develop a scaled-down modeling method for large-span prestressed concrete beams that facilitates relevant experimental testing, thus ensuring experimental accuracy. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a modeling method for a scaled-down model of a large-span prestressed concrete beam, which facilitates the relevant experimental testing of the large-span prestressed concrete beam to meet the accuracy of the experiment, and solves the problem that the prototype beam is too large and it is not convenient to carry out relevant experimental testing when conducting experimental testing and analysis of large-span prestressed concrete beams.

[0005] The present invention solves the above-mentioned technical problems by means of the following technical solution:

[0006] This invention discloses a method for modeling a scaled-down model of a large-span prestressed concrete beam. The method achieves the stress characteristics of an actual beam by establishing a scaled-down model beam. The steps for fabricating the scaled-down model beam are as follows:

[0007] S1 determines the actual beam's proportional dimensions and the reinforcement ratio of the tension and compression zones, and establishes a proportionally scaled concrete beam based on the above parameters.

[0008] S2 establishes a plane coordinate system for the post-tensioned prestressed steel reinforcement of the actual beam;

[0009] S3 derives the curve equation of the prestressed steel reinforcement of the actual beam based on the coordinates and slope of the actual beam end, mid-span, and inflection point.

[0010] S4 calculates the first batch of prestress loss of the actual beam using the above equation;

[0011] S5 calculates the effective mid-span prestress of the actual beam based on the above-mentioned losses;

[0012] Based on the above curve equation derivation method, S6 derives the prestressed steel curve equation of the scaled-down model beam by assuming the coordinates of the prestressed steel beam ends, mid-span, and inflection points of the scaled-down model beam.

[0013] S7 determines the number of prestressed tendons and the tension control stress of the scaled-down model beam based on the prestressed reinforcement curve equation.

[0014] S8 calculates and determines whether the effective prestressing effect after the first batch of loss is the same for the scaled model beam and the actual beam. If not, return to S6 to repeat the trial calculation to ensure that the mid-span stress caused by prestressing is the same for the scaled model beam and the actual beam.

[0015] After the S9 scaled-down model calculation is successful, the actual scaled-down model beam is made. Ordinary reinforcing bars and corrugated pipes are laid in the scaled-down concrete beam according to the scale ratio. Prestressed steel bars and cement grout are placed in the corrugated pipes. Anchors are fixed at both ends of the prestressed steel bars. Displacement gauges are placed against the center wire of the prestressed steel bars and the lower side of the beam mid-span and the upper side of the beam end.

[0016] After the internal concrete components are arranged in S10, concrete is poured. The concrete grade is the same as or from the same batch as the actual beam grade. The scaled-down model is cured after pouring. When the concrete strength reaches 75% of the strength grade, strain gauges are attached to the four sides of the mid-span of the scaled-down concrete beam, and displacement gauges are installed according to the positioning. Then, the prestressed steel bars are threaded and tensioned. The required number of prestressed steel bars and the tensioning control stress are determined according to the above. During and after the tensioning process, a dynamic signal acquisition instrument is used to continuously collect data from the attached strain gauges and installed displacement gauges.

[0017] S11 When the strength of concrete reaches 100% of the strength grade, a bending test is conducted on the scaled-down model beam to achieve a certain experimental purpose.

[0018] In S6, the following assumptions are made before deriving the prestressed steel reinforcement curve equation for the scaled-down model beam:

[0019] (1) The plane section assumption is followed when calculating the normal section of prestressed concrete flexural members;

[0020] (2) The tensile strength of concrete is not considered;

[0021] (3) The equation of the curved prestressed tendon is quadratic;

[0022] (4) Prestressed steel has a good bond strength with concrete, and the strain of steel caused by load is the same as the strain of concrete at the same location.

[0023] In step S1, the proportional dimensions of the actual beam are the length, width, and height of the actual beam; the reinforcement ratio of the tension and compression zone is the ordinary steel reinforcement ratio of the compression and tension zones in the concrete beam; establishing a proportionally scaled concrete beam means that the length, width, and height of the scaled concrete beam are the same as those of the actual beam, and the ordinary steel reinforcement ratio is the same as that of the actual beam.

[0024] In step S2, establishing a plane coordinate system for the post-tensioned curved prestressed steel bars of the actual beam means establishing an xoy plane coordinate system on the plane where the planar post-tensioned curved prestressed steel bars are located. At this time, the origin of the coordinate system is on the surface of the concrete beam at the mid-span section, the x-axis is parallel to the beam length direction, and the positive y-axis is the concave direction of the prestressed tendon.

[0025] Step S3, deriving the curve equation of the prestressed steel reinforcement, specifically includes establishing the curve equation as if the prestressed steel reinforcement curve is a two-segment quadratic parabola. Based on the coordinate system established in step S2, the coordinates of the prestressed steel reinforcement beam end, mid-span, inflection point, and slope are determined. The curve equation is then derived as follows:

[0026] Crossing the middle section:

[0027] Beam end section: y1(x) is the equation of the prestressed tendon curve at the mid-span; y2(x) is the equation of the prestressed tendon curve at the beam end; δ1 is the Y-axis coordinate of the mid-span point of the curve; δ2 is the Y-axis coordinate of the beam end point of the curve; x d is the X-axis coordinate of the inflection point; l is the length of the beam.

[0028] Step S4, which involves calculating the first batch of prestress loss of the actual beam using the above equation, specifically includes calculating the first batch of prestress loss value of the actual beam. This calculation is performed in accordance with Article 4.3 of the "Code for Design of Prestressed Concrete Structures" JGJ 369-2016.

[0029] Step S5, which involves calculating the effective mid-span prestress of the actual beam based on the aforementioned losses, specifically includes calculating the effective mid-span prestress of the actual beam. This calculation is performed in accordance with Article 7.1.4 of the Code for Design of Concrete Structures GB 50010-2010.

[0030] Step S6, which involves deriving the curve equation based on the above equation derivation method and assuming the coordinates of the prestressing tendon ends, mid-span, and inflection points of the scaled-down model, specifically includes deriving the prestressing curve equation in the scaled-down model beam by assuming the coordinates of the prestressing tendons at the beam ends and mid-span points, and the X-axis coordinates of the inflection points determined according to the actual beam proportions, using the method in step S3.

[0031] Step S7, which involves determining the number of prestressing tendons and tension force of the scaled-down model beam based on the prestressing tendon curve equation, specifically includes calculating the stress of ordinary steel bars at the mid-span of the actual beam based on the tension control stress, ensuring that the stress of ordinary steel bars is the same, thereby determining the required tension control stress and number of prestressing tendons for the scaled-down model.

[0032] In step S8, the calculation and judgment of whether the effect of the effective prestress after the first batch of prestress loss in the scaled model and the actual beam is the same is required. If not, the calculation is repeated in step S6. Specifically, this includes calculating the first batch of prestress loss in the scaled model based on the curve equation of the prestressing tendons and the tension control stress determined in steps S6 and S7, according to the formula in step S4, and judging the effect of the effective prestress after the first batch of prestress loss in the scaled model and the actual beam. If they are the same, the model calculation is successful. If the difference is too large, the calculation needs to be repeated in step S6.

[0033] This invention provides a modeling method for scaled-down large-span prestressed concrete beams. It comprehensively considers various factors, including the model's length-width-height ratio, reinforcement ratio in the tension and compression zones, the influence of the actual beam's self-weight, and the impact of prestressed steel loss measured by displacement gauges and monitored by strain gauges. This ensures the scaled-down model closely resembles the actual beam's stress state, guaranteeing experimental accuracy. The scaled-down large-span prestressed concrete beam model established using this method effectively reflects the stress characteristics of the prototype beam, is easy to fabricate and use in experiments, and has the advantage of being networked with dynamic data acquisition instruments for both short-term and long-term experimental testing. Attached Figure Description

[0034] Figure 1 The main view of the cross-section of the scaled-down model beam established by the method of the present invention.

[0035] Figure 2 for Figure 1 Detailed cross-sectional view of the scaled-down model beam.

[0036] Figure 3 for Figure 1 Left view of the scaled-down model beam.

[0037] Figure 4 This is a three-dimensional perspective view of the scaled-down model beam established by the method of this invention.

[0038] In the diagram: 1. Scaled-down concrete beam; 2. Ordinary reinforcing steel bars; 3. Corrugated pipe; 4. Prestressed steel bars; 5. Cement grout; 6. Anchorage; 7. Strain gauge; 8. Displacement gauge. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. When the drawings are mentioned repeatedly in the following description, unless otherwise stated, the same numbers in different drawings represent the same elements.

[0040] Reference Figures 1-4 This invention provides a method for modeling a scaled-down model of a large-span prestressed concrete beam. The scaled-down model beam achieves the stress characteristics of an actual beam by establishing a scaled-down concrete beam 1, ordinary reinforcing bars 2, corrugated pipes 3, prestressed reinforcing bars 4, cement grout 5, anchors 6, strain gauges 7, and displacement gauges 8. The ordinary reinforcing bars 2 are placed within the scaled-down concrete beam 1; the corrugated pipes 3 are arranged proportionally within the scaled-down concrete beam 1; the prestressed reinforcing bars 4 and cement grout 5 are placed within the corrugated pipes 3; the anchors 6 are fixed to both sides of the head of the prestressed reinforcing bars 4; the strain gauges 7 are attached to the mid-span of the ordinary reinforcing bars 2, and to the top, bottom, and four sides of the mid-span of the scaled-down concrete beam 1. Multiple strain gauges 7 can be attached to the four sides of the mid-span of the concrete beam 1 at certain intervals on the same surface; the displacement gauges 8 are abutted against the center wire of the prestressed reinforcing bars 4, the lower side of the mid-span of the beam, and the upper side of the beam end. The displacement gauges 8 must ensure accurate and precise positioning.

[0041] The ordinary reinforcing steel bars 2 in the scaled-down model beam can be arranged in single or multiple rows in the tension and compression zone of the scaled-down concrete beam 1, depending on the actual reinforcement ratio.

[0042] The diameter of the corrugated pipe 3 should be selected based on the prestressed steel reinforcement calculated in the scale model.

[0043] The material of the prestressed steel bar 4 can be selected according to the actual situation.

[0044] The material properties of the cement grout 5 should be the same as those of the material used in the actual beam.

[0045] The model and size of the anchorage 6 can be selected based on the actual prestressed tendons calculated for the scaled-down model beam.

[0046] The specific operation process of the modeling method for scaled-down models of large-span prestressed concrete beams in this invention is as follows:

[0047] 1. Determine the actual beam's proportional dimensions and reinforcement ratio in the tension and compression zones, and establish a scaled-down concrete beam model based on these parameters. Specifically, this includes determining the actual beam's proportional dimensions as length, width, and height, as well as the ordinary steel reinforcement ratios in the compression and tension zones of the concrete beam. Ensuring the establishment of a scaled-down concrete beam model means that the model's length, width, and height proportions are the same as the actual beam, and the ordinary steel reinforcement ratio is also the same.

[0048] 2. Establish a plane coordinate system for the post-tensioned curved prestressing tendons of the actual beam. Establishing a coordinate system for the post-tensioned curved prestressing tendons means establishing an xoy plane coordinate system on the plane where the planar post-tensioned curved prestressing tendons are located. At this time, the origin of the coordinate system is on the surface of the concrete beam at the mid-span section, the x-axis is parallel to the beam length direction, and the positive y-axis is the concave direction of the prestressing tendons.

[0049] 3. Derive the prestressing tendon curve equation based on the actual beam end, mid-span, and inflection point coordinates and slope. Specifically, this involves establishing the curve equation as a two-segment quadratic parabola. Using the coordinate system established in step 2 above, determine the coordinates of the prestressing tendon beam end, mid-span, inflection point, and slope. The resulting curve equation is as follows:

[0050] Crossing the middle section:

[0051] Beam end section: y1(x) is the equation of the prestressed tendon curve at the mid-span; y2(x) is the equation of the prestressed tendon curve at the beam end; δ1 is the Y-axis coordinate of the mid-span point of the curve; δ2 is the Y-axis coordinate of the beam end point of the curve; x d The x-coordinate of the inflection point is given by ; l is the length of the beam.

[0052] 4. Calculate the first batch of prestress loss in the actual beam using the above equations. Specifically, this includes calculating the first batch of prestress loss value for the actual beam. This calculation can be performed according to the relevant design specifications, referring to the "Code for Design of Prestressed Concrete Structures" JGJ369-2016. The formula for calculating the prestress loss is as follows:

[0053] Prestress loss σ caused by anchor deformation and steel bar shrinkage l1 Calculate using the following formula:

[0054]

[0055] reverse friction influence coefficient l f The following formula can be used for calculation:

[0056]

[0057] l f The length (m) affected by reverse friction; γ cThe radius of curvature of the arc-shaped prestressed tendon (m); x: distance from the tensioning end to the calculated section (m); a: deformation of the tensioning end anchorage and rebar retraction (mm) (taken according to the specification); κ: friction coefficient considering local deviation per meter of duct length (1 / m) (taken according to the specification); μ: friction coefficient between the prestressed tendon and the duct wall (1 / rad); E s Elastic modulus of prestressed tendons (MPa);

[0058] The prestress loss σ caused by friction between the prestressing tendon and the duct wall l2 Calculate using the following formula:

[0059]

[0060] When (κx+μθ)≤0.3, σ l2 It can be approximated by the following formula:

[0061]

[0062] θ is the angle between the tensioning end and the tangent of the duct section of the calculated cross-section curve (rad); κ is the friction coefficient considering local deviations per meter of duct length (1 / m); μ is the friction coefficient between the prestressing tendon and the duct wall (1 / rad).

[0063] Prestress loss σ caused by stress relaxation of prestressed steel bars l4 Calculate using the following formula:

[0064] Stress-relieving steel wire and steel strand

[0065] Normal relaxation:

[0066]

[0067] Low relaxation:

[0068]

[0069]

[0070] f ptk This represents the standard value of the ultimate strength of prestressed steel bars.

[0071] 5. Calculate the effective mid-span prestress of the actual beam based on the above losses. Specifically, this includes calculating the effective mid-span prestress of the actual beam, characterized by considering the effective prestressing force in the beam after the first batch of prestress losses, and reflected in the stress magnitude of the ordinary steel reinforcement at mid-span. This calculation can be performed according to the relevant design specifications, referring to the "Code for Design of Concrete Structures" GB50010-2010.

[0072] The mid-span stress is calculated according to the following formula in accordance with the "Code for Design of Concrete Structures" GB 50010-2010:

[0073]

[0074]

[0075] e p =y ps -e p0 (14)

[0076] A p For members under bending, the cross-sectional area of ​​the longitudinal prestressing tendons in the tension zone is N. p0 The prestressing force when the normal prestress of the concrete on the cross section is equal to zero; N k M k Axial force and bending moment values ​​calculated according to the standard load combination. z: Distance from the resultant point of the longitudinal ordinary steel bars and prestressing tendons in the tension zone to the resultant point of the compression zone of the section; α1: Equivalent reduction factor for unbonded prestressing tendons, taken as 1.0 for grouted post-tensioned prestressing tendons; e p The prestressing force N when the normal prestress of the concrete on the calculation section is equal to zero p0 The distance from the point of application to the resultant force point of the longitudinal prestressing tendons and ordinary steel bars in the tension zone; y ps The eccentricity of the resultant force point of the longitudinal prestressing tendons and ordinary steel bars in the tension zone; e p0 The prestressing force N when the normal prestress of the concrete on the calculation section is equal to zero p0 The eccentricity of the point of application.

[0077] 6. Based on the above equation derivation method, the curve equation is derived by assuming the coordinates of the prestressing tendon ends, mid-span, and inflection points in the scaled-down model beam. Specifically, according to the derivation method described in step 3 above, the coordinates of the prestressing tendons at the beam ends and mid-span points in the scaled-down model beam are assumed, as well as the X-axis coordinate of the inflection point determined according to the actual beam proportion. The prestressing curve equation in the scaled-down model beam is then derived using the method described in step 3 above.

[0078] 7. Based on the prestressing tendon curve equation of the scaled-down model, determine the number of prestressing tendons and the tension control stress of the scaled-down model beam. Specifically, this includes calculating the stress of the ordinary steel bars at mid-span based on the tension control stress of the actual beam, ensuring that the stress of the ordinary steel bars is the same, thereby determining the required tension control stress and number of prestressing tendons for the scaled-down model. The specific calculation formula is the same as the formula in step 5 above.

[0079] 8. Calculate and determine whether the effect of the effective prestress after the first batch of prestress loss is the same for the scaled model and the actual beam. If not, return to step 6 and repeat the trial calculation. Specifically, this includes calculating the first batch of prestress loss for the scaled model based on the curve equation of the prestressing tendons and the tension control stress determined in steps 6 and 7 above, and then calculating the effect of the effective prestress after the first batch of prestress loss for the scaled model and the actual beam according to the formula in step 4. If they are the same, the model calculation is successful; if the difference is too large, it is necessary to return to step 6 and recalculate.

[0080] 9. After the model calculation is successful, the actual scaled-down model beam is fabricated. During the fabrication process, strain gauges are attached at the mid-span position of the ordinary stressed steel bars in the tension and compression zone, while controlling the positioning of the prestressed steel bars.

[0081] 10. After the internal concrete components are arranged, pour the concrete. The concrete grade should be the same as or from the same batch as the actual beam. Cure the poured scaled-down model beam. When the concrete strength reaches 75% of its strength grade, attach strain gauges to all four sides of the concrete span and install displacement gauges according to the positioning. Then, thread and tension the prestressing tendons, determining the required number of prestressing tendons and the tensioning control stress based on the above. During and after tensioning, continuously collect data from the attached strain gauges and installed displacement gauges using a dynamic signal acquisition device.

[0082] 11. When the strength of the concrete reaches 100% of its strength grade, a bending test is conducted on the scaled-down model beam to achieve a certain experimental objective.

[0083] Application examples:

[0084] Taking the prestressed beam YKL1 of the roof of a student activity center at a certain ethnic university as an example, the steel strands used in the actual project and the production of the scaled-down model are all φ15.2 (1×7) high-strength, low-relaxation steel strands. ptk =1860KN / mm 2 Other specific data are shown in the table below:

[0085]

[0086]

[0087] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for modeling a scaled-down model of a large-span prestressed concrete beam, characterized by: To achieve the stress characteristics of an actual beam, a scaled-down model beam is constructed. The steps for creating the scaled-down model beam are as follows: S1 determines the actual beam's proportional dimensions and the reinforcement ratio of the tension and compression zones, and establishes a proportionally scaled concrete beam based on the above parameters. S2 establishes a plane coordinate system for the post-tensioned prestressed steel reinforcement of the actual beam; S3 determines the coordinates of the prestressed tendon beam end, mid-section, and inflection point, as well as the slope, based on the plane coordinate system established in step S2, and derives the curve equation of the prestressed tendon of the actual beam. S4 calculates the first batch of prestress loss of the actual beam using the above equation; S5 calculates the effective mid-span prestress of the actual beam based on the above-mentioned losses; Based on the above curve equation derivation method, S6 derives the prestressed steel curve equation of the scaled-down model beam by assuming the coordinates of the prestressed steel beam ends, mid-span, and inflection points of the scaled-down model beam. S7 determines the number of prestressed tendons and the tension control stress of the scaled-down model beam based on the prestressed steel reinforcement curve equation. S8 calculates and determines whether the effective prestressing effect after the first batch of loss is the same for the scaled model beam and the actual beam. If not, return to S6 to repeat the trial calculation to ensure that the mid-span stress caused by the prestressing of the scaled model beam and the actual beam is the same. After the S9 scaled-down model calculation is successful, the actual scaled-down model beam is made. Ordinary reinforcing bars and corrugated pipes are laid in the scaled-down concrete beam according to the scale ratio. Prestressed steel bars and cement grout are placed in the corrugated pipes. Anchors are fixed at both ends of the prestressed steel bars. Displacement gauges are placed against the center wire of the prestressed steel bars and the lower side of the beam mid-span and the upper side of the beam end. After the internal concrete components are arranged in S10, concrete is poured. The concrete grade is the same as or from the same batch as the actual beam grade. The scaled-down model beam is cured after pouring. When the concrete strength reaches 75% of the strength grade, strain gauges are attached to the four sides of the mid-span of the scaled-down concrete beam, and displacement gauges are installed according to the positioning. Then, the prestressed steel bars are threaded and tensioned to determine the required number of prestressed steel bars and the tensioning control stress. During and after the tensioning process, a dynamic signal acquisition instrument is used to continuously collect data from the attached strain gauges and installed displacement gauges. S11 When the strength of concrete reaches 100% of the strength grade, a bending test is conducted on the scaled-down model beam to achieve a certain experimental purpose. In S6, the following assumptions are made before deriving the prestressed steel reinforcement curve equation for the scaled-down model beam: (1) The plane section assumption is followed when calculating the normal section of prestressed concrete flexural members; (2) The tensile strength of concrete is not considered; (3) The equation of the curved prestressed tendon is quadratic; (4) Prestressed steel has a good bond strength with concrete, and the strain of steel caused by load is the same as the strain of concrete at the same location.

2. The method for modeling a scaled-down model of a large-span prestressed concrete beam according to claim 1, characterized in that: In step S1, the proportional dimensions of the actual beam are the length, width, and height of the actual beam; the reinforcement ratio of the tension and compression zone is the ordinary steel reinforcement ratio of the compression and tension zones in the concrete beam; establishing a proportionally scaled concrete beam means that the length, width, and height of the scaled concrete beam are the same as those of the actual beam, and the ordinary steel reinforcement ratio is the same as that of the actual beam.

3. The method for modeling a scaled-down model of a large-span prestressed concrete beam according to claim 1, characterized in that: In step S2, establishing a plane coordinate system for the post-tensioned curved prestressed steel bars of the actual beam means establishing an xoy plane coordinate system on the plane where the planar post-tensioned curved prestressed steel bars are located. At this time, the origin of the coordinate system is on the surface of the concrete beam at the mid-span section, the x-axis is parallel to the beam length direction, and the positive y-axis is the concave direction of the prestressed steel bars.

4. The method for modeling a scaled-down model of a large-span prestressed concrete beam according to claim 1, characterized in that: Step S3, deriving the curve equation of the prestressed steel reinforcement, specifically includes establishing the curve equation as if the prestressed steel reinforcement curve is a two-segment quadratic parabola. Based on the coordinate system established in step S2, the coordinates of the prestressed steel reinforcement beam end, mid-span, inflection point, and slope are determined. The curve equation is then derived as follows: Crossing the middle section: (1) Beam end section: (2) The equation for the prestressed tendon curve in the mid-span section; The equation for the prestressed tendon curve of the beam end section; The Y-axis coordinate of the midpoint of the curve; The Y-axis coordinate of the endpoint of the curved beam; is the X-axis coordinate of the inflection point; l is the length of the beam.

5. The method for modeling a scaled-down model of a large-span prestressed concrete beam according to claim 1, characterized in that: Step S4, which involves calculating the first batch of prestress loss of the actual beam using the above equation, specifically includes calculating the first batch of prestress loss value of the actual beam. This calculation is performed in accordance with Article 4.3 of the "Code for Design of Prestressed Concrete Structures" JGJ 369-2016.

6. The method for modeling a scaled-down model of a large-span prestressed concrete beam according to claim 1, characterized in that: Step S5, which involves calculating the effective mid-span prestress of the actual beam based on the aforementioned losses, specifically includes calculating the effective mid-span prestress of the actual beam. This calculation is performed in accordance with Article 7.1.4 of the Code for Design of Concrete Structures GB 50010-2010.

7. The method for modeling a scaled-down model of a large-span prestressed concrete beam according to claim 1, characterized in that: Step S6, which involves deriving the curve equation based on the above equation derivation method, assuming the coordinates of the prestressing tendon ends, mid-span, and inflection points of the scaled-down model, specifically includes deriving the prestressing curve equation in the scaled-down model beam by assuming the coordinates of the prestressing tendons at the beam ends and mid-span points, and the X-axis coordinates of the inflection points determined according to the actual beam proportions, using the method in step S3.

8. The method for modeling a scaled-down model of a large-span prestressed concrete beam according to claim 1, characterized in that: Step S7, which involves determining the number of prestressing tendons and tension force of the scaled-down model beam based on the prestressing tendon curve equation, specifically includes calculating the stress of ordinary steel bars at the mid-span of the actual beam based on the tension control stress, ensuring that the stress of ordinary steel bars is the same, thereby determining the required tension control stress and number of prestressing tendons for the scaled-down model.

9. The method for modeling a scaled-down model of a large-span prestressed concrete beam according to claim 1, characterized in that: In step S8, the calculation and judgment of whether the effect of the effective prestress generated after the first batch of prestress loss in the scaled-down model beam and the actual beam is the same. If not, the calculation is repeated in step S6. Specifically, this includes calculating the first batch of prestress loss in the scaled-down model beam based on the curve equation of the prestressing tendons and the tension control stress determined in steps S6 and S7, according to the formula in step S4. The calculation of the effective prestress generated after the first batch of prestress loss in the scaled-down model beam and the actual beam is judged. If they are the same, the model calculation is successful. If the difference is too large, the calculation needs to be repeated in step S6.

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