Pre-bending force prediction method, system and construction method for pre-bent composite beams

Abstract

The present invention provides a pre-bending force prediction method, system and construction method for a pre-bent composite beam, including: obtaining the mechanical parameters of the pre-bent composite beam; inputting the mechanical parameters into a pre-bending moment prediction model, which determines a first relationship between the pre-bending moment and the first lower edge stress of the steel beam based on the mechanical parameters, determines a second relationship between the pre-bending moment and the safety factor of the steel beam based on the first relationship, determines a third relationship between the pre-bending moment and the first upper edge stress of the concrete bridge deck based on the mechanical parameters, and determines a fourth relationship between the pre-bending moment and the safety factor of the concrete bridge deck based on the third relationship; determining the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the second relationship and the fourth relationship; applying a pre-bending force to the steel beam of the pre-bent composite beam based on the determined pre-bending moment value. The present invention can accurately predict the pre-bending moment of the pre-bent composite beam, and thus can ensure the reliable construction of the pre-bent composite beam.

Description

Technical Field

[0001] The present invention relates to the technical field of pre-bent composite beams, and particularly to a method and system for predicting the pre-bending force of a pre-bent composite beam and a construction method thereof. Background Art

[0002] Steel-concrete composite beams are widely used in medium and small span bridges due to their excellent performance and strong load-bearing capacity. Common construction methods for composite beams include: the method of beam first and then slab, the one-time forming erection method, etc. The construction method of beam first and then slab is mainly that all the initial loads of the composite beam are borne by the steel beam, the composite beam bears the second-stage dead load and live load, and the first-stage dead load is borne by the steel beam. At this time, the peak stress of the steel beam under the load action is relatively large, while the concrete does not exert its own compressive performance. At this time, the steel beam needs to have sufficient stiffness, resulting in a waste of materials in terms of structure; while the one-time forming erection method is completely stressed in the form of a composite beam, that is, the steel beam and the concrete act as a community to bear their own loads, and the steel beam and the concrete bridge deck each play their own material advantages, and the stress form is better; however, when the composite beam is erected into a bridge at one time, the weight is relatively large, and it is difficult for conventional bridge erection equipment to lift and erect it at one time, and good site conditions are required, which is difficult for bridges across roads, lines, rivers and seas, etc. in terms of construction. In view of the above problems existing in the steel-concrete composite beam, the development of the pre-bent composite beam has successfully solved this problem. The pre-bent composite beam not only ensures the lightness of the upper structure, but also facilitates the construction of the composite beam and has good enough economic benefits.

[0003] At present, the commonly used construction method for pre-bent composite beams is the temporary lifting method by a bridge erection machine, that is, after the steel beam is erected by the bridge erection machine, temporary pulling and lifting cables are arranged on the bridge erection machine to temporarily lift the steel beam, then the concrete bridge deck is laid, and the wet joint concrete of the bridge deck is poured after the second lifting and locking to complete the superposition of the composite beam. When the concrete strength reaches the design requirement, the pre-bending force is released. At this time, the composite beam deflects and bears the load, and the concrete is stressed first due to the rebound of the steel beam. The originally single steel beam stress is transformed into the common stress of the composite beam, greatly alleviating the stress state of the steel beam. The essence of the pre-bending construction is to redistribute and adjust the internal force of the first-stage dead load of the composite beam, and the distribution ratio between the steel beam and the concrete is affected by the magnitude of the pre-bending force. Therefore, the magnitude of the pre-bending force has a significant influence on the initial internal force state of the composite beam.

[0004] When the prior art performs pre-bending construction on the steel beam of the pre-bent composite beam, generally, the steel beam is directly lifted based on the actual lifting capacity of the bridge erection machine, without considering in detail the influence of the pre-bending construction on the internal force of the composite beam, so that the determined pre-bending force cannot accurately reflect the actual stress state of the steel beam. And when the steel beam is lifted with the pre-bending force determined based on the actual lifting capacity of the bridge erection machine, there are also phenomena such as too large pre-bending force resulting in too high construction cost, or too small pre-bending force resulting in unreasonable stress of the steel beam. Therefore, how to accurately predict the pre-bending moment of the pre-bent composite beam to achieve reliable construction of the pre-bent composite beam is a technical problem to be solved urgently. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a method and system for predicting the pre-bending force of a pre-bent composite beam, as well as a construction method, to eliminate or improve one or more defects existing in the prior art.

[0006] One aspect of the present invention provides a method for predicting the pre-bending force of a pre-bent composite beam, the method comprising the following steps:

[0007] Obtain the mechanical parameters of the pre-bent composite beam;

[0008] Input the obtained mechanical parameters into a pre-bending moment prediction model, which determines a first relationship between the pre-bending moment and the first lower edge stress of the steel beam of the pre-bent composite beam based on the mechanical parameters, determines a second relationship between the pre-bending moment and the safety factor of the steel beam based on the first relationship, determines a third relationship between the pre-bending moment and the first upper edge stress of the concrete bridge deck of the pre-bent composite beam based on the mechanical parameters, and determines a fourth relationship between the pre-bending moment and the safety factor of the concrete bridge deck based on the third relationship;

[0009] Determine the value of the pre-bending moment when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the second relationship and the fourth relationship;

[0010] Apply a pre-bending force to the steel beam of the pre-bent composite beam based on the determined value of the pre-bending moment.

[0011] In some embodiments of the present invention, the pre-bending moment prediction model determines the first relationship between the pre-bending moment and the first lower edge stress of the steel beam of the pre-bent composite beam based on the mechanical parameters, including:

[0012] The pre-bending moment prediction model determines the first relationship between the pre-bending moment and the first lower edge stress of the steel beam of the pre-bent composite beam under the action of the first-stage permanent load based on the mechanical parameters; and / or

[0013] The pre-bending moment prediction model determines the third relationship between the pre-bending moment and the first upper edge stress of the concrete bridge deck of the pre-bent composite beam based on the mechanical parameters, including:

[0014] The pre-bending moment prediction model determines the third relationship between the pre-bending moment and the first upper edge stress of the concrete bridge deck of the pre-bent composite beam under the action of the first-stage permanent load based on the mechanical parameters.

[0015] In some embodiments of the present invention, the first relationship is expressed as: The third relationship is expressed as:

[0016] Among them, M T is the pre-bending moment, and M s represents the mid-span bending moment value of the steel beam under the action of self-weight, and M c represents the mid-span bending moment value of the steel beam under the action of the concrete bridge deck, represents the first lower edge stress, and I s represents the moment of inertia of the steel beam section, and I z represents the moment of inertia of the composite beam section, and y b represents the distance from the neutral axis of the steel beam to the lower edge of the steel beam, represents the first upper edge stress, and E c represents the elastic modulus of the concrete bridge deck, and E s represents the elastic modulus of the steel beam, and z b represents the distance from the neutral axis of the composite beam to the lower edge of the composite beam, and z t represents the distance from the neutral axis of the composite beam to the upper edge of the composite beam.

[0017] In some embodiments of the present invention, determining the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the second relationship and the fourth relationship includes:

[0018] Determining a first curve of the safety factor of the steel beam varying with the pre-bending moment based on the second relationship, and determining a second curve of the safety factor of the concrete bridge deck varying with the pre-bending moment based on the fourth relationship;

[0019] Determining the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the first curve and the second curve.

[0020] In some embodiments of the present invention, determining the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the first curve and the second curve includes:

[0021] Determining the intersection point of the first curve and the second curve;

[0022] Taking the pre-bending moment value corresponding to the intersection point as the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam.

[0023] In some embodiments of the present invention, determining the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the second relationship and the fourth relationship includes:

[0024] Determining the second lower edge stress of the steel beam and the second upper edge stress of the concrete bridge deck under the action of the second-stage permanent load and live load;

[0025] Determine the value of the pre-bending moment when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the second relationship, the fourth relationship, the second lower edge stress, and the second upper edge stress.

[0026] In some embodiments of the present invention, the safety factor of the steel beam is: Where γ s represents the safety factor of the steel beam, represents the first lower edge stress, [σ s represents the standard value of the yield strength of the steel beam, and / or.

[0027] The safety factor of the concrete bridge deck is: γ c represents the safety factor of the concrete bridge deck, [σ c represents the standard value of the compressive strength of the concrete bridge deck, represents the first upper edge stress.

[0028] In some embodiments of the present invention, the calculation formula for the value of the pre-bending moment is:

[0029]

[0030] Where M T is the pre-bending moment, M H is the mid-span bending moment value of the steel beam under the action of the second-stage dead load and live load, I s represents the moment of inertia of the steel beam section, I z represents the moment of inertia of the composite beam section, z t represents the distance from the neutral axis of the composite beam to the upper edge of the composite beam, y b represents the distance from the neutral axis of the steel beam to the lower edge of the steel beam, z b represents the distance from the neutral axis of the composite beam to the lower edge of the composite beam, M s represents the mid-span bending moment value of the steel beam under the action of its own weight, M c represents the mid-span bending moment value of the steel beam under the action of the concrete bridge deck, α = E c / E s ,E c represents the elastic modulus of the concrete bridge deck, E s represents the elastic modulus of the steel beam, β = [σ s / [σ c , [σ s represents the standard value of the yield strength of the steel beam, [σ c represents the standard value of the compressive strength of the concrete bridge deck.

[0031] According to another aspect of the present invention, a pre-bending force prediction system for a pre-bent composite beam is also disclosed, which includes a processor, a memory, and a computer program stored on the memory. The processor is used to execute the computer program, and when the computer program is executed, the system implements the steps of the method described in any one of the above embodiments.

[0032] According to still another aspect of the present invention, a construction method for a pre-bent composite beam is also disclosed, and the method includes the following steps:

[0033] Install the steel beams in pairs and fix them in the loading and unloading tooling;

[0034] Perform pre-bending construction on the steel beams based on the optimal pre-bending moment determined by the method described in any one of the above embodiments;

[0035] Pour the concrete of the lower flange. After the strength of the concrete of the lower flange reaches more than 90%, unload the pre-bending force and pour the concrete of the web;

[0036] After the concrete of the web reaches the preset strength, hoist it into place;

[0037] Pour the concrete of the bridge deck and cross beam.

[0038] The pre-bending force prediction method for the pre-bent composite beam of the present invention determines the pre-bending moment value based on the relationship between the pre-bending moment and the safety factor of the steel beam, and the relationship between the pre-bending moment and the safety factor of the concrete bridge deck, and takes the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam as the optimal pre-bending moment value. This pre-bending moment value fully considers the specific stress of the steel beam and the concrete bridge deck during prediction, as well as the material utilization rate of the steel beam and the concrete material, ensuring the accuracy of the predicted pre-bending moment. Furthermore, the predicted pre-bending moment value can more accurately reflect the actual stress state of the steel beam, and avoid waste of construction costs, thus ensuring the reliable construction of the pre-bent composite beam.

[0039] The additional advantages, objects, and features of the present invention will be partially described below, and will become partially apparent to those of ordinary skill in the art after studying the following text, or can be learned from the practice of the present invention. The objects and other advantages of the present invention can be achieved and obtained by the structure specifically pointed out in the specification and the drawings.

[0040] Those skilled in the art will understand that the objects and advantages that can be achieved by the present invention are not limited to the above specific descriptions, and the above and other objects that the present invention can achieve will be more clearly understood according to the following detailed description. Description of the Drawings

[0041] The accompanying drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and do not limit the present invention. The components in the drawings are not drawn to scale, but are only for showing the principles of the present invention. For the convenience of showing and describing some parts of the present invention, the corresponding parts in the drawings may be enlarged, that is, may become larger relative to other components in the exemplary device actually manufactured according to the present invention. In the drawings:

[0042] Figure 1 It is a schematic flow chart of the pre-bending force prediction method for the pre-bent composite beam in an embodiment of the present invention.

[0043] Figure 2 It is a schematic diagram of the stress comparison of the composite beam during pre-bending construction and conventional construction.

[0044] Figure 3 It is a schematic diagram of the first curve and the second curve in an embodiment of the present invention. Detailed implementation manners

[0045] To make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in combination with the implementation manners and the accompanying drawings. Herein, the illustrative implementation manners of the present invention and their descriptions are used to explain the present invention, but do not limit the present invention.

[0046] Herein, it also needs to be noted that in order to avoid obscuring the present invention due to unnecessary details, only the structures and / or processing steps closely related to the solution according to the present invention are shown in the drawings, while other details less related to the present invention are omitted.

[0047] It should be emphasized that the term "including / containing" when used herein refers to the presence of features, elements, steps or components, but does not exclude the presence or addition of one or more other features, elements, steps or components.

[0048] Herein, it also needs to be noted that if not otherwise specified, the term "connection" in this article can not only refer to direct connection, but also represent indirect connection with an intermediate object.

[0049] For the construction of composite beams, the steel beams can be hoisted and erected first, and then the composite beams can be laminated after the steel beams are pre-bent on site. At this time, the load originally borne by the steel beams is transferred to the composite beams together, and the stress state of the steel beams will be significantly improved. This can not only avoid the difficulty of erecting composite beams due to excessive self-weight, but also prevent the steel beams from being subjected to large forces. In view of the problems existing in the prior art, such as unclear stress of pre-bent composite beams, insufficient utilization of steel beam and concrete materials, and failure to achieve the optimal bending effect, this application proposes a pre-bending force prediction method and system for pre-bent composite beams. This method analyzes the influence of pre-bending construction on the stress of composite beams, clarifies the improvement of the pre-bending moment on the stress of composite beams, and takes the materials of the composite beams to reach the same safety factor as the goal, and solves to obtain the optimal pre-bending moment.

[0050] For the conventional construction method of composite beams using the erection method of beam first and then slab, the stress at the lower edge of the steel beam under the action of the first-stage dead load is expressed as The stress at the upper edge is expressed as At this time, the concrete of the bridge deck does not participate in the structural stress. The construction of pre-bent composite beams refers to the construction method of pre-bending the steel beam upward before combining the bridge deck to generate pre-bending stress, and releasing the pre-bending stress after the lamination construction of the composite beam is completed. The load originally borne by the steel beam is changed to be borne by the composite beam together. The pre-bending construction effectively reduces the stress level of the steel beam and enables the concrete of the bridge deck to participate in the stress in advance; during the construction of the pre-bent composite beam, the upper edge of the steel beam, the lower edge of the steel beam, the upper edge of the concrete bridge deck, and the lower edge of the concrete bridge deck are all stressed under the action of the first-stage dead load, and the stress of the upper edge of the steel beam, the lower edge of the steel beam, the upper edge of the concrete bridge deck, and the lower edge of the concrete bridge deck during the pre-bending construction is all related to the pre-bending moment, that is, the improvement of the stress of the composite beam by the pre-bending construction completely depends on the size of the pre-bending moment, that is, the larger the pre-bending moment, the greater the pre-bending degree, and the better the improvement of the stress of the steel beam, but too large a pre-bending moment will also cause excessive compression of the concrete; therefore, it is necessary to determine a more optimal pre-bending moment to guide the construction of pre-bent composite beams.

[0051] In addition, as Figure 2As shown, compared with the conventional construction method of composite beams, the pre-bending construction of steel-concrete composite beams can effectively reduce the tensile and compressive stresses of steel beams and increase the compressive stress of the concrete bridge deck, and improve the material utilization rate in the way of initial internal force redistribution. From the results, the pre-bending construction of composite beams is beneficial to the stress change of steel beams. On the one hand, compared with steel beams, composite beams have a larger section moment of inertia and can resist deformation. On the other hand, the concrete participates in the force in advance and shares the load borne by the steel beam; while the pre-bending construction is unfavorable to the force of the bridge deck, that is, when unloading the pre-bending force, the steel beam will apply a large compressive stress to the concrete bridge deck. On this basis, the compressive stress of the bridge deck will further increase when bearing the second-stage dead load, which increases the risk of concrete compression failure. Therefore, the pre-bending construction of composite beams has a reasonable pre-bending moment value, which can effectively improve the force condition of composite beams while ensuring the structural safety, and make the material utilization rate of composite beams reach the optimal value.

[0052] In the following, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar components, or the same or similar steps.

[0053] Figure 1 It is a schematic flow chart of a pre-bending force prediction method for a pre-bending composite beam according to an embodiment of the present invention. As Figure 1 shown, the method at least includes steps S10 to S40.

[0054] Step S10: Obtain the mechanical parameters of the pre-bending composite beam.

[0055] In this step, firstly obtaining the mechanical parameters of the pre-bending composite beam is to facilitate determining the relationship between the pre-bending moment and the stress at the lower edge of the steel beam, and the relationship between the pre-bending moment and the stress at the upper edge of the concrete bridge deck in the subsequent steps. Among them, the actual mechanical parameters of the pre-bending composite beam depend on the actual application scenario of the pre-bending composite beam, etc. The types of mechanical parameters include but are not limited to: the mid-span bending moment value of the steel beam under self-weight, the mid-span bending moment value of the steel beam under the action of the concrete bridge deck, the section moment of inertia of the steel beam, the section moment of inertia of the composite beam, the elastic modulus of the concrete bridge deck, the elastic modulus of the steel beam, etc.

[0056] Step S20: Input the obtained mechanical parameters into the pre-bending moment prediction model. The pre-bending moment prediction model determines a first relationship between the pre-bending moment and the first lower edge stress of the steel beam of the pre-bending composite beam based on the mechanical parameters, determines a second relationship between the pre-bending moment and the safety factor of the steel beam based on the first relationship, the pre-bending moment prediction model determines a third relationship between the pre-bending moment and the first upper edge stress of the concrete bridge deck of the pre-bending composite beam based on the mechanical parameters, and determines a fourth relationship between the pre-bending moment and the safety factor of the concrete bridge deck based on the third relationship.

[0057] In this step, based on the pre-bending moment prediction model and the mechanical parameters determined in step S10, the relationships between the pre-bending moment and the stress at the lower edge of the steel girder, and between the pre-bending moment and the stress at the upper edge of the concrete bridge deck are determined. Further, based on the relationship between the pre-bending moment and the stress at the lower edge of the steel girder, the relationship between the pre-bending moment and the safety factor of the steel girder is determined, and based on the relationship between the pre-bending moment and the stress at the upper edge of the concrete bridge deck, the relationship between the pre-bending moment and the safety factor of the concrete bridge deck is determined.

[0058] In one embodiment, both the first relationship and the third relationship are relationships under the action of the first-stage permanent load. That is, at this time, the pre-bending moment prediction model determines the first relationship between the pre-bending moment and the first stress at the lower edge of the steel girder of the pre-bending composite beam based on the mechanical parameters, including: the pre-bending moment prediction model determines the first relationship between the pre-bending moment and the first stress at the lower edge of the steel girder of the pre-bending composite beam under the action of the first-stage permanent load based on the mechanical parameters; and the pre-bending moment prediction model determines the third relationship between the pre-bending moment and the first stress at the upper edge of the concrete bridge deck of the pre-bending composite beam based on the mechanical parameters, including: the pre-bending moment prediction model determines the third relationship between the pre-bending moment and the first stress at the upper edge of the concrete bridge deck of the pre-bending composite beam under the action of the first-stage permanent load based on the mechanical parameters.

[0059] In the above embodiment, under the action of the first-stage permanent load of the pre-bending steel-concrete composite beam, the stress at the lower edge of the steel girder is expressed as The stress at the upper edge is expressed as The stress at the upper edge of the concrete bridge deck is expressed as The stress at the lower edge is expressed as

[0060] In this embodiment, based on the expression of the stress at the lower edge of the steel girder, the first relationship between the pre-bending moment and the first stress at the lower edge of the steel girder of the pre-bending composite beam can be determined, and based on the expression of the stress at the upper edge of the concrete bridge deck, the third relationship between the pre-bending moment and the first stress at the upper edge of the concrete bridge deck of the pre-bending composite beam can be determined. That is, the first relationship is expressed as: The third relationship is expressed as:

[0061] Further, based on the stress in the conventional construction method of the steel girder and the stress in the pre-bending construction method under the action of the first-stage permanent load, the stress increment of the steel girder and the stress increment of the concrete bridge deck can be obtained:

[0062]

[0063] In the above formula, represents the stress increment at the upper edge of the steel girder, represents the stress increment at the lower edge of the steel girder, represents the increment of the upper edge stress of the concrete bridge deck, represents the increment of the lower edge stress of the concrete bridge deck, "-" represents the stress reduction of the steel beam, and "+" represents the stress increase of the concrete bridge deck. Among them, M T is the pre-bending moment, M s represents the mid-span bending moment value of the steel beam under the action of self-weight, M c represents the mid-span bending moment value of the steel beam under the action of the concrete bridge deck, represents the first lower edge stress, I s represents the moment of inertia of the steel beam section, I z represents the moment of inertia of the composite beam section, y t represents the distance from the neutral axis of the steel beam to the upper edge of the steel beam, y b represents the distance from the neutral axis of the steel beam to the lower edge of the steel beam, represents the first upper edge stress, E c represents the elastic modulus of the concrete bridge deck, E s represents the elastic modulus of the steel beam, z b represents the distance from the neutral axis of the composite beam to the lower edge of the composite beam, z t represents the distance from the neutral axis of the composite beam to the upper edge of the composite beam, h c represents the thickness of the concrete bridge deck. It can be seen from the above calculation formulas of the stress increment of the steel beam and the stress increment of the concrete bridge deck that the improvement of the mechanical properties of the composite beam by pre-bending construction completely depends on the magnitude of the pre-bending moment, that is, the larger the pre-bending moment, the greater the degree of pre-bending, and the better the improvement of the steel beam stress. However, too large a pre-bending moment will also cause excessive compression of the concrete.

[0064] In addition, after determining the relationship between the pre-bending moment and the lower edge stress of the steel beam, and the relationship between the pre-bending moment and the upper edge stress of the concrete bridge deck, further determine the relationship between the pre-bending moment and the safety factor of the steel beam based on the safety factor expression of the steel beam, and determine the relationship between the pre-bending moment and the safety factor of the concrete bridge deck based on the safety factor expression of the concrete bridge deck.

[0065] Furthermore, the safety factor of the steel beam is: Among them, γ s represents the safety factor of the steel beam, represents the first lower edge stress, [σ s represents the standard value of the yield strength of the steel beam. The safety factor of the concrete bridge deck is: γ c represents the safety factor of the concrete bridge deck, [σ c represents the standard value of the compressive strength of the concrete bridge deck, represents the first upper edge stress.

[0066] Step S30: Determine the value of the pre-bending moment when the safety factor of the concrete bridge deck is equal to that of the steel beam based on the second relationship and the fourth relationship.

[0067] During the construction of the beam first and then the slab, the first-stage permanent load is entirely borne by the steel beam, resulting in excessive stress in the steel beam during the operation period and a relatively low safety reserve. As the pre-bending moment increases, under the action of the first-stage permanent load, the internal force of the steel beam gradually transfers to the concrete, and the safety factor of the steel beam gradually increases. Correspondingly, the safety factor of the concrete slab decreases during the operation period due to its participation in the first-stage permanent load. To maximize the utilization of the steel-concrete material properties during the service life of the composite beam, this step proposes that the principle for determining the optimal pre-bending moment value is that the safety factors of the steel beam and the concrete bridge deck are consistent, that is, the stress ratios of the bridge deck and the steel beam to their respective material strengths are equal.

[0068] Specifically, after determining the second relationship and the fourth relationship based on Step S20, further determine the optimal pre-bending moment value based on the relationship between the determined pre-bending moment and the safety factor of the steel beam, and the relationship between the pre-bending moment and the safety factor of the concrete bridge deck. Based on the above safety factor expressions of the steel beam and the concrete bridge deck, it can be known that when the safety factor of the steel beam is equal to that of the concrete bridge deck, the materials of the pre-bent composite beam can obtain the optimal utilization rate.

[0069] In one embodiment, determining the value of the pre-bending moment when the safety factor of the concrete bridge deck is equal to that of the steel beam based on the second relationship and the fourth relationship includes: determining a first curve of the safety factor of the steel beam changing with the pre-bending moment based on the second relationship, and determining a second curve of the safety factor of the concrete bridge deck changing with the pre-bending moment based on the fourth relationship; determining the value of the pre-bending moment when the safety factor of the concrete bridge deck is equal to that of the steel beam based on the first curve and the second curve. As Figure 3 shown, it can be known from the first curve that the safety factor of the steel beam increases with the increase of the pre-bending moment, and the safety factor of the concrete bridge deck decreases with the increase of the pre-bending moment. Then, when the selected pre-bending moment is reasonable, it can ensure that the steel beam and the concrete bridge deck have the same safety factor, that is, when the selected pre-bending moment is used to lift the steel beam, the steel beam and the concrete bridge deck reach the optimal material utilization rate and have the same strength redundancy.

[0070] Further, determining the value of the pre-bending moment when the safety factor of the concrete bridge deck is equal to that of the steel beam based on the first curve and the second curve includes: determining the intersection point of the first curve and the second curve; taking the pre-bending moment value corresponding to the intersection point as the value of the pre-bending moment when the safety factor of the concrete bridge deck is equal to that of the steel beam. From Figure 3It can be seen that at the intersection of the first curve and the second curve, the safety factor of the steel beam is equal to the safety factor of the concrete bridge deck. Therefore, the pre-bending moment corresponding to the intersection point is the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam.

[0071] Step S40: Apply a pre-bending moment to the steel beam of the pre-bending composite beam based on the determined pre-bending moment value.

[0072] In this step, a pre-bending force is applied to the steel beam of the pre-bending composite beam based on the predicted optimal pre-bending moment of the pre-bending composite beam.

[0073] In some embodiments of the present invention, determining the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the second relationship and the fourth relationship may specifically include: determining the second lower edge stress of the steel beam and the second upper edge stress of the concrete bridge deck under the action of the second-stage dead load and live load; determining the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the second relationship, the fourth relationship, the second lower edge stress, and the second upper edge stress.

[0074] In the above embodiment, when predicting the optimal pre-bending moment of the pre-bending composite beam, taking the design value of the structural material strength as the benchmark, respectively considering the changes in the safety factors of the steel beam and the bridge deck under the action of the dead load + live load, the safety factor of the concrete bridge deck under the action of the dead load + live load can be expressed as: The safety factor of the steel beam can be expressed as: When γ c = γ s At this time, σ b represents the lower edge stress of the steel beam, which includes the lower edge stress of the steel beam under the action of the first-stage dead load and the lower edge stress of the steel beam under the action of the second-stage dead load and live load in this embodiment; σ t represents the upper edge stress of the concrete bridge deck, which includes the upper edge stress of the concrete bridge deck under the action of the first-stage dead load and the upper edge stress of the concrete bridge deck under the action of the second-stage dead load and live load in this embodiment; [σ s represents the standard value of the yield strength of the steel beam, and [σ c represents the standard value of the compressive strength of the concrete bridge deck. Further, substituting the expression of the lower edge stress of the steel beam of the pre-bending steel-concrete composite beam under the action of the first-stage dead load, the expression of the upper edge stress of the concrete bridge deck of the pre-bending steel-concrete composite beam under the action of the first-stage dead load, the expression of the lower edge stress of the steel beam of the pre-bending steel-concrete composite beam under the action of the second-stage dead load and live load, and the expression of the upper edge stress of the concrete bridge deck of the pre-bending steel-concrete composite beam under the action of the second-stage dead load and live load into Get: Further solve the pre-bending moment Among them, M Tis the pre-bending moment, M H is the mid-span bending moment value of the steel beam under the action of the second-stage dead load and live load, I s represents the moment of inertia of the steel beam section, I z represents the moment of inertia of the composite beam section, z t represents the distance from the neutral axis of the composite beam to the upper edge of the composite beam, y b represents the distance from the neutral axis of the steel beam to the lower edge of the steel beam, z b represents the distance from the neutral axis of the composite beam to the lower edge of the composite beam, M s represents the mid-span bending moment value of the steel beam under the action of self-weight, M c represents the mid-span bending moment value of the steel beam under the action of the concrete bridge deck. α is the ratio of the elastic modulus of the concrete bridge deck to the elastic modulus of the steel beam, i.e., α = E c / E s ,E c represents the elastic modulus of the concrete bridge deck, E s represents the elastic modulus of the steel beam, β = [σ s / [σ c , [σ s represents the standard value of the yield strength of the steel beam, [σ c represents the standard value of the compressive strength of the concrete bridge deck. Further, for the convenience of later calculation, let a = I s / I z 、b = z b / y b 、c = z t / y b , and we get

[0075] Through the above embodiments, it can be found that the present invention proposes a prediction method for the reasonable pre-bending moment of a composite beam in view of the problems of unclear force of the pre-bent steel-concrete composite beam, insufficient utilization of steel beam and concrete materials, and failure to achieve the optimal bending effect. This method analyzes the influence of pre-bending construction on the force of the composite beam, clarifies the improvement of the pre-bending moment on the force of the composite beam, and takes the materials of the composite beam reaching the same safety factor as the goal to solve and obtain the optimal pre-bending moment, and applies the obtained optimal pre-bending moment to the steel beam.

[0076] In summary, the pre-bending force prediction method for the pre-bent composite beam disclosed in the above embodiments calculates the influence of pre-bending construction on the internal force of the composite beam, and solves the optimal pre-bending moment according to the determined principle of the optimal material utilization rate. It can effectively improve the stress state of the steel beam, avoid the waste of construction cost caused by excessive lifting moment, and the determined optimal pre-bending moment can more accurately reflect the actual stress state of the steel beam, so as to realize the effective construction of the pre-bent composite beam bridge. In addition, based on the determined pre-bending moment, the improvement degree of the stress of the steel beam and the bridge deck under the current pre-bending moment construction can be obtained through each stress expression, that is, the reduction of the stress of the steel beam after the lifting and superimposing construction and the situation of the concrete of the bridge deck participating in the force of the composite beam in advance.

[0077] Correspondingly, the present invention also provides a pre-bending force prediction system for a pre-bent composite beam, including a processor, a memory, and a computer program stored on the memory. The processor is used to execute the computer program, and when the computer program is executed, the system realizes the steps of the method described in any of the above embodiments.

[0078] According to another aspect of the present invention, a construction method for a pre-bent composite beam is also disclosed. The method may include the following steps: installing the I-shaped steel beams in pairs and fixing them in the loading and unloading tooling; further performing pre-bending construction on the steel beam based on the optimal pre-bending moment determined in the above embodiments; pouring the concrete of the lower flange, and after the strength of the concrete of the lower flange reaches more than 90%, unloading the pre-bending force and pouring the concrete of the web; after the concrete of the web reaches the preset strength, hoisting it in place; pouring the concrete of the bridge deck base cross beam, and then making the bridge deck paving and railing.

[0079] Those of ordinary skill in the art should understand that the various exemplary components, systems, and methods described in connection with the embodiments disclosed herein can be implemented in hardware, software, or a combination of both. Specifically, whether to implement in hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention. When implemented in hardware, it can be, for example, an electronic circuit, an application-specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, and so on. When implemented in software, the elements of the present invention are programs or code segments used to execute the required tasks. The program or code segment can be stored in a machine-readable medium or transmitted through a data signal carried in a carrier wave on a transmission medium or a communication link.

[0080] It should be clear that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order between steps after understanding the spirit of the present invention.

[0081] In the present invention, features described and / or illustrated for one embodiment can be used in the same or a similar manner in one or more other embodiments, and / or combined with the features of other embodiments or replace the features of other embodiments.

[0082] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various changes and variations can be made to the embodiments of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for predicting the pre-bending force of a pre-bent composite beam, characterized in that: The method comprises the following steps: Obtain the mechanical parameters of the pre-bent composite beam; The obtained mechanical parameters are input into a pre-bending moment prediction model, the pre-bending moment prediction model determines a first relationship between the pre-bending moment and a first lower edge stress of a steel beam of the pre-bending composite beam based on the mechanical parameters, determines a second relationship between the pre-bending moment and a safety factor of the steel beam based on the first relationship, the pre-bending moment prediction model determines a third relationship between the pre-bending moment and a first upper edge stress of a concrete bridge deck of the pre-bending composite beam based on the mechanical parameters, and determines a fourth relationship between the pre-bending moment and a safety factor of the concrete bridge deck based on the third relationship; Determine the prebending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the second relationship and the fourth relationship; Applying a pre-bending force to the steel beam of the pre-bending composite beam based on the determined pre-bending moment value; The pre-bending moment prediction model determines a first relationship between the pre-bending moment and a first lower edge stress of the steel beam of the pre-bending composite beam based on the mechanical parameters, including: The pre-bending moment prediction model determines a first relationship between the pre-bending moment and the first lower edge stress of the steel beam of the pre-bending composite beam under the action of a first-stage dead load based on the mechanical parameters; The pre-bending moment prediction model determines a third relationship between the pre-bending moment and the first upper edge stress of the concrete bridge deck of the pre-bending composite beam based on the mechanical parameters, including: The prebending moment prediction model determines, based on the mechanical parameters, a third relationship between the prebending moment and the first upper edge stress of the concrete deck of the prebending composite beam under the action of a first-stage dead load; The first relationship is expressed as: The third relationship is expressed as: Among them, M T is the prebending moment, M s It represents the mid-span bending moment of the steel beam under the action of its own weight, M c represents the mid-span bending moment of the steel beam under the action of the concrete bridge deck, represents the first lower edge stress, I s represents the moment of inertia of the steel beam section, I z represents the moment of inertia of the composite beam section, y b Indicates the distance between the neutral axis of the steel beam and the lower edge of the steel beam. represents the first upper edge stress, E c represents the elastic modulus of the concrete bridge deck, E s represents the elastic modulus of the steel beam, z b Indicates the distance between the neutral axis of the composite beam and the lower edge of the composite beam, z t It indicates the distance between the neutral axis of the composite beam and the upper edge of the composite beam.

2. The method for predicting the pre-bending force of a pre-bent composite beam according to claim 1, characterized in that: Determining the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the second relationship and the fourth relationship includes: Determine a first curve showing how the safety factor of the steel beam varies with the prebending moment based on the second relationship, and determine a second curve showing how the safety factor of the concrete bridge deck varies with the prebending moment based on the fourth relationship; The pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam is determined based on the first curve and the second curve.

3. The method for predicting the pre-bending force of a pre-bent composite beam according to claim 2, characterized in that: Determining the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the first curve and the second curve includes: determining an intersection point of the first curve and the second curve; The prebending moment value corresponding to the intersection point is taken as the prebending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam.

4. The method for predicting the pre-bending force of a pre-bent composite beam according to claim 1, characterized in that: Determining the pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam based on the second relationship and the fourth relationship includes: Determine the stress at the second lower edge of the steel beam and the stress at the second upper edge of the concrete bridge deck under the second-stage dead load and live load; The pre-bending moment value when the safety factor of the concrete bridge deck is equal to the safety factor of the steel beam is determined based on the second relationship, the fourth relationship, the second lower edge stress and the second upper edge stress.

5. The method for predicting the pre-bending force of a pre-bent composite beam according to claim 4, characterized in that: The safety factor of the steel beam is: Among them, γ s represents the safety factor of the steel beam, represents the first lower edge stress, [σ s ] represents the standard value of the yield strength of the steel beam, and / or, The safety factor of the concrete bridge deck is: γ c represents the safety factor of the concrete bridge deck, [σ c ] represents the standard value of compressive strength of concrete bridge deck. represents the first upper edge stress.

6. The method for predicting the pre-bending force of a pre-bent composite beam according to claim 5, characterized in that: The calculation formula of the pre-bending moment value is: Among them, M T is the prebending moment, M H is the mid-span bending moment of the steel beam under the second-stage dead load and live load, I s represents the moment of inertia of the steel beam section, I z represents the moment of inertia of the composite beam section, z t Indicates the distance between the neutral axis of the composite beam and the upper edge of the composite beam, y b Indicates the distance between the neutral axis of the steel beam and the lower edge of the steel beam, z b Indicates the distance between the neutral axis of the composite beam and the lower edge of the composite beam, M s It represents the mid-span bending moment of the steel beam under the action of its own weight, M c It represents the mid-span bending moment of the steel beam under the action of the concrete bridge deck, α=E c / E s , E c represents the elastic modulus of the concrete bridge deck, E s represents the elastic modulus of the steel beam, β=[σ s ] / [σ c ],[σ s ] represents the standard value of the yield strength of the steel beam, [σ c ] represents the standard value of compressive strength of concrete bridge deck.

7. A system for predicting the pre-bending force of a pre-bent composite beam, comprising a processor, a memory and a computer program stored in the memory, characterized in that: The processor is used to execute the computer program. When the computer program is executed, the system implements the steps of the method according to any one of claims 1 to 6.

8. A construction method for pre-bent composite beams, characterized in that: The method comprises the following steps: Install the steel beams in pairs and fix them in the loading and unloading fixtures; Pre-bending of steel beams according to the optimal pre-bending moment determined by the method according to any one of claims 1 to 6; Pour the lower wing concrete. When the strength of the lower wing concrete reaches more than 90%, unload the pre-bending force and pour the web concrete. After the web concrete reaches the preset strength, it is hoisted into place; Pouring concrete for bridge deck and beams.

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