A method for improving the anti-cracking performance of the bridge deck of a steel-UHPC composite beam cable-stayed bridge auxiliary pier and tail cable area

Abstract

The application discloses a method for improving the anti-cracking performance of a steel-UHPC combined beam auxiliary pier and tail cable area bridge deck of a cable-stayed bridge, and comprises the following steps: determining the range of the steel-UHPC combined beam whose anti-cracking performance does not meet the requirements; determining the target value of the compressive stress required by the bridge deck in the completed bridge state; obtaining the maximum deflection value of the simply-supported combined beam under the action of the self weight, and the compressive stress of the control section of the bridge deck; obtaining the stress difference value of the control section in the two construction stages after the beam falling and the completion of the bridge; obtaining the deflection displacement curve of the single-span simply-supported beam under the action of the self weight after considering the self weight load coefficient, and the maximum deflection value; obtaining the hog line shape of the steel main beam during the manufacturing process by inversely symmetrical hog of the deflection displacement curve; setting the beam falling control points, and the total displacement of each control point is the vertical displacement value corresponding to the deflection displacement curve; and grading the maximum total displacement of the beam falling and implementing it. The application does not need to set a large number of internal or external prestressed steel strands at the combined beam of the auxiliary pier and the edge span tail cable area, and is more economical.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering technology, specifically to a method for improving the crack resistance of the auxiliary piers and tail cable zone of a steel-UHPC composite beam cable-stayed bridge. Background Technology

[0002] Ultra-high performance concrete (UHPC) boasts advantages such as light weight, high strength, low late-stage shrinkage and creep, and excellent crack resistance, impermeability, and durability. With the deepening of scientific research on UHPC and the increasing maturity of its preparation technology, it has been gradually applied to various major load-bearing structures in engineering. In composite beam cable-stayed bridges, the main girder consists of a concrete bridge deck and a steel main girder connected by shear keys. Using UHPC material in the concrete bridge deck can significantly reduce the thickness of the concrete slab, thereby significantly reducing the structural self-weight, meeting the load-bearing requirements of ultra-long span composite beam cable-stayed bridges, and further expanding the economically applicable span range of composite beam cable-stayed bridges.

[0003] Steel-UHPC composite girder cable-stayed bridges are suitable for large main spans. The use of auxiliary piers in the side spans effectively improves the overall stiffness and seismic performance of the bridge, as well as its overall stress distribution. During operation, the support constraints of the auxiliary piers under loads from vehicles, temperature, and wind can generate negative bending moments in the composite girder, affecting both the auxiliary pier area and the tail cable area of ​​the side spans. When the negative bending moment becomes excessive, causing the tensile stress in the bridge deck to exceed the initial cracking tensile strength of the UHPC, the bridge deck will crack, affecting the normal use and durability of the bridge. Therefore, reliable measures must be taken to apply compressive stress to improve the crack resistance of the bridge deck in the auxiliary piers and the tail cable area of ​​the side spans.

[0004] Common measures to improve the crack resistance of bridge decks in the auxiliary pier area and the tail cable area of ​​the side span of composite girder cable-stayed bridges include: installing internal or external prestressed steel strands; and the single-point displacement method of auxiliary piers. For composite girder sections, a large portion of the compressive stress applied by tensioning steel strands acts on the steel beam itself, resulting in low efficiency in applying prestress to the bridge deck, large steel strand usage, and poor economic efficiency. As the span increases, the tensile stress on the bridge deck in the auxiliary pier and the tail cable area of ​​the side span also increases. The inefficient application method leads to a sharp increase in the amount of steel strands used, but it still cannot meet the prestress requirements of the bridge deck. The support displacement method involves pre-setting an upward displacement at the support point of the auxiliary pier. The composite girder is erected and the stay cables are installed according to the set alignment. The upward displacement at the support point is then removed, and the beam is lowered to apply prestress to the bridge deck. However, after the composite girder is suspended by cables, it becomes a continuous structure with multiple elastic supports. When lowering the beam at the support point, it is constrained by the stay cables, resulting in a small range of applied prestress and low efficiency. It cannot effectively apply compressive stress to the bridge deck outside the auxiliary pier and in the tail cable area of ​​the side span. Existing measures have limited effectiveness in improving the crack resistance of bridge deck panels in the auxiliary pier area and the tail cable area of ​​the side span of steel-UHPC composite girder cable-stayed bridges. Summary of the Invention

[0005] To overcome the shortcomings of the aforementioned background technology, the present invention aims to provide a method for improving the crack resistance of the bridge deck in the auxiliary piers and tail cable zone of a steel-UHPC composite girder cable-stayed bridge. This method does not employ tensioned prestressed steel strands or single-support beam lowering, but rather applies compressive stress to the bridge deck efficiently, precisely, easily, and over a wide range. This effectively leverages the high compressive strength of UHPC materials, improves the crack resistance of the bridge deck in the auxiliary piers and tail cable zone of the side span of the steel-UHPC composite girder cable-stayed bridge, and ensures the durability and safety of the structure.

[0006] To further achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for improving the crack resistance of the auxiliary piers and tail cable zone bridge deck of a steel-UHPC composite girder cable-stayed bridge includes the following steps:

[0008] (1) Based on the stress distribution of the bridge deck under the most unfavorable load combination during the operation period of the composite beam in the auxiliary pier area and the side span tail cable area, the range of steel-UHPC composite beams whose crack resistance does not meet the requirements is determined to be L1+L2.

[0009] Where L1 represents the distance from the auxiliary pier facing the main tower to the beam segment whose crack resistance meets the requirements, and L2 represents the distance from the auxiliary pier facing away from the main tower to the transition pier; L1+L2 together cover the auxiliary pier area and the side span tail cable area;

[0010] (2) The target compressive stress σ required for the bridge deck in the completed bridge state is determined by the difference between the stress value of the bridge deck in the auxiliary pier area and the end cable area of ​​the side span under the normal service limit state and the stress value that can meet the requirements for crack resistance. t ;

[0011] Among them, the control section is the section with the largest tensile stress on the bridge deck of the steel-UHPC composite beam in the auxiliary pier area and the side span tail cable area under the normal service limit state of the long-term condition.

[0012] (3) Taking the beam segment within the range of "L1+L2" of the steel-UHPC composite beam as a single-span simply supported beam, the maximum deflection of the simply supported composite beam under its own weight is calculated to be Δ. ZZ The compressive stress of the bridge deck at the control section is σ. ZZ ;

[0013] (4) Correct the construction steps of the calculation model for the steel-UHPC composite cable-stayed bridge, and calculate the stress difference between the control sections at the two construction stages: after the beam is lowered and after the bridge is completed. This is the stress correction value σ for the system transformation during the construction process of the control section. △ ;

[0014] (5) Adjust the self-weight load factor γ of the single-span simply supported beam. Y (0<γ Y<1), with stress value "σ t +σ △ "The compressive stress generated at the control section during beam lowering is used to calculate the self-weight load factor γ of a single-span simply supported beam." Y Deflection curve S under self-weight Y The maximum downward deflection value is △ ZY The antisymmetric arch shape obtained from the downward deflection displacement curve is the arch shape obtained during the processing and manufacturing of the steel main beam.

[0015] (6) Within the auxiliary pier area and the side span tail cable area of ​​the steel-UHPC composite beam, n beam-dropping control points are set at intervals of 6 to 9 meters within the "L1+L2" range. The total beam-dropping displacement S at each control point is... Z1 To S Zn That is, the curve S with the downward deflection displacement. Y The corresponding vertical displacement value, the maximum total displacement of the beam is Δ ZY ;

[0016] (7) The maximum total displacement of the beam during drop Δ ZY The process is implemented in stages, with each stage divided into equal parts based on a maximum single displacement not exceeding 3cm, resulting in a stage number of m. The "synchronous beam dropping" construction stage in step 4 is further subdivided into m stages of staged implementation. Based on the displacement of each stage of beam dropping, the self-weight load reduction factor γ1 to γ2 of the main beam at each stage is calculated. m The self-weight load reduction factor γ of the last stage m With γ Y equal;

[0017] (8) During the graded implementation process, the beam displacement of each beam control point at each grade is determined according to the corresponding self-weight load reduction factor γ1 to γ2. m The deflection curve of a simply supported beam is calculated inversely;

[0018] (9) During the graded implementation process, the support reaction force of each drop beam control point at each grade is the vertical reaction force corresponding to the current graded drop beam displacement when the self-weight of each grade of the composite beam is loaded. The value is taken according to the calculation model in step (7).

[0019] (10) The graded beam drop is carried out according to the calculation results, and the support reaction force and support displacement are controlled to apply the required compressive stress to the steel-UHPC composite beam bridge deck in the auxiliary pier area and the tail cable area of ​​the side span, thereby improving the crack resistance of the bridge deck.

[0020] Furthermore, the steel-UHPC composite beam adopts the method of prefabricating and hoisting the UHPC bridge deck and the steel main beam in whole segments, and the bridge deck between the beam segments is connected by transverse wet joints.

[0021] Furthermore, the construction steps of the modified steel-UHPC composite beam cable-stayed bridge assembly calculation model are as follows: set up supports at the beam drop control points → install the composite beams in the auxiliary pier area and the side span tail cable area to form a joint section → drop the beams at each control point simultaneously → close the side span → install the cable stays and the mid-span composite beams symmetrically segment by segment → close the mid-span → remove the supports at the beam drop control points → construct the bridge deck system → complete the bridge.

[0022] Furthermore, the location of the beam drop control points should correspond to the transverse diaphragms of the composite beam.

[0023] Furthermore, the compressive stress "σ" generated at the control section during beam lowering... t +σ △ "It should be less than the compressive stress σ of the bridge deck at the control section under its own weight." ZZ .

[0024] Furthermore, the maximum deflection Δ during beam lowering... ZY It should be less than the maximum deflection Δ under its own weight. ZZ .

[0025] Furthermore, the self-weight load factor γ is the compressive stress generated by the control section, which is "σ". t +σ △ "The self-weight load should be reduced accordingly by a factor."

[0026] The present invention has at least the following advantages over the prior art:

[0027] (1) It eliminates the need for a large number of internal or external prestressed steel strands at the auxiliary piers and the composite beams in the end span of the side span, resulting in better economic efficiency. It also avoids the weakening of the cross-section and adverse effects on the casting quality caused by internal prestressed steel strand ducts within the UHPC bridge deck, and reduces the workload of maintenance and repair of external prestressed steel strands during the bridge's operational phase. Furthermore, it avoids the problems of small application range and low efficiency of the single-support displacement method for prestressing, which prevents the application of prestress to the end span of the side span.

[0028] (2) Taking advantage of the structural characteristics of the steel-UHPC composite cable-stayed bridge, before the stay cables are tensioned, the composite beam bridge deck of the auxiliary piers and the tail cable area of ​​the side span can be subjected to compressive stress in a high-efficiency, high-precision, high-operability and wide-range manner by dropping the beams in stages on the support, which fully utilizes the compressive strength of UHPC material and has a high material utilization rate. The pre-stressing is applied by adjusting the internal force of the main beam itself, which has high application efficiency and reliable application method, further improving the crack resistance of the auxiliary piers and the tail cable area of ​​the side span of the steel-UHPC composite cable-stayed bridge, and ensuring the durability and safety of the structure.

[0029] (3) The method of applying prestress is not limited by the space of steel strand arrangement. For larger spans, it can still provide the required prestress for the composite beam bridge deck of auxiliary piers and side span tail cable area, which can further enhance the spanning capacity of steel-UHPC composite beam cable-stayed bridge and promote the development of composite beam cable-stayed bridge. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0031] Figure 1 This is a schematic diagram of the auxiliary pier and side span tail cable area of ​​the composite beam of the present invention;

[0032] Figure 2 This is a schematic diagram of the deflection curve of the simply supported composite beam of the present invention under its own weight.

[0033] Figure 3 The composite beam of this invention takes into account the adjustment coefficient γ Y Deflection curve S under self-weight Y Schematic diagram;

[0034] Figure 4 This is a schematic diagram of the composite beam segment being positioned and arched according to the present invention;

[0035] Figure 5 This is a schematic diagram of the arrangement of beam support points for controlling the combined cross section of the composite beam according to the present invention;

[0036] Figure 6 This is a schematic diagram showing the completion of the composite beam placement in this invention;

[0037] In the diagram: 1-Steel main beam, 2-UHPC bridge deck, 3-Beam lowering control point. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] A method for improving the crack resistance of the auxiliary piers and tail cable zone bridge deck of a steel-UHPC composite girder cable-stayed bridge includes the following steps:

[0040] (1) Based on the stress distribution of the bridge deck under the most unfavorable load combination during operation in the auxiliary pier area and the side span tail cable area of ​​the composite beam, the range of steel-UHPC composite beams whose crack resistance does not meet the requirements is determined to be L1+L2, such as Figure 1 As shown;

[0041] Where L1 represents the distance from the auxiliary pier facing the main tower to the beam segment whose crack resistance meets the requirements, and L2 represents the distance from the auxiliary pier facing away from the main tower to the transition pier; L1+L2 together cover the auxiliary pier area and the side span tail cable area;

[0042] (2) The target compressive stress σ required for the bridge deck in the completed bridge state is determined by the difference between the stress value of the bridge deck in the auxiliary pier area and the end cable area of ​​the side span under the normal service limit state and the stress value that can meet the requirements for crack resistance. t ;

[0043] Among them, the control section is the section with the largest tensile stress on the bridge deck of the steel-UHPC composite beam in the auxiliary pier area and the side span tail cable area under the normal service limit state of the long-term condition.

[0044] (3) Taking the beam segment within the range of "L1+L2" of the steel-UHPC composite beam as a single-span simply supported beam, the maximum deflection of the simply supported composite beam under its own weight is calculated to be Δ. ZZ The compressive stress of the bridge deck at the control section is σ. ZZ ,like Figure 2 As shown;

[0045] (4) Correct the construction steps of the calculation model for the steel-UHPC composite cable-stayed bridge, and calculate the stress difference between the control sections at the two construction stages: after the beam is lowered and after the bridge is completed. This is the stress correction value σ for the system transformation during the construction process of the control section. △ ;

[0046] (5) Adjust the self-weight load factor γ of the single-span simply supported beam. Y (0<γ Y <1), with stress value "σ t +σ △ "The compressive stress generated at the control section during beam lowering is used to calculate the self-weight load factor γ of a single-span simply supported beam." Y Deflection curve S under self-weight Y The maximum downward deflection value is △ ZY The antisymmetric arch shape obtained from the downward deflection displacement curve is the arch profile during the fabrication of the steel main beam, such as... Figure 3 , Figure 4 As shown;

[0047] (6) Within the auxiliary pier area and the side span tail cable area of ​​the steel-UHPC composite beam, n beam-dropping control points are set at intervals of 6 to 9 meters within the "L1+L2" range. The total beam-dropping displacement S at each control point is... Z1 To S Zn That is, the curve S with the downward deflection displacement. Y The corresponding vertical displacement value is Δ, where the maximum total displacement of the beam is the same as the maximum downward deflection value in step 5. ZY ,like Figure 5 As shown;

[0048] (7) To improve the precision and operability of the beam lowering process and ensure the effectiveness and safety of the beam lowering implementation, the maximum total displacement Δ of the beam lowering is measured. ZY The process is implemented in stages, with each stage divided into equal parts based on a maximum single displacement not exceeding 3cm, resulting in a stage number of m. The "synchronous beam dropping" construction stage in step 4 is further subdivided into m stages of staged implementation. Based on the displacement of each stage of beam dropping, the self-weight load reduction factor γ1 to γ2 of the main beam at each stage is calculated. m The self-weight load reduction factor γ of the last stage m With γ Y equal;

[0049] (8) During the graded implementation process, the beam displacement of each beam control point at each grade is determined according to the corresponding self-weight load reduction factor γ1 to γ2. m The deflection curve of a simply supported beam is calculated inversely;

[0050] (9) The support reaction force of each drop beam control point in each stage during the graded implementation process is the vertical reaction force corresponding to the current graded drop beam displacement when the self-weight of each stage of the composite beam is loaded. The value is taken according to the calculation model in step 7.

[0051] (10) The tiered girder lowering was strictly implemented based on the calculation results, and dual control was exercised using support reactions and support displacements. This ensured that the required compressive stress was applied to the steel-UHPC composite girder bridge deck in the auxiliary pier area and the end cable area of ​​the side span, thereby improving the crack resistance of the bridge deck. Once the tiered girder lowering was completed, as... Figure 6 As shown.

[0052] In this invention, the steel-UHPC composite beam is constructed by prefabricating and hoisting the UHPC bridge deck 2 and the steel main beam 1 in one section, and the bridge deck between the beam sections is connected by transverse wet joints.

[0053] In this invention, the construction steps of the modified steel-UHPC composite beam cable-stayed bridge assembly calculation model are as follows: set up supports at the beam drop control points → install the composite beams in the auxiliary pier area and the side span tail cable area to form a joint section → drop the beams at each control point simultaneously → close the side span → install the cable stays and the mid-span composite beams symmetrically segment by segment → close the mid-span → remove the supports at the beam drop control points → construct the bridge deck system → complete the bridge.

[0054] In this invention, the arrangement position of the beam drop control point 3 should correspond to the cross diaphragm of the composite beam.

[0055] In this invention, the compressive stress "σ" generated at the control section during beam lowering is described. t +σ △ "It should be less than the compressive stress σ of the bridge deck at the control section under its own weight." ZZ .

[0056] In this invention, the maximum downward deflection Δ during beam lowering is... ZY It should be less than the maximum deflection Δ under its own weight. ZZ .

[0057] In this invention, the self-weight load factor γ is the compressive stress generated by the control section, which is "σ". t +σ △ "The self-weight load should be reduced accordingly by a factor."

[0058] Those skilled in the art can make various modifications and variations to the embodiments of the present invention. If such modifications and variations are within the scope of the claims of the present invention and their equivalents, then such modifications and variations are also within the protection scope of the present invention.

[0059] The contents not described in detail in the specification are prior art known to those skilled in the art.

Claims

1. A method for improving the crack resistance of the bridge deck in the auxiliary pier and tail cable zone of a steel-UHPC composite girder cable-stayed bridge, characterized in that, Includes the following steps: (1) Based on the stress distribution of the bridge deck under the most unfavorable load combination during the operation period of the composite beam in the auxiliary pier area and the side span tail cable area, the range of steel-UHPC composite beams whose crack resistance performance does not meet the requirements is determined to be L1+L2. Where L1 represents the distance from the auxiliary pier facing the main tower to the beam segment whose crack resistance meets the requirements, and L2 represents the distance from the auxiliary pier facing away from the main tower to the transition pier; L1+L2 together cover the auxiliary pier area and the side span tail cable area; (2) The target compressive stress σ required for the bridge deck in the completed bridge state is determined by the difference between the stress value of the bridge deck in the auxiliary pier area and the end cable area of ​​the side span under the normal service limit state and the stress value that can meet the requirements for crack resistance. t ; Among them, the control section is the section with the largest tensile stress on the bridge deck of the steel-UHPC composite beam in the auxiliary pier area and the side span tail cable area under the normal service limit state of the long-term condition. (3) Taking the beam segment within the range of "L1+L2" of the steel-UHPC composite beam as a single-span simply supported beam, the maximum deflection of the simply supported composite beam under its own weight is calculated to be Δ. ZZ The compressive stress of the bridge deck at the control section is σ. ZZ ; (4) Correct the construction steps of the steel-UHPC composite beam cable-stayed bridge assembly calculation model, and calculate the stress difference of the control section in the two construction stages after the beam is lowered and after the bridge is completed. This is the stress correction value σ of the system transformation during the construction process of the control section. △ ; The construction steps of the modified steel-UHPC composite beam cable-stayed bridge calculation model are as follows: set up supports at the beam drop control points → install the composite beams in the auxiliary pier area and the side span tail cable area to form a joint section → drop the beams at each control point simultaneously → close the side span → install the cable stays and the middle span composite beams symmetrically segment by segment → close the middle span → remove the supports at the beam drop control points → construct the bridge deck system → complete the bridge. (5) Adjust the self-weight load factor γ of the single-span simply supported beam. Y , with stress value "σ t +σ △ "The compressive stress generated at the control section during beam lowering is used to calculate the self-weight load factor γ of a single-span simply supported beam." Y Deflection curve S under self-weight Y The maximum downward deflection value is △ ZY The antisymmetric arch shape obtained from the downward deflection displacement curve is the arch shape obtained during the processing and manufacturing of the steel main beam. (6) Within the auxiliary pier area and the tail cable area of ​​the steel-UHPC composite beam, n beam-dropping control points are set at intervals of 6 to 9 m within the "L1+L2" range. The total beam-dropping displacement S at each control point is... Z1 To S Zn That is, the curve S with the downward deflection displacement. Y The corresponding vertical displacement value, the maximum total displacement of the beam is Δ ZY ; (7) For the maximum total displacement of the beam during drop Δ ZY The implementation is carried out in stages, with the maximum displacement in a single instance not exceeding 3cm, and the number of stages is determined to be m. The "synchronous beam dropping" construction stage in the calculation model of step (4) is subdivided into m construction stages of staged implementation. The self-weight load reduction coefficient γ1 to γ2 of the main beam at each stage is calculated based on the displacement of each stage of beam dropping. m The self-weight load reduction factor γ of the last stage m With γ Y equal; (8) During the graded implementation process, the beam displacement of each beam control point at each grade is determined according to the corresponding self-weight load reduction factor γ1 to γ2. m The deflection curve of a simply supported beam is calculated inversely; (9) The support reaction force of each drop beam control point in each stage during the graded implementation process is the vertical reaction force corresponding to the current graded drop beam displacement when the self-weight of each stage of the composite beam is loaded. The value is taken according to the calculation model in step (7). (10) The graded beam dropping is carried out according to the calculation results, and the fulcrum reaction force and fulcrum displacement are used for dual control to realize the graded beam dropping.

2. The method for improving the crack resistance of the auxiliary piers and tail cable zone of a steel-UHPC composite girder cable-stayed bridge according to claim 1, characterized in that, The steel-UHPC composite beam is constructed by prefabricating and hoisting the UHPC bridge deck and the steel main beam in whole segments, with the bridge deck between the beam segments connected by transverse wet joints.

3. The method for improving the crack resistance of the auxiliary piers and tail cable zone of a steel-UHPC composite girder cable-stayed bridge according to claim 1, characterized in that, The location of the beam drop control points should correspond to the transverse diaphragms of the composite beam.

4. The method for improving the crack resistance of the auxiliary piers and tail cable zone of a steel-UHPC composite girder cable-stayed bridge according to claim 1, characterized in that, The compressive stress "σ" generated at the control section during beam lowering. t +σ △ "It should be less than the compressive stress σ of the bridge deck at the control section under its own weight." ZZ .

5. The method for improving the crack resistance of the auxiliary piers and tail cable zone of a steel-UHPC composite girder cable-stayed bridge according to claim 1, characterized in that, The maximum deflection Δ during beam lowering is mentioned. ZY It should be less than the maximum deflection Δ under its own weight. ZZ .

6. The method for improving the crack resistance of the auxiliary piers and tail cable zone of a steel-UHPC composite girder cable-stayed bridge according to claim 1, characterized in that, The self-weight load factor γ is the compressive stress generated at the control section, which is σ. t +σ △ "The self-weight load should be reduced accordingly by a factor."

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