Bridge jacking support cushion stone heightening limit value calculation method and construction method

Abstract

This invention discloses a method for calculating and constructing the limit value of the height increase of the bearing pad stone in bridge jacking, including the following steps: determining the temperature force and braking force on the bearing, comparing them with the frictional resistance, and taking the smaller of the two as the bearing frictional force; calculating the bearing reaction force under the lane load, and calculating the critical bending moment when the minimum pressure at the interface between the old and new pad stones is 0; calculating the height h of the pad stone height increase limit value based on the obtained bearing frictional force and the obtained critical bending moment; and adopting different construction methods based on the height h of the pad stone height increase limit value. This invention is reasonably designed, provides a scientific theoretical basis for bridge jacking schemes, ensures the safety and stability of the bridge structure, improves the safety of the construction process, provides a theoretical basis for the modification method of increasing the bearing pad stone in bridge jacking, clarifies the applicable scope of the method, improves the construction safety during the bridge jacking process, and ensures the stability of the structure after jacking.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering technology, specifically to a method for calculating and constructing the limit value of the height increase of the bearing pad stone of a bridge jacking bearing. Background Technology

[0002] With the continuous development of bridge jacking technology, more and more bridges are being lifted, and the lifting heights are also increasing. Within the same span, due to the difference in elevation between the new and old bridges, the required lifting height varies significantly for different beam segments. For beams with a small lifting height, the elevation of the new bridge can be achieved by raising the bearing pads after lifting the beam. For bridges with a large lifting height, in addition to raising the bearing pads, the cap beam can be thickened to meet the elevation requirements of the new bridge. However, theoretical research on bridge jacking still cannot meet the requirements of engineering practice. The applicable scope of the above two bridge jacking methods is still unclear, which brings significant safety risks to bridge jacking projects and threatens the safety of the bridge structure after lifting. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for calculating the limit value of the height increase of the bridge jacking bearing pad stone, including the following steps:

[0004] S1. Determine the frictional force of the support;

[0005] S2. Calculate the support reaction force under lane load and the critical bending moment when the minimum pressure at the interface between the old and new bearing stones is 0.

[0006] S3. The height limit value for raising the pad stone is calculated by using the support friction force obtained from S1 and the critical bending moment obtained from S2.

[0007] Optionally, the height h of the paving stone's height limit value is calculated using the following formula (1):

[0008]

[0009] Where M k F is the critical bending moment. f This refers to the frictional force of the support.

[0010] Optional, critical bending moment M k Calculate using the following formula (2):

[0011]

[0012] Among them G k The reaction force of the support due to its own weight; F k denoted as , where is the force exerted by the lane load on the top of the bearing pad; A is the cross-sectional area of ​​the support; and W is the section modulus of the support.

[0013] Optional, support friction force Ff The horizontal force F less than that of a single support, and the frictional force F of the support. f Calculate using the following formula (3):

[0014] F f =G k μ (3).

[0015] Optionally, the horizontal force F at a single support is calculated using the following formula (4):

[0016] F = F t +F D (4)

[0017] Where F t The horizontal force caused by the shrinkage and temperature changes of the superstructure concrete; F D This provides braking force for the supports of each pier.

[0018] This invention also provides a construction method for raising the bearing pad of a bridge jacking structure, comprising the following steps: calculating the limit value for raising the bearing pad of the bridge jacking structure; when the limit value is below 35cm, raising and modifying the bearing pad; when the limit value is in the range of 35-65cm, raising the cap beam and redoing the pad; when the limit value is greater than 65cm, using the method of breaking the column and jacking the entire structure simultaneously.

[0019] The beneficial effects of this invention are: it is reasonably designed, provides a scientific theoretical basis for bridge jacking schemes, ensures the safety and stability of bridge structures, improves the safety of the construction process, provides a theoretical basis for the modification method of increasing the bearing pad stone in bridge jacking, clarifies the applicable scope of the method, improves the construction safety during bridge jacking, and ensures the stability of the structure after jacking. Attached Figure Description

[0020] The present invention will be described by way of example and with reference to the accompanying drawings, wherein:

[0021] Figure 1 This is a flowchart of the calculation method for the height limit value of the bridge jacking bearing pad stone according to the present invention;

[0022] Figure 2 This is a schematic diagram of the support pad heightening scheme in this invention;

[0023] Figure 3 This is a schematic diagram of the lane load loading scheme in this invention.

[0024] In the diagram: 1. Original support pad; 2. Raised pad; 3. Support; 4. Beam leveling block; 5. Beam. Detailed Implementation

[0025] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is merely one example of a series of equivalent or similar features.

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0027] In the description of the invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of the invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," and "connected," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, such as welding, riveting, or bonding; it can also be a detachable connection, such as threaded connection, keyed connection, or pin connection; or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; or it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] like Figure 1-2 The method for calculating the limit value of the height increase of the bridge jacking bearing pad stone, as shown, includes the following steps:

[0030] S1. Determine the frictional force of the support;

[0031] S2. Calculate the support reaction force under lane load and the critical bending moment when the minimum pressure at the interface between the old and new bearing stones is 0.

[0032] S3. The height limit for raising the bearing pad is calculated using the support friction force obtained from S1 and the critical bending moment obtained from S2. It should be noted that the small eccentric compression design concept is used to control the absence of tensile stress at the interface between the new and old bearing pads, thereby calculating the height of the support system and determining the jacking limit.

[0033] Specifically, the height h of the paving stone's height limit is calculated using the following formula (1):

[0034]

[0035] Where M k F is the critical bending moment. f This refers to the frictional force of the support.

[0036] Specifically, the optional critical bending moment M k Calculate using the following formula (2):

[0037]

[0038] Among them G k The reaction force of the support due to its own weight; F k denoted as , where is the force exerted by the lane load on the top of the bearing pad; A is the cross-sectional area of ​​the support; and W is the section modulus of the support.

[0039] Specifically, the bearing friction force F f The horizontal force F less than that of a single support, and the frictional force F of the support. f Calculate using the following formula (3):

[0040] F f =G k μ (3).

[0041] Specifically, the horizontal force F at a single support is calculated using the following formula (4):

[0042] F = F t +F D (4)

[0043] Where F t The horizontal force caused by the shrinkage and temperature changes of the superstructure concrete; F D This provides braking force for the supports of each pier.

[0044] As an example, the support cross-sectional area A is 0.3 m², and the support section modulus W is 0.03 m. 3 The support stiffness k is 8888.9 kN / m, the calculated span of the simply supported beam is 32.5 m, and the weight of the precast beam is 7945.63 kN.

[0045] The longitudinal horizontal force on the support is distributed according to the stiffness of each pier support. The stiffness of the plate rubber bearing on a single pier of a simply supported beam is k = nAG / t = 5 × 0.4 × 0.4 × 1 × 106 / 0.09 = 8888.9 kN / m.

[0046] Where n is the number of supports in a row, A is the rubber area of ​​the support, G is the shear modulus of the rubber support, and t is the thickness of the rubber support.

[0047] Distance from fixed point to pier #0 Where k i Let L be the top stiffness of pier i. i The distance between pier i and pier 0 is the horizontal force F caused by the shrinkage and temperature changes of the superstructure concrete at the top of the supports of each pier. t = Distance from bridge pier to fixed point × k × α × Δt, calculated as follows:

[0048] F t1 =(32.25-16.25)×8888.9×0.00001×40=57.8kN

[0049] F t2 =(0-16.25)×8888.9×0.00001×40=-57.8kN.

[0050] Furthermore, according to Article 4.3.5 of the "General Specifications for Design of Highway Bridges and Culverts" (JTG D60-2015), the braking force of the vehicle is calculated as follows:

[0051] F D0 =(10.5×32.5+2×(32.5+130))×0.1=66.625kN<165kN

[0052] The total braking force is calculated as follows:

[0053] F Dt =165×3×0.78=386.1kN

[0054] The braking force at the top of the supports of each pier is calculated as follows:

[0055]

[0056] The aforementioned precast beam weight of 7945.63kN is the sum of the following: the weight of the superstructure guardrail G1 = 0.4948 × 2 × 32.5 × 26 = 836.212kN; the weight of the bridge deck pavement G2 = (0.08 + 0.05) × 14.75 × 32.5 × 26 = 1620.3kN; and the weight of the precast T-beam G3 = (1.5844 × 2.6 × 2 × 5 + 0.8924 × 27.3 × 5 + 0.3701 × 32.5 × 4) × 26 = 5489.12kN.

[0057] Furthermore, the gravity acting on the top of a single support pad is calculated as follows:

[0058] G k =(836.212+1620.3+5489.12) / 2 / 5=794.563kN

[0059] The bearing frictional resistance, also known as bearing friction force, is calculated as follows:

[0060] F f =G k μ = 794.563 × 0.3 = 283.36 kN

[0061] The horizontal force at a single support is calculated as follows:

[0062] F = F t +F D =57.8 + 193.1 = 250.9 kN > F f =238.36kN.

[0063] Therefore, it can be seen that the beam slipped under the action of the horizontal force, so the support friction is used as the control horizontal force for verification.

[0064] Furthermore, the lane load consists of two parts: concentrated force and uniformly distributed force. When the concentrated force is on one pier, this is the most unfavorable working condition. Figure 3 As shown, the force calculation for the lane load acting on the top of the bearing pad is as follows:

[0065] F k1 =(2×(32.5+130) / 5+10.5×32.5 / 2 / 5)×3×0.78=231.95kN,

[0066] F k2 =(10.5×32.5 / 2 / 5)×3×0.78=79.85kN.

[0067] Furthermore, when the minimum pressure value p at the interface between the new and old pad stones... min When M = 0, the critical bending moment is M k The calculation is as follows:

[0068]

[0069]

[0070] Furthermore, the height h, the limit value for raising the foundation stone, is calculated as follows:

[0071]

[0072]

[0073] Based on the above calculations and analysis, the maximum height h for the bearing pad is 0.36–0.43 m, with a minimum of 0.36 m. The bearing pad height is controlled at 0.35 m. For bridge spans where the original bridge elevation is less than 0.35 m, the cap beams are used to jack up the spans to the design elevation, and the bearing pads are then heightened and modified.

[0074] A construction method for raising the bearing pad of a bridge jacking structure includes the following steps: calculating the limit value for raising the bearing pad of the bridge jacking structure, and determining the possible height h2 of the cap beam through finite element modeling analysis; when the original bridge lifting height is less than the minimum limit value h1, the bearing pad is raised; when the original bridge lifting height is within the range of the minimum limit value h1 to the minimum limit value h1 + the possible height h2 of the cap beam, the cap beam is raised and the pad is redone; when the original bridge lifting height is greater than the minimum limit value h1 + the possible height h2 of the cap beam, the entire structure is jacked up by breaking the column, and the entire structure is jacked up synchronously. It should be noted that pad 2 is raised on the basis of the original bearing pad 1, and after the pad is raised, the bearing 3 and the beam leveling block 4 are placed to lift the superstructure beam 5.

[0075] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A method for calculating the limit value of the height increase of the bridge jacking bearing pad stone, characterized in that, Includes the following steps: S1. Determine the frictional force of the support; S2. Calculate the support reaction force under lane load and the critical bending moment when the minimum pressure at the interface between the old and new bearing stones is 0. S3. The height limit for raising the pad stone is calculated using the support friction force obtained from S1 and the critical bending moment obtained from S2. ; The height of the raised foundation stone is at the limit value. Calculate using the following formula (1): ； in The critical bending moment; For the support friction force; The critical bending moment Calculate using the following formula (2): ； in The reaction force of the support due to its own weight; The force exerted by the lane load on the top of the bearing pad; The cross-sectional area of ​​the support; The section modulus of the support; The friction of the support Horizontal force less than a single support The friction of the support Calculate using the following formula (3): ； The horizontal force of the single support Calculate using the following formula (4): ； in The horizontal force is caused by the shrinkage of the superstructure concrete and temperature changes. This provides braking force for the supports of each pier.

2. A construction method for raising the bearing pad of a bridge, characterized in that, Includes the following steps: According to claim 1, the method for calculating the height limit of bridge jacking bearing pad stone is used to calculate the height limit of bridge jacking bearing pad stone. When the limit value is below 35cm, the bearing pad stone is heightened and modified; when the limit value is in the range of 35-65cm, the cap beam is heightened and the pad stone is redone; when the limit value is greater than 65cm, the column is broken and the whole structure is jacked up synchronously.

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