Temporary submerged area bridge design method and bridge
By employing a two-stage design approach and construction measures, the safety and rapid recovery of bridges under super-standard flood conditions were addressed, enhancing the stability and post-disaster recovery capabilities of bridges under extreme hydrological conditions, and achieving a safe, economical, and sustainable bridge design.
Patent Information
- Application Number
- CN202511511598.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-22
- Publication Date
- 2026-02-27
AI Technical Summary
Existing bridge design codes fail to adequately consider the effects of floods exceeding standard levels, especially in temporary inundation areas. This results in insufficient safety of bridge structures under extreme hydrological conditions, weak post-disaster recovery capabilities, and a lack of a full life-cycle design concept.
A two-stage design approach was adopted. First, the bridge structure was designed according to the standard of a once-in-a-century flood. Then, systematic calculations and structural measures were carried out for a once-in-three-hundred-year flood, such as anti-buoyancy calculations, bearing calculations and pier calculations, to ensure the safety of key components. Structural measures such as tension bearings, limit rods and increased reinforcement were also adopted.
It significantly improved the stability and resilience of bridges under extreme floods, ensured rapid traffic restoration, reduced post-disaster damage, and achieved safe, economical, and sustainable engineering construction.
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of traffic and water conservancy engineering, and particularly relates to a temporary inundation area bridge design method and a bridge. BACKGROUND
[0002] In the prior art, as an important livelihood project, the flood control reservoir improves the downstream riverway and town flood control standard, and has functions of irrigation, power generation, water supply, etc. The flood control capacity is a key index for measuring the flood control capacity of the reservoir, and the larger the capacity is, the greater the water level amplitude of the temporary inundation area under different flood control standards is under the condition of steep terrain. The traffic reconstruction project around the reservoir area usually adopts the mountainous area highway design standard, and the bridge structure is usually used when crossing the riverway or the reservoir area.
[0003] At present, the conventional river-crossing bridge design is mainly designed according to the traffic industry specification, and the beam bottom elevation must be higher than the design flood level. The design flood level is generally determined according to the road grade and bridge grade, and the common flood control standard is 50 to 100 years. However, in the temporary inundation area of the flood control reservoir, the flood control standard may cover a wide range from 20 to 300 years.
[0004] The prior art has the following main problems: Lack of systematic research on super-standard flood effect: the existing bridge design specification does not fully consider the effect of flood higher than the traffic industry standard (such as 100 years), especially in the temporary inundation area, the static and dynamic response of the bridge superstructure, support and pier under the super-high water level lacks systematic analysis and calculation basis.
[0005] Insufficient post-disaster rapid recovery capability: the existing design method does not fully consider the structure performance evaluation, reinforcement measures and rapid recovery requirements of the bridge after encountering super-standard flood, which may cause serious damage such as support destruction, beam falling and even overall collapse of the bridge after the flood, seriously affecting the post-disaster traffic recovery and livelihood protection.
[0006] Lack of whole life cycle design concept: the existing technology fails to implement the whole life cycle design concept, and the long-term impact of super-standard flood is not predicted in the bridge design stage, and there is a lack of targeted structural measures and repair strategies, which makes it difficult to realize the economy and sustainability of the project.
[0007] Therefore, it is urgent to develop a special design method for the bridge in the temporary inundation area to make up for the technical blank of the existing specification under the action of super-standard flood, and to improve the safety and rapid recovery capability of the bridge under extreme hydrological conditions. SUMMARY
[0008] The present application aims to provide a temporary inundation area bridge design method and a bridge to solve the problems in the background art.
[0009] To achieve the above object, the present application provides the following technical solution: a temporary inundated area bridge design method, comprising the following steps: First stage design: determine the flood control standard of the bridge according to the traffic industry specification, and perform limit state and normal use state checking of the bearing capacity of the bridge pier and foundation under the 100-year flood to ensure the safety of the structure; Second stage design: perform checking on the superstructure, support and pier of the bridge using a flood control standard higher than the traffic industry specification, and take corresponding structural measures based on the checking results to ensure that the key components of the bridge do not enter the plastic state under the action of the flood; the flood control standard higher than the traffic industry specification is the 300-year flood standard or the reservoir checking flood standard.
[0010] Preferably, in the second stage design, the checking of the superstructure beam body is the anti-floating capacity checking, which includes: calculating the anti-floating coefficient of the superstructure beam body under the 300-year flood or the reservoir checking flood, the anti-floating coefficient = (the weight of the superstructure + the pulling force of the support on the superstructure + the pulling force of the pulling rod on the superstructure) / the total floating force; when the anti-floating coefficient is less than a first threshold value, take anti-floating structural measures to make the anti-floating coefficient after taking the structural measures not less than a second threshold value.
[0011] Preferably, the first threshold value is 1.05, and the second threshold value is 1.2.
[0012] Preferably, the anti-floating structural measures include one or more of the following: using a pulling support, setting a vertical limiting pulling rod, weighting the beam body, or using a solid section beam body.
[0013] Preferably, in the second stage design, the checking of the bridge support includes at least one of the following: shear deformation checking, anti-sliding checking and horizontal bearing capacity checking; Based on the checking results, adjust the support arrangement, set pier beam consolidation, set transverse bridge pulling rod, set damper or increase the size of the transverse bridge block to meet the performance requirements of the support.
[0014] Preferably, the flow water pressure (F) for the checking of the support is calculated by the following formula: F = KAγv² / 2g wherein, K is the shape coefficient of the pier or the main beam, A is the water blocking area of the pier or the beam body (㎡), γ is the specific weight of water (KN / m³), v is the design flow rate (m / s), g is the acceleration of gravity.
[0015] Preferably, in the second stage of design, the verification of the bridge piers includes the verification of the internal forces at the pier base section, which includes: By combining the water pressure with temperature effects and vehicle braking force effects as loads, the combined bending moment of the pier bottom section is obtained. The yield bending moment of the pier bottom section was obtained by bending moment-curvature analysis; The combined bending moment is controlled to be less than the yield bending moment to ensure that the bridge pier does not enter the plastic stage; If the verification fails, optimization can be achieved by increasing the cross-section of the pier column or increasing the reinforcement of the pier column.
[0016] Preferably, the construction measures further include: designing the bridge as a continuous rigid frame bridge system, or optimizing the column piers into rectangular hollow piers.
[0017] The present invention also discloses a bridge designed and constructed using the aforementioned design method.
[0018] The beneficial effects of this invention are: it effectively fills the gap in existing transportation industry standards for bridge safety design under super-standard flood conditions. In the first stage, this method ensures the safety and reliability of bridges under a conventional 100-year flood, and in the second stage, it systematically verifies and strengthens the superstructure's anti-buoyancy, bearing anti-thrust, and pier anti-plastic deformation capabilities for a 300-year flood or a check flood. This significantly improves the overall stability and resilience of bridges in extreme flood disasters, avoiding catastrophic consequences such as bearing washout and beam collapse.
[0019] From a life-cycle perspective, this invention, through optimized overall design and targeted structural measures such as vertical restraints, tension supports, and pier-beam consolidation, achieves the goal of "rapid repairability" of bridges after major floods with relatively low economic investment. This not only ensures the rapid restoration of vital transportation arteries after disasters and greatly reduces the impact of temporary flooded areas on residents' lives and livelihoods, but also embodies the modern engineering construction concepts of safety, economy, reliability, and sustainability, resulting in significant social and economic benefits. Detailed Implementation
[0020] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.
[0021] The specific implementation of the present invention will now be described in detail with reference to preferred embodiments. Example
[0022] This embodiment uses a prestressed concrete continuous beam bridge spanning a temporary inundation zone of a large flood control reservoir as an example to illustrate the specific implementation process of the invention. The flood control standard for this reservoir is once every 300 years.
[0023] The core process of the design method described in this invention includes two stages: Phase 1: Standard Design First, the flood control standard for the bridge was determined according to transportation industry standards, and this bridge was designed for a 100-year flood event. Under this standard, conventional bridge structural design was carried out, including determining the bridge span arrangement, beam cross-section form (box section was initially selected in this example), pier dimensions, and foundation type. Subsequently, a bridge model was built using finite element software to calculate the ultimate limit state (strength) and serviceability limit state (crack width) of the piers and foundations under the combined effects of a 100-year flood level, vehicle load, and temperature load, ensuring that all indicators meet the specifications and guaranteeing the safety and reliability of the bridge under normal service conditions.
[0024] Phase Two: Flood Defense Design Above Standard This stage involves the specific design and verification of the 300-year flood level, which is the main innovation of this invention.
[0025] Calculation and design of the buoyancy resistance of the superstructure beams: During a 300-year flood event, part of the box girder section was submerged. Calculate the total buoyancy of the girder and, based on the core formula, calculate the buoyancy resistance coefficient: Buoyancy coefficient = (self-weight of superstructure + tension of supports on superstructure + tension of tie rods on superstructure beam) / total buoyancy.
[0026] Calculations show that the anti-buoyancy coefficient in this embodiment is 0.98, which is less than the first threshold of 1.05. Therefore, anti-buoyancy structural measures must be taken. In this embodiment, vertical limiting tie rods are added to both ends of the beam, and some supports are replaced with tension supports that can provide upward pull-out force. After taking these measures and recalculating, the anti-buoyancy coefficient increased to 1.25, which is greater than the second threshold of 1.2, thus meeting the safety requirements.
[0027] Bridge bearing calculation and design: First, the design flow velocity under a 300-year flood event is obtained as v = 3.5 m / s. The water pressure on the main beam and piers is calculated using the formula F = KAγv² / 2g. The beam is box-shaped with a shape factor K of 1.3; the unit weight of water γ is 10 KN / m³; and the acceleration due to gravity g is 9.81 m / s².
[0028] After calculating the total water pressure F acting on the main beam, this force is distributed to each pier bearing according to stiffness. Shear deformation is checked for the plate rubber bearings: Δ = Fh / GA, ensuring that the shear deformation Δ ≤ 0.5t~e~ (total thickness of the rubber layer). The horizontal bearing capacity of the fixed supports of the pot bearings is checked to ensure that their nominal horizontal bearing capacity is greater than the distributed water pressure.
[0029] Calculations revealed that the shear deformation of the plate bearings for a single pier exceeded the limit in the original design. To address this issue, this embodiment optimized the bearing arrangement by designating one of the central piers as a pier-beam integrated structure and strengthening the lateral restraint blocks at the tops of the remaining piers. This allowed the horizontal force to be shared by multiple pier columns, ultimately ensuring that all bearing calculations met the requirements.
[0030] Pier bearing capacity calculation and design: The key focus is on verifying the bottom section of the pier column, which bears the greatest horizontal force. The water pressure (combination coefficient of 1.0) calculated in the second stage is combined with the most unfavorable loads such as temperature effect, shrinkage and creep, and vehicle braking force to obtain the controlling bending moment at the bottom of the pier.
[0031] The yield moment of the pier base section was obtained through moment-curvature analysis using finite element method (FEM) software. Comparison revealed that the combined load moments were very close to but did not exceed the yield moment. To ensure safety and allow for a margin of safety, this embodiment adopted a structural measure to increase the reinforcement ratio of the pier column, raising the longitudinal reinforcement ratio by 15%. Recalculation confirmed that the combined bending moment was less than the new yield moment, ensuring that the pier would not enter the plastic stage under severe flooding and could be quickly restored to use without large-scale reinforcement after the flood receded. Example
[0032] As an alternative embodiment of the present invention, for another bridge located in a temporary flooding zone, the superstructure directly uses solid T-beams with excellent anti-buoyancy performance, fundamentally avoiding the anti-buoyancy problem. In the support design, a transverse bridge damper is used throughout to dissipate the impact energy of the flowing water, replacing the pier-beam consolidation scheme. The pier form is optimized to rectangular hollow piers, which reduces the structural weight and improves bending stiffness while ensuring load-bearing capacity.
[0033] As can be seen from this embodiment, the core of the present invention lies in the "two-stage" design concept and the principle of systematic verification. The specific construction measures can be flexibly selected and combined according to the actual situation. Any design that adopts the idea of the present invention under the standard of flood control exceeding the industry standard falls within the protection scope of the present invention.
[0034] It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.
Claims
1. A method of designing a bridge in a temporary inundated area, characterized in that, The method comprises the following steps: The first stage design: determining the flood control standard of the bridge according to the traffic industry standard, checking the bearing capacity limit state and the normal use limit state of the bridge pier and the foundation under the flood of once in a hundred years to ensure the safety of the structure; The second stage design: checking the bridge superstructure, support and pier under a flood control standard higher than the traffic industry standard, and taking corresponding structural measures based on the checking result to ensure that the key components of the bridge do not enter the plastic state under the action of the flood; the flood control standard higher than the traffic industry standard is the flood standard of once in three hundred years or the reservoir checking flood standard.
2. The interim flood zone bridge design method of claim 1, wherein, In the second stage design, the checking of the superstructure beam body is the anti-floating capacity checking, which comprises: Calculating the anti-floating coefficient of the superstructure beam body under the flood of once in three hundred years or the reservoir checking flood, the anti-floating coefficient = (the weight of the superstructure + the pulling force of the support on the superstructure + the pulling force of the pulling rod on the superstructure) / the total floating force; When the anti-floating coefficient is less than a first threshold value, taking anti-floating structural measures to make the anti-floating coefficient after taking the structural measures not less than a second threshold value.
3. The interim flood zone bridge design method of claim 2, wherein, The first threshold value is 1.05, and the second threshold value is 1.
2.
4. The interim flood zone bridge design method of claim 2, wherein, The anti-floating structural measures comprise one or more of the following: using a pulling support, setting a vertical limiting pulling rod, weighting the beam body, or using a solid section beam body.
5. The interim flood zone bridge design method of claim 1, wherein, The checking of the bridge support in the second stage design comprises at least one of the following: shear deformation checking, anti-sliding checking and horizontal bearing capacity checking; Based on the checking result, the performance requirements of the support are met by adjusting the support arrangement, setting pier beam consolidation, setting transverse bridge pulling rod, setting damper or increasing the size of the transverse bridge block.
6. The interim flood zone bridge design method of claim 5, wherein, The flow water pressure (F) for the checking of the support is calculated by the following formula: F = KAγv² / 2g Wherein, K is the shape coefficient of the pier or the main beam, A is the water blocking area of the pier or the beam body (㎡), γ is the specific gravity of water (KN / m³), v is the design flow rate (m / s), g is the acceleration of gravity.
7. The interim flood zone bridge design method of claim 1, wherein, The checking of the pier in the second stage design is the pier bottom section internal force checking, which comprises: Combining the flow water pressure with the temperature effect and the automobile braking force effect to obtain the combined bending moment of the pier bottom section; Obtaining the yield bending moment of the pier bottom section through the bending moment-curvature analysis; Controlling the combined bending moment to be less than the yield bending moment to ensure that the pier does not enter the plastic state; If the checking fails, the structure is optimized by increasing the pier column section or increasing the pier column reinforcement.
8. The interim flood zone bridge design method according to any one of claims 1 to 7, wherein, The structural measures further comprise: designing the bridge as a continuous rigid frame bridge system, or optimizing the column pier to a rectangular hollow pier.
9. A bridge, characterized by The bridge is designed and built using the design method of any one of claims 1 to 8.