A method for maintaining access to a temporary road by having an elevated trestle bridge pass under an existing railway frame bridge.

Abstract

This invention discloses a method for maintaining a temporary access road when an elevated trestle bridge passes under an existing railway frame bridge. The existing railway frame bridge is a double-span drainage culvert. The method includes: constructing a traffic culvert on one side of the double-span drainage culvert, while retaining the other side as a drainage culvert; constructing a temporary steel bridge within the traffic culvert to form a construction passage across the bottom slab of the existing frame culvert; connecting the temporary steel bridge with the passages on both sides of the double-span drainage culvert to form a temporary access road; maintaining clearance between the temporary steel bridge and the bottom of the traffic culvert; and spacing between the temporary steel bridge and the two sides of the traffic culvert; the temporary steel bridge is a single-lane bridge with height and width restrictions. This invention enables low-clearance crossing while ensuring smooth drainage during the flood season.

Description

Technical Field

[0001] This invention relates to the field of temporary access roads during bridge construction. More specifically, this invention relates to a method for maintaining access to a temporary access road when an elevated trestle bridge passes under an existing railway frame bridge. Background Technology

[0002] This application addresses a major bridge construction project that crosses the up and down lines of a railway. There are no suitable frame culverts or bridges on either side of the railway to allow construction equipment to pass through several piers corresponding to the major bridge between the two lines. Surveying revealed that a double-span frame drainage culvert at a certain point on the down line is the most likely location suitable for equipment passage. A passageway for construction equipment can be constructed there, forming a temporary road. However, conventional railway frame drainage culverts prohibit vehicle passage. Firstly, the low clearance of the frame drainage culvert necessitates consideration of ensuring safe passage. Secondly, ensuring the necessary drainage flow within the frame drainage culvert after its construction equipment passageway is established, without impacting drainage during the flood season, also requires consideration. Furthermore, how to construct a passageway within the frame drainage culvert to ensure its structural rigidity and strength, thereby enabling the smooth passage of large machinery, is also a key consideration. Summary of the Invention

[0003] One objective of this invention is to provide a method for maintaining access to an existing railway frame bridge via an elevated trestle bridge, which enables low-clearance crossing and ensures smooth drainage during the flood season.

[0004] To achieve these objectives and other advantages according to the present invention, a method is provided for an elevated trestle bridge to pass under an existing railway frame bridge as a temporary access road. The existing railway frame bridge is a double-span frame drainage culvert. The method includes: constructing one side of the double-span frame drainage culvert as a traffic culvert, while retaining the other side as a drainage culvert; constructing a steel temporary bridge within the traffic culvert to form a construction passage crossing the bottom slab of the existing frame culvert; connecting the temporary bridge with the passages on both sides of the double-span frame drainage culvert to form a temporary access road; leaving clearance between the steel temporary bridge and the bottom of the traffic culvert; spacing between the steel temporary bridge and the two sides of the traffic culvert; and the steel temporary bridge being a single-lane bridge with height and width restrictions.

[0005] Preferably, the foundations of the abutments on both sides of the temporary steel bridge are L-shaped enlarged foundations, with plain concrete backfill at a thickness of not less than 50cm and the backfill plane extending at least 50cm beyond the bottom edge of the foundation. The ends of the longitudinal beams of the temporary steel bridge are supported on the embedded parts of the abutments on both sides. The steel bridge deck is laid on the longitudinal beams and welded and fixed. Temporary bridge railings are installed on both sides of the temporary steel bridge for protection, and kick plates are installed at the bottom of the railings. Support beams are installed under the longitudinal beams of the temporary steel bridge, and the support beams support a concrete base plate. The concrete base plate is a concrete structure constructed on the pad layer at the bottom of the original frame bridge, serving as the support base plate.

[0006] Preferably, multiple concrete drainage pipes are installed on the downstream side of the frame drainage culvert to assist drainage, so that the upstream water of the frame drainage culvert can flow smoothly into the downstream ditch.

[0007] Preferably, the road surface is paved on the riverbed downstream of the frame drainage culvert, and the replacement and hardening treatment is carried out sequentially from top to bottom. The paved road surface is at the same level as or lower than the riverbed elevation so as not to raise the existing riverbed.

[0008] Preferably, the dam body within several hundred meters downstream of the frame drainage culvert is excavated at least 1.5 meters to lower the downstream river elevation and ensure smooth drainage within the frame drainage culvert.

[0009] Preferably, the underground foundation structure treatment assisting in the construction of the temporary steel bridge includes:

[0010] Upstream of the frame culvert, the existing riverbed is replaced with fill at a set height, and then concrete of a set height is constructed to form a hardened road surface, the height of which is level with the abutment height of the steel temporary bridge.

[0011] Within the scope of the temporary steel bridge, firstly, a plain concrete enlarged foundation of a predetermined height and size is set under the abutment of the temporary steel bridge, and then a concrete structure is set on the cushion layer of the existing frame bridge between the two abutments as a supporting base plate.

[0012] On the downstream side of the frame culvert, a sloping concrete road surface is first constructed on the existing subbase to form a hardened pavement. A concrete circular culvert for drainage is installed inside the road surface. The slope extends from the abutment to the downstream riverbed. The downstream riverbed is then filled to a set height, and a concrete road surface of the set height is constructed to form a hardened pavement. The height of the road surface is not higher than the height of the original downstream riverbed.

[0013] Preferably, a monitoring system is installed after the steel temporary bridge is constructed. This system includes water level monitoring and roadbed settlement and deformation monitoring. The roadbed settlement and deformation monitoring uses multiple levels and total stations to monitor horizontal lateral displacement and vertical elevation changes in real time. The water level monitoring uses water level sensors to monitor water level changes in real time. The monitoring system is also equipped with an alarm device that is connected to each monitoring device. When the monitoring system detects that the roadbed horizontal lateral displacement, vertical elevation changes, or water level exceeds the set values, it will activate the alarm device to automatically sound an alarm. Construction personnel will then take appropriate early warning measures based on the monitoring system.

[0014] Preferably, the width and height limiting structure includes a buffer limiting structure and an alarm structure disposed on both sides of the top bottom plate of the culvert. The buffer limiting structure is an elastic structure fixedly disposed on the top of the culvert, with its bottom protruding below the top bottom plate of the culvert and higher than the top of the temporary steel bridge. A fixed baffle is disposed behind the elastic structure on the top bottom plate of the culvert, which is closely attached to the elastic structure. A pressure sensor is disposed on the fixed baffle to monitor the pressure of the elastic structure on the fixed baffle. The pressure sensor is connected to the controller of the alarm structure. When the controller detects that the pressure value of the pressure sensor is greater than the set value, it issues an alarm signal and simultaneously controls the limiting structures pre-embedded on both sides of the temporary steel bridge to move toward the side of the temporary steel bridge to achieve deceleration and limiting. The limiting structure and the elastic structure are located in the same vertical plane. The initial state of the limiting structure is located on the two outer sides of the temporary steel bridge in the transverse direction and is set to move along the transverse direction of the temporary steel bridge.

[0015] Preferably, the structural strength of the temporary steel bridge should be verified after construction, using the following method:

[0016] First, based on the structure used in the steel temporary bridge, determine its design values ​​for tensile, compressive, and bending strengths, as well as its design value for shear strength. Simultaneously, design the load on the steel temporary bridge during traffic. When calculating structural strength, use the basic combination: 1.2 × dead load (bridge self-weight + guardrail self-weight) + 1.4 × (transport vehicle load); when calculating structural stiffness, use the standard combination: dead load (bridge self-weight + guardrail self-weight) + transport vehicle load.

[0017] Secondly, a steel temporary bridge model was established to aid in analysis and calculation;

[0018] Next, calculate the maximum wheel pressure of the transport vehicle, and use this to calculate whether the tensile, compressive and bending strength values ​​of the bridge deck are less than the design values, and whether the shear strength value of the bridge deck is less than the design value;

[0019] Then, calculate whether the maximum stress value of the longitudinal beam is less than the design values ​​of tensile, compressive and bending strength, whether the maximum shear force value is less than the design value of shear strength, and whether the maximum deformation is less than the deformation design requirement value;

[0020] Finally, by calculating the pressure value at the bridge abutment base, the minimum bearing capacity of the foundation after replacement was determined.

[0021] The present invention has at least the following beneficial effects:

[0022] 1. The steel temporary bridge of the present invention crosses the railway water-passing frame culvert in an elevated manner, avoiding the impact of crushing on the bottom plate of the railway water-passing frame culvert. It can ensure that large mechanical equipment can cross the bottom plate of the culvert and pass through the 6-meter frame culvert. Thus, with this structural form, the low clearance crossing and the impact on drainage are guaranteed.

[0023] 2. This invention implements drainage measures for low-clearance crossings of steel temporary bridges in various ways, thereby ensuring effective drainage during the flood season.

[0024] 3. The monitoring system of this invention can achieve real-time monitoring, timely early warning, and multi-faceted monitoring, thus providing comprehensive security.

[0025] 4. This invention achieves safety during construction by setting width and height limiting structures.

[0026] 5. This invention performs advance calculations on the structural strength and stiffness of the steel temporary bridge to ensure it meets construction requirements and guarantees safety.

[0027] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0028] Figure 1 This is an elevation layout diagram of the steel temporary bridge of the present invention;

[0029] Figure 2 For the present invention Figure 1 A cross-sectional view of the Zhonggang temporary bridge (AA section).

[0030] Figure 3 This is a plan view of the steel temporary bridge of the present invention;

[0031] Figure 4 This is a schematic diagram of the steel temporary bridge structure of the present invention;

[0032] Figure 5 This is an elevation view of the vehicle load arrangement according to the present invention;

[0033] Figure 6 This is a plan view of the vehicle load arrangement according to the present invention;

[0034] Figure 7 This is a lateral arrangement diagram of the vehicle load of the present invention;

[0035] Figure 8 This is the overall stress model of the temporary bridge of the present invention;

[0036] Figure 9 This is a diagram showing the maximum bending stress (MPa) of the longitudinal beam of the present invention.

[0037] Figure 10 This is a diagram showing the maximum shear stress (MPa) of the longitudinal beam in this invention.

[0038] Figure 11 This is a diagram showing the maximum deformation (mm) of the longitudinal beam of the present invention.

[0039] Figure 12The maximum support reaction force (kN) of the abutment when the vehicle load is at the end of the bridge according to the present invention;

[0040] Figure 13 This represents the maximum support reaction force (kN) of the bridge abutment when the vehicle load is at mid-span. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0042] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials described are all commercially available unless otherwise specified. In the description of this invention, the terms "lateral", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and 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 this invention.

[0043] like Figures 1 to 4 As shown, the present invention provides a method for maintaining a temporary access road under an existing railway frame bridge via an elevated trestle bridge. The existing railway frame bridge is a double-arch drainage culvert 1. The method includes: constructing a traffic culvert 2 on one side of the double-arch drainage culvert 1, while retaining the other side as a drainage culvert 3; constructing a steel temporary bridge 4 within the traffic culvert 2 to form a construction passage, which is connected to the passages on both sides of the double-arch drainage culvert 1 to form a temporary access road; leaving clearance between the bottom of the steel temporary bridge 4 and the traffic culvert 2; and spacing between the steel temporary bridge 4 and the two sides of the traffic culvert 2; and the steel temporary bridge 4 is a single-lane bridge with height and width restrictions.

[0044] The temporary access road and steel bridge in this application are constructed to allow construction machinery and equipment to cross the existing railway down line, facilitating bridge construction between the up and down lines. Since the access road utilizes the existing frame culvert, surveys have confirmed that there are no railway or local pipelines beneath the ground at either end of the culvert, eliminating the need for relocation work. The double-span frame drainage culvert itself has drainage functionality. The construction of the steel bridge must not impair this function. After ensuring sufficient clearance for the steel bridge, the clearance between the steel bridge and the culvert bottom should be maximized. Simultaneously, after meeting the required width for the steel bridge, the maximum possible distance should be maintained between the steel bridge and the culvert on both sides to preserve the drainage function of the frame culvert to the greatest extent possible. To ensure smooth drainage from the frame culvert, the steel bridge is designed as a single-lane bridge to meet traffic requirements. Furthermore, based on the actual needs and requirements of the construction machinery and equipment, and provided the steel bridge meets the required clearance and width, height and width restriction structures will be installed to protect the steel bridge and frame culvert, preventing conflicts. Warning signs indicating height and width restrictions will also be provided.

[0045] In one specific embodiment, there is an existing 2-6.2m frame culvert, with its drainage direction between the two railway tracks. Each culvert is 6m high and 6.2m wide, approximately 60m away from the bridge to be constructed above. The left culvert is planned to be used as a traffic culvert, while the right culvert will retain its drainage function. The top elevation of the frame culvert's bottom slab is 24.67m. A 5m clearance is provided for the temporary steel bridge inside the culvert. The temporary steel bridge is a single-lane bridge with a total deck width of 3.8m and a lane width of 3.6m. The temporary steel bridge is 9.35m long, with a steel deck length of 8.27m and an abutment length of 0.5m. A 4cm expansion joint is provided between the abutment and the temporary steel bridge.

[0046] In another implementation, such as Figure 1 and Figure 2 As shown, the foundations of the abutments 405 on both sides of the temporary steel bridge are L-shaped enlarged foundations, which are filled with plain concrete 410 with a thickness of not less than 50cm. The replacement plane extends beyond the bottom edge of the foundation by not less than 50cm. The ends of the longitudinal beams 402 of the temporary steel bridge are supported on the embedded parts of the abutments 405 on both sides. The steel bridge deck 401 is laid on the longitudinal beams 402 and welded and fixed. Temporary bridge railings 404 are set on both sides of the temporary steel bridge for protection. The bottom of the temporary bridge railings is equipped with kick plates. Support beams 403 are set under the longitudinal beams of the temporary steel bridge. The support beams support the concrete base plate. The concrete base plate is a concrete structure 412 constructed on the pad layer at the bottom of the original frame bridge, which serves as the support base plate.

[0047] The steel temporary bridge deck is made of 16mm thick checkered steel plate. The longitudinal beams under the deck are made of HN400×200 steel, with a 5cm spacing between the lanes. The ends of the longitudinal beams are supported on the embedded parts of the abutments on both sides. The foundations of the abutments on both sides of the temporary bridge are L-shaped enlarged foundations with a base size of 5m×1.5m. C25 plain concrete is used for backfilling under the foundation, with a backfill thickness of not less than 50cm, and the backfill plane extends not less than 50cm beyond the bottom edge of the foundation.

[0048] The bridge deck reinforcement is fully welded to the longitudinal beam HN400×200 using hf=8mm fillet welds. One end of the longitudinal beam is fully welded to the bridge abutment embedded part using hf=8mm fillet welds as a fixed constraint. The other end uses steel plates or angle steel limiters to restrict its lateral displacement as a lateral fixed and longitudinal movable constraint.

[0049] The steel temporary bridge railing is welded from 48mm diameter steel pipes, with a kick plate at the bottom of the railing, and yellow and black warning signs on the kick plate.

[0050] In another implementation scheme, multiple concrete drainage pipes 413 are installed on the downstream side of the frame drainage culvert to assist drainage, allowing upstream water to flow smoothly into the downstream ditch. A road surface is paved on the downstream riverbed of the frame drainage culvert, undergoing replacement and hardening treatment from top to bottom. The paved road surface is at or below the riverbed elevation to avoid raising the existing riverbed. The dam body within several hundred meters downstream of the frame drainage culvert is excavated at least 1.5 meters to lower the downstream riverbed elevation, ensuring smooth drainage within the frame drainage culvert.

[0051] In addition to controlling the net height and width of the temporary steel bridge, this application also includes several other drainage and flood control measures, listed below: 1) A 30cm clearance is left between the steel longitudinal beams of the temporary steel bridge and the bottom of the culvert for drainage, and there are 1.3m channels on both sides of the temporary steel bridge and the culvert for flood discharge; 2) Four 30cm inner diameter concrete circular pipe drainage culverts are installed on the downstream side of the frame culvert; 3) The downstream riverbed paving is 13.2m away from the existing river slope toe, and only replacement and hardening treatment is carried out without raising the existing riverbed elevation, which can meet the requirements for both vehicle passage and flood discharge; 4) There is a dam about 200m downstream of the frame culvert (currently full and used for irrigation by local residents), with a water level difference of about 3m. Through communication with local residents, the dam body can be excavated 1.5m down, and after the river channel is cleared, the water in the culvert can be drained and the irrigation water needs of residents can be met.

[0052] In another implementation, such as Figure 1 As shown, the underground foundation structure treatment assisting in the construction of the temporary steel bridge includes:

[0053] On the upstream side of the frame culvert, the existing riverbed paving is replaced with a set height, and then concrete of a set height is constructed to form a hardened road surface, the height of which is level with the abutment height of the temporary steel bridge; the existing riverbed consists of an existing 15cm thick crushed stone cushion layer 406 and an existing 30cm thick masonry rubble riverbed paving 407 from bottom to top, the replacement is 50cm thick brick rubble 408, and the hardened road surface is 20cm thick hardened concrete 409.

[0054] Within the scope of the temporary steel bridge, a plain concrete enlarged foundation of a predetermined height and size is first set under the abutment of the temporary steel bridge. Then, a concrete structure is set on the existing frame bridge pad between the two abutments as a supporting base plate. The enlarged foundation is a C25 concrete enlarged foundation 410, and the abutment is a C30 concrete abutment. The pad between the abutments is a 55cm thick masonry pad 411, and above it is a 45cm thick concrete base plate 412.

[0055] Downstream of the frame culvert, a sloping concrete hardened pavement 414 is first constructed on the existing subbase, with a drainage concrete circular culvert (i.e., the upper drainage circular pipe 413) installed inside. The slope extends from the abutment to the downstream riverbed at a gradient of 6.8%. It is located above the existing 15cm thick crushed stone subbase 406 and the existing 30cm thick masonry rubble riverbed paving 407. The downstream riverbed is replaced at a set height, similar to the above, with a 50cm thick brick rubble 408. Then, a concrete hardened pavement of a set height is constructed, with its height not exceeding the height of the original downstream riverbed. Similarly, the hardened pavement is a 20cm thick hardened concrete 409.

[0056] In another implementation scheme, a detection system is installed after the steel temporary bridge is constructed. This system includes water level monitoring and roadbed settlement and deformation monitoring. The roadbed settlement and deformation monitoring uses multiple levels and total stations to monitor horizontal lateral displacement and vertical elevation changes in real time in both horizontal and vertical directions. The water level monitoring uses water level sensors to monitor water level changes in real time. The detection system is also equipped with an alarm device that is connected to the signals of each monitoring device. When the monitoring system detects that the roadbed horizontal lateral displacement, vertical elevation changes, or water level exceeds the set values, it controls the alarm device to activate and automatically sound an alarm. Construction personnel then take appropriate early warning actions based on the monitoring system.

[0057] This application specifies a 30cm clearance between the steel temporary bridge and the culvert bottom slab. The supports at both ends consist of concrete spread foundations and concrete abutments. Construction vehicles will not contact the frame culvert, and settlement monitoring will not be conducted. Monitoring primarily includes roadbed deformation, and, where necessary, water level changes and deep soil displacement. Deformation monitoring will utilize instruments such as levels, total stations, and water level sensors. The elevation error of vertical displacement measurement observation points will not exceed 1mm, and the elevation error between adjacent deformation observation points will not exceed 0.5mm. The positional error of horizontal displacement measurement observation points will not exceed 3mm. Settlement and deformation monitoring will be conducted according to a fixed observation route and method. The observation route must form a closed or continuous path, using fixed working benchmarks to correspond to the settlement and deformation observation points. Observations must be conducted promptly according to the required timeframe.

[0058] Measurements should be taken at various points to monitor the vertical and horizontal displacements of the roadbed, the vertical displacement of the overhead contact line supports, and the tilt of the overhead contact line supports. An observation section (including observation points for the roadbed and bridge piers) should be set up every 5 meters along the route. For sections with a construction length of less than 100 meters, at least four observation sections should be set up along the route, with increased density as abnormal changes in roadbed deformation are observed during construction. Monitoring sections should include both horizontal displacement monitoring and vertical elevation difference monitoring. Observation stakes should preferably be made of steel bars with a diameter of not less than 30mm or precast reinforced concrete of No. 150, with a length of 150-200cm. A semi-circular wear-resistant probe should be pre-embedded in the top of the reinforced concrete, with a embedding depth of not less than 100cm. Automated real-time monitoring technology should be adopted, with an automatic alarm function after exceeding the warning value.

[0059] In another implementation,

[0060] In another implementation plan, the structural strength of the temporary steel bridge is verified after construction to ensure it meets the requirements, using the following method:

[0061] First, design parameters.

[0062] (1) Strength design value of steel structure

[0063] The design values ​​for steel structure strength shall be taken in accordance with the provisions of the "Standard for Design of Steel Structures" (GB 50017-2017).

[0064]

[0065] Therefore, the design values ​​for tensile, compressive, and bending strengths, and the design value for shear strength of Q235 grade steel.

[0066] (2) Vehicle load parameters

[0067] 12m 3 Concrete transport truck: Overall dimensions (length × width × height) 9200 × 2490 × 3880 mm, total load capacity 46 t, wheelbase 3.545 m + 1.35 m.

[0068] Secondly, the load values ​​and combinations.

[0069] A. Load values

[0070] (1) Dead load: The self-weight of the temporary bridge and its deck facilities.

[0071] (2) Live load: 12m 3 Concrete mixer truck.

[0072] Table 1 12m 3 Key technical indicators of concrete mixer truck vehicle load

[0073] project unit Technical indicators project unit Technical indicators Standard value of front axle gravity kN 2×30 Front wheel contact width and length m 0.3×0.2 Standard value of central axis gravity kN 2×100 Ground contact width and length of the middle and rear wheels m 0.6×0.2 Standard value of rear axle gravity kN 2×100 Vehicle external dimensions (length × width) m 2.49×9.2 wheelbase m 3.545+1.35 The vehicle was fully loaded with its own weight t 46

[0074] See concrete mixer truck load. Figure 5 , Figure 6 , Figure 7 As shown.

[0075] B. Load Combination

[0076] The basic combination used in calculating structural strength is: 1.2 × dead load (self-weight of temporary bridge + self-weight of railing) + 1.4 × (12m) 3 (Concrete truck load)

[0077] The standard combination used in calculating structural stiffness is: dead load (self-weight of temporary bridge + self-weight of guardrail) + 12m. 3 Concrete truck load

[0078] *Only one of the above-mentioned vehicles is considered to pass along the center of the line, and the most unfavorable working condition is taken for calculation.

[0079] Next, the calculation results.

[0080] A temporary bridge model was built using Midas Civil-2020 software for analysis and calculation. The temporary bridge model is as follows: Figure 8 As shown.

[0081] A. Bridge deck

[0082] The bridge deck is made of 16mm steel plate, under which longitudinal HN400*200 beams are laid, with a center-to-center spacing of 200mm under the wheel track. Each wheel has an area of ​​200mm (longitudinal) × 300mm (lateral). The rear axle of the concrete mixer truck has the highest wheel pressure. Each rear axle has two wheels, with a longitudinal contact length of 200mm and a lateral contact length of 600mm with the bridge deck. The maximum wheel pressure of the concrete mixer truck is q = 100 / 0.2 / 0.6 = 833KN / m. 2 .

[0083] Calculated as a one-way slab

[0084]

[0085]

[0086] All requirements are met.

[0087] B. HN400×200 longitudinal beam

[0088] The longitudinal beams are HN400×200, with a center-to-center spacing of 20 / 25cm, supported at both ends on the bridge abutments, with a total length of 9m and a span of 8.5m. The stress on the longitudinal beams is as follows... Figure 9 , Figure 10 , Figure 11 As shown.

[0089] The maximum stress of the HN400×200 longitudinal beam is σ = 87.6 MPa < [σ] = 215 MPa, and the maximum shear stress is...

[0090] τ=19.6MPa<[τ]=125MPa, the maximum deformation is f=7.2mm<[f]=8500 / 400=21.25mm, the strength and deformation of the HN400×200 longitudinal beam meet the specifications.

[0091] C. Abutment Calculation

[0092] like Figure 12 , Figure 13 As shown.

[0093] Through calculation and analysis, the total maximum support reaction force on one side is F = 446.3 kN.

[0094] Base pressure The bearing capacity of the foundation after replacement should not be less than 120 kPa.

[0095] Finally, in conclusion.

[0096] The above calculations show that the strength and stiffness of the temporary bridge meet the requirements.

[0097] (1) Only one vehicle as calculated above is allowed to pass over the temporary bridge. When driving, the vehicle should try to drive along the center line of the temporary bridge.

[0098] (2) Sandbags can be used to protect the side of the access road that is adjacent to the culvert to reduce the erosion of the roadbed.

[0099] (3) After the foundation of the bridge abutments on both sides of the temporary bridge is excavated, if there is a soft stratum, the concrete can be used to replace it to ensure that the bearing capacity of the foundation after replacement is not less than 120 kPa.

[0100] (4) The heaviest vehicle load is calculated as 12m 3 The concrete mixer trucks are calculated to ensure they pass along the centerline of the temporary bridge; any changes require recalculation.

[0101] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for constructing a temporary passage under an existing railway frame bridge, the existing railway frame bridge being a double-hole frame drainage culvert, characterized in that, include: One side of the double-hole frame drainage culvert will be constructed as a traffic culvert, while the other side will remain as a drainage culvert. A temporary steel bridge will be constructed inside the traffic culvert to form a construction passage that crosses the bottom slab of the existing frame culvert. This passage will be connected to the passages on both sides of the double-hole frame drainage culvert to form a temporary access road. There will be clearance between the temporary steel bridge and the bottom of the traffic culvert. The temporary steel bridge will be spaced apart from the two sides of the traffic culvert. The temporary steel bridge will be a single lane and will be equipped with height and width restriction structures.

2. The method of claim 1, wherein, The foundations of the abutments on both sides of the temporary steel bridge are L-shaped enlarged foundations, with plain concrete backfill at a thickness of not less than 50cm. The backfill plane extends at least 50cm beyond the bottom edge of the foundation. The ends of the longitudinal beams of the temporary steel bridge are supported on the embedded parts of the abutments on both sides. The steel bridge deck is laid on the longitudinal beams and welded and fixed. The temporary bridge is equipped with railings on both sides for protection, and kick plates are installed at the bottom of the railings. Support beams are installed under the longitudinal beams of the temporary steel bridge, and the support beams support the concrete base plate. The concrete base plate is a concrete structure constructed on the pad layer at the bottom of the original frame bridge, serving as the support base plate.

3. The method of claim 1, wherein, Multiple concrete drainage pipes are installed on the downstream side of the frame drainage culvert to assist drainage, so that the upstream water of the frame drainage culvert can flow smoothly into the downstream ditch.

4. The method of claim 1, wherein, The road surface is paved on the downstream riverbed of the frame drainage culvert. The replacement and hardening treatment is carried out from top to bottom. The paved road surface is at the same level as or lower than the riverbed elevation in order not to raise the existing riverbed.

5. The method of claim 1, wherein, The dam body within several hundred meters downstream of the frame drainage culvert will be excavated at least 1.5 meters to lower the downstream river elevation and ensure smooth drainage within the frame drainage culvert.

6. The method of claim 2, wherein, The underground foundation treatment assisting in the construction of the temporary steel bridge includes: Upstream of the frame culvert, the existing riverbed is replaced with fill at a set height, and then concrete of a set height is constructed to form a hardened road surface, the height of which is level with the abutment height of the steel temporary bridge. Within the scope of the temporary steel bridge, firstly, a plain concrete enlarged foundation of a predetermined height and size is set under the abutment of the temporary steel bridge, and then a concrete structure is set on the cushion layer of the existing frame bridge between the two abutments as a supporting base plate. On the downstream side of the frame culvert, a sloping concrete road surface is first constructed on the existing subbase to form a hardened pavement. A concrete circular culvert for drainage is installed inside the road surface. The slope extends from the abutment to the downstream riverbed. The downstream riverbed is then filled to a set height, and a concrete road surface of the set height is constructed to form a hardened pavement. The height of the road surface is not higher than the height of the original downstream riverbed.

7. The method of claim 6, wherein, After the steel temporary bridge is constructed, a monitoring system is installed, which includes water level monitoring and roadbed settlement and deformation monitoring. The roadbed settlement and deformation monitoring uses multiple levels and total stations to monitor horizontal lateral displacement and vertical elevation changes in real time in both horizontal and vertical directions. The water level monitoring uses water level sensors to monitor water level changes in real time. The monitoring system is also equipped with an alarm device that is connected to the signals of each monitoring device. When the monitoring system detects that the roadbed horizontal lateral displacement, vertical elevation changes, or water level exceeds the set values, it controls the alarm device to automatically sound an alarm. Construction personnel then take appropriate early warning actions based on the monitoring system.

8. The method of claim 1, wherein, The height and width limiting structure includes a buffer limiting structure and an alarm structure installed on both sides of the top bottom plate of the culvert. The buffer limiting structure is an elastic structure fixedly installed on the top of the culvert, with its bottom protruding below the top bottom plate of the culvert and higher than the top of the temporary steel bridge. A fixed baffle is installed behind the elastic structure on the top bottom plate of the culvert, which is closely attached to the elastic structure. A pressure sensor is installed on the fixed baffle to monitor the pressure of the elastic structure on the fixed baffle. The pressure sensor is connected to the controller of the alarm structure. When the controller detects that the pressure value of the pressure sensor is greater than the set value, it issues an alarm signal and simultaneously controls the limiting structures pre-embedded on both sides of the temporary steel bridge to move towards the side of the temporary steel bridge to achieve deceleration and limiting. The limiting structure and the elastic structure are located in the same vertical plane. The initial state of the limiting structure is located on the two outer sides of the temporary steel bridge in the transverse direction and is set to move along the transverse direction of the temporary steel bridge.

9. The method of claim 1, wherein, After the construction of the temporary steel bridge, its structural strength should be verified to ensure it meets the requirements. The method is as follows: First, based on the structure used in the steel temporary bridge, determine its design values ​​for tensile, compressive, and bending strengths, as well as its design value for shear strength. Simultaneously, design the loads on the steel temporary bridge during traffic. The basic combination used in calculating structural strength is: 1.2 × dead load + 1.4 × transport vehicle load. The standard combination used in calculating structural stiffness is: dead load + transport vehicle load. The dead load in the calculation is the self-weight of the temporary bridge + the self-weight of the guardrail. Secondly, a steel temporary bridge model was established to aid in analysis and calculation; Next, calculate the maximum wheel pressure of the transport vehicle, and use this to calculate whether the tensile, compressive and bending strength values ​​of the bridge deck are less than the design values, and whether the shear strength value of the bridge deck is less than the design value; Then, calculate whether the maximum stress value of the longitudinal beam is less than the design values ​​of tensile, compressive and bending strength, whether the maximum shear force value is less than the design value of shear strength, and whether the maximum deformation is less than the deformation design requirement value; Finally, by calculating the pressure value at the bridge abutment base, the minimum bearing capacity of the foundation after replacement was determined.

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