Bridge replacement construction methods

Abstract

This bridge replacement method eliminates the need for large-scale erection equipment on the bridge and allows for rapid construction by prioritizing work on the support points, thereby reducing the risk of project delays. [Solution] Bends 2 are installed before and after the intermediate support points in a specific section of the existing bridge to support the superstructure 1. After removing the road section 3 on the existing girder 1a, the existing girder between the bents 2 is cut and removed, and a bridge support 5 is installed. A new girder 11a is installed on top of the remaining existing girder 1a, and in parallel, the top of the bridge pier is modified and a new bearing 7 is installed. The load is transferred to jacks 8, and the upper part of the bents 2 is removed. After removing the bridge support 5, the new girder 11a is supported by the new bearing 7 by jacking down. The existing girder 1a is further lowered to the removal position and removed. This process is carried out for the entire span.

Description

Technical Field

[0007]

[0001] The present invention relates to a replacement construction method for aging bridges by rapid construction.

Background Art

[0002] A large number of bridges constructed during the period of high economic growth have passed more than about 50 years since construction. In addition, due to the increase in automobile traffic volume and the spraying of antifreeze agents in cold regions, the deterioration of bridges has progressed, and the number of cases where replacement is being considered has increased.

[0003] Unlike the case of newly constructing a bridge, the replacement of a continuous viaduct of an existing highway is often required to be carried out under traffic operation. Usually, traffic is diverted to one side by stopping traffic on either the upper or lower line and taking measures such as two-way traffic, and replacement is carried out from under the girder (directly below, sidewalk, or other areas occupying under the girder).

[0004] However, when the area under the girder cannot be used, it is necessary to remove the existing bridge by crane from the bridge deck or install a large erection girder on the bridge deck to remove and renew the existing bridge (install a new girder). Compared with the construction from under the girder, the construction period is longer and the rapid construction performance is inferior. Therefore, it is necessary to stop traffic for a long time, and there have been many problems in making a decision to start the construction.

[0005] Patent Document 1 discloses a bridge having precast cross girders and precast longitudinal girders and a construction method thereof, which is known as the SCBR method (SCBR is a registered trademark of Oriental白石株式会社). Erection equipment is installed from above the girder, the existing concrete bridge is cut into blocks and removed, and the bridge is renewed after installing the precast girders.

[0006] Patent Document 2 discloses a construction method using a newly installed girder as an erection girder. It is a construction method in which a newly installed girder (steel bridge) is assembled on the girder, and the newly installed girder is used as an erection girder to shorten the renewal work after removing the existing girder.

[0007] Patent Document 3 discloses a bridge replacement method, known as the HOLLOWAL method (HOLLOWAL is a registered trademark of Obayashi Corporation). In this method, temporary girders are installed on top of the existing girders, the temporary girders are removed, and precast high-strength PC girders are installed as new girders. Blocks are then joined together using PC steel materials to complete the replacement.

[0008] Non-patent document 1 describes a construction method in which a new girder is built beneath an existing bridge, the existing bridge is removed, the new girder is rapidly jacked up and installed, the existing girder support blocks are removed, and then the new girder support blocks are installed from the bridge deck. Although the construction is not carried out from the bridge, it is a rapid construction method.

[0009] In addition, Patent Document 4 by the applicants of the present application discloses a joint structure for a precast composite deck slab perpendicular to the bridge axis, in which a bottom steel plate is erected between the main girders, a structural steel is fixed to its upper surface, and concrete is poured on the bottom steel plate, and the joints between adjacent deck slabs are integrated with concrete via overlapping structural steel. This minimizes the area to be poured for cast-in-place concrete and eliminates the need for formwork and shoring, thereby enabling rapid construction in bridge replacement projects.

[0010] Furthermore, Patent Document 5 by the applicants of the present application discloses a bridge replacement method using a precast composite deck bridge in which the main girders and precast composite deck are integrated. This method involves erecting a precast composite deck panel unit on-site, which consists of multiple main girders, a bottom steel plate stretched between their upper flanges, multiple structural steels placed on the bottom steel plate, and a concrete deck integrated therewith. By joining the main girders and decks together, the on-site rebar assembly and concrete pouring processes are significantly reduced, resulting in shorter traffic restriction periods and reduced construction labor. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2009-256873 [Patent Document 2] Japanese Patent Publication No. 2024-058425 [Patent Document 3] Japanese Patent Publication No. 2023-079417 [Patent Document 4] Patent No. 6375079 [Patent Document 5] Patent No. 6425848 [Non-patent literature]

[0012] [Non-Patent Document 1] Road Structure Journal NET, "NEXCO West Japan Replaces 9 Girder Span on Chugoku Expressway between Takarazuka IC and Suita JCT", [online], September 21, 2021, Steel Structure Publishing Co., Ltd., [Retrieved August 22, 2025], Internet<URL:https: / / www.kozobutsu-hozen-journal.net / walks / 22381 / ?sPage=2> [Overview of the project] [Problems that the invention aims to solve]

[0013] When bridge construction is carried out using the invention described in Patent Document 1, the assembly and dismantling of the erection equipment takes a certain number of days, extending the construction period and the number of days of traffic restrictions. New girders designed under current standards tend to be heavier than existing girders, and in some cases the replacement itself may not be structurally feasible.

[0014] The invention described in Patent Document 2 solves problems such as dead load when replacing with a steel bridge, but the construction equipment is as large-scale as the invention described in Patent Document 1, and because it is a structure that protects the above, below, left, and right of the existing girder, it cannot be applied unless there is a gap of about 1m or more between the up and down lines, and cannot be applied to bridges where the up and down lines are a single structure or where the gap between the up and down lines is about 100mm or less.

[0015] The invention described in Patent Document 3 requires a certain number of days for the assembly and dismantling of the erection equipment. The invention described in Non-Patent Document 1 allows for rapid construction, but the removal of existing bridges requires construction from below the girders or from on adjacent bridges, and the constraints during construction become particularly strict when working from below the girders. In addition, generally, when removing an inbound lane, it is necessary to completely close the outbound lane and install a crane, so even when construction is carried out from on adjacent bridges, it is necessary to close the adjacent bridge to traffic, making it difficult to carry out construction while keeping the road open with lane restrictions.

[0016] The inventions described in Patent Documents 1 to 3 involve continuously installing erection equipment on existing girders, which necessitates taking reaction forces from the intermediate support points of the existing girders. Removing the existing girder support blocks requires constructing support structures by stacking sandals in the vicinity, similar to the bridge lowering operation, and then lowering the bridge while gradually removing the sandals over time, thus requiring many days for the lowering operation.

[0017] Furthermore, the reinforcing bars placed within the concrete around the intermediate support points, and the metal components installed later due to changes in seismic design standards since the initial construction, are often complex and inconsistent with the design drawings from several decades ago. This raises concerns that constructing the support structure for the new girders will require many construction days and traffic restrictions. These tasks inevitably have to be carried out in the latter half of the overall construction schedule, and the risk of increased construction days translates into an increase in the total number of traffic restrictions.

[0018] Furthermore, when installing erection equipment on existing girders, a gate-like shape is generally required in the width direction to absorb the reaction force of the equipment, and in the height direction, a working space height is required to move the new girder from the unloading area to the installation site in the bridge axis direction, resulting in a higher equipment height on the bridge deck. When removing the removed existing girder from the bridge deck, the equipment needs to be wider than the current road width in the width direction, which may bring it close to road traffic operating on adjacent girders, raising significant safety concerns.

[0019] The present invention aims to solve the above-described problems, and provides a bridge replacement method that shortens the time required for assembling and disassembling construction equipment (erection girders), and rapidly removes and generally updates (installs supports around the new girders before the intermediate girder support between spans) the structural members around the support points almost simultaneously.

Means for Solving the Problems

[0020] The present invention is a bridge replacement method for renewing the superstructure of a specific section of an existing bridge, and is characterized by including the following steps. 1) A step of installing braces in the front and rear in the bridge axis direction of the intermediate support points in the specific section, and supporting the existing superstructure by the braces. 2) A step of removing the road portion on the existing girders constituting the superstructure of the specific section. 3) A step of cutting and removing the existing girders in the portion located between the braces in the front and rear in the bridge axis direction of the intermediate support points. 4) A step of installing a temporary bridge in the portion where the existing girders have been removed. 5) A step of sequentially installing new girders other than the intermediate support points on the existing girders that are left in a state supported by the braces other than the existing girders of the intermediate support points to be removed. 6) A step of modifying the support located at the top of the pier of the intermediate support point into a support for the new girders, or removing it and replacing it with a support for the new girders. 7) A step of transferring the loads of the remaining existing girders and the new girders to jacks or the like installed near the braces and supporting them, and removing the upper part of the braces whose loads have been transferred to the jacks or the like. 8) A step of removing the temporary bridge. 9) A step of collectively lowering the existing girders and the new girders on the existing girders by jacking down the jacks or the like, and depositing and supporting the load of the new girders on the support for the new girders at the top of the pier. 10) A step of further lowering the existing girders to the removal position by jacking down the jacks or the like, and removing the existing girders. 11) A step of removing the remaining braces. 12) A process of performing the steps 1) to 11) above for all spans between support points in the specified section, either sequentially or in parallel.

[0021] The aforementioned "specific section" refers to the section to be replaced within a predetermined construction period, and may include the entire bridge. If the bridge is long and the overall construction period is long, the bridge may be divided into multiple sections, and the replacement may be carried out over a period of time.

[0022] During construction, the affected bridge section will either be completely closed to traffic or only the width of that section will be closed. In other words, on bridges with separate lanes for northbound and southbound traffic, such as on expressways, one of the bridges will be closed to traffic for construction, while the other bridge will remain open to traffic in both directions.

[0023] On bridges with two or more lanes in each direction, one lane will be closed to traffic while the other remains open. Furthermore, on routes with heavy traffic, construction may be required to be completed within a period (90-100 days) excluding peak seasons (generally periods of increased traffic such as Golden Week, Obon, and the New Year holidays).

[0024] In step 1), "existing superstructure" includes not only the existing girders but also road components formed on top of them, such as deck slabs, pavement, wall railings, and guardrails.

[0025] In step 2), the term "existing girder" refers not only to the original girder but also to a deck slab resting on the existing girder or a deck slab integrated with the existing girder. In that case, it also includes cases where the deck is composed of multiple blocks in the direction perpendicular to the bridge axis.

[0026] In step 3), the cutting and removal of existing girders located between bents may be carried out from the bridge deck using cranes or other construction machinery installed on the bridge deck. However, it is not necessarily required that all work be carried out from the bridge deck.

[0027] The connecting platform installed in step 4) shall be constructed to withstand the load of workers and transport trucks moving back and forth, and may also be used as a work platform after the removal of existing girders at intermediate support points, as well as for fall prevention and for fixing remaining existing girders together.

[0028] The work of sequentially installing new girders on top of existing girders in step 5) can be carried out from the bridge deck using cranes or other construction machinery installed on the bridge deck. However, it is not necessarily required that all work be carried out from the bridge deck. Furthermore, the term "new girder" here includes not only the original girder but also the deck slab resting on the new girder, the deck slab integrated with the new girder, or the steel deck slab that serves as both a girder and a deck slab. In addition, this includes cases where the structure is composed of multiple blocks in the direction perpendicular to the bridge axis.

[0029] In step 6), a more specific form may be to revise the structural height above the support points (top of the substructure), which may involve chipping away the concrete at the top, drilling anchor bolt holes for fixing the new support, and then fixing the support for the new girder. In addition, there are cases where the new support is attached to the new girder in advance and erected simultaneously with the new girder.

[0030] In particular, steps 6), 7), and 8) can be rearranged or performed in parallel. Other steps can also be rearranged or performed in parallel as appropriate to improve efficiency.

[0031] Regarding step 9), various options can be considered regarding the connections between members and work procedures, depending on the type of bridge and other factors, as will be described later.

[0032] In step 10), the existing girders can be divided and cut into pieces that are easily removable and transported, and then removed.

[0033] 11) The process of removing the remaining vents.

[0034] After the new girder is supported by the bearings for the new girder as described in step 9) above, various bridge deck construction and road paving work will be carried out on the new girder at appropriate times. These various bridge deck construction and road paving work can be carried out in parallel with other processes.

[0035] For the entire construction period of a specific section to be built within a particular construction period, it is efficient to first carry out steps 1) to 11) between the central intermediate supports in the said specific section, and then sequentially carry out steps 1) to 11) in parallel with a delay between the intermediate supports on both sides of the bridge axis. However, it is not necessary to limit the process to this case.

[0036] In step 9), for example, it is possible to join and integrate one of the existing girders located on either side of the intermediate support point, the new girder assembled on the ground on the existing girder, and the new intermediate support girder to be newly installed at the intermediate support point, and then jack down the new girder until its height is the support height for the new girder bearing, and support the new girder with the new girder bearing.

[0037] Furthermore, another procedure in step 9) is to pre-attach the support for the newly installed girder (including cases where the entire support is attached or where only the upper part of the support is attached) to the underside of the newly installed girder at the intermediate support point and then perform the jack-down in an integrated state. [Effects of the Invention]

[0038] The bridge replacement method of the present invention has the above configuration and provides the following effects. (1) In existing girder bridges with continuous girders spanning multiple spans, the removal of support points that connect to the substructure is difficult because various repairs and reinforcements have been carried out from the beginning of construction due to seismic reinforcement work on the substructure and the increasing structural performance requirements of the bearings of the upper and lower structures during the construction period, which may result in inconsistencies between the latest actual structure and the design drawings. With conventional technology, the removal and replacement of support blocks are carried out in relatively later stages, which has a significant impact on the overall construction process. The present invention allows for the removal of existing girder support blocks, which take a long time to construct, by first supporting parts other than the existing girder support points (span blocks) with bents, etc., and prioritizing the removal of existing girder support blocks. This makes it possible to carry out the removal of existing bearings and other unnecessary seismic members, substructure modification, installation of bearings for new girders, and the installation of support block girders (intermediate support cross girders) of new girders in advance.

[0039] (2) As for the construction work on the bridge, by using cranes positioned on the bridge deck to remove the existing girder support points and install the new girders, the time required for assembling large, continuous erection girders, which is necessary with conventional technology (inventions described in Patent Documents 1 to 3), is eliminated. Furthermore, by performing this work sequentially from the intermediate spans to the end spans of a series of bridges, continuous construction becomes possible, and rapid construction is made easier.

[0040] (3) Furthermore, the new girders are sequentially assembled on the existing girders, and the required spans are lowered together with the existing girders. The new girders are then lowered and installed to the height of the modified substructure top, thereby completing the installation of one span of new girders. This process is applied continuously to all spans, allowing all spans of new girders to be installed at the specified height and creating a continuous network of new girders. After the new girders have received the reaction force from the substructure, the jacks supporting the existing girders are lowered further until they are finally low enough to be broken into smaller pieces and removed from below the girders, and the members are removed from below the new girders. In parallel with this work, it is possible to carry out formwork, reinforcement, and concrete pouring work for the areas of the new girders where on-site pouring is required. In the conventional "removal and installation using erected girders" method, installation must always be carried out after removal, making the present invention advantageous in terms of process.

[0041] (4) By carrying out these operations continuously, for example, from near the center of a six-span continuous girder to the ends, the loading of cranes, loading of new components, and on-site assembly of new components can be carried out continuously in a series of operations from the front and rear of the bridge, and the work is not affected by the removal of the lowered existing girders, thus improving the construction speed on the bridge.

[0042] (5) The prior art described in Non-Patent Document 1 also allows for rapid "jacking up" of the span blocks, but it is not possible to install the support blocks by jacking up from below (from bottom to top), and the removal and installation of the support blocks require separate processes using cranes. When constructing continuous spans sequentially, the work requires the installation of cranes under the girders or on adjacent girders (by closing off traffic), and the traffic access of the adjacent girder sections cannot be satisfied.

[0043] (6) Since the continuous girders are cut into simple girders, by installing a connecting frame and fixing the simple girders that straddle the support points, it is possible to have functions such as preventing lateral displacement during construction and seismic countermeasures during construction.

[0044] (7) The existing girders are used as a work platform to assemble the new girders on the ground, and the existing girders that serve as the work platform are sequentially jacked down from the center to set the new girders at the predetermined height. This continuous process enables rapid construction.

[0045] (8) Furthermore, by selecting a precast composite slab bridge such as the NY Rapid Bridge (NY Rapid Bridge is a registered trademark of Yokogawa NS Engineering Corporation and Nippon Steel Engineering Corporation) for the new girders (see, for example, Patent Documents 4 and 5 mentioned above), the construction of the slab concrete is reduced to the portion that fills the gaps between the new girder blocks, further shortening the post-construction work for the new girders after lowering (jacking down), and enabling rapid construction.

[0046] (9) By making the newly constructed girder a continuous steel deck structure (known technology) with a transverse beam at the intermediate support, the installation of deck concrete becomes unnecessary, and the period for formwork, reinforcement, concrete pouring, and curing is shortened compared to construction methods that involve concrete pouring, thereby enabling rapid construction.

[0047] (10) As a newly constructed girder for the NY Rapid Bridge, the support structure and span structure described in Patent Document 4 (Patent No. 6425848 "Precast Composite Slab Bridge") and Patent Document 5 (Patent No. 6375079 "Joint Structure for Precast Composite Slab in the Direction Perpendicular to the Bridge Axis and Method of Construction Thereof") above are adopted as new girders, and the new girder structure can also be joined to the existing girder structure and the updated girder structure at an intermediate span by the present applicant's Patent Application No. 2024-101620, which contains the following details: "Joint Structure between Existing Girder and Updated Girder".

[0048] Specifically, a precast composite deck girder can be used as a new girder, which has multiple main girders extending in the direction of the bridge axis, a bottom steel plate spanning between the upper flanges of adjacent main girders, multiple structural steels joined to the upper surface of the bottom steel plate so as to extend in the direction of the bridge axis or perpendicular to the bridge axis, and a concrete deck slab cast on the bottom steel plate so as to embed the structural steels, with these components integrated into one structure.

[0049] Furthermore, in a more specific embodiment, a precast composite deck panel unit manufactured in advance outside the construction site, such as a factory, can be used as a new girder. This precast composite deck panel unit consists of a steel main girder extending in the direction of the bridge axis, a bottom steel plate spanning between the upper flanges of the main girder and functioning as an embedded formwork during concrete pouring and as a lower tensile reinforcement for the composite deck, a plurality of shaped steels fixed to the upper surface of the bottom steel plate so as to extend in the direction of the bridge axis or perpendicular to the bridge axis and functioning to ensure the rigidity of the deck and prevent slippage with the concrete, and deck concrete poured on the bottom steel plate so as to embed the shaped steels.

[0050] In step 5) above, when installing the new girders sequentially, a predetermined width of gap is provided between adjacent composite deck panel units in the bridge axis direction or perpendicular to the bridge axis. In this gap, the bottom steel plates of adjacent composite deck panel units are joined together using splice plates or the like to form a closed cross section. The joint reinforcement bars protruding from the end faces of the deck concrete are then crossed or overlapped within the gap. Cast-in-place concrete or non-shrink mortar is then poured and hardened only in the gap and, if necessary, in the areas on the main girders where the deck has not yet been poured. This minimizes the amount of concrete poured on site while structurally integrating adjacent new girders.

[0051] Japanese Patent Application No. 2024-101620, "Joint Structure for Existing Girder and Replacement Girder," is a structure in which multiple transverse girders are arranged perpendicular to the axis between the end of the existing girder and the end of the replacement girder at the upper end of a pier of a continuous elevated bridge, and the two girders are joined via these girders. By slidably arranging a joint plate that extends in the girder axis direction along the upper surface of the existing girder side to the upper member fixed on the pier, the drivability and seismic resistance at the joint are improved, maintenance space necessary for maintenance and inspection of the joint is secured, and replacement work on the existing girder can be carried out efficiently.

[0052] For example, even if the construction length is 200m and the 90-day constraint limits construction to about 100m, by pre-determining the locations of different types of connections, it becomes possible to open the road to traffic without exceeding the time constraint, and the risk of delays in opening the road to traffic due to project delays can be significantly reduced. [Brief explanation of the drawing]

[0053] [Figure 1] This diagram shows steps 1 to 5 in one embodiment of the present invention, viewed from a direction perpendicular to the bridge axis. [Figure 2] This diagram shows steps 6-9, following Figure 1, viewed from a direction perpendicular to the bridge axis. [Figure 3] This diagram shows steps 10-13, following Figure 2, viewed from a direction perpendicular to the bridge axis. [Figure 4]This diagram shows steps 14-18, following Figure 3, viewed from a direction perpendicular to the bridge axis. [Figure 5] This diagram shows steps 19-23, following Figure 4, viewed from a direction perpendicular to the bridge axis. [Figure 6] This figure shows steps 24-26, following Figure 5, viewed from a direction perpendicular to the bridge axis. [Figure 7] This diagram, viewed perpendicular to the bridge axis, shows an example of the procedure for jacking down existing and new girders according to the present invention. [Figure 8] This diagram shows the procedure following Figure 7, viewed from a direction perpendicular to the bridge axis. [Figure 9] This diagram shows the procedure following Figure 8, viewed from a direction perpendicular to the bridge axis. [Figure 10] This diagram shows the procedure following Figure 9, viewed from a direction perpendicular to the bridge axis. [Figure 11] This diagram shows the procedure following Figure 10, viewed from a direction perpendicular to the bridge axis. [Figure 12] This is a view of an example of the installation of a bridge platform in one embodiment of the present invention, as seen from a direction perpendicular to the bridge axis. [Figure 13] This is a plan view corresponding to Figure 12. [Figure 14] This is a cross-sectional view taken from the bridge axis direction, corresponding to Figure 12. [Modes for carrying out the invention]

[0054] Specific embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the embodiments shown below.

[0055] Figures 1 to 6 show the overall construction procedure of a bridge replacement method according to one embodiment of the present invention, viewed from a direction perpendicular to the bridge axis, and illustrate an example of updating the superstructure of a specific section including the intermediate support points (piers P6 to P10) of a continuous girder bridge having multiple spans.

[0056] [Step 1] (See Figure 1(a)) The target of the construction is an existing bridge with intermediate support points such as bridge piers P1, P2, P3, etc. (the diagram shows the section from P3 to P11). In this embodiment, the superstructure 1 of this existing bridge will be replaced. The superstructure 1 consists of an existing girder 1a, such as an RC hollow slab girder, and a road section 3 on top of it, such as pavement 3b, wall railings 3a, and guardrails 3c. This is the initial state before construction.

[0057] [Step 2] (See Figure 1(b)) First, as step 1), bents 2 are installed on the front and rear sides of the intermediate support point (pier P8 in the diagram) in the specific section to be replaced, along the bridge axis. These bents 2 support the existing superstructure 1. Here, "existing superstructure" 1 refers to the entire structure that was supported by piers P1, P2, P3, etc., including the existing girders 1a, deck slab, and road portion 3 formed on top of them, such as pavement 3b, wall railings 3a, and guardrails.

[0058] [Step 3] (See Figure 1(c)) Next, in step 2), the existing road portion 3 (wall parapet 3a, pavement 3b, guardrail 3c, etc.) on the existing girder 1a that constitutes a specific section of the superstructure 1 is removed. This removal work is carried out in order to cut the existing girder 1a in a later step and to secure working space for placing the new girder 11a. In this application, "existing girder" 1a includes a deck slab that is separate from or integrated with the main girder. It also includes cases where it is composed of multiple blocks in the direction perpendicular to the bridge axis.

[0059] [Step 4] (See Figure 1(d)) After the removal of road section 3, in step 3), the existing girder 1a located between the bents 2, 2 in the bridge axis direction of the intermediate support section (pier P8) is cut and removed. This work can be efficiently carried out on the bridge deck using construction machinery such as a crane 4 (e.g., a rough terrain crane) installed on the bridge deck, as shown in the figure.

[0060] Next, in step 4), a connecting platform 5 is installed in the space above pier P8 where the existing girder 1a was removed. This connecting platform 5 is designed to withstand the loads of workers and material transport trucks moving back and forth during subsequent work, and is used as a work platform and fall prevention measure after the removal of the existing girder at the intermediate support point.

[0061] [Step 5] (See Figure 1(e)) Next, in step 5), the new girders 11a, excluding the intermediate support section, are sequentially installed (assembled on the ground) using a crane 4 or the like on top of the existing girders 1a that remain supported by the bent 2, excluding the existing girders at the intermediate support section (girders on pier P8) that are to be removed. In this step, the remaining existing girders 1a function as a stable "working platform" for assembling the new girders 11a on the ground.

[0062] In parallel with this, as step 6), the existing girder 1a is removed, and the intermediate support section (pier P8) exposed at the top of the pier is replaced with the bearing 7 (see Figure 7) for the new girder 11a. Specifically, in order to revise the structural height above the support (top of the substructure), the concrete at the top is chipped away, anchor bolt holes are drilled to fix the new bearing 7, and then the bearing 7 for the new girder is fixed in place. A major feature of this construction method is that this high-risk work can be carried out at an early stage of construction.

[0063] [Step 6] (See Figure 2(a)) The processes described in Steps 4 and 5 above (i.e., removal of the existing girder 1a at the intermediate support section, installation of the connecting frame 5, installation of the new girder 11a on top of the remaining existing girder 1a, and modification of the top of the bridge pier and installation of new bearings) are carried out sequentially or in parallel for other intermediate support sections in the specified section (in this example, bridge piers P7 and P9 on both sides). In this step, the existing girder 1a at the intermediate support section on bridge piers P7 and P9 is removed and the connecting frame 5 is installed.

[0064] [Step 7] (See Figure 2(b)) Work will commence on modifying the top surfaces of piers P7 and P9 (substructure modification) and installing the new bearings 7 (see Figure 7), while simultaneously proceeding with the installation of the new girders 11a on top of the existing girders 1a supported by bents 2.

[0065] [Step 8] (See Figure 2(c)) While continuing the modification of the top surfaces of piers P7 and P9 and the installation of new bearings 7, the installation of new girders 11a will be further advanced.

[0066] [Step 9] (See Figure 2(d)) At the intermediate support points on both sides of the specified section (piers P6 and P10), the existing girder 1a located between bents 2 and 2 will be cut and removed, and a connecting platform 5 will be installed.

[0067] [Step 10] (See Figure 3(a)) Work will commence on modifying the top surfaces of piers P6 and P10 and installing new bearings 7 (see Figure 7), while simultaneously proceeding with the installation of the new girder 11a on top of the existing girder 1a.

[0068] [Step 11] (See Figure 3(b)) We will continue the installation of the new girder 11a.

[0069] [Step 12] (See Figure 3(c)) At piers P5 and P11, the existing girder 1a supported by bent 2 will be removed and the connecting frame 5 will be installed (the diagram shows that the connecting frame installation at P5 and P11 has been completed).

[0070] [Step 13] (See Figure 3(d)) While continuing the modification of the top surfaces of piers P5 and P11 and the installation of new bearings 7, the installation (ground assembly) of almost all new girders 11a within the specified section will be completed.

[0071] [Step 14] (See Figure 4(a)) This shows the completed state of the bridge piers P5 and P11 after modification (substructure modification) and the installation of the new bearing 7 (see Figure 7). As a result, all intermediate support points (P5 to P11) within the specified section are ready to receive the new girder 11a.

[0072] [Step 15] (See Figure 4(b)) Next, in step 7), near the intermediate support points (piers P7-P9), the load of the remaining existing girder 1a and the new girder 11a installed on top of it is transferred from the supporting bent 2 to the lowering jacks 8 installed near the bent 2 and supported thereby. After the load has been completely transferred to the lowering jacks 8, the upper part of the bent 2 (the part that would obstruct the jack-down) which no longer needs to support the load is removed.

[0073] Next, in step 8), the connecting platform 5 that was installed at the intermediate support points (piers P7 to P9) is removed.

[0074] [Step 16] (See Figure 4(c)) Next, in step 9), the existing girder 1a and the new girder 11a on top of the existing girder 1a are lowered together by jacking down the lowering jack 8. When the height of the new girder 11a reaches the support height (normal height) provided by the bearing 7 for the new girder, the load of the new girder 11a is supported by the bearing 7 for the new girder at the top of the bridge piers P7 to P9.

[0075] In this case, it is also possible to join and integrate the newly constructed intermediate support girder with the newly constructed girders 11a on both sides before lowering, or to lower the girder with the support 7 (or its upper part) for the new girder already attached to the new girder side.

[0076] [Step 17] (See Figure 4(d)) After the newly installed girder 11a is supported by the bearing 7, in step 10), the jacking down of the lowering jack 8 is further continued to lower the existing girder 1a to the removal position (the space below the newly installed girder 11a).

[0077] In parallel with the lowering of the existing girder 1a, work on the new girder deck and paving (such as filling the gaps with concrete for the deck, waterproofing, and paving) can be started on top of the new girder 11a, which has been installed at the correct height.

[0078] [Step 18] (See Figure 4(e)) Near the intermediate support points (piers P6, P7, P9, P10), similar to step 7), the loads of the existing girder 1a and the new girder 11a are transferred from the bent 2 to the lowering jacks 8 for support, and the upper part of the bent 2 is removed.

[0079] [Step 19] (See Figure 5(a)) At the intermediate support points (piers P6, P7, P9, P10), the connecting platform 5 is removed, similar to steps 8) and 9), and the new girder 11a is lowered by jacking down the lowering jacks 8 and supported by the bearings 7 for the new girder.

[0080] [Step 20] (See Figure 5(b)) At piers P6, P7, P9, and P10, similar to process 10), the existing girder 1a is lowered to the removal position using the lowering jack 8, while simultaneously proceeding with the construction of the new girder deck and paving.

[0081] [Step 21] (See Figure 5(c)) Near the intermediate support points (piers P5, P6, P10, P11), the load is transferred from bent 2 to the lowering jack 8, similar to step 7), and the upper part of bent 2 is removed.

[0082] [Step 22] (See Figure 5(d)) At the intermediate support points (piers P5, P6, P10, P11), the connecting platform 5 is removed, similar to steps 8) and 9), and the new girder 11a is lowered by jacking down the lowering jacks 8 and supported by the bearings 7 for the new girder.

[0083] [Step 23] (See Figure 5(e)) At piers P5, P6, P10, and P11, the existing girder 1a is lowered to its removal position, similar to process 10), while simultaneously proceeding with the construction of the new girder deck and paving.

[0084] [Step 24] (See Figure 6(a)) All existing girders 1a, which have been lowered below the newly constructed girder 11a, are divided and cut into appropriately manageable sizes for removal and transport, and then transported out and removed from beneath the bridge and girders (completion of process 10). This work is carried out in parallel with the construction of the new girder bridge deck and paving work that is underway above.

[0085] [Step 25] (See Figure 6(b)) After the removal of the existing girder 1a is completed, in step 11), all remaining temporary materials such as the remaining parts of the bent 2 and the lowering jacks 8 are removed and dismantled.

[0086] [Step 26] (See Figure 6(c)) This shows the state after the construction of the new girder bridge deck and paving have been completed, and the superstructure 11 in the specific section has been replaced with the new girder 11a. With this, the bridge replacement is complete and traffic can be opened to the public.

[0087] By performing the above steps [Step 1] to [Step 26] (Steps 1) to 11)) sequentially or in parallel for all spans between intermediate supports in a specific section (Step 12)), rapid replacement of a continuous girder bridge can be achieved.

[0088] Figures 7 to 11 are views taken perpendicular to the bridge axis, illustrating in more detail an example of the jack-down procedure (Steps 15 to 17), which is one of the central steps of the present invention.

[0089] Figure 7 shows the initial state of [Step 15], where the new girder 11a is placed on top of the existing girder 1a, and its entire load is supported by the bent equipment (bent 2). Lowering jacks 8 are installed near bent 2.

[0090] Figure 8 shows the completed state of [Step 15], where the loads of the new girder 11a and the existing girder 1a have been transferred from the bent 2 to the lowering jack 8, and the upper part of the bent 2 (which would be an obstacle during lowering) has been removed.

[0091] Figure 9 shows the progress of the jack-down (first stage) in [Step 16], where the lowering jack 8 retracts, causing the new girder 11a and the existing girder 1a to descend together as a single unit.

[0092] Figure 10 shows the completed state of [Step 16], where the lower surface of the new girder 11a abuts against the support 7 for the new girder installed on the top of the bridge pier, the load of the new girder 11a is supported by the support 7, and the support is complete.

[0093] Figure 11 shows the jack-down (second stage) in [Step 17], where the new girder 11a remains supported by the bearing 7, and as the lowering jack 8 retracts further, only the existing girder 1a separates from the new girder 11a and descends further to the removal position below. This makes it possible to carry out bridge deck construction above the new girder 11a and removal work of the existing girder 1a below in parallel.

[0094] Figures 12 to 14 show examples of the installation of the bridge platform 5, which is installed in [Step 4], etc. Figure 12 is a view from the direction perpendicular to the bridge axis, Figure 13 is a plan view, and Figure 14 is a cross-sectional view from the bridge axis direction, corresponding to section AA of Figure 13.

[0095] The connecting bridge 5 is installed so as to straddle the space created after the removal of the existing girder 1a at the intermediate support point.

[0096] As shown in Figure 13, for example, multiple H-shaped steel beams 5a (such as H250x250x9x14) are arranged parallel to each other in the direction of the bridge axis, and both ends are supported by the ends of the remaining existing girder 1a.

[0097] As shown in Figures 12 and 14, the H-shaped steel is fixed to the existing girder 1a using support bases installed on the upper surface of the existing girder 1a, or driven anchors as shown in the drawings.

[0098] This connecting platform 5 not only functions as a work platform and fall prevention equipment, but also as a temporary passage that allows construction vehicles such as trucks to pass through for the installation of the new girder 11a and for transporting materials.

[0099] Furthermore, since the existing girder 1a is cut at the intermediate support point and temporarily becomes a simple girder, this connecting frame 5 can also serve to connect the cut girder ends, thus preventing lateral displacement during construction and improving seismic resistance. [Explanation of symbols]

[0100] 1…Existing superstructure 1a…Existing girder 2... Vent (venting equipment) 3…Road section (existing) 3a...Wall railing (existing) 3b... Pavement (existing) 3c... Guardrail (existing) 4... Crane 5…bridge 7…Bearings for newly installed girders 8…Lowering jacks 11…Newly constructed superstructure 11a... New girder 13a...Wall railing (newly installed) 13c... Guardrail (newly installed) P3~P11…Bridge piers (intermediate support points)

Claims

1. , , , , , , , , , , , , , , , A bridge replacement method according to claim 1, characterized in that, after supporting the new girder on the bearing for the new girder in step 9), the construction of the new girder bridge deck and paving are carried out in parallel with the other steps. , 9) A step of lowering the existing girder and the new girder on the existing girder by jacking down the jacks, and supporting the load of the new girder on the bearing for the new girder at the top of the bridge pier. ,

2. , 8) The process of removing the aforementioned connecting platform. , A bridge replacement method according to claim 4, characterized in that the bearing for the new girder is joined in advance to the lower surface side of the new girder at the intermediate support point and jacked down in an integrated state. , 12) A process of performing the steps 1) to 11) above for all spans between intermediate support points in the specified section, either sequentially or in parallel. ,<00... A bridge replacement method for renewing the superstructure of a specific section of an existing bridge, characterized by including the following steps. 1) A step of installing bents on the front and rear sides of the bridge axis direction of the intermediate support points in the specified section, or on the center side of the span of the end support points, and supporting the existing superstructure with the bents. 2) The process of removing the road portion on the existing girders that constitute the superstructure of the specified section. 3) The process of cutting and removing the existing girders located between the bents. 4) The process of installing a bridge platform in the area where the existing girder was removed. 5) A step of sequentially installing new girders other than the intermediate support section on top of the existing girders that remain in place and are supported by the bents other than the existing girders at the intermediate support section that will be removed. 6) The process of modifying the bearing located at the top of the bridge pier at the intermediate support point into a bearing for the new girder, or removing it and replacing it with a bearing for the new girder. 7) The process of transferring the load of the remaining existing girders and the newly installed girders from the bent to jacks installed near the bent and supporting them there, and then removing the upper part of the bent to which the load has been transferred to the jacks. 8) The process of removing the aforementioned connecting platform. 9) A step of lowering the existing girder and the new girder on the existing girder by jacking down the jacks, and supporting the load of the new girder on the bearing for the new girder at the top of the bridge pier. 10) The process of lowering the existing girder further to the removal position by jacking down the jacks, and removing the existing girder. 11) The process of removing the remaining vents. 12) A process of performing the steps 1) to 11) above for all spans between intermediate support points in the specified section, either sequentially or in parallel.

2. A bridge replacement method according to claim 1, characterized in that, after supporting the new girder on the bearing for the new girder in step 9), the construction of the new girder bridge deck and paving are carried out in parallel with the other steps.

3. A bridge replacement method according to Claim 1, characterized in that the steps 1) to 11) above are first performed between the intermediate support points in the central part of the specified section, and then the steps 1) to 11) above are performed sequentially between the intermediate support points on both sides in the bridge axis direction in parallel work with a delay.

4. A bridge replacement method according to claim 1, characterized in that in step 9) above, one of the existing girders located on both sides of the intermediate support section, the new girder assembled on the existing girder, and the new intermediate support section girder newly installed at the intermediate support section are joined and integrated, and the new girder is jacked down until its height becomes the support height for the new girder bearing, and the new girder is supported by the new girder bearing.

5. <e000038> A bridge replacement method according to claim 4, characterized in that the bearing for the new girder is joined in advance to the lower surface side of the new girder at the intermediate support point and jacked down in an integrated state.

6. A bridge replacement method according to claim 1, characterized in that the deck slab portion of the newly installed girder is a steel deck slab.

7. A bridge replacement method according to claim 1, characterized in that the newly installed girder comprises a plurality of main girders extending in the direction of the bridge axis, a bottom steel plate spanning between the upper flanges of adjacent main girders, a plurality of structural steels joined to the upper surface of the bottom steel plate so as to extend in the direction of the bridge axis or perpendicular to the bridge axis, and a concrete deck plate cast on the bottom steel plate so as to embed the structural steels, wherein these are integrated into a precast composite deck girder.

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