Construction Method of Unbalanced Continuous Beam Bridge

Abstract

The present invention provides a bridge construction method for an unbalanced continuous beam, comprising: when a symmetrical section is constructed and a hanging basket is moved to a lower section, construction is performed by pre-pressing and balancing the weight on the upper section before pouring to balance the forces on both sides of the cantilever, comprising the following steps: constructing 0# blocks and 1# blocks on the bridge columns to obtain bridge piers with a starting section; using the columns of the 0# blocks as temporary piers, installing temporary supports on the temporary piers to form a temporary support system; tensioning the bridge piers with the starting section to assemble hanging baskets on both sides of the bridge piers; performing standard section construction and moving the hanging basket; constructing the side span joint section on the standard section; constructing the middle span section on the side span joint section; and removing the temporary support system and the counterweight.

Description

Technical Field

[0001] The invention relates to the field of bridge construction, and in particular to a method for constructing an unbalanced continuous beam bridge. Background Art

[0002] In the development of bridge construction to date, simply supported beam bridges have relatively small spans and are mostly constructed using prefabricated and assembled systems, making reinforcement techniques simple and the cost of replacing the main beams low. Therefore, when a simply supported beam bridge experiences damage that results in insufficient bearing capacity, existing passive reinforcement techniques can often achieve the desired reinforcement effect. When the damage is severe and the bearing capacity seriously fails to meet requirements, the main beam is often replaced.

[0003] Prestressed concrete continuous beam bridges are typically constructed using cantilever casting with a hanging basket and segmental cantilever assembly. To ensure the cantilever beam segments on both sides of the pier remain relatively balanced during construction, a temporary consolidation system is installed along the longitudinal direction of the bridge, on both sides of the permanent supports at the pier top. This system typically consists of temporary high-strength concrete compressive supports and tensile reinforcement.

[0004] Bridge design documents usually specify the maximum unbalanced moment allowed during the continuous beam construction phase (the maximum value of the product of the unbalanced load and the beam cantilever length), which is controlled by the construction party during the construction process. Specific control measures generally include limiting the bridge deck load and symmetrically pouring concrete in alternating cantilever beam sections on both sides.

[0005] Continuous beams are generally constructed with symmetrical cross-sections, requiring only counterweights during the closure phase. Asymmetrical cross-sections, however, require additional counterweights during construction to maintain equilibrium. Under asymmetrical cross-section loading conditions, a large unbalanced bending moment will be generated at one end of the continuous beam. The tensile stress in the cross-section top plate caused by the counterweights can cause significant linear deviations in the main beam during construction, leading to overturning and cracking.

[0006] In existing large-span continuous beam construction, the longest longitudinal prestressed steel strands on the top surface exceed 200 meters, and the box chamber is limited by the transverse beams. This makes it difficult to thread the strands, tension them, grout them, and anchor them within this limited space, creating a technical challenge for successfully completing the steel stranding of large-span continuous beams.

[0007] To avoid construction interference and other load-induced collapse and landslide accidents caused by setting up protective scaffolding on the side of the existing road, and at the same time, the design of the boom beam and the construction process cause unbalanced loads on the side and middle spans. Currently, there is little research on the construction of unbalanced continuous beams and a lack of complete construction technology. Especially when the main bridge crosses an existing highway and road closure is not allowed during construction, the in-situ assembly of the reinforced steel tube arch is a high safety risk. Summary of the Invention

[0008] Based on this, the present invention proposes a bridge construction method for unbalanced continuous beams, which solves the problem of ensuring that the side and middle spans always maintain bending moment balance when the hanging blue is moved to the next segment after each symmetrical segment is constructed.

[0009] The present invention provides a bridge construction method for an unbalanced continuous beam, comprising: after the construction of a symmetrical section is completed and the hanging basket is moved to the next section, the construction is performed by pre-pressing and balancing the previous section before pouring to balance the forces on both sides of the cantilever, including the following steps:

[0010] The 0# block and 1# block are constructed on the bridge column to obtain the bridge pier with the starting segment;

[0011] The columns of the 0# block are used as temporary piers, and temporary brackets are installed on the temporary piers to form a temporary bracket system;

[0012] Tensing the bridge pier with the starting segment to assemble hanging baskets on both sides of the bridge pier;

[0013] Carry out standard segment construction and move the hanging basket, including:

[0014] Calculate the theoretical counterweight based on the moment difference of the symmetrical segments;

[0015] Tensioning and anchoring the longitudinal prestressed steel tendons of the standard segment An and standard segment Bn beam segments, as well as the vertical and transverse prestressed tendons of the standard segment An-1 and standard segment Bn-1 beam segments;

[0016] According to the theoretical counterweight, pre-compression blocks are arranged on the beam surface of the corresponding beam segment to eliminate the unbalanced weight of each segment;

[0017] Cantilevering and symmetrically casting the standard segment An and the standard segment Bn beam segments on the hanging basket;

[0018] During the casting of the standard segment An and the standard segment Bn beam segments, corresponding counterweights are added to the standard segment An-1 beam segment of the side span next to the standard segment An beam segment of the side span according to symmetrical balance.

[0019] Repeat the construction until the side span is connected;

[0020] The side span closure section is constructed on the standard segment, including:

[0021] Tension and anchor the longitudinal prestressed steel tendons of the side span closure section An and the side span closure section Bn, as well as the vertical and transverse prestressed tendons of the side span closure section An-1 and the side span closure section Bn-1;

[0022] According to the theoretical counterweight, the side span closure section An-1 is preloaded in the form of

[0023] and balancing weights are applied to the side span closure section Bn-1 to offset the deformation of the beam body caused by the increase in load during the pouring of concrete in the closure section;

[0024] According to the height difference between the side span closure section An and the side span closure section Bn, additional counterweights are placed on the side span closure section An and the side span closure section Bn;

[0025] The side span closure section An and the side span closure section An are symmetrically cast on the hanging basket.

[0026] Bn beam segment, obtain the side span closure segment;

[0027] Constructing the middle span section on the side span closure section;

[0028] The temporary support system and the counterweight are removed.

[0029] Furthermore, the construction of the 0# block and the 1# block on the bridge column to obtain the bridge pier with the starting segment includes:

[0030] A support system for locking the beam body is installed on the bridge pier with the starting segment to temporarily consolidate the pier and beam.

[0031] Furthermore, the construction of the 0# block and the 1# block on the bridge column to obtain the bridge pier with the starting segment also includes:

[0032] Construction 0# block;

[0033] Install a temporary support on the 0# block and pre-press the temporary support;

[0034] temporarily consolidating the temporary support;

[0035] Installing a permanent support on the 0# block;

[0036] Installing bottom formwork and side formwork on the temporary support and the permanent support;

[0037] Installing steel bars and inner molds in the bottom mold and side molds;

[0038] Installing arch foot steel bars and arch seat formwork on the temporary support and the permanent support;

[0039] pouring concrete in the bottom formwork and the side formwork;

[0040] Tension grouting is carried out after pouring;

[0041] The construction of block 0# and block 1# is completed, and the bridge pier with the starting segment is obtained.

[0042] Furthermore, the calculation of the theoretical counterweight according to the moment difference of the symmetrical segments includes:

[0043] The weight difference of the cast symmetrical sections is calculated with each beam section as a unit, the midpoint of the 0# block is taken as the moment zero point, and the accumulated moment on both sides is made zero by counterweighting to calculate the theoretical counterweight.

[0044] Furthermore, the method of eliminating the unbalanced weight of each segment by disposing pre-compression blocks on the beam surface of the corresponding beam segment according to the theoretical counterweight includes:

[0045] During the installation of the steel bars, pre-compression blocks with a weight of 1 / 2 of the theoretical counterweight are arranged in the standard segment and the standard segment beam section;

[0046] During the concrete pouring process, the pre-compression blocks with gradually increasing weight are arranged at the center of gravity of the standard segment An-1 and the standard segment Bn-1 beam segments.

[0047] Furthermore, the method of eliminating the unbalanced weight of each segment by configuring pre-compression blocks on the beam surface of the corresponding beam segment according to the theoretical counterweight also includes: after the counterweight is completed, determining the final counterweight based on linear monitoring measurement.

[0048] Furthermore, during the casting of the standard segment An and the standard segment Bn beam segments, corresponding counterweights are added gradually to the standard segment An-1 beam segment on the side span in close proximity to the standard segment An beam segment on the side span in accordance with symmetrical balance, including: after the casting of the standard segment An and the standard segment Bn beam segments is completed, the counterweight blocks of corresponding weights of the standard segment An-1 and the standard segment Bn-1 are moved to the standard segment An and the standard segment Bn beam segments.

[0049] Furthermore, the adding of counterweights to the side span closure section An and the side span closure section Bn according to the height difference between the side span closure section An and the side span closure section Bn includes:

[0050] When the height difference between the side span closure section An and the side span closure section Bn is within the allowable range of the height difference, no additional counterweight loading is performed;

[0051] or

[0052] When the height difference between the side span closure section An and the side span closure section Bn exceeds the allowable range, and the bottom of the end beams of the side span closure section An-1 and the side span closure section Bn-1 are higher than the theoretical value, additional counterweights are applied to the side span closure section An-1 and the side span closure section Bn-1;

[0053] or

[0054] When the height difference between the side span closure section An and the side span closure section Bn exceeds the allowable range, and the bottom of the end beams of the side span closure section An-1 and the side span closure section Bn-1 are lower than the theoretical value, the balancing weight is reduced in the side span closure section An-1 and the side span closure section Bn-1.

[0055] Furthermore, the method of performing balanced counterweighting on the side span closure section An-1 and the side span closure section Bn-1 in the form of advance loading according to the theoretical counterweight to offset the beam deformation caused by the load increase during the pouring of concrete in the closure section includes:

[0056] Pre-compression blocks with a weight equivalent to 1 / 2 of the total weight of concrete of the side span closure section are respectively arranged on the beam surfaces of the side span closure section An-1 and the side span closure section Bn-1.

[0057] Furthermore, the side span joint section An and the side span joint section Bn beam section are symmetrically cast on a cantilever on a hanging basket to obtain the side span joint section, including: in the process of casting the side span joint section An and the side span joint section Bn, the balancing counterweights of the side span joint section An-1 and the side span joint section Bn-1 are unloaded, and the unloading speed is synchronized with the casting speed.

[0058] It can be seen from the above technical solutions that the bridge construction method of the unbalanced continuous beam provided by the present invention has the following beneficial effects:

[0059] The present invention solves the problem of ensuring that the side and middle spans always maintain bending moment balance (i.e., the product of the counterweight after casting and the center length of the main pier) when each symmetrical section is constructed and moved to the next section by means of counterweighting each section. This method is to pre-load the previous section with counterweights before casting, and before the current section is cast and tensioned, move the counterweight blocks of the corresponding weight of the previous section to the current section. This allows each symmetrical beam section to achieve balanced construction at both ends during construction. The weight difference of the cast symmetrical sections is calculated using each beam section as a unit, and the midpoint of the 0# block is used as the torque zero point. The accumulated torque on both sides is made zero by counterweighting, and the theoretical counterweight is calculated. After the counterweighting is completed, linear monitoring measurements under the counterweight working condition are carried out in a timely manner to determine the final counterweight. The pre-loaded blocks use standard pre-loaded blocks, and the weight of each pre-loaded block is 3t. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is a flow chart of an embodiment of the present invention;

[0061] Figure 2 A schematic diagram of a pre-pressed block configuration according to an embodiment of the present invention;

[0062] Figure 3 Schematic diagram of the arrangement of the 0# block bracket according to an embodiment of the present invention;

[0063] Figure 4This is a construction drawing of a standard section of an embodiment of the present invention;

[0064] Figure 5 This is a schematic diagram of a side span closure according to an embodiment of the present invention;

[0065] Figure 6 This is a schematic diagram of the mid-span hanging basket closure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0066] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0067] At present, the main methods for continuous beam construction are: scaffolding method, rotation method, and cantilever casting method. The scaffolding method requires the installation of temporary supports below the casting position of the continuous beam. When casting long beams with many sections, this construction method is greatly affected by the geographical environment and the scaffolding construction time is long. When constructing the jacking method and the rotation method, for large-span arch-stiffened unbalanced load continuous beams, the additional load is large, the loads on the middle span and side spans are unbalanced, and the longer the cantilever casting, the greater the unbalanced load. The construction linearity is difficult to control, and the unbalanced moments at both ends are difficult to balance, resulting in a high safety risk. The above methods have great technical risks and safety hazards in terms of safety control, construction costs, overall construction period, and on-site construction. They cannot meet on-site construction needs. It is difficult to achieve low-risk and high-efficiency construction for large-span unbalanced load continuous beams.

[0068] Cantilever construction is one of the most commonly used construction methods for continuous beam bridges. It has great advantages for high-altitude, large-span, deep valley and special conditions. Cantilever construction generally uses a pair of cantilever hanging baskets for symmetrical casting. However, due to the stress requirements of the design structure or the complexity of on-site construction conditions, there will inevitably be problems with the weight symmetry of the cantilever cast beam section.

[0069] Existing large-span arch-reinforced continuous beams with unbalanced loads suffer from high material consumption, long construction times, high risks, and low efficiency during construction. This project utilizes a double-track, large-span arch-reinforced continuous beam, designed to span the highway. Because the mid-span cantilevered hanging basket construction takes place above the highway, safety considerations necessitate comprehensive protective construction of the construction surface. Furthermore, the uneven distribution of the boom crossbeams and internal tooth blocks within the box beam design results in significant load deviations at the side and mid-span ends, generating unbalanced loads within the continuous beam cantilever construction segment.

[0070] like Figure 1 As shown, the present invention provides a method for constructing an unbalanced continuous beam bridge, comprising: after the construction of the symmetrical section is completed and the hanging basket is moved to the lower section, the upper section is pre-loaded with a counterweight before pouring to balance the forces on both sides of the cantilever, comprising the following steps:

[0071] S1: construct 0# and 1# blocks on the bridge columns to obtain bridge piers with starting segments;

[0072] S2: Use the columns of block 0# as temporary piers and install temporary supports on the temporary piers to form a temporary support system;

[0073] S3: tensioning the bridge piers with the starting segments to assemble the hanging baskets on both sides of the bridge piers;

[0074] S4: Carry out standard segment construction and move the hanging basket, including:

[0075] S401: Calculate theoretical counterweight based on moment difference of symmetrical segments;

[0076] S402: Tensioning and anchoring the longitudinal prestressed steel tendons of the standard segment An and standard segment Bn beam segments, as well as the vertical and transverse prestressed tendons of the standard segment An-1 and standard segment Bn-1 beam segments;

[0077] S403: Disposing pre-compression blocks on the beam surface of the corresponding beam segment according to the theoretical counterweight to eliminate the unbalanced weight of each segment;

[0078] S404: Cantilever and symmetrically cast standard segment An and standard segment Bn beam segments on the hanging basket;

[0079] During the casting of the standard segment An and standard segment Bn beam segments, corresponding counterweights are added to the side span standard segment An-1 beam segment adjacent to the side span standard segment An beam segment according to symmetrical balance.

[0080] S405: Repeat the construction until the side span closure section;

[0081] S5: Construction of the side span closure section on the standard segment, including:

[0082] S501: Tension and anchor the longitudinal prestressed steel tendons of the side span closure An and side span closure Bn beam segments, as well as the vertical and transverse prestressed steel tendons of the side span closure An-1 and side span closure Bn-1 beam segments;

[0083] S502: Based on theoretical counterweights, balance weights are applied to the side span closure sections An-1 and Bn-1 in advance to offset beam deformation caused by increased loads during concrete pouring of the closure sections.

[0084] S503: adding counterweights to the side span closure section An and the side span closure section Bn according to the height difference between the side span closure section An and the side span closure section Bn;

[0085] S504: symmetrically cast the side span closure section An and the side span closure section Bn beam segments on the cantilever on the hanging basket to obtain the side span closure section;

[0086] S6: Construction of the middle span section on the side span closure section;

[0087] S7: Remove the temporary support system and counterweight.

[0088] The present invention solves the problem of ensuring that the side and middle spans always maintain bending moment balance (i.e., the product of the counterweight after casting and the center length of the main pier) when each symmetrical section is constructed and moved to the next section by means of counterweighting each section. This method is to pre-load the previous section with counterweights before casting, and before the current section is cast and tensioned, move the counterweight blocks of the corresponding weight of the previous section to the current section. This allows each symmetrical beam section to achieve balanced construction at both ends during construction. The weight difference of the cast symmetrical sections is calculated using each beam section as a unit, and the midpoint of the 0# block is used as the torque zero point. The accumulated torque on both sides is made zero by counterweighting, and the theoretical counterweight is calculated. After the counterweighting is completed, linear monitoring measurements under the counterweight working condition are carried out in a timely manner to determine the final counterweight. The pre-loaded blocks use standard pre-loaded blocks, and the weight of each pre-loaded block is 3t.

[0089] The main bridge of this invention adopts a construction sequence of beams first, then arches. The prestressed concrete continuous beams are constructed using symmetrical cantilever casting using a fully enclosed hanging basket. Under construction conditions with asymmetrical cross-section loads, segmented counterweights are used to avoid large unbalanced bending moments at one end. This prevents significant deviations in the main beam's linear alignment and the possibility of the beam tipping during construction, ensuring smooth bridge closure and achieving the desired main beam linear alignment. This effectively reduces tensile stress in the cross-section top plate caused by the counterweights, thereby preventing cracks.

[0090] Furthermore, the 0# block and the 1# block are constructed on the bridge column to obtain a bridge pier with a starting segment including:

[0091] A bracket system for locking the beam is installed on the bridge pier with the starting segment to temporarily consolidate the pier and beam.

[0092] Furthermore, the construction of the 0# block and the 1# block on the bridge column to obtain the bridge pier with the starting segment also includes:

[0093] S101: Construction of block 0#;

[0094] S102: Install a temporary support on the 0# block and pre-press the temporary support;

[0095] S103: Temporary consolidation of temporary supports;

[0096] S104: Install permanent supports on 0# blocks;

[0097] S105: Install bottom formwork and side formwork on temporary supports and permanent supports;

[0098] S106: Install the steel bars and inner formwork in the bottom formwork and side formwork;

[0099] S107: Install arch foot reinforcement and arch seat formwork on temporary supports and permanent supports;

[0100] S108: pouring concrete in the bottom formwork and side formwork;

[0101] S109: tension grouting after pouring;

[0102] S110: Complete the construction of block 0# and block 1#, and obtain the bridge pier with the starting segment.

[0103] Further, such as Figure 2 As shown in the figure, the configuration of the pre-load block, based on the moment difference of the symmetrical segments, calculates the theoretical counterweight including:

[0104] The weight difference of the cast symmetrical sections is calculated with each beam section as a unit, the midpoint of the 0# block is taken as the moment zero point, and the accumulated moment on both sides is made zero by counterweighting to calculate the theoretical counterweight.

[0105] Among them, according to the following formula to calculate the theoretical counterweight, the bending moment balance of the arch-stiffened continuous beam is equal to:

[0106] ΣM1+ΣM2+M3+M4=M5+ΣM6+M7+M8

[0107] M1: side span segment counterweight bending moment;

[0108] M2: bending moment during casting of side span segments;

[0109] M3: Bending moment of hanging basket and construction load;

[0110] M4: Basket counterweight bending moment;

[0111] M5: bending moment of segment arch stiffener foot;

[0112] M6: mid-span segment casting bending moment;

[0113] M7: bending moment of stiffening beam;

[0114] M8: Bending moment of hanging basket with protective shed.

[0115] Furthermore, according to the theoretical counterweight, pre-compression blocks are arranged on the beam surface of the corresponding beam segment to eliminate the unbalanced weight of each segment, including:

[0116] During the installation of steel bars, pre-compression blocks with a weight of 1 / 2 of the theoretical counterweight are configured in the standard segments and standard segment beams;

[0117] During the concrete pouring process, pre-compression blocks with gradually increasing weight are arranged at the center of gravity of the standard segment An-1 and standard segment Bn-1 beam sections.

[0118] Furthermore, eliminating the unbalanced weight of each segment by configuring pre-compression blocks on the beam surface of the corresponding beam segment according to the theoretical counterweight also includes: after the counterweight is completed, determining the final counterweight according to the linear monitoring measurement.

[0119] Furthermore, during the casting of the standard segment An and standard segment Bn beam sections, corresponding counterweights are added to the side span standard segment An-1 beam section adjacent to the side span standard segment An beam section according to symmetrical balance, including: after the casting of the standard segment An and standard segment Bn beam sections is completed, the counterweight blocks of corresponding weights of the standard segment An-1 and standard segment Bn-1 are moved to the standard segment An and standard segment Bn beam sections.

[0120] Furthermore, according to the height difference between the side span closure section An and the side span closure section Bn, additional counterweights are added to the side span closure section An and the side span closure section Bn, including:

[0121] When the height difference between the side span closure section An and the side span closure section Bn is within the allowable range of height difference, no additional counterweight loading is performed;

[0122] Or when the height difference between the side span closure section An and the side span closure section Bn exceeds the allowable range, and the bottom of the end beams of the side span closure section An-1 and the side span closure section Bn-1 are higher than the theoretical value, additional counterweights shall be applied to the side span closure section An-1 and the side span closure section Bn-1. The specific amount shall be determined based on the measured height difference combined with the simulation calculation of the monitoring unit;

[0123] Or when the height difference between the side span closure section An and the side span closure section Bn exceeds the allowable range, and the bottom of the end beams of the side span closure section An-1 and the side span closure section Bn-1 are lower than the theoretical value, the balancing weight is reduced in the side span closure section An-1 and the side span closure section Bn-1.

[0124] Furthermore, according to the theoretical counterweight, balanced counterweights are applied in advance on the side span closure sections An-1 and Bn-1 to offset the beam deformation caused by the increased load during concrete pouring of the closure sections, including:

[0125] Pre-compression blocks with a weight equivalent to 1 / 2 of the total weight of the concrete of the side span closure section are arranged on the beam surface of the side span closure section An-1 and the side span closure section Bn-1.

[0126] Furthermore, the side span closure section An and the side span closure section Bn beam sections are symmetrically cast on the cantilever on the hanging basket to obtain the side span closure section, including: in the process of casting the side span closure section An and the side span closure section Bn, the balancing weights of the side span closure section An-1 and the side span closure section Bn-1 are unloaded, and the unloading speed is synchronized with the casting speed.

[0127] Furthermore, counterweight loading is mainly divided into two types: one is additional counterweight, which offsets the unbalanced load caused by the displacement of the cantilever basket during the construction of the joint section; the other is balanced counterweight. Because the arch hanger on the arch reinforcement side is designed with a hanger beam, which leads to the difference in the side and mid-span cross-section, counterweight is needed to balance the side and mid-span. The balanced counterweight is not unloaded during the concrete pouring of the joint section, and is unloaded after the concrete strength reaches 100% and the prestressing is completed.

[0128] Furthermore, when the side spans are connected, only the balancing weights on the side spans are unloaded, and the balancing weights on the middle spans are retained.

[0129] Furthermore, the middle span section is constructed on the side span joint section, including: removing the temporary brackets next to the side piers and releasing the temporary locks of the side pier supports. Move the middle hole hanging basket and pour the concrete of the side span joint section An and the side span joint section Bn beam section. The large mileage side hanging basket retreats one section from the end to the side span joint section An-1 and the side span joint section Bn-1. The basket is lowered by 0.8 meters before retreating. At the same time, the bottom basket and the outer sliding beam are kept level to ensure the smooth retreat of the basket. The small mileage side hanging basket moves forward to the joint section. The bottom formwork is anchored to the reserved holes of the bottom plate of the adjacent sections on both sides with 32mm finely rolled threaded steel bars, and the side formwork is anchored to the reserved holes of the top plate of the adjacent sections on both sides with 32mm finely rolled threaded steel bars.

[0130] Furthermore, the temporary support system and counterweight shall be removed after the concrete strength of the side span closure section An reaches 100% of the design value and the elastic modulus reaches 100% of the design value, and it must be ensured that the concrete age of the beam body is greater than 5 days during tensioning.

[0131] Remove the external supports, tension and anchor to the design value, and grout. Tension and anchor the remaining steel tendons in the side span to the design value, and grout.

[0132] Separate the cast-in-place side span from the beam, remove the temporary locks on the side pier supports, move the mid-span gantry, and pour the concrete for the side span closure section Bn. This should be done only after the concrete strength and elastic modulus of the side span closure section Bn reach 100% of the design values. The beam concrete must be at least 5 days old at the time of tensioning. Tension the prestressing tendons to the design value.

[0133] Move the mid-span hanging basket and pour the mid-span closure section. This section should be poured after the concrete strength and elastic modulus reach 100% of the design values. The concrete age of the beam must be at least 5 days at the time of tensioning. Remove the external supports, tension and anchor to the design values, and then grout.

[0134] Remove the temporary buttresses on the middle pier, complete the system conversion, and remove the hanging basket. Tension and anchor the remaining prestressing tendons on the bottom plate. Tension the tendons symmetrically and simultaneously for the symmetrical spans. Tension the tendons of the side spans and main spans alternately, ensuring that the long tendons are tensioned first and the short tendons laterally. Tension each tendon symmetrically. Tension the top plate tendons. After all the prestressing tendons are tensioned, remove the symmetrical weights from the hanging point beams.

[0135] The technical solutions of the present invention are described in detail below through preferred embodiments. It should be noted that the specific embodiments below are only for illustration and are not intended to limit the present invention.

[0136] Example 1:

[0137] A double-track super-large bridge crosses the expressway at DK364+057.3~DK364+496.05.

[0138] Within the intersection, the expressway passes through in the form of fill, and the roadbed is a retaining wall embankment (about 6.5m high). The highway is a two-way two-lane highway with a single road width of 12.5m and an angle of 30 degrees with the maximum mileage of the line. The design adopts a 1-(91.3+180+91.3)m continuous beam arch span.

[0139] The longitudinal slope of this continuous beam is flat. The K15 section of the 38# main pier and the K6 section of the 39# main pier begin to enter the highway range. The cross-road operation protection adopts a 8.4m long and 18.95m wide protective bottom hanging basket. For cross-road operation, the lowest point elevation of the bottom of the continuous beam (K7 section) is +182.844m, the lowest position elevation of the suspended pouring construction template is +181.114m, the highest point elevation of the top surface of the highway is +171.77m, the bottom of the hanging basket is 1m lower than the bottom of the side formwork, and the clearance is 8.344m.

[0140] The main span of this bridge adopts an arch-reinforced continuous beam structure. The spacing between the steel tube arch hangers along the bridge is 9m. There are 18 sets of double hangers in the whole bridge. A hanger crossbeam is set on the main beam in the middle of the span, and the tooth blocks in the box beam are unevenly distributed. The design results in inconsistent weights at the side and middle spans. The middle span of this bridge crosses the existing expressway, and the mid-span hanging basket requires full enclosed protection. This causes imbalance between the side and middle ends during construction, and it is necessary to simultaneously apply counterweights to the side spans.

[0141] Based on the bridge length and other conditions, the bridge is closed from the 0# block to the middle. Each arch is divided into 0# blocks to 20# blocks from both sides to the center of gravity. Blocks 2# to 18# are standard segments, block 19# is the side span closure section, and block 20# is the middle span section. The construction process includes the following steps:

[0142] The 0# block, A1# and B1# blocks are constructed on the bridge columns to obtain the bridge piers with starting segments.

[0143] Use the 0# block columns as temporary piers, install temporary supports on the temporary piers to form a temporary support system, such as Figure 3 The bridge pier with the starting segment is tensioned to assemble the hanging basket on both sides of the bridge pier.

[0144] Carry out standard segment construction and move the hanging basket. The standard and fast construction process is as follows Figure 4 As shown, the method includes calculating theoretical counterweight based on the moment difference between symmetrical segments; tensioning and anchoring the longitudinal prestressing steel tendons of standard segments A2# and B2#, as well as the vertical and transverse prestressing tendons of segments A1# and B1#; and arranging preload blocks on the beam surfaces of the corresponding segments to eliminate the unbalanced weight of each segment. Standard segments A2# and B2# are symmetrically cast on a cantilevered gantry. This process is repeated until standard segments A18# and B18# are reached.

[0145] On the standard segments A18# and B18#, the side span closure segments A19# and B19# are constructed. Figure 5 As shown, the method includes: tensioning and anchoring the longitudinal prestressed steel strands of the side span closure section A19# and the side span closure section B19# beam segments and the vertical and transverse prestressed tendons of the standard section A18# and the standard section B18# beam segments; applying balanced counterweights on the standard section A18# and the standard section B18# in the form of advance loading according to theoretical counterweights to offset the deformation of the beam body caused by the load increase during the pouring of concrete in the closure section; applying additional counterweights on the side span closure section A19# and the side span closure section B19# according to the height difference between the side span closure section A19# and the side span closure section B19#; and symmetrically pouring the side span closure section A19# and the side span closure section B19# beam segments by cantilever on a hanging basket to obtain the side span closure section.

[0146] like Figure 6 As shown, construction of the middle span section 20# is being carried out on the side span closure section A19# and the side span closure section B19#, including: removing the temporary brackets next to the side piers and releasing the temporary locks of the side pier supports. The middle hole hanging basket is moved to pour the concrete of the side span closure section A19# and the side span closure section B19# beam sections. The long-distance side hanging basket retreats one section from the end to the standard section A18# and the standard section B18#. The entire hanging basket is lowered by 0.8 meters before retreating, while ensuring that the bottom basket and the outer sliding beam are level to ensure the smooth retreat of the hanging basket. The short-distance side hanging basket moves forward to the closure section. The bottom formwork is anchored to the reserved holes of the bottom plate of the adjacent sections on both sides with 32mm fine-rolled threaded steel bars, and the side formwork is anchored to the reserved holes of the top plate of the adjacent sections on both sides with 32mm fine-rolled threaded steel bars.

[0147] Remove the temporary support system and counterweight.

[0148] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for constructing a bridge with an unbalanced continuous beam, characterized in that: include: When the symmetrical section is constructed and the hanging basket is moved to the next section, the construction is carried out by pre-loading and balancing the previous section before pouring to balance the forces on both sides of the cantilever, including the following steps: The 0# block and 1# block are constructed on the bridge column to obtain the bridge pier with the starting segment; The columns of the 0# block are used as temporary piers, and temporary brackets are installed on the temporary piers to form a temporary bracket system; Tensing the bridge pier with the starting segment to assemble hanging baskets on both sides of the bridge pier; Carry out standard segment construction and move the hanging basket, including: Calculate the theoretical counterweight based on the moment difference of the symmetrical segments; Tensioning and anchoring the longitudinal prestressed steel tendons of the standard segment An and standard segment Bn beam segments, as well as the vertical and transverse prestressed tendons of the standard segment An-1 and standard segment Bn-1 beam segments; According to the theoretical counterweight, pre-compression blocks are arranged on the beam surface of the corresponding beam segment to eliminate the unbalanced weight of each segment; Cantilevering and symmetrically casting the standard segment An and the standard segment Bn beam segments on the hanging basket; During the casting of the standard segment An and the standard segment Bn beam segments, corresponding counterweights are added to the standard segment An-1 beam segment of the side span next to the standard segment An beam segment of the side span according to symmetrical balance. Repeat the construction until the side span is connected; The side span closure section is constructed on the standard segment, including: Tension and anchor the longitudinal prestressed steel tendons of the side span closure section An and the side span closure section Bn, as well as the vertical and transverse prestressed tendons of the side span closure section An-1 and the side span closure section Bn-1; According to the theoretical counterweight, the side span closure section An-1 is preloaded in the form of and balancing weights are applied to the side span closure section Bn-1 to offset the deformation of the beam body caused by the increase in load during the pouring of concrete in the closure section; According to the height difference between the side span closure section An and the side span closure section Bn, additional counterweights are placed on the side span closure section An and the side span closure section Bn; The side span closure section An and the side span closure section An are symmetrically cast on the hanging basket. Bn beam segment, obtain the side span closure segment; Constructing the middle span section on the side span closure section; The temporary support system and the counterweight are removed.

2. The method according to claim 1, characterized in that The construction of the 0# block and the 1# block on the bridge column to obtain the bridge pier with the starting section includes: A support system for locking the beam body is installed on the bridge pier with the starting segment to temporarily consolidate the pier and beam.

3. The method according to claim 2, characterized in that The step of constructing the 0# block and the 1# block on the bridge column to obtain the bridge pier with the starting section further includes: Construction 0# block; Install a temporary support on the 0# block and pre-press the temporary support; temporarily consolidating the temporary support; Installing a permanent support on the 0# block; Installing bottom formwork and side formwork on the temporary support and the permanent support; Installing steel bars and inner molds in the bottom mold and side molds; Installing arch foot steel bars and arch seat formwork on the temporary support and the permanent support; pouring concrete in the bottom formwork and the side formwork; Tension grouting is carried out after pouring; The construction of block 0# and block 1# is completed, and the bridge pier with the starting segment is obtained.

4. The method according to claim 1, wherein Calculating the theoretical counterweight according to the moment difference of the symmetrical segments includes: The weight difference of the cast symmetrical sections is calculated with each beam section as a unit, the midpoint of the 0# block is taken as the moment zero point, and the accumulated moment on both sides is made zero by counterweighting to calculate the theoretical counterweight.

5. The method according to claim 1, wherein The method of eliminating the unbalanced weight of each segment by disposing pre-compression blocks on the beam surface of the corresponding beam segment according to the theoretical counterweight includes: During the installation of the steel bars, pre-compression blocks with a weight of 1 / 2 of the theoretical counterweight are arranged in the standard segment and the standard segment beam section; During the concrete pouring process, the pre-compression blocks with gradually increasing weight are arranged at the center of gravity of the standard segment An-1 and the standard segment Bn-1 beam segments.

6. The method according to claim 5, characterized in that The method of eliminating the unbalanced weight of each segment by configuring pre-compression blocks on the beam surface of the corresponding beam segment according to the theoretical counterweight also includes: after the counterweight is completed, determining the final counterweight according to linear monitoring measurement.

7. The method according to claim 1, characterized in that During the casting process of the standard segment An and the standard segment Bn beam segments, corresponding counterweights are added gradually to the standard segment An-1 beam segment of the side span close to the standard segment An beam segment of the side span according to symmetrical balance, including: after the casting of the standard segment An and the standard segment Bn beam segments is completed, the counterweight blocks of the corresponding weights of the standard segment An-1 and the standard segment Bn-1 are moved to the standard segment An and the standard segment Bn beam segments.

8. The method according to claim 1, characterized in that The step of adding counterweights to the side span closure section An and the side span closure section Bn according to the height difference between the side span closure section An and the side span closure section Bn includes: When the height difference between the side span closure section An and the side span closure section Bn is within the allowable range of the height difference, no additional counterweight loading is performed; or When the height difference between the side span closure section An and the side span closure section Bn exceeds the allowable range, and the bottom of the end beams of the side span closure section An-1 and the side span closure section Bn-1 are higher than the theoretical value, additional counterweights are applied to the side span closure section An-1 and the side span closure section Bn-1; or When the height difference between the side span closure section An and the side span closure section Bn exceeds the allowable range, and the bottom of the end beams of the side span closure section An-1 and the side span closure section Bn-1 are lower than the theoretical value, the balancing weight is reduced in the side span closure section An-1 and the side span closure section Bn-1.

9. The method according to claim 1, characterized in that The method of performing balanced counterweight on the side span closure section An-1 and the side span closure section Bn-1 in the form of advance loading according to the theoretical counterweight to offset the beam deformation caused by the load increase during the concrete pouring of the closure section includes: Pre-compression blocks with a weight equivalent to 1 / 2 of the total weight of concrete of the side span closure section are respectively arranged on the beam surfaces of the side span closure section An-1 and the side span closure section Bn-1.

10. The method according to claim 1, characterized in that The side span joint section An and the side span joint section Bn beam section are symmetrically cast on a cantilever on a hanging basket to obtain the side span joint section, including: in the process of casting the side span joint section An and the side span joint section Bn, the balancing counterweights of the side span joint section An-1 and the side span joint section Bn-1 are unloaded, and the unloading speed is synchronized with the casting speed.

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