A construction technology for pre-embedded inner formwork and post-casting of tie beams in casting construction of double-pier bridge

Abstract

The invention relates to a construction process for casting a double-pier bridge with a pre-embedded inner mold and a tie beam post-casting, which effectively solves the problems of poor bonding of the tie beam post-casting, long construction period of synchronous casting and high construction cost; the pre-embedded inner mold is embedded in the pier column concrete when the pier column is cast to form an umbrella-shaped cavity, and connecting steel bars are embedded together when the inner mold is embedded; when the tie beam is post-casted, the tie beam mold cavity is connected with the cavity formed by the inner mold, and an umbrella-shaped anchoring structure anchored in the pier column is formed at the end of the tie beam; while adopting the construction process for post-casting the tie beam, the long-term stability of the connection between the tie beam and the pier column is guaranteed, and the defect of poor bonding of new and old concrete is compensated.

Description

Technical Field

[0001] The invention relates to the field of bridge construction, in particular to a construction process for casting a double-pier bridge with a pre-buried inner formwork and a tie beam post-casting. Background Art

[0002] Double-pier bridge is also called double-column bridge pier, which means that two piers are set along the width of the bridge at the same longitudinal support position of the bridge. It is mostly used for super-wide bridges and super-high bridges. One or more horizontal tie beams are often set between the super-high double piers to connect the two piers, which limit the piers and make the two piers form a whole to improve stability. There are two types of casting construction of piers with tie beams:

[0003] First, the tie beam is cast after the pier is cast. The disadvantage of this method is that the bonding between the new and old concrete of the tie beam and the pier is poor. For the reverse construction of bridge piers, since the method of first drilling and casting the bridge piers and then excavating the earthwork is adopted, the tie beam cannot be cast in place, and only this post-casting construction method can be adopted. When the earthwork is excavated to the position of the tie beam, the tie beam is cast later, such as the invention patent with application number: CN201911185322.7. Since the stability of the bonding between new and old concrete has always been a difficult technical problem to solve, and concrete has the characteristics of being resistant to compression but not tension, in this post-casting method, the bonding surface between the end face of the tie beam and the side wall of the pier is at risk of cracking when the tie beam is subjected to alternating tensile and compressive stress for a long time. Once the concrete cracks, the limiting effect of the tie beam will be greatly weakened or even lost.

[0004] The second is the synchronous casting method of tie beams and piers. When the piers are cast to the height of the tie beams, a tie beam mold cavity connected to the pier mold cavity is built, and then concrete is poured to complete the simultaneous casting of the tie beams and piers. For example, the invention patent with application number: CN201911002742.7, in this way, the tie beams and piers are cast as a whole, and the tensile performance of the tie beams is stable. It is for this reason that, except for reverse construction and other construction methods that must adopt post-cast tie beams, the rest are turning to the synchronous casting method; however, this method also has corresponding disadvantages: the casting construction method of the longitudinal structure has climbing Formwork construction, sliding formwork construction, flip formwork construction, climbing formwork construction and sliding formwork have the advantages of fast construction progress, low construction cost, and low equipment investment due to the small amount of formwork used and the need to not remove the formwork during the pouring process. However, they can only be used for the pouring of upper and lower equal-section components. When the piers with tie beams are poured simultaneously, sliding formwork and climbing formwork construction cannot be used due to the obstruction of the tie beams, and only flip formwork construction can be used. Flip formwork construction requires repeated removal of the lower formwork and connecting it to the upper formwork. Therefore, the construction progress is slow, the construction period is long, the formwork consumption is large, special formwork is required at the tie beam position, and the construction cost is high. Summary of the invention

[0005] In view of the above situation, in order to solve the problems of poor bonding of tie beams after casting, long construction period and high construction cost of synchronous casting, the present invention provides a pre-embedded inner mold for casting construction of double pier bridges and a tie beam after casting construction process.

[0006] A pre-buried inner formwork for casting construction of a double-pier bridge comprises a main tube and a plurality of side tubes, wherein the inner end of the main tube is closed and the outer end is open, the two ends of the side tubes are closed, a plurality of through holes are opened on the inner end surface of the main tube, the circumference of the plurality of side tubes is evenly distributed outside the main tube and forms a fixed angle with the axis of the main tube, the inner end of the side tube is in contact with the side wall of the main tube, and the outer end is flush with the outer end of the main tube, and the plurality of main tubes and the side tubes form an umbrella-like structure.

[0007] The inner end of the side tube is fixed to the main tube via bolts.

[0008] The outer end of each side tube is provided with a threaded hole.

[0009] A radial cross brace is fixed in the main cylinder.

[0010] A post-casting construction process for a tie beam with a pre-embedded inner formwork for casting construction of a double-pier bridge comprises the following construction steps:

[0011] Step 1: Casting of pier columns: hoisting the pier column reinforcement cage to the marked position, setting up the pier column formwork system, and casting the pier column concrete section by section from bottom to top;

[0012] Step 2: Pre-embed the inner mold. When the pier is cast to a section below the bottom elevation of the tie beam, use bolts to fix the side tube to the outer wall of the main tube, so that the main tube and the side tube form an umbrella-shaped inner mold. Then, pre-embed the inner mold at the connection position between the end of the tie beam and the pier, insert a pre-embedded connecting steel bar into each through hole of the main tube and tie it to the pier steel cage;

[0013] Step 3: Plant additional pre-buried connecting steel bars, and add additional pre-buried connecting steel bars located outside the main tube within the projection range of the tie beam end surface;

[0014] Step 4: Continue pouring pier column concrete to the elevation;

[0015] Step 5: Pull out the inner formwork, build the tie beam formwork, hoist the tie beam reinforcement cage, and connect the ends of the tie beam reinforcement with the embedded connecting reinforcement;

[0016] Step 6: Pour the tie beam concrete to the tie beam top elevation;

[0017] Step 7: After the concrete solidifies, remove the tie beam formwork and complete the post-pouring operation of the tie beam.

[0018] In step 2, before tying the embedded connecting steel bars, horizontal transverse bars perpendicular to the embedded connecting steel bars are tied on the pier column steel cage. The inner ends of the embedded connecting steel bars can be tied to the steel cage or to the horizontal transverse bars.

[0019] In step 2 and step 3, the embedded connecting steel bars and the through holes are sealed with foam glue, the outer end of the main tube is sealed with bamboo plywood or foam board, and the threaded holes at the outer ends of the side tubes and the outer ports of all threaded sleeves are blocked with plastic film or rubber plugs.

[0020] In step 2, an internal threaded pipe is embedded at a position lower than the bottom elevation of the tie beam, and the internal threaded pipe is arranged radially along the pier. When the tie beam formwork is constructed in step 5, the internal threaded pipe is used to install the corbel to support the tie beam formwork system.

[0021] In step five, a micro steel cage frame is implanted in the hole formed in each side tube, the inner end of the frame is tied and fixed to the embedded connecting steel bars in the hole of the main tube, and the outer end of the frame is tied and fixed to the tie beam steel bars.

[0022] In step five, after the inner mold is pulled out, the inner wall of the inner mold cavity is roughened, and then the hole is cleaned, and the outer wall of the pier column at the junction with the end of the tie beam is roughened.

[0023] The present invention adopts the construction technology of post-casting of tie beams, and at the same time, through the umbrella-shaped anchoring structure at the ends of the tie beams, ensures the long-term stability of the connection between the tie beams and the piers, and makes up for the defect of poor bonding between new and old concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the main sectional view of the inner mold.

[0025] Figure 2 This is the right view of the inner mold.

[0026] Figure 3 This is the main sectional view when the inner mold is embedded.

[0027] Figure 4 for Figure 3 Enlarged view of position A in the middle.

[0028] Figure 5 This is the main cross-sectional view of the mold cavity position after the inner mold is removed.

[0029] Figure 6 This is the main cross-sectional view after the tie beam steel formwork and tie beam reinforcement cage are in place.

[0030] Figure 7 for Figure 6 Enlarged view of position B in the middle.

[0031] Figure 8 This is the main section view after the tie beam is cast.

[0032] In the above figures, 1-main tube, 2-side tube, 3-through hole, 4-bolt, 5-threaded hole, 6-cross brace, 7-pier steel cage, 8-pier formwork, 9-pier concrete, 10-embedded connecting steel bars, 11-threaded sleeve, 12-tie beam formwork, 13-tie beam steel cage, 14-horizontal transverse reinforcement, 15-inner threaded pipe, 16-corbel, 17-supporting beam, 18-micro steel cage skeleton, 19-tie beam concrete. DETAILED DESCRIPTION

[0033] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0034] The inner mold comprises a main tube 1 and multiple side tubes 2. The inner end of the main tube 1 is closed and the outer end is open, and the two ends of the side tube 2 are closed. Before the pier is cast to the height of the tie beam, the main tube 1 is installed on the pier column steel cage 7 along the radial direction of the pier, and the main tube 1 is opened outward. A plurality of through holes 3 are opened on the inner end surface of the main tube 1. Pre-buried connecting steel bars 10 are inserted into the through holes 3. The inner ends of the pre-buried connecting steel bars 10 are tied and fixed to the pier column steel cage 7, and the outer ends are inserted into the main tube 1 to be connected with the tie beam steel bars when the tie beam is cast; multiple side tubes 2 are evenly distributed outside the main tube 1 and form a fixed angle with the axis of the main tube 1. The inner ends of the side tubes 2 are fitted with the side walls of the main tube 1, and the outer ends are flush with the outer ends of the main tube 1. After the pier column formwork 8 at the tie beam position is in place, the inner wall of the formwork is fitted with the main tube 1 and the outer ends of the multiple side tubes 2. The multiple main tubes 1 and the side tubes 2 form an umbrella-like structure. After pouring concrete, an umbrella-like cavity is formed at the positions of the main tube 1 and the side tubes 2.

[0035] The inner end of the side tube 2 is fixed to the main tube 1 by bolts 4. After the inner end of the side tube 2 is fitted with the main tube 1, the bolts 4 are screwed on from inside the main tube 1 to fix the side tube 2 to the main tube 1 to ensure that the side tube 2 will not shift when pouring concrete.

[0036] Each of the side tubes 2 has a threaded hole 5 at its outer end. When removing the formwork, a bolt 4 is screwed into the threaded hole 5 to pull the pull ring, thereby conveniently pulling the side tube 2 out of the concrete to complete the demoulding.

[0037] A radial cross brace 6 is fixed inside the main tube 1, and the embedded connecting steel bars 10 are tied and fixed to the cross brace 6, so that the position of the main tube 1 is completely fixed so that it will not shift. Another invention is that the main tube 1 can also be easily pulled out of the concrete through the cross brace 6 when removing the formwork.

[0038] The method of using the above inner formwork for pier column casting and tie beam post-casting construction is as follows:

[0039] Step 1: Casting of pier columns. Hoist the pier column reinforcement cage 7 to the marked position. Strictly control the position and verticality of the centerline axis. Set up the pier column formwork 8 system at the bottom of the pier column. The formwork system is unlimited. Climbing formwork, sliding formwork and flip formwork can be used for construction. After the formwork is brushed with a release agent and in place, its position, elevation and horizontal stability are checked. After passing the inspection, cast the pier column concrete 9 from bottom to top section by section. The single casting height of the pier column shall not exceed two meters. During casting, use an inserted vibrating rod to vibrate and compact. It is strictly forbidden to insert the vibrator on the steel bar for vibration. Keep a distance of 5 to 10 cm from the formwork. The sign of compaction is that the concrete no longer collapses, no bubbles emerge, and the surface is flat and slurry.

[0040] Step 2: Pre-embed the inner mold. When the pier is cast to a section below the bottom elevation of the tie beam, use bolts 4 to fix the side tube 2 to the outer wall of the main tube 1, so that the main tube 1 and the side tube 2 form an umbrella-shaped inner mold, and then pre-embed the inner mold at the connection position between the end of the tie beam and the pier; specifically, after the inner mold is assembled, insert a pre-embedded connecting steel bar 10 into each through hole 3 at the bottom of the main tube 1, and install a threaded sleeve 11 at the outer end of the pre-embedded connecting steel bar 10 for subsequent connection with the tie beam steel bar, and then the main tube 1 Hoist to the marked position, with the tube mouth facing outwards, and the tube mouth is flush with the inner wall of the pier column template 8. In order to fit with the inner wall of the pier column template 8, the outer ends of the main tube 1 and the side tube 2 are both in the shape of intersecting lines intersecting with the inner wall of the pier column template 8; then adjust the position of the embedded connecting steel bar 10 so that the outer end of the threaded sleeve 11 does not extend out of the tube mouth of the main tube 1, and then tie and fix the inner end of the embedded connecting steel bar 10 to the pier column steel cage 7, and then tie and fix the embedded connecting steel bar 10 abutting against the cross brace 6 to the cross brace 6;

[0041] Step 3: Plant additional pre-buried connecting steel bars 10. Add additional pre-buried connecting steel bars 10 located outside the main tube 1 within the projection range of the tie beam end face; the inner end of the pre-buried connecting steel bar 10 is tied and fixed to the pier column steel cage 7, and the outer end is installed with a threaded sleeve 11. The outer end of the threaded sleeve 11 is flush with the inner wall of the pier column formwork 8 for subsequent connection with the tie beam steel bars;

[0042] Step 4: Continue pouring the pier column concrete 9 to the elevation; after the inner mold is fixed in place, apply a release agent to the outer wall of the inner mold, and then continue pouring the pier column concrete 9 to the pier column top elevation position, remove the mold after solidification to complete the pier column pouring operation;

[0043] Step 5: Pull out the inner mold, build the tie beam template 12, hoist the tie beam steel cage 13, and connect the ends of the tie beam steel bars with the embedded connecting steel bars 10; before the post-casting of the tie beam, first pull out the inner mold, the specific method is: unscrew the bolts 4 from the main tube 1, remove the connection between the main tube 1 and the side tube 2, and then remove the binding of the embedded connecting steel bars 10 and the cross brace 6, pull out the main tube 1 through the cross brace 6, screw the pull ring on the threaded hole 5 at the outer end of the side tube 2 to pull out the side tubes 2 one by one; after the inner mold is removed, build the tie beam template 12 at the marked position and hoist the steel cage of the tie beam into place, apply a release agent on the template, check the template position, elevation, and stability, and connect the two ends of the tie beam steel bars to the threaded sleeves 11 at the ends of the embedded connecting steel bars 10 in the piers at both ends respectively;

[0044] Step 6: pour the tie beam concrete 19 to the tie beam top elevation; during pouring, vibrate with an inserted vibrator, and pay attention to inserting the vibrator into the reserved cavity at the position of the main tube 1 for vibration, ensuring that the concrete in the reserved cavity of the inner mold is also vibrated and compacted;

[0045] Step 7: After the concrete solidifies, the tie beam formwork 12 is removed to complete the post-pouring operation of the tie beam.

[0046] In step two, before tying the embedded connecting steel bars 10, horizontal transverse bars 14 perpendicular to the embedded connecting steel bars 10 are tied on the pier column steel cage 7. The inner ends of the embedded connecting steel bars 10 can be tied to the steel cage or to the horizontal transverse bars 14 to avoid the situation where the embedded connecting steel bars 10 are too far away from the main bars of the pier column steel cage 7 and cannot be tied.

[0047] In step 2 and step 3, the embedded connecting steel bars 10 and the through holes 3 are sealed with foam glue, the outer end of the main tube 1 is sealed with bamboo plywood or foam board, and the threaded holes 5 at the outer ends of the side tubes 2 and the outer ports of all threaded sleeves 11 are blocked with plastic film or rubber plugs to prevent concrete from entering the inner mold cavity.

[0048] In step 2, an internal threaded pipe 15 is pre-buried at a position lower than the bottom elevation of the tie beam, and the internal threaded pipe 15 is arranged radially along the pier column. When the tie beam formwork 12 is built in step 5, the internal threaded pipe 15 is used to install the corbel 16, which is used to carry the tie beam formwork 12 system; the inner end of the internal threaded pipe 15 is welded and fixed to the pier column steel cage 7 and closed, and the outer end is 3 to 5 cm away from the inner wall of the pier column formwork 8. Before pouring concrete in step 4, the outer end of the internal threaded pipe 15 is blocked with a rod, and the outer end of the rod is flush with the inner wall of the pier column formwork 8, so that the internal threaded pipe 15 is completely buried in the pier column. In step five, when building the tie beam formwork 12, pull out the columnar plug at the outer end of the internal threaded tube 15, screw it with the internal threaded tube 15, and then fix the corbel 16 on the screw with a nut, and then fix the supporting beam 17 on the corbel 16, and set up the tie beam formwork 12 on the supporting beam 17; after dismantling the tie beam formwork 12 in step seven, remove the corbel 16, and pressure-fill the internal threaded tube 15 with concrete slurry to seal it. Since the outer end of the internal threaded tube 15 does not extend to the surface of the pier, the internal threaded tube 15 is completely buried in the pier and will not leak out or rust, thereby ensuring the integrity of the exterior facade of the pier.

[0049] In step five, a micro steel cage skeleton 18 is implanted in the cavity formed in each side tube 2, the inner end of the skeleton is tied and fixed to the embedded connecting steel bars 10 in the cavity of the main tube 1, and the outer end of the skeleton is tied and fixed to the tie beam steel bars.

[0050] In step five, after the inner mold is pulled out, the inner wall of the inner mold cavity is roughened and then cleaned, and the outer wall of the pier column at the junction with the end of the tie beam is roughened to improve the bonding strength between the new and old concrete.

[0051] The present invention adopts a construction process of post-casting of tie beams, which is suitable for reverse construction of bridges. It also enables climbing formwork casting and sliding formwork casting to be used for casting operations of double-pier bridge piers with tie beams in normal construction procedures, which can greatly improve casting efficiency and reduce investment in equipment and personnel in casting construction. Moreover, the inner mold device and pre-embedding method of the present invention are simple and hardly increase equipment cost and construction cost.

[0052] The present invention pre-buries an umbrella-rib-shaped inner mold and reserves an umbrella-rib-shaped cavity in the pier corresponding to the end of the tie beam. After pouring the tie beam concrete 19, a stable umbrella-rib-shaped anchoring structure is formed between the end of the tie beam and the pier. The structure bears the main tension of the tie beam, and the concrete bonding force between the end face of the tie beam and the surface of the pier is an auxiliary load-bearing force, thereby avoiding the weakening or even loss of function of the post-cast tie beam due to cracking of the bonding surface between the new and old concrete, thereby ensuring the long-term stability of the post-cast tie beam.

Claims

1. A post-casting construction process for tie beams with embedded inner molds for casting construction of double-pier bridges, characterized in that: The inner mold comprises a main tube (1) and a plurality of side tubes (2); the main tube (1) has a closed inner end and an open outer end; the side tubes (2) are closed at both ends; a plurality of through holes (3) are opened on the inner end surface of the main tube (1); the plurality of side tubes (2) are evenly distributed outside the main tube (1) and form a fixed angle with the axis of the main tube (1); the inner ends of the side tubes (2) are in contact with the side walls of the main tube (1) and the outer ends are flush with the outer ends of the main tube (1); the plurality of main tubes (1) and the side tubes (2) form an umbrella-like structure; the inner ends of the side tubes (2) are fixed to the main tube (1) by bolts (4); the outer ends of each side tube (2) are opened with threaded holes (5); a radial cross brace (6) is fixed inside the main tube (1); The construction process includes the following construction steps: Step 1: Casting of pier columns, hoisting the pier column reinforcement cage (7) to the marked position, setting up the pier column formwork (8) system, and casting the pier column concrete (9) section by section from bottom to top; Step 2: pre-embed the inner mold. When the pier is cast to a section below the bottom elevation of the tie beam, the side tube (2) is fixed to the outer wall of the main tube (1) with bolts (4), so that the main tube (1) and the side tube (2) form an umbrella-shaped inner mold. Then, the inner mold is pre-embedded at the connection position between the end of the tie beam and the pier. A pre-embedded connecting steel bar (10) is inserted into each through hole (3) of the main tube (1) and tied and fixed to the pier steel bar cage (7); Step 3: Planting additional pre-buried connecting steel bars (10), and planting additional pre-buried connecting steel bars (10) located outside the main tube (1) within the projection range of the tie beam end surface; Step 4: Continue pouring the pier column concrete (9) to the elevation; Step 5: Pull out the inner mold, build the tie beam template (12), hoist the tie beam reinforcement cage (13), and connect the ends of the tie beam reinforcement to the embedded connecting reinforcement (10); Step 6: pouring tie beam concrete (19) to the tie beam top elevation; Step 7: After the concrete solidifies, the tie beam formwork (12) is removed to complete the post-casting of the tie beam.

2. The post-casting construction process of tie beams with embedded inner molds for casting construction of double-pier bridges according to claim 1 is characterized in that: In step 2, before tying the embedded connecting steel bars (10), horizontal transverse bars (14) perpendicular to the embedded connecting steel bars (10) are tied on the pier column steel bar cage (7), and the inner ends of the embedded connecting steel bars (10) can be tied on the steel bar cage or on the horizontal transverse bars (14).

3. The post-casting construction process of tie beams with embedded inner molds for casting construction of double-pier bridges according to claim 1 is characterized in that: In step 2 and step 3, the pre-buried connecting steel bar (10) and the through hole (3) are sealed with foam glue, the outer end of the main tube (1) is sealed with a bamboo plywood or a foam board, and the threaded hole (5) at the outer end of the side tube (2) and the outer ends of all threaded sleeves (11) are blocked with plastic film or rubber plugs.

4. The post-casting construction process of tie beams with embedded inner formwork for casting construction of double-pier bridges according to claim 1 is characterized in that: In step 2, an internally threaded pipe (15) is pre-buried at a position lower than the bottom elevation of the tie beam, and the internally threaded pipe (15) is arranged along the radial direction of the pier column. When the tie beam formwork (12) is constructed in step 5, the internally threaded pipe (15) is used to install the corbel (16) for supporting the tie beam formwork (12) system.

5. The post-casting construction process of tie beams with embedded inner formwork for casting construction of double-pier bridges according to claim 1 is characterized in that: In step five, a micro steel cage frame (18) is implanted in the cavity formed in each side tube (2), the inner end of the frame is tied and fixed to the pre-buried connecting steel bars (10) in the cavity of the main tube (1), and the outer end of the frame is tied and fixed to the tie beam steel bars.

6. The post-casting construction process of tie beams with embedded inner formwork for casting construction of double-pier bridges according to claim 1 is characterized in that: In step five, after the inner mold is pulled out, the inner wall of the inner mold cavity is roughened, and then the hole is cleaned, and the outer wall of the pier column at the junction with the end of the tie beam is roughened.

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