A construction method for cast-in-situ box girder pouring of an ultra-wide taxiway bridge

Abstract

The application provides a kind of cast-in-situ box girder pouring construction method suitable for ultra-wide taxiway bridge, four spans in longitudinal direction are divided into two sections, the third span 1 / 4 is taken as the boundary, two post-pouring bands are arranged transversely, left, middle and right three sections are poured and constructed, the longitudinal first section beam body is constructed first, and then the longitudinal second section beam body is constructed.The construction method innovates the conventional construction steps, adopts the segmented section pouring mode, introduces the post-pouring band construction technology, shortens the pouring time of each concrete, reduces the probability of construction cracks caused by the instability of structure caused by beam body temperature change, and simultaneously changes the flow operation to parallel operation for the cast-in-situ beam body construction, improves the overall efficiency of beam body construction.

Description

Technical Field

[0001] This invention mainly relates to the technical field of construction of ultra-wide aircraft taxiway bridges, specifically a method for casting in-situ box girders for ultra-wide taxiway bridges. Background Technology

[0002] With the improvement of people's living standards, air travel is becoming increasingly popular. The demand for airport expansion and renovation projects is growing, leading to increased research into the construction technology of cast-in-place box girders for aircraft taxiway bridges. Given the unique and complex traffic conditions at airports, traditional one-time casting is no longer sufficient for constructing ultra-wide, large-span, high-volume, and high-efficiency cast-in-place box girders.

[0003] Currently, there are relatively few aircraft taxiway bridges in China, and there is little research on the construction methods for cast-in-place box girders for ultra-wide taxiway bridges. As a type of cast-in-place box girder bridge characterized by its ultra-wide width, large span, large volume, heavy weight, and complex traffic flow during construction, the safe, efficient, and correct concrete pouring of ultra-wide taxiway bridges directly impacts bridge quality, corporate reputation, and construction progress. Summary of the Invention

[0004] To address the shortcomings of current technology, this invention combines existing technologies and continuously optimizes and improves the theoretical methods for casting-in-place box girder concrete pouring for ultra-wide aircraft taxiway bridges in actual construction. While successfully completing the construction task, it also summarizes and proposes a construction method suitable for casting-in-place box girder concrete pouring for ultra-wide taxiway bridges.

[0005] The specific technical solution of the present invention is as follows: A construction method for cast-in-place box girder construction of ultra-wide skid bridges involves dividing the four longitudinal spans into two sections, with the third span at 1 / 4 of its length serving as the dividing line. Two post-cast strips are then set laterally, and the construction is carried out in three sections: left, middle, and right. The specific construction method is as follows: Step 1: Construct the first longitudinal beam segment, specifically including: Step 11: Construct the base slab and web slab in three sections: the first span, the second span, and 1 / 4 of the third span, on the left, middle, and right. Pour the concrete for the base slab and web slab. Step 12: Construct the top slab in three sections (left, middle, and right) of the first span, the second span, and 1 / 4 of the third span, and pour the top slab concrete. Step 13: 14 days after the three sections are poured, pour the concrete for the post-pouring strip between the three sections; Step 14: Prestressing tensioning and grouting of the first beam segment; Step 15: Remove the mid-span supports of the first and second spans and open the road to traffic, but the supports at the piers and within a certain range in front of and behind the piers must not be removed; Step 2: Construct the second longitudinal beam segment, specifically including: Step 21: The third and fourth spans of 3 / 4 are constructed in three horizontal sections (left, middle, and right), with the base slab and web slab constructed separately, and the concrete for the base slab and web slab is poured. Step 22: The third and fourth spans of 3 / 4 are constructed in three horizontal sections (left, center, and right), with the top slab being poured in sections. Step 23: 14 days after the three sections are poured, pour the concrete for the post-pouring strip between the three sections. The post-pouring strip uses micro-expansion or non-shrinkage concrete, and the formwork for the post-pouring strip uses a quick-closing formwork. Step 24: Prestressing tensioning and grouting of the second beam section; Step 25: Tensioning and grouting of the entire prestressed steel strands along the bridge; Step 26: End sealing of beams and sealing of manholes; removal of supports for the third and fourth spans and the remaining supports for the first and second spans.

[0006] Furthermore, step 14 specifically includes: when the concrete strength of the post-cast strip reaches 90% of the design strength and the elastic modulus is over 100%, the prestressed steel strand tensioning and grouting operation can begin. The tensioning sequence is as follows: first, tension the transverse prestressed tendons of the 0# end crossbeam and the 1# and 2# middle crossbeams, starting with the upper tendons and then the lower tendons. Next, tension the longitudinal tendons of the web, starting from the middle and moving outwards, with symmetrical skip tensioning. Finally, tension the short prestressed steel strands of the top slab toothed blocks of the first and second spans, with the tensioning sequence being symmetrical tensioning from both sides towards the middle. All prestressed steel strand tensioning was carried out using a two-end tensioning method.

[0007] Furthermore, step 24 specifically includes: When the concrete strength of the post-cast strip reaches 90% of the design strength and the elastic modulus is over 100%, the prestressed steel strand tensioning and grouting operation can begin. The tensioning sequence is as follows: first tension the transverse prestressed tendons of the No. 4 end crossbeam and the No. 3 middle crossbeam, then tension the upper tendons first, followed by the lower tendons, using a two-end tensioning method. Next, the longitudinal web tendons are tensioned, starting from the middle and moving outwards in a symmetrical, skip-tenting manner; the tensioning operation is carried out using a single-end tensioning method. Finally, the short prestressed steel strand bundles of the top plate teeth blocks in the third and fourth spans are tensioned, with the tensioning sequence being symmetrical tensioning from both sides towards the middle.

[0008] Furthermore, in step S13, the post-cast strip uses micro-expansion or non-shrinkage concrete, and the post-cast strip formwork uses a quick-closing formwork.

[0009] Furthermore, in step S23, the post-pouring strip uses micro-expansion or non-shrinkage concrete, and the post-pouring strip formwork uses a quick-closing formwork.

[0010] The beneficial effects of this invention are: 1. This construction method innovates the conventional construction steps by adopting a segmented and sectioned pouring method and introducing the post-pouring strip construction technology, which shortens the pouring time of each concrete pouring, reduces the probability of construction cracks caused by structural instability due to temperature changes in the beam, and changes the cast-in-place beam construction from a continuous operation to a parallel operation, thereby improving the overall efficiency of beam construction.

[0011] 2. This construction method not only tracks, optimizes, improves, and summarizes the timeline of the concrete pouring sequence of the cast-in-place box girder, but also the spatial line of the girder's segmented construction on the on-site work surface, combined with scientific and reasonable process model tests.

[0012] 3. This construction method is based on the actual conditions of the project site. The construction methods adopted are conventional post-pouring strip construction technology, cast-in-place box girder concrete pouring construction method, and tension grouting construction technology. After summarization and refinement, it is easy for technicians and on-site construction personnel to understand, and can thoroughly understand each key action in the concrete construction process. Attached Figure Description

[0013] Figure 1 This is a schematic diagram showing the location of the longitudinal section lines during construction; Figure 2 This is a schematic diagram showing the location of the transverse section lines during construction; Figure 3 This is a schematic diagram of the horizontal post-cast strip division. Detailed Implementation

[0014] The present invention will be further described in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0015] This embodiment provides a construction method for cast-in-place box girder construction of an ultra-wide taxiway bridge. In this embodiment, the ultra-wide aircraft taxiway bridge consists of four spans: a 38.44m first span, a 45m second span, a 35m third span, and a 27.94m fourth span. It crosses a subway tunnel section, a high-speed rail tunnel section, and an airport access road. The superstructure is a variable-height, equal-width, fully prestressed concrete box girder structure, with a bridge width of 40m. The substructure uses ordinary reinforced concrete slab piers and pile foundations. The box girder adopts a single-box 16-cell box section, with a bottom width of 38m, a cantilever length of 1.0m on both sides of the flange plate, a beam height of 3.0~4.2m, and a main beam web thickness of 60cm and 45cm at mid-span, and 100cm, 120cm, and 80cm near the support, using a linear variation method. The main beam top plate thickness is 40cm, the bottom plate mid-span thickness is 45cm, and the bottom and top plates at the crossbeam positions of the middle crossbeam end are 80cm thick, using a linear transition method.

[0016] refer to Figure 1 As shown, in this embodiment, the concrete pouring of the box girder is considered to be divided into two longitudinal sections (the dividing line is at 1 / 4 of the third span). The first section is: the first span + the second span + 1 / 4 of the third span. The second section is: the remaining 3 / 4 of the third span + the fourth span.

[0017] refer to Figure 2 , Figure 3 As shown, two horizontal post-pouring strips (60cm wide) are set up for pouring construction in three sections: left, middle, and right.

[0018] The steps for pouring concrete for cast-in-place box girders are as follows.

[0019] ① (First span + second span + 1 / 4 of the third span) Three horizontal sections, left, middle and right, are constructed separately for the base slab and web slab, and the concrete for the base slab and web slab is poured.

[0020] ② (First span + second span + 1 / 4 of the third span) The top slab is constructed in three horizontal sections (left, middle and right), and the top slab concrete is poured in sections.

[0021] ③ Fourteen days after the completion of the three sections of concrete pouring, pour the concrete for the post-pouring strip between the three sections. The post-pouring strip uses concrete with the same strength as the beam and slight expansion or no shrinkage. The formwork for the post-pouring strip uses quick-closing formwork.

[0022] ④ Prestressed tensioning and grouting operation of the first section of the beam: When the concrete strength of the post-cast strip reaches 90% of the design strength and the elastic modulus is over 100%, the prestressed steel strand tensioning and grouting operation can begin.

[0023] The tensioning sequence is as follows: first tension the transverse prestressed tendons of the 0# end crossbeam and the 1# and 2# middle crossbeams, then tension the upper layer tendons first, followed by the lower layer tendons.

[0024] Next, tension the longitudinal bundles of the web plate, symmetrically jumping the bundles from the middle to both sides.

[0025] Finally, the short prestressed steel strands of the top plate toothed blocks in the first and second spans are tensioned, with the tensioning sequence being symmetrical tensioning from both sides towards the middle.

[0026] All prestressed steel strand tensioning was carried out using a two-end tensioning method.

[0027] ⑤ Remove the mid-span supports of the first and second spans to open the road to traffic. However, the supports at the piers and within a certain range in front of and behind the piers must not be removed.

[0028] ① (3 / 4 of the third span + fourth span) The bottom slab and web are constructed in three sections: left, middle and right. The concrete for the bottom slab and web is poured.

[0029] ② (3 / 4 of the third span + fourth span) The top slab is constructed in three sections: left, middle and right, and the top slab concrete is poured.

[0030] ③ Fourteen days after the completion of the three sections of concrete pouring, pour the concrete for the post-pouring strip between the three sections. The post-pouring strip uses concrete with the same strength as the beam and slight expansion or no shrinkage. The formwork for the post-pouring strip uses quick-closing formwork.

[0031] ④ Prestressed tensioning and grouting operation of the second beam section: When the concrete strength of the post-cast strip reaches 90% of the design strength and the elastic modulus is above 100%, the prestressed steel strand tensioning and grouting operation can begin.

[0032] The tensioning sequence begins with tensioning the transverse prestressed tendons of the No. 4 end crossbeam and the No. 3 middle crossbeam, starting with the upper tendons and then moving to the lower tendons, using a two-end tensioning method.

[0033] Next, the longitudinal web tendons are tensioned, starting from the middle and moving outwards symmetrically. A single-end tensioning method is used for the tensioning operation.

[0034] Finally, the short prestressed steel strand bundles of the top plate teeth blocks in the third and fourth spans are tensioned, with the tensioning sequence being symmetrical tensioning from both sides towards the middle.

[0035] ⑤ Tensioning and grouting of the entire prestressed steel strands of the bridge.

[0036] ⑥ Seal the beam ends and manholes, and remove the supports for the third and fourth spans, as well as the remaining supports for the first and second spans.

[0037] In this embodiment, a construction method of longitudinally segmenting and transversely utilizing post-cast strips for segmented casting is adopted, which solves the problems of high construction difficulty, high safety risk, and complex traffic flow in the cast-in-place box girder construction of ultra-wide aircraft taxiway bridges.

Claims

1. A construction method for cast-in-place box girder pouring of an ultra-wide skid bridge, characterized in that, The four longitudinal spans are divided into two sections, with the third span at 1 / 4 of its length serving as the dividing line. Two post-pouring strips are set laterally, and the pouring is carried out in three sections: left, middle, and right. The specific construction method is as follows: Step 1: Construct the first longitudinal beam segment, specifically including: Step 11: Construct the base slab and web slab in three sections: the first span, the second span, and 1 / 4 of the third span, on the left, middle, and right. Pour the concrete for the base slab and web slab. Step 12: Construct the top slab in three sections (left, middle, and right) from the first span, the second span, and 1 / 4 of the third span, and pour the top slab concrete. Step 13: 14 days after the three sections are poured, pour the concrete for the post-pouring strip between the three sections; Step 14: Prestressing tensioning and grouting of the first beam segment; Step 15: Remove the mid-span supports of the first and second spans and open the road to traffic, but the supports at the piers and within a certain range in front of and behind the piers must not be removed; Step 2: Construct the second longitudinal beam segment, specifically including: Step 21: The third and fourth spans of 3 / 4 are constructed in three horizontal sections (left, middle, and right), with the base slab and web slab constructed separately, and the concrete for the base slab and web slab is poured. Step 22: For the third and fourth spans of 3 / 4, construct the top slab in three sections (left, center, and right) and pour the top slab concrete. Step 23: 14 days after the three sections are poured, pour the concrete for the post-pouring strip between the three sections. The post-pouring strip uses micro-expansion or non-shrinkage concrete, and the formwork for the post-pouring strip uses a quick-closing formwork. Step 24: Prestressing tensioning and grouting of the second beam section; Step 25: Tensioning and grouting of the entire prestressed steel strands along the bridge; Step 26: End sealing of beams and sealing of manholes; removal of supports for the third and fourth spans and the remaining supports for the first and second spans.

2. The construction method for cast-in-place box girder construction of ultra-wide skid bridges according to claim 1, characterized in that, Step 14 specifically includes: when the concrete strength of the post-cast strip reaches 90% of the design strength and the elastic modulus is over 100%, the prestressed steel strand tensioning and grouting operation can begin. The tensioning sequence is as follows: first, tension the transverse prestressed tendons of the 0# end crossbeam and the 1# and 2# middle crossbeams, starting with the upper tendons and then the lower tendons. Next, tension the longitudinal tendons of the web, starting from the middle and moving outwards, with symmetrical skip tensioning. Finally, tension the short prestressed steel strands of the top slab toothed blocks of the first and second spans, with the tensioning sequence being symmetrical tensioning from both sides towards the middle. All prestressed steel strand tensioning was carried out using a two-end tensioning method.

3. The construction method for cast-in-place box girder construction of ultra-wide skid bridges according to claim 1, characterized in that, Step 24 specifically includes: When the concrete strength of the post-cast strip reaches 90% of the design strength and the elastic modulus is over 100%, the prestressed steel strand tensioning and grouting operation can begin. The tensioning sequence is as follows: first tension the transverse prestressed tendons of the No. 4 end crossbeam and the No. 3 middle crossbeam, then tension the upper tendons first, followed by the lower tendons, using a two-end tensioning method. Next, the longitudinal web tendons are tensioned, starting from the middle and moving outwards in a symmetrical, skip-tenting manner; the tensioning operation is carried out using a single-end tensioning method. Finally, the short prestressed steel strand bundles of the top plate teeth blocks in the third and fourth spans are tensioned, with the tensioning sequence being symmetrical tensioning from both sides towards the middle.

4. The construction method for cast-in-place box girder construction of ultra-wide skid bridges according to claim 1, characterized in that, In step S13, the post-pouring strip uses micro-expansion or non-shrinkage concrete, and the post-pouring strip formwork uses a quick-closing formwork.

5. The construction method for cast-in-place box girder construction of ultra-wide skid bridges according to claim 1, characterized in that, In step S23, the post-pouring strip uses micro-expansion or non-shrinkage concrete, and the post-pouring strip formwork uses a quick-closing formwork.

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