An assembled portal frame bridge and a construction method thereof

Abstract

The application discloses an assembled portal frame bridge and a construction method thereof, and belongs to the field of bridge engineering. The bridge comprises a lower structure, integrally prefabricated U-shaped upper prefabricated structure units and rigid connecting nodes connecting the two. The nodes are formed by pouring UHPC in the bending moment reverse bending point area of the upper prefabricated structure units and wrapping the connecting steel bars matched with each other at the connecting interface, so that the rigid connection of the upper and lower structures is realized. During construction, the connecting interfaces of the upper and lower structures are respectively prefabricated and treated, the upper units are hoisted to align the connecting steel bars, and then self-compacting UHPC is poured in the reserved gap to form the nodes. The application combines the factory prefabrication of complex nodes with high-performance site connection, retains the overall stress advantages of the portal frame bridge, avoids a large number of formwork on site, significantly improves the construction efficiency and quality, reduces the cost and environmental interference, and is especially suitable for areas with limited construction conditions such as soft soil and river channels.

Description

Technical Field

[0001] This invention belongs to the field of bridge engineering technology, specifically relating to a prefabricated portal rigid frame bridge and its construction method. Background Technology

[0002] Portal frame bridges, as a type of bridge that eliminates the rigid connection between traditional supports, main beams, and abutments, offer advantages such as good structural integrity, high load-bearing capacity, and low maintenance requirements. They are particularly suitable for soft soil foundations with high abutment horizontal thrust and river environments where supports are susceptible to water erosion. However, this type of bridge has traditionally been constructed using a full-span scaffolding and cast-in-place method. This method not only requires the erection of numerous temporary supports on-site, leading to difficulties in controlling foundation settlement and significant impacts on river flood control, but also results in inherent drawbacks such as long construction periods, high costs for mitigation measures, and difficulty in precisely controlling the quality of on-site casting.

[0003] To overcome the drawbacks of cast-in-place construction, prefabrication and assembly technology has become an important development direction in bridge construction. However, conventional prefabricated bridges typically use bearings to support the superstructure and substructure, rather than rigidly connecting them, thus failing to form the integrated load-bearing system unique to portal frame structures. If portal frame bridges are simply disassembled into independent prefabricated components such as beams and columns and then connected on-site, the reliability of connections at key nodes and the overall load-bearing performance often fail to meet the standards of the original cast-in-place structure. This poses technical risks such as the connection points becoming weak points and insufficient overall structural stiffness.

[0004] Therefore, how to achieve efficient and high-quality industrialized construction of portal frame bridges while preserving their excellent load-bearing performance is a technical problem that urgently needs to be solved in the field of bridge engineering. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a prefabricated portal frame bridge and its construction method, solving the technical challenge of ensuring the connection reliability of key nodes and the overall structural stress performance of the portal frame bridge to meet the standards of cast-in-place construction while achieving prefabricated assembly construction.

[0006] The objective of this invention can be achieved through the following technical solution: a prefabricated portal frame bridge, comprising a substructure, a prefabricated superstructure unit, and a rigid connection node connecting the two; wherein, the prefabricated superstructure unit is an integral U-shaped reinforced concrete component cast in one piece; the rigid connection node is formed by casting UHPC at the moment inflection point region of the prefabricated superstructure unit between the corresponding connection interface of the substructure and the prefabricated superstructure unit; and, the connection interface is provided with mutually cooperating connecting steel bars, and the rigid connection node connects the prefabricated superstructure unit and the substructure into an integral portal frame by wrapping and holding the connecting steel bars.

[0007] As a preferred embodiment of the present invention, the substructure includes pile foundations, abutments, and abutments; the precast upper structure unit includes a horizontal main beam, an upper abutment extending downward from both ends of the main beam, and a bridge deck portion located above the main beam; the rigid connection node is a UHPC connection structure, which fills the reserved gap between the top surface of the lower abutment and the bottom of the upper abutment.

[0008] As a preferred embodiment of the present invention, in the areas corresponding to the reserved gap, on the top surface of the lower bridge abutment and the bottom end of the upper bridge abutment, the connecting steel bars extending into the gap are respectively embedded, and the connecting steel bars are staggered and overlapped with each other or connected by sleeve connectors within the gap.

[0009] As a preferred embodiment of the present invention, the top surface of the lower bridge abutment and the bottom end of the upper bridge abutment, within the corresponding area of ​​the reserved gap, both have rough joint surfaces with shear keys; the depth of the shear keys is 30-50mm, the spacing is 200-300mm, and the average texture depth of the rough joint surface is not less than 3mm.

[0010] As a preferred embodiment of the present invention, the cross-section of the shear key is trapezoidal or rectangular, and its protrusion direction is perpendicular to the expected force direction of the UHPC connection structure.

[0011] As a preferred technical solution of the present invention, the upper prefabricated structural unit is prefabricated with concrete of strength grade not lower than C50, and the manufacturing deviation of the key structural dimensions at the corner of the main beam and the upper bridge abutment is controlled within ±5mm, and the planar positioning deviation of the connecting steel bars pre-embedded at the bottom of the upper bridge abutment is controlled within ±3mm.

[0012] As a preferred technical solution of the present invention, the bridge deck portion of the upper prefabricated structural unit is integrally formed into a complete bridge deck in the transverse direction, or a post-cast strip groove is reserved in the transverse direction, and concrete is later poured into the post-cast strip groove to form the bridge deck post-cast strip.

[0013] As a preferred embodiment of the present invention, the full width of the bridge deck of the portal rigid frame bridge is assembled from at least two prefabricated superstructure units arranged side by side along the transverse direction of the bridge, and the longitudinal joints between adjacent units are connected by the bridge deck portion or the post-cast strip of the bridge deck.

[0014] A construction method comprising the following steps: Step S1: Construct the substructure, and pre-embed connecting steel bars at its connection interface and perform interface treatment; Step S2: In the prefabrication yard, the upper prefabricated structural unit is prefabricated as a whole, and connecting steel bars are pre-embedded at its connection interface and interface treatment is performed; Step S3: Transport the upper prefabricated structural unit to the bridge site and hoist it as a whole, so that the connecting steel bars at the connection interface are aligned with the connecting steel bars of the lower structure. Step S4: In the reserved gap between the connection interfaces and in the region of the bending moment inflection point of the upper precast structural unit, pour UHPC with self-compacting properties, and cure to form the rigid connection node that wraps around and holds the connecting steel bars. Step S5: When there is a bridge deck post-cast strip, pour the concrete for the bridge deck post-cast strip to complete the entire bridge deck system.

[0015] As a preferred embodiment of the present invention, in step S4, the 28-day compressive strength of the UHPC is not less than 150 MPa; after casting, the rigid connection node is subjected to non-destructive testing. In step S3, a balance beam lifting device specially designed based on the center of gravity and lifting point of the upper prefabricated structure unit is used for hoisting. The installation accuracy is controlled by a real-time measurement and positioning system to ensure that the planar position deviation of the upper prefabricated structure unit after it is in place is no more than 10mm and the elevation deviation is no more than 5mm.

[0016] The beneficial effects of this invention are as follows: By prefabricating the main beam, abutment, and bridge deck into U-shaped units, and setting rigid nodes with UHPC-wrapped connecting steel bars in the inflection point region, several significant benefits are achieved: First, the U-shaped prefabrication greatly reduces on-site high-altitude wet operations and formwork work, realizing the factory-based and standardized production of key components, making quality easier to control, and significantly improving construction efficiency; Second, setting UHPC rigid nodes in the inflection point region cleverly utilizes the stress characteristics of small bending moments in this area, greatly reducing the concentration of internal forces at the nodes. This design maximizes the effect of local reinforcement using UHPC, a high-performance material, ensuring connection reliability and structural integrity, with load-bearing performance comparable to cast-in-place structures. Thirdly, this construction connects the heaviest abutment to the substructure on-site, effectively reducing the lifting weight of prefabricated units, decreasing reliance on large lifting equipment, and broadening its applicability. Fourthly, the ultra-high strength, high durability, and self-compacting properties of UHPC material, combined with pre-designed shear keys and rough surfaces at the interface, jointly ensure the durability and fatigue resistance of the joints under long-term use and harsh environments. In summary, this invention retains the core advantages of traditional portal frame bridges, such as being unsupported, having good integrity, and adapting to soft soil foundations, while successfully achieving rapid, economical, and high-quality prefabricated construction, resulting in significant social and economic benefits. Attached Figure Description

[0017] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0018] Figure 1This is a structural schematic diagram of a prefabricated portal rigid frame bridge according to the present invention.

[0019] Figure 2 This is another structural schematic diagram of a prefabricated portal rigid frame bridge according to the present invention.

[0020] Explanation of main component symbols In the diagram: 100, substructure; 101, pile foundation; 102, pile cap; 103, sub-abutment; 200, superstructure precast unit; 201, main beam; 202, super-abutment; 203, bridge deck post-cast strip; 300, UHPC connection structure. Detailed Implementation

[0021] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0022] Please see Figure 1 and Figure 2 This invention provides a prefabricated portal frame bridge and its construction method. This bridge design aims to solve the problems of low efficiency and high cost in traditional cast-in-place portal frame bridge construction, as well as the difficulty of achieving equivalent overall load-bearing performance to cast-in-place structures using conventional prefabricated techniques, through innovative structural design and construction processes.

[0023] The core of this prefabricated portal rigid frame bridge lies in the coordinated design of its three main components. The bridge as a whole consists of a substructure 100, a prefabricated superstructure unit 200, and rigid connection nodes connecting the two.

[0024] First, the substructure 100 is a cast-in-place portion, typically designed according to geological conditions, and includes pile foundations 101 extending into the soil, a pile cap 102 connecting the pile foundations 101, and a lower abutment 103 situated on the pile cap 102. The top of the lower abutment 103 is the key interface for subsequent connection with precast units.

[0025] Secondly, the precast superstructure unit 200 is one of the core precast components of the entire invention. This unit, manufactured in a prefabrication plant using high-precision steel molds, integrates the horizontal main beam 201, the superstructure abutments 202 extending downwards from both ends of the main beam 201, and the bridge deck above the main beam 201 into a single, inseparable, monolithic U-shaped reinforced concrete component through a single concrete pour. This monolithic prefabrication method ensures that the most complex and stress-critical joints between the main beam 201 and the abutments—traditionally cast-in-place—are completed to a high standard in the factory, greatly guaranteeing the integrity and mechanical properties of the component itself.

[0026] The key to connecting the upper and lower structures 100 is the rigid connection node, specifically the UHPC connection structure 300. This structure is not a pre-embedded part, but is formed during the on-site assembly stage. Its design concept is ingenious: the connection position is not arbitrarily selected, but precisely located in the inflection point region of the upper abutment 202 under operating loads, where the bending moment is close to zero, through structural calculation and analysis. Connecting in this region maximizes the stress on the node.

[0027] To achieve this connection, outward-extending connecting steel bars are pre-embedded on the top surface of the lower abutment 103 and the bottom end of the upper abutment 202 of the upper precast structural unit 200, corresponding to the inflection point area. When the upper precast structural unit 200 is hoisted into place, the outward-extending connecting steel bars of the upper and lower parts will intersect within a reserved gap. Specifically, these connecting steel bars can be designed to overlap in a staggered manner, or precise docking can be achieved using sleeve connectors.

[0028] Furthermore, to ensure that the new UHPC material and the old concrete interface can work together and share stress, the concrete surfaces of the lower abutment 103 and the upper abutment 202, within the corresponding areas of the reserved gap, require special interface treatment. The treated surfaces become rough bonding surfaces with an average texture depth of not less than 3 mm, and raised shear keys are regularly formed on these bonding surfaces. These shear keys are 30 to 50 mm deep, spaced 200 to 300 mm apart, and typically have trapezoidal or rectangular cross-sections. The direction of the protrusions is designed to be perpendicular to the expected main stress direction of the UHPC connection structure 300 to maximize shear resistance.

[0029] After completing the above preparations, self-compacting ultra-high performance concrete (UHPC) can be poured into the reserved gaps. The 28-day compressive strength of this UHPC should not be less than 150 MPa. During pouring, the self-compacting UHPC will fully fill every corner of the gaps, tightly wrap all intersecting or butt-jointed reinforcing bars, and achieve excellent bonding with the rough concrete interface with shear keys. After the UHPC has cured and hardened, a high-strength, high-durability UHPC connection structure 300 is formed. This structure, through wrapping and holding the reinforcing bars and mechanically interlocking with the concrete interface, firmly connects the upper precast structural unit 200 and the lower structure 100 into a whole load-bearing portal frame, with joint performance comparable to cast-in-place concrete.

[0030] For bridges with a large deck width, the entire width of the bridge deck of this invention can be assembled from at least two precast superstructure units 200 arranged side-by-side along the transverse direction. The deck portion of a single precast superstructure unit 200 can be integrally formed into a complete bridge deck in the transverse direction. Another preferred embodiment is to pre-reserve a groove for a post-cast strip in the transverse direction during prefabrication. After adjacent units are installed, concrete is poured into the groove to form a post-cast strip 203 on the bridge deck. The longitudinal joints between adjacent units are ultimately connected as a whole through their own deck portions or the post-cast strip 203, completing the entire bridge deck system.

[0031] Accordingly, the construction method for this prefabricated portal frame bridge, as a systematic process, specifically includes the following five core steps: Step S1: Construction and Connection Interface Preparation of Substructure 100. First, construct the pile foundation 101, pile cap 102, and substructure abutment 103 on-site according to the design. Crucially, before pouring the concrete for the substructure abutment 103, accurately embed and fix the exposed connecting steel bars at the calculated inflection point area on its top. After the concrete reaches a certain strength, perform specialized interface treatment on its top surface: using high-pressure water jetting, mechanical roughening, or other processes, create a rough bonding surface with an average texture depth of not less than 3 mm; simultaneously, through pre-embedded irregular templates or subsequent cutting, form regular shear keys with a depth of 30 to 50 mm and a spacing of 200 to 300 mm on this rough surface. The cross-section should preferably be trapezoidal or rectangular, with the protrusion direction perpendicular to the expected shear force direction.

[0032] Step S2: Factory prefabrication of the superstructure unit 200. In the prefabrication plant, the superstructure unit 200 is cast using integrated high-precision steel formwork. During the reinforcement cage binding, the connecting reinforcement bars must be fixed with a planar positioning accuracy of ±3mm at the corresponding position at the bottom of the superstructure abutment 202. Concrete with a strength grade of not less than C50 is used for casting, ensuring thorough compaction. After demolding and curing, the concrete surface at the bottom of the superstructure abutment 202 undergoes the same interface treatment as in Step S1, forming a rough bonding surface with shear keys. The entire prefabrication process requires strict quality control to ensure that the manufacturing deviation of key structural dimensions, such as the corners of the main beam 201 and the superstructure abutment 202, is controlled within ±5mm.

[0033] Step S3: Overall hoisting and high-precision alignment. The precast upper structure unit 200, having passed curing and reached transport strength, is transported to the bridge site. Before hoisting, a specialized balance beam hoisting device is designed and used based on the component's center of gravity and structural characteristics. During hoisting, real-time measurement and positioning systems such as total stations or GPS must be used for continuous dynamic monitoring and adjustment. The operation must be slow and smooth, ultimately ensuring that the bottom end of the upper abutment 202 of the upper precast structure unit 200 is precisely positioned on the top surface of the lower abutment 103, ensuring that the pre-embedded connecting steel bars achieve the pre-set staggered lap or sleeve connection within the reserved gap. The installation accuracy in this step is crucial; the planar position deviation must be no greater than 10mm, and the elevation deviation no greater than 5mm.

[0034] Step S4: Casting and Curing of UHPC Connection Nodes. After the hoisting and alignment are accepted, the connection interface is cleaned and moderately moistened. Then, ultra-high performance concrete (UHPC) with self-compacting properties is cast into the reserved gap. The 28-day compressive strength of the UHPC used should not be less than 150 MPa. Utilizing its excellent fluidity and filling properties, the gap is ensured to be completely and densely filled, especially around dense reinforcement and shear keys, thereby fully wrapping and binding the upper and lower connecting reinforcements into a single unit. Immediately after casting, it is covered and cured with water until the UHPC reaches its design strength, ultimately forming a high-strength, high-durability UHPC connection structure 300, completing the rigid connection of the upper and lower structures 100.

[0035] Step S5: Construction and System Closure of Post-cast Strip 203 on Bridge Deck. This step is performed if the bridge design uses post-cast strip 203 to connect multiple precast units or to the abutment slabs. Before construction, the concrete bonding surfaces on both sides of the post-cast strip groove are roughened, cleaned, and then the bridge deck reinforcement mesh is laid. Then, concrete with micro-expansion properties is poured, carefully vibrated, and thoroughly cured to eliminate shrinkage cracks and ensure effective bonding between the new and old concrete, ultimately forming a complete and continuous bridge deck system, marking the completion of the entire bridge construction.

[0036] Through the above-described specific implementation methods and systematic construction techniques, this invention transforms complex on-site casting operations into efficient factory prefabrication and precise on-site assembly operations. While ensuring the structural integrity and safety of the portal frame bridge, it achieves a significant improvement in construction quality, efficiency, and economic benefits.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A prefabricated portal rigid frame bridge, characterized in that: It includes a substructure, a precast upper structural unit, and a rigid connection node connecting the two; wherein, the precast upper structural unit is an integral U-shaped reinforced concrete component cast in one piece; the rigid connection node is formed by casting UHPC at the moment inflection point region of the precast upper structural unit between the corresponding connection interface of the substructure and the precast upper structural unit; and, the connection interface is provided with mutually cooperating connecting steel bars, and the rigid connection node connects the precast upper structural unit and the substructure into an integral portal frame by wrapping and holding the connecting steel bars.

2. The prefabricated portal rigid frame bridge according to claim 1, characterized in that: The substructure includes pile foundations, abutments, and lower bridge abutments; the upper precast structure unit includes a horizontal main beam, upper bridge abutments extending downwards integrally from both ends of the main beam, and a bridge deck portion located above the main beam; the rigid connection node is a UHPC connection structure, which fills the reserved gap between the top surface of the lower bridge abutment and the bottom end of the upper bridge abutment.

3. A prefabricated portal rigid frame bridge according to claim 2, characterized in that: On the top surface of the lower bridge abutment and at the bottom end of the upper bridge abutment, in the area corresponding to the reserved gap, the connecting steel bars extending into the gap are respectively embedded. The connecting steel bars are staggered and overlapped with each other in the gap or connected by sleeve connectors.

4. A prefabricated portal rigid frame bridge according to claim 3, characterized in that: The top surface of the lower bridge abutment and the bottom end of the upper bridge abutment, within the corresponding area of ​​the reserved gap, both have rough joint surfaces with shear keys; the depth of the shear keys is 30-50mm, the spacing is 200-300mm, and the average texture depth of the rough joint surface is not less than 3mm.

5. A prefabricated portal rigid frame bridge according to claim 4, characterized in that: The shear key has a trapezoidal or rectangular cross-section, and its protrusion direction is perpendicular to the expected force direction of the UHPC connection structure.

6. A prefabricated portal rigid frame bridge according to claim 1, characterized in that: The upper precast structural unit is made of concrete with a strength grade of not less than C50. The manufacturing deviation of the key structural dimensions at the corner of the main beam and the upper abutment is controlled within ±5mm, and the planar positioning deviation of the connecting steel bars embedded at the bottom of the upper abutment is controlled within ±3mm.

7. A prefabricated portal rigid frame bridge according to claim 2, characterized in that: The bridge deck portion of the superstructure unit is integrally formed into a complete bridge deck in the transverse direction, or a post-cast strip groove is reserved in the transverse direction, and concrete is later poured into the post-cast strip groove to form the bridge deck post-cast strip.

8. A prefabricated portal rigid frame bridge according to claim 1, characterized in that: The full width of the portal rigid frame bridge deck is assembled from at least two precast superstructure units arranged side by side along the transverse direction, and the longitudinal joints between adjacent units are connected by the bridge deck portion or the post-cast strip of the bridge deck.

9. A construction method applied to a prefabricated portal frame bridge as described in any one of claims 1-8, characterized in that, Includes the following steps: Step S1: Construct the substructure, and pre-embed connecting steel bars at its connection interface and perform interface treatment; Step S2: In the prefabrication yard, the upper prefabricated structural unit is prefabricated as a whole, and connecting steel bars are pre-embedded at its connection interface and interface treatment is performed; Step S3: Transport the upper prefabricated structural unit to the bridge site and hoist it as a whole, so that the connecting steel bars at the connection interface are aligned with the connecting steel bars of the lower structure. Step S4: In the reserved gap between the connection interfaces and in the region of the bending moment inflection point of the upper precast structural unit, pour UHPC with self-compacting properties, and cure to form the rigid connection node that wraps around and holds the connecting steel bars. Step S5: When there is a bridge deck post-cast strip, pour the concrete for the bridge deck post-cast strip to complete the entire bridge deck system.

10. A construction method according to claim 9, characterized in that: In step S4, the 28-day compressive strength of the UHPC is not less than 150 MPa; after casting, the rigid connection node is subjected to non-destructive testing. In step S3, a balance beam lifting device specially designed based on the center of gravity and lifting point of the upper prefabricated structure unit is used for hoisting. The installation accuracy is controlled by a real-time measurement and positioning system to ensure that the planar position deviation of the upper prefabricated structure unit after it is in place is no more than 10mm and the elevation deviation is no more than 5mm.

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