A curved arm grating type lap joint structure

Abstract

The present application belongs to the field of bridge structure, and provides a curved arm grating type deck structure, which comprises steel bars implanted in a bridge deck slab, a concrete curved arm deck, a transverse diaphragm beam under the deck, and a ground beam at the rear end of the deck. The bridge will shrink under the effect of temperature change, and placing a deck that can provide deformation between the bridge and the road surface can form a seamless bridge. The deformation of the bridge can cause the curved arm grating type deck to deform through the steel bars implanted in the deck slab at the front end of the deck, and the transverse diaphragm beam under the deck can reduce the contact between the foundation and the deck, providing good deck sliding effect, and the ground beam at the rear end of the deck plays the role of anchoring the foundation. The use of high ductility concrete to make the curved arm grating type deck can ensure that the deck does not easily break when stretched and deformed, and the service life is improved. The present application uses a deck in the form of a curved arm, which uses component deformation to absorb bridge deformation, so as to eliminate the easily damaged expansion joint, and can save the construction cost of the bridge throughout its life.

Description

Technical Field

[0001] This invention belongs to the field of bridge structure and relates to a curved arm grid-type approach slab structure, which is a curved arm grid-type approach slab structure particularly suitable for seamless bridges. Background Technology

[0002] Bridges typically require expansion joints to accommodate temperature deformation. However, these joints are the weakest points in the structure, making them highly susceptible to damage from concentrated structural deformation, external environmental erosion, and repeated impacts from vehicle loads. Regular replacement and maintenance of these expansion joints throughout the structure's service life is necessary, impacting traffic safety. Therefore, for small- and medium-span bridges, eliminating expansion joints using specialized seamless technology is undoubtedly of great significance.

[0003] Seamless bridge structures evolved from traditional continuous bridge decks. They retain traditional abutments and bearings, but eliminate the expansion joints. The reinforced concrete pavement and deck panels are made continuous and seamless, extending to the road surface at both ends of the bridge. A planar approach slab typically connects the bridge to the road surface (a "seamless bridge"). The approach slab helps to overcome the approach slab problem caused by settlement of the backfill behind the abutments, and the deformation caused by temperature is also mainly transferred or absorbed by the approach slab.

[0004] Transfer-type approach slabs themselves do not provide significant deformation and can be connected to either rigid or flexible pavement. When a transfer-type approach slab is connected to a rigid pavement, a road joint capable of accommodating repeated expansion and contraction is required between them to absorb the temperature deformation transferred by the approach slab. This road joint is also relatively susceptible to damage during its service life and requires regular replacement and maintenance. When a transfer-type approach slab is connected to a flexible pavement, the temperature deformation transferred by the approach slab can be absorbed by the flexible pavement; therefore, the length of the flexible pavement is usually longer.

[0005] Absorbing approach slabs typically use flat slabs with a thinner profile than the bridge deck deck. The slab surface has a certain slope or pre-sawed joints, and a sliding layer is installed at the bottom. When the bridge experiences temperature deformation, the reinforced concrete approach slab absorbs the deformation by generating multiple micro-cracks within itself. However, to control the width and density of individual cracks, the length of the absorbing approach slab is relatively large.

[0006] The aforementioned traditional seamless bridges face significant challenges in cold regions with large annual temperature variations, or in environments exposed to de-icing salt and marine corrosion. The construction length and cost of flexible pavements or approach slabs increase dramatically, making them difficult to apply in practical engineering. Therefore, there is an urgent need to develop a new type of absorbent approach slab that is shorter, has greater deformation capacity, is more economical, and exhibits superior durability, along with corresponding construction methods. Summary of the Invention

[0007] To address the aforementioned technical requirements, this invention provides a concrete curved arm grid-type approach slab structure. It comprises reinforcing bars embedded within the bridge deck, a concrete curved arm approach slab, a transverse diaphragm beam beneath the approach slab, and a ground beam at the rear end of the approach slab. The reinforcing bars embedded within the bridge deck must retain sufficient length to ensure adequate connection strength between the bridge deck and the approach slab, allowing bridge temperature deformation to be transferred to the approach slab through the embedded reinforcing bars.

[0008] The technical solution of the present invention is as follows:

[0009] A curved arm grid-type approach slab structure includes an approach slab body, a transverse diaphragm beam system, and connecting reinforcement bars. The approach slab body is composed of multiple curved arm-shaped reinforced concrete members arranged transversely. Each curved arm is transversely connected only at the front and rear ends of the approach slab, and the middle area is not transversely connected. The transverse diaphragm beam system consists of multiple longitudinally discontinuous concrete pad beams. The connecting reinforcement bars are reinforcement bars that pass through both ends of the approach slab body. The approach slab body rests on the transverse diaphragm beam system or directly on the foundation.

[0010] A further feature is that the curved arm shape of the approach slab body includes a broken line and an arc, which is directly connected to the bridge deck or connected through a bridge abutment.

[0011] Further features include: the connecting steel bars at the front end of the approach slab are placed on the abutment and extend into the bridge deck; the connecting steel bars at the rear end of the approach slab are integrally cast with the ground beam; the ground beam is embedded in the backfill foundation, and its rear end connects to the connecting roadbed. The ground beam is responsible for fixing to the rear end of the approach slab and embedding itself in the foundation, thus terminating deformation transfer there. To reduce the impact on the soil foundation at the front end of the ground beam, multiple ground beams can be arranged and connected at the rear end. The ground beam can be constructed using common reinforced concrete components. The ground beam is simply connected to the connecting road surface.

[0012] A further feature is that the gap between the articulated arm and the approach plate is controlled to be less than the width of the vehicle tires, ensuring that any vehicle load can be stably applied to the articulated arm. The articulated arm approach plate can be flush with the bridge deck, and the tensile stiffness of the body can be flexibly controlled by adjusting the gap between the articulated arms to adapt to the temperature deformation requirements of different bridges. When the bridge cools and deforms, the articulated arm will be pulled straight to absorb the deformation. To ensure good deformation capacity, high-ductility concrete and steel reinforcement are used to construct the articulated arm.

[0013] The longitudinally arranged transverse diaphragm beams on the underside of the curved arm grid-type approach slab structure reduce the contact area between the foundation and the curved arm approach slab, facilitating longitudinal sliding of the slab. The transverse diaphragm beams and the curved arm approach slab interweave to form a grid system, providing structural stiffness in both the transverse and longitudinal directions. The transverse diaphragm beams can be made of commonly used reinforced concrete components and appropriately embedded in the foundation.

[0014] The curved arm grid-type approach slab structure and the foundation can be filled with a low elastic modulus material as a sliding layer, or no sliding layer can be added; if the foundation is reinforced, the settlement and deformation of the soil behind the abutment can be reduced, and the transverse diaphragm beam system can be eliminated.

[0015] The present invention also provides a construction method for a curved arm grid-type slab structure, comprising the following steps:

[0016] S1. First, the roadbed is pretreated, the backfill pit is excavated, and the backfill is reinforced.

[0017] S2. Next, tie the steel reinforcement cage of the transverse diaphragm beam system, install the formwork, pour concrete, and cure it to more than 75% of the design strength to form a support system;

[0018] S3. Next, filler material is laid on the top of the transverse diaphragm pad beam system and the surface of the backfill foundation. Then, the formwork for the approach slab, bridge deck and ground beam is erected, and the steel bars are tied before pouring; or the approach slab body is directly prefabricated, or the bridge deck is directly prefabricated, but it must be ensured that the front end is connected to the bridge deck and the rear end is anchored into the ground beam.

[0019] S4. Finally, the connecting road construction is carried out. The connecting roadbed is filled behind the ground beam, and the roadbed surface is constructed.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] In this invention, the curved arm approach slab is connected to the bridge deck near the abutment, and to the ground beam and connecting road surface at the far end. When the bridge undergoes axial deformation due to temperature changes, the concrete curved arm approach slab provides stronger longitudinal deformation capacity primarily through the deformation of its zigzag curve. Simultaneously, it forms a grid system with the lower transverse diaphragm beams, ensuring sufficient bending and shear stiffness in both the longitudinal and transverse directions. By optimizing the zigzag curve shape of the curved arm, the deformation capacity of the approach slab in the tensile and compressive directions can be enhanced, significantly reducing the longitudinal length of the approach slab and saving construction costs. The transverse diaphragm beams on the lower side of the approach slab only provide support and a moderate amount of friction for the curved arm approach slab, facilitating longitudinal sliding of the approach slab and reducing the impact of subgrade deformation behind the abutment. The ground beam at the rear end of the approach slab terminates the impact of bridge temperature deformation and reduces the influence on the subgrade behind the abutment. Attached Figure Description

[0022] Figure 1 This is a three-dimensional schematic diagram of the present invention.

[0023] Figure 2 This is a top view of the present invention.

[0024] In the diagram: 1. Approach slab body; 2. Transverse diaphragm beam system; 3. Connecting reinforcement; 4. Bridge main beam; 5. Bridge deck;

[0025] 6. Bridge abutment; 7. Filled soil foundation; 8. Ground beam; 9. Connection roadbed. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the technical solutions and accompanying drawings.

[0027] Example 1: A curved arm grid-type ramp structure

[0028] The approach slab body 1 is composed of multiple laterally arranged curved arms. Each curved arm is laterally connected only at the front and rear ends of the approach slab, with no lateral connection in the middle area. The gap between the curved arms is controlled to be less than the width of a vehicle tire, ensuring that any vehicle load can be stably applied to the curved arms. The approach slab body 1 is flush with the bridge deck 5. By adjusting the gap between the curved arms, the tensile stiffness of the approach slab can be flexibly controlled—a smaller gap results in greater tensile stiffness, and vice versa, to adapt to the temperature deformation requirements of different bridges.

[0029] The transverse diaphragm beam system 2 consists of multiple longitudinally arranged reinforced concrete beams, each with a cross-sectional dimension of 30cm × 40cm (width × height). Adjacent beams are spaced 1.5m apart and are embedded 38cm deep into the backfill foundation 7, forming stable support. The transverse diaphragm beam system 2 and the curved arms of the approach slab body 1 are staggered, forming a grid-like system—the transverse diaphragm beams provide lateral support stiffness, while the curved arms transfer loads longitudinally, jointly ensuring the bending and shear resistance of the approach slab structure. Simultaneously, a 2cm thick low-elasticity modulus sliding layer (selected in this embodiment) is laid between the approach slab body 1 and the backfill foundation 7 to further reduce the frictional resistance during longitudinal sliding of the approach slab.

[0030] The connecting steel bar 3 is made of HRB400 grade threaded steel with a diameter of 25mm. Its front end is embedded in the bridge deck 5 with a length of not less than 80cm, and its rear end is bent into the ground beam 8 to ensure the connection strength between the bridge deck 5, the approach plate body 1 and the ground beam 8, and to realize the effective transfer of bridge temperature deformation.

[0031] The ground beam 8 is a reinforced concrete component with a cross-sectional dimension of 60cm × 80cm (width × height), and is embedded to a depth of 65cm into the backfill foundation 7. The ground beam 8 is connected to the roadbed 9 in a stepped manner, and a geogrid is laid at the connection point to enhance the integrity of the roadbed.

[0032] Example 2: A construction method for a concrete curved-arm grid-type approach slab structure suitable for seamless bridges

[0033] Step 1: First, pre-treat the roadbed 9 and reinforce the backfill foundation 7 behind the bridge abutment 6. Then, excavate the foundation pit of the ground beam and the foundation pit of the transverse diaphragm pad beam. Lay a graded sand and gravel cushion layer on the bottom of the foundation pit and compact it.

[0034] Step 2: Next, tie the steel reinforcement cage of the transverse diaphragm beam system 2, install the formwork, pour concrete, and cure it to more than 75% of the design strength to form a support system;

[0035] Step 3: Next, lay filler material on the surface of the diaphragm pad beam system 2 and the backfill foundation 7. Then, install the template according to the design dimensions of the approach slab body 1, bridge deck 5 and ground beam 8, tie the reinforcing bars 3, and then pour concrete. Vibration is required during the pouring process. After compaction, water is sprinkled for curing. Alternatively, the prefabricated approach slab body 1 can be placed directly on top of the diaphragm pad beam system 2, with a certain length of reinforcing bars exposed at the front end for connection with the bridge deck, and a certain length of reinforcing bars bent at the rear end for anchoring into the ground beam. The bridge deck and ground beam are then cast in place. Alternatively, a certain length of reinforcing bars can be extended from the prefabricated bridge deck 5 and ground beam 8 and connected to the cast-in-place approach slab body 1.

[0036] Step 4: Finally, construct the connecting road. Fill the connecting roadbed 9 behind the ground beam 8, level the roadbed, use graded crushed stone as fill material, fill and compact in layers, and lay geogrid at the joint.

Claims

1. A curved arm grid-type ramp structure, characterized in that, The structure includes a slab body (1), a transverse diaphragm beam system (2), and connecting steel bars (3). The slab body (1) is composed of multiple curved arm type reinforced concrete members arranged laterally. Each curved arm is only laterally connected at the front and rear ends of the slab, and the middle area is not connected laterally. The transverse diaphragm beam system (2) consists of multiple longitudinally discontinuous concrete pad beams. The connecting steel bars (3) are steel bars that pass through both ends of the slab body (1). The slab body (1) sits on the transverse diaphragm beam system (2) or sits directly on the foundation (7). The gap between the curved arms of the slab body (1) is controlled within a range smaller than the width of the vehicle tires to ensure that any vehicle load can be stably applied to the curved arms. The tensile stiffness of the body (1) can be flexibly controlled by adjusting the size of the gap between the curved arms to adapt to the temperature deformation requirements of different bridges.

2. The curved arm grid-type ramp structure as described in claim 1, characterized in that, The curved arm shape of the aforementioned ramp body (1) includes a broken line and an arc.

3. The curved arm grid-type ramp structure as described in claim 1, characterized in that, The aforementioned approach plate body (1) is directly connected to the bridge deck (5) or connected through the bridge abutment (6).

4. A curved arm grid-type ramp structure as described in any one of claims 1-3, characterized in that, The connecting steel bar (3) at the front end of the approach slab body (1) is placed on the bridge abutment (6) and extends into the bridge deck; the connecting steel bar (3) at the rear end of the approach slab body (1) is cast integrally with the ground beam (8); the ground beam (8) is embedded in the backfill foundation (7), and the rear of the ground beam (8) is connected to the connecting roadbed (9).

5. The construction method of the curved arm grid-type ramp structure according to any one of claims 1-4, characterized in that... Includes the following steps: S1. First, the roadbed is pretreated, the backfill pit is excavated, and the backfill is reinforced. S2. Next, tie the steel reinforcement cage of the transverse diaphragm beam system, install the formwork, pour concrete, and cure it to more than 75% of the design strength to form a support system; S3. Next, filler material is laid on the top of the transverse diaphragm pad beam system and the surface of the backfill foundation. Then, the formwork for the approach slab, bridge deck and ground beam is erected, and the steel bars are tied before pouring; or the approach slab body is directly prefabricated, or the bridge deck is directly prefabricated, but it must be ensured that the front end is connected to the bridge deck and the rear end is anchored into the ground beam. S4. Finally, the connecting road construction is carried out. The connecting roadbed is filled behind the ground beam, and the roadbed surface is constructed.

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