Construction method of prestressed concrete bridge deck pavement

Abstract

The application relates to a construction method of prestressed concrete bridge deck pavement and belongs to the technical field of highway bridges. The construction method comprises the following steps: first, installing a prestressed concrete main beam and making an anti-collision belt; second, applying prestressed load to the main beam; third, making a rabbet joint / wet joint and bridge deck pavement; fourth, curing the rabbet joint / wet joint and bridge deck pavement concrete; and fifth, unloading and forming prestress. When the prestressing of the bridge deck pavement concrete is carried out, the load applied to the main beam is scientifically and reasonably determined, the need of the bridge deck pavement concrete to produce deformation is met, and the prestress reserve is sufficient but not redundant.

Description

Technical Field

[0001] This invention relates to the field of highway bridge technology, and in particular to a construction method for prestressed concrete bridge deck paving. Background Technology

[0002] Bridges are an important component of highways.

[0003] Precast prestressed concrete bridges (including hollow slab bridges, box girder bridges, and T-shaped bridges) are a common and widely used type of highway bridge, characterized by their large span capacity, simple structure, clear stress distribution, low cost, convenient construction, factory production capability, and high efficiency. Therefore, they are widely used in various levels of highway and urban road bridges, and precast construction is the future trend. However, precast prestressed concrete bridges also present the most problems, with the easily damaged bridge deck pavement concrete (including tongue-and-groove joint concrete / wet joint concrete) being a major issue.

[0004] In the longitudinal direction of precast prestressed concrete bridges, the main beams (referring to hollow slab beams, box beams, or T-beams) are prestressed concrete, while the bridge deck pavement is non-prestressed concrete. These are components with significantly different performance characteristics. When two components with such different performance characteristics work together and generate large deformations, one of them will inevitably fail first. Prestressed concrete components can completely or partially offset the deformation caused by the load, possessing the ability to withstand large deformations without cracking. Non-prestressed concrete components do not possess this property. Moreover, the non-prestressed concrete bridge deck pavement is the weakest in load-bearing capacity compared to the prestressed concrete main beams. Therefore, the bridge deck pavement concrete fails first. Under repeated vehicle loads, the bridge deck pavement concrete breaks down, further weakening the bond between it and the main beam concrete. It gradually loses its function of distributing loads laterally, resulting in single-slab stress, creating safety hazards, and accelerating the damage to the main beams and bridge deck pavement. Generally, repairs are required every 3 to 5 years, and in severe cases, it can even lead to safety accidents.

[0005] Currently, some researchers have applied transverse or oblique prestressing to bridge deck pavement concrete. However, this is not prestressing in the traditional sense, and the mechanism of prestressing is different. The oblique prestressing can be decomposed into transverse and longitudinal prestressing. This longitudinal prestressing can offset the prestressing of the main beam, reducing the bridge's load-bearing capacity. Other inventions include "A Method for Prestressing Wet Joint Concrete and Bridge Deck Pavement Concrete in Prestressed Concrete Bridges" and "A Construction Method for Longitudinal Prestressed Concrete Bridge Deck Pavement." These inventions share the common goal of prestressing the large deformation components of the superstructure of precast prestressed concrete bridges as a whole, enabling them to undergo large deformations without damage, thus ensuring the bridge's quality and service life. However, when prestressing the bridge deck pavement concrete, these methods lack scientific calculations; they rely solely on experience to apply prestressing loads to the main beam, reducing the camber value to zero, before constructing the bridge deck pavement concrete. Once the concrete strength meets the requirements, the load is unloaded, thus creating prestress within the bridge deck pavement concrete. Studies have shown that the problems are as follows: First, the load applied to the main beam is too large, which is 4 to 5 times the weight of the main beam itself, or even more (far exceeding the design bearing capacity). This not only results in a large workload and high cost, but also poses a significant safety hazard. Second, according to the design load specified in the (JTG D60-2015) "General Specifications for Design of Highway Bridges and Culverts", the vertical deformation of the bridge deck pavement concrete will not be equal to the camber value of the main beam. In other words, the prestress applied to the bridge deck pavement concrete is excessive and unnecessary, and may even lead to concrete cracks, i.e., the concrete is in an inelastic state. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies in addressing the problem of easy damage to bridge deck pavement concrete, this invention provides a construction method for prestressed concrete bridge deck pavement. When prestressing the bridge deck pavement concrete, this invention scientifically and rationally determines the load applied to the main beam, which satisfies the need for deformation of the bridge deck pavement concrete and provides sufficient prestress reserves without being excessive.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A construction method for prestressed concrete bridge deck pavement includes the following steps:

[0009] The first step is to install the prestressed concrete main beams and construct crash barriers.

[0010] The relevant provisions of (JTG / T F50-2011) "Technical Specifications for Highway Bridge and Culvert Construction" shall be followed.

[0011] The second step is to apply prestressed loads to the main beam.

[0012] After the prestressed concrete main beams are installed, a suspended basket is placed under each main beam, and a uniformly distributed load is applied to the main beams using sandbags at a rate of p (kg / m).

[0013] The third step is to install tongue and groove joints / wet joints and bridge deck paving.

[0014] For prestressed concrete hollow slab bridges, tongue and groove joints are constructed first; for prestressed concrete box girder bridges and T-shaped bridges, wet joints are constructed first, followed by bridge deck paving; or tongue and groove joints / wet joints are constructed together with bridge deck paving.

[0015] The construction methods, techniques, and quality requirements for tongue-and-groove joints / wet joints and bridge deck pavement shall be implemented in accordance with the relevant provisions of (JTG / T F50-2011) "Technical Specifications for Highway Bridge and Culvert Construction".

[0016] The fourth step is the curing of tongue-and-groove joints / wet joints and bridge deck concrete.

[0017] The methods, techniques, and quality requirements for curing tongue-and-groove joints / wet joints and bridge deck pavement concrete shall be implemented in accordance with the relevant provisions of (JTG / TF50-2011) "Technical Specifications for Highway Bridge and Culvert Construction".

[0018] Step 5: Unloading and forming prestress.

[0019] When the strength of the tongue-and-groove joint / wet joint and the bridge deck pavement concrete reaches more than 80% of the design strength, the prestressed load applied to the main beam is removed.

[0020] During unloading, longitudinal unloading should be carried out in small batches, symmetrically, and slowly; transverse unloading of all main beams should be synchronized. Manual unloading is beneficial for controlling longitudinal small-batch, symmetrical, and slow unloading as well as transverse synchronous unloading.

[0021] During the unloading process, the camber value of the main beam gradually recovers, and the bridge deck pavement concrete gradually undergoes vertical deformation, forming longitudinal tensile stress inside the bridge deck pavement concrete; at the same time, the bridge deck pavement concrete becomes longer and narrower, forming transverse tensile stress on both sides of the bridge towards the bridge centerline; furthermore, prestressing with upward tension and downward compression is formed in the longitudinal direction of the tongue and groove joint concrete / wet joint concrete.

[0022] Prestressing of bridge deck concrete includes prestressing of tongue-and-groove joint concrete / wet joint concrete.

[0023] Furthermore, in the second step, the uniformly distributed load applied to the main beam is calculated according to the following formula (1):

[0024]

[0025] In equation (1): p——the uniformly distributed load applied to the main beam (called the prestressing load), kg / m;

[0026] k — load factor;

[0027] m — Self-weight of the main beam, kg;

[0028] l — Calculated span of the main beam, in meters.

[0029] Furthermore, the load factor is selected based on the traffic load level and the main beam span, and the range selected in this invention is 1.45 to 1.86. Specifically: a smaller value is used for moderate and light traffic, a medium value for heavy traffic, and a larger value for extremely heavy and extra-heavy traffic; a smaller value is used for the main beam span less than 16m; a medium value is used for the main beam span equal to 16m; and a larger value is used for the main beam span greater than 16m. The classification of moderate, light, heavy, extremely heavy, and extra-heavy traffic is based on the traffic load level classification in (JTG / T F20-2015) "Technical Specifications for Construction of Highway Pavement Base Layer". The smaller value range is 1.45 to 1.655, the medium value range is 1.55 to 1.75, and the larger value range is 1.655 to 1.86. The ability of the prestressed bridge deck pavement concrete and tongue-and-groove joint concrete / wet joint concrete to offset the deformation caused by vehicle loads is directly proportional to the load factor; understanding this relationship allows for accurate selection of the load factor.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. Compared with the prior art, the prestressed load applied to the main beam by the present invention is much smaller, but it can still meet the needs of deformation of the bridge deck pavement concrete and tongue-and-groove joint concrete / wet joint concrete. The prestress reserve is sufficient and not excessive. The bridge deck pavement concrete and tongue-and-groove joint concrete / wet joint concrete are always in an elastic state, and the prestress magnitude is within a reasonable range.

[0032] 2. Through extensive research, this invention has scientifically and rationally determined the prestressed load applied to the main beam, overcoming the drawbacks of existing technologies such as large workload, high cost, and significant safety hazards. Attached Figure Description

[0033] Figure 1 A cloud map showing the camber value after applying prestressed load;

[0034] Figure 2 This is a cloud map showing the camber value after prestressing.

[0035] Figure 3 This is a cloud map showing the camber value of the lane under prestressed load.

[0036] Figure 4 This is a contour map of the longitudinal tensile stress in the prestressed bridge deck concrete.

[0037] Figure 5 This is a contour map of the longitudinal tensile stress in the concrete pavement of the bridge deck after applying lane loads following prestressing.

[0038] Figure 6A cloud diagram showing the transverse stress of the prestressed bridge deck concrete.

[0039] Figure 7 A cloud diagram of transverse stress in the bridge deck concrete after applying lane loads following prestressing.

[0040] Figure 8 This is a longitudinal stress cloud diagram of the prestressed tongue-and-groove joint concrete.

[0041] Figure 9 This is a longitudinal stress cloud diagram of the tongue-and-groove concrete after applying lane loads following prestressing. Detailed Implementation

[0042] The technical solution and effects of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0043] Example 1

[0044] Given conditions: A bridge structure consists of 7 prestressed concrete hollow slab bridges with a span of 16m (calculated span 15.4m). The self-weight of the middle slab is 19200kg, and the self-weight of the side slabs is 24550kg. The self-weight of the railings is negligible (i.e., 0). The design camber of the middle slab under its own weight (or primary dead load) is 16mm. Under the application of the weight of the tongue-and-groove joint and the bridge deck pavement (i.e., the construction of the tongue-and-groove joint and bridge deck pavement) (or secondary dead load), the camber decreases by 2mm. The concrete grade of the bridge deck pavement is C50, and the thickness is 10cm. The bridge deck pavement is reinforced with a double-layer 100mm×100mm steel mesh using 12mm diameter Grade II steel bars. Heavy traffic is expected. The specific process for constructing the prestressed concrete bridge deck pavement is as follows.

[0045] 1. Calculate the prestressing load applied to the main beam.

[0046] The bridge has a span of 16m and is heavily trafficked. The median value of the load factor range is taken, i.e., k = 1.655.

[0047] The prestressing load applied to the middle plate is:

[0048]

[0049] The prestressing load applied to the edge plate is:

[0050]

[0051] 2. Construction Method

[0052] The first step is to install prestressed concrete hollow slabs and then install the railings.

[0053] The relevant provisions of (JTG / T F50-2011) "Technical Specifications for Highway Bridge and Culvert Construction" shall be followed.

[0054] The second step is to apply prestressing loads to the prestressed concrete hollow slab.

[0055] After the prestressed concrete hollow slabs are installed, a suspended basket is placed under each hollow slab, and a prestressed uniformly distributed load is applied using sandbags at a rate of p (kg / m). The uniformly distributed load applied to the middle slab is 2063 kg / m, and the uniformly distributed load applied to the edge slabs is 2638 kg / m.

[0056] The prestressed loads are arranged within the calculated span.

[0057] The prestressed uniformly distributed load applied to a prestressed concrete hollow slab can also be equivalently transformed into a concentrated load. The equivalent means that the change in the camber value of the hollow slab before and after the load is applied is equal.

[0058] The third step is to install the tongue and groove joints and the bridge deck paving.

[0059] First, install the tongue and groove joints and the bridge deck pavement reinforcement, and then pour the tongue and groove joints and the bridge deck pavement concrete together.

[0060] The construction methods, techniques, and quality requirements for tongue-and-groove joints and bridge deck pavement shall be implemented in accordance with the relevant provisions of (JTG / T F50-2011) "Technical Specifications for Highway Bridge and Culvert Construction".

[0061] The fourth step is the curing of the tongue-and-groove joints and the concrete pavement of the bridge deck.

[0062] The curing methods, techniques, and quality requirements for tongue-and-groove joints and bridge deck pavement concrete shall be implemented in accordance with the relevant provisions of (JTG / T F50-2011) "Technical Specifications for Highway Bridge and Culvert Construction".

[0063] Step 5: Unloading and forming prestress.

[0064] When the strength of the tongue-and-groove joint and the concrete of the bridge deck pavement reaches more than 80% of the design strength, the prestressed load applied to the hollow slab is removed.

[0065] During unloading, the longitudinal process should be carried out in small batches, symmetrically, and slowly; the transverse process should involve simultaneous unloading of all hollow plates. Manual unloading is beneficial for controlling the longitudinal small-batch, symmetrical, and slow unloading as well as the transverse synchronous unloading.

[0066] During the unloading process, the camber value of the hollow slab gradually recovers, and the bridge deck pavement concrete gradually undergoes vertical deformation, forming longitudinal prestress inside the bridge deck pavement concrete; at the same time, the bridge deck pavement concrete becomes longer and narrower, forming transverse tensile stress on both sides of the bridge towards the bridge centerline; furthermore, longitudinal prestress of upward tension and downward pressure is formed in the tongue and groove joint concrete.

[0067] Prestressing was performed using the above method, and simulation was conducted using finite element software. The calculations show that:

[0068] (1) After applying a prestressed load of 2063 kg / m to the middle slab, the camber value changes from 16 mm to 7.9 mm (e.g. Figure 1 As shown), after removing the prestressed load, the maximum camber is 13.77 mm, and the minimum camber is 10.35 mm (as shown). Figure 2 As shown), then apply lane loads to the bridge according to the provisions of (JTGD60-2015) "General Specifications for Design of Highway Bridges and Culverts". The maximum camber value is 11.77 mm, and the minimum camber value is 9.03 mm (as shown). Figure 3 As shown in the figure, this indicates that the prestressing of the bridge deck pavement concrete and the tongue-and-groove joint concrete meets the requirements for deformation and that the prestress reserve is sufficient.

[0069] (2) After prestressing, the maximum longitudinal tensile stress of the bridge deck pavement concrete is located at the mid-span, with a value of 2.688e+06 Pa (e.g., ...). Figure 4 As shown), then according to the provisions of (JTG D60-2015) "General Specifications for Design of Highway Bridges and Culverts", lane loads are applied to the bridge, and the maximum longitudinal tensile stress is 2.328e+06Pa (as shown). Figure 5 As shown in the diagram, the concrete pavement of the bridge deck remains in an elastic state and has sufficient prestress reserve. Therefore, it is evident that the design method of this invention is scientifically sound and reasonable.

[0070] (3) After prestressing, the maximum transverse tensile stress of the bridge deck pavement concrete is 2.609e+06Pa (e.g. Figure 6 As shown), then according to the provisions of (JTG D60-2015) "General Specifications for Design of Highway Bridges and Culverts", lane loads are applied to the bridge, and the maximum lateral tensile stress is 2.621e+06Pa (as shown). Figure 7 As shown, the bridge deck concrete is always in an elastic state and has sufficient prestress reserves; the lateral tensile stress in the bridge deck concrete is the tensile stress on both sides of the bridge towards the centerline of the bridge. It can increase the friction between the main beam and the tongue and groove joint, enhance the lateral integrity and stiffness of the bridge, improve the lateral load distribution capacity, and thus improve the bearing capacity of the bridge.

[0071] (4) After prestressing, the maximum longitudinal compressive stress at the lower edge of the tongue-and-groove joint concrete is 2.308e+06Pa (e.g. Figure 8 As shown), then according to the provisions of (JTG D60-2015) "General Specifications for Design of Highway Bridges and Culverts", lane loads are applied to the bridge, and the maximum longitudinal compressive stress at the lower edge is 1.930e+06Pa (as shown). Figure 9As shown in the figure, the prestress reserve is sufficient and not excessive; the upper edge of the tongue and groove concrete, whether under its own weight or when the bridge is subjected to lane load according to the provisions of (JTG D60-2015) "General Specifications for Design of Highway Bridges and Culverts", is under tensile stress in the longitudinal direction, which is less than the longitudinal tensile stress in the bridge deck pavement concrete; from the perspective of tensile and compressive stress, the tongue and groove concrete is always in an elastic state.

[0072] (5) From the perspective of the tongue and groove concrete and the bridge deck pavement concrete as a whole, a longitudinal prestressing force of upward tension and downward pressure is formed, which is consistent with the prestressing condition of the main beam. This enables the tongue and groove concrete and the bridge deck pavement concrete to deform in coordination with the main beam, thereby achieving the ability of both to generate large deformations without damage.

[0073] As can be seen from the above calculation results, the design method of the present invention is scientific and reasonable, which can meet the needs of deformation of bridge deck pavement concrete and tongue and groove joint concrete. The prestress reserve is sufficient and not excessive. The bridge deck pavement concrete and tongue and groove joint concrete are always in an elastic state, and the prestress magnitude is within a reasonable range, thus overcoming the problems existing in the prior art.

[0074] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A construction method for prestressed concrete bridge deck pavement, characterized in that, The construction method includes the following steps: The first step is to install the prestressed concrete main beams and construct crash barriers. The second step is to apply prestressed loads to the main beam. After the prestressed concrete main beams are installed, a suspended scaffold is placed under each main beam, and sandbags are used to press them down. Apply a uniformly distributed load to the main beam; The third step is to install tongue and groove joints / wet joints and bridge deck paving. For prestressed concrete hollow slab bridges, tongue and groove joints are constructed first; for prestressed concrete box girder bridges and T-shaped bridges, wet joints are constructed first, followed by bridge deck paving; or tongue and groove joints / wet joints are constructed together with bridge deck paving. The fourth step is the curing of tongue-and-groove joints / wet joints and bridge deck concrete. Step 5: Unloading and forming prestress. When the strength of the tongue-and-groove joint / wet joint and the bridge deck pavement concrete reaches more than 80% of the design strength, the prestressed load applied to the main beam is removed. In the second step, the uniformly distributed load applied to the main beam is calculated according to the following formula (1): （1） In formula (1): —Uniformly distributed load applied to the main beam, kg / m; —Load factor; —Weight of the main beam, kg; —Calculated span of the main beam, in meters; The load factor is selected based on the traffic load level and the main beam span. For moderate and light traffic, a smaller value is used; for heavy traffic, a medium value is used; and for extremely heavy and extra-heavy traffic, a larger value is used. For main beam spans less than 16m, a smaller value is used; for main beam spans equal to 16m, a medium value is used; and for main beam spans greater than 16m, a larger value is used. Among them, medium, light, heavy, extremely heavy, and extra-heavy traffic are the classifications of traffic load levels in JTG / T F20-2015 "Technical Specifications for Construction of Highway Pavement Base". The smaller values ​​range from 1.45 to 1.655, the middle values ​​range from 1.55 to 1.75, and the larger values ​​range from 1.655 to 1.

86. During the unloading process, the camber value of the main beam gradually recovers, causing the bridge deck pavement concrete to gradually undergo vertical deformation, forming longitudinal tensile stress inside the bridge deck pavement concrete; at the same time, the bridge deck pavement concrete becomes longer and narrower, forming transverse tensile stress on both sides of the bridge towards the bridge centerline; prestressing with upward tension and downward compression is formed in the longitudinal direction of the tongue and groove joint concrete / wet joint concrete; the bridge deck pavement concrete and the tongue and groove joint concrete / wet joint concrete are always in an elastic state.

2. The construction method for prestressed concrete bridge deck pavement according to claim 1, characterized in that, In the fifth step of unloading, the longitudinal unloading should be done in small batches, symmetrically, and slowly; the transverse main beams should be unloaded synchronously; manual unloading is beneficial for controlling the longitudinal small-batch, symmetrical, and slow unloading and the transverse synchronous unloading.

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