A segmental pre-compressed assembled concrete pier structure and construction method thereof
By arranging prestressed tendons above plastic hinge areas in bridge pier structures, the solution addresses construction complexity and durability issues while improving seismic performance and energy dissipation.
Patent Information
- Application Number
- CN202010735912.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2020-07-28
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2040-07-28
AI Technical Summary
Existing prestressed assembled bridge piers face challenges with complex construction, poor durability, and limited segmentation at joints, which affect seismic performance due to prestress tendons passing through plastic hinge areas and increasing axial compression ratios.
The solution involves arranging prestressed tendons to connect non-plastic hinge sections of concrete pier columns, with the lower fixed end set above the plastic hinge area, and using fixed-end anchoring devices located above the plastic hinge zone to reduce axial compression and enhance seismic performance.
This approach improves construction efficiency, reduces workload, and enhances the structure's energy dissipation capacity and seismic performance by minimizing axial compression in plastic hinge areas.
Smart Images
Figure CN111733692B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of civil engineering, and in particular to a segmental pre-pressed assembled concrete pier structure and a construction method thereof. Background Art
[0002] In existing bridge structures, the lower pier system of the bridge is mostly cast-in-place, which will cause problems such as lengthy bridge construction period and deterioration of the ecological and living environment near the bridge site, which is contrary to the concept of efficient and ecological transportation infrastructure construction. Prefabrication and assembly technology has the advantages of fast construction, good quality and little impact on the environment, and can be effectively applied to the construction process of pier structures.
[0003] Existing prefabricated piers mostly use reinforced concrete structures, and the connections between prefabricated segments of the pier body are mostly connected by anchoring methods such as grouting sleeves or grouting bellows. The overhang of the reserved steel bars on the prefabricated components makes prefabrication formwork difficult, and careful operation is required during transportation and hoisting to avoid deformation of the steel bars caused by collisions. The docking and grouting between the reserved steel bars and the connecting sleeves are time-consuming and labor-intensive, with low work efficiency and difficult to ensure the quality of splicing. In order to reduce the workload of splicing, the pier body is mostly prefabricated as a whole, which puts higher requirements on the hoisting equipment, especially in large-size pier column structures. The hoisting capacity often becomes a bottleneck problem. On the other hand, reinforced concrete prefabricated piers often crack during hoisting and use, which affects the durability of the structure and increases the cost of the entire life cycle of the structure. The use of prestressed assembly technology can effectively alleviate or even completely solve the above problems. Prestressing is not only a means of splicing, but also prestressed tendons can be used as main force-bearing tendons to replace steel bars. The high strength characteristics of prestressed tendons can save the use of materials. At the same time, their through-length characteristics can reduce the number of anchor connections of ordinary steel bars in the joints, or even eliminate the need for anchor connections. During the construction phase, prestressing technology provides prestressing stress to the joints, which can effectively improve the splicing quality of the joints. The compressive stress provided by prestressing during the service period can reduce or even avoid cracks in the structure during its service life, improve the durability of the structure, and reduce the cost of the entire service life cycle. Prestressed assembly technology has been widely used in the construction of bridge superstructures. The use of prestressed assembly technology in bridge pier structures, especially in small and medium span extra-large bridge pier structures, can better reflect the quality and greenness of the assembled structure.
[0004] Prestressed prefabricated bridge piers have many advantages, but they are deficient in some aspects. Prestressed tendons will increase the axial compression ratio of the pier column structure while providing preload. Under the action of earthquakes, the piers are subjected to reciprocating horizontal loads while bearing the vertical loads transmitted from the superstructure. The internal force at the bottom of the pier is the largest. During an earthquake, plastic hinges are easily formed at the bottom of the piers, and their plastic properties are used to dissipate seismic energy. That is, the potential plastic hinge area is at the bottom of the pier. The axial compression ratio is an important indicator that affects the seismic performance of the structure. Generally, the larger the axial compression ratio, the worse the rotation capacity of the plastic hinge area of the pier, and the worse the ability to dissipate seismic energy and the seismic performance of the pier structure.
[0005] In the existing conventional thinking, in order to improve the seismic performance of the bottom of prestressed prefabricated bridge piers, a variety of methods can be adopted, such as using steel pipes to constrain or wrap FRP fiber cloth to strengthen the pier bottom segment, adding fiber-reinforced cement-based composite materials to the pier bottom concrete, and setting additional energy-absorbing components on the side of the pier bottom to absorb seismic energy. These methods can achieve good damage control effects, but at the same time they also increase the complexity of design and construction, which is not conducive to economic efficiency.
[0006] The existing prestressed segmented prefabricated bridge piers connect the entire structure into one through the prestress effect generated by tensioning the prestressed tendons. Except for some prestressed tendons whose specific positions of the bottom anchorage ends are not clear, the remaining prestressed tendons pass through the plastic hinge area at the bottom of the pier and are anchored at the bottom of the concrete cap.
[0007] Among the several patents that have been published, Chinese invention patent CN 102493335 A discloses a prefabricated prestressed steel tube concrete bridge pier, which divides the entire pier into prefabricated sections of a certain length. After prefabrication in the factory, it is transported to the site for hoisting and assembly. Prestress is applied by prestressed steel bundles to strengthen the connection between the prefabricated sections of the pier. However, the invention does not specify the specific height requirement of the bottom anchor end of the prestressed steel bundle.
[0008] Chinese invention patent CN 110565533 A discloses segmented prefabricated assembled bridge piers and their construction methods. Although prestressed steel bars are used to connect the prefabricated segments together, the invention also does not emphasize the specific height requirements of the bottom anchor end of the prestressed steel strand.
[0009] Chinese utility model patent CN 209227365 U discloses a self-resetting assembled pier with replaceable additional mild steel. Unbonded prestressed steel bars are used to connect prefabricated pier segments and concrete caps as a whole. Bolt anchors are used to connect the additional mild steel to the longitudinal reinforcement of the pier and the longitudinal reinforcement of the concrete cap at the bottom of the pier. The additional mild steel is used to reduce the residual deformation of the structure and consume seismic energy to a certain extent. The fixed end anchor of the lower end of the unbonded prestressed steel bar is buried in the bottom of the prefabricated concrete cap.
[0010] In the existing prestressed assembled pier column structure, the prestressed tendons pass through the bottom plastic hinge area, and the lower ends are anchored at the bottom of the concrete cap. This is the result of long-term experience and common practices in engineering practice. The main function of prestressing technology is to control the development of structural cracks. When prestressing technology was used in early concrete beam-slab structures, the prestressed tendons were usually made to run through the entire length of the component, and the anchoring devices were set at both ends of the component, which can effectively prevent the beam body from cracking. Therefore, after the prestressed assembled technology was introduced into the bridge pier column structure, the traditional view was to regard the pier as a cantilever column, which has certain commonalities with the cantilever beam in the prestressed concrete beam-slab structure. For the cantilever structure, the root bending moment caused by shear force is the largest, which is the key part of the structural crack control. In the traditional practice, the technical characteristics of the prestressed cantilever beam structure in the past were transferred to the prestressed assembled pier structure, and the anchoring devices were also set at both ends of the pier, which is also conducive to controlling the cracks at the bottom (root) of the pier. This approach can also objectively improve the self-reset effect of the pier. However, for bridge pier structures, the bottom of the pier is mainly subjected to axial pressure under normal load conditions and small earthquakes. Only under strong earthquakes will the horizontal force cause a large bending moment at the bottom of the pier. The crack control at this location is not the main problem faced during the stress process. On the contrary, the installation of prestressed tendons at the bottom of the pier will increase the axial compression ratio in this area, reduce the seismic energy dissipation capacity of the pier structure, and be detrimental to the seismic performance of the structure. Prestressing is an effective means of splicing, and the non-plastic hinge section hopes to provide sufficient compressive stress to ensure the integrity of the pier. The requirements for prestressing at different positions in the pier structure are inconsistent. The advantages of prestressing in the existing prestressed assembled pier structure are contradictory to the seismic performance of the pier, and the two cannot be achieved at the same time. Summary of the invention
[0011] In view of the above technical problems, the present invention provides a segmental prestressed assembled concrete pier structure and a construction method thereof, aiming to solve the problems of complex construction, poor durability, and limited segmentation of the existing assembled piers with anchor connections at the joints, and the problem that the prestress in the existing prestressed assembled piers affects the seismic performance of the structure. Prestressed tendons are used to connect the non-plastic hinge sections of the concrete pier columns, and the lower fixed end of the prestressed tendons is set above the plastic hinge area at the bottom of the pier to reduce the axial compression ratio of the plastic hinge area and ensure that the structure has excellent energy consumption capacity and seismic performance. This new structural form can effectively improve construction efficiency and reduce the workload on the construction site.
[0012] In order to achieve the above technical objectives, the present invention adopts the following technical solution: a segmental pre-stressed assembled concrete pier structure, comprising:
[0013] The prefabricated non-plastic hinge section is an integral prefabricated segment or is composed of a plurality of prefabricated non-plastic hinge section segments connected in sequence from top to bottom;
[0014] The bottom concrete cap is set at the bottom of the concrete pier;
[0015] A plastic hinge section is provided between the prefabricated non-plastic hinge section and the bottom concrete cap;
[0016] The prestressed tendon is arranged through the prefabricated non-plastic hinge section and the section containing plastic hinge, and its upper end passes through the top of the prefabricated non-plastic hinge section and is fixedly connected to the top of the prefabricated non-plastic hinge section through a tensioning end anchoring device; its lower end is fixed in the section containing plastic hinge through a fixed end anchoring device and is reliably connected to the longitudinal reinforcement of the section containing plastic hinge;
[0017] After the prestressed tendons are tensioned, the segmental prestressed prefabricated concrete pier becomes a whole;
[0018] The fixed-end anchoring device is located at the upper part of the estimated plastic hinge zone in the plastic hinge-containing section.
[0019] The estimated height of the plastic hinge zone is the length of the stirrup densification zone within the plastic hinge section.
[0020] The prefabricated non-plastic hinge section and the section containing plastic hinge are provided with channels for the prestressed tendons to pass through.
[0021] The bottom concrete pedestal and the section containing the plastic hinge are integrally cast and formed.
[0022] The plastic hinge section and the concrete pedestal are prefabricated separately. The longitudinal reinforcement of the plastic hinge section needs to reserve a section of overhanging length at the interface. The upper end of the longitudinal anchor reinforcement at the corresponding position of the concrete pedestal is pre-embedded with a reinforcement connector. The longitudinal reinforcement of the plastic hinge section is connected to the longitudinal anchor reinforcement of the concrete pedestal through the reinforcement connector.
[0023] A prefabricated cap beam is arranged on the upper portion of the prefabricated non-plastic hinge section.
[0024] A construction method for the segmental prestressed assembled concrete pier structure includes the following steps: the first step is to prepare a prefabricated non-plastic hinge section, a section containing a plastic hinge and a concrete cap, and prepare prestressed tendons; wherein the prefabricated non-plastic hinge section and the section containing a plastic hinge are respectively pre-set with a hole for the prestressed tendons to pass through; the fixed end anchoring device is located at the upper part of the estimated plastic hinge area in the section containing a plastic hinge, and is reliably connected to the longitudinal reinforcement of the section containing a plastic hinge;
[0025] The second step is to hoist the prefabricated non-plastic hinge section and the section with plastic hinge into place in sequence, ensuring that the duct of the prefabricated non-plastic hinge section and the duct of the section with plastic hinge are aligned up and down;
[0026] The third step is to pass the prestressed tendons through the prefabricated non-plastic hinge section channel and the plastic hinge section channel from top to bottom in sequence, and when the lower end of the prestressed tendons is inserted into the fixed end anchoring device pre-buried in the plastic hinge section, effective anchoring is formed;
[0027] The fourth step is to fix the tensioning end anchoring device to the uppermost part of the prefabricated non-plastic hinge section, and pass the upper end of the prestressed tendon into it, and tension the prestressed tendon to form an anchor.
[0028] The fifth step is to pour cement mortar into the prefabricated non-plastic hinge section channel and the plastic hinge section channel.
[0029] Shear key teeth may be provided or not provided between the plurality of prefabricated non-plastic hinge sections and between the prefabricated non-plastic hinge sections and the sections containing plastic hinges according to the requirements of horizontal shear bearing capacity.
[0030] When the plastic hinge section and the concrete cap are prefabricated separately, shear key teeth may be provided or not provided between the plastic hinge section and the concrete cap according to the horizontal shear bearing capacity requirements.
[0031] Beneficial effects: Compared with the prior art, the present invention has the following advantages:
[0032] (1) Ordinary steel bars are arranged in the plastic hinge section to effectively ensure the energy dissipation capacity of the structure. The prestressed steel bars do not pass through the plastic hinge area, which can reduce the axial compression ratio of the plastic hinge area and improve the seismic performance of the structure;
[0033] (2) Prestressed steel bars are the main force-bearing steel bars in the non-plastic hinge area, which can reduce the use of ordinary steel bars. At the same time, the full-length connection of prestressed steel bars can be used to avoid the complex anchorage connection of ordinary steel bars at the joints in the non-plastic hinge area;
[0034] (3) Since the connection of ordinary longitudinal steel bars at the joints is avoided, the height of the prefabricated pier segments can be determined according to the transportation and lifting requirements, which can adapt to the construction of engineering projects under various conditions, especially complex transportation conditions. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 This is a structural diagram of the present invention in which the plastic hinge section at the bottom of the pier and the concrete cap are integrally cast; Figure 2 This is a structural diagram of a prefabricated segment containing a plastic hinge section at the bottom of the pier of the present invention designed according to the "equivalent cast-in-place" design theory.
[0036] Among them, 1. Prefabricated non-plastic hinge section; 2. Section containing plastic hinge; 3. Concrete cap; 4. Prestressed system; 41. Prestressed tendons; 42. Tensioning end anchorage device; 43. Fixed end anchorage device; 51. Prefabricated non-plastic hinge section channel; 52. Section containing plastic hinge channel. DETAILED DESCRIPTION
[0037] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1As shown, when the plastic hinge section 2 at the bottom of the pier is cast integrally with the concrete cap 3, the solid / hollow section prefabricated non-plastic hinge section 1 which is prefabricated as a whole or in sections is located above the plastic hinge section 2, the plastic hinge section 2 and the concrete cap 3 are cast integrally, and the longitudinal reinforcement of the plastic hinge section 2 is vertically connected with the longitudinal anchor reinforcement of the concrete cap 3.
[0038] A prefabricated non-plastic hinge section channel 51 is reserved in the prefabricated non-plastic hinge section 1, and a plastic hinge section channel 52 is reserved in the plastic hinge section 2, and the two are aligned up and down.
[0039] The prestressed system 4 includes a continuously arranged prestressed tendon 41, a tensioning end anchoring device 42 and a fixed end anchoring device 43. The prestressed tendon 41 passes through the prefabricated non-plastic hinge section channel 51 and the plastic hinge section channel 52 from top to bottom, and its upper end is inserted into the tensioning end anchoring device 42 for effective fixation, and its lower end is inserted into the fixed end anchoring device 43 for effective fixation. The tensioning end anchoring device 42 is fixed to the upper part of the prefabricated non-plastic hinge section 1.
[0040] The fixed end anchor device 43 is embedded in the upper part of the estimated plastic hinge area in the plastic hinge section 2. The height of its bottom from the top surface of the concrete pedestal 3 should be greater than the estimated plastic hinge area height, and it should be reliably connected to the longitudinal reinforcement of the plastic hinge section 2.
[0041] like Figure 2 As shown, as an improvement of the present invention, when the plastic hinge section at the bottom of the bridge pier is prefabricated separately according to the "equivalent cast-in-place" design theory, there is a splicing interface between the plastic hinge section 2 and the concrete cap 3. The longitudinal reinforcement of the plastic hinge section 2 needs to reserve a section of overhanging length at the interface, and a steel bar connector is pre-embedded at the upper end of the longitudinal anchor reinforcement at the corresponding position of the concrete cap 3, and the longitudinal reinforcement of the plastic hinge section 2 is connected to the longitudinal anchor reinforcement of the concrete cap 3 through the steel bar connector.
[0042] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The design and construction and installation process of the present invention is now explained: (1) Based on the cross-sectional size, height, reinforcement and other relevant design parameters of the pier, the height of the plastic hinge zone at the bottom of the pier is estimated according to relevant specifications, and the length of the prefabricated non-plastic hinge zone segment is divided according to conditions such as on-site lifting capacity.
[0043] The height of the plastic hinge area at the bottom of the bridge pier refers to the area where severe plastic failure actually occurs at the bottom of the pier. The following is an example of applying a segmental prestressed assembled concrete pier structure proposed by the present invention to a domestic highway bridge.
[0044] Article 3.4.2 of the industry recommended standard of the People's Republic of China "Code for Seismic Design of Highway Bridges" (JTG / T 2231-01-2020, hereinafter referred to as "the Code") gives a schematic diagram of the potential plastic hinge area at the bottom of continuous beams and simply supported beam-column piers, but does not clearly give the calculation formula for the range of the potential plastic hinge area.
[0045] Article 8.2.1 of the Code states that the potential plastic hinge zone of conventional bridge piers in areas with high seismic fortification intensity should be designed with ductile structural details with denser stirrups, and specifies the method for selecting the length of the denser stirrup zone.
[0046] Article 8.2.3 of the Code states that the stirrup ratio of the outer stirrups of the potential plastic hinge densification zone of the pier column should be gradually reduced. Considering that one of the main functions of the stirrups here is to constrain the concrete in the plastic hinge zone at the bottom of the pier, and the Code has conservatively determined the length of the stirrup densification zone at the bottom of the pier to include the entire potential plastic hinge zone, the length of the stirrup densification zone at the bottom of the pier can be approximately taken as the height of the plastic hinge zone. When the present invention is applied to other types of bridge structures, a similar method can also be used to approximately determine the height of the plastic hinge zone at the bottom of the pier.
[0047] (2) The prefabricated non-plastic hinge section is manufactured according to the design dimensions in the component factory.
[0048] When the integral casting method of the section containing plastic hinge and the concrete cap is adopted, the steel bars of the concrete cap and the section containing plastic hinge shall be tied as a whole, the fixed-end anchor device shall be embedded in the upper part of the estimated plastic hinge area in the section containing plastic hinge, the fixed-end anchor device shall be reliably connected to the longitudinal steel bars of the section containing plastic hinge, and the concrete of the non-plastic hinge section and the concrete cap shall be cast as a whole; when the separate prefabrication method of the section containing plastic hinge is adopted, the section containing plastic hinge shall be prefabricated in the component factory, and the concrete cap shall be cast on site. A section of overhanging length shall be reserved at the lower end of the longitudinal steel bars of the section containing plastic hinge, and the steel bar connector shall be embedded at the upper end of the longitudinal anchor steel bars at the corresponding position of the concrete cap, and the fixed-end anchor device shall be embedded in the designated position in the section containing plastic hinge and reliably connected to the longitudinal steel bars of the section containing plastic hinge.
[0049] (4) Assemble the prefabricated components in sequence to ensure that the center of the reserved prestressed channel section in each component is vertically aligned. If the plastic hinge section is prefabricated separately, the longitudinal reinforcement of the plastic hinge section must be reliably anchored in the concrete cap.
[0050] (5) The prestressed tendons are inserted into the reserved holes one by one, and the lower ends of the prestressed tendons are inserted into the fixed end anchoring devices embedded in the plastic hinge section to form effective fixation.
[0051] (6) Insert the tensioning end anchor device into the upper end of the prestressed tendon and tension the prestressed tendon to form the concrete pier structure. If there is a cap beam on the top, the cap beam can be connected with the prestressed tendon.
Claims
1. A segmental pre-compressed assembled concrete pier structure, comprising: The prefabricated non-plastic hinge section is an integral prefabricated segment or is composed of a plurality of prefabricated non-plastic hinge section segments connected in sequence from top to bottom; The bottom concrete cap is set at the bottom of the concrete pier; A plastic hinge section is provided between the prefabricated non-plastic hinge section and the bottom concrete cap; The prestressed tendon is arranged through the prefabricated non-plastic hinge section and the section containing plastic hinge, and its upper end passes through the top of the prefabricated non-plastic hinge section and is fixedly connected to the top of the prefabricated non-plastic hinge section through a tensioning end anchoring device; its lower end is fixed in the section containing plastic hinge through a fixed end anchoring device and is reliably connected to the longitudinal reinforcement of the section containing plastic hinge; After the prestressed tendons are tensioned, the segmental prestressed prefabricated concrete pier becomes a whole; It is characterized in that the fixed-end anchoring device is located at the upper part of the estimated plastic hinge zone in the section containing the plastic hinge; the height of the estimated plastic hinge zone is the length of the stirrup densification zone in the section containing the plastic hinge.
2. The segmental pre-stressed assembled concrete pier structure according to claim 1, characterized in that: The prefabricated non-plastic hinge section and the section containing plastic hinge are provided with channels for the prestressed tendons to pass through.
3. The segmental pre-stressed assembled concrete pier structure according to claim 1, characterized in that: The bottom concrete pedestal and the section containing the plastic hinge are integrally cast and formed.
4. The segmental pre-stressed assembled concrete pier structure according to claim 1, characterized in that: The plastic hinge section and the concrete pedestal are prefabricated separately. The longitudinal reinforcement of the plastic hinge section needs to reserve a section of overhanging length at the interface. The upper end of the longitudinal anchor reinforcement at the corresponding position of the concrete pedestal is pre-embedded with a reinforcement connector. The longitudinal reinforcement of the plastic hinge section is connected to the longitudinal anchor reinforcement of the concrete pedestal through the reinforcement connector.
5. The segmental pre-stressed assembled concrete pier structure according to claim 1, characterized in that: A prefabricated cap beam is arranged on the upper portion of the prefabricated non-plastic hinge section.
6. A construction method for a segmental pre-stressed assembled concrete pier structure as claimed in any one of claims 1 to 5, characterized in that: The method comprises the following steps: first, making a prefabricated non-plastic hinge section, a section containing a plastic hinge and a concrete cap, and preparing prestressed tendons; wherein the prefabricated non-plastic hinge section and the section containing a plastic hinge are respectively provided with holes for the prestressed tendons to pass through; the fixed end anchoring device is located at the upper part of the estimated plastic hinge area in the section containing a plastic hinge, and is reliably connected to the longitudinal reinforcement of the section containing a plastic hinge; The second step is to hoist the prefabricated non-plastic hinge section and the section with plastic hinge into place in sequence, ensuring that the duct of the prefabricated non-plastic hinge section and the duct of the section with plastic hinge are aligned at the top and bottom; The third step is to pass the prestressed tendons through the prefabricated non-plastic hinge section channel and the plastic hinge section channel from top to bottom in sequence, and when the lower end of the prestressed tendons is inserted into the fixed end anchoring device pre-buried in the plastic hinge section, effective anchoring is formed; The fourth step is to fix the tensioning end anchoring device to the uppermost part of the prefabricated non-plastic hinge section, and insert the upper end of the prestressed tendon into it, tensioning the prestressed tendon to form an anchor; The fifth step is to pour cement mortar into the prefabricated non-plastic hinge section channel and the plastic hinge section channel.
7. The construction method of the segment pre-stressed assembled concrete pier structure according to claim 6 is characterized in that: Shear key teeth may be provided or not provided between the plurality of prefabricated non-plastic hinge sections and between the prefabricated non-plastic hinge sections and the sections containing plastic hinges according to the requirements of horizontal shear bearing capacity.
8. The construction method of the segment pre-stressed assembled concrete pier structure according to claim 6 is characterized in that: When the plastic hinge section and the concrete cap are prefabricated separately, shear key teeth may be provided or not provided between the plastic hinge section and the concrete cap according to the horizontal shear bearing capacity requirements.