A PRECAST SEGMENTAL PIER REINFORCED WITH BOTH FRP BARS AND CONVENTIONAL STEEL BARS

Abstract

A precast segmental pier reinforced with both FRP bars and steel bars according to one or more embodiments of the present application includes a footing, a segmental pier, longitudinal bars and unbonded post-tensioned tendons, characterized in that: the segmental pier is comprised of one or more precast segments , the longitudinal bars are comprised of both the steel bar and the high-strength steel bar, connecting the footing and the segmental pier together with unbonded post-tensioned tendons to form an entire pier.

Claims

1. A precast segmental pier reinforced with both fiber reinforced polymer (FRP) bars and steel bars, comprising a footing, a segmental pier, longitudinal bars and unbonded post-tensioned tendons, characterized in that: the segmental pier is comprised of one or more precast segments, the longitudinal bars are comprised of both the FRP bar and the steel bar, connecting the footing and the segmental pier together with unbonded post-tensioned tendons to form an entire pier.

2. A precast segmental pier reinforced with both fiber reinforced polymer (FRP) bars and steel bars, comprising a footing, a segmental pier, longitudinal bars and unbonded post-tensioned tendons, characterized in that: the segmental pier is comprised of two or more precast segments, the longitudinal bars are comprised of both the FRP bar and the steel bar, connecting the footing and the segmental pier together with unbonded post-tensioned tendons to form an entire pier; the steel bar and the high-strength steel bar only pass through several precast segments of the lower part of the segmental pier, and are not arranged along the entire pier.

3. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 1, wherein: the upper surface and the lower surface of each precast segment are flat or be provided with one or more shear keys.

4. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 1, wherein: corrugated ducts are reserved in the footing and each precast segment, the FRP bar and the steel bar are placed in the same corrugated duct.

5. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 1, wherein: the FRP bars are positioned on the outer side of the cross section, and the steel bars are positioned on the inner side of the cross section.

6. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 1, wherein: steel bars are HRB400, HRB500, HRBF400, HRBF500, HRB400E, HRB500E, HRBF400E or HRBF 500E, and the FRP bars are BFRP bars, CFRP bars, GFRP bars or AFRP bars.

7. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 6, wherein: the lower end of the unbonded post-tensioned tendons are anchored in the footing, the tendons sequentially pass through the ducts for post-tensioned tendons with smooth inner wall reserved in each precast segment when the pier is assembled, and the upper tendons are anchored in the recess for the anchor of post-tensioned tendons.

8. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 6, wherein: the unbonded prestressed tendons are steel strands, deformed steel bars or FRP bars.

9. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 1, wherein: the ratio of the reinforcement ratio of the FRP bar to the reinforcement ratio of the steel bar is 0.5 to 2.0, and the longitudinal bars are arranged symmetrically in the cross-section.

10. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 1, wherein: the cross-section of the precast segmental pier is a rectangular thin-walled hollow section, the four corners of the cross-section are provided with the corrugated ducts using circular metal corrugated pipes, and the rest are provided with the corrugated ducts using flat metal corrugated pipes; only one FRP bar is placed in each circular corrugated ducts, and both a FRP bar and a steel bar are placed in each flat corrugated ducts.

11. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 7, wherein: the unbonded prestressed tendons are steel strands, deformed steel bars or FRP bars.

12. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 2, wherein: the upper surface and the lower surface of each precast segment are flat or be provided with one or more shear keys.

13. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 2, wherein: corrugated ducts are reserved in the footing and each precast segment, the FRP bar and the steel bar are placed in the same corrugated duct.

14. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claims 2, wherein: the FRP bars are positioned on the outer side of the cross section, and the steel bars are positioned on the inner side of the cross section.

15. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 2, wherein: the ratio of the reinforcement ratio of the FRP bar to the reinforcement ratio of the steel bar is 0.5 to 2.0, and the longitudinal bars are arranged symmetrically in the cross-section.

16. The precast segmental pier reinforced with both the FRP bars and the steel bars according to claim 2, wherein: the cross-section of the precast segmental pier is a rectangular thin-walled hollow section, the four corners of the cross-section are provided with the corrugated ducts using circular metal corrugated pipes, and the rest are provided with the corrugated ducts using flat metal corrugated pipes; only one FRP bar is placed in each circular corrugated ducts, and both a FRP bar and a steel bar are placed in each flat corrugated ducts.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a schematic longitudinal cross-sectional view of a precast segmental pier according to embodiment 1;

[0018] FIG. 2 is a schematic cross-sectional view of a precast segmental pier according to embodiment 1;

[0019] FIG. 3 is a schematic view of a locating brace for longitudinal bars according to embodiment 1;

[0020] FIG. 4 is a schematic longitudinal cross-sectional view of a precast segmental pier according to embodiment 2;

[0021] FIG. 5 is a schematic longitudinal cross-sectional view of a precast segmental pier according to embodiment 3.

[0022] Footing 1; a segmental pier 2; recess for the anchor of post-tensioned tendons 3; a precast segment 4; a corrugated duct 5; longitudinal bars (that are continuous across the segment joints) 6; unbonded post-tensioned tendons 7; ducts for post-tensioned tendons 8; a metal corrugated pipe 9; a conventional steel bar 10; a FRP bar 11; a steel hoop 12; locating brace for longitudinal bars 13.

DETAILED DESCRIPTION

[0023] The invention is described in further detail below with reference to the following figures and embodiments:

[0024] Embodiment 1, as shown in FIG. 1, the invention provides a precast segmental pier reinforced with both FRP bars 11 and conventional steel bars 10, comprising a footing 1, a segmental pier 2, longitudinal bars 6 and unbonded post-tensioned tendons 7. The segmental pier 2 is composed of one or more precast segments 4, and the footing 1 and the segmental pier 2 are connected together by unbonded post-tensioned tendons 7 to form an entire pier. Each precast segment 4 has a round-ended cross-section with the same cross-sectional dimension and the same segment height. The height of the segments is 1.5 to 4 times of the size of the long side of the section, so that the plastic hinge of the precast segmental pier can be fully developed to ensure the energy dissipation capacity in seismic design, and the volume and the weight of a single precast segment 4 are small for assembling conveniently. Each precast segment 4 is provided with the same number of corrugated ducts 5 at the same cross-sectional position. Therefore, the corrugated ducts 5 and the ducts for post-tensioned tendons 8 can be achieved after assembly. After the precast segments 4 are assembled and the unbonded post-tensioned tendons 7 are tensioned, the longitudinal bars 6 are placed into the corrugated ducts 5. If the length of the single longitudinal bar 6 is smaller than the height of the segmental pier 2, the longitudinal bar 6 is extended in the approach of mechanical connection, welding or binding connection. The longitudinal bars 6 are composed of a FRP bar 11 and a conventional steel bar 10, and the ratio of the reinforcement ratio of the FRP bar 11 to the reinforcement ratio of the conventional steel bar 10 is 0.5 to 2.0. The post-yielding stiffness of the precast segmental pier can be effectively improved by configuring the two kind of longitudinal bars, so that the seismic performance and the self-centering capability of the precast segmental pier are comprehensively improved. More importantly, as shown in FIG. 2, the corrosion-resistant FRP bars 11 are positioned on the outer side of the cross section, and the conventional steel bars 10 are positioned on the inner side of the cross section, so that the durability of the precast segmental pier can be remarkably improved. To accurately determine the geometric positions of these two longitudinal bars, a locating brace for longitudinal bars 13 is employed. And the locating brace for longitudinal bars 13 is arranged at intervals of 2 to 5 meters along the vertical direction of the longitudinal bars, and the locating brace for longitudinal bars 13 is shown in FIG. 3. After the longitudinal bars 6 are placed, pressure grouting is carried out in the corrugated ducts 5, and grouting quality is ensured. The longitudinal bars 6 are restrained by the surrounding grouting material, the metal corrugated pipes 9 and the steel hoops 12, so that the longitudinal bars generally do not suffer from buckling failure under compression during an earthquake. The high-strength grouting material confined by the metal corrugated pipe can resist compression together with the concrete, so that the compression stress level and the degree of damage of the concrete can be lower. Therefore, the precast segmental pier has better durability and post-seismic performance than the cast-in-situ pier, and reduces the maintenance cost of the bridge, accelerates the construction of the bridge and ensures the rapid recovery of the bridge traffic network in the earthquake disaster areas.

[0025] 2. Embodiment 2, as shown in FIG. 4, the difference between this embodiment and the embodiment 1 is that the precast segmental pier is a rectangular thin-walled hollow section, the four corners of the cross-section are provided with the corrugated ducts 5 using circular metal corrugated pipes 9, and the rest are provided with the corrugated ducts 5 using flat metal corrugated pipes 9. Only one FRP bar is placed in each circular corrugated ducts 5, and both a FRP bar 11 and a conventional steel bar 10 are placed in each flat corrugated ducts 5. When the precast segmental pier reinforced with both FRP bars 11 and conventional steel bars 10 has a rectangular thin-wall hollow cross-section, the FRP bars can be close to the edge of the cross-section, so that the tensile strength of the FRP bars can be more fully utilized, and the post-yield stiffness of the precast segmental pier is improved; meanwhile, the concrete cover of the conventional steel bars is obviously thickened, the initial corrosion time of the conventional steel bars is greatly delayed, and the durability of the precast segmental pier is obviously improved.

[0026] 3. Embodiment 3, as shown in FIG. 5, the present embodiment is different from the embodiment 1 in that FRP bars and conventional steel bars only pass through several precast segments of the lower part of the segmental pier, and are not arranged along the whole pier. For a cantilever pier, the bending moment of the bottom of the pier is the largest under the action of an earthquake, and the bending moment is gradually reduced from the bottom of the pier to the top of the pier. In seismic design, longitudinal bar reinforcement ratio can be gradually reduced according to bending moment distribution of pier, and finally, the longitudinal bar is cut at a certain reasonable height. The cutting of the longitudinal bar is in accordance with the corresponding seismic design specification. Because the cost of the FRP bar is higher than that of the conventional steel bar, when the height of the pier reinforced with both FRP bars and conventional steel bars is larger, the amount of FRP bars and conventional steel bars can be effectively reduced by this method while the seismic performance is ensured, so that the economic benefit and the construction efficiency are favorably improved.

[0027] Finally, the above embodiments are only used to illustrate the technical solution of the present invention and are not limited.