Pre-tensioned centrifugal concrete structure with steel strands

Abstract

A pre-tensioned centrifugal concrete pillar includes a concrete body, a steel cage including a plurality of pre-stressed rebars, a plurality of stirrups; and two plates, the rebars are steel strands, a plurality of conical through holes are provided on the plate, and multiple clips are disposed inside each conical through hole, each clip having a toothed inner surface, the multiple clips are spliced together to form a chock assembly for clamping each steel strand, and a peripheral surface of the chock assembly has a conical surface; a clamping hole is formed in the center of the chock assembly, the steel strand passes through a clamping hole and is clamped tightly. A method for manufacturing a pre-tensioned centrifugal concrete pillar is also included.

Claims

1. A pre-tensioned centrifugal concrete pillar comprising a hollow concrete body with two ends; a steel cage having an axis and disposed inside the concrete body, the steel cage comprises a plurality of pre-stressed rebars disposed parallel to the axis of the steel cage, a plurality of stirrups placed around the plurality of rebars; and a first plate and a second plate covering the two ends of the body, each of the first plate and the second plate has an inside facing the body and an outside facing away from the body, each plate defining a center opening; wherein, the pre-stressed rebars are steel strands, and an end of each steel strand is connected to the first plate through a clip connecting mechanism; the clip connecting mechanism comprises: a plurality of conical through holes provided on the first plate, each conical through hole has a diameter increasing from the inside toward the outside of the first plate, a position of each conical through hole corresponds to each steel strand; and multiple clips disposed inside each conical through hole, each clip is composed by three conical parts with a toothed inner surface; the multiple clips are spliced together to form a chuck assembly for clamping each steel strand, and a peripheral surface of the chuck assembly has a conical surface matching with corresponding conical through hole; a clamping hole is formed in the center of the chuck assembly with the toothed inner surface for receiving and clamping a steel strand, the steel strand passes through a corresponding clamping hole and is clamped tightly; and an outer surface of the chuck assembly is flush with or is lower than an outer surface of the first plate.

2. The concrete pillar of claim 1, wherein each chuck assembly comprises three clips, an annular recess is formed on the peripheral surface of each chuck assembly, and a retention ring placed in the annular recess.

3. The pre-tensioned centrifugal concrete pillar of claim 1, wherein the first plate has a plurality of threaded holes for connection.

4. A pre-tensioned centrifugal concrete pillar, comprising a hollow concrete body with two ends; a steel cage having an axis and disposed inside the concrete body, the steel cage comprises a plurality of pre-stressed rebars disposed parallel to the axis of the steel cage, a plurality of stirrups placed around the plurality of rebars; and a first plate and a second plate covering the two ends of the body, each of the first plate and the second plate has an inside facing the body and an outside facing away from the body, each plate defining a center opening; wherein, the pre-stressed rebars are steel strands, and an end of each steel strand is connected to the first plate through a clip connecting mechanism; the clip connecting mechanism comprises: a plurality of counter recesses provided on the first plate; a transition element matched with the counter recesses in dimension is disposed inside each counter recess, the transition element has an annular stop shoulder resting on the counter recess and a conical transition through hole, the conical transition through hole has a diameter increasing from the inside toward the outside of the plate and a position of each conical transition through hole corresponds to each steel strand; and multiple clips disposed inside each transition through hole, each clip is composed by three conical parts with a toothed inner surface; the multiple clips are spliced together to form a chuck assembly for clamping each steel strand, and a peripheral surface of the chuck assembly has a conical surface matching with corresponding conical transition through hole; a clamping hole is formed in the center of the chuck assembly with the toothed inner surface for receiving and clamping a steel strand, the steel strand passes through a corresponding clamping hole and is clamped tightly; an outer surface of the chuck assembly is flush with or is lower than an outer surface of the first plate.

5. The concrete pillar of claim 4, wherein each chuck assembly comprises three clips, an annular recess is formed on the peripheral surface of each chuck assembly, and a retention ring placed in the annular recess.

6. The pre-tensioned centrifugal concrete pillar of claim 4, wherein the first plate has a plurality of threaded holes for connection.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a plan view of a pre-tensioned centrifugal concrete pillar according to a first embodiment of the present invention, with a sectional view showing a first clip-type connecting mechanism in the first embodiment;

(2) FIG. 2 is an enlarged view of Part-A of FIG. 1;

(3) FIG. 3 is a sectional view in B-B direction of FIG. 1;

(4) FIG. 4 is a side view of the pre-tensioned centrifugal concrete pillar according to the first embodiment of the present invention;

(5) FIG. 5 is a perspective view of a chuck assembly according to the two embodiments of the present invention;

(6) FIG. 6 is an exploded view of the chuck assembly according to the two embodiments of the present invention;

(7) FIG. 7 is a plan view of a pre-tensioned centrifugal concrete pillar according to a second embodiment of the present invention, with a sectional view showing a second clip-type connecting mechanism in the second embodiment;

(8) FIG. 8 is an enlarged view of Part-C of FIG. 7;

(9) FIG. 9 is a sectional view in D-D direction of FIG. 7;

(10) FIG. 10 is a side view of the pre-tensioned centrifugal concrete pillar according to the second embodiment of the present invention;

(11) FIG. 11 is a plan view of a method for manufacturing the pre-tensioned centrifugal concrete pillar according to the first embodiment of the present invention mentioned above (with the upper half-die removed), with a sectional view showing the position of the first clip-type connecting mechanism in the first embodiment;

(12) FIG. 12 is an enlarged view of Part-E of FIG. 11;

(13) FIG. 13 is a plan view of a method for manufacturing the pre-tensioned centrifugal concrete pillar according to the second embodiment of the present invention mentioned above (with the upper half-die removed), with a sectional view showing the position of the second clip-type connecting mechanism in the second embodiment;

(14) FIG. 14 is an enlarged view of Part-F of FIG. 13; and

(15) FIG. 15 is a perspective view of a die used in the two methods mentioned above.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(16) To enable a further understanding of the innovative and technological content of the invention herein refer to the detailed description of the invention and the accompanying drawings below:

(17) FIG. 1 to FIG. 6 show a pre-tensioned centrifugal concrete pillar according to the first embodiment the present invention.

(18) The pre-tensioned centrifugal concrete pillar comprises a hollow concrete pillar body 1 with two ends and a steel cage having an axis and disposed inside the concrete body 1. The body 1 can be a circular pillar, and can also be a square pillar, a polygon pillar and various pre-tensioned centrifugal concrete pillars with special shapes. the steel cage comprises a plurality of pre-stressed rebars disposed parallel to the axis of the steel cage and a plurality of stirrups 4 placed around the plurality of rebars, and the pre-tensioned pre-stressed rebars are steel strands 3. Stirrups 4 and steel strands 3 can be fixed by binding manually or by an automatic binding machine, or can be fixed by other mechanical means. Non-pre-stressed steel rebars, anchor rebars and pillar stirrups can also be arranged in an axial direction on the body 1, and this is a conventional design of centrifugal concrete pillars.

(19) Two plates 2 are connected to an end of each steel strand 3 through a first clip-type connecting mechanism. That is, a plurality of conical through holes 21 provided on the plates 2, each conical through hole has a diameter gradually increasing from the inside toward the outside of the plate 2, a position of each conical through hole corresponds to each steel strand 3; and multiple clips 5 disposed inside each conical through hole 21, each clip 5 having a toothed inner surface 51; each chuck assembly 6 comprises three clips 5, an annular recess 63 is formed on the periphery surface of each chuck assembly 6, and a retention ring 64 placed in the annular recess 63.

(20) A peripheral surface of the chuck assembly 6 has a conical surface 61 matching with corresponding conical through hole 21; a clamping hole 62 is formed in the center of the chuck assembly 6 with the toothed inner surface for receiving and clamping a steel strand 3, the steel strand 3 passes through a corresponding clamping hole 62; after the steel strands 3 are tensioned and then loosened, due to the retraction of steel strands 3, the steel strands 3 are clamped and locked tightly by the clamping hole 62 inside the chuck assembly; and meanwhile, also due to the retraction of the steel strands 3, the chuck assembly 6 retracts towards the small diameter of the conical through holes 21 so that the chuck assembly 6 is firmly fixed with the conical through hole 21. An outer surface of the chuck assembly 6 is flush with or is slightly lower than an outer surface of the plate 2.

(21) The plate 2 has a plurality of threaded holes 22 for connecting an anchor plate or a tension plate.

(22) The main rebars are all steel strands 3, and the steel strands 3 are fixed with the conical through holes 21 inside the plate 2 by the chuck assembly 6 constituted of clips 5. When the integral tensioning is performed, a mandrel jack is used to resist against a support plate, and then a screw stem is used for pulling the tension plate and the tension plate is pre-tensioned to a prescribed numerical value and locked by a locknut. This is a conventional tensioning method for a centrifugal pillar. By combining the integral tensioning method with single-steel-strand pre-tensioning method, when a single steel strand is pre-tensioned, a mandrel jack can be deposed to resist against the outer side surface of the chuck assembly 6, and the steel strand 3 is inserted through the clamping hole 62. The steel strand 3 is tensioned by the traction portion of the mandrel jack on the outside, and when the mandrel jack is removed, the steel strand 3 retracts back, and meanwhile the chuck assembly 6 is driven to move towards the small diameter of the conical transition holes 72, so that the chuck assembly 6 is firmly clamped inside the conical transition holes 72, accordingly, the steel strand 3 is further clamped and locked by the clamping hole 62 of the chuck assembly 6; then, the integral tensioning is performed; then, centrifugal shaping is performed, and the anchor plate and tension plate are removed after the shaping process to release the tension of the steel strand 3; and finally, the steel strand 3 exposed from the plate 2 is cut and polished. The manufactured centrifugal concrete pillar, without an anchor portion exposed from the end portion, is a practical and feasible centrifugal concrete pillar having steel strands. In addition, the centrifugal concrete pillar is simple and reasonable in the way of connecting and locking the steel strands, convenient in operation and low in cost, so that it is possible to use steel strands in the centrifugal concrete pillar and this have practical value in industrial application. The anti-bending, anti-shearing, and anti-tensioning performance of the centrifugal concrete pillar have been greatly enhanced since steel strands with extremely excellent performance have been used in the centrifugal concrete pillar of the present invention.

(23) FIG. 5 to FIG. 10 show a pre-tensioned centrifugal concrete pillar according to the second embodiment of the present invention.

(24) In this embodiment the differences from the first embodiment is as below: two plates 2 are connected to an end of each steel strand 3 through a second clip-type connecting mechanism; a plurality of counter recesses 23 are provided on the plates 2; a transition element 7 matched with the counter recesses 23 in dimension is disposed inside each counter recess 23, the transition element has an annular stop shoulder 71 resting on the counter recess 23 and a conical transition through hole 72, the conical transition through hole has a diameter gradually increasing from the inside toward the outside of the plate 2 and a position of each conical transition through hole corresponds to each steel strand 3; and multiple clips 5 disposed inside each transition through hole 72, each clip 5 having a toothed inner surface 51; the multiple clips 5 are spliced together to form a chuck assembly 6 for clamping each steel strand 3, and a peripheral surface of the chuck assembly 6 has a conical surface 61 matching with corresponding conical transition through hole 72; a clamping hole 62 is formed in the center of the chuck assembly 6, the steel strand 3 passes through a corresponding clamping hole 62; after the steel strand 3 is tensioned and becomes loose, due to the retraction of the steel strand 3, the steel strand 3 is clamped and locked tightly by the clamping hole inside the chuck assembly; and also due to the retraction of the steel strand 3, the chuck assembly 6 is driven to move towards the small diameter of the conical transition through holes 72, so that the chuck assembly 6 is firmly clamped inside the conical transition through holes 72; and meanwhile, the transition element 7 is driven to move backward so that the annular stop shoulder 71 on the transition element 7 is tightly bonded to the big hole portion of the counter recess 23. The outer end surface of the chuck assembly 6 is flush with or is slightly lower than an outer surface of the plate.

(25) The main rebars are all steel strands 3, and the steel strands 3 are fixed with the conical transition through holes 72 inside the plate 2 by the chuck assembly 6 constituted of clips 5. When the integral tensioning is performed, a mandrel jack is used to resist against a support plate, and then a screw stem is used for pulling the tension plate, and the tension plate is pre-tensioned to a prescribed numerical value and locked by a locknut. This is a conventional tensioning method for a centrifugal pillar. By combining the integral tensioning method with single-steel-strand pre-tensioning method, when a single steel strand is pre-tensioned, a mandrel jack can be deposed to resist against the outer side surface of the chuck assembly 6, and the steel strand 3 is inserted through the clamping hole 62. The steel strand 3 is tensioned by the traction portion of the mandrel jack on the outside, and when the mandrel jack is removed, the steel strand 3 retracts back, and meanwhile the chuck assembly 6 is driven to move towards the small diameter of the conical transition holes 72, so that the chuck assembly 6 is firmly clamped inside the conical transition holes 72, accordingly, the steel strand 3 is further clamped and locked by the clamping hole 62 of the chuck assembly 6; and meanwhile, the transition element 7 is driven to move backward so that the annular stop shoulder 71 on the transition element 7 is tightly bonded to the big hole portion of the counter recess 23; then, the integral tensioning is performed; then, centrifugal shaping is performed, and the anchor plate and tension plate are removed after the shaping process to release the tension of the steel strand 3; and finally, the steel strand 3 exposed from the plate 2 is cut and polished. The manufactured centrifugal concrete pillar, without an anchor portion exposed from the end portion, is a practical and feasible centrifugal concrete pillar having steel strands. In addition, the centrifugal concrete pillar is simple and reasonable in the way of connecting and locking the steel strands, convenient in operation and low in cost, so that it is possible to use steel strands in the centrifugal concrete pillar and this have a practical value in industrial application. The anti-bending, anti-shearing, and anti-tensioning performance of the centrifugal concrete pillar have been greatly enhanced since steel strands with extremely excellent performance have been used in the centrifugal concrete pillar of the present invention.

(26) The centrifugal concrete pillar having steel strands provided by the present invention can be used as a pole body of a telegraph pole, as a ground support pole for a telecom base station and for a wind power generation system, and as a support for other ground construction projects. Such a pillar has a wide application range.

(27) FIG. 11 to FIG. 15 show a method for manufacturing the pre-tensioned centrifugal concrete pillar mentioned above, comprises the following steps:

(28) (1) cutting each steel strand 3 into a predetermined length;

(29) (2) manufacturing a steel cage;

(30) (3) inserting each end of each steel strand 3 into a clamping hole 62 of a chuck assembly 6 inside a conical through hole 21 on a plate 2, or inside a conical transition through hole 72 of a transition element 7 on a corresponding plate 2

(31) (4) mounting an anchor plate 8 on an outside of a first of two plates 2 through bolts 14, and mounting a tension plate 10 on an outside of a second of the two plate 2 through bolts, then, putting the steel cage into a lower half-die 9a with a tension plate 10 located in a die cavity of the lower half-die 9a and attaching the anchor plate 8 to an outside surface of one end of the lower half-die 9a;

(32) (5) pouring concrete into the lower half-die 9a, and putting an upper half-die 9b onto the lower half-die 9a;

(33) (6) stretching the steel cage by pulling the tension plate 10 at one end until the steel strand 3 are tensioned to a prescribed numerical value; at the same time, retracting the chuck assemblies 6 towards a small diameter of the conical through holes 21 or the conical transition through hole 72 to make each chuck assembly 6 firmly positioned inside the corresponding conical through hole 21 or the corresponding conical transition through hole 72, and clamping and locking the end of each steel strand 3 inside the clamping hole;

(34) (7) shaping through rotating by means of centrifugal force;

(35) (8) curing through steaming; and

(36) (9) removing the dies, and disconnecting the tension plate 10 and the anchor plate 8 from the corresponding plate 2 to release the tension.

(37) A support plate 11, a screw stem 12 and a locknut 13 should be used in Step 6, the support plate 11 is attached to an outside surface of the other end of the die; the tension plate 8 has a counter recesses 81, and the screw stem portion of the screw stem 12 passes through the counter recess 81 and then passes through the support plate 11; and the head of the screw stem 12 is located inside the big hole portion of the counter recess 101 on the tension plate 10; the locknut 13 is coupled to the screw stem portion of the screw stem 12 and is located out of the support plate 11; and then, the screw stem 12 is pulled to pull the tension plate 8, the plate 2 and the steel strands 3, until each steel strand 3 is locked by the locknut 13 after being tensioned to a prescribed numerical value.

(38) Preferably, a pre-tensioning step for pre-tensioning each steel strand can be added between the step 6 and the step 5, and the pre-tensioning step is an optional step, and the pre-tensioning step comprises: inserting each steel strand 3 through one of the plurality of counter bores 81 on the anchor plate; disposing a head portion of a mandrel jack 15 against the outer side surface of the chuck assembly 6, and inserting the steel strand 3 through the head portion of the mandrel jack 15, and then connecting the steel strand 3 to a traction portion of the mandrel jack 15; the traction portion of the mandrel jack 15 is not shown in the drawings, and this is the conventional structure of a mandrel jack; the steel strand 3 is withdrawn and pre-tensioned to a prescribed numerical value by the traction portion of the mandrel jack 15 so that the steel strand 3 is elongated; then, the mandrel jack 15 is removed, the steel strand 3 retracts back due to own retracting force after being elongated, and meanwhile the chuck assembly 6 is driven to move towards the small diameter of the conical through holes 21 or the conical transition holes 72, so that the chuck assembly 6 is firmly clamped inside the conical through holes 21 or the conical transition holes 72, accordingly, the steel strand 3 is further clamped and locked by the clamping hole 62 of the chuck assembly 6; a Step 10 is added after Step 9, in which the end of each steel strand 3 exposed outside of the plate 2 is cut and polished to make each steel strand 3 not exposed outside of the plate 2.