CN117248452A - Construction method of epoxy steel strand stay cable of large-span cable-stayed bridge - Google Patents

Abstract

The invention relates to a construction method of an epoxy steel strand stay cable of a large-span cable-stayed bridge, and belongs to the field of bridge cable construction. In the method, when a single cable is hung, a steel strand is led upwards from a bridge deck (or an upper cross beam), passes through a tensioning end anchor in a tower after passing through a tower top tower cable penetrating machine, passes through a main beam fixed end anchor from an HDPE pipe downwards, respectively tightens clamping pieces at two ends of the tower beam, and then installs a single tensioning jack for tensioning and pre-tightening, and the next cycle is continued after tensioning. And (3) installing the cable tensioning devices one by one in sequence from the outer side to the inner side, and tensioning the cable by adopting an equivalent tensioning method until the cable hanging work of the stay cable is completed. Greatly improves the construction efficiency and accuracy, ensures the installation accuracy, the installation quality and the installation speed of the stay cable, and achieves good economic and social benefits.

Description

Construction method of epoxy steel strand stay cable of large-span cable-stayed bridge

Technical Field

The invention relates to the field of bridge engineering, in particular to a construction method of a stay cable of a cable-stayed bridge.

Background

The steel strand inhaul cable is a cable structure commonly used in modern cable stayed bridge inhaul cables, and is widely applied in European and Japanese countries. The steel strand inhaul cable has the following maximum advantages: the installation and tensioning process of the stay cable is simple, the construction is convenient, the whole stay cable can be transported in a stranding way, and the transportation of water and land is not limited; in the construction process of the steel strand stay cable, a winch is mostly adopted for circulating rope threading, single tensioning and integral rope adjusting. The bridge steel strand inhaul cable technology has the advantage of replacing a single steel strand in the process of continuous development. Because of the obvious advantages, the steel strand inhaul cable is widely applied to the construction of domestic large-span cable-stayed bridges.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a construction method of stay cables of a cable-stayed bridge aiming at the prior art, a tower top support is built, a winch and a high tower cable threading machine are installed on the tower top support, continuous threading of stranded wires is carried out, the stranded wires pass through (HDPE) outer sleeves from top to bottom after being led up, clamping pieces are respectively tightened at two ends of the tower beam, all stranded wires of each stay cable are tensioned by adopting an equivalent tensioning method (one), whole bundle tensioning (two) is carried out after the single tensioning is finished, and the next cycle is continued after the tensioning is finished. The stay cables are installed one by one from the outside to the inside according to the sequence from top to bottom until the hanging operation of all the stay cables is completed.

The construction method for hanging the stay cable greatly improves the construction efficiency and accuracy, ensures the installation accuracy, the installation quality and the installation speed of the stay cable, and aims to obtain good economic benefit and social benefit.

The technical scheme adopted by the invention is as follows: a construction method of an epoxy steel strand stay cable of a large-span cable-stayed bridge comprises the following steps of

Step one, construction preparation: the method comprises the steps of constructing a beam end platform, a tower outer platform, a tower inner platform and a tower top support, wherein a high tower rope penetrating machine and a winch are arranged on the tower top support, a traction steel wire rope is coiled on a winding drum of the high tower rope penetrating machine in advance, one end of the steel wire rope is placed down to a tower end anchor, the other end of the steel wire rope is placed down to a place where a steel strand below a tower is placed, and the steel wire rope is connected with a first lengthened steel strand;

step two, steel strand blanking:

after blanking of each steel strand is completed according to the blanking length, stripping sleeves at two ends of each steel strand to expose steel wires, connecting two adjacent steel strands subjected to blanking end to end, continuously coiling on a cable tray, and storing the whole coil of steel strands to a fixed position;

step three, (HDPE) outer sleeve splicing

Splicing the (HDPE) outer sleeve to the design length required by each stay cable, and connecting the (HDPE) outer sleeve with a waterproof cover into a whole;

fourth, anchor installation

After the anchors at the two ends of the tower beam are assembled and checked to be correct, temporarily fixing the anchors on an anchor backing plate;

step five, installing a porous reaction frame

The porous reaction frame comprises a bearing plate, a support column and a support plate, wherein the bearing plate is supported on the support plate through the support column, the porous reaction frame is installed at the tail part of the anchor plate of the tower end anchor, the support plate is connected with the anchor plate, the bearing plate is opposite to the anchor plate at intervals, and the installation of the porous reaction frame and the anchor plate is adjusted to enable the hole site arrangement on the bearing plate to be consistent with the hole site arrangement of the anchor plate;

step six, (HDPE) outer sleeve hoisting

Before threading, hoisting an (HDPE) outer sleeve pipe to a tower end embedded pipe in advance, and temporarily fixing two ends of the (HDPE) outer sleeve pipe with a tower and a beam respectively, wherein in the process, a threading machine is started until two ends of a first lengthened steel strand are respectively pulled into a tower end anchor and a beam end anchor and fixed, the lengthened steel strand passes through the (HDPE) outer sleeve pipe, and the (HDPE) outer sleeve pipe supported on the lengthened steel strand is pulled and straightened by tensioning the lengthened steel strand;

step seven, rope threading and tensioning of single steel strand

7.1 Single lashing of high tower lashing machine

Placing the steel strands coiled in the second step on a tower lowering rope disc, pulling a first steel strand, rotating the rope disc to pull the steel strands to the top of a tower by using a high tower rope penetrating machine, sequentially penetrating the steel strands from the top of the tower to the inner cavity of the tower, an anchor at the tower end, a pre-buried pipe in the tower, an outer sleeve (HDPE) outside the tower and a beam surface by using the self weight of the steel strands, connecting the front steel strand and the rear steel strand end to realize continuous rope penetrating, disconnecting the front steel strand and the rear steel strand end to end at the tower end after the front steel strand is placed at the beam end to anchor in the anchor at the beam end, tensioning the front steel strand, and then lowering the penetrating rope from the anchor in the tower after the front steel strand is tensioned;

7.2 Single Steel strand tensioning

Tensioning the steel strands one by one, calculating the (tensile force) force value of each steel strand by using an electric algorithm according to more than 90% of the tensile force, taking the rest tensile force as a cable force average, checking the cable force uniformity of each steel strand after tensioning all the steel strands of each stay cable one by one, and carrying out cable force adjustment according to the rest tensile force to ensure that the tensile force of all the steel strands is average;

repeating the step 7.1 and the step 7.2 to complete the threading and tensioning of all the steel strands of one stay cable;

step eight, secondary tensioning

After the single stretching of all the steel strands of one stay cable in the step seven is completed, stretching the whole bundle of steel strands of the stay cable, stretching in a grading manner until reaching 100%, and protecting the steel strands exposed at the tower end and the beam end from exposure after stretching is completed;

step nine, clamping piece jacking

For low-stress anchoring of the stay cable, the cable force of a single steel strand is smaller than 0.4sigma after the cable force is adjusted to ensure the anchoring reliability _con The clamping piece is jacked by a jacking jack.

As a preferred operation of the above-described process: in the first step, one end of the traction steel wire rope is lowered from a manhole at the top of the tower to an anchor at the end of the tower (the path of the traction steel wire rope is consistent with that of a rope penetrating path), and the other end of the traction steel wire rope is lowered from a penetrating pipe which is pre-installed outside the tower wall to a place where a steel wire strand below the tower is placed, and is connected with a first lengthened steel wire strand. When the steel strand is pulled, the steel strand rises to the high tower rope penetrating machine through the penetrating pipe (PE pipe, the purpose is to protect the stranded wire, and damage caused by friction in the pulling process is avoided).

As a preferred operation of the above-described process: in the second step, steel strand discharging is carried out on the pay-off rack, the steel strands are supported by rollers, the central wire is upset after the sleeves are peeled at the two ends of each steel strand, the steel strands after two adjacent discharging are connected end to end by adopting wire binding, until the cable tray is full, and the whole coil of steel strand is protected during storage.

As a preferred operation of the above-described process: in the fourth step, the tower end anchor comprises an anchor plate, a supporting cylinder, a nut and a tensioning end sealing cylinder, wherein the anchor plate is positioned at the tail end of the supporting cylinder, the nut is screwed outside the supporting cylinder, the supporting cylinder is supported on an anchor backing plate, and the nut is tightly attached to the anchor backing plate; the beam end anchorage comprises an anchor plate, a fixed end sealing cylinder and a backing ring, the backing ring is positioned at the tail part of the fixed end sealing cylinder and welded with the fixed end sealing cylinder into a whole, a water draining groove is arranged on one side of the backing ring, which is close to the anchor backing plate, the water draining groove is positioned below the backing ring, and the side surface of the backing ring, where the water draining groove is positioned, is tightly attached to the anchor backing plate; before the construction of the hanging rope, the anchor is fixed on the anchor plate in advance, and after the nut or the backing ring is tightly attached to the anchor backing plate, the anchor is temporarily fixed on the anchor backing plate.

As a preferred operation of the above-described process: step six, the (HDPE) outer sleeve pipe passes through the extension pipe and extends out for a certain length; clamping the front end and the rear end of the extension pipe by using temporary hoops; the HDPE outer sleeve is erected by the roller frame and the sleeper, so that the HDPE outer sleeve is prevented from being damaged when moving; lifting (HDPE) outer sleeves by adopting a tower crane, lifting (HDPE) outer sleeves to a bridge deck in advance through the tower crane, then hanging the outer sleeves on a lifting point outside the tower after the outer sleeves are converted by using a chain block, respectively pulling lengthened steel strands into an anchor in the tower and an anchor at a beam end, installing clamping pieces in anchor holes of the anchor to fix the lengthened steel strands, and stretching the lengthened steel strands to straighten the outer sleeves so as to support (HDPE).

As a preferred operation of the above-described process: in step 7.1, the steel strand passes through the pipe orifice embedded in the tower, and then enters the cable guide pipe through the tower end anchor by using the guide pipe (the guide pipe is used as a guide pipe between the anchor hole on the porous reaction frame bearing plate and the anchor hole on the tower end anchor plate), the electric hanging basket is adopted at the outlet of the tower outer cable guide pipe to be used as a construction platform for carrying out manual auxiliary penetration into the HDPE outer sleeve, and the steel strand is penetrated into the beam end anchor by using the traction rope when reaching the beam end anchor.

As a preferred operation of the above-described process: in step 7.1, wrapping the pipe orifice of the beam end cable guide pipe and the port of the waterproof cover at the end part of the (HDPE) outer sleeve pipe by using a hose in the process of threading the steel strands (namely wrapping the pipe orifice through which the strands pass in the process of threading the steel strands so as to prevent scratch); and meanwhile, when the number of the steel strands for threading is half, binding the steel strands for threading into bundles, and wrapping the ends of the steel strands which are being threaded into bundles, so as to prevent the steel strands from crossing in the threading process.

As a preferred operation of the above-described process: in step 7.1, in the process of lowering the steel strands, calculating the lowering length of the steel strands by arranging a metering device so as to control the start and stop of the high tower rope threading machine, fixedly arranging a metering inductor on a support of the high tower rope threading machine, arranging a plurality of induction points on the circumference of a winding drum of the high tower rope threading machine for paying off, and periodically inducing the metering inductor in the circumferential travel of the winding drum in the process of paying off the steel strands by the plurality of induction points, wherein the metering inductor is connected with a control cabinet, so that the paying-off length is calculated, and constructors control the speed and start and stop of the high tower rope threading machine according to the paying-off length.

As a preferred operation of the above-described process: in step 7.2, in order to monitor the cable force change of the steel strands when the steel strands are tensioned one by one and verify the tensioning precision, a sensor is arranged during construction to monitor the cable force change of the first steel strand in the subsequent tensioning process of the steel strands, the reading of the sensor arranged on the first steel strand is recorded, and the synchronous and electrically calculated tensioning calculation value is compared, so that double control of calculation and actual tensioning process is realized;

and (3) checking the uniformity of the cable force, after the single tension of all the steel strands of one stay cable is completed, selecting a plurality of steel strands at different positions in the same bundle of cables, performing pulling test by using a jack, acquiring an oil pressure value corresponding to the cable force, and if the force value exceeds an error range, performing cable force averaging on each strand according to the residual tension value.

As a preferred operation of the above-described process: in step seven, in step 7.2, the tensioning of the single steel strand is performed at the tower end, and the steps are as follows:

a. penetrating a jacking rod through the steel stranded wire and the porous reaction frame, and sleeving a jacking sleeve on the jacking rod;

b. the single-hole jack passes through the steel strand and is propped against the jacking sleeve, so that the head groove of the piston of the jack is fully embedded on the jacking sleeve, namely, the initial state is in place;

c. starting an oil pump, calculating the force value of each steel strand by using an electric algorithm according to 90% of the tensile force, and tensioning the steel strands, wherein the residual tensile force of 10% is used as the cable force average;

d. when the tension reaches the given tension, stabilizing the oil pressure to stop tensioning, observing a jack ruler or measuring the piston stroke by using a steel ruler, and recording the value;

e. according to the recorded data, calculating the elongation of the steel strand, comparing the elongation with a theoretical value, and judging whether the allowable deviation is met, if the allowable deviation is within the deviation range, continuing to construct; otherwise, stopping tensioning and checking the reason;

f. meanwhile, whether the cable force value on the sensor accords with the tension force or not is observed, the dispersion degree of the cable force of a single stranded wire is within a range of +/-2%, if the cable force exceeds the designed allowable range, the cable force is required to be tensioned evenly according to the rest 10% force value until the display reading of the sensor is within the allowable range of the design value when the last steel stranded wire is tensioned, and therefore the whole bundle of cable force error is ensured to be within a range of +/-5%;

g. after all the strands are tensioned, removing the single Kong Mao and the sensor on the first steel strand, installing a working clamping piece, and re-tensioning by using a single-hole jack to ensure that the tensioning and anchoring force of the first steel strand is consistent with the display reading of the last steel strand.

Compared with the prior art, the invention has the advantages that:

the construction method for installing the epoxy steel strand stay cable of the large-span cable-stayed bridge has the following characteristics:

1. the top of the cable-stayed bridge cable is provided with a tower top support, a high tower cable penetrating machine is arranged on the tower top support, traction power is provided by the high tower cable penetrating machine, single steel strands are drawn to the tower top from the lower part of the tower, the single steel strands pass through a wire dividing wheel set of the high tower cable penetrating machine, and the steel strands penetrate to the bridge deck from the lower part of the HDPE outer sleeve by the dead weight of the steel strands, so that the cable penetrating process is completed.

2. For the cable-stayed bridge of the reinforced concrete composite beam, the bridge deck is not paved when the stay cable is installed, the interface of the arrangement of the bridge deck winch is needed to be considered when the traditional winch circularly wears the cable, and the cable-penetrating mode of the high-tower cable-penetrating machine is not needed to be considered for the bridge deck construction interface.

3. By utilizing the automatic rope threading device, the steel strand is threaded by adopting a high tower rope threading machine, the rope threading device is arranged in place at one time, the installation time is saved, and the rope hanging efficiency is greatly improved. The complexity of arranging a circulating rope threading system for each rope number when the traditional winch is used for threading ropes is avoided.

4. The rope is threaded by the high tower rope threading machine, the power of the rope threading machine and the steel stranded wires freely slide downwards along the HDPE outer sleeve under the action of dead weight, the rope threading speed is high, the rope threading work efficiency of the stay rope with the length of more than 100 meters is obvious, and the high tower rope threading machine is suitable for installation construction of the stay rope with a large span.

Drawings

FIG. 1 is a flow chart of a method according to an embodiment of the invention;

FIG. 2 is a schematic diagram of stay cable construction in an embodiment of the invention, wherein a tower top bracket 1, a tower penetrating machine 2, a steel strand 3, a pay-off rack 4, a steel anchor beam 5, a hanging basket 6, an HDPE outer sleeve 7, an upper cross beam 8, a main tower 9 and a main beam 10 are arranged;

FIG. 3 is a schematic view of a tower end anchor according to an embodiment of the present invention;

FIG. 4 is a schematic view of a beam-end anchor according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a porous reaction frame according to an embodiment of the present invention;

FIG. 6 is a flowchart of a single rope threading construction of a high tower rope threading machine in an embodiment of the invention;

FIG. 7 is a schematic drawing showing the tensioning of a single steel strand according to an embodiment of the present invention, wherein the drawing shows an 18 single jack, a 19 single anchor, and a 20 sensor;

FIG. 8 is a schematic diagram of a secondary tensioning (overall tensioning) in an embodiment of the invention, wherein a hollow pull rod 21, a pull rod nut 22, a reducing sleeve 23, a supporting foot 24 and a jack 25 are shown;

fig. 9 is a schematic view of clamping piece jacking, and 26 is a jacking jack according to an embodiment of the invention.

Detailed Description

The present invention is described in further detail below with reference to the accompanying drawings, which are exemplary and intended to be illustrative of the invention and not to be construed as limiting the invention. The text description in the embodiment corresponds to the drawings, the description related to the orientation is also based on the drawings, and the description is not to be construed as limiting the protection scope of the invention.

The embodiment relates to a hanging rope construction method of an epoxy steel strand stayed cable of a large-span cable-stayed bridge, a construction process flow and operation points.

1 construction process flow

Preparation of construction, blanking of steel strands, welding of HDPE (high-density polyethylene) pipes, installation of a high-tower rope threading machine in place, installation of an anchor, hoisting of the HDPE pipes, single rope threading and tensioning (equivalent tensioning method), two-piece tensioning, clamping piece jacking, temporary protection, full-bridge closure, rope adjusting, installation of accessory components and protection of a stay rope.

2 key points of operation

2.1 preparation for construction

The construction preparation work mainly comprises: equipment preparation, personnel preparation, construction platform and construction channel erection.

(1) Beam end platform: the movable independent platform is formed by welding angle steel and steel pipes, and the operation platform is paved by steel springboards.

(2) Outer platform of tower: a vertical lifting type electric hanging basket is adopted.

(3) Platform in tower: the main tower stay cable is anchored on the steel anchor beam, and the platforms can be erected on the two sides of the steel anchor beam by using steel springboards.

(4) The tower top support 1 mainly provides high-altitude hanging points for lifting of a platform outside the tower and material transportation of equipment in the tower, and mainly comprises an embedded part and a steel support, wherein the steel support is of a portal structure consisting of a main longitudinal beam, a cross beam and an inclined strut, and a tower top channel is formed by erecting a single-layer Bailey sheet and a pattern steel plate.

2.2 steel strand discharging

Calculating the blanking length of each cable number according to a blanking length formula, and compiling a blanking length table, wherein the following should be noted during blanking:

(1) after the blanking of each steel strand is completed according to the blanking length, the sleeve is peeled at the two ends of each steel strand strictly according to the sleeve peeling length set by a field technician, and the center wire is upset by using an upsetter.

(2) The steel strand wires unloading is gone on pay off rack (plastic gyro wheel), and the steel strand wires that two adjacent unloading completed adopt wire ligature end to end, coil on the cable tray until the cable tray is full down, and the whole steel strand wires of utilization scene hoisting equipment are deposited to fixed position to cover the raincloth, prevent surface pollution.

2.3 welding of HDPE outer sleeve

And selecting a proper welding area on site, welding the HDPE pipe with the length of 11m to a required length by using a thermal fusion welding machine, welding the HDPE length of each cable number according to the length calculated by a technician, and finally connecting the HDPE outer sleeve with the waterproof cover into a whole through the HDPE connecting sleeve. The strength of the joint position after welding must be higher than that of the base material, and defects such as voids and depressions are not allowed to occur.

2.4 high tower lasso in place

After the tower top steel bracket is installed, installing a high tower rope penetrating machine and a lifting winch in the tower in place, pre-coiling a traction steel wire rope on a winding drum of the high tower rope penetrating machine, wherein one end of the steel wire rope is lowered from a manhole at the tower top to an anchor at the tower end, and the other end of the steel wire rope is lowered from the inside of a penetrating pipe pre-installed outside the tower wall to a steel strand placement position on the girder surface and is connected with a first lengthened steel strand; the function of the penetrating pipe is to prevent the steel strand from rubbing with the tower column.

2.6 Anchor mounting

After the anchors at the two ends of the tower beam are assembled and checked, the anchors are pre-fixed on the anchor backing plate before the hanging rope construction. And after the nuts or the backing rings are tightly attached to the anchor backing plates, temporarily fixing the anchor on the anchor backing plates. The structure of the tower end anchor is shown in fig. 3, the structure of the beam end anchor is shown in fig. 4, the tower end anchor comprises an anchor plate 11, a supporting cylinder 12, a nut 13 and a tensioning end sealing cylinder 14, the anchor plate 11 is positioned at the tail end of the supporting cylinder 12, the nut 13 is screwed outside the supporting cylinder 12, the supporting cylinder 12 is supported on an anchor backing plate 15, and the nut 13 is tightly attached to the anchor backing plate 15; the beam end anchorage comprises an anchor plate 11, a fixed end sealing cylinder 16, a backing ring 17 and an anchor backing plate 15, wherein the backing ring 17 is positioned at the tail part of the fixed end sealing cylinder 16 and welded with the fixed end sealing cylinder 16 into a whole, one side of the backing ring 17 is provided with a water draining groove, the water draining groove is positioned below the backing ring 17, and the side face of the backing ring 17 where the water draining groove is positioned is tightly attached to the anchor backing plate 15.

(1) When the anchors are installed, the anchor holes of the cable-stayed tower beams are ensured to correspond one by one, and the steel strands are not twisted and twisted after being reeled;

(2) the fixed end (beam end) is provided with a water draining groove on one side of the anchor backing ring 17, the water draining groove is arranged under the backing ring when the anchor backing ring is installed, and one surface of the backing ring with the water draining groove is tightly attached to the anchor backing plate so as to enable water to drain.

(3) When the nut is installed, the screwing length of the nut on the anchor plate is controlled so as to facilitate the requirement of integral cable adjustment in the future;

2.7 Single hole tensioning reaction frame installation

The porous reaction frame 100 is installed on the tower end anchor, the porous reaction frame supporting plate is well connected with the anchor plate of the tower end anchor, and the hole site arrangement of the bearing plate is adjusted to be consistent with the hole site arrangement of the anchor plate.

The porous reaction frame 100 is divided into a plurality of types according to the specifications of the anchorage device, has the same total height, and is respectively composed of a bearing plate 101, a support column 102 and a support plate 103 from top to bottom, and plays roles of dispersing steel strands and supporting tensioning reaction force in the single tensioning process.

2.8HDPE outer sleeve hoisting

Before rope threading, the HDPE outer sleeve pipe is required to be hung to the embedded pipe of the main tower in advance, and two ends of the HDPE outer sleeve pipe are respectively and temporarily fixed with the main tower and the main girder.

(1) Passing the HDPE outer sleeve through the extension pipe and extending out for a certain length; clamping the front end and the rear end of the extension pipe by using temporary hoops; the HDPE protective sleeve is erected by the roller frame and the sleeper, so that the HDPE protective sleeve is prevented from being damaged during moving;

(2) and hoisting the HDPE outer sleeve by adopting a tower crane. The HDPE outer sleeve is hoisted to the bridge deck in advance through the tower crane, and then is hung on a hoisting point (the position of the next section of cable guide pipe) outside the tower after being converted by the chain block. And respectively pulling the lengthened steel strands into the anchor in the tower and the anchor at the beam end by utilizing a rope penetrating machine, and installing and clamping the steel strands. Stretching the lengthened steel strand to straighten the HDPE sheath pipe supported on the lengthened steel strand.

2.9 Single steel strand pulling and tensioning

2.9.1 Single lashing of high tower lashing machine

The method comprises the steps of placing processed steel strands on a rope placing disc on a girder surface, pulling a first steel strand, rotating the rope placing disc to pull the steel strands to the top of a tower from the inside of a penetrating pipe outside the tower wall by utilizing rope penetrating power, enabling single steel strands to pass through a wire dividing wheel set of a high tower rope penetrating machine, sequentially penetrating ropes from the top of the tower to the inner cavity of the tower, an anchor device of the tower end, an embedded pipe in the tower, an HDPE pipe outside the tower to the girder surface by utilizing the self weight of the steel strands, connecting the front steel strand and the rear steel strand end to end, and completing the installation of the whole bundle of steel strands, wherein the steel strand connection is realized by locking a pier head part through a connector. In order to prevent the connector from bending, damaging and falling off when bypassing the wire dividing wheel and the roller of the high tower rope penetrating machine, a section of protecting pipe is sleeved at the joint of the upsets, and the two ends of the protecting pipe are wound by adhesive tape paper, so that the protection effect is realized, and the connector more conveniently penetrates through the wire dividing wheel and the roller of the high tower rope penetrating machine.

When the steel stranded wires pass through the pre-buried pipe orifice in the tower, the steel stranded wires enter the cableway pipe through the anchor device by using the guide pipe, the outlet of the cable guide pipe outside the tower adopts the electric hanging basket as a construction platform to manually assist in penetrating into the HDPE pipe, and when the steel stranded wires reach the pipe orifice (anchor device) of the cable guide pipe at the beam end, the steel stranded wires are penetrated out of the anchor device at the beam end by using the traction rope.

In order to prevent damage caused by the forward or backward movement of the steel strands, the pipe orifice of the beam end cable guide pipe and the waterproof cover opening are wrapped by a hose; and meanwhile, when the number of the reeving wires is half, the reeved steel strands are tightly bound, and the end heads of the reeving steel strands are provided with guide heads, so that the crossing in the reeving process is prevented.

The length of a single stay cable steel strand is longer, the cable threading is continuously carried out by adopting a high tower cable threading machine, and the head and the tail of each well-blanked steel strand are connected together in the blanking process so as to realize continuous traction cable threading of the steel strands. In the construction process, the distance between the anchor points of the tower beam is large, constructors control the start and stop of the high tower rope penetrating machine at the top of the tower, when the stranded wires reach the beam end, the start and stop key is required to be controlled at any time, the length of the stranded wires is judged by arranging the metering device, and the constructors can conveniently control the speed of the rope penetrating machine and start and stop.

The method comprises the steps that a meter sensor is arranged on a support of a high tower rope threading machine, 8 sensing points are arranged on the circumferential plane of a winding drum and the positions of the sensor, the sensor is connected into a rope threading machine control cabinet, and the rope threading length is output through a meter display screen on the control cabinet. The length of each record is 1/8 of the circumference of the winding drum, the circumference of the winding drum is 5m, the length of each sensor senses 1 time and is 0.625 m, and constructors can judge specific lengths through numerical values on a display screen.

2.9.2 calculating the Single Steel strand tensile force

1. Construction control conditions

In order to ensure that the stress of each steel strand in a single-strand inhaul cable meets the design requirement, the cable force error between the single steel strands in each stayed cable in construction is not more than +/-2%, the process is strictly controlled during tensioning, and the calculation of the single tensile force requires the following calculation basis:

(1) The stay cable is provided with a control tension force based on a monitoring instruction;

(2) Under the action of the tension force of the stay cable installation control, the relative displacement (or deformation) of the stay cable anchoring point is calculated, namely the vertical displacement of the lower end anchoring point and the horizontal displacement of the upper anchoring point in the vertical plane of the cable are temporarily given by a monitoring unit;

(3) The relevant physical parameters of the corresponding section of the girder are generally determined according to design;

(4) Stay cable body geometry and physical parameters.

2. Single equivalent tensioning calculation principle

In the bridge structure model, the 1 st steel strand is stretched to a preset load, so that a new balance state is formed between the bridge deck and the connected components, the bridge structure is deformed corresponding to the applied force, and the sagging of the steel strand and the HDPE outer sleeve is reduced. When the 2 nd steel strand is tensioned, the following conditions mainly occur: due to the increase of the cable force, the structural deformation of the tower beam is increased, so that the cable force on the 1 st steel strand is reduced. Because of the influence of the stretch-draw sequence of the steel strands, when the steel strands are installed and stretched, the stretch-draw force of the 1 st steel strand is the largest, and the stretch-draw force of other steel strands is gradually reduced along with the installation of more steel strands. For example, when the first root is tensioned, and when the second root starts to be tensioned, the first root is lowered when the second root loads the cable force, the cable forces of the first root and the second root must have the same point, and the value when the cable forces are equal can be recorded by combining the reading of the sensor with the reading of the oil pump.

2.9.3 tensioning of individual Steel strands

(1) Stretch monitoring

In order to monitor the change of the cable force and verify the stretching precision, a sensor is installed during construction. And recording the reading of the sensor arranged on the first steel strand by a special person, and comparing the reading with the electrically calculated stretch-draw calculation value synchronously to realize double control of calculation and actual stretch-draw process.

For the test of cable force uniformity, after one of all the steel strands of one stay cable is completed, 5 steel strands at different positions in the same bundle of cable are selected, a jack is used for drawing test, and oil pressure values on a precise oil pressure gauge are used for comparison. If the reading values are different, each stranded wire is subjected to cable force averaging according to 10% of the residual tension value.

When hanging the cable, install monitoring sensor on first steel strand, the installation order is: spacer-sensor-single hole tool anchor.

(2) A single tensioning operation, as shown in figure 7,

a. the oil pipes of the oil pump and the jack are connected, whether the precision pressure gauge is consistent with the jack is checked, and before tensioning, the precision pressure gauge can move for two strokes under the condition of no load, so that the jack is ensured to have no problem during tensioning;

b. the integral reaction frame passes through the steel stranded wire and is arranged on an anchorage device;

c. penetrating a jacking rod through the steel stranded wire and the counter-force frame, and sleeving a jacking sleeve on the jacking rod;

d. the single-hole jack penetrates through the steel stranded wire and is propped against the jacking sleeve, so that the head groove of the piston of the jack is fully embedded in the jacking sleeve;

e. starting an oil pump, calculating the force value of each steel strand by using an electric algorithm according to 90% of the tensile force, and tensioning the rest 10% serving as the cable force average;

f. when the tension reaches the given tension, stabilizing the oil pressure to stop tensioning, observing a jack scale or measuring the piston stroke by using a steel ruler, and recording the value on a table;

g. and according to the data recorded by the table, calculating the elongation of the steel strand and comparing the elongation with a theoretical value to see whether the deviation requirement allowed by the specification is met. If the deviation is within the deviation range, continuing to construct; otherwise, stopping tensioning and checking the reason;

h. and meanwhile, whether the cable force value on the sensor accords with the tensile force or not is observed, and the dispersion degree of the single cable force is within a range of +/-2%. If the cable force exceeds the designed allowable range, carrying out cable force average tensioning according to the residual 10% force value until the sensor display reading is within the allowable range of the design value when the cable force is tensioned to the last steel strand, so as to ensure that the whole cable force error is within +/-5%;

i. and removing the single Kong Maoban and the sensor, installing the working clamping piece, and re-tensioning by using a single-hole jack, wherein the tensioning anchoring force is consistent with the display reading of the last steel strand.

2.10 double tensioning, as shown in figure 8,

and carrying out second tensioning of the stay cable according to the main beam construction process and the monitoring instruction. And the whole tensioning tool is used for whole bundle tensioning, and the whole bundle tensioning is realized by adjusting nuts on the anchor. The hydraulic jack is carried out by a through jack, and is provided with a supporting foot 24, a jack 25, a reducing sleeve 23, a hollow pull rod 21 and a pull rod nut 22. In order to reduce the loss of prestress, the two stretching is performed by adopting a graded stretching method, and after 50% of the first stretching, 100% stretching is performed.

After the two steel strands are completed, the exposed steel strands at the ends of the tower and the beam are subjected to sealing treatment to serve as a temporary protection measure.

2.11 clamping sheet roof pressure

For low-stress anchoring of the stay cable, the cable force is adjusted to be smaller than 0.4sigma after the cable force is adjusted to ensure the anchoring reliability _con The clamping piece is jacked by a jacking jack, which is a prior art in the art, as shown in fig. 9.

2.12 Steel strand Length-keeping cutting

After the girder is closed, the cable force is adjusted according to the monitoring instruction, the steel stranded wires are cut off according to the reserved length after the completion, the reserved length of the steel stranded wires is matched with the length of the protective cover, the reserved length tail ends of the whole bundle of steel stranded wires are cut and flushed, each length is consistent, the reserved length of the whole bundle of steel stranded wires is ensured to be 5-20 mm shorter than the protective cover, and the steel stranded wires cannot be too short, so that the requirement of cable replacement in the future is met.

2.13 entering the subsequent procedures

After the epoxy steel strand stay cable is installed, the following working procedures of accessory component installation and corrosion prevention are carried out.

In addition to the above embodiments, the present invention also includes other embodiments, and all technical solutions that are formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims (10)

1. A construction method of an epoxy steel strand stay cable of a large-span cable-stayed bridge is characterized by comprising the following steps of: comprising

Step one, construction preparation: the method comprises the steps of constructing a beam end platform, a tower outer platform, a tower inner platform and a tower top support, wherein a high tower rope penetrating machine and a winch are arranged on the tower top support, a traction steel wire rope is coiled on a winding drum of the high tower rope penetrating machine in advance, one end of the steel wire rope is placed at an anchor in the tower, and the other end of the steel wire rope is connected with a first lengthened steel strand from the outer lower part of the tower to a place of the steel strand below the tower;

step two, steel strand blanking:

after blanking of each steel strand is completed according to the blanking length, stripping sleeves at two ends of each steel strand to expose steel wires, connecting two adjacent steel strands subjected to blanking end to end, continuously coiling on a cable tray, and storing the whole coil of steel strands to a fixed position;

step three, splicing the outer sleeve

Splicing the outer sleeve to the design length required by each stay cable, and connecting the outer sleeve with the waterproof cover into a whole;

fourth, anchor installation

After the anchors at the two ends of the tower beam are assembled and checked to be correct, temporarily fixing the anchors on an anchor backing plate;

step five, installing a porous reaction frame

The porous reaction frame comprises a bearing plate, a support column and a support plate, wherein the bearing plate is supported on the support plate through the support column, the porous reaction frame is installed at the tail part of the anchor plate of the tower end anchor, the support plate is connected with the anchor plate, the bearing plate is opposite to the anchor plate at intervals, and the installation of the porous reaction frame and the anchor plate is adjusted to enable the hole site arrangement on the bearing plate to be consistent with the hole site arrangement of the anchor plate;

step six, hoisting the outer sleeve

Before threading, hoisting the outer sleeve pipe to the pre-buried pipe of the tower in advance, and temporarily fixing the two ends of the outer sleeve pipe with the tower and the beam respectively, wherein in the process, the lengthened steel strands are respectively pulled into the tower end anchor and the beam end anchor and fixed, the lengthened steel strands penetrate through the outer sleeve pipe, and the outer sleeve pipe supported on the lengthened steel strands is pulled to be straightened by tensioning the lengthened steel strands;

step seven, rope threading and tensioning of single steel strand

7.1 Single lashing of high tower lashing machine

Placing the steel strands coiled in the second step on an upper tower lowering rope plate, pulling a first steel strand, rotating the rope plate to pull the steel strands to the top of a tower by using a high tower rope penetrating machine, sequentially penetrating the single steel strand from the top of the tower to the inner cavity of the tower by using the self weight of the steel strands, anchoring the tower end, pre-buried pipes in the tower, outer sleeve pipes outside the tower and beam surfaces, connecting the front steel strand and the rear steel strand end to realize continuous rope penetrating, disconnecting the front steel strand and the rear steel strand at the tail end of the tower after the front steel strand is placed in the beam end anchor for anchoring, tensioning the front steel strand, and then lowering the penetrating rope from the tower anchor after the front steel strand is tensioned;

7.2 Single Steel strand tensioning

Tensioning the steel strands one by one, calculating the force value of each steel strand according to more than 90% of the tension force by using an electric algorithm, taking the rest tension force as a cable force average, checking the cable force uniformity of each steel strand after tensioning all the steel strands of each stay cable one by one, and carrying out cable force adjustment according to the rest tension force to ensure that the tension force of all the steel strands is average;

repeating the step 7.1 and the step 7.2 to complete the threading and tensioning of all the steel strands of one stay cable;

step eight, secondary tensioning

After the single stretching of all the steel strands of one stay cable in the step seven is completed, stretching the whole bundle of steel strands of the stay cable, stretching in a grading manner until reaching 100%, and protecting the steel strands exposed at the tower end and the beam end from exposure after stretching is completed;

step nine, clamping piece jacking

For low-stress anchoring of the stay cable, the cable force of a single steel strand is smaller than 0.4sigma after the cable force is adjusted to ensure the anchoring reliability _con The clamping piece is jacked by a jacking jack.

Step ten, cutting the steel strand with remained length

And after the girder is closed, the cable force is adjusted according to the monitoring instruction, and after the cable force is finished, the steel strand is cut off according to the reserved length, the reserved length of the steel strand is matched with the length of the protective cover, and the distance between the end part of the reserved length of the steel strand and the protective cover is 5-20 mm.

2. The method according to claim 1, characterized in that: in the first step, one end of the traction steel wire rope is lowered from a manhole at the top of the tower to an anchor in the tower, the other end of the traction steel wire rope penetrates through an upper cross beam or a bridge deck steel strand placement position from the inside of a penetrating pipe which is pre-installed outside the tower wall, and is connected with a first lengthened steel strand, and when the steel strand is pulled, the steel strand ascends to a high tower rope penetrating machine through the penetrating pipe.

3. The method according to claim 1, characterized in that: in the second step, steel strand discharging is carried out on the pay-off rack, the steel strands are supported by rollers, the center wire is upset after the sleeves are peeled at the two ends of each steel strand, wire binding is carried out at the position, close to the upset, of the center wire, the two adjacent steel strands are connected end to end by adopting a connector, and the whole coil of steel strand is protected during storage.

4. The method according to claim 1, characterized in that: in the fourth step, the tower end anchor comprises an anchor plate, a supporting cylinder, a nut and a tensioning end sealing cylinder, wherein the anchor plate is positioned at the tail end of the supporting cylinder, the nut is screwed outside the supporting cylinder, the supporting cylinder is supported on an anchor backing plate, and the nut is tightly attached to the anchor backing plate; the beam end anchorage comprises an anchor plate, a fixed end sealing cylinder, a backing ring and an anchor backing plate, wherein the backing ring is positioned at the tail part of the fixed end sealing cylinder and welded with the fixed end sealing cylinder into a whole, one side of the backing ring is provided with a water draining groove, the water draining groove is positioned below the backing ring, and the side face of the backing ring where the water draining groove is positioned is tightly attached to the anchor backing plate;

before the construction of the hanging rope, the anchor is fixed on the anchor plate in advance, and after the nut or the backing ring is tightly attached to the anchor backing plate, the anchor is temporarily fixed on the anchor backing plate.

5. The method according to claim 1, characterized in that: step six, the outer sleeve pipe penetrates through the extension pipe and extends out for a certain length; clamping the front end and the rear end of the extension pipe by using temporary hoops; the outer sleeve is erected by the roller frame and the sleeper, so that the outer sleeve is prevented from being damaged when moving; the outer sleeve is lifted by adopting a tower crane, the outer sleeve is lifted to a bridge deck in advance through the tower crane, then the outer sleeve is hung on a lifting point outside the tower after being converted by a chain block, the lengthened steel strands are respectively pulled into an anchor in the tower and an anchor at a beam end, and clamping pieces are arranged in anchor holes of the anchor to fix the lengthened steel strands, so that the lengthened steel strands are stretched to be straightened.

6. The method according to claim 1, characterized in that: in step 7.1, the steel strand enters the cable guide pipe through the tower end anchor by using the guide pipe when passing through the pre-buried pipe orifice in the tower, the electric hanging basket is adopted as a construction platform at the outlet of the cable guide pipe outside the tower to manually assist in penetrating the outer sleeve, and the traction rope is used for penetrating the steel strand into the beam end anchor when reaching the beam end anchor.

7. The method according to claim 1, characterized in that: step seven, in step 7.1, wrapping the pipe orifice of the beam end cable guide pipe and the port of the waterproof cover at the end part of the HDPE outer sleeve by using a hose in the process of threading the steel strands; and meanwhile, when the number of the steel strands for threading is half, binding the steel strands for threading into bundles, and wrapping the ends of the steel strands which are being threaded into bundles, so as to prevent the steel strands from crossing in the threading process.

8. The method according to claim 1, characterized in that: in step seven, in step 7.1,

in the process of lowering the steel strand, the lowering length of the steel strand is calculated by arranging a metering device so as to control the speed and start and stop of the high tower rope penetrating machine.

The method comprises the steps that a meter sensor is fixedly arranged on a support of a high tower rope threading machine, a plurality of sensing points are arranged on the circumference of a winding drum of the high tower rope threading machine for rope paying-off, in the process of winding drum rotation rope paying-off, the plurality of sensing points periodically sense with the meter sensor in the circumferential travel of the winding drum, the meter sensor is connected to a control cabinet, accordingly, the rope paying-off length is calculated, and constructors control the speed and start and stop of the high tower rope threading machine according to the rope paying-off length.

9. The method according to claim 1, characterized in that: in step 7.2, in order to monitor the cable force change of the steel strands when the steel strands are tensioned one by one and verify the tensioning precision, a sensor is arranged during construction to monitor the cable force change of the first steel strand in the subsequent tensioning process of the steel strands, the reading of the sensor arranged on the first steel strand is recorded, and the synchronous and electrically calculated tensioning calculation value is compared, so that double control of calculation and actual tensioning process is realized;

and (3) for checking the uniformity of the cable force, after the single tension of all the steel strands of one stay cable is completed, selecting a plurality of steel strands at different positions in the same bundle of cables, performing pulling test by using a jack, acquiring an oil pressure value corresponding to the cable force, and if the test value exceeds an error range, performing cable force averaging on each strand according to the residual tension value.

10. The method according to claim 1 or 9, characterized in that: in step seven, in step 7.2, the tensioning of the single steel strand is performed at the tower end, and the steps are as follows:

a. penetrating a jacking rod through the steel stranded wire and the porous reaction frame, and sleeving a jacking sleeve on the jacking rod;

b. the single-hole jack passes through the steel strand and is propped against the jacking sleeve, so that the head groove of the piston of the jack is fully embedded on the jacking sleeve, namely, the initial state is in place;

c. starting an oil pump, calculating the force value of each steel strand by using an electric algorithm according to 90% of the tensile force, and tensioning the steel strands, wherein the residual tensile force of 10% is used as the cable force average;

d. when the tension reaches the given tension, stabilizing the oil pressure to stop tensioning, observing a jack ruler or measuring the piston stroke by using a steel ruler, and recording the value;

e. according to the recorded data, calculating the elongation of the steel strand, comparing the elongation with a theoretical value, and judging whether the allowable deviation is met, if the allowable deviation is within the deviation range, continuing to construct; otherwise, stopping tensioning and checking the reason;

f. meanwhile, whether the cable force value on the sensor accords with the tension force or not is observed, the dispersion degree of the cable force of a single stranded wire is within a range of +/-2%, if the cable force exceeds the designed allowable range, the cable force is required to be tensioned evenly according to the rest 10% force value until the display reading of the sensor is within the allowable range of the design value when the last steel stranded wire is tensioned, and therefore the whole bundle of cable force error is ensured to be within a range of +/-1%;

g. after all the strands are tensioned, removing the single Kong Mao and the sensor on the first steel strand, installing a working clamping piece, and re-tensioning by using a single-hole jack to ensure that the tensioning and anchoring force of the first steel strand is consistent with the display reading of the last steel strand.