CN110184930B

CN110184930B - Construction method of stay cable of short-tower cable-stayed bridge

Info

Publication number: CN110184930B
Application number: CN201910443268.5A
Authority: CN
Inventors: 金平; 王昀; 秦涌汐; 匡建国; 周强生; 姚永峰; 陈军; 周珏
Original assignee: Jiangsu Fasten Steel Cable Co ltd; Fasten Group Co Ltd
Current assignee: Jiangsu Fasten Steel Cable Co ltd; Fasten Group Co Ltd
Priority date: 2019-05-27
Filing date: 2019-05-27
Publication date: 2021-11-02
Anticipated expiration: 2039-05-27
Also published as: CN110184930A

Abstract

The invention relates to a construction method of a stay cable of a short-tower cable-stayed bridge, which comprises the following steps of hoisting an outer sleeve: the anti-slide anchorage device end at the front end of the outer sleeve reaches the cable saddle at the tower end and is temporarily butted with the cable saddle inlet; and (3) stay cable steel strand reeving: the steel strand wires are paid off and threaded at the same time, penetrate through the outer sleeve from the left side of the tower, penetrate through the tower end wire-dividing tubular cable saddle, enter the outer sleeve on the right side and reach the right side beam end, and are respectively pretensioned; tensioning the steel strand: single steel strand is adopted for simultaneous stretching in the left and right directions, and a single-hole jack is adopted for symmetric stretching in a grading manner; and (3) antiseptic treatment: and respectively carrying out anti-corrosion treatment on the beam end anchorage and the tower end anti-sliding anchorage. The adoption of the wire separating tube and the anti-sliding anchor technology ensures the installation precision and the installation quality of the stay cable, and facilitates the maintenance and the normal cable replacement during the use of the stay cable.

Description

Construction method of stay cable of short-tower cable-stayed bridge

Technical Field

The invention belongs to the technical field of construction of stay cables of buildings and bridges, and particularly relates to a construction method of a stay cable of a short-tower cable-stayed bridge.

Background

A cable-stayed combined system bridge of a short-tower cable-stayed bridge between a cable-stayed bridge and an external prestressed box girder bridge has the characteristics of short tower, rigid girder and concentrated cable. The main beam of the short-tower cable-stayed bridge has higher rigidity and is a main bearing component, the stay cable has the functions of stiffening the beam and adjusting the stress, the proportion of the dead load cable force of the stay cable in the total cable force (dead load cable force and ten dead load cable force) is higher than that of the cable-stayed bridge, the stress amplitude of the stay cable is smaller, the fatigue problem is not obvious, and the construction cost is favorably reduced. Compared with a continuous beam, the short-tower cable-stayed bridge has the advantages of novel structure, large spanning capacity, simple construction, economy and the like; compared with a cable-stayed bridge, the cable-stayed bridge has the advantages of convenience in construction, material saving, high rigidity of the main beam and the like. Therefore, the short-tower cable-stayed bridge has wide development space.

With the development of bridge technology, the construction engineering of the short-tower cable-stayed bridge is more and more, and therefore, the construction method of the stay cable of the short-tower cable-stayed bridge needs to be continuously optimized and standardized, so that the installation precision and the installation quality of the stay cable are ensured, and the maintenance and the normal cable replacement during the use of the stay cable are facilitated.

Disclosure of Invention

The invention aims to solve the technical problem of providing a construction method of a stay cable of a short-tower cable-stayed bridge aiming at the prior art, so that the construction of the short-tower stay cable is more standard, the installation precision and quality are improved, and the maintenance of the stay cable in service period is realized later.

The technical scheme adopted by the invention for solving the problems is as follows: a construction method of a stay cable of a short-tower cable-stayed bridge mainly comprises the following steps

(1) Preparation before cable hanging: welding and lengthening an outer sleeve, blanking a steel strand, connecting the outer sleeve and accessories thereof with extension pipes, installing an anchorage device and a sensor, and preparing a beam surface and a tower end working platform;

(2) hoisting an outer sleeve: sleeving the front end of the outer sleeve into the extension pipe, connecting an anti-slip anchor at the front end of the extension pipe, hoisting the outer sleeve to enable the anti-slip anchor end to reach a cable saddle at the tower end and be temporarily butted with an inlet of the cable saddle, and hoisting the outer sleeve on the left side and the right side of the tower respectively;

(3) and (3) stay cable steel strand reeving: the steel strand wires are paid off and threaded at the same time, the steel strand wires penetrate into the outer sleeve from bottom to top from the left side of the tower to reach the left side anti-sliding anchorage device, correspondingly penetrate into the tower cable saddle wire dividing pipe until reaching the right side cable saddle opening, penetrate through the right side anti-sliding anchorage device to enter the right side outer sleeve pipe and downwards until reaching the right side beam end, and then the steel strand wires on the left side and the right side are respectively clamped into the anchorage devices of the embedded pipes and are pre-tensioned; repeating the above actions to complete the reeving of all the steel strands;

(4) tensioning the steel strand: the single steel strand is synchronously tensioned left and right, a single-hole jack graded symmetrical tensioning process is adopted, and the stay cable force of which is required to be adjusted is adjusted according to on-site monitored data in the stages of complete installation and closure of the full-bridge stay cable;

(5) installing accessories: after the stay cable is tensioned, bridge accessories are installed, and the accessories relate to: one or more of a stay cable clamp, an anti-slide anchorage sealing gasket, an extension pipe of an outer sleeve, a beam end shock absorber and a waterproof cover;

(6) and (3) antiseptic treatment: and respectively carrying out anti-corrosion treatment on the beam end anchorage and the tower end anti-sliding anchorage.

Specifically, in the step (1), the outer sleeve is an HDPE pipe, each section of the outer sleeve is lengthened to a required length by adopting a hot-melt welding mode, a correct cutting length is determined according to the operating temperature, for a longer outer sleeve, an extension pipe is prepared, the front end part of the outer sleeve extends into the extension pipe, the outer sleeve freely stretches and retracts in the extension pipe according to environmental factors, and the outer sleeve is ensured not to exceed the extension pipe all the time; the cutting length calculation of the outer sleeve needs to consider the influence factors of the waterproof cover, the connecting sleeve, the length of the outer sleeve entering the extension pipe and the temperature on the pipe length.

Specifically, the step (1) of blanking the steel strand refers to preparing the steel strand for each stay cable to be blanked before threading, and the steel strand is blanked according to the following operation mode

(1) The whole process of blanking the epoxy coating steel strand is carried out on a pay-off rack, a bracket is installed every 2-3 meters, and the bracket is used for ensuring that the environment-friendly steel strand is not in contact with the bridge floor so as to protect the steel strand from being damaged;

(2) stripping partial sheaths at the ends of the steel strands, cutting off steel wires outside the epoxy-coated steel strands at a position 40-80 mm away from the ends of the epoxy-coated steel strands, only leaving a central steel wire, polishing and chamfering outer-layer steel wires at the cut ends, upsetting the central steel wires by using an upsetting machine, wrapping the epoxy-coated steel strands at the cut parts by using an electric adhesive tape, and preventing sharp edges of the steel wires from abutting against an anchorage device when the steel strands penetrate into the anchorage device to influence smooth threading;

(3) after blanking, marks of 'head', 'tail' and 'cable number' are made at the end of the steel strand, and the anti-slip key is extruded at the corresponding position according to the design requirement.

Specifically, step (1) installation of anchorage device and sensor: the anchorage devices are arranged in the embedded pipes, the beam end anchor plates are provided with glue injection holes which are distributed up and down, the hole sites are ensured to be consistent with the hole sites of the cable saddle at the tower end when the anchorage devices are installed, the hole sites of the anchorage devices and the cable saddle are respectively numbered, and the consistency of the hole site numbers is ensured; the sensor is a full-bridge magnetic flux sensor and is fixed with the anchorage device.

When the outer sleeve is hoisted, the front end of the outer sleeve is stretched into the extension pipe, an anti-slide anchorage device is installed at the front end of the extension pipe, then cable hoops are installed in front of the anti-slide anchorage device and behind the extension pipe respectively, the anti-slide anchorage device and the extension pipe are fixed through hemp ropes by utilizing hoisting holes in lug plates of the cable hoops, and the outer sleeve is prepared to be hoisted; arranging a steering pulley on the tower column, and welding and fixing a lifting point for the outer sleeve; arranging an operator on the vertical working surface along the height direction of the tower column to assist the positioning of the outer sleeve; controlling the hoisting speed during hoisting, hoisting the outer sleeve in place, connecting a cable hoop at the front end of the anti-skid anchorage device with a wire-separating tubular cable saddle on the tower column at the position of the tower column cable saddle, ensuring the distance between the rear end of the outer sleeve and the embedded pipe at the rear end of the outer sleeve to be 1 +/-0.2 m, turning off hoisting equipment, and transmitting the load to a connecting steel wire rope for hoisting; for each outer sleeve, after the outer sleeves on the two sides of the tower are lifted and connected with a cable saddle at the tower end, the beam end also temporarily fixes the outer sleeves by using ropes, so that the HDPE outer sleeves can eliminate the verticality and form certain linearity, and the HDPE outer sleeves can be prevented from deflecting with the wind.

Step (3), the operation steps of penetrating the stay cable steel strand are as follows:

(1) paying off the steel strand by using a paying off rack, wherein the paying off speed is consistent with the cable penetrating speed;

(2) the steel strand is sent into the outer sleeve and passes through the left anti-slip anchorage device to reach a cable saddle opening at the tower end at the left side;

(3) according to the corresponding relation between the threading sequence and the hole site numbers, the steel strand is threaded into the corresponding cable saddle wire dividing pipe until the steel strand reaches the right cable saddle opening;

(4) continuously pushing the steel strand to enable the steel strand to penetrate through the right anti-sliding anchorage device until the steel strand reaches the pipe orifice of the embedded pipe at the right beam end; on the right side, a guide rod is led out from the inside of the anchorage device from the lower part of the beam and penetrates upwards until the guide rod extends out of the pipe orifice of the embedded pipe, a threading connector at the end part of the guide rod is connected with an upset head of a working steel strand, and the upset head part of the steel strand is clamped in the threading connector;

(5) continuously pushing the working steel strand, simultaneously drawing the draw bar downwards, penetrating the steel strand out of the anchorage device at the right beam end, removing the connection between the reeving connector and the steel strand, and installing and tightening the working clamping piece after reserving the designed working length to clamp the steel strand;

(6) the leading bar of the left anchorage device extends upwards out of the pipe orifice of the embedded pipe, the leading bar and the steel strand are connected through the reeving connector, and the working steel strand is pulled to penetrate out of the anchorage device at the beam end on the left side;

(7) drawing the steel strand out of an anchor outlet, removing the connection between the reeving connector and the steel strand, installing the clamping piece and tightening the clamping piece to clamp the steel strand;

(8) pre-tensioning by using a single-hole jack, and jacking and anchoring the current steel strand after tensioning;

(9) and repeating the rope penetrating and pre-tensioning steps, wherein the rope penetrating sequence of the steel strands generally starts from the uppermost row of holes of the anchorage device until the last row of holes, and the rope penetrating of the rest steel strands is completed until the stay ropes on each tower are completely installed.

Tensioning the steel strand: after each cable penetrating is finished, pre-tensioning is required to be immediately carried out to temporarily fix the cable penetrating device, a single-hole sensor is installed on a first tensioned steel strand, when other steel strands are tensioned, the cable force and the cable force dispersion of the single steel strand are detected by detecting the cable force index variable quantity on the sensor, and the tensioning operation steps are as follows

a. Connecting an oil pump and an oil pipe of the jack, checking whether the precision pressure gauge is consistent with the jack, and before tensioning, moving the two strokes under the condition of no load to ensure that the jack has no problem during tensioning;

b. penetrating the integral reaction frame through the steel strand and installing the integral reaction frame on an anchorage device;

c. the top pressure rod penetrates through the steel strand and the integral reaction frame, and the top pressure sleeve is sleeved on the top pressure rod;

d. the single-hole jack penetrates through the steel strand to be propped against the jacking sleeve, so that the grooves in the head of the jack piston are completely embedded in the jacking sleeve;

e. starting an oil pump, and stretching according to design cable force grading of initial tension force 10% → second stage 80% → 100%;

f. when the stretching force reaches the designed stretching force, stabilizing the oil pressure and stopping stretching, observing a staff gauge on the jack or measuring the piston stroke by using a steel ruler, and recording the value on a table;

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

h. meanwhile, observing whether the cable force value on the sensor is consistent with the tension force to ensure that the error of the whole cable force is within the range of +/-1 percent and the dispersion of the cable force of the single steel strand is within the range of +/-2 percent, if the dispersion exceeds the standard allowable range, carrying out cable force average tensioning until the reading displayed by the sensor is within the allowable range of the design value when the last steel strand is tensioned;

i. and (3) removing the single-hole anchor plate and the sensor, installing the working clamping piece, and re-tensioning by using a single-hole jack, wherein the tensioning and anchoring force is consistent with the display reading of the last epoxy coating steel strand.

And (6) corrosion prevention of the anti-sliding anchor at the tower end: foaming agent is adopted, the anti-slip anchorage and the connection gap thereof are completely foamed in the reserved hole channel of the anti-slip anchorage at the tower end, and epoxy mortar is poured in the anti-slip anchorage of the anti-slip anchorage. Corrosion prevention of the beam end anchorage device: pouring anti-corrosive grease into the embedded pipe where the beam-end anchorage device is located for protection, pouring the anti-corrosive grease into a special grouting machine, and pouring the grease into the embedded pipe through pressure injection of the grouting machine; cutting off the steel strand according to the reserved length of the steel strand after the cable force of the stay cable is adjusted, filling wax between the anti-loosening pressing plate and the anchor plate which are positioned on the rear side of the anchor plate, and then coating wax oil on the periphery of the exposed part of the strand, wherein the specific anti-corrosion construction steps are as follows;

(1) glue injection

Connecting an oil pump with a glue injection gun, putting polyurethane sealant into the glue injection gun, and connecting a glue injection bent pipe;

injecting polyurethane sealant into each anchorage device, and uniformly injecting the polyurethane sealant into the glue injection holes on the anchorage devices by using oil pressure of 2.5-3.0 MPa;

(2) package (I)

Winding a circle of kraft paper-plastic composite cloth around the anchor plate, and fixing the periphery of the anchor plate by using an adhesive tape;

winding the kraft paper-plastic composite cloth for one or more circles by using an adhesive tape behind the anti-loosening pressure plate, and checking whether the kraft paper-plastic composite cloth, the anchor plate and the edge of the anti-loosening pressure plate are completely wrapped or not after winding;

opening a hole at the top to fill wax;

(3) wax filling machine

Filling the wax oil in a barrel for primary dissolution, and then heating for melting;

liquid wax oil was slowly poured into the hole until it overflowed.

(4) Corrosion protection of exposed part of steel strand

Cotton cloth is wound at the front end of the steel strand wiping pipe, the steel strand wiping pipe with wax oil is used for wiping the epoxy coating steel strands behind the anti-loosening pressing plate once, and all the epoxy coating steel strands are guaranteed to be coated with the wax oil;

2) the protective cover made of cotton cloth is sleeved on the steel strand bundle, one side close to the anti-loosening pressing plate is tightly attached to the anti-loosening pressing plate, and the protective cover is firmly adhered to the box sealing adhesive tape.

3) And installing the protective cover of the anchorage device in place to finish the anticorrosion work.

Engineering quality assurance measures

(1) The stacking place of the steel strand is paved with sand stones, the epoxy coating steel strand steel disc is placed on a sleeper after entering the field, and rain-proof and leakage-proof measures are made.

(2) The steel strand tensioning adopts double control measures of elongation and cable force. Mainly cable force and secondarily elongation. And (5) guiding tensioning construction.

(3) When the two ends are tensioned, the two ends are synchronously carried out. During tensioning, it is necessary to ensure that tensioning personnel should stand on two sides of the jack, so that the operators are prevented from being injured when the sliding rope condition occurs.

(4) After the steel strand is tensioned, the supervision is required to be reported, the main construction unit observes the line shape of the bridge in time, and the cable force of each group cannot exceed the design rule. And after the external cable is installed, the external cable is protected in time.

Compared with the prior art, the invention has the advantages that: the construction method is adopted for construction, the investment of equipment and personnel is less, a single tensioning device is light, the working procedure is simple, the labor intensity is low, the occupied field is small, and the blanking and the sleeve stripping can be carried out on the finished bridge deck; the tensioning process is advanced, the cable force is monitored by adopting a high-tech instrument, and the installation speed of the stay cable is high.

Drawings

FIG. 1 is a schematic structural diagram of an outer sleeve and a waterproof cover according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of an epoxy coated steel strand cutting and heading according to an embodiment of the invention;

FIG. 3 is a schematic view of a bridge deck reeving platform according to an embodiment of the present invention;

FIG. 4 is a schematic view of a tower crane sling construction platform according to an embodiment of the invention;

FIG. 5 is a schematic view of the connection of the front end of the outer sleeve according to the embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a cable saddle as the wire-dividing pipe on the main tower according to the embodiment of the present invention;

FIG. 7 is a schematic representation of a reeving embodiment of the present invention;

FIG. 8 is a schematic drawing of a steel strand tension according to an embodiment of the present invention;

FIG. 9 is a schematic view of the connection of a tower end anti-slide anchor to a saddle end in accordance with an embodiment of the present invention;

FIG. 10 is a schematic structural view of a beam-end embedded pipe according to an embodiment of the present invention;

FIG. 11 is a schematic structural diagram of a pay-off stand according to an embodiment of the present invention;

FIG. 12 is an external view of a lanyard device according to an embodiment of the present invention;

fig. 13 is a cross-sectional view of a reeving device in accordance with an embodiment of the present invention.

In the figure, 1 steel strand, 101 center steel wire, 102 center steel wire, 2HDPE outer sleeve, 3 extension pipe, 4 anti-slide anchorage, 401 anti-slide anchorage sealing gasket, 5 cable hoop, 6 waterproof cover, 7 connecting pipe, 8 split-wire tubular cable saddle, 801 cable saddle anchor backing plate, 802 stiffening plate, 803 steel hoop, 804 steel pipe, 9 embedded pipe, 10 pay-off rack, 11 single-hole jack, 12 arrangement reaction rack, 13 beam end anchor plate, 14 nut, 15 protective cover, 16 shock absorber and 17 anti-loose pressing plate; 1001 base, 1002 roller, 1003 support frame, 1004 fence, 1005 pivoting support and 1006 diagonal brace; 18 connecting rods, 19 connector caps I, 20 connectors, 21 connector heads, 22 connector caps II, 24 bearings, 25 washers, 1801 bolder.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

The embodiment specifically relates to the construction of a filled epoxy coating steel strand stay cable for a short tower (partial) cable-stayed bridge, and the construction process and the operation are as follows

Preparation before threading

1.1HDPE outer sleeve welding

The HDPE pipe is used as a first protective layer of the stay cable and is an important component of a stay cable anticorrosion measure. Therefore, the welding quality of the HDPE pipe is important, and it not only needs to bear the temporary load of the hoisting construction, but also directly affects the durability of the HDPE pipe during the normal use. The welding of HDPE pipes requires the use of a pipe butt welder operated by a skilled worker to weld 9m lengths of pipe to the required length. The hot-melting welding process of the HDPE pipe comprises the following steps:

1) determining the welding length of the HDPE pipe to be welded according to a design drawing;

2) adjusting parameter settings (such as welding temperature, pressure and the like) of welding equipment according to the diameter of the HDPE pipe to be welded;

3) arranging supports on both sides of the welding machine and ensuring that they are flush, which would otherwise affect the alignment of the pipes;

4) putting a 6m long pipe on a support frame, putting the other pipe on the other side of the welding machine, ensuring that the pipes are in a line and flush with the welding machine, and removing an outer plastic film;

5) moving the two pipes together and placing the two pipes into a hoop of a welding machine;

6) the pipes are clamped tightly by a clamp, and a gap of about 90mm is reserved between the two pipes (when the clamp is clamped, the torque needs to be balanced, otherwise the smoothness of the pipes is influenced);

7) the alignment test is performed by moving the two tubes together, with appropriate adjustments to the tubes if necessary;

8) placing the electric milling cutter between the two pipes, starting a power supply, and cutting the end parts of the two pipes until the end parts are flush;

9) removing the electric milling cutter from the welding machine, and checking whether the cutting meets the requirements;

10) separating the two tubes and placing them in a heating plate;

11) moving the two tubes close to the heating plate, applying the required pressure and starting to record the electrofusion welding time. An annular welding seam appears immediately, and after the outer sleeve is installed, the welding seam is not obvious, so that the welding seam does not need to be removed, and the welding seam is kept to be firmer;

12) heating to the last few seconds prepares the heating plate to be removed from the welder and applies the required pressure to bring the two tubes together. The process must be completed within 3-4 seconds, so to obtain good welding effect, the action must be rapid;

13) removing the heating plate, connecting the two pipes together, applying the required pressure and cooling according to the specification of the manufacturer;

14) after cooling, removing the clamp and wrapping the welding seam joint with a plastic film to protect the welding position;

15) moving the welded pipe to one end of a welding machine, and placing the next 9m long pipe at the other end;

16) the above operations are repeated until the final desired length is achieved. Since temperature changes will cause thermal expansion or contraction, the field engineer should make detailed calculations and provide data to the field welder;

17) welding the smooth end of the HDPE connecting pipe with the external threads at one end and the last section of the HDPE pipe into a whole, and polishing the external weld joint of the welding part to ensure that the stainless steel protective pipe can be sleeved on the HDPE pipe.

18) The high density polyethylene pipe is cut to a correct length, the cut length is determined according to the external temperature, and since the HDPE pipe expands or contracts with temperature change, the cut length must be monitored and adjusted accordingly. If the field temperature changes violently and the HDPE pipe after welding is long, theoretically, calculation is carried out according to the temperature influence coefficient provided by the HDPE pipe supplier so as to determine the final blanking length. In fact, according to the design of a stay cable system, a 3 m-long HDPE extension pipe is arranged on a stay cable, and the length of the HDPE extension pipe extending into the extension pipe is determined to be 1.2-1.5 m according to the length of an HDPE outer sleeve pipe. In the length range, no matter what the external temperature changes, the HDPE outer sleeve cannot be separated from the extension pipe, so that aiming at the project, the length change of the HDPE pipe caused by the temperature change and the length of the outer sleeve entering the extension pipe are comprehensively considered during actual blanking of the HDPE pipe, and blanking operation is carried out.

19) And (4) performing blanking and welding by field operators according to specific data, wherein the welded pipes need to be numbered for later use. The finished HDPE pipe, which must still be protected with a packaging plastic film, is welded at the job site.

In addition to the welding procedure of the HDPE outer sleeve, attention needs to be paid to:

1) when the length of the HDPE outer sleeve is calculated, the length of the waterproof cover, the HDPE connecting sleeve and the HDPE outer sleeve entering the extension pipe and the influence factors of temperature on the length of the pipe need to be considered;

the HDPE outer sleeve and the HDPE connecting sleeve are connected into a whole in a hot-melt butt welding mode; the waterproof cover is connected with the HDPE connecting sleeve, and the outer coating of the waterproof cover is not damaged as shown in figure 1.

1.2 Steel strand Blanking

Before threading, the stranded wires for all the cables need to be prepared for blanking. According to the actual situation of the site, the materials are discharged in a factory or a cable placing area, coiled into coils and transported to a bridge deck cable penetrating position through a transport machine. Along with the increase of the construction length of the main beam, the material can be loaded and unloaded on the beam surface, and the cable is laid and coiled by a take-up machine.

(1) Discharging

The whole process of blanking the epoxy-coated steel strand is carried out on a pay-off stand, referring to fig. 11, a special bracket is installed about every 2-3 meters, the bracket is used for ensuring that the epoxy-coated steel strand cannot be in contact with the ground so as to avoid damage of the epoxy-coated steel strand, and the epoxy coating is protected in the blanking process, as shown in fig. 4-7.

And (3) blanking the epoxy coating steel strand according to quality inspection to provide blanking row length table blanking, wherein the length error is controlled to be +/-5 cm during blanking.

And stripping a certain length of PE sheath at the end part of the stranded wire. And (3) cutting off 6 steel wires outside the epoxy coating steel strand at a position which is about 60mm away from the end part of the epoxy coating steel strand by using a hand-held grinding wheel machine, only leaving a central steel wire, and grinding and chamfering the outer steel wire at the cut end part. And upsetting the central wire by using an upsetting machine. The epoxy coating steel strand wires at the cutting part are wrapped by the electric adhesive tape, so that the sharp edges of the epoxy coating steel strand wires are prevented from being ejected to the anchorage device when the epoxy coating steel strand wires penetrate into the anchorage device, and smooth threading is prevented from being influenced.

(2) Identification (if the design needs to install the anti-slide key, the anti-slide key needs to be subjected to identification extrusion)

After blanking, marks of 'head', 'tail' and 'cable number' are made at the end of the stranded wire, and the anti-slip key is extruded at the corresponding position according to the design requirement.

And extruding the anti-sliding key:

1) the extruding machine, the extruding sleeve and the extruding spring are in place;

2) the stripping sleeve is 80mm long;

3) wrapping the electrician adhesive tape for 3 circles;

4) fixing 2-3 wires of the extrusion spring;

5) the extrusion sleeve and the extrusion spring are in place;

6) manually fixing stranded wires at two ends of the extruder;

7) and (4) extruding (the pressure of the extrusion oil is controlled between 8MPa and 9 MPa).

(3) Stacking

And uniformly coiling the epoxy coating steel strands after blanking into coils and temporarily storing the coils, and paying attention to the direction of the mark when coiling, wherein the head part of the mark is outside and the tail part of the mark is inside.

When the steel strand is stacked on a bridge floor, square wood or carpet cloth is used for temporary protection under a reel to prevent the steel strand from being contacted with the ground to scratch the epoxy of the epoxy coating steel strand; adopt the waterproof cloth to comprehensively shield the reel of stacking, prevent to influence stranded conductor appearance quality.

1.3 mounting of anchors and sensors

(1) Anchor on-site installation

1) The anchor plate is provided with glue injection holes which are distributed up and down;

2) the rear wire dividing plate of the anchor sealing cylinder is provided with a sensor mounting groove, the rear wire dividing plate needs to be detached before the anchor is mounted, and the rear wire dividing plate and the sealing cylinder are reassembled after the sensor is fixed by using the hexagon socket head cap screws;

3) when the anchorage assembly part is lifted in place, attention should be paid to the mutual matching of personnel on the beam and personnel under the beam, so that damage or casualties caused by the falling of the anchorage are avoided;

4) when the anchorage device is installed, the hole position of the tower column cable saddle and the hole position of the bridge deck anchorage device are required to be ensured to be consistent, so that the hole positions of the anchorage device and the cable saddle are required to be numbered in advance, and the consistency of the hole position numbers is ensured.

(2) Sensor field installation

When the fixed sensor is installed, the data line is towards the outside; and the full-bridge magnetic flux sensor is fixed with the anchorage device. When the anchorage device is installed on the embedded pipe, attention is paid to protecting the sensor data wire; after the anchorage device is installed in place, the data line is led out to the threading hole of the embedded pipe, and measures are taken to ensure that the data line is close to the inner wall of the embedded pipe and cannot be pulled; during rope threading, attention is paid to avoiding the data wire, and the data wire is prevented from being damaged or wound on the stranded wire; after the tension of the epoxy coating steel strand is finished, a gap between a threading hole of the embedded pipe and the data line is coated and plugged with polyurethane sealant; coordinating wiring and debugging of the magnetic flux sensor; after the construction is finished, the hand-held magnetic flux sensor monitor and the portable computer are handed over to the Party A.

1.4 Tower end work platform preparation

Before the construction of the hanging cable, a proper tower end construction platform is adopted on a tower end construction platform. Generally, steel pipe scaffolds are adopted for erection. The HDPE outer sleeve can also be lifted when the tower crane is used for transferring the epoxy coating steel strand and the HDPE outer sleeve which are wound on the reel to the bridge deck and installing the stay cable, and the tower crane platform is shown in figure 4.

1.5 bridge deck reeving work platform preparation

Before cable hanging construction, an epoxy coating steel strand pay-off rack and related equipment need to be installed at a proper position of a bridge deck, so that epoxy coating steel strands transported in a coiled mode are convenient to install, and the epoxy coating steel strands are shown in figure 3. During threading, the ends of the stranded wires are distinguished, and the position of the anti-sliding key is taken as a protection measure to prevent the anti-sliding key from damaging PE sheaths of other steel stranded wires during threading.

Hoisting of HDPE outer sleeve

Sleeving the front end of the HDPE outer sleeve into the extension pipe and the anti-slide anchorage at one time, then respectively installing cable hoops in front of the anti-slide anchorage and behind the extension pipe, and fixing the anti-slide anchorage and the extension pipe through hemp ropes by using holes on lug plates of the cable hoops, as shown in figure 5; arranging a steering pulley on the tower column, and welding and fixing a lifting point for the outer sleeve; on the vertical working surface, an operator is arranged along the height direction of the tower column to assist the positioning of the outer sleeve.

Hoisting the outer sleeve: the hoisting speed should be controlled during hoisting, and if the hoisting is carried out under the condition of wind, the ascending speed of the hoisting pipe is slow. If the wind is too great, the operation is temporarily stopped until the wind weakens. Once the pipe is lifted in place, the cable hoop at the front end of the anti-skid anchorage device is connected with the wire-separating tubular cable saddle on the tower column at the cable saddle position of the tower column, the distance from the rear end of the HDPE outer sleeve to the embedded pipe is ensured to be about 1m, the hoisting equipment is turned off, and the load is transmitted to a connecting steel wire rope for lifting;

for each cable number, after the HDPE outer sleeves on the two sides of the main tower are lifted and connected with the cable saddle of the main tower, the beam ends of the main tower are temporarily fixed by using the ropes, so that the verticality of the HDPE outer sleeves can be eliminated, certain linearity can be realized, and the HDPE outer sleeves can be prevented from deflecting along with wind.

Third, epoxy coating steel strand reeving

The main tower of the short-tower cable-stayed bridge is provided with a wire-separating tubular cable saddle, and the epoxy coating steel strand penetrates through the outer sleeves at the two sides and is anchored in the box girders at the two sides of the main tower. The specific installation method is as follows: and placing the pay-off frame on the left side of the tower, and paying off from left to right.

Due to the fact that the height of the main tower of the short-tower cable-stayed bridge is small, mechanical auxiliary manual cable penetrating can be adopted during the cable penetrating construction of a part of the cable-stayed bridge.

(1) The epoxy coating steel strand factory carries out blanking, sleeve stripping, heading, anti-slip key extrusion and coiling packaging, and a special pay-off rack is required for paying off the epoxy coating steel strand. When paying off, the epoxy coating steel strand is pulled out manually, and meanwhile, a specially-assigned person rotates a pay-off rack;

(2) sending the epoxy coating steel strand into an HDPE outer sleeve pipe to reach a cable saddle opening at the tower end at the left side (penetrating through a left anti-slip anchor device);

(3) according to the corresponding relation between the reeving sequence and the hole site numbers, penetrating the epoxy coating steel strand into the corresponding cable saddle wire dividing pipe until the epoxy coating steel strand reaches the right cable saddle opening;

(4) continuously pushing the epoxy coating steel strand to pass through the right anti-slip anchorage device until the end of the embedded pipe at the right beam end is reached; on the right side, the guide rod which is completely pier-headed when the anchorage device is installed under the beam penetrates upwards until the guide rod extends out of the pipe orifice of the embedded pipe. Connecting a threading connector at the end part of the guide rod with an upset head of a working epoxy coating steel strand, and clamping the upset head part of the epoxy coating steel strand in the threading connector;

(5) continuing to push the working steel strand, simultaneously drawing the draw bar downwards, penetrating the steel strand out of the anchorage device at the right beam end, removing the reeving connector, referring to fig. 12-13, connecting the reeving connector with the steel strand, and installing and tightening the working clamping piece after reserving the designed working length to clamp the steel strand;

Special pay off rack 10 of steel strand wires, including base 1001, unwrapping wire support body and 4 gyro wheels 1002, the unwrapping wire is erect in base 1001 top, is fixed with the circular shape guide rail on the

base

1001, and 4 gyro wheels 1002 set up in unwrapping wire support body bottom circumference round the even interval in unwrapping wire support body center, and 4 gyro wheels 1002 cooperate with the guide rail, and gyro wheel 1002 rolls along the orbit of guide rail respectively, realizes that the unwrapping wire rack is rotatory round base 1001. The steel strand wires are sleeved outside the pay-off rack, the steel strand wires are provided with pulling force, the idler wheels 1002 rotate along the guide rails, the pay-off rack rotates around the center of the base 1001, automatic paying-off of the steel strand wires is achieved, and the device is simple in structure, convenient to operate and free in paying-off.

The pay-off rack body comprises a fence 1004, a

support frame

1003, 4 inclined support rods 1006 and a rotary support 1005, wherein the rotary support 1005 is fixed at the center of the support frame 1003, the fence 1004 is vertically fixed on the support frame 1003, the 4 inclined support rods 1006 are uniformly arranged at intervals in the circumferential direction of the rotary support 1005, one ends of the inclined support rods 1006 are respectively fixed on the fence 1004, and the other ends of the inclined support rods 1006 are respectively fixed on the rotary support 1005, so that the pay-off rack can rotate stably.

The reeving connector comprises a connecting rod 18, a connector cap I19, a connector 20, a joint head 21 and a connector cap II22, wherein the rear portion of the connecting rod 18 extends into the front end of the connector 20, the front end of the connector 20 is locked through the connector cap I19, a through hole is formed in the connector cap I, the connecting rod 18 penetrates through the through hole connector cap I of the connector cap I, four bearings 24 are sleeved on the periphery of the connecting rod 18 extending into the connector 20, and the four bearings 24 are fixed on the inner wall of the connector 20, so that the connecting rod 20 can rotate relatively in the connector 20.

In order to prevent the rear end of the connecting rod 18 from being pushed backwards, a gasket 25 is arranged in the connector, and the end part of the connecting rod 18 is pressed against the gasket 25 in a front-back mode to form a limit position of the rear end of the connecting rod 18. And the end of the connecting rod 18 extending into the connector 20 is shaped into a thick head 1801, the surface of the thick head 1801 is shaped into a multi-step, and the gasket 25 abuts against one step end face matched with the position in the connector. The end 101 and the transition portion of the connecting rod body also form a step end face, and correspondingly, the inner wall of the connector is formed with a plurality of limiting steps, and the bearing 24 is correspondingly arranged at the limiting steps on the inner wall of the connector 20, so that the bearing 24 is positioned and prevented from sliding.

The front end of the adapter 21 extends into the rear end of the connector 20, and the rear end of the connector 20 is terminated with a bayonet extending toward the center axis of the connector, and the bayonet engages with a recess on the outer wall of the adapter, thereby fixedly coupling the adapter 21 and the connector 20. The rear end of the joint long head 21 is provided with a deep hole for inserting the pier head steel strand 101, the connector cap II22 is locked at the rear end of the joint long head 21 to lock the steel strand 101 in the joint long head 21, and the steel strand penetrates through the connector cap II.

During operation, the connector cap II is unscrewed from the end part of the extension head 21 to expose the deep hole, the connector cap II is firstly sleeved on the steel strand 101, then the pier head end of the steel strand 101 is inserted into the deep hole of the extension head 21, and then the connector cap II is screwed on the extension head 21. Because the connecting rod 18 is movable within the connector 20, i.e., can rotate freely relative to the connector, torsional stress can be released in time during reeving, preventing the steel strand from twisting.

Four, epoxy coating steel strand tensioning

In the process of installing the stay cable, the influence of integral tensioning on the stress of the full bridge is great, and in order to ensure the stable process and reduce the construction risk, single epoxy coating steel stranded wires are recommended to be adopted for tensioning, so that the process of hierarchical symmetrical tensioning by using a single jack is adopted according to the design requirement and the actual condition of the bridge; and (5) performing cable force adjustment on the stay cable needing to adjust the cable force according to the data monitored on site in the stages of finishing the installation and closing of the full-bridge stay cable.

(1) Epoxy coating steel strand tensioning mode

The construction process of single reeving and single tensioning of the epoxy coating steel strand is adopted. The single tensioning equipment is light and convenient, the operation is simple and flexible, after each rope is threaded, the rope needs to be pretensioned immediately to be temporarily fixed, and the single epoxy coating steel strand is tensioned as shown in figure 8. A single-hole sensor is installed on a first tensioned steel strand, and when other epoxy coating steel strands are tensioned, the cable force and the cable force dispersion of a single strand are detected by detecting the cable force index variation on the sensor.

Tensioning:

Fifth, the accessories are installed

After the stay cable is tensioned, the auxiliary installation and the anticorrosion treatment can be carried out. Generally, the method mainly comprises the following steps: and accessories such as cable clamps, sealing gaskets, extension pipes, vibration absorbers, waterproof covers and the like are installed.

(5.1) Cable clip installation

(1) And (3) installing the cable tightener at the outer side of the stay cable epoxy coating steel strand bundle, and paying attention to the fact that the hexagonal inner edge of the cable tightener is tightly attached to the stay cable peripheral epoxy coating steel strand without deflection. A cable clamp is arranged at the tower end at a position 1100mm away from a cable saddle base plate, and the cable clamps at two sides of the cable saddle are arranged at the same position;

(2) 3 locking screws on the cable tightener are screwed down circularly, and 3 positioning blocks of the cable tightener are ensured to contract synchronously;

(3) after the epoxy coating steel stranded wires in the cable tightener are bundled and formed, sleeving a half-type working cable clamp on the stay cable, and tightening a bolt on the cable clamp;

(4) and loosening the locking screw on the cable tightener and withdrawing the cable tightener.

(5.2) installing a sealing gasket, an anti-sliding anchorage and a pressure-bearing nut

(1) Coating polyurethane sealant on two sides of a sealing gasket of the anti-skid anchorage device;

(2) a screw hole of a set screw on the anti-slide anchorage device faces downwards;

(3) and (4) screwing the pressure-bearing nut by adopting a wrench tool, and locking the pressure-bearing nut by using a set screw.

(5.3) extension pipe mounting

The extension pipe is disassembled from the HDPE outer sleeve, and is pulled upwards to the anti-sliding anchorage device by using a chain block; installing a locking screw into a screw hole on the extension pipe, and symmetrically tightening the screw by using a tool; when the extension pipe is installed, the sealing gaskets at the two ends are required to be respectively in close contact with the anti-slip anchorage device and the outer sleeve, and the sealing gaskets with polyurethane sealant smeared on the two sides are arranged on the contact surface of the anti-slip anchorage device, so that the sealing effect is ensured, and rainwater is prevented from entering the outer sleeve.

(5.4) installing the vibration damper,

the vibration damper is generally a beam end vibration damper, and the vibration damper is a commercially available product and plays a role in vibration damping.

(1) Before the shock absorber is installed, whether the stay cable body deflects or not is checked. If the inclined stay cable has a large deflection degree, the inclined stay cable needs to be subjected to deviation rectification by using tools such as a chain block or a jack;

(2) sleeving a beam end shock absorber on the periphery of a stay cable body, pushing the stay cable body into an embedded pipe, tightening 4 locking screws on the shock absorber, and tightening 4 sliding blocks of the shock absorber to the inner wall of the embedded pipe until the shock absorber is tightly attached to the inner wall of the embedded pipe;

(3) and lifting the locking plate below the screw head on the shock absorber by using a spanner to fix the screw head.

(5.5) waterproof case mounting

And releasing the cable of the HDPE outer sleeve temporarily fixed at the beam end, and pulling the HDPE outer sleeve integrally downwards to the end face of the waterproof cover to abut against the inner step of the embedded pipe.

Sixth, stay cable anticorrosion measure

(6.1) Corrosion prevention of Beam-end Anchor

In order to prevent the beam end anchorage from being corroded, anti-corrosion grease is required to be poured into the beam end anchorage embedded pipe for protection. And (3) filling the anticorrosive grease into a special grouting machine, and filling the grease into the beam-end anchor embedded pipe through pressure injection of the grouting machine.

And after the cable force is adjusted, the epoxy coating steel strand is cut off according to the reserved length of the epoxy coating steel strand which is changed later. The scheme of corrosion prevention of the beam end of the stay cable is that wax is filled between the anti-loosening pressing plate and the anchor plate, and then wax oil is smeared on the periphery of the exposed part of the stranded wire, and referring to fig. 10, the specific corrosion prevention construction steps are as follows:

(1) glue injection

1) Connecting an oil pump with a glue injection gun, putting polyurethane sealant into the glue injection gun, and connecting a glue injection bent pipe;

2) and (3) injecting polyurethane sealant into each anchorage device, and injecting the polyurethane sealant into the glue injection holes on the anchorage devices by using the oil pressure of 2.5-3.0 MPa in a slow and average manner.

(2) Package (I)

1) Winding a circle of kraft paper-plastic composite cloth around the anchor plate, fixing the periphery of the anchor plate by a high-strength composite self-adhesive tape, and firmly connecting the joints;

2) winding the kraft paper-plastic composite cloth for 1-2 circles by using a high-strength composite self-adhesive tape behind the anti-loosening pressure plate, and checking whether the kraft paper-plastic composite cloth, the anchor plate and the edge of the anti-loosening pressure plate are intact after winding;

3) a hole is formed at the top, and an iron sheet is bent into a groove to be inserted into the hole so as to fill wax;

(3) wax filling machine

1) Filling the wax oil in an iron bucket for primary dissolution, and then heating and melting by using a 2000W heating rod;

2) protective measures are taken beside the iron bucket, liquid wax oil is slowly poured into the holes by a stainless steel ladle and is poured into the holes as stably as possible, and people are prevented from being injured by splashing until the wax oil overflows.

(4) Anticorrosion measure for exposed part of epoxy coating steel strand

1) Cotton cloth is wound at the front end of the stranded wire wiping pipe, and the stranded wire wiping pipe with the wax oil is used for wiping the epoxy coating steel stranded wires behind the anti-loosening pressing plate once, so that all the epoxy coating steel stranded wires are coated with the wax oil;

2) and sleeving a protective cover made of cotton cloth on the stranded wire bundle, tightly attaching the anti-loosening pressure plate to one surface close to the anti-loosening pressure plate, and firmly adhering the protective cover to the box sealing adhesive tape.

3) And (5) installing the protective cover of the anchorage device in place, and finishing the anticorrosion work.

(6.2) Corrosion prevention of anti-slip anchor at tower end

In order to prevent the tower end anchorage from rusting, the tower end anchorage needs to be subjected to anticorrosion treatment, and a foaming agent is generally adopted. And foaming the anti-sliding anchor and the gap thereof from the pore channel reserved in the outer sleeve of the anti-sliding anchor at the tower end to isolate air, water vapor and the like. And epoxy mortar is poured into the anti-slip anchorage of the anti-slip anchorage, see fig. 9.

Later maintenance: the cable replacing operation of the single stay cable can be carried out: releasing the cable force of the single epoxy coating steel strand, connecting a new epoxy coating steel strand, moving away the jack, temporarily protecting the epoxy coating steel strand before drawing out the epoxy coating steel strand, finally installing a new epoxy coating steel strand, reinstalling an anchorage device protective cover after the epoxy coating steel strand is replaced, and reinjecting anti-corrosion grease to perform corresponding anti-corrosion treatment.

Compiling description

(1) All the used epoxy coating steel strands conform to the regulation of GB/T21073-2007 Steel Strand seven-wire prestressed epoxy coating steel strands;

(2) the stay cable outer sleeve material is required to meet the requirements of high-density polyethylene sheathing material for bridge cables (GJ/T297 + 2008);

(3) the anchorage matched with the stay cable meets the requirements of prestressed anchorage, clamps and connectors (GB/T14370-;

(4) the used anti-corrosive grease meets the regulation of JG/T430-2014 'Special anti-corrosive grease for unbonded prestressed tendons'.

In addition to the above embodiments, the present invention also includes other embodiments, and any technical solutions formed by equivalent transformation or equivalent replacement should fall within the scope of the claims of the present invention.

Claims

1. A construction method of a stay cable of a short-tower cable-stayed bridge is characterized by comprising the following steps: the main steps comprise

(2) hoisting an outer sleeve: for a longer outer sleeve, preparing an extension pipe, wherein the front end part of the outer sleeve extends into the extension pipe, the outer sleeve freely stretches in the extension pipe according to environmental factors and ensures that the outer sleeve does not exceed the extension pipe all the time, the front end of the outer sleeve is sleeved into the extension pipe, an anti-slide anchor is connected to the front end of the extension pipe, then cable hoops are respectively arranged in front of the anti-slide anchor and behind the extension pipe, the anti-slide anchor and the extension pipe are fixed through hemp ropes by utilizing lifting holes on lug plates of the cable hoops, the outer sleeve is lifted in preparation, so that the end of the anti-slide anchor reaches a tower end cable saddle and is temporarily butted with a cable saddle inlet, and the outer sleeve is lifted on the left side and the right side of the tower respectively;

the specific operation of hoisting:

arranging a steering pulley on the tower column, and welding and fixing a lifting point for the outer sleeve;

arranging an operator on the vertical working surface along the height direction of the tower column to assist the positioning of the outer sleeve;

controlling the hoisting speed during hoisting, hoisting the outer sleeve in place, connecting a cable hoop at the front end of the anti-skid anchorage device with a wire-separating tubular cable saddle on the tower column at the position of the tower column cable saddle, ensuring the distance between the rear end of the outer sleeve and the embedded pipe at the rear end of the outer sleeve to be 1 +/-0.2 m, turning off hoisting equipment, and transmitting the load to a connecting steel wire rope for hoisting;

for each outer sleeve, after the outer sleeves on the two sides of the tower are lifted and connected with a cable saddle at the tower end, temporarily fixing the outer sleeves at the beam end by using a rope;

2. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: in the step (1), the outer sleeve is an HDPE pipe, each section of the outer sleeve is lengthened to a required length in a hot-melt welding mode, the correct cutting length is determined according to the operation temperature, and the influence factors of the length of the waterproof cover, the connecting sleeve and the outer sleeve entering the extension pipe and the temperature on the pipe length need to be considered in the calculation of the cutting length of the outer sleeve.

3. The construction method of a stay cable of a short tower cable-stayed bridge according to claim 2, wherein: the beam-end outer sleeve is connected with the waterproof cover through a connecting sleeve, the waterproof cover is finally arranged at the pipe orifice of the beam-end embedded pipe, and the rear end of the outer sleeve is connected with the connecting sleeve into a whole in a hot-melting butt welding mode; the waterproof cover is connected with the connecting sleeve.

4. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: the step (1) of blanking the steel strand refers to that before threading, the steel strand used by each stay cable needs to be blanked,

(3) after blanking, marking the head, the tail and the cable number at the end of the steel strand, and extruding the anti-sliding key at the corresponding position according to the design requirement;

(4) the epoxy coating steel strand wires after the unloading is finished are uniformly coiled into coils and are temporarily stored, the identification direction is noticed during coiling, the head part of the identification is arranged outside, the tail part of the identification is arranged inside, and when the steel strand wires are stacked on the bridge floor, square wood or carpet cloth must be used for temporary protection under the steel strand wire coiling disc to prevent the epoxy coating steel strand wires from being in contact with the bridge floor to scratch, and the coiled disc which is stacked is completely shielded by rain cloth.

5. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: step (1) anchor and sensor installation: the anchorage devices are arranged in the embedded pipes, the beam end anchor plates are provided with glue injection holes which are distributed up and down, the hole sites are ensured to be consistent with the hole sites of the cable saddle at the tower end when the anchorage devices are installed, the hole sites of the anchorage devices and the cable saddle are respectively numbered, and the consistency of the hole site numbers is ensured; the sensor is a full-bridge magnetic flux sensor and is fixed with the anchorage device.

6. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: step (1) preparing a beam surface working platform: installing a steel strand pay-off rack at a proper position of the bridge floor, paying off the steel strands conveyed by the coiling through the pay-off rack, and leading out the head of the steel strand during threading; preparing a tower end working platform: before the cable penetrating construction, a scaffold is erected on a tower body, a tower crane is arranged on the tower side, and the tower crane is used for transferring the steel strand and the outer sleeve which are coiled to the bridge floor and hoisting the outer sleeve.

7. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: arranging a wire-separating tubular cable saddle on the tower, enabling the steel strand to penetrate through the outer sleeves on the two sides and be anchored in anchorage devices on the two sides of the tower, and performing the operation step of penetrating the steel strand of the stay cable in the step (3):

(9) and repeating the rope penetrating and pre-tensioning steps, wherein the steel strand rope penetrating starts from the uppermost row of holes of the anchorage device until the last row of holes, and the rope penetrating of the rest steel strands is completed until the stay ropes on each tower are completely installed.

8. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: tensioning the steel strand: after each cable penetrating is finished, pre-tensioning is required to be immediately carried out to temporarily fix the cable penetrating device, a single-hole sensor is installed on a first tensioned steel strand, when other steel strands are tensioned, the cable force and the cable force dispersion of the single steel strand are detected by detecting the cable force index variable quantity on the sensor, and the tensioning operation steps are as follows

9. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: the cable clamp is arranged on the outer side of the stay cable steel strand bundle, the inner wall of the cable clamp is tightly attached to the stay cable peripheral epoxy coating steel strand bundle, the cable clamp is arranged at the position of 1100 +/-100 mm away from a cable saddle base plate at the tower end, and the cable clamps on the two sides of the cable saddle are symmetrical; the cable clamp is a Harvard structure, is closed and locked at the periphery of the stay cable steel strand by two cable clamp sleeves, and is assisted by a cable tightener: installing the cable tightener outside the steel strand bundle of the stay cable, paying attention to the fact that the inner wall of the cable tightener is tightly attached to the steel strand on the outer ring of the stay cable, circularly tightening a locking screw on the cable tightener, synchronously contracting 3 positioning blocks of the cable tightener to enable the steel strand in the cable tightener to be bundled and formed, then sleeving the cable clamp on the steel strand bundle in a matched mode, and tightening a bolt on the cable clamp; and finally, loosening the locking screw on the cable tightener and withdrawing the cable tightener.

10. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: and (5) installing the sealing gasket of the anti-slide anchorage device, namely, the sealing gasket of the anti-slide anchorage device is in sealed butt joint with the anchor backing plate of the cable saddle, polyurethane sealing glue is coated on two sides of the sealing gasket of the anti-slide anchorage device, and then the sealing gasket is arranged between the anchor plate of the anti-slide anchorage device and the anchor backing plate of the cable saddle and is locked through bolts and nuts.

11. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: step (5) installation of the extension pipe: the extension pipe is disassembled from the outer sleeve, and is pulled upwards to the anti-sliding anchorage device by using the chain block; installing locking screws into screw holes on the extension pipe, and symmetrically tightening the screws; when the extension pipe is installed, the sealing gaskets at two ends are required to be respectively in close contact with the anti-sliding anchorage and the outer sleeve, and the sealing gaskets with polyurethane sealant smeared on two sides are arranged on the contact surface of the anti-sliding anchorage and the outer sleeve.

12. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: and (5) mounting a beam end shock absorber: before installing the shock absorber, checking whether the stay cable body deflects, or else, carrying out deviation rectification treatment on the stay cable; and sleeving the beam end shock absorber on the periphery of the stay cable body, pushing the stay cable body into the embedded pipe, and adjusting the shock absorber to enable the outer wall to be tightly attached to the inner wall of the embedded pipe.

13. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: and (5) installing a waterproof cover: and releasing the temporary fixation of the beam end to the outer sleeve, and integrally drawing the outer sleeve to the embedded pipe until the end face of the waterproof cover abuts against the inner step of the embedded pipe.

14. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: and (6) corrosion prevention of the beam end anchorage device: pouring anti-corrosive grease into the embedded pipe where the beam-end anchorage device is located for protection, pouring the anti-corrosive grease into a special grouting machine, and pouring the grease into the embedded pipe through pressure injection of the grouting machine; cutting off the steel strand according to the reserved length of the steel strand after the cable force of the stay cable is adjusted, filling wax between the anti-loosening pressing plate and the anchor plate which are positioned on the rear side of the anchor plate, and then coating wax oil on the periphery of the exposed part of the strand, wherein the specific anti-corrosion construction steps are as follows;

(1) glue injection

(2) package (I)

opening a hole at the top to fill wax;

(3) wax filling machine

slowly pouring liquid wax oil into the hole until the wax oil overflows;

(4) corrosion protection of exposed part of steel strand

sleeving a protective cover made of cotton cloth on the steel strand bundle, tightly attaching the anti-loosening pressure plate to one surface close to the anti-loosening pressure plate, and firmly adhering the protective cover with a box sealing adhesive tape;

and installing the protective cover of the anchorage device in place to finish the anticorrosion work.

15. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 1, wherein: and (6) corrosion prevention of the anti-sliding anchor at the tower end: foaming agent is adopted, the anti-slip anchorage and the connection gap thereof are completely foamed in the reserved hole channel of the anti-slip anchorage at the tower end, and epoxy mortar is poured in the anti-slip anchorage of the anti-slip anchorage.

16. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 6, wherein: the pay-off rack includes base pay-off rack and a plurality of roller train, and the steel strand wires of lapping that coil are as for on the pay-off rack, the shaping has an annular guide rail on the base, a plurality of roller trains are the annular and are fixed in the pay-off rack bottom, and the pay-off rack supports on the annular guide rail of base through a plurality of roller trains, a plurality of roller trains make the pay-off rack from the gyration along the annular guide rail gyration.

17. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 16, wherein: the pay-off rack comprises a fence, a support frame, an inclined strut and a slewing bearing, the steel strand wound into a coil is sleeved on the fence, the slewing bearing is arranged in the center of the support frame, the fence is erected on the support frame, and the inclined strut is fixedly supported between the fence and the slewing bearing.

18. The method for constructing a stay cable of a short tower cable-stayed bridge according to claim 7, wherein: the reeving connector comprises a connecting rod, a connector cap I, a connector, a joint length head and a connector cap II, wherein the rear part of the connecting rod extends into the front end of the connector, the connector cap I is locked at the front end of the connector, the connecting rod extends forwards out of the connector cap I, and one or more bearings are sleeved around the connecting rod extending into the connector to enable the connecting rod to rotate in the connector; the front end of the extension head extends into the rear end of the connector and is fixed, the rear end of the extension head is provided with a deep hole for inserting the pier head steel strand, the connector cap II is locked at the rear end of the extension head, and the steel strand penetrates through the connector cap II.