CN112627437A - Construction method of large-span prestressed concrete structure of clean electronic factory building - Google Patents
Construction method of large-span prestressed concrete structure of clean electronic factory building Download PDFInfo
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- CN112627437A CN112627437A CN202011517893.9A CN202011517893A CN112627437A CN 112627437 A CN112627437 A CN 112627437A CN 202011517893 A CN202011517893 A CN 202011517893A CN 112627437 A CN112627437 A CN 112627437A
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/08—Members specially adapted to be used in prestressed constructions
- E04C5/10—Ducts
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
- E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
- E04C5/08—Members specially adapted to be used in prestressed constructions
- E04C5/12—Anchoring devices
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
- E04G21/00—Preparing, conveying, or working-up building materials or building elements in situ; Other devices or measures for constructional work
- E04G21/02—Conveying or working-up concrete or similar masses able to be heaped or cast
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Abstract
The invention relates to a construction method of a large-span prestressed concrete structure of a clean electronic factory building, which comprises the following steps of 1, blanking and bundling prestressed tendons: the blanking length of the prestressed tendon should be the net length of the pore passage plus the working length of the two ends. Step 2, reserving a prestressed duct: step 3, pre-stressed tendon penetration: step 4, pouring concrete: step 5, tensioning the prestressed tendons: step 6, pore grouting: step 7, sealing the anchor: the invention provides a construction method which can reduce the structure height, increase the floor clearance and reduce the consumption of concrete and common steel bars; meanwhile, the method also reduces the net weight born by the supporting member and the foundation, thereby achieving larger span.
Description
Technical Field
The invention relates to the field of construction of large-span structures of electronic plants, in particular to a construction method of a large-span prestressed concrete structure of a clean electronic plant.
Background
With the development of the economic and technological levels, the plane area of an electronic factory building is continuously increased, and the structure is continuously complicated; meanwhile, the construction period is not increased, so the pre-stress operation task of the current electronic factory building is heavy; the prestressed tensioning end is uniquely arranged, and the arrangement and the structure of the tensioning end are the key technical problems in the whole workshop construction. The process of pre-stressing is complicated and requires multiple kinds of coordination. Therefore, how to make the prestressing operation in the large-span structure operation of the electronic factory building is a difficult problem in the electronic factory building.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a method for building a large-span prestressed concrete structure of a clean electronic factory building, and solves the problem that the prestress is well made in the operation of the large-span structure in the electronic factory building.
In order to solve the technical problem, the invention is realized as follows:
a method for building a large-span prestressed concrete structure of a clean electronic factory building is characterized by comprising the following steps:
step 1, blanking and bundling of prestressed tendons:
the blanking length of the prestressed tendon should be the net length of the pore passage plus the working length of the two ends. The parabolic channel length is calculated according to the following formula:
Lt＝（1+8H2/3L2）*L （5-1）
in the formula: l ist-tunnel curve length
H-curve rise
L-curve horizontal projection length
The stretching working length is determined according to the type of the jack, and is determined according to real calculation during variable-angle stretching;
cutting the prestressed tendons by a grinding wheel cutting machine without electric welding or oxy-acetylene cutting, coiling the cut prestressed tendons into 2 m-diameter disks, binding, numbering and stacking the disks in a classified manner. Extruding and mounting an extrusion anchorage at one end of the prestressed tendon with one end stretched;
(1) and (3) paying off the position of the pore channel: according to the design construction drawing and the turnover drawing, marking the hole channel position control point on a template or a common steel bar, paying attention to the influence of a steel bar protective layer, and particularly deducting the radius of the hole channel;
(2) mounting the pore channel bracket: the distance between the brackets is 0.8-1.0 m, phi 12 steel bars with the same width as the stirrups are generally adopted, the two ends of each bracket are fixed at the marked positions of the stirrups in a spot welding manner by electric welding, middle welding spots are added to the multi-limb stirrups, and the level of the brackets is ensured;
(3) and (3) pore channel installation: the prestressed duct is usually reserved by double-wave metal (plastic) corrugated pipe, the corrugated pipe is bound with the support by 22 # lead wire, and if necessary, U-shaped or well-shaped clamping points are installed for welding and fixing, and the integrity of the corrugated pipe needs to be protected. The length of the corrugated pipe is generally 6m, and the corrugated pipe needs to be penetrated into the steel reinforcement framework in sections and placed on the installed support. The joint of the corrugated pipe is screwed by a connecting pipe with a first size (the inner diameter is 5 mm), two ends of the corrugated pipe are sealed by waterproof adhesive tapes, the length of the connecting pipe is 30d, d is the inner diameter of a pore channel, and is generally 200-300 mm;
after the pore channels are lengthened and fixed, reserving bleeding (grouting) holes at the wave crest (bottom) of the pore channels, wherein the pore diameter is phi 25, binding and fixing the pore channels at the hole positions by adopting a special plastic cover plate, filling a sponge sheet to prevent slurry leakage, lengthening the upper parts of the pore channels to the outside of the member by using a plastic pipe for 400mm, sealing the top parts of the pore channels by using a waterproof adhesive tape, and staggering the bleeding (grouting) holes when a plurality of pore channels are arranged on the same section;
after the prestressed duct is completely installed, the position and the line shape of the duct need to be checked, the duct needs to be repaired to be damaged so as to seal the whole length of the duct, and finally the side template of the component is sealed;
step 3, pre-stressed tendon penetration:
(1) the lacing is that the prestressed tendon is penetrated into the arranged pore channel, and can be divided into a front threading mode and a rear threading mode, wherein the front threading is finished lacing before concrete pouring, and the rear threading is finished lacing after concrete pouring, and the construction adopts the front threading mode;
(2) the manual bundling can adopt two modes of penetrating one by one and penetrating the whole bundle, a bundling group is organized according to the length of each prestressed tendon and the number of each bundle of prestressed tendons, a bundling method is determined, a front-end traction whole bundle penetrating method is needed for continuous multi-span super-long bundles with more number, a power assisting section can be reserved in the middle of a pore channel if necessary, the power assisting section is generally 1-2 m long, a connecting pipe of a first-size corrugated pipe is adopted for rotary connection, and the first-size corrugated pipe of the power assisting section is rotated back and sealed after the bundling is finished;
(3) during the strand pulling, a specially-made bullet head is arranged on a penetrating end sleeve of the prestressed tendon to facilitate the strand pulling and protect the corrugated pipe, special attention needs to be paid to avoiding drawing back the steel strand, and the steel strand is required to be rotated for a plurality of weeks and then is continuously pulled to be stranded when the steel strand is blocked;
step 4, pouring concrete:
(1) the concrete pouring and tamping technology is carried out in advance, and the importance is placed on the compactness of the concrete in the anchoring area and the protection of the duct corrugated pipe;
(2) before concrete pouring, all prestressed finished products must be checked again, and the sealing performance of the pore channel is particularly emphasized;
(3) tracking and monitoring the whole pouring and tamping process, and timely processing the problems of corrugated pipe damage, displacement and the like;
(4) hole cleaning of a pore passage: the hole cleaning is to prevent cement slurry from leaking into the pore channel and affecting tensioning, and the prestressed tendons should be pulled back and forth at two ends of the pore channel which is firstly penetrated in the hole cleaning process before the initial setting of concrete in the pouring process of each hole or each component; for the hole passage of the rear penetrating beam, a special hole cleaner is adopted to pull the hole in the hole passage;
(5) note that a set of concrete test blocks are additionally reserved to guide the tensioning time;
step 5, tensioning the prestressed tendons:
prestress tension is a key process of a prestress technology, and must be paid high attention to, and various preparation works such as technology, data, field, equipment, personnel and the like are well done before tension;
(1) three tests: anchorage device performance detection, jack-pressure gauge calibration detection and concrete test block compressive strength detection;
(2) calculation of theoretical elongation value of prestressed tendon
The theoretical elongation values can be superposed after respectively calculating the elongation values of all the zigzag line segments according to the following formula;
in the formula: l, chi-the actual length (m) of the curve segment
E-modulus of elasticity under prestress
Theta-curve angle (rad)
k-pore offset coefficient
μ — coefficient of friction (note taking the latest specification values or field testing);
the principle of segmentation of the prestress curve is as follows:
(3) and (3) converting tension force-pressure gauge reading: according to the calculated tension force and a jack-pressure gauge calibration report, calculating the pressure gauge reading by adopting an interpolation method, and checking by using a correlation coefficient formula;
(4) confirming a tensioning sequence and a tensioning program in a tensioning scheme, ensuring that tensioning is strictly carried out according to a symmetrical principle, and adopting measures such as batch graded tensioning, ultra-tensioning or ultra-tensioning loosening technology and the like according to actual conditions under the conditions of variable angle tensioning, ultra-long bundle tensioning or increased slurry leakage friction loss of a duct;
(5) before the anchorage device is installed, the beam end embedded part must be cleaned, the anchorage plate is firstly installed, and then the clamping pieces are installed hole by hole. When the anchorage device is installed, the anchor plate corresponds to the center of the right hole channel or the groove on the anchor backing plate, the clamping pieces are fastened, and the gaps of the clamping pieces are uniform;
(6) when the tensioning equipment is installed, the action line of the tensioning force of the jack is coincided with the tangent line of the tail end of the prestressed tendon, the initial tension from zero loading to the starting point of the measured elongation value is loaded firstly, then the required tensioning force is loaded in a grading manner, the oil inlet speed is strictly controlled during tensioning, and the oil return is stable;
(7) carefully measuring the actual elongation of each prestressed tendon, comparing the actual elongation with a theoretical elongation value in time, judging whether the actual elongation is abnormal (exceeds the standard requirement), analyzing the reason, taking corresponding measures and making field records;
step 6, pore grouting:
(1) the grouting material adopts pure cement slurry or is doped with a proper amount of chloride-free admixture according to the design requirement, and normal portland cement with the water-cement ratio of not less than 32.5 grade is adopted, wherein the water-cement ratio is 0.35-0.42;
(2) the method comprises the following steps of firstly mechanically stirring cement paste, ensuring uniform stirring, adopting pressure for grouting at a beam end, sieving the paste before entering a grouting pump, ensuring continuous pressure in the grouting process, continuously and slowly performing grouting without interruption, plugging a secretion hole after filling a pore channel, blocking an exhaust hole after exhausting air from an exhaust hole on an anchor backing plate and spraying thick paste, pressurizing to 0.5-0.7 MPa, sealing the grouting hole after stabilizing the pressure for 1-2 min, continuously performing manual grout supplement on the secretion hole after grouting, and discharging the secretion until the paste surface does not drop;
(3) the horizontal hole grouting should be carried out from one end or the middle of the hole, and the grouting hole is not required to be replaced; the vertical channel grouting is carried out from bottom to top, and a valve is arranged at the grouting hole to prevent slurry from flowing back;
(4) when grouting is interrupted due to pore channel blockage, mechanical failure and the like, immediately flushing pore channels and grouting equipment to prepare for grouting again;
(5) not less than two groups of cement paste test blocks are reserved in each shift while grouting, one group is used for determining the frame falling time of the prestressed beam, and the other group is maintained for 28 days to be used as completion data;
(6) the removal of the bottom die and the support with the bonded beam or the movement and hoisting of the prefabricated part must be carried out after the grouting strength of the pore channel reaches 20 MPa;
step 7, sealing the anchor:
(1) cutting off redundant prestressed tendons outside the tensioned anchorage by adopting a grinding wheel cutting machine or oxy-acetylene, wherein the residual length outside the anchorage is not suitable to be less than 15d or 30 mm;
(2) cleaning temporary plugging cement slurry and other impurities on the anchorage device during grouting, roughening the opening and washing the opening; before the protruding anchor head is sealed, a reinforcing mesh is configured, and the sealing material is fine aggregate concrete, micro-expansion concrete or low-shrinkage mortar with the same strength grade as the member;
(3) and (3) falling: the prestressed component with a large span can be removed by immediately falling down the frame after tensioning, and the construction load of the upper floor is considered when the template support is removed.
The invention has the beneficial effects that: the structure height can be reduced, the floor clearance is increased, and a construction method for reducing the consumption of concrete and common steel bars is introduced; meanwhile, the method also reduces the net weight born by the supporting member and the foundation, thereby achieving larger span.
Drawings
The invention is described in further detail below with reference to the following figures and embodiments:
fig. 1 is a flow chart of the present application.
Fig. 2 is a schematic view of installation of the bleeding pipe.
FIG. 3 is a sectional view of a pre-stressed tensile elongation curve.
Detailed Description
As shown in fig. 1-3: a construction method of a large-span prestressed concrete structure of a clean electronic factory building comprises the following steps:
step 1, blanking and bundling prestressed tendons
The blanking length of the prestressed tendon should be the net length of the pore passage plus the working length of the two ends. The parabolic channel length is calculated according to the following formula:
Lt＝（1+8H2/3L2）*L （5-1）
in the formula: l ist-tunnel curve length
H-curve rise
L-curve horizontal projection length
The stretching working length is determined according to the type of the jack, and is determined according to real calculation during variable-angle stretching.
The prestressed bar is cut by a grinding wheel cutting machine, and electric welding and oxy-acetylene cutting are not required. And coiling the cut round pieces according to the diameter of 2m, binding, numbering and then stacking in a classified manner. And extruding and mounting the extrusion anchorage device at one end of the prestressed tendon with one end stretched.
(1) And (3) paying off the position of the pore channel: and marking the hole position control points on the template or the common steel bars according to the design construction drawing and the turnover drawing. Note the effect of the steel bar protection layer, especially to subtract out the radius of the tunnel.
(2) Mounting the pore channel bracket: the distance between the brackets is 0.8-1.0 m, phi 12 steel bars with the same width as the stirrups are generally adopted, the two ends of each bracket are fixed at the marked positions of the stirrups in a spot welding manner by electric welding, and middle welding spots are added to the multi-limb stirrups and the level of the brackets is ensured by paying attention to the multi-limb stirrups.
(3) And (3) pore channel installation: the prestressed duct is usually reserved by double-wave metal (plastic) corrugated pipe, the corrugated pipe is bound with the support by 22 # lead wire, and if necessary, U-shaped or well-shaped clamping points are installed for welding and fixing, and the integrity of the corrugated pipe needs to be protected. The length of the corrugated pipe is generally 6m, and the corrugated pipe needs to be penetrated into the steel reinforcement framework in sections and placed on the installed support. The joint of the corrugated pipe adopts a large-size (the inner diameter is large by 5 mm) connecting pipe to be screwed, two ends of the corrugated pipe are sealed by waterproof adhesive tapes, and the length of the connecting pipe is 30d (d is the inner diameter of a pore passage), generally 200-300 mm.
As shown in fig. 2: after the pore canal is lengthened and fixed, a bleeding (grouting) hole 1 with a diameter phi 25 is reserved at the crest (bottom) of the pore canal. The special plastic cover plate 3 is adopted to be bound and fixed at the position of the hole and is bound by an iron wire 4, an iron nail 5 is nailed in the hole, the lower sponge sheet 2 is used for preventing slurry leakage, the upper part of the lower sponge sheet is lengthened to 400mm outside the component by a plastic pipe, the top of the lower sponge sheet is sealed by a waterproof adhesive tape, and bleeding (grouting) holes are arranged in a staggered way when a plurality of pore channels are arranged on the same section.
After the prestressed duct is completely installed, the position and line shape of the duct need to be checked, the duct needs to be repaired and damaged so as to seal the whole length of the duct, and finally the side formwork (generally one side formwork and the wide beam two side formworks) of the closed component is closed.
Step 3, penetrating the prestressed tendons
(1) The lacing is to lead the prestressed tendon into the arranged pore channel and can be divided into a front threading mode and a rear threading mode. The front penetrating is to finish penetrating before concrete pouring, and the rear penetrating is to penetrate after concrete pouring.
(2) The manual lacing can adopt two modes of threading one by one and threading the whole tendon, and the lacing group is organized according to the length of the prestressed tendons and the number of each tendon, so that the lacing method is determined. For the continuous multi-span super-long bundle with more number, a front end traction whole bundle penetrating method is needed, a power assisting section can be reserved in the middle of a pore channel if necessary, the power assisting section is generally 1-2 m long, a connecting pipe of a large corrugated pipe is adopted for screwing, and the large corrugated pipe of the power assisting section is screwed back and sealed after the bundle penetrating is completed.
(3) During the bundle penetrating, a special bullet head is arranged on the penetrating end sleeve of the prestressed tendon to facilitate the bundle penetrating and protect the corrugated pipe, special attention needs to be paid to avoid drawing back the steel strand, and the steel strand is required to be rotated for a plurality of weeks and then continuously penetrated and bundled when the steel strand is blocked.
Step 4, pouring concrete
(1) The technology of concrete pouring and tamping is carried out in advance, and the emphasis is placed on the compactness of concrete in an anchoring area and the protection of a pore corrugated pipe.
(2) Before concrete pouring, all prestressed finished products must be checked again, and the sealing performance of the pore channel is particularly considered.
(3) The whole process of pouring and tamping is tracked and monitored, and the problems of corrugated pipe damage, displacement and the like are found and timely treated.
(4) Hole cleaning of a pore passage: the hole cleaning is to prevent the cement slurry from leaking into the pore channel to influence the tensioning. The hole cleaning is carried out before the initial setting of the concrete in the pouring process of each hole or each component. For the pore canal which is penetrated and bound firstly, the prestressed tendons are pulled back and forth at the two ends; and for the hole passage of the rear penetrating beam, a special hole cleaner is adopted to pull the hole in the hole passage for cleaning.
(5) Note that an additional set of concrete blocks was left in order to guide the tensioning time.
Step 5, tensioning the prestressed tendons
Prestress tension is a key process of a prestress technology, and must be highly regarded, and various preparation works such as technology, data, field, equipment, personnel and the like are well done before tension.
(1) Three tests: anchorage device performance detection, jack-pressure gauge calibration detection and concrete test block compressive strength detection.
(2) Calculation of theoretical elongation value of prestressed tendon
The theoretical elongation values can be superposed after the elongation values of the various zigzag line segments are respectively calculated according to the following formula.
In the formula: l, chi-the actual length (m) of the curve segment
E-modulus of elasticity under prestress
Theta-curve angle (rad)
k-pore offset coefficient
Mu-coefficient of friction (Note taking the latest standard values or field tests)
The principle of segmentation of the prestress curve is as follows:
(3) and (3) converting tension force-pressure gauge reading: and calculating the reading of the pressure gauge by adopting an interpolation method according to the calculated tension force and the calibration report of the jack-pressure gauge, and checking by using a correlation coefficient formula.
(4) And (4) confirming a tensioning sequence and a tensioning program in the tensioning scheme, and ensuring that tensioning is strictly carried out according to a symmetrical principle. For the conditions of variable angle tensioning, ultra-long bundle tensioning, increased slurry leakage friction loss of a pore channel and the like, measures such as batch graded tensioning, ultra-tensioning or ultra-tensioning loosening technology and the like are adopted according to actual conditions.
(5) Before the anchorage device is installed, the beam end embedded part must be cleaned, the anchorage plate is firstly installed, and then the clamping pieces are installed hole by hole. When the anchorage device is installed, the anchor plate is corresponding to the center of the right hole channel or the groove on the anchor backing plate, the clamping pieces are required to be tightened, and the gaps of the clamping pieces are required to be uniform.
(6) When the tensioning equipment is installed, the action line of the tensioning force of the jack is coincided with the tangent line of the tail end of the prestressed tendon. The initial tension from zero load to the starting point of measuring elongation value is loaded first, and then the required tension is loaded in stages. The oil inlet speed is strictly controlled during tensioning, and the oil return is stable;
(7) and carefully measuring the actual elongation of each prestressed tendon, comparing the actual elongation with a theoretical elongation value in time, judging whether the actual elongation is abnormal (exceeds the standard requirement), analyzing the reason, taking corresponding measures and making field records.
Step 6, grouting pore canals
(1) The grouting material adopts pure cement slurry or is mixed with a proper amount of chloride-free admixture according to the design requirement, and the cement is not less than 32.5-grade ordinary portland cement with the water-cement ratio of 0.35-0.42.
(2) The cement paste is preferably mechanically stirred, so that the uniform stirring is ensured. The grouting holes at the beam ends are filled by adopting pressure, the grout needs to be sieved before entering a grouting pump, the continuous pressure is ensured in the grouting process, and the grouting is continuously and slowly carried out without interruption. And after the pore channel is filled, blocking the drainage hole after the drainage hole on the anchor backing plate exhausts air and sprays out thick slurry, pressurizing to 0.5-0.7 MPa, stabilizing the pressure for 1-2 min, and then sealing the grouting hole. After grouting, manual grout supplement is carried out on the bleeding hole continuously, and bleeding is discharged until the grout surface does not fall.
(3) The horizontal hole grouting should be carried out from one end or the middle of the hole, and the grouting hole is not required to be replaced; the vertical channel grouting should be carried out from bottom to top, and a valve is arranged at the grouting hole to prevent slurry from flowing back.
(4) When the grouting is interrupted due to the blockage of the pore channel, mechanical failure and the like, the pore channel and grouting equipment are flushed immediately to prepare for re-grouting.
(5) At the same time of grouting, not less than two groups of cement paste test blocks are reserved in each shift, one group is used for determining the frame falling time of the prestressed beam, and the other group is maintained for 28 days to be used as completion data.
(6) The removal of the bottom die and the support with the bonded beam or the movement and the hoisting of the prefabricated part must be carried out after the grouting strength of the pore channel reaches 20 MPa.
Step 7, sealing the anchor
(1) And cutting off redundant prestressed tendons outside the tensioned anchorage by adopting a grinding wheel cutting machine or oxy-acetylene, wherein the residual length outside the anchorage is not suitable to be less than 15d or 30 mm.
(2) Cleaning temporary plugging cement slurry and other impurities on the anchorage device during grouting, roughening the opening and washing the opening; and a reinforcing mesh is arranged before the protruding anchor head is sealed. The sealing material adopts fine aggregate concrete, micro-expansion concrete or low-shrinkage mortar with the same strength grade as the member.
And (3) falling: and the prestress can be immediately dropped after tensioning is finished, and the bottom templates of the beams and the plates are removed. For the prestressed component with extremely large span, the construction load of the upper floor is considered when the formwork support is removed.
Claims (1)
1. A method for building a large-span prestressed concrete structure of a clean electronic factory building is characterized by comprising the following steps:
step 1, blanking and bundling of prestressed tendons:
the blanking length of the prestressed tendon should be the net length of the pore passage plus the working lengths of the two ends, and the parabolic pore passage length is calculated according to the following formula:
Lt＝（1+8H2/3L2）*L （5-1）
in the formula: l ist-tunnel curve length
H-curve rise
L-curve horizontal projection length
The stretching working length is determined according to the type of the jack, and is determined according to real calculation during variable-angle stretching;
cutting the prestressed tendons by a grinding wheel cutting machine without electric welding or oxy-acetylene cutting, coiling the cut prestressed tendons into 2 m-diameter disks, binding, numbering and stacking the disks in a classified manner. Extruding and mounting an extrusion anchorage at one end of the prestressed tendon with one end stretched;
step 2, reserving a prestressed duct:
(1) and (3) paying off the position of the pore channel: according to the design construction drawing and the turnover drawing, marking the hole channel position control point on a template or a common steel bar, paying attention to the influence of a steel bar protective layer, and particularly deducting the radius of the hole channel;
(2) mounting the pore channel bracket: the distance between the brackets is 0.8-1.0 m, phi 12 steel bars with the same width as the stirrups are generally adopted, the two ends of each bracket are fixed at the marked positions of the stirrups in a spot welding manner by electric welding, middle welding spots are added to the multi-limb stirrups, and the level of the brackets is ensured;
(3) and (3) pore channel installation: the prestressed duct is usually reserved by double-wave metal (plastic) corrugated pipe, the corrugated pipe is bound with the support by 22 # lead wire, and if necessary, U-shaped or well-shaped clamping points are installed for welding and fixing, and the integrity of the corrugated pipe needs to be protected. The length of the corrugated pipe is generally 6m, and the corrugated pipe needs to be penetrated into the steel reinforcement framework in sections and placed on the installed support. The joint of the corrugated pipe is screwed by a connecting pipe with a first size (the inner diameter is 5 mm), two ends of the corrugated pipe are sealed by waterproof adhesive tapes, the length of the connecting pipe is 30d, d is the inner diameter of a pore channel, and is generally 200-300 mm;
after the pore channels are lengthened and fixed, reserving bleeding (grouting) holes at the wave crest (bottom) of the pore channels, wherein the pore diameter is phi 25, binding and fixing the pore channels at the hole positions by adopting a special plastic cover plate, filling a sponge sheet to prevent slurry leakage, lengthening the upper parts of the pore channels to the outside of the member by using a plastic pipe for 400mm, sealing the top parts of the pore channels by using a waterproof adhesive tape, and staggering the bleeding (grouting) holes when a plurality of pore channels are arranged on the same section;
after the prestressed duct is completely installed, the position and the line shape of the duct need to be checked, the duct needs to be repaired to be damaged so as to seal the whole length of the duct, and finally the side template of the component is sealed;
step 3, pre-stressed tendon penetration:
(1) the lacing is that the prestressed tendon is penetrated into the arranged pore channel, and can be divided into a front threading mode and a rear threading mode, wherein the front threading is finished lacing before concrete pouring, and the rear threading is finished lacing after concrete pouring, and the construction adopts the front threading mode;
(2) the manual bundling can adopt two modes of penetrating one by one and penetrating the whole bundle, a bundling group is organized according to the length of each prestressed tendon and the number of each bundle of prestressed tendons, a bundling method is determined, a front-end traction whole bundle penetrating method is needed for continuous multi-span super-long bundles with more number, a power assisting section can be reserved in the middle of a pore channel if necessary, the power assisting section is generally 1-2 m long, a connecting pipe of a first-size corrugated pipe is adopted for rotary connection, and the first-size corrugated pipe of the power assisting section is rotated back and sealed after the bundling is finished;
(3) during the strand pulling, a specially-made bullet head is arranged on a penetrating end sleeve of the prestressed tendon to facilitate the strand pulling and protect the corrugated pipe, special attention needs to be paid to avoiding drawing back the steel strand, and the steel strand is required to be rotated for a plurality of weeks and then is continuously pulled to be stranded when the steel strand is blocked;
step 4, pouring concrete:
(1) the concrete pouring and tamping technology is carried out in advance, and the importance is placed on the compactness of the concrete in the anchoring area and the protection of the duct corrugated pipe;
(2) before concrete pouring, all prestressed finished products must be checked again, and the sealing performance of the pore channel is particularly emphasized;
(3) tracking and monitoring the whole pouring and tamping process, and timely processing the problems of corrugated pipe damage, displacement and the like;
(4) hole cleaning of a pore passage: the hole cleaning is to prevent cement slurry from leaking into the pore channel and affecting tensioning, and the prestressed tendons should be pulled back and forth at two ends of the pore channel which is firstly penetrated in the hole cleaning process before the initial setting of concrete in the pouring process of each hole or each component; for the hole passage of the rear penetrating beam, a special hole cleaner is adopted to pull the hole in the hole passage;
(5) note that a set of concrete test blocks are additionally reserved to guide the tensioning time;
step 5, tensioning the prestressed tendons:
prestress tension is a key process of a prestress technology, and must be paid high attention to, and various preparation works such as technology, data, field, equipment, personnel and the like are well done before tension;
(1) three tests: anchorage device performance detection, jack-pressure gauge calibration detection and concrete test block compressive strength detection;
(2) calculation of theoretical elongation value of prestressed tendon
The theoretical elongation values can be superposed after respectively calculating the elongation values of all the zigzag line segments according to the following formula;
in the formula: l, chi-the actual length (m) of the curve segment
E-modulus of elasticity under prestress
Theta-curve angle (rad)
k-pore offset coefficient
μ — coefficient of friction (note taking the latest specification values or field testing);
the principle of segmentation of the prestress curve is as follows:
(3) and (3) converting tension force-pressure gauge reading: according to the calculated tension force and a jack-pressure gauge calibration report, calculating the pressure gauge reading by adopting an interpolation method, and checking by using a correlation coefficient formula;
(4) confirming a tensioning sequence and a tensioning program in a tensioning scheme, ensuring that tensioning is strictly carried out according to a symmetrical principle, and adopting measures such as batch graded tensioning, ultra-tensioning or ultra-tensioning loosening technology and the like according to actual conditions under the conditions of variable angle tensioning, ultra-long bundle tensioning or increased slurry leakage friction loss of a duct;
(5) before the anchorage device is installed, the beam end embedded part must be cleaned, the anchorage plate is firstly installed, and then the clamping pieces are installed hole by hole. When the anchorage device is installed, the anchor plate corresponds to the center of the right hole channel or the groove on the anchor backing plate, the clamping pieces are fastened, and the gaps of the clamping pieces are uniform;
(6) when the tensioning equipment is installed, the action line of the tensioning force of the jack is coincided with the tangent line of the tail end of the prestressed tendon, the initial tension from zero loading to the starting point of the measured elongation value is loaded firstly, then the required tensioning force is loaded in a grading manner, the oil inlet speed is strictly controlled during tensioning, and the oil return is stable;
(7) carefully measuring the actual elongation of each prestressed tendon, comparing the actual elongation with a theoretical elongation value in time, judging whether the actual elongation is abnormal (exceeds the standard requirement), analyzing the reason, taking corresponding measures and making field records;
step 6, pore grouting:
1) the grouting material adopts pure cement slurry or is doped with a proper amount of chloride-free admixture according to the design requirement, and normal portland cement with the water-cement ratio of not less than 32.5 grade is adopted, wherein the water-cement ratio is 0.35-0.42;
2) the method comprises the following steps of firstly mechanically stirring cement paste, ensuring uniform stirring, adopting pressure for grouting at a beam end, sieving the paste before entering a grouting pump, ensuring continuous pressure in the grouting process, continuously and slowly performing grouting without interruption, plugging a secretion hole after filling a pore channel, blocking an exhaust hole after exhausting air from an exhaust hole on an anchor backing plate and spraying thick paste, pressurizing to 0.5-0.7 MPa, sealing the grouting hole after stabilizing the pressure for 1-2 min, continuously performing manual grout supplement on the secretion hole after grouting, and discharging the secretion until the paste surface does not drop;
3) the horizontal hole grouting should be carried out from one end or the middle of the hole, and the grouting hole is not required to be replaced; the vertical channel grouting is carried out from bottom to top, and a valve is arranged at the grouting hole to prevent slurry from flowing back;
4) when grouting is interrupted due to pore channel blockage, mechanical failure and the like, immediately flushing pore channels and grouting equipment to prepare for grouting again;
5) not less than two groups of cement paste test blocks are reserved in each shift while grouting, one group is used for determining the frame falling time of the prestressed beam, and the other group is maintained for 28 days to be used as completion data;
6) the removal of the bottom die and the support with the bonded beam or the movement and hoisting of the prefabricated part must be carried out after the grouting strength of the pore channel reaches 20 MPa;
step 7, sealing the anchor:
1) cutting off redundant prestressed tendons outside the tensioned anchorage by adopting a grinding wheel cutting machine or oxy-acetylene, wherein the residual length outside the anchorage is not suitable to be less than 15d or 30 mm;
2) cleaning temporary plugging cement slurry and other impurities on the anchorage device during grouting, roughening the opening and washing the opening; before the protruding anchor head is sealed, a reinforcing mesh is configured, and the sealing material is fine aggregate concrete, micro-expansion concrete or low-shrinkage mortar with the same strength grade as the member;
and (3) falling: the prestressed component with a large span can be removed by immediately falling down the frame after tensioning, and the construction load of the upper floor is considered when the template support is removed.
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| CN116220213A (en) * | 2023-03-12 | 2023-06-06 | 北京市地震局 | Assembled dense rib plate node |
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