CN112627540A - Construction method of prestressed waffle slab for large-scale clean electronic factory building - Google Patents
Construction method of prestressed waffle slab for large-scale clean electronic factory building Download PDFInfo
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- CN112627540A CN112627540A CN202011439480.3A CN202011439480A CN112627540A CN 112627540 A CN112627540 A CN 112627540A CN 202011439480 A CN202011439480 A CN 202011439480A CN 112627540 A CN112627540 A CN 112627540A
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- unbonded
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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
- E04G21/12—Mounting of reinforcing inserts; Prestressing
- E04G21/121—Construction of stressing jacks
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- E—FIXED CONSTRUCTIONS
- E04—BUILDING
- E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
- E04B5/00—Floors; Floor construction with regard to insulation; Connections specially adapted therefor
- E04B5/16—Load-carrying floor structures wholly or partly cast or similarly formed in situ
- E04B5/32—Floor structures wholly cast in situ with or without form units or reinforcements
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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
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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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Abstract
The invention relates to a construction method of a prestressed waffle slab for a large-scale clean electronic factory building, which comprises the following steps of firstly, blanking without bonding ribs and bundling; secondly, paving without bonding ribs: 1) paying off at the position without the bonding ribs; 2) mounting a bracket without the bonding ribs; 3) mounting an anchor backing plate; 4) laying unbonded ribs; 5) after the unbonded ribs are laid, checking the conditions of the number, the damage, the position and the exposed length of the unbonded ribs, and processing the problems; thirdly, pouring concrete; fourthly, tensioning the prestressed tendons; fifthly, sealing the anchor; sixthly, falling the shelf: and the frame can be immediately dropped after the tensioning is finished. The invention utilizes the prestressed waffle slab structure to reduce the influence of the temperature stress of the concrete, control the generation of shrinkage cracks of the waffle slab and simultaneously reduce the construction interval time of each construction section of the waffle slab.
Description
Technical Field
The invention relates to the field of electronic factory building construction, in particular to a method for constructing a prestressed waffle slab of a large-scale clean electronic factory building.
Background
In recent years, the iteration updating of the electronic technology is very frequent, and the construction of corresponding electronic factory building engineering is generally and continuously emerging like bamboo shoots in spring after rain. The construction of the electronic factory building is generally finished in a short period, and the requirements on the flatness of the waffle slab and the cleanliness, micro-shock resistance, static resistance and airflow control of a production area of the electronic factory building are required to be met. The clean electronic factory building has short construction period and high requirement on the cleanliness of the air inside the factory building space, and the cleanliness is ensured by regulating and controlling air circulation through internal air pressure, so that the requirements on the flatness and the apparent smoothness of the structure are very strict. In the process, if cracks appear on the concrete surface, the cleanliness of the plant is greatly influenced, so that the control of the concrete cracks in the rapid construction process of the electronic clean plant is very important.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a construction method of a prestressed waffle slab for a large-scale clean electronic factory building, which can control concrete cracks in the construction process and has long construction period.
In order to solve the technical problem, the invention is realized as follows:
a method for building a prestressed waffle slab for a large-scale clean electronic factory is characterized by comprising the following steps:
firstly, blanking and bundling without bonding ribs:
the blanking length of the unbonded rib is 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 （6-1）
in the formula: l ist-tunnel curve length;
h-curve rise;
l is the horizontal projection length of the curve;
the stretching working length is determined according to the type of the jack, generally 400mm at each end, and is determined according to real calculation during variable-angle stretching;
the blanking is cut by a grinding wheel cutting machine, and electric welding and oxy-acetylene cutting are not adopted. After cutting, coiling according to the diameter of 2m, binding, numbering and then stacking in a classified manner, and after material breaking, carrying out extrusion installation on an extrusion anchor at one end of the prestressed tendon stretched at one end;
secondly, paving without bonding ribs:
1) paying off at the position without the bonding ribs: according to the design construction drawing and the turnover drawing, the position control points of the unbonded ribs are marked on the template or the common steel bars, the influence of the steel bar protective layer is noticed, the radius of the unbonded ribs (bundles) is deducted, the unbonded ribs at the tensioning end penetrate out of the template and are marked on the template one by one, and holes or grooves are punched at the corresponding positions of the template before the unbonded ribs penetrate out of the template, so that the unbonded ribs extend out of the template;
2) installation of the unbonded rib bracket: the non-adhesive ribs in the plate are generally made of phi 12 steel bars to control the curve elevation of the stirrup, the stirrups are not more than 2m apart from control points such as reverse bending points, and the like, and the stirrups are fixed on the steel bars of the bottom plate in a spot welding manner during installation; for unbonded reinforcements arranged in a beam in a bundling manner, short reinforcements with the same width as the stirrups are adopted to be fixed by spot welding, middle welding spots are added for multi-limb stirrups, the support is ensured to be horizontal, and the support interval is 1-1.5 m;
3) installing an anchor backing plate: for the convex tensioning end, the anchor backing plate is tightly attached to the corresponding position of the end die, the anchor backing plate is fixed with the non-prestressed ribs by electric welding (auxiliary connecting steel bars are added if necessary), the spiral ribs are tightly attached to the anchor backing plate and fixed, the spiral ribs are spot-welded on the anchor backing plate, the concave tensioning end is fixed at the position of 100mm in the template, plastic or foam is used as a cavity die, and the position of the anchor backing plate is kept vertical to the non-prestressed ribs when the anchor backing plate is installed;
4) laying unbonded ribs: when the unbonded ribs in the plate are laid, the unbonded ribs are placed on the stirrups according to numbers, the whole length of the unbonded ribs is parallel and cannot be twisted, the unbonded ribs stretched at one end penetrate through the fixed end, and finally the helical ribs, the anchor backing plate, the hole mold (simultaneously placed in) and the template penetrate out from the stretching end, the length of the unbonded ribs penetrating out of the template is not less than 300mm, and the unbonded ribs are straightened and straightened after the bundle penetrating is finished and are bound by lead wires and the stirrups; for the bidirectional prestressed plate, drawing a net-weaving graph of the unbonded reinforcement, determining the position relation of the cross point of the bidirectional unbonded reinforcement according to a curve coordinate, laying the unbonded reinforcement in the lower direction of a vertical coordinate during construction, laying the unbonded reinforcement in the other direction, and passing through the lower part of the unbonded reinforcement when part of the coordinate is lower than that of the unbonded reinforcement laid firstly; bundling unbonded ribs in the beams one by one, straightening at any time to keep the beams in a parallel state, straightening and binding with a bracket after each bundle is penetrated; the fixed end of the unbonded rib stretched at one end is placed at a designed position for spot welding and fixing;
5) after the unbonded ribs are laid, checking the conditions of the number, the damage, the position and the exposed length of the unbonded ribs, and processing the problems;
thirdly, pouring concrete:
1) the concrete pouring and tamping technology is carried out in advance, and the emphasis is placed on the compactness of the concrete in the anchoring area and the protection without bonding ribs;
2) before concrete pouring, all prestressed finished products must be checked again, and particularly, the damage and the displacement of the unbonded ribs should be noticed;
3) tracking and monitoring the whole pouring and tamping process, and timely processing the problems of damage, displacement and the like of the unbonded rib sheath when being found;
4) paying attention to another group of concrete construction test blocks to guide tensioning time;
fourthly, 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) calculating the theoretical elongation value of the 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, χ -the actual length of the curve segment (m);
e-modulus of elasticity under prestress;
θ -Curve angle (rad);
k is the offset coefficient;
μ — coefficient of friction (note taking the latest specification values or field testing);
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;
4) tensioning sequence of the unbonded ribs: sequentially tensioning the unbonded ribs in the plate; the unbonded ribs in the beam are symmetrically tensioned according to the plane position of the prestressed beam; when the beam slab has prestressed ribs, the unbonded ribs in the beam slab are firstly tensioned, and then the unbonded ribs (or the bonded ribs) in the beam are tensioned;
5) stretching program of the unbonded rib: the unbonded ribs stretched at two ends can be stretched to design stress at one end, then the stretching force is complemented at the other end, variable angle stretching and ultra-long bundle stretching are carried out, and measures such as graded stretching, ultra-stretching or ultra-stretching loosening technology and the like are adopted according to actual conditions:
normal tensioning: 0 → 0.1 σ con → σ con → anchor;
ultra-tensioning: 0 → 0.1 σ con → 1.03 σ con → anchor;
and (3) ultra-tension loosening: 0 → 0.1 σ con → 1.05 σ con → σ con → anchor;
6) before the anchorage device is installed, the embedded part at the tensioning end needs to be cleaned, an anchor plate is installed firstly, then clamping pieces are installed hole by hole, when the anchorage device is installed, the anchor plate is aligned to the center of the prestressed tendon, the clamping pieces are tightened, and gaps of the clamping pieces are uniform;
7) 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;
8) 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 reasons, taking corresponding measures and making field records;
fifthly, anchor sealing:
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 sundries in the stretched hole, chiseling and washing clean, wherein the sealing material is preferably fine stone concrete with the same strength grade as the member, or micro-expansion concrete or low-shrinkage mortar or according to the design requirement;
sixthly, falling the shelf:
the unbonded prestress can be immediately dropped after tensioning is finished, a bottom template of a beam and a plate is removed, and the construction load of an upper floor is considered when a template support is removed for an unbonded prestress member with a particularly large span.
The invention has the beneficial effects that: the application is that direct extrusion molding forms the surrounding layer on prestressing tendons to pack special grease in prestressing tendons between the surrounding layer, make prestressing tendons can slide in the surrounding layer. When in construction, the unbonded prestressed tendons are directly arranged in the steel bar framework, the prestressed tendons are tensioned after concrete is poured and reaches the design strength, and the prestress is transmitted to the component through the anchors at the two ends, so that the effective prestress is established in the structure. The tension equipment for the unbonded prestressed concrete structure is light and handy, does not need grouting, and is relatively simple and rapid in construction.
Drawings
The invention is described in further detail below with reference to the following figures and embodiments:
fig. 1 is a schematic view of a convex tensioning end.
FIG. 2 is a schematic view of a female tensioning end.
Fig. 3 is a schematic view of a unbonded rib stent format.
Detailed Description
As shown in fig. 1-3: a method for building a prestressed waffle slab for a large-scale clean electronic factory building comprises the following steps:
firstly, blanking and bundling without bonding ribs:
the blanking length of the unbonded rib is 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 （6-1）
in the formula: l ist-tunnel curve length;
h-curve rise;
l is the horizontal projection length of the curve;
the stretching working length is determined according to the type of the jack, generally 400mm at each end, and is determined according to real calculation during variable-angle stretching;
the blanking is cut by a grinding wheel cutting machine, and electric welding and oxy-acetylene cutting are not adopted. After cutting, coiling according to the diameter of 2m, binding, numbering and then stacking in a classified manner, and after material breaking, carrying out extrusion installation on an extrusion anchor at one end of the prestressed tendon stretched at one end;
secondly, paving without bonding ribs:
1) paying off at the position without the bonding ribs: according to the design construction drawing and the turnover drawing, the position control points of the unbonded ribs are marked on the template or the common steel bars, the influence of the steel bar protective layer is noticed, the radius of the unbonded ribs (bundles) is deducted, the unbonded ribs at the tensioning end penetrate out of the template and are marked on the template one by one, and holes or grooves are punched at the corresponding positions of the template before the unbonded ribs penetrate out of the template, so that the unbonded ribs extend out of the template;
2) installation of the unbonded rib bracket: the non-adhesive ribs in the plate are generally made of phi 12 steel bars to control the curve elevation of the stirrup, the stirrups are not more than 2m apart from control points such as reverse bending points, and the like, and the stirrups are fixed on the steel bars of the bottom plate in a spot welding manner during installation; for unbonded reinforcements arranged in a beam in a bundling manner, short reinforcements with the same width as the stirrups are adopted to be fixed by spot welding, middle welding spots are added for multi-limb stirrups, the support is ensured to be horizontal, and the support interval is 1-1.5 m;
3) installing an anchor backing plate: for the convex tensioning end, the anchor backing plate is tightly attached to the corresponding position of the end die, the anchor backing plate is fixed with the non-prestressed ribs by electric welding (auxiliary connecting steel bars are added if necessary), the spiral ribs are tightly attached to the anchor backing plate and fixed, the spiral ribs are spot-welded on the anchor backing plate, the concave tensioning end is fixed at the position of 100mm in the template, plastic or foam is used as a cavity die, and the position of the anchor backing plate is kept vertical to the non-prestressed ribs when the anchor backing plate is installed;
4) laying unbonded ribs: when the unbonded ribs in the plate are laid, the unbonded ribs are placed on the stirrups according to numbers, the whole length of the unbonded ribs is parallel and cannot be twisted, the unbonded ribs stretched at one end penetrate through the fixed end, and finally the helical ribs, the anchor backing plate, the hole mold (simultaneously placed in) and the template penetrate out from the stretching end, the length of the unbonded ribs penetrating out of the template is not less than 300mm, and the unbonded ribs are straightened and straightened after the bundle penetrating is finished and are bound by lead wires and the stirrups; for the bidirectional prestressed plate, drawing a net-weaving graph of the unbonded reinforcement, determining the position relation of the cross point of the bidirectional unbonded reinforcement according to a curve coordinate, laying the unbonded reinforcement in the lower direction of a vertical coordinate during construction, laying the unbonded reinforcement in the other direction, and passing through the lower part of the unbonded reinforcement when part of the coordinate is lower than that of the unbonded reinforcement laid firstly; bundling unbonded ribs in the beams one by one, straightening at any time to keep the beams in a parallel state, straightening and binding with a bracket after each bundle is penetrated; the fixed end of the unbonded rib stretched at one end is placed at a designed position for spot welding and fixing;
5) after the unbonded ribs are laid, checking the conditions of the number, the damage, the position and the exposed length of the unbonded ribs, and processing the problems;
thirdly, pouring concrete:
1) the concrete pouring and tamping technology is carried out in advance, and the emphasis is placed on the compactness of the concrete in the anchoring area and the protection without bonding ribs;
2) before concrete pouring, all prestressed finished products must be checked again, and particularly, the damage and the displacement of the unbonded ribs should be noticed;
3) tracking and monitoring the whole pouring and tamping process, and timely processing the problems of damage, displacement and the like of the unbonded rib sheath when being found;
4) paying attention to another group of concrete construction test blocks to guide tensioning time;
fourthly, 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) calculating the theoretical elongation value of the 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, χ -the actual length of the curve segment (m);
e-modulus of elasticity under prestress;
θ -Curve angle (rad);
k is the offset coefficient;
μ — coefficient of friction (note taking the latest specification values or field testing);
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;
4) tensioning sequence of the unbonded ribs: sequentially tensioning the unbonded ribs in the plate; the unbonded ribs in the beam are symmetrically tensioned according to the plane position of the prestressed beam; when the beam slab has prestressed ribs, the unbonded ribs in the beam slab are firstly tensioned, and then the unbonded ribs (or the bonded ribs) in the beam are tensioned;
5) stretching program of the unbonded rib: the unbonded ribs stretched at two ends can be stretched to design stress at one end, then the stretching force is complemented at the other end, variable angle stretching and ultra-long bundle stretching are carried out, and measures such as graded stretching, ultra-stretching or ultra-stretching loosening technology and the like are adopted according to actual conditions:
normal tensioning: 0 → 0.1 σ con → σ con → anchor;
ultra-tensioning: 0 → 0.1 σ con → 1.03 σ con → anchor;
and (3) ultra-tension loosening: 0 → 0.1 σ con → 1.05 σ con → σ con → anchor;
6) before the anchorage device is installed, the embedded part at the tensioning end needs to be cleaned, an anchor plate is installed firstly, then clamping pieces are installed hole by hole, when the anchorage device is installed, the anchor plate is aligned to the center of the prestressed tendon, the clamping pieces are tightened, and gaps of the clamping pieces are uniform;
7) 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;
8) 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 reasons, taking corresponding measures and making field records;
fifthly, anchor sealing:
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 sundries in the stretched hole, chiseling and washing clean, wherein the sealing material is preferably fine stone concrete with the same strength grade as the member, or micro-expansion concrete or low-shrinkage mortar or according to the design requirement;
sixthly, falling the shelf:
the unbonded prestress can be immediately dropped after tensioning is finished, a bottom template of a beam and a plate is removed, and the construction load of an upper floor is considered when a template support is removed for an unbonded prestress member with a particularly large span.
Claims (1)
1. A method for building a prestressed waffle slab for a large-scale clean electronic factory is characterized by comprising the following steps:
firstly, blanking and bundling without bonding ribs:
the blanking length of the unbonded rib is 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 （6-1）
in the formula: l ist-tunnel curve length;
h-curve rise;
l is the horizontal projection length of the curve;
the stretching working length is determined according to the type of the jack, generally 400mm at each end, and is determined according to real calculation during variable-angle stretching;
the blanking is cut by a grinding wheel cutting machine, and electric welding and oxy-acetylene cutting are not adopted. After cutting, coiling according to the diameter of 2m, binding, numbering and then stacking in a classified manner, and after material breaking, carrying out extrusion installation on an extrusion anchor at one end of the prestressed tendon stretched at one end;
secondly, paving without bonding ribs:
1) paying off at the position without the bonding ribs: according to the design construction drawing and the turnover drawing, the position control points of the unbonded ribs are marked on the template or the common steel bars, the influence of the steel bar protective layer is noticed, the radius of the unbonded ribs (bundles) is deducted, the unbonded ribs at the tensioning end penetrate out of the template and are marked on the template one by one, and holes or grooves are punched at the corresponding positions of the template before the unbonded ribs penetrate out of the template, so that the unbonded ribs extend out of the template;
2) installation of the unbonded rib bracket: the non-adhesive ribs in the plate are generally made of phi 12 steel bars to control the curve elevation of the stirrup, the stirrups are not more than 2m apart from control points such as reverse bending points, and the like, and the stirrups are fixed on the steel bars of the bottom plate in a spot welding manner during installation; for unbonded reinforcements arranged in a beam in a bundling manner, short reinforcements with the same width as the stirrups are adopted to be fixed by spot welding, middle welding spots are added for multi-limb stirrups, the support is ensured to be horizontal, and the support interval is 1-1.5 m;
3) installing an anchor backing plate: for the convex tensioning end, the anchor backing plate is tightly attached to the corresponding position of the end die, the anchor backing plate is fixed with the non-prestressed ribs by electric welding (auxiliary connecting steel bars are added if necessary), the spiral ribs are tightly attached to the anchor backing plate and fixed, the spiral ribs are spot-welded on the anchor backing plate, the concave tensioning end is fixed at the position of 100mm in the template, plastic or foam is used as a cavity die, and the position of the anchor backing plate is kept vertical to the non-prestressed ribs when the anchor backing plate is installed;
4) laying unbonded ribs: when the unbonded ribs in the plate are laid, the unbonded ribs are placed on the stirrups according to numbers, the whole length of the unbonded ribs is parallel and cannot be twisted, the unbonded ribs stretched at one end penetrate through the fixed end, and finally the helical ribs, the anchor backing plate, the hole mold (simultaneously placed in) and the template penetrate out from the stretching end, the length of the unbonded ribs penetrating out of the template is not less than 300mm, and the unbonded ribs are straightened and straightened after the bundle penetrating is finished and are bound by lead wires and the stirrups; for the bidirectional prestressed plate, drawing a net-weaving graph of the unbonded reinforcement, determining the position relation of the cross point of the bidirectional unbonded reinforcement according to a curve coordinate, laying the unbonded reinforcement in the lower direction of a vertical coordinate during construction, laying the unbonded reinforcement in the other direction, and passing through the lower part of the unbonded reinforcement when part of the coordinate is lower than that of the unbonded reinforcement laid firstly; bundling unbonded ribs in the beams one by one, straightening at any time to keep the beams in a parallel state, straightening and binding with a bracket after each bundle is penetrated; the fixed end of the unbonded rib stretched at one end is placed at a designed position for spot welding and fixing;
5) after the unbonded ribs are laid, checking the conditions of the number, the damage, the position and the exposed length of the unbonded ribs, and processing the problems;
thirdly, pouring concrete:
1) the concrete pouring and tamping technology is carried out in advance, and the emphasis is placed on the compactness of the concrete in the anchoring area and the protection without bonding ribs;
2) before concrete pouring, all prestressed finished products must be checked again, and particularly, the damage and the displacement of the unbonded ribs should be noticed;
3) tracking and monitoring the whole pouring and tamping process, and timely processing the problems of damage, displacement and the like of the unbonded rib sheath when being found;
4) paying attention to another group of concrete construction test blocks to guide tensioning time;
fourthly, 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) calculating the theoretical elongation value of the 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, χ -the actual length of the curve segment (m);
e-modulus of elasticity under prestress;
θ -Curve angle (rad);
k is the offset coefficient;
μ — coefficient of friction (note taking the latest specification values or field testing);
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;
4) tensioning sequence of the unbonded ribs: sequentially tensioning the unbonded ribs in the plate; the unbonded ribs in the beam are symmetrically tensioned according to the plane position of the prestressed beam; when the beam slab has prestressed ribs, the unbonded ribs in the beam slab are firstly tensioned, and then the unbonded ribs (or the bonded ribs) in the beam are tensioned;
5) stretching program of the unbonded rib: the unbonded ribs stretched at two ends can be stretched to design stress at one end, then the stretching force is complemented at the other end, variable angle stretching and ultra-long bundle stretching are carried out, and measures such as graded stretching, ultra-stretching or ultra-stretching loosening technology and the like are adopted according to actual conditions:
normal tensioning: 0 → 0.1 σ con → σ con → anchor;
ultra-tensioning: 0 → 0.1 σ con → 1.03 σ con → anchor;
and (3) ultra-tension loosening: 0 → 0.1 σ con → 1.05 σ con → σ con → anchor;
6) before the anchorage device is installed, the embedded part at the tensioning end needs to be cleaned, an anchor plate is installed firstly, then clamping pieces are installed hole by hole, when the anchorage device is installed, the anchor plate is aligned to the center of the prestressed tendon, the clamping pieces are tightened, and gaps of the clamping pieces are uniform;
7) 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;
8) 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 reasons, taking corresponding measures and making field records;
fifthly, anchor sealing:
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 sundries in the stretched hole, chiseling and washing clean, wherein the sealing material is preferably fine stone concrete with the same strength grade as the member, or micro-expansion concrete or low-shrinkage mortar or according to the design requirement;
sixthly, falling the shelf:
the unbonded prestress can be immediately dropped after tensioning is finished, a bottom template of a beam and a plate is removed, and the construction load of an upper floor is considered when a template support is removed for an unbonded prestress member with a particularly large span.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011439480.3A CN112627540A (en) | 2020-12-11 | 2020-12-11 | Construction method of prestressed waffle slab for large-scale clean electronic factory building |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202011439480.3A CN112627540A (en) | 2020-12-11 | 2020-12-11 | Construction method of prestressed waffle slab for large-scale clean electronic factory building |
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| 潘珉: "超长多层多跨现浇连廊后张法预应力施工技术", 《建材与装饰》 * |
| 王玉国等: "某工程双向加腋大跨预应力框架梁变角张拉施工技术", 《安徽建筑》 * |
| 陈冬泉等: "189m超长混凝土结构无缝施工技术", 《施工技术》 * |
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