阅读说明：本技术 一种预应力现浇空心楼板加固施工方法 (Prestressed cast-in-place hollow floor slab reinforcing construction method ) 是由 相超 刘庆毅 周烨 余海梅 全有维 于 2021-08-31 设计创作，主要内容包括：本发明提供一种预应力现浇空心楼板加固施工方法,包括下述步骤：S1、现场测量放线；S2、梁底部设置支撑；S3、静力切割；S4、预应力筋放张；S5、转换锚具；S6、分隔楼板连接。本发明可实现对预应力现浇空心楼板加固的有效控制,保证楼板加固的质量。(The invention provides a construction method for reinforcing a prestressed cast-in-place hollow floor slab, which comprises the following steps: s1, measuring and setting out the line on site; s2, arranging a support at the bottom of the beam; s3, carrying out static cutting; s4, releasing the prestressed tendons; s5, converting anchors; and S6, connecting the partition floor. The invention can realize effective control on the reinforcement of the prestressed cast-in-place hollow floor slab and ensure the quality of the floor slab reinforcement.)

1. A construction method for reinforcing a prestressed cast-in-place hollow floor slab is characterized by comprising the following steps:

s1, field measurement and setting-out: estimating the distribution position of the prestressed tendons according to the measurement paying-off position of the large surface and making corresponding marks;

s2, arranging a support at the bottom of the beam: arranging a full-space support frame on the lower side of the floor slab at the tension releasing part for temporary support and applying stress;

s3, static force cutting: determining a prestressed tendon, chiseling off cut concrete, and clamping into a V-shaped anchorage device;

s4, releasing and tensioning the prestressed tendons: installing a jack and a tool anchor, starting a pump for tensioning, and performing oil return anchoring;

s5, switching anchors: after the prestressed tendons are tensioned, fixing the prestressed tendons by using a U-shaped anchorage device; after the U-shaped anchorage device is fixed, grouting at the upper opening of the anchorage device;

s6, connecting the partition floor: and carrying out subsequent concrete dismantling operation.

2. The prestressed cast-in-place hollow floor slab reinforcement construction method according to claim 1, wherein in S2, the concrete operations are:

1) measuring the distance from the wall and the top surface at the bottom of the beam in the range needing to open the hole according to the construction requirements by using a ruler, and marking; straightening by using a steel tape, separating the position of the upright rod, and pointing out the upright rod mark by using a small bamboo chip; the base plate and the base are accurately placed on the positioning line, and the base plate is stably laid and cannot be suspended in the air;

2) in the process of building a first-layer scaffold, an inclined strut is arranged in each frame grid along the periphery, corners are increased in two directions, and the scaffold at the position can be detached after being reliably tied with the wall connecting rod piece of the main structure; when the scaffold operation layer is higher than the wall connecting piece by two steps, taking temporary stabilizing measures until the wall connecting piece is completely built and then being disassembled;

3) the scaffold extends from the middle to two sides; connecting and fixing the longitudinal and transverse rods and the upright rods in sequence according to positioning, then installing the longitudinal and transverse flat rods in the step 1, fixing the rods after the upright rods are corrected to be vertical, and continuously upwards erecting according to the requirement;

4) before the first row of wall connecting pieces are arranged, the scaffold is provided with a necessary number of throwing supports for ensuring the stability of the framework and the safety of operators on the scaffold.

3. The method for reinforcing the prestressed cast-in-situ hollow floor slab as claimed in claim 2, wherein when the scaffold boards are laid in a butt-joint manner, the distance between the butt-joint portion and the supporting cross bars at the lower two sides of the scaffold boards is controlled to be between 100mm and 200 mm; when the scaffold boards are laid in a vertical direction, the distance between the lower supporting cross rods of the scaffold boards is not more than 1.0 m; the longitudinal paving scaffold board is bound and fixed with the lower supporting cross bar according to the following specified parts: two ends and corners of the scaffold, positions every 1.5-2.0m in the length direction of the plate and two ends of the ramp.

4. The prestressed cast-in-place hollow floor slab reinforcement construction method according to claim 1, wherein in S3, the concrete operation of determining the prestressed tendons is:

1) after the support system is built, referring to the original structure prestress construction drawing, corresponding to the beam-column axis in the solid structure, determining the direction and the position of the internal prestress rib according to the pouring sequence of the original prestress cast-in-place hollow floor slab, and marking the floor slab;

2) scanning the position of a prestressed floor slab needing to be dismantled by using a three-dimensional scanner, modeling and estimating the approximate distribution of prestressed tendons by using BIM and rhinoceros software, checking the reverse direction of the built BIM with the prestressed tendons marked on the site floor slab, finding out a deviation point and carrying out second marking;

3) the prestressed tendons marked on the two sides are detected by using a steel bar detecting instrument, the prestressed tendons are slowly moved from one side to the other side, which needs to be cut off, the steel bars are ensured to be displayed in the center of a display screen of the detecting instrument in the detection process, along with the marks during detection, and the thickness of the concrete protective layer is recorded every 200 mm.

5. The prestressed cast-in-place hollow floor slab reinforcement construction method as claimed in claim 1, wherein in S3, the concrete chiseling and cutting operation is:

1) after the position of the prestressed tendon is determined, chiseling the prestressed tendon by using a small manual machine along the direction of the prestressed tendon, and flattening the edge of the opening and being vertical to the prestressed tendon;

2) when the concrete around the prestressed tendons is chiseled, firstly, the marked two prestressed tendons are broken, the paying-off is carried out from outside to inside, the breaking is carried out from the periphery to the inside by one circle, the uniform unloading force between the concrete and the prestressed tendons is ensured, and the chiseling of the concrete is carried out on the basis of ensuring that the strength of the steel bars meets the conditions; when the prestressed ribs are broken, the points are broken first, and then different points are connected to form a long strip shape so as to expose the prestressed ribs in the middle; when the root of the prestressed tendon is cut off, the traditional chiseling tool is used for knocking out the concrete at the root, and the concrete is repaired neatly along the edge of the opening, so that the V-shaped anchorage device can be placed.

6. The prestressed cast-in-place hollow floor slab reinforcement construction method as claimed in claim 1, wherein, in S3, the concrete operation of clipping in the V-shaped anchorage device is:

1) after the hole is formed, the side surface of the concrete is trimmed, so that the V-shaped anchorage has a smooth surface with uniform stress, and the uniform stress is ensured; exposing the original prestressed tendons after chiseling concrete around the prestressed tendons, checking the thickness and the damage degree of the steel bars, and removing and cleaning the roots of the steel bars and a concrete floor slab without a hole to prepare for clamping into a V-shaped anchorage device;

2) sleeving the prestressed tendons into a V-shaped anchorage device, aligning an upper conical opening of an opening clamping piece of the V-shaped anchorage device with a concrete floor slab, aligning a lower conical opening with a perforated floor slab, gradually screwing M16 high-strength bolts perpendicular to the V-shaped anchorage device after an upper clamp and a lower clamp are clamped, and fixing the prestressed tendons in a grouping symmetry mode when the high-strength bolts are fastened;

3) and clamping the V-shaped anchor and clamping the clamping piece to implement temporary transition conversion of the anchor.

7. The prestressed cast-in-place hollow floor slab reinforcement construction method according to claim 1, wherein in S4, the concrete operations are:

1) two steel rods with the diameter of 100mm are arranged between the tensioning limit plate and the working anchor, a jack is arranged, and a jack oil cylinder extends out 15mm before tensioning; a tool anchor and a tool clamping piece are arranged, a steel strand needing to be stretched is installed on the clamping piece, and an oil pump is started to stretch;

2) after the clamping piece is taken out, the pressure is released and oil return is carried out, and the steel strand is retracted along with the oil cylinder; the prestressed tendon achieves stability in tension control stress, and the deviation between the actual measurement elongation and the theoretical elongation is not more than +/-6%, so that anchoring can be realized; after the anchoring is finished and the testing is qualified, the redundant prestressed tendons at the end head can be cut, and the exposed length after the anchoring is not less than 30 mm.

8. The prestressed cast-in-place hollow floor slab reinforcement construction method according to claim 1, wherein in S5, the concrete operations are:

1) after the prestressed tendons are tensioned, fixing the prestressed tendons by using a U-shaped anchorage device, wherein the end of the U-shaped anchorage device is provided with three holes, three strands of steel strands can be anchored simultaneously, the tensioned steel bars penetrate into the end of the anchorage device, a conical member is inserted into the round holes, and the anchorage device is used for realizing permanent fixation on the tensioned prestressed tendons by using the friction force of steel bar retraction and the conical member, so that anchorage device conversion is realized;

2) after the U-shaped anchorage device is fixed, grouting at the upper opening of the anchorage device; starting a grouting pump, connecting a conveying pipe on the pump to an outlet pipe on a U-shaped anchor when slurry output by the grouting pump reaches the required consistency, and starting grouting; and (4) continuing to work by the grouting pump, closing the grout inlet valve when the pore canal grouting is pressurized to 0.6-0.7MPa, and continuously shielding the grout for 2-3 minutes before closing.

9. The prestressed cast-in-place hollow floor slab reinforcement construction method according to claim 1, wherein in S6, the concrete operations are: after the tension releasing is finished, the subsequent concrete dismantling operation can be carried out; for concrete which is not removed before releasing construction and reinforcing steel bars which need to be cut off, static cutting is adopted for removal, the connection between the prestressed plate and the removal part is separated, and the prestressed plate is prevented from being greatly disturbed by the removal; a specially-assigned person is arranged at the lower part of the hole opening part to prevent striking injury; after the concrete and the anchorage device are completely separated, the opening and the reinforcement of the middle part of the prestressed cast-in-situ hollow floor slab due to function improvement are realized.

Technical Field

The invention relates to the technical field of prestressed cast-in-place hollow floor slab reinforcement, in particular to a construction method for reinforcing a prestressed cast-in-place hollow floor slab.

Background

With the overall advance of the modern industrialization of the construction industry, new buildings are continuously generated and replaced by old buildings. However, for buildings with special memorial significance and history, it is one of the important links in the construction industry to preserve the original historical features and to perform modification and internal upgrade on the basis to meet the modern use requirements, and it is also a hot issue in recent years to perform repair and modification by using the original buildings.

Disclosure of Invention

Aiming at the prior art, the invention provides a construction method for reinforcing a prestressed cast-in-place hollow floor slab, which is based on the structural foundation of the original prestressed cast-in-place hollow floor slab, analyzes the structural model and the stress, further refines and perfects the structural model and the stress, and determines the feasibility and the construction sequence of reinforcing the hollow floor slab, thereby realizing the possibility of transforming and reinforcing the prestressed cast-in-place hollow floor slab, improving the function utilization rate of old buildings, not only keeping the original historical appearance, but also realizing the new internal functions.

The invention provides a construction method for reinforcing a prestressed cast-in-place hollow floor slab, which comprises the following steps:

s1, field measurement and setting-out: estimating the distribution position of the prestressed tendons according to the measurement paying-off position of the large surface and making corresponding marks;

s2, arranging a support at the bottom of the beam: arranging a full-space support frame on the lower side of the floor slab at the tension releasing part for temporary support and applying stress;

s3, static force cutting: determining a prestressed tendon, chiseling off cut concrete, and clamping into a V-shaped anchorage device;

s4, releasing and tensioning the prestressed tendons: installing a jack and a tool anchor, starting a pump for tensioning, and performing oil return anchoring;

s5, switching anchors: after the prestressed tendons are tensioned, fixing the prestressed tendons by using a U-shaped anchorage device; after the U-shaped anchorage device is fixed, grouting at the upper opening of the anchorage device;

s6, connecting the partition floor: and carrying out subsequent concrete dismantling operation.

Preferably, in S2, the specific operation is:

1) measuring the distance from the wall and the top surface at the bottom of the beam in the range needing to open the hole according to the construction requirements by using a ruler, and marking; straightening by using a steel tape, separating the position of the upright rod, and pointing out the upright rod mark by using a small bamboo chip; the base plate and the base are accurately placed on the positioning line, and the base plate is stably laid and cannot be suspended in the air;

2) in the process of building a first-layer scaffold, an inclined strut is arranged in each frame grid along the periphery, corners are increased in two directions, and the scaffold at the position can be detached after being reliably tied with the wall connecting rod piece of the main structure; when the scaffold operation layer is higher than the wall connecting piece by two steps, taking temporary stabilizing measures until the wall connecting piece is completely built and then being disassembled;

3) the scaffold extends from the middle to two sides; connecting and fixing the longitudinal and transverse rods and the upright rods in sequence according to positioning, then installing the longitudinal and transverse flat rods in the step 1, fixing the rods after the upright rods are corrected to be vertical, and continuously upwards erecting according to the requirement;

4) before the first row of wall connecting pieces are arranged, the scaffold is provided with a necessary number of throwing supports for ensuring the stability of the framework and the safety of operators on the scaffold.

Preferably, when the scaffold boards are butted and tiled, the distance between the scaffold boards and the supporting cross bars at the lower two sides of the scaffold boards is controlled to be between 100mm and 200 mm; when the scaffold boards are laid in a vertical direction, the distance between the lower supporting cross rods of the scaffold boards is not more than 1.0 m; the longitudinal paving scaffold board is bound and fixed with the lower supporting cross bar according to the following specified parts: two ends and corners of the scaffold, positions every 1.5-2.0m in the length direction of the plate and two ends of the ramp.

Preferably, in S3, the specific operation of determining the tendon is:

1) after the support system is built, referring to the original structure prestress construction drawing, corresponding to the beam-column axis in the solid structure, determining the direction and the position of the internal prestress rib according to the pouring sequence of the original prestress cast-in-place hollow floor slab, and marking the floor slab;

2) scanning the position of a prestressed floor slab needing to be dismantled by using a three-dimensional scanner, modeling and estimating the approximate distribution of prestressed tendons by using BIM and rhinoceros software, checking the reverse direction of the built BIM with the prestressed tendons marked on the site floor slab, finding out a deviation point and carrying out second marking;

3) the prestressed tendons marked on the two sides are detected by using a steel bar detecting instrument, the prestressed tendons are slowly moved from one side to the other side, which needs to be cut off, the steel bars are ensured to be displayed in the center of a display screen of the detecting instrument in the detection process, along with the marks during detection, and the thickness of the concrete protective layer is recorded every 200 mm.

Preferably, in S3, the concrete chiseling and cutting operation is as follows:

1) after the position of the prestressed tendon is determined, chiseling the prestressed tendon by using a small manual machine along the direction of the prestressed tendon, and flattening the edge of the opening and being vertical to the prestressed tendon;

2) when the concrete around the prestressed tendons is chiseled, firstly, the marked two prestressed tendons are broken, the paying-off is carried out from outside to inside, the breaking is carried out from the periphery to the inside by one circle, the uniform unloading force between the concrete and the prestressed tendons is ensured, and the chiseling of the concrete is carried out on the basis of ensuring that the strength of the steel bars meets the conditions; when the prestressed ribs are broken, the points are broken first, and then different points are connected to form a long strip shape so as to expose the prestressed ribs in the middle; when the root of the prestressed tendon is cut off, the traditional chiseling tool is used for knocking out the concrete at the root, and the concrete is repaired neatly along the edge of the opening, so that the V-shaped anchorage device can be placed.

Preferably, in S3, the specific operation of snapping into the V-shaped anchor is:

1) after the hole is formed, the side surface of the concrete is trimmed, so that the V-shaped anchorage has a smooth surface with uniform stress, and the uniform stress is ensured; exposing the original prestressed tendons after chiseling concrete around the prestressed tendons, checking the thickness and the damage degree of the steel bars, and removing and cleaning the roots of the steel bars and a concrete floor slab without a hole to prepare for clamping into a V-shaped anchorage device;

2) sleeving the prestressed tendons into a V-shaped anchorage device, aligning an upper conical opening of an opening clamping piece of the V-shaped anchorage device with a concrete floor slab, aligning a lower conical opening with a perforated floor slab, gradually screwing M16 high-strength bolts perpendicular to the V-shaped anchorage device after an upper clamp and a lower clamp are clamped, and fixing the prestressed tendons in a grouping symmetry mode when the high-strength bolts are fastened;

3) and clamping the V-shaped anchor and clamping the clamping piece to implement temporary transition conversion of the anchor.

Preferably, in S4, the specific operations are:

1) two steel rods with the diameter of 100mm are arranged between the tensioning limit plate and the working anchor, a jack is arranged, and a jack oil cylinder extends out 15mm before tensioning; a tool anchor and a tool clamping piece are arranged, a steel strand needing to be stretched is installed on the clamping piece, and an oil pump is started to stretch;

2) after the clamping piece is taken out, the pressure is released and oil return is carried out, and the steel strand is retracted along with the oil cylinder; the prestressed tendon achieves stability in tension control stress, and the deviation between the actual measurement elongation and the theoretical elongation is not more than +/-6%, so that anchoring can be realized; after the anchoring is finished and the testing is qualified, the redundant prestressed tendons at the end head can be cut, and the exposed length after the anchoring is not less than 30 mm.

Preferably, in S5, the specific operations are:

1) after the prestressed tendons are tensioned, fixing the prestressed tendons by using a U-shaped anchorage device, wherein the end of the U-shaped anchorage device is provided with three holes, three strands of steel strands can be anchored simultaneously, the tensioned steel bars penetrate into the end of the anchorage device, a conical member is inserted into the round holes, and the anchorage device is used for realizing permanent fixation on the tensioned prestressed tendons by using the friction force of steel bar retraction and the conical member, so that anchorage device conversion is realized;

2) after the U-shaped anchorage device is fixed, grouting at the upper opening of the anchorage device; starting a grouting pump, connecting a conveying pipe on the pump to an outlet pipe on a U-shaped anchor when slurry output by the grouting pump reaches the required consistency, and starting grouting; and (4) continuing to work by the grouting pump, closing the grout inlet valve when the pore canal grouting is pressurized to 0.6-0.7MPa, and continuously shielding the grout for 2-3 minutes before closing.

Preferably, in S6, the specific operations are: after the tension releasing is finished, the subsequent concrete dismantling operation can be carried out; for concrete which is not removed before releasing construction and reinforcing steel bars which need to be cut off, static cutting is adopted for removal, the connection between the prestressed plate and the removal part is separated, and the prestressed plate is prevented from being greatly disturbed by the removal; a specially-assigned person is arranged at the lower part of the hole opening part to prevent striking injury; after the concrete and the anchorage device are completely separated, the opening and the reinforcement of the middle part of the prestressed cast-in-situ hollow floor slab due to function improvement are realized.

Compared with the prior art, the invention has the beneficial effects that:

1. the prestressed rib detecting and locating chiseling technology. The invention utilizes a three-dimensional model and a detecting instrument to determine the position of an internal prestressed tendon of the original prestressed cast-in-situ hollow floor slab, and supports are arranged at the bottom of a partially prestressed beam slab to be dismantled and apply a jacking force. The concrete is chiseled on the basis of ensuring that the strength of the steel bars meets the conditions, so that the middle part of the floor slab is provided with a hole and the building function is increased.

2. A prestressed bar stretching anchorage device conversion technology. The method provided by the invention can be used for cutting the damaged prestressed tendons and redundant steel strands and finishing the flatness of the side edge of the concrete. The V-shaped anchorage device is clamped and the clamping piece is clamped, so that the anchorage device is temporarily fixed. And after the stress relaxation of the opening is finished, the V-shaped anchorage device is replaced by a single-cable anchorage device to realize permanent fixation, and the conversion of the stretching anchorage device is finished.

3. And (5) placing and tensioning and floor slab reinforcing technology. The prestressed reinforcing steel at the opening position is longer, the prestressed reinforcing steel can be greatly retracted when the reinforcing steel is cut and expanded, a construction scheme of sequentially and slowly expanding the prestressed reinforcing steel along a concrete surface is adopted, a V-shaped anchorage device is adopted for anchoring in place before expanding, a mode of manually digging and chiseling the concrete around the original anchorage device is adopted for expanding, static cutting is adopted after expanding is completed, the prestressed plate is separated from the dismantling part, great disturbance on the prestressed plate due to dismantling is prevented, the function utilization rate of old buildings is improved, the original historical appearance is kept, and new functions inside the old buildings are realized.

4. The invention solves the problems that the original building function can not meet the existing building requirements and the existing building can not be reformed and reinforced on the old building of the prestressed cast-in-situ hollow floor slab with special significance. Compared with other old buildings, the invention has simple operation principle, realizes local dismantling and reinforcing in the building without damaging the external building effect and the structure safety, meets the requirement of current city renewal, retains and renovates the building function, and meets the requirement of creating green buildings.

Drawings

Fig. 1 is a schematic flow chart of a construction method for reinforcing a prestressed cast-in-place hollow floor slab according to an embodiment of the present invention.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further explained below by combining the specific drawings.

Examples

As shown in fig. 1, a construction method for reinforcing a prestressed cast-in-place hollow floor slab includes the following steps:

s1, field measurement and setting-out: and (4) estimating the distribution position of the prestressed tendons according to the measurement and paying-off position of the large surface and making corresponding marks.

S2, arranging a support at the bottom of the beam: in order to ensure the structural safety of the tension releasing position plate and prevent the over-large deflection of the plate caused by the self retraction of the prestressed tendon after the prestressed steel strand is released and tensioned, the structural safety is threatened; meanwhile, as the temporary V-shaped anchorage is disturbed in the stress releasing and tensioning process, in order to prevent failure of temporary anchoring, a full-space support frame is arranged at the lower side of the floor slab at the releasing and tensioning part for temporary support and stress application, so that the safety of the prestressed plate is ensured.

The method comprises the following specific operations:

1) measuring the distance from the wall and the top surface at the bottom of the beam in the range needing to open the hole according to the construction requirements by using a ruler, and marking; straightening by using a steel tape, separating the position of the upright rod, and pointing out the upright rod mark by using a small bamboo chip; the base plate and the base are accurately placed on the positioning line, and the base plate is stably laid and cannot be suspended in the air;

2) in the process of building a first-layer scaffold, an inclined strut is arranged in each frame grid along the periphery, corners are increased in two directions, and the scaffold at the position can be detached after being reliably tied with the wall connecting rod piece of the main structure; when the scaffold operation layer is higher than the wall connecting piece by two steps, taking temporary stabilizing measures until the wall connecting piece is completely built and then being disassembled;

3) the scaffold extends from the middle to two sides; connecting and fixing the longitudinal and transverse rods and the upright rods in sequence according to positioning, then installing the longitudinal and transverse flat rods in the step 1, fixing the rods after the upright rods are corrected to be vertical, and continuously upwards erecting according to the requirement;

4) before the first row of wall connecting pieces are arranged, the scaffold is provided with a necessary number of throwing supports for ensuring the stability of the framework and the safety of operators on the scaffold.

Wherein, the scaffold board or other planks are paved, laid and fixed stably and bound when necessary; when the scaffold boards are butted and tiled, the distance between the scaffold boards and the supporting cross bars at the lower two sides of the scaffold boards is controlled between 100mm and 200 mm; when the scaffold board is laid, the lapping length of the scaffold board is not less than 200mm, and a supporting cross rod is arranged in the middle of the lapping section; when the long scaffold boards are laid longitudinally, the distance between the lower supporting cross rods is not more than 1.0 m; the longitudinal paving scaffold board is bound and fixed with the lower supporting cross bar according to the following specified parts: two ends and corners of the scaffold, every 1.5-2.0m in the length direction of the slab, two ends of the ramp and other parts which can slide and tilt; when the wall connecting piece or other bracing and pulling rod pieces are arranged, the degree of tightness of bracing and pulling is required to be mastered, so that the rod pieces and the whole frame are prevented from being obviously deformed; the design of the framework cannot be changed at will during erection, the arrangement of rod fittings is reduced, and the framework size of the longitudinal distance of the opposite rods is enlarged by more than or equal to 100 mm.

S3, static force cutting: determining the prestressed tendons: the concrete is chiseled off and cut, and the V-shaped anchorage is clamped in.

The specific operation of determining the prestressed tendons is as follows:

1) after the support system is built, referring to the original structure prestress construction drawing, corresponding to the beam-column axis in the solid structure, determining the direction and the position of the internal prestress rib according to the pouring sequence of the original prestress cast-in-place hollow floor slab, and marking the floor slab;

2) scanning the position of a prestressed floor slab needing to be dismantled by using a three-dimensional scanner, modeling and estimating the approximate distribution of prestressed tendons by using BIM and rhinoceros software, checking the reverse direction of the built BIM with the prestressed tendons marked on the site floor slab, finding out a deviation point and carrying out second marking;

3) use reinforcing bar detecting instrument to detect the prestressing tendons of both sides mark, from the one side slow movement that needs the excision to the opposite side, guarantee in the testing process that the reinforcing bar shows at the center of detecting instrument display screen, along with detecting along with the mark to every 200mm record concrete protective layer's thickness, so that follow-up chisel removes the accuracy, reduces the risk of chisel removal damage prestressing tendons.

The concrete operation of chiseling and cutting concrete is as follows:

1) after the position of the prestressed tendon is determined, chiseling the prestressed tendon in the direction of the prestressed tendon by using a method of carefully chiseling by using a small manual machine, wherein the edge of a hole is smooth and is vertical to the prestressed tendon; the size of the hole is suitable for operating the V-shaped anchorage device, and the V-shaped anchorage device can be operated generally in a 15cm square;

2) when the concrete around the prestressed tendons is chiseled, firstly, the marked two prestressed tendons are broken, the paying-off is carried out from outside to inside, the breaking is carried out from the periphery to the inside by one circle, the uniform unloading force between the concrete and the prestressed tendons is ensured, and the chiseling of the concrete is carried out on the basis of ensuring that the strength of the steel bars meets the conditions; when the prestressed ribs are broken, the points are broken first, and then different points are connected to form a long strip shape so as to expose the prestressed ribs in the middle; when the root of the prestressed tendon is cut off, the traditional chiseling tool is used for knocking out the concrete at the root, and the concrete is repaired neatly along the edge of the opening, so that the V-shaped anchorage device can be placed.

The specific operation of the snap-in V-anchor is:

1) after the hole is formed, the side surface of the concrete is trimmed, so that the V-shaped anchorage has a smooth surface with uniform stress, and the uniform stress is ensured; exposing the original prestressed tendons after chiseling concrete around the prestressed tendons, checking the thickness and the damage degree of the steel bars, and removing and cleaning the roots of the steel bars and a concrete floor slab without a hole to prepare for clamping into a V-shaped anchorage device;

2) sleeving a prestressed tendon into a V-shaped anchorage, aligning an upper conical opening of an opening clamping piece of the V-shaped anchorage to a concrete floor, aligning a lower conical opening to a perforated floor, after an upper clamp and a lower clamp are clamped, gradually screwing an M16 high-strength bolt perpendicular to the V-shaped anchorage, fixing the prestressed tendon in a grouping symmetry mode when fastening the high-strength bolt, wherein the speed is first and the speed is second during fixing, so that disturbance to a structure caused by uneven retraction of a steel bar due to over-tightening of one end is avoided, the retraction of the steel bar needs to be considered at the fixed distance of the V-shaped anchorage, and a certain distance is reserved between the V-shaped anchorage and the floor;

3) clamping the V-shaped anchor and clamping the clamping piece to implement temporary transition conversion of the anchor; the clamping piece type anchorage device anchors the steel strand by utilizing the friction resistance of the clamping piece and the steel strand.

S4, releasing and tensioning the prestressed tendons: and (5) installing a jack and a tool anchor, starting a pump for tensioning, and performing oil return anchoring.

The method comprises the following specific operations:

1) two steel rods with the diameter of 100mm are arranged between the tensioning limit plate and the working anchor, a jack is arranged, and a jack oil cylinder extends out 15mm before tensioning; a tool anchor and a tool clamping piece are arranged, a steel strand needing to be stretched is installed on the clamping piece, and an oil pump is started to stretch; the tensioning sequence of the prestressed tendons meets the design requirement, the prestressed tendons are symmetrically tensioned in batches and stages, the upward pressure is required to be slow, whether the working clamping pieces are loosened or not is observed, the clamping pieces can be pulled out by a screwdriver when the oil cylinder is pulled to about 17cm, and tensioning construction operators and oil pump operators need to keep good communication. According to the calibration report of the jack, calculating the oil meter value corresponding to the tension stress in advance, and performing bottom crossing on oil pump operators to realize the purpose of counting in mind;

2) after the clamping piece is taken out, the pressure is released and oil return is carried out, and the steel strand is retracted along with the oil cylinder; the prestressed tendon achieves stability in tension control stress, and the deviation between the actual measurement elongation and the theoretical elongation is not more than +/-6%, so that anchoring can be realized; after the anchoring is finished and the testing is qualified, cutting redundant prestressed tendons at the end head, wherein the exposed length after the anchoring is not less than 30 mm; the electric arc welding cutting is strictly forbidden, and a grinding wheel machine is used for cutting. According to the method, the anchoring can be finished by circulating for one or two times.

S5, switching anchors: after the prestressed tendons are tensioned, fixing the prestressed tendons by using a U-shaped anchorage device; and after the U-shaped anchorage device is fixed, grouting at the upper opening of the anchorage device.

The method comprises the following specific operations:

1) after the prestressed tendons are tensioned, fixing the prestressed tendons by using a U-shaped anchorage device, wherein the end of the U-shaped anchorage device is provided with three holes, three strands of steel strands can be anchored simultaneously, the tensioned steel bars penetrate into the end of the anchorage device, a conical member is inserted into the round holes, and the anchorage device is used for realizing permanent fixation on the tensioned prestressed tendons by using the friction force of steel bar retraction and the conical member, so that anchorage device conversion is realized;

2) after the U-shaped anchorage device is fixed, grouting at the upper opening of the anchorage device; starting a grouting pump, connecting a conveying pipe on the pump to an outlet pipe on a U-shaped anchor when slurry output by the grouting pump reaches the required consistency, and starting grouting; and (4) continuing to work by the grouting pump, closing the grout inlet valve when the pore canal grouting is pressurized to 0.6-0.7MPa, and continuously shielding the grout for 2-3 minutes before closing.

S6, connecting the partition floor: and carrying out subsequent concrete dismantling operation.

The method comprises the following specific operations: after the tension releasing is finished, the subsequent concrete dismantling operation can be carried out; for concrete which is not removed before releasing construction and reinforcing steel bars which need to be cut off, static cutting is adopted for removal, the connection between the prestressed plate and the removal part is separated, and the prestressed plate is prevented from being greatly disturbed by the removal; a specially-assigned person is arranged at the lower part of the hole opening part to prevent striking injury; after the concrete and the anchorage device are completely separated, the opening and the reinforcement of the middle part of the prestressed cast-in-situ hollow floor slab due to function improvement are realized.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures made by using the contents of the present specification and the drawings can be directly or indirectly applied to other related technical fields, and are within the scope of the present invention.