CN111364370A - Cast-in-place box girder support construction process - Google Patents
Cast-in-place box girder support construction process Download PDFInfo
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- CN111364370A CN111364370A CN202010255276.XA CN202010255276A CN111364370A CN 111364370 A CN111364370 A CN 111364370A CN 202010255276 A CN202010255276 A CN 202010255276A CN 111364370 A CN111364370 A CN 111364370A
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- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
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Abstract
The invention discloses a construction process of a cast-in-place box girder bracket, belonging to the field of bridge construction, and the process comprises the following steps: s1, foundation treatment; s2, assembling a frame body; s3, installing a template, wherein an adjustable bracket is arranged at the top end of the upright rod, and a plate supporting assembly and a bottom template are arranged on the adjustable bracket; s4, preloading, namely paving a plurality of interference pressing pieces on the bottom template, and preloading the frame body by the total weight of the pre-pressing pieces according to 120% of the dead weight of the box girder; s5, adjusting the bottom template, and after pre-pressing is finished, adjusting the elevation, the pre-camber and the transverse curve of the bottom template through an adjustable bracket according to pre-pressing data; and S6, casting the box girder, binding and molding a box girder bottom plate and a web plate reinforcing steel bar on the template, and casting concrete.
Description
Technical Field
The invention relates to the field of bridge construction, in particular to a construction process of a cast-in-place box girder support.
Background
With the improvement of bridge technology in China, the quality requirement of bridges is higher and higher, and the cast-in-place box beam plays an important role in bridge construction due to the advantages of simple appearance, high torsional rigidity, good integrity, strong applicability and the like. The construction of the box girder support is very important in the construction process of the cast-in-place box girder, the construction problem of the box girder is complex, the domestic research is not completely mature, and the overall design ideas of enterprises on the construction of the box girder support are different, so that the design diversity and the construction quality of the cast-in-place box girder support are different, and therefore, the construction process of the cast-in-place box girder support is necessary to be provided to improve the construction quality of the cast-in-place box girder.
Disclosure of Invention
The invention aims to provide a cast-in-place box girder support construction process to improve the construction quality of a cast-in-place box girder.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a construction process of a cast-in-place box girder support comprises the following steps:
s1, treating a foundation, namely pouring a concrete layer on the ground to form the foundation, and mounting a plurality of height-adjustable supporting bases on the foundation;
s2, assembling a frame body, namely installing a plurality of vertical rods on a foundation through a supporting base, connecting longitudinal and transverse horizontal rods as ground sweeping rods at the bottommost parts of the vertical rods through fasteners respectively, erecting a plurality of horizontal cross rods among the vertical rods, and arranging a horizontal rod as a sealing ejector rod at the fastener at the topmost end of the vertical rod;
s3, installing a template, wherein an adjustable bracket is arranged at the top end of the upright rod, and a plate supporting assembly and a bottom template are arranged on the adjustable bracket;
s4, pre-pressing load, namely paving a pressing part on the bottom template, pre-pressing the frame body by the total weight of the pressing part according to 120% of the dead weight of the box girder, and unloading the pressing part if the accumulated settlement of the frame body is not more than 3mm for not less than 3 days continuously; then, checking the height change of the floor template, the elasticity, the inelastic deformation and the stability of the frame body again at intervals of 6-8 hours to obtain prepressing data;
s5, adjusting the bottom template, and after pre-pressing is completed, adjusting the elevation, the pre-camber and the transverse curve of the bottom template through an adjusting rod according to pre-pressing data;
and S6, pouring the box girder, binding and molding the box girder bottom plate and the web plate reinforcing steel bars on the template, and pouring concrete.
Furthermore, the frame body is composed of the cross rods, the vertical rods, the floor sweeping rods and the top sealing rods, a plurality of vertical cross braces are longitudinally and transversely arranged on the periphery of the outer side and inside of the frame body respectively, and horizontal cross braces are continuously arranged on each layer of top sealing rods and each layer of horizontal rods.
Further, when the vertical rods are used as the beam supports, the vertical rods are encrypted to be not less than 4 rows, and the transverse distance of each row is not more than 300 mm.
Further, in step S3, the adjustable bracket includes a U-shaped bracket body and a threaded rod, the upper end of the threaded rod is connected to the bracket body, and the lower end of the threaded rod is connected to a nut disposed at the top end of the upright rod;
the plate supporting component comprises a plurality of square timbers, and the square timbers are arranged in the U-shaped grooves of the bracket body;
the bottom template comprises a wood plate and a bamboo plywood; the wood board is laid on the square wood, and the bamboo plywood is laid on the wood board.
Further, in step S4, the pre-pressing loading of the rack body adopts a three-time loading method:
the first loading method is that the weight of the pre-pressing piece is loaded to 60% of the self weight of the box girder, and the observation is carried out for at least 24 hours until the settlement difference of the frame body is stable;
the second loading method is that the weight of the pre-pressing piece is loaded to 90% of the self weight of the box girder, and the observation is carried out for at least 24 hours until the settlement difference of the frame body is stable;
and in the third loading method, the weight of the prepressing piece is loaded to 120% of the self weight of the box girder, and the observation is carried out for at least 24 hours until the settlement difference of the frame body is stable.
Furthermore, when the pre-pressing piece is loaded for the first time, the pre-pressing piece is gradually stacked from the middle of the span beam to the two ends so as to ensure the force balance;
after the pre-pressing piece is loaded for the second time, measuring the settlement difference of the frame body every at least 24 hours to ensure that the settlement difference is less than 12mm/24 h;
and (3) entering a settlement observation period after the pre-pressing piece is loaded for the second time, measuring every 3-5 hours on the first day, and measuring every 7-9 hours on the second day and the third day until the accumulated settlement is not more than 3mm in 3 consecutive days.
Furthermore, before the pre-pressing piece is stacked, observation points are arranged on the bottom template and on the basis corresponding to the bottom template, 5 positions are longitudinally arranged at the two ends of the beam span, the 1/4 beams, the span center and the 3/4 beam span, 3 points are transversely arranged at every other position to serve as the observation points, and instruments are used for detecting the deformation condition of each observation point before pre-pressing, before unloading, after unloading and in the pre-pressing process to generate observation data.
Further, calculating the elastic and inelastic deformation values of the frame body according to the observation data, and adjusting the elevation of the bottom template through the adjustable bracket, wherein the elevation of the bottom template is the designed elevation, the elastic deformation value and the reserved camber;
and the elastic deformation value is the height difference of each elevation observation point before and after load unloading, and the inelastic deformation value is the height difference of each elevation observation point after load unloading and before prepressing.
Furthermore, the pre-camber of the bottom template is adjusted by adjusting the adjustable bracket;
the pre-camber delta is delta 1+ delta 2+ delta 3+ delta 4+ delta 5;
wherein, the vertical deflection generated by the dead weight of the upper structure and half of the live load after the unloading of the frame body is delta 1;
the elastic compression deformation value of the frame body under the action of load is delta 2;
the inelastic compression value of the frame body under the action of load is delta 3;
the inelastic settlement value of the supporting base under the load action is delta 4;
the deflection value caused by the concrete shrinkage and temperature change of the foundation is delta 5;
after the frame body is pre-pressed by 100 percent of the weight of the load, only three kinds of deformation of delta 1, delta 2 and delta 5 are considered because the inelastic compression value delta 3 and the inelastic settlement value delta 4 are eliminated; the maximum value of the pre-camber is arranged at the midspan position of the beam, the pre-camber is distributed according to a parabolic form, and the pre-camber is adjusted after the pre-camber value at each point is calculated, so that the pre-camber accords with a design value.
Further, the calculation method of settlement observation comprises the following steps:
arranging measurement elevation points and recording an initial elevation value H1 of each elevation point;
loading the load to 60% of the self weight of the box girder, and measuring the elevation value H2' of each elevation point;
loading the load to 100% of the self weight of the box girder, and measuring the elevation value H2 of each elevation point;
loading the load to 110% of the self weight of the box girder, and measuring the elevation value H3 of each elevation point;
after the load is loaded for 24 hours and before the load is unloaded, the elevation value H4 of each measurement elevation point is measured;
after the load is unloaded, measuring the elevation value H5 of each elevation point;
the deformation of each measurement elevation point can be calculated as follows:
inelastic deformation △ 1 ═ H1-H5;
elastic deformation △ 2 ═ H5-H4;
according to the elastic deformation value, pre-camber △ 2 is set on the bottom formwork, so that the line type of the beam body meets the design requirement after the frame body is deformed.
By adopting the technical scheme, the construction process of the cast-in-place box girder support provided by the application has the following technical effects:
1. a plurality of height-adjustable support bases are arranged on the foundation, so that the height of the upright rod can be conveniently adjusted.
2. When assembling the support body, connect vertical and horizontal pole as sweeping the ground pole through the fastener respectively in the bottommost of pole setting, should set up one horizontal pole as sealing the ejector pin in the fastener department at pole setting topmost, improve the stability of support body.
3. When the template is installed, the adjustable bracket is arranged at the top end of the upright rod, the plate supporting assembly and the bottom template are arranged on the adjustable bracket, and the height of the bottom template can be conveniently adjusted by using the adjustable bracket.
4. When preloading is carried out, the frame body is preloaded according to 120% of the dead weight of the box girder by the total weight of the prepressing piece, and if the accumulated settlement of the frame body is not more than 3mm for not less than 3 days continuously, the prepressing piece can be unloaded; and then, the change of the elevation of the floor formwork, the elasticity, the inelastic deformation and the stability of the frame body are checked again at intervals of 6-8 hours, prepressing data are obtained, and the accuracy of the prepressing data is improved.
5. After the prepressing is completed, the elevation, the pre-camber and the transverse curve of the bottom template are adjusted through the adjustable bracket according to the prepressing data, and then reliable guarantee is provided for the subsequent box girder pouring.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a flow chart of a cast-in-place box beam support construction process provided by an embodiment of the invention;
FIG. 2 is a schematic view of a cast-in-place box girder support provided by an embodiment of the invention;
FIG. 3 is a schematic view of an adjustable bracket provided in accordance with an embodiment of the present invention;
reference numbers: 1-foundation, 2-supporting base, 3-upright rod, 4-sweeping rod, 5-sealing ejector rod, 6-adjustable bracket, 61-bracket body, 62-threaded rod, 7-plate supporting component, 8-bottom template, 9-vertical cross brace and 10-nut.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that certain terms of orientation or positional relationship are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referred devices or elements must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
In the description of the present invention, it should be noted that "connected" is to be understood broadly, for example, it may be fixed, detachable, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The present invention will be described in further detail below with reference to specific embodiments and with reference to the attached drawings.
A construction process of a cast-in-place box girder support comprises the following steps:
s1, foundation treatment, namely pouring a concrete layer on the ground to form a foundation 1, installing a plurality of height-adjustable supporting bases 2 on the foundation 1, requiring strict treatment on the foundation 1, and pouring a C20 concrete layer with the thickness of 150mm to increase the stability; according to the scheme and the size of the frame assembly, the position of the bottom feet of the frame is determined, the supporting bases 2 are placed, and the supporting bases 2 in the same array are ensured to be positioned on the same horizontal plane;
s2, assembling a frame body, namely installing a plurality of vertical rods 3 on a foundation 1 through a supporting base 2, connecting longitudinal and transverse horizontal rods as floor sweeping rods 4 at the bottommost parts of the vertical rods 3 through fasteners respectively, erecting a plurality of horizontal cross rods among the vertical rods 3, and arranging a horizontal rod as a sealing ejector rod 5 at the fastener at the topmost end of the vertical rods 3;
s3, installing a template, arranging an adjustable bracket 6 at the top end of the upright rod 3, and arranging a plate supporting component 7 and a bottom template 8 on the adjustable bracket 6;
s4, preloading load, namely paving a pressing part on the bottom template 8, preloading the frame body by the total weight of the pressing part according to 120% of the dead weight of the box girder, and unloading the pressing part if the accumulated settlement of the frame body is not more than 3mm for not less than 3 days continuously; then, checking the height change of the floor template, the elasticity, the inelastic deformation and the stability of the frame body again at intervals of 6-8 hours to obtain prepressing data;
s5, adjusting the bottom template, and after pre-pressing is finished, adjusting the elevation, the pre-camber and the transverse curve of the bottom template 8 through an adjusting rod according to pre-pressing data;
and S6, pouring the box girder, binding and molding the box girder bottom plate and the web plate reinforcing steel bars on the template, and pouring concrete.
It should be noted that the cast-in-place box girder support construction system adopts a bowl buckle type scaffold, main components, upright rods 3, cross rods, horizontal rods and the like adopt Q235 steel pipes, and fasteners made of cast and forged iron are selected for local reinforcement; the steel pipe is seamless steel pipe.
The bowl-buckled scaffold takes a specification of 0.6m as a main support and is matched with other specifications and other structural components to form an integral support system.
The vertical rods 3 are 0.6m apart in both the transverse direction and the longitudinal direction, wherein the side vertical rods are 0.6cm apart. The height-adjustable supporting base 2 is adopted to adjust the height error of the flatness of the foundation, and the installation precision of the frame body is ensured.
The horizontal pole interval 0.6mm twice, 1.2cm twice, the local encryption processing of taking strengthens the stability of support body, the adjustable bracket 6 of the upper portion installation of scaffold frame to the level of adjusting the die plate 8.
Further, in step S2, when the frame body is assembled, the bottom upright stanchions 3 are installed at intervals of 600mm along the bridge direction and 600mm along the transverse bridge direction from one end, the upright stanchions 3 are in a square grid shape, wherein the intervals of 900mm of side rods and 600mm of transverse rods are three, the intervals of 1200mm are one, and the upper and lower third parts of the height direction of the upright stanchions 3 are encrypted to form horizontal rods with the lengths of 300 and 400 mm. After the verticality and the position of the upright stanchions 3 are adjusted, fastening the fasteners, and after the upright stanchions 3 and the cross rods on one layer are installed, installing the upright stanchions 3 and the cross rods on the second layer until the top layer is reached;
a longitudinal horizontal rod and a transverse horizontal rod are respectively arranged at the bottommost bowl buckle of the vertical rod 3 to serve as the floor sweeping rods 4, and the height of the floor sweeping rods 4 from the ground is not more than 400 mm.
The horizontal rods, the vertical rods 3, the sweeping rods 4 and the sealing and ejecting rods 5 form a frame body, a plurality of vertical cross braces 9 are longitudinally and transversely arranged on the periphery of the outer side and inside the frame body respectively, the inclined angle between the inclined steel pipe of each vertical cross brace 9 and the ground is 45-60 degrees, and the distance and the span between the inclined steel pipe and the ground are 4-5 m. The full planes of each layer of the sealing top rods 5 and the middle horizontal rods are continuously provided with horizontal cross braces, and the span of each horizontal cross brace is preferably the same as that of the vertical cross brace 9. After the frame body is finished, the adjustable bracket 6 can be ensured to be installed.
Further, when the vertical rods 3 are used as the beam supports, the vertical rods 3 are arranged in at least 4 rows in an encrypted manner, the transverse distance between each row is not more than 300mm, and the encrypted parts of the vertical rods in the attached drawings are specifically referred to.
Further, in step S3, the adjustable bracket 6 includes a U-shaped bracket body 61 and a threaded rod 62, the upper end of the threaded rod 62 is connected to the bracket body 61, and the lower end of the threaded rod 62 is connected to the nut 10 disposed at the top end of the upright rod 3; when the bracket is used, the purpose of adjusting the height of the bracket body 61 is achieved by controlling the rotation of the threaded rod 62; the length from the center line of the horizontal rod of the top layer of the threaded rod 62 to the top supporting point of the threaded rod 62 is required to be not more than 650 mm;
the plate supporting component 7 comprises a plurality of square timbers, and the square timbers are arranged in the U-shaped grooves of the bracket body 61;
the bottom template 8 comprises a wood plate and a bamboo plywood; the wood board is laid on the square wood, and the bamboo plywood is laid on the wood board.
Specifically, after the bracket body 61 is adjusted, longitudinal square timber is laid, the distance between the square timber is 600mm, when the longitudinal square timber is laid, the longitudinal square timber is connected with the bracket body 61, then thick wood boards are fully laid, the distance between the board seams is not more than 100mm, a 15mm thick template is laid on the wood boards, and plastic-coated boards are laid according to the center line of lofting and serve as bottom templates 8 of the box girder.
According to the design requirement, the bottom formwork 8 is pre-pressed to the frame body after installation (before the lining plate is placed). The purpose of prepressing is as follows: the strength and stability of the frame body and the foundation 1, namely the safety of the frame body, are tested; and measuring the plastic deformation of the whole frame body, the settlement deformation of the foundation 1 and the elastic deformation of the support, and guiding the subsequent construction of the cast-in-place continuous beam support.
The prepressing piece adopts ton bagged sand and stone materials, 1.2 ton after each bag of stone materials is fully filled, a crane is adopted, according to the mechanical distribution characteristics of the box girder, the materials are hoisted, densely distributed and stacked on the bottom template 8 and the flange plates at two sides, the upper sand bag is stacked in layers, the upper sand bag and the lower sand bag are longitudinally staggered by one half and are stacked on the lower sand bag. The loading weight is not lower than the dead weight of the beam body, and 120% of the self weight of the box beam is loaded according to the design requirement.
Further, before the pre-pressing piece is stacked, the frame body is adjusted according to the designed elevation. And after pre-pressing, the plastic deformation of the foundation and the inelastic deformation of the bracket are basically eliminated. Through prepressing, observing and calculating to obtain a numerical value of the elastic deformation of the support, and adjusting the elevation of the beam bottom template 8;
and arranging observation points on the bottom template 8 and a corresponding foundation, transversely arranging 3 points at two ends of a beam span, 1/4 beams, span center and 3/4 beam span positions along the longitudinal direction, taking 15 points as the observation points in total, and detecting the deformation condition of each observation point by using an instrument before prepressing, before unloading, after unloading and in the prepressing process to generate observation data.
Further, the elastic deformation value and the inelastic deformation value of the frame body are calculated according to the observation data, the elevation of the bottom template 8 is adjusted through the adjustable bracket 6, and the elevation of the bottom template 8 is the designed elevation, the elastic deformation value and the reserved camber;
and the elastic deformation value is the height difference of each elevation observation point before and after load unloading, and the inelastic deformation value is the height difference of each elevation observation point after load unloading and before prepressing.
After the prepressing is finished and the bottom template 8 is adjusted, whether the fasteners of the frame body and the template are firm or not is checked again.
Further, in step S4, the pre-pressing loading of the rack body adopts a three-time loading method:
the first loading method is that the weight of the pre-pressing piece is loaded to 60% of the self weight of the box girder, and the observation is carried out for at least 24 hours until the settlement difference of the frame body is stable;
the second loading method is that the weight of the pre-pressing piece is loaded to 90% of the self weight of the box girder, and the observation is carried out for at least 24 hours until the settlement difference of the frame body is stable;
and in the third loading method, the weight of the prepressing piece is loaded to 120% of the self weight of the box girder, and the observation is carried out for at least 24 hours until the settlement difference of the frame body is stable.
More specifically, when the pre-pressing piece is loaded for the first time, the pre-pressing piece is gradually stacked from the middle of the span beam to the two ends so as to ensure the force balance;
after the pre-pressing piece is loaded for the second time, measuring the settlement difference of the frame body every at least 24 hours to ensure that the settlement difference is less than 12mm/24 h;
and (3) entering a settlement observation period after the pre-pressing piece is loaded for the second time, measuring every 3-5 hours on the first day, and measuring every 7-9 hours on the second day and the third day until the accumulated settlement is not more than 3mm in 3 consecutive days. I.e. the foundation 1 and the frame have settled in place. If the phenomena of overlarge sedimentation amount, sunken cracks of the foundation 1 and deformation of the frame body are found in the loading and observation processes, the stacking and unloading should be immediately stopped, and the reason can be found out in time to take remedial measures.
The sandbag piling load is gradually increased layer by layer, and the sandbag piling load cannot be centralized and too high. And checking the working condition of the frame body in the pre-pressing process, wherein whether the rod piece is bent or deformed, whether the square wood is fractured or not and the like.
Through continuous prepressing and timing observation, the frame body can be unloaded when being stable and no settlement exists, the unloading is carried out by layering stably, symmetrically and evenly, unilateral unloading is strictly forbidden, weight loss eccentricity is caused, the sand bag is piled and loaded all around and then in the middle, monitoring amount measuring point positions are kept, the unloading sequence of the support is opposite to the loading sequence, and the support is unloaded layer by layer.
Further, after the pre-pressing is completed, the bottom template 8 and the corresponding side template are checked in detail in the plane position and the elevation, the pre-camber and the transverse curve of the bottom template 8 are adjusted through the adjusting rod according to pre-pressing data.
The pre-camber of the bottom template 8 is adjusted by adjusting the adjustable bracket 6; the pre-camber delta is delta 1+ delta 2+ delta 3+ delta 4+ delta 5;
wherein, the vertical deflection generated by the dead weight of the upper structure and half of the live load after the unloading of the frame body is delta 1;
the elastic compression deformation value of the frame body under the action of load is delta 2;
the inelastic compression value of the frame body under the action of load is delta 3;
the inelastic settlement value of the supporting base 2 under the load action is delta 4;
the deflection value caused by the concrete shrinkage and temperature change of the foundation 1 is delta 5;
after the frame body is pre-pressed by 100 percent of the weight of the load, only three kinds of deformation of delta 1, delta 2 and delta 5 are considered because the inelastic compression value delta 3 and the inelastic settlement value delta 4 are eliminated; the maximum value of the pre-camber is arranged at the midspan position of the beam, the pre-camber is distributed according to a parabolic form, and the pre-camber is adjusted after the pre-camber value at each point is calculated, so that the pre-camber accords with a design value.
Further, the calculation method of settlement observation comprises the following steps:
arranging measurement elevation points and recording an initial elevation value H1 of each elevation point;
loading the load to 60% of the self weight of the box girder, and measuring the elevation value H2' of each elevation point;
loading the load to 100% of the self weight of the box girder, and measuring the elevation value H2 of each elevation point;
loading the load to 110% of the self weight of the box girder, and measuring the elevation value H3 of each elevation point;
after the load is loaded for 24 hours and before the load is unloaded, the elevation value H4 of each measurement elevation point is measured;
after the load is unloaded, measuring the elevation value H5 of each elevation point;
the deformation of each measurement elevation point can be calculated as follows:
inelastic deformation △ 1 ═ H1-H5;
elastic deformation △ 2 ═ H5-H4;
according to the elastic deformation value, the pre-camber △ 2 is set on the bottom formwork 8, so that the line type of the beam body meets the design requirement after the frame body is deformed, and in addition, according to the difference value of H3 and H4, the influence degree of the continuous load on the deformation of the bracket can be generally seen.
The observation staff is required to be fixed in each observation, the same instrument and equipment are used, and the same leveling rod is adopted in the front-back vision observation. And observing the settlement deformation observation point by using the fixed working base point. So as to minimize the system error of observation and achieve the purpose of improving precision.
The following points need to be noticed during the acceptance after the support is pre-pressed:
1. after all the weight and unloading work is finished, one-time comprehensive measurement is carried out, and whether the frame body per se has obvious abnormal conditions such as deformation or the like is carefully checked;
2. the compression of the wood block under the bottom form 8 is checked for normality.
3. And (3) according to the settlement observation point data recorded in the preloading process, the measurer calculates a preset value according to the settlement amount of each observation point to determine the elevation of the bottom template 8 for continuous box girder construction, and adjusts the elevation one by one according to the data.
4. The structure of the pre-pressed frame body is checked, the weak point after pre-pressing is reinforced, the defective support component must be replaced, and the construction safety is ensured.
5. The bottom template 8 after prepressing debugging has the phenomena of staggered joints, staggered platforms, obvious unevenness and up-down looseness, and needs to be regulated, reinforced and tightly attached to prevent the bottom of the box girder from being defective in appearance caused by the quality of the bottom template 8.
In step S6, when the box girder is poured, the bottom formwork 8 and the web reinforcing steel bars are bound and formed at one time, the binding of the bottom plate is performed first, and then the web reinforcing steel bars are arranged, and the top plate reinforcing steel bars begin to be bound after the first concrete pouring is completed.
During pouring, the cover beam concrete is vibrated by the inserted vibrating rod, the box beam concrete is poured twice, the top surface of the web plate is poured once, and the concrete of the top plate is poured twice. The concrete is poured by a continuous pouring method every time, two pump trucks are selected, and one pump truck is used for standby. The pouring direction is carried out from the lower end to the higher end, and the pouring direction is folded from the two ends of the beam to the middle. The plug-in vibrating rod is used for tamping, and an external vibrator is used for reinforcing vibration in an anchoring area at the end part.
Attention points of concrete pouring
The capping beam plate concrete pouring and tamping adopts a pouring mode of expanding from the middle part of the capping beam to two sides, and the actual construction load is strictly controlled not to exceed the design load in the pouring and tamping process. In the pouring process, the beam side and the beam bottom are compacted by using a phi 30 inserted vibrating rod, and reinforcing steel bars and embedded parts cannot be touched during vibrating. When the reinforcing steel bars of the joints of the beam and the column are dense, a small-diameter vibrating rod is used for vibrating, the rod points are encrypted, after vibrating, the rod points are stricken off, a wooden trowel is used for troweling, the leveling height of the surface of the beam is checked, and the flatness is strictly controlled.
The application provides a cast-in-place box girder support construction technology has following advantage at least:
1. a plurality of height-adjustable supporting bases 2 are arranged on the foundation 1, so that the height of the upright stanchion 3 can be conveniently adjusted.
2. When assembling the support body, connect vertical and horizontal pole as sweeping the ground pole 4 through the fastener respectively at the bottommost of pole setting 3, should set up one horizontal pole as sealing ejector pin 5 in the fastener department at pole setting 3 topmost, improve the stability of support body.
3. When the template is installed, the adjustable bracket 6 is arranged at the top end of the upright rod 3, the plate supporting component 7 and the bottom template 8 are arranged on the adjustable bracket 6, and the height of the bottom template 8 is convenient to adjust by using the adjustable bracket 6.
4. When preloading is carried out, the frame body is preloaded according to 120% of the dead weight of the box girder by the total weight of the prepressing piece, and if the accumulated settlement of the frame body is not more than 3mm for not less than 3 days continuously, the prepressing piece can be unloaded; and then, the change of the elevation of the floor formwork, the elasticity, the inelastic deformation and the stability of the frame body are checked again at intervals of 6-8 hours, prepressing data are obtained, and the accuracy of the prepressing data is improved.
5. After the prepressing is completed, the elevation, the pre-camber and the transverse curve of the bottom template 8 are adjusted through the adjustable bracket 6 according to the prepressing data, and then reliable guarantee is provided for the subsequent box girder pouring.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A construction process of a cast-in-place box girder support is characterized by comprising the following steps:
s1, treating a foundation, namely pouring a concrete layer on the ground to form the foundation, and mounting a plurality of height-adjustable supporting bases on the foundation;
s2, assembling a frame body, namely installing a plurality of vertical rods on a foundation through a supporting base, connecting longitudinal and transverse horizontal rods as ground sweeping rods at the bottommost parts of the vertical rods through fasteners respectively, erecting a plurality of horizontal cross rods among the vertical rods, and arranging a horizontal rod as a sealing ejector rod at the fastener at the topmost end of the vertical rod;
s3, installing a template, wherein an adjustable bracket is arranged at the top end of the upright rod, and a plate supporting assembly and a bottom template are arranged on the adjustable bracket;
s4, pre-pressing load, namely paving a pressing part on the bottom template, pre-pressing the frame body by the total weight of the pressing part according to 120% of the dead weight of the box girder, and unloading the pressing part if the accumulated settlement of the frame body is not more than 3mm for not less than 3 days continuously; then, checking the height change of the floor template, the elasticity, the inelastic deformation and the stability of the frame body again at intervals of 6-8 hours to obtain prepressing data;
s5, adjusting the bottom template, and after pre-pressing is finished, adjusting the elevation, the pre-camber and the transverse curve of the bottom template through an adjustable bracket according to pre-pressing data;
and S6, pouring the box girder, binding and molding the box girder bottom plate and the web plate reinforcing steel bars on the template, and pouring concrete.
2. The cast-in-place box girder support construction process according to claim 1, wherein the cross bars, the vertical bars, the floor sweeping bars and the capping bars constitute a support body, a plurality of vertical cross braces are respectively arranged on the outer periphery and the inner longitudinal and transverse directions of the support body, and horizontal cross braces are continuously arranged on each layer of the capping bars and the horizontal bars.
3. A cast-in-situ box girder erection process as claimed in claim 1, wherein when the vertical poles are used as beam supports, the vertical poles are densely arranged in not less than 4 rows, and the transverse spacing between each row is not more than 300 mm.
4. The cast-in-place box girder erection process of claim 1, wherein in step S3, the adjustable bracket comprises a U-shaped bracket body and a threaded rod, the upper end of the threaded rod is connected with the bracket body, and the lower end of the threaded rod is connected with a nut arranged at the top end of the upright rod;
the plate supporting component comprises a plurality of square timbers, and the square timbers are arranged in the U-shaped grooves of the bracket body;
the bottom template comprises a wood plate and a bamboo plywood; the wood board is laid on the square wood, and the bamboo plywood is laid on the wood board.
5. The cast-in-place box girder support construction process according to claim 1, wherein in the step S4, the pre-compression loading of the support body adopts a three-time loading method:
the first loading method is that the weight of the pre-pressing piece is loaded to 60% of the self weight of the box girder, and the observation is carried out for at least 24 hours until the settlement difference of the frame body is stable;
the second loading method is that the weight of the pre-pressing piece is loaded to 90% of the self weight of the box girder, and the observation is carried out for at least 24 hours until the settlement difference of the frame body is stable;
and in the third loading method, the weight of the prepressing piece is loaded to 120% of the self weight of the box girder, and the observation is carried out for at least 24 hours until the settlement difference of the frame body is stable.
6. The cast-in-place box girder erection process of claim 5,
when the pre-pressing piece is loaded for the first time, the pre-pressing piece is stacked from the middle of the span beam to the two ends gradually to ensure the force balance;
after the pre-pressing piece is loaded for the second time, measuring the settlement difference of the frame body every at least 24 hours to ensure that the settlement difference is less than 12mm/24 h;
and (3) entering a settlement observation period after the pre-pressing piece is loaded for the second time, measuring every 3-5 hours on the first day, and measuring every 7-9 hours on the second day and the third day until the accumulated settlement is not more than 3mm in 3 consecutive days.
7. The cast-in-place box girder erection process of claim 6,
before the pre-pressing piece is stacked, observation points are arranged on the bottom template and on the basis corresponding to the bottom template, 3 points are transversely arranged at the positions of 5 positions at the two ends of the beam span, the 1/4 beams, the span center and the 3/4 beam span along the longitudinal direction and are used as the observation points, and instruments are used for detecting the deformation condition of each observation point before pre-pressing, before unloading, after unloading and in the pre-pressing process to generate observation data.
8. The cast-in-place box girder erection process of claim 7,
calculating the elastic and inelastic deformation values of the frame body according to the observation data, and adjusting the elevation of the bottom template through the adjustable bracket, wherein the elevation of the bottom template is the designed elevation, the elastic deformation value and the reserved camber;
and the elastic deformation value is the height difference of each elevation observation point before and after load unloading, and the inelastic deformation value is the height difference of each elevation observation point after load unloading and before prepressing.
9. The cast-in-place box girder erection process of claim 8,
the pre-camber of the bottom template is adjusted by adjusting the adjustable bracket;
the pre-camber delta is delta 1+ delta 2+ delta 3+ delta 4+ delta 5;
wherein, the vertical deflection generated by the dead weight of the upper structure and half of the live load after the unloading of the frame body is delta 1;
the elastic compression deformation value of the frame body under the action of load is delta 2;
the inelastic compression value of the frame body under the action of load is delta 3;
the inelastic settlement value of the supporting base under the load action is delta 4;
the deflection value caused by the concrete shrinkage and temperature change of the foundation is delta 5;
after the frame body is pre-pressed by 100 percent of the weight of the load, only three kinds of deformation of delta 1, delta 2 and delta 5 are considered because the inelastic compression value delta 3 and the inelastic settlement value delta 4 are eliminated; the maximum value of the pre-camber is arranged at the midspan position of the beam, the pre-camber is distributed according to a parabolic form, and the pre-camber is adjusted after the pre-camber value at each point is calculated, so that the pre-camber accords with a design value.
10. The cast-in-place box girder erection process of claim 9,
the settlement observation calculation method comprises the following steps:
arranging measurement elevation points and recording an initial elevation value H1 of each elevation point;
loading the load to 60% of the self weight of the box girder, and measuring the elevation value H2' of each elevation point;
loading the load to 100% of the self weight of the box girder, and measuring the elevation value H2 of each elevation point;
loading the load to 110% of the self weight of the box girder, and measuring the elevation value H3 of each elevation point;
after the load is loaded for 24 hours and before the load is unloaded, the elevation value H4 of each measurement elevation point is measured;
after the load is unloaded, measuring the elevation value H5 of each elevation point;
the deformation of each measurement elevation point can be calculated as follows:
inelastic deformation △ 1 ═ H1-H5;
elastic deformation △ 2 ═ H5-H4;
according to the elastic deformation value, pre-camber △ 2 is set on the bottom formwork, so that the line type of the beam body meets the design requirement after the frame body is deformed.
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