CN112609584A - Prefabricated small box girder installation construction method for intelligent express way - Google Patents

Abstract

The invention discloses a prefabricated small box girder installation construction method for an intelligent express way, which specifically comprises the following steps: s1: construction preparation; before the box girder is installed, the construction of a preposed procedure is completed, and the strength of a bent cap wet joint concrete structure meets the design requirement; grouting is finished by the upright post capping beam sleeve; the cover beam completes the first tensioning and grouting; numbering the box girders from small pile size to large pile size; s2: construction measurement lofting; paying off and controlling positions, namely paying off the longitudinal central line, the longitudinal and transverse central lines of the support, the plate end position transverse line and the support bottom contour line of each hole beam on the pier surface according to the actually paid-out line central line and the pier center mileage, and arranging the bottom edge point of each beam on the plate end position transverse line; the invention adopts the bridge girder erection machine to erect the box girder, has less construction interference, simple process and lower construction cost; the crane can be used for hoisting the prefabricated stand column and the cover beam, the beam erecting construction is flexible, and continuous span operation is not needed.

Description

Prefabricated small box girder installation construction method for intelligent express way

Technical Field

The invention belongs to the technical field of medical test tube racks, and particularly relates to a prefabricated small box girder installation construction method for an intelligent express way.

Background

The box girder of the reinforced concrete structure is divided into a prefabricated box girder and a cast-in-place box girder. The box girder prefabricated in the independent site can be erected after the lower project is finished by combining the bridge girder erection machine, so that the project progress can be accelerated, and the construction period can be saved; cast-in-place box girders are mostly used for large continuous bridges. The common materials are divided into two types, namely a prestressed reinforced concrete box girder and a steel box girder. The prestressed reinforced concrete box girder is constructed on site, and transverse prestress is also arranged in some cases besides longitudinal prestress; the steel box girder is generally processed in a factory and then transported to a site for installation, and has an all-steel structure and a partially reinforced concrete pavement layer.

The box girder erection procedure is loaded down with trivial details in the work progress of current prefabricated little box girder, and the construction is disturbed greatly, improves construction cost on the one hand, and on the other hand has prolonged construction period.

Disclosure of Invention

The invention aims to provide a small prefabricated box girder installation construction method for an intelligent express way, wherein a bridge girder erection machine is adopted to erect box girders, so that the construction interference is less, the process is simple, and the construction cost is saved; the crane can be used for hoisting the prefabricated stand column and the cover beam, the beam erecting construction is flexible, and continuous span operation is not needed.

The purpose of the invention can be realized by the following technical scheme:

a prefabricated small box girder installation and construction method for an intelligent express way specifically comprises the following steps:

s1: construction preparation; before the box girder is installed, the construction of a preposed procedure is completed, and the strength of a bent cap wet joint concrete structure meets the design requirement; grouting is finished by the upright post capping beam sleeve; the cover beam completes the first tensioning and grouting; numbering the box girders from small pile size to large pile size;

s2: construction measurement lofting; before the box girder is erected and installed, an instrument is used for checking the elevation and the plane position of the supporting structure; during checking, marking a rack mounting axis and an end line on the supporting structure to accurately position the box girder;

paying off and controlling positions, namely paying off the longitudinal central line, the longitudinal and transverse central lines of the support, the plate end position transverse line and the support bottom contour line of each hole beam on the pier surface according to the actually paid-out line central line and the pier center mileage, and arranging the bottom edge point of each beam on the plate end position transverse line;

s3: preparing a crane; before the preparation of the crane, a bridge installation scheme is formulated, an engineer is reported, and before the crane enters a field, a transportation road and a hoisting operation field in a hoisting range are prepared;

s4: self-checking and reporting to an engineer; after the preparation process is finished, safety inspection is carried out, and the inspection result is reported to an engineer to prepare box girder installation construction;

s5: transporting the box girder component to an installation site; conveying the prefabricated small box girder components to be installed to an installation site by using a crane for waiting installation, numbering the box girders from small pile numbers to large pile numbers one by one from left to right, and transporting and hoisting the box girders in sequence;

s6: mounting a support; before the support is installed, a support detection test needs to be carried out, the support detection test result is reported to an engineer for approval, and the support is purchased according to the support detection test result; before the box girder is installed in place, the support is installed, and when the box girder at the discontinuous pier or the abutment is installed, the stainless steel plate and the permanent support are firmly installed; when the continuous pier box girder is installed, a temporary support is installed in advance;

s7: hoisting the box girder; the prefabricated box girder adopts a method of reserving hoisting holes on a panel to hoist the girder body, 2 hoisting holes are arranged on each side of the end part of the box girder and are symmetrically arranged, and riggings are connected with the box girder to be erected by penetrating through the bottoms of the hoisting holes;

the crane lifts the box girder, carries out alignment and then slowly puts down the box girder to be in place; after the box girder is in place, checking whether a lower support is loosened and the girder is stable; if the beam plate is not flat, the beam plate is lifted again, and the support is leveled by the stainless steel plate until the support is stable; after the first box girder is erected, erecting the box girders according to the method in sequence until all the box girders of the span are erected;

s8: construction acceptance inspection; the prefabricated small box girder is actually measured in installation inspection, the installation required position of the small box girder is accurate, each girder end is neatly drawn, the seam of the girder end is straight, and the width meets the design requirement that the girder bottom is tightly connected with the support.

As a further scheme of the invention: pre-treating and reinforcing the foundation within the traveling and hoisting range of the crane, paving a roadbed box, and simultaneously arranging drainage ditches at two sides of the foundation; removing obstacles on a transportation road, filling a base layer of a construction pavement with old materials with the thickness of 100cm, paving gravels or gravels with the thickness of 10cm on a surface layer, and making the width of the pavement be 5 meters; and leveling and compacting the periphery of a construction site and a transportation road before erecting a beam, and clearing obstacles on a construction access road, including uneven ground and overhead cables on the construction access road.

As a further scheme of the invention: in the preparation construction process of the S3 crane, the track crane walking line of the hoisting operation field is filled with old materials with the thickness of 100cm, gravels or gravels with the thickness of 10cm are paved on the surface layer, and a road roller is used for rolling and leveling and paving steel plates.

As a further scheme of the invention: in the installation and construction process of the S6 support, the steel backing plate is pre-embedded during the construction of the bent cap and the pad stone, and the steel plate is provided with the exhaust holes to ensure the concrete pouring of the bottom of the steel backing plate to be compact; the top surface elevation and the flatness of the embedded steel backing plate meet the design requirements;

the beam bottom of the permanent support is parallel and flat with the top surfaces of the supporting cushion stone and the steel base plate, so that the permanent support is tightly attached to the upper surface and the lower surface of the support.

As a further scheme of the invention: in the S7 box girder hoisting construction process, the outdoor hoisting work is stopped when the wind speed is more than 8m/S, the visibility is lower than 50m in fog days and the rainfall occurs.

As a further scheme of the invention: in the hoisting construction process of the box girder S7, two cranes vertically hoist and the boom does not change the amplitude during hoisting; and when the member is lifted to a height of 20-30cm higher than the supporting point, the suspension arms rotate in the same direction, and when the fulcrum of the member is confirmed to rotate above the bearing point, the box girder is lowered down by the crane.

As a further scheme of the invention: in the S6 support installation work process, the temporary support adopts a steel structure sand cylinder, adopts a cylindrical sandbox made of seamless steel tubes, and the cylindrical sandbox is divided into a lower-layer sand cylinder and an upper-layer sleeve.

As a further scheme of the invention: a lower base plate is welded at the bottom of the lower-layer sand cylinder in a sealing mode, a sand opening is opened on the side face of the steel pipe sand cylinder, a vehicle screw opening is combined with a sealing steel plate, and screws are screwed; dry fine sand is placed in the lower sand cylinder and falls on the cover beam; the upper and lower backing plates of the upper sleeve are sealed by welding; the upper layer sleeve is sleeved in the lower layer sandbox, and the girder falls on the upper layer sleeve when the beam is erected.

As a further scheme of the invention: in the S6 support installation construction process, the permanent support installation comprises the following steps:

A. the steel base plate is pre-embedded during construction of the bent cap and the base stone, and the steel plate is provided with the exhaust holes, so that concrete pouring at the bottom of the steel base plate is guaranteed to be compact, and the top surface elevation and the flatness of the pre-embedded steel base plate meet the design requirements;

B. the beam bottom of the permanent support is parallel and flat with the top surfaces of the supporting cushion stone and the steel base plate, so that the permanent support is closely attached to the upper surface and the lower surface of the support;

C. the support is arranged on the supporting cushion steel plate, and the central line of the support is superposed with the central line of the supporting cushion; after the support is installed, filling the gap position of the support foot with mortar;

D. before pouring the concrete beam, a supporting steel plate which is larger than the plane of the support is required to be additionally arranged on the support, and anchoring steel bars are welded on the steel plate to be connected with the beam; filling yarn waste, putty or cork plates in the gaps around the supporting steel plates; later on when the formwork is removed, the filling is removed again.

The invention has the beneficial effects that: the box girder is erected by the bridge girder erection machine, so that the construction interference is less, the process is simple, and the construction cost is saved; the crane can hoist the prefabricated upright post and the cover beam, the beam erecting construction is flexible, and continuous span operation is not needed; according to the construction condition analysis of the work area, the box girder erection is carried out by adopting the crane in the work area, the lifting effect is good, the efficiency is higher, and the construction period is effectively reduced.

Drawings

In order to facilitate understanding for those skilled in the art, the present invention will be further described with reference to the accompanying drawings.

FIG. 1 is a schematic flow chart of the construction method of the present invention.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.

Referring to fig. 1, a prefabricated box girder installation construction method for an intelligent express way specifically includes the following steps:

s1: construction preparation; before the box girder is installed, the construction of a preposed procedure is completed, and the strength of a bent cap wet joint concrete structure meets the design requirement; grouting is finished by the upright post capping beam sleeve; the cover beam completes the first tensioning and grouting; numbering the box girders from small pile size to large pile size;

s2: construction measurement lofting; before the box girder is erected and installed, an instrument is used for checking the elevation and the plane position of the supporting structure; during checking, marking a rack mounting axis and an end line on the supporting structure to accurately position the box girder;

paying off and controlling positions, namely paying off the longitudinal central line, the longitudinal and transverse central lines of the support, the plate end position transverse line and the support bottom contour line of each hole beam on the pier surface according to the actually paid-out line central line and the pier center mileage, and arranging the bottom edge point of each beam on the plate end position transverse line;

s3: preparing a crane; before the preparation of the crane, a bridge installation scheme is formulated, an engineer is reported, and before the crane enters a field, a transportation road and a hoisting operation field in a hoisting range are prepared;

s4: self-checking and reporting to an engineer; after the preparation process is finished, safety inspection is carried out, and the inspection result is reported to an engineer to prepare box girder installation construction;

s5: transporting the box girder component to an installation site; conveying the prefabricated small box girder components to be installed to an installation site by using a crane for waiting installation, numbering the box girders from small pile numbers to large pile numbers one by one from left to right, and transporting and hoisting the box girders in sequence;

before the beam car and the hoisting mechanical equipment enter a construction operation field, the project department and the traffic management department perform coordination work. And if necessary, temporarily carrying out traffic control and maintaining the on-site traffic order. Enough safety warning signs are arranged on site, and a person is dispatched to perform safety operation during construction of the monitoring frame beam.

The construction site temporary road and the site ensure the smoothness of the road surface, and the hoisting mechanical equipment access road is smooth.

And the crawler crane is assembled and disassembled on site, a 25T steam crane is adopted to install the crawler crane, after the crawler crane is assembled, a special design inspection center is invited to accept, and after the crawler crane is qualified, a bridge is erected.

Before the beam is erected, hoisting mechanical equipment and hoisting tools are comprehensively inspected and maintained, and parts with poor performance are found and replaced, so that the hoisting construction is ensured to be smoothly carried out.

The original construction pavement on the construction site is overhauled again when necessary, and the pavement needs to be leveled and compacted. The turning points must meet the transportation requirements of large-scale components, and a roadbed box and a steel plate are adopted for laying when necessary.

S6: mounting a support; before the support is installed, a support detection test needs to be carried out, the support detection test result is reported to an engineer for approval, and the support is purchased according to the support detection test result; before the box girder is installed in place, the support is installed, and when the box girder at the discontinuous pier or the abutment is installed, the stainless steel plate and the permanent support are firmly installed; when the continuous pier box girder is installed, a temporary support is installed in advance;

s7: hoisting the box girder; the prefabricated box girder adopts a method of reserving hoisting holes on a panel to hoist the girder body, 2 hoisting holes are arranged on each side of the end part of the box girder and are symmetrically arranged, and riggings are connected with the box girder to be erected by penetrating through the bottoms of the hoisting holes;

the crane lifts the box girder, carries out alignment and then slowly puts down the box girder to be in place; after the box girder is in place, checking whether a lower support is loosened and the girder is stable; if the beam plate is not flat, the beam plate is lifted again, and the support is leveled by the stainless steel plate until the support is stable; after the first box girder is erected, erecting the box girders according to the method in sequence until all the box girders of the span are erected;

attention should be paid to double-machine lifting construction:

a. during hoisting, 2 cranes vertically hoist, and the suspension arm does not have amplitude change under common conditions. The downward amplitude is strictly forbidden, and an overload state is easily generated due to the downward amplitude, and if the downward amplitude is upwards changed, the generated component force is large and overload instability is easily generated.

b. When the member is lifted to a height of 20-30cm higher than the supporting point, the suspension arms rotate in the same direction, and when a commander confirms that the fulcrum of the member rotates to a position above the bearing point, the member falls down slowly, so that the member can safely perform amplitude variation and alignment in place.

c. The components of the double-crane lifting crane are generally heavy and large, the strength of the lifting arm needs to be paid great attention at the moment, the arm extending length needs to be controlled according to the specification of the use, the lifting arm cannot be extended blindly, and accidents caused by arm folding are avoided. And (4) paying attention to checking whether the length of the steel wire rope of the winch is enough or not, wherein the multiplying power of the steel wire rope and the pulley block must meet the use requirement of the hoisting operation.

d. When the heavy object is hung, the uniform command is needed, and the commander determines the position of the crane. Generally, when a plurality of cranes operate simultaneously, each crane must be provided with a contact person to transmit the command of a commander and pay attention to the dangerous conditions of no sinking, no floating and the like of the foundation. When the moment of the crane is close to the rated moment, the contact person should immediately report to the commander, and the commander makes a safety instruction to ensure the safety of hoisting.

S8: construction acceptance inspection; the prefabricated small box girder is actually measured in installation inspection, the installation required position of the small box girder is accurate, each girder end is neatly drawn, the seam of the girder end is straight, and the width meets the design requirement that the girder bottom is tightly connected with the support.

Pre-treating and reinforcing the foundation within the traveling and hoisting range of the crane, paving a roadbed box, and simultaneously arranging drainage ditches at two sides of the foundation; removing obstacles on a transportation road, filling a base layer of a construction pavement with old materials with the thickness of 100cm, paving gravels or gravels with the thickness of 10cm on a surface layer, and making the width of the pavement be 5 meters; and leveling and compacting the periphery of a construction site and a transportation road before erecting a beam, and clearing obstacles on a construction access road, including uneven ground and overhead cables on the construction access road.

In the preparation construction process of the S3 crane, the track crane walking line of the hoisting operation field is filled with old materials with the thickness of 100cm, gravels or gravels with the thickness of 10cm are paved on the surface layer, and a road roller is used for rolling and leveling and paving steel plates.

In the installation and construction process of the S6 support, the steel backing plate is pre-embedded during the construction of the bent cap and the pad stone, and the steel plate is provided with the exhaust holes to ensure the concrete pouring of the bottom of the steel backing plate to be compact; the top surface elevation and the flatness of the embedded steel backing plate meet the design requirements;

the beam bottom of the permanent support is parallel and flat with the top surfaces of the supporting cushion stone and the steel base plate, so that the permanent support is tightly attached to the upper surface and the lower surface of the support.

The support is accurately placed on the supporting cushion steel plate, and the central line of the support is required to be coincident with the central line of the supporting cushion. And after the support is installed, filling the gap position of the support foot by adopting mortar.

In the S7 box girder hoisting construction process, the outdoor hoisting work is stopped when the wind speed is more than 8m/S, the visibility is lower than 50m in fog days and the rainfall occurs. The electric winch is required to have enough rainproof facilities in rainy seasons, and the installation and operation parts are cleaned to be operated when frost and snow exist in winter.

In the hoisting construction process of the box girder S7, two cranes vertically hoist and the boom does not change the amplitude during hoisting; and when the member is lifted to a height of 20-30cm higher than the supporting point, the suspension arms rotate in the same direction, and when the fulcrum of the member is confirmed to rotate above the bearing point, the box girder is lowered down by the crane.

In the S6 support installation work process, the temporary support adopts a steel structure sand cylinder, adopts a cylindrical sandbox made of seamless steel tubes, and the cylindrical sandbox is divided into a lower-layer sand cylinder and an upper-layer sleeve.

A lower base plate is welded at the bottom of the lower-layer sand cylinder in a sealing mode, a sand opening is opened on the side face of the steel pipe sand cylinder, a vehicle screw opening is combined with a sealing steel plate, and screws are screwed; dry fine sand is placed in the lower sand cylinder and falls on the cover beam; the upper and lower backing plates of the upper sleeve are sealed by welding; the upper layer sleeve is sleeved in the lower layer sandbox, and the girder falls on the upper layer sleeve when the beam is erected.

In the S6 support installation construction process, the permanent support installation comprises the following steps:

A. the steel base plate is pre-embedded during construction of the bent cap and the base stone, and the steel plate is provided with the exhaust holes, so that concrete pouring at the bottom of the steel base plate is guaranteed to be compact, and the top surface elevation and the flatness of the pre-embedded steel base plate meet the design requirements;

B. the beam bottom of the permanent support is parallel and flat with the top surfaces of the supporting cushion stone and the steel base plate, so that the permanent support is closely attached to the upper surface and the lower surface of the support;

C. the support is arranged on the supporting cushion steel plate, and the central line of the support is superposed with the central line of the supporting cushion; after the support is installed, filling the gap position of the support foot with mortar;

D. before pouring the concrete beam, a supporting steel plate which is larger than the plane of the support is required to be additionally arranged on the support, and anchoring steel bars are welded on the steel plate to be connected with the beam; filling yarn waste, putty or cork plates in the gaps around the supporting steel plates; later on when the formwork is removed, the filling is removed again.

The construction method comprises the steps of simply supporting and then continuously constructing, firstly hoisting box girders onto temporary supports on the tops of the bent roofs, adopting steel-structure sand cylinders for the temporary supports, erecting a small box girder after the small box girders are erected on site, then temporarily welding and fixing transverse steel bars in time, firmly loosening hooks, binding the steel bars on site according to each unit, erecting a formwork and pouring wet joint concrete, performing negative bending moment tensioning grouting construction after the strength is reached, and finally, dropping the temporary supports, wherein all permanent supports are used for bearing and completing conversion work of the system.

The conversion of the simply supported continuous beam system can be roughly divided into 3 stages, and the specific construction stages are as follows:

stage 1: and erecting the prefabricated box girder to form a simply supported state supported by the temporary support, wherein a beam span has a positive bending moment. At the moment, the main beam mainly bears the dead weight action of the first-stage dead load and the corresponding construction load, and the two box beams are in a simply supported state.

Stage 2: and (4) pouring joint concrete between the spans, stretching the steel bundles in the hogging moment area when the joint concrete reaches the designed strength, and pressing and injecting cement paste. And the tension of the secondary steel strand is gradually converted from a statically determinate structure to a statically indeterminate structure. At the moment, the box girder mainly bears the first-stage self-weight effect of the structure and the corresponding construction load; in the formed continuous beam section, creep deformation of the structure begins to be constrained, creating creep sub-internal forces.

Stage 3: and (4) removing the temporary support, and after the temporary support is removed, converting the statically determinate system into a statically indeterminate system to complete the conversion from simple support to continuous support. The transverse joint is manufactured, and secondary negative bending moment is generated at the pier top due to the occurrence of secondary stress at the pier top, so that the positive bending moment of the span is reduced to a great extent, and a large shearing force exists at the pier top. Thereby forming a continuous beam bridge; at this time, the structure receives a self-weight action, a construction load, and a creep secondary internal force.

System conversion construction scheme

1) Temporary support design and placement

The prefabricated box girder adopting the process of simply supporting and then continuously constructing needs a temporary support when being erected. The temporary support adopts a sand cylinder design, 2 simply supported variable continuous beam ends are placed at the bottom, and 368 temporary supports are totally arranged in the section.

A. Design of sand cylinder

This sand section of thick bamboo formula temporary support adopts the cylindric sandbox of seamless steel pipe preparation, and the sandbox divide into lower floor's sand section of thick bamboo and upper sleeve, and lower floor's sand section of thick bamboo bottom seal welding lower bolster plays the effect firm and closed end mouth. Opening a sand opening on the side surface of the steel tube sand cylinder, combining a vehicle screw opening with a sealing steel plate and screwing down screws. And dry fine sand is placed in the lower sand cylinder and falls on the cover beam. The upper and lower backing plates of the upper sleeve are sealed by welding. The upper layer sleeve is sleeved in the lower layer sandbox, and the girder falls on the upper layer sleeve when the beam is erected.

When the sand cylinder type temporary support is used, when the crossbeam falls on the temporary support, sand which is loosely packed has high sedimentation, and sedimentation observation needs to be done in advance. A prepressing method can be adopted: after the sand cylinder is loosely filled with sand, an upper sleeve is sleeved, and a load is added to the upper sleeve to press the sand in the compaction cylinder and measure the settling volume of the sand. The settlement value between the loose sand and the compacted sand can be used as the value increased in advance when the sand cylinder is filled with the sand. The sand loaded into the sand cylinder needs to be dry and uniform grit.

The height of the temporary support can be adjusted by controlling the amount of sand if necessary. But the settlement observation needs to be done from the beginning. After prepressing, the inner and outer cylinders of the sand cylinder are fixed to prevent looseness.

The design size of the sand cylinder is as follows: the outer diameter of the lower sand cylinder is 273mm, the wall thickness of the lower sand cylinder is 10mm, and the lower backing plate is made of a 10mm steel plate. The upper sleeve is a steel pipe with the outer diameter of 219mm and the wall thickness of 8 mm. The upper and lower backing plates are sealed by 8mm steel plates.

C. Temporary support sand cylinder calculation

A) Temporary support force calculation

This engineering temporary support sets up two temporary support according to every beam-ends, and monolithic case roof beam sets up 4 temporary support. The maximum stress of the sand cylinder temporary support is 32m, and the weight of the sand cylinder temporary support is 184.65 t.

Then, the stress of the single temporary support is 185.12t/4 46.28 t; and taking the coefficient K as 1.3, and taking the maximum stress of each temporary support as 46.28, 1.3 as 60.16t as 589.61 KN.

B) Sand cylinder selection calculation

a. Calculating and selecting the outside diameter of the sand feeding barrel

The sand is passed through the leakage in advance, dried and pre-pressed to a certain degree, if [ sigma ] is 20MPa,

looking up the national standard seamless steel pipe specification, the sand cylinder top core selects the seamless steel pipe with the outer diameter D1 being 219mm and the wall thickness being delta being 8 mm.

b. Selection of sand cylinder

D1-D0 + 0.02-0.219 + 0.02-0.221 m, so that a seamless steel pipe with an outer diameter D2-273 mm and a wall thickness delta-10 mm is actually selected.

c. Checking calculation of stress

a) Checking calculation of apical tolerance

According to the height and section size of the top core, the top core is judged to be a non-long thin rod, and the structure and material of the top core can be seen, the top core is a short thick steel pipe upright column, the calculated axial center compression resistance value is,

Fy＝As*fy

in the formula: fy-calculating the bearing capacity (N);

as-the cross-sectional area of the steel pipe (mm2), the outer diameter D1 is 219mm, the wall thickness is 8mm, the cross-sectional area of the seamless steel pipe is 5300, 32mm 2;

and fy, namely the design value of the compression strength and the compression tensile strength of the steel pipe, and taking 140MPa according to the No. 20 seamless steel pipe.

And Fy is 5300.32, 140 is 742.04KN, F is 588.08KN, and the design requirement is met.

b) Checking calculation of sand cylinder wall

The yield strength of the structural seamless steel pipe is that [ sigma ] steel pipe is 245MPa when delta is 10mm and is less than or equal to 22 mm;

h is 0.15m, d2 is 0.02m, and H0 is 0.15 m.

The allowable value of sigma [ is 4, 60, 01, 0, 273, 0, 15/((3, 14, 0, 219) (0, 15, 0, 02) 0, 01) ([ sigma ] steel pipe is 233.11MPa, 245MPa, and the stress of the sand cylinder meets the requirement.

2) Mounting bottom die and permanent support

A. Permanent support mounting

a. The steel base plate is pre-buried when the bent cap stone setting is under construction to establish the exhaust hole on the steel sheet, guarantee that steel base plate base concrete placement is closely knit. The top surface elevation and the flatness of the embedded steel backing plate meet the design requirements.

b. The permanent support seat can ensure the beam bottom to be parallel and flat with the top surfaces of the supporting cushion stone and the steel backing plate as far as possible, so that the permanent support seat is tightly attached to the upper surface and the lower surface of the support seat, and the occurrence of bias pressure, void and uneven support is avoided.

c. The support is accurately placed on the supporting cushion steel plate, and the central line of the support is required to be coincident with the central line of the supporting cushion. And after the support is installed, filling the gap position of the support foot by adopting mortar.

d. Before pouring concrete beam, a supporting steel plate slightly larger than the plane of the support is added on the support, and anchoring steel bars are welded on the steel plate to be connected with the beam. The supporting steel plate is used as a part of a cast-in-place beam template for pouring. In order to prevent slurry leakage, the gaps at the periphery between the supporting steel plates can be filled with yarn waste, putty or cork plates. When the template is dismantled later, the filler is removed, and the upper surface and the lower surface of the support can be completely and closely attached to the top surfaces of the beam bottom steel plate and the base stone according to the construction.

B. Bottom die mounting

After the permanent support is placed, a bottom die is arranged on the periphery of the permanent support, according to actual conditions, a bamboo plywood is adopted as the bottom die in the contract section, the gap between the permanent support and the bottom die is sealed by sealant for strictly preventing slurry leakage.

C. Installation of reinforcing bars

Binding the steel bars according to the wet joint steel bar structural drawing, and connecting the longitudinal steel bars according to the design requirement. The upper layer of the top plate and the lower layer of the bottom plate, which extend out of the precast beam, are connected by adopting single-side welding; other construction steel bars extending out of the precast beam can be bound by binding wires.

D. Installation prestressing force channel

In order to prevent the increase of stress loss caused by friction between the tendon and the pipe and to change the stress of the tendon, the position of the tendon should be strictly controlled. The position deviation of the beam path at the joint of the two precast beam ends and the cast-in-place section is controlled within 2 mm. Pre-buried in the cast-in-place section and the precast beam in the same material prestressed beam way, must be with the corresponding beam way of precast beam section in the same direction as the connection, ensure to connect reliably, not leak thick liquid.

And (4) inspecting the steel strand entering the field according to requirements, and putting the steel strand into use after the steel strand is qualified.

The blanking length of the prestressed steel strand is the net length of the pore passage plus the reserved length for tensioning at the two ends of the member; the cutting of the prestressed beam adopts a grinding wheel cutting machine to ensure that the notch is smooth and the wire ends are not scattered. And forbidding adopting electric arc cutting for blanking. When the steel strand is cut, binding with iron wires at the position 30-50 mm away from the notch at each end.

The steel strand wire has the advantages of large coil weight, small coil amount and large elasticity, and a simple iron cage is manufactured in advance in order to prevent the steel strand wire from being disordered and popping out to hurt people in the blanking process. During blanking, the steel strand is coiled in the iron cage and gradually drawn out from the center of the coil so as to ensure safety.

The steel strand is bound by a No. 20 iron wire, the iron wire is buckled inwards, and the distance is 1-1.5 m. When the steel strands are bundled, the steel strands are firstly straightened, and the tightness of each steel strand is consistent as much as possible. And stacking the bound steel strand bundle serial number hanging plate.

The prestressed steel bundles should be arranged and straightened before penetrating and bundled together by iron wires at intervals of 2-3 m along the length direction. The strand is generally directly threaded manually, or can be threaded by a winder by using a long steel wire with the diameter of 5 mm as a lead.

E. Vertical side mould

Because box girder hank seam and horizontal wet seam need two construction, need stand the side form in hank seam department, the wet seam template of bridge sideboard department adopts the steel form with the same shape of bridge sideboard side form, other set up the template according to actual need. And wet joints are constructed by adopting a suspended steel template.

F. Pouring cast-in-place concrete

And when the solar temperature is lowest, pouring concrete of the continuous joint, the middle cross beam and the bridge deck slab (the hinge joint between the beams) with the two sides in the same length range as the hogging moment beam of the top plate.

In order to prevent the cast-in-place section and the precast beam from cracking and prestress loss caused by concrete shrinkage, an expanding agent is added into the concrete. Because the steel bars are dense, the particle size of the concrete stone is not more than 2 cm. The use amount of each material is strictly controlled according to the mixing proportion, and the micro-cracks at the pier top are prevented due to the negative bending moment at the pier top connecting part. Because the pier top connecting steel bars are dense, in order to ensure the pier top concrete pouring quality, the pier top concrete pouring is slow, and the vibrating rod must be vibrated compactly to prevent the cavity from being generated. The pier top connection can be poured twice, the beam ribs are firstly poured and connected, after pouring is finished, the face plate is bound with the connecting reinforcing steel bars before concrete is not initially set, and then face plate concrete is poured. The casting speed of the concrete is ensured during casting, and the generation of construction joints is prevented.

In order to prevent the phenomena of difficult vibration and stick clamping, a small-diameter vibrating bar is matched with a large-diameter vibrating bar. And finally, ensuring the concrete of the cast-in-place section to be compact by using a flat plate vibrator. The full-bridge should prevent that the dynamic load from acting on the bridge floor within three days after the pier top is poured after forming continuous structure, prevents that the pier top concrete department from appearing the crazing crack.

After the concrete construction is finished, in order to prevent cracks from appearing in early shrinkage, the concrete is covered by the plastic film after tamping and leveling, before the concrete is initially set, the plastic film is lifted, the concrete can be flooded to the surface, and then secondary slurry collection is carried out, so that the flatness is controlled and the cracks are prevented from appearing. After the slurry is collected, the plastic film is covered for the next watering and curing, the soil is replaced by the geotextile for watering to replace the plastic film for the curing.

G. Stretching a prestressed tendon and grouting;

and tensioning the prestressed tendons after the strength of the cast-in-place concrete reaches 100% and the age reaches 10 days. The prestressed tendons are anchored by adopting flat anchors, and each prestressed tendon in the prestressed tendons is tensioned by a jack, then is sealed and is grouted in time.

a. Preparation work

Concrete strength test

Before the prestressed tendons are tensioned, a strength pressure test report of the same-condition maintenance test piece of the member concrete needs to be provided. When the strength of the concrete sample reaches 100% of the design strength and the age reaches 10 days, the prestressed steel beam can be tensioned. During tensioning, the tension stress and the elongation are adopted for double control, the tension stress is taken as the main, and the elongation is checked. The tension process is well recorded, and the phenomena of wire sliding, wire breaking and the like in the tension process are timely treated to ensure the tension quality.

② cleaning the end of the component

And welding slag, burrs, concrete residues and the like at the contact part of the embedded steel plates at the end parts of the members and the anchorage device are cleaned.

Installing anchorage device and tensioning equipment

Steel strand bundle clip anchoring system: when the anchorage device is installed, the working anchor ring or the anchor plate needs to be centered, and the clamping pieces are uniformly tightened and exposed uniformly; the hole positions of the tool anchors on the jack are consistent with the hole positions of the working anchors at the end parts of the members, so that the steel strands are prevented from being forked in the through holes of the jack.

When installing the tensioning equipment, aligning the linear prestressed tendons, and enabling the action line of the tensioning force to coincide with the central line of the pore channel; for the curve prestressed tendon, the action line of the tension force should coincide with the tangent line of the tail end of the central line of the pore channel.

b. Prestressed tendon tensioning sequence

Simultaneously tensioning two ends, wherein the specific tensioning sequence is as follows: t3 → T2 → T1; the steel bundles of the same number are made in the order from the center to both sides and must be tensioned simultaneously to the sides.

The process is as follows: initial stress (0.1 σ con) → σ con (holding load 5mi n) → anchoring.

The engineering prestressed steel strand adopts the national standard of 1 × 7-15.2-1860-GB/T5224-2014, the standard strength fpk is 1860MPa, the E is 1.95 × 105MPa, and the tension stress 1395MPa is designed and controlled.

The single steel strand tensioning control force 1395 140 1 199.29KN, so 2 jacks 25t are adopted, and two sides are symmetrically tensioned simultaneously.

c. Checking stretch-draw elongation value

Elongation values should be measured for each tensioning.

When the prestressed tendon is tensioned, whether the tensioning force is enough, whether the friction loss of the pore channel is larger, whether the prestressed tendon has abnormal phenomena or not can be comprehensively reflected through checking the elongation value. Therefore, attention is paid to the verification of the tensile elongation value. And (3) checking the control stress of the prestressed box girder during tensioning by using the actual elongation value and the theoretically-calculated elongation value during tensioning. And controlling the difference between the actual elongation value and the theoretical elongation value within 6%, otherwise suspending the tensioning, checking reasons, adjusting by taking measures, and continuing the tensioning.

d. Pore canal grouting

The box girder prestressed duct grouting adopts a vacuum grouting process, relevant process tests are carried out before formal construction to test the mechanical performance of grouting equipment, the technical indexes of slurry and the process parameters of grouting operation, and after the construction process is confirmed to meet the requirements, large-scale construction can be carried out. The grouting work is generally performed 48 hours after the completion of the tensioning work.

H. Removing temporary supports

After the secondary tensioning, grouting and anchor sealing are completed and the grouting strength reaches 100%, the temporary support can be dismantled, the structural bearing is converted on the permanent support, and the conversion from a simple support to a continuous system is completed. When the temporary support is released, special attention should be paid to strictly preventing the high temperature from influencing the quality of the rubber support. When the temporary support is dismantled, the stress on each permanent support at the pier top is ensured to be simultaneously applied, so that the phenomenon of stress concentration is avoided, and the safety of system conversion is ensured.

After the pouring of the pier top concrete is finished, the temporary supports are dismantled one by one. The safety belt tie down must be ensured during the removal of the temporary support. The unloading sequence is symmetrically carried out from side span to middle span, and a plurality of people are arranged on the top of each pier to unload the sand box at the same time, so that the synchronism of beam falling is ensured as much as possible.

And after the joint construction is finished, pouring the rest part of bridge deck wet joint concrete, wherein the rest part of bridge deck wet joint concrete is poured from the midspan to the fulcrum.

The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims (9)

1. The method for mounting and constructing the prefabricated small box girder for the intelligent express way is characterized by comprising the following steps of:

s1: construction preparation; before the box girder is installed, the construction of a preposed procedure is completed, and the strength of a bent cap wet joint concrete structure meets the design requirement; grouting is finished by the upright post capping beam sleeve; the cover beam completes the first tensioning and grouting; numbering the box girders from small pile size to large pile size;

s2: construction measurement lofting; before the box girder is erected and installed, an instrument is used for checking the elevation and the plane position of the supporting structure; during checking, marking a rack mounting axis and an end line on the supporting structure to accurately position the box girder;

paying off and controlling positions, namely paying off the longitudinal central line, the longitudinal and transverse central lines of the support, the plate end position transverse line and the support bottom contour line of each hole beam on the pier surface according to the actually paid-out line central line and the pier center mileage, and arranging the bottom edge point of each beam on the plate end position transverse line;

s3: preparing a crane; before the preparation of the crane, a bridge installation scheme is formulated, an engineer is reported, and before the crane enters a field, a transportation road and a hoisting operation field in a hoisting range are prepared;

s4: self-checking and reporting to an engineer; after the preparation process is finished, safety inspection is carried out, and the inspection result is reported to an engineer to prepare box girder installation construction;

s5: transporting the box girder component to an installation site; conveying the prefabricated small box girder components to be installed to an installation site by using a crane for waiting installation, numbering the box girders from small pile numbers to large pile numbers one by one from left to right, and transporting and hoisting the box girders in sequence;

s6: mounting a support; before the support is installed, a support detection test needs to be carried out, the support detection test result is reported to an engineer for approval, and the support is purchased according to the support detection test result; before the box girder is installed in place, the support is installed, and when the box girder at the discontinuous pier or the abutment is installed, the stainless steel plate and the permanent support are firmly installed; when the continuous pier box girder is installed, a temporary support is installed in advance;

s7: hoisting the box girder; the prefabricated box girder adopts a method of reserving hoisting holes on a panel to hoist the girder body, 2 hoisting holes are arranged on each side of the end part of the box girder and are symmetrically arranged, and riggings are connected with the box girder to be erected by penetrating through the bottoms of the hoisting holes;

the crane lifts the box girder, carries out alignment and then slowly puts down the box girder to be in place; after the box girder is in place, checking whether a lower support is loosened and the girder is stable; if the beam plate is not flat, the beam plate is lifted again, and the support is leveled by the stainless steel plate until the support is stable; after the first box girder is erected, erecting the box girders according to the method in sequence until all the box girders of the span are erected;

s8: construction acceptance inspection; the prefabricated small box girder is actually measured in installation inspection, the installation required position of the small box girder is accurate, each girder end is neatly drawn, the seam of the girder end is straight, and the width meets the design requirement that the girder bottom is tightly connected with the support.

2. The method for installing and constructing the prefabricated small box girder for the intelligent express way as claimed in claim 1, wherein foundations within the traveling and hoisting range of a crane are treated and reinforced in advance, a roadbed box is laid, and drainage ditches are arranged on two sides of the foundations; removing obstacles on a transportation road, filling a base layer of a construction pavement with old materials with the thickness of 100cm, paving gravels or gravels with the thickness of 10cm on a surface layer, and making the width of the pavement be 5 meters; and leveling and compacting the periphery of a construction site and a transportation road before erecting a beam, and clearing obstacles on a construction access road, including uneven ground and overhead cables on the construction access road.

3. The method for installing and constructing the prefabricated small box girder for the intelligent express way as claimed in claim 1, wherein in the preparation construction process of the S3 crane, the walking line of the crawler crane in the hoisting operation site is filled with old materials with the thickness of 100cm, gravels or gravels with the thickness of 10cm are paved on the surface layer, and a road roller is used for rolling and flattening and paving steel plates.

4. The method for installing and constructing the prefabricated small box girder for the intelligent express way is characterized in that in the installation and construction process of the S6 support, a steel base plate is pre-embedded during construction of a cover beam pad stone, and a steel plate is provided with exhaust holes to ensure that concrete is poured and tightly poured at the bottom of the steel base plate; the top surface elevation and the flatness of the embedded steel backing plate meet the design requirements;

the beam bottom of the permanent support is parallel and flat with the top surfaces of the supporting cushion stone and the steel base plate, so that the permanent support is tightly attached to the upper surface and the lower surface of the support.

5. The method for installing and constructing the prefabricated small box girder for the intelligent express way as claimed in claim 1, wherein in the process of S7 box girder hoisting, the operation of hoisting in the open air should be stopped when the wind speed is more than 8m/S, the visibility in fog is lower than 50m, and the rain falls.

6. The method for installing and constructing the prefabricated small box girder for the intelligent express way as claimed in claim 1, wherein in the S7 box girder hoisting construction process, two cranes vertically hoist and the boom does not change the amplitude during hoisting; and when the member is lifted to a height of 20-30cm higher than the supporting point, the suspension arms rotate in the same direction, and when the fulcrum of the member is confirmed to rotate above the bearing point, the box girder is lowered down by the crane.

7. The method for installing and constructing the prefabricated small box girder for the intelligent express way as claimed in claim 1, wherein during the installation and construction of the S6 supporting seat, the temporary supporting seat is made of a steel-structured sand cylinder and a cylindrical sand box made of seamless steel tubes, and the cylindrical sand box is divided into a lower sand cylinder and an upper sleeve.

8. The method for installing and constructing the prefabricated small box girder for the intelligent express way is characterized in that a lower base plate is welded at the bottom of a lower sand cylinder in a sealing mode, a sand opening is formed in the side face of a steel pipe sand cylinder, a sealing steel plate is combined through a turning screw opening, and screws are screwed; dry fine sand is placed in the lower sand cylinder and falls on the cover beam; the upper and lower backing plates of the upper sleeve are sealed by welding; the upper layer sleeve is sleeved in the lower layer sandbox, and the girder falls on the upper layer sleeve when the beam is erected.

9. The method for installing and constructing the prefabricated box girder for the intelligent express way as claimed in claim 1, wherein in the S6 support installation construction process, the permanent support installation comprises the following steps:

A. the steel base plate is pre-embedded during construction of the bent cap and the base stone, and the steel plate is provided with the exhaust holes, so that concrete pouring at the bottom of the steel base plate is guaranteed to be compact, and the top surface elevation and the flatness of the pre-embedded steel base plate meet the design requirements;

B. the beam bottom of the permanent support is parallel and flat with the top surfaces of the supporting cushion stone and the steel base plate, so that the permanent support is closely attached to the upper surface and the lower surface of the support;

C. the support is arranged on the supporting cushion steel plate, and the central line of the support is superposed with the central line of the supporting cushion; after the support is installed, filling the gap position of the support foot with mortar;

D. before pouring the concrete beam, a supporting steel plate which is larger than the plane of the support is required to be additionally arranged on the support, and anchoring steel bars are welded on the steel plate to be connected with the beam; filling yarn waste, putty or cork plates in the gaps around the supporting steel plates; later on when the formwork is removed, the filling is removed again.

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