阅读说明：本技术 120m跨预应力三角钢管桁架梁施工方法 (120 m-span prestressed triangular steel pipe truss girder construction method ) 是由 鲍金晶 肖石头 邢俊 纪雯琇 邢美芳 于 2021-07-09 设计创作，主要内容包括：本发明公开了一种120m跨预应力三角钢管桁架梁施工方法,包括拼装场地布置、钢屋盖安装等步骤；钢屋盖安装包括拼装胎架的制作、胎架拼装、桁架拼装、桁架吊装、桁架张拉等步骤。本发明施工方便,施工质量好。(The invention discloses a construction method of a 120 m-span prestressed triangular steel pipe truss girder, which comprises the steps of assembling site arrangement, steel roof installation and the like; the steel roof installation comprises the steps of manufacturing of an assembling jig frame, assembling of the jig frame, assembling of a truss, hoisting of the truss, stretching of the truss and the like. The invention has convenient construction and good construction quality.)

1. A120 m span prestressed triangular steel pipe truss girder construction method is characterized by comprising the following steps: comprises the following steps:

the large-span steel roof structure is supported by concrete columns, the roof is a beam-string truss structure, the overall plane shape of the roof is rectangular, the length of the roof is 300m, the width of the roof is 120m, the cross section of the truss is in an inverted triangular form, the span of a main truss reaches 120m, the elevation of the highest part is 19.3m, the total number of the main trusses is 21, the diameter of an upper chord is 377mm, and the diameter of a lower chord is 450 mm; the upper part of the truss is of a skylight frame and a C-shaped purline structure; the maximum weight of a single main truss is 67 tons;

(I) arrangement of assembly sites

(1) The assembly site is arranged in the installation construction site, so that the truss can be conveniently and directly transported to an installation in-place position after the crawler crane is demolded;

(2) the truss in the area A is 120m long and is divided into four sections for assembling and mounting;

(3) selecting a truss assembling field:

arranging a truss assembling field inside a truss installation field or in an external area close to the installation field;

the span of the main truss is 120 meters, the main truss is required to be assembled in four sections, each section is 30 meters, demolding, transporting and hoisting are carried out by using a crawler crane, the assembly field is set into two assembly fields, the occupied area of each field is 125m by 19m, and two auxiliary assembly jig frames are arranged on each field;

(3) reinforcing the water gallery part passed by the crawler crane in the walking process so as to ensure that the walking and hoisting of the crawler crane do not damage the constructed water gallery;

firstly, arranging a supporting scaffold consisting of a cross rod and a vertical rod at a water gallery part where a crawler crane walks; the distance between the upright posts of the scaffold is 0.5 meter, the distance between the cross rods is 1 meter, and adjustable shores are arranged at the shoring parts of the cross rods and the upright posts and used for tightly jacking concrete on the side surfaces and the top of the water gallery; then paving 30cm thick ballast on a walking road of the crawler crane, and paving two 250mm 1600mm 8400mm roadbed boxes on the walking road across the water gallery, wherein the distance between the two roadbed boxes is the width of the crawler;

(II) Steel roof installation

The roof is of a beam string truss structure, the plane shape of the roof is rectangular, the length of the roof is 300m, and the width of the roof is 120 m; the cross section of the truss is in an inverted triangular form, the span of the main truss reaches 120m, the elevation at the highest position is 19.3m, the total number of the main trusses is 21, the pipe diameter of the upper chord is 377mm, the pipe diameter of the lower chord is 450mm, the heaviest weight of the single-truss is 67 tons, and the main trusses and the secondary trusses are welded in a penetrating manner; the upper part of the truss is of a skylight frame and a C-shaped purline structure; the roof adopts a beam string structure;

when the truss is assembled, the main truss is assembled in sections by adopting a factory overall pre-assembly mode; the main truss and the secondary truss are inverted triangular trusses, and the assembly adopts integral vertical assembly;

(1) manufacturing an assembled jig frame:

materials: the jig frame is built by using the steel pipe, section steel and rectangular pipe excess materials in the previous engineering;

main truss bed-jig: the vertical rods and the diagonal rods are all welded steel pipes, and the base is made of large-size H-shaped steel; the two ends of the supporting rod are welded to ensure the stability of the jig frame, the vertical rod is welded with the H-shaped steel at the bottom, the inclined supporting tube is additionally arranged on the outer side of the vertical rod, the vertical rod also plays a role of a limiting explorator, and the outer side of the chord member is tightly attached to the vertical rod during assembly; in order to ensure that enough space is reserved on the jig frame for welding the web members, the placing position of the jig frame avoids the nodes;

the method comprises the following steps that the positions of jig frames are determined according to the positions of joints of main truss chord members, the space between the jig frames is not more than 5m, 4 pairs of jig frames are required to be manufactured for assembling each section of main truss, the assembling of the main truss is guaranteed, and hoisting equipment and the jig frames are added according to the actual construction progress in the later stage;

the specific height of each pair of jig frames is controlled and lofted by a field technician according to a truss assembly jig frame layout;

(2) jig frame assembling process

a. Drawing a lofting drawing by a technician computer, and marking the lofting size;

b. the constructor lofts on the ground, and the marking pen marks the splicing control point;

c. placing the jig frame according to the lofting drawing;

d. controlling the bed jig to be horizontal by using a level meter and a theodolite, and unifying the elevation of the bed jig;

5. hoisting chord members by the steam cranes, and placing the chord members at corresponding positions in the jig frame;

e. measuring the node positions of the web members on the chord members according to a lofting map of the ground;

f. assembling and welding web members;

g. demolding the assembled integral component;

(3) truss assembly

The primary and secondary trusses are inverted triangular trusses, and the main trusses are integrally horizontally assembled in consideration of convenience in demoulding and transporting;

the first step is as follows: laying out the ground model and arranging an assembling jig frame;

before the jig frame is arranged, according to the actual projection size of the assembling unit, drawing a center line of X, Y directions of the nodes and the rod pieces projected on the platform, then arranging the jig frame, wherein the height of the jig frame must be strictly controlled, the height of the jig frame is correspondingly converted according to the size in the structural model, the elevation positioning of the jig frame is accurately positioned by adopting a total station, the elevation error of the jig frame is ensured to be not more than 0.5mm, and the work is implemented in the early morning or under the condition of relatively stable temperature in order to avoid the temperature difference influence caused by sunshine change under the outdoor operation environment;

the arrangement of the jig frame template ensures that the nodes are convenient to position and safe and reliable, so that a special positioning template needs to be arranged, the jig frame steel member can be adopted after being processed by a milling machine, and the requirement on the levelness of a contact plane of the member is ensured;

because the varieties of the field truss are more, the assembling jig frames are manufactured in a plurality of types, and the setting of the jig frames must meet the requirement of secondary recycling, the jig frames can be conveniently assembled and disassembled and combined into the assembling jig frames with different lengths and different heights by adopting tool type H-shaped steel and steel pipe manufacturing;

the second step is that: assembled steel truss chord member

Hanging the lower chord of the main truss which is qualified in butt joint on an assembling jig frame, aligning a positioning datum line on a ground sample, correcting the parallelism of the datum line and the lower chord, and temporarily fixing the lower chord on the jig frame; after the upper chord is assembled in place, the upper chord of the truss is assembled in the same way, and the parallelism between the upper chord and the lower chord is adjusted at the same time, and then the upper chord is temporarily fixed on a jig frame;

the third step: assembled steel truss web member

Re-measuring the upper chord and the lower chord of the truss, assembling web members after the truss is qualified, hanging the cut and qualified web members on an assembly jig platform for assembling, aligning and positioning the center line, and then fixing the center line on the chord members; as the contact of the web members is the intersecting surface contact, the CO2 gas shielded welding is adopted for positioning, assembling and welding the web members and the chord members;

the fourth step: the assembled and formed truss is transported to a hoisting part in sections for hoisting;

(a) sub-truss assembly

The secondary trusses among the main trusses are also three-dimensional inverted triangular trusses, the structure is simple, the number of rod pieces is small, and the assembly time cost is small, so that the main trusses are assembled synchronously when being assembled;

(b) truss welding with CO₂ Gas shielded welding, wherein the welding is symmetrically welded by adopting an even number of welders, the welding is carried out from the middle part to two ends, the butt weld of the lower chord member is welded firstly during the welding so as to ensure that the camber of the truss is a positive value, the butt weld of the upper chord member is welded later, the lower chord web member is welded, and finally the web members between the upper chord member and the lower chord member are welded, the main truss has to pay attention to the deflection and the lateral deformation of the truss at any time during the welding process, the measurement is carried out at any time, otherwise, the welding sequence is adjusted;

(c) welding with CO₂The gas shielded welding carries out multilayer multi-pass welding, reduces heat input quantity, and carries out welding from the middle part to two ends of the truss during welding, thereby preventing overlarge deformation caused by overlarge welding stress when the segments are disassembled; after welding, repairing, polishing and self-checking are carried out;

(d) the field quality inspector must inspect and measure the welding quality according to the design and specification and meet the qualified requirements, and rework the unqualified welding line according to the requirements of the welding process; after the product is qualified, submitting to supervision and acceptance, brushing and demoulding;

(e) the beam-string trusses are divided into four truss types, namely ZHJ-1, ZHJ-2, ZHJ-3 and ZHJ-4, and each truss is symmetrical about the midspan axis; because the span is large, a sectional hoisting method is adopted, each beam truss is divided into four sections, and each section is about 30m long; in the process of sectional hoisting, the installation of the web members near the butt joint position is not influenced when the jig supports the upper chord, so that intersecting nodes of the upper chord web members need to be avoided when the jig is arranged;

(4) truss hoisting

Determining a lifting point and a gravity center:

the hoisting points of the hoisting units are arranged on the upper chord of the truss, the steel wire ropes are connected with the upper chord nodes of the truss, and each unit is hoisted by four points;

hoisting working conditions are as follows:

according to the structural characteristics, the truss is divided into 4 sections, each section is independently hoisted, the maximum hoisting weight is 18.5t, and a 100-ton crawler crane is selected;

the working condition I is as follows: the operation radius is 18 meters, and the self weight of the segmented truss is 15 tons; the hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

working conditions are as follows: installing a second subsection after the installation of the first subsection is finished; the operation radius of the second subsection is 18 meters, and the self weight of the truss is 16 tons; the hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

working conditions are as follows: installing a third subsection after the installation of the second subsection is finished; the radius of the third subsection operation is 18 meters, and the self weight of the truss is 17.5 tons; the hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

working conditions are as follows: finally, installing a subsection four; the self weight of the segmented four-truss is 18.5 tons; the hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

supporting and setting:

the string-stretching net rack main truss is uniformly divided into four sections for installation, and during installation, a supporting jig frame is erected at a folding position and supports and fixes two upper string steel pipes of the truss;

(5) truss tensioning

For the prestressed truss string, single truss string is stretched, and the installation and welding of the main structure, the secondary truss and the skylight frame of the two adjacent truss string spans before stretching are finished; mounting roof purlins and roof boards after all beams in the same expansion joint section in the single area are tensioned;

(a) erecting a jig frame, and assembling an upper rigid frame of a first truss string according to the size of a construction drawing by adopting a high-altitude sectional hoisting method;

(b) assembling a second truss string by the same method, connecting the truss string with a support in place, and padding a tetrafluoroethylene plate under the support;

(c) assembling longitudinal connection trusses, skylight frames, cross braces and the like between the two trusses, and completing welding of all rod piece nodes;

(d) repeating the steps (b) and (c) to finish the installation and welding of the 3 rd truss and the connection members between the trusses;

(e) stretching the prestressed guy cable of the first truss on the ground, installing the guy cable at high altitude and stretching the prestressed guy cable of the first truss;

(f) repeating the steps (b), (c) and (e), completing the installation and welding of the connection members between the 4 th truss and the truss, and tensioning the 2 nd truss; sequentially carrying out flow construction according to the steps (a) to (f);

and after all the tensioning of the same unit is finished, mounting the roof purlines between the tensioned trusses, mounting the roof panel, and finally fixing the support base plate.

Technical Field

The invention relates to a truss girder construction method.

Background

The existing truss girder construction has complex working procedures and unsatisfactory engineering quality, and particularly has the problems of difficult construction and the like when the large-span triangular steel pipe truss girder is constructed, and needs to be further improved.

Disclosure of Invention

The invention aims to provide a 120 m-span prestressed triangular steel pipe truss girder construction method with good construction quality.

The technical solution of the invention is as follows:

a120 m span prestressed triangular steel pipe truss girder construction method is characterized by comprising the following steps: comprises the following steps:

the large-span steel roof structure is supported by concrete columns, the roof is a beam-string truss structure, the overall plane shape of the roof is rectangular, the length of the roof is 300m, the width of the roof is 120m, the cross section of the truss is in an inverted triangular form, the span of a main truss reaches 120m, the elevation of the highest part is 19.3m, the total number of the main trusses is 21, the diameter of an upper chord is 377mm, and the diameter of a lower chord is 450 mm; the upper part of the truss is of a skylight frame and a C-shaped purline structure; the maximum weight of a single main truss is 67 tons;

(I) arrangement of assembly sites

(1) The assembly site is arranged in the installation construction site, so that the truss can be conveniently and directly transported to an installation in-place position after the crawler crane is demolded;

(2) the truss in the area A is 120m long and is divided into four sections for assembling and mounting;

(3) selecting a truss assembling field:

arranging a truss assembling field inside a truss installation field or in an external area close to the installation field;

the span of the main truss is 120 meters, the main truss is required to be assembled in four sections, each section is 30 meters, demolding, transporting and hoisting are carried out by using a crawler crane, the assembly field is set into two assembly fields, the occupied area of each field is 125m by 19m, and two auxiliary assembly jig frames are arranged on each field;

(3) reinforcing the water gallery part passed by the crawler crane in the walking process so as to ensure that the walking and hoisting of the crawler crane do not damage the constructed water gallery;

firstly, arranging a supporting scaffold consisting of a cross rod and a vertical rod at a water gallery part where a crawler crane walks; the distance between the upright posts of the scaffold is 0.5 meter, the distance between the cross rods is 1 meter, and adjustable shores are arranged at the shoring parts of the cross rods and the upright posts and used for tightly jacking concrete on the side surfaces and the top of the water gallery; then paving 30cm thick ballast on a walking road of the crawler crane, and paving two 250mm 1600mm 8400mm roadbed boxes on the walking road across the water gallery, wherein the distance between the two roadbed boxes is the width of the crawler;

(II) Steel roof installation

The roof is of a beam string truss structure, the plane shape of the roof is rectangular, the length of the roof is 300m, and the width of the roof is 120 m; the cross section of the truss is in an inverted triangular form, the span of the main truss reaches 120m, the elevation at the highest position is 19.3m, the total number of the main trusses is 21, the pipe diameter of the upper chord is 377mm, the pipe diameter of the lower chord is 450mm, the heaviest weight of the single-truss is 67 tons, and the main trusses and the secondary trusses are welded in a penetrating manner; the upper part of the truss is of a skylight frame and a C-shaped purline structure; the roof adopts a beam string structure;

when the truss is assembled, the main truss is assembled in sections by adopting a factory overall pre-assembly mode. The main truss and the secondary truss are inverted triangular trusses, and the assembly adopts integral vertical assembly;

(1) manufacturing an assembled jig frame:

materials: the jig frame is built by using the steel pipe, section steel and rectangular pipe excess materials in the previous engineering;

main truss bed-jig: the vertical rods and the diagonal rods are all welded steel pipes, and the base is made of large-size H-shaped steel; the two ends of the supporting rod are welded to ensure the stability of the jig frame, the vertical rod is welded with the H-shaped steel at the bottom, the inclined supporting tube is additionally arranged on the outer side of the vertical rod, the vertical rod also plays a role of a limiting explorator, and the outer side of the chord member is tightly attached to the vertical rod during assembly; in order to ensure that enough space is reserved on the jig frame for welding the web members, the placing position of the jig frame avoids the nodes;

the method comprises the following steps that the positions of jig frames are determined according to the positions of joints of main truss chord members, the space between the jig frames is not more than 5m, 4 pairs of jig frames are required to be manufactured for assembling each section of main truss, the assembling of the main truss is guaranteed, and hoisting equipment and the jig frames are added according to the actual construction progress in the later stage;

the specific height of each pair of jig frames is controlled and lofted by a field technician according to a truss assembly jig frame layout;

(2) jig frame assembling process

a. Drawing a lofting drawing by a technician computer, and marking the lofting size;

b. the constructor lofts on the ground, and the marking pen marks the splicing control point;

c. placing the jig frame according to the lofting drawing;

d. controlling the bed jig to be horizontal by using a level meter and a theodolite, and unifying the elevation of the bed jig;

5. hoisting chord members by the steam cranes, and placing the chord members at corresponding positions in the jig frame;

e. measuring the node positions of the web members on the chord members according to a lofting map of the ground;

f. assembling and welding web members;

g. demolding the assembled integral component;

(3) truss assembly

The primary and secondary trusses are inverted triangular trusses, and the main trusses are integrally horizontally assembled in consideration of convenience in demoulding and transporting;

the first step is as follows: laying out the ground model and arranging an assembling jig frame;

before the jig frame is arranged, according to the actual projection size of the assembling unit, drawing a center line of X, Y directions of the nodes and the rod pieces projected on the platform, then arranging the jig frame, wherein the height of the jig frame must be strictly controlled, the height of the jig frame is correspondingly converted according to the size in the structural model, the elevation positioning of the jig frame is accurately positioned by adopting a total station, the elevation error of the jig frame is ensured to be not more than 0.5mm, and the work is implemented in the early morning or under the condition of relatively stable temperature in order to avoid the temperature difference influence caused by sunshine change under the outdoor operation environment;

the arrangement of the jig frame template ensures that the nodes are convenient to position and safe and reliable, so that a special positioning template needs to be arranged, the jig frame steel member can be adopted after being processed by a milling machine, and the requirement on the levelness of a contact plane of the member is ensured;

because the varieties of the field truss are more, the assembling jig frames are manufactured in a plurality of types, and the setting of the jig frames must meet the requirement of secondary recycling, the jig frames can be conveniently assembled and disassembled and combined into the assembling jig frames with different lengths and different heights by adopting tool type H-shaped steel and steel pipe manufacturing;

the second step is that: assembled steel truss chord member

Hanging the lower chord of the main truss which is qualified in butt joint on an assembling jig frame, aligning a positioning datum line on a ground sample, correcting the parallelism of the datum line and the lower chord, and temporarily fixing the lower chord on the jig frame; after the upper chord is assembled in place, the upper chord of the truss is assembled in the same way, and the parallelism between the upper chord and the lower chord is adjusted at the same time, and then the upper chord is temporarily fixed on a jig frame;

the third step: assembled steel truss web member

Re-measuring the upper chord and the lower chord of the truss, assembling web members after the truss is qualified, hanging the cut and qualified web members on an assembly jig platform for assembling, aligning and positioning the center line, and then fixing the center line on the chord members; as the contact of the web members is the intersecting surface contact, the CO2 gas shielded welding is adopted for positioning, assembling and welding the web members and the chord members;

the fourth step: the assembled and formed truss is transported to a hoisting part in sections for hoisting;

(a) sub-truss assembly

The secondary trusses among the main trusses are also three-dimensional inverted triangular trusses, the structure is simple, the number of rod pieces is small, and the assembly time cost is small, so that the main trusses are assembled synchronously when being assembled;

(b) truss welding with CO₂ Gas shielded welding, wherein the welding is symmetrically welded by adopting an even number of welders, the welding is carried out from the middle part to two ends, the butt weld of the lower chord member is welded firstly during the welding so as to ensure that the camber of the truss is a positive value, the butt weld of the upper chord member is welded later, the lower chord web member is welded, and finally the web members between the upper chord member and the lower chord member are welded, the main truss has to pay attention to the deflection and the lateral deformation of the truss at any time during the welding process, the measurement is carried out at any time, otherwise, the welding sequence is adjusted;

(c) welding with CO₂The gas shielded welding carries out multilayer multi-pass welding, reduces heat input quantity, and carries out welding from the middle part to two ends of the truss during welding, thereby preventing overlarge deformation caused by overlarge welding stress when the segments are disassembled; after welding, repairing, polishing and self-checking are carried out;

(d) the field quality inspector must inspect and measure the welding quality according to the design and specification and meet the qualified requirements, and rework the unqualified welding line according to the requirements of the welding process; after the product is qualified, submitting to supervision and acceptance, brushing and demoulding;

(e) the beam-string trusses are divided into four truss types, namely ZHJ-1, ZHJ-2, ZHJ-3 and ZHJ-4, and each truss is symmetrical about the midspan axis. Because the span is large, a sectional hoisting method is adopted, each beam truss is divided into four sections, and each section is about 30m long; in the process of sectional hoisting, the installation of the web members near the butt joint position is not influenced when the jig supports the upper chord, so that intersecting nodes of the upper chord web members need to be avoided when the jig is arranged;

(4) truss hoisting

Determining a lifting point and a gravity center:

the hoisting points of the hoisting units are arranged on the upper chord of the truss, the steel wire ropes are connected with the upper chord nodes of the truss, and each unit is hoisted by four points;

hoisting working conditions are as follows:

according to the structural characteristics, the truss is divided into 4 sections, each section is independently hoisted, the maximum hoisting weight is 18.5t, and a 100-ton crawler crane is selected;

the working condition I is as follows: the operation radius is 18 meters, and the self weight of the segmented truss is 15 tons; the hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

working conditions are as follows: installing a second subsection after the installation of the first subsection is finished; the operation radius of the second subsection is 18 meters, and the self weight of the truss is 16 tons; the hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

working conditions are as follows: installing a third subsection after the installation of the second subsection is finished; the radius of the three-section operation is 18 meters, and the self weight of the truss is 17.5 tons. The hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

working conditions are as follows: finally, installing a subsection four; the self weight of the segmented four-truss is 18.5 tons; the hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

supporting and setting:

the string-stretching net rack main truss is uniformly divided into four sections for installation, and during installation, a supporting jig frame is erected at a folding position and supports and fixes two upper string steel pipes of the truss;

(5) truss tensioning

For the prestressed truss string, single truss string is stretched, and the installation and welding of the main structure, the secondary truss and the skylight frame of the two adjacent truss string spans before stretching are finished; mounting roof purlins and roof boards after all beams in the same expansion joint section in the single area are tensioned;

(a) erecting a jig frame, and assembling an upper rigid frame of a first truss string according to the size of a construction drawing by adopting a high-altitude sectional hoisting method;

(b) assembling a second truss string by the same method, connecting the truss string with a support in place, and padding a tetrafluoroethylene plate under the support;

(c) assembling longitudinal connection trusses, skylight frames, cross braces and the like between the two trusses, and completing welding of all rod piece nodes;

(d) repeating the steps (b) and (c) to finish the installation and welding of the 3 rd truss and the connection members between the trusses;

(e) stretching the prestressed guy cable of the first truss on the ground, installing the guy cable at high altitude and stretching the prestressed guy cable of the first truss;

(f) repeating the steps (b), (c) and (e), completing the installation and welding of the connection members between the 4 th truss and the truss, and tensioning the 2 nd truss; sequentially carrying out flow construction according to the steps (a) to (f);

and after all the tensioning of the same unit is finished, mounting the roof purlines between the tensioned trusses, mounting the roof panel, and finally fixing the support base plate.

The invention has convenient construction and good construction quality.

Drawings

The invention is further illustrated by the following figures and examples.

Fig. 1 is a schematic view of a road reinforcing structure at a water corridor part of the invention.

Detailed Description

A120 m span prestressed triangular steel pipe truss girder construction method comprises the following steps:

the large-span steel roof structure is supported by concrete columns, the roof is a beam-string truss structure, the overall plane shape of the roof is rectangular, the length of the roof is 300m, the width of the roof is 120m, the cross section of the truss is in an inverted triangular form, the span of a main truss reaches 120m, the elevation of the highest part is 19.3m, the total number of the main trusses is 21, the diameter of an upper chord is 377mm, and the diameter of a lower chord is 450 mm; the upper part of the truss is of a skylight frame and a C-shaped purline structure; the maximum weight of a single main truss is 67 tons;

(I) arrangement of assembly sites

(1) The assembly site is arranged in the installation construction site, so that the truss can be conveniently and directly transported to an installation in-place position after the crawler crane is demolded;

(2) the truss in the area A is 120m long and is divided into four sections for assembling and mounting;

(3) selecting a truss assembling field:

arranging a truss assembling field inside a truss installation field or in an external area close to the installation field;

the span of the main truss is 120 meters, the main truss is required to be assembled in four sections, each section is 30 meters, demolding, transporting and hoisting are carried out by using a crawler crane, the assembly field is set into two assembly fields, the occupied area of each field is 125m by 19m, and two auxiliary assembly jig frames are arranged on each field;

(3) reinforcing the water gallery part passed by the crawler crane in the walking process so as to ensure that the walking and hoisting of the crawler crane do not damage the constructed water gallery;

firstly, arranging a supporting scaffold consisting of a cross rod 1 and a vertical rod 2 at a water gallery part where a crawler crane walks; the distance between the upright posts of the scaffold is 0.5 meter, the distance between the cross rods is 1 meter, and the top bracing parts of the cross rods and the upright posts are provided with adjustable top bracing 3 for tightly bracing the side surface and the top concrete 4 of the water gallery; then paving 30 cm-thick ballast 5 on a walking road of the crawler crane, and paving two road base boxes 6 of 250mm 1600mm 8400mm at the position of the walking road crossing the water gallery, wherein the distance between the two road base boxes is the width of the crawler;

(II) Steel roof installation

The roof is of a beam string truss structure, the plane shape of the roof is rectangular, the length of the roof is 300m, and the width of the roof is 120 m; the cross section of the truss is in an inverted triangular form, the span of the main truss reaches 120m, the elevation at the highest position is 19.3m, the total number of the main trusses is 21, the pipe diameter of the upper chord is 377mm, the pipe diameter of the lower chord is 450mm, the heaviest weight of the single-truss is 67 tons, and the main trusses and the secondary trusses are welded in a penetrating manner; the upper part of the truss is of a skylight frame and a C-shaped purline structure; the roof adopts a beam string structure;

when the truss is assembled, the main truss is assembled in sections by adopting a factory overall pre-assembly mode. The main truss and the secondary truss are inverted triangular trusses, and the assembly adopts integral vertical assembly;

(1) manufacturing an assembled jig frame:

materials: the jig frame is built by using the steel pipe, section steel and rectangular pipe excess materials in the previous engineering;

main truss bed-jig: the vertical rods and the diagonal rods are all welded steel pipes, and the base is made of large-size H-shaped steel; the two ends of the supporting rod are welded to ensure the stability of the jig frame, the vertical rod is welded with the H-shaped steel at the bottom, the inclined supporting tube is additionally arranged on the outer side of the vertical rod, the vertical rod also plays a role of a limiting explorator, and the outer side of the chord member is tightly attached to the vertical rod during assembly; in order to ensure that enough space is reserved on the jig frame for welding the web members, the placing position of the jig frame avoids the nodes;

the method comprises the following steps that the positions of jig frames are determined according to the positions of joints of main truss chord members, the space between the jig frames is not more than 5m, 4 pairs of jig frames are required to be manufactured for assembling each section of main truss, the assembling of the main truss is guaranteed, and hoisting equipment and the jig frames are added according to the actual construction progress in the later stage;

the specific height of each pair of jig frames is controlled and lofted by a field technician according to a truss assembly jig frame layout;

(2) jig frame assembling process

a. Drawing a lofting drawing by a technician computer, and marking the lofting size;

b. the constructor lofts on the ground, and the marking pen marks the splicing control point;

c. placing the jig frame according to the lofting drawing;

d. controlling the bed jig to be horizontal by using a level meter and a theodolite, and unifying the elevation of the bed jig;

5. hoisting chord members by the steam cranes, and placing the chord members at corresponding positions in the jig frame;

e. measuring the node positions of the web members on the chord members according to a lofting map of the ground;

f. assembling and welding web members;

g. demolding the assembled integral component;

(3) truss assembly

The primary and secondary trusses are inverted triangular trusses, and the main trusses are integrally horizontally assembled in consideration of convenience in demoulding and transporting;

the first step is as follows: laying out the ground model and arranging an assembling jig frame;

before the jig frame is arranged, according to the actual projection size of the assembling unit, drawing a center line of X, Y directions of the nodes and the rod pieces projected on the platform, then arranging the jig frame, wherein the height of the jig frame must be strictly controlled, the height of the jig frame is correspondingly converted according to the size in the structural model, the elevation positioning of the jig frame is accurately positioned by adopting a total station, the elevation error of the jig frame is ensured to be not more than 0.5mm, and the work is implemented in the early morning or under the condition of relatively stable temperature in order to avoid the temperature difference influence caused by sunshine change under the outdoor operation environment;

the arrangement of the jig frame template ensures that the nodes are convenient to position and safe and reliable, so that a special positioning template needs to be arranged, the jig frame steel member can be adopted after being processed by a milling machine, and the requirement on the levelness of a contact plane of the member is ensured;

because the varieties of the field truss are more, the assembling jig frames are manufactured in a plurality of types, and the setting of the jig frames must meet the requirement of secondary recycling, the jig frames can be conveniently assembled and disassembled and combined into the assembling jig frames with different lengths and different heights by adopting tool type H-shaped steel and steel pipe manufacturing;

the second step is that: assembled steel truss chord member

Hanging the lower chord of the main truss which is qualified in butt joint on an assembling jig frame, aligning a positioning datum line on a ground sample, correcting the parallelism of the datum line and the lower chord, and temporarily fixing the lower chord on the jig frame; after the upper chord is assembled in place, the upper chord of the truss is assembled in the same way, and the parallelism between the upper chord and the lower chord is adjusted at the same time, and then the upper chord is temporarily fixed on a jig frame;

the third step: assembled steel truss web member

Re-measuring the upper chord and the lower chord of the truss, assembling web members after the truss is qualified, hanging the cut and qualified web members on an assembly jig platform for assembling, aligning and positioning the center line, and then fixing the center line on the chord members; as the contact of the web members is the intersecting surface contact, the CO2 gas shielded welding is adopted for positioning, assembling and welding the web members and the chord members;

the fourth step: the assembled and formed truss is transported to a hoisting part in sections for hoisting;

(a) sub-truss assembly

The secondary trusses among the main trusses are also three-dimensional inverted triangular trusses, the structure is simple, the number of rod pieces is small, and the assembly time cost is small, so that the main trusses are assembled synchronously when being assembled;

(b) truss welding with CO₂ Gas shielded welding, wherein the welding is symmetrically welded by adopting an even number of welders, the welding is carried out from the middle part to two ends, the butt weld of the lower chord member is welded firstly during the welding so as to ensure that the camber of the truss is a positive value, the butt weld of the upper chord member is welded later, the lower chord web member is welded, and finally the web members between the upper chord member and the lower chord member are welded, the main truss has to pay attention to the deflection and the lateral deformation of the truss at any time during the welding process, the measurement is carried out at any time, otherwise, the welding sequence is adjusted;

(c) welding with CO₂The gas shielded welding carries out multilayer multi-pass welding, reduces heat input quantity, and carries out welding from the middle part to two ends of the truss during welding, thereby preventing overlarge deformation caused by overlarge welding stress when the segments are disassembled; after welding, repairing, polishing and self-checking are carried out;

(d) the field quality inspector must inspect and measure the welding quality according to the design and specification and meet the qualified requirements, and rework the unqualified welding line according to the requirements of the welding process; after the product is qualified, submitting to supervision and acceptance, brushing and demoulding;

(e) the beam-string trusses are divided into four truss types, namely ZHJ-1, ZHJ-2, ZHJ-3 and ZHJ-4, and each truss is symmetrical about the midspan axis. Because the span is large, a sectional hoisting method is adopted, each beam truss is divided into four sections, and each section is about 30m long; in the process of sectional hoisting, the installation of the web members near the butt joint position is not influenced when the jig supports the upper chord, so that intersecting nodes of the upper chord web members need to be avoided when the jig is arranged;

(4) truss hoisting

Determining a lifting point and a gravity center:

the hoisting points of the hoisting units are arranged on the upper chord of the truss, the steel wire ropes are connected with the upper chord nodes of the truss, and each unit is hoisted by four points;

hoisting working conditions are as follows:

according to the structural characteristics, the truss is divided into 4 sections, each section is independently hoisted, the maximum hoisting weight is 18.5t, and a 100-ton crawler crane is selected;

the working condition I is as follows: the operation radius is 18 meters, and the self weight of the segmented truss is 15 tons; the hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

working conditions are as follows: installing a second subsection after the installation of the first subsection is finished; the operation radius of the second subsection is 18 meters, and the self weight of the truss is 16 tons; the hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

working conditions are as follows: installing a third subsection after the installation of the second subsection is finished; the radius of the three-section operation is 18 meters, and the self weight of the truss is 17.5 tons. The hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

working conditions are as follows: finally, installing a subsection four; the self weight of the segmented four-truss is 18.5 tons; the hoisting weight of the 100-ton crawler crane is 20.9 tons under the working condition that the working radius is 18 meters, so that the hoisting requirement is met; after the main truss is installed, a 25-ton truck crane is adopted to install a secondary truss and a skylight frame between two main trusses;

supporting and setting:

the string-stretching net rack main truss is uniformly divided into four sections for installation, and during installation, a supporting jig frame is erected at a folding position and supports and fixes two upper string steel pipes of the truss;

(5) truss tensioning

For the prestressed truss string, single truss string is stretched, and the installation and welding of the main structure, the secondary truss and the skylight frame of the two adjacent truss string spans before stretching are finished; mounting roof purlins and roof boards after all beams in the same expansion joint section in the single area are tensioned;

(a) erecting a jig frame, and assembling an upper rigid frame of a first truss string according to the size of a construction drawing by adopting a high-altitude sectional hoisting method;

(b) assembling a second truss string by the same method, connecting the truss string with a support in place, and padding a tetrafluoroethylene plate under the support;

(c) assembling longitudinal connection trusses, skylight frames, cross braces and the like between the two trusses, and completing welding of all rod piece nodes;

(d) repeating the steps (b) and (c) to finish the installation and welding of the 3 rd truss and the connection members between the trusses;

(e) stretching the prestressed guy cable of the first truss on the ground, installing the guy cable at high altitude and stretching the prestressed guy cable of the first truss;

(f) repeating the steps (b), (c) and (e), completing the installation and welding of the connection members between the 4 th truss and the truss, and tensioning the 2 nd truss; sequentially carrying out flow construction according to the steps (a) to (f);

and after all the tensioning of the same unit is finished, mounting the roof purlines between the tensioned trusses, mounting the roof panel, and finally fixing the support base plate.