Steel truss section beam separating method and steel truss construction method

Abstract

The invention relates to the technical field of steel structure installation, in particular to a steel truss section beam separating method and a steel truss construction method. The beam falling method comprises the following steps that a permanent buttress and a temporary buttress are installed according to design, and a jack is arranged on the temporary buttress; the steel truss comprises a plurality of sections in the span direction. The multiple sections are subjected to beam falling, and each section is subjected to beam falling through the following steps that the sections are hoisted to the positions where beams are to be subjected to beam falling; the welding ends of the segments are connected with an existing structure in a rough welding mode; the whole segment falls onto the jack, and the jack is adjusted to correct the position of the segment; welding ends of the segments are fixed to an existing structure in a fine welding mode; the existing structure comprises at least one of the permanent buttress and the segments which are fixed through fine welding. On the basis of beam falling of the jack, the steps of rough welding, beam falling and adjusting and fine welding are adopted, and the effect of improving installation stability and structural durability is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of steel structure installation, and in particular to a steel truss segment beam method and a steel truss construction method. Background Art

[0002] During the hoisting process of the steel truss segment, in order to facilitate the positioning of the segment, crawler cranes are usually used for hoisting. After the segment is in place, personnel are arranged to measure the segment and the temporary pier on site to determine the specific height difference, and then the L-shaped angle steel is cut on site. The cut angle steel is then hoisted between the segment and the temporary pier for welding to support the segment, thereby completing the segment's beam drop. The existing construction method has the following disadvantages: First, when measuring the distance between the steel truss segment and the temporary pier during the hoisting process, it is easy to be disturbed by the outside world, resulting in inaccurate data and affecting the subsequent beam drop positioning; second, each segment hoisting requires the production of the corresponding angle steel adjustment tube on site, which cannot be reused after use, resulting in large material loss.

[0003] Some existing technologies use jacks to adjust the positioning of the beams, such as the steel truss beam construction system and method disclosed in the patent document with publication number CN117468728A, in which a truck crane is used to lift the steel truss beam segments in sections according to the construction sequence, and the steel truss beam segments are assisted in correction by a total station, a jack and an adjustable support plate; the jack at the bottom of the steel truss beam segment is adjusted with the assistance of the total station, and after the position is corrected correctly, the connecting end of the steel truss beam segment is welded and fixed to the support on the steel tube concrete column, and the adjustable support plate at the bottom of the free end is welded to the temporary support. Another example is the installation method of a large-span steel truss cantilevered special-shaped structure disclosed in the patent document with publication number CN117027425A, in which the truss beam is lifted in sections, the posture of the truss beam is adjusted by the jack on the temporary support column, and then the truss beam is welded and fixed.

[0004] It can be seen that in the prior art, when using jacks to assist in the segmentation of steel trusses, the position of the steel truss segments is always adjusted by the jacks first, and then the steel truss segments are welded and fixed to the existing structure. This method has the following problems: First, the steel trusses are only temporarily fixed by jacks during the adjustment stage. If external loads (such as wind loads) or operational errors cause displacement, it may cause safety hazards; second, during the welding process, the structural position may be offset due to thermal deformation, which requires the use of jacks to adjust the position for the second time after welding. On the one hand, there is an inconvenient operation problem, and on the other hand, welding has residual stress, and the secondary adjustment is a forced adjustment based on welding fixation. In this process, the steel trusses will undergo elastic or plastic deformation and may further generate residual stress. The residual stress in the adjustment stage and the welding residual stress are superimposed at the nodes to form a high stress area, which concentrates local stress and reduces the durability of the structure. Summary of the invention

[0005] The present invention aims to solve the above-mentioned problems and provides a steel truss segment beam method and a steel truss construction method which can improve installation stability and structural durability.

[0006] The technical solution to solve the problem of the present invention is to first provide a steel truss section beam method, comprising the following steps: S1. Install permanent piers and temporary piers according to the design, and the temporary piers are provided with jacks; S2. The steel truss includes several segments along the span direction, and the two ends of the segment along the span direction are respectively a welded end and a free end; Several of the segments are dropped separately, and each segment is dropped by the following steps: S21. Hoisting the segment to the position where the beam is to be dropped; S22. The welding end of the segment is connected to the existing structure by rough welding; S23. Dropping the entire segment onto the jack, and adjusting the jack to correct the position of the segment; S24. Fixing the welding end of the segment to the existing structure by precision welding; The existing structure includes at least one of the permanent pier and a segment that has been finished with welding and fixing.

[0007] In step S1, as a preferred embodiment of the present invention, the temporary pier includes a first supporting part, a second supporting part and a load-bearing part in sequence from the ground to the upper direction, and the jack is arranged on the load-bearing part; the first supporting part includes a plurality of first supporting piles, the second supporting part includes a plurality of second supporting piles, and a shear brace arranged between adjacent second supporting piles, the outer diameter of the second supporting pile is smaller than the outer diameter of the first supporting pile, and the first supporting pile and the second supporting pile are connected by a truncated cone-shaped connecting column.

[0008] As a preferred embodiment of the present invention, the outer diameter of the first support pile is 1.2 to 1.8 times the outer diameter of the second support pile, for example, it can be 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, preferably 1.5 times.

[0009] As a preferred embodiment of the present invention, at least two jacks are provided on the temporary pier along the span direction.

[0010] As a preferred embodiment of the present invention, the load-bearing part includes a first load-bearing beam for installing a jack close to the welding end of the segment, and a second load-bearing beam for installing a jack away from the welding end of the segment, the first load-bearing beam is connected to the second support part through a shear key, and the second load-bearing beam is connected to the second support part through a hollow circular tube.

[0011] In step S2, as a preferred embodiment of the present invention, the order of dropping the beams of the plurality of segments is: closing from both ends to the middle along the span direction.

[0012] As a preferred embodiment of the present invention, the segment includes an upper chord, a lower chord, and a web disposed between the upper chord and the lower chord; the upper chord and the lower chord are both H-shaped, and both include two flange plates and a web disposed between the two flange plates.

[0013] In step S21, as a preferred embodiment of the present invention, during hoisting, two hoisting points are set for each segment.

[0014] As a preferred embodiment of the present invention, the suspension point is located at the junction of the upper chord and the web member of the segment, or / and the junction of the lower chord and the web member.

[0015] In step S22, as a preferred embodiment of the present invention, the two flange plates of the lower chord of the segment are roughly welded to the existing structure, and the web plate of the upper chord of the segment is roughly welded to the existing structure.

[0016] As a preferred embodiment of the present invention, the two flange plates of the lower chord are symmetrically spot-welded to the existing structure using V-shaped grooves; and the web plate of the upper chord is jump-welded to the existing structure using K-shaped grooves.

[0017] As a preferred embodiment of the present invention, firstly, the two flange plates of the lower chord are roughly welded to the existing structure; and then the web plate of the upper chord is roughly welded to the existing structure.

[0018] As a preferred embodiment of the present invention, the shrinkage distance a of the segment after rough welding relative to that before rough welding is measured.

[0019] In step S23, as a preferred embodiment of the present invention, the segment falls as a whole onto at least two of the jacks.

[0020] As a preferred embodiment of the present invention, after the segment is corrected to the designed position by the jack, the jacking distance b is continued; b=(1.1~1.5)a, for example, it can be 1.1a, 1.2a, 1.3a, 1.4a, 1.5a, preferably 1.2a.

[0021] In step S24, as a preferred embodiment of the present invention, the finishing welding is full penetration welding.

[0022] Secondly, another object of the present invention is to provide a steel truss construction method, including any of the steel truss section beam construction methods described above.

[0023] Beneficial effects of the present invention: 1. The present invention provides a method for laying beams in steel trusses. On the basis of using jacks to drop beams, the method adopts the steps of rough welding - dropping beams and adjusting - fine welding, thereby achieving the effect of improving installation stability and structural durability.

[0024] Specifically: First, since the rough-welded segments and the existing structure have formed a preliminary integrity, the force is more uniform when the jack is adjusted, which can avoid the risk of local instability and improve Installation stability , and the displacement control during the adjustment process is more reliable. Second, the thermal deformation of the rough welding can be actively corrected in the subsequent jack adjustment; and the rough welding has both connectivity and adjustability. During the jack adjustment process, multiple pairs of welding points will work. On the one hand, it can release or balance the residual stress of the rough welding, and on the other hand, it will not cause the steel truss itself to deform and produce residual stress; thus, it can optimize the stress state of the overall structure, reduce the risk of structural deformation in the later stage, and improve Structural durability Third, the structure after rough welding and adjustment is in a more stable geometric state, making the influence of heat input during fine welding on the overall deformation more controllable, so as to control the thermal deformation caused by fine welding within an acceptable error range. After fine welding, there is no need to forcibly adjust the position of the steel truss again to cause stress superposition problems, further ensuring Knot Structural durability .

[0025] 2. In some embodiments, the degree of thermal deformation during fine welding can be predicted based on the thermal deformation law during rough welding, and the reverse deformation amount can be reserved during adjustment, so that the structure is closer to the designed position and the installation accuracy of the structure is further improved.

[0026] 3. In some embodiments, in order to further apply to the beam-dropping system of the present invention that has higher requirements for the support and stability of the temporary pier, the structure of the temporary pier is adjusted: the first support pile with a larger outer diameter is used at the bottom to form high rigidity, and the second support pile with a smaller outer diameter is used at the top to form low rigidity. At the same time, the second support pile is designed with a shear support, and a local high rigidity area is formed in the partial area of ​​the second support pile, so that the temporary pier finally forms a rigidity classification of "lower high-middle low-upper local high". Under this rigidity classification design, the high rigidity at the bottom can resist the large bending moment caused by the deadweight of the segment and the adjustment load, the low rigidity in the middle allows the controllable elastic deformation to occur during the segment adjustment, absorbs the welding residual stress and installation error, and the local high rigidity at the top resists the concentrated shear force caused by the vibration during the welding and adjustment process; at the same time, the bottom rigid area can also absorb the high-frequency impact of the start and stop of the jack, and the top rigid area can suppress the low-frequency swing, forming a "high-frequency-low-frequency double filtering" mechanism; based on this, the stability of the temporary pier can be synergistically improved to be applicable to the beam-dropping system of the present invention that has higher requirements for the support and stability of the temporary pier.

[0027] 4. In some embodiments, during rough welding, the upper chord is only welded to the web, and the lower chord is only welded to the flange plate, retaining a certain degree of freedom to facilitate segment adjustment. At the same time, the welding paths of the upper chord and the lower chord are respectively consistent with their own main force transmission paths (the upper chord transmits force through the web for compression, and the lower chord transmits force through the flange for tension), so that the welding residual stress can be naturally released, and stable compressive and tensile skeletons are respectively established to facilitate stress dispersion during subsequent fine welding; this avoids local stress concentration and further improves structural stability and durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of a steel truss segment beam; Figure 2 yes Figure 1 Enlarged view of point A in the middle; Figure 3 yes Figure 1 Enlarged view of point B in the middle; In the figure: temporary pier 1, first supporting pile 111, second supporting pile 121, shear brace 122, first load-bearing beam 131, second load-bearing beam 132, hollow circular tube 133, jack 2, segment 3, upper chord 31, lower chord 32, web member 33. DETAILED DESCRIPTION

[0029] The following are specific implementations of the present invention, and in conjunction with the accompanying drawings, the technical solution of the present invention is further described, but the present invention is not limited to these embodiments.

[0030] A steel truss segment beam method can be used in the construction process of steel truss structures, especially suitable for the construction process of bridges, overpasses and other buildings with steel trusses as main load-bearing components. In this embodiment, a bridge is used as an example for explanation.

[0031] like Figure 1 As shown, this beam dropping method mainly divides the steel truss into a number of small segments 3 along its span direction, or in other words, along its length direction (for the convenience of subsequent description, the two ends of each segment 3 along the span direction are respectively recorded as a welding end and a free end; as shown in FIG. Figure 1 As shown, the right end of segment 3 is the welding end and the left end is the free end), the welding end of control segment 3 is firstly rough welded, then its overall position is adjusted by jack 2, and finally fine welded, specifically including the following steps: S1. Install permanent piers and temporary piers 1 according to the design. Permanent piers refer to structures that are retained for a long time after the bridge is built. They are part of the main body of the bridge and bear the permanent load of the bridge. There are no restrictions on their structure and installation methods. Conventional methods in the prior art can be used. For example, permanent piers are mostly made of high-strength and durable materials such as reinforced concrete. They are located in permanent load-bearing positions such as piers and abutments, and are generally located at both ends of the bridge span.

[0032] The temporary pier 1 is an auxiliary structure used in a short period of time during the construction process. It only provides temporary support during the construction or maintenance stage of the bridge and is removed after completion. The temporary pier 1 is mostly composed of detachable materials such as steel structures. According to the number of segments 3, several temporary piers 1 can be installed along the span direction. Jacks 2 are provided on the temporary piers 1 to assist the steel truss segment 3 in dropping the beam.

[0033] In principle, the structure of the temporary pier 1 is not limited, and any temporary pier structure in the prior art can be used, but its supporting strength for the steel truss segment 3 during the welding process and the adjustment process should be guaranteed. However, the beam dropping method of the present invention has higher requirements for the temporary pier 1. Specifically, the steel truss segment 3 is adjusted in position by the jack 2 after rough welding. During adjustment, since the steel truss segment 3 has been fixed by the rough welding part, the jack 2 needs to overcome the welding constraint force, and the release of welding residual stress may cause instantaneous impact load, which places higher requirements on the supporting capacity of the temporary pier 1; and the thermal deformation caused by rough welding may cause non-uniform force on the contact point between the steel truss segment 2 and the temporary pier 1, inducing dynamic vibration during adjustment, which also places higher requirements on the stability of the temporary pier 1. In some embodiments, when used for an arched steel truss, and the beam dropping method of the segment 3 is to close from both ends to the middle along the span direction, such as Figure 1 As shown, each segment 3 is dropped onto the temporary pier 1 in an inclined state, which requires the temporary pier 1 to cope with asymmetric loads and withstand bending moments. The temporary pier 1 is prone to overturning and sideways displacement, which places higher requirements on the stability of the temporary pier 1. Therefore, when conventional temporary piers are used, it may not be conducive to the smooth implementation of the specific beam dropping method of the present invention.

[0034] Therefore, in some embodiments, the temporary pier 1 is further designed to cooperate with the specific beam dropping method of the present invention: Figure 1 As shown, each temporary pier 1 includes a first supporting part, a second supporting part and a load-bearing part in sequence from the ground upward.

[0035] The first support part includes at least four first support piles 111, and several first support piles 111 are evenly arranged in a square or circular shape to form a symmetrical structure, which can reduce the non-uniform force caused by geometric asymmetry, thereby reducing the vibration risk of the temporary pier 1. For example, in this embodiment, the four first support piles 111 are arranged in a square shape. The first support pile 111 can be made of Q460C high-strength steel with a yield strength of not less than 460MPa, and filled with C40 self-compacting concrete at the root, and the filling height is about half of the height of the first support pile 111, so as to improve the ultimate lateral bearing capacity and improve stability. In some embodiments, 2 to 3 layers of carbon fiber cloth can also be wrapped around the outer surface of the first support pile 111 to improve the shear resistance.

[0036] The first support pile 111 is anchored on the ground through a base, which can be a precast concrete block or a steel plate. The length and width of the base are at least three times greater than the outer diameter of the first support pile 111, and the thickness is at least 3 cm. The first support pile 111 and the base are welded with full penetration welds to further enhance the lateral resistance of the temporary pier 1 and improve stability.

[0037] The second support part first includes the same number of second support piles 121 as the first support piles 111. The second support piles 121 are respectively installed on the first support piles 111. The second support piles 121 can also be made of Q460C high-strength steel with a yield strength of not less than 460MPa. Figure 2 As shown, the present application also specifically controls the outer diameter of the second support pile 121 to be smaller than the outer diameter of the first support pile 111. Preferably, the outer diameter of the first support pile 111 is 1.2 to 1.8 times, preferably 1.5 times, of the outer diameter of the second support pile 121. Since the bending moment is nonlinearly distributed along the height when the support pile is bent, the bending moment at the bottom is usually the largest and gradually decays upward. By initially forming a structure that is thick at the bottom and thin at the top of the temporary pier 1, the large-diameter first support pile 111 below the temporary pier 1 can resist the high bending moment at the bottom by increasing the moment of inertia of the section, while the small-diameter second support pile 121 at the top matches the smaller bending moment, thereby maximizing material efficiency. Among them, in order to reduce the stress concentration problem caused by the sudden change of cross section at the connection caused by the difference in outer diameter between the first support pile 111 and the second support pile 121, the first support pile 111 and the second support pile 121 are connected by a truncated cone-shaped connecting column, the upper diameter of the connecting column is the same as that of the second support pile 121, and the lower diameter is the same as that of the first support pile 111. The connecting column forms a transition section with a gradually changing cross-sectional area, which can effectively reduce stress concentration and make the force transmission smoother to enhance stability. During installation, the first support pile 111 is connected to the connecting column with flange bolts, and the connecting column is connected to the second support pile 121 with flange bolts, and reinforcing ribs are evenly arranged on the flange.

[0038] Since the second support part is located at the upper part and has a thinner outer diameter, it is easy to cause lateral displacement or buckling, so the second support part also includes a shear support 122 arranged between adjacent second support piles 121. Figure 3As shown, the scissor brace 122 is installed on the connection plate welded in advance on the second support pile 121. The connection plate has pre-reserved bolt holes, and the connection plate and the scissor brace 122 are bolted together by the connection plate bolts. The shear brace 122 forms a truss structure with the second support part, improving the lateral stiffness and stability of the structure and resisting horizontal loads. At the same time, the shear brace 122 forms a local high stiffness area on the second support part, so that the first support part and the second support part form a stiffness grading of "lower high-middle low-upper local high" as a whole. Under this graded stiffness design, the high stiffness at the bottom can resist the large bending moment caused by the deadweight of segment 3 and the adjustment load, the low stiffness in the middle allows controllable elastic deformation of segment 3 during adjustment, absorbs welding residual stress and installation errors, and the local high stiffness at the top resists the concentrated shear force caused by vibration during welding and adjustment. At the same time, the bottom rigid area can also absorb the high-frequency impact of the start and stop of the jack 2, and the top rigid area can suppress the low-frequency swing, forming a "high-frequency-low-frequency double filtering" mechanism. Based on this, the stability of the temporary pier 1 can be synergistically improved to be suitable for the beam-dropping system of the present invention that has higher requirements on the support and stability of the temporary pier 1.

[0039] After controlling the height of the first support part and the second support part so that the overall height reaches the specified elevation, a flange is installed on the top of the second support pile 121, and then a load-bearing part is welded on the flange, and a jack 2 is arranged on the load-bearing part. In order to improve the stability of supporting and adjusting the segment 3, at least two jacks 2 are arranged on the load-bearing part along the span direction, such as Figure 1 As shown, the two jacks 2 respectively support the two ends of the segment 2 in the span direction and respectively adjust the heights of the two ends of the segment 3, thereby adjusting the overall position of the segment 3.

[0040] To adapt to the installation of two jacks 2, as Figure 1 As shown, the four second support piles 121 are divided into two groups along the span direction of the bridge. The two second support piles 121 of the right group are close to the welding end of the segment 3, and a first load-bearing beam 131 is welded thereon; the two second support piles 121 of the left group are far from the welding end of the segment 3, and a second load-bearing beam 132 is welded thereon. The first load-bearing beam 131 and the second load-bearing beam 132 are both made of double-joined I-beams.

[0041] In some embodiments, the first load-bearing beam 131 and the second load-bearing beam 132 may be directly welded to the flange plate on the top of the second supporting pile 121 , respectively.

[0042] In other embodiments, when used for an arched steel truss, each segment 3 falls onto the temporary pier 1 in an inclined state, so it is further designed that the first load-bearing beam 131 is connected to the second support pile 121 by a shear key to prevent sliding at the connection. The second load-bearing beam 132 is connected to the second support pile 121 by a hollow circular tube 133, one end of the hollow circular tube 133 is connected to the second support pile 121 by a flange, and the other end is provided with a flange to install the second load-bearing beam 132. On the one hand, the role of the hollow circular tube 133 is to increase the height and adapt to segments 3 with different inclinations; on the other hand, the hollow circular tube 133 can allow a greater elastic deformation capacity while maintaining a certain rigidity, so as to absorb the impact during the welding and adjustment of the segment 3 through deformation, reduce the force transmitted to other parts, and thus protect the stability of the temporary pier 1. For example, during the vertical jacking process, the center position of the segment 3 changes, causing the eccentric load to cause a combined compression and bending deformation of the temporary pier 1. At this time, the hollow circular tube 133 deforms and absorbs energy before elastic buckling.

[0043] After the load-bearing part is installed, jacks 2 are respectively arranged in the middle of the first load-bearing beam 131 and the second load-bearing beam 132 .

[0044] S2. The steel truss includes several segments 3 along the span direction of the bridge, and the two ends of the segment 3 along the span direction are respectively a welding end and a free end. The structure is basically the same as that of the steel truss in the prior art, such as Figure 1 As shown, each segment 3 includes an upper chord 31, a lower chord 32, and a web 33 disposed between the upper chord 31 and the lower chord 32; the upper chord 31 and the lower chord 32 are both H-shaped, and each includes two flange plates and a web plate disposed between the two flange plates. Several segments 3 are dropped in the order of merging from both ends to the middle, that is, along the direction from the end of the steel truss to the center, the first segment 3, the second segment 3 ... the Nth segment 3 are dropped in sequence, and the only difference is that the welding end of the first segment 3 is welded to the permanent pier, the welding end of the second segment 3 is welded to the free end of the first segment 3, the welding end of the third segment 3 is welded to the free end of the second segment 3, and so on. The specific beam dropping includes the following steps: S21. Lift the segment 3 to the position where the beam is to be dropped via crawler crane. During lifting, two lifting points are set for each segment 3 and lifted by wire rope. The lifting points are selected at the junction of the lower chord 32 and the web 33. The wire ropes are 2 Ф50mm fiber core high-strength steel wire ropes with a nominal tensile strength of 1770MPa and a minimum breaking tensile force of 1460kN.

[0045] S22. Roughly weld the welded end of segment 3 to the permanent pier or the free end of the segment 3 in front of it (collectively referred to as the existing structure). In principle, the rough welding method is not limited, for example, the welded end of segment 3 can be spot welded to the existing structure. In some embodiments, based on the structure and stress conditions of segment 3, the following welding method is adopted: first, the end of the lower chord 32 of segment 3 is roughly welded to the existing structure, and the lower chord 32 is under tension. After welding, it can provide basic constraints for the whole structure to prevent the free end from sagging out of control due to its own weight; then, the end of the upper chord 31 of segment 3 is roughly welded to the existing structure, and the subsequent welding of the upper chord 31 can reduce the direct impact of welding thermal deformation on its stability.

[0046] When welding the lower chord 32, specifically, the flange plate of the lower chord 32 and the existing structure are symmetrically spot-welded using a V-shaped groove: two operators simultaneously weld the two flange plates to the existing structure, and when welding each flange plate, the spot welding is symmetrical along the direction from the end of the flange plate to the center, and the length of each weld is 50mm and the interval is 300mm; wherein the V-shaped groove is a single-sided V-shaped groove with an angle of 60°~70°, a blunt edge of 2~3mm, and a root gap of 3~4mm. The V-shaped groove can improve the tensile strength of the weld and is suitable for the flange plate that plays a tensile force transmission role. The lower chord 32 is only welded with the flange plate, which not only retains a certain degree of freedom to facilitate the horizontal adjustment of the segment 3; at the same time, the tensile force is transmitted through the flange plate, the tensile direction is locked, and the risk of slippage of the segment 3 is reduced; the welding path is consistent with its main force transmission path, and the welding residual stress can be naturally released; in addition, the flange plate is welded in the rough welding stage, and a stable tensile skeleton can be established first. When the web is subsequently fine-welded, the newly added welding stress can be dispersed through the flange skeleton to avoid local concentration.

[0047] When welding the upper chord 31, the web of the upper chord 31 of segment 3 is specifically welded with the existing structure by K-type groove jump welding: the operator jump welds along the direction from the flange plate to the web, and each weld is 200mm long and 300mm apart. Preferably, double-sided alternating welding is adopted: first weld 50% of the weld on one side, then weld the other side after flipping to reduce distortion. The K-type groove is a double-sided K-type groove with a single-side angle of 30°~35°, a blunt edge of 1~2mm, and a root gap of 2~3mm. The K-type groove can improve the compressive stability of the weld and is suitable for the web that plays a role in compressive resistance and force transmission. Similarly, the upper chord 31 is only welded to the web, retaining a certain degree of freedom to facilitate the vertical adjustment of segment 3; at the same time, it can transmit force through the web to resist compression, enhance local stability, and avoid buckling during adjustment; and the welding path is consistent with the main force transmission path, and the welding residual stress can be naturally released; in addition, when welding the web in the rough welding stage, a stable compressive skeleton can be established first, and when the flange is subsequently fine-welded, the newly added welding stress can be dispersed through the web skeleton to avoid local concentration.

[0048] In some embodiments, the shrinkage distance a of the segment 3 after rough welding relative to that before rough welding is measured.

[0049] S23. After the rough welding is completed, control the crawler crane to drop the segment 3 as a whole onto the two jacks 2 of a temporary pier 1. After the segment 3 remains stable, slowly adjust the jack 2 to make it reach the specified elevation. If the jack 2 is used without hitting, first loosen the drain screw on the pump body, vertically raise the pump body and hit it a few times, then tighten the drain screw and continue to use it. Since the jack 2 uses oil as the medium, the oil and machine maintenance must be done well to avoid siltation or oil leakage, which will affect the use effect. The high-pressure oil pipe must be tested before leaving the factory, but since the rubber hose is easy to age, it needs to be checked frequently, generally once every six months, and once every three months for frequent use.

[0050] In some embodiments, after the jack 2 corrects the segment 3 to the designed position, it further lifts the segment 3 by a distance b; b=1.2a.

[0051] S24. Fix the welding end of segment 3 to the existing structure by precision welding: When precision welding the end of the lower chord 32 of segment 3 to the existing structure, first repair the flange plate to the existing structure until it is fully penetrated. During welding, the welding is performed in sections from the middle of the flange plate to both ends, and the length of each weld is 150mm. Then, the web plate is pressed against the existing structure and fully penetrated. During welding, symmetrical sectioned welding is used, and the length of each weld is 200mm. Alternate welding is performed from the center of the web plate to both ends. Finally, the T-joint of the flange plate and the web plate is repaired to ensure that the weld penetration is ≥80% of the plate thickness.

[0052] When the end of the upper chord 31 of segment 3 is used for precision welding of the existing structure, the web and the existing structure are first repaired and welded to a full penetration state. Symmetrical segmented back-welding is used during welding. Each weld is 200 mm long and welded alternately from the center of the web to both ends to offset the longitudinal shrinkage stress. As the main load-bearing component, the web is given priority for precision welding to ensure the continuity and rigidity of the force transmission path. Then, the flange plate is pressed against the existing structure and fully welded. During welding, the flange plate is back-welded in segments from the middle of the flange plate to both ends. Each weld is 150 mm long to reduce lateral shrinkage deformation. Finally, the T-joint of the flange plate and the web is repaired and welded to ensure that the weld penetration is ≥80% of the plate thickness.

[0053] Based on this, the beam drop of steel truss segment 3 was completed.

[0054] A steel truss construction method comprises the following steps: (1) Install permanent buttresses, temporary buttresses 1, steel box girders and tie rods according to the design.

[0055] (2) The column top elevation, centerline and span of the assembled support group are re-measured. The beams can be dropped only when the error is within the allowable range of the design and specifications. Then, the steel truss segment 3 is dropped in sequence according to the above-mentioned beam dropping method.

[0056] (3) Remove temporary pier 1.

[0057] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A method for sectioning steel trusses, characterized in that: The following steps are involved: S1. Installing permanent piers and temporary piers (1) according to the design, wherein the temporary piers (1) are provided with jacks (2); S2. The steel truss includes a plurality of segments (3) along the span direction, wherein the two ends of the segment (3) along the span direction are a welding end and a free end respectively; Several of the segments (3) are dropped separately, and each segment (3) is dropped by the following steps: S21. Hoisting the segment (3) to the position where the beam is to be dropped; S22. The welding end of the segment (3) is connected to the existing structure by rough welding; S23. Dropping the segment (3) as a whole onto the jack (2), and adjusting the jack (2) to correct the position of the segment (3); S24. Fixing the welding end of the segment (3) to the existing structure by precision welding; The existing structure includes at least one of the permanent pier and the segment (3) that has been completed with precision welding.

2. A steel truss section beam method according to claim 1, characterized in that: The order of beam placement of the plurality of segments (3) is: closing the beams from both ends toward the middle along the span direction.

3. A steel truss section beam method according to claim 1, characterized in that: At least two jacks (2) are provided on the temporary pier (1) along the span direction; in step S23, the segment (3) falls as a whole onto at least the two jacks (2).

4. A method for steel truss segment beam laying according to claim 3, characterized in that: The temporary pier (1) comprises, in order from the ground upward, a first supporting part, a second supporting part and a load-bearing part, and the jack (2) is arranged on the load-bearing part; The first support portion comprises a plurality of first support piles (111), the second support portion comprises a plurality of second support piles (121), and a shear brace (122) arranged between adjacent second support piles (121). The outer diameter of the second support pile (121) is smaller than the outer diameter of the first support pile (111), and the first support pile (111) and the second support pile (121) are connected via a truncated cone-shaped connecting column.

5. A steel truss section beam method according to claim 4, characterized in that: The load-bearing portion comprises a first load-bearing beam (131) for mounting a jack (2) close to a welding end of the segment (3), and a second load-bearing beam (132) for mounting a jack (2) away from the welding end of the segment (3), the first load-bearing beam (131) being connected to the second support portion via a shear key, and the second load-bearing beam (132) being connected to the second support portion via a hollow circular tube (133).

6. A steel truss segment beam method according to claim 1 or 3, characterized in that: In step S22, the shrinkage distance a of the segment (3) after rough welding relative to that before rough welding is measured; In step S23, during adjustment, after the segment (3) is corrected to the designed position by the jack (2), the jacking distance b is continued; b=(1.1~1.5)a.

7. A steel truss segment beam method according to claim 1 or 3, characterized in that: The segment (3) comprises an upper chord (31), a lower chord (32), and a web (33) arranged between the upper chord (31) and the lower chord (32); the upper chord (31) and the lower chord (32) are both H-shaped, and each comprises two flange plates and a web plate arranged between the two flange plates; In step S22, the two flange plates of the lower chord (32) of the segment (3) are roughly welded to the existing structure, and the web plate of the upper chord (31) of the segment (3) is roughly welded to the existing structure.

8. A steel truss section beam method according to claim 7, characterized in that: The two flange plates of the lower chord (32) are symmetrically spot-welded to the existing structure using a V-shaped groove; and the web plate of the upper chord (31) is spot-welded to the existing structure using a K-shaped groove.

9. A steel truss section beam method according to claim 7, characterized in that: First, the two flange plates of the lower chord (32) are roughly welded to the existing structure; and then the web plate of the upper chord (31) is roughly welded to the existing structure.

10. A steel truss construction method, characterized in that: The method comprises the steel truss segment beam laying method as described in any one of claims 1 to 9.

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