A method for segmented beam construction of steel trusses and a method for steel truss construction.

Abstract

This invention relates to the field of steel structure installation technology, and more particularly to a method for segmenting steel truss beams and a construction method for steel trusses. This beam-lowering method includes the following steps: installing permanent and temporary supports according to the design, with jacks mounted on the temporary supports; the steel truss comprising several segments along its span; lowering each segment separately, each segment being lowered through the following steps: hoisting the segment to the desired lowering position; rough-welding the welded end of the segment to the existing structure; lowering the segment entirely onto the jacks, adjusting the jacks to correct the segment's position; and fine-welding the welded end of the segment to the existing structure; the existing structure includes at least one of the permanent supports and the segments that have been finely welded. This invention, based on jack-lowering, employs a rough-welding-lowering and adjustment-fine-welding process, achieving improved installation stability and structural durability.

Description

Technical Field

[0001] This invention relates to the field of steel structure installation technology, and in particular to a method for segmenting steel truss beams and a method for constructing steel trusses. Background Technology

[0002] During the hoisting of steel truss segments, crawler cranes are typically used to facilitate segment placement. After the segment is in place, personnel measure the distance between the segment and the temporary support on-site to determine the specific height difference. L-shaped angle steel is then cut on-site and hoisted between the segment and the temporary support for welding to support the segment, thus completing the lowering of the beam. The existing construction method has the following drawbacks: First, measuring the distance between the steel truss segment and the temporary support during hoisting is easily affected by external interference, leading to inaccurate data and affecting subsequent beam lowering positioning. Second, each segment hoisting requires the on-site fabrication of corresponding angle steel adjustment pipes, which cannot be reused after use, resulting in significant material waste.

[0003] Some existing technologies use jacks for beam positioning and adjustment during lowering. For example, patent document CN117468728A discloses a steel truss beam construction system and method, in which a truck crane is used to hoist the steel truss main beam segments in sequence according to the construction plan, and the steel truss main beam segments are assisted in correction using a total station, jacks, and adjustable support plates. The jacks at the bottom of the steel truss main beam segments are adjusted with the assistance of the total station. After the position is correct, the connecting ends of the steel truss main beam segments are welded and fixed to the supports on the steel pipe concrete columns, and the adjustable support plates at the bottom of the free ends are welded to temporary supports. Another example is the installation method of a large-span steel truss cantilever irregular structure disclosed in patent document CN117027425A, in which the truss beam is hoisted in segments, the posture of the truss beam is adjusted by jacks on temporary support columns, and then the truss beam is welded and fixed.

[0004] It can be seen that in existing technologies, when using jacks to assist in segmenting steel truss beams, the position of the steel truss segments is always adjusted first using jacks before being welded and fixed to the existing structure. This method has the following problems: First, during the adjustment phase, the steel truss is only temporarily fixed by jacks. If external loads (such as wind loads) or operational errors cause displacement, it may lead to safety hazards. Second, during the welding process, thermal deformation may cause the structure to shift position, which requires a second adjustment using jacks after welding. This is inconvenient to operate, and welding already creates residual stress. The second adjustment is a forced adjustment based on the welded fixation. This process can cause elastic or plastic deformation of the steel truss, potentially generating further residual stress. The residual stress from the adjustment phase and the welding residual stress are superimposed at the joints, forming a high-stress zone. Local stress concentration reduces the structural durability. Summary of the Invention

[0005] This invention aims to solve the above-mentioned problems by providing a method for improving the installation stability and structural durability of steel truss segmented beams, as well as a steel truss construction method.

[0006] The technical solution to the problem of this invention is to first provide a method for segmenting steel truss beams, comprising the following steps:

[0007] S1. Install permanent and temporary supports according to the design, with jacks provided on the temporary supports;

[0008] S2. The steel truss comprises several segments along the span direction, wherein the two ends of each segment along the span direction are a welded end and a free end, respectively;

[0009] Several of the aforementioned segments are respectively lowered into the beam, and each of the aforementioned segments is lowered into the beam through the following steps:

[0010] S21. Hoist the segment to the position where the beam is to be lowered;

[0011] S22. Roughly weld the welded end of the segment to the existing structure;

[0012] S23. Lower the entire segment onto the jack, and adjust the jack to correct the position of the segment;

[0013] S24. Fix the welded end of the segment to the existing structure by precision welding;

[0014] The existing structure includes at least one of the permanent support and the segment that has been fixed by precision welding.

[0015] In step S1, as a preferred embodiment of the present invention, the temporary support includes, in sequence from the ground upwards, a first support part, a second support part, and a load-bearing part, and the jack is disposed on the load-bearing part; the first support part includes a plurality of first support piles, the second support part includes a plurality of second support piles, and shear braces disposed between adjacent second support piles, the outer diameter of the second support piles is smaller than the outer diameter of the first support piles, and the first support piles and the second support piles are connected by a frustum-shaped connecting column.

[0016] 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, or 1.8 times, preferably 1.5 times.

[0017] As a preferred embodiment of the present invention, at least two jacks are provided on the temporary support along the span direction.

[0018] As a preferred embodiment of the present invention, the load-bearing part includes a first load-bearing beam for installing a jack near the welded end of the segment, and a second load-bearing beam for installing a jack away from the welded end of the segment. The first load-bearing beam is connected to the second support part by a shear key, and the second load-bearing beam is connected to the second support part by a hollow round tube.

[0019] In step S2, as a preferred embodiment of the present invention, the order of lowering the beams of the several segments is as follows: closing from both ends toward the middle along the span direction.

[0020] As a preferred embodiment of the present invention, the segment includes an upper chord, a lower chord, and a web member disposed between the upper chord and the lower chord; both the upper chord and the lower chord are H-shaped and each includes two flanges and a web member disposed between the two flanges.

[0021] In step S21, as a preferred embodiment of the present invention, each segment is provided with two lifting points during hoisting.

[0022] 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 at the junction of the lower chord and the web member.

[0023] In step S22, as a preferred embodiment of the present invention, the two flange plates of the lower chord of the segment are rough welded to the existing structure, and the web plate of the upper chord of the segment is rough welded to the existing structure.

[0024] As a preferred embodiment of the present invention, the two flange plates of the lower chord are symmetrically spot-welded with the existing structure using a V-groove; the web plate of the upper chord is skip-welded with the existing structure using a K-groove.

[0025] As a preferred embodiment of the present invention, the two flange plates of the lower chord are first rough welded to the existing structure; then the web plate of the upper chord is rough welded to the existing structure.

[0026] As a preferred embodiment of the present invention, the shrinkage distance 'a' of the segment after rough welding relative to before rough welding is measured.

[0027] In step S23, as a preferred embodiment of the present invention, the segment is lowered onto at least two of the jacks.

[0028] As a preferred embodiment of the present invention, after the segment is corrected to the design position by the jack, it is lifted a further distance b; b = (1.1~1.5)a, for example, it can be 1.1a, 1.2a, 1.3a, 1.4a, 1.5a, preferably 1.2a.

[0029] In step S24, as a preferred embodiment of the present invention, the precision welding is a full penetration welding.

[0030] Secondly, another objective of this invention is to provide a steel truss construction method, including the steel truss segment beam method described in any of the above-mentioned methods.

[0031] The beneficial effects of this invention are:

[0032] 1. This invention provides a method for segmenting steel truss beams. Based on the jacking of the beams, the method employs a series of steps: rough welding, beam lowering and adjustment, and fine welding, which improves installation stability and structural durability.

[0033] Specifically: First, because the segments and existing structure have formed a preliminary integral after rough welding, the force is more evenly distributed during jack adjustment, which can avoid the risk of local instability and improve efficiency. Installation stability Furthermore, displacement control is more reliable during adjustment. Secondly, the thermal deformation of the rough weld can be actively corrected during subsequent jack adjustments; moreover, the rough weld combines connectivity and adjustability, acting on multiple weld joints during jack adjustments. On the one hand, it can specifically release or balance residual stress from the rough weld; on the other hand, it will not cause residual stress due to deformation of the steel truss itself. This optimizes the overall structural stress state, reduces the risk of later structural deformation, and improves... Structural durability Third, the structure after rough welding and adjustment is in a more stable geometric state, making the impact of heat input during fine welding on overall deformation more controllable. This allows the thermal deformation generated during fine welding to be kept within an acceptable error range. Furthermore, after fine welding, there is no need to forcibly adjust the position of the steel truss to avoid stress superposition problems, further ensuring... Knot structural durability .

[0034] 2. In some implementations, the degree of thermal deformation during fine welding can be predicted based on the thermal deformation law during rough welding, and a reverse deformation amount can be reserved during adjustment to make the structure closer to the design position and further improve the installation accuracy of the structure.

[0035] 3. In some embodiments, to further adapt to the beam-dropping system of the present invention, which has higher requirements for the support and stability of temporary supports, the structure of the temporary supports is adjusted: a first support pile with a larger outer diameter is used at the bottom to form high stiffness, and a second support pile with a smaller outer diameter is used at the top to form low stiffness. At the same time, the second support pile is designed with shear bracing, and a local high stiffness zone is formed in part of the second support pile, ultimately resulting in a stiffness hierarchy of "high at the bottom - low in the middle - locally high at the top" for the temporary supports. Under this stiffness hierarchy design, the high stiffness at the bottom can resist the large bending moment caused by the segment's self-weight and adjustment load, the low stiffness in the middle allows for controllable elastic deformation during segment 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 rigid zone at the bottom can also absorb the high-frequency impact of jack start-stop, and the rigid zone at the top can suppress low-frequency oscillation, forming a "high-frequency-low-frequency dual filtering" mechanism. Based on this, the stability of the temporary supports can be improved synergistically to adapt to the beam-dropping system of the present invention, which has higher requirements for the support and stability of temporary supports.

[0036] 4. In some embodiments, during rough welding, only the web of the upper chord is welded, and only the flange of the lower chord is welded. This retains a certain degree of freedom to facilitate segment adjustment, while the welding paths of the upper and lower chords are consistent with their own main force transmission paths (the upper chord transmits compressive force through the web, and the lower chord transmits tensile force through the flange). This allows residual welding stress to be released naturally, and stable compressive and tensile skeletons are established respectively, which facilitates stress dispersion during subsequent fine welding. All of these measures avoid local stress concentration and further improve structural stability and durability. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a segmental beam in a steel truss configuration;

[0038] Figure 2 yes Figure 1 Enlarged view of point A in the middle;

[0039] Figure 3 yes Figure 1 Enlarged view at point B in the middle;

[0040] In the diagram: Temporary support 1, first support pile 111, second support pile 121, shear brace 122, first load-bearing beam 131, second load-bearing beam 132, hollow round tube 133, jack 2, segment 3, upper chord 31, lower chord 32, web member 33. Detailed Implementation

[0041] The following are specific embodiments of the present invention, and the technical solution of the present invention will be further described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0042] A method for segmenting steel trusses into beams can be used in the construction of steel truss structures, especially suitable for the construction of bridges, overpasses and other buildings with steel trusses as the main load-bearing components. This embodiment uses a bridge as an example for illustration.

[0043] like Figure 1 As shown, this method of lowering the beam mainly involves dividing the steel truss into several small segments 3 along its span direction, or in other words, along its length direction (for ease of subsequent explanation, the two ends of each segment 3 along the span direction are respectively referred to as the welded end and the free end; such as...). Figure 1 As shown, segment 3 has a welded end on the right and a free end on the left. The welding end of segment 3 is first rough welded, then its overall position is adjusted using jack 2, and finally fine welded. The specific steps include:

[0044] S1. Install permanent and temporary piers according to the design. Permanent piers are structures that remain permanently after the bridge is built, forming part of the main bridge structure and bearing the bridge's permanent load. Their structure and installation method are not restricted; conventional methods from existing technologies can be used. For example, permanent piers are often made of high-strength, durable materials such as reinforced concrete and are located at permanent load-bearing locations such as piers and abutments, generally at both ends of the bridge span.

[0045] Temporary pier 1 is an auxiliary structure used for a short period of time during the construction process. It only provides temporary support during the bridge construction or maintenance phase and is removed after completion. Temporary pier 1 is mostly made of steel structure and other materials that can be disassembled. Depending on the number of segments 3, several temporary piers 1 can be installed along the span direction. The temporary pier 1 is equipped with jacks 2 to assist in the lowering of the steel truss segments 3.

[0046] In principle, the structure of the temporary support 1 is not restricted and any structure of the temporary support 1 in the existing technology can be used, but its support strength for the steel truss segment 3 during the welding and adjustment processes should be guaranteed. However, since the beam lowering method of the present invention has higher requirements for the temporary support 1, specifically: after the rough welding, the position of the steel truss segment 3 is adjusted by the jack 2. During the adjustment, since the steel truss segment 3 has been fixed by the rough welding, the jack 2 needs to overcome the welding constraint force, and may be subject to instantaneous impact load due to the release of welding residual stress. This places higher demands on the support capacity of the temporary support 1; moreover, the thermal deformation generated by the rough welding may cause non-uniform stress at the contact point between the steel truss segment 2 and the temporary support 1, inducing dynamic vibration during the adjustment. This also places higher demands on the stability of the temporary support 1. In some embodiments, when used for arched steel trusses, and the beam lowering method of segment 3 is to close from both ends to the middle along the span direction, such as Figure 1As shown, each segment 3 is lowered onto the temporary support 1 at an angle. This requires the temporary support 1 to withstand asymmetrical loads and bending moments, making it prone to overturning and lateral displacement. This places higher demands on the stability of the temporary support 1. Therefore, using conventional temporary supports may not be conducive to the successful implementation of the specific beam lowering method of this invention.

[0047] Therefore, in some embodiments, the temporary support 1 has been further designed to accommodate the specific beam lowering method of this invention: such as Figure 1 As shown, each temporary support 1 includes a first support part, a second support part, and a load-bearing part in sequence along the direction from the ground upward.

[0048] The first support section includes at least four first support piles 111. These first support piles 111 are arranged in a square or circular pattern to form a symmetrical structure, which reduces uneven stress caused by geometric asymmetry, thereby lowering the vibration risk of the temporary support 1. For example, in this embodiment, the four first support piles 111 are arranged in a square pattern. The first support piles 111 can be made of Q460C high-strength steel with a yield strength of not less than 460MPa, and the base is filled with C40 self-compacting concrete to a height approximately half the height of the first support pile 111, thereby increasing the ultimate lateral bearing capacity and improving stability. In some embodiments, two to three layers of carbon fiber cloth can be wrapped around the outer surface of the first support piles 111 to enhance shear resistance.

[0049] The first support pile 111 is anchored to the ground by 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 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 connected by a full penetration weld to further improve the lateral resistance of the temporary support 1 and improve its stability.

[0050] The second support section first includes second support piles 121 in the same number 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. Meanwhile, such as Figure 2As shown, this 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 the outer diameter of the second support pile 121, and more preferably 1.5 times. Since the bending moment of a support pile exhibits a non-linear distribution along its height when bent, the bending moment is typically largest at the bottom and gradually decreases upwards. By initially forming a structure that is thicker at the bottom and thinner at the top, the large-diameter first support pile 111 below the temporary support pile 1 can resist the high bending moment at the bottom by increasing the moment of inertia of its cross-section, while the small-diameter second support pile 121 at the top matches a smaller bending moment, thus maximizing material efficiency. To mitigate stress concentration at the connection point caused by the abrupt change in cross-section due to the difference in outer diameter between the first support pile 111 and the second support pile 121, the two support piles are connected by a frustum-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. This connecting column forms a transition section with a gradually changing cross-sectional area, effectively reducing stress concentration and making force transmission smoother, thereby enhancing stability. During installation, the first support pile 111 is connected to the connecting column using flange bolts, and the connecting column is connected to the second support pile 121 using flange bolts. Reinforcing ribs are evenly distributed on the flanges.

[0051] Because the second support is located at the top and has a smaller outer diameter, it is prone to lateral displacement or buckling. Therefore, the second support also includes shear braces 122 disposed between adjacent second support piles 121. Figure 3 As shown, the shear brace 122 is installed on a connecting plate pre-welded to the second support pile 121. The connecting plate has pre-drilled bolt holes, and the connecting plate and the shear brace 122 are bolted together using connecting plate bolts. The shear brace 122 forms a truss structure for the second support section, improving the lateral stiffness and stability of the structure and resisting horizontal loads. At the same time, the shear brace 122 also forms a locally high-stiffness zone on the second support section, so that the first and second support sections as a whole form a stiffness hierarchy of "high at the bottom - low in the middle - locally high at the top". Under this stiffness-graded design, the high stiffness at the bottom can resist the large bending moment caused by the self-weight of segment 3 and the adjustment load, the low stiffness in the middle allows for controllable elastic deformation during the adjustment of segment 3, 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 rigid area at the bottom can also absorb the high-frequency impact of starting and stopping the jack 2, and the rigid area at the top can suppress low-frequency oscillation, forming a "high-frequency-low-frequency dual filtering" mechanism. Based on this, the stability of the temporary support 1 can be improved in a synergistic way, so as to be suitable for the beam dropping system of the present invention with higher requirements for the support and stability of the temporary support 1.

[0052] After controlling the height of the first and second support sections to achieve the designated elevation, a flange is installed on the top of the second support pile 121. A load-bearing section is then welded onto the flange, and jacks 2 are installed on the load-bearing section. To improve the stability of supporting and adjusting the segment 3, at least two jacks 2 are installed on the load-bearing section along the span direction. Figure 1 As shown, the two jacks 2 support the two ends of segment 2 in the span direction and adjust the height of the two ends of segment 3 respectively, thereby adjusting the overall position of segment 3.

[0053] To accommodate the installation of the 2000 jack 2, such as Figure 1 As shown, the four second support piles 121 are divided into two groups along the bridge span. The two second support piles 121 in the right group are close to the welded ends of segment 3, and a first load-bearing beam 131 is welded to them. The two second support piles 121 in the left group are away from the welded ends of segment 3, and a second load-bearing beam 132 is welded to them. Both the first load-bearing beam 131 and the second load-bearing beam 132 are composed of double-section I-beams.

[0054] In some embodiments, the first load-bearing beam 131 and the second load-bearing beam 132 can be directly welded to the flange at the top of the second support pile 121.

[0055] In other embodiments, when used for arched steel trusses, each segment 3 is lowered onto the temporary support 1 at an angle. Therefore, a further design is employed: the first load-bearing beam 131 is connected to the second support pile 121 via a shear key to prevent slippage at the connection. The second load-bearing beam 132 is connected to the second support pile 121 via a hollow circular tube 133. One end of the hollow circular tube 133 is connected to the second support pile 121 via a flange, and the other end is fitted with a flange to install the second load-bearing beam 132. The hollow circular tube 133 serves two purposes: firstly, it increases the height to accommodate segments 3 with varying inclinations; secondly, it allows for greater elastic deformation while maintaining a certain rigidity, absorbing the impact during the welding and adjustment of segments 3, reducing the force transmitted to other parts, and thus protecting the stability of the temporary support 1. For example, during vertical jacking, the center position of segment 3 changes, potentially causing eccentric loads that result in combined compression and bending deformation of the temporary support 1. In this case, the hollow circular tube 133 absorbs energy before elastic buckling.

[0056] After the load-bearing components are installed, jacks 2 are respectively installed in the middle of the first load-bearing beam 131 and the second load-bearing beam 132.

[0057] S2. The steel truss comprises several segments 3 along the bridge span direction, with each segment 3 having a welded end and a free end at its two ends along the span direction. The structure is essentially the same as that of steel trusses in the prior art, such as... Figure 1As shown, each segment 3 includes an upper chord 31, a lower chord 32, and a web member 33 located between the upper chord 31 and the lower chord 32. Both the upper chord 31 and the lower chord 32 are H-shaped, each including two flange plates and a web plate located between the two flange plates. Several segments 3 are lowered in sequence from both ends towards the middle, that is, along the direction from the end of the steel truss to the center, the segments are sequentially designated as the first segment 3, the second segment 3…the Nth segment 3. The only difference is that the welded end of the first segment 3 is welded to the permanent support, the welded end of the second segment 3 is welded to the free end of the first segment 3, the welded end of the third segment 3 is welded to the free end of the second segment 3, and so on. The specific lowering process includes the following steps:

[0058] S21. Segment 3 is lifted to the position to be lowered by crawler crane. During the lifting, each segment 3 is set with two lifting points and lifted by steel wire rope. The lifting points are selected at the junction of the lower chord 32 and the web member 33. Two Ф50mm fiber core high-strength steel wire ropes are selected, with a nominal tensile strength of 1770MPa and a minimum breaking strength of 1460kN.

[0059] S22. Roughly weld the welded end of segment 3 to the permanent support or the free end of 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, rough weld the end of the lower chord 32 of segment 3 to the existing structure. The lower chord 32 is under tension, and its welding can provide basic constraints for the whole, preventing the free end from sagging uncontrollably due to its own weight; then rough weld the end of the upper chord 31 of segment 3 to the existing structure. Welding the upper chord 31 afterward can reduce the direct impact of welding heat deformation on its stability.

[0060] When welding the lower chord 32, the flange plate of the lower chord 32 is symmetrically spot-welded to the existing structure using a V-groove: two operators simultaneously weld the two flange plates to the existing structure. When welding each flange plate, symmetrical spot welding is performed along the direction from the end of the flange plate towards the center. Each weld segment is 50mm long and spaced 300mm apart. The V-groove is a single-sided V-groove with an angle of 60°~70°, a blunt edge of 2~3mm, and a root gap of 3~4mm. The V-groove can improve the tensile strength of the weld and is suitable for the flange plate that plays a role in tensile force transmission. The lower chord 32 is welded only with flange plates, which not only retains a certain degree of freedom to facilitate the horizontal adjustment of segment 3, but also transmits tensile force through the flange plates, locks the direction of tensile force, and reduces the risk of slippage of segment 3. Moreover, the welding path is consistent with its main force transmission path, and the residual welding stress can be released naturally. In addition, welding the flange plates in the rough welding stage can first establish a stable tensile skeleton. When the web is subsequently finely welded, the newly added welding stress can be dispersed through the flange skeleton to avoid local concentration.

[0061] When welding the upper chord 31, the web of segment 3 upper chord 31 is specifically welded to the existing structure using a K-groove skip welding method: the operator skips welds along the direction from the flange to the web, with each weld segment being 200mm long and spaced 300mm apart. Preferably, double-sided alternating welding is used: first, 50% of the weld on one side is welded, then flipped over and the other side is welded to reduce torsional deformation. The K-groove is a double-sided K-groove with a single-sided angle of 30°~35°, a blunt edge of 1~2mm, and a root gap of 2~3mm. The K-groove can improve the compressive stability of the weld and is suitable for the web, which plays a role in resisting compressive 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 compressive force through the web, enhance local stability, and avoid buckling during adjustment; moreover, the welding path is consistent with the main force transmission path, and the welding residual stress can be released naturally; in addition, welding the web in the rough welding stage can first establish a stable compressive skeleton, and when the flange is subsequently finely welded, the newly added welding stress can be dispersed through the web skeleton to avoid local concentration.

[0062] In some implementations, the shrinkage distance 'a' of segment 3 after rough welding relative to before rough welding is measured.

[0063] S23. After rough welding is completed, control the crawler crane to lower segment 3 as a whole onto two jacks 2 on a temporary support 1. Once segment 3 is stable, slowly adjust jacks 2 to bring it to the designated elevation. If jacks 2 experience dry-running during operation, loosen the drain screw on the pump body, stand the pump body vertically and run it dry a few times, then tighten the drain screw to continue use. Since jacks 2 use oil as the medium, proper maintenance of the oil and the equipment is essential to prevent clogging or leaks that could affect performance. High-pressure oil hoses must be tested at the factory, but because hoses are prone to aging, they require frequent inspection, generally every six months, or every three months for frequent use.

[0064] In some implementations, after jack 2 corrects segment 3 to the designed position, it further lifts it a distance b; b = 1.2a.

[0065] S24. Fix the welded 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 weld the flange plate to the existing structure to a full penetration weld state. During welding, weld in sections from the middle of the flange plate to both ends, with each weld section being 150mm long. Then, after pressing the web plate to the existing structure, perform a full penetration weld. During welding, use symmetrical sections for back-welding, with each weld section being 200mm long, alternating from the center of the web plate to both ends. Finally, weld the T-joints of the flange plate and web plate to ensure that the weld penetration depth is ≥80% of the plate thickness.

[0066] When using the end of the upper chord 31 of segment 3 for precision welding of the existing structure, the web is first welded to the existing structure to full penetration. Symmetrical segmented back-welding is used during welding, with each weld segment 200mm long, alternating from the center of the web towards both ends to offset longitudinal shrinkage stress. As the main load-bearing component, the web is preferentially precision welded to ensure the continuity and rigidity of the force transmission path. Then, the flange is pressed tightly against the existing structure and subjected to full penetration welding. Welding is done in segments from the middle of the flange towards both ends, with each weld segment 150mm long to reduce lateral shrinkage deformation. Finally, the T-joint between the flange and the web is welded to ensure the weld penetration depth is ≥80% of the plate thickness.

[0067] Based on this, the lowering of steel truss segment 3 was completed.

[0068] A method for constructing a steel truss includes the following steps:

[0069] (1) Install permanent supports, temporary supports 1, steel box girders and tie rods according to the design.

[0070] (2) The top elevation, centerline and span of the assembled support group of the column are re-measured. The beam can be lowered only if the error is within the allowable range of the design and specification. Then, the steel truss segment 3 is lowered in sequence according to the above beam lowering method.

[0071] (3) Remove temporary support 1.

[0072] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for segmenting steel truss beams, characterized in that: Includes the following steps: S1. Install permanent and temporary supports (1) according to the design, and jacks (2) are provided on the temporary supports (1); S2. The steel truss includes several segments (3) along the span direction, and the two ends of the segments (3) along the span direction are the welded end and the free end, respectively; Several segments (3) are respectively lowered into the beam, and each segment (3) is lowered into the beam through the following steps: S21. Hoist the segment (3) to the position where the beam is to be lowered; S22. The welding end of the segment (3) is roughly welded to the existing structure; The segment (3) includes an upper chord (31), a lower chord (32), and a web member (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 flanges and a web member disposed between the two flanges; In step S22, the two flange plates of the lower chord (32) of the segment (3) are rough welded to the existing structure. The rough welding is as follows: during welding, the length of each weld is 50mm and the interval is 300mm. The web of the upper chord (31) of the segment (3) is rough welded to the existing structure. The rough welding is as follows: during welding, each weld is 200mm long and spaced 300mm apart. S23. Place the entire segment (3) onto the jack (2) and adjust the jack (2) to correct the position of the segment (3); S24. Fix the welding end of the segment (3) to the existing structure by precision welding; the precision welding is a full penetration weld; The existing structure includes at least one of the permanent support and the segment (3) that has been fixed by precision welding.

2. The method for segmenting steel truss beams according to claim 1, characterized in that: The order of lowering the beams of several segments (3) is as follows: from both ends to the middle along the span direction.

3. The method for segmenting steel truss beams according to claim 1, characterized in that: At least two jacks (2) are provided on the temporary support (1) along the span direction; in step S23, the segment (3) is placed on the at least two jacks (2) as a whole.

4. The method for segmenting steel truss beams according to claim 3, characterized in that: The temporary support (1) includes a first support part, a second support part and a load-bearing part in sequence from the ground upwards, and the jack (2) is set on the load-bearing part; The first support portion includes a plurality of first support piles (111), and the second support portion includes a plurality of second support piles (121) and shear braces (122) disposed between adjacent second support piles (121). The outer diameter of the second support pile (121) is smaller than that of the first support pile (111), and the first support pile (111) and the second support pile (121) are connected by a frustum-shaped connecting column.

5. The method for segmenting steel truss beams according to claim 4, characterized in that: The load-bearing part includes a first load-bearing beam (131) for installing a jack (2) near the welded end of the segment (3) and a second load-bearing beam (132) for installing a jack (2) away from the welded end of the segment (3). The first load-bearing beam (131) is connected to the second support part by a shear key, and the second load-bearing beam (132) is connected to the second support part by a hollow round tube (133).

6. A method for segmenting steel truss beams 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 before rough welding is measured; In step S23, during adjustment, after the segment (3) is corrected to the design position by the jack (2), the jacking distance b continues; b = (1.1~1.5)a.

7. The method for segmenting steel truss beams according to claim 1, characterized in that: The two flanges of the lower chord (32) are symmetrically spot-welded with the existing structure using a V-groove; the web of the upper chord (31) is skip-welded with the existing structure using a K-groove.

8. The method for segmenting steel truss beams according to claim 1, characterized in that: First, the two flange plates of the lower chord (32) are rough welded to the existing structure; then the web plate of the upper chord (31) is rough welded to the existing structure.

9. A method for constructing a steel truss, characterized in that: This includes the steel truss segmented beam method as described in any one of claims 1 to 8.

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