Construction Technology for Anti-Settlement Installation of Long-Span Trusses

Abstract

The present invention relates to the technical field of steel truss construction, and specifically to a large-span truss anti-settlement installation construction process, which comprises the following steps: setting 2N fixed temporary supports; assembling a building steel reinforcement body into a plurality of trusses, and hoisting each truss into 2N+1 sections; during hoisting, hoisting is performed in sequence from both sides to the middle, and welding is performed immediately after each hoisted truss section is in place; firstly, the hook of the crane of the middle truss section is unhooked to perform the first unloading, and a secondary truss is installed between the truss being hoisted and the previous truss; and in a left-right order, temporary supports are removed in sequence from the middle to both sides to perform 2N unloading. The present invention first unloads the middle truss section by its own weight, thereby eliminating a part of the unloading error in advance, and then connecting the secondary truss, thereby greatly reducing the collateral impact on the remaining installed trusses when unloading other trusses, and making the installation precision more accurate.

Description

Technical Field

[0001] The invention relates to the technical field of steel truss construction, in particular to a large-span truss anti-settlement installation construction process. Background Art

[0002] Nowadays, steel structure projects are becoming more and more common in our lives. Under the current favorable conditions of low steel prices, large structural spans, short construction periods, high recyclability and low overall costs, the utilization rate of steel structures is getting higher and higher, and they are widely used in large industrial plants, gymnasiums, gas stations, super high-rise buildings and other fields. For arched span steel trusses with super large spans, the installation methods are mostly high-altitude in-situ bulk method, overall lifting method, etc. The bulk method requires the construction of full-floor supports to provide a high-altitude shelving of components and an operating platform for workers. The construction of full-floor supports is time-consuming and labor-intensive. The overall lifting method is to lift the trusses at the same time by multiple large cranes after they are assembled on the ground. The overall deformation control of the steel trusses after lifting must be considered, as well as the strength of the arch foot supports. The overall lifting method has problems such as expensive crane rental fees, high material consumption, high manpower investment, many construction processes, and difficult quality control.

[0003] In the prior art, in order to avoid erecting full-floor supports, avoiding the high cost of crane rental, the difficulty in controlling overall deformation and other problems, for structures with longer lengths and heavier masses, a segmented hoisting method can be used for hoisting, such as a high-altitude in-situ construction method for an ultra-large-span cable-stayed arch steel structure with application number 201911403632.1, the construction process of which includes: setting a support frame at the connection point between the unit trusses, hoisting each section of the truss one by one, installing the secondary trusses at the same time, and then installing the force-bearing cables, and then dismantling the support frame in sequence until each section of the truss is unloaded; prior art There are the following disadvantages: the length, direction, and thickness of the load-bearing cables need to be designed in advance, the design process is relatively cumbersome, the design must be accurate and no errors can occur, and adjustments are relatively cumbersome when errors occur; and each time a support frame is dismantled, the unit trusses on both sides of the support frame will sink at the same time, which is not conducive to the slow and balanced transmission of the overall load of the steel truss to the arch foot and each load-bearing support frame. At the same time, since the secondary trusses and the load-bearing cables are connected in advance, each truss will have a chain effect on other unit trusses when it is unloaded, thereby causing the truss elevation to drop, which will ultimately affect the accuracy of the overall steel structure frame. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the object of the present invention is to provide a large-span truss anti-settlement installation construction process that can reduce deformation and sinking.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] A large-span truss anti-settlement installation construction process includes the following steps:

[0007] S1, the base site is leveled and hardened;

[0008] S2, fix the temporary support to the predetermined position and fix it firmly with embedded bolts; there are 2N temporary supports, which are staggered and welded at different positions. Except for the truss in the middle, there is a temporary support under each truss section;

[0009] S3: The main body of the building reinforcement is divided into several trusses and assembled from front to back or back to front. Each truss is hoisted in 2N+1 sections. When hoisting, hoist from both sides to the middle. After each truss section is hoisted into place, welding is immediately carried out. When hoisting the truss section in the middle, welding is immediately carried out after the centerline height of the truss section in the middle is the same as that of the first two trusses. During welding, the crane cooperates with the surveyors below to always pay attention to the truss arch elevation.

[0010] S4, first unhook the crane hook of the middle section of the truss, and let the middle section of the truss unload for the first time by its own weight. After unhooking, wait for 10 minutes, observe and record the settlement height after the first unloading;

[0011] S5, installing a secondary truss between the truss being hoisted and the previous truss. When the truss being hoisted is the first truss of the building reinforcement body, directly proceed to step S7;

[0012] S6, remove the temporary supports from the middle to both sides in sequence, and unload the load 2N times in the order of left and right. Wait for 10 minutes after each removal of the temporary supports, and then observe and record the settlement height;

[0013] S7. Each time a truss is unloaded, observe for 24 hours, and record the changes in elevation and truss deflection.

[0014] Preferably, when the span of each truss is not greater than 80m, each truss is hoisted in three sections, and the span of the third section, that is, the middle section, shall not exceed 30m.

[0015] Preferably, the interface of the welding end of each truss section is set as a Z-shaped interface, that is, the truss upper chord, truss lower chord and connecting rod at the interface are arranged in a Z shape as a whole.

[0016] Preferably, before step S4, the method further includes performing flaw detection on all welds, and after the flaw detection is qualified, waiting for the truss welds to cool naturally, and then unloading the load after the temperature drops to the outdoor temperature.

[0017] Compared with the prior art, the present invention adopting the above technical solution has the following outstanding features:

[0018] The present invention first unloads the middle section of the truss by relying on its own weight, eliminating part of the unloading error in advance, and then connects the secondary trusses, which greatly reduces the collateral impact on the remaining installed trusses when unloading other sections of the truss, and makes the installation accuracy more accurate; the remaining sections of the truss are unloaded 2N-1 times, which greatly reduces the deformation and sinking of the truss caused by the sudden and huge change in its own weight, and significantly improves the installation quality of the truss; at the same time, by providing a Z-shaped interface, the overall seismic strength can be further enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 1 is a schematic structural diagram of a large-span truss during hoisting according to an embodiment of the present invention;

[0020] Figure 2 It is a structural diagram of the Z-shaped interface in an embodiment of the present invention.

[0021] Explanation of the accompanying symbols: 1. Temporary support; 2. A section of truss on the left; 3. A section of truss on the right; 4. A section of truss in the middle position; 5. Z-shaped interface. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific embodiments. The purpose is only to better understand the content of the present invention. Therefore, the examples given do not limit the scope of protection of the present invention.

[0023] In order to prevent the truss elevation from dropping (settling) due to its own weight and the weight of subsequent curtain wall and other construction processes after the temporary supports are removed after the trusses are assembled and welded, thereby affecting the accuracy of the overall steel structure frame, the large-span trusses will be provided with corresponding pre-arching during assembly and welding, and the final elevation of the large-span trusses is the elevation after the temporary supports are removed and the trusses are unloaded. The truss elevation is a difficult point in quality control and a key control point in the steel structure. Furthermore, how to better control the truss elevation of the large-span trusses after unloading the load is also an important discussion point in this embodiment.

[0024] The present invention is applicable to steel structure projects, combining temporary support systems and crawler crane hoisting methods, such as Figure 1 As shown, a large-span truss anti-settlement installation construction process is shown. In this embodiment, the building steel body is pre-divided into several trusses and assembled from front to back or from back to front. Each truss is further divided into 2N+1 sections for hoisting. The specific steps are as follows:

[0025] S1, the base site is leveled and hardened.

[0026] S2, except for the 2N+1th truss, that is, the truss 4 in the middle position, a temporary support 1 is set under each of the remaining 2N trusses, that is, there are 2N temporary supports 1 in total, and the 2N temporary supports 1 are staggered and welded. The temporary supports 1 are fixed to the predetermined position with embedded bolts, and wind ropes are set at the high places of the temporary supports 1 with steel cables to ensure that the temporary supports 1 are firmly fixed.

[0027] S3. The main body of the building reinforcement is divided into several trusses and assembled from front to back or from back to front. Each truss is hoisted in 2N+1 sections, where N is greater than or equal to 1. When hoisting, it is hoisted from both sides to the middle in sequence. Each truss is welded immediately after it is hoisted into place. When hoisting a section of truss 4 in the middle position, welding is carried out immediately after the center line height of the section of truss 4 in the middle position is the same as that of the first two trusses (that is, the trusses adjacent to the left and right sides of the section of truss 4 in the middle position). During welding, the crane cooperates with the surveying personnel below and always pays attention to the arch elevation of the truss.

[0028] Then, all welds are inspected for flaws. After passing the inspection, wait for the truss welds to cool naturally and the temperature drops to the outdoor temperature.

[0029] S4, first unhook the crane hook of the middle section of the truss 4, and unload the middle section of the truss 4 for the first time by its own weight. After unhooking, wait for 10 minutes, observe and record the settlement height after the first unloading;

[0030] S5, installing a secondary truss between the truss being hoisted and the previous truss. When the truss being hoisted is the first truss of the building reinforcement body, directly proceed to step S7;

[0031] S6, remove the temporary support 1 from the middle to both sides in the order of left and right, and perform unloading 2N times. Wait for 10 minutes after each removal of the temporary support 1, and then observe and record the settlement height;

[0032] Before unloading, the settlement amount is predicted based on construction experience or by consulting professional information. Each unloading point is equipped with technical personnel and complete communication equipment. When unloading, the principle of "one listen, two look" is followed. First, listen to see if there is any abnormal sound when unloading. If an abnormal sound occurs, stop unloading immediately and continue after eliminating the hidden dangers. Second, look to see if the elevation changes after the truss settles and whether the deflection value of the truss tube changes. If the deflection value exceeds 1 / 1000 or the elevation change is greater than or equal to 20mm, stop unloading immediately.

[0033] S7. Each time a truss is unloaded, observe for 24 hours, and record the changes in elevation and truss deflection.

[0034] Example 2: When the span of each truss is not more than 80m, N=1, each truss is hoisted in 3 sections, the span of the third truss, the middle section of the truss shall not exceed 30m; the temperature should be controlled at about 15°C when closing; when the span of each truss is 66.763m, 1 / 1200 arching, the arching value is 55.6mm; each truss is divided into 3 sections, each section is 22.251m, divided into left, middle and right sections, corresponding to which two temporary supports 1 are set, and the hoisting order is, first hoist Install a section of truss 2 on the left side, weld it and fix it, then hoist a section of truss 3 on the right side, weld it and fix it, then hoist a section of truss 4 in the middle position, weld and fix the section of truss 4 in the middle position, and perform non-destructive testing. After the weld temperature drops to room temperature, unhook the section of truss 4 in the middle position and perform the first unloading. Then weld the secondary truss and weld it to the previous truss. Then remove the temporary support 1 on the left side and perform the second unloading. Then remove the temporary support 1 on the right side and perform the third unloading.

[0035] Further, such as Figure 2 The interface of the welding end of each truss is set as a Z-shaped interface 5, that is, the upper chord of the truss, the lower chord of the truss, and the connecting rod at the interface are arranged in a Z shape as a whole; thereby avoiding the welding joints from being on the same vertical plane, thereby enhancing the overall seismic strength.

[0036] During the above construction process, the installation unit must calculate the stress on the cradle and each stage of construction according to the formulated construction plan.

[0037] The present invention improves and innovates on a large amount of collected relevant large-span truss hoisting methods. On the basis of relevant technologies of truss segmented hoisting and temporary support system solutions, a segmented hoisting method is determined. When unloading, the first unloading is performed without connecting the secondary trusses, eliminating part of the unloading error in advance, and then the secondary trusses are connected, which greatly reduces the collateral impact on the remaining installed trusses when unloading other trusses, makes the installation precision more accurate, and significantly improves the truss installation quality.

[0038] The above description is only a preferred embodiment of the present invention and does not limit the scope of the present invention. Any equivalent changes made using the contents of the present invention specification and its drawings are included in the scope of the present invention.

Claims

1. A long-span truss anti-settlement installation construction process, comprising the following steps: S1, the base site is leveled and hardened; S2, fix the temporary support to the predetermined position and secure it firmly with embedded bolts; S3: The main body of the building reinforcement is divided into several trusses and assembled from front to back or back to front. Each truss is hoisted in 2N+1 sections. It is characterized by: In step S2, 2N temporary supports are provided, staggered at the welding positions, and a temporary support is provided under each truss section except for the truss section at the most middle position; Step S3: During hoisting, hoist from both sides to the middle in sequence, and weld immediately after each truss section is hoisted into place; when hoisting the truss section at the most middle position, weld immediately after the centerline height of the truss section at the most middle position is the same as that of the first two trusses. During welding, the crane cooperates with the surveyor below, and always pays attention to the truss arch elevation; Also includes, S4, first unhook the crane hook of the middle section of the truss, and let the middle section of the truss unload for the first time by its own weight. After unhooking, wait for 10 minutes, observe and record the settlement height after the first unloading; S5, installing a secondary truss between the truss being hoisted and the previous truss. When the truss being hoisted is the first truss of the building reinforcement body, directly proceed to step S7; S6: When removing temporary supports, remove them from the middle to both sides in sequence, one on the left and one on the right, and perform 2N unloading operations. After each removal of temporary supports, wait for 10 minutes, and then observe and record the settlement height. S7. Each time a truss is unloaded, observe for 24 hours, and record the changes in elevation and truss deflection.

2. The long-span truss anti-settlement installation construction process according to claim 1 is characterized in that: When the span of each truss is not greater than 80m, each truss shall be hoisted in three sections. The span of the third truss, that is, the middle section, shall not exceed 30m.

3. The long-span truss anti-settlement installation construction process according to claim 1 is characterized in that: The interface of the welding end of each truss section is set as a Z-shaped interface, that is, the truss upper chord, truss lower chord and connecting rod at the interface are set in a Z shape as a whole.

4. The long-span truss anti-settlement installation construction process according to claim 2 is characterized in that: Before step S4, the process also includes performing flaw detection on all welds. After the flaw detection is qualified, the truss welds are allowed to cool naturally until the temperature drops to the outdoor temperature before unloading the load.

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