CN116882002A - Construction method of space truss with prestressed structure - Google Patents

Abstract

The application discloses a construction method of a space truss with a prestressed structure, which comprises the following steps: step 1: simulation calculation and hanging point design; step 2: according to the step 1, simulating calculation, and determining a prestress tensioning mode; step 3: carrying out actual construction according to the calculation results of the step 1 and the step 2; in step 2, model parameters are set through model calculation to obtain an optimal tensioning mode of the prestress so as to reduce the influence of the tensioning prestress on the original structure, and the model parameters in step 2 are as follows: the integral stress ratio of the original structure is not more than 0.8, and the displacement is not more than 1/250. According to the application, by optimizing the prestress tensioning method and sequence, reasonably designing the lifting points, setting the hydraulic jacks and carrying out staged synchronous equal-ratio unloading, the stability of the structure in the whole construction process and the convenience of construction are ensured, and the safety of construction is improved.

Description

Construction method of space truss with prestressed structure

Technical Field

The application relates to the field of steel structure construction, in particular to a construction method of a space truss with a prestressed structure.

Background

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

Along with the development of national economy and urban construction, various museums, exhibition halls, concert halls, gymnasiums and airports are required to be constructed in many cities to meet the urban development requirements and improve urban images, the buildings are often landmark buildings of one city and represent the urban development level, and in order to achieve the effects, the buildings are often required to be provided with personalized appearance models and unique different structures, and the structures are complex in structure and peculiar in model, and are often of new structural structures designed by the latest design theory, so that the technical requirements of the buildings on construction cannot be met by the traditional and single construction technology.

There are numerous technical difficulties with respect to the construction of space steel tube truss structures:

1. how the steel strands are not disordered in the process of threading; due to self weight of the steel cable, a natural downwarping exists in the middle of the two ends after the two ends are tensioned, and the steel stranded wires penetrating in the rear are easy to be entangled with the steel stranded wires in the front, so that the traction effect is affected.

2. How to set the lifting points and how to set the hydraulic jacks to ensure the integral synchronous lifting of the space truss structure;

3. how to design a reasonable hanging point structure, so that the lifting and closing can be directly performed when the opening is closed, and the rod is not required to be replaced and then closed.

4. How to ensure the synchronization and stability of the roof truss during unloading.

Disclosure of Invention

The application aims at: aiming at the current technical problem, the space truss construction method with the prestressed structure is provided, the influence of the prestressed construction on the existing structure can be reduced, and the convenience and safety of construction are improved.

The technical scheme of the application is as follows:

a construction method of a space truss with a prestressed structure comprises the following steps:

step 1: modeling through structural software, and designing a hanging point;

step 2: according to the hanging point, determining a prestress tensioning mode based on structural software;

step 3: and carrying out actual construction based on the hanging point and the prestress tensioning mode.

According to a preferred embodiment, the suspension point is set according to the deflection value or the location of the force.

According to a preferred embodiment, said step 2 comprises: according to the hanging points, setting model parameters based on structural software, and determining an optimal prestress tensioning mode;

the model parameters include: the integral stress ratio of the original structure is not more than 0.8, the displacement is not more than 1/250, and a reference value that the maximum arch camber value in the truss assembly process is consistent with the deflection value in the dead weight state is adopted.

When the existing construction mode of one-time tensioning prestress is used, as the prestress tensioning force is a design value of the roof structure in a normal working state, the load of the roof is not completely loaded in the prestress construction process, namely the following two conditions are easy to occur: 1. when the prestress starts the unloading effect, unloading is possibly not in place; 2. when the prestressing force acts as a load increase, there is a possibility that a load increase overload occurs. In order to avoid the two conditions, the application determines the magnitude of the pre-stress which is applied currently according to the structure difference of different construction stages, determines the tensioning method of the pre-stress, and tensions the pre-stress with different magnitudes in different construction stages, thereby ensuring that the pre-stress tensioned in different construction stages does not influence the structure.

According to a preferred embodiment, step 3 further comprises the sub-steps of:

step 3.1: constructing a main truss and assembling a jig frame;

step 3.2: lifting;

step 3.3: after lifting in place, aligning the main truss;

step 3.4: performing second-stage installation;

step 3.5: and unloading the temporary support after the second section is installed.

And in the steps 3.1-3.5, the prestress step tensioning and the prestress step tensioning are synchronously carried out according to the prestress tensioning mode determined in the step 2. The synchronous step tensioning is carried out in each step of step tensioning, and the step tensioning is carried out in each step of step tensioning.

According to a preferred embodiment, the prestressing graded tensioning comprises: the first stage is to pre-stretch step by step when the steel cable is penetrated, so that stirring among each group of steel strands is prevented: the second stage is to prestress tensioning the truss on the assembly jig frame, and the tensioning value is determined according to the computer simulation structural stress; the third stage is stretching after lifting; standing after lifting, and stretching to a final design value in a stepping way.

The prestressing force step-by-step tensioning comprises the following steps: according to a certain prestress change gradient, prestress tensioning is carried out to a preset value in multiple steps;

the prestress tensioning method comprises the following steps of: carrying out prestress steel strand threading according to the sequence from top to bottom and from right to left; and sequentially tensioning the steel strands positioned in opposite directions from bottom to top. A plurality of groups of steel strands need to be penetrated into the steel pipe, the lengths of the steel strands are longer, a natural downwarping exists in the middle of the two ends of the steel strands after the two ends of the steel strands are tensioned, through the penetrating sequence, the steel strands penetrating into the steel pipe at the back and the steel strands in the front can be prevented from being stirred, and no confusion among the groups is ensured.

The dead weight of the roof before lifting is borne by the temporary support to bear the lower chord of the steel pipe without bearing the tensile force, namely the prestress tension force cannot play a role in counteracting the tension of the lower chord of the steel pipe, and the prestress tension position is easy to cause overlarge stress. In order to ensure that the prestress tensioning construction has the least influence on the original structure, a step-by-step fractional tensioning method is adopted to obtain more favorable prestress tensioning construction steps and matched tensioning force values through simulation calculation of each stage, so that the influence on the original structure is reduced.

According to a preferred embodiment, in the step 1, the hanging points are designed by modeling, and the arranged hanging points are mainly set according to the position with larger deflection value or larger stress in the analog calculation.

According to a preferred embodiment, in step 3.2, the hoisting point crane is configured in the following manner: when the load requirement of lifting points is met, the hydraulic counter force is fed back through the built-in sensor, and the loading condition of each lifter is adjusted to be equivalent; the number of the hydraulic equipment driven by each hydraulic station is equivalent, and the utilization rate of the hydraulic pump station is improved.

According to the lifting force, the distance and the number of the hydraulic cylinders, a method for controlling the multiple cylinders by multiple pump stations is provided, each pump station drives the multiple cylinders to work simultaneously, finally, all the pump stations and the cylinders are controlled in a centralized manner through a computer, and all the cylinders work synchronously, so that all lifting points of a lifting truss are lifted synchronously, and the stability and the structural safety of the whole lifting are ensured.

According to a preferred embodiment, in step 3.2 and step 3.3, two welded balls at the main truss sections are selected as the lower suspension points at the two ends of the main truss; and a lifting lower anchor point is arranged at the upper chord member node of the radial truss, and two diagonal braces are arranged on the side surface of the lifting point of the lifting lower anchor point, so that the replacement of rod pieces and the change of a structural stress system are avoided.

According to a preferred embodiment, in step 3.2 and step 3.3, synchronous monitoring is performed during lifting, and the roof is adjusted when the roof level difference is greater than a preset value. Preferably, the preset value of the height difference is 20mm.

Meanwhile, a measuring point is arranged at each lifting point, the stable and synchronous lifting of the whole truss is monitored through continuous measurement, the accurate spatial position coordinates of the interface are controlled, and the spatial accurate position of the truss is ensured.

According to a preferred embodiment, in step 3.3, the main structure or temporary support structure is used to replace the hydraulic equipment stress after lifting alignment, in particular by: the beam is placed beside the position in place in advance, and after the beam is lifted to the position in place, the beam is immediately installed to the designated position, and then the beam is used for supporting the stress.

According to a preferred embodiment, step 3.5 uses a method of phased synchronous equal ratio unloading to unload the temporary support: and obtaining a mid-span maximum deflection value of the inner ring truss through calculation, and grading according to the maximum deflection value and the limit of deformation of not more than 20mm generated by unloading of each stage, wherein the first stage unloading is not more than 15mm.

The whole roof unloading is equivalent to synchronous unloading by controlling the relative displacement difference value of unloading, so that the whole roof structure is basically in a static unloading state. The unloading method is suitable for projects with more unloading control points and small unloading displacement. The method has the advantages of improving unloading safety and saving unloading cost.

According to a preferred embodiment, in step 3.5, the overhanging portion is unloaded from the outside-in direction, the truss main span is unloaded from the inside-out direction, the circumferential direction is synchronized, and the overhanging portion and the truss main span are cyclically carried out according to the stress change, and the unloading is performed at equal ratio.

The arrangement mode prevents excessive and large-height-difference unloading, completes the conversion of a space truss structure stress system, and realizes the safe and stable unloading of the whole roof. When unloading, the fulcrum adjusting plate is subjected to equal-ratio cutting in advance, so that the unloading error is controlled within 20mm, excessive unloading is prevented, the stress system conversion of the rod piece at the fulcrum position of the space three-dimensional truss is smoothly completed, and the whole roof is safely and stably unloaded.

Compared with the prior art, the application has the beneficial effects that:

1. according to the construction method of the space truss with the prestressed structure, the prestress is stretched step by step, graded and ordered according to the stress and displacement calculation of different construction states of the structure in different construction stages, so that the influence of single-time prestressing on the original structure can be avoided, and the safety of the construction process is improved;

2. the construction method of the space truss with the prestressed structure realizes the integral synchronous lifting of the space truss structure by reasonably designing the lifting points and arranging the hydraulic jacks, and realizes the direct alignment and closure after the lifting without rod replacement operation by improving the structure of the lifting points, thereby improving the convenience of the construction process and avoiding the risk of truss instability in the closure process after the lifting;

3. a space truss construction method with a prestressed structure adopts a method of phased synchronous equal ratio unloading, controls single unloading height difference, realizes synchronous unloading based on reasonable calculation and a single-point cyclic unloading method, can ensure the stability of a truss in the process of unloading a temporary supporting structure, and improves the safety of the construction process.

Drawings

FIG. 1 is a schematic view showing a strand pulling sequence of example 1 of the present application;

FIG. 2 is a schematic drawing showing the tensioning sequence of each group of steel strands according to example 1 of the present application;

FIG. 3 is a lifting point setting schematic of embodiment 2 of the present application;

fig. 4 is a schematic view of a lifting hydraulic jack configuration of embodiment 2 of the present application;

fig. 5 is a schematic view of the unloading of the cutting adjustment plate of embodiment 2 of the present application.

Detailed Description

It is noted that relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

Example 1

A construction method of a space truss with a prestressed structure comprises the following steps:

step 1: modeling through structural software, and designing a hanging point;

step 2: according to the hanging points, a prestress tensioning mode (the tensioning stage number and the prestress of each stage of tensioning) is determined based on structural software;

step 3: and carrying out actual construction based on the hanging point and the prestress tensioning mode.

And in the step 3, the prestress step tensioning and the prestress step tensioning are synchronously carried out according to the prestress tensioning mode determined in the step 2.

Preferably, in step 1, through midas structural software modeling, the hanging points are mainly set according to the positions with larger deflection values or larger stress in analog calculation, which is a conventional technical means in the field.

Preferably, the basis for determining the prestress tensioning mode in the step 2 is that the maximum displacement and the stress meet the standard requirements, and the maximum displacement and the stress should be smaller. The method comprises the following steps: the structural comprehensive stress (pulling, pressing, bending, shearing and twisting) ratio is not more than 0.8 and the displacement is not more than 1/250 through the midas structural software simulation calculation, so that the influence of prestress tension construction on the original structure is minimum. Preferably, when the prestress tensioning is simulated, the tensioning stage number and each stage of tensioning force of the prestress tensioning are determined by calculating whether the structural comprehensive stress and displacement of the main truss in each substep in the step 3 meet the requirements, and a reference value that the maximum arch lifting value in the truss assembly process is consistent with the deflection value in the dead weight state is adopted.

When the existing construction mode of one-time tensioning prestress is used, as the prestress tensioning force is a design value of the roof structure in a normal working state, the load of the roof is not completely loaded in the prestress construction process, namely the following two conditions are easy to occur: 1. when the prestress starts the unloading effect, unloading is possibly not in place; 2. when the prestressing force acts as a load increase, there is a possibility that a load increase overload occurs. In order to avoid the two conditions, the application determines the magnitude of the pre-stress which is applied currently according to the structure difference of different construction stages, determines the tensioning method of the pre-stress, tensions the pre-stress with different magnitudes in different construction stages, and reduces the influence of the tensioned pre-stress in different construction stages on the structure.

According to a preferred embodiment, step 3 further comprises the sub-steps of:

step 3.1: constructing a main truss and assembling a jig frame;

step 3.2: lifting;

step 3.3: after lifting in place, aligning the main truss;

step 3.4: performing second-stage installation;

step 3.5: and unloading the temporary support after the second section is installed.

And in the steps 3.1-3.5, the prestress step tensioning and the prestress step tensioning are synchronously carried out according to the prestress tensioning mode determined in the step 2. The synchronous step tensioning is carried out in each step of step tensioning, and the step tensioning is carried out in each step of step tensioning.

According to a preferred embodiment, the prestressing graded tensioning comprises: the first stage is to pre-stretch step by step when the steel cable is penetrated, so that stirring among each group of steel strands is prevented: the second stage is to prestress tensioning the truss on the assembly jig frame, and the tensioning value is determined according to the computer simulation structural stress; the third stage is stretching after lifting; standing after lifting, and stretching to a final design value in a stepping way. The optimal and safest tensioning value is determined through the computer model simulation calculation, so that the structural safety and the structural quality are ensured, and the design requirement is met. And finally, 5% of overstretching, so that the stress loss of the steel strand is solved, and the structural prestress requirement is met.

The prestressing force step-by-step tensioning comprises the following steps: according to a certain prestress change gradient, prestress tensioning is carried out to a preset value in multiple steps;

the prestress tensioning method comprises the following steps of: as shown in fig. 1, the prestress steel strand is threaded from top to bottom and from right to left; as shown in fig. 2, the steel strands located in opposite directions are sequentially tensioned in a bottom-up manner. A plurality of groups of steel strands need to be penetrated into the steel pipe, the lengths of the steel strands are longer, a natural downwarping exists in the middle of the two ends of the steel strands after the two ends of the steel strands are tensioned, through the penetrating sequence, the steel strands penetrating into the steel pipe at the back and the steel strands in the front can be prevented from being stirred, and no confusion among the groups is ensured.

The dead weight of the roof before lifting is borne by the temporary support to bear the lower chord of the steel pipe without bearing the tensile force, namely the prestress tension force cannot play a role in counteracting the tension of the lower chord of the steel pipe, and the prestress tension position is easy to cause overlarge stress. In order to ensure that the prestress tensioning construction has the least influence on the original structure, a step-by-step fractional tensioning method is adopted to obtain more favorable prestress tensioning construction steps and matched tensioning force values through simulation calculation of each stage, so that the influence on the original structure is reduced.

Because the dead weight of the roof before lifting bears the tensile force of the lower chord of the steel pipe by the temporary support, namely the prestress tensioning force cannot play a role in counteracting the tensile force of the lower chord of the steel pipe, the prestress tensioning position is easy to cause overlarge stress, and therefore the prestress tensioning construction before lifting needs to be calculated, and the overlarge tensioning stress is prevented from damaging the original structure. According to the application, through simulation calculation of each stage, the prestress tensioning construction is carried out step by step in the process of bearing the self weight of the structure, and a step-by-step and step-by-step grading tensioning method is adopted, so that the more favorable prestress tensioning construction steps and matched tensioning force values can be obtained, the influence of prestress tensioning on the original structure is reduced, and the minimal influence of prestress tensioning construction on the original structure is ensured.

Preferably, in step 3.3, the main structure or the temporary support structure is used to replace the hydraulic equipment stress after lifting alignment, and the specific method is as follows: the beam is placed beside the position in place in advance, and after the beam is lifted to the position in place, the beam is immediately installed to the designated position, and then the beam is used for supporting the stress. The existing construction method is characterized in that the hydraulic equipment is stressed after the hydraulic equipment is lifted in place, and the hydraulic equipment is gradually stressed and converted to the main structure or the temporary supporting structure after the main structure is in butt joint. The docking time is longer than 1 month after lifting into place. In order to ensure the structural safety, the application converts the stress of the hydraulic jack to a reliable temporary supporting structure, thereby increasing the construction safety coefficient.

Preferably, hemispherical members are arranged at the wall attaching positions of the lifting support frames, so that the mutual influence and overlapping of the rod pieces can be avoided. Since the number of support bars is large, the bar section is relatively large (the diameter of the steel pipe is about Φ299x 10). After the hemispherical members are additionally arranged, the force transmission of each support can be effectively ensured after the supports are connected with the wall body.

Preferably, in step 3.2, the crane is configured for the suspension point designed in step 1 as follows:

(1) The load requirement of lifting points is met, and the loading condition of each lifter is as good as possible; the hydraulic counter force is fed back through the built-in sensor, and then adjustment control is carried out;

(2) The number of hydraulic equipment driven by each hydraulic station is guaranteed to be equal as much as possible, and the utilization rate of the hydraulic pump station is improved.

According to the lifting force, the distance and the number of the hydraulic cylinders, a method for controlling the multiple cylinders by multiple pump stations is provided, each pump station drives the multiple cylinders to work simultaneously, finally, all the pump stations and the cylinders are controlled in a centralized manner through a computer, and all the cylinders work synchronously, so that all lifting points of a lifting truss are lifted synchronously, and the stability and the structural safety of the whole lifting are ensured. Meanwhile, a measuring point is arranged at each lifting point, the stable and synchronous lifting of the whole truss is monitored through continuous measurement, the accurate spatial position coordinates of the interface are controlled, and the spatial accurate position of the truss is ensured.

In step 3.3, the truss structure needs to be replaced after being lifted in place, the replacement of the truss structure changes a stress system during lifting, the truss structure is a rod in a tensile state, the rod is easy to change from stress reversal to a compression bar during the replacement of the truss structure, and accidents are easy to occur because the compression stability of the steel structure is lower than the tension stability.

The application improves the structure of the hanging point. In the step 3.2 and the step 3.3, two welding balls at the section of the main truss are selected as lower hanging points at two ends of the main truss; and a lifting lower anchor point is arranged at the upper chord member node of the radial truss and is connected with a lifting steel strand through a ground anchor. The anchor point is located the intermediate position for two pin annular trusses under the radial truss promotes, in order to guarantee the stability of hoisting position, and anchor point position side sets up two diagonal draw bars under promoting, avoids the member to replace and changes the structure atress system. Through the arrangement of the lower hanging point and the lifting lower anchor point, the rod replacing work after lifting in place is effectively avoided, namely, lifting in place only reinforces the lifting unit, and the risk of instability does not exist.

Preferably, in steps 3.2 and 3.3, synchronous monitoring is performed during lifting, and the roof is adjusted when the roof height difference is greater than a preset value. Preferably, the relative height adjustment value is 20mm, i.e. the relative height of any two points is greater than 20mm, i.e. the roof is adjusted.

Preferably, the method of synchronous detection can be: accumulating and recording the stroke of the hydraulic cylinder: and the stroke of the hydraulic cylinder is 250mm each time, the stroke of each lifting is accumulated and summed, and the roof is synchronously regulated by the sum of the strokes of the lifters.

Preferably, the method of synchronous detection can also be: and (3) total station space positioning monitoring:

and (3) attaching a reflection patch in advance, detecting the position of each lifting butt joint opening through a total station, and detecting and adjusting theoretical positioning coordinates of each pipe opening at the pipe opening position of each butt joint steel pipe before lifting through a roof structure.

The reflection patch is arranged at the upper chord pipe orifice position of all main pipe trusses needing to be opposite, a piece of flat iron is welded on any diameter of the pipe orifice in advance, the outer surface of the flat iron is flush with the pipe orifice, and then the reflection patch is attached to the center point of the steel pipe. Preferably, the size of the flat iron is 6mm.

Preferably, the method of synchronous detection can also be: and (3) monitoring the travel of the level gauge: consider that the monitoring point of total powerstation in the lifting process may be blocked by the building, which increases the travel of the level gauge. And hanging a scale with scales at the lower chord opening of each main truss, recording basic data of each point, recording and comparing the travel of each point by using a level after each 4 travels, and adjusting the roof when the height difference exceeds 20mm. Preferably, the scale can be a 50m hanging tape measure.

The stable synchronous lifting of the whole truss is monitored through continuous measurement, the accurate spatial position coordinates of the interface are controlled, and the spatial accurate position of the truss is ensured.

Preferably, in step 3.5, after the installation is completed, the temporary support is unloaded by adopting a whole unloading method, namely a method of 'staged synchronous equal ratio unloading'. Through simulation comparison and calculation of the scheme, a mid-span maximum deflection value of the inner ring truss is calculated, and classification is carried out according to the limit that deformation generated by unloading of each stage is not more than 20mm according to the maximum deflection value, wherein the unloading of the first stage is not more than 15mm.

The whole roof unloading is equivalent to synchronous unloading by controlling the relative displacement difference value of unloading, so that the whole roof structure is basically in a static unloading state. The unloading method is suitable for projects with more unloading control points and small unloading displacement. The method has the advantages of improving unloading safety and saving unloading cost.

Preferably, the outer ring truss is unloaded, 2 sets of jig frames (1 unloading point per set) are respectively selected at two ends of the central axis, and two areas are synchronously and symmetrically unloaded.

In step 3.5, the adjusting plate is set to be larger than the downwarping value calculated by simulating the roof truss during installation, and only the adjusting plate is required to be cut to descend the jack during unloading. The adjusting plate is arranged in the manner shown in fig. 5.

The overhanging part is adopted in construction to synchronously carry out the truss main span from outside to inside and the annular direction, the overhanging and the span are carried out circularly according to the stress change, the unloading is carried out in equal proportion, the unloading with excessive and large height difference is prevented, the conversion of a space truss structure stress system is completed, and the safe and stable unloading of the whole roof is realized.

When unloading, the fulcrum adjusting plate is subjected to equal-ratio cutting in advance, so that the unloading error is controlled within 20mm, excessive unloading is prevented, the stress system conversion of the rod piece at the fulcrum position of the space three-dimensional truss is smoothly completed, and the whole roof is safely and stably unloaded.

The whole roof unloading is equivalent to synchronous unloading by controlling the relative displacement difference value of unloading, so that the whole roof structure is basically in a static unloading state. The unloading method is suitable for projects with more unloading control points and small unloading displacement. The method has the advantages of improving unloading safety and saving unloading cost.

Example 2

Taking the Chengdu magic cube project as an example, the roof of the magic cube is of a space steel pipe truss structure, the plane is a nearly round scallop, the diameter is 146.9m, the height is 4.5m, and the magic cube is located on 12 fixed and 22 slideable supports. The upper part of the stage opening is provided with a main truss of 8m multiplied by 8m 'fish web girder', and a prestressed steel strand of 1178t is stretched in a steel pipe of the lower chord of the main truss, so that the total weight is more than 3000 tons. After the structure is fully completed, the whole roof truss is supported by 92 supporting points.

Hanging point design: according to the study of this structure: the structure is large in span, the rod piece is small in section, the flexibility of the lifting part component is large, in order to ensure that the downwarping in the structure lifting process does not exceed the standard allowable deviation, 14 lifting points are arranged in total for lifting through calculation, and the synchronous lifting of the structure is ensured. The hanging points are mainly set according to the positions with larger deflection values or larger stress in analog calculation. The suspension point reaction force is shown in table 1:

TABLE 1

The lifting hydraulic jack configuration is shown in fig. 4, according to the lifting reaction force of the lifting point.

(1) The main truss has 4 lifting points, and 2 lifting cylinders are configured at the lifting point with the largest stress, and 6 lifting cylinders are provided. 10 lifting cylinders are arranged on the 14 truss radial frames, and 5 pump stations are arranged. Maximum lift cylinder 200t, minimum 60t.

(2) The stroke of the lifting oil cylinders is unified to 250mm, and the lifting is synchronous and controlled by a computer. And (3) assisting a conventional measurement method to correct the accumulated error generated by lifting.

The area of the lifted steel roof is 3 truss main trusses (TR 19, TR20, TR 21) and radial trusses (between Ab axis and Ac axis) connected with the truss main trusses. According to the structural characteristics of the steel roof, 14 groups of lifting hanging points are arranged in total in combination with a lifting process. Wherein, 1 suspension point is respectively arranged between the 3 truss main trusses TR19 and TR20 and between TR20 and TR21, and the total number of the suspension points is 4; one suspension point is arranged at each radial truss upper chord node, and the total number of the suspension points is 10. The suspension point arrangement is shown in fig. 3.

And (3) establishing a computer model to perform simulation calculation of prestress tensioning, wherein the prestress and displacement under each working condition are shown in table 2:

TABLE 2

And (3) calculating conclusion: the prestressing force is more reasonable by stretching twice, and is specifically divided into three steps: the first step is to stretch 50% of the assembled jig frame; step two, trial lifting is carried out; and thirdly, stretching to 100% in lifting test. The maximum displacement and the stress of the three steps meet the standard requirements and are smaller.

In order to ensure that the prestress tensioning construction has minimal influence on the original structure. The steps of the prestress tension construction and the matched tension values are obtained through the simulation calculation of each stage. The classification method is carried out according to 10% sigma con, 30% sigma con, 50% sigma con, 80% sigma con and 100% sigma con,

the first stage: stretching the roof in a free state on the support frame from 0-10% sigma con-30% sigma con to 50% sigma con.

And a second stage: and (3) performing trial lifting on the roof when the roof is tensioned to 50% sigma con, namely observing when the roof bears self-weight load.

And a third stage: after the roof bears the load, the prestress tensioning construction is finished step by step according to 50% -80% -100% -sigma con.

And after the construction is finished, carrying out staged synchronous equal-ratio unloading so as to control the stable and safe conversion of the junction system as a target, and finally determining the unloading scheme of the structure through the simulation comparison calculation of the scheme. And calculating according to a design model to obtain the midspan maximum deflection of the inner ring truss of 80mm. According to this value, to the extent that the deformation generated by unloading at each stage is not more than 20mm, the whole unloading process can be divided into 3 stages, each stage is reduced in steps (grading) and the first stage unloading is not more than 15mm.

The unloading is divided into four steps, the displacement amounts are respectively 20%, 50%, 80% and 100%, and the control of the displacement amounts meets the design requirements.

The whole roof is mainly unloaded by the inner truss, namely 10 stress areas generated by temporarily supporting 10 sets of inner rings are slowly and stably unloaded by selecting 10 unloading points of 10 sets of supporting jig frames, so that the main truss structure is completely supported by the self structure in a state of being supported by external force.

Because the outer ring truss has 16 truss supporting jig frames, according to the structural characteristics of the outer ring truss, only 2 sets of jig frames (each set of 1 unloading point) are respectively selected at two ends of the central axis for synchronous and symmetrical unloading in two areas.

When unloading, the adjusting plate is cut by the cutting knife, and unloading is carried out according to the unloading sequence and the unloading cutting quantity each time. The support is carried out by a 32T jack before cutting, the maximum counter force of the lifting node position is about 24T according to lifting simulation calculation, the maximum weight of the first support point of the second section support frame is 4T, and the maximum force simulation maximum force values of the support 1 and the support 2 are 28T. The two support points are used for supporting, each support point is 14T at the maximum, and the support points are cut by a cutter after being supported. And gradually loosening the jack after cutting.

When unloading, the deformation of the adjacent supports is observed at the same time, so that the safety in the unloading process is ensured. When the unloading is completed in one step, the observation is needed to be stopped for half an hour, and when no abnormality exists, the next step is performed.

The above examples merely illustrate specific embodiments of the application, which are described in more detail and are not to be construed as limiting the scope of the application. It should be noted that it is possible for a person skilled in the art to make several variants and modifications without departing from the technical idea of the application, which fall within the scope of protection of the application.

This background section is provided to generally present the context of the present application and the work of the presently named inventors, to the extent it is described in this background section, as well as the description of the present section as not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present application.

Claims (10)

1. The construction method of the space truss with the prestressed structure is characterized by comprising the following steps of:

step 1: modeling through structural software, and designing a hanging point;

step 2: according to the hanging point, determining a prestress tensioning mode based on structural software;

step 3: and carrying out actual construction based on the hanging point and the prestress tensioning mode.

2. The construction method of a space truss with a prestressed structure according to claim 1, wherein said hanging point is set according to a deflection value or a stressed portion.

3. The method for constructing a space truss having a prestressed structure according to claim 1, wherein said step 2 includes: according to the hanging points, setting model parameters based on structural software, and determining an optimal prestress tensioning mode;

the model parameters include: the integral stress ratio of the original structure is not more than 0.8, and the displacement is not more than 1/250.

4. The method for constructing a space truss having a prestressed structure according to claim 1, wherein said step 3 includes the sub-steps of:

step 3.1: constructing a main truss and assembling a jig frame;

step 3.2: lifting;

step 3.3: after lifting in place, aligning the main truss;

step 3.4: performing second-stage installation;

step 3.5: unloading the temporary support after the second section is installed,

and in the steps 3.1-3.5, the prestress step tensioning and the prestress step tensioning are synchronously carried out according to the prestress tensioning mode determined in the step 2.

5. The method for constructing a space truss having a prestressed structure according to claim 4, wherein said prestressing step-wise stretching includes: the first stage is step-by-step pretension when the steel cable is penetrated: the second stage is to prestress tension the truss on the assembly jig frame; the third stage is stretching after lifting;

the prestressing force step-by-step tensioning comprises the following steps: according to a certain prestress change gradient, prestress tensioning is carried out to a preset value in multiple steps;

the prestress tensioning method comprises the following steps of: carrying out prestress steel strand threading according to the sequence from top to bottom and from right to left; and sequentially tensioning the steel strands positioned in opposite directions from bottom to top.

6. The method for constructing a space truss with a prestressed structure according to claim 4, wherein the temporary support is unloaded by a method of phased synchronous equal ratio unloading in step 3.5: and obtaining a mid-span maximum deflection value of the inner ring truss through calculation, and performing graded unloading according to the maximum deflection value and the limit that the deformation generated by unloading at each stage is not more than 20mm, wherein the first stage unloading is not more than 15mm.

7. The method of constructing a space truss having a prestressed structure of claim 6, wherein said unloading temporary support carriers includes:

unloading is carried out from the outside to the inside when the temporary support of the overhanging part is unloaded;

unloading is carried out in the direction from inside to outside when the temporary support seats in the truss main span are unloaded, and the circumferential synchronization is carried out;

and unloading the temporary support seats of the overhanging part and unloading the temporary support seats in the main span of the truss according to the stress change cycle.

8. The construction method of a space truss with a prestressed structure according to claim 4, wherein in step 3.2 and step 3.3, two welding balls at the sections of the main truss are selected as the lower hanging points at the two ends of the main truss; and a lifting lower anchor point is arranged at the upper chord member node of the radial truss, and two diagonal braces are arranged on the side surface of the lifting point of the lifting lower anchor point, so that the replacement of rod pieces and the change of a structural stress system are avoided.

9. The method according to claim 4, wherein in step 3.2 and step 3.3, synchronous monitoring is performed during lifting, and the roof is adjusted when the roof height difference is greater than a predetermined value.

10. The construction method of a space truss with prestressed structure according to claim 4, wherein in step 3.3, the main structure or temporary supporting structure is used to replace the hydraulic equipment to be stressed after the lifting alignment, specifically comprising the following steps: the beam is placed beside the position in place in advance, and after the beam is lifted to the position in place, the beam is immediately installed to the designated position, and then the beam is used for supporting the stress.