A design method for reducing solar radiation of a section steel combined support

Abstract

The present application belongs to the technical field of foundation pit engineering, and particularly relates to a design method for reducing solar radiation of a steel combined support, comprising the following steps: classifying each steel bar in a steel combined support component; obtaining a first internal force value of each steel bar after classification without considering temperature effect and a second internal force value considering temperature effect; checking the cross-sectional bearing capacity of each steel bar according to the first internal force value and the second internal force value of each steel bar; classifying and adjusting the steel bar whose checking result does not meet the cross-sectional bearing capacity requirement, and returning to step S3 to check the cross-sectional bearing capacity again until the corresponding steel bar meets the cross-sectional bearing capacity requirement; and determining the corresponding blocking material of each type of steel bar according to the type of each steel bar, and covering the blocking material. The method can effectively reduce the temperature effect of the steel combined support and improve the safety and economy of the steel combined support structure.

Description

Technical Field

[0001] This invention belongs to the field of foundation pit engineering technology, specifically relating to a design method for reducing solar radiation from steel composite supports. Background Technology

[0002] With the increasing complexity of urban environments and the extension of construction cycles, truss-type steel composite supports, as a new type of foundation pit support, have been widely used in foundation pit engineering due to their advantages such as rapid construction, environmental friendliness, and controllable deformation. However, steel structures are significantly affected by environmental factors such as temperature changes and solar radiation, leading to temperature variations in the steel. During temperature cycles, the steel's thermal expansion and contraction characteristics cause repeated changes in the internal forces of the members. Simultaneously, the shadows cast by surrounding buildings on some steel support members within the foundation pit result in significant differences in surface temperature across different locations. Therefore, members exposed to solar radiation are prone to loosening of connections and stress concentration, directly impacting the safety of the foundation pit. Thus, reducing the impact of temperature effects on the steel composite supports during foundation pit construction is a crucial aspect.

[0003] Currently, the main countermeasures to address the temperature effect problem faced by steel composite supports are: on the one hand, selecting periods of relatively weak solar radiation for support installation; on the other hand, optimizing the overall layout of the support system, setting reasonable support spacing, etc., to increase the redundancy of the support structure and ensure the safety of the members under stress as much as possible.

[0004] These measures have not yet been widely applied in actual engineering projects, mainly because choosing to construct during periods of weak solar radiation prolongs the construction period and increases project costs. Optimizing the layout of the support system involves a comprehensive consideration of the entire support system structure, requiring solid professional knowledge and practical experience. It is difficult to quantify the effectiveness of the design in reducing temperature effects, resulting in poor practicality. Therefore, there is an urgent need to invent a design method to reduce the solar radiation intensity of steel composite supports. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide a design method for reducing solar radiation in steel composite supports, which can effectively reduce the temperature effect of steel composite supports, improve the safety and economy of steel composite support structures, and provide a solid guarantee for the safety of foundation pits.

[0006] The technical solution of this invention is:

[0007] A design method for reducing solar radiation in steel composite supports includes the following steps:

[0008] S1. Based on the duration of sunlight exposure to different parts of the steel support structure, classify the various steel members in the composite steel support structure.

[0009] S2. Obtain the first internal force value of each type of steel member after classification. Second internal force value Wherein, the first internal force value These are the internal force values ​​of various types of steel members without considering temperature effects; the second internal force value. These are the internal force values ​​of various types of steel members considering temperature effects;

[0010] S3. Based on the obtained first internal force values ​​of each type of steel member. Second internal force value The cross-sectional bearing capacity of various types of steel members is verified.

[0011] S4. For steel members whose verification results do not meet the section bearing capacity requirements, classify and adjust the corresponding steel members, and return to step S3 to verify the section bearing capacity of the classified and adjusted steel members until the corresponding steel members meet the section bearing capacity requirements.

[0012] S5. Based on the categories of the steel rods obtained, determine the corresponding barrier materials for each type of steel rod and cover them with barrier materials.

[0013] Preferably, the method for obtaining the duration variation of sunlight on various parts of the steel support component is as follows: the basic information of the construction site, the fluctuation range of ambient temperature and the fluctuation trend of solar radiation during the construction period are used as input parameters and input into the sunlight analysis software to obtain the shading of the steel support component inside the foundation pit by the shadows cast by surrounding buildings during the construction period, thereby obtaining the duration variation of sunlight on various parts of the steel support component.

[0014] Preferably, the classification method for each steel member in the composite steel support component is as follows: members with sunshine duration varying from 8h to 14h are classified as Class I members; members with sunshine duration varying from 2h to 8h are classified as Class II members; and members with sunshine duration varying from 0h to 2h are classified as Class III members.

[0015] Preferably, the first internal force value of each type of steel member Second internal force value The method to obtain it is as follows:

[0016] Each type of steel rod after classification is simplified into a rod element, and a finite element model is established.

[0017] Without considering temperature effects, a load is applied as the earth pressure exerted by the soil on the steel composite support members during the foundation pit excavation process. This earth pressure is then applied to the finite element model to obtain the first internal force values ​​of each steel member without considering temperature effects. ;

[0018] Under the temperature field of strongest solar radiation in sunshine conditions, the temperature field is transformed into a temperature load. The numerical values ​​of the internal force fluctuations of the steel composite support members caused by the temperature load are input into the finite element model to obtain the second internal force values ​​of each steel member considering the temperature effect. .

[0019] Preferably, the temperature load is determined according to the following formula:

[0020] ,

[0021] In the formula, It is a temperature load; It is the elastic modulus of the steel rod material; It is the linear thermal expansion coefficient of the steel member; It's a temperature change.

[0022] Preferably, the cross-sectional bearing capacity of the steel member is verified based on the following formula:

[0023] ,

[0024] In the formula, It is the gross cross-sectional area of ​​the steel member, in mm²; It is the design value of the bending strength of the steel member in N / mm²; It is the axial force on the steel member, in N; For steel members to rotate in three-dimensional space x The design value of the second-order bending moment of the shaft, in N·mm; For steel members to rotate in three-dimensional space y The design value of the second-order bending moment of the shaft, in N·mm; For steel members to rotate in three-dimensional space x Design value of the bending capacity of the shaft, N·mm; For steel members to rotate in three-dimensional space y Design value of the bending bearing capacity of the shaft, N·mm.

[0025] Preferably, the method for classifying and adjusting the steel members is as follows:

[0026] ① The Class I members are downgraded to Class II members;

[0027] ② The Class I members are downgraded to Class III members;

[0028] ③ Downgrade Class I members to Class II members, and Class II members to Class III members;

[0029] ④ The Class I members will be downgraded to Class III members, and the Class II members will be downgraded to Class III members.

[0030] Preferably, the method for selecting the barrier material is as follows: for Class I rods, a barrier material with a light-blocking rate of 30% to 65% is selected; for Class II rods, a barrier material with a light-blocking rate of 45% to 85% is selected; and for Class III rods, a barrier material with a light-blocking rate of 75% to 95% is selected.

[0031] Preferably, barrier materials with a shading rate of 30% to 65% include low-density polyester tarpaulins. Barrier materials with a shading rate of 45% to 85% include polyvinyl chloride (PVC) plastic film and polyethylene (PE) twill woven tarpaulins. Barrier materials with a shading rate of 75% to 95% include black high-density polyethylene (HDPE) geomembranes.

[0032] Compared with the prior art, the method for reducing solar radiation of composite steel supports according to the present invention has the following beneficial effects:

[0033] (1) This method considers solar radiation factors in the design stage and arranges barrier materials differently to ensure the safety of the foundation pit; in the foundation pit design stage, by analyzing and studying the duration of solar sunshine, it can effectively avoid safety problems caused by solar radiation and provide a solid guarantee for the safety of the foundation pit.

[0034] (2) This method uses the classification design of steel members to cover the steel members with different barrier materials, which is widely applicable and reduces construction costs. By laying the barrier materials, the adverse effects of solar radiation on the stress state of the components are effectively reduced, ensuring the stability of the structural performance. At the same time, it meets the actual engineering needs of reducing costs and improving efficiency, and achieves the organic unity of technical feasibility and economic rationality.

[0035] (3) This method constructs a systematic and complete theoretical framework and analysis approach to reduce the impact of temperature effect on steel components. Through numerical simulation and theoretical derivation, it comprehensively assesses the impact of temperature change on steel components and conducts quantitative analysis on solar radiation blocking performance, providing solid data support for improving the safety of foundation pit steel support components. Attached Figure Description

[0036] Figure 1 This is a flowchart of the method in an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram illustrating the interaction between the steel composite support member and temperature field conditions in an embodiment of the present invention;

[0038] Figure 3 This is a reference table for the light-blocking rate of the barrier material in the embodiments of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0042] See Figure 1 and Figure 2 As shown, in order to effectively reduce the temperature effect of steel composite supports, improve the safety and economy of steel composite support structures, and provide a solid guarantee for the safety of foundation pits, this embodiment provides a design method for reducing solar radiation of steel composite supports, including the following steps:

[0043] S1. Conduct basic information surveys of the construction site and predict environmental temperature fluctuations during the construction period, perform solar radiation analysis, and classify the various steel members in the composite steel support components based on the duration changes of solar radiation on each part of the steel support components.

[0044] Basic information about the construction site includes: foundation pit design data, surrounding environment of the foundation pit, distance between surrounding buildings and the foundation pit, surrounding building structure, infrastructure and underground pipeline conditions.

[0045] Method for obtaining the duration variation of sunlight on various parts of the steel support structure: The basic information of the construction site, the fluctuation range of ambient temperature and the fluctuation trend of solar radiation during the construction period are used as input parameters. These are input into a sunlight analysis software (preferably Tianzheng Architecture Software, which can obtain three-dimensional information from each floor plan, combine floor plans, generate elevation and section views by removing hidden elements, and perform rendering to produce effect diagrams, helping designers to more intuitively display design results). The results show the shading of the surrounding buildings' shadows on the steel support structure inside the foundation pit during the construction period, thus obtaining the duration variation of sunlight on various parts of the steel support structure.

[0046] Based on the obtained data on the duration of sunshine affecting various parts of the steel support structure, the steel members were classified as follows: Class I members had sunshine duration of 8-14 hours; Class II members had sunshine duration of 2-8 hours; and Class III members had sunshine duration of 0-2 hours. Furthermore, based on the received sunshine duration and the peak temperature rise during the sunshine period, the steel members were further classified as follows: Class I members experienced a temperature increase of 10%-20%; Class II members experienced a temperature increase of 5%-10%; and Class III members experienced a temperature increase of 0%-5%.

[0047] S2. Obtain the first internal force value of each type of steel member after classification. Second internal force value Among them, the first internal force value These are the internal force values ​​of various types of steel members without considering temperature effects; the second internal force value. These are the internal force values ​​of various types of steel members considering temperature effects.

[0048] First internal force values ​​of various types of steel members Second internal force value The method to obtain it is as follows:

[0049] Each type of steel member after classification is simplified into a bar element, and a finite element model is established. On the one hand, without considering the temperature effect, a load is applied as the earth pressure exerted by the soil on the steel composite support member during the foundation pit excavation process. The earth pressure is loaded into the finite element model to obtain the first internal force value of each type of steel member without considering the temperature effect. On the other hand, under the temperature field with the strongest solar radiation during sunshine, the temperature field is transformed into a temperature load. The numerical values ​​of the internal force fluctuations of the steel composite support members caused by the temperature load are imported into the finite element model to obtain the internal force distribution of the steel composite support members under the action of the temperature load. In this way, the second internal force values ​​of each steel member are obtained when considering the temperature effect. .

[0050] like Figure 2 As shown, the temperature field with the greatest solar radiation needs to consider the following conditions: heat exchange and convection between atmospheric temperature and steel members, reflected radiation from the ground, total solar radiation, direct solar radiation on steel members, scattered solar radiation, and shading radiation from the atmosphere and clouds.

[0051] The formula for calculating temperature load is as follows: In the formula, It is a temperature load (stress in steel members caused by temperature changes). It is the elastic modulus of the steel rod material; It is the linear thermal expansion coefficient of the steel member; It's a temperature change.

[0052] S3. Based on the obtained first internal force values ​​of each type of steel member. Second internal force value The cross-sectional bearing capacity of various steel members is verified. Specifically, according to the current national standard "Standard for Design of Steel Structures" GB 50017-2017, the direct analysis design method is used to verify the cross-sectional bearing capacity of steel members. The bearing capacity of steel members should meet the following requirements:

[0053] ,

[0054] In the formula, It is the gross cross-sectional area of ​​the steel member, in mm²; It is the design value of the bending strength of the steel member in N / mm²; It is the axial force on the steel member, in N; For steel members to rotate in three-dimensional space x The design value of the second-order bending moment of the shaft, in N·mm; For steel members to rotate in three-dimensional space y The design value of the second-order bending moment of the shaft, in N·mm; For steel members to rotate in three-dimensional space x Design value of the bending capacity of the shaft, N·mm; For steel members to rotate in three-dimensional space y Design value of the bending bearing capacity of the shaft, N·mm.

[0055] S4. For steel members whose verification results do not meet the section bearing capacity requirements, implement classified adjustments (temperature effect reduction schemes), and implement them one by one according to the following four schemes:

[0056] ① The Class I pole will be downgraded to Class II pole;

[0057] ② The Class I pole will be downgraded to Class III pole;

[0058] ③ Downgrade Class I poles to Class II poles, and Class II poles to Class III poles;

[0059] ④ Downgrade Class I poles to Class III poles, and Class II poles to Class III poles.

[0060] For each temperature reduction scheme implemented, the process must return to step S3 to perform a cross-sectional bearing capacity verification (safety verification) on the steel members for which the temperature reduction scheme is implemented. If the safety requirements are met, the design documents can be generated; if the safety requirements are not met, the next temperature reduction scheme is adopted until the safety specifications are met, and the final design documents are generated.

[0061] S5. Based on the final classification of each type of steel member, determine the corresponding barrier material for each type of steel member and apply the barrier material. The selection method for barrier materials is as follows: for Class I members, use barrier materials with a shading rate of 30%~65%; for Class II members, use barrier materials with a shading rate of 45%~85%; and for Class III members, use barrier materials with a shading rate of 75%~95%.

[0062] See Figure 3 As shown, barrier materials with a shading rate of 30% to 65% include low-density polyester tarpaulins. Barrier materials with a shading rate of 45% to 85% include polyvinyl chloride (PVC) plastic film and polyethylene (PE) twill woven tarpaulins. Barrier materials with a shading rate of 75% to 95% include black high-density polyethylene (HDPE) geomembranes.

[0063] Based on the above-mentioned design method for reducing solar radiation through steel composite supports, it has the following advantages compared with existing technologies:

[0064] (1) This method considers solar radiation factors in the design stage and arranges barrier materials differently to ensure the safety of the foundation pit; in the foundation pit design stage, by analyzing and studying the duration of solar sunshine, it can effectively avoid safety problems caused by solar radiation and provide a solid guarantee for the safety of the foundation pit.

[0065] (2) This method uses the classification design of steel members to cover the steel members with different barrier materials, which is widely applicable and reduces construction costs. By laying the barrier materials, the adverse effects of solar radiation on the stress state of the components are effectively reduced, ensuring the stability of the structural performance. At the same time, it meets the actual engineering needs of reducing costs and improving efficiency, and achieves the organic unity of technical feasibility and economic rationality.

[0066] (3) This method constructs a systematic and complete theoretical framework and analysis approach to reduce the impact of temperature effect on steel components. Through numerical simulation and theoretical derivation, it comprehensively assesses the impact of temperature change on steel components and conducts quantitative analysis on solar radiation blocking performance, providing solid data support for improving the safety of foundation pit steel support components.

[0067] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A design method for reducing solar radiation in composite steel supports, characterized in that, Includes the following steps: S1. Based on the duration of sunlight exposure to different parts of the steel support structure, classify the various steel members in the composite steel support structure. S2. Obtain the first internal force value of each type of steel member after classification. Second internal force value Wherein, the first internal force value These are the internal force values ​​of various types of steel members without considering temperature effects; the second internal force value. These are the internal force values ​​of various types of steel members considering temperature effects; S3. Based on the obtained first internal force values ​​of each type of steel member. Second internal force value The cross-sectional bearing capacity of various types of steel members is verified. S4. For steel members whose verification results do not meet the section bearing capacity requirements, classify and adjust the corresponding steel members, and return to step S3 to verify the section bearing capacity of the classified and adjusted steel members until the corresponding steel members meet the section bearing capacity requirements. S5. Based on the categories of the steel rods obtained, determine the corresponding barrier materials for each type of steel rod and cover them with barrier materials.

2. The method for reducing solar radiation through composite steel supports according to claim 1, characterized in that, The method for obtaining the duration variation of sunlight on various parts of the steel support components is as follows: The basic information of the construction site, the fluctuation range of ambient temperature and the fluctuation trend of solar radiation during the construction period are used as input parameters and input into the sunlight analysis software to obtain the shading of the steel support components inside the foundation pit by the shadows cast by surrounding buildings during the construction period, thereby obtaining the duration variation of sunlight on various parts of the steel support components.

3. The method for reducing solar radiation through composite steel supports according to claim 1, characterized in that, The classification method for the various steel members in the composite steel support structure is as follows: members with sunshine duration varying from 8h to 14h are classified as Class I members; members with sunshine duration varying from 2h to 8h are classified as Class II members; and members with sunshine duration varying from 0h to 2h are classified as Class III members.

4. The method for reducing solar radiation through composite steel supports according to claim 1, characterized in that, The first internal force value of each type of steel member Second internal force value The method to obtain it is as follows: Each type of steel rod after classification is simplified into a rod element, and a finite element model is established. Without considering temperature effects, a load is applied as the earth pressure exerted by the soil on the steel composite support members during the foundation pit excavation process. This earth pressure is then applied to the finite element model to obtain the first internal force values ​​of each steel member without considering temperature effects. ; Under the temperature field of strongest solar radiation in sunshine conditions, the temperature field is transformed into a temperature load. The numerical values ​​of the internal force fluctuations of the steel composite support members caused by the temperature load are input into the finite element model to obtain the second internal force values ​​of each steel member considering the temperature effect. .

5. The method for reducing solar radiation through composite steel supports according to claim 4, characterized in that, The temperature load is determined according to the following formula: ， In the formula, It is a temperature load; It is the elastic modulus of the steel rod material; It is the linear thermal expansion coefficient of the steel member; It's a temperature change.

6. The method for reducing solar radiation through composite steel supports according to claim 1, characterized in that, The cross-sectional bearing capacity of the steel member is verified based on the following formula. ， In the formula, It is the gross cross-sectional area of ​​the steel member, in mm²; It is the design value of the bending strength of the steel member in N / mm²; It is the axial force on the steel member, in N; For steel members to rotate in three-dimensional space x The design value of the second-order bending moment of the shaft, in N·mm; For steel members to rotate in three-dimensional space y The design value of the second-order bending moment of the shaft, in N·mm; For steel members to rotate in three-dimensional space x Design value of the bending capacity of the shaft, N·mm; For steel members to rotate in three-dimensional space y Design value of the bending bearing capacity of the shaft, N·mm.

7. The method for reducing solar radiation through composite steel supports according to claim 3, characterized in that, The method for classifying and adjusting the steel members is as follows: ① The Class I members are downgraded to Class II members; ② The Class I members are downgraded to Class III members; ③ Downgrade Class I members to Class II members, and Class II members to Class III members; ④ The Class I members will be downgraded to Class III members, and the Class II members will be downgraded to Class III members.

8. The method for reducing solar radiation through composite steel supports according to claim 3, characterized in that, The method for selecting the barrier material is as follows: for Class I poles, a barrier material with a light-blocking rate of 30% to 65% is selected; for Class II poles, a barrier material with a light-blocking rate of 45% to 85% is selected; and for Class III poles, a barrier material with a light-blocking rate of 75% to 95% is selected.

9. The method for reducing solar radiation through composite steel supports according to claim 8, characterized in that, Barrier materials with a shading rate of 30% to 65% include low-density polyester tarpaulins; barrier materials with a shading rate of 45% to 85% include polyvinyl chloride plastic film and polyethylene twill woven tarpaulins; and barrier materials with a shading rate of 75% to 95% include black high-density polyethylene geomembrane.

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