[Technology] Discussion on Calculation of Perforated Aluminum Plate Curtain Wall _ Load

Original Title: [Technology] Discussion on Calculation of Perforated Aluminum Curtain Wall I. Application in Engineering Perforated aluminum sheet means a rectangular material of uniform thickness with a rectangular cross section obtained by press working (shearing or sawing) of pure aluminum or aluminum alloy material. Perforation rate, hole diameter, plate thickness and plate type are the key elements, among which perforation rate is the core factor affecting the unit of perforated aluminum plate, and it is the key design factor affecting the expression of visual integrity and reducing building energy consumption. Due to the influence of processing cost, unit weight, unit flatness and other factors, the thickness of perforated aluminum plate used as the outer skin is usually 1. 0 mm ~ 6.0 mm. Glass-Perforated Aluminum Double Curtain Wall Application Examples: Figure 1. Intelligent Manufacturing Technology Research Institute of Hefei University of Technology II. Discussion on Wind Pressure Value of Glass-Perforated Aluminum Curtain Wall Glass-perforated aluminum panel curtain wall, the outer skin is perforated aluminum panel, and the inner skin is glass panel; the outer skin directly bears the wind load However, due to the existence of holes, the wind can act on the inner skin through the holes, and the inner skin also bears the wind load. The values of the wind loads on the two skins are very complex. In practical engineering, the distributions of the external pressure on the outer skin, the internal pressure on the outer skin and the external pressure on the inner skin can be obtained through the simulation of wind tunnel tests, so as to obtain more accurate values of the wind loads on the outer and inner skins. When there is no wind tunnel test report, the author refers to some domestic and foreign wind load codes, double-layer curtain wall codes and related documents, hoping to get ideas and methods that can be used in practical engineering design. 1. Technical Code for Curtain Wall Engineering of Shanghai (DGJ 08-56-2012/J 12028-2012) Article 14.1.6 of Shanghai Code for Curtain Wall specifies the value of wind load for external ventilation double-layer curtain wall. The outer curtain wall bears all the wind load, and the inner curtain wall is reduced according to the ratio of cavity volume to effective ventilation area. By analogy with the glass-perforated curtain wall, it is assumed that the floor height is 3.6m, the curtain wall grid is 1.5m, the size of the middle cavity is 1.0m, and the perforation rate is 40%. The calculation V/Aen = 2.5m, which belongs to the range of 0 ~ 20m, and the proportion of the inner curtain wall bearing the wind is 100%, that is, all of them bear the wind. The wind load of the outer perforated aluminum plate is the same as that of the inner glass curtain wall, and the wind load value of the conventional curtain wall is taken. 2. Eurocode 1: Actions on structures-Part 1-4: General actions-Wind actions BS EN 1991-1-4: 2005 Clause 7.2.10 of the Eurocode specifies in detail the value of the wind pressure on more than one skin. By analogy with glass-perforated aluminum curtain wall, the outer skin is perforated and the inner skin is closed, and the total pressure coefficient of the outer layer is: positive pressure coefficient = 2/3 (conventional external pressure coefficient); negative pressure coefficient = 1/3 (conventional external pressure coefficient). Value of total pressure coefficient of inner layer : normal external pressure coefficient-normal internal pressure coefficient = normal total pressure coefficient. By analogy with the Chinese load code, the local shape coefficient of wind load is as follows: Expand the full text Curtain Wall Type/Area Large Area External Pressure Corner External Pressure Closed Internal Pressure Conventional curtain wall + 1.0-1.4 ± 0.2 Glass-perforated aluminum plate double-layer curtain wall outer layer 0.67-0.470 Inner + 1.0-1.4 ± 0.2 Note: The large face refers to the windward face, and the corner refers to the corner area of the face adjacent to the windward face. 3. Documents related to wind tunnel test The scale of the wind tunnel test model is generally 1:100. Due to the small aperture on the perforated aluminum plate, it is difficult for the wind tunnel test model to simulate the real situation of the perforated aluminum plate. After consulting the relevant literature,keychain tape measure, the conclusions of similar wind tunnel test reports are cited as a reference: (1) “Research on the Wind Load of the Envelope Structure of Changsha Meixi Lake International Culture and Art Center”-State Key Laboratory of Civil Engineering Disaster Prevention, Tongji University, the test model is a partial model, the scale ratio is 1:15, the outer layer of the double-layer curtain wall roof slab is GRC slab, the inner layer is a closed waterproof layer, and the distance between the two layers of skin is about 600 mm. There are 20mm and 50mm seams between the outer GRC plates along the vertical and horizontal directions. Conclusion of the test report: Based on the wind tunnel test results, it can be found that for the double-layer roof panel structure, the wind pressure on the inner surface of the outer layer and the wind pressure on the outer surface of the inner layer at the same position are basically the same, that is, the wind pressure in the cavity is basically the same. On the other hand, when the wind pressure on the outer surface of the outer curtain wall is a positive value,bra tape measure, the wind pressure on the cavity at the corresponding position is also basically a positive value, but the pressure is reduced; similarly, (Suction), the wind pressure at the cavity at the corresponding position is also basically negative, and the absolute value of the pressure is also reduced. These results show that the pressure of the cavity part of the double-deck roof structure is basically related to the wind force on its outer surface, but the absolute value is reduced. Fig. 2 Photo of test model (2) Wind Load Characteristics and Gust Coefficient of Double-layer Curtain Wall of Rectangular Building-School of Civil Engineering and Architecture of Zhejiang University, the wind tunnel test project is Hangzhou Huanglong Comprehensive Office Building, the building plane is rectangular, the curtain wall type is external ventilation double-layer curtain wall, the scale ratio of the test model is 1:100, and holes are opened at the corresponding positions of the external curtain wall to simulate ventilation shutters. The results of the wind tunnel simulation are shown in the following table: The conclusion of the test is that for rectangular (L-shaped) corridor ventilation curtain wall, the wind load of the inner wall can be taken as the value of the single curtain wall, and it is safer; ? When it is located at the long side of the rectangle, it can be reduced appropriately according to the single curtain wall. When it is located at the corner and short side of the rectangle, it needs to be enlarged. (3) “Wind Pressure Distribution Test of Double-layer Curtain Wall of Typical High-rise Building”-School of Civil Engineering and Architecture of Zhejiang University, the wind tunnel test project is Lishui Electric Power Production and Dispatching Center of Zhejiang Province, the building plane is circular with small grooves, the curtain wall type is external ventilation double-layer curtain wall, the permeability rate is 7.2%, and the scale ratio of the test model is 1:150. Holes shall be drilled at corresponding positions on the outer curtain wall to simulate the ventilation louver. The results of the wind tunnel simulation are shown in the following figure: Test conclusion: For the arc-shaped corridor ventilation curtain wall, the wind load of the inner curtain wall can be taken as the value of the single curtain wall, which is safer; ? When it is located in the middle of the arc, it can be reduced appropriately according to the single curtain wall, and when it is located at the end of the arc, bespoken tape measure ,seamstress measuring tape, it needs to be enlarged. Summary: The value of the local shape coefficient of the wind load on the inner and outer layers of the double-layer glass-perforated aluminum panel curtain wall is quite different from that of the single-layer curtain wall.The main influencing factors include the distribution of the double-layer curtain wall on the building surface, the opening of the aluminum panel, the distance between the inner and outer cavities, and the air circulation. When there is no wind tunnel test data in the actual engineering curtain wall design, the local shape coefficient of the curtain wall wind load can refer to the following values (mainly refer to the European standard and wind tunnel conclusions): the local shape coefficient of the outer perforated aluminum plate wind load is 0.67 in the large area, and 1.8 ~ 1.9 in the corner area; the local shape coefficients of the inner glass curtain wall wind load are taken according to the single-layer curtain wall 。 The inner and outer curtain wall panels bear the wind load directly, and the local shape coefficient is not reduced. The local shape coefficient of the supporting keel not directly bearing the wind is reduced according to the subordinate area, and the final calculated wind load value is not less than 1 kPa. III. Calculation and Analysis of Perforated Panel 1. Aluminum plate design of aluminum plate curtain wall In general, stiffeners are set on the back of the aluminum plate to divide the aluminum plate into small grids. The side ribs and middle ribs form constraints on the four sides of the grid plate. The aluminum plate grid is calculated according to the model of the four-side supporting plate. Take the aluminum single plate with a thickness of 2400 mm X 1200 mm and 3 mm as an example, the standard value of wind pressure is 1.5kPa, the stiffeners are arranged along the short side, and the spacing of stiffeners is 800 mm according to the calculation formula of metal plate in Technical Code for Metal and Stone Curtain Wall Engineering (JGJ 133-2001), which meets the requirements of strength and deflection. 2. The perforated aluminum plate has many holes on the plate, which weakens the rigidity of the panel, but at the same time, the wind bearing area of the panel is also reduced, both of which have an impact on the bearing capacity of the perforated plate. According to the actual engineering situation, the perforated aluminum plate is divided into two types: the first type is the plate with regular holes and spatial arrangement of stiffeners without affecting the appearance effect; the second type is the plate with irregular holes or not allowed to arrange stiffeners. The plates analyzed here are all large plates, and the plates with small size and narrow strips are not analyzed (they can be designed according to the conventional aluminum veneer). ① Perforated plate with stiffeners The calculation idea and method are based on the calculation of aluminum veneer, and the grid element and the corresponding edge support model are selected. The finite element method is used to analyze the aluminum plate without opening and the aluminum plate with two opening ratios. ANSYS model (1200×800 mm, 3mm thick, face element Shell163): Panel deformation cloud chart: Summary of calculation results: Aluminum Plate Type Maximum Deflection (mm) Ratio Unperforated aluminium plate 11.371.00 18.7% Perforation aluminum plate 12.68 1.12 32.5% Perforation rate Aluminum plate 13.291.17 It can be seen from the ratio of the results that the maximum deflection of the perforated aluminum plate is larger than that of the non-perforated aluminum plate, and the deflection will increase slightly with the increase of the perforation rate. Considering that the perforation rate is generally not too large in practical engineering (limited by the arrangement of holes), the utilization rate of the calculation results can be controlled below 85% by using the conventional aluminum plate calculation method, which can meet the needs of practical engineering design. ② Perforated plate without stiffener Because the plate is large and there is no stiffener, if we design and calculate according to the design idea of conventional aluminum plate, we can increase the thickness of the perforated plate to improve its stiffness to resist external load, but in actual engineering, the way of increasing the thickness will make the cost too high, which is not suitable for the needs of general engineering. In the standard, the constraint conditions of the folded edges around the metal plate are considered as simply supported edges, and the calculation formula is given according to the classical elastic mechanics plate and shell theory, which has certain limitations. If the constraint conditions of the folded edges around the plate are strengthened, not only the out-of-plane translation of the plate is constrained, but also the in-plane translation is constrained, that is, the displacement in the three directions of X/Y/Z is constrained. In this way, when the panel deforms under external load, the peripheral constraints will pull the panel, thus preventing the further increase of deformation. ANSYS model (1200×2400 mm, 3mm thick, face element): Panel stress and deformation nephogram: From the analysis results of stress and deformation nephogram, it can be seen that the maximum stress is around the holes in the middle of the perforated plate, and the stress distribution is mainly concentrated in the vertical holes parallel to the short side direction and the strip area between the holes. The maximum stress of the two kinds of perforated plates is 27 MPa, which meets the design value of bending strength of 3003-H24 aluminum alloy plate 100 MPa. The maximum deflection occurs in the middle of the panel, and the maximum deflection of the perforated plate is 9. 4 mm, which meets the requirements of the deformation limit. The maximum deformation calculation results are summarized as follows: Aluminum Plate Type 18.9% Perforation Aluminum Plate 33.8% Perforation Aluminum Plate Edge Constraint Case Constrained in Face Unconstrained in Face Constrained in Face Unconstrained in Face Maximum deflection (mm) 9.073 7.44 9.413 8.2 Check the side constraint counterforce. The counterforce of the long side in the in-plane direction is 34 kN, which is converted into a line load of 14.2k N/m. If the connecting bolts are arranged according to @ 200, a single bolt bears a standard shear value of about 3 kN, and the selection of M6 bolts or machine wires can meet the requirements. The lateral force will also have an adverse effect on the support keel in the long side direction. When the left and right grids of the keel are consistent, the adverse effects of the lateral force will offset each other. The keel with only one side grid at the edge needs to resist the load in the direction perpendicular to the panel ? Can also resist the lateral load action of parallel panels. The constraint of edge X/Y/Z can be realized through specific node practices (for reference): Note: The node in Scheme II is quoted from the perforated aluminum plate node on the outer layer of the frame open double-layer curtain wall of the BBVA Bank Project in Mexico. The building height of this project is 234.85 m, the outer panel is made of 3mm thick diamond perforated aluminum plate, the side length is 1.7 m, and the diagonal size is 2686 m2 100m. Fourth, the limitations and shortcomings of this paper. In the part of wind load value of glass-perforated aluminum panel double-skin facade, this paper lists the codes of various countries and the relevant literature and works in recent years, and gives the recommended value of local shape coefficient of wind load on the inner and outer layers of glass-perforated aluminum panel double-skin facade in practical engineering by means of induction, summary and analogy, but there is a lack of real theoretical derivation, actual test data and corresponding verification methods. In the part of the calculation and analysis of the perforated aluminum plate, by comparing the calculation methods and ideas of the standard formula, combined with the calculation results of the finite element analysis, this paper gives the calculation ideas and solutions of two forms of perforated aluminum plate with or without stiffeners. Some of the conclusions made in this paper only represent the author’s own words, if there are more rigorous theoretical basis and ideas, as well as the corresponding experimental data, you are welcome to criticize and correct. References: [1] Load Code for the Design of Building Structures GB 50009-2012 [2] Technical Code for Metal and Stone Curtain Wall Engineering JGJ 133 [3] Technical Code for Double Curtain Wall Engineering QB/JH 102-2008 [4] Technical Code for Curtain Wall Engineering of Shanghai DGJ 08-56-2012/J 12028-2012 [5] Static Calculation Manual of Building Structures Compilation Group of Static Calculation Manual of Building Structures [6] 《Eurocode 1: Actions on structures-Part 1-4:General actions-Wind actions》BS EN1991-1-4:2005 [7] 《Minimum Design Loads for Buildings and Other Structures》ASCE/SEI 7-10 [8] Research on Wind Load of Envelope Structure of Changsha Meixi Lake International Culture and Art Center, State Key Laboratory of Civil Engineering Disaster Prevention, Tongji University [9] Wind Load Characteristics and Gust Coefficient of Double-layer Curtain Wall of Rectangular Building, School of Architecture and Engineering, Zhejiang University [10] Wind Pressure Distribution Test for Double-skin Curtain Wall of Typical High-rise Building, School of Architecture and Civil Engineering, Zhejiang University [11] Research on Simple Calculation of Uniformly Perforated Aluminum Plate under Uniformly Distributed Load, Beijing Jianghe,personalized tape measure, Luo Zhengwu [12] Research on Design of Large Plate Perforated Aluminum Plate without Stiffener, Shenyang yuanda Hongxin; Shenyang Architectural Design Institute Wang Youqing Author: Yang Qing Liao Jie Wang Bin Source: Jianghe Chuangjian Group Co., Ltd. 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