Wind-resistant design method for oversized overhanging balcony

Abstract

The invention relates to the field of building design, and provides a wind-resistant design method for a super-large overhanging balcony in order to facilitate wind-resistant design of the super-large overhanging balcony, which comprises the following steps: step 1, extracting a typical section based on a building design scheme, the typical section being a minimum unit of a building in periodic change; 2, the balcony in the typical section is partitioned according to the stress condition of the balcony; step 3, establishing a numerical model based on the typical section and arranging monitoring points; 4, setting a numerical simulation experiment condition, and testing under different wind direction angles to obtain the wind pressure moment of each monitoring point; step 5, extracting extreme points in all wind pressure moments; and 6, judging whether the distribution condition of the wind pressure moment extreme value meets the requirement or not based on the inspection standard, if not, adjusting and optimizing the building design scheme, and repeating the steps 2-6 until the distribution condition of the wind pressure moment extreme value meets the requirement. By the adoption of the mode, wind resistance design can be conveniently conducted on the oversized overhanging balcony.

Description

Technical Field

[0001] The invention relates to the field of architectural design, in particular to a wind-resistant design method for an ultra-large overhanging balcony. Background Art

[0002] In the prior art, the balcony usually does not consider the wind load, and only needs to carry out the structural design of the combined control of the dead load and live load. This is because the wind load of the traditional balcony is small, and because the cantilever length is not large, the structural response of the wind load is small compared to the dead load and live load, and it does not play a control role. When designing the structure, the load combination of the dead load + live load is used as the control load to ensure the safety of the structure.

[0003] However, the increase in the cantilever length and platform area of ​​super-large overhanging balconies (overhanging length exceeds 2.5m, even reaches 4-5m, and the balcony area exceeds 20 square meters) leads to an increase in the wind load area, and the effect of wind load can no longer be ignored. In addition, due to the increase in the size of the balcony, it has changed from an original building exterior surface appendage to an aerodynamic shape component of the entire building. Therefore, targeted wind resistance design for super-large overhanging balconies has become an indispensable step, and how to carry out wind resistance design has become an urgent problem to be solved. Summary of the invention

[0004] In order to facilitate the wind-resistant design of extra-large extended balconies, the present application provides a wind-resistant design method for extra-large extended balconies.

[0005] The technical solution adopted by the present invention to solve the above problems is:

[0006] Wind resistance design methods for extra-large extended balconies include:

[0007] Step 1, extracting a typical segment based on the architectural design plan, wherein the typical segment is the smallest unit of the building showing periodic changes; in the architectural design plan, the dimensions of the balcony are length B and width d, the height between two adjacent balconies is h, the vertical projection overlap width between two adjacent balconies is b, and the distance between the balcony and the corner of the building is l;

[0008] Step 2, partition the balconies in the typical section according to the stress conditions of the balconies;

[0009] Step 3: Establish a numerical model based on the typical section and arrange monitoring points;

[0010] Step 4, setting numerical simulation experimental conditions and conducting experiments under different wind direction angles to obtain the wind pressure at each monitoring point and calculate the wind pressure moment;

[0011] Step 5: Extract all the extreme points in the wind pressure moments. The extreme point is defined as the point with the largest wind pressure moment value among a total of 9 points in its surrounding circle. For the 8 monitoring points around the extreme point, if the difference between the wind pressure moment and the value of the extreme point is less than x%, they are also regarded as extreme points;

[0012] Step 6: Based on the inspection criteria, judge whether the distribution of the extreme values of the wind pressure moment meets the requirements. If not, adjust and optimize the building design plan, and repeat Steps 2 - 6 until the distribution of the extreme values of the wind pressure moment meets the requirements.

[0013] Further, Step 2 is specifically as follows:

[0014] The range of length l1 at one end of the balcony close to the building corner is defined as Zone I, the range of length b within the overlapping projection area of the upper and lower balconies is defined as Zone III, and the remaining intermediate range of length l2 is defined as Zone II; each zone is further divided into inner and outer parts, with a total of six zones: outer I, outer II, outer III, inner I, inner II, and inner III. Among them, l1 + l2 + b = B.

[0015] Further, in Step 2, the basis for the inner - outer division is: the outer 1 / 3d is the outer zone, and the inner 2 / 3d is the inner zone.

[0016] Further, in Step 2, if l2 is greater than l1, then take l1 = l; otherwise, take l1 = l2 = (B - b) / 2.

[0017] Further, in Step 3, the layout method of the monitoring points is: starting from the outermost edge of the balcony, arrange n rows of monitoring points at equal intervals along the width direction.

[0018] When l1 < l2, at least three columns of monitoring points are arranged in Zone I, with at least one column centered and the left and right sides close to the area boundary lines; at least four columns of monitoring points are arranged in Zone II, with at least two columns centered and the left and right sides close to the area boundary lines.

[0019] When l1 = l2, at least three columns of monitoring points are arranged in both Zone II and Zone I, with at least one column centered and the left and right sides close to the area boundary lines.

[0020] When b ≤ l2, at least three columns of monitoring points are arranged in Zone III, with at least one column centered and the left and right sides close to the area boundary lines.

[0021] When b > 12, at least four columns of monitoring points are arranged in Zone III, with at least two columns centered and the left and right sides close to the area boundary lines.

[0022] Further, in Step 3, the measuring points in the centered arrangement are arranged at equal intervals.

[0023] Furthermore, the calculation method of the wind pressure moment in step 4 is: establish a coordinate system with the point on the intersection line of the balcony and the building as the origin, and set Pu i,j is the surface wind pressure at the monitoring point P(i, j), Pd i,j is the surface wind pressure under the monitoring point P(i, j), then the wind pressure moment MP is: MP i,j =P i,j ×j,P i,j =Pu i,j -Pd i,j .

[0024] Furthermore, in step 6, the inspection standard is: the number of extreme points in the six partitions except the inner II zone does not exceed 1, more than k% of the extreme points are located in the inner zone, and more than k% of the extreme points in the inner zone are located in the inner II zone.

[0025] Furthermore, the method for adjusting and optimizing the architectural design scheme in step 6 includes:

[0026] When more than half of the extreme points fall in zone I, adjust l;

[0027] When more than half of the extreme points fall in zone III, adjust b;

[0028] When more than half of the extreme points fall in the outer area, adjust d;

[0029] When the extreme point appears at the corner of the outer I or outer III zone, the balcony at that location will be changed to an arc shape.

[0030] Furthermore, in step 4, the incoming flow direction from the balcony directly opposite is 0°, and within the range of positive and negative 45°, a wind direction angle of every 15° is taken, and a total of 7 incoming flow direction conditions are used for numerical simulation.

[0031] Compared with the prior art, the present invention has the following beneficial effects: the balcony is partitioned based on the stress conditions of the balcony, monitoring points are arranged in each partition, wind load evaluation is achieved by calculating the wind pressure moment of the monitoring point, and wind resistance design optimization is performed according to the wind load evaluation result. The evaluation index of this method is simple, with only a single index of wind pressure moment; the analysis logic is simple, with only one logical main line, and there is no need to perform multi-dimensional and multi-level alternating analysis, so the analysis efficiency is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A flow chart of the wind-resistant design method for extra-large extended balconies;

[0033] Figure 2 It is a typical segment schematic diagram;

[0034] Figure 3 Design stereograms for architectural sections;

[0035] Figure 4 Design elevations for building sections;

[0036] Figure 5 This is a schematic diagram of the balcony partition;

[0037] Figure 6 It is a schematic diagram of the numerical model;

[0038] Figure 7 This is a schematic diagram of the measurement point layout;

[0039] Figure 8 It is the location map of the measuring points;

[0040] Fig. 9 Schematic diagram for setting boundary conditions for numerical models;

[0041] Fig.10 It is a schematic diagram of the simulated working condition;

[0042] Fig.11 It is a schematic diagram of the extreme value distribution of wind pressure moment;

[0043] Fig.12 An example of the extreme value distribution of wind pressure moment to meet the inspection requirements. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] like Figure 1 As shown in the figure, the wind-resistant design method for the extra-large extended balcony includes:

[0046] Step 1: extract typical segments based on the architectural design scheme, where the typical segments are the smallest units showing periodic changes in the building.

[0047] The large extension platforms are basically high-rise and super high-rise residential buildings. These buildings have the same characteristics, that is, the appearance is almost unchanged and shows periodic changes. Because the most significant influence on the wind load of the platform is the flow state of the wind field above and below the platform, there is almost no mutual influence between multiple platforms. Therefore, the first step is to select a typical segment: intercept a part of its regular periodic changes and take a group as a typical segment, such as Figure 2 As shown, in order to show the periodic variation pattern and facilitate parameterized annotation, the display diagram only captures two typical segments for illustration.

[0048] According to the air flow conditions of conventional building surfaces and cantilevered panels, the key dimensions of the structural design are parameterized. Since the corners of the building are the main places where airflow separates and forms vortices, the distance between the balcony and the corner of the building is defined as l. The upper and lower balconies constrain the movement of the airflow in the vertical direction, causing a large number of vortices to remain in this area. The energy cannot diffuse outward and will act on the balcony. The distance between the upper and lower balconies is defined as h. Taking the schematic diagram as an example, the distance between the upper and lower balconies of the same specification is 2h, while the distance between two adjacent balconies of different specifications is only h. The reduction in the distance between the balconies will inevitably increase the wind load at the corresponding position, so it is necessary to focus on inspecting this part, and the vertical projection overlapping width is defined as b. At the same time, the size of the balcony itself is also an important influencing factor. The balcony length is defined as B, and the cantilever length (width) is defined as d. See the details. Figure 3 , Figure 4 The sizes of the two staggered balconies can be the same, both length B and width d, or different, respectively length B1 width d1 and length B2 width d2. This embodiment is described by taking the same sizes as an example.

[0049] Step 2: Partition the balconies in the typical section according to the stress conditions of the balconies.

[0050] Since the wind load on the balcony will be affected by its own geometric dimensions, the shape of the facade of the main structure to which it is attached, and interference from other balconies, and the influence range and location of various factors are also different, the balcony can be divided into different influence zones accordingly. The wind will separate in front of the balcony to form a vortex and then attach to the structure, so that the outside is mainly controlled by the negative pressure of the separation vortex, while the inside is mainly affected by the impact and slip caused by the re-attachment of the separation vortex. Therefore, the inside and outside have significantly different wind load characteristics, and can be divided into outer and inner zones; in the overlapping area of ​​staggered balconies, the distance between the platforms becomes smaller, the movement space of the airflow after separation on the outside of the balcony is reduced, and the vertical constraint increases, which may cause a more violent back and forth impact between the upper and lower platforms and escape horizontally; the airflow at the corner of the building separates to form a large number of vortices, and the side of the balcony close to the corner will be affected by it; the middle of the balcony is mainly affected by the wind load caused by the flow directly opposite the balcony. Therefore, the balcony can be divided along the length direction:

[0051] The length l1 of the balcony near the corner of the building is defined as Zone I, and the overlapping area d of the balcony projections on the upper and lower sides is defined as Zone III. The remaining length l2 in the middle is Zone II. Each zone is further divided into inner and outer areas, with the outer 1 / 3d as the outer area and the inner 2 / 3d as the inner area. The inner and outer areas can also be divided according to actual conditions. So there are a total of six zones: outer I, outer II, outer III, inner I, inner II, and inner III. l1+l2+b=B, such as Figure 5As shown in the figure. The range of Zone I affected by the corner vortex is taken as the width equal to the distance from the balcony to the corner, i.e., l1 = l; if l2 < l1, then l1 = l2 = (B - b) / 2, that is, the range of Zone II is not less than that of Zone I. This is because Zone I is affected by the diffusion of the separated vortex at the corner of the building main body, while Zone II is the main area directly impacted by the oncoming flow, and the wind load on Zone II has a greater impact on the overall wind load.

[0052] According to the relative position relationship of the balconies, the following two special cases may exist.

[0053] (1) If the balconies overlap completely vertically, then l2 = 0, and b = B - l1, that is, only Zone I and Zone III remain.

[0054] (2) If the balconies are completely misaligned vertically, then b = 0, that is, only Zone I and Zone II remain.

[0055] Step 3: Establish a numerical model based on the typical section and arrange monitoring points.

[0056] Use various 3D modeling software to create a geometric model, export the geometric information of the model, and import it into ICEM or Meshing to establish a numerical model. Perform structured grid division on the numerical model and densify the grid around the building.

[0057] When establishing the model for numerical calculation analysis, it is sufficient to include three typical sections. The building main body extends upward and downward by no less than 4h in length, so as to provide vertical development space for the flow field. Designate the middle group as the test section, as Figure 6 shown. All calculations are carried out on this test section.

[0058] Both the upper and lower surfaces of the balcony are subject to wind load. Therefore, monitoring points are arranged on the upper and lower surfaces of the platform, and the upper and lower points correspond one by one. The outermost monitoring points should be arranged at the outermost edge positions.

[0059] As Figure 7 shown, in this embodiment, 6 points are evenly distributed at intervals of 1 / 5d in width. Since the innermost point is very close to the outer wall and the effect of the wind load is not significant, the innermost point is ignored, and only the outer five points are left. Multiple rows of measurement points can also be set according to the actual situation.

[0060] When l1 < l2, three columns of measurement points are arranged in Zone I, with the left and right sides closely adjacent to the regional boundary lines and one column arranged in the middle; four columns of measurement points are arranged in Zone II, with the left and right sides closely adjacent to the regional boundary lines and two columns arranged equidistantly in the middle;

[0061] When b ≤ l2, three columns of measurement points are arranged in Zone III, with the left and right sides closely adjacent to the regional boundary lines and one column arranged in the middle;

[0062] When b>12, four rows of measuring points are arranged in Zone III, with the left and right sides close to the area boundary and two rows arranged in the middle;

[0063] When l1=l2, zone II is arranged in three columns like zone I.

[0064] If the length of each partition is long, several more columns of measuring points can be set in the middle of each area according to the actual situation to improve accuracy.

[0065] In order to distinguish, locate and confirm the relative position relationship of each measuring point, two coordinate axes, i and j, are defined along the length and width directions respectively. The coordinates represent the sequence relationship, such as Figure 8 shown.

[0066] Step 4: Set the numerical simulation experimental conditions and conduct experiments under different wind direction angles to obtain the wind pressure at each monitoring point and calculate the wind pressure moment.

[0067] The numerical simulation was performed using computational fluid dynamics simulation software ANSYS Fluent. The turbulence model was selected as LES large eddy simulation. Figure 6 In the proposed model, the boundary conditions of the flow domain are symmetrical boundaries at the top, bottom, left and right, the velocity inlet at the inlet, and the pressure outlet at the outlet. Since the wind speed of the surface boundary layer is small near the ground, the wind load on the balcony of the lower floor is small, while the wind speed at the high place is large, and the wind speed and turbulence intensity change trend is small. Therefore, the inlet velocity is taken as a constant value, and the turbulence intensity at the corresponding height of the balcony is selected as the turbulence characteristic of the incoming flow according to the turbulence intensity profile specified in the building structure load code, such as Fig. 9 shown.

[0068] Because the flow field around the balcony will be significantly different under different impact angles, the wind load will be greatly different. Fig.10 As shown in the figure, the incoming flow direction from the balcony opposite is 0°, and the numerical simulation is performed every 15° in the range of positive and negative 45°. After numerical simulation, the wind pressure time history data of each measuring point is obtained.

[0069] Since the force arm in the outer zone is larger, instantaneous strong load may cause sudden damage, so pulsating wind pressure is used at the measuring points in the outer zone and average wind pressure is used at the measuring points in the inner zone.

[0070] Since balconies are mostly plate structures with a thickness much smaller than their length and width, the loads on the upper and lower surfaces act together on one component. Therefore, it is sufficient to superimpose the loads on the upper and lower surfaces as a single overall wind load, without having to discuss the wind load effects on the upper and lower surfaces separately. i,j is the wind pressure on the upper surface, Pd i,j is the wind pressure on the lower surface, and the wind pressures at corresponding positions on the upper and lower surfaces are superimposed, P i,j =Pui,j -Pd i,j (j=4, 5 are pulsation values, j=1~3 are average values)

[0071] Since the monitoring points are evenly distributed along the width direction, there is no need to perform complex statistical calculations on the actual position of each point. Instead of using its j-direction coordinates to replace its arm as the moment coefficient, the wind pressure moment MP of each point can be obtained by multiplying the wind pressure and moment coefficient at each point: MP i,j =P i,j ×j.

[0072] After calculation, the overall wind pressure moment distribution of the balcony at different wind direction angles can be obtained.

[0073] Step 5, extract the extreme point among all wind pressure moments, the extreme point is defined as the point with the largest wind pressure moment value among a total of 9 points in a circle around it, and the wind pressure moments of the 8 monitoring points in a circle around the extreme point whose difference with the extreme point value is less than x% are also regarded as extreme points; in this embodiment, x is 10, and it can also be taken according to actual needs.

[0074] Step 6: Based on the inspection standard, determine whether the distribution of wind pressure moment extreme values ​​meets the requirements. If not, adjust and optimize the building design plan, and repeat steps 2-6 until the distribution of wind pressure moment extreme values ​​meets the requirements.

[0075] Mark the several wind pressure moment extreme points extracted in step 5 on the measurement point distribution diagram, as shown in Fig.11 As shown, the white dots are the extracted wind pressure moment extreme points. The wind load on the balcony is evaluated according to the wind pressure moment extreme value distribution to test the aerodynamic performance of the balcony. The test criteria are as follows: the number of extreme points in the six partitions except for the inner II zone does not exceed 1; more than k% of the extreme points are located in the inner zone, and more than k% of the extreme points in the inner zone are located in the inner II zone. In this embodiment, k is 60. An example of the wind pressure moment extreme value distribution that meets the test requirements is shown in Fig.12 shown.

[0076] If the extreme value distribution of wind pressure moment does not meet the inspection standard, the corresponding structural parameters of the balcony shall be adjusted and optimized according to the following optimization method.

[0077] Optimization method 1: When more than half of the extreme points fall in zone I, it means that the airflow in zones II and III is relatively gentle, while the airflow disturbance in zone I is large and the flow field is intense. Therefore, l can be adjusted, that is, the distance between the balcony and the corner of the building can be changed.

[0078] Optimization method 2: When more than half of the extreme points fall in zone III, it means that a large number of separation vortices appear in the airflow between the upper and lower balconies and oscillate back and forth between the platforms, causing severe loads. At this time, b can be adjusted to change the relative staggered position between the upper and lower balconies, thereby reducing vortices and quickly attenuating and dissipating them.

[0079] Optimization method 3: When more than half of the extreme points fall in the outer area, it means that the airflow separates in front of the balcony and forms a violent vortex. At this time, d can be adjusted to control the vortex separation condition.

[0080] Optimization method 4: If it appears at the corner of the outer I or outer III zone ( Fig.12 If the balcony is in the lower left or lower right corner of the center, you can consider changing the local structure and making the balcony in that place into an arc shape.

[0081] The adjusted and optimized building will be re-tested and optimized according to steps 2-6. When the test results meet the test standards, the wind-resistant design is completed.

Claims

1. The wind-resistant design method for super-large extended balconies is characterized by: Including: Step 1: Extract typical segments based on the architectural design scheme. The typical segment is the smallest unit with periodic changes in the building. In the architectural design scheme, the balcony has a length of B, a width of d, the height between adjacent balconies is h, the vertically projected overlapping width between adjacent balconies is b, and the distance from the balcony to the building corner is l. Step 2: Divide the balconies in the typical segment according to the force conditions of the balconies. Step 3: Establish a numerical model based on the typical segment and arrange monitoring points. Step 4: Set the numerical simulation experimental conditions and conduct tests under different wind direction angles to obtain the wind pressure at each monitoring point and calculate the wind pressure moment. Step 5: Extract the extreme points among all the wind pressure moments. The extreme point is defined as the point with the largest wind pressure moment value among a total of 9 points in its surrounding circle. For the 8 monitoring points around the extreme point where the difference between the wind pressure moment and the value of this extreme point is less than x%, they are also regarded as extreme points. Step 6: Judge whether the distribution of the extreme values of the wind pressure moment meets the requirements based on the inspection criteria. If not, adjust and optimize the architectural design scheme, and repeat Steps 2 - 6 until the distribution of the extreme values of the wind pressure moment meets the requirements.

2. The wind-resistant design method for a super-large overhanging balcony according to claim 1 is characterized in that: The specific content of Step 2 is as follows: The range within the length l1 at the end of the balcony close to the building corner is defined as Zone I, the range within the overlapping area b of the projections of the upper and lower balconies is defined as Zone III, and the remaining middle position with a length range of l2 is Zone II. Each zone is further divided into inner and outer parts, resulting in a total of six zones: outer I, outer II, outer III, inner I, inner II, and inner III. Among them, l1 + l2 + b = B.

3. The wind-resistant design method for a super-large overhanging balcony according to claim 2 is characterized in that: In Step 2, the basis for the inner and outer division is: the outer 1 / 3d is the outer zone, and the inner 2 / 3d is the inner zone.

4. The wind-resistant design method for a super-large overhanging balcony according to claim 2 is characterized in that: In Step 2, if l2 is greater than l1, then take l1 = l; otherwise, take l1 = l2 = (B - b) / 2.

5. The wind-resistant design method for a super-large overhanging balcony according to claim 2 is characterized in that: In Step 3, the arrangement method of the monitoring points is: starting from the outermost edge of the balcony, arrange n rows of monitoring points at equal intervals along the width direction. When l1 < l2, at least three columns of monitoring points are arranged in Zone I, with the left and right sides closely attached to the area boundary lines, and at least one column is arranged in the middle; at least four columns of monitoring points are arranged in Zone II, with the left and right sides closely attached to the area boundary lines, and at least two columns are arranged in the middle. When l1 = l2, at least three columns of monitoring points are arranged in both Zone II and Zone I, with the left and right sides closely attached to the area boundary lines, and at least one column is arranged in the middle. When b ≤ l2, at least three columns of monitoring points are arranged in Zone III, with the left and right sides closely attached to the area boundary lines, and at least one column is arranged in the middle. When b > l2, at least four columns of monitoring points are arranged in Zone III, with the left and right sides closely attached to the area boundary lines, and at least two columns are arranged in the middle.

6. The wind-resistant design method for a super-large overhanging balcony according to claim 5 is characterized in that: In Step 3, the monitoring points arranged in the middle of each column are arranged at equal intervals.

7. The wind-resistant design method for a super-large overhanging balcony according to claim 6 is characterized in that: The calculation method of the wind pressure moment in step 4 is: establish a coordinate system with the point on the intersection line of the balcony and the building as the origin, and set Pu i,j is the surface wind pressure at the monitoring point P(i, j), Pd i,j is the surface wind pressure under the monitoring point P(i, j), then the wind pressure moment MP is: MP i,j =P i,j ×j,P i,j =Pu i,j -Pd i,j .

8. The wind-resistant design method for a super-large extended balcony according to claim 2 is characterized in that: In Step 6, the inspection criteria are: the number of extreme points in the other regions except the inner II region among the six regions does not exceed 1, more than k% of the extreme points are located in the inner region, and more than k% of the extreme points in the inner region are located in the inner II region.

9. The wind-resistant design method for a super-large overhanging balcony according to claim 8 is characterized in that: The method for adjusting and optimizing the architectural design scheme in Step 6 includes: When more than half of the extreme points fall in Zone I, adjust l; When more than half of the extreme points fall in Zone III, adjust b; When more than half of the extreme points fall in the outer region, adjust d; When the extreme point appears at the corner of the outer I or outer III zone, the balcony at that location will be changed to an arc shape.

10. The wind-resistant design method for a super-large overhanging balcony according to any one of claims 1 to 9, characterized in that: In step 4, the incoming flow direction from the balcony directly opposite is 0°, and the numerical simulation is performed in a range of positive and negative 45°, with a wind direction angle of every 15°, for a total of 7 incoming flow direction conditions.

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