Method for Evaluating Wind Load on Exterior Material

Abstract

To provide a wind load evaluation method of an exterior material in which a fatigue damage to a repetitive wind load is considered.SOLUTION: A wind load evaluation method of an exterior material includes the steps of: creating a time history waveform F(t) of a wind load of the exterior material; calculating a stress time history waveform of a fatigue collation place of the exterior material on the basis of the time history waveform F(t); calculating a fatigue damage degree Dj of each wind speed level j; calculating a fatigue damage degree DTotal in the in-service time where the fatigue damage degree Dj of each wind speed level j is added all and assumed; dividing the time history waveform of the wind load by a fatigue burden rate η (>1), gradually increasing the fatigue burden rate η from a numerical value close to 1 at this time, repeating this until the fatigue damage degree DTotal becomes less than a threshold value, when the fatigue damage degree DTotal exceeds the threshold value; calculating a wind load Ff for fatigue by using the fatigue burden rate η, at the time when the fatigue damage degree DTotal becomes less than the threshold value; and assuming the wind load in consideration of the fatigue damage by using the wind load Ff for fatigue.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for evaluating the wind load of exterior materials.

Background Art

[0002] Conventionally, wind-resistant design considering wind loads has been carried out for buildings and the like (see Patent Document 1 below), and elastic design for equivalent static wind loads has been carried out for exterior materials.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the wind-resistant design of exterior materials, the design is carried out according to the following formula (1).

[0005]

Number

[0006] However, this method is a wind-resistant design for static wind loads and is not a wind-resistant design method that takes into account the fatigue damage of exterior material members under repeated wind loads.

[0007] In view of the above circumstances, the present invention provides a method for evaluating the wind load of exterior materials that takes into account fatigue damage under repeated wind loads.

Means for Solving the Problems

[0008] To achieve the above object, the present invention employs the following means. That is, the method for evaluating the wind load of exterior materials according to the present invention is the time history waveform C of the wind force coefficient obtained from the air density ρ, the design wind speed U, the wind tunnel experiment, and the numerical fluid calculation fBased on (t) (where t is time) and the load area A, the time history waveform F(t) of the wind load on the exterior material is created using the following formula (2),

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[0009] In the method for evaluating the wind load of the exterior material configured in this way, it is possible to calculate the wind load considering the fatigue damage to the repeated wind load of the exterior material during the assumed service period.

Advantages of the Invention

[0010] According to the method for evaluating the wind load of the exterior material according to the present invention, it is possible to design considering the fatigue damage to the repeated wind load.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0012] Hereinafter, a method for evaluating the wind load of an exterior material according to an embodiment of the present invention will be described.

[0013] In the method for evaluating the wind load of the exterior material of the present embodiment, based on the wind load and cumulative action time at each wind speed level generated during the assumed service period, and the stress time history waveform of the member or position to be inspected, the fatigue damage degree during the service period (fatigue inspection period) is evaluated.

[0014] By considering the fatigue burden rate less than the defined threshold value of the fatigue damage degree in the wind load for wind resistance design, the wind load for fatigue reflecting the fatigue damage during the service period is calculated. Thereby, it becomes possible to evaluate the wind load of the exterior material considering wind fatigue. The detailed procedure will be described.

[0015] (Step 1) Based on the cumulative action time of the wind speed during a typhoon and the probability distribution of the wind speed during non-typhoon periods, the cumulative action time at each wind speed level in the assumed service period is calculated. FIG. 1 shows an example of the relationship between wind speed and cumulative action time.

[0016] (Step 2) Based on the air density ρ, the design wind speed U, the time history waveform C f (t) (where t is time) of the wind force coefficient obtained from wind tunnel experiments and numerical fluid calculations, and the load area A, the time history waveform F(t) of the wind load on the exterior material is created by the following formula (5). This time history waveform of the wind load is an input condition for FEM time history response analysis. FIG. 2 shows an example of the time history waveform of the wind load which is an input condition for FEM time history response analysis.

[0017]

Number

[0018] (Step 3) Based on the FEM time history response analysis with the time history waveform of the wind load created in Procedure 2 as the input condition, calculate the stress time history waveform at the fatigue inspection location of the exterior material. Since the stress time history waveform calculated here is a value based on the design wind speed, after converting the stress time history waveform considering each wind speed level and the time step based on each wind speed level according to the following formula (6), create the stress time history waveform for the cumulative action time of each wind speed level. An example of the stress time history waveform is shown in Figure 3.

[0019] [Number]

[0020] Note that when calculating the stress time history waveform of the member or location to be inspected for fatigue, although FEM time history response analysis is used here, among the types of exterior materials, there are generally those with a damping of about several percent and a high natural frequency of several tens of Hz. Therefore, in some cases, the vibration of the exterior material due to wind speed variation (variation of wind load) may be considered to follow the wind speed variation (variation of wind load). In that case, it is also possible to calculate the stress time history waveform from the time history waveform of the wind load by assuming that the wind load and the stress at the target location are in a proportional relationship.

[0021] Also, here, the fatigue damage degree is calculated by focusing on the stress generated at the member or location to be evaluated, but it is also possible to evaluate based on strain or displacement.

[0022] Also, here, the stress time history waveform at the fatigue inspection location is created by FEM time history response analysis with the time history waveform F(t) of the wind load based on the design wind speed U as the input condition. However, for each wind speed level j, FEM time history response analysis with the time history waveform F(t) of the wind load based on each wind speed level u j can be performed to create the stress time history waveform. j (t) as the input condition.

[0023] (Step 4) Apply the rainflow method to the stress time history waveform created in Procedure 3 to count the stress range and its occurrence times, and calculate the fatigue damage degree D of each wind speed level j according to the linear cumulative damage rule (such as Miner's rule or modified Miner's rule). j Calculate it. The fatigue damage degree D j Is shown in the following formula (7).

[0024]

Equation

[0025] (Procedure 5) Add up all the fatigue damage degrees D of each wind speed level j to calculate the fatigue damage degree D during the assumed service period. j Is shown in the following formula (8). Total

[0026]

Equation

[0027] (Procedure 6) Determine the threshold value of the fatigue damage degree in advance, and confirm that the fatigue damage degree D during the service period Total Is less than the threshold value. If the fatigue damage degree D during the service period Total Is less than the threshold value, perform the wind resistance design using the equivalent static wind load obtained by the conventional calculation method. If it exceeds the threshold value, return to Procedure 2, divide the time history waveform of the wind load by the fatigue burden ratio η (>1), and create the time history waveform F of the wind load, which is the input condition for the FEM time history response analysis p (t) using the following formula (9).

[0028]

Equation

[0029] Note that the threshold value is a condition for non-fatigue failure when it is less than 1. However, since the wind has a longer duration compared to earthquakes, etc., it is desirable to set the threshold value to about D < 0.1.

[0030] For example, assume that the threshold value is 0.1 and D Total = 0.6. In this case, since the threshold value of 0.1 is exceeded, return to Step 2, divide the time history waveform of the wind load by the fatigue load rate η, and update the time history waveform of the wind load.

[0031] (Step 7) While the fatigue damage degree D Total during the service period is less than the threshold value, gradually increase the value of the fatigue load rate η from a value close to 1 and repeat Steps 2 to 6.

[0032] For example, in the first repetition, if D Total = 0.45 when divided by η = 1.1, since the threshold value of 0.1 is exceeded, perform the second repetition. In the second repetition, if D Total = 0.35 when divided by η = 1.2, since the threshold value of 0.1 is exceeded, perform the third repetition. Continue this until the threshold value is less than 0.1. In the fifth repetition, if D Total = 0.05 when divided by η = 1.5, since it is less than the threshold value of 0.1, end. In this embodiment, η is increased by 0.1 each time, but the gradually increasing width can be set as appropriate.

[0033] (Step 8) When the fatigue damage degree D Total during the service period becomes less than the threshold value, multiply the fatigue load rate η (>1) used at that time by the wind load F (Equation (10) below: equivalent static wind load obtained by the conventional calculation method) calculated using the design wind speed U and the peak wind force coefficient C f (^C (hat) above C) to calculate the wind load F f (Equation (11) below: referred to as "wind load for fatigue") that takes into account the fatigue damage of the fatigue inspection target location of the exterior material for the repeated wind load during the assumed service period.

[0034]

Equation

[0035]

Equation

[0036] In the method for evaluating the wind load of the exterior material configured as described above, it is possible to calculate the wind load considering the fatigue damage to the repeated wind load of the exterior material during the assumed service period.

[0037] As described above, one embodiment of the method for evaluating the wind load of the exterior material according to the present invention has been described. However, the present invention is not limited to the above-described one embodiment, and can be appropriately changed without departing from the gist thereof.

Claims

【Claim 1】 Based on the air density ρ, the design wind speed U, the time history waveform C of the wind force coefficient obtained from wind tunnel experiments and numerical fluid calculations, ｆ (t) (where t is time) and the loading area A, the time history waveform F(t) of the wind load on the exterior material is created using the following formula (1), 【Number 1】 Based on this, calculate the stress time history waveform at the fatigue inspection location of the exterior material, calculate the fatigue damage degree Dj at each wind speed level j using the following formula (2), 【Number 2】 The fatigue damage degree D at the assumed service time is calculated by adding up all the fatigue damage degrees Dj of the respective wind speed levels j. Ｔｏｔａｌ and the fatigue damage degree D Ｔｏｔａｌ When it exceeds the threshold value, the time history waveform of the wind load is divided by the fatigue load rate η (>1), and at this time, the fatigue load rate η is gradually increased from a value close to 1, and the fatigue damage degree D Ｔｏｔａｌ is repeated until it becomes less than the threshold value. The fatigue damage degree D Ｔｏｔａｌ When the fatigue burden rate η when it becomes less than the threshold value is used, the fatigue wind load F is calculated from the following formula (3). ｆ and 【Number 3】 The wind load for fatigue F ｆ A method for evaluating the wind load of an exterior material, which is a wind load considering fatigue damage using the above-mentioned wind load for fatigue.

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