Interpolation

Forum|Forum|8 years ago
February 1, 2018
2 replies
6716 views

I am trying to code ASCE7-10 table 27.6-2 to find my wind pressure of my roof but it is based on different parameters like the slope and the height and the wind speed.

Is there a way I can interpolate a table instead of having to do a bunch of matrices and interpolate each individually to find the pressure? The image below is what i am trying to avoid, doing a bunch of matrices to then get the final answer.

Statistics_Analysis

Best answer by Werner_E

The values in data_clz2 were taken from the picture of the table you posted.

First rows are corresponding to 30 ft and second row to 40 ft

Columns correspond to speed 110, 115, 120 and for every slope there is its own 2x3 matrix.

As written earlier this is my attempt to simulate a 3-dimensional matrix which MC unfortunately does not support.

But as you are only interested in speed 110 mph a simple 2D interpolation is all it takes. And as you are not interested in heights greater than 40, the attached approach which uses the data matrices you provided should do the job.

W

Werner_E

25-Diamond I

Is there a way I can interpolate a table instead of having to do a bunch of matrices and interpolate each individually to find the pressure?

You would have to provide the table and explain what exactly you need as answer. Do you need 9 values for every ratio L/B or is it a simple 2D table interpolation you are looking for?

J

jenny29

Author

1-Visitor

This is the table I am trying to input. I have already defined what the wind speed and height of the building and slope of roof is so from there I want it to spit out the different pressures for the zones.

W

Werner_E

25-Diamond I

So the input is height, slope and speed. But I also see loadcase which can be 1 or 2. You will have to provide that, too. this would make up for a 4-dimensional table.It would be quite possible to interpolate for any of those four input values, but unfortunately Mathcad does not support multidimensional arrays and so we would have to use some kind of artificial data structure.

The output should be a vector with 5 values - is this correct?

In your screenshot you calculated 9 values, not just 5, and load case could even be 0,5 in some cases??

I also see no connection between the values you provide in the screen shot and in the table you posted!?

I would have guessed that you want to interpolate between heights, speeds and slopes. maybe even between zones and load cases.

It should be possible to create a function which gives you the interpolated value for height=37 ft, wind speed = 17 mph, slope=24 deg and zone=3.2 with loadcase=2. But is sure would be quite some work to create the necessary tables in Mathcad format.