Mullions Section properties
Mullions Section properties
(OP)
Hi All,
I am working on a project with aluminum mulions. How does one get the section properties of the mullions. What is the typical way?
Especially if you need the torsional constant.
Thank you,
I am working on a project with aluminum mulions. How does one get the section properties of the mullions. What is the typical way?
Especially if you need the torsional constant.
Thank you,






RE: Mullions Section properties
RE: Mullions Section properties
RE: Mullions Section properties
Normally what would happen is that the supplier would provided me with the mullion profile and the shop drawings. I would then use mechanics of materials ( Parallel Axis Theorem ), to determine the centroid, moment of inertia and the section modulas.
Today with CAD and other programs the manufacturers may already have that information as par060 indicated. However in the early 80's I would just do a hand sketch of the individual elements of the mullion calculate their properties and determine the properties of the total section.
In most cases to get the mullion to check, I had to included every small part of the mullion.
RE: Mullions Section properties
RE: Mullions Section properties
What is the shape of the mullion?
Are you doing a complex blast analysis on windows and window frames?
RE: Mullions Section properties
RE: Mullions Section properties
A google could well find the required information for you, it's what I use if I don't have the relevant books with me. Of course, verifying the accuracy from 2 different sources is always a good idea when using the internet.
RE: Mullions Section properties
The extruders do usually have basic section properties all worked out. The trick is to speak to the right person as the extruders or the system manfacturers are not likely to have the right background to understand your requirements.
Also get confirmation on the alloy used as we have encountered so very strange metal being used for basic extrusions.
RE: Mullions Section properties
Thanks for your replies.
I guess phrased my question incorrectly.
I know how to calculate the properties of a section. What I am looking for is an efficient and quick way to calculate J. The mullion sections are highly complex (http://www
It is time consuming and inefficient to hand calc the J(torsional constant). A worksheet wont work as each section is unique.
I am not doing Blast analysis, however I have to include windload. The new code has included the J in one of the equations to get the allowable stress.
The values of area, moment of inertia, radius of gyration can be calculated for these complex sections in matter of seconds usinf AutoCad, it is the J, "torsional constant" I am have problems with.
THe manufactures donot have the values for J, they can provide with the Ix and Iy which is easier to calcuate using AutoCad
What I really am looking for is a program that calculates J for non conventioananl sections, or if AUtoCad has a LISP developed that covers J.
RE: Mullions Section properties
I pulled out several of my college text books including one called "Advanced Strength and Applied Elasticity". When I saw all the intergral symbols I started getting a headache.
I now understand how complex of a problem that you are trying to solve.
From your experience it is clear that you understand that most of the time if you just consider the most simple shape of the mullion the wind stress will never check. I wonder if the samething would be ture if you base the J constant on the main elements.
I wonder if you would have more luck posting your question on a mechanical forum which is part of this website. I go to the mechanical forum once in a while and have learned quiet a bit. I think mechanical engineers deal with the properties of more complex shapes on a regular basis. After all for us structural engineers in you need the J constant of a wide flange you just look in the steel book.
RE: Mullions Section properties
Don't confuse J with polar moment of inertia.
RE: Mullions Section properties