How to Calculate Area and Inertia Moment using Autocad

بِسْـــــــــــمِ اللّهِ الرَّحْمَنِ الرَّحِيْـــــــمِ

this post is my first time with English. I hope that my explanation more easier for reader. 

In a structure building, especially steel structure. we should know how to calculate area. this is used for us to calculate such as shear force, weldment area and others. it would be explain in next post. apparently. ok let's start our discussion based on case. 

There are risers hanging to jacket platform. Riser is a pipe that connects an offshore Floating Production Structure or a Drilling Rig or Fix offshore structure to a sub-sea system either for production purposes such as drilling, production, injection and export, or for drilling, completion and workover purposes ( They are a key component for the offshore industry and maintaining theri functionality is central to the success of the production system. Actually there are 3 types of riser clamp depend on function (as far i know), Fix clamp, adjustable clamp and hanger clamp. we are now talking about fix clamp and hanger clamp because we look for the connection that using weld connection. 

during hanging the riser tie up with riser clamp, and among of them are connected with stub. the connection between stub and riser are using clamp, and other side using weldment connection to horizontal bracket. take a look to below for example figure.

Ilustration Riser Clamp at Plan View

In a riser clamp system, at least there are 3 necessary components that is riser clamp, stub and bracing where is will be connected. in figure above, plan view illustration from riser clamp that we are talking about. alright  we will see the connection stub and horizontal bracing, section F.

Section F
Section F describe connection stub to horizontal bracing. the component consist of stub with OD 6-5/8 " and 0.75 WT and stiffener with dimension rectangular (assume) 4"x0.5" there are doubler plate between horizontal brace and stub, however we can ignore it. 

how to calculate the area of them in Cad (as far i know, with cad, this exactly fastest way to get area better than hand calculation.)

1. Open your CAD and drawing stiffener and Stub that we describe above

OD stub = 6-5/8" x 0.75 WT
Stiffener = 4"x1/2"
angle     =  45 deg 

2. click command : UCS -> put in center of circular stub [enter/ok]

Location local UCS
3. click command : trim -> trim circular between inner stiffener [enter/ok]

after trimming
3. click command : PE -> M -> select all drawing except inner circular [enter/ok]

click [y] in command convert lines, arcs, and splines to polylines

4. click command : PE -> M -> select all drawing except inner circular [enter/ok]

click [J] in command enter an option (close/join/etc)[enter/ok] twice

4. click command : RE -> select all drawing [enter/ok]


4. click command : MASSPROP -> select all drawing [enter/ok]

ok, congratulation you made it. if you wanna know that your assumption is correct, please check the centroid. it should be zero, than you are able to make this output for your necessary action.

for exercise, you can click here for soft file 

source :


  1. Nice good article english and indo

  2. wah.. kerjaannya temen sekantorq nih.. tiap hari kerjaannya utak atik autocad mulu.. :D


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