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Wednesday, 20 September 2017

Calculations of Moment using STAAD, replacing the Tedious Frame Analysis | SD3 Termwork

Frame Analysis

BLC: Be Lazy When you Have a Computer to Compute

It has been a common approach in structural analysis and especially while analysing for earthquake forces to use the Frame Analysis methods such as Cantilever Method and et cetera. These methods are very time-consuming error prone, a single mistake and the entire ship could sink. 

The best part of living in the 21st century is the availability of software that could do the task for you, simply a few inputs and boom! your task is done. I personally use STAAD pro for a number of my analysis purposes and it is at the starting a bit difficult to get a grip over the software environment of STAAD but once you've learned it, its a skill you that could trade off your efforts. One such project is the designing of building for earthquake loads. And in order to analyze the forces and the moments acting on the structure you need to perform a frame analysis of the entire building which is very time consuming and tedious, it involves a number of computations if done manually. If I wouldn't have learned about STAAD pro I would have simply made an excel sheet to perform the analysis, but now I'm having the software so I simply don't need to waste my time on preparing excel sheets.

So let's get back to work:

In my analysis I used Excel sheet to calculate the loads that would be acting on each storey using IS codes, I could have done this on STAAD but the university syllabus necessitates me to manually estimate the earthquake forces :-) but bad hand-writing and extreme laziness to calculate manually every modification force me to code down an excel sheet to get the work done!

Check out the excel sheet I prepared to calculated the forces that were acting on the structure:

This required a little effort but its' completely automated now and I could simply have an active instantaneous modification with automatic adaptation of fields that are constrained by formulas.

Once this task is done, comes the terrible task of manually performing all calculations but here we have software for our assistance and we shall be performing the calculation on STAAD pro.

I made a model of the structure in STAAD, assigned the properties and loadings and then performed the analysis to get the outputs. Within a few seconds, the task that would have required me at least 30 minutes was completed. As the building was not symmetric I had to perform two different analysis in two different forms for the X-Z plane and the other for the Y-Z plane.

Output for BMD of Structure X-Z plane through STAAD

This one is for the X-Z plane and the BMD is just the same as we obtain by solving manually using the portal frame method, now as the building is asymmetric, there is need of performing the earthquake forces and portal frame analysis for the other direction also.

Output for BMD of Structure Y-Z plane through STAAD

So this is how you can use STAAD for calculating the BMD within a few minutes and save time and efforts.

Apply the loads in in the form of concentrated nodal loads on the floors in acting the X or Y directions only. Let me know about your experiences analysing structures on STAAD.

Until then


  1. Nice work shadaab.. go ahead like this and shine with your work. Inshallah I will meet you in your office.