This blog is the continuation to BLOG 5 (SOM) in a series of GATE preparation tips blog articles for Civil Engineering Students. The blog author, Rohit Sachdeva has secured AIR 93 in GATE 2017 and is currently studying at IISc Bangalore. You can read the rest of the articles under the CE section for GATE blogs at http://gate.vidyalankar.org/category/civil-engineering/.
A rough breakup of questions of various topics in last 30 years in GATE is as follows:
||No. of Questions
||Determinacy/Indeterminacy and Stability/Instability
||ILD and Rolling Loads
||Methods of Indeterminate Analysis
||Matrix Methods of Analysis
As mentioned in the previous blog, an analysis of last 5 years of GATE papers reflects that SOM and Structures combined carry 10-12 marks, which is huge! And considering their importance in interviews, this subject requires thorough preparation.
Time required for preparation
8-10 days (if you have 8-10 month of preparation) with 3-4 hours daily
4-5 days (if you have 4-5 months of preparation) with 6-8 hours daily
Both SOM & Structural Analysis will have mostly numerical questions, with equal weightage in 1-mark and 2 mark questions. There are some formulas which you should remember, which I will specifically mention; and it is better to make a formula sheet for future revision. The textbook(s) to be referred are mentioned in BLOG-3 which you can utilize.
A topic-wise discussion is as follows, with most important concepts in bold & italics:
1. DETERMINACY/INDETERMINACY AND STABILITY/INSTABILITY (1 DAY)
One sure question can be expected every year from this topic. Static (Ds) and Kinematic (Dk) Indeterminacy of Trusses and Frames (both 2D and 3D) are the possible combinations. While it is important to know the formula for each case, it is equally important to know how to apply them, what axially rigid members are, and how hinges play a role in increasing Dk or decreasing Ds. Understand properly both internal and external stability.
Write down formulas in the formula book and practice a lot of numericals; you would not want to miss out on those sure shot marks!
2. ILD AND ROLLING LOADS (1 DAY)
Muller Breslau’s principle for qualitative idea of ILD is important. Then, the most important concept is movement of series of wheel loads on a beam: Centre of beam is midway between CG of wheel loads and load under consideration. Mostly one question will be asked from this concept.
Another concept to be learned is introduction of hinges in continuous beam and finding out ILD of various supports. Practice 2-3 numericals for each concept.
3. ARCHES (1/2 DAYS)
3-hinged arch questions are common for which you should remember the equation of parabolic arch and proceed similar to a beam keeping in mind that BM at hinge is zero.
A theoretical question from 2 hinge arch (mostly from temperature change) or linear arch could be asked.
4. METHODS OF INDETERMINATE ANALYSIS (2 DAYS)
These are the displacement methods of analysis and include slope-deflection, moment distribution, Castigliano’s method and column analogy methods. Since these methods themselves are lengthy as a whole, sub-topics which are very important are:
Fixed end moments (to be noted in your formula book), near and far end moments, moment due to support sink, sway of frame (qualitative), Distribution factors (and ratio). These topics are directly utilized further in Topic No. 6 below.
Practicing 1-2 full conventional questions from each topic can clear these concepts in single go! You can also practice 5-10 small questions from each topic to cover this section.
5. TRUSSES (1 DAY)
Members carrying 0-force could be the most probable question from this topic. Application of method of sections, strain energy method and ILD of truss can also be asked.
Another favorite question is finding the displacement of a single joint in a simple truss for a given loading: this question is solved using unit load method. Practice 1-2 numericals in each section.
6. MATRIX METHODS OF ANALYSIS (2 DAYS)
This topic contains two sections – Flexibility matrix and Stiffness matrix. This is the 2nd most important & asked topic in Structural Analysis after indeterminacy in the recent years, and is very easy to score.
Practice 2-3 questions each of stiffness matrix and flexibility matrix (this will require direct utilization of concepts of sub-topics mentioned in Topic No. 4 above).