---
title: "Use of computers in structural analysis"
subject: "Theory of Structures I"
chapter: 1
key: "semester_4/theory_of_structures_i:use-of-computers-analysis"
source: https://www.bctengineer.com/q/semester_4/theory_of_structures_i/use-of-computers-analysis
site: BCT Engineering
---

# Use of computers in structural analysis

Theory of Structures I · Chapter 1: Introduction

- Asked in: 2077 Chaitra, 2 marks; 2068 Bhadra, 4 marks (asked 2 times)
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/theory_of_structures_i/use-of-computers-analysis
- Whole chapter: https://www.bctengineer.com/md/semester_4/theory_of_structures_i/chapter-1

## Question

Explain briefly the use of computer based methods in structural analysis.

## Short answer

Computer analysis uses matrix stiffness or finite element formulation: model nodes, elements, supports and loads, assemble [K], solve [K]{D}={F} for displacements, then compute member forces. It can handle highly indeterminate 3D frames, many load combinations, nonlinear and dynamic analysis quickly. Results depend on model correctness, so the engineer must verify reactions and approximate results.

## Answer

Computer based methods use matrix formulation of the force or displacement method (matrix stiffness method, finite element method) so that large structures can be analysed quickly by software such as SAP2000, ETABS, STAAD.Pro and ANSYS.

#### Steps in computer analysis
1. Model the structure: joints (nodes), members (elements), supports, material and section properties.
2. Apply loads and load combinations.
3. The program forms member stiffness matrices, assembles the global matrix $[K]$, and solves $[K]\{\Delta\} = \{F\}$ for joint displacements.
4. Member forces, reactions and stresses are back-calculated and presented as diagrams and tables.

#### Uses and advantages
- Handles highly indeterminate structures (multi-storey frames, 3D frames, shells, plates) that are impractical by hand.
- Very fast and accurate; many load combinations (dead, live, wind, earthquake) can be run quickly.
- Allows non-linear, dynamic, buckling and soil-structure interaction analysis.
- Easy to repeat the analysis after changing member sizes in design iterations.
- Gives graphical output (deformed shape, bending moment diagrams).

#### Cautions
- Results depend on the correctness of the model, so the engineer must check them, e.g. equilibrium of reactions and approximate hand calculations.
- "Garbage in, garbage out": wrong supports or loads give wrong results.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What equation does the program solve for joint displacements?
   A. [F]{Δ} = {K}
   B. {Δ} = [K]{F}^2
   C. [K] + {Δ} = {F}
   D. [K]{Δ} = {F}
   Answer: D. The global stiffness matrix relates joint displacements to loads. (Key point: Core equation)

2. In which order does computer analysis proceed?
   A. Model, apply loads, assemble and solve, back-calculate member forces
   B. Apply loads, solve, then model
   C. Back-calculate forces, then assemble stiffness
   D. Design members, then model
   Answer: A. Modelling comes first, then loads, solution and output. (Key point: Steps)

3. A key advantage of computer analysis is:
   A. It removes the need to check results
   B. Handling highly indeterminate and 3D structures with many load combinations quickly
   C. It works only for determinate beams
   D. It gives exact results even with wrong input
   Answer: B. Software handles large problems that are impractical by hand. (Key point: Advantage)

4. What does 'garbage in, garbage out' warn?
   A. Computers always give correct results
   B. Output is unaffected by the model
   C. Wrong supports or loads in the model give wrong results
   D. Only hand calculations can have errors
   Answer: C. Engineers must check models and results. (Key point: Caution)

## Related in Theory of Structures I

- [Two basic approaches of structural analysis](https://www.bctengineer.com/question.md?key=semester_4%2Ftheory_of_structures_i%3Atwo-basic-approaches) — Theory of Structures I, chapter 1, asked 3×
- [Non-linearity in structural analysis](https://www.bctengineer.com/question.md?key=semester_4%2Ftheory_of_structures_i%3Anonlinearity-structural-analysis) — Theory of Structures I, chapter 1
- [Characteristics of structural mechanics](https://www.bctengineer.com/question.md?key=semester_4%2Ftheory_of_structures_i%3Astructural-mechanics-characteristics) — Theory of Structures I, chapter 1
- [Types of structures based on material](https://www.bctengineer.com/question.md?key=semester_4%2Ftheory_of_structures_i%3Atypes-structures-material) — Theory of Structures I, chapter 1, asked 2×
- [Structure analysis and its basic approaches](https://www.bctengineer.com/question.md?key=semester_4%2Ftheory_of_structures_i%3Astructure-analysis-approaches) — Theory of Structures I, chapter 1

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