Structural engineering

UNIT – I

Chapter – 1 (A)

STRUCTURAL ENGINEERING

STRUCTURAL ENGINEERING - AN OVERVIEW

1. INTRODUCTORY CONCEPTS

Structural engineering is a field of civil engineering which focuses on the design of structures to withstand the loads and remain safe, stable and secure throughout their use. A structure, in a building context, is “a device for channeling loads that results from the use or presence of the building in relation to the ground”. The study of structures involves many important and varying concerns. The fundamental concern is to understand the basic principles that define and characterize the behavior of physical objects subjected to forces.

2. BASIC ISSUES IN THE DESIGN AND ANALYSIS OF STRUCTURES

In structures, the applied forces can cause the form to slide or overturn as a whole or to collapse internally. Alternatively, components could break apart or deform badly. The forces causing overturning or collapse come from the specific environmental or use context (e.g., from the effects of wind, earthquake or occupancy) or from the self-weight of structure itself. The above external forces produce internal forces in a structure that results in development of stresses. Civil engineers are expected to analyse and check the safety of structures. This check involves determining the stresses developed at critical locations and comparing them with the strength of the material used. The material could be wood, steel, concrete etc. Engineers ensure that the stress developed in structures is always less than the strength of the material for safety.

Another fundamental consideration in designing a structure is that of assuring its stability under any type of loading condition. All structures undergo some changes in shape under load. In a stable structure, the deformations induced by the load are typically small. Further, the internal forces generated by the action of the load tend to restore the structure to its original shape after the removal of load. By contrast, unstable structure does not generate internal forces that tend to restore its structure to its original configurations.

Thus, it is the fundamental responsibility of a structural engineer to assure that the proposed structure is (i) safe based on strength and (ii) stable with deformations within the acceptable limits. The application of mechanics enables the structural engineer to assemble elements, such as beams and columns, into a structure that will resist both static and dynamic loads, such as gravity, wind, snow and earthquakes.

3. MECHANICS

Mechanics is the branch of physical science. It deals with the state of rest or state of motion of bodies under the action of forces.

Archimedes (287–212 BC), Galilio (1564–1642), Sir Issac Newton (1624–1727) and Einstein (1878–1955) have contributed a lot to the development of mechanics. Substantial contributions have also been made by Varignon, Euler, D'Alembert and others.