STRUCTURAL ANALYSIS vs STRUCTURAL DESIGN

 STRUCTURAL ANALYSIS    vs  STRUCTURAL DESIGN

 

A structure is an assembly of materials which can carry applied loads (forces). If an engineering structure fails, people are likely to get injured/killed, hence, engineers study and investigate the behavior of structures with utmost precision.

Man-made structures include buildings, bridges, dams, ships, airplanes, rockets, trains, cars, and other large structures. Structural engineers design and access structure to ensure that they are efficient and stable under the effects of various forces. Structural engineers are responsible for both structural analysis as well as design.  A civil engineer must have clear understanding of the differences between both.

STRUCTURAL ANALYSIS

Structure analysis is the process to determine the response of a structure under applied loading conditions or combinations of various loads.

portal frame with uniformly distributed load

Analysis is done by making assumptions. We assume the dimensions of the structural elements (I, b, d), their loading conditions (DL, LL, EL, etc.), material properties (E, fck, fy), and support conditions (fixed, hinged, roller, etc.).

Analysis of a structure includes the study of: strength, stiffness, stability, and response of all elements.

In analysing, the support reactions, shear forces, bending moment, torsion, deflection, stress, strains etc. are calculated, that the particular member would undergo due to the applications of loads.

For structural analysis, knowledge about the behavior of structural elements, and hence basic mathematics, and basically physics i.e. structure mechanics is important.

A basic reason that structural analysis is beneficial is to determine the cause of a structural failure.

When conducting analysis, structural engineer investigates magnitude of force applied on the structure, it’s direction, and orientation.

Steps for Analysis of Structure:

• Structural Idealization
• Applying Loads
• Calculating Reactions
• Calculating Internal Forces
• Calculating Internal Stresses
• Evaluating Efficiency and safety

The geometry is assumed prior to finding shear force and bending moments.

Methods of Structural Analysis: Analytical Method:
method of joints
method of sections
Force method
Displacement method
Matrix methods
Numerical Methods:
Finite element method

There is only one specific solution.

From the analysis we can get bending moment diagram, shear force diagram, deflection curve, shear stress and strain etc.

Software Used for Structural Analysis

• STAAD.Pro
• ETABS
• SAP
• ANSYS
• EdiLus
• Tekla
• MIDAS

STRUCTURAL DESIGN

Structural design is the process to find out the safe, durable and economical specifications of the structure including materials, geometry, the size of structural members which can carry loads during the lifetime of the structure.

The design process of any structure starts with the selection of materials, and the structural system. The choice of material depends on local availability and economy of design.

Design of structure includes: the criteria of serviceability, safety, and durability.

In designing, the geometry, size and shape of all the members of structure are calculated. In structural design individual elements as well as joints are designed

The process of design requires knowledge of mechanics materials. And also, sound knowledge of design codes, and bye-laws which provide the guideline for the safe structural design.

Structural design is important as it provide safety to the occupants during its intended life without failure.

In the structural design the geometry is checked against the design load criteria as per codal provisions. The stresses in member should not exceed permissible limits and permissible deflection etc. All the elements are checked for its load resisting capacity i.e. stress of different types i.e. flexure, direct shear and stress etc., strain, deflection, rotation etc. If these values exceeds the permissible limits, the members are redesigned.

For given loading, geometry is checked as per codes, and checked against permissible values.

Methods of Structural Design
Working stress method
Ultimate load method
Limit state method

There can be many possible solutions, with variation in materials and its properties.

From the design we can prepare detailed drawing for execution with details of reinforcement in case of RCC structures or details of weld or bolts in case of steel structure.

Software Used for Structural Design

• STAAD.Pro
• ETABS
• SAP
• SAFE
  
  
  
• STAAD Foundation Advanced
• Tekla Structures