The structure is composed of several components or elements connected by joints or supports to fulfill the function for which it is constructed; in such a way that they can transmit the forces coming on the structure to the foundation safely without showing considerable deformation.
Structural analysis is a process used in engineering to predict the behavior of structures and components under various loading conditions. The goal is to ensure that a structure can safely support its intended loads while meeting design criteria such as strength, stability, and serviceability.
What Is Structural Analysis?
Structural analysis is the method of determining and calculating the effects of loads and internal forces acting on a structure, building, or object. It is a process determining the response of the structure to specified arbitrary external loads.
Structural Analysis of structure is essential before starting construction work. It provides the details of the size of the foundation, the size of the column and beam, and reinforcement details that are sufficient to carry the load acting on the structure. Before constructing any structure, there are several documents required like plan, elevation & section details.
This process of finding out the load that a structure can carry safely, without failure is called Structure Analysis.
Structural Analysis Basic Concepts
The concept of structural analysis is applied not only in building constructions but also in our day-to-day life.
For instance,
- The aluminum container for carrying food parcels is provided with vertical ribs, which can impart stiffness to it. As a result, it becomes easier to carry it without bending.
- The game of building blocks, which you might have played in childhood, is also based on principles of structural analysis. If you insert several blocks in a straight line, then the blocks will fall.
A similar phenomenon happens in the case of buildings. Slender buildings that are very tall tend to collapse.
However, you can prevent this by providing a firm base, i.e., increasing the fixity at the base.
Structural Elements
As discussed earlier, a structure is composed of many parts joined together to transfer the loads. These parts are referred to as elements/members in structural analysis. Some of the structural elements are mentioned below:
Beam: A horizontal member transmitting transverse loads. Resistance loads are applied laterally to the beam axis. The load produces shear and bending moments in the beam.
Column: A vertical member carrying only gravity loads. It transmits axial force or bending force.
Truss: A structure having slender members connected by pin-joint. It carries axial load only, applied at joints. Members undergo either compression or tension.
Grid: Network of beams intersecting each other at right angles. Vertical loading is transmitted through grids.
Frame: Network of beams and columns with rigid joints.
Plates: Members carrying bending in two directions are called plate structures.
Continuum mechanics principles are followed in their analysis. A concrete flat slab is an example of a plate structure
Arch: Members carrying compression in one direction only.
Types of Load Act on Structure
Following are the load act on structure,
1. Dead Loads
The loads on the structure due to the self-weight of the building and the weight of the permanent furniture are classified as dead loads.
To calculate dead load,
- Assess the quantity of the material
- Multiply it by the unit weight of the material
Dead Load = Quantity of Material x Unit Weight
The unit weights of the material can be found from IS: 875(Part I)- 1987.
2. Imposed Loads
The loads that are ‘imposed’ on the structure are called imposed loads. The following loads are included I imposed loads:
3. Live Load
The loads which change their position with respect to time are called live loads. E.g., the weight of a person, furniture, moving partitions, etc.
The minimum values to be taken for the design purpose are given in IS:875 (Part II)- 1987 based on the occupancy of the building, i.e., whether the structure is residential, warehouse, etc.
4. Crane load
Loads from the crane and other moving machinery are called crane loads. These loads are vital for the structure. If they are not considered, then the structure may undergo failure during its erection itself!
These loads can be known from the manufacturer’s data.
5. Wave Load
For off-shore structures, these loads are essential.
e.g., the force exerted by water current on the bridge piers, abutments, and other waterfront structures
These are random loads, and specialists with enough experience are needed to determine them.
6. Earth Pressure Load
The pressure exerted by the soil on the structures or part of the structure embedded partly or fully in the ground is called earth pressure. These loads are required for the foundation of the structures. These are also needed for the design of retaining walls, underground water tanks, culverts, bridges, etc.
7. Impact Load
The structures carrying moving loads are to be designed for impact loads. e.g., bridge
8. Wind Loads
The force exerted on the structures by the horizontal component of the wind is considered under the wind load. It is considered for the design of tall buildings.
9. Earthquake Loads
The earthquake causes shaking of ground in all directions, and role reversal in the structural elements take place. As the ground shakes horizontally, horizontal inertia forces are generated. These lateral forces are transferred through slabs, beams, and columns.
And Columns that are designed to carry compressive loads start getting tensile loads too. So, the lateral forces are evaluated to make the structure earthquake-resistant.
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