TITLE: DESIGN OF ISOLATED AND WALL FOOTING INSTRUCTIONS: Research for two (2) past board exam problems with the following topic: • Design of wall footing
Answer (1)
The design of wall footings is an important aspect of structural engineering, particularly in ensuring that walls are supported adequately to resist loads and prevent settlement. Here’s a step-by-step guide to understanding the design of wall footings:
Definition of Wall Footing : Wall footings are structural elements that distribute the load of walls to the foundation soil. They are typically used for walls that require a strong foundation to prevent overturning and settling.
Design Objectives : The primary aim of designing a wall footing is to ensure stability of the structure by properly distributing the loads onto the soil, thereby avoiding excessive settlement, tilting, or cracking of the walls.
Load Calculations :
Determine the loads from the wall that will be transferred to the footing, including dead loads (weight of the wall itself and any other permanent components) and live loads (temporary or changeable loads such as furnishings).
Geotechnical Investigation :
Conduct soil tests to understand soil bearing capacity, type of soil, and other characteristics that could affect the strength and stability of the footing.
Footing Dimensions :
Calculate the width and depth of the footing. For example, the footing width can be determined from the formula: B = q allow P where P is the load per unit length of the wall, and q allow is the allowable soil bearing capacity.
Depth should ensure that footing is placed below the frost line and provide enough depth for stability.
Material Selection :
Choose appropriate materials (like concrete and reinforcement steel) depending on environmental conditions, load requirements, and design specifications.
Reinforcement Design :
Determine reinforcement for the footing to resist tensile forces and prevent cracking. This involves calculating the required area of steel based on bending moments and designing the spacing of rebars.
Checking Design Codes : Adhere to local building codes and practices (such as ACI, Eurocode, or IS codes) to ensure the design meets safety and performance standards.
Construction Techniques :
Proper placement of concrete, adequate curing, and inspection to ensure that the footing has been constructed as per design specifications.
Following these steps will help ensure that a wall footing is designed correctly and will perform its function throughout the lifespan of the building.
