Podcast
Questions and Answers
What is an isolated footing primarily designed for?
What is an isolated footing primarily designed for?
- To distribute load evenly across a large area
- To accommodate lateral forces from soil pressure
- To transfer load from a single column to the underground soil (correct)
- To support multiple columns simultaneously
Which of the following specifications is NOT allowed for footings?
Which of the following specifications is NOT allowed for footings?
- Footings resting on fill (correct)
- Footings resting on solid rock
- Footings with a depth of at least 150mm
- Footings with a minimum concrete cover of 75mm
What does the effective soil pressure, $q_e$, account for?
What does the effective soil pressure, $q_e$, account for?
- Only the weight of the footing itself
- The lateral pressure from surrounding soil
- The total weight of all objects above the lower base of the footing (correct)
- The shear forces acting on the footing
In the context of footings, how are one-way and two-way footings differentiated?
In the context of footings, how are one-way and two-way footings differentiated?
According to the guidelines, what is the required minimum depth of footing above bottom reinforcement?
According to the guidelines, what is the required minimum depth of footing above bottom reinforcement?
What is the primary purpose of providing a foundation for a structure?
What is the primary purpose of providing a foundation for a structure?
Which type of shallow foundation is used to support a single column?
Which type of shallow foundation is used to support a single column?
Which of the following describes a strap or cantilever footing?
Which of the following describes a strap or cantilever footing?
What is not a characteristic of deep foundations?
What is not a characteristic of deep foundations?
Which structural analysis concept involves the study of stress and strain?
Which structural analysis concept involves the study of stress and strain?
Which factor is considered in structural design?
Which factor is considered in structural design?
What type of foundation is characterized by its width being greater than its depth?
What type of foundation is characterized by its width being greater than its depth?
Which structural component helps prevent lateral movement of a building?
Which structural component helps prevent lateral movement of a building?
What is the primary goal of structural design?
What is the primary goal of structural design?
Which of the following is NOT one of the objectives of structural design?
Which of the following is NOT one of the objectives of structural design?
In structural drawings, what does the foundation plan illustrate?
In structural drawings, what does the foundation plan illustrate?
What is meant by 'serviceability' in the context of structural design?
What is meant by 'serviceability' in the context of structural design?
Which component of structural drawing provides specific details such as cross sections and steel reinforcement?
Which component of structural drawing provides specific details such as cross sections and steel reinforcement?
What does the term 'dead load' refer to in structural design?
What does the term 'dead load' refer to in structural design?
For optimal structural integrity, where should columns ideally be positioned?
For optimal structural integrity, where should columns ideally be positioned?
Which aspect of a building structure is primarily concerned with its longevity and resistance to degradation over time?
Which aspect of a building structure is primarily concerned with its longevity and resistance to degradation over time?
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Study Notes
Structural Design
- The art and science of designing safe, serviceable, and durable structures under loads.
- Structural engineers use structural plans which detail members, specifications, and schedules.
Objectives of Structural Design
- Determine the methodology for construction.
- Ensure safety by preventing failure under loads.
- Maintain stability, preventing movement under expected loads.
- Achieve serviceability, preventing unreasonable deformation or cracking under loads.
- Ensure durability for a reasonable lifespan.
Components of Structural Drawing
- Construction Notes & Specifications: Include general notes, methods, and construction specifications.
- Foundation Plan: Shows the location and size of footings, columns, foundation walls, and supporting beams.
- Framing Plan: Shows the location and sizes of columns, beams, and slab designations.
- Details: Separate plans showing specific details like cross-sections, steel reinforcement, and sizes.
- Schedules: Provide section, sizes, and steel reinforcement for beams, slabs, columns, and footings.
Process of Structural Design
- Structural Planning & Layouting:
- Place columns symmetrically, near the corners of the building, and at beam intersections.
- Avoid large center-to-center distances between columns.
- Establish design criteria, selecting materials, their strength, and identifying the building loads.
- Structural Analysis:
- Study stresses, strains, and slope deflections of structural members.
- Structural Design:
- Design members considering strength, economy, and serviceability.
- Structural Detailing:
- Prepare structural drawings and information for construction.
Foundation Plan
- A plan view showing the location and size of footings, footing tie beams, wall footing, columns, and slabs.
Footings
- Structural members supporting columns and walls.
- Distribute loads from columns and walls.
Wall Footing
- A strip footing supporting load bearing walls.
- Typically uses CHB materials (6” exterior walls, 4" interior walls).
- The width of the footing is 2-3 times the width of the wall.
Isolated Footing
- A single footing designed to support a single column.
Foundation Notes:
- Footings should not rest on fill.
- Minimum concrete cover is 75 mm.
- As per NSCP Section 5.15.7, the depth of footing above bottom reinforcement should not be less than 150 mm for footings in soil.
- The required footing area (A) is calculated using NSCP Section 5.15.2.2.
- Effective soil pressure (qe) considers the weight of all objects above the lower footing base.
- L = W = √Areq'a if the footing is square.
Determining Depth of Footing:
- Ultimate pressure is used to calculate the depth of the footing.
Shear Strength of Slabs and Footings:
- The shear strength in the vicinity of columns, concentrated loads, or reactions is determined by the more severe of two conditions.
Thickness of the Footing:
- The thickness is calculated using specific equations and considerations.
Distribution of Flexural Reinforcement.
- One-way footings, reinforced in one direction.
- Two-way footings, reinforced in two directions.
Sample Problem:
- Provide a footing detail for grid B-2.
- SBC: 120 kPa
- f'c = 20.7 MPa
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