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Discuss in detail two functional requirements of a foundation for a dwelling house - Leaving Cert Construction Studies - Question 2 - 2009
Question 2
Discuss in detail two functional requirements of a foundation for a dwelling house. Using notes and freehand sketches show three different foundation types suitable... show full transcript
Worked Solution & Example Answer:Discuss in detail two functional requirements of a foundation for a dwelling house - Leaving Cert Construction Studies - Question 2 - 2009
Step 1
Discuss in detail two functional requirements of a foundation for a dwelling house.
Answer
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Load Distribution: A foundation must efficiently distribute the dead loads, including the weight of the building and live loads, across a large area to prevent excessive settlement and ensure stability.
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Anchoring and Stability: The foundation must anchor the structure securely to the ground, preventing movement due to lateral forces such as wind or seismic activity. This ensures the building's integrity during varying weather conditions.
Step 2
Using notes and freehand sketches show three different foundation types suitable for a dwelling house. Show the position of the reinforcing and indicate typical dimensions of each foundation type.
Answer
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Strip Foundation:
- Description: Suitable for low-rise buildings, it runs continuously along the walls.
- Reinforcement Positioning: Steel bars are placed on the bottom and sides to handle tensile stresses.
- Typical Dimensions: Width of approximately 450mm to 600mm and depth of 1m, depending on soil quality.
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Raft Foundation:
- Description: The entire structure rests on a thick concrete slab to spread the load evenly across a large area.
- Reinforcement Positioning: Steel mesh is integrated within the slab to enhance load-bearing capacity.
- Typical Dimensions: Thickness generally varies from 200mm to 500mm based on structural requirements.
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Short-bored Pile Foundation:
- Description: Used where soil properties vary; piles reach deeper layers with adequate bearing capacity.
- Reinforcement Positioning: Reinforced concrete piles with steel sections to withstand lateral loads.
- Typical Dimensions: Diameter of 300mm to 600mm and depths can exceed 10m depending on soil conditions.
Step 3
Discuss two factors that must be taken into account to ensure the maximum strength of concrete in a foundation.
Answer
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Water-Cement Ratio: The proportion of water to cement is crucial, as too much water can weaken the mixture. An optimal ratio ensures the concrete achieves the desired strength and durability.
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Mixing Techniques: Proper mixing is vital to achieve a uniform distribution of materials. Techniques include batching by weight or volume and using consistent methods to avoid segregation of aggregates during the mixing process.