Foundation Design and Soil Types in Architecture

What are the main ingredients in concrete composition?

10-15% Cement, 15-20% Water, 60-75% Aggregates, 0-5% Admixtures.

What is the role of cement in concrete?

Cement acts as a binding agent.

What types of aggregates are used in concrete?

Coarse aggregates like sand, gravel, and pebbles.

What are the basic issues in foundation design?

Site exploration, site design, and selection of foundation type.

How are soils classified in terms of stability?

From most stable to most variable: Solid Rock, Sands + Gravels, Silts, Clays, Organics.

What is the load-bearing pressure of crystalline bedrock?

12,000 lbs/sq.ft.

What is the load-bearing pressure of sandy gravel?

5,000 lbs/sq.ft.

What are the principal properties of soils relevant to foundation design?

Strength, strain resistance, and stability.

What is a geotechnical survey?

A report that determines the subsurface soil profile through soil borings.

What issues can arise from expansive soils?

Shrinking and swelling can cause upward and sideways stresses on foundations.

What is differential settlement in foundation design?

Uneven settling of foundation elements that can lead to cracking.

What is hydrostatic pressure in relation to soil?

The build-up of water in soil causing uneven pressure, leading to waterproofing issues.

What is the effect of temperature on soil?

Most soils expand and heave when frozen; foundations must be placed below the frost line.

What are shallow bearing foundations?

Foundations that transfer vertical loads by direct bearing on soil strata close to the ground surface.

What are deep foundations?

Foundations that extend deeper into the ground to provide stability for larger structures.

What is the purpose of damp-proofing in foundation design?

To prevent moisture in the soil from invading below-grade structures.

What is the significance of soil bearing capacities in foundation design?

They help determine the best foundation type based on the load and soil conditions.

What are the effects of volume change in soil?

Soil settling or expanding can place uneven stress on the foundation.

What is the maximum depth of frost penetration in New York City?

Approximately 1 meter (40 inches).

What is the maximum depth of frost penetration in Lubbock?

Approximately 0.25 meters (12 inches).

What is the purpose of core borings in foundation design?

To identify the strata present below grade and assess soil properties.

What is the load-bearing pressure of clay soils?

2,000 lbs/sq.ft.

What are the characteristics of silts in soil classification?

Cohesive, fine-grained soils that are between clays and sands.

What is the role of admixtures in concrete?

To achieve specific characteristics like fast/slow curing and water resistance.

Name two types of shallow bearing foundations.

Wall Footing and Combined Column Footing.

What is a moment-resistive footing?

A type of footing designed to resist bending moments.

What is a cantilever wall?

A wall that is supported on one side and extends outward, often used to retain soil.

What problems can arise with shallow foundations?

Excavation undermines upper footings, settlement of lower footings drags down upper footings, and lateral pressure can push footings sideways.

Why are deep foundations necessary?

When soil conditions are inadequate for bearing footings, for extremely heavy loads, or due to potential instability of ground-level soil.

What is an end-bearing pier?

A type of deep foundation that transfers loads directly to a stable stratum.

What are friction piles?

Deep foundations that transfer loads through skin friction along the sides of the pile.

What materials are commonly used for driven piles?

Steel H-Pile, Precast Concrete Pile, Timber Pile, and Steel Pipe Pile.

What is a typical reinforced concrete pile cap?

A structure that transfers loads from a building column to a group of piles.

What is a belled end in pier construction?

An enlarged bearing area at the bottom of a pier to distribute loads more effectively.

What is a matt or raft foundation?

A large foundation type that spreads loads over a wide area, creating a 'floating' effect.

What is the maximum soil capacity for a footing?

The sum of the unfactored superimposed load and the unfactored weight of the footing must not exceed the bearing pressure limit.

What is shear capacity limit for concrete footings?

The critical stress in the footing, which must be managed to minimize reinforcement needs.

What is the importance of flexural tension stress in footings?

It concerns the bending action and the development of steel bars needed for reinforcement.

What is one-way shear in footing design?

Shear calculated over a rectangular area under the footing.

What is two-way shear?

Shear calculated over the area outside a square section of the footing.

What factors determine footing width?

Allowable bearing pressure, assumed thickness, and total load including the weight of the footing.

What is the role of longitudinal reinforcing in lightly loaded walls?

To provide temperature reinforcement and assist in spanning weaker soil conditions.

What is a strap or cantilever type column footing?

A combined footing type that connects multiple columns to distribute loads over a larger area.

What determines the required thickness of footings without transverse reinforcement?

The tension stress limit of the concrete in either flexural stress or diagonal stress due to shear.

What is the recommended maximum thickness for unreinforced footings according to ACI code?

8 inches.

What is the recommended maximum thickness for reinforced footings according to ACI code?

10 inches.

What is the minimum coverage for reinforcement from formed edges?

2 inches.

What is the minimum coverage for reinforcement from unformed edges?

3 inches.

What type of footings act like inverted beams?

Simple spread footings.

What causes bending in the upward direction of a footing?

Upward soil pressure resisted by downward column action.

What must be added near the bottom of the footing if tension is significant?

Tension reinforcing.

What is the general concrete coverage for slabs cast against the ground?

3 inches.

What is the concrete coverage for exposed rebar in contact with the ground for #6-#18 bars?

2 inches.

What is the formula for earth pressure at any given point on a retaining wall?

P = Co(W)(h), where Co is the coefficient of earth pressure, W is the equivalent weight of soil, and h is the depth.

What is the simplified formula for earth pressure using a fluid weight of 30 lb/ft³?

P = 30(h).

What is the total earth pressure acting through the centroid of the triangle?

P = W(h)(1/2)(h) or P = ½(W)h².

What is the maximum earth pressure formula?

P = W(h).

How much lateral force must a 10-ft high retaining wall resist?

1,500 lb/ft.

What are the three ways retaining walls can fail?

Overturning, sliding, and undermining.

What is a cantilever retaining wall made from?

Steel-reinforced, cast-in-place concrete or mortared masonry.

What is the function of counterfoots in a counterfoot wall?

They act as diagonal bracing for the wall.

What type of wall uses cables driven into soil or rock for stabilization?

Anchored wall.

What type of retaining wall depends on the mass of materials to resist forces?

Gravity wall.

What is the purpose of transverse reinforcement in footings?

To address shear in the concrete and tension in the reinforcement.

What is the minimum coverage for beams and columns' primary reinforcement?

1.5 inches.

What is the coverage for pre-stressed beams?

1 inch.

What is the role of mechanically stabilized earth (MSE) in retaining walls?

It holds back tons of fill and decouples the earth-retaining function from the architecture.

What is the habitat bench in the Olympic Sculpture Park case study?

Layers of riprap and smaller diameter rock incorporated into the buttress at the intertidal zone.