CLASS 7 Q&A

Concrete Structure Construction

Monolithic Pour: Columns and slabs can be poured simultaneously in a concrete structure, creating a strong, unified structure.

Re-shoring: Necessary when a slab hasn’t gained sufficient strength to support loads typically before reaching 75-100% of its design strength.
Slab Types:
- One-way Slab: Carries load along one direction between two supports.
- Two-way Slab: Distributes load in both directions, supported on all sides.
Importance of Rebar: The bottom layer of rebar is crucial in a two-way slab for resisting bending moments, providing tensile strength.
Pour Stopping Points: Typically stops at mid-span between support points or predetermined construction joints.
Formwork Removal: Formwork and shores for an upper-level slab can be removed after 3-4 days or when reaching the necessary strength.
Weak Points in Lift Slab: Control joints are considered the weakest points in a lift slab.

Mat Foundation: A concrete slab that spreads across the entire footprint of a building, transferring weight to the soil.
Floating Foundation: Constructed by excavating soil such that the weight of the structure balances the weight of the soil removed, including water weight.

Concrete Evaluation: If a monolithic slab shows severe cracking, it must be evaluated by a Structural Engineer for necessary repairs, which may include re-pouring or using an epoxy mix.

Visible Effects: When concrete freezes, it appears frosty or icy, has a rough texture, and may exhibit cracks or pitting.

Glacial Till: Dense, unsorted mixture of materials deposited by glaciers.
Backfilling Technique: Backfill concrete foundation walls in lifts of 6-24" thick, compacting each lift before the next.
Dozer Operation: Run the dozer perpendicular to the wall to minimize lateral pressure on the foundation.
Backfilling Timing: Do not backfill a high concrete wall immediately after stripping.
Well Point System: A dewatering method using small-diameter pipes to lower groundwater levels surrounding construction sites.
Unbalanced Fill: Occurs when one side of a foundation has higher backfill, causing uneven pressure.
Slope Requirements: The grade for a commercial building should slope away at 2% for drainage purposes.
Guinea Definition: A blue-painted grade stake used for elevation marking.

Bedrock Evaluation: When encountering bedrock during excavation, have it evaluated by an engineer, typically doweling into the bedrock to integrate it into the structure.
Tying Footings to Bedrock: Use rebar or anchor bolts installed into drilled holes in bedrock, pouring concrete around them.

Slurry Wall Construction: Involves creating a trench filled with bentonite slurry for stabilization, followed by placing reinforcement and concrete. Guide walls are typically 3 feet wide.
Tiebacks: Horizontal anchors that stabilize retaining walls by connecting them to a stable structure behind.
Pile Definition: Deep foundation elements used to transfer heavy loads to deeper, stable soil or bedrock.
Pile Cap: A thick slab that distributes loads from columns/walls to a group of piles.
Pile Heave: Upward movement occurring during pile driving; must be monitored and possibly addressed by redriving or creating voids.
Pipe Pile vs. Bell Caisson: Pipe piles are hollow tubes driven into the ground; bell caissons have a wider base for increased capacity.
Franki Pile: A driven cast-in-place concrete pile with a compacted base plug, named after its inventor, Edgard Frankignoul.
Installation Method: Driven by a drop hammer that compacts a concrete plug to stabilize the casing.
Removing Deviations: Engage a structural engineer for corrective procedures if piles deviate from tolerances.
Caisson Description: Drilled foundations expanded at the base, unlike piles.
Wood Pile Guidelines: Cutoff point should be below the lowest expected groundwater level.

AISC: The American Institute of Steel Construction; sets steel design standards.
Moment Connection: A joint allowing the transfer of bending moments between structural members such as beams and columns.
Shear Stud Definition: Transfers shear forces between steel beams and concrete, creating composite action.
Erection Tolerance: Typically ranges from 1/8 to 1/4 inch for steel structures.
Commercial Stair Specifications:
- Riser Height: 7 inches
- Tread Depth: 11 inches
Relieving Angle: Supports masonry, relieving it of structural load.
Plumbness Tolerance: 1/500 of steel column height in any direction as per AISC guidelines.
Adjusting Out-of-Plumb Steel: Consult the structural engineer for adjustments, preferably in small increments.
Beam Penetration Method: Can be reinforced with stiffeners or additional framing.
Cold Rolled Steel Usage: Typically used in applications requiring thinner, precise materials.
Tension Control Bolt: Pre-tensioned bolts torqued until the spline shears off, commonly used in structural connections.