Structural Engineering Quiz

Flooring Systems Overview

Flooring systems transfer loads horizontally to beams, columns, or load-bearing walls.

Key materials used include concrete, steel, and wood.

Types of Loads

Live loads: Include people, furnishings, and movable equipment.

Dead loads: Include the weight of the floor construction itself.

Key Materials in Flooring Systems

Concrete: Precast concrete planks supported by beams or load-bearing walls.

Steel: Steel beams support steel decking or precast concrete planks.

Wood: Wood beams support structural planking or decking.

Reinforced Concrete Beams

Reinforced concrete beams work together with longitudinal and web reinforcement to resist applied forces.

Reinforcing Bars in Concrete Beams

Reinforcing bars extend into and down column support for structural continuity and develop required embedment length for anchorage.

Types of Reinforcing Bars

Top bar: Longitudinal bars serving as tension reinforcement in the upward bending of a negative moment section of a beam.

Bottom bar: Longitudinal bars serving as tension reinforcement in the downward bending of a positive moment section of a beam.

Bent bars: Longitudinal bars bent at a 30-degree or greater angle to the beam axis, intersecting potential diagonal tension cracks.

Stirrups: U-shaped or closed-loop bars placed perpendicular to longitudinal reinforcement, resisting vertical component of diagonal tension.

Hooks: Bends at the end of tension bars to develop equivalent embedment length for anchorage (90°, 135°, or 180°).

Concrete Slabs

Concrete slabs are plate structures reinforced to span either one or both directions of a structural bay.

Types of Concrete Slabs

One-way slab: Uniformly thick, reinforced in one direction, cast integrally with parallel supporting beams.

One-way joist slab: Cast integrally with a series of closely spaced joists supported by a parallel set of beams.

Two-way slab and beam: Uniform thickness, reinforced in two directions, cast integrally with supporting beams and columns on all four sides of the square bays.

Two-way waffle slab: Two-way concrete slab reinforced by ribs, carrying heavier loads and spanning longer distances than flat slabs.

Two-way flat plate: Uniform thickness, reinforced in two or more directions, resting directly on columns without beams or girders.

Two-way flat slab: Flat plate thickened at column supports to increase shear strength and resisting moment capacity.

Prestressed Concrete

Reinforced by pre-tensioning or post-tensioning high-strength steel tendons within their elastic limit.

Two Types of Prestressing Techniques

Pre-tensioning: Pre-stresses a concrete member by stretching the reinforcing tendons before concrete is cast.

Post-tensioning: Pre-stresses a concrete member by tensioning the reinforcing tendons after the concrete has set.

Pre-tensioning Process

Steel tendons stretched across the casting bed between abutments until a predetermined tensile force is developed.

Concrete cast in formwork around stretched tendons and fully cured.

Tendons placed eccentrically to reduce maximum compressive stress.

Tendons cut/released, tensile stresses transferred to concrete.

Member develops slight upward curvature (camber).

Deflection of member under loading equalizes the upward curvature.

Post-tensioning Process

Unstressed steel tendons draped inside the beam/slab form, coated/sheathed to prevent bonding during concrete casting.

Tendons clamped on one end and jacked against the concrete on the other end until the required force is developed.

Tendons securely anchored and the jack removed.

Tendons left unbonded or bonded to surrounding concrete by injecting grout into annular spaces around sheathed strands.

Deflection of the member under loading equalizes the upward curvature.

Precast Concrete Floor Systems

Units cast and steam-cured in a plant off-site, transported to the construction site, and set in place as rigid components with cranes.

Precast Concrete Units

Solid flat slabs

Hollow core slabs

Single tees

Double tees

Rectangular beams

L-shaped beams

Inverted tee beams

AASHTO girders

Structural Steel Framing

Structural steel girders, beams, and columns used as a skeleton frame for structures from one-story buildings to skyscrapers.

Types of Beams Systems

One-way beam system: Suitable for long, narrow buildings when column-free space is desired.

Two-way beam system: Increases floor depth considerably but provides more space for mechanical services.

Triple beam system: Long-spanning plate girders or trusses used to carry primary beams supporting secondary beams when extensive column-free space is required.

Steel Beams

Lightest steel section that will resist bending and shear forces within allowable limits of stress and without excessive deflection.

More structurally efficient wide-flange (W) shapes largely supersede classic I-beams (S).

Beams also come in channel (C) sections, structural tubing, or composite sections.

Open-Web Steel Joists

Lightweight, shop-fabricated steel members with a trussed web.

Types of Open-Web Steel Joists

K series joist: Web consists of a single bent bar running in a zigzag pattern between the upper and lower chords.

LH and DH series joists: Heavier web and chord members for increased loads and spans.

Floor Decks of Open-Web Joist Framing

Metal decking with concrete fill

Precast concrete planks

Plywood panels or wood planking

Metal Decking

Corrugated to increase stiffness and spanning capability.

Common types include Form decking, Composite Decking, and Cellular Decking.

What is Form Decking?

Serves as permanent formwork for a reinforced concrete slab until the slab can support itself and its live load.

What is Composite Decking?

Serves as textile reinforcement for the concrete slab and bonded with an embossed rib.

What is Cellular Decking?

Manufactured by welding corrugated sheet to a flat steel sheet; it serves as an acoustic ceiling when the perforated cells are filled with fiberglass.

Light-Gauge Steel Joists

Cold-forming steel sheets or strip steel.

Lighter, more dimensionally stable, and can span longer distances.

Common span ranges are 6", 8", 10", and 12" joists covering various span lengths.

Overhangs and floor openings are framed similarly to wood framing.

Connections are made with screws, pins, or welding when appropriate.

Wood Joists

Essential subsystem in wood light-frame construction; horizontal beams that support the floor.

Because of flammability, finish flooring and ceiling materials must be used.

Susceptibility to decay requires positive site drainage, adequate separation from the ground, appropriate pressured lumber used.

Joists spaced 12", 16", or 24" o.c. (305, 405, or 610)

Platform Framing

Predominantly used in wood-frame buildings where each floor is framed separately with studs or support posts that run from the bottom to the top of the same floor level.

Using larger but fewer structural members that can span greater distances translates to potential savings in material and labor.

Sill plates and holds downs secure the framing and anchor it to the supporting structure against uplift forces and seismic activity..

Balloon Framing

Extends studs vertically across the building's height.

Studs connect to a foundation plate and a top plate, which supports the roof.

Typically uses a solid blocking system to act as firestops with multiple nailed joints.

Beam Pocket

Recessed space designed to accommodate the ends of intersecting beams, within a concrete, masonry, or column.

Minimum 1/2" air space for wood beam entrance. Includes additional sheathing for stability and protection from concrete penetration.

Wood Beam and Joists Framing

Joist hangers are used to securely anchor wood beams into wood and support the weight of floors, decking, and roofs.

Wooden beams are used for structural support and can provide a decorative look and feel.

Steel Beam and Ledger Framing

Steel beams primarily function to counteract applied loads perpendicular to the beams axis.

The steel beams, through their structure are able to function as a redirection method. For example opposing loads with minimal or no distortion.

Wood Beam with Spliced Joists

Wood beams and spliced joists work together by supporting the structure with the use of a solid blocking system. The structural member requires a minimum lap and support at the splice points.

Non Bearing Partition Framing

Non-bearing partitions are dividing walls that only support their own weight and do not bear the weight of other parts of the structure such as floors or ceilings.

Bearing Partition Framing

Bearing partitions serve as both dividers, but more importantly, these bear the weight of the structure above and below, and run parallel to joists, and support the structure.

Wood Plank and Beam Framing

Characterized by a grid of posts or columns, this framing system uses larger, but fewer, members that can span greater distances, translating into material and labor cost savings.

The framework needs to be carefully integrated with structural partitions and visually appealing aesthetics.

Wood Decking

Consists of plywood, lumber, or glued-laminated members placed over structural members to give structural support and a base for roofing or flooring.

Types of Wood Decking

Solid: 2x6, 2x8, 3x6, and 4x6 (nominal sizes).

Laminated: 3x6, 3x8, 3x10 laminates, 4x6, 4x8, 6x6, and 6x8 nominal sizes.

Surface Patterns for Exposed Ceilings

V-groove

Channel groove

Plain or molded spline

Striated

Wood Decking Types of Span

Simple span: Planks rest on each end and will have the most deflection to a given load; this is the least efficient approach.

Double span: Often the most efficient in terms of material usage; this design provides the most stability and rigidity.

Continuous span: Extending across multiple supports, continuous spans reduce material waste and will distribute overall load efficiently.

Wood Subflooring

Provides a structural base over joists, enabling consistent surface for construction and the base layer for flooring; often made from panels, plywood, lumber, and laminated materials.

Prefabricated Joists and Trusses

Pre-engineered wood joists and trusses increasingly replace dimensional lumber in flooring applications due to their lighter weight, dimension stability, and wide spanning capabilities.

Solid Sawn Lumber

Commonly used for heavy timber or post and beam construction; often oversized to offer greater strength and a wider spanning ability.

Glue-Laminated Timber

Made by laminating stress-grade lumber with adhesive under controlled conditions, usually considering grain orientation.

Parallel Strand Lumber (PSL)

A structural lumber produced through bonding long and narrow wood strands under controlled heat and pressure, using waterproof adhesive.

Laminated Veneer Lumber (LVL)

Structural lumber made by bonding layers of wood veneers together under heat and pressure.

Wood Beam Supports

Provide resistance to uplift and horizontal forces. Connectors use metal, wood-to-wood, and metal-to-wood connectors that can withstand a variety of conditions

Wood Posts and Beam Connections

Methods for connecting wood posts to beams and girders, including using bolts, steel plates, and connections.

These fasteners increase the load bearing capabilities of both wood and metal members.

Wood Plank and Beam Framing

Wood plank and beam framing is a common construction method utilizing a series of horizontal beams, or joists, to support a floor's weight. These joists run from one side to the other of the structure.

Wood Decking

Typical decking can consist of panels produced from glue-laminated timber, plywood, lumber, or glued laminated members, placed over structural members for rigidity and flooring or roofing.