Slabs, Trusses, and Building Joints

This set of vocabulary flashcards covers slab types, truss definitions and methods, and various building joints as presented in structural engineering lecture notes.

Slab

A rigid, flat structural element constructed to create flat and useful surfaces such as floors, roofs and ceilings.

One-Way Slab

A slab supported by beams on 2 opposite sides to carry the load along one direction where the ratio of the longer span (L) to the shorter span (B) is $\text{L/B} \geq 2$.

One-Way Banded Slab

A slab type that reduces the span between units using bands with smaller depth than beams, resulting in reduced slab thickness and more clear height or reduced storey height.

One-Way Ribbed Slab

A system where reinforcements are concentrated in spaced ribs or joists to make the slab thinner and lighter.

Wide-module / Skip Joist

Thicker slabs that can span greater spans with joists placed $4'$ to $6'$ apart.

Two-Way Slab

A slab supported by beams on all 4 sides to carry the load along both directions where the ratio of the longer span (L) to the shorter span (B) is $\text{L/B} < 2$.

Flat Slab

A two-way slab without beams where the slab is thickened to resist forces, including variations like flat plates, drop panels, and mushroom capitals.

Punching Shear Failure

A failure in reinforced concrete (RC) slabs caused by concentrated loads creating shear.

Waffle Slab

A two-way ribbed or joist system consisting of perimeter beams, column heads, and a grid of interior/edge panels.

Truss

A structural frame based on the geometric rigidity of a triangle composed of linear members subject only to axial tension or compression.

Space Frame

A truss made 3-dimensional that bends along both of its axes.

Diagrid

A form of space truss consisting of a perimeter grid formed by intersecting diagonal and horizontal components.

Method of Joints

A procedure for determining member forces in a truss by considering the equilibrium of the various joints.

Method of Sections

A procedure for determining member forces in a truss by considering the equilibrium of any portion of the truss assembly.

Nonmovement Joints

Typical joints used to connect pieces of material (e.g. nailed wood, mortar in masonry, welded steel) that can only be made to move by overloading the joint.

Movement Joints

Joints that have the ability to adjust to expected amounts of motion without distress.

Working Joints

Movement joints created in the normal process of assembling a building, such as a shingle roof overlapping pattern that allows thermal or moisture movement.

Structure/Enclosure Joints

Joints that separate structural from nonstructural elements (e.g. soft sealant, shelf angle) so they act independently.

Isolation Joints

Joints that separate materials that must be able to move independently without interfering with one another.

Control Joints

Purposely created lines of weakness along which cracking will occur as a surface of brittle material shrinks (contraction).

Building Separation Joints

Joints that divide a large or complex building mass into smaller structures that can move independently.

Volume-Change Joint

A type of building separation joint that relieves large-scale effects of expansion and contraction.

Settlement Joint

A building separation joint designed to avoid distress caused by different rates of anticipated settlement.

Construction Joint

A joint between 2 successive placements of concrete, often keyed or doweled to provide lateral stability across the joint.

Cold Joint

Weakened planes between hardened and fresh concrete due to delay or interruption in concreting works.

Max Unbroken Wall Length (Masonry)

The length beyond which an expansion joint is required, which should not exceed $125'$ ($40\,m$).

Max Unbroken Wall Length (Steel/Concrete)

The length beyond which an expansion joint is required, which should not exceed $200'$ ($60\,m$).