structures I test 1

Section-Active Structures

Section-Active Structures

Structures that rely on the mass and organization of their cross sections to resist forces. Forces generally applied perpendicularly to the span. Examples are: column and beam structures.

Vector-Active Structures

Structures that rely on multiple linear elements arranged such that each member takes on either tension or compression forces. The stability of triangles is a key feature to this structural type. Examples are: trusses and space frames.

Form-Active Structures

Structures that rely on their form to create purely compressive or purely tensile configurations to move forces to the ground. Each arch is able to hit the ground. Examples are: arches, cable structures, pneumatic structures, and tent structures.

Surface-Active Structures

Structures that rely on a surface and its formal configuration to resist forces. Spans end to end. (Differs from Form-Active in that these surfaces work to balance forces of tension and compression which are both present in the structural surfaces). Examples are: shell structures, folded structures, and plate structures.

Beam

A structural member that resists bending forces. Generally a horizontal spanning member that uses its cross section to balance forces of tension and compression in order to resist perpendicular loads.

Span

The clear distance between vertical supports. Can be applied to any structural type.

Deflection

The degree to which a structural member changes shape under loading. For example, the sagging of a beam at its midpoint because of self weight or applied loads.

Column

A structural member that carries axial loads (loads applied parallel to it’s length). Generally a vertical member carrying gravity loads and designed to resist both compression and buckling.

Joist

A secondary type of beam that is repeated at close spacing, generally spanning between primary beams or girders.

Tension

A type of force in which a material’s fibers tend to be pulled away from each other.

Compression

A type of force in which a material’s fibers tend to be pushed into one another.

Load

Any external force acting on a structure. Often represented by arrows with length representing magnitude and direction representing the orientation that the load is applied.

Live Load

Those loads produced by the use and occupancy of a building or structure and do not include construction loads, environmental loads or dead loads. These loads are transient in nature and vary in magnitude over the life of a structure, such as the weight of people and moving objects.

Dead Load

Loads that are fixed and permanent. The actual weights of construction materials and fixed service equipment that are attached to or supported by the building or structure.

Lateral Load

A load applied to a structure along lines other than those between the object and the earth’s center, such as wind and earthquake loads. These forces push or pull horizontally or diagonally on a structure, as opposed to the typically vertical nature of gravity forces.

Environmental Loads

Loads that consist of rain loads, wind loads, snow loads, earthquakes, and flood loads. These loads are transient in nature and vary in magnitude over the life of a structure. These loads can be gravitational, such as snow loads on a roof, or lateral, such as wind or earthquake loads.

Distributed Load

A load that is spread out over a line or surface. These can be evenly distributed or not, and they are often represented by a series of arrows connected at the top by a line.

Point Load (AKA Concentrated Load)

A load that is applied at a discreet point. These are often represented by a single force arrow.

Thrust

A horizontal/outward force. An inevitable consequence of two-dimensional arched structures. The geometry of these systems creates a resultant force—outward in compression structures and inward in tension structures—that must be countered for the structure to stand.

Load Path

Every load applied to the building will travel through the structural system until it is transferred to the supporting soil. This is the path of travel of these loads through the structure.

Vector

A representation of some force that has both direction and magnitude, usually an arrow whose direction represents orientation of force and length represents size.

Free Body Diagram

A diagrammatic abstraction of the forces at work on a single monolithic structure. Uses vectors to indicate applied forces and reactions, which in a stable structure lead to equilibrium.

Equilibrium

The condition of being at rest. Any forces acting on the object must be balanced by forces adding up to equal and opposite reactions. There are two major states of this: translational (movement side to side), and rotational.

Fixed Connection (AKA Moment Connection)

A structural connection that does not permit a structural member to translate or rotate.

Pinned Connection

A structural connection that allows rotation, but does not allow translation.

Roller Connection

A structural connection that allows rotation and some, but limited, side to side translation.

Pneumatic Structure

A structure that relies on pressurized air to keep a thin membrane in constant tension, enabling it to span considerable distances.

Space Frame

A network of trusses arranged at an angle to one another and interconnected to span in two dimensions. A two-way spanning vector-active structure. These can take on a flat form, or they can be made to accommodate vaulted or double-curved forms.

Truss

A structural member that is made up of smaller linear elements, arranged such that each one takes on either compression or tension forces. It replaces the solid web of a beam with a network of members, usually arranged in triangular panels. Like a beam, these resist bending forces, and loads are generally applied perpendicularly to their span.

Tributary Area

The total area of floor plate with weight that flows into a specific column or beam. Calculating this allows one to determine the overall live load and dead load required to be resisted by that particular member.

Web (of beam or truss)

In beam design, the element designed to space flanges apart from each other, and thus away from the neutral axis. In beams, these components are solid, while in trusses, these components are made up of multiple linear elements, lightening the weight of the member, and connecting top and bottom chords.

Flange

In beam design, top and bottom elements designed to put the most possible material in the most efficient places—far from the neutral axis—in order to resist tension on the bottom and compression on the top.

Catenary

The form taken by a hanging cable, rope or chain structure that is only resisting tensile forces.

Torsion Forces

Twisting a beam like a spiral long-ways.

Shear Forces

An internal force in any material which is usually caused by any external force acting perpendicular to the material.

Bending Forces

Literally bending the beam.

Morphology

A scientific study of the structure and form of animals and plants(and other things).

Lateral Forces

Horizontal forces, such as pressure and suction. A type of live load because it is variable.

Depth

Refers to the vertical height of beams.

2-Way Span

Decking, joists, beams, and some slabs are this type of span.

1-Way Span

Slabs are this type of span.

Load Path

Every load applied to the building will travel through the structural system until it is transferred to the supporting soil.