Structural Design Principles and Concrete Testing Methods

AA (1:1½:3)

Concrete under water, retaining walls.

A (1:2:4)

Footings, column beams, Reinforced Concrete slabs.

B (1:2½:5)

Slab on fill, non-bearing walls.

C (1:3:6)

Concrete plant boxes, etc.

Slump Test

Checks freshly mixed concrete to ensure the specified slump is consistently attained.

Standard Slump Cone

12 inches (0.30 m) high, 8 inches (0.20 m) diameter at the bottom, and 4 inches (0.10 m) on top, open on both ends.

Procedure of Slump Test

The cone is filled in three equal layers, each tamped or rodded 25 times with a standard 5/8" bullet-nosed rod. The cone is then lifted, and the slump is measured.

Allowable Deflection 'X' for Beams and Columns

7.5 cm (0.075 m) or 3 inches.

Allowable Deflection 'X' for Slabs and Tunnel Inverts

5.0 cm (0.05 m) or 2 inches.

Allowable Deflection 'X' for Side Walls and Arch in Tunnel Lining

10.0 cm (0.10 m) or 4 inches.

Allowable Deflection 'X' for Canal Lining

7.5 cm (0.075 m) or 3 inches.

Allowable Deflection 'X' for Heavy Mass Construction

5.0 cm (0.05 m) or 2 inches.

Allowable Deflection 'X' for Beam, Column, Slab

2" to 4" or 0.05 to 0.10.

Compressive Strength Test

A common quality-control test of concrete, based on 7 and 28-day curing periods.

Specimens for Compressive Strength Test

Usually cylindrical with a length equal to twice the diameter; standard size is 12 inches high and 6 inches diameter.

Procedure of Compressive Strength Test

Filling is done similarly to the slump test, but specimens are taken out of the mold in 24 hours and sent to a compression testing laboratory after marking.

Common Compressive Stresses

2,000 psi, 2,500 psi, 3,000 psi.

Beam

A rigid structural member designed to carry and transfer transverse loads across space to supporting elements.

Span

The extent of space between two supports of a structure; also, the structure so supported.

Clear Span

The distance between the inner faces of the supports of a span.

Effective Span

The center-to-center distance between the supports of a span.

Bending Moment

An external moment tending to cause part of a structure to rotate or bend.

Resisting Moment

An internal moment equal and opposite to a bending moment, generated by a force couple to maintain equilibrium.

Deflection

The perpendicular distance a spanning member deviates from a true course under transverse loading.

Camber

A slight convex curvature intentionally built into a beam, girder, or truss to compensate for anticipated deflection.

Transverse Shear

An external shear force at a cross-section of a beam or other member subject to bending.

Horizontal Shearing Stress

Shearing stress developed to prevent slippage along longitudinal planes of a beam under transverse loading.

Vertical Shearing Stress

Shearing stress developed along the cross-section of a beam to resist transverse shear.

Shear Diagram

A graphic representation of the variation in magnitude of external shears in a structure.

Moment Diagram

A graphic representation of the variation in magnitude of bending moments in a structure.

Simple Beam

A beam resting on simple supports at both ends, free to rotate and having no moment resistance.

Cantilever Beam

A projecting beam supported at only one fixed end.

Overhanging Beam

A simple beam extending beyond one of its supports.

Double Overhanging Beam

A simple beam extending beyond both of its supports.

Fixed-End Beam

A beam having both ends restrained against translation and rotation.

Cantilever

A beam or other rigid structural member extending beyond a fulcrum and supported by a balancing member or a downward force behind the fulcrum.

Positive Shear

A net resultant of shear forces that acts vertically upward on the left part of the structure.

Negative Shear

A net resultant of shear forces that acts vertically downward on the left part of the structure.

Positive Moment

A net resultant of shear forces that acts vertically downward on the left part of the structure being considered.

Inflection Point

A point at which a structure changes curvature from convex to concave or vice versa as it deflects under a transverse load; theoretically an internal hinge and a point of zero moment.

Negative Moment

A bending moment that produces a convex curvature at a section of a structure.

Haunch

The part of a beam that is thickened or deepened to develop greater moment resistance.

Suspended-Span (Hung-span)

A simple beam supported by the cantilevers of two adjoining spans with pinned construction joints at points of zero moment.

Effective Length

The distance between inflection points in the span of a fixed-end or continuous beam, equivalent to the actual length of a simply supported beam.

Load

Any of the forces to which a structure is subjected.

Concentrated Load

A load acting on a very small area in a particular point of a supporting structural element.

Distributed Load

A load extending over the length or area of the supporting structural element.

Uniformly Distributed Load

A distributed load of uniform magnitude.

Occupancy Load

The live load on a structure resulting from the weight of people, furniture, stored material, and other similar items in a building.

Water Load

The live load of water that may accumulate on a roof.

Live Load

Any moving or movable load on a structure resulting from occupancy.

Dead Load

The static load acting vertically downward on a structure, comprising the self-weight of the structure and the weight of building elements, fixtures, and equipment permanently attached to it.

Settlement Load

A load imposed on a structure by subsidence of a portion of the supporting soil.

Static Load

A load applied slowly to a structure until it reaches its peak value without fluctuating rapidly in magnitude or position.

Addition

An extension or increase in floor area or height of a building or structure.

Allowable Stress Design (Working Stress Design)

A method of proportioning structural elements such that computed stresses do not exceed specified allowable stress.

Alter or Alteration

Any change, addition or modification in construction or occupancy.

Load and Resistance Factor Design (LRFD) Method

A method of proportioning structural elements using load and resistance factors such that no applicable limit state is reached. Used in the design of steel and wood structures.

Strength Design

A method of proportioning structural elements such that computed forces do not exceed the factored element strength. Used in the design of concrete and masonry structures.

Structure

That which is built or constructed, an edifice or building of any kind, or any piece of work, artificially built up or composed of parts joined together in some definite manner.

Prefabricated Assembly

A structural unit whose integral parts have been built up or assembled prior to incorporating in the building.

Access Floor System

An assembly of panels mounted on pedestals to provide under-floor space.

Assembly Building

A building or portion for the gathering of 50 or more persons.

Awning

A shelter supported entirely from the exterior wall of the building.

Balcony, Exterior

An exterior floor system projecting from a structure and supported by that structure, with no additional independent supports.

Deck

An exterior floor system supported on at least two opposing sides by an adjoining structure and/or posts, piers, or other independent supports.

Essential Facilities

Buildings and other structures intended to remain operational during extreme environmental loading from wind or earthquakes.

Garage

A building or portion where motor vehicles containing flammable or combustible liquids or gas are stored, repaired, or kept.

Limit State

A condition in which a structure or component is judged either to be no longer useful for its intended function (serviceability limit state) or to be unsafe (strength limit state).

Marquee

A permanent roofed structure attached to and supported by the building and projecting over public property.

Bearing Wall

Any metal or wood stud wall that supports more than 0.5 kN per linear meter of superimposed load, or any masonry or concrete wall that supports more than 1.0 kN per linear meter superimposed loads, or any such wall supporting its own weight for more than one story.

Exterior Wall

Any wall or element that defines the exterior boundaries or courts of a building and has a slope of 60 degrees or greater with the horizontal plane.

Nonbearing Wall

Any wall that is not a bearing wall.

Parapet Wall

That part of any wall entirely above the roof line.

Retaining Wall

A wall designed to resist lateral displacement of soil or other materials.

Building, Enclosed

A building that does not comply with the requirements for open or partially enclosed buildings.

Building, Open

A structure having all walls at least 80% open.

Building, Partially Enclosed

A building complying with specific conditions regarding opening areas.

Building, Low Rise

An enclosed or partially enclosed building with a mean roof height less than or equal to 18 meters, and the mean roof height does not exceed the least horizontal dimension.

Components and Cladding

Elements that do not qualify as part of the main wind-force resisting system.

Design Force, F

The equivalent static force for determining wind loads for open buildings and other structures.

Design Pressure, P

The equivalent static pressure for determining wind loads for buildings.

Flexible Buildings and other Structures

Slender buildings and other structures with a fundamental natural frequency less than 1 Hz, or a height exceeding four times the least horizontal dimension.

Base Shear, V

The total design lateral force or shear at the base of a structure.

Bearing Wall System

A structural system without a complete vertical load-carrying space frame.

Boundary Element

An element at the edges of openings or at perimeters of shear walls or diaphragms.

Braced Frame

An essentially vertical truss system (concentric or eccentric) to resist lateral forces.

Building Frame System

An essentially complete space frame that provides support for gravity loads.

Cantilevered Column Element

A column element in a lateral-force-resisting system that cantilevers from a fixed base with minimal moment capacity at the top.

Concentrically Braced Frame

A braced frame where members are subjected primarily to axial forces.

Diaphragm

A horizontal or nearly horizontal system transmitting lateral forces to vertical-resisting elements; includes horizontal bracing systems.

Horizontal Bracing System

A horizontal truss system serving the same function as a diaphragm.

Lateral-Force-Resisting System

The part of the structural system designed to resist Design Seismic Forces.

Shear Wall (Vertical Diaphragm or Structural Wall)

A wall designed to resist lateral forces parallel to the plane of the wall.

Soft Story

A story where the lateral stiffness is less than 70 percent of the stiffness of the story above.

Story Drift

The lateral displacement of one level relative to the level above or below.

Strength

The capacity of an element or a member to resist factored load.

Weak Story

A story where the story strength is less than 80 percent of the story above.

Modulus of Elasticity

The ratio of normal stress to corresponding strain for tensile or compressive stresses below the proportional limit of material.

Shores

Vertical or inclined support members designed to carry the weight of formwork, concrete, and construction loads above.