Structural Steel Engineering Basic Concepts

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Steel Structure Basic Conceptes Statics Applied Forces – All external forces that act on a structure or member Center of Gravity – A point of balance where the tendency of forces to rotate one side of an object are countered by equal and opposite forces located on the other side of the object Center of Mass – In an object or system of objects in motion, the center of mass is one point that moves in the same path that a particle would if subjected to the same net force Centroid – The center of gravity for a two-dimensional shape Collinear Forces – Forces that act along the same line of action Component of a Force - Two or more forces that compose a single force Composite Shapes – Refers to a combination of 2 or more built up shapes Concurrent Forces - Forces that pass through the same point or intersect at a common point Coplanar Forces - Forces that act along lines that lie in the same plane Couple – The effect produced from two forces that have the same magnitude, parallel line of action and opposite sense Elastic Deformation - Temporary deformation of a material where the material subjected to a load or force returns to its original dimensions once the load or force is removed External Force - The applied forces that cause an object to translate, rotate or stay at rest Elastic Range – Range on the stress/strain curve in which a material will return to its original state once the stress is removed Fixed Support - A fixed support resists translation and rotation of a member at the connection point The reactions of a fixed support compose three unknown forces, including both a vertical and a horizontal component and a resisting moment. Force - The action of one object exerted on another Free Body Diagram - A simplified and conceptual diagram that isolates a structural member under investigation from the rest of the structure Internal Force – Forces that are developed within an object in response to the external loads Modulus of Elasticity - The ratio of the stress inflicted on an element to the strain that is produced Moment - The tendency to make an object or a point rotate Moment Arm - The perpendicular distance between the line of the action of the force and the point Moment of Inertia – A mathematical concept that incorporates the effect of cross sectional shape and orientation to study the strength of a structural member Non-Collinear Forces – Two or more forces that act along different lines of action Non-Concurrent Forces - Forces that do not pass the same point or do not intersect. Parallel forces are an example of non-concurrent forces.

Transcript of Structural Steel Engineering Basic Concepts

Page 1: Structural Steel Engineering Basic Concepts

S t e e l S t r u c t u r e

B a s i c C o n c e p t e s

S t a t i c s

• Applied Forces – All external forces that act on a structure or member • Center of Gravity – A point of balance where the tendency of forces to rotate one

side of an object are countered by equal and opposite forces located on the other side of the object

• Center of Mass – In an object or system of objects in motion, the center of mass is one point that moves in the same path that a particle would if subjected to the same net force

• Centroid – The center of gravity for a two-dimensional shape • Collinear Forces – Forces that act along the same line of action • Component of a Force - Two or more forces that compose a single force • Composite Shapes – Refers to a combination of 2 or more built up shapes • Concurrent Forces - Forces that pass through the same point or intersect at a

common point • Coplanar Forces - Forces that act along lines that lie in the same plane • Couple – The effect produced from two forces that have the same magnitude,

parallel line of action and opposite sense • Elastic Deformation - Temporary deformation of a material where the material

subjected to a load or force returns to its original dimensions once the load or force is removed

• External Force - The applied forces that cause an object to translate, rotate or stay at rest

• Elastic Range – Range on the stress/strain curve in which a material will return to its original state once the stress is removed

• Fixed Support - A fixed support resists translation and rotation of a member at the connection point The reactions of a fixed support compose three unknown forces, including both a vertical and a horizontal component and a resisting moment.

• Force - The action of one object exerted on another • Free Body Diagram - A simplified and conceptual diagram that isolates a

structural member under investigation from the rest of the structure • Internal Force – Forces that are developed within an object in response to the

external loads • Modulus of Elasticity - The ratio of the stress inflicted on an element to the strain

that is produced • Moment - The tendency to make an object or a point rotate • Moment Arm - The perpendicular distance between the line of the action of the

force and the point • Moment of Inertia – A mathematical concept that incorporates the effect of cross

sectional shape and orientation to study the strength of a structural member • Non-Collinear Forces – Two or more forces that act along different lines of action • Non-Concurrent Forces - Forces that do not pass the same point or do not

intersect. Parallel forces are an example of non-concurrent forces.

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• Non-Coplanar Forces - Forces that do not lie in the same plane and have a have a three dimensional arrangement

• Parallel Axis Theorem – A mathematical method by which the moment of inertia of a shape with respect to its centroidal axis can be transferred to a prescribed parallel axis that is normally the centroidal axis of the composite shape

• Pinned/Hinged Support – A pin or a hinge support resists translation of a member in both horizontal and vertical directions. The reactions of a pin support represent two unknown force components

• Plastic Deformation - Deformation that remains permanent in a material subjected to load or force and remains in place even after the load or force is removed

• Plastic Range – Range on the stress/strain curve where a material permanently deforms once stress is removed

• Radius of Gyration – Defined as the square root of the moment of inertia divided by the cross sectional area of the shape; a shape factor that measures the resistance to bending about a defined axis

• Reaction Forces - Equal and opposing forces that resist applies forces • Resultant of a Force – A single force that replaces a system of concurrent forces • Roller Support – A roller support resists translation of a member in the

perpendicular direction to the contact surface. This reaction of a roller connection represents one unknown force component.

• Static Equilibrium – The state when the net effect of all the forces acting on an object equal zero

• Statics – One of three branches of mechanics that deals with the study of forces that are in a state of balance

• Stiffness – Measure of a material’s rigidity; a material’s ability to withstand deformations under stress; slope of the stress/strain curve

• Strain – Deformation of the physical dimensions of an object subjected to a stress • Stress – Describes the intensity of a force and is expressed by the amount of

force acting per unit of area • Transmissibility of Forces – Law that states that the point of application of an

external force acting on a body can be moved anywhere along the line of action of the force without creating a change in the overall external forces applied on the body

• Ultimate Strength – The maximum force that can be applied to a material without breaking the material

• Yield Stress – The point at which stress causes a material to permanently deform

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L o a d s

• Area Load – A uniform load that acts across the entire area or surface of a structural member

• Center of Mass – A point on an oject or system of objects in motion that moves in the same path that a particle would if subjected to the same net force

• Concentrated Load – Loading that is applied on a particular portion of a structural member • Dead Load – Loads that consist of the weight of permanent and fixed components of a

structure • Deflection - The deviation of a structural member from its original position due to applied

loading • Gravity Load – Loading that is the result of the earth’s gravitational pull • Lateral Load – Loading that occurs in the horizontal direction with respect to the ground • Live Load – non-permanent and movable loads on a structure • Occupancy Load – Live, gravity loads that consist of the weight of people, furniture,

equipment, and stored materials. • Overturning – A structural failure that is normally associated with tall and slender

buildings with relatively small foundations • Seismic Load – Earthquake forces that result from the slippage of rock plates along the

fault line • Sliding – Structural failure caused from the effect of lateral forces on inadequately

designed foundation systems • Snow Load – A gravity live load caused from the accumulation of snow on a horizontal

surface • Torsion – A twisting effect induced by the action of lateral forces • Uniformly Distributed Load – Loading that occurs along a portion or the length of a

structural member • Uniformly Increasing Load – A load that is increased at a constant rate • Wind Load – A lateral load caused from wind force

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M e c h a n i c s o f M a t e r i a l s

• Bearing Stress – Stress produced by the pressure or intensity of a force at the contact point of two bodies or structural members

• Breaking Point – The maximum point in which a material can elongate; the point at which a material fails or breaks when subjected to a stress

• Compression Force – A force caused from the compacting or pushing in of structural fibers

• Creep – Deformation of a structure over an extended time • Elastic Deformation – Temporary deformation of a material where the material

subjected to a load or force returns to its original dimensions once the load or force is removed

• Flexure – The bending of a material under load application • Hook’s Law – Law discovered by Robert Hook in 1678 that describes the linear

and proportional relationship of stress and strain in elastic materials subjected to moderate loading.

• Modulus of Elasticity (Young’s Modulus) – A measure of stiffness of a material that is measured by the slope of the elastic portion of the stress-strain curve

• Normal (Axial) Stress – Stress produced by a tension or compression force acting perpendicular to the surface area under stress

• Plastic Deformation – Deformation that remains permanent in a material subjected to load or force and remains in place even after the load or force is removed

• Shear Force – An effect that produces shifting of horizontal or vertical parallel plains of a material

• Shear Stress – Stress that is produced by a force applied parallel to the stressed area. Shear stress is calculated by dividing the shear force by the parallel area resisting the force.

• Stiffness – The ability of a material to withstand deformation under stress • Strain – The deformation of the physical dimension of a body under stress • Strain Hardening – A stage beyond yield stress where steel goes through

structural changes that result in increased strength and resistance to further deformation

• Stress – Describes the intensity of a force and is expressed by the amount of force acting per unit of area

• Stress Concentration – The accumulation of stress on a small section or area of an object

• Tension Force – A force that pulls or stretches the fibers of a material away from each other

• Thermal Strain – The change in material dimensions as a result of temperature changes

• Thermal Stress – The expansion and contraction of a material due to thermal change

• Torsion – The twisting and distortion of a material’s fibers in response to an applied load

• Ultimate Stress – The maximum stress level of a material at which it breaks or ruptures

• Yield Stress – The point at which stress causes a material to permanently deform

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S t r u c t u r a l M a t e r i a l s

• Angles – steel members used fro truss members and connection elements; designated by the letter ‘L’

• Built-Up Section – steel section formed by welding or bolting various rolled shapes

• Cast Iron – a hard, brittle and nonmalleable alloy composed of iron, 2-4.5% carbon, and 1-4% silicon; strong in compression, weak in tension

• Cementiferous Spray – a concrete-vermiculite like substance that is sprayed on steel members for fireproofing

• Channels – C-shaped steel members mostly used for purlins and structural fascias; designated by the letter ‘C’

• Concrete – a mixture of sand, cement, aggregate and water used in construction • Corten (Weathering) Steel – a type of steel that contains high levels of copper and

phosphorous that form a thin protective layer of brown rust on the surface that stops further corrosion when exposed to weather

• Glu-Laminated Lumber – wood that is composed of an assembly of wood laminations

• I-Beams – steel member that has a lower depth to width ratio than wide flanges; designated by the letter ‘S’

• Intumescent Coatings – thin film coatings that are sprayed or brushed on metal surfaces to provide fire protection Posttensioned Concrete – prestressed concrete in which steel tendons are tensioned after the concrete has cured

• Prestressed Concrete – concrete in which forces are applied prior to loading that counteract the effect of subsequent loads

• Pretensioned Concrete – prestessed concrete in which steel tendons are stretched and tensioned prior to the casting of the concrete

• Reinforced Concrete – concrete that is supplemented with steel bars that make it more efficient in resisting tensile forces as well as compressive forces

• Reinforcing Steel – steel that is used to add strength to concrete • Sawn Lumber – wood that is cut directly from a log • Stainless Steel – steel that contains 10-30% chromium that provides resistance to

rust • Steel – an iron alloy with low carbon that is strong in both compression and

tension • Tee Sections – T shaped steel members used for truss chords and structural

lintels • Thermal Sprayed Metal Coatings – aluminum or zinc alloys that are melted and

sprayed onto a metal surface to prevent corrosion • Wide Flange – steel member that has a high depth to width ratio; designated by

the letter ‘W’ • Wrought Iron – an alloy of iron that contains carbon and silicon that was used

throughout the 19th century in bridge and building construction

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C o n n e c t i o n s

• Arc Welding – a process of welding that passes an electric current through a metal electrode that produces intense heat that melts and fuses the electrode rod as well as a small portion of the connecting elements

• Beam Hangar – a steel connection that is used to anchor a flush/face beam connection

• Bolt – a type of fastener that can resist withdrawal and lateral loads significantly more than nails and screws

• Common Bolts (Unfinished Bolts, ASTM A307) – structural steel bolts composed of low carbon steel that have a smaller load capacity than high strength bolts

• Direct Tension Indicator Bolts – a type of high strength steel bolt that releases silicone that is embedded in the depressions of the washer when the desired amount of torque is applied

• Filet Weld – a type of weld that is used to join overlapping elements • Framing Anchors – • Groove Weld – a type of weld that is used between adjacent members • High Strength Bolts (A325, A490) – structural bolts composed of high strength

steel that are tightened with an impact wrench to produce friction type connections

• Impact/Torque Wrench – a wrench that can be calibrated to apply a specific amount on torque

• Joist Hangar – a steel connection that is used to anchor a flush/face joist connection

• Nail – a type of simple wood fastener used in small-scale construction that resists shear but does not resist tension forces

• Post Base/Cap – a steel fastener used to anchor a post or column into the foundation and/or ceiling

• Rebar Jacket • Rigid Connection – a type of structural joinery that resists both shear forces and

bending moments • Rivet – a smooth, screw like fastener that is pushed through adjacent members

and pneumatically hammered and heated to produce an anchoring head on the opposite side of the rivet head

• Screw - a type of simple wood fastener that is somewhat more efficient than nails used in small-scale construction that resists shear but does not resist tension forces

• Semi-Rigid Connection – a type of structural joinery that restrains translation and permits partial rotation of the connecting members

• Simple Connection – a type of structural joinery that resists shear forces but does not resist bending moments

• Twist Off/Tension Controlled Bolts – a type of high strength bolt that releases the splined extension of the bolt when the optimum amount of torque is applied

• Welding – a method of joining steel elements by heat • Withdrawal Load

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L a t e r a l S y s t e m s

• Braced Frames – truss structures that provide diagonal paths for moving the lateral loads through the structure in vertical planes

• Building Configuration – the form, geometry, scale, arrangement of the building mass and structure

• Cross Bracing – bracing used in frames that resist lateral forces in two or more directions

• Diaphragms – structural elements that resist and collect lateral forces in the horizontal planes of a structure and transfer them to the vertical bearing elements

• Drift – deflection of a building under lateral loads • Earthquake (Seismic) Forces – lateral forces caused by the shifting of plates

below the earth’s surface that act mostly at the base of a structure • Knee (K) Bracing – short diagonal bracing linking horizontal and vertical

members that effectively makes a rigid connection where two members are pinned

• Moment Resistant Frames – structural systems that are constructed with rigidly connected joints

• Re-Entrant Corners – differential stiffness in a structure caused by irregular geometries

• Shear Walls – structural elements made of rigid materials that resist lateral loads in the vertical plane Soft Story – the result of insufficient strength and stiffness of a specific floor structure that is inconsistent with the rest of the building floors

• Torsion – a twisting effect that results when applied loads located at the center of mass of a structure do not coincide with the center of stiffness

• Wind Forces – lateral forces caused by wind that affect the exposed surface area of a structure

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F o u n d a t i o n s

• Battered Pile – a type of pile that is used when lateral forces exceed the loading capacity of vertical piles

• Bearing Pile – a type of pile that is used to resist lateral loads and uplift forces • Cantilever Wall – a type of foundation wall that consists of a stem and a base slab that is

held in equilibrium by self-weight, horizontal soil pressure, and the reaction of the base structure acting upward

• Combined Footing • Crib Wall – a type of foundation wall • Deep Foundation – a type of foundation that is used when the soil near the ground surface

is weak • Foundation – the interface of a building structure with the ground • Foundation Wall – a structural element that is constructed below grade to support the

earth and resist water pressure • Friction Pile – a type of pile that resists gravity loads by friction and transfers loads to the

surrounding soil using the adhesive resistance between the pile surface and its surrounding soil

• Gravity Wall – a type of foundation wall • Mat/Raft Foundation – a type of shallow footing that is equal to the area of the building

footprint • Pile – a long and slender prefabricated type of deep foundation that are driven into the

ground • Shallow Foundation – a type of foundation that is used when the earth directly beneath a

structure has sufficient bearing capacity to sustain the loads from the structure • Sheet Pile - a type of foundation wall • Spread Footing – the most widely used type of shallow foundation that are designed to

receive the concentrated gravity loads directly on their centroid to prevent unequal pressure distribution and overturning of the footing

• Table Wall Footing – a type of shallow foundation

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T r u s s e s

S t r u c t u r a l S y s t e m

• Baltimore Truss - A trapezoidal, flat truss • Bowstring Truss - A truss with an arched upper chord and a central triangual

configuration converging on the upper chord • Cambered Fink Truss - A triangular truss characterized by parallel diagonal compression

members that are perpendicular to the top chord and a cambered lower chord • Fan Truss - A simple or multi-paneled triangular truss where all of the diagonal members

radiate from one point on the lower chord • Fink Truss - A triangular truss characterized by parallel diagonal compression members

that are perpendicular to the top chord • Gusset Plate – A common plate that is used to connect truss members at their ends • Howe Truss – Truss in which the top chords and diagonal members are in compression,

and all vertical members and bottom chord members are in tension • Ideal Truss – A truss that assumes that all members are connected with pinned joints, that

members will remain straight after loading, and that all loading is concentrated only at panel points

• K-Truss - A truss in which the vertical and diagonal members are arranged in the shape of a "k"

• King Post - A truss that is composed of a simple triangle with a central post • Method of Joints – Method of analyzing trusses that uses the equilibrium of each truss

joint to determine the forces in the members • Method of Sections – Method of analyzing trusses that conceptually cuts the truss into

sections and thus allowing the analysis of each section by using the equations of static equilibrium

• Open Web Joists – a steel truss that is used and spaced like a joist to support floor or roof decking

• Panel Points – Joints located along the top member of a truss that are directly connected to the structure. The uniform load of the structure is concentrated at the panel points and thus allows the truss to behave like a simply supported beam.

• Parker Truss - A truss with an arched upper chord and a central triangular arrangement converging on the bottom chord

• Pins/Bolts – Connection type used to join truss members • Pratt Truss – A truss in which the top chords and vertical members are in compression,

and diagonals and bottom chord in tension • Scissors Truss – A truss in which the bottom chord is raised to increase the clear height

near the mid span; top chords are in compression and vertical members in the center of the truss are in tension

• Static Equilibrium - The state when the net effect of all the forces acting on an object equal zero

• Statically Determinate Truss (Simple Truss) – A truss in which the static equations of equilibrium can be used to determine the force in each member

• Statically Indeterminate Truss – A truss that contains a series of redundant members that cannot be resolved with the equations of static equilibrium

• Tension Member - Structural member subjected to tension forces • Truss – A structural system composed of short and straight structural members that are

arranged in a pattern of triangles • Two-Force Member – A structural member that is hinged or pinned at each end and does

not carry any loads between the ends • Warren Truss – A flat truss with parallel and equal length top and bottom chord members

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• Zero Force Member – Members in a truss that do not carry loads that are used to provide stability and insure triangulation

B e a m s

• Beam Deflection – The deviation of a beam from its original position due to applied loading

• Bearing Stresses – Forces that exist when forces are transferred from one member to another

• Bending – Deformation of a horizontal structural member that is a result of the application of external loads

• Bending Stresses – Stresses that are produced in a structural member’s cross - section when subjected to bending. Compressive stresses are generated at concave fibers and tensile stresses are generated at convex fibers.

• Cantilever Beams – Beams that are fixed or anchored at one end and free at the other end

• Center of Gravity – A point of balance where the tendency of forces to rotate one side of an object are countered by equal and opposite forces located at the other side of the object; the resultant force of the earth’s gravitational forces acting on individual particles composing an object

• Centroid – The center of gravity for the area of a two dimensional shape • Centroidal Axis – Also called the neutral axis; a line that passes through the

centroid of a beam’s cross- section where beam fibers are neither shortened under compression or elongated under tension

• Compression Forces – Forces that tend to crush or buckle an element; forces act inwardly on an object

• Concentrated Loads – Loads that act on a single or concentrated point of a structural member

• Continuous Beams – Beams that span over more than two supports • Equations of Static Equilibrium – Equations used to determine unknown reactions

that assume all forces and moments in all directions sum to zero • External Forces – Forces applied to a structure • Fixed End Beams – A beam that is restrained from any movement or rotation at

both of its two end supports • Fixed Support – A support condition that does not permit translation or rotation

and thus develops three unknown reactions, including a vertical and horizontal component and a resisting moment

• Fixed-Pinned Beams – A beam that is fixed at one end and pinned at the other end • Free Body Diagram - A simplified and conceptual diagram that isolates a

structural member under investigation from the rest of the structure • Horizontal Shear Force – Equal and opposite forces that are generated in adjacent

horizontal fibers of a structural member in response to applied loads • Horizontal Shear Stress – Stresses produced by the movement of the adjacent

fibers of a member in the horizontal direction due to opposing and equal forces • Internal Forces – Forces that occur within a structural member • Internal Resisting Moment – Moment generated from tension and compression

forces in a beam cross section that counterbalance the external moment produced by the applied loads

• Lateral Buckling – Buckling in the horizontal direction • Neutral Axis (see centroidal axis)

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• Open Web Joist - A steel truss that is used and spaced like a joist to support floor or roof decking

• Overhanging Beams – A simply supported beam that has one or both of its ends extending beyond the supports

• Pin/Hinge Support – A support condition that that can resist a single force in any direction on the plane containing and thus develops two unknown force components

• Principle of Superposition – Method that consists of finding the effect of several loading conditions acting on a beam simultaneously by determining the effect of each individual load on the beam separately

• Resisting Moment – A moment generated by tension and compression forces in the cross section of a structural member that counterbalances the external moment produced by the applied loads

• Roller Support – A support condition that develops a reaction force perpendicular to the point of contact, thus restricting movement in that direction

• Shear – A force that is the result of opposing forces that cause the sliding of one portion of a structural member along an adjacent portion

• Shear and Moment Diagram – Graphical diagrams that determine the intensity of shear force and bending moment at any point along a structural member

• Simply Supported Beams – A beam in which one end is connected by a hinge and the other end is connected by a roller

• Statically Determinate Beams – Beams that allow the application of the basic equations of static equilibrium to determine up to three unknown reactions

• Statically Indeterminate Beams – A beam that contains more than three unknown reactions and thus does not permit the use of the static equations of equilibrium

• Tension Forces – Forces that tend to pull an element apart • Torsion – A twisting effect on an object • Tributary Area – The portion of an area load that is carried by each beam in a

frame • Uniformly Distributed Loads – An evenly distributed load that is applied over an

area • Uniformly Increasing Loads – Loads that are applied over a given area that

gradually increase over or at certain portions of the structure • Vertical Shear Force – Equal and opposite forces that are generated in adjacent

vertical fibers of a structural member in response to applied loads • Vertical Shear Stress – Stress produced by the movement of the adjacent fibers of

a member in the vertical direction due to opposing and equal forces resulted from the external loading

• Wide Flange – A rolled steel section in the shape of an I

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C o l u m n s

• Allowable Stress – Maximum amount of stress a column can take before it fails • Beam Columns – Columns that are subjected to moment and axial forces • Buckling – The bowing or bending of a column when subjected to loading • Buckling Direction – The direction that a column will tend to bend when subjected

to loading • Column Effective Length – Column length subjected to buckling • Column End Condition – The type of connection between the column and the

adjacent structural elements • Column Moment Diagrams – Diagram that graphically depicts the moments of a

column under loading • Compression Elements – Structural elements that collect loads from horizontal

spanning members and transfer them to the foundation or other structural elements

• Concentric Loading (Axial Loading) – Loading that is directly applied at the centroid of the column cross section along its long axis

• Crushing – Common failure mode of short columns • Critical Load –The maximum load at which a column buckles • Eccentric Loading – Loading that is applied at a distance from the centroid of a

column • Effective Length (Critical Length) - The length of a column that is susceptible to

buckling • Euler Elastic Theory – Formula that predicts the value of critical load and critical

stresses for long columns • Fixed Columns - Columns that are fixed or restrained from movement at both

ends • Hinged Columns – A Column that is hinged at both of its ends • Inflection Points (Contraflexure Points) – Location of curvature changes in the

buckled column; the bending moment is zero at this point. • Intermediate Column – A column that fails by a combination of crushing and

buckling • K Value – A modifier that takes into account the end condition of the column and

thus effects the slenderness ratio; a larger k-value will increase the slenderness ratio

• Lateral Loads – Loads applied in the horizontal direction such as wind, earthquakes, and impacts

• Leonard Euler – A Swiss mathematician who recognized that a long column’s failure under axial loads is caused by buckling and not by strength failure.

• Load Capacity – The amount of load a structure or structural element can take before failing

• Long Column – A column that is defined as having a small cross sectional area in relation to its length

• Masts – A type of large column • Modules of Elasticity –The ratio of the stress inflicted on an element to the strain

that is produced; • Moment of Inertia – A mathematical concept that is used to study the strength of a

structural member by factoring the effect of cross sectional shape and orientation of the member with respect to loading

• Piers – A type of large column • Pilasters – A type of large column • Posts – A type of smaller column • Pylons – A type of larger column

Page 13: Structural Steel Engineering Basic Concepts

• Radius of Gyration – Defined as the square root of the moment of inertia divided by the cross sectional area of the shape; a shape factor that measures the resistance to bending about a defined axis

• Section Modulus – A measure of bending resistance • Short Column – A column that has a relatively large cross sectional area when

compared to its length; usually fails by crushing • Slenderness Ratio – Defined as the column’s effective length divided by the

radius of gyration; a dimensional property that identifies the critical length of the column

• Strong/ Major Axis – The axis of a column about which there exists greater resistance to buckling

• Struts – A type of smaller column • Weak/Minor Axis – The axis of a column that will be initially subjected to buckling

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F r a m e s

• Cross Bracing – Structural members that are configured between columns and beams that stabilized a frame from lateral loads that are applied in both directions

• Deflection – The deformation or bowing of a structural member when subjected to a load • Knee Bracing – A type of bracing used in frames that strengthens the joints and prevents

them from lateral deformation • Moment Resistant Joints – Rigid joints that resist horizontal and vertical forces and

moments • Post and Beam Frames – A frame in which the horizontal and vertical members of the

frame are connected with simple joints • Rigid Frames – A frame in which the horizontal and vertical members are connected with

moment resistant joints that prevent independent action of the beam element from the columns

• Rigid Diaphragms (Panels) – Structural systems that act as thin horizontal beam elements spanning between vertical shear planes

• Shear Walls – Walls that are organized in the short dimension of a building that provide lateral stability

• Single Bay Frames – Frames that are one story in height and one single unit spanned along the ground plane

• Stacked Frames – A series of single bay frames repeated in the vertical and horizontal direction producing a multi-story frame

• Statically Determinate Frame – A frame that has only three reaction components • Statically Indeterminate First Degree – A frame that has four unknown reaction

components • Statically Indeterminate Third Degree – A frame that has five or six unknown reaction

components • Three Hinged Frames – A frame with three hinged connections; develops higher moments

and higher deflections than a two hinged frame • Two Hinged Frames – A frame with two hinged connection

C a b l e s

• Cables – Flexible structural elements often made of steel, polypropylene, nylon, or fiberglass that carry tensile loads

• Cable Net Systems – A category of cable systems that includes cable-stayed systems and double cable systems; refers to a system of cables designed to resist lateral loads

• Cable Stayed Systems – A structure in which a series of linear cables directly support rigid horizontal members and masts under all anticipated loading conditions

• Cold Stretching – a process that produces high strength steel • Double Cable Systems – A cable system that contains a linear main cable carrying the

gravity load that is stiffened by secondary cables • Parabolic Cables – A cable that is subjected to a uniformly distributed load • Single Bolt Clam – A connection used for joining cables in a net • Strand – A composition of a number of wires that are helically formed around a central

wire • Two Force Member - A structural member that is hinged or pinned at each end and does

not carry any loads between the ends • U-Bolts – A connection used for joining cables in a net

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A r c h e s

• Arch – a structural element that carries loads by developing compressive forces • Axial Thrust • Counter-Front Walls • Fixed Ended Arches – Arches that have fixed end connections • Flying Buttress – an external bracing system that resists the effect of outward thrust • Ideal Arch – An arch that carries loads by compression only and cannot resist any lateral

forces • Shear Force • Statically Determinate Arches – Arches with three or less number of reactions • Statically Indeterminate Arches – Arches with greater than three reactions, including both

two-hinged and fixed arches • Struts • Three Hinged Arch – An arch with three hinge connections • Tied Arch – An arch that resists outward thrust by tying the two supports below the floor

level • Two-Hinged Arch (Parabolic Arch) – An arch with two hinges at the supports that transfers

the axial thrust and the shear force as horizontal and vertical forces to the foundation

S u r f a c e S t r u c t u r e s

• Surface Structures – non linear rigid or soft structural elements that are continuous in two axes

• Fabric Structure – a soft surface spanning structure that can only resist tensile forces • Slab – a monolithic surface spanning structure usually made of concrete that carry loads

by bending • One-Way Slab – a reinforced concrete plate that is supported at two opposite edges and

that carries loads by bending in one direction only • Two-Way Slab – a reinforced concrete plate that is supported at four corners and that

carries loads in two directions perpendicular to each other • Flat Plates – a category of reinforced concrete two-way slabs that are reinforced in two

directions and transfer loads directly to vertical supporting elements without using beams or girders

• Folded Plates – a type of two-way slab that is folded or corrugated thus providing stiffness and a high moment of inertia

• Shells – thin, lightweight, curved structures that resist axial and shear forces • Cylindrical Shells – a shell structure that is extended in the longitudinal direction • Shell Dome – an arch that is revolved about its vertical axis forming a hemispherical shell • Hyper-bolic Paraboloids – a structure that is composed of a double contour curved plane

that can carry surface tension, compression, and shear stress • Tension Structures – structures that are composed of light weight materials such as

cables and fabrics • Cable Nets – a type of tension structure that is composed of cable segments that are

connected to form a three dimensional framework • Fabric Structure – a tensile structure where fabric is curved and stretched between

supporting elements to provide a continuous surface for the flow of tension forces • Air Supported Structures – a tensile structure that uses air pressure to support and

stabilize fabric or other membranes

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• B a s i c C o n c e p t s

• The basic concepts section contains terms that are fundamental in understanding statics, strength of materials, and structural behavior. Many of the terms and definitions include images, animations, and tabulated information to communicate the concepts.

• Statics Structural Loads and Structural Behavior

Mechanics of Material Structural Materials

Connections Lateral Systems Foundations

Page 17: Structural Steel Engineering Basic Concepts

S t a t i c s

Statics is one of three branches of mechanics that deals with the study of forces that are in a state of balance. Topics that are examined in statics include force characteristics, equilibrium, moments and reactions, and structural properties of areas.

• Forces • Force Systems • Support Conditions • Cross-Sectional properties of areas • Moment and Couples

Page 18: Structural Steel Engineering Basic Concepts

• F o r c e s

Type Description Image

Force the action of one object exerted on another -

Applied Forces all external forces that act on a structure or member -

Internal Forces

forces that are developed within an object in response to the external loads

External Forces

the applied forces that cause an object to translate rotate or stay at rest

Components of a Force

a single force can be replaced by two or more forces that produce the same effect. These forces are called components of the force.

Resultant of Forces

a single force that replaces a32.- system of concurrent forces is called a resultant force -

Transmissibility of Forces

law that states that the point of application of an external force acting on a body can be moved anywhere along the line of action of the force without creating a change in the overall external forces applied on the body

-

Reaction Forces equal and opposing forces that resist applies forces

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Page 19: Structural Steel Engineering Basic Concepts

F o r c e S y s t e m s

Type Description Image

Static Equilibrium

the state when the net effect of all the forces acting on an object equal zero

Free Body Diagram

a simplified and conceptual diagram that isolates a structural member under investigation from the rest of the structure

Concurrent Forces

forces that pass through the same point or intersect at a common point

Non-Concurrent Forces

forces that do not pass the same point or do not intersect. Parallel forces are an example of non-concurrent forces

Collinear Forces forces that act along the same line of action

Non-Collinear Forces

two or more forces that act along different lines of action.

Coplanar Forces forces that act along the same plane

Page 20: Structural Steel Engineering Basic Concepts

Non-Coplanar Forces

forces that do not lie in the same plane and have a have a three dimensional arrangement

S u p p o r t C o n d i t i o n s

Type Description Image Free-Body Diagram

Fixed Support

a fixed support resists translation and rotation of a member at the connection point. The reactions of a fixed support compose three unknown forces, including both a vertical and a horizontal component and a resisting moment.

Rocker Support

a rocker support resists translation of a structural member in the perpendicular direction to the contact surface. This reaction of a rocker connection represents one unknown force component.

Pin/Hinge Support

pinned/hinged support – A pin or a hinge support resists translation of a structural member in both horizontal and vertical directions. The reactions of a pin support represent two unknown force components

Roller Support

a roller support resists translation of a structural member in the perpendicular direction to the contact surface. This reaction of a roller connection represents one unknown force component.

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Page 21: Structural Steel Engineering Basic Concepts

C r o s s - S e c t i o n a l P r o p e r t i e s o f A r e a s

Type Description

Center of Gravity

a point of balance where the tendency of forces to rotate one side of an object are countered by equal and opposite forces located on the other side of the object

Centroid the center of gravity for a two-dimensional shape

Composite Shapes

refers to a combination of 2 or more structural shapes that compose a structural member’s cross section

Moment of Inertia

a mathematical concept that incorporates the effect of cross sectional shape and orientation to study the strength of a structural member

Parallel Axis Theorem

a mathematical method by which the moment of inertia of a shape with respect to its centroidal axis can be transferred to a prescribed parallel axis which is normally the centroidal axis of the composite shape

Radius of Gyration

defined as the square root of the moment of inertia divided by the cross sectional area of the shape; a shape factor that measures the resistance to bending about a defined axis

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Page 23: Structural Steel Engineering Basic Concepts

M o m e n t A r m

C o u p l e s

Page 24: Structural Steel Engineering Basic Concepts

S t r u c t u r a l L o a d s a n d S t r u c t u r a l B e h a v i o r

Structural loads are defined as forces that tend to produce deformation in a structure. This section includes concepts dealing with the classification and analysis of loads and how structures withstand the effect of the applied loads with safety and adequacy.

• Load Types • Load Distribution Categories • Structural Behavior under Loads

L o a d T y p e s

Loads Description Table

Dead Loads Loads that consist of the weight of permanent and fixed components of a structure -

Live Loads non-permanent and movable loads on a structure -

Wind Load A live load caused from wind force -

Gravity Load Loads that are the result of the earth’s gravitational pull -

Snow Load

A gravity live load caused from the accumulation of snow on a horizontal surface

Occupancy Load

Gravity live loads that consist of the weight of people, furniture, equipment, and stored materials.

Seismic Load Live load produced in Earthquakes that result from the slippage of rock plates along the fault line -

Lateral Load Loading that occurs in the horizontal direction with respect to the ground -

Page 27: Structural Steel Engineering Basic Concepts

M e c h a n i c s o f M a t e r i a l

• Forces and Stress • Stress/Strain

F o r c e a n d S t r e s s

Type Description Animation/ Image

Axial Stress

stress produced by a tension or compression force that acts perpendicular (or normal) to the surface area under stress. Normal stress is calculated by dividing the tension or compression force by the cross-sectional area resisting the force.

--

Bearing Stress

stress produced by the pressure or intensity of a force at the contact point of two bodies or structural members

Compression Force

a force that pushes the fibers of a material closer to each other

Creep deformation of a structure over an extended time

Flexure the bending of a material under load application

Lateral Forces forces applied in the horizontal direction ---

Normal (axial) Stress

stress produced by a tension or compression force acting perpendicular to the surface area under stress ---

Page 28: Structural Steel Engineering Basic Concepts

Shear Force

an effect that produces shifting of horizontal or vertical parallel plains of a material

Shear stress stress that is produced by a force applied parallel to the stressed area. Shear stress is calculated by dividing the shear force by the parallel area resisting the force.

---

Stress

describes the intensity of a force and is expressed by the amount of force acting per unit of area

Stress Concentration the accumulation of stress on a small section or area of an object ---

Tension Force

a force that pulls or stretches the fibers of a material away from each other

Thermal Strain the change in material dimensions as a result of temperature changes ---

Thermal Stress the expansion and contraction of a material due to thermal change ---

Torsion

the twisting and distortion of a material’s fibers in response to an applied load

Page 29: Structural Steel Engineering Basic Concepts

S t r e s s / S t r a i n

Type Description Diagrams

Breaking Point The maximum point in which a material can elongate; the point at which a material fails or breaks when subjected to a stress

Elastic Deformation Temporary deformation of a material where the material subjected to a load or force, returns to its original dimensions once the load or force is removed

Elastic Range

Range on the stress/strain curve in which a material will return to its original state once the stress is removed

Hook’s Law Law named after Robert Hook in 1678 that describes the stress-strain relationship in elastic materials is linear and proportional under moderate loading.

Modulus of Elasticity (Young’s Modulus)

The ratio of the stress inflicted on an element to the strain that is produced

Plastic Deformation Permanent deformation in a material subjected to load that remains in place after the load is removed

Plastic Range

Range on the stress/strain curve where a material permanently deforms and remains deformed after the stress is removed

Stiffness Measure of a material’s rigidity; a material’s ability to withstand deformations under stress; slope of the stress/strain curve

Page 30: Structural Steel Engineering Basic Concepts

Strain Deformation of the physical dimensions of an object subjected to a stress

Strain Hardening A stage beyond yield stress where steel goes through structural changes that result in increased strength and resistance to further deformation

Stress Describes the intensity of a force and is expressed by the amount of force acting per unit of area

Ultimate Strength The maximum force that can be applied to a material without breaking the material

Yield Stress

The point at which stress causes a material to permanently deform

Page 31: Structural Steel Engineering Basic Concepts

C o n n e c t i o n s

Connections are key elements that bind one or more structural elements together. Connections can be used to allow or disallow certain types of motion and vary according to material and/or system.

• Connection Types • Connection Type Matrix • Wood Connections • Steel and Concrete Connections

C o n n e c t i o n T y p e s

Type Description Animations

Simple (Shear) Connection

a type of structural joinery that resists shear forces but does not resist bending moments

Semi-Rigid Connection

a type of structural joinery that restrains translation and permits partial rotation of the connecting members

Rigid (Moment) Connection

a type of structural joinery that resists both shear forces and bending moments

Page 33: Structural Steel Engineering Basic Concepts

S t e e l a n d C o n c r e t e C o n n e c t i o n s

Type Description Image

Arc Welding

a welding process to connect steel elements. An electric current passes through a metal electrode producing intense heat that melts and fuses the electrode rod as well as a small portion of the connecting elements

-

Bolt a type of fastener that can resist withdrawal and lateral loads significantly more than nails and screws -

Common Bolts (Unfinished Bolts, ASTM A307)

structural steel bolts composed of low carbon steel that have a smaller load capacity than high strength bolts -

Corbel an extrusion or cleat on a concrete column in which beams rest on -

Direct Tension Indicator Bolts

a type of high strength steel bolt that releases silicone that is embedded in the depressions of the washer when the desired amount of torque is applied

-

Fillet Weld a type of weld that is used to join overlapping elements

Groove Weld a type of weld that is used between adjacent members

High Strength Bolts (A325, A490)

structural bolts composed of high strength steel that are tightened with an impact wrench to produce friction type connections

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Haunch a structural steel section cast in a column that provides an overhanging bracket for beam attachment -

Impact/Torque Wrench a wrench that can be calibrated to apply a specific amount on torque -

Rivet

a smooth, screw like fastener that is pushed through adjacent members and pneumatically hammered and heated to produce an anchoring head on the opposite side of the rivet head

-

Rebar Jacket a sleeve that is used to join reinforcement steel bars to provide a continuous connection between two structural elements -

Twist Off/Tension Controlled Bolts

a type of high strength bolt that releases the splined extension of the bolt when the optimum amount of torque is applied

Welding a method of joining steel elements by heat -

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Page 35: Structural Steel Engineering Basic Concepts

L a t e r a l S y s t e m s

Lateral Systems are structural devices that supplement the primary components of a structure to provide additional stability against lateral forces

• Lateral Load Resisting Systems

L a t e r a l L o a d R e s i s t i n g S y s t e m s

Type Description Animation/ Image

Braced Frames Truss structures that provide diagonal paths for transferring lateral loads through a structure in vertical planes. Examples include cross bracing and knee bracing.

Building Configuration

the form, geometry, scale, arrangement of the building mass and structure

Cross Bracing

bracing used in frames that resist lateral forces in two or more directions

Diaphragms

structural elements that resist and collect lateral forces in the horizontal planes of a structure and transfer them to the vertical bearing elements

Drift deflection of a building under lateral loads

Earthquake (Seismic) Forces

lateral forces caused by the shifting of plates below the earth’s surface that act mostly at the base of a structure

Knee (K) Bracing

short diagonal bracing linking horizontal and vertical members that effectively makes a rigid connection where two members are connected

Page 36: Structural Steel Engineering Basic Concepts

Moment Resistant Frames

structural frames that are constructed with rigidly connected joints

Re-Entrant Corners

differential stiffness in a structure caused by irregular geometries

Shear Walls structural walls made of rigid materials that resist lateral loads in the vertical plane

Soft Story

the result of insufficient strength and stiffness of a specific floor structure that is inconsistent with the rest of the building floors

Torsion

a twisting effect that results when applied loads located at the center of mass of a structure do not coincide with the center of stiffness

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Page 37: Structural Steel Engineering Basic Concepts

F o u n d a t i o n s

Foundations consist of the array of structural elements that connect a structure to the ground. The design of foundations is affected by several factors, including the size and shape of the structure, and geological and geographical conditions of the site.

• Shallow and Deep Foundations • Retaining Walls

S h a l l o w a n d D e e p F o u n d a t i o n s

Foundation the interface of a building structure with the ground

Shallow Foundation

a type of foundation that is used when the earth directly beneath a structure has sufficient bearing capacity to sustain the loads from the structure

Deep Foundation a type of foundation that is used when the soil near the ground surface is weak

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S h a l l o w F o u n d a t i o n s

Type Description Images

Cantilever Wall

a type of foundation wall that consists of a stem and a base slab that is held in equilibrium by self-weight, horizontal soil pressure, and the reaction of the base structure acting upward

Combined Footing

a footing that is used under two or more vertical elements to prevent overturning from eccentric loading

Mat/Raft Foundation

a large slab foundation that is used instead of multiple spread footings

Spread Footing

the most widely used type of shallow foundation that is designed to receive the concentrated loads directly on the centroid to prevent unequal pressure distribution and overturning of the footing

Strip Footing an extended footing used under foundation walls; strip footings are used in basements, crawlspaces, and for slabs-on grade.

Wall Footing

elongated spread footings that transfer loads from load bearing walls. Wall footings are used in substructures such as slabs-on-grade, crawlspaces and basements.

Page 39: Structural Steel Engineering Basic Concepts

D e e p F o u n d a t i o n s

Type Description Images

Battered Piles

an inclined pile that is used that can resist lateral forces as well as vertical forces

Bearing Piles a type of pile that is used to resist lateral loads and uplift forces

Caissons a type of deep foundation that is achieved by casting concrete into drilled holes

Friction Piles

a type of pile that resists loads by friction and transfers loads to the surrounding soil using the adhesive resistance between the pile surface and its surrounding soil

Pile a long and slender deep foundation that is driven pushed into the ground -

R e t a i n i n g W a l l s

Type Description Images

Crib Wall a retaining wall used for outdoor earthworks and landscaping

Page 40: Structural Steel Engineering Basic Concepts

Foundation Wall

a structural element that is constructed below grade to support the earth and resist water pressure

Gravity Wall

foundation wall that relies on its own weight to resist overturning forces from soil and water pressure

Key extrusion on the base of a cantilevered retaining wall that prevents sliding

Sheeting temporary walls that hold back the soil during excavation

Sheet Pile type of sheeting that consists of vertical planks of wood, steel, or reinforced concrete that are driven into the earth

Slurry Wall

a type of sheeting that consists of trenching the ground, reinforcing the trench, and filling the trench with concrete.

Soldier Beams a type of sheeting that uses vertical piles tied together by lagging

Stem portion of foundation wall that extends or cantilevers into the soil

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