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94 Cards in this Set
- Front
- Back
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DIAPHRAGM
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A structural system used to transfer lateral loads to shear walls or frames primarily through in-plane shear stress. Usually constructed of plywood or OSB in timber construction, metal deck or composite metal deck in steel construction, or a concrete slab in concrete construction. It operates like a wide flange beam on its side with the web being the diaphragm and the shear walls being the compression and tension flanges. The connections of the walls are critical to get the loads to the foundations.
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RESONANCE
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The state of a system in which an abnormally large vibration is produced in response to an external stimulus, occurring when the frequency of the stimulus is the same, or nearly the same, as the natural vibration frequency of the system.
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DAMPING
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Any effect, either deliberately engendered or inherent to a system, that tends to reduce the amplitude of oscillation of an oscillatory system
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ALLUVIUM
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Soil or sediments deposited by a river or other running water. Typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel.
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SHALE
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A fine grained sedimentary rock whose original constituents were clay minerals or mud.
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STRESS
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Force per unit of area
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STRAIN
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The deformation of a physical body under stress.
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STRENGTH
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A materials ability to resist an applied force.
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STIFFNESS
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The resistance of an elastic body to deflection or deformation by an applied force. Opposite of ductility.
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STRESSED SKIN PANELS
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An insulated building panel that is comprised of a foam core sandwiched between two "skins". The core, made from urethane or styrene foam, is both durable and light weight. The skins are most often made from OSB, but other materials such as gypsum board, sheetrock, plywood, wafer board, and sheet metal are used as well. The exterior skin must be nailable material since the panels are attached to the buildings exterior enclosing the frame to create a thermal envelope.
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MASONRY HANGERS
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A reinforcing bar support or hanger for use in a masonry block wall. Incorporates a pair of supporting arms for contacting the surface of a supporting block and includes vertically extending hanger members terminating in a rebar cradle for receiving and supporting a rebar to be positioned within the wall.
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SEICHE
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A standing wave in an enclosed or partially enclosed body of water.
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ACCELERATION
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Any increase or decrease in speed
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MAXIMUM ACCELERATION
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Occurs when the period of a building is 0.5 seconds. Results in 2-3 times the ground acceleration being experienced by the building.
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TORSION
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The twisting of an object due to an applied torque. In circular sections, the resultant shearing stress is perpendicular to the radius.
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P-DELTA EFFECT
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A phenomenon of combined vertical and horizontal stresses occurring when lateral loads (either seismic or wind related) cause horizontal deflection from the centroid and building mass in the resulting line of action crushes the column beneath.
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HERTZ
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A unit of frequency measured in the number of cycles per second. One Hz is one complete cycle back and forth per second.
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DRIFT
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Horizontal deformation. The structural fram must be stiff to limit horizontal displacement when acted on by a lateral force.
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IMPACT LOAD (KINETIC LOAD)
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A dynamic short term impact that affects a structure. Examples are moving vehicles or elevator movement.
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DEFORMATION
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A change in shape due to an applied force. This can be a result of tensile (pulling) forces, compressive (pushing) forces, shear, bending, or torsion (twisting). Often described in terms of strain.
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ABUTMENT
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To transmit the horizontal and vertical forces of superstructure to the foundations. Usually a structure that supports an arch.
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PARABOLIC
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The shape of a hanging flexible chain or cable when supported at its ends and acted upon by a uniform load. (example: deck of bridge)
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CATENARY
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The shape of a hanging flexible chain or cable when supported at its ends and acted upon by a uniform gravitational force. (example: its own weight)
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SPANDREL
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The space between two arches or between an arch and a rectangular enclosure.
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COLLECTOR ELEMENT
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A part of the structural system that absorbs lateral forces and transfers them from horizontal to vertical members (example: bent tie or drag strut)
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BENT
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A component of the rigid frame system to resist lateral loads. Consists of a planar framework of beams and columns with moment resisting connections.
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DRAG STRUT
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An engineering term for a member that transfers lateral forces from a vertical member to another member or element in the structural frame of a building. An example of a drag strut is a floor joist above a shear wall that is tied to the shear wall and extends across or along the floor diaphragm above. Also called a collector or tie.
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LINK BEAM
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A beam (concrete, steel, or wood) that connects two different lateral elements such that they may act as one lateral element. For example, if there are two separate shear walls of different stiffness then a link beam may be used to connect the two walls. The overall system would be stiffer than the individual elements, and thus cause less deflection. It is the horizontal distance between any combination of vertical column, diagonal brace, or shear wall.
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SURCHARGE
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Any loading from above the soil line upon earth being supported by a retaining wall.
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ANGLE OF REPOSE
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Also referred to as Angle of Friction. An engineering property of granular materials. The maximum angle of a stable slope determined by friction, cohesion, and the shapes of the particles.
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REDUNDANCY
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A safety built into structural systems so if a main structural system fails, backup connections will work to prevent progressive collapse.
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GRADE BEAM
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The part of a foundation system (usually in a building without a basement) which supports the exterior wall fo the superstructure; commonly designed as a beam which bears directly on the column footings, or may be self-supporting as a long strap footing.
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DOG BONE
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A method used to strengthen a beam to column connection in a moment resisting frame by selectively reducing the top and bottom flanges (purposely weakening the beam) to make the connection itself stronger. Increases ductility.
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CENTER OF MASS
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In a structure, this is the centroid of all the structural and non-structural components.
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CENTER OF RIGIDITY
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The centroid of only those members that participate in resisting lateral forces.
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SHEAR KEY
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A short longitudinal stub of concrete below a footing used to prevent slippage and increase soil friction.
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FORM TIE
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Any tie, in tension, which is used to prevent concrete forms from spreading as a result of fluid pressure of freshly places, unhardened concrete.
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FASCIA
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A term which general descibes any verical surface which spans across the top of columns or across the top of a wall.
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BACKUP BAR
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A strip of steel used to provide a solid base for beginning a structural steel weld.
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NEUTRAL AXIS
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The line in a beam web located directly in the middle between point of tension and compression in which there are no stresses.
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BOX BEAMS
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A bending member of metal or plywood whose cross sectional area resembles a closed rectangular box.
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DIAPHRAGM SHEAR
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A diaphragm is a flat structural unit acting like a deep, thin beam. The term "diaphragm" is usually applied to roofs and floors. A shear wall, however, is a vertical, cantilevered diaphragm. These construction systems can be used when designing a building for lateral loads, such as those generated by wind or earthquakes.
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CHORD FORCES
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Forces exerted by a principal member of a truss extending from end to end, usually one of a pair of such members, more or less parallel and connected by a web composed of various compression and tension members.
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MOMENT OF INERTIA
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The rotational analog of mass. The inertia of a rigid rotating body with respect to its rotation. Determines the relationship between angular momentum and angular velocity, torque and angular acceleration.
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AREA OF THE SECTION
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A measure of the multiplication of the height x depth of a cross section.
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DEPTH OF THE SECTION
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The height of the section of a member. In steel beams, this is the web and thickness of flanges.
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SECTION MODULUS
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The ration in a beam of a cross sections second moment of area to its greatest distance from the neutral axis.
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RIGID FRAME
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Two columns and a beam (or beams) attached to one another with moment connections. A moment-resisting building frame.
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COUPLING
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Any device used to connect two beams together at their ends for the purpose of transmitting load. There are two types: rigid and flexible. Rigid couplings are used when precise shaft alignment is required. Flexible couplings are designed to transmit torque while permitting some radial and axial and angular misalignment.
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CREEP
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A permanent inelastic deformation in a material due to changes in the material caused by prolonged compressive forces.
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SOFT STORY
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Generall refers to a first story whose stiffness is significantly lower than that of the stories above (usually due to larger external openings); whose lateral stiffness is less than 70% of the stiffness of the story above.
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WEAK STORY
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A story where the overall strength is less than 80% of the story above.
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FIXED CONNECTION
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A connection between two members that restrains all three degrees of freedom of the connected member with respect to one another. Sometimes called a rigid connection or a moment-resisting connection. It restrains both rotation and translation.
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PINNED CONNECTION
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A connection that can resist both vertical and horizontal forces but not a moment. It will allow the structural member to rotate, but not to translate in any direction. Many connections are assumed to be pinned even though they may resist a small amount of moment in reality. These are the typical connections found in almost all trusses.
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ROLLER CONNECTION
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A connection free to rotate and translate along the surface upon which the roller rests. The surface can be horizontal, vertical, or sloped at any angle. The resulting reaction force is always a single force that is perpendicular to, and away from, the surface. Commenly located at one end of long bridges to allow for expansion and contraction from temperature changes.
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PARAPET
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A wall-like barrier at the edge of a roof or structure. It may serve to prevent unwanted falls over the edge or it maybe a defensive, constructional, or stylistic feature.
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K-BRACING
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A type of braced frame with two diagonal supports representing a "K". The are often associated with a link beam.
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SEISMIC RETROFITTING
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The modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. Other retrofit techniques are applicable to areas subject to tropical cyclones, tornadoes, and severe winds from thunderstorms.
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EPICENTER
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The point on the Earth's surface that is directly above the focus where an earthquake or underground explosion originates.
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HYPOCENTER
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The site of an earthquake. The direct point of earthquake, miles below the Earth's surface.
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FAULT LINE
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A planar rock fracture which shows evidence of relative movement. Large faults within the Earth's crust are the result of differential or shear motion and active fault zones ar the causal locations of most earthquakes. Earthquakes are caused by energy release during rapid slippage along a fault.
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STRONG MOTION ACCELEROGRAPH
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An instrument that measures ground or building acceleration and provides this data during an earthquake.
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BASE ISOLATION
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The separation of a buildings foundation for direct rigid contact with the ground. This can be achieved through base isolators made of rubber and steel laminates and act as shock absorbers. This technique allows a building and the earth to move independently during an earthquake.
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VIBRATION ISOLATORS
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Spring and neoprene/fiberglass isolators used to reduce the transmission of noise, shock, and vibration produced by mechanical, industrial, or process equipment and seismic activity into or within a building structure.
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TUNED MASS DAMPER (AKA: ACTIVE MASS DAMPER OR HARMONIC ABSORBER)
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A device mounted in structures to prevent discomfort, damage or outright structural failure by vibration.
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CRIPPLE WALL
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A platform connected to a perimeter foundation through low stud walls resting directly on a foundation.
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MUD SILL
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The lowest sill of a structure, placed directly on the foundation or directly on the ground.
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RE-ENTRANT CORNER
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An interior corner in a building found in "L" and "C" shaped plans which is particularly susceptible to lateral forces and torsion.
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LIQUEFACTION
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The behavior of loose saturated unconsolidated soils (i.e. loose sands) which go from a solid state to have the consistency of a heavy liquid, or reach a liquefied state as a consequence of increasing water pressures, and thus decreasing effective stress.
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SUBSIDENCE
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The resulting aeration of the soil leads to the oxidation of its organic components, such as peat, and this decomposition process may cause significant voids. If the roof of these voids becomes too weak, it can collapse.
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TECTONIC UPLIFT
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A geologinal process, most often caused by plate tectonics, which increases elevation.
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POUNDING
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Occurs when two adjacent structures repeatedly bump into each other due to lateral seismic forces.
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CHINOOK
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A warm, dry wind that blows at intervals down the eastern slopes of the Rocky Mountains.
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SANTA ANA
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A hot winter wind that blows toward the coast from the desert in Southern California.
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STAGNATION PRESSURE
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Direct wind pressure in lbs. per square foot on a verical surface.
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Name 5 types of building irregularities
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TORSION IRREGULARITY - result of asymmetrical plans on a discontinuity in the bracing system.
RE-ENTRANT CORNERS - Plans in the following interior corner shapes - L T U C O +. DIAPHRAGM CONTINUITY - Either resulting from diaphragms with different degrees of stiffness or from having openings or cutouts. OUT-OF-PLANE OFFSETS - Lack of continuity in the lateral force resistance path. NON-PARALLEL SYSTEMS - Elements of the structural system are not in line or symetrical with the major axis of the system. |
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Name four lateral force bracing systems.
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SHEAR WALL - Vertical walls and horizontal diaphragms.
BRACED FRAME - A frame that incorporates diagonal bracing members, tension wires, and struts to stabilize pinned connections. MOMENT RESISTING FRAME - A frame with fixed end connections. Moment forces transfer from one element to the next with redundancy. DUAL SYSTEM - A combination of a moment resisting frame with either shear walls or a braced frame. |
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Name five types of Moment Resisting Frames.
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SMRF - Special Moment Resisting Frame
IMRF - Intermediate Moment Resisting Frame OMRF - Ordinary Moment Resisting Frame MMRWF - Masonry Moment Resisting Wall Frame STMF - Special Truss Moment Frame |
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Types of Retaining Walls
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GRAVITY - Uses its own weight to hold itself in place.
SHEET PILING - Made of fiberglass, steel, or wood driven far into the ground. CANDILEVERED - (or heel) relatively thin stem wall attached to the retaining wall held by mass of soil. ANCHORED - Uses cables or stays anchored back into soil or rock. SOIL NAILING - Technique where soil slopes are held in place by steel reinforcing bars. MECHANICAL STABILIZATION - (MSE) Soil constructed with artificial reinforcing by fixed layered mats. COUNTERFORT - A retaining wall built vertically with buttressed fin walls in tension. |
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Hierarchy of Building Structural Systems from Ductile to Rigid
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1) Moment Resisting Frame
2) Braced Frames 3) Shear Walls |
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DUCTILITY VS. RIGIDITY
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A ductile system will absorb energy better than a rigid one but will suffer interior system stresses, like ceiling tiles, grids, and lights falling). Ductile systems result in less seismic force because they tend to be lighter than rigid systems. Ductile systems on bedrock work better than on clay.
A rigid system will not transfer energy as well to the member and is subject to more lateral force into the system which could result in failure. Rigid structure should be used on soft site (long period) and flexibile structure should be used on stiff soil (short period). |
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Lateral Force Resistive Systems for Tall Buildings
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BAY TYPE SYSTEM - Rigid frames in plan and elevation. Lateral loads are transferred out to the foundations at interior and exterior bays. Example: Home Insurance Building; William Jenney; Chicago, IL
TUBE SYSTEM - Perimeter walls are rigid and rigidly connected at the corners. Lateral loads transferred at perimeter to the foundation. Example: Sears (Willis) Tower; Skidmore, Owings, and Merrill (SOM); Chicago, IL CORE SYSTEM - Shear walls are placed inside the structure. Structure free plates are cantilevered from this core. Often used dually with a tube system. Example: 7 World Trade Center; David Childs (SOM); New York, NY SUSPENSION SYSTEM - Floors are suspended from the structure and loads are transferred via massive compression piers. Example: Hong Kong & Shanghai Bank Building; Sir Norman Foster and Partners; Hong Kong |
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Recommended Seismic Design Practices
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1) Symmetry in systems
2) Keeping the resistant design elements as far from the center of gravity / rotation for the building as possible. 3) Continuity in the building 4) Redundancy in the design 5) Torsion problems 6) Avoid system irregularities |
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Earthquake Importance Factors
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Category I: Low hazard to human life [Storage facilities, Agricultural] - I = 1.00
Category II: Other structures not listed - I = 1.00 Category III: Substantial Hazard [Assembly halls, Schools, Health, Etc.] - I = 1.25 Category IV: Essential Facilities [Hospitals, Fire, Rescue, Power Stations, Defense] - I = 1.50 |
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Construction Sequencing
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1) Installation of soil erosion and sediment control SE/SC measures (silt fence, construction fence, stabilized construction entrance)
2) Tree removal where necessary (clear & grub) 3) Construct sediment trapping devices (sediment traps, basins) 4) Construct detention facilities and outlet control structure with restrictor & temporary perforated riser 5) Strip topsoil, stockpile topsoil, and grade site 6) Temporarily stabilize topsoil stockpiles (seed and silt fence around toe of slope) 7) Install storm sewer, sanitary sewer, water and associated inlet & outlet protection 8) Permanently stabilize detention basins with seed and erosion control blanket 9) Temporarily stabilize all areas including lots that have reached temporary grade 10) Install roadways 11) Permanently stabilize all outlot areas 12) Install structures and grade individual lots 13) Permanently stabilize lots 14) Remove all temporary SE/SC measures after the site is stabilized with vegetation |
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Cost of various construction systems in order of least to most expensive
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1) Wood
2) Concrete 3) Steel Frame |
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Accidental Torsion
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All buildings will experience torsion, called accidental torsion, to some degree, even due to someone moving a desk or file cabinet. The building code wants this to be included.
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Gulf of Mexico seismic zone?
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The Gulf of Mexico is in Seismic Zone 0.
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Cost of various construction systems in order of least to most expensive
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1) Wood
2) Concrete 3) Steel Frame |
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Accidental Torsion
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All buildings will experience torsion, called accidental torsion, to some degree, even due to someone moving a desk or file cabinet. The building code wants this to be included.
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Gulf of Mexico seismic zone?
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The Gulf of Mexico is in Seismic Zone 0.
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Method for Determining Seismic Resistance (IBC)
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Seismic Response History Procedure - Mathematical model for the building is developed with software and subjected to ground shaking. Method is complex but always accepted.
Modal Response Spectrial Analysis - Distribution of seismic forces is based on deformed shaped of natural modes of vibration - determined by mass and stiffness of the building. Equivalent Force Analysis - Static horizontal forces are applied producing similar forces to those found in an earthquake. Used to design most buildings. |
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Method for Wind Analysis (IBC/ASCE 7)
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Method 1 - Simplified Procedure: Wind pressures can be selected from a table with minimal calculations to the building. Primary use is for regular shaped, low rise buildings.
Method 2 - Analytical Procedure: Wind pressures are determined using formulas, tables, and figures provided by the code. Used to design many types of structures. Method 3 - Wind Tunnel Procedure: General guidelines for conducting wind tunnel tests. Expensive and primarily used only for irregular or tall buildings. |
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Site Exposure Categories
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B - Urban/Suburban areas, Wooded areas, Terrain with numerous low obstructions.
C - Open terrain with scattered obstructions generally under 30 feet. D - Flat unobstructed areas, including mud flats & slat flats. |
