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Structures I Exam 1
Terms in this set (50)
When the number of unknown exceed the number of equations of equilibrium, the rigid body is said to be _________ externally.
Structural components and complex system of buildings are __________ that do not deform. (Cannot see deformation).
Resolving a Force
The process of replacing a force with an alternate set of forces that have the same effect on the structure as the original force is called
Study of the relationship of forces and objects at rest that remain at rest. (Refers to gravity type forces with "loads").
_________ is the perpendicular distance from the line of action of a force to the moment center, about which rotation is assumed to take place.
The primary function of a _________ is to support and redirect loads and forces safely to the ground.
Forces or Load (Weight)
Is a push or pull exerted on an object. (To move something or deform it) Either upsets equilibrium or creates it.
States that the moment of a about a point is equivalent to to the moment of the force's two components about the point.
Rotation & Translation
A force applied to a rigid body at rest can cause 2 types of motion _________ & __________.
________ forces are the applied loads and/or the weights of members.
The ________ of a force is the tendency of the force to cause a rotation about some axis or point.
Active forces & Reactive forces
Forces which tend to set a rigid body in motion are called __________ and forces which tend to prevent motion are called _________.
Defined as something made up of interdependent parts in a definite pattern of organization.
State of balance of zero motion.
Defined as two forces having the same magnitude , parallel lines of action, but opposite sense.
A simplified representation of a particle or rigid body that is isolated from its surroundings and on which all applied forces and reactions are shown.
Roller, Rocker, Short Link
List 3 support types/conditions that can prevent translational motion in only 1 direction
List 2 support types/conditions that can prevent translational motion in only 2 perpendicular directions.
List a support type/condition that can prevent tranlational motion in two perpendicular directions as well as rotational motion.
Carry static loads, but have considerable stiffness and sheer dead weight, which may absorb the energy of dynamic forces with less distortion. CHANGE in shape.
Force under a structure. Classification is due to inertia or momentum of the mass of the structure (earthquakes). More sudden, greater force will be. (STUDY OF RELATIONSHIP BETWEEN FORCES AND OBJECTS IN MOTION)
Loads resulting from the self weight of the building or structure and of any permanently attached components, such as partition walls, flooring, framing elements, and fixed equipment. (Fixed) (Balcony)
Transient and moving loads that include occupancy loads, furnishings, and storage are classified as _______ loads. _______ loads are extremely variable by nature during a structure's lifetime as occupancy changes. (Examples - Occupants / Environmental)
Special type of live load because of variability involved.
Study of forces and their effects on objects that are either at rest or in motion.
Creates a load on buildings that is dynamic in nature. Kinetic energy is changed to potential energy when hitting the building.
Earthquake (Seismic) loads
(Inertial) Produce dynamic force on a building. Come from the "focus or "hypocenter." Above hypocenter is epicenter. All building have a "natural" or "fundamental" point of vibration.
Strength of materials
Study of relationship between forces and and deformation of an object. Example: Crumbling, smashing
Functional requirements of a building structure
1. stability and equilibrium - concerned with balancing of forces to ensure that a building and its components will not move
2. strength and stiffness - concerned with strength of building's component parts (beams, columns, walls)
3. continuity and redundancy - direct, uninterrupted path for loads through the building of the structure from the roof level down to the foundation. Redundancy concerned with multiple load paths in a structural framework so that one system acts as a backup to another in the event of localized structural failure.
Principle of Transmissability
(Push or Pull force in same direction cause same result) The external effects on a body remain unchanged when a force 1 acting at a point A is replaced by another force 2 of equal magnitude at point B, provided that both forces have the same sense and line of action. (APPLIED ON A RIGID BODY & STATES THAT A FORCE MAY BE MOVED ANYWHERE ALONG ITS LINE OF ACTION WITHOUT CHANGING THE EXTERNAL EFFECTS ON THE BODY)
Occur between bodies within a system. Also may occur within the members themselves, holding together the particles forming the rigid body. (Reaction or resistance offered by a body to applied forces)
Forces acting along a straight line
Group of 2 or more forces that act on a body at the same time.
Forces that are parallel (Can only act on rigid body) (Coplanar)
All forces acting on same plane.
All forces skewed.
Vector (What forces characterized by)
Line represents a force. A quantity possessing both magnitude and direction, represented by an arrow the direction of which indicates the direction of the quantity and the length of which is proportional to the magnitude
1. Magnitude (lbs, N, etc.)
3. Sense (arrow head)
4. Point of Application (where hits)
A collection of forces acting at specified locations (may also include couples).
A _____________ is a force that acts on a large part of a surface, not just on one place.
Refer to structural components and complex systems of buildings and bridges.
Newton's First Law
(Equilibrium) Any body at rest will remain at rest, and any body in motion will move uniformly in a straight line, unless acted upon by a force.
Newton's Second Law
(F = mass x acceleration) The time rate of change in momentum is equal to the force producing it, and the change takes place in the direction in which the force is acting.
Newton's Third Law
(Basic Force) For every force of action there is a reaction that is equal in magnitude, but opposite in direction, and has the same line of action.
Forces Due to Settlments
(Static) Leaning Tower of Piza. (Ground settled unevenly caused change in building's structure.)
Forces Due to Thermal Effects
(Static) Expanding when heated and contracting when cooled.
Residual Stress (Force)
(Static) Occur due to process taken place. (Welding)
(Dynamic) Blasting / Demolishing a building.
Force that acts at a single point. (walls, foundations)
Uniformly Distributed Forces
Magnitude of force is constant everywhere.
Nonuniformly Distributed Force
Force distributed in multiple places. Examples: Soil pressure, hydrostatic, earthquake
Recommended textbook explanations
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Charles Alexander, Matthew Sadiku
Mechanics of Materials
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Alan S. Willsky, Alan V. Oppenheim, S. Hamid
Thermodynamics: An Engineering Approach
Yunus A. Cengel
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