Moment of Inertia
A geometric property of a cross-section that measures its resistance to bending. Calculated as the integral of the area times the square of the distance from the neutral axis.
Shear Force
An internal force acting perpendicular to the longitudinal axis of a structural member, caused by transverse loads. Represented on shear force diagrams to analyze beam behavior.
Bending Moment
An internal moment that causes a structural member to bend. Equal to the sum of moments about a point caused by external forces on one side of that point.
Bearing Capacity
The maximum pressure that soil can support from a foundation without shear failure or excessive settlement. Determined by soil type, depth of foundation, and groundwater conditions.
Hydraulic Gradient
The change in hydraulic head per unit distance along the flow path. Drives groundwater flow according to Darcy law and is dimensionless.
Modulus of Elasticity
The ratio of stress to strain in the elastic region of a material. Also called Young modulus, it quantifies a material stiffness and is measured in units of pressure.
Factor of Safety
The ratio of the ultimate strength of a structure or component to the maximum expected load or stress. Values greater than 1 indicate a margin of safety against failure.
Deflection
The displacement of a structural member under load, measured perpendicular to the member original position. Excessive deflection can cause serviceability problems even without structural failure.
Consolidation
The time-dependent compression of saturated clay soils under sustained loading as pore water is squeezed out. Governs long-term settlement predictions for foundations.
Manning Equation
An empirical formula for calculating the velocity of open-channel flow based on hydraulic radius, channel slope, and a roughness coefficient. Widely used in civil hydraulics design.
Effective Stress
The portion of total stress in soil carried by the solid particle skeleton, equal to total stress minus pore water pressure. Controls soil strength and compressibility.
Reinforced Concrete
Concrete with embedded steel reinforcement (rebar) to resist tensile forces. The concrete resists compression while the steel resists tension, creating a composite structural material.
Horizontal Curve
A circular arc in the plan view of a roadway that transitions between two tangent sections. Designed using minimum radius formulas based on design speed and superelevation.
Vertical Curve
A parabolic curve in the profile view of a roadway that provides a smooth transition between two grades. Designed for adequate stopping sight distance and driver comfort.
Retaining Wall
A structure designed to hold back soil or rock from a building, structure, or area. Resists lateral earth pressure using gravity, cantilever action, or anchored mechanisms.
Truss
A structural framework of members connected at joints (nodes) that carries loads primarily through axial forces (tension and compression) in the members rather than bending.
Compaction
The densification of soil by mechanical means to reduce void ratio and increase density. Measured using the Proctor test to determine optimum moisture content and maximum dry density.