GENERAL PLANS and DETAILS (Not Inc. Grading + SW) Flashcards
Layout method for complex angular and curvilinear designs
Angles, bearings, and arcs
Dimension lines are extended from an object at a ___ angle
90 degree
Best pH for most plants
6.0 - 7.5
Diameter of a tree 4” or less measured 6” above the ground
Caliper
Layout Plan: Problem associated with under-dimensioning
Greater interpretation by the contractor / loss of control of the design
Layout Plan: Problem associated with over-dimensioning
Greater potential for error or confusion; implies an inflexibility in accommodating field conditions
Hierarchy of Dimensioning
Fixed dimensions > Semi-fixed dimensions > Flexible dimensions
Dimension type that locates features w/ high level of accuracy; Usually for legal purposes; Typically located by a licensed land surveyor
Also BASELINES; defines features w/ semi-fixed locations
e.g. property lines, ROW, building locations, setbacks, and other aspects governed by code requirements)
Fixed dimensions
Dimension type for points, lines, or planes located by fixed dimensions (baselines)
Used to locate most landscape improvements
Semi-Fixed Dimensions
Dimension type used to locate site elements that do not require precision and / or may be adjusted based on field conditions
May uses ‘+/-‘ or ‘VIF’
Flexible Dimensions
Dimensions that can be determined only after construction has progressed to a point where an actual measurement can be taken
Field Dimensions
Level of precision is usually assumed to be:
½ of the smallest unit indicated
e.g 84’-3” = +/- ½” precision
When dimensions are provided as a decimal (e.g. 84.25ft, eg) assumed precision is ½ of the lowest decimal point (e.g. .005ft)
Degree of precision should reflect realistic tolerances that can achieved in construction of a particular feature / material
Identifies the distance bw two points
Dimension Line
- Should be heavier in weight than dimension lines
- Should not be broken
Extend at a right angle from the dimension line to the object measured
Extension Line
Should be lighter in weight than dimension lines
Convention of locating dimension line labels
- Above the dimension line
- Read from bottom right hand side of sheet
Horz. Layout Method:
Used when a considerable % of side elements are orthogonal to the Fixed Features (PL, new / ex. Building, etc)
Baselines (e.g. building walls) serve as reference points from which objects are measured
String / chain dimensions are closely associated w this method
Perpendicular Offsets
Horz. Layout Method:
Often used w/ curvilinear elements that do not require a high degree of accuracy
Uses offsets at fixed intervals taken from a baseline to the edge or centerline of an element
Accuracy of the shape is limited by the offset interval
Baseline System
Horz. Layout Method:
Distances provided along an X,Y axis to provide unique geographical positions of points from a known POB or PO (point of origin)
Coordinate System
Horz. Layout Method:
Latitude (N-S); departure (E-W)
Either a bearing angle or a length is provided for ea. Point (but not both)
Latitude and Departure
Horz. Layout Method:
Used for the layout of complex curvilinear designs
Bearing: direction of a line specified by a given angle bw the line and an established meridian
Arc: segment of a circle; defined by a center point, a radius and an internal angle; its end points and orientation must be defined
Angles, Bearings, and Arc
Horizontal Curve Type:
Two curves in the same direction connected by a tangent; to be avoided in road design
Broken-back curve
Horizontal Curve Type:
Single radius; most commonly used for low speed roads
Simple curve
Horizontal Curve Type:
Two or more radii in the same direction; difference in the length of the radii should not be more than 50%
Compound
Horizontal Curve Type:
Two arcs in opposite directions; usually requires a tangent between them
Length of tangent depends on road’s design speed
Reverse curve
Horizontal Curve Type:
Typical curves for high speed roads entail a series of curves with a constantly changing radius
Spiral Transitional Curves
More difficult to calculate and lay out; typically not used by LAs since it is primarily for high speed roads
Marks the beginning of the curve at which the road alignment diverges from the tangent line in the direction of stationing
Point of Curvature (PC)
Marks the end of the curve at which the road alignment returns to a tangent line in the direction of stationing
Point of Tangency (PT)
Where two tangent lines intersect
Point of Intersection (PI)
Central angle of the curve; equal to the deflection angle between the tangents
Included Angle (I)
Distant from the PI to either the PC or the PT; always equal for simple circular curves
Tangent Distance (T)
Distance from PC to PT measured along a straight line
Chord (C)
Point about which the included angle (I) is turned
Center of Curve (O)
Used in surveying linear routes (e.g. streets, power lines, stationary storm sewers, etc)
Marked along a centerline from a starting point (0+00)
Full station intervals are indicated along a center line; key areas will also be indicated
Stationing
In stationing, FULL stations are at ___ intervals
100 ft (represented at 1+00)
In stationing, HALF stations are at ___ intervals
50 ft (represented at 0+50)
Forward sight distance should not be ___
Less than the safe stopping distance for the design speed of the curve
Banking / tilting to compensate for centrifugal forces acting on a vehicle as it travels around a curve
Superelevation
BVC
Beginning of vertical curve
PVI
Point of vertical intersection
EVC
End of vertical curve
(2) Types of Vertical Sight Distance
- Safe stopping distance
- Safe passing distance
(LA’s typically only address stopping distances)
