Cross Sections CTC 440 Objectives n n Know

Cross Sections CTC 440

Objectives n n Know what a cross section is and what is typically shown Know how to calculate areas and volumes Know how to use the simple stripping method to calculate areas Know the other ways to calculate areas n n Squares Planimeter CAD programs Know how to calculate volumes using the average end area method

Cross Sections n n A view, at a particular station, of all features Plotted perpendicular to the station Typical sections/cross sections are different A cross section is a “snapshot” at a particular location

Cross Sections - Use n n n Earthwork quantities Drainage Driveways/intersecting roads Right-of-Way Cut/fill slopes Utilities

Cross Sections n n Show existing elevations (usually dashed) Show new features (usually solid) n n n Road structure Ditches Sideslopes Drainage Utilities Guide railing

Cross Sections n Example

Calculating Areas n Various methods n n Stripping method Count squares Planimeter Computer software

Stripping Method n n Say you have a cross-section at a scale of 1”=5’ Break area into 1” strips, measure the lengths of the center of the strips and add them up Multiply by 1” to get square inches Convert square inches to square feet

Calculating Volumes n n n Most common method is the average end area method Take the sum of the areas at two different stations, average them, and then multiply the average by the length between the stations Calculate volumes 2 stations at a time; don’t try w/ 3 or 4 stations

Calc. Volumes-Example n n n At Sta 2+50; Area=8 sf At Sta 2+75; Area=20 sf’ Length between stations=25’ There are 27 cubic ft per cubic yard Volume=(8+20)/2*25=350 cf Volume=350 cf/27=13 cy

Next Lecture n Intersections