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This is a geometry question.
for the sake of quantity take off, you can do assumptions. Ex: elbows equivalent to1.5m of straight duct, Tee equivalent to2.5m of straight duct...
ABRAR AFRIDI
SPECIFICATIONS AND FORMULAS
SPECIFICATION
WIDTH
HEIGHT
LENGTH
RADIUS
DEGREE
QTY
OFFSET
FORMULAS
STRAIGHT FORMULA:
(WIDTH + HEIGHT) X 2 X LENGTH x QTY = AREA
ELBOW FORMULA:
(WIDTH + HEIGHT) X 2 X LENGTH X QTY = AREA
LENGTH = (R+W/2) X 3.14 X (DEGREE/180)
TAPER FORMULA:
(WIDTH 1 + HEIGHT 1+WIDTH 2+ HEIGHT 2) X LENGTH x QTY = AREA
IF UP/DOWN TAPER FORMULA:
(WIDTH 1 + HEIGHT 1+WIDTH 2+ HEIGHT 2) X (LENGTH + OFFSET) x QTY = AREA
OFFSET FORMULA:
(WIDTH + HEIGHT) X 2 X (LENGTH + OFFSET) x QTY = AREA
SHOE FORMULA:
(WIDTH + HEIGHT) X 2 X (LENGTH + 50 MM) x QTY = AREA
DUMMY:
WIDTH X HEIGHT = AREA
YEE PIECE FORMULA:
STRAIGHT AREA + ELBOW AREA = AREA
TEE PIECE FORMULA:
ELBOW AREA + ELBOW AREA = AREA
NOTE: IF ALL DIMENSIONS ARE IN MM, AREA IN SQ.MM
Calculating Area of Bend required to following calculation
2 x ((Area of Circle based on duct Width +150mm as Radius /4)-(Area of circle based on 150mm as Radius/4))+Height of duct x (2 xPi()x (Duct width+150mm)/4)+(height of Duct x 2x Pi()x 150mm/4)
Calculating Reducer required Trapezium calculation
the exact area in educational field is OK to calculate but in professional it is not like this
Normally it is given by some factor added in the duct length
Anyhow if you very keen to do so you can make a model in auto CAD and fine area of different sizes by area command
Hope this will work
another option is to measure the weight and than divide by the gauge number
means if you bend is 15 kilo and you know the gauge of elbow or bend than by this info how many kilos in that gauge you can find the almost exact area
any QS can answer this question for certifying the payment application ? exact area to be calculated for billing purposes.
when the quantity take of is complete take ten % extra of duct this will resolve the quantity assumption .
Very useful for Fresher and experienced Engineer also
