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Trapezoid

on . Posted in Plane Geometry

  • trapezoid 12Trapezoid (a two-dimensional figure) is a quadrilateral that has a pair of parallel opposite sides.
  • Acute angle measures less than 90°.
  • Diagonal is a line from one vertices to another that is non adjacent.
  • No interior angles are equal.
  • Obtuse angle measures more than 90°.
  • Quadrilateral (a two-dimensional figure) is a polygon with four sides.
  • a & c are bases
  • b & d are legs
  • a ∥ c
  • a ≠ c
  • ∠A + ∠B = 180°
  • ∠C + ∠D = 180°
  • 2 diagonals
  • 4 edges
  • 4 vertexs

Trapezoid Index

 

Area of a Trapezoid formulas

\(\large{  A_{area} =  h \; \left(  \frac{c \;+\; a}{2 }  \right)   }\) 

\(\large{  A_{area} =  m\;h   }\) 
Symbol English Metric
\(\large{ A_{area} }\) = area \(\large{ in^2 }\)  \(\large{ mm^2 }\)
\(\large{ a, b, c, d }\) = edge \(\large{ in }\) \(\large{ mm }\)
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ m }\) = midline \(\large{ in }\) \(\large{ mm }\)

 

Diagonal of a Trapezoid formulas

\(\large{  d' = \sqrt{  a^2 \;+\; b^2 \;-\; 2\;a\; \sqrt{b^2 \;-\; h^2}  }  }\) 

\(\large{  D' = \sqrt{  a^2 \;+\; d^2 \;-\; 2\;a\; \sqrt{d^2 \;-\; h^2}  }  }\) 
Symbol English Metric
\(\large{ d', D' }\) = diagonal \(\large{ in }\)  \(\large{ mm }\)
\(\large{ a, b, c, d }\) = edge \(\large{ in }\) \(\large{ mm }\)
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)

  

Distance from Centroid of a Trapezoid formulas

\(\large{  C_x =  \frac{ 2\;c\;g \;+\; c^2 \;+\; g\;a \;+\; c\;a \;+\; a^2 }{ 3 \left(  { c \;+\; a }  \right)  }   }\) 

\(\large{  C_y =  \frac { h }{ 3} \; \left(  \frac{ 2c \;+\; a }{c \;+\; a}  \right)    }\) 
Symbol English Metric
\(\large{ C }\) = distance from centroid \(\large{ in }\)  \(\large{ mm }\)
\(\large{ a, b, c, d }\) = edge \(\large{ in }\) \(\large{ mm }\)
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ g }\) = offset \(\large{ in }\) \(\large{ mm }\)

 

Elastic Section Modulus of a Trapezoid formulas

\(\large{  S_x =  \frac{ I_x }{ C_y  }   }\) 

\(\large{  S_y =  \frac{ I_y }{ C_x  }   }\) 
Symbol English Metric
\(\large{ S }\) = elastic section modulus \(\large{in^3}\)  \(\large{ mm^3 }\)
\(\large{ C }\) = distance from centroid \(\large{ in }\) \(\large{ mm }\)
\(\large{ I }\) = moment of inertia \(\large{\frac{lbm}{ft^2-sec}}\)  \(\large{\frac{kg}{m^2}}\) 

 

Height of a Trapezoid formulas

\(\large{  h =  \frac  { 2\; A_{area} }{c \;+\; a}  }\) 

\(\large{  h =  \frac  { A_{area} }{m}  }\) 
Symbol English Metric
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ A_{area} }\) = area \(\large{ in^2 }\)  \(\large{ mm^2 }\)
\(\large{ a, b, c, d }\) = edge \(\large{ in }\) \(\large{ mm }\)

 

Midline of a Trapezoid formula
\(\large{  m = \frac{a \;+\; c}{2}   }\) 
Symbol English Metric
\(\large{ m }\) = midline \(\large{ in }\)  \(\large{ mm }\)
\(\large{ a, b, c, d }\) = edge \(\large{ in }\) \(\large{ mm }\)

 

Perimeter of a Trapezoid formulas

\(\large{  P =  a + b + c + d   }\) 

\(\large{  P =  \sqrt {h^2 + g^2} + \sqrt {h^2 + \left( a - c - g  \right)^2   }  + a + c   }\) 
Symbol English Metric
\(\large{ P }\) = perimeter \(\large{ in }\)  \(\large{ mm }\)
\(\large{ a, b, c, d }\) = edge \(\large{ in }\) \(\large{ mm }\)
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)

 

Plastic Section Modulus of a Trapezoid formulas

\(\large{  Z_x =  \frac{  h^2   \;  \left(  g\;c^2 \;+\; 14\;c\;a \;+\; g\;a^2   \right)  }{ 12\; \left(  c \;+\; a   \right)  }   }\) 

\(\large{  Z_y =  \frac{  6\;c\;a\;h \;-\; 3\;c^2\; h \;-\; 8\;c \;+\; 8\;a \;+\; 4\;g^2 \;h \;-\; 8\;g  }{ 24}   }\) 
Symbol English Metric
\(\large{ Z }\) = plastic section modulus \(\large{ in^3 }\)  \(\large{ mm^3 }\)
\(\large{ a, b, c, d }\) = edge \(\large{ in }\) \(\large{ mm }\)
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)

 

Polar Moment of Inertia of a Trapezoid formulas

\(\large{  J_{z} =  I_x + I_y    }\) 

\(\large{  J_{z1} =  I_{x1}  +   I_{y1}    }\) 
Symbol English Metric
\(\large{ J }\) = torsional constant \(\large{ in^4 }\) \(\large{mm^4 }\)
\(\large{ I }\) = moment of inertia \(\large{\frac{lbm}{ft^2-sec}}\) \(\large{\frac{kg}{m^2}}\)

 

Radius of Gyration of a Trapezoid formulas

\(\large{  k_{x} =  \frac {h}{6} \; \sqrt{ 2 + \frac{ 4\;c\;a}{ \left( c \;+\; a \right)^2 }  }   }\) 

\(\large{  k_{y} =   \sqrt {  \frac {I_y} {A_{area}}    }    }\) 

\(\large{  k_{z} =   \sqrt  { k_{x}{^2}  + k_{y}{^2}  }   }\) 

\(\large{  k_{x1} =   \frac{1}{6} \;  \sqrt{  \frac{ 6\;h^2 \; \left( 3\;c \;+\; a \right)  }{c \;+\; a}  }    }\)

\(\large{  k_{y1} =    \sqrt {  \frac {I_{y1}} {A_{area}}    }    }\)

\(\large{  k_{z1} =  \sqrt  { k_{x1}{^2}  + k_{y1}{^2}  }    }\)
Symbol English Metric
\(\large{ k }\) = radius of gyration \(\large{ in }\)  \(\large{ mm }\)
\(\large{ a, b, c, d }\) = edge \(\large{ in }\) \(\large{ mm }\)
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)

 

Second Moment of Area of a Trapezoid formulas

\(\large{  I_{x} =  \frac{    h^3   \;  \left(  c^2\; 4\;c\;a \;+\; a^2   \right)   }{  36   \;  \left( c \;+\; a \right) }   }\) 

\(\large{  I_{y} = \frac{  h \; \left( 4\;c\;a\;g^2   \;+\; 3\;c^2\; a\;g \;-\; 3\;c\;a^2\; g   \;+\; c^4  \;+\; a^4  \;+\; 2\;c^3 \;a  \;+\; c^2 \;g^2  \;+\; c^3 \;g \;+\; 2\;c\;a^3 \;-\; g\;a^3 \;+\; a^2\; g^2    \right) }   { 36  \;   \left( c \;+\; a   \right)  }   }\) 

\(\large{  I_{x1} =   \frac{  h^3 \; \left( 3\;c\;+\;a \right)  }{12}   }\) 

\(\large{  I_{y1} =  \frac{  h  \;  \left( c^3 \;+\; 3\;c\;g^2 \;+\; 3\;c^2\; g \;+\; a^3 \;+\; g\;a^2  \;+\; c\;a^2 \;+\; a\;g^2 \;+\; 2\;c\;a\;g \;+\; a\;c^2  \right)  }{12}   }\)
Symbol English Metric
\(\large{ I }\) = moment of inertia \(\large{in^4}\) \(\large{mm^4}\)
\(\large{ a, b, c, d }\) = edge \(\large{ in }\) \(\large{ mm }\)
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ k }\) = radius of gyration \(\large{ in }\) \(\large{ mm }\)

 

Edge of a Trapezoid formulas

\(\large{  a =  2 \; \frac { A_{area} }{h} - c   }\) 

\(\large{  b =  P - c - a - d   }\) 

\(\large{  c =  2 \; \frac {A_{area} }{h} - a   }\) 

\(\large{  d =  P - c - a - b   }\)
Symbol English Metric
\(\large{ a, b, c, d }\) = edge \(\large{ in }\) \(\large{ mm }\)
\(\large{ A_{area} }\) = area \(\large{ in }\)  
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)

 

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Tags: Structural Steel Quadrilateral

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