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Unequal I Beam

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I beam unequal 1An unequal I-beam, also called unequal I-section or unequal beam, is a type of structural steel member with an I-shaped cross-sectional profile where the flanges (horizontal top and bottom parts) have different widths.  This results in an asymmetrical shape where one flange is wider than the other.  The unequal I-beam is designed to accommodate specific load and structural requirements where the loads are not symmetrically distributed.  Unequal I-beams are commonly used in situations where the loads, spans, and other design considerations vary along the length of the beam.  The wider flange typically corresponds to the side that experiences higher loads or needs to provide greater resistance to bending and shear forces.

The design of an unequal I-beam involves calculating the dimensions of both flanges and the web (the vertical part connecting the flanges) to ensure that the beam can effectively handle the applied loads while maintaining structural stability.  Engineering considerations such as bending moments, shear forces, and deflection are taken into account during the design process.

Unequal I Beam Index

 

area of a Unequal I Beam formula
\(\large{ A =  b\;s  +  h\;t  +  w\;s  }\) 
Symbol English Metric
\(\large{ A }\) = area \(\large{ in^2 }\) \(\large{ mm^2 }\)
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ s }\) = thickness \(\large{ in }\) \(\large{ mm }\)
\(\large{ t }\) = thickness \(\large{ in }\) \(\large{ mm }\)
\(\large{ b }\) = width \(\large{ in }\) \(\large{ mm }\)
\(\large{ w }\) = width \(\large{ in }\) \(\large{ mm }\)

 

Distance from Centroid of a Unequal I Beam formulas

\(\large{ C_x =  0  }\)

\(\large{ C_y =  l \;-\;  \frac{ 1 }{2\;A} \; \left[  t\;l^2  +  s^2 \; \left(b \;-\; t \right)  +  s\; \left(w \;-\; t \right) \; \left(2\;l \;-\;  s \right)    \right]  }\) 
Symbol English Metric
\(\large{ C }\) = distance from centroid \(\large{ in }\) \(\large{ mm }\)
\(\large{ A }\) = area \(\large{ in^2 }\) \(\large{ mm^2 }\)
\(\large{ l }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ s }\) = thickness \(\large{ in }\) \(\large{ mm }\)
\(\large{ t }\) = thickness \(\large{ in }\) \(\large{ mm }\)
\(\large{ b }\) = width \(\large{ in }\) \(\large{ mm }\)
\(\large{ w }\) = width \(\large{ in }\) \(\large{ mm }\)

 

Elastic Section Modulus of a Unequal I Beam 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 \(\large{ in^4 }\) \(\large{ mm^4 }\)

 

Perimeter of a Unequal I Beam formula
\(\large{ P =  2 \; \left( w  +  b  +  l - t  \right)   }\)
Symbol English Metric
\(\large{ P }\) = perimeter \(\large{ in }\) \(\large{ mm }\)
\(\large{ l }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ t }\) = thickness \(\large{ in }\) \(\large{ mm }\)
\(\large{ b }\) = width \(\large{ in }\) \(\large{ mm }\)
\(\large{ w }\) = width \(\large{ in }\) \(\large{ mm }\)

 

Radius of Gyration of a Unequal I Beam formulas

\(\large{ k_{x} =    \frac{    \frac{1}{3}  \;   \left[    b \;  \left(l \;-\; C_y \right)^3  \;+\;  wC_{y}{^3}    \;-\; \left(b \;-\; t \right)   \;   \left(l \;-\; C_y  \;-\; s \right)^3      \;-\;  \left(w  \;-\;  t \right)     \;  \left(C_y  \;+\;  s \right)^3       \right]   }        {b\;s  \;+\; h\;t  \;+\; w\;s}    }\) 

\(\large{ k_{y} =     \frac{  \sqrt {  s \; \left(s^2  \;+\;  3 \right) \;  \left(w \;-\;  t \right)^3  \;+\;  2\;h\;t^3 }  }{ 2\; \sqrt{6} \; \sqrt{w\;s  \;+\;  b\;s  \;+\;  h\;t }    }    }\) 
Symbol English Metric
\(\large{ k }\) = radius of gyration \(\large{ in }\) \(\large{ mm }\)
\(\large{ C }\) = distance from centroid \(\large{ in }\) \(\large{ mm }\)
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ l }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ s }\) = thickness \(\large{ in }\) \(\large{ mm }\)
\(\large{ t }\) = thickness \(\large{ in }\) \(\large{ mm }\)
\(\large{ b }\) = width \(\large{ in }\) \(\large{ mm }\)
\(\large{ w }\) = width \(\large{ in }\) \(\large{ mm }\)

 

Second Moment of Area of a Unequal I Beam formulas

\(\large{ I_x =  \frac{1}{3}   \;  \left[    b \;  \left(l \;-\; C_y \right)^3  +  wC_{y}{^3}  - \left(b \;-\; t \right) \left(l - C_y  - s \right)^3   -  \left(w  -  t \right)       \left(C_y -  s \right)^3    \right]   }\) 

\(\large{ I_y =   2 \; \left[ 2 \; \left(   \frac{1}{96} \; s^3 \;  \left(w - t \right)^3  +  \frac{1}{32} \; s \; \left(w -  t \right)^3   \right) +  \frac{h\;t^3}{24}      \right]    }\) 

\(\large{ I_z =   l_x  +  I_y }\) 
Symbol English Metric
\(\large{ I }\) = moment of inertia \(\large{ in^4 }\) \(\large{ mm^4 }\)
\(\large{ C }\) = distance from centroid \(\large{ in }\) \(\large{ mm }\)
\(\large{ h }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ l }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ s }\) = thickness \(\large{ in }\) \(\large{ mm }\)
\(\large{ t }\) = thickness \(\large{ in }\) \(\large{ mm }\)
\(\large{ b }\) = width \(\large{ in }\) \(\large{ mm }\)
\(\large{ w }\) = width \(\large{ in }\) \(\large{ mm }\)

 

Torsional Constant of a Unequal I Beam formula
\(\large{ J  =   \frac{ w\;s^3 \;+\;  b\;s^3  \;+\; \left( l \;-\; 5 \right) \; t^3  }{  3  }  }\) 
Symbol English Metric
\(\large{ J }\) = torsional constant \(\large{ in^4 }\) \(\large{ mm^4 }\)
\(\large{ l }\) = height \(\large{ in }\) \(\large{ mm }\)
\(\large{ s }\) = thickness \(\large{ in }\) \(\large{ mm }\)
\(\large{ t }\) = thickness \(\large{ in }\) \(\large{ mm }\)
\(\large{ b }\) = width \(\large{ in }\) \(\large{ mm }\)
\(\large{ w }\) = width \(\large{ in }\) \(\large{ mm }\)

 

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Tags: Structural Steel

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