| THEORY & FORMULAE |
An arch can be viewed as a curved beam (girder) supported at its ends and carrying transverse load. Consider an elastic parabolic arch ACB rigidly fixed at its ends. When the arch is subjected to a continuous uniformly distributed vertical load, the forces and bending moments acting on the system can be described by the following equations:
    
where
     L = width (span) of arch
     h = height (central rise) of arch
     w = force per unit length
     H = horizontal reactive force at column base
     Ha = horizontal reactive force at point A
     Hb = horizontal reactive force at point B
     Ra = vertical reactive force at point A
     Rb = vertical reactive force at point B
     Ma = bending moment at point A
     Mb = bending moment at corner B
     Mc = bending moment at corner C
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