ced according to the particular plane in whichit acts. In a wide flange girder, vertical shear occurs in the beam cross section if the beamis loaded vertically. Horizontal shear acts along the length of a girder if the member isloaded longitudinally. One can visualize the effects of shear stress as one cross-sectionalpiece moving in the opposite direction and another, adjacent cross-sectional piece movingin the opposite direction.An internal shear force is induced by a load acting in the opposing direction. In abridge, the greatest danger for shear occurs at supports where a load, combined with abeam reaction, can result in high shear stress. From basic strength of materials, we canfind that average shearing stress is defined as the load divided by the resisting area. Taking a wide flange girder as an example, vertical shear would be computed as the loaddivided by the beam web area.It is know from basic engineering physics that torsion is a twisting about thelongitudinal axis of a member. When the effects of torsion are severe, box girderstructures are used because of their ability to resist torsional forces. Torsional forces arecaused by eccentric loads (i.e. loads that are not placed on top of the member).(3)In highway bridge, torsional forces could result from wind forces, eccentric wheelloading, or other overturning type loads. When a torsional force is applied to a member,the maximum stresses will occur at the outer face of the element. Similar to bending,where stress is zero at the neutral surface, torsional stresses are zero along the longitudinalaxis.An axial force is one which acts along the longitudinal axis of a member. Depending on the direction of the force, the axial force will induce either compression ortension. If the load is acting toward the member, it will be compressed, and if it acts awayfrom it, the member will be in tension. An example of an element under compression axialforce would be a pier column. ...
