Indicates the direction, using the left measured value of cross section fs=fa and the right measured value of cross section fs=-fa.
When calculating the internal force of a beam (horizontal or horizontal), the lower edge fiber is in tension and the upper edge fiber is in compression, which means that the bending moment is positive. If it is a vertical beam, the beam section becomes negative bending moment clockwise and positive bending moment shear force counterclockwise:
The left direction of the section is positive (horizontal bar) upward, or positive (vertical bar) to the right, negative (horizontal bar) downward and negative (vertical bar) to the left; The right direction of the section is negative downward (horizontal column), or negative left (vertical column), positive upward (horizontal column) and positive right (vertical column).
Extended data:
Shear wall structure is a structure that uses the inner wall or outer wall of a building to make the shear wall bear vertical and horizontal loads. Shear walls are generally reinforced concrete walls with the same height and width as the whole building. Because its main load is horizontal load, it is called shear wall because it bears shear and bending. Shear wall structure has large lateral stiffness, small deformation, load-bearing and enclosure, and is suitable for residential and tourist buildings.
When the vertical load-bearing components in a building are mainly borne by walls, such walls not only bear vertical loads from horizontal components, but also bear horizontal earthquakes from wind or earthquake. Therefore, the shear wall is named (seismic code named seismic wall).
Baidu encyclopedia-shear force