Evaluation of the shear capacity of short span beams using sectional analysis

Structural analyses are often based on sectional analysis principles. While this method works well for moment and axial load, there are special conditions that apply to shear. In particular, if the shear strength is evaluated immediately beside a point load or a support, somewhat conservative results will be obtained. One reason for this is the presence of “clamping stresses”, which are internal self-equilibrating vertical compressive stresses through the thickness of the member. Thus, in these regions, shear strength is not checked, and the critical section for shear is located a specified distance from the face of the loading column or support plate. While this is very practical advice, it is limiting in analyses relatively short shear spans particularly in the case of a deep beams. A more refined determination of behavior can be made via strut-and-tie analyses or specialized theories such as the two- or three-parameter kinematic theory (2PKT/3PKT). However, there remains value in a purely sectional approach using moments and shears as these tend to be easy to determine, apply and understand. The paper presents a new approach to determine the behaviour of such disturbed regions using sectional analysis via the use of clamping stresses. The shear capacity and the critical location of a deep beam and a moderately-deep beam are evaluated according to the new approach and compared to the experimental results.