The use of miscellaneous structural steel to transfer the diaphragm shear provides a direct path for the load transfer to the structure. The use of the joist bearing seats to transfer this force can create unintended secondary moments. The joist bearing seat can be designed and manufactured to transfer this force, provided the project’s EOR has considered all the effects of the eccentricity of the force in the structural design.

This will vary depending on the bearing seat depth and angle size used. The SJI has not formally published these values because of the variables involved in the calculation. An approximate value can be obtained by assuming a bearing seat thickness and a 4″ long bearing seat and checking the bending capacity for a given bearing seat depth. The bearing seat thickness can be controlled by the weld specified for the bearing seat connection to the structure.

There is not a common value. The SJI currently does not have published values for bearing seat rollover forces as bearing seat angle sizes, depth and length can vary between projects. Bearing seat angle sizes may be L2x2x1/8″, 3/16″ or 1/4″ for K-Series joists. LH- Series joists seats can be 2½” or 5″ deep and the bearing seat angles can vary more widely than the K-Series.

Joist roll-over is created when the horizontal shears along the building perimeter must be resisted by the joist bearing seat when no structural steel is provided between the joists to absorb the horizontal shear.