For this reason, the Code requires ties to be embedded in grout in Seismic Performance Categories D and E. The Code allows lateral ties to be placed in either mortar or grout, although placement in grout more effectively prevents buckling and results in more ductile behavior. (76 mm) below the lowest reinforcement in the shallowest beam or bracket. Where beams or brackets frame into a column from four directions, the lateral ties must be placed within 3 in. Vertical lateral tie spacing is halved above the top of the footing or slab in any story, as well as below the lowest horizontal reinforcement in a beam, girder, slab, or drop panel above. The size and spacing requirements ensure the ties prevent buckling of reinforcement acting in compression as well as provide shear resistance to columns subjected to lateral loads. Lateral ties enclose and support the vertical reinforcement. The requirement for at least four vertical bars allows the lateral ties to provide a confined core of masonry. In addition, Table 1 lists allowable reinforcement for various column sizes, based on the Code required minimum and maximum vertical steel area. The basic requirements are illustrated in Figure 1. 1) requires a minimum amount of vertical column reinforcement as well as lateral ties to confine the vertical steel. If the actual eccentricity exceeds this minimum, the actual eccentricity should be used in the design. This minimum eccentricity is intended to account for construction tolerances. As a minimum, the Code requires that the design consider an eccentricity of 0.1 times each side dimension, with each axis considered independently. Eccentricity may be introduced by eccentric axial loads, lateral loads, or a column that is out of plumb. If the designer can demonstrate that there is reliable restraint against both translation and rotation at the supports, the effective height may be reduced in accordance with conventional design principles.Įccentricity also affects the structural capacity of masonry columns. The effective height of a column is typically taken as the clear height between supports.

For columns, the Code also limits the effective height to thickness ratio to 25, and requires a minimum nominal side dimension of 8 in. 1, referred to hereafter as the Code), slenderness effects are included in the calculation of allowable compressive stress for reinforced masonry. In Building Code Requirements for Masonry Structures (ref. The capacity of columns may be reduced due to either buckling or to additional bending moment caused by deflection ( P– D effects). Because a column failure has the potential to cause collapse of other structural members, a series of special requirements are imposed on columns in addition to the requirements for reinforced concrete masonry wall design.

Concrete column capacity calculator