Corbels and Beam Ledges

Brackets or corbels are short-haunched cantilevers that project from the inner part of columns to support heavy concentrated loads or beam reactions. Its design has become increasingly important with the extended use of precast and prestressed concrete members and larger spans, resulting in heavier shear loads at supports. A beam ledge is a cantilever that projects from a concrete column to support perperndicular precast beams.

The program performs the design of a reinforced concrete corbel or beam ledge subjected to vertical and horizontal combined factored loads, based on the Strut Theory approach and the ACI Ultimate Strength Design Method. The program designs the reinforcing steel as well as the bearing plate.

Input Data

The required input data consists of the materials' properties, the corbel dimensions, the applied loads, and its position. For the reinforcement design, the bar size and spacing for the main tension steel and the horizontal stirrups are required.

Example

As an example, design the corbel to project from a 14" square column supporting a factored vertical load of 86.4 kips acting at a distance of 3.0 in. from the face of the column, as shown. Use f'c=4 ksi and Fy=60 ksi.

Output

Once the input data is entered, the program performs the computations and checks the adequacy of the design. The output consists of three non-dimensional numbers indicating the limitations in shear capacity and the steel area provided. All these ratios should be no greater than 1.0.

In addition, the program computes the required bearing plate area under the load to avoid concrete bearing failure. Figures show the template and graphs generated by this program.