How to Design a Rectangular Concrete Beam to ACI 318-14
How to Design a Rectangular Concrete Beam to ACI 318-14
The ClearCalcs Concrete Beam Calculator allows users to design concrete beams by specifying the desired load cases and dimensions of the beam. In this article, each section of the calculator will be explained followed by a few worked examples.The Rectangular Concrete Beam Calculator has 4 main sections
The concrete weight classification needs to be selected from the drop-down menu shown below.Note that one can select βcustomβ and input the concrete density and an lightweight concrete factor to create their own concrete weight classification.
Strength is limited to 80 ksi for regular columns, and 60 ksi in special seismic systems. This requirement is imposed to ensure steel yields before concrete crushes in the column.
Distance from concrete surface to edge of ties. Minimum cover: 1-1/2β for unexposed members, 2β for exposed members with bars >= #6, and 3β for any concrete cast against the ground.
The hard maximum deflection allowed for the beam, regardless of span length. Normally, your local building code will dictate this. For the IBC, Table 1604.3 provides the limits.
Calculated independently for each span. For cantilevers, βLβ is taken to be twice the length of the cantilever. Normally, your local building code will dictate this limit. For the IBC 2018, Table 1604.3 provides the limits.
Calculated independently for each span. For cantilevers, βLβ is taken to be twice the length of the cantilever. Normally, your local building code will dictate this limit. For the IBC, Table 1604.3 provides the limits.
Tension bars are the reinforcement bars which are in tension when the concrete beam is subjected to vertical loads. These are located towards the bottom of the cross-section (indicated in green in the figure below). Compression bars are the reinforcement bars which are in compression when the concrete beam is subjected to vertical loads. These are located towards the top of the cross-section (indicated in blue in the figure below.)
In the fifth column, the depth corresponding to each row must be specified. Depth is the distance from the row to the top surface of the concrete beam.
A Stirrup is a closed loop of reinforcement bar, which holds the main reinforcement bars in place. In this section, the user can specify whether or not to include stirrups in their design. Stirrups are required if more than half the concrete shear strength is utilized.
Spacing between stirrups at the supports. Note that as shear will typically be much lower at midspan under a UDL, this spacing may change. This sheet is intended to provide basic design info only, but the shear force diagram may be used to check additional spacings.
The table in this section prompts the user to input distributed loads. For further instructions on how to fill out this table, check out our help article on how to input distributed loads.
In this section, the table must be filled out as follows:
In column 1, the user can name the load as they prefer.
In the second column, the location of the load must be specified in feet as measured from the left end of the beam.
The following table will appear when one clicks on the third column.
The load type must be selected from the drop-down menu given. If it is a vertical load, its magnitude must be specified in pounds (lb). If it is a moment load, the magnitude must be specified in Pounds feet (lb.ft).
The user can choose whether or not they include the self-weight of the beam in their calculations. The calculator is set to include the self-weight by default unless the user specifies otherwise.
The user can select whether reduced companion live load is used in their calculations or not. For live loads under 100 psf which are not in a garage or a place of public assembly, a 50% reduction in the live load is allowed when it is used as a companion load.
A factor which accounts for the effects of creep in concrete. In most structures, the design life should conservatively remain at 5+ years. Sustained duration factor must be selected from the drop-down menu given below.