
Flexural Design of Reinforced Concrete Beams 
Table of Contents  

Design Data: Required design data is specified based on the design control option selected in the Laboratory Setup section. The user must input values that conform to ACI318 requirements.
Load Conditions for Maximum Span Moment: These load conditions are used to specify the factored beam moment demand (along the beam length) corresponding to the maximum moment within the span. A combination of factored design beam end moments, span distributed loads, and span concentrated loads may be used. The sign convention for the loads can be found by clicking here. Beam span distributed and calculated loads acting in the upward direction are not allowed.
Load Conditions for Maximum Support Moment: These load conditions are used to specify the factored beam moment demand (along the beam length) corresponding to the maximum moments at the supports. A combination of factored design beam end moments, span distributed loads, and span concentrated loads may be used. The sign convention for the loads can be found by clicking here. Beam span distributed and calculated loads acting in the upward direction are not allowed.
Window 1 Control: The design number and section number to be displayed in Window 1 are selected. The design details at three critical sections along the length of the beam can be displayed as follows. Section 1: Section adjacent to the left support; Section 2: Section at beam midspan; and Section 3: Section adjacent to the right support.
Window 2 Control: The design number to be displayed in Window 2 is selected.
Window 3 Control: The design number to be displayed in Window 3 is selected.
Window 4 Control: Input and output parameters to be displayed in Window 4 are selected.
FIG. 1. Java Module A interface. Users will complete the input sections above and then click on the solve button to view the beam design in Windows 14.
The beam is treated as a simply supported beam with end moments in order to solve for the moment as a function of position along the length of the beam. Moment diagrams for both the max span moment loading condition and the max support moment loading condition are determined this way. These two moment diagrams form the demand curves displayed in Control Window 3 (see Fig. 1).
The maximum moments at the critical sections can be determined from the two demand curves. These moments are used to design the beam.
Module A determines the valid bar combinations for the required steel area at each critical section using the minimum and maximum bar size numbers specified by the user in the Design Data section of the module.
The module considers combinations of one bar size and two bar sizes. It finds the combinations with the smallest steel area and determines the maximum number of bars that can fit in the first layer given the clear spacing, sb, defined by the user in the Design Data section of the module. The module then checks these combinations for symmetry to ensure that they are acceptable configurations (see Fig. 4 in the Design 1 Calculations for acceptable bar configurations).
Thus, the steel bar combination chosen for each critical section is the one with the smallest steel area and with acceptable symmetry and clear spacing.
Once the reinforcing bar combinations for the critical sections have been determined, the module designs the cutoff locations for the bars along the beam length. The user specifies the maximum cutoff ratio for the span reinforcement and for the support reinforcement in the Design Data section of the module. Sample bar cutoff calculations can be seen in Design 1 Calculations..
Disclaimer: No responsibility is assumed by the authors, the University of Notre Dame, or the Portland Cement Association for any errors or misrepresentations in the laboratory modules, or that occur from the use of these modules.