AASTHTO Reinforced Concrete Beam Capacity Program for the HP-48
1995 Ted Cashin (internet: dtbrejc@vax.dot.state.ga.us)

These are the programs which actually calculate the moment capacity of a beam section.  See DRCBA for a beam with compression reinforcement, CBM and BETA for accessories to these programs, and VCAP for shear capacity of a section

RCBA is used for a rectangular concrete beam with tension reinforcement only.  If Flag 4 is set, it can also be called by other programs.  

TBMA analyzes a t-beam but if the t-beam behaves as a rectangular beam, the user is notified and RCBA analyzes the section.  

DRCBA is used for a doubly reinforced concrete beam (a beam with compression steel).  Like TBMA, if the compression steel should be neglected, the user is notified and RCBA is called.

All three programs check for an over-reinforced beam.  RCBA checks for minimum reinforcement using the 200/fy criteria instead of moment of intertia and cracking moment criteria.

CBM is used to input information and is called by the analysis programs.  If the user chooses not to input new information, analysis is run on existing values.  This  is useful when a user has already input information and then only wants to change one variable (say area of steel) which can be done by hand before running the program.

BETA calculates the beta factor based on concrete strength.

VCAP calculates the ultiimate shear capacity of a beam section given values stored in fc, d, b, fy, Av (area of steel per stirrup), and s (stirrup spacing).  The strength reduction factor of f = 0.85 is included.  Checks are made for reduced allowble stirrup spacing and maximum allowable shear resistance of stirrups based on concrete strength (AASHTO Sec. 8.)
