Drift Controlled Preliminary Frame Design

Using this program, you can obtain preliminary values of frame member section properties required to satisfy drift and strength requirements. Using the preliminary design procedure by Mahin and simple plastic analysis, the elastic section modulus (S), plastic section modulus (Z), and effective moment of inertia (I) can be determined and used to select initial beam member sizes. Strong column-weak girder design is assumed and it is the responsibility of the user to satisfy this assumption by selecting beam and column sections appropriately. Results given are for beam section properties. Please note also that the value of S for gravity load-only case is based on beam fixed-end moments, and that the moment for the distributed load case is calculated using the ACI approximation wL^2/11.

Gravity Load Definition and Configuration Specification  

Elastic (Young's) Modulus (ksi):          

Yield stress (ksi):          Overstrength multiplier a:

Number of bays:

Story height (ft):           Span length (ft):

Choose a gravity load configuration:

Gravity load (k or k/ft):


Preliminary Elastic Analysis - Serviceability level earthquake  

Enter the parameters you wish to use:

Drift limit (% story height):

Elastic story shear (k):

Beam to column stiffness ratio Ib/Ic:


Preliminary Plastic Analysis - Collapse Prevention level earthquake  

Select the desired plastic mechanism (see below):

Drift limit (% story height):

Plastic story shear Vstory (k):


Results - Required Section Properties

Prevention EQ

S (in3)

Z (in3)
I (in4)

Please note that each load case is presented separately (ie. the Serviceablility EQ case doesn't include the
demands from the gravity loads).

Copyright 1999 Janise Rodgers, Pacific Earthquake Engineering Research Center, University of California, Berkeley.