SAP2000 and CSiBridge are two well-known software that Computers and Structures, Inc. (CSI) develops in the past 30+ years. It aims at resolve finite element analysis problems mainly in the fields of Civil, Structural, and Mechanical Engineering. This series is to address a few bugs I came across when using CSI SAP2000/CSiBridge. Although these bugs are minor and hardly affect your works, I still want to write them down as a note for future reference.
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Bug#1, Incorrect Output of “Volumetric Ratio of Tranverse Confinement Steel” in Section Designer.
Section Designer is a built-in sectional analysis tool shared by ETABS, SAP, and CSiBridge. With it, users can define a section more arbitrarily and one of its convenient features is to provide confined concrete property based on Mander’s equations that are adopted by Caltrans Seismic Design Criteria (SDC) and other codes.
The outputs that Section Designer provides for a Caltrans confined concrete section are all look good except the ρs, Volumetric ratio of transverse confinement steel to the concrete core. Please be cautious if you intend to use this number for your subsequent calculation, as it is absolutely wrong. You may have to compute it by SDC equation (3.31).
Except that, I have not found any other error in Section Designer’s output for confined concrete section. And the erroneous output of ρs does not affect other parameters in Section Designer’s output. So it may only be a bug localized for some unknown reason.
Reference:
1. Mander, JB; Priestley, MJN. “Observed Stress-Strain Behavior of Confined Concrete”, Journal of Structural Engineering, ASCE, Vol. 114, No. 8, Aug 1988, pp. 1827-1849.
2. Caltrans Seismic Design Criteria, version 1.6, Nov 2010.
Hao Luo 