Evaluation of Analysis and Design Results of Reinforced Concrete Walls Carried out using ETABS
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Date
2008-03
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Addis Ababa University
Abstract
The use of commercial application programs is well established in the local structural design
offices working in Ethiopia. Among the most widely used programs are SAP2000 and
ETABS by CSI, California, Berkeley.
User confidence in respect of analysis results is reasonably high for building structures or
bridges whose lateral force resisting systems comprise 3-D rigid frames. For buildings with
wall or dual wall-frame systems, however, the comparison is not so straight forward, and has
not yet been systematically investigated and reported.
More recently some users while accepting the drawbacks in respect of the design of columns
tend to accept the design results of walls as valid. Clearly, response of structural walls to axial
load and biaxial bending is much more involved than their column counterpart.
In an effort to show the proximity and/or divergence of the results of ETABS with other soft
wares and analysis methods the following processes has been performed.
1. Lateral load distribution results of ETABS were compared with those of the approximate
elastic analysis procedure for a system of walls.
2. Column reinforcement results of ETABS were compared with those from interaction
charts of EBCS 2 Part2.
3. Reinforcement of the walls from ETABS was checked by software specially developed
for checking capacities of structural walls of any shape under normal load and biaxial
bending.
From the lateral load distribution comparison result, it was observed that there were
differences between the outputs of ETABS and the approximate elastic analysis. The
percentage difference varies from one wall arrangement type to another and wall section to
wall section. In case of the design results, column reinforcement areas obtained from ETABS
were larger than those from interaction charts of EBCS 2 Part 2. For the simple rectangular
structural walls considered, the reinforcement from ETABS was found to be insufficient to
resist the design actions on it. The same thing was observed on the L-shaped walls. Where as
for the C-shaped walls designed by ETABS the capacity to demand ratio were nearly 1.
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Based on the comparison results of the design of a limited number of columns and walls, it
may be concluded that the design of walls and columns performed by ETABS may lie on the
safe side or the unsafe side.
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Keywords
Evaluation ; Analysis