] [Thread] [Date] [Author]

[Kevin Elbury <kelbury(--nospam--at)awinc.com>]

I am currently designing a two way slab slab system for the parkade portion
of a four storey appartment structure. The width of the parkade is 64ft with
columns located at 17'-6" from the foundation walls. The columns are spaced
at 27' o/c. I am proposing a drop panel system (over a slab band) mainly to
facilitate mechanical services. We have the ADOSS software package by PCA
and we also have a 3-D finite element package for any numerical analysis we
require. My questions are:

1. What are your experiences using dropped panel vs. slab band systems from
a construction and economical point of view. Slab bands are very popular in
British Columbia; Dropped panels are more popular in Eastern Canada.

2. In the design of a two way slab system, can anyone give some guidance
with respect to analysis and design for line and point loads in 2 way slabs?
I have line loads in the order of 3500plf and point loads in the order of 30
kips applied nowhere near any columns. The ADOSS program handles these types
of loads by 'averaging' them over the complete width of the band (27'). I
have a hard time agreeing with this assumption. I plan to deal with this by
modelling the slab using FE's and superimposing these moments onto the ones
calculated by ADOSS for normal loadings. Are there any implications in
proportioning these moments between column and middle strips?

Your recommendations will be much appreciated.


Kevin Elbury, P.Eng.
British Columbia, Canada.