16  |  SPRING 2026 ADVANTAGE STEEL
ENGINEERS’ CORNER
The CISC Solutions Centre has received recurring questions about the design forces to be 
used when sizing shallow footings for concentrically braced frames in the conventional 
construction category. In an effort to reduce total concrete volume and rebar tonnage, 
engineers are looking at designing the footings as non-capacity protected, following the 
provisions in the National Building Code. This article aims to highlight key considerations to 
keep in mind when designing such footings.
CISC Engineers’ Corner
MICHAEL MASI, Eng., M. Eng. 
Manager, Engineering
CISC-ICCA
Design of Shallow Footings for Conventional Construction 
Concentrically Braced Frames
N
o n - c a p a c i t y  
p r o t e c t e d 
foundations – designed for 
loads less than the capacity 
of the SFRS – must have adequate 
overturning resistance to resist the 
gravity loads plus seismic loads, 
evaluated as the maximum of those 
calculated using RdRo = 2.0 and 
those evaluated at 75 per cent of the 
overturning capacity of the SFRS.
NBC 
uses 
terms 
like 
“lateral 
load 
capacity” 
and 
“overturning 
capacity” of the SFRS and leaves it 
to the material standard of the SFRS 
to say whether this corresponds to 
the yielding members developing 
t h e i r  
n o m i n a l  
o r  
p r o b a b l e 
resistances. When looking to apply 
the 
requirements 
of 
NBC 
2025 
Cl.4.1.8.16 to the design of the 
foundations for a steel-braced frame 
in 
the 
conventional 
construction 
category, S16:24 Cl.27.12.1.4 says 
that the “lateral load capacity” 
or 
“overturning 
capacity” 
to 
use is that corresponding to the 
yielding members reaching their 
nominal resistances.
F o r  c o n c e n t r i c a l l y  b r a c e d 
frames, 
the 
lateral 
loads 
that 
must be calculated are those that 
correspond to the tension braces 
reaching 
their 
nominal 
tensile 
resistances simultaneously with the 
compression braces reaching their 
nominal 
compressive 
resistances 
(see figure). The nominal resistance 
is determined by taking φ = 1.0. For 
HSS bracing members conforming 
to ASTM A500, it is suggested that 
nominal resistances be calculated 
using nominal section properties 
based on unreduced wall thickness. 
This accounts for the potential dual-
certification of ASTM A500 members, 
which may result in actual wall 
thicknesses closer to nominal values 
than design values.
The relevant requirements from 
CSA 
A23.3:24 
Cl.21.10.3 
should 
also be met for NCP foundations. 
Cl.21.10.3.4 deals with the design 
of the footing and Cl.21.10.3.3.3 
sets out the requirements on how to 
calculate the foundation movements 
that need to be accommodated by 
the structure.
Note 
that 
the 
foundation 
movements for NCP foundations 
will be much greater than for those 
that are capacity protected. These 
foundation movements come into 
play both when you are checking 
drift limits and when calculating 
p-delta effects. For conventional 
construction, 
it 
can 
make 
the 
difference between having U2 < 1.1 
and being able to ignore p-delta 
effects vs having U2 > 1.1 and having 
to amplify your seismic loads. For 
that reason, we’ve found it to be 
better to go with capacity-protected 
foundations 
for 
Type 
CC 
CBFs, 
following the requirements of NBC 
2025 Cl.4.1.8.16(3). It is for CBFs and 
EBFs with Rd > 1.5 where we’ve seen 
a benefit with using NCP foundations 
where 
U2 
was 
greater 
than 
1.1 regardless.  AS

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