HS - Note 1-L
INTRODUCTION
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Lateral Loads
There types of the loads acting on any structure in the lateral (horizontal) direction
are: the wind loads, Earthquake loads and the notional loads (as a result of
imperfection).
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Wind loads
p= qCeCgCp
NBCC
pe = [0.613(VsXSb)2](Cpe)(Ca)
BS6399
p= qsCeCqIw
UBC94
Earthquake loads (UBC)
ZIC
V=
W
Rw
The UBC is the most common code used in calculating the lateral loads on the
buildings due to the earthquake.
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Notional loads
Depending on the design code, there should be a minimal eccentricities in the building
and imperfection in the construction process of the vertical members ( columns and
walls)
The calculation of the load magnitude and the distribution of the loads on the building
will be discussed in a separate note. The calculation of the loads depends on the codes
used in the design.
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HS - Note 1-L
INTRODUCTION
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Lateral Resisting Systems of Steel Buildings
The most important element is the braced frame. Different types of bracings are
shown in the figure below.
Outrigger
Cross Bracing
Chevron Bracing
Single Bracing
Knee Bracing
A good coordination between the structural engineer and the architect is very
important to determine the type of the bracing to avoid any conflict in the interior
layout (doors and bracing locations). Also the façade design and the building shape is
very critical.
The use of the outrigger in combination an exterior truss (Belt truss) at mechanical
levels is common.
Lateral Resisting Systems of Concrete Buildings
There are many different systems to resist the lateral forces acting on a concrete
building. The main elements are listed below. It is important to mention that
combining any of these elements is often used based on the building height and site
conditions.
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HS - Note 1-L
INTRODUCTION
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The main elements resisting the lateral loads in concrete structures are:
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Moment Resisting Frames ( up to 10 stories)
Shear Walls (to 20 Stories)
Coupled Walls ( up to 30 stories)
Concrete Core
Perimeter Tube
The layout below of a 60 floor tower - design by Buro Happold - is an example of this
structural system.
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