Stability - ICE Manual of Structural Design: Buildings - page 245

Chapter 15
Stability
John Butler Technical Director, Structures, GHD, Philippines

doi: 10.1680/mosd.41448.0245

CONTENTS

15.1 Introduction 245

15.2 General considerations 245

15.3 Low-rise buildings 246

This chapter discusses how stability is provided for various types of building. The different
actions (forces) on buildings that give rise to instability are reviewed. The effects of building
'sway' are considered. First‑ and second‑order structural analysis is described. Low‑rise
steel, masonry and timber framed buildings are reviewed together with high‑rise buildings
constructed of steel, in situ and precast concrete. For each form of construction, different
types of structural arrangement are discussed and typical details are shown of how stability is
achieved. Various types of bracing, floor diaphragms and shear walls are discussed. Stressed
skin design is also considered. Some special stability requirements relating to industrial
structures, construction below ground, stability of buildings during erection, safe working
practices and temporary structures are considered. Stability of aluminium structures is reviewed.

15.4 Multi-storey buildings 255

15.5 Precast concrete

framed buildings 259

15.6 Further stability

requirements 261

15.7 Conclusions 265

15.8 References 265

15.1 Introduction
The stability of a building is its ability to satisfactorily resist
horizontal or other disturbing actions or forces which could
cause overturning, uplift or cause the building to sway. Stability
is one of the most important aspects of the structural design of
buildings. In order to design for stability, the engineer must
have a clear understanding of how the horizontal or disturbing
actions (forces) are transferred to the building foundations. The
load paths should be clearly defined and should be as direct as
possible. Typically the roof or floors of a building will act as
diaphragms transmitting the horizontal actions, for example,
wind on cladding, to vertical braced frames or shear walls and
then to the foundations. Design should ensure that adequate
horizontal and vertical framing exists to prevent sway and
transmit these actions.

For a more detailed discussion on loading, see Chapter 10:
Loading .

F bldg,k - Characteristic dead wt. of building (including foundations)
F w,k - Characteristic wind force (ignoring the effects of sway)
γ G - Partial factor for permanent loads (0.9)
γ Q - Partial factor for variable loads (1.5)
Taking moments about 'X'
Design overturning moment (OM) = F w,k γ Q H/2 = F w,k 1.5H/2
Design restoring moment (RM) = F bldg,k γ G L/2 = F bldg,k 0.9L/2
OM < RM

15.2.2 Structural arrangement
The structure should be designed to resist the horizontal actions
in two orthogonal directions by means of points of restraint or
braced bays. Horizontal wind loads or other lateral actions are
transferred to the foundations by various means as follows:

15.2 General considerations
The following are general stability considerations which apply
to different types of building.

The diaphragm action of floors or walls acting as plates or shear

■

15.2.1 Actions to be considered
Below are examples of loads that may impose lateral actions
on the structure:

walls.
Horizontal and vertical bracing carrying the lateral actions as axial

■

load in triangulated frames.
Moment frames with 'pinned' connections at the supports.

Wind loads

■

■

■

Crane and machinery loads ■

Vertical cantilever columns with 'fixed' base connections at foun‑

dation level.
Vertical cantilever concrete core walls (enclosing lifts, stairs or

Earthquake

■

■

■

Geometrical imperfections in the framing (sway stability)

service ducts).
Buttressing by means of diaphragm or fin walls.

Horizontal component of soil, water loads and drifted snow

■

■

■

Accidental loads (vehicle impact, explosions).

Where movement joints are provided in a structure each part
of the structure must be independently stable with its own pro‑
vision for stability.
Points of restraint or shear walls should be arranged on plan
so that the centre of shear coincides with the resultant hori‑
zontal action. Where this is not possible the resulting eccentric

When designing to ensure stability, partial load factors (BS
EN1990: 2002) must be applied to the lateral actions (overturn‑
ing) and to the restoring actions. To ensure an adequate factor
of safety in the design low partial load factors are applied to
the restoring actions ( Figure 15.1 ).