Transcript Frames and Walls Lateral Stability

Frames and Walls
Lateral Stability
• A beam simply supported by two columns is
not capable of resisting lateral forces unless it
is braced.
• If the joints connecting the columns and beam
are capable of resisting both forces and
moments, then the assembly becomes a rigid
frame.
• If we fill in the plane defined by two columns
and a beam, it becomes a loadbearing wall
that acts as a long, thin column in transmitting
forces to the ground.
• Any opening in a loadbearing wall weakens its
structural integrity. A lintel or arch must
support the load above a door or window
opening and allow the flow around the
opening to sections of the wall
Lateral Stability
• The structural elements of a building must be
sized, configured, and joined to form a stable
structure under any possible load conditions.
• A structural system must be designed to not
only carry vertical gravity loads, but also
withstand lateral wind and seismic forces from
any direction.
Lateral Forces
• They are considered to act parallel to the
ground plane
• They may occur at many angles other than the
horizontal
Types of Lateral Forces
External Lateral Forces:
1. Wind Force
2. Seismic Force
3. Fluid pressure from water and other liquid
4. Soil against a basement or retaining wall
5. Sand, grain, coal or wood chips in a storage
bin
• Wind Load is influenced greatly by local
terrain
• Upon contact with a building, it can produce
pressure and suction forces on any surface of
a building and the pressure will tend to
balloon the building outward.
• Seismic Load – forces generated by inertia of
building mass as ground moves below the
structure
• The effect is internal
• Flood waters can produce devastating effect
and can destroy foundations of bridges and
buildings
• Internal Lateral Force – restrained movement
associated with temperature change
• If prevented from expanding or contracting, a
material will undergo internal forces and
stresses.
Horizontal Diaphragm
• A rigid floor structure, acting as a flat, deep
beam, transfers lateral loads to vertical shear
walls, braced frames or rigid frames
• Rigid Frame – a steel or reinforced concrete
frame with rigid joints capable of resisting
changes in angular relationships.
• Shear Wall – a wood, concrete, or masonry
wall capable of resisting changes in shape and
transferring lateral loads to the ground
foundation.
• Braced Frame – a timber or steel braced with
diagonal members.
Structural Patterns
References:
• http://arch.umd.edu/Tech/Tech_III/Lectures/Lateral_Forces_&_Framing/I
ntroduction_to_Lateral_Forces.pdf
• Building Construction Illustrated
Francis DK Ching
Fourth Edition