Q
7 small wood screws
VOCABULARY
reinforcing elements for one wall
Q
2 pieces of string, each approximately 25 cm (10 in.) long
Braces or Bracing:
structural elements built
into a wall to add
strength. These may be
Q
1 piece of thin wood (about as thick as the craft sticks) 20 cm x 2 cm
(about 8 in. x 1 in.)
Q
1 piece of lightweight cardboard, about 15 cm x 15 cm (a little less
than 6 in. square)
Q
8 small paper clamps to fasten wood and cardboard
for each small group
Q
One set of the above supplies if they are each building a model wall
Q
One copy of Master 4.2b, Load Paths Worksheet
Q
Pens and pencils
P ROC E DUR E
Teacher Preparation
Assemble the model wall, following the diagram on Master 4.2a,
Building a Model Wall, and try it out before class. Be sure the bolts
are just tight enough to hold the structure upright when no force is
applied.
A. Introduction
Tell students that this lesson is designed to demonstrate how the
structural elements of a wall carry forces. The activity deals with three
structural elements that carry the lateral shear forces caused by ground
shaking during an earthquake: diagonal bracing, shear walls, and rigid
connections. It is designed around an apparatus called the model wall.
Remind the students that this is a model, designed to demonstrate only
certain characteristics of real walls.
B. Lesson Development
1. Show students the model and tell them that it represents part of the
frame of a building. Describe the components of the wall, and ask
them, “What holds this wall up?” The answer is in the interaction of
the vertical and horizontal elements, but try to keep the students
focused on discovery, since in this activity they will see the
architectural principles demonstrated. Explain to students that what
they refer to as weight will be called the force of gravity in this lesson.
2. Now ask students to predict what would happen if you quickly
pushed the base of the wall, simulating an earthquake. Remind them
that an earthquake may cause ground shaking in many directions, but
for now we are modeling shaking in one direction only.
3. Divide the class into the same seismic engineering teams (SETs) as
for Lesson 1 and give each group one copy of Master 4.2b, Load Paths
Worksheet. Invite students to take turns investigating the model’s
response in their small groups.
made of various materials and
connected to the building and each
other in various ways. Their ability to
withstand stress depends on the
characteristics of the materials and
how they are connected.
Lead:
the sum of vertical forces
(gravity) and horizontal forces (shear
forces) acting on the mass of a
structure. The overall load is further
broken down into the loads of the
various parts of the building.
Different parts of a building are
designed and constructed to carry
different loads.
Lead path:
the path a load or force
takes through the structural
elements of a building.
Rigid connections:
connections
that do not permit any motion of the
structural elements relative to each
other.
Shear force:
force that acts
horizontally (laterally) on a wall.
These forces can be caused by
earthquakes and by wind, among
other things. Different parts of a wall
experience different shear forces.
Shear walls:
walls added to a
structure to carry horizontal (shear)
forces. These are usually solid
elements, and are not necessarily
designed to carry the structure’s
vertical load.
Structural elements or structural
features:
a general term for all the
essential, non-decorative parts of a
building that contribute structural
strength. These include the walls,
vertical column supports, horizontal
beams, connectors, and braces.
A G U
/
F E M A
234
S
E I S M I C
S
L E U T H S
