Center of Mass and Rigidity

• Often called the Stiffness

• Will determine how well a wall will react to lateral forces

Wall Rigidities

The rigidity of a wall is dependent on the?

1. cross-sectional dimensions,

2. the height of the wall, and

3. the material it is made of

The rigidity of a wall is defined as ____________. For example, for wall i the rigidity R₁ = 1/8i.

the reciprocal of the deflection

is fixed at its base or foundation and is a vertical cantilever

Cantilever wall

is fixed both at its base and at the top and restrained against rotation

Fixed wall

• Define the formula for deflection of cantilever wall and fixed wall.

• Define also the meaning of each letter in the formula.

• Define the formula for deflection of cantilever wall and fixed wall.(SIMPLE MODE)

• Define also the meaning of each letter in the formula.

What are considered as horizontal diaphragms?

Floors and flat roofs of buildings

• is considered to be rigid or flexible based on its stiffness

• which is idealized as rigid, is typically a solid concrete slab or concrete on metal deck slab having a span-to-depth (aspect) ratio of 3 or less.

Diaphragm

• assumes that the diaphragm is sufficiently stiff to retain its form and engage the vertical elements based on their stiffness or rigidity.
  

• Designed to distribute lateral loads to the vertical supporting structural elements of the lateral load resisting system such as shear walls or frames.

rigid diaphragm analysis

• It needs to be calculated to determine the location of the seismic shear to be applied to the building.

Center of Mass

What is the formula of Center of Mass?

is the origin whereby the seismic force applied to the center of mass of the floor will rotate.

Center of Rigidity

In Center of Rigidity.

• When forces are parallel to the length of the wall, its rigidity must be?

• When forces are perpendicular to the wall, its rigidity is?
  

1. determined

2. conservatively taken as zero.

What is the formula of Center of Rigidity?