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 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: Wind Force Seismic Force Fluid pressure from water and other liquid Soil against a basement or retaining wall 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/Introduction_to_Lateral_Forces.pdf Building Construction Illustrated Francis DK Ching Fourth Edition