23-03-2012, 12:03 PM
design of special moment
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Introduction
1.1 Overview:
In the present modern world, the technology has seen bright advancements in analyzing the nature and behavior of the earth. However, understanding the seismic behavior of the earth layers is comparatively at a very low index.
The construction of civil structures such as buildings, bridges and dams etc in the seismic regions became major challenge for the engineers. Studies and research help us in facing the challenges by understanding the phenomenon of moment of inertia, which is a key for constructing structures to withstand the earthquakes
Seismic design is a specific area of architecture dedicated to the structural analysis of buildings, bridges, and roads, with the aim of making them resistant to earthquakes and other seismic activity. Its ethical goal is the protection of the occupants and users of these structures. In an earthquake, unsound structures are more likely to collapse and cause damage. Heavily urbanized areas become more lethal because of the high density of structures and the threat of structural collapse. In this sense, structures can be viewed as heightening the danger created by any seismic activity and increasing the risk to life.
1.2 Moment Frame :
Most of the structures are dependent on the frames that connect the structure. There by, giving the name as moment frame.
The word "moment" in the term moment frame, or joint, refers to the inertia placed on a building when in wind or earthquake conditions. A building faces two primary types of inertia. One is outer inertia caused by wind pressure. This is the same pressure applied to a person if they are standing in a strong wind. Inner inertia, like that from an earthquake, comes from the ground up. A person feels similar inertia when standing on a train that takes off quickly and they are shaken from the feet up.
1.3 Types of Moment Frames:
A moment frame is a box-shaped frame with special moment connections or joints that help in the resistance of wind and earthquake damage. The frame helps a building to flex as necessary to remain the building's integrity. There are three types of moment frames: ordinary moment frames (OMF), intermediate moment frames (IMF), and special moment frames (SMF).
An ordinary moment frame (OMF) is used in low-seismic areas and is expected to remain elastic through regular conditions. They do not have the rigid standards in place that a moment frame used in a high seismic region must. They are not intended to handle any interstory drift, which means that the floors should not shift relative to one another.