Soft storey is a situation when the upper levels of a building is stiffer than the lower storey. This can result in undesirable performance of the building. There are many situations when a storey above can be stiffer than that below it.
How do you stop a soft story?
In case it is necessary, irregularities can be eliminated by increasing the lateral rigidity of this storey by putting up additional walls between single structural elements on the soft storey; placing diagonals between the columns and shear walls; increasing the rigidity of the soft storey by increasing beam-column …
What is vertical irregularity?
Vertical irregularities are characterized by vertical discontinuities in the distribution of mass, stiffness and strength. … In set-back structures there is a sudden change in the vertical distribution of mass, stiffness, and in some cases, strength.
What is the soft story mechanism and why is it a source of earthquake failure?
Soft stories experience a sudden reduction in lateral stiffness and larger story drift (see figure above), resulting in a concentration of deformation in the ground floor that can cause severe damage to total collapse. The soft story issue has been widely observed in historical earthquakes around the world.What do you understood by soft story write an appropriate example of it?
A soft story building is a multi-story building in which one or more floors have windows, wide doors, large unobstructed commercial spaces, or other openings in places where a shear wall would normally be required for stability as a matter of earthquake engineering design.
What causes soft storey?
The common sources of soft story vulnerability include: Ground floor tuck-under parking beneath wood-framed residential apartment buildings. Tall first floor story heights, typical in older mid-rise and high-rise commercial office buildings where the first floor is generally twice the height of a normal floor above.
What is mass irregularity?
Mass irregularity is considered to exist where the seismic weight of any storey is more than 200 percent of that of its adjacent storey. … One regular building with uniform mass is studied with 4 irregular buildings with varying masses for Base shear, Mode shapes, storey drift, story shear, Torsion moment.
What is base shear?
Base shear is an estimate of the maximum expected lateral force on the base of the structure due to seismic activity. It is calculated using the seismic zone, soil material, and building code lateral force equations (Figure 10.3). … Proximity to potential sources of seismic activity (such as geological faults)What is a stilt floor?
A stilt floor is a partially covered parking space on the ground floor of a commercial or residential building. Its height ranges from 2.4 m to 2.7m. A stilt floor is supported by pillars with all four sides open, it usually contains a generator room, switch room, society & information room, etc.
How do you identify a soft story?What is a soft-story building? A soft-story building is a structure which has a weaker first floor and is unable to carry the weight of the stories above during an earthquake. The first floor generally would have large openings in the perimeter walls such as garages, tuck under parking or even large windows.
Article first time published onWhy are soft story buildings in danger during an earthquake?
The soft-story apartment buildings with carports under them are more susceptible to collapse in an earthquake because the heavier upper floors are resting on a weaker ground floor. The wood and cement columns cannot support the entire buildings during violent shaking.
What is story drift?
Storey drift is the lateral displacement of a floor relative to the floor below, and the storey drift ratio is the storey drift divided by the storey height. … You can obtain graphs showing the height-wise distribution of displacement, storey drift and storey drift ratio.
What is stiffness irregularity?
Stiffness irregularity (soft storey): A soft storey is one in which the lateral stiffness is less than 70 percent of that in the storey above, or less than 80 percent of the average stiffness of the three storeys above.
Which type of irregularity exists in weak storeys?
The storey weak in stiffness can also be considered weak in strength thus strength irregularity exists in the building. As the lateral load resisting members are the same in the floors there seems no distinct way defines by the standard to determine the strength. Such columns are not present in the building considered.
What is story stiffness?
In this method, storey stiffness is estimated as the lateral force producing unit translational lateral deformation in that storey, with the bottom of the storey restrained from moving laterally, i.e., only translational motion of the bottom of the storey is restrained while it is free to rotate.
What is the difference between a hard and soft news story?
Hard news refers to the news stories that have an big impact at the society as a whole and need to be reported urgently. … Soft news on the other hand refers to the stories that provide other background information about world events, human interest stories or entertainment news.
What is a soft story in journalism?
Soft news journalism focuses on lifestyle and entertainment and typically revolves around culture, art, and human interest events. Soft news includes sports journalism, entertainment journalism, and celebrity coverage.
What is lateral stiffness?
The lateral stiffness Ks of a story is generally defined as the ratio of story shear to story drift. … Conse- quently, the lateral stiffness of a story is not a stationary property, but an apparent one that depends on lateral load distribution.
What is irregular building?
Irregular building has a large portion of the modern urban infrastructure. Building structure has mass, stiffness and strength irregularity known as irregular building. Irregular buildings are situated in high seismicity zone; the role of structural engineer is more challengeable.
What is diaphragm discontinuity?
Diaphragm is defined as discontinuities or variations in stiffness and mass in the form of slab openings and variation in slab thicknesses is called as diaphragm discontinuity, Fig2.
What is irregular structure?
1. A structure that has difference between center of mass and center of resistance. Technically all the structures are irregular.
Is a magnitude 7 earthquake bad?
Intensity 7: Very strong — Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Intensity 6: Strong — Felt by all, many frightened.
What are floating columns?
Floating column is a type of column which is is constructed over beams or slabs of any intermediate floors of a structure. These columns are not attached to any footings or pedestal. Floating columns are also known as hanging column. ( Refer to the below image)
What is a cripple wall?
Wooden floors and stud walls are sometimes built on top of an exterior foundation to support a house and create a crawl space. These are called cripple walls and they carry the weight of the house. During an earthquake, these walls can collapse if they are not braced to resist horizontal movement.
Why is a basement called a basement?
basement (n.) “lowest story of a building, wholly or partly underground,” 1730, from base (v.) + -ment.
What is stilt and cellar?
Difference between stilt floor and cellar It is the room where you store utility items like coal. In some cases cellar is also referred to as the basement of the building. Both basement and cellar are below the ground level of the building. A stilt, on the other hand, is an area immediately above the ground level.
Why do houses have basements?
Basements built in California are often below sea level, so extra measures must be taken to prevent flooding and other water-related issues. Most contractors working in California try to reduce expenses wherever possible, and excluding basements from homes fulfills this goal.
What is pushover analysis?
Pushover analysis is a static procedure that uses a simplified nonlinear technique to estimate seismic structural deformations. … Pushover analysis is commonly used to evaluate the seismic capacity of existing structures and appears in several recent guidelines for retrofit seismic design.
What is stiffness of building?
Stiffness is a measure of how much force is required to displace a building by a certain amount. If it requires more force to shift Building A than Building B, we would say that Building A is stiffer.
What is meant by response spectrum?
A response spectrum is a plot of the peak or steady-state response (displacement, velocity or acceleration) of a series of oscillators of varying natural frequency, that are forced into motion by the same base vibration or shock.
What is a soft story structure?
What is a Soft-Story Building? A typical soft story building is a multi-level structure located over a ground level with large openings. For instance, a building with tuck under parking, garage, or commercial store front.
