What is meant by soft story?

Asked by: Courtney Fleming

The term “soft-story” refers to one level of a building that is significantly more flexible or weak in lateral load resistance than the stories above it and the floors or the foundation below it (70% or greater reduction from one floor to the next according to the modern, International Building CodeInternational Building CodeThe International Building Code (IBC) is a model building code developed by the International Code Council (ICC). It has been adopted for use as a base code standard by most jurisdictions in the United States.

What is soft and weak storey?

SUMMARY: “Soft story” and “weak story” are irregular building configurations that are a significant source of serious earthquake damage. These configurations that are essentially originated due to architectural decisions have long been recognized by earthquake engineering as seismically vulnerable.

What is a soft first story?

A soft or weak story floor, wood-frame building is a structure where the first story is substantially weaker and more flexible than the stories above due to lack of walls or frames at the first floor.

What is meant by weak storey?

Weak-storey is simply formed by the neighbor floors which have redundant columns, concrete walls and brick-wall areas. The most common observed earthquake damage types encountered in Turkey is caused by the weak-storey irregularities.

What is soft storey problem?

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.

What is a soft story structure?

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.

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 soft story retrofitting?

What is a soft-story retrofit? A soft-story retrofit simply adds to and reinforces the structure of the building so it can hold up much better in an earthquake. The main goal is to make sure the building is still standing after an earthquake hits and ensure the safety of everyone in and around the building.

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.

How is a soft story irregularity defined in Nscp 2015?

The National Structural Code of the Philippines (NSCP) defines soft story irregularities based on the reduction of stiffness in adjacent stories. Since the study is used for an ocular preliminary risk assessment of existing buildings, the soft story definition is simplified.

What is ductile detailing?

Objective. To provide adequate toughness and ductility. to resist severe earthquake shocks without. collapse.

What is lateral stiffness?

… the generic systems, the story lateral stiffness is defined as the ratio between the story shear force provided by an inverted triangular force distribution and the corresponding inter-story drift.

What is base shear in building?

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).

How does a frame with soft storey behave under earthquake?

During an earthquake motion, the soft story behavior is based on the criteria that the ground motion will look for all possible weakness in the structure. This weakness may be a sharp variation in the stiffness, ductility or in the strength parameters.

What is the meaning of story building?

A storey (British English) or story (American English) is any level part of a building with a floor that could be used by people (for living, work, storage, recreation, etc.). Plurals for the word are storeys (UK) and stories (US).

Why is stiffness important in structures?

Stiffness can be advantageous with respect to earthquake damage because it can limit the deformation demands on a building. You can, however, have too much of a good thing. A structure that is too stiff (often referred to as brittle) will be prone to failure under relatively small deformation demands.

What is the remedy if a building is a soft story?

How to Fix A Soft Story? A soft story retrofit involves strengthening and stiffening the first story, so it does not “pancake” or collapse. The retrofit might involve the addition of steel moment frames, shear walls, diagonal bracing, or fusing systems.

What is storey 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 storey displacement?

1) Story displacement is the lateral displacement of the story relative to the base. The lateral force-resisting system can limit the excessive lateral displacement of the building. The acceptance lateral displacement limit for wind load case could be taken as H/500 (some may take H/400).

What is ductile detailing?

Objective. To provide adequate toughness and ductility. to resist severe earthquake shocks without. collapse.

Is code for RCC detailing?

IS:5525 -1969: Recommendation for detailing of reinforcement in reinforced concrete works. IS:9077 -1979: Code of practice for corrosion protection of steel reinforcement in RB & RCC construction.

Is code for shear wall?

Shear walls are very suitable for resisting earthquake induced lateral forces in multistoreyed building systems. They can be made to behave in a ductile manner by adopting proper detailing techniques. IS:456-1978 and IS:4326-1976 do not give specifications for them. Hence, provisions are proposed for the same.