Shear Walls – Types of Shear Wall and its Efficiency
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What is a Shear Wall?
Shear wall is a vertical structural element used to resist the horizontal forces such as wind force, seismic force. These forces acts parallel to the plane of the wall. Shear walls are generally used in high rise buildings where effect of wind forces and seismic forces is more.
Types of Shear Walls
Based on type of material used, shear walls are classified into following types.
Reinforced Concrete Shear Wall
Concrete Block Shear Wall
Steel Shear Wall
Plywood Shear Wall
Mid-Ply Shear Wall
1. Reinforced Concrete Shear Wall
Reinforced concrete shear walls are widely used shear walls for residential buildings. The reinforcement is provided in both horizontal and vertical directions. But at the end of each wall, bars are closely spaced and anchored. So, the end zones of RC shear wall is called as boundary elements or barbells.
The wall thickness of RC shear wall is varied depending upon many factors like thermal insulation requirements of building, age of building, number of floors of building etc. It varies from 140 mm to 500 mm. In general, the provision of shear wall is continuous throughout the height of building. But sometimes it is discontinued where there is a building entrance or parking space etc.
Fig 1: Reinforced Concrete Shear Wall
2. Concrete Block Shear Wall
Concrete block shear walls are constructed using Hollow concrete blocks along with Steel reinforcement bars. Reinforcement is generally used to maximize the effect of concrete block masonry against seismic loads.
The Reinforcement bars are arranged through spaces of concrete blocks in both vertical and horizontal directions. After placing bars in concrete block masonry, fresh concrete grout is poured into the hollow space and is allowed to set.
This type of walls can take both gravity loads and lateral loads. So, they can work like shear wall as well as load bearing wall.
Fig 2: Reinforced Concrete Block Shear Wall Construction
3. Steel Shear Wall
Steel shear wall consists of a steel plate wall, boundary column and horizontal floor beam. The action of steel shear wall is more like a plate girder. Steel plate wall acts as web of plate girder, boundary columns acts as flanges and horizontal beams acts as stiffeners of plate girder.
Fig 3: Steel Plate Shear Wall
4. Plywood Shear Wall
Plywood shear walls are traditional type walls which are also called as timber shear walls. It consists of plywood sheets and studs. Plywood sheets transfer shear force while studs resists the tension or compression.
Now a days plywood shear walls are redesigned using new technical advancements. Steel sheets, sure boards etc. are using in place of plywood.
Fig 4: Plywood Shear Wall
5. Mid-Ply Shear Wall
Mid-ply shear wall is an improved version of normal plywood shear wall. In this case, extra plywood sheet is arranged at the center of normal plywood wall and series of pairs of studs are positioned on the both sides of mid-ply. Studs joint the mid-ply with outer plywood sheets. Here, Studs are rotated to 90o relative to those is plywood shear walls.
The mid-ply shear wall eliminates the problems caused in standard shear walls and lateral load carrying capacity is higher for mid-ply shear walls.
Fig 5: Mid-ply Shear Wall
Efficiency of Shear Walls
Efficiency of a shear wall is purely depends upon its rigidity or its stiffness. A solid shear wall is more efficient than a shear wall with openings. But sometimes it is not possible to construct a shear wall without openings such as openings for doors, windows etc.
Fig 6: Shear Walls - Solid, with Openings, Coupled
In case of openings to improve the efficiency of shear wall, connect the piers of shear walls by spandrels. Pier is nothing but the portion of shear wall between two openings and spandrel is the portion of shear wall above the opening. The resulting wall appeared by interconnecting spandrels of piers of shear walls is known as coupled shear wall. Provision of openings in balanced pattern can also make the shear wall efficient.
In flanged shear walls, the walls will meet at right angles to each other. This type of shear walls are less efficient since they are effected by seismic forces in both principal directions of the building.