Shear failure within floor diaphragm
by Admin
Posted on 09-09-2024 10:35 AM
Diaphragms: floors and roofs can be used as rigid horizontal planes, or diaphragms, to transfer lateral forces to vertical resisting elements such as walls or frames. Shear walls: strategically located stiffened walls are shear walls and are capable of transferring lateral forces from floors and roofs to the foundation. Braced frames: vertical frames that transfer lateral loads from floors and roofs to foundations.
Like shear walls, braced frames are designed to take lateral loads but are used where shear walls are impractical. Moment-resistant frames: column/beam joints in moment-resistant frames are designed to take both shear and bending thereby eliminating the space limitations of solid shear walls or braced frames.
Foundation upgrades: strengthening the building’s foundation is fundamental to seismic retrofitting. This may involve adding new foundation elements or reinforcing existing ones to improve load-bearing capacity. Bracing systems: installing bracing systems, such as shear walls or diagonal braces, helps distribute seismic forces throughout the structure, preventing concentrated stress points that can lead to failure. Soft-story retrofits: multifamily buildings often have soft stories, typically ground floors with large openings like parking garages. Retrofitting these areas involves adding structural elements to enhance lateral stability. Damping systems: adding damping systems, such as base isolators or energy dissipation devices, can absorb and dissipate seismic energy, reducing the impact on the building structure. https://en.wikipedia.org/wiki/Glued_laminated_timber
In earthquake prone areas of the world, building codes require that structures meet certain requirements to help protect buildings and their occupants. Many of the techniques below are used to help make buildings more resilient. Reinforced structure one of the most common ways to prevent damage and protect buildings and occupants is to provide a reinforced structure that can withstand the horizontal stresses caused by shaking. Shear walls, cross braces, diaphragms, and moment-resisting frames are used to redistribute the energy safely, without major structural damage. Shear walls are made up of multiple panels and are usually cross braced for extra support.
Reinforced concrete column burst
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strengthening is all about imparting strength to the structures and making them sustainable and durable so that they can resist various forces. A seismic force applies acceleration, velocity, and displacement to the structure.
The rigid reinforced structures may collapse or crack due to the instant seismic force. So many reinforced structures existing in the present world are not good enough to withstand seismic forces like earthquakes and are inadequate for these dynamic loads. Concrete jacketing is one of the processes by which we can strengthen structures and hence durability also increases. Concrete jacketing can be performed on different major structural elements such as beams, columns, and also beam-column joints.
To increase the strength of a building and prevent it from shaking, columns made from reinforced concrete may be constructed on the exterior of the building. The addition of these columns to an already existing building is one of the most practical seismic retrofitting techniques. It encases the building in a protective frame and ensures higher resistance to damage from seismic activity. Sometimes, a structure needs additional support to withstand lateral forces during an earthquake but does not have enough interior space to accommodate new columns. In such cases, reinforced concrete columns are strategically placed at the corners of the building and along its sides to provide maximum support.
When we use seismic repair to add strength to a building’s original design, we target areas of the building that are pivotal to its erection – such as columns, joints, and hinges. These areas of the original design are often rushed, misjudged, or completed by an amateur – so they require strengthening and reinforcement later down the line. The areas we treat with seismic repair are: joints: when the joints of a building need to be strengthened, they are usually inadequately reinforced and require immediate attention. Seismic repair includes reinforcing beam-column joints by using carbon fibre polymer strips and sprayed concrete.
Reinforced concrete wall burst
[ edit ] seismic retrofit (or rehabilitation) strategies have been developed in the past few decades following the introduction of new seismic provisions and the availability of advanced materials (e. G. Fiber-reinforced polymers (frp) , fiber reinforced concrete and high strength steel). Increasing the global capacity (strengthening). This is typically done by the addition of cross braces or new structural walls. Reduction of the seismic demand by means of supplementary damping and/or use of base isolation systems. Increasing the local capacity of structural elements. This strategy recognises the inherent capacity within the existing structures, and therefore adopts a more cost-effective approach to selectively upgrade local capacity (deformation/ductility, strength or stiffness) of individual structural components.
The most crucial and first step for improving the seismic response of existing masonry structures is the tying of masonry walls and floors, which provides structural integrity and box-like behavior [ 7 ]. The tying is usually done by adding steel or reinforced concrete ties at the floor level. Vertical tying elements may be added as well, but this is rarely used because the corners of the masonry walls are their strongest part. Experimental investigation and the review of theoretical approaches have shown that tying resulted in an increased compressive strength and, more importantly, in-plane shear strength of masonry walls [ 12 ].
Seismic retrofitting involves modifying existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. Techniques vary based on the building’s design, age, and the seismic demands of the region but typically include: base isolation: installing isolators between the building and its foundation to absorb seismic energy. Shear walls: adding walls in strategic locations to improve lateral stability. Moment frames: incorporating steel or reinforced concrete frames that allow the building to bend without breaking. Flexible utility connections: upgrading utilities to flex and move without breaking during an earthquake.
After the assessment of the damage of individual structural elements, appropriate repair methods are to be carried out component wise depending upon the extent of damage. The restoration work may consist of the following: removal of portions of cracked masonry walls and piers and rebuilding them in richer mortar. Use of non-shrinking mortar will be preferable, addition of reinforcing mesh on both faces of the cracked wall, holding it to the wall through spikes or bolts and then covering it, suitably, with micro-concrete (maximum size of aggregate limited to 6 mm or less as suitable), and may be with use of micro-reinforcement as fibre or ferro-cement.