a) Reinforced Concrete Jacketting
Jacketing involves placing an additional layer of concrete around the existing beam, together with additional main rebars and links to enhance the flexural and/or shear capacities. This technique can be executed on beams, beam-column junctions, columns, foundations, and slabs. It is needed to increase bearing load capacity following a modification of the structural design or to restore structural design integrity due to a failure or potential failure in the structural member. With Joist, this technique can be utilised on vertical surfaces such as walls, columns and other combinations such as beam sides and bottoms
b) Composite Wrapping
Composite wraps or carbon fibre jackets are used to strengthen and add ductility to reinforced concrete and masonry components without requiring any penetration. Composite wraps are most effective on reinforced concrete columns by providing additional confinement.
c) Base Isolation
Base isolation is one of the most popular means of protecting a structure against earthquake forces. It is a collection of structural elements which should substantially decouple a superstructure from its substructure that is, in turn, resting on the shaking ground, thus protecting a building or non-building structure’s integrity and is one of the most powerful tools of earthquake engineering pertaining to the passive structural vibration control technologies. The isolation can be obtained by the use of various techniques like rubber bearings, friction bearings, ball bearings, spring systems and other means. It is meant to enable a building or non-building structure to survive a potentially devastating seismic impact through a proper initial design or subsequent modifications. In some cases, the application of base isolation can raise both a structure’s seismic performance and its seismic sustainability considerably.
d) Wall Thickening
The existing walls of a building are added certain thickness by adding bricks, concrete and steel aligned at certain places as reinforcement, such that the weight of the wall increases and it can bear more vertical and horizontal loads, and also designed under special conditions that the transverse loads does not cause sudden failure of the wall.
e) Tuned Mass Dumping
A tuned mass damper (TMD), also known as a harmonic absorber or seismic damper, is a device mounted in structures to reduce the amplitude of mechanical vibrations. Their application can prevent discomfort, damage, or outright structural failure. They are frequently used in power transmission, automobiles, and buildings. A tuned mass damper (TMD) is a device consisting of a mass, a spring, and a damper that is attached to a structure to reduce the dynamic response of the structure. The frequency of the damper is tuned to a particular structural frequency so that when that frequency is excited, the damper will resonate out of phase with the structural motion. Energy is dissipated by the damper inertia force acting on the structure.
f) Prestressing
Usually by postensioning, it is considered one of the potentially efficient retrofit options for reinforced concrete or masonry buildings. Masonry has a relatively large compressive strength but only a low tensile strength. Hence, it is most effective in carrying gravity loads. Commonly, induced tensile stresses exceed the compressive stresses and reinforcing must be added to provide the necessary strength and ductility.
g) Addition of Shear Walls
A shear wall is a structural member used to resist lateral forces i.e. parallel to the plane of the wall. For slender walls where the bending deformation is greater, the Shear wall resists the loads due to Cantilever Action. In other words, Shear walls are vertical elements of the horizontal force-resisting system. A shear wall is stiffer in its principal axis than it is in the other axis. It is considered a primary structure which provides relatively stiff resistance to vertical and horizontal forces acting in its plane. Under this combined loading condition, a shear wall develops compatible axial, shear, torsional and flexural strains, resulting in a complicated internal stress distribution. In this way, loads are transferred vertically to the building’s foundation. Therefore, there are four critical failure mechanisms. The factors determining the failure mechanism include geometry, loading, material properties, restraint, and construction.
h) Glass and Carbon Wrapping
Since carbon fibre is known for its lightweight and very high tensile strength properties, it can add significant strength without adding weight that would increase the load on foundations and other structural members when it is bonded to the exterior of concrete elements. The primary reason to use this technique is to add strength to an existing structure. In some cases, it might be used on new construction, although at this time that is usually only in response to some sort of design or construction error. In appropriate applications
