Jacketing is a way of structural retrofitting and strengthening it’s far used to boom bearing load capacity following a amendment of the structural layout or to repair structural design integrity due to a failure within the structural member.
Jacketing is the procedure wherein a segment of an existing structural member is restored to unique dimensions or increased in size by using encasement the usage of suitable substances. A metallic reinforcement cage or composite cloth wrap can be built across the damaged segment onto which shotcrete or cast-in- vicinity concrete is located. Collars are jackets that surround best for a part of a column or pier. those are generally used to provide elevated aid to the slab or beam at the pinnacle of the column. The shape for the jacket includes wooden, corrugated metal, precast concrete, rubber, fiberglass, or unique cloth; and may be everlasting in a few cases. The shape must be furnished with spacers to make sure same clearance among it and the existing member.
materials, like traditional concrete and mortar, epoxy mortar, grout, and latex-changed mortar and concrete, are used as encasement substances. For jacketing, the void among the form and the present member is crammed the usage of pumping, tremie, or preplaced aggregate concrete. Jacketing is especially used for the restore of deteriorated columns, piers, and lumps and may without difficulty be hired in underwater applications. The technique is relevant for defensive concrete, metallic, and wooden sections in opposition to in addition deterioration and for strengthening. everlasting forms are preferred in which safety against weathering, abrasion, and chemical pollutants is desired. The collar affords increased shear capacity for the slab, and it decreases the effective duration of the column. Architecturally collars are considered better than jacketing but acting the equal structural feature. earlier than applying jackets or collars, all deteriorated concrete ought to be removed, cracks need to be repaired, existing reinforcement must be wiped clean, and surfaces ought to be organized. The floor coaching improves the bond of the newly positioned materials with the prevailing shape, which is hard for underwater repairs. For underwater situations, a plastic shell can be carried out on the splash zone to help reduce abrasion. A drawback of jackets and collars is they occupy area that became earlier to be had for different makes use of. wood, cardboard and corrugated metal paperwork may be used as temporary or permanent paperwork. permanent fiberglass, rubber, and material forms have received full-size popularity because they provide resistance to chemical assault after the restore is whole. Jacketing used for functions apart from masking the deteriorated concrete and presenting lateral confinement, such as to undergo longitudinal loads, desires unique considerations. the existing column may additionally have undergone complete shrinkage and most of the creep and additionally has elastic strains because of carried loads, while the shrinkage and creep of the brand new cloth has to arise. the burden switch to jacketing is likewise a massive issue. it’s far better to use jacking to launch the weight on the member earlier than jacketing, to use non-shrinking materials for jacketing and to hammer metal shims on the switch factors of the jacketing after curing. If the fabric used for jacketing is cement mortar or concrete, the cement content material should be precisely consistent with the necessities; both excessive and less cement contents can be dangerous. Use smooth, stable and the largest possible length aggregates. on the way to lessen shrinkage, manage the temperature of the substances and the on the spot environment for the duration of placing and curing. Use of admixtures such as plasticizers, air-entraining agents, retarders, accelerators and waterproofing admixtures is extra beneficial in restore than even the ordinary construction. expanding mortars / concretes may be made with the aid of adding aluminum powder to the matrix to overcome the setting shrinkage and some a part of the drying shrinkage. using iron fillings or powder also can carry out this feature if moisture and air are available. In case grout is used for filling the bureaucracy, it is allowed to settle for about 20 minutes after gratifying after which is stuffed to overflowing situation. The top of the jacket ought to be completed with pneumatically projected or hand located concrete.
Table of Contents
Jacketing Introduction
• It is a part of retrofitting i.e. repair, renovation, strengthening.
• Retrofitting is the modification of existing structures to make them more resistant.
• Jacketing is the most popularly used method for strengthening of building columns.
• Jacketing consists of added concrete with longitudinal and transverse reinforcement around the existing column.
. It improves axial and shear strength of column and major strengthening of foundation may be avoided.
NECESSITY OF JACKETING
The load carried by column is increased.
• When there is error in design.
• Deterioration of column due to weathering action.
• Dilapidation of column.
Heavy damage due to other causes like earthquake, fire etc.
ADVANTAGES OF JACKETING
- It increases the seismic capacity of column.
- Amount of work is less as foundation strengthening does not required.
- It increases the shear strength of column.
- .It also increases confinement of concrete in circular columns.
- Steel jacketing does not increase significant weight of column and also saves construction time (curing).
TYPES OF JACKETING
- Reinforced concrete jacketing
- Steel jacketing
- Fiber reinforced polymer composite jacket
- Jacket with high tension materials like carbon fiber, glass fiber etc.
What Jacketing is used for?
Jacketing is used to strengthen susceptible RCC columns that have been deteriorated over a period of time because of unfavorable atmospheric conditions or because of bad maintenance.
in this method vulnerable concrete is completely eliminated . Rusted rebars are also removed. extra rebars are provided and general sectional are is elevated to boom compressive energy of columns. more rebars are supplied with stirrups and related to vintage concrete with shear keys.Bond coat is implemented on vintage concrete floor and polymer concrete is poured in form work.
Jacketing can be finished from all facets or it is able to be from three/ facets. it is able to be from one side also.