Structural strengthening techniques Essay

Chapter 1


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Strengthening or upgrading of a construction may be required rather frequently due to several grounds. Many a times, tonss due to seismal forces or air current forces are non taken into history while planing the construction or sometimes a higher burden transporting capacity is required in instance the usage of the construction alterations. In such instances, beef uping of a construction may be required. Strengthening may besides be required in instance of any lack in the ability of a construction to transport the expected design loads. There may be several grounds for such lacks in a construction. These include structural harm, loss of concrete subdivision, corrosion of steel rebars, mistake while building or defects in the design. Several techniques can be employed to get the better of such jobs. Arriving at a best and optimal strengthening solution for each undertaking depends on assorted factors like addition in strength required, constructability limitations, size and importance of undertaking, handiness, clip handiness, and handiness of skilled/unskilled labor, handiness of natural stuff and other equipments, environmental conditions, cost or many such other issues.

Out of the available strengthening techniques, the most fantastic characteristic of beef uping by FRP laminates is its non-corrosive nature. It is due to corrosion of rebars that one million millions of capital of a state is wasted every twelvemonth. Replacing steel support by the non-corrosive FRP support is an effectual option that obviates the job of loss of strength of a structural component due to corrosion.

Therefore, probe of the behavior or response of such beef uping techniques is really important before it is adopted in existent constructions. Experimental based testing has been carried out by research workers for long. This method of probe is both time-consuming and expensive. Therefore, analytical and numerical methods of probe are in trend. Finite Element Method ( FEM ) is one of the numerical methods of analysis. With the promotion in computing machine and engineering, FEM softwares like ANSYS are dependable along with being less time-consuming and cost-efficient. In the present research, numerical probe of RC beams strengthened with FRP laminates is carried out.

1.2 Strengthening Exploitation FRP COMPOSITES

There are several grounds for which strengthening of a construction may be required. And for this purpose several conventional techniques like usage of steel home bases have been used since ages. But in the recent old ages, usage of Fibre reinforced polymers for structural strengthening has come into being. Fibre Reinforce Polymers or FRPs exhibit several improved belongingss, like non-corrosiveness, high stiffness-weight ratio, high strength-weight ratio, high weariness strength, flexibleness and easiness of application due to its light weight.

In recent old ages, several research workers have been analyzing the usage of FRP sheets or laminates to beef up concrete structural members. Using FRPs for beef uping have turned out be an effectual technique suited for several structural elements such as beams, columns, walls, and slab. For beef uping of bing constructions externally, FRP stuffs are considered most suited as it is non-corrosive, immune to chemicals and non-magnetic.

From the past research, it has been found that Glass Fibre Reinforced Polymers or GFRP is really effectual in increasing flexural every bit good as shear strength of the strengthened concrete constructions when bonded externally.

FRP laminates is one of the emerging stuff for beef uping of RC beams. It can be used for beef uping the beams weak in flection by adhering the laminate at the bottom soffit and for beef uping the beam weak in shear, laminates are bonded to the side faces of the RC beam. But unluckily, no proper guidelines or commissariats are included in the current Indian design codifications for beef uping of concrete structural elements with FRP laminates. At the same clip, research in recent old ages concentrating on the application of FRP laminates for beef uping of RC constructions has led to its increasing application practically.

FRP laminates are composite stuffs that consist of high strength fibers of glass, C or aramid in a matrix, where the chief burden is carried by the fibers. These laminates are plates that may be bonded to the surface by either dry bonding or wet bonding technique. These laminates can be used to beef up beams and slabs weak in shear or flection, columns to increase the concrete parturiency or even walls to increase the sidelong burden transporting capacity.1.3 MERITS AND DEMERITS OF FIBRE REINFORCED POLYMER COMPOSITES

1.3.1 Merits

FRP or Fibre Reinforced Polymers are really efficient in beef uping of strengthened concrete structural elements. They have high ultimate strength and hold lower denseness as compared to that of steel. It is really convenient to manage and transport because of its light weight. Furthermore, its flexible nature makes installing procedure much convenient as compared to installing of heavy steel home bases. Another major advantage of utilizing FRP laminates in strengthening of RC structural elements is that it doesn’t require full staging while installing at soffits of span. In instance of beef uping RC constructions by utilizing FRP laminates, no bulky raising cogwheel is required and there is no demand of adjustments such as bolts that are susceptible to corrosion. Furthermore, application of FRP laminates is merely every bit easy as application of wallpapers on wall. Besides, there is no hazard of harm to the steel support as no boring is required for infixing bolts. Presents, wet-bonding technique is used which further reduces the hazard of debonding of the laminates. Furthermore, another most of import advantage in the usage of FRP laminates in strengthening of RC constructions is that these laminates are available in long lengths and changing breadths due to which no articulations or laps are required.

Application of FRP laminates on irregular surfaces or curved profiles is non a job due to its flexible nature. If the application of FRP laminates is done carefully by maintaining attention of proper steps, it proves to be lasting. Furthermore, it is relatively convenient to mend by application of another bed.

Use of FRP laminates for beef uping of Bridgess and other of import constructions like tunnels is really suited as their light weight and less thickness do non change the dimensions of the reinforced component or add to the weight of construction.

Most of import advantage of the usage of FRP laminates for beef uping RC structural elements is that it is non-corrosive in nature. Because of the easiness in application, it consequences in salvaging both the man-power and utile resources.

Therefore, all these virtues in combination consequences in a important and effectual agencies of beef uping technique that is much more quicker and simpler as compared to other beef uping techniques like usage of steel home bases.

1.3.2 Demerits

Along with several advantages of FRP or Fibre Reinforced Polymers, there are few disadvantages that may impede its application. FRP laminates that are chiefly used for external strengthening of constructions are susceptible to exposure of external environment. So, in order to protect it from fire or any other inadvertent harm, proper protection steps are to be adopted. Another major job occurred in the application of FRP laminates in strengthening of RC constructions is delamination or debonding of the laminate. It job can be overcome by taking proper steps while adhering it with the aid of epoxy. Nowadays, even the technique of wet bonding is in pattern in order to extinguish such jobs.

Another major disadvantage that may impede its application is its high cost. But, after a complete comparing of the entire cost and the beef uping achieved with that of other beef uping methods like usage of steel home bases etc. , the application of FRP in beef uping may turn out to be economical and more efficient.


Finite Element Method or ( FEM )is an approximative numerical technique for finding solutions to boundary jobs for differential equations. In this method, a stable solution is produced by cut downing mistake map by using variational method. In this method, a construction or a theoretical account to be analyzed is discretized or broken down in figure of little sub-domains, and are called elements or finite elements. These elements are connected to one another by points known as nodes. There are many finite component bundles available.

ANSYS which means Analysis System is a FEM package bundle which offers technology simulation solution sets in technology simulation that a design procedure requires. Companies in a broad assortment of industries use ANSYS package. The tools put a practical merchandise through a strict proving process before it becomes a physical object.


It is hard to pattern the complex behavior of strengthened concrete analytically in its non-linear zone. And we know that experimental proving which has been used since ages for the intent of research work is really clip devouring along with being expensive. But with the promotion in computing machine and engineering, and powerful techniques of analysis such as Finite Element Method or FEM, many attempts have been under taken by the research workers to rid of the demand for making multiple theoretical accounts in instance of experimental probe. Therefore, finite component attack is deriving popularity non merely because it is cost effectual and less clip consuming, along with this it obviates the demand to make multiple theoretical accounts for the intent of research or probe, forestalling wastage of utile resources. Along with this, it is a powerful tool that allows mold and analysing complex non-linear behavior of RC structures expeditiously. Furthermore, non merely patterning and analysing, it is besides utile in obtaining the burden warp behaviour and cleft forms under assorted loading conditions. Therefore, Numeric probe or finite component analysis is relatively much more effectual and less complicated than development of analytical theoretical accounts because of the several obvious grounds.


The specific aims of the present probe are as follows:

  1. To numerically look into the behavior of RC beams strengthened with FRP laminates utilizing ANSYS
  2. To obtain the corresponding burden warp curve of RC beam without FRP and RC beams strengthened with changing constellation of GFRP and CFRP laminates.
  3. To pull the comparing between ANSYS consequences & A ; experimental consequences available in the literature.
  4. To analyze the comparing between the behavior and the burden warp profile of RC beams strengthened with glass fiber and C fiber laminates.


Experimental testing is one of the most normally used methods for anticipation of the behavior of strengthened concrete elements till failure. This is both clip consuming and dearly-won. Therefore, finite component attack is deriving popularity non merely because it is cost effectual and less clip consuming, along with this it obviates the demand to make multiple theoretical accounts for the intent of research or probe, forestalling wastage of utile resources and work force.

In the present probe, the non-linear response of strengthened concrete ( RC ) beams strengthened with FRP laminates has been carried out with the purpose to look into the effectivity of GFRP and CFRP laminates bonded in changing constellation. In this probe, ANSYS package is used to transport out Finite component modeling of RC beam. A sum of nine beams are modelled and analyzed utilizing ANSYS package up to the failure and the burden distortion curves are plotted and the checking behavior is monitored.

Concrete block is modelled by utilizing SOLID65 component while the steel support is modelled utilizing LINK180 component by utilizing distinct method. While, for modeling of FRP laminates SOLID185 ( layered solid ) component is used. The consequence obtained from finite component probe is so compared with the experimental consequences in the referred literature ( Sandeep G. Sawant, 2013 ) with regard to load-deflection values, formation of initial cleft, failure manner and the ultimate burden transporting capacity of the RC beam.


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