This paper explores the flexural behavior of carbon fiber reinforced polymer (CFRP) strengthened reinforced concrete (RC) beams. For flexural strengthening of RC beams, total ten beams were cast and tested over an effective span of 3000 mm up to failure under monotonic and cyclic loads. The beams were designed as under-reinforced concrete beams. Eight beams were strengthened with bonded CFRP fabric in single layer and two layers which are parallel to beam axis at the bottom under virgin condition and tested until failure; the remaining two beams were used as control specimens. Static and cyclic responses of all the beams were evaluated in terms of strength, stiffness, ductility ratio, energy absorption capacity factor, compositeness between CFRP fabric and concrete, and the associated failure modes. The theoretical moment-curvature relationship and the load-displacement response of the strengthened beams and control beams were predicted by using FEA software ANSYS. Comparison has been made between the numerical (ANSYS) and the experimental results. The results show that the strengthened beams exhibit increased flexural strength, enhanced flexural stiffness, and composite action until failure.

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Deterioration and degradation of aging structures is a major concern worldwide. It is often necessary to evaluate the integrity of such structural systems. Early detection and eventual quantification of damage are important for improved safety, to prevent potential catastrophic events, and to extend the service life by repairing/retrofitting the components of the structure. Different methodologies have been proposed in the literature for the identification and localization of damage based on optimization techniques and modal-based approaches. The main drawback in using the optimization approach based on evolutionary algorithms is that it requires the evaluation of the objective function for the total population in each generation. As this is computationally intensive, in this study, a multi-stage approach has been proposed. In this, at first, localization of the damage was achieved so as to reduce the number of parameters of the objective function in the optimization approach. These identified damaged elements were analyzed further for exact identification and quantification of the damage using genetic algorithm (GA)-based optimization approach. To demonstrate the efficiency of the proposed hybrid approach, numerical studies have been carried out on selected structures. The approach of using modal strain energy change ratio to identify damage at first-stage identification is found to be very useful in reducing the objective function parameters in the optimization method. This multi-stage approach is found to be very efficient in the exact identification and quantification of damage in structures. The proposed approach could be used for identifying damage in large-scale structures.

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Concrete usage around the world is second only to water. Ordinary Portland Cement (OPC) is conventionally used as the primary binder to produce concrete. But the amount of carbon dioxide released during the manufacture of OPC due to the calcinations of lime stone and combustion of fossil fuel is in the order of 600 kg for every ton of OPC produced. In addition, the extent of energy requires to produce OPC is only next to steel and aluminum. On the other hand, the abundant availability of fly ash worldwide creates opportunity to utilize (by-product of burning coal, regarded as a waste material) as substitute for OPC to manufacture concrete. Binders could be produced by polymeric reaction of alkali liquids with the silicon and the aluminum in the source materials such as fly ash and rice husk ash and these binders are termed as Geopolymer. In Geopolymer Concrete, fly ash and aggregates are mixed with alkaline liquids such as a combination of Sodium Silicate and Sodium Hydroxide. United Nation's Intergovernmental panel on Climate Change (IPCC) prepared a report on global warming during April 2007 which enlists various methods of reduction of CO2 emissions into atmosphere. As per that report, unmindful pumping of CO2 into the atmosphere is the main culprit for the climate change. Large volume of fly ash is being produced by thermal power stations and part of the fly ash produced is used in concrete industry, low laying area fill, roads and embankment, brick manufacturing etc. The balance amount of fly ash is being stored in fly ash ponds. Hence it is imperative on the part of Scientists and Engineers to devise suitable methodologies for the disposal of fly ash. Disposal of fly ash has the objective of saving vast amount of land meant for ash pond to store fly ash. Further, use of fly ash as a value added material as in the case of geopolymer concrete, reduces the consumption of cement. Reduction of cement usage will reduce the production of cement which in turn cut the CO2 emissions. Many researchers have worked on the development of geopolymer cement and concrete for the past ten years. The time has come for the review of progress made in the field of development of geopolymer concrete. Consequently 102 papers pertaining to the ingredients and technology of geopolymer concrete have been reviewed in this state of the art paper.