Experimental study on reinforced concrete columns partially confined with carbon fiber reinforced polymer (CFRP)

The requirement of strengthening of reinforced concrete structures may emerge not only due to timed degradation but also due to various reasons like construction faults, increased loads and changes in utilization purpose etc. Rehabilitation of reinforced concrete structures using Carbon Fibre Reinforced Polymer materials is recognized as a very effective retrofitting method. The current practice on strengthening reinforced concrete columns with external CFRP jacketing is to provide full wrapping all over the column with less care on the required strength increment As CFRP is a costly material, providing partial wrapping may be a viable option for cost reduction rather than providing full confinement. An experimental study was carried out with 17 specimens to study the partial confinement effect. The test specimens consist of 6 plain concrete columns with 3 control specimens and 3 fully confined columns. 11 reinforced concrete columns with 3 control specimens, 3 columns with full confinement and 5 columns with partial confinement. Two wrapping patterns were used for partially confined columns with 75mm and 50mm laminate width, keeping the volumetric ratio of CFRP constant to study the effect of wrapping pattern and jacket location for strength and ductility increment. The results of experimental study revealed that the load carrying capacity increment for fully wrapped reinforced concrete columns were 100% while for plain concrete columns it was 47% and for partially confined columns, the specimens with two 75mm wraps showed a capacity increment of 59% while specimens with three 50mm wraps showed an increment of 83%. It was observed that, by only changing the jacket location 15% ultimate load carrying capacity increment can be obtained. When ductility increment is considered it was observed that ductility increment is proportional to the strength increment

Behavior of reinforced concrete columns confined with CFRP (Carbon fibre reinforced polymer)

In modern world the retrofitting of structures is promoted rather than demolishing and reconstruction of deteriorated structures.Attentionhas also given to increase the load carrying capacity of existing structures to increase the usage capacity or to change the intended usage. Retrofitting of structures using Carbon Fibre Reinforced Polymer materials is accepted as a sustainable and effective method comparatively to most of other well-known methods like steel plate bonding and external post tensioning. This paper presents anexperimental study carried out to understand the effectiveness of external CFRP confinement for square reinforced concrete columns and validation of ananalytical stress strain model,using experimental results. Four reinforced concrete columns, one control specimen without external confinement and three specimens with full external confinement were tested for compression to monitor the strength gain against axial loading. The results showed a considerable increase of the axial strength, about 50% and improved ductility, up to about 20% for the columns with external confinement. The analyticalstress stain modelpresented anacceptable agreement with obtained experimental results

Geotechnical investigations on earth dams in Sri Lanka unnichchai dam as a case study

Sri Lanka is a country where there are large numbers of earth dams. Most of them are suffering partial failures due to excessive seepage, piping, excessive lateral deformations etc. But limited investigations have conducted on the performance of earth dams from the geotechnical point of view. This paper draws attention to some of the possible failure mechanisms based on steady state seepage, rapid draw down, and response due to an earthquake by analysing a set of computer based models of Unnichchai earth dam. The main objective is to evaluate the risk of failure for above mentioned mechanisms. The analysis revealed that the factor of safety against rapid draw down condition and in steady state conditionis lying closely for selected conditions and fairly high enough to obtain good performance. Behaviour of the dam under seismic loads urn analysed using computer models and manual methods and showed acceptable factor of safety against liquefaction. When overall result is considered it can be stated that the Unnichchai earth dam is performing well under normal conditions prevails in Sri Lanka