Asian journal of civil engineering
Volume:13 Issue: 5, Oct 2012

The paper deals with the analysis of experimental results in terms of load-carrying capacityand strains, obtained from tests on circular concrete column, strengthened with externalglass fibre composite. A total of seven specimens of 150mm diameter and having a height of 600 mm were cast and tested. One specimen was used as reference and remaining sixspecimens were wrapped with three GFRP materials having different thickness. Thecolumns were tested under uni-axial compression up to failure. Necessary measurement was taken for each load increment. The HSC columns with GFRP wrapping exhibited better performance in terms of strength, deformation and ductility capacity.

In this paper an efficient method is developed for the formation of null bases of finiteelement models (FEMs) composed of rectangular and triangular plane stress and plane strain elements, corresponding to highly sparse and banded flexibility matrices. This is achieved by associating special graphs to the finite element models and selecting appropriate subgraphs for the formation of localized self stress systems. The efficiency of the present method is illustrated through some examples.

A numerical investigation has been carried out to examine the behavior of reinforcedconcrete slabs subjected to uniform blast loading. The aim of this work is to determine the effects of various parameters on the results. Finite element simulations were performed in the non linear dynamic range using an elasto-plastic damage model. The main parameters considered are: the negative phase of blast loading, time duration, equivalent weight of TNT, stand-off distance of the explosive, and slab dimensions. Numerical modeling has been performed using ABAQUS/Explicit. The results obtained in terms of displacements and propagation of damage show that the above parameters influence considerably the nonlinear dynamic behavior of reinforced concrete slabs under uniform blast loading.

Geopolymer and geopolymer concretes, being versatile in nature, have been acknowledged by research fraternity around the world. Many researches been undertaken, to date, dealt with the study on basic engineering properties of geopolymer mortars and unreinforced geopolymer concrete. Papers on application of geopolymer concretes as structural elements are found to be countable. This paper describes about the heat-cured geopolymer concrete slender circular columns using ASTM Class F Fly ash. This research focuses on the adaptability of Indian fly ash into geopolymer concrete structural members used primarily to support compressive loads. In this paper, geopolymer concrete slender circular columns of size 100mm diameter and length 1800mm with 2.16 % reinforcement are cast, tested and results are compared with its OPC concrete counterparts. Totally, 12 specimens of M30 and M50 grade slender columns were fabricated. Six specimens each for low calcium fly ash based reinforced Geopolymer concrete as well as for ordinary Portland cement reinforced concrete. The results have shown that the geopolymer concrete columns have exhibited increase in load carrying capacity, stiffness and ductility until failure.

Endurance Time (ET) method is a dynamic analysis procedure using intensifyingaccelerograms which can be used to assess the structural performance at different excitation levels. In generation process of current ET accelerograms, the compatibility between acceleration spectrum produced by the ET accelerograms and acceleration spectrum associated with the real ground motions is applied, whereas the duration consistency is not directly considered. It is generally accepted that the strong-motion duration can strongly influence the response of structures which have stiffness or strength degrading characteristics. In this study, the number of cycles that a structure should resist due to a ground motion is considered as a parameter related to shaking characteristics of that ground motion. In addition, the number of cycles of a structure when is subjected to the ET records and the real ground motions are compared. This study further determines how the ET records should be modified to have the best duration consistency with the real ground motions. Two methods are proposed to achieve this objective. It is shown that determining a specific target time for the ET records alone is not a suitable approach to achieve the best duration consistency.

Supplemental damping using passive energy dissipation (PED) devices is often used forenhancing the seismic performance of a seismically deficient structure to reduce the seismic response under earthquake loading. Such PED devices are normally incorporatedwithin the frame structure between adjacent floors through different bracing schemeslike diagonal, chevron, scissors and toggle or through non-structural in-fill walls, so thatthey efficiently enhance the overall energy dissipation ability of the seismically deficientframe structure under earthquake loading. These PED devices function based on the large and stable energy dissipation obtained using energy dissipation mechanisms like visco-elastic and elasto-plastic. This paper presents a methodology based on the direct displacement based design (DBD) for designing PED devices for providing supplemental damping to enhance the energy dissipation ability of frame structures subjected to earthquake loading. The presented design methodology is validated through an experimental study consisting of shake table tests of sweep sine, steady state and seismic types, conducted on a single bay-three storey reinforced concrete (RC) frame structure incorporated with designed visco-elastic PED devices.

Near Surface Mounted Reinforcement (NSMR) method is a recent strengthening technique based on bonding Fiber Reinforced Polymer (FRP) into grooves on the concrete cover of the elements to be strengthened. In this paper, an experimental program was carried out to assess the effectiveness of the NSMR technique in the shear strengthening of reinforced concrete beams. A number of beams were strengthened in shear using NSM Glass Fibre Reinforced Polymer (GFRP) and tested to analyze the influence of selected test parameters such as the type, spacing, and inclination of the NSM reinforcement on the structural behaviour and failure mode. One beam specimen was strengthened in shear using GFRP sheet as U wrap over the entire shear span by the conventional Externally Bonded Reinforcement (EBR) technique and tested for direct comparison with NSMR technique.

Concrete shear walls are one of the main lateral resisting members in buildings. Thefunctional requirements like architectural and even mechanical requirements entail thatopenings have to be installed in structural walls as well as floors. In this study, nonlinearstatic analysis was utilized to study the effects of fiber reinforced plastic (FRP) on theultimate load capacity of concrete shear walls with openings using the finite elementanalysis software ABAQUS. In order to verify the accuracy of the numerical model, acomparison was done between the results of experimental and numerical analysis of aconcrete shear wall. Subsequent to verification of the Finite Element Model (FEM), theeffects of creating cut-off openings as well as strengthening effects of applying FRP havebeen studied. Whereas the numerical results show good correlation between the FEM andthe experimental results of reinforced concrete (RC) shear walls, the numerical analysisrepresents a remarkable improvement in ultimate lateral load capacity of shear wall withopening strengthened using fiber reinforced plastic. The results obtained are presented inrelative diagrams and tables.