12th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC12, 2011
The effects of far distant earthquakes felt in regions with low and moderate seismicity has incre... more The effects of far distant earthquakes felt in regions with low and moderate seismicity has increased markedly over the last decade. Henceforth fragility curves in this study are to indicate whether buildings are safe to enter or not after an earthquake event occurring more than 300km away. The probability of light, moderate and severe damage states occurring on two and four storey reinforced concrete buildings up to a peak ground acceleration of 0.2g were predicted. The building models were constructed using finite element software based on eight node brick elements with three degrees of freedom at each node. The analysis was carried out using a dynamic response spectrum to calculate the peak inter-storey drift ratios. For the development of fragility curves, the results were collated following a log-normal mean distribution. The results showed that light damage is likely to occur with a probability of over 10% within a 50 year period, while the existing record is unlikely to cause structural damage. The fragility curves were comparable to those for RC moment resisting frames obtained by (Rossetto and Elnashai 2003) at a lower drift limit, with approximately 2% of inter-storey drift ratio.
Proceedings of the International Modal Analysis Conference - IMAC, 2001
This paper describes the detection and identification of cracking severity in a reinforced concre... more This paper describes the detection and identification of cracking severity in a reinforced concrete beam using modal data. Experimental modal test was performed on the beam before and after application of load of increasing intensity to induce a single crack at a fixed location. Modal parameters extracted were categorised into two groups, namely local response parameter (mode shape data) and global response parameters. Localised changes such as cracking reduce the stiffness of the structure, and therefore caused a localised change in the discrete function of the mode shape. From a previous research, Laplacian Operator was initially proposed. However, when applied to a non-homogeneous and composite material such as reinforced concrete, the operator was too sensitive and did not yield meaningful results. Hence, a simplified Laplacian operator was suggested. In this investigation, it was found that global response such as natural frequency is a good indicator to detect the occurrence of the deterioration in the structure. However, the local response data such as mode shape was required to detect the defect location accurately and a simplified Laplacian operator worked quite successfully. Furthermore, it was observed that the higher frequency modes tend to detect the occurrence of cracking in the earlier stages.
Arabian Journal for Science and Engineering, Oct 1, 2010
This paper reports the details of investigations carried out to study the performance of industri... more This paper reports the details of investigations carried out to study the performance of industrial waste incineration bottom ash and refined kaolin to produce controlled low-strength material (CLSM). CLSM mixes were designed with varying amounts of incineration bottom ash, refined kaolin, and cement. Water content was adjusted to get sufficient flowability. Tests for density, stiffening time, bleed, settlement, sorptivity, water absorption, moisture content, California bearing ratio, initial surface absorption, and compressive strength were carried out on the CLSM mixtures. Study for corrosivity and leaching of heavy metals and salts on the bleed and leachate were also performed. The compressive strength of CLSM tested ranged from 0.36 to 4.40 MPa. CBR values ranged from 10 to 46 and ISAT values at 1 hour from 0.56 to 4.76 ml/m2/s. None of the heavy metals tested exceeded the threshold limits in leachate. Addition of kaolin controls the compressive strength development, and reduces initial surface absorption, California bearing ratio, and water absorption values. It is shown that the incineration bottom ash, along with refined kaolin, can be successfully employed in CLSM, thereby contributing to sustainability in civil engineering practice.
Lightweight clay bricks were produced using a chemical cellulation technique from a residual soil... more Lightweight clay bricks were produced using a chemical cellulation technique from a residual soil of high clay content, mostly non-crystalling. The cellulation technique introduces cells into the material during the mixing stage as a result of the chemical reaction between aluminium powder and quicklime, which liberates hydrogen gas. The technique also requires the use of sodium silicate to achieve a proper cellulated structure. The mechanisms of reaction of the abovementioned chemicals with each other as well as with the raw material were investigated. Engineering properties of the fired product, namely compressive strength, bulk density, water absorption, and volumetric shrinkage, were determined and compared with solid bricks prepared in the laboratory. Based on the results of the study, a mechanism for the cellulation process, though complex, is postulated. The process is a combination of chemical reaction between the chemical additives used and the response of the soil to the chemicals or to the reaction products. The study also reveals the possibility of producing lightweight clay bricks, mostly of loadbearing performance, using the residual soil.
12th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC12, 2011
The effects of far distant earthquakes felt in regions with low and moderate seismicity has incre... more The effects of far distant earthquakes felt in regions with low and moderate seismicity has increased markedly over the last decade. Henceforth fragility curves in this study are to indicate whether buildings are safe to enter or not after an earthquake event occurring more than 300km away. The probability of light, moderate and severe damage states occurring on two and four storey reinforced concrete buildings up to a peak ground acceleration of 0.2g were predicted. The building models were constructed using finite element software based on eight node brick elements with three degrees of freedom at each node. The analysis was carried out using a dynamic response spectrum to calculate the peak inter-storey drift ratios. For the development of fragility curves, the results were collated following a log-normal mean distribution. The results showed that light damage is likely to occur with a probability of over 10% within a 50 year period, while the existing record is unlikely to cause structural damage. The fragility curves were comparable to those for RC moment resisting frames obtained by (Rossetto and Elnashai 2003) at a lower drift limit, with approximately 2% of inter-storey drift ratio.
Proceedings of the International Modal Analysis Conference - IMAC, 2001
This paper describes the detection and identification of cracking severity in a reinforced concre... more This paper describes the detection and identification of cracking severity in a reinforced concrete beam using modal data. Experimental modal test was performed on the beam before and after application of load of increasing intensity to induce a single crack at a fixed location. Modal parameters extracted were categorised into two groups, namely local response parameter (mode shape data) and global response parameters. Localised changes such as cracking reduce the stiffness of the structure, and therefore caused a localised change in the discrete function of the mode shape. From a previous research, Laplacian Operator was initially proposed. However, when applied to a non-homogeneous and composite material such as reinforced concrete, the operator was too sensitive and did not yield meaningful results. Hence, a simplified Laplacian operator was suggested. In this investigation, it was found that global response such as natural frequency is a good indicator to detect the occurrence of the deterioration in the structure. However, the local response data such as mode shape was required to detect the defect location accurately and a simplified Laplacian operator worked quite successfully. Furthermore, it was observed that the higher frequency modes tend to detect the occurrence of cracking in the earlier stages.
Arabian Journal for Science and Engineering, Oct 1, 2010
This paper reports the details of investigations carried out to study the performance of industri... more This paper reports the details of investigations carried out to study the performance of industrial waste incineration bottom ash and refined kaolin to produce controlled low-strength material (CLSM). CLSM mixes were designed with varying amounts of incineration bottom ash, refined kaolin, and cement. Water content was adjusted to get sufficient flowability. Tests for density, stiffening time, bleed, settlement, sorptivity, water absorption, moisture content, California bearing ratio, initial surface absorption, and compressive strength were carried out on the CLSM mixtures. Study for corrosivity and leaching of heavy metals and salts on the bleed and leachate were also performed. The compressive strength of CLSM tested ranged from 0.36 to 4.40 MPa. CBR values ranged from 10 to 46 and ISAT values at 1 hour from 0.56 to 4.76 ml/m2/s. None of the heavy metals tested exceeded the threshold limits in leachate. Addition of kaolin controls the compressive strength development, and reduces initial surface absorption, California bearing ratio, and water absorption values. It is shown that the incineration bottom ash, along with refined kaolin, can be successfully employed in CLSM, thereby contributing to sustainability in civil engineering practice.
Lightweight clay bricks were produced using a chemical cellulation technique from a residual soil... more Lightweight clay bricks were produced using a chemical cellulation technique from a residual soil of high clay content, mostly non-crystalling. The cellulation technique introduces cells into the material during the mixing stage as a result of the chemical reaction between aluminium powder and quicklime, which liberates hydrogen gas. The technique also requires the use of sodium silicate to achieve a proper cellulated structure. The mechanisms of reaction of the abovementioned chemicals with each other as well as with the raw material were investigated. Engineering properties of the fired product, namely compressive strength, bulk density, water absorption, and volumetric shrinkage, were determined and compared with solid bricks prepared in the laboratory. Based on the results of the study, a mechanism for the cellulation process, though complex, is postulated. The process is a combination of chemical reaction between the chemical additives used and the response of the soil to the chemicals or to the reaction products. The study also reveals the possibility of producing lightweight clay bricks, mostly of loadbearing performance, using the residual soil.
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