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11.
Seismic pounding between adjacent frames in multiple-frame bridges and girder ends in multi-span simply supported bridges has been commonly observed in several recent earthquakes. The consequences of pounding include damage to piers, abutments, shear keys, bearings and restrainers, and possible collapse of deck spans. This paper investigates pounding in bridges from an analytical perspective. A simplified nonlinear model of a multiple-frame bridge is developed including the effects of inelastic frame action and nonlinear hinge behavior, to study the seismic response to longitudinal ground motion. Pounding is implemented using the contact force-based Kelvin model, as well as the momentum-based stereomechanical approach, Parameter studies are conducted to determine the effects of frame period ratio, column hysteretic behavior, energy dissipation during impact and near source ground motions on the pounding response of the bridge. The results indicate that pounding is most critical for highly out-of-phase frames and is not significant for frame period ratios greater than 0.7. Impact models without energy dissipation overestimate the displacement and acceleration amplifications due to impact, especially for elastic behavior of the frames. Representation of stiffness degradation in bridge columns is essential in capturing the accurate response of pounding frames subjected to far field ground motion. Finally, it is shown that strength degradation and pounding can result in significant damage to the stiffer frames of the bridge when subjected to large acceleration pulses from near field ground motion records. 相似文献
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B. Ramesh Babu B.E. P.G.D.C.A. Ph.D. S. Maruthamuthu M.Sc. M.Phil. Ph.D. A. Rajasekar M.Sc. N. Muthukumar M.Sc. M.Phil. N. Palaniswamy M.Sc. Ph.D. 《International Journal of Environmental Science and Technology》2006,3(2):159-166
In the dairy industry mild steel is used as the construction material for the effluent treatment plants, pipelines, reinforcement in concrete structures etc. The steel exposed to the dairy effluent faces corrosion due to the microbes. In the present study the role of microbes in dairy effluent on the corrosion of mild steel has been investigated. Pseudomonas sp., Streptococcus sp., Micrococcus sp., Bacillus sp., Neisseria sp. and Lactobacillus sp. were identified in dairy effluent. Corrosion rate has been estimated by weight loss measurements and polarization technique. The Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD) studies were found helpful in investigating the chemical pathway leading to the formation of corrosion products on the mild steel during fermentation. Initiation of pitting corrosion was noticed on steel specimens by scanning electron microscope (SEM). A mechanism has been proposed for microbiologically influenced corrosion in dairy effluent. 相似文献
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Antibiotic resistant pathogens versus human impacts: a study from three eco-regions of the Chennai coast, southern India 总被引：1，自引：0，他引：1
We assessed the occurrence of pollution indicators and antibiotic resistant bacterial isolates from water and sediment samples of three different eco-regions of the Chennai coast between March - May of 2010. Total of 960 bacterial strains belonging to four genera were isolated which show the highest frequencies of resistance to vancomycin (53.6%) and penicillin (52.6%) (except Enterococcus sp., which is highly resistant to erythromycin) and lowest frequencies of resistance to chloramphenicol (3.43%), ciprofloxacin (3.95%), gentamicin (4.68%), and tetracycline (6.97%). The E. coli, Vibrio sp., Salmonella sp. and Enterococcus sp. show high frequency of resistance to 2-5 antibacterials of 60.4%, 45.83%, 69.16% and 46.6%, respectively. High pollution indices (PI - 6.66-14.06) and antibiotic resistance indices (ARI - 0.29-0.343) indicate that the coastal environment is highly exposed to antibiotic sources that suggesting to avoid direct contact. 相似文献
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The present work focuses on the performance of Fenton, sono‐Fenton, and sono‐photo‐Fenton processes for the oxidation of phenol present in aqueous solution. The effects of H2O2 concentration, Fe2+ concentration, pH, and initial phenol concentration on the oxidation of phenol were studied. The optimum Fe2+ and H2O2 concentrations for the Fenton process were 45 and 800 mg/L, respectively. For the sono‐Fenton process, the optimum Fe2+ and H2O2 concentrations were 30 and 800 mg/L, respectively. The optimal conditions for the sono‐photo‐Fenton process were found to be 20 mg/L of Fe2+ and 700 mg/L of H2O2. The optimum pH was found to be 3 for the processes investigated in the present study. The analysis of results showed that the sono‐photo‐Fenton method reduced the Fe2+ concentration by 30–50% and the H2O2 concentration by 12.5%. It was found that the sono‐photo‐Fenton technique showed better performance than the Fenton and sono‐Fenton processes for the oxidation of phenol. A lumped kinetic model was used to predict the chemical oxygen demand reduction and the model was found to fit the data. 相似文献
16.
Granular pile-anchor (GPA) technique has been found to be an innovative foundation technique for expansive clays posing the dual problem of swelling and shrinkage. Swelling occurs during absorption of water and shrinkage during evaporation of water. Generally, in field expansive clay beds, swelling takes place during rainy seasons and shrinkage during summers. GPA is a recent innovative foundation technique devised to ameliorate the dual swell-shrink problem of structures founded on expansive clay beds. The other innovative techniques are drilled piers, belled piers and under-reamed piles. Laboratory scale model studies and field scale experiments on GPAs yielded useful results and revealed that swelling of expansive clay beds was effectively controlled by GPA technique. Studies on swell-shrink behaviour of GPA-reinforced clay beds have not been performed so far. This paper presents results obtained from laboratory scale model studies on GPA-reinforced expansive clay beds subjected to alternate cycles of swelling and shrinkage. The data presented in this paper pertain to the swelling of test clay beds under the influence of three swell-shrink cycles (N) spanning a time period of 300 days. The test clay beds were reinforced with varying number of GPAs (n = 0, 1, 2 and 3). Heave (mm) in a given swell-shrink cycle decreased with increasing number of GPAs. Further, for a given number of GPAs (n), heave (mm) also decreased with increase in depth from the top of the clay bed. It was found that the resultant thickness of the clay bed (Hr) for swelling increased with increasing number of cycles. However, the percentage heave (ΔH/Hr) decreased as the number of swell-shrink cycles (N) increased. 相似文献
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ABSTRACT Granular pile-anchor (GPA) technique is an innovative tension-resistant foundation technique which can effectively ward off the dual swell–shrink problem posed by expansive clays. The other tension-resistant foundation techniques are drilled piers, belled piers and under-reamed piles. Laboratory scale model studies and field scale experiments on GPAs revealed that swelling of expansive clay beds could be effectively controlled by GPA technique. This paper presents results obtained from laboratory scale model studies on GPA-reinforced expansive clay beds subjected to alternate cycles of wetting and drying. Swelling and shrinkage of the clay beds were monitored for three wetting–drying cycles (N) spanning a time period of 300 days. The clay beds were reinforced with varying number of GPAs (n = 0, 1, 2 and 3). Swelling (mm) and shrinkage (mm) of the clay beds in a given wetting–drying cycle decreased with increasing number of GPAs. Further, swelling (mm) and shrinkage (mm) significantly decreased with increasing number of wetting–drying cycles (N) also. For a given number of GPAs (n), swelling and shrinkage decreased with increase in depth from the top of the clay bed too. 相似文献
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Implications of seismic pounding on the longitudinal response of multi-span bridges - an analytical perspective 总被引：2，自引：0，他引：2
ReginaldDesRoches SusendarMuthukumar 《地震工程与工程振动(英文版)》2004,3(1):57-65
Seismic pounding between adjacent frames in multiple-frame bridges and girder ends in multi-span simply supported bridges has been commonly observed in several recent earthquakes. The consequences of pounding include damage to piers, abutments, shear keys, bearings and restrainers, and possible collapse of deck spans. This paper investigates pounding in bridges from an analytical perspective. A simplified nonlinear model of a multiple-frame bridge is developed including the effects of inelastic frame action and nonlinear hinge behavior, to study the seismic response to longitudinal ground motion. Pounding is implemented using the contact force-based Kelvin model, as well as the momentum-based stereomechanical approach. Parameter studies are conducted to determine the effects of frame period ratio, column hysteretic behavior, energy dissipation during impact and near source ground motions on the pounding response of the bridge. The results indicate that pounding is most critical for highly out-of-phase frames and is not significant for frame period ratios greater than 0.7. Impact models without energy dissipation overestimate the displacement and acceleration amplifications due to impact, especially for elastic behavior of the frames. Representation of stiffness degradation in bridge columns is cssential in capturing the accurate response of pounding frames subjected to far field ground motion. Finally, it is shown that strength degradation and pounding can result in significant damage to the stiffer frames of the bridge when subjected to large acceleration pulses from near field ground motion records. 相似文献
20.
Optimization of aqueous methylparathion biodegradation by Fusarium sp in batch scale process using response surface methodology 总被引：1，自引：0，他引：1
K. Usharani M. Muthukumar 《International Journal of Environmental Science and Technology》2013,10(3):591-606
Biotreatment of methylparathion (O,O-dimethyl-O-4-nitrophenyl phosphorothioate) was studied in aqueous mineral salts medium containing fungal culture to demonstrate the potential of the pure culture (monoculture) of Fusarium sp in degrading high concentration of methylparathion. A statistical Box–Behnken design of experiments was performed to evaluate the effects of individual operating variables and their interactions on the methylparathion removal with initial concentration of 1,000 mg/L as fixed input parameter. A full factorial Box–Behnken design of experiments was used to construct response surfaces with the removal, the extent of methylparathion biodegradation, removal of chemical oxygen demand and total organic carbon, and the specific growth rate as responses. The temperature (X 1), pH (X 2), reaction time (X 3) and agitation (X 4) were used as design variables. The result was shown that experimental data fitted with the polynomial model. Analysis of variance showed a high coefficient of determination value of 0.99. The maximum biodegradation of methylparathion in terms of the methylparathion removal (Y 1), chemical oxygen demand removal (Y 2) and total organic carbon removal (Y 3) were found to be 92, 79.2 and 57.2 % respectively. The maximum growth in terms of dry biomass (Y 4) was 150 mg/L. The maximum biodegradation corresponds to the combination of following factors of middle level of temperature (X 1 = 30 °C), pH (X 2 = 6.5), agitation (X 4 = 120 rpm) and the highest level of reaction time (X 3 = 144 h). The removal efficiency of methylparathion biodegradation was achieved 92 %. It was observed that optimum biotreatment of methylparathion can be successfully predicted by response surface methodology. 相似文献