Influence of phase difference between kinematic and inertial loads on seismic behaviour of pile foundations in layered soils

A series of dynamic centrifuge experiments was conducted on model pile foundations embedded in a two-layered soil profile consisting of soft-clay layer underlain by dense sand. These experiments were specifically designed to investigate the individual effect of kinematic and inertial loads on a single pile and a 3 × 1 row pile group during model earthquakes. It was observed that the ratio of free-field soil natural frequency to the natural frequency of structure might not govern the phase relationship between the kinematic and inertial loads for pile foundations as reported in some previous research. The phase relationship obtained in this study agrees well with the conventional phase variation between the force and displacement of a viscously damped simple oscillator subjected to a harmonic force. Further, as expected, the pile accelerations and bending moments can be smaller when the kinematic and inertial loads act against each other compared to the case when they act together on the pile foundations. This study also revealed that the peak kinematic pile bending moment will be at the interface of soil layers for both single pile and pile group. However, in the presence of both kinematic and inertial loads, the peak pile bending moment can occur either at the shallower depths or at the interface of soil layers depending on the pile cap rotational constraint. First author funded by Commonwealth Scholarshi

Seismic Response of Pile Foundations in Soft Clays and Layered Soils

Pile foundations are widely used to support large engineering structures by transferring loads to deeper layers of soil. During earthquakes, in addition to the axial loads, pile foundations are subjected to inertial loads and kinematic loads due to the motion of the superstructure and the vibrations of surrounding soil, respectively. Due to the significant damage caused by earthquake induced soil liquefaction, studies in the past few decades have focused more on liquefaction induced effects on pile foundations embedded in sands. However, post-reconnaissance reports of several earthquakes have concluded that pile foundations in soft clays and layered soils with significant stiffness contrast have also undergone severe damage during earthquakes. In this research, three different series of centrifuge experiments were performed to investigate the dynamic behaviour of soft clays, two-layered soils with significant stiffness contrast and the dynamic response of pile foundations embedded in these soil types. The first series of centrifuge experiments were focused on studying the dynamic response of floating piles in soft clay, which in turn depends on the dynamic behaviour of the soft clay layer around the pile. It was found that the dynamic response of clay depends on the earthquake intensity as well as the shear strength and stiffness of the clay layer. The second and third series of centrifuge experiments were specifically designed to investigate the seismic kinematic and inertial loads acting on pile foundations embedded in two-layered soil models with soft clay underlain by dense sand. The results have shown that obtaining a reliable value for the kinematic pile bending moment using established methods in the literature required accurate assessment of the earthquake-induced shear strain at the interface between the two soil layers. Moreover, it was found that non-linearity effects in soil are significant and need to be accounted for. Further, the phase difference between the kinematic and inertial loads and its influence on pile accelerations, rotations and bending moments was evaluated. This research has revealed that the ratio of free-field soil natural frequency to the natural frequency of the embedded structure might not govern the phase relationship between the kinematic and inertial loads as reported in previous research. Instead, the phase relationship between the two loads agrees well with the conventional phase variation between the force and displacement of a viscously damped simple oscillator subjected to a harmonic force. Lastly, the pile displacements (y) and corresponding soil pressures (p) were determined from the experimentally measured pile bending moments to establish p-y curves and compared with the corresponding curves recommended by design standards. The drawbacks of adopting p-y curves developed for monotonic or cyclic loading to dynamic loading conditions were highlighted through this comparison. The influence of earthquake characteristics such as frequency and intensity, pile group effects and soil layering on soil stiffness and ultimate lateral resistance of p-y curves were discussed in detail. Eventually, the analysis and interpretation of the centrifuge tests provided a better insight into the previously unexplored aspects of seismic soil-pile-structure interaction in soft clays and layered soils with significant stiffness contrast. This research also highlighted the importance of considering soil non-linearity effects in seismic analysis and design of pile foundations

The moral and philosophical implications of Karma and Jnana in Shreemad Bhagavadgita in the Perspectiue of Shree Shankaracharya and Shree Madhusudan Saraswati

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A clinical observational study in cases of eclampsia

Background: Eclampsia is a life threatening condition and one of the leading causes of maternal deaths worldwide. It is also associated with complications like acute renal failure, DIC, postpartum hemorrhage, etc. and adverse fetal outcomes.  Hence we aimed to study fetomaternal outcomes in cases of Eclampsia.Methods: A total of 75 cases of eclampsia out of 13524 deliveries were evaluated, from 1st January 2016 to 30th June 2017 at RZ Hospital, a government tertiary referral centre. Maternal outcomes were studied for its complications, effectiveness of magnesium sulphate treatment, fetal outcome and mode of delivery.Results: Incidence rate of eclampsia was 0.55%, 62.66% of all cases were primigravida, 76% of cases were in age group of 21-26 years, 84% cases were from lower socio economic status, maternal mortality occurred in 2 of 75 cases. 66.67% of patients were of term pregnancy (37 to 42 weeks). 71%(53) patients delivered vaginally out of which 9 deliveries were spontaneous and 44 deliveries were induced vaginal delivery. 22 patients required caesarean section.Conclusions: Early detection and prevention of pregnancy induced hypertension and pre-eclampsia and other associated risk factors for eclampsia might help to reduce the incidence of eclampsia. Maternal adverse outcomes in this study were magnesium toxicity, acute renal failure (ARF), disseminated intravascular coagulation (DIC) and post partum hemorrhage (PPH) while 92% patients had no complications

Somatization and health seeking behavior

Background:Somatization is the state of being symptomatic which is not explained medically associated with psychological distress and health-seeking behavior and is present in at least 10% to 15% in OPD.Methods:50 patients with long standing history of MUS were evaluated by using modified Bradford inventory.Results: Somatization was most common in younger age, female and lower socio-economical class. Feeling of weakness or lack of energy much of the time in both male and female respectively 94.7% and 96.7% are the most common symptomatic presentation in Somatization during last 2 years, although there were symptomatic differences in males and females. Severity of symptoms was higher among females. 13% of female pts had undergone hysterectomy due to persistent gynecological problems during course of illness. 82% pts had illness of more than 2 years. The mean duration of illness at the time of assessment was 6.8 years. Most of the patients had visited to multiple consultants and underwent many costly diagnostic procedures for their symptoms .Most of the patients after multiple investigations and consultations were not ready to accept psychological origin of their physical illness and continued to see next practitioner as they remained dissatisfied and distressed. One or more physical illness is the common explanation by physicians. Patients presented with somatization has an another diagnosis in significant cases like Major depressive disorder, anxiety disorder, alcohol use disorder.Conclusion:Somatization was common among female, but it was not uncommon in male. Patient suffering from somatization disorder has very high rate of health care utilization and they perceived themselves as severely ill and were willing to undergo multiple hospitalizations, diagnostic studies, and operations, remained dissatisfied. Need to strengthened consultation liaison between physician and psychiatrist.

The study of prevalence of Hepatitis B surface antigen during pregnancy

Background: Hepatitis B virus infection is a major public health problem accounting to 400 million chronic infections worldwide and great majority of the transmission of Hepatitis B in India and other developing countries occurs by vertical transmission from an infected carrier mother to the neonate, intrapartum or antenatally. Objective: To determine the prevalence of Hepatitis B surface antigen (HBsAg) in Pregnant Women. Methods: The study was conducted at M.P. Shah Govt. medical college and G.G. hospital, Jamnagar, Gujarat, India during July 2013 to December 2013, including 1810 antenatal women. All of them were evaluated using history, examination, and test for serum HBsAg using Commercial enzyme immunoassay kits. Result: Of the total 1810 antenatal women, 15 were found to be positive for HBsAg (0.83%). Highest prevalence was found in age group 21-25 years (53.3%) followed by age group 26-30 years (33.3%), age group 17-20 and age more than 30 years (6.7%). Conclusion: Hepatitis B is highly infectious, associated with maternal complications and transmission to the child. It is mandatory that all the antenatal women should be screened for HBsAg and appropriately managed

Analysis of Linear and Non-Linear Stress-Strain Properties for Graphene and Single Walled Carbon Nanotubes

Carbon Nanotube (CNT) has revolutionized the world of nanotechnology with several novel applications in the field of sensors and actuators. Such popularity of CNT is due to its excellent mechanical and electrical properties. There are several studies done on understanding the modeling of mechanical and electrical properties using different approaches ranging from molecular to continuum based method. In this thesis, we focus on estimating the mechanical properties of single walled carbon nanotube (SWCNT) mainly based on stress-strain relationship. There are several approaches such as molecular mechanics, molecular dynamics, coupled molecular-structural mechanics, exponential Cauchy born based continuum method, etc, for estimating the linear and nonlinear stress-strain relationship in order to find elastic modulus of SWCNT. In this thesis, we first find the analytical model using molecular mechanics approach to study the variation of elasticity with the diameter of SWNT under different configurations. It is found that the elasticity becomes size independent if the diameter is above 1 nm. Moreover this approach does not help us to get accurate nonlinear stress-strain relationship. Therefore, we used coupled molecular-structural approach to study the nonlinear variation of stress-strain relationship for different configurations. Then, we come up with compact formulas in order to predict the nonlinear stress-strain relationship. Capitalizing on this approach, we find the equivalent mechanical properties of a beam element for the corresponding C-C bond that exists in CNT. Thereafter, we use these properties to do structural modeling in ANSYS which drastically reduces the modeling effort as compared to molecular dynamics approach. In order to standardize this approach, we do several comparisons and tests with existing results based on other methods. It is found that the results are in good agreement with the literature. After validating the stress-strain properties of SWCNT under different configurations, we do modal analysis to find the first few frequencies for fixed-fixed and cantilever kinds of support. On comparing the results with analytical model based from continuum theory, we get relatively good match for cantilever under vii wider range of aspect ratio- a ratio of length to diameter of SWNT. However, analytical result for the fixed-fixed condition matches well only for larger length to diameter ratio. Furthermore, we investigate different modes of graphene and SWCNT under different configurations to demonstrate the capabilities of this method

Role of Pile Spacing on Dynamic Behavior of Pile Groups in Layered Soils

This research investigates the influence of pile spacing on the dynamic behavior of pile groups by performing a series of specifically designed dynamic centrifuge experiments on pile foundations embedded in a two-layered soil profile. A single pile and two 3×1 row pile groups with different pile spacing were used as model pile foundations, and the soil models consisted of a soft clay underlain by dense sand. The influence of earthquake frequency on the dynamic behavior of two-layered soils is discussed using the centrifuge data and 1D site response analysis from DEEPSOIL. Further, the results of these centrifuge tests agreed with the conviction that the group effects will be diminished with the increase in pile-to-pile spacing in a pile group due to reduced pile-soil-pile interaction. However, these reduced pile group effects can lead to larger kinematic pile bending moments in the widely spaced pile group compared with a closely spaced pile group. Moreover, the single pile always has larger bending moments than both the tested pile groups—an exception to this is when there is a significant phase difference between the kinematic and inertial loads for a single pile but not for the widely spaced pile group. The influence of pile spacing on the shadowing effects and location of peak bending moments in the piles of a group are also discussed in this paper. Lastly, an attempt is made to evaluate the individual contribution of inertial and kinematic loads for the seismic design of pile foundations considering soil-pile-structure interaction effects

Experimental investigation of kinematic pile bending in layered soils using dynamic centrifuge modelling

This research provides an insight into the previously unexplored aspects of kinematic pile bending, especially for large-intensity earthquakes where the soil behaviour is highly non-linear. In this study, a series of dynamic centrifuge experiments was conducted on pile foundations embedded in a two-layered soil profile to investigate the kinematic effects on pile foundations during model earthquakes. A single pile and a closely spaced 3 × 1 row pile group were used as model pile foundations, and the soil model consisted of a soft clay underlain by dense sand. It was observed that the peak kinematic pile bending moment occurs slightly beneath the interface of the soil layers and this depth is larger for the pile group compared to a single pile. Also, the piles in a group attract lower bending moments but carry larger residual kinematic pile bending moments compared to a single pile. Furthermore, the elastic solutions available in the literature for estimating the kinematic pile bending moments are shown to yield satisfactory results only for small-intensity earthquakes, but vastly underestimate for large-intensity earthquakes, if methods are applied injudiciously. The importance of considering soil non-linearity effects and accurate determination of shear strain at the interface of layered soils during large-intensity earthquakes for a reliable assessment of kinematic pile bending moment from methods in the literature is demonstrated using dynamic centrifuge test data. </jats:p

Prevalence & antibiogram of Pseudomonas aeruginosa at S.S.G. Hospital, Baroda, Gujarat, India

Background: Pseudomonas aeruginosa is a gram negative bacterium that continues to be a major cause of opportunistic nosocomial infections, causing around 9-10% of hospital infections. It is hard to treat because of intrinsic resistance of the species and its ability to further resistance to multiple groups including β-lactams, aminoglycosides and fluoroquinolones. Aims: This study was undertaken to determine the prevalence of Pseudomonas and their susceptibility pattern at S.S.G. Hospital, BARODA. Materials and Methods: Between March 2015 to May 2015, 150strains of P. aeruginosa were isolated from different clinical specimens. The samples were selected on the basis of their growth on Mac Conkey and nutrient agar medium with oxidase positive. Colonies were subjected to biochemical tests to identify species. Antimicrobial susceptibility of all the isolates was performed by disc diffusion (Kirby –Bauer) method according to CLSIs guidelines. Results: Majority of isolates of P. aeruginosa were obtained from specimens of blood, pus, wound, sputum, tracheal aspirates, pleural fluid, ICD fluid, bile fluid.The prevalence of pathogen was 4.15% and 98% pathogens were sensitive Piperacillin+Tazobactum followed by Meropenem (93.33%), Levofloxacin (92.66%) , Ceftazidime (82%), Cefoperazone(81.33%), Piperacillin (80.66%), Amikacin(56%), Gentamicin(54.66%). Conclusion: The results confirmed the occurrence of drug resistant strains of P. aeruginosa. Meropenem, Levofloxacin and Piperacillin+Tazobactumwere found to be the most effective antimicrobial drugs. It is rational treatment regimens prescription by the physicians to limit the further spread of antimicrobial resistance among the P. aeruginosa strains