Field Investigation on Ground and Structural Vibrations During Prototype Pile Driving

As the land is very precious in urban areas and coastal regions, many structures are built in close proximity. When the soil is weak and heavy loads are to be carried, pile foundation is adopted for such structures. The impact caused by pile driving is a potential hazard to neighbourhood structures. Berthing structures are constructed using piles and the effect of pile driving on already installed adjacent piles is important. To predict the effect of pile driving on neighbourhood piles, measurement of ground and structural vibrations during prototype pile driving was carried out at a site in the city of Chennai, India. The soil at the site up to a depth of 19 m is mainly fine to medium sand. A driven cast in-situ pile of 600 mm diameter (D) was driven up to a depth of 15.8 m. The 25mm thick mild steel (M.S) tube casing is driven by 4.1t hammer with a drop height of 2.5m. During the pile driving, for every blow of hammer, the acceleration of the ground at various distances 5D, 8.33 D and 25 D from the pile are measured. Piezoelectric acceleration transducers, power amplifiers and taper recorder are used for measurement. The time history of vertical and horizontal ground accelerations as well as time history of vertical acceleration of an already installed pile at a distance of 6.25 m was analysed using PC based data acquisition systems. The time-histories and spectrum of ground and structural accelerations are presented

Prototype Piling in Soft Clay — A Case Study of Ground Vibrations: Field Measurement

Ground vibrations are generated either by natural phenomena or by human activities. Among the natural phenomena, earthquake is the principal source of ground vibrations of most interest. Ground vibrations generated by human activities are called manmade vibrations and these vary greatly in intensity depending on the particular source of vibration. The seismic waves associated with man-made vibrations propagate in the ground and inevitably interact with structures that are above-ground or underground. This interaction induces vibrations in the structure and, in extreme cases, affect its serviceability and integrity seriously. Still, there is no method to quantify the levels of piling vibration. Estimation of amplitudes and frequencies of vibration are based on experience and site testing. Therefore, in order to characterize the ground vibration due to piling, field measurement of ground vibration during prototype pile driving in soft clay was carried out. This paper presents the details of field measurement, instrumentation, collection of vibration data, acquisition and processing of data using PC-based data acquisition system made during the pile driving. The measurement of ground and already installed pile vibrations during prototype pile driving at a construction site in Chennai was carried out. The soil at this site is loose soft clay. The pile was of the type driven casing cast-in-situ pile of 500mm (OD) diameter. The depth of penetration of the pile was 13.25m. A 4 tonne hammer with a drop height of 1m drove the 25mm thick Mild Steel (MS) tube casing. During driving, ground acceleration was measured at a distance of 5D and 25D, where D is the diameter of pile, from the centre of pile. The vertical acceleration of an already installed pile situated at a distance of 37D from the driven pile were recorded. Piezoelectric acceleration transducers, power amplifiers, and tape recorder were used for the measurement. Acceleration signals were recorded using TEAC recorder. The recorded signals were processed using PC-based Data Acquisition System with DASYLAB software. The response time-histories and spectra of ground vibrations are presented and discussed

Valuing life and limb : understanding the risk-return trade-off

This policy brief is based on SANDEE working paper no. 9-04, "Measuring the value of life and limb : estimating compensating wage differentials among workers in Chennai and Mumbai"Across the developing world improvements in public health and environmental safety are becoming an ever-greater priority. One way to understand how the public values improvements in health is by assessing what individuals are willing to pay or forgo for small decreases in risks that may affect their longevity. For example, workers frequently make decisions that trade-off increased work-place risk and higher wages. This estimate of the financial gain required to take on increased risks can be used to assess public policies that seek to decrease the risk of death from environmental factors such as air pollution

Parallel network file systems using authenticated key exchange protocols

The keyestablishment for secure many-to-many communications is very important nowadays. The problem is inspired by the proliferation of large-scale distributed file systems supporting parallel access to multiple storage devices. In this, a variety of authenticated key exchange protocols that are designed to address the issues. This shows that these protocols are capable of reducing the workload of the metadata server and concurrently supporting forward secrecy and escrow-freeness. All this requires only a small fraction of increased computation overhead at the client. This proposed three authenticated key exchange protocols for parallel network file system (pNFS). The protocols offer three appealing advantages over the existing Kerberos-based protocol. First, the metadata server executing these protocols has much lower workload than that of the Kerberos-based approach. Second, two of these protocols provide forward secrecy: one is partially forward secure (with respect to multiple sessions within a time period), while the other is fully forward secure (with respect to a session). Third, designed a protocol which not only provides forward secrecy, but is also escrow-free

Image sharing privacy policy on social networks using A3P

User Image sharing social site maintaining privacy has become a major problem, as demonstrated by a recent wave of publicized incidents where users inadvertently shared personal information. In light of these incidents, the need of tools to help users control access to their shared content is apparent. Toward addressing this need an Adaptive Privacy Policy Prediction (A3P) system to help users compose privacy settings for their images. The solution relies on an image classification framework for image categories which may be associated with similar policies and on a policy prediction algorithm to automatically generate a policy for each newly uploaded image, also according to user’s social features. Image Sharing takes place both among previously established groups of known people or social circles and also increasingly with people outside the users social circles, for purposes of social discovery-to help them identify new peers and learn about peers interests and social surroundings, Sharing images within online content sharing sites, therefore, may quickly lead to unwanted disclosure. The aggregated information can result in unexpected exposure of one’s social environment and lead to abuse of one’s personal information

Strengthening of Load Bearing Masonry Wall Panels with Externally Bonded Precast Textile Reinforced Concrete Laminate

241-245Textile Reinforced Concrete (TRC) has gained worldwide popularity as a strengthening material for masonry structures in the recent years. As of today, the application of TRC for masonry strengthening is either by cast-in-place methodology or by spraying method. The present work is a first-of-its kind study, which explores the feasibility of using externally bonded precast TRC laminate for strengthening of load bearing brick masonry wall panels. The binder used in TRC itself is used as adhesive for adhering the TRC laminate to masonry wall panels. Experimental investigations were carried out on unstrengthened and strengthened brick masonry wall panels under axial compression and combined axial compression and shear loading. The influence of TRC strengthening system is assessed by examining the performance indicators such as strength, stiffness and deformation. Based on the investigations, the use of externally bonded precast TRC laminate is found to be a feasible solution to strengthen brick masonry walls to have the required structural adequacy

Strengthening of Load Bearing Masonry Wall Panels with Externally Bonded Precast Textile Reinforced Concrete Laminate

Textile Reinforced Concrete (TRC) has gained worldwide popularity as a strengthening material for masonry structures in the recent years. As of today, the application of TRC for masonry strengthening is either by cast-in-place methodology or by spraying method. The present work is a first-of-its kind study, which explores the feasibility of using externally bonded precast TRC laminate for strengthening of load bearing brick masonry wall panels. The binder used in TRC itself is used as adhesive for adhering the TRC laminate to masonry wall panels. Experimental investigations were carried out on unstrengthened and strengthened brick masonry wall panels under axial compression and combined axial compression and shear loading. The influence of TRC strengthening system is assessed by examining the performance indicators such as strength, stiffness and deformation. Based on the investigations, the use of externally bonded precast TRC laminate is found to be a feasible solution to strengthen brick masonry walls to have the required structural adequacy

Impact of living with a bilateral central vision loss due to geographic atrophy—qualitative study

Objective- Geographic atrophy (GA), a type of dry age-related macular degeneration, affects vision as central vision loss (CVL). The challenges faced due to bilateral CVL in activities of daily living and strategies taken to overcome those challenges are not very well understood in the Indian population. This qualitative study aims to understand the impact on everyday life activities and related adaptive and coping strategies in people with long-standing bilateral CVL due to GA in India. Design, participants, setting and methods- A qualitative study using a semistructured face-to-face interview was conducted on 10 people with bilateral CVL after obtaining written informed consent. The interviews were audio-recorded, and were transcribed verbatim. Thematic analysis was carried out to understand the challenges faced and adaptive methods due to the impact of CVL. Results-Ten participants (50% male) with a median age (IQR) of 72 (70, 74) years were interviewed. All the participants had best-corrected visual acuity of ≤6/60 in the better eye and reported an absolute central scotoma with the home Amsler chart. Qualitative thematic analysis identified four main themes: challenges in everyday living (difficulty in face identification, reading), challenges with lifestyle and socialisation (driving, cooking, reading for a longer duration, watching TV, socially inactive), psychological implications (depression, poor self-esteem, fear due to poor vision) and strategies to overcome the challenges (voice identification, technology support). Conclusion- GA has a severe negative impact on the quality of life in people with CVL. Inability to recognise faces was the main reason for dependency on others and being socially disconnected. The findings will help clinicians in providing improved rehabilitative care

Investigation on behaviour of reinforced geopolymer concrete slab under repeated low velocity impact loading

ABSTRACT: Geopolymers are a novel class of materials that are formed by the polymerisation of silicon, aluminum, and oxygen species to form an amorphous 3-D framework structure. Concrete made out of these binder system possess several advantages compared to conventional ordinary Portland cement concretes (OPCCs). Substantial research work has been reported on the impact behaviour of reinforced concrete structural elements whereas similar studies have not been reported on GPCs. This paper describes the experimental and numerical investigation on the behaviour of reinforced GPC slabs under repeated impact loading. The aim is to study the impact behavior of reinforced GPC slabs with and without steel fibers and compare with that of OPCC slabs. The overall dimensions of the GPC slab are 1m x 1m, with 60mm thickness. Finite element modeling of slab was also carried out using ANSYS software. The Solid 65 element and link 8 elements were used to model the concrete slab and Reinforcement respectively. Displacement boundary conditions are applied at the supports. The measured impact load time history is used to excite the structure. Transient dynamic analysis was carried out. The response was obtained in terms of deflection time histories. The peak acceleration of analytical studies showed a pattern similar to that obtained from experimental results. The failure crack pattern of plain and steel fibre reinforced slabs predicted by Finite Element analyses are compared with experimental results. The studies emphasize that by proper design, GPCC can be used in lieu of OPCC for structural components subjected to low velocity impact