SHEAR BEHAVIOR OF STEEL FIBER REINFORCED PRECAST PRESTRESSED CONCRETE BEAMS

Precast industries constantly look for better alternative solutions to reduce the secondary reinforcement to speed up the production process. Addition of fibers in concrete helps in reducing the use of secondary reinforcement. Presence of fiber reinforcement has proven to enhance the ductility and energy dissipation capacity of the concrete under flexure and shear. Shear behavior of concrete members mainly depends on the compressive strength of concrete, shear span to depth ratio (a/d), amount of stirrups, aggregate interlock and dowel action of longitudinal reinforcement. The present study focuses on the shear behavior of steel fiber reinforced PSC beams with different volume fractions i.e., 0.50% and 1.00%. Fiber reinforced prestressed concrete (FRPC) beams were cast using long line method and tested with a shear span to depth ratio of 2.4 to simulate shear dominant behavior. Strain gauges were attached to the strands at loading point and at the center of shear span (a/2) to measure strain variation at different stages such as prestressing, de-tensioning and testing. During experimentation, load-deflection and strand strain was recorded. Test results indicate that the addition of steel fibers improved the shear resistance and ductility of the prestressed concrete beams

Efficiency of steel and macro-synthetic structural fibers on the flexure-shear behaviour of prestressed concrete beams

The efficiency of steel and structural synthetic fibers on the performance improvement of prestressed concrete (PSC) beams under combined flexure-shear is studied. Results of eleven PSC beams tested at a shear span (a) to depth (d) ratio of five are presented. Discrete steel and macro synthetic structural polyolefin fibers of varying dosages of 0.35%, 0.7% and 1.0% by volume of concrete were used. The effect of fiber addition on overall load - displacement, load-strain, and strain energy absorption capacity of PSC beams is analysed. Other parameters such as shear span to depth ratio (a/d), compressive strength of concrete, prestressing reinforcement ratio were kept constant. The test results portray that the addition of steel fibers stiffens the post cracking response, increases the strain energy absorption capacity more efficiently when compared to macro synthetic fibers (Polyolefin). The failure mode changed from less ductile flexure-shear to more ductile flexure dominant mode at 0.35% and 0.70% volumetric dosage of steel and synthetic fibers, respectively. The strain energy absorption capacity increased by more than 100% at 1.0% fiber addition for both steel and macro-synthetic fibers

Comparative bioequivalence studies of tramadol hydrochloride sustained-release 200 mg tablets

Suhas S Khandave1, Satish V Sawant1, Santosh S Joshi1, Yatish K Bansal2, Sonal S Kadam21Accutest Research Laboratories (I) Private Limited, Koparkhirne, Navi Mumbai, Maharashtra, India; 2Ipca Laboratories Limited, Kandivli Mumbai, Maharashtra, IndiaBackground: Tramadol hydrochloride is available as 50 mg immediate-release (IR) and 100 mg, 200 mg, and 300 mg sustained-release (SR) tablets. The recommended dose of tramadol is 50–100 mg IR tablets every 4–6 hours. The tramadol SR 200 mg tablet is a better therapeutic option, with a reduced frequency of dosing, and improved patient compliance and quality of life. The present study evaluated the bioequivalence of a generic tramadol SR 200 mg tablet.Methods: A comparative in vitro dissolution study was performed on the test and reference products, followed by two separate single-dose bioequivalence studies under fasting and fed conditions and one multiple-dose bioequivalence study under fasting conditions. These bioequivalence studies were conducted in healthy human subjects using an open-label, randomized, two-treatment, two-period, two-sequence, crossover design. The oral administration of the test and reference products was done on day 1 for both the single-dose studies and on days 1–5 for the multiple-dose study in each study period as per the randomization code. Serial blood samples were collected at predefined time points in all the studies. Analysis of plasma concentrations of tramadol and O-desmethyltramadol (the M1 metabolite) was done by a validated liquid chromatography-mass spectrometry analytical method. The standard acceptance criterion of bioequivalence was applied on log-transformed pharmacokinetic parameters for tramadol and its M1 metabolite.Results: The ratios for geometric least-square means and 90% confidence intervals were within the acceptance range of 80%–125% for log-transformed primary pharmacokinetic parameters for tramadol and its M1 metabolite in all the three studies.Conclusion: The test product is bioequivalent to the reference product in terms of rate and extent of absorption, as evident from the single-dose and multiple-dose studies. Both the treatments were well tolerated.Keywords: tramadol, multiple-dose, steady state, bioequivalenc

Numerical Modeling of Excimer Laser Curved Surface Ablation

Laser ablation has been widely used in the fabrication of miniature parts. The technique is also used in the fabrication of micro lens or micro-curved surfaces which find potential applications in various optical, bio- medical, electronics, MEMS applications. This work presents development of two novel techniques employing profile path approach and beam profile approach for fabrication of curved surfaces by Excimer laser ablation. Laser ablation is widely used for their fabrication on account of its exceptional capabilities. In this paper, a two-dimensional finite element model is developed to predict temperature distribution and ablation depth in a laser ablation process. A correlation between the incident laser fluence and depth of the ablated crater is analytically gener-ated based on the FEM model. Using this correlation, the profiles of the surface ablated using profile path and beam path approach is predicted based on a finite element model incorporating the pulse variation in profile path approach and spatial variation of intensity of the incident beam in the beam path approach. Modeling of various profiles like flat, circular, Gaussian and other is also presented. An attempt has been made to validate the proposed techniques experimentally

Sandeep Dhanik Modeling of a Single Resistance Capacitance Pulse Discharge in Micro-Electro Discharge Machining

Micro-EDM (electro discharge machining) is a derived form of ED

BEHAVIOR OF HYBRID FIBER REINFORCED PRESTRESSED CONCRETE BEAMS UNDER FLEXURE-SHEA

The present study aims at understanding the effect of hybridization of the steel and synthetic fibers on the flexure-shear behavior of prestressed concrete (PSC) beams. The first phase of the test program consists of evaluating the efficiency of individual fibers viz. steel and structural synthetic fibers on the performance of prestressed concrete (PSC) beams. Later, a hybrid fiber combination consisting of steel and synthetic fibers are introduced to understand the behavior. The effect of different fiber reinforcement on the behavior of prestressed concrete beams are evaluated in two stages. First, fracture tests are conducted to understand the influence of fibers at the material level. Secondly, full-scale prestressed concrete beams are tested for evaluating the effect of fiber addition on the flexure-shear behavior. The test matrix consists of seventeen beams with fiber reinforced concrete, having fiber dosages of 0.35%, 0.70% and 1.0% by volume of concrete. All the beam specimens are tested at a shear span (a) to depth ratio (d) of five under four-point bending configuration. Effect of hybrid fiber addition on the overall load-displacement, load-strain, and strain energy absorption capacity of PSC beams are analyzed. Other parameters such as shear span to depth ratio (a/d), the compressive strength of concrete, prestressing reinforcement ratio are kept constant. Results of hybrid fiber reinforced specimens is compared with the results of steel and Synthetic (polyolefin) fiber reinforced beams. The test results portray that the addition of fibers stiffen the post-cracking response and increases the energy absorption capacity. Additionally, failure mode changed from flexure-shear (brittle) to flexure (ductile) mode with the addition of fibers. Change of failure mode occurred at dosages of 0.35% for steel and hybrid fibers and 0.70% for synthetic (Polyolefin) fibers. The strain energy absorption capacity increased by more than 100% at 1.0% fiber addition for both steel and macro-synthetic fibers. Flexural capacity of the tested vi specimens is verified with the RILEM recommendation for fiber reinforced concrete specimens. RILEM recommendations always underpredicted the actual value, indicating the conservative estimates of design guidelines. Cracking behavior of PSC beams are analyzed viz. crack width and crack spacing parameters using Eurocode, CEB-FIP modal code and Moffatt’s modified formulation. It is observed that, as the fiber dosage is increased, corresponding crack widths are reduced in the post-cracking regime

Flexure-Shear Behavior of Hybrid Fiber-Reinforced Prestressed Concrete Beams

This study aims at understanding the effect of hybridization of the steel and synthetic fibers on the flexure-shear behavior of prestressed concrete (PSC) beams. The effect of different fiber reinforcement on the behavior of PSC beams are evaluated in two stages. First, fracture tests were conducted to understand the influence of fibers at the material level. Secondly, full-scale PSC beams were tested for evaluating the effect of hybrid fiber addition on the flexure-shear behavior. The test matrix consists of beams cast with fiber-reinforced concrete (FRC) having fiber dosages of 0.35%, 0.70%, and 1.0% by volume of concrete. All the beam specimens were tested at a shear span-to-depth ratio (a/d) of five under four-point bending configuration. Effect of hybrid fiber addition on the overall load-displacement, load-strain, and strain energy absorption capacity of PSC beams was analyzed. Results of hybrid fiber-reinforced specimens was compared with the results of steel and polyolefin fiber-reinforced beams. The test results portray that the addition of hybrid fibers stiffen the post-cracking response and increases the energy absorption capacity. The failure mode changed from flexure-shear (brittle) to flexure (ductile) mode with the addition of hybrid fibers. Change of failure mode occurred at dosages of 0.35% for steel and hybrid fibers and 0.70% for synthetic (polyolefin) fibers