Effect of construction joints on the splitting tensile strength of concrete

AbstractThe purpose of this study is to experimentally correlate the compressive strength (f′c) of concrete to the splitting tensile strength (T) for plain concrete in the existence of a construction joint, and formulate an empirical equation relating T to f′c. Both the American Concrete Institute code (ACI 318-08 (ACI Committee 318, 2008)) and the American Society for Testing and Materials (ASTM (ASTM Standard C496, 2002; ASTM Standard C192/C192M, 2002; ASTM Standard C39/C39M, 2005; ASTM Standard C617, 2002)) provide the testing methods and standards, as well as the applicable theoretical and experimental formulas for the correlation between T to f′c for concrete specimens, which are monolithic, indicating that the specimens lack any construction joints. Providing a useful reduction factor in the splitting tensile strength of concrete due the existence of a construction joint is essential. It is a well known fact that construction joints are used in every concrete structure, which indicates that engineers would definitely benefit from an equation that could relate the splitting tensile strength of concrete in function of its compressive strength.The results suggest that the reduction in the splitting tensile strength in the presence of a construction joint is not as much as most engineers tend to believe. Due to that belief, most engineers tend to overdesign for steel reinforcement at those joints to compensate for this reduction. The objective of the study is to better the understanding of the effects of a construction joint on the splitting tensile strength. Thus provide an empirical equation to assist engineers in their design calculations, therefore reducing the amount of steel reinforcement at the construction joints. Thus also leading to cost saving on projects

Numerical and Experimental Study of Impulsive Sound Attenuation of an Earmuff

This work compares the results of laboratory experiments with numerical modelling using the finite element method in order to assess the attenuation of hearing protectors under conditions of high amplitude impulse noise. Comparative data for the finite element simulation was provided from a series of experiments using a shock tube, acoustic test fixture, ear canal simulator and partial head form. The numerical model comprised a finite element mesh of fluid and porous materials in order to model the earmuff hearing protector coupled to the auditory canal. The results show that a simple 2-D finite element model is capable of making a reasonable prediction of the attenuation of an earmuff provided that headband force is also included in the model

Determination of the Noise Attenuation of Hearing Protectors by Numerical Modeling of the Outer Ear

ABSTRACT: This paper addresses the important practical issues of hearing protectors used in industry to protect the workers from high noise levels. Comments on the difficulties in measuring hearing protectors noise attenuation is discussed. A new work is presented on the numerical modeling of the outer ear canal as a straight tub, considering eardrum acoustic impedance, using finite elements (FEM), for the quantification of noise attenuation is presented. This numerical model can serve as a quick and low cost tool for the optimization of the protector project and the investigation of the effect of different parameters such as protector insertion, effect of leakage, materials, and others on the protector noise attenuation

Flow ripple reduction in power steering hydraulic pumps

Noise in hydraulic power steering systems is mainly generated by the hydraulic pump due to the cyclic pumping mechanism that creates pulsating flow transmitted by the fluid. This flow ripple and pressure ripple, propagating through the hydraulic circuit, interacts in a complex way with the other parts of the vehicle, generating audible noise inside the vehicle. The present work shows two ways to reduce the flow ripple amplitude generated by a vane pump through the redesigning of the pump rotating group. First, a nine-vane rotor pump is proposed and, secondly, a pump with three discharge ports is proposed. To check their results, a MatLab/Simulink based pump model was created according to the new geometrical characteristics and the results are compared with the regular pump ones. Also, a flow ripple experimental test was run using the Secondary Source Method to validate the numerical model results of the regular pump. The new designs simulation results show large flow ripple amplitude reduction (from 6dB to 16dB per harmonic) as well as frequency displacement in the discharge flow ripple spectra in both designs. Also, the simulations show perpendicular force on the pump shaft generated by the non-balanced conditions created by the new designs

Dual role of the exocyst in AMPA receptor targeting and insertion into the postsynaptic membrane

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102104/1/emboj7601065.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/102104/2/emboj7601065-sup-0001.pd

Understanding Russia's return to the Middle East

Over recent years, there has been a significant resurgence of Russian power and influence in the Middle East, which has been evident in the diplomatic and military intervention into Syria. This article identifies the principal factors behind Russia’s return to the region. First, there are domestic political influences with the coincidence of the uprisings in the Middle East, the so-called ‘Arab Spring,’ with large-scale domestic opposition protests within Russia during the elections in 2011–2012. Second, there is the role of ideas, most notably the growing anti-Westernism in Putin’s third presidential term, along with Russia’s own struggle against Islamist terrorism. These ideational factors contributed to Russia’s resolve to support the Assad government against both Western intervention and its domestic Islamist opposition. Third, Russia has benefited from a pragmatic and flexible approach in its engagement with the region. Moscow seeks to ensure that it is a critical actor for all the various states and political movements in the Middle East

Broadly neutralizing antibodies abrogate established hepatitis C virus infection

In most exposed individuals, hepatitis C virus (HCV) establishes a chronic infection; this long-term infection in turn contributes to the development of liver diseases such as cirrhosis and hepatocellular carcinoma. The role of antibodies directed against HCV in disease progression is poorly understood. Neutralizing antibodies (nAbs) can prevent HCV infection in vitro and in animal models. However, the effects of nAbs on an established HCV infection are unclear. We demonstrate that three broadly nAbs—AR3A, AR3B, and AR4A—delivered with adeno-associated viral vectors can confer protection against viral challenge in humanized mice. Furthermore, we provide evidence that nAbs can abrogate an ongoing HCV infection in primary hepatocyte cultures and in a human liver chimeric mouse model. These results showcase a therapeutic approach to interfere with HCV infection by exploiting a previously unappreciated need for HCV to continuously infect new hepatocytes to sustain a chronic infection

Statistical evaluation of a new resistance model for cold-formed stainless steel cross-sections subjected to web crippling

This paper presents a statistical evaluation according to Annex D of EN 1990 (2002) of a new resistance function for web crippling design of cold-formed stainless steel cross-sections. This resistance function was derived by Bock et al. (2013) through the use of carefully validated numerical models with the aim to propose a design expression for stainless steel sections, which are currently designed following the provisions for cold-formed carbon steel sections given in EN 1993-1-3 (2006). Although it was shown that the proposed design equation is appropriate for application to various stainless steels, the statistical uncertainties in material properties that the different types of stainless steels exhibit require an assessment of various partial safety factors. The statistical assessment showed that the proposed resistance function by Bock et al. (2013) requires adjustment to satisfy the safety level set out in EN 1993-1-4 (2006); A recalibration is performed herein. The web crippling design provisions given in EN 1993-1-3 (2006) and SEI/ASCE 8-02 (2002) American standard for application to stainless steel are also statistically evaluated herein. Comparison with test and numerical data showed that the predictions of the recalibrated resistance function are better suited and consistent than existing design provisionsResearch Fund for Coal and Stee