Behavior of external column- wide beam joint with different bar arrangement and existence of joint shear link under gravity.

An experimental investigation done on the RC exterior wide beam-column joint when subjected to the gravity load up to failure is reported in this paper. This study was conducted by applying the concentrated gravity load on full scaled wide beam-column joints with same area of longitudinal reinforcement to resist for negative moment due to concentrated gravity load. The joints behavior was considered by effect of different layout of beam longitudinal bars, existence of the shear link in connection zone, spandrel bar and width of the beam in terms of failure capacity, crack patterns, deflection and rotation. The results shown that the failure capacity of joints with concentrated longitudinal bars of beam that two-third of bars anchored in the column zone was 24 % higher than even bar distribution. And also the existence of the shear links in connection area and spandrel bar to anchor the longitudinal beam reinforcements that were outside the connection area is higher than the other specimens without them. Moreover, the width of beam played important role to enhance the failure capacity

A Novel Damage Index for Online Monitoring of RC Slabs under Monotonic Loading by Integration of Process Controlling into Acoustic Emission Technique

This study introduces a novel structural health monitoring scheme for cementitious composite slabs with the aid of acoustic emission (AE) technique coupled with statistical process controlling (SPC) method. The adopted framework is an integrated monitoring solution that effectively relates current state (damaged) to reference state of the structure. Evaluation of the latter was made possible using autoregressive model incorporating a set of damage-sensitive feature. In order to provide a benchmark damage indicator, the collected data were processed using control chart analysis. The damage indicators for the former was similarly obtained and then compared with the benchmark to gauge the structural damage. These control charts offer a robust framework meticulously identifying inconsistency in the damage-sensitive feature imposed over the monitoring period. Linear and quadratic projections were also incorporated into SPC model to enhance identification of system transition to other damage states

Failure reliability and damage detection of ferrocement composite slabs

This paper introduces suitable features and methods to define hazard rate function by acoustic emission parameters to develop robust damage statement index and reliability analysis. AE signal energy was first examined to find out relation between damage progress and AE signal energy so that a damage index based on AE signal energy was proposed to quantify progressive damage imposed to composite slabs. Moreover by using AE signal strength, historic index was utilized to develop a modified hazard rate function through integration bathtub curve and Weibull function

Fracture characterization of multi-layer wire mesh rubberized ferrocement composite slabs by means of acoustic emission

This study investigated the fracture behaviour of multi-layer ferrocement composite slabs with partial replacement of tire rubber powder as filler utilizing acoustic emission (AE) technique for characterization. Ferrocement slab specimens prepared using normal-compact cement mortar, self-compact cement mortar, fly ash, and rubberized self-compact cement mortar –with varying steel mesh reinforcement layers– were statically loaded to failure. The inclusion of 10% rubber powder (by weight) was found capable of altering the failure mode of composite slabs from brittle to ductile with a slight reduction in the ultimate flexural strength. Fracture development of the specimens was closely monitored using AE for enhanced characterization. It is seemingly evident that the measured AE parameters could be effectively processed to distinguish different modes of fracture. The collected AE data was utilized to quantify stiffness reduction in the specimens due to progressive damage.No Full Tex

Monitoring Fracture of Steel Corroded Reinforced Concrete Members under Flexure by Acoustic Emission Technique

Acoustic emission (AE) technique is used for monitoring and evaluating the influence of corrosion on the structural behaviour of steel reinforced concrete (RC) beams under three-point flexure test. In this study, steel corrosion was accelerated by electro-chemical method utilising a direct current (DC) power supply and 5% sodium chloride (NaCl) solution. The steel corrosion that was induced into beam specimens casting were estimated at 0%, 4.55% and 32.37%, respectively, according to mass loss of steel reinforcement. Based on observations during static load test, the damage developed in the specimens could be classified into four different stages, namely, micro-cracking, first visible cracks, cracks distribution, as well as damage localization and yielding. Analysis of the AE data reveals distinguishable trends for RA value and average frequency (AF) registered for different corrosion levels, respectively. Moreover, the index of damage (ID) derived from the AE energy parameters obtained during the first stage of damage was found to be useful as an indicator for evaluating the extent of corrosion damage of RC beam specimens at initial loadings. In addition, to provide a practical application of AE toward life span estimation of corroded beam specimen, a Weibull damage function was introduced to estimate the remaining flexural capacity of the beam specimens. Based on analysis as well, it is noted that tensile fracture became more dominant with an increase in corrosion level

Fracture Evaluation of Multi-layered Precast Reinforced Geopolymer-Concrete Composite Beams by Incorporating Acoustic Emission into Mechanical Analysis

In this study, a multi-layered steel reinforced composite beams which are composed of geopolymer concrete section at tensile zone and Portland cement based concrete at compression are investigated. The beams were tested to failure to compare the toughness, post peak behaviour and failure mode based on the variation of the depth of layers. The mechanical analysis incorporated into acoustic emission technique showed that the geopolymer beam endured more deflection than the ordinary Portland cement based beams, however their ultimate load carrying capacities were quite similar. Further, the composite beams, resulted in transition of failure mode of shear to a flexural

Association of urinary bisphenols and triclosan with thyroid function during early pregnancy

© 2019 The Authors. Background Bisphenols and triclosan are considered as potential thyroid disruptors. While mild alterations in maternal thyroid function can result in adverse pregnancy and child developmental outcomes, there is still uncertainty whether bisphenols or triclosan can interfere with thyroid function during pregnancy. Objectives We aimed to investigate the association of urinary bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF) and triclosan with early pregnancy thyroid function. Methods This study was embedded in the Swedish Environmental Longitudinal, Mother and child, Asthma and allergy study (SELMA), a population-based prospective pregnancy cohort. In total, 1996 participants were included in the current study. Maternal urinary concentrations of three bisphenols and triclosan, collected at median (95% range) 10 (6–14) weeks of pregnancy as well as serum concentrations of thyroid stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), total thyroxine (TT4), and total triiodothyronine (TT3) were measured. Results Higher BPA levels were associated with lower TT4 concentrations (non-monotonic, P = 0.03), a lower FT4/FT3 ratio (β [SE] -0.02 [0.01], P = 0.03) and a lower TT4/TT3 ratio (β [SE] -0.73 [0.27], P = 0.008). Higher BPF levels were associated with a higher FT3 (β [SE] 0.01 [0.007], P = 0.04). There were no associations between other bisphenols or triclosan and absolute TSH, (F)T4 or (F)T3 concentrations. The association of BPA with thyroid function differed with gestational age. The negative association of BPA with FT4/FT3 and TT4/TT3 ratios was only apparent in early but not late gestation (P for interaction: 0.003, 0.008, respectively). Conclusion These human data during pregnancy substantiate experimental findings suggesting that BPA could potentially affect thyroid function and deiodinase activities in early gestation.European Union of Medical Specialists; European Union's Horizon 2020 Programme for research; echnological development and demonstration; Swedish Research Council; County Council of Värmland, Swede

Characterization of fracture behavior of concrete structural elements using acoustic emission technique / Arash Behnia

In this study, basically, acoustic emission technique was applied to develop its application in concrete structural members. Four different types of experimental sets were conducted to study the structural concrete members fracture and condition monitoring. The first experiment set was carried out for pure torsion fracture analysis to characterize fracture parameters under pure torsion by means of acoustic emission incorporated with statistical approach (Weibull method). As a first study, the damage Weibull parameters for torsional fracture were calibrated by acoustic emission so that damage probability function was proposed. In the next study, a pattern recognition technique, kernel fuzzy c-means (KFCM), was applied to cluster different damage stages so that a novel damage index called spatial intelligent b-value was proposed to quantify damage in an unsupervised approach. Thereafter, the second experiment was conducted for large scales multi-cells beams subjected to pure torsional loading. The fracture process was qualitatively and qualitatively characterized by means of AE analysis. The third set of experiment aims to study the concrete slab fracture behaviour and provide early warning of occurrence of damage whist the type of failure can be characterized by means of AE. AE could quantify stiffness reduction in composite slabs under concentrated loading other than offering an early warning system. In the next step, by means of statistical process control and autoregressive method a novel structural health monitoring scheme was proposed to detect damage and analyse reliability of failure in composite slabs. The last experiments utilized fiber reinforced concrete beams subjected to flexural loading to investigate the combination of AE with travel time tomography technique to provide a robust global and local technique. Innovatively, global and local structural condition could be evaluated by integration acoustic emission signal strength and velocity of time tomography in a combined plot