Characterization of smart brass fiber reinforced concrete under various loading conditions

Self-sensing smart cementitious materials can enable development of load carrying structural systems with an intrinsic condition monitoring system. This paper discusses extensive experimental tests conducted on the brass fiber reinforced concrete composites that incorporates coarse aggregates. First, compressive and split tensile tests were conducted to assess strain sensitivity of the developed smart concrete. In addition, notch bending tests were performed to evaluate ability of the developed concrete in crack or damage sensing. Furthermore, the influence of different parameters such as loading rate, cyclic loading, electrode type, current type, and specimen age on the compressive strain sensitivity of smart concrete was assessed. The governing mechanisms for the self-sensing during the split tensile test and notched bending tests were described. Results indicate that the developed smart concrete with lowcost brass fibers exhibits high compressive strain sensitivity both under monotonic and cyclic loading conditions. The gage factor under compressive loading ranged from 20 to 54 at different loading rates. In addition, a gage factor of 3 was observed under tensile loading. Smart concrete also revealed a very strong correlation between the crack length and change in the electrical resistivity during notched bending tests. These findings suggest that the developed smart concrete can be used as a loading bearing multifunctional material that can sense its own damage and strain. (C) 2020 Elsevier Ltd. All rights reserved

Strain sensitivity of steel-fiber-reinforced industrial smart concrete

Self-sensing cementitious composites can enable structures that are capable of carrying the loads applied on them while monitoring their condition. Most of earlier research has focused on the incorporation of nanofillers or microfibers into cement paste or mortar composites. However, there have been very limited number of studies on the development of steel-fiber-reinforced cementitious composites with self-sensing capabilities. This study explores strain sensitivity of concrete mixtures that include coarse aggregates up to 15 mm diameter and steel fibers with a length of 13 mm and a diameter of 0.25 mm. Five different concrete mixtures with steel fibers at 0%, 0.2%, 0.35%, 0.5%, and 0.8% volume ratios were fabricated. Compression tests with simultaneous measurement of strain and electrical resistance were conducted on the cubic specimens. Gauge factor and percent linearity that is a measure of error in strain sensing were calculated. Concrete mixtures with 0.5% steel fibers possess a strong linear relationship between applied strain and electrical resistance change with a gauge factor over 20 times larger than that of traditional metal strain gauges. Phenomenological models for different resistivity and gauge factors of cement paste/mortar with respect to concrete with large aggregates and short-long fiber cement composites were presented

Cross tension and compression loading and large-scale testing of strain and damage sensing smart concrete

Multifunctional self-sensing smart concrete can provide a structural health monitoring (SHM) solution that is robust, reliable, and low-cost. Smart concrete, which includes coarse aggregates with 15 mm size, brass fibers, silica fume, superplasticizer and water, has been developed as a promising multifunctional material. The normal and cross compression and split tensile tests were conducted on 75 mm cube samples; large scale compression test was conducted on 15 x 15 x 30 cm prism; large scale bending tests were applied to prisms with sizes 15 x 15 x 75 cm and 15 x 30 x 150 cm. The normal and cross compressive strain gage factors were 54 and 59 while linearities were 6.6% and 7%, respectively. Normal and cross tensile strain gage factors were 3.0 and 2.9 while corresponding linearities were 6.6% and 13%. As the sample size increased, the electrical resistivity increased and strain sensitivity decreased due to obstruction of electrons by aggregates that revealed a "size effect" for piezoresistivity of smart concrete. Large scale bending test results verified the piezoresistivity of smart concrete while crack formation and propagation increased the electrical resistance dramatically. Smart concrete can be utilized to monitor both strain and damage

Ectopic spleen and left-sided vena cava in Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome (BWS) is a congenital overgrowth syndrome characterized by anterior abdominal wall defects, macroglossia, and gigantism. A variety of other abnormalities have been described, however association with ectopic spleen and left-sided vena cava has not been reported previously. We report ectopic spleen, left-sided vena cava and the other abdominal imaging findings of an adult BWS case who came up to date without any follow-up from the early childhood. (C) 2002 Elsevier Science Ltd. All rights reserved

A Multidisciplinary Approach for the Assessment of Great Historical Structures: Ties of ???Duomo di Milano???

An investigation methodology, based on a scientific approach for historical structures, has been applied to the case study of the Duomo di Milano. In particular, a continuous process of data acquisition, analysis of structural behaviour, diagnosis and safety evaluation is followed with the aim of assessing metallic ties present in the Cathedral. Different techniques and fields of expertise were used for data acquisition: historical investigation gave important information on the ties origin, their structural purpose and the construction process of the Cathedral; the wide experimental campaign included visual inspection, material characterization, and dynamic tests on the original ties and contributed to the understanding of the structural system. The main results and considerations from such a multidisciplinary investigation are presented in the paper, providing a reference from a real case-study. Relevant aspects for the study of the Cathedral’s structural behaviour are addressed, various approaches to be used are proposed, such as limit analysis or Finite Element Modelling (FEM) and their benefits are outlined. These models, once validated through the prediction of past and present states of the structure, will be used during diagnosis and safety evaluation to predict the future behaviour, or identify potential causes of eventual observed damage, as well as to evaluate the current state of the stress in ties measured with a more refined Non-destructive testing (NDT) approach