Mechanical properties of high-strength steel–polyvinyl alcohol hybrid fibre engineered cementitious composites

With the advancement of material technology, the use of high-strength and high-performance materials in the construction industry is gaining popularity. Steel–polyvinyl alcohol (steel–PVA) hybrid fibre engineered cementitious composites (ECC) is one of such high-performance class of construction materials whose mechanical properties are not well studied in the literature especially in high-strength matrix. Therefore, in this paper, the mechanical properties of four different grades of high-strength steel–PVA ECC are experimentally investigated. ECC with nominal compressive strengths from 60 to 100 MPa are developed. Their mechanical properties including compressive and tensile stress–strain behaviour, elastic modulus and toughness are studied with particular focus on high-strength matrix. Test results show that the developed steel–PVA ECC could achieve good tensile (~0.8%) and compressive (~0.5%) ductility for general structural applications. Simple empirical relationships to predict the elastic modulus and tensile strength of the developed steel–PVA ECC as a function of their compressive strength are suggested. Moreover, an analytical model to generate a complete compressive stress–strain curve of the high-strength steel–PVA ECC is proposed and verified against the experimental results. The proposed stress–strain model would present a useful reference for non-linear analysis of structural elements utilising steel–PVA ECC

Compressive behaviour of engineered cementitious composites and concrete encased steel composite columns

This paper presents the results of an experimental study on the compressive behaviour of engineered cementitious composites and concrete encased steel (ECC-CES) composite columns. Two configurations of ECC-CES composite columns based on fully and partially concrete encasement were considered. A total of eleven short columns with different ECC and concrete encasing configurations were tested under pure compression. The effects of ECC strength, concrete strength and column configuration on the column compressive behaviour were investigated and reported in terms of failure modes, load-deformation curves, ductility and toughness. In addition, in order to study the confinement effect of different thickness ECC covers on high strength concrete (HSC), three ECC encased HSC short columns without encased steel section were also tested. The experimental results were compared with the ultimate strength predictions from different design codes for the tested columns. It was found that current design guidelines were generally conservative. Therefore, new equations with modified factors to predict the ultimate strength of ECC-CES columns were proposed. Finally, a comparison of performance of ECC-CES with conventional CES columns suggested that the ECC encasement could provide an alternative way to confine concrete core in columns applications

Compressive performance of ECC-concrete encased high strength steel composite columns

The use of high strength steel (HSS) in the construction of concrete encased steel (CES) composite columns is often limited by the strain incompatibility issue between HSS and concrete at peak-load. This study proposes an alternative approach to confine the high strength concrete with Engineered Cementitious Composite (ECC) to improve its compatibility with high strength steel. The main purpose of this study is to experimentally evaluate the axial compressive performance of the proposed composite column cross-section configuration. Behaviours of fifteen short columns including twelve ECC-CES columns are investigated in terms of failure modes, load-deformation curves, ductility and energy absorption capacity. The test parameters included ECC and concrete strengths, ECC cover thickness, steel section shape and column section's aspect ratio. It was found that ECC generally improved the failure behaviour of high strength steel CES columns and increased the deformation and energy absorption capacity. On average ECC-CES columns showed around 12% and 8% higher ductility and toughness than control concrete column, respectively. A detailed 3D nonlinear finite element model was developed and validated against experimental results. Applicability of current design codes to predict the ultimate strength of ECC-CES columns was also evaluated. Finally, a method to calculate the ECC-CES column's capacity considering effective material stresses at peak-load was proposed

Engineered cementitious composites (ECC) encased concrete-steel composite stub columns under concentric compression

This paper presents an experimental investigation on the behaviour of a new form of engineered cementitious composites (ECC) encased concrete-steel composite stub columns. The proposed column section uses ECC encasement as a potential confinement layer to control the premature concrete spalling and explosive brittle failure of concrete encased steel composite columns. In this study, twelve stub columns including two bare steel and ten composite sections are tested under concentric compression. The effects of some key parameters such as material strengths, steel section type and column section configuration on the performance of proposed column sections were investigated in terms of failure behaviour, load deformation response, toughness and ductility. It was found that ECC encasement improved the compressive failure behaviour of encased composite columns and enhanced their ductility and toughness. Strain analysis was performed to trace the strain development and damage patterns of different materials. Finally, a simple equation to estimate ultimate strength of proposed columns was proposed which gave good predictions agreed well with test results

Characterization of Hilly Chickens in Consideration of Climate Change Factors: Light and Heat

ABSTRACT Hilly chickens were characterized from January 2015 to September 2016 considering climate factors (light and heat). The experimental birds were divided into three groups (heat stress; light and control). The heat was generated in the chicken’s shelter by a black shaded light (Lantern) for two to three hours more after sunset. A lighting device (Lantern) was kept in the chicken’s shelter for the same period for increasing daylight duration. The individual chicken’s egg production, egg weight and mature live weight were studied from onset of egg production. It was observed that reddish brown hilly type chicken produced more (100.80 no/year/chicken) and larger sized (43.21g) eggs than spotted chicken (83.4 no/year/chicken and 40.46g). Among the three treatments, the lighting group produced 7.71 and 5.60 more eggs than the control and heat stress group, and one hour lighting lengths increased egg production 4 to 5.8%. Fifty-five blood samples were collected, and DNA was isolated from whole blood. For genetic characterization, 10 microsatellites markers from FAO recommendation list were used in this study. PCR amplification was performed in an MJ PTC-200 Peltier Thermal Cycler. The gene flow among breeds and genetic differentiation was assessed by computing between-breed genetic parameters: molecular co-ancestry (fij). It was found that genetic diversity of these two types of chickens was moderate. Results indicated that they were originated from the same ancestor. Therefore, priority should be given for implementation of appropriate breeding programme and strategies are necessary to avoid loss of genetic diversity