The main objective of this study was to assess the performance of concrete containing recycled springs with various volume fractions of 0·2, 0·4 and 0·6% at temperatures of 25, 100, 250, 500, 700 and 900°C. In addition, a comparison between concrete mixes containing steel and polypropylene fibres was performed using tensile and compressive strength tests to attain an optimum mix design. The results showed that the compressive and tensile strengths of concrete specimens were improved by adding the percentages of 0·2, 0·4 and 0·6% springs. However, these strengths decreased by increasing the volume fraction of springs. Furthermore, the optimal compressive strength of concrete containing springs was 2–3 times greater than that of concrete containing steel and polypropylene fibres at various temperatures, but there was no significant difference between the tensile strengths of concrete containing springs and steel fibres. In addition, the use of fibre in concrete caused a decrease in the width of the cracks created after the splitting tensile test, by up to three times.

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The technical and economic advantages of porous concrete pavement have drawn the attention of many researchers. Accordingly, in this study, the effects of cement replacement (10 and 20 %) by pozzolanic materials such as silica fume, zeolite, fly ash, and granulated blast-furnace slag (GBFS) on the performance of porous concrete was evaluated by conducting compressive and tensile strength as well as water absorption tests at the ages of 7 and 28 days. To conduct the strength tests, cylindrical and cubic specimens were built with dimensions of 100 by 200 mm and 100 by 100 by 100 mm, respectively. Based on the results, application of silica fume and GBFS managed to improve the compressive and tensile strengths by 60 and 300 %, respectively. Moreover, the inclusion of zeolite, fly ash, and GBFS enhanced the specimen’s water absorption and stood at fair and good ranking provided by the International System of Unified Standard Codes of Practice for Structures (CEB-FIP) standard.

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This paper studies the impact of temperature rise on the performance of Concrete-Filled Double Skin Tubular Steel Columns with prismatic geometry. In doing so, several columns whose interior cores were square, diamond, and circularly shaped and whose exterior cores were prismatic with a square cross-sectional area that increases with the slope of 2.1 degrees from top to the bottom, were constructed and exposed to the temperatures of 25°C, 250°C, 500°C, and 700°C. Afterward, all column specimens were subjected to cyclic loads adopted from the Applied Technology Council (ATC)-24 loading protocol, which proceeded until the specimens failed to further carry loads. The results indicate that although the failure modes of the columns with an interior core of a square or diamond shape are similar to each other, the columns whose interior cores were circularly shaped experienced more intensive damages compared to the others. The base of the columns was fractured diagonally with a degree of 45 by the temperature of 500°C, but at 700°C, the damages have occurred horizontally at the height of 10 cm from the column base. Moreover, the initial stiffness and ductility ratio of the columns with a diamond-shaped interior core was approximately two times greater than the other columns.

Earthquake-resistant structure systems should be designed to stand large deformation to absorb and attenuate imposed energy due to an earthquake while providing sufficient stiffness to transfer the forces to the base without collapse. Knee Braced Frames (KBF), which involves added additional diagonal elements to a frame to increase its ability to withstand lateral loads, is suggested by several researches. In this study, the seismic performance of KBFs are evaluated and compared with Eccentric Braced Frames (EBF). Nonlinear static analyses were utilized for seismic evaluation and comparison between the mentioned frame systems. Three steel structures of 5, 10, and 15-story were numerically modeled, and the seismic parameters such as lateral stiffness, inter-story drift, ductility, and response modification factors were calculated for each structure system. It was observed that using KBF systems resulted in a reduction in intersotry drifts compared to EBFs. KBF systems show more stiff responses in comparison with EBFs and they presented much more stiff response by reducing the knee element length. The KBFs have more ductile behavior in comparison with EBFs, although base shear in KBFs is less than EBFs.

Underlying fabrics can change the appearance, function and quality of the garment, and also add so much longevity of the garment. Nowadays, with the increasing use of various types of fabrics in the garment industry, their resistance to bagging is of great importance with the aim of determining the effectiveness of textiles under various forces. The current paper investigated the effect of underlying on the bagging behavior of denim fabrics. The experiments carried out on four different denim fabrics as the main components including cotton, polyester and lycra, as well as three types of adhesive interlining and three common lining as the underlying components. The adhesive interlining was added to the fabric by using a fusing machine, and the lining was sewn to the fabric. The bagging behavior was assessed by extraction of the residual bagging height using the image processing method and the bagging fatigue percentage by stress-strain diagram. The results showed that with the addition of adhesive interlining and lining to the fabric, the bagging fatigue percentage increased. The lining sewn to the fabric reduced the residual bagging height. Also, the friction between the face fabric and the lining was an important factor that, the bagging fatigue percentage increased with increasing the friction, regardless of the fabric material.

In this article, the effect of multiwalled carbon nanotubes on the properties of concrete was evaluated in the postheat-treated condition. For this, a number of cylindrical specimens (10 by 20 cm), including multiwalled carbon nanotubes in different percentages of 0.5, 1, and 1.5 % by weight of cement, were cast. Then, the concrete specimens were exposed to temperatures of 25°C, 100°C, 250°C, 500°C, and 700°C in an electric furnace, and after they cooled down, compressive and tensile strength tests were carried out on them. The results show that by increasing the number of multiwalled carbon nanotubes in concrete, the compressive and tensile strengths of concrete increase up to 138 and 88 %, respectively. In addition, the dissipation of energy and modulus of elasticity of the concrete specimens were up to two times greater than those of the control specimens. The scanning electron microscope test results indicated that a strong bond between concrete particles exists at room temperature and above.