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Volume 10, Number 3, Septmber 2021

(1) Civil Engineering Department, University of Tiaret, Algeria; (2) Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria.This research presents a careful theoretical investigation on interfacial stresses in damaged porous RC cantilever beams strengthened with externally bonded composite plate (several types of composites have been used). The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened cantilever beam, i.e., the damaged porous concrete cantilever beam, the perfect and/or imperfect composite plate and the adhesive layer. The analytical predictions are compared with other existing solutions and which shows a very good agreement of the results. It is shown that both the normal and shear stresses at the interface are influenced by the material and geometry parameters of the composite beam. In the end, I think this research is very useful for understanding the mechanical behavior of the interface and the design of the hybrid structures.

Key Words
composite plate; damaged RC cantilever beam; interfacial stresses; porosity; strengthening

(1) Civil Engineering Department, University of Tiaret, Algeria;
(2) Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria.

This research work describes the design and method of development of microwave absorber and was conducted for analysis of reflection loss performance with the magnetic modifications of Multi-Walled Carbon Nanotubes (MWCNTs). Cobalt coated Multi-Walled Carbon Nanotubes composites were prepared by three step methods. Composites were developed with varying weight percentage of Cobalt (II) Chloride Hexahydrate and Multi-Walled Carbon Nanotubes. The morphology, elementary analysis and absorbing properties of Cobalt coated Multi-Walled Carbon Nanotubes composites were studied by FESEM, EDX and Vector Network Analyzer. The obtained Co coated MWCNTs/PU composite demonstrated the maximum reflection loss of -21.06 dB at 12.63 GHz and the maximum absorption bandwidth of 3.7 GHz, in the frequency range of 8-13 GHz with 3 mm thickness. These microwave absorption parameters can be credited to synergistic effect of improved matched impedance and greater microwave attenuation properties of the absorber. The combined usage of dielectric loss and magnetic loss absorber design shows great diversity and can be a promising candidate for designing high performance microwave absorbing materials.

Key Words
co-precipitation method; electromagnetic; microwave absorption; Multi-Walled Carbon Nanotubes (MWCNTs); reflection loss

Department of Electronics and Communication Engineering, DAV University, Jalandhar-144012, Punjab, India.

Recycled concrete aggregate (RCA) obtained from demolished structures can be used for concrete making, and is established as a promising material in the field of construction. In the present study, the effect of RCA on the mechanical properties of different strength concretes admixed with Micro silica, fly ash and nano-silica as a part replacement to cement was considered. The quantity of cement varied from 350-690 kg/m3 with the additions of Fly ash at 0, 20 and 30%, micro silica at 0, 5, 10 and 15%, and Nano silica at 0, 1, 2, 3 and 4%. The samples were cured for 7, 28, 56 and 90 days and tested for Compressive strength. Split tensile and flexural strength evaluation was carried out on samples which have been cured for 28 days. The workability of fresh concrete was determined. With the help of the tested database, equations for prediction of compressive strength using modified Bolomey's equation were generated. Equations for the flexural strength and split tensile strengths based on compressive strength were developed and compared with equations available in the literature.

Key Words
Bolomey's equation; Construction & Demolition (C&D) waste; fly ash (FA); mechanical properties; Micro silica (SF); Nano silica (NSF)

(1) M.V.S.S. Sastri:
Department of Civil Engineering, Vasavi College of Engineering (A), Ibrahimbagh, Hyderabad, 500 031, Telangana, India;
(2) K. Jagannadha Rao:
Department of Civil Engineering, Chaitanya Bharathi Institute of Technology (A), Hyderabad, 500 075, Telangana, India;
(3) V. Bhikshma:
Department of Civil Engineering, University College of Engineering (A), Osmania University, Hyderabad, 500 007, Telangana, India.

Determining grain-size and grading distribution of river-side sediments is very important for issues related to lateral embankment drift, river-side nourishment, management plans, and riverbank stability. In this regard, experimental procedures such as sieve analysis are used in regular assessments which require special laboratory equipment that are quite time consuming to perform. The presented study provides a machine vision and image processing-based approach for determining coarse grained sediment size and distribution that is relatively quick and effective. In this regard, an image image processing-based method was used to determine the particle size of sediments as justified by screening tests which were conducted on samples taken from the riverside granular sediments. As a methodology, different grain identification stages were applied to extract sediment features such as pre-processing, edge detection, granular size classification and post-processing. According to the results of the grain identification stages, the applied technique identified about 35% sand, 55% gravel and 7% cobble which is approximately near to the screen test results which were determined as 30% sand, 52% gravel, and 5% cobble. These results obtained from computer-based analyses and experiments indicated that the utilised processing technique provided satisfactory results for gradation distribution analysis regarding riverside granular sediments.

Key Words
geotechnics; grading distribution; image processing; particle-size analysis; sediments

(1) Mohammad Azarafza::
Department of Civil Engineering, University of Tabriz, Tabriz, Iran;
(2) Yaser A. Nanehkaran, Yimin Mao:
School of Information Engineering, Jiangxi University of Science and Technology, Ganzhou, Jiangxi, China;
(3) Haluk Akgün:
Geotechnology Unit, Department of Geological Engineering, Middle East Technical University (METU), Ankara, Turkey.

Coupled steel plate shear wall (C-SPSW) is one of the resisting systems with high ductility and energy absorption. Energy dissipation in the C-SPSW system is accomplished by the bending and shear behavior of the link beams and SPSW. Energy dissipation and floor displacement control occur through link beams at low seismic levels, easily replaced after an earthquake. In this study, a coupled steel plate shear wall with a yielding fuse is presented. The system uses a high-ductility fuse pin element instead of a link beam, which has good replaceability after the earthquake. In this study, four models of coupled steel plate shear walls were investigated with I-shaped link beam, Ishaped link beam with reduced beam section (RBS), box-link beam with RBS, and fuse pin element under cyclic loading. The finite element method was used through ABAQUS software to develop the C-SPSW models. To verify the finite element model results, two test specimens of coupled steel plate shear walls were validated. Comparative results of the hysteresis curves obtained from the finite element analysis with the experimental curves indicated that the finite element model offered a good prediction of the hysteresis behavior of C-SPSW. The results of the C-SPSW models revealed that the fuse pin caused an increase in the ultimate capacity by approximately 19% and the energy dissipation by 20% compared to the other C-SPSW.

Key Words
Coupled steel plate shear wall (C-SPSW); energy dissipation; fuse; finite element method

(1) Mahdi Usefvand, Ahmad Maleki:
Department of Civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran;
(2) Babak Alinejad:
Department of Civil Engineering, University of Maragheh, Maragheh, Iran.

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