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Durability Properties and Microstructure of Ground Granulated Blast Furnace Slag Cement Concrete
Bahador Sabet Divsholi,Tze Yang Darren Lim,Susanto Teng 한국콘크리트학회 2014 International Journal of Concrete Structures and M Vol.8 No.2
Ground granulated blast-furnace slag (GGBS) is a green construction material used to produce durable concrete. The secondary pozzolanic reactions can result in reduced pore connectivity; therefore, replacing partial amount of Portland cement (PC) with GGBS can significantly reduce the risk of sulfate attack, alkali?silica reactions and chloride penetration. However, it may also reduce the concrete resistance against carbonation. Due to the time consuming process of concrete carbonation, many researchers have used accelerated carbonation test to shorten the experimental time. However, there are always some uncertainties in the accelerated carbonation test results. Most importantly, the moisture content and moisture profile of the concrete before the carbonation test can significantly affect the test results. In this work, more than 200 samples with various water?cementitious material ratios and various replacement percentages of GGBS were cast. The compressive strength, electrical resistivity, chloride permeability and carbonation tests were conducted. The moisture loss and microstructure of concrete were studied. The partial replacement of PC with GGBS produced considerable improvement on various properties of concrete.
Bahador Bagheri,오상훈,신승훈 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.4
The structural behavior of reinforced concrete coupled shear wall structures is greatly infl uenced by the behavior of their coupling beams. This paper presents a process of the seismic analysis of reinforced concrete coupled shear wall-frame system linked by hysteretic dampers at each fl oor. The hysteretic dampers are located at the middle portion of the linked beams which most of the inelastic damage would be concentrated. This study concerned particularly with wall-frame structures that do not twist. The proposed method, which is based on the energy equilibrium method, off ers an important design method by the result of increasing energy dissipation capacity and reducing damage to the wall’s base. The optimum distribution of yield shear force coeffi cients is to evenly distribute the damage at dampers over the structural height based on the cumulative plastic deformation ratio of the dissipation device. Nonlinear dynamic analysis indicates that, with a proper set of damping parameters, the wall’s dynamic responses can be well controlled. Finally, based on the total plastic strain energy and its trend through the height of the buildings, a prediction equation is suggested.
Bahador Karami,Saeed Khodabakhshi,Niloofar Safikhani,Afsaneh Arami 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.1
A facile and simple procedure for the synthesis of novel and known calix[4]resorcinarene derivatives were developed via a reaction of arylaldehydes with resorcinol in the presence of catalytic amounts of tungstate sulfuric acid (TSA) under solvent-free conditions. This eco-friendly method has many appealing attributes,such as excellent yields, short reactions times, use of safe and recoverable catalyst, and simple work-up procedures. TSA was characterized by powdered X-ray diffraction (XRD), X-ray fluorescence (XRF) and FTIR spectroscopy.
Bahador Bagheri,최광용,오상훈,유홍식 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.1
This study represents a summary of a current experimental program in the application of an energy dissipation system for seismic protection of structures. Shaking table test has been carried out for the structures with and without a hysteretic damper device for two types of structures in one direction (CBSS: Concentrically Braced Steel Structure, HDSS: Hysteretic Damper Steel structure). The hysteretic damper device which is proposed in this study has been developed to provide relatively high initial stiffness, stable hysteresis with the limited but controlled yield strength in different stories in order to have equal plastic deformation in high intensity of ground motion, and excellent energy dissipation capabilities. The experimental results and test method have been outlined here. In this experiment, the non-linear dynamic response analysis has been performed with different scaling factor for the two types of idealized three-story concentrically braced steel structures. It has been emphasized that the hysteretic damper can absorb the majority of input energy from earthquakes in order to reduce the displacement and damage to the main steel frame. The mechanical properties of dampers such as yield strength and stiffness are defined to have the equal damage at each story.
Bahador Bagheri,오상훈 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.1
In coupled shear wall systems, the excessive shear forces are induced in the coupling beams. As a result, in such systems, the coupling beam and the joint of wall-coupling may yield first. The critical concern about the coupling beam is ductility demand. In order to have such ductility, the coupling beams are required to be properly detailed with significantly complicated reinforcement arrangement and insignificant strength degradation during ground motion. To solve these problems and to increase energy dissipating capacities, this study presents an investigation of the seismic behavior of coupled shear wall-frame system, in which energy dissipation devices are located at the middle portion of the linked beam. The proposed method, which is based on the energy equilibrium method, offers an important design method by the result of increasing energy dissipation capacity and reducing damage to the structure. The design procedure was prescribed and discussed in details. Nonlinear dynamic analysis indicates that, with a proper set of damping parameters, the wall’s dynamic responses can be well controlled. Thereafter, an optimized formula is proposed to calculate the distribution of the yield shear force coefficients of energy dissipation devices. Thereby, distributing equal damages through different heights of a building as well as considering the permissible damage at the wall’s base. Finally, numerical examples demonstrate the applicability of the proposed methods.