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Performance of Low-yield Strength Plates in Beam-column Connections against Progressive Collapse
Ahmad Karimian,Arastoo Armaghani,Alaeddin Behravesh 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.1
In many studies about progressive collapse in steel moment frames, the effect of connections in all of structural frames has not been investigated. This is while the connections can have a significant impact on structure behavior against abnormal loads. This study highlights the effect of mechanical and geometric properties of beam-column connections in steel moment frames against progressive collapse. For this purpose, variable parameters include beam-column connection type (Welded Flange Plate connection or WFP and Welded Unreinforced Flange-Welded web connection or WUF-W), mechanical properties of beam-column connection (St37 building steel and low-yield strength plates) and the column removal location in different stories (without removing column and removing column on the ground, first and second floors). Three-storey steel frames which are designed to withstand earthquakes are examined. Finite element ABAQUS software is used for simulation. Moreover, the alternative load path method in which the structure response is examined against the column removal is used to evaluate steel frames response against progressive collapse. The results show that the use of low-yield strength steel plates depending on connection type can be efficient in improving the behavior of steel moment frames against progressive collapse.
Farnaz Tahmasebi,Mahmood Alimohammadi,Ramin Nabizadeh,Mehdi Khoobi,Kamaledin Karimian,Ahmad Zarei 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.6
We investigated the removal efficiency of humic acid from aqueous solutions by cotton coated with graphene oxide. This research has been conducted as batch on an experimental scale. A self-arrangement approach was introduced in fabrication of the cotton adsorbent coated with graphene oxide. To determine the effect of parameters, including initial concentration, pH, adsorbent dosage and contact time, central composite design (CCD) was employed in response surface method (RSM). The adsorption kinetics were determined based on different times of adsorption of humic acid. Further, the adsorption isotherms were also examined using different concentrations of humic acid. The results obtained showed that with increasing adsorbent dosage and contact time, the removal efficiency increased, while with increasing pH and initial concentration of humic acid, the removal efficiency decreased. The optimal values based on RSM method were obtained as the following: humic acid initial concentration=13.61mg/L, pH=3.87, adsorbent dosage=0.61 g, and contact time=168.43min. Langmuir isotherm with R2=0.9987 has been the most suitable model for explaining the adsorption process. Investigation of the adsorption kinetics indicated that humic acid adsorption follows pseudo-second-order model (R2=0.9822). The results indicated that the cotton adsorbent coated with graphene oxide has a good potential for removal of humic acid from aqueous solutions. Mechanical flexibility, availability, and low operational energy costs are among the advantages of this method for fabrication of this adsorbent, which can be developed and used for reducing environmental contaminants.