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Conceptual configuration and seismic performance of high-rise steel braced frame
Shengfang Qiao,Xiaolei Han,Kemin Zhou,Weichen Li 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.2
Conceptual configuration and seismic performance of high-rise steel frame-brace structure are studied. First, the topology optimization problem of minimum volume based on truss-like material model under earthquake action is presented, which is solved by full-stress method. Further, conceptual configurations of 20-storey and 40-storey steel frame-brace structure are formed. Next, the 40-storeystructure model is developed in Opensees. Two common configurations are utilized for comparison. Last, seismic performance of 40-storey structure is derived using nonlinear static analysis and nonlinear dynamic analysis. Results indicate that structural lateral stiffness and maximum roof displacement can be improved using brace. Meanwhile seismic damage can also be decreased. Moreover, frame-brace structure using topology optimization is most favorable to enhance lateral stiffness and mitigate seismic damage. Thus, topology optimization is an available way to form initial conceptual configuration in high-rise steel frame-brace structure.
Seismic analysis of steel structure with brace configuration using topology optimization
Shengfang Qiao,Kemin Zhou,Jing Ji,Xiaolei Han 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.3
Seismic analysis for steel frame structure with brace configuration using topology optimization based on truss-like material model is studied. The initial design domain for topology optimization is determined according to original steel frame structure and filled with truss-like members. Hence the initial truss-like continuum is established. The densities and orientation of truss-like members at any point are taken as design variables in finite element analysis. The topology optimization problem of least-weight truss-like continuum with stress constraints is solved. The orientations and densities of members in truss-like continuum are optimized and updated by fully-stressed criterion in every iteration. The optimized truss-like continuum is founded after finite element analysis is finished. The optimal bracing system is established based on optimized truss-like continuum without numerical instability. Seismic performance for steel frame structures is derived using dynamic time-history analysis. A numerical example shows the advantage for frame structures with brace configuration using topology optimization in seismic performance.
Topology optimization of reinforced concrete structure using composite truss-like model
Yang Zhiyi,Zhou Kemin,Qiao Shengfang 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.1
Topology optimization of steel and concrete composite based on truss-like material model is studied in this paper. First, the initial design domain is filled with concrete, and the steel is distributed in it. The problem of topology optimization is to minimize the volume of steel material and solved by full stress method. Then the optimized steel and concrete composite truss-like continuum is obtained. Finally, the distribution of steel material is determined based on the optimized truss-like continuum. Several numerical results indicate the numerical instability and rough boundary are settled. And more details of manufacture and construction can be presented based on the truss-like material model. Hence, the truss-like material model of steel and concrete is efficient to establish the distribution of steel material in concrete.
Lee, Philah,Raj, Subramanian Mohan,Zhou, Shengfang,Ashok, Somasundar,Edwardraja, Selvakumar,Park, Sunghoon 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.1
This study examined the role and physiological relevance of 3-hydroxyisobutyrate dehydrogenase-I (3HIBDH-I) of Pseudomonas denitrificans ATCC 13867 in the degradation of 3-hydroxypropionic acid (3-HP) during 3-HP production. The gene encoding 3HIBDH-I of P. denitrificans ATCC 13867 was cloned and expressed in Escherichia coli BL21 (DE3). The recombinant 3HIBDH-I was then purified on a Ni-NTA-HP column and characterized for its choice of substrates, cofactors, metals, reductants, and the optimal temperature and pH. The recombinant 3HIBDH-I showed a high catalytic constant ($k_{cat}/K_m$) of $604.1{\pm}71.1$ mM/S on (S)-3-hydroxyisobutyrate, but no detectable activity on (R)-3-hydroxyisobutyrate. 3HIBDH-I preferred $NAD^+$ over $NADP^+$ as a cofactor for its catalytic activity. The $k_{cat}/K_m$ determined for 3-HP was $15.40{\pm}1.43$ mM/S in the presence of $NAD^+$ at $37^{\circ}C$ and pH 9.0. In addition to (S)-3-hydroxyisobutyrate and 3-HP, 3HIBDH-I utilized L-serine, methyl-D,L-serine, and methyl-(S)-(+)-3-hydroxy-2-methylpropionate; on the other hand, the kcat/Km values determined for these substrates were less than 5.0mM/S. Ethylenediaminetetraacetic acid, 2-mercaptoethanol, dithiothreitol and $Mn^{2+}$ increased the activity of 3HIBDHI significantly, whereas the presence of $Fe^{2+}$, $Hg^{2+}$ and $Ag^+$ in the reaction mixture at 1.0 mM completely inhibited its activity. This study revealed the characteristics of 3HIBDH-I and its significance in 3-HP degradation.