Partitioned analysis of nonlinear soil-structure interaction using iterative coupling

Jahromi, H. Zolghadr,Izzuddin, B.A.,Zdravkovic, L. Techno-Press 2008 Interaction and multiscale mechanics Vol.1 No.1

This paper investigates the modelling of coupled soil-structure interaction problems by domain decomposition techniques. It is assumed that the soil-structure system is physically partitioned into soil and structure subdomains, which are independently modelled. Coupling of the separately modelled partitioned subdomains is undertaken with various algorithms based on the sequential iterative Dirichlet-Neumann sub-structuring method, which ensures compatibility and equilibrium at the interface boundaries of the subdomains. A number of mathematical and computational characteristics of the coupling algorithms, including the convergence conditions and choice of algorithmic parameters leading to enhanced convergence of the iterative method, are discussed. Based on the presented coupling algorithms a simulation environment, utilizing discipline-oriented solvers for nonlinear structural and geotechnical analysis, is developed which is used here to demonstrate the performance characteristics and benefits of various algorithms. Finally, the developed tool is used in a case study involving nonlinear soil-structure interaction analysis between a plane frame and soil subjected to ground excavation. This study highlights the relative performance of the various considered coupling algorithms in modelling real soil-structure interaction problems, in which nonlinearity arises in both the structure and the soil, and leads to important conclusions regarding their adequacy for such problems as well as the prospects for further enhancements.

A new PSRO algorithm for frequency constraint truss shape and size optimization

Kaveh, A.,Zolghadr, A. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.3

In this paper a new particle swarm ray optimization algorithm is proposed for truss shape and size optimization with natural frequency constraints. These problems are believed to represent nonlinear and non-convex search spaces with several local optima and therefore are suitable for examining the capabilities of new algorithms. The proposed algorithm can be viewed as a hybridization of Particle Swarm Optimization (PSO) and the recently proposed Ray Optimization (RO) algorithms. In fact the exploration capabilities of the PSO are tried to be promoted using some concepts of the RO. Five numerical examples are examined in order to inspect the viability of the proposed algorithm. The results are compared with those of the PSO and some other existing algorithms. It is shown that the proposed algorithm obtains lighter structures in comparison to other methods most of the time. As will be discussed, the algorithm's performance can be attributed to its appropriate exploration/exploitation balance.

A new PSRO algorithm for frequency constraint truss shape and size optimization

A. Kaveh,A. Zolghadr 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.3

In this paper a new particle swarm ray optimization algorithm is proposed for truss shape and size optimization with natural frequency constraints. These problems are believed to represent nonlinear and non-convex search spaces with several local optima and therefore are suitable for examining the capabilities of new algorithms. The proposed algorithm can be viewed as a hybridization of Particle Swarm Optimization (PSO) and the recently proposed Ray Optimization (RO) algorithms. In fact the exploration capabilities of the PSO are tried to be promoted using some concepts of the RO. Five numerical examples are examined in order to inspect the viability of the proposed algorithm. The results are compared with those of the PSO and some other existing algorithms. It is shown that the proposed algorithm obtains lighter structures in comparison to other methods most of the time. As will be discussed, the algorithm's performance can be attributed to its appropriate exploration/exploitation balance.

Optimal analysis and design of large-scale domes with frequency constraints

A. Kaveh,A. Zolghadr 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.4

Structural optimization involves a large number of structural analyses. When optimizing large structures, these analyses require a considerable amount of computational time and effort. However, there are specific types of structure for which the results of the analysis can be achieved in a much simpler and quicker way thanks to their special repetitive patterns. In this paper, frequency constraint optimization of cyclically repeated space trusses is considered. An efficient technique is used to decompose the large initial eigenproblem into several smaller ones and thus to decrease the required computational time significantly. Some examples are presented in order to illustrate the efficiency of the presented method.

Interfacial resistance in CO2-normal alkane and N2-normal alkane systems: An experimental and modeling investigation

Fatemeh Nikkhou,Peyman Keshavarz,Shahab Ayatollahi,Ali Zolghadr 한국화학공학회 2015 Korean Journal of Chemical Engineering Vol.32 No.2

Gas-liquid systems are one of the most common systems which appear in hydrocarbon reservoirs; therefore,the investigation of the interfacial properties and effect of temperature and pressure on these systems is crucial foroptimizing the plan of production. In this study, interfacial resistances for N2-alkane and CO2-alkane systems were estimatedat different pressures and temperatures. A model was developed to calculate interfacial resistance using the equilibriumand dynamic interfacial tension data which were measured by pendant drop technique at different pressuresand temperatures. Interfacial resistances were estimated for a temperature range from 313 to 393 K and pressures from0.34 to 41.7MPa. The results showed that interfacial resistance in N2-alkane and CO2-alkane systems decreased athigher pressure. Moreover, In N2-alkane systems, the interfacial resistance decreases as the temperature increases; however,in CO2-alkane system the interfacial resistance depends on the diffusion and solubility interactions; it will decrease,increase or remain constant.

Dendrosomal Curcumin Inhibits Metastatic Potential of Human SW480 Colon Cancer Cells through Down-regulation of Claudin1, Zeb1 and Hef1-1 Gene Expression

Esmatabadi, Mohammad Javad Dehghan,Farhangi, Baharak,Safari, Zahra,Kazerooni, Hanif,Shirzad, Hadi,Zolghadr, Fatemeh,Sadeghizadeh, Majid Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.6

Colon cancer is one of the leading causes of cancer-associated death worldwide. The prognosis for advanced colorectal cancers remains dismal, mainly due to the propensity for metastatic progression. Accordingly, there is a need for effective anti-metastasis therapeutic agents. Since a great body of research has indicated anticancer effects for curcumin, we investigated the effects of dendrosomal curcumin (DNC) on cellular migration and adhesion of human SW480 cells and possible molecular mechanisms involved. Different methods were applied in this study including MTT, Scratch and adhesion assays as well as real-time PCR and transwell chamber assays. Based on the results obtained, DNC inhibits metastasis by decreasing Hef 1, Zeb 1 and Claudin 1 mRNA levels and can reduce SW480 cell proliferation with $IC_{50}$values of 15.9, 11.6 and $7.64{\mu}M$ at 24, 48 and 72h post-treatment. Thus it might be considered as a safe formulation for therapeutic purpose in colorectal cancer cases.

Comparative study of factors influencing tension lap splices in reinforced concrete beams

Karkarna, Yakubu M.,Bahadori-Jahromi, Ali,Jahromi, Hamid Zolghadr,Bonner, Emily,Goodchild, Charles Techno-Press 2020 Advances in concrete construction Vol.10 No.4

The practice of splicing reinforcing bars in reinforced concrete structures to manage insufficient bar length is a common approach, which is mainly due to transportation limitations on bar length. The splicing of reinforcing bars side by side offers a simple and economical solution to the problem of continuity. This paper examines the influence of different structural parameters such as concrete cover, lap splice length, shear links confinement and concrete strength on the lap splices based on an extensive experimental database of laps and anchorage. The current study shows that increasing the lap splices beyond 50Ø has no additional benefit for increasing its strength. The results also show that relative to the measured stress, specimens with larger concrete side covers shows higher splice stress compared to the samples with smaller concrete covers.