Unconfined Compressive Strength of Clayey Soils Stabilized with Waterborne Polymer

Seyed Abolhassan Naeini,Bahman Naderinia,Ehsan Izadi 대한토목학회 2012 KSCE Journal of Civil Engineering Vol.16 No.6

Improvement and stabilization of soils are widely used as an alternative to substitute the lacking of suitable material on site. Soils may be stabilized to increase strength and durability or to prevent erosion and dust generation. The use of nontraditional chemical stabilizers in soil improvement is growing daily. A new stabilizing agent was developed to improve the mechanical performance and applicability of clayey soils. In this study a laboratory experiment is conducted to evaluate the effects of plasticity index and waterborne polymer on the Unconfined Compression Strength (UCS) of clayey soils. The laboratory tests include sieve analysis,hydrometer, Atterberg limits, modified compaction and unconfined compression tests. Three clayey soils with different plasticity indexes were mixed with various amounts of polymer (2, 3, 4 and 5%) and compacted at the optimum water content and maximum dry density. The unstabilized and stabilized samples were subjected to unconfined compression tests to determine their strength at different curing times. The results of the tests indicated that the waterborne polymer significantly improved the strength behavior of unsaturated clayey soils. Also, an increase in plasticity index causes a reduction in unconfined compression strength.

Seismic Behavior of Composite Shear Wall Systems and Application of Smart Structures Technology

Qiuhong Zhao,Abolhassan Astaneh-Asl 한국강구조학회 2007 International Journal of Steel Structures Vol.7 No.1

Shear wall systems are one of the most comonly used lateral load resisting systems in high-rise buildings. This paperconcentrates on the experimental and analytical studies of two composite shear wal systems and presents a sumary anddiscussion of research results. In addition, the paper discusses application of smart structures technology into the design of thesesystems. The composite shear wal system studied herein consists of a steel boundary frame and a steel plate shear wall withe reinforced concrete wal by bolts. In the system caled “traditional” the reinforced concrete wall is in direct contact withthe boundary stel frame, while in the system caled “innovative” there is a gap in betwen.

Optimal Control of a MIMO Bioreactor System Using Direct Approach

Abolfazl Simorgh,Abolhassan Razminia,Saleh Mobayen,Dumitru Baleanu 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.3

In this paper, the optimal control of a continuous type bioreactor with multi-input-multi-output signals is presented for the two active phases: growth and stationary. The underlying criterion to be minimized generalizes the classic quadratic forms to address some crucial objectives in controlling the bioreactor. In particular, the protection of actuators against fast switching in the controller output is considered by including a weighting term of the control signal derivatives. The direct optimal control approach is used to carry out the optimization in the presenceof various limiting constraints. Direct methods are based on transcribing the infinite-dimensional problem to a finite-dimensional one. In this manuscript, direct single shooting and trapezoidal collocation methods are used for transcription, and the successive quadratic programming method is employed to solve the resulting nonlinear programming problem. It is shown that the trapezoidal method is an effective method for controlling the bioreactor in all the active phases, whereas the single shooting fails in dealing with the unstable one (i.e., growth). To analyzesolutions in a more accurate manner, an auxiliary criterion is defined, and then the cheap control analysis is studied. The convergence to the lowest value of the auxiliary cost function and the effects on the optimal state and control trajectories are then examined by varying cheap parameters. Several numerical simulations support the presented theoretical formulation.

Seismic Behavior of Steel Shear Wall Systems and Application of Smart Structures Technology

Qiuhong Zhao,Abolhassan Astaneh-Asl 한국강구조학회 2007 International Journal of Steel Structures Vol.7 No.1

Stel shear walls have been used more frequently in recent years as the lateral load resisting system in the design and retrofitof high-rise buildings. This paper concentrates on the experimental studies of an innovative steel shear wal system used intechnology into the design of steel shear wall system. The steel shear wall system studied herein consists of steel plate shearwalls welded inside a multi-bay steel moment frame. The steel moment frame consists of large concrete filed steel tubes (CFT)at the edges, internal wide flange (WF) columns, and horizontal WF beams. Most of the gravity load is resisted by the CFTcolumns, and lateral loads are resisted by the dual system consisting of the moment frame and the steel plate shear wall.

Experimental Lnvestigation on Mechanical Characteristics and Environmental Effects on Rubber Concrete

Khorrami, Morteza,Vafai, Abolhassan,Khalilitabas, Ahmad A.,Desai, Chandrakant S.,Ardakani, M. H. Majedi Korea Concrete Institute 2010 International Journal of Concrete Structures and M Vol.4 No.1

The feasibility of the use of scrap tire rubber in concrete was investigated. The tests conducted in two groups: replacing of coarse aggregates with crumb rubber and cement particles with rubber powder. To distinguish the properties of new concrete, the following mechanical and durability tests were designed: compressive, tensile and flexural strength, permeability and water absorption. Rubber addition could affect the concrete properties depend on the type and percentage of the rubber added. Although the rubber addition modifies the mechanical characteristics of concrete in a way, but higher rubber content could not be useful. Concrete durability showed more dependency to the type of rubber instead of percentage of rubber. Moreover, to optimize the mechanical and durability of rubberized concrete, the useful percentage of rubber has been recommended.

Imrovement of Loose Sandy Soil Deposits using Micropiles

Reza Ziaie Moayed,Seyed Abolhassan Naeini 대한토목학회 2012 KSCE JOURNAL OF CIVIL ENGINEERING Vol.16 No.3

Micropiles are being used today for a variety of applications. The increased awareness of the sound performance of micropiles especially under seismic conditions has led to the widespread use of this technology for ground treatment. Micropiles have been used effectively in many applications of ground improvement to increase the bearing capacity and reduce the settlements particularly in strengthening the existing foundations. This paper describes a case study in which 350 micropiles of 75 mm diameter and 15-20 m long have been used for the improvement of loose sandy soil deposits. The effect of micropile injection on liquefaction remedation and improving of soil stress-displacement behavior are evaluated using the results of Standard Penetration Tests (SPT) and Plate Load Tests (PLT) on a real site before and after micropile installation. The load-displacement responses of micropiles under tensile axial loading are also presented in this paper. The results show that, by using micropiles, the response of loose silty sand soils under surface loading can be significantly improved and the bearing capacity of loose sandy soil increased considerably. Also, the modulus of subgrade reaction of the soil (KS) is increased. The SPT values of soil layers are increased after soil improvement with micropile installation. Therefore, the liquefaction resistances of sandy soil are also improved.

Experimental Investigation of Steel Frames Braced with Symmetrical Pairs of y-shaped Concentric Bracings

Sohail Majid Zamani,Abolhassan Vafaei,A. A. Aghakouchak,Chandrakant Desai 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.2

Concentric bracings composed of three members arranged in y shaped geometry have been traditionally used to provide openings in braced bays. However, simultanous occurance of compression in three braces leads to instability and out of plane buckling of braces accompanied by low hysteretic energy absorption. In order to study the behavior of y-braced frames, a research program including experimental tests was conducted at BHRC† structural engineering laboratory. Quasi-static cyclic loading was applied to specimens including four full-scale two-bay frames with y-bracings of different cross sections and connection types.The bays are braced symmetrically to have a combination of tensile and compressive braces at all loading stages. The results show that out-of-plane buckling with single curvature in braces can be substituted by in plane, double curvature buckling through appropriate detailing of cross sections and connections.Thus, hysteretic energy dissipation of ybracing is remarkably improved due to spreading of plastic strains in braces. In this paper, seismic performance of y-braced frame specimens and a reference X-braced frame are also assessed by capacity spectrum method.

Does Economic Instability Affect Healthcare Provision? Evidence Based on the Urban Family Physician Program in Iran

Enayatollah Homaie Rad,Sajad Delavari,Afsoon Aeenparast,Abolhassan Afkar,Faranak Farzadi,Farzaneh Maftoon 대한가정의학회 2017 Korean Journal of Family Medicine Vol.38 No.5

Background: The main aim of this study was to evaluate the achievements of some important goals of Iran’s urban family physician plan. This plan was implemented when the country experienced economic instability. We exam-ine whether an economic crisis affects the efficacy of a healthcare program.Methods: We used the household income and expenditures survey data for 2011 (before program implementa-tion) and 2012 (after program implementation). Changes in out-of-pocket payments and healthcare utilization were investigated using the propensity score matching estimator. Furthermore, changes in inequality in these two dimensions were examined.Results: No changes in out-of-pocket payments and healthcare utilization were found after the implementation of this program; however, inequality in out-of-pocket payments increased during the reform.Conclusion: The urban family physician program was not implemented completely and many of its fundamental settings were not conducted because of lack of necessary healthcare infrastructure and budget limitations. Family physician programs should be implemented under a strong healthcare infrastructure and favorable economic con-ditions.