The controllable fluid dash pot damper performance

Samali, Bijan,Widjaja, Joko,Reizes, John Techno-Press 2006 Smart Structures and Systems, An International Jou Vol.2 No.3

The use of smart dampers to optimally control the response of structures is on the increase. To maximize the potential use of such damper systems, their accurate modeling and assessment of their performance is of vital interest. In this study, the performance of a controllable fluid dashpot damper, in terms of damper forces, damper dynamic range and damping force hysteretic loops, respectively, is studied mathematically. The study employs a damper Bingham-Maxwell (BingMax) model whose mathematical formulation is developed using a Fourier series technique. The technique treats this one-dimensional Navier-Stokes's momentum equation as a linear superposition of initial-boundary value problems (IBVPs): boundary conditions, viscous term, constant Direct Current (DC) induced fluid plug and fluid inertial term. To hold the formulation applicable, the DC current level to the damper is supplied as discrete constants. The formulation and subsequent simulation are validated with experimental results of a commercially available magneto rheological (MR) dashpot damper (Lord model No's RD-1005-3) subjected to a sinusoidal stroke motion using a 'SCHENK' material testing machine in the Materials Laboratory at the University of Technology, Sydney.

Wind Induced Response and Control of a Sixty-Storey Building

B. Samali,H. Gao,K. C. S. Kwok 대한기계학회 1997 Asia-Pacific Vibration Conference Vol.2 No.1

A rare case report of Mirizzi syndrome type III treatment algorithm in situs inversus totalis, large ventricular septal defect and transposition of great arteries in a young diabetic patient

Raju Badipati,Samali Maity,Muralidharsai Maddasani,Syed Mazhar Galib Ali,Farha Naaz Khatoon,Lakshmi Durga Kasinikota,Kushal Gunturu,Gopu Prameela 한국간담췌외과학회 2023 Annals of hepato-biliary-pancreatic surgery Vol.27 No.3

Situs inversus totalis (SIT) is a rare condition in which cardiac and abdominal organs are inverted from their normal left-sided orientation. Mirizzi syndrome, characterized by the obstruction of the common hepatic duct or the common bile duct by gallstone, is a rare condition. Mirizzi syndrome co-occurrence in SIT patients is rare. Gallbladder in sinistroposition is extremely uncommon in SIT patients. We report a known case of diabetes, ventricular septal defect with transposition of the great arteries in a 32-year-old female who presented with jaundice, cholangitis, chills, and fever that had lasted for 10 days. She was confirmed to have SIT with type III Mirizzi syndrome following a series of diagnostic procedures. Primarily, endoscopic retrograde cholangiopancreatography along with common bile duct stenting was performed to initially reduce cholangitis. After an eight-week follow-up after the reduction of cholangitis, surgery was conducted. Mirror-imaged ports were used for the laparoscopic procedure, and the surgeon was on the patient’s right side rather than the usual left side. The patient was discharged from the hospital following two days of uneventful healing.

Predicting the bond between concrete and reinforcing steel at elevated temperatures

Aslani, Farhad,Samali, Bijan Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.5

Reinforced concrete structures are vulnerable to high temperature conditions such as those during a fire. At elevated temperatures, the mechanical properties of concrete and reinforcing steel as well as the bond between steel rebar and concrete may significantly deteriorate. The changes in the bonding behavior may influence the flexibility or the moment capacity of the reinforced concrete structures. The bond strength degradation is required for structural design of fire safety and structural repair after fire. However, the investigation of bonding between rebar and concrete at elevated temperatures is quite difficult in practice. In this study, bond constitutive relationships are developed for normal and high-strength concrete (NSC and HSC) subjected to fire, with the intention of providing efficient modeling and to specify the fire-performance criteria for concrete structures exposed to fire. They are developed for the following purposes at high temperatures: normal and high compressive strength with different type of aggregates, bond strength with different types of embedment length and cooling regimes, bond strength versus to compressive strength with different types of embedment length, and bond stress-slip curve. The proposed relationships at elevated temperature are compared with experimental results.

Pull-out Strengths of GFRP-Concrete Bond Exposed to Applied Environmental Conditions

Kabir, Muhammad Ikramul,Samali, Bijan,Shrestha, Rijun Korea Concrete Institute 2017 International Journal of Concrete Structures and M Vol.11 No.1

This paper presents results of an experimental investigation on the behaviour of bond between external glass fibre reinforced polymer reinforcement and concrete exposed to three different environmental conditions, namely, temperature cycles, wet-dry cycles and outdoor environment separately for extended durations. Single shear tests (pull-out test) were conducted to investigate bond strengths (pull-out strengths) of control (unexposed) and exposed specimens. Effect of the exposure conditions on the compressive strength of concrete were also investigated separately to understand the effect of changing concrete compressive strength on the pull-out strength. Based on the comparison of experimental results of exposed specimens to control specimens in terms of bond strengths, failure modes and strain profiles, the most significant degradation of pull-out strength was observed in specimens exposed to outdoor environment, whereas temperature cycles did not cause any deterioration of strength.

Hysteresis modeling for cyclic behavior of concrete-steel composite joints using modified CSO

Yang Yu,Bijan Samali,Chunwei Zhang,Mohsen Askari 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.2

Concrete filled steel tubular (CFST) column joints with composite beams have been widely used as lateral loading resisting elements in civil infrastructure. To better utilize these innovative joints for the application of structural seismic design and analysis, it is of great importance to investigate the dynamic behavior of the joint under cyclic loading. With this aim in mind, a novel phenomenal model has been put forward in this paper, in which a Bouc-Wen hysteresis component is employed to portray the strength and stiffness deterioration phenomenon caused by increment of loading cycle. Then, a modified chicken swarm optimization algorithm was used to estimate the optimal model parameters via solving a global minimum optimization problem. Finally, the experimental data tested from five specimens subjected to cyclic loadings were used to validate the performance of the proposed model. The results effectively demonstrate that the proposed model is an easy and more realistic tool that can be used for the pre-design of CFST column joints with reduced beam section (RBS) composite beams.

Pull-out Strengths of GFRP-Concrete Bond Exposed to Applied Environmental Conditions

Muhammad Ikramul Kabir,Bijan Samali,Rijun Shrestha 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.1

This paper presents results of an experimental investigation on the behaviour of bond between external glass fibre reinforced polymer reinforcement and concrete exposed to three different environmental conditions, namely, temperature cycles, wet–dry cycles and outdoor environment separately for extended durations. Single shear tests (pull-out test) were conducted to investigate bond strengths (pull-out strengths) of control (unexposed) and exposed specimens. Effect of the exposure conditions on the compressive strength of concrete were also investigated separately to understand the effect of changing concrete compressive strength on the pull-out strength. Based on the comparison of experimental results of exposed specimens to control specimens in terms of bond strengths, failure modes and strain profiles, the most significant degradation of pull-out strength was observed in specimens exposed to outdoor environment, whereas temperature cycles did not cause any deterioration of strength.

Predicting the bond between concrete and reinforcing steel at elevated temperatures

Farhad Aslani,Bijan Samali 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.5

Reinforced concrete structures are vulnerable to high temperature conditions such as those during a fire. At elevated temperatures, the mechanical properties of concrete and reinforcing steel as well as the bond between steel rebar and concrete may significantly deteriorate. The changes in the bonding behavior may influence the flexibility or the moment capacity of the reinforced concrete structures. The bond strength degradation is required for structural design of fire safety and structural repair after fire. However, the investigation of bonding between rebar and concrete at elevated temperatures is quite difficult in practice. In this study, bond constitutive relationships are developed for normal and high-strength concrete (NSC and HSC) subjected to fire, with the intention of providing efficient modeling and to specify the fireperformance criteria for concrete structures exposed to fire. They are developed for the following purposes at high temperatures: normal and high compressive strength with different type of aggregates, bond strength with different types of embedment length and cooling regimes, bond strength versus to compressive strength with different types of embedment length, and bond stress-slip curve. The proposed relationships at elevated temperature are compared with experimental results.

Finite element modelling of FRP-strengthened RC beam-column connections with ANSYS

Rijun Shrestha,Bijan Samali,Scott T. Smith 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.11 No.1

There is an abundance of research on the strengthening of reinforced concrete (RC) structural elements such as beams, columns and slabs with fibre reinforced polymer (FRP) composites. Less research by comparison has been conducted on the strengthening of RC beam-column connections and the majority of such research has been predominantly experimental to date. Few existing experimental studies have reported extensive instrumentation of test specimens which in turn makes understanding the behavior of the connections and especially the contributions made by the FRP difficult to ascertain. In addition, there has been even more limited research on the analytical and numerical modelling of FRP-strengthened connections. In this paper, detailed descriptions of key strategies to model FRP-strengthened RC connections with finite elements are provided. An extensively instrumented and comprehensively documented set of experiments on FRP-strengthened connections is firstly presented and finite element models are then constructed using ANSYS. The study shows that the finite element approach is able to capture the overall behavior of the test specimens including the failure mode as well as the behavior of the FRP which will most importantly lead to a detailed understanding of the FRP and the future development of rational analytical models. The finite element models are, however, unable to model the stiffness of the connections with accuracy in the ultimate load range of response.

The controllable fluid dashpot damper performance

John Reizes,Bijan Samali,Joko Widjaja 국제구조공학회 2006 Smart Structures and Systems, An International Jou Vol.2 No.3

The use of smart dampers to optimally control the response of structures is on the increase. To maximize the potential use of such damper systems, their accurate modeling and assessment of their performance is of vital interest. In this study, the performance of a controllable fluid dashpot damper, in terms of damper forces, damper dynamic range and damping force hysteretic loops, respectively, is studied mathematically. The study employs a damper Bingham-Maxwell (BingMax) model whose mathematical formulation is developed using a Fourier series technique. The technique treats this one-dimensional Navier-Stokes momentum equation as a linear superposition of initial-boundary value problems (IBVPs): boundary conditions, viscous term, constant Direct Current (DC) induced fluid plug and fluid inertial term. To hold the formulation applicable, the DC current level to the damper is supplied as discrete constants. The formulation and subsequent simulation are validated with experimental results of a commercially available magneto rheological (MR) dashpot damper (Lord model No RD-1005-3) subjected to a sinusoidal stroke motion using a SCHENK material testing machine in the Materials Laboratory at the University of Technology, Sydney.