INTERNATIONAL JOURNAL OF ADVANCED STRUCTURAL ENGINEERING
Year:2011 | Volume:3 | Issue:1|Papers Count:7

Dynamic behavior of the wind excited benchmark building using Semi-Active Electro-Magnetic Friction Dampers (SAEMFDs), with modulated homogeneous friction algorithm is presented. The performance of the benchmark building is studied under across wind loads by installing the SAEMFDs with smooth boundary layer semi-active friction (SBLSAF) algorithm. The governing equations of motion are solved by employing state space formulation. Initially, one damper in each of the upper 26 storeys of the building is installed and later on the optimization of the location and the number of dampers required is carried out till the comparable performance criteria are obtained. The criterion selected for optimality was controllability index, obtained with the help of root-mean-square (RMS) value of the interstorey drift. The performance of SAEMFDs is compared with that of passive friction dampers. Further, a parametric study is carried out by varying the value of controller gain (β). For each value of β, a parametric study of SAEMFDs by varying the value of the parameter representing the measure of the thickness of the boundary layer (a) is carried out. From the numerical study, it is found that SBLSAF algorithm is quite effective in enhancing the quality of the performance of the benchmark building. Optimization of location of dampers gives an economical solution to the vibration control of the benchmark building.

This paper deals with optimum shape brick masonry vaults under dynamic loads by cellular automata. In this paper, the vaults are modeled. Then, they are analyzed and optimized under acceleration–time components of Elcentro earthquake. For vault response optimization, the results were used in cellular automata computational model. Then vaults are analyzed and optimized by modeling rules. The results of error range and time of analysis in automata cellular model and FEM software compared. Finally, comparing the results of CA (Cellular Automata) method and FEM (Finite Element Method) method, shows that although precision is less in CA method, but the time of analysis and optimization is so much smaller.

This paper presents the results of an experimental investigation of the axial behavior of small scale square reinforced concrete columns with fiber reinforced polymer (FRP) bars, as a solution to overcome the corrosion problems, where this material represents a relatively new technology; therefore more research is needed to determine its characteristics and gain confidence to be accepted by engineers for practical applications. Eight columns were tested in a vertical position and under compressive axial static loading, where all columns had the same dimensions 250*250mm and 1250mm height, main reinforcement 4#12mm, 6#12mm, and 8#12mm, the transverse reinforcement was ø6@120mm closed stirrups along the columns. The major parameters included in this research were the main reinforcement ratios, the main reinforcement types, the transverse reinforcement ratios in the column, and the characteristic strength of the concrete. Results from a series of tests on small-scale specimens showed that increasing main reinforcement, transverse reinforcement ratios in the column ends and increasing characteristic strength of the concrete have a significant effect on the behavior of reinforced concrete columns with FRP.

Plate and shell analysis using classical plate theory (CPT) has a lack of accuracy in predicting the influence of transverse deformation, because of its assumption that the line normal to the surface remains straight and normal to the midplane before and after deformation. The next revision by constant shear deformation theory or famous as first order shear deformation theory (CSDT/FOSDT) still suffers a disadvantage that has a constant value in the shear term that is called shear locking phenomenon. This matter has been corrected by higher order shear deformation theory (HOSDT) using a refined assumption that the line normal to the surface should be in a parabolic function and not normal to the midplane, but normal to the surfaces so that it fulfills the zero strain in the surface. The analysis of the bending part of laminated composite flat shell element is applied by higher order lamination theory (HOLT) that is adopted from HOSDT. This model is accurate for thicknesses variation and complex materials. HOLT model is implemented into finite element procedure to find deflection, stresses and internal forces. It can be concluded that the displacement and stresses in HOLT model are higher than FOLT the ones (first order lamination theory) in small ratio of a/h dan its result almost the same value for a/h ratio more than 10. In a square plate case, the displacement gets smaller if the fiber arranged into cross-ply sequence. Interlaminar stresses along the thickness is not distributed continuously, but they have certain modes that depend on the depth of point position, the lamina or layer number, fiber orthotropic angle of each layer and a/h ratio.

Base isolation is one of the most widely accepted techniques to protect structures and to mitigate the risk to life and property from strong earthquakes. In this paper, the effect of mass asymmetry in symmetric building with unidirectional and bidirectional eccentricities and asymmetric building with upward and downward eccentricities in elevation is studied. To study the effect of torsion in seismic behavior of base isolated structures, a symmetric and asymmetric thirteen story concrete building is chosen as reference model. These models with mass eccentricity of 5%, 10%, 15% and 20% of greatest dimension of building in unidirection and bidirection are considered. The response spectrum and linear time history analysis of this eccentric model of fixed base and base isolated building using ETABS software is done. The symmetric and asymmetric fixed base and base isolated building having eccentricity in plan and elevation are compared for parameters such as maximum shear force, torsion, bending moment, lateral displacement, storey drift, storey acceleration and base shear. It is concluded that base isolation is very effective for various mass eccentric models. Response of base isolated mass eccentric model even in large mass eccentricity reduces as compared to fixed base building.

Pressure vessels are one of the most important equipment in the refining of the crude oil. For this reason, these equipment must resist against the loads resulting from the earthquake. Pressure vessels are found in different units of refineries and in different vertical and horizontal shapes. This equipment are located on different foundations and their seismic behavior are quite different. For seismic study of pressure vessels, at first this equipment must be screened and categorized in order to find their real behavior. The selected sample should be one that in comparison to others must have critical condition in terms of seismic vulnerabilities. According to the qualitative studies, mechanical specifications such as dimensions, temperature, weight, and the dimensions of the foundation will be determined. After analytical modeling and calculations the amount of vessel vulnerabilities will be found. All the modeling is done with the SAP2000 and SAFE2000 software. For modal and spectrum dynamic analysis shell elements and frame elements is used. After the analysis is done, the stresses and the displacement in the body of vessel and also stresses in pedestal and bolts will be determined and then it will be compared to the allowable values. At the end those elements which do not have adequate strength, will be retrofitted and all drawing and details will be presented.

Seismic evaluation of pipe rack supporting structures in a petrochemical complex as one of the most important parts of structural systems for safe and stable production processes have been studied in this paper. The behavior of these supporting structures is similar to steel or reinforced concrete frame supporters for elevated processing pipes. Qualitative and quantitative methods of seismic vulnerability evaluations have been used according to the ASCE-1998 standards. In qualitative evaluation, the seismic vulnerability factors are determined by visual inspections and walk down the structural systems. Computer modelings have been used in quantitative evaluation of the supporting structures, including equivalent static analysis and linear dynamic analysis by considering torsion and P-Δ effects. Site specific earthquake records and design spectrum have been used as input seismic forces. Also, gravity and thermal loads based on the existing documents and design calculation sheets and specification notes have been considered in the analyses. Gravity and lateral load combinations have been considered for seismic evaluation of foundation systems. Overturning stability of structures and uplifting of foundation systems due to the gravity and lateral loads, and also, lateral displacements, frame element and connection capacities have been investigated. However, different methods of seismic strengthening and retrofitting of structural system have been proposed.