Sriman Kumar Bhattacharyya

Time-domain analysis of infinite reservoir by finite element method using a novel far-boundary condition

Abstract The focus of the present paper is on the time-domain analysis of a dam–reservoir system using a novel far-boundary condition to model an infinite fluid domain to a finite one. The method is based on the finite element discretization of the complete system assuming only pressure to be the nodal unknown parameter and the fluid to be compressible. The truncation boundary condition is derived numerically from the classical wave equation. Studies show the accuracy of the proposed far-boundary condition, using finite element method, while comparing with the existing ones available in the literature.

A parametric study on fluid–structure interaction problems

Abstract This paper deals with finite element analysis of the fluid–structure systems considering the coupled effect of elastic structure and fluid. The equations of motion of the fluid considered inviscid and compressible are expressed in terms of the pressure variable alone. The elastic structure and the fluid domain are treated as two separate systems and discretized with finite elements. The solution of the coupled system is accomplished by solving the two systems separately with the interaction effects at the fluid–solid interface enforced by a developed iterative scheme. Non-divergent pressure and displacement are obtained simultaneously through a few numbers of iterations. Studies show the accuracy of the proposed algorithm, while comparing with the existing ones available in the literature. The parametric study of the coupled system shows the importance of fluid height and material property of the structure.

Finite Element Dynamic Analysis of Laminated Composite Plates with Multiple Delaminations

A simple multiple delamination model is developed for the dynamic analysis of multi-layered laminated composite plates having arbitrarily located multiple delaminations. The displacements of any sub-laminate are expressed with respect to the mid-plane of the original laminate for finding the stiffnesses of the corresponding sub-laminate. The finite element dynamic equations are accordingly derived based on eight-noded isoparametric quadratic elements, assuming the first order shear deformation of each lamina. The present results compare well with those existing in the open literature. Several parametric studies are carried out to investigate the dynamic behaviour in the presence of single and multiple delaminations. Numerical results for free vibration and transient response are presented both for single and multiple delaminated plates with various boundary conditions, stacking sequences and other geometric parameters.

Finite Element Coupled Slosh Analysis of Rectangular Liquid Filled Laminated Composite Tanks

This paper presents the sloshing response and coupled dynamic behaviour of rectangular liquid filled laminated composite tanks under harmonic base excitation. For the numerical simulation of the problem, the finite element method is used to develop an integrated computational scheme in 3-D, which accounts for the coupling effect between liquid sloshing and the tank vibration. Dynamic responses are computed in the time domain using Newmarks predictor-multicorrector-algorithm. Both fluid transients and structural dynamics problems are dealt with separately before solving the coupled slosh problems. A computer code is developed which generates numerical data for the slosh frequency, sloshing displacement, free surface profiles, hydrodynamic pressure, deformed structural modes and the container response due to the change in the hydrodynamic pressure. The solution procedures are applied to both rigid and flexible containers to demonstrate the effect of tank flexibility on the overall slosh phenomenon and structural response. The effects of lamination scheme, free surface wave and decoupled analysis approach on the tank wall response are also investigated. To the best knowledge of the authors, the results of similar cases involving the interaction of fluid with laminated composite tanks, are not available in the open literature.

Coupled Dynamic Response of Liquid Filled Composite Cylindrical Tanks With Baffles

The slosh frequencies of liquid in a liquid-filled cylindrical tank, made of laminated composites, are investigated in the present paper. An annular laminated plate is used as a baffle, which is fitted to the inner periphery of a cylindrical tank. Finite element codes are accordingly developed and are then used to analyze both the liquid domain and the structural domain i.e., the tank and the baffle. The slosh frequencies of liquid are computed for different dimensions and positions of the baffle. The coupled vibration frequencies of the tank-baffle system are computed considering the effect of sloshing of liquid. The asymmetric modes corresponding to circumferential wave number one are studied in the present investigation. The results obtained for a liquid filled elastic isotropic tank without baffle and a rigid tank with rigid baffle are compared with the available results, and they are found to be in good agreement. The results for composite tanks cover the effects of a wide range of parameters including composite baffles as well as different lamination schemes and number of layers of the tank wall on the slosh frequencies and coupled vibration frequencies.Copyright

Dynamic Behavior and Impact Induced First Ply Failure of Multiple Delaminated Composite Shells

This analytical study is concerned with the free vibration, forced vibration, low velocity impact response as well as impact induced first ply failure of delaminated composite shells. It is based on a simple multiple delamination modeling which can take care of any arbitrary number and size of delaminations placed at any location of the laminate. Sanders shallow shell theory is applied for the shell analysis. First order shear deformation theory in conjunction with an eight noded isoparametric quadratic delaminated shell element with five degrees of freedom per node are used to develop the finite element formulation. Newmarks time integration algorithm is employed for solving the time dependent multiple equations of the plate and the impactor. Tsai-Wu failure criterion is used to predict the first ply failure of a laminate due to impact at every time step. Numerical results are generated for different cases by varying the size and location of delaminations as well as the stacking sequences. It is observed that the delaminations reduce the natural frequencies and increase the dynamic displacements. Critical impactor velocity to cause the first ply failure in a laminate is also reduced in the presence of a delamination.

Properties of Recycled Aggregates

This chapter emphasizes the physical and mechanical characteristics of recycled aggregate along with findings of different researchers. The physical properties such as grading, size and texture, density, specific gravity, water absorption, flakiness and elongation indices of recycled aggregates are discussed in detail. The factors such as crushing methodology, crushing age and quality of old concrete greatly affect the gradation of recycled aggregates and the findings reported by different researchers are elaborated. The main factors that influence the density of RA are particle size, amount of adhered mortar and strength of parent concrete from which the recycled aggregate derived are illustrated in this chapter. The relationship between water absorption and adhered mortar content, water absorption and density are described. Further, the influence of strength of parent concrete from which the RA derived and its size are also illustrated. In general, the recycled aggregates are found to be weaker than the natural aggregates against mechanical resistance such as aggregate crushing value, ten percent fines value, impact value and Los Angeles abrasion loss value. The results of mechanical properties of RA reported by various researchers are discussed in this chapter.

Structural Behavior of RAC

The structural performance of recycled aggregate concrete (RAC) made with different proportions of recycled coarse aggregate under various types of loads are presented. A detailed investigation carried out on the behavior of RAC under low-velocity impact load is discussed. The behavior of the RAC beams is discussed in terms of acceleration, strains, and support reaction histories under impact load. It is found that for a given impact energy (the energy imparted by the hammer per blow) the reactions and strains of RAC with 50% and 100% RCA are significantly lower and higher, respectively, than those of normal concrete and RAC with 25% RCA. The investigations carriedout by different researchers on the behavior of reinforced concrete beams made with RAC under flexure and shear are also explained. Further, the performance of reinforced concrete columns prepared with recycled aggregate concrete under axial load is described.

Microstructure of Recycled Aggregate Concrete

The microstructural characterization of concrete prepared with RCA is described in this chapter. The interfacial transition zone (ITZ) between the aggregate and the cement mortar matrix is the most important interface in concrete. Particularly, this is very important in RAC, as the recycled aggregate concrete has more interfaces than normal concrete, i.e., the interfacial transition zone between the original aggregate and the adhered mortar (old ITZ), and another interface between the adhered mortar and new mortar matrix (new ITZ) in recycled aggregate concrete. Therefore, the characteristics of ITZ of RAC in terms of hydration compounds, anhydrous cement, porosity examined by using SEM are discussed in this chapter. A detailed procedure of specimen preparation for scanning electron microscope (SEM) examination is also discussed. Further, the influence of these parameters on the strength of concrete is elaborated. ITZ characteristics were also examined by using Vickers microhardness and a relationship between compressive strength and ITZ microhardness was established. Furthermore, it discussed the influence of the binder, quality, and quantity of adhered mortar, strength of source concrete from which the RCA derived on interfacial transition zone of RAC.

Long-Term and Durability Properties

The long-term properties like shrinkage and creep and the durability properties such as permeability, chloride penetration, and depth of carbonation of recycled aggregate concrete are discussed. The important factors like amount of RA, w/c ratio, residual cement paste significantly affect these long-term properties and are discussed with illustrations in this chapter. The research findings reported by different researchers reveal that both shrinkage and creep of RAC are significantly higher than that of conventional concrete due to the high absorption capacity of RA. But, the incorporation of fly ash in RAC can minimize these to a certain extent, and the results reported by different researchers are described. The research results of various researchers reveal that the durability performance of RAC is more hapless than normal concrete. The poor durability performance of RAC is associated with many factors such as poor quality of RA, the presence of numerous microcracks, the presence of old and new interfacial transition zones, w/c ratio. The influence of these factors on the durability of the performance of RAC in terms of permeability, carbonation, and chloride penetration is discussed in this chapter too.