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CONTENTS
Volume 4, Number 2, June 2015
 

Abstract
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Key Words
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Address
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Abstract
We present for one-dimensional model for elastoplastic bar with combined hardening in FPZ - fracture process zone and softening with embedded strong discontinuities. The simplified version of the model without FPZ is directly compared and validated against analytical solution of Bazant and Belytschko (1985). It is shown that deformation localizes in an area which is governed by the chosen element size and therefore causes mesh sensitivity and that the length of the strain-softening region tends to localize into a point, which also agrees with results obtained by stability analysis for static case. Strain increases in the softening domain with a simultaneous decrease of stress. The problem unloads elastically outside the strain-softening region. The more general case with FPZ leads to more interesting results that also account for induced strain heterogeneities.

Key Words
dynamics; FPZ - fracture process zone; strain-softening; localization; finite element; embedded discontinuity

Address
Xuan Nam Do and Delphine Brancherie: Université de Technologie Compiègne / Sorbonne Universités, Laboratoire Roberval de Mécanique Centre de Recherche Royallieu, Rue
Personne de Roberval, 60200 Compiègne, France
Adnan Ibrahimbegovic: Université de Technologie Compiègne / Sorbonne Universités, Laboratoire Roberval de Mécanique Centre de Recherche Royallieu, Rue Personne de Roberval, 60200 Compiègne, France;
Chair for Computational Mechanics, Computational Mechanics

Abstract
This paper presents a simple procedure to obtain a substitute, homogenized mechanical response of single layer graphene sheet. The procedure is based on the judicious combination of molecular mechanics simulation results and homogenization method. Moreover, a series of virtual experiments are performed on the representative graphene lattice. Following these results, the constitutive model development is based on the well-established continuum mechanics framework, that is, the non-linear membrane theory which includes the hyperelastic model in terms of principal stretches. A proof-of-concept and performance is shown on a simple model problem where the hyperelastic strain energy density function is chosen in polynomial form.

Key Words
graphene; elastic properties, molecular mechanics; homogenization

Address
Eduard Marenić and Adnan Ibrahimbegovic:Sorbonne Universités / Université de Technologie de Compiegne
Chaire de Mécanique, Lab. Roberval de Mécanique,
Centre de Recherches de Royallieu 60203 Compiegne, France


Abstract
Control of potable water treatment plant (PWTP) is nowadays based on experience. The aim of this article is to show that model based control of treatment process is more efficient than process operation based on experience. Stimela environment is used for modeling of processes of potable water treatment. Application of the model was conducted on PWTP \"Crkvice\" in Zenica (BiH). This plant has used conventional rapid sand filters. By effective application of the model it is determined the optimal filter run time for different input turbidity of raw water. This results in the possibility of reducing the consumption of backwashing water, lower costs for its pumping and reducing the amount of coagulants. In the existing practice, based on experience, these benefits are not used.

Key Words
mathematical model; potable water treatments; rapid sand filtration; filter run time; model based control

Address
Suvada Jusic: Department of Water Resources Engineering and Environmental Engineering, Faculty of Civil Engineering, University of Sarajevo, 30 Patriotske lige street Sarajevo, Bosna i Hercegovina
Zoran Milasinovic: Department of Theoretical and Applied Hidromechanics and Hydraulic Structures and Facilities, Faculty of Civil Engineering, University of Sarajevo, 30 Patriotske lige street Sarajevo, Bosna i Hercegovina

Abstract
In reality, masonry infill modifies the seismic response of reinforced concrete (r.c.) frame structures by increasing the overall rigidity of structure which results in: increasing of total seismic load value, decreasing of deformations and period of vibration, therefore masonry infill frame structures have larger capacity of absorbing and dissipating seismic energy. The aim of the paper is to explore and assess actual influence of masonry infill on seismic response of r.c. frame structures, to determine whether it\'s justified to disregard masonry infill influence and to determine appropriate way to consider infill influence by design. This was done by modeling different structures, bare frame structures as well as masonry infill frame structures, while varying masonry infill to r.c. frame stiffness ratio and seismic intensity. Further resistance envelope for those models were created and compared. Different structures analysis have shown that the seismic action on infilled r.c. frame structure is almost always twice as much as seismic action on the same structure with bare r.c. frames, regardless of the seismic intensity. Comparing different models resistance envelopes has shown that, in case of lower stiffness r.c. frame structure, masonry infill (both lower and higher stiffness) increased its lateral load capacity, in average, two times, but in case of higher stiffness r.c. frame structures, influence of masonry infill on lateral load capacity is insignificant. After all, it is to conclude that the optimal structure type depends on its exposure to seismic action and its masonry infill to r.c. frame stiffness ratio.

Key Words
masonry infill; reinforced concrete frame; stiffness ratio; lateral load capacity; storey resistance envelope

Address
Amila Muratović and Naida Ademovića: Department of Construction, Faculty of Civil Engineering, University of Sarajevo, Patriotske lige 30, 71000 Sarajevo, Bosnia and Herzegovina


Abstract
Hybrid girders can be constructed in different geometrical forms and from different materials. Selection of beam\'s effective constellation represents a complex process considering the variations of geometrical parameters, changes of built in material characteristics and their mutual relations, which has important effect on the behavior of the girder. This paper presents the theoretical and experimental research on behavior of the timber-steel hybrid girders\'different geometrical constellation with external prestressing and in different conditions of timber moisture. These researches are based on linear elastic analysis, and further refine by using the plasticity and damage models.

Key Words
hybrid girder; glued laminated timber; cable; effective force of prestressing; geometrical rigidity/stiffness; self-rigidity/stiffness

Address
Sladana Miljanović: Faculty of Architecture, Sarajevo, Bosnia and Herzegovina
Muhamed Zlatar: Faculty of Civil Engineering, Sarajevo, Bosnia and Herzegovina


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