Numerical model for nonlinear analysis of composite concrete-steel-masonry bridges Goran Baloevic, Jure Radnic, Nikola Grgic, Domagoj Matesan and Marija Smilovic
Abstract; Full Text (5754K) .	pages 1-20.	DOI: 10.12989/csm.2016.5.1.001

Abstract
This paper firstly briefly describes developed numerical model for both static and dynamic analysis of planar structures made of concrete, steel and masonry. The model can simulate the main nonlinearity of such individual and composite structures. The model is quite simple and based on a small number of material parameters. After that, three real composite concrete-steel-masonry bridges were analyzed using the presented numerical model. It was concluded that the model can be useful in practical analysis of composite bridges. However, future verifications of the presented numerical model are desirable.

Key Words
numerical model; concrete-steel-masonry composite bridges; static and dynamic analysis

Address
Goran Baloevic, Jure Radnic, Nikola Grgic, Domagoj Matesan and Marija Smilovic: Faculty of Civil Engineering, Architecture and Geodesy, University of Split,
Matice hrvatske 15, 21 000 Split, Republic of Croatia

Wastewater process modeling Amra Serdarevic and Alma Dzubur
Abstract; Full Text (1934K) .	pages 21-39.	DOI: 10.12989/csm.2016.5.1.021

Abstract
Wastewater process models are the essential tools for understanding relevant aspects of wastewater treatment system. Wastewater process modeling provides more options for upgrades and better understanding of new plant design, as well as improvements of operational controls. The software packages (BioWin, GPS-X, Aqua designer, etc) solve a series of simulated equations simultaneously in order to propose several solutions for a specific facility. Research and implementation of wastewater process modeling in combination with computational fluid dynamics enable testing for improvements of flow characteristics for WWTP and at the same time exam biological, physical, and chemical characteristics of the flow. Application of WWTP models requires broad knowledge of the process and expertise in modeling. Therefore, an efficient and good modeling practice requires both experience and set of proper guidelines as a background.

Key Words
wastewater treatment plant; modeling; activated sludge process; simulation

Address
Amra Serdarevic and Alma Dzubur: Department of Sanitary Engineering and Department of Environmental Engineering,
Faculty of Civil Engineering, University of Sarajevo, Sarajevo, Bosnia and Herzegovina

Soil –structure interaction analysis of a building frame supported on piled raft H.S. Chore and M.J. Siddiqui
Abstract; Full Text (1781K) .	pages 041-58.	DOI: 10.12989/csm.2016.5.1.041

Abstract
The study deals with physical modeling of a typical building frame resting on pile raft foundation and embedded in cohesive soil mass using finite element based software ETABS. Both- the elements of superstructure and substructure (i.e., foundation) including soil is assumed to remain in elastic state at all the time. The raft is modelled as a thin plate and the pile and soils are treated as interactive springs. Both- the resistance of the piles as well as that of raft base - are incorporated into the model. Interactions between raft-soil-pile are computed. The proposed method makes it possible to solve the problems of uniformly and large non-uniformly arranged piled rafts in a time saving way using finite element based software ETABS. The effect of the various parameters of the pile raft foundation such as thickness of raft and pile diameter is evaluated on the response of superstructure. The response included the displacement at the top of the frame and bending moment in columns. The soil-structure interaction effect is found to increase displacement and increase the absolute maximum positive and negative moments. The effect of the soil- structure interaction is observed to be significant for the type of foundation and soil considered in the present study.

Key Words
soil-structure interaction; piled raft; raft thickness; pile diameter; top displacement; bending moment

Address
H.S. Chore: Department of Civil Engineering, Datta Meghe College of Engineering, Sector-3, Airoli, Navi Mumbai- 400 708, India
M.J. Siddiqui: Department of Civil Engineering, School of Technology, A.I. Kalsekar Technical Campus, Panvel, Navi Mumbai, India

Free vibration analysis of gravity dam-reservoir system utilizing 21 node-33 Gauss point triangular elements Seyed Hamid Ziaolhagh, Meghdad Goudarzi and Ahmad Aftabi Sani
Abstract; Full Text (2276K) .	pages 59-86.	DOI: 10.12989/csm.2016.5.1.059

Abstract
This paper deals with the free vibration analysis of a dynamical coupled system: flexible gravity dam- compressible rectangular reservoir. The finite element method is used to compute the natural frequencies and modal shapes of the system. Firstly, the reservoir and subsequently the dam is modeled by classical 8-node elements and the natural frequencies plus modal shapes are calculated. Afterwards, a new 21-node element is introduced and the same procedure is conducted in which an efficient method is employed to carry out the integration operations. Finally, the coupled dam-reservoir system is modeled by solely one 21-node element and the free vibration of dam-reservoir interaction system is investigated. As an important result, it is clearly concluded that the one high-order element treats more precisely than the eight-node elements, since the first one utilizes fifth-degree polynomials to construct the shape functions and the second implements polynomials of degree two.

Key Words
dam–reservoir interaction; Finite element method; mathematica; Gauss integration

Address
Seyed Hamid Ziaolhagh: Civil Engineering Department, Shahrood University of technology, Shahrood, Iran
Meghdad Goudarzi and Ahmad Aftabi Sani:Civil Engineering Department, Mashhad Branch, Islamic Azad University, Mashhad, Iran

Resonance of a rectangular plate influenced by sequential moving masses Mohsen Ebrahimzadeh Hassanabadi, Nader K.A. Attari, Ali Nikkhoo and Stefano Mariani
Abstract; Full Text (1642K) .	pages 87-100.	DOI: 10.12989/csm.2016.5.1.087

Abstract
In this work, an improved semi-analytical technique is adopted to track the dynamic response of thin rectangular plates excited by sequential traveling masses. This technique exploits a so-called indirect definition of inertial interaction between the moving masses and the plate and leads to a reduction, in the equations of motion, of the number of time-varying coefficients linked to the changing position of the masses. By employing this optimized method, the resonance of the plate can be obtained according to a parametric study of relevant maximum dynamic amplification factor. For the case of evenly spaced, equal masses travelling along a straight line, the resonance velocity of the masses themselves is also approximately predicted via a fast methodology based on the fundamental frequency of the system only.

Key Words
thin rectangular plate; resonance; traveling masses; semi-analytical procedures; optimized method

Address
Mohsen Ebrahimzadeh Hassanabadi and Nader K.A. Attari: Department of Structural Engineering, Building and Housing Research Center (BHRC), Tehran, Iran
Ali Nikkhoo: Department of Civil Engineering, University of Science and Culture, Tehran, Iran
Stefano Mariani: Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133 - Milano, Italy