The greatest advantage of fiber-reinforced composite materials is the freedom to tailor their strength and stiffness properties, while the most significant disadvantage consists in their high costs. Therefore, the design process and especially the optimization phase becomes an important step. The geometry of the fabric of each lamina as well as their stacking sequence need to be carefully defined, starting from some basic geometric variables. The input parameters are the widths and the heights of the tows, the laminate-stacking sequence and the gaps between two successive tows or the height of the neat matrix. This paper is a follow-up to a previous work on using and improving an in-house software called SOMGA (Satin Optimization with a Modified Genetic Algorithm), aimed to optimize the geometrical parameters of satin-reinforced multi-layer composites. The final goal is to find out the way in which various types of woven fabrics can affect the best possible solution to the problem of designing a composite material, able to withstand a given set of in-plane loads. The efficiency of the composite structure is evaluated by its ultimate strains using a fitness function that analyses and compares the mechanical behavior of different fabric-reinforced composites. Therefore, the ultimate strains corresponding to each configuration are considered intermediate data, being analyzed comparatively until obtaining the optimal values. When the software is running, for each analysis step, a set of intermediate values is provided. However, the users do not have to store these values, because the final result of the optimization directly provides the composite configuration with maximum efficiency, whose structural response meets the initially imposed loading conditions. To illustrate how the SOMGA software works, six different satin-woven-fabric-reinforced composites, starting from plain weave (satin 2/1/1), then satin 3/1/1, satin 4/1/1, satin 5/1/1, satin 5/2/1 and finally satin 5/3/1, were evaluated in the SOMGA interface. The results were rated against each other in terms of the composite efficiency and the case characterized by minimal reinforcement undulation (thinnest laminate) were highlighted.

The particular behaviour of joints with hollow sections is not an easy task, leading to a lack of agility in the design process. The available market profiles of the elements must be chosen judiciously early from the design stage, in order to avoid subsequent problems at the connection design stage. These limitations have given rise to the need to obtain further information on the performance of joints with hollow sections in what concerns resistance, stiffness and deformation capacity. The study of joints with square hollow sections described in the present paper evaluates the differences in design between EN 1993-1-8 and ISO 14346 (2013). The latest norm is based on CIDECT design guide (Packer et al., 2009).

The purpose of this paper is to develop a practical and realistic mathematical programming for finding the optimal layer thickness of the flexible pavement of roads and highways in order to obtain a minimum-cost solution represented by the unit costs of pavement components and constraining equations required by AASHTO design method [1]. Physical limitations imposed by the distress caused by rutting prevention complete the realism of the mathematical model in describing the actual behavior of the flexible pavement system. An optimization algorithm written in MATLAB code is advanced herein and solved by non-linear programming. The optimized thicknesses of the pavement layers are then verified in order to check the specified structural number and the damage performance of the resulting pavement structure.By this design procedure substantial cost savings result in the selection of flexible pavement sections.

The climate behaviour suffers important changes as result of the impact with a rapid extension of the anthropic space. The abrupt modification of season temperature and severe wind storms are put in evidence now all over the world. Simulation of the dynamic effects of wind action upon the built environment in laboratory is a process of scaling at reduced dimensions of a complex combination of factors insuring similarity between the natural phenomenon and the one artificially reproduced. Usually, the design wind dynamic action on structures is identified with the so-called extra-tropical depressions, specific for middle global latitudes; the atmosphere is considered neutrally stratified, the vertical profile is in equilibrium with the terrain roughness in A.B.L. The simulations of wind speeds and pressures in the boundary layer of the air moving at the surface of the earth are based on vertical profile of the mean speeds, turbulence intensity, spectral power and histograms of the recorded values. The analysis of data is based on the model of the wind speed in A.B.L. fairly considered as a random, stationary, Gaussian process. Lately, the observations put in evidence the fact that it is the strong winds associated with thunder storms along with the so called gust fronts that affect the built environment and that they are not stationary and Gaussian processes. The paper presents the analysis of series of measured speeds in the wind tunnel SECO 2 at different time intervals, different sampling rates in different types of boundary layers, analyzing the possibility of reproducing some of the characteristics of the wind speed in a non-neutrally stratified boundary layer.

The high complexity of the load transfer mechanism at the steel column base connection yields for special care in both analysis/ design as well as in the actual errection stage of frame steel structures. Describing the real behaviour of the joint represents a key aspect in the overall structural analysis. The fully rigid or fully pinned assumptions on the column base joint behaviour have already been surpassed by more complex approaches in the analysis. As the dissipative capacity assessement is still under debate among specialists, the paper aims at delivering additional data to the problem. Laboratory tests, backed-up by numerical modeling investigations were performed on two natural scale steel columns base connection configurations under cyclic lateral loading conditions. Results of in terms of load - displacement and moment - rotation diagrams are hereinafter advanced for further studies purposes.

The paper uses the layerwise theory, i.e. the zigzag behaviour of the in-plane displacements through the thickness, and the Lagrange interpolation functions for finite element to compute the stresses and displacements in beams made by composite materials. The layerwise method can determine the interlaminar stresses and other localized effects with the same accuracy as 2D finite element method but less computer effort. We present as illustration two examples.

The mechanical properties of composite fabrics rely on a fabric made by a textile weaving process. In order to use their special ability of being drapeable, instead of just plain weave fabrics, satin or twill reinforcement can be selected. Although some other advantages of the resulting composite, such as good impact resistance or damage tolerance are similar to all woven reinforcement composites, the superior drapeability of satin is a major reason to favour this type of textile reinforcement. This paper is focused on the modelling procedures of stiffness characteristics, specific to satin reinforced laminated composites, using a semi-discrete approach. This method is a compromise between the continuous and pure discrete approaches and is associated with a mesoscopic analysis of the repetitive unit cell (RUC). The elastic properties of the textile reinforced epoxy composite, namely longitudinal modulus and transverse modulus, in case of carbon and fibre glass based 5-harness satin reinforcement, are determined. The differences between the two resulting composite materials and the influence of the various geometric and material parameters involved are studied.

The structure of the fabric, when it is used as a composite reinforcement, have a major influence on the mechanical properties of a fabric reinforced composite material. Composite design and analysis requires a computer tool, not only to link composite properties to fabric micro and macro geometry, but also to link fabric micro geometry to the weaving pattern. The complex structure of textile composite comprises of several hierarchical levels: macro (composite component or sub-component), meso (unit cell of the reinforcement structure) and micro (fibre placement inside yarns and fibrous plies). The most specific to textile composites is meso level, where the structure dependent behaviour of the material is most pronounced. This is the most important level at which the optimization of the structure and the constituents should be performed. Continuous and discrete approaches are possible for the forming simulations of composite textile reinforcements because of their multi-scale structure. In recent years, due to the advancement of structural and material modelling technology, a relatively accurate geometrical textile composites models have been developed through computer aided engineering and textile geometric modelling software. This paper emphasizes the modelling procedures of mechanical elastic proprieties specific to woven laminated composites.

In the last decade, a family of assembled methods termed meshless methods are important topics in the computer-aided design with respect to engineering problems. A possible classification of the meshless methods may be derived with respect the approximation spaces, i.e. class of radial basis functions (RBF). The purpose this paper is to study and compare the computational efficiency and derivative generation capability of the RBF methods for the approximation of functions and their derivatives. by applying these methods to several numerical examples. The least squares formulation for RBF methods is employed instead the collocation approach because it can result in smaller errors.

Solar energy is one of the most important renewable resources due to its unique set of advantages. In urban configurations, wide open spaces used for parking areas close to malls, stadiums and industrial areas become justified challenges in revaluating them by placing solar panels on their wide roofs.The paper is a first attempt that reflects the scientific interest in the particularities of wind action upon the solar panels sustained by structural framed elements and which cover the parking areas. These complex studies consist in experiments on physical scale models in wind tunnel in parallel with numerical simulations of wind flow over the solar panels, highlighting the variations of the wind pressure along the rows of solar panels for the situations that may occur, of either a completely free parking area or, fully occupied with vehicles. The aim was to evaluate from both qualitative and quantitative point of view the nature of the air flow in the solar panels field, having in view the essential differences from the situation when the solar panels are directly placed on the roofs of the buildings. The experiments considered different degrees of filling the parking areas with vehicles. The physical modelling uses an original methodology of pneumatic averaging of the pressures for the determination of the resultant wind pressure on the surfaces of the panels, which avoids blocking of the free flow stream under the rows of the solar panels and the numerical simulation of turbulent wind flow uses ANSYS 12 CFX programs.

The heterogeneity and anisotropy of structural composites make the application of the standard mesh-based methods using the meshing of interfacial region between matrix and fibers a difficult task. The objective of this study is to present the EFG formulation for problems of composite micromechanics. It is expected that the tediousness and approximations involved in mesh generation, and hence inaccuracies in the results can be avoided using the new meshless techniques such as the Element Free Galerkin (EFG) method. The theoretical methodologies, computer implementations and practical application are carried out. Periodic boundary conditions of the unit cell under tensile load are set up. The method of Lagrange multipliers is introduced for the treatment of material discontinuity at the fiber-matrix interface in which both the displacement continuity and traction reciprocity are satisfied. The EFG method is formulated for the generalized plane strain problems. Examples are presented to illustrate the effectiveness of the proposed micromechanical model, and it is validated by comparing the results with available numerical solutions.

Studies have been developed all over the world regarding the evaluation of the wind action on solarpanels, placed single or in arrays of elements, justified by the lack of comprehensive recommendations in the codes of practice regarding these specific situations. Placing the solar panels in consecutive rows on parking places is an alternative which has never been covered by codes for wind actions on structures. An original analysis is developed in the present paper considering the distribution of wind pressures on solar panels mounted abovethe large car parking places, where their presence would bring economy in construction while protecting and increasing the comfort of the parking space.Two constructive solutions have been considered and analysed through physical modelling and testing in atmospheric boundary layer tunnel and a numerical simulation in ANSYS 12 CFX program was in parallel run for a visualization of the flow field characteristics. Key-Words: solar panels, wind pressure coefficients, wind tunnel, numerical simulation

Optimization of floor girders is a complex nonlinear problem for which a simple computational procedure has been suggested. The Generalized Reduced Gradient (GRG). Nonlinear algorithm available in Excel Solver were utilized to optimize the design of plate girder for minimum weight and maximum allowable distance between secondary beams, given the span and grade of the material of the girder. Optimizing a girder for bending moment is achieved by moving material away from the neutral axis of the beam, in other words, by making the web more slender. When lateral supports are used to prevent from lateral torsional buckling, all the forms of the compressed flange instability will become the critical failure mechanism. Due to high slenderness values, the deflection of the beam is not a gouverning condition. In this paper, the maximum spacing between lateral supports against lateral-torsional buckling were maximized meanwhile respecting the provisions of the norm SR EN 1993-1-1. Results of the numerical computations considering various lengths of beams and girders are presented herein. Girders are considered to be efficiently designed with respect of the presented technique of optimization.

The paper presents a study on modelling the wind drifting of the snow deposited on the flat roofs of buildings in wind tunnel. The physical model of snow drifting in wind tunnel simulating the urban exposure to wind action is not frequently reported in literature, but is justified by the serious damages under accidental important snow falls combined with strong wind actions on the roofs of various buildings. A uniform layer of snow deposited on the flat roof was exposed to wind action in order to obtain the drifting. The parameters involved in the modelling at reduced scale, with particles of glass beads, of the phenomenon of transportation of the snow from the roof were analysed, particularly the roughness length and the friction wind speed. A numerical simulation in ANSYS CFX program was developed in parallel, by which a more accurate visualization of the particularities of the wind flow over the roof was possible, in the specific areas where the phenomenon of snow transportation was more susceptible to occur. Modified roughness length and friction wind speed were determined through methods used in the literature, an attempt being made in this work to analyse the factors that influence their values.

Solar collectors may be situated in numerous positions within the volume created by the presence of the buildings. In particular, the space offered by the terraces of the buildings is generous and adequate for covering a whole area with solar panels.Modern design to wind action is based on the study of wind flow over the field of collectors and the determination of the forces induced by wind upon the solar panels; numerous studies were developed both in situ and in laboratory regarding wind local coefficients of pressure/suction on these elements had the purpose to emphasize specific aspects of local turbulence that have to be taken into account.The paper presents studies based on numerical simulations and tests run in the wind tunnel of the Faculty of Civil Engineering and Building Services in Iasiparticularly regarding the wind flow over a field of solar collectors placed in parallel rows on the terrace of a residential building. The experimental results were compared with the numerical simulation in ANSYS 12 CFX in order to put in evidence the wind flow characteristics and to analyze the accuracy of the model by comparing the results from the laboratory with the computer simulation.

In this paper, the underneath the base plate together with the base plate is referred to as component in compression and base plate in bending or in short concrete in compression. The strength of the in compression depends on the base material, the behaviour of the grout layer and the complex phenomena in the contact area between the base plate and the concrete. Models are presented for the determination of the resistance of this component. The models have been validated with tests. In this paper a brief description of literature reviewed is presented along with their various assumptions adopted during modeling.

Wind actions determines the most important load in the design of the support systems of the solar panels, wherever they are located - on flat or pitched roofs or at the ground level. The goal of simulations of the interaction between wind and the solar panels by Computational Fluid Dynamics (CFD) is to estimate the complex wind flow and pressures that act upon their surface. In the study presented herein, the wind pressure acting on 12 solar panels is simulated. The solar panels are placed in a regular array, mounted at ground level and tilted at 30o. Five wind directions (0o, 30o, 45o, 135o, 180o) have been analyzed with the computer code ANSYS 12 CFX.

For solving a partial different equation by a numerical method, a possible alternative may be either to use a mesh method or a meshless method. A flexible computational procedure for solving 1D linear elastic beam problems is presented that currently uses two forms of approximation function (moving least squares and kernel approximation functions) and two types of formulations, namely the weak form and collocation technique, respectively, to reproduce Element Free Galerkin (EFG) and Smooth Particle Hydrodynamics (SPH) meshless methods. The numerical implementation for beam problems of these two formulations is discussed and numerical tests are presented to illustrate the difference between the formulations.