Mathematical simulation of the nonlinear tri-dimensional mechanical behavior of quasi-brittle materials like concrete is one of the biggest challenges in the engineering science. It is vital to have the knowledge of the response of concrete specimens subjected to low and high strain rate deformation for the analysis of concrete structures under the static and dynamic loading cases. The behavior of this material is generally known to be strain rate sensitive. Among phenomena of different orientation, the multi plane models, like multi-laminate models using a constitutive equation in a vectorial form rather than tensorial form by means of capturing interactions, can meet this goal adequately. This paper suggests a robust rate dependent damage based model in the multi-planes framework accomplished with minimum parameters for calibration and appropriate for engineering purposes. This damage formulation has been built on the basis of two types of essential damage, axial damage and shear damage, that basically can happen on each sampling plane and based on this concept two new axial and shear damage functions are proposed. Model verification has been studied under different compressive and tensile loading rates, comparing the results of the proposed model with the experimental data and Mohr-Coulomb failure criterion envelope line.

This paper focuses on addition of fillers in epoxy resin and aggregate for polymer concrete (PC)preparation. For the preparation of PC, two kinds of fillers, i.e. rice husk ash and broom stem ash were used.According to experimental results, addition of fillers had a positive impact on the physical and mechanicalproperties of the PC. In the PC sample with rice husk ash, with the filler/aggregate ratio of 0.075 and 18.4%polymer, maximum compressive strength of 86.41 Mpa was obtained; while the compressive strength of thepolymer concrete without filler was 71.2 Mpa. The PC sample with broom stem ash, with the filler/aggregate ratioof 0.12 and 23% polymer showed the maximum flexural strength

Abstract. The prediction of material response is necessary for the analysis of structure under static or dynamic loading. Mathematical modeling of the nonlinear tri-dimensional mechanical behavior of quasi-brittle materials, like concrete, caused by damaging and plasticity e ects is one of the most serious classical challenges we face in the engineering science. Among phenomena of di erent orientations, the micro-plane models, like multiplanes models, which use a constitutive equation in a vectorial form rather than tensorial form by means of capturing interactions, can serve this goal adequately. This paper presents a simple realistic and robust damage based model in the multi-plane framework accomplished with a few parameters for calibration and suitable for engineering purposes without volumetric-deviatoric split of strain tensor and its problems. This damage formulation has been built on the basis of two types of fundamental damage, namely, axial damage and shear damage, that can essentially occur on each micro-plane and, based on this concept, two new axial and shear damage functions are presented. By comparing the results of the proposed model and experimental data, model veri cation has been done under di erent loading/unloading/reloading stress/strain paths.

Steel plate shear walls (SPSWs) have advantages such as high elastic stiffness, stable hysteresis behavior, high energy absorption capacity, and decent ductility. However, one of the main drawbacks of SPSWs is their buckling under lateral loading. To address this issue, a simple and practical solution in the form of using a trapezoidal plate moment connection (PMC) and a narrow gap between the infill plate and columns is presented. The PMC will act as an energy absorber, similar to a yielding steel plate, and keep the other structural members in an elastic state. Extensive three-dimensional finite element (FE) models of the SPSW system were investigated under monotonic and cyclic loading. The results revealed that by separating the infill plate from the vertical boundary elements and using two vertical edge stiffeners at both edges of the wall, the same lateral bearing capacity of the conventional system can be achieved. In addition, by increasing the thickness of the PMC from 6.5 to 26 mm, the load-bearing capacity, energy dissipation, and elastic stiffness increased approximately 2, 2.5, and 3.2 times, respectively. It was also found that the flexural capacity ratio of the connection to the beam had little effect on the overall force–displacement behavior. However, it can affect the system failure mechanism. Finally, the tension field inclination angle for such SPSWs was proposed in the range of 30 to 35°.

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Separators are a vital part of almost every oil and gas production facility. Because of their importance, optimal separator design is critical. Semi-empirical design method is a conventional and more primitive way of determining the optimal dimensions for separators. However, because of the simplifying assumptions used to derive semi-empirical correlations, this method can only be used to obtain a rough estimate for separator dimensions. In this study, a novel hybrid method to design multiphase separators is presented using experimentation, dimensional analysis, and CFD simulation. This method contains performing experiments on a pilot two-phase separation unit; CFD simulating of the laboratory-scale separator and validating the simulation using the experimental data; determining a range for the slenderness ratio of practical surface separators using dimensional analysis; CFD simulating the separators with slenderness ratios within the specified range using the procedure, and determining the optimum slenderness ratio. The pilot two-phase separation unit consists of a laboratory-scale horizontal two-phase separator, pumps, compressors and a static mixer to create a two-phase flow, and a liquid filter to extract liquid droplets from the separator gas outflow. The diameter of the trapped liquid droplets and their weight are, then, determined by imaging and weighing processes. The CFD model is validated with the experimental data (with less than 8% relative error). Using these steps, the dimensions of a surface separator for one of the production wells located in phase 9 of South Pars gas field are determined. One of the most important achievements of this research is to provide the necessary basis for the optimal design of surface separators.

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