Massood Mofid

Herein, two novel Physics Informed Neural Network (PINN) architectures are proposed for output-only system identification and input estimation of dynamic systems. Using merely sparse output-only measurements, the proposed PINNs architectures furnish a novel approach to input, state, and parameter estimation of linear and nonlinear systems with multiple degrees of freedom. These architectures are comprised of parallel and sequential PINNs that act upon a set of ordinary differential equations (ODEs) obtained from spatial discretization of the partial differential equation (PDE). The performance of this framework for dynamic system identification and input estimation was ascertained by extensive numerical experiments on linear and nonlinear systems. The advantage of the proposed approach, when compared with system identification, lies in its computational efficiency. When compared with traditional Artificial Neural Networks (ANNs), this approach requires substantially smaller training data and does not suffer from generalizability issues. In this regard, the states, inputs, and parameters of dynamic state-space equations of motion were estimated using simulated experiments with “noisy” data. The proposed framework for PINN showed excellent great generalizability for various types of applications. Furthermore, it was found that the proposed architectures significantly outperformed ANNs in generalizability and estimation accuracy.

The non-linear response of steel plate shear walls (SPSWs) with perforated infill plates are studied by considering the interaction effect between the frame and the infill plate. A number of single and 14-stories SPSWs with solid and perforated infill panels with different perforation ratios are studied numerically. The results are utilized to discuss (a) the influence of perforated ratio and placement of the holes on system behavior (b) changes in system strength, stiffness, damping ratio and ductility due to the introduction of perforation in infill panels, and (c) evaluate the change in behavior of low and high-rise structures by the introduction of perforations. The results reveal that the perforation ratio is not the only controlling factor in strength and ductility of the shear wall specimens, and the strength and ductility of SPSW also depend upon the placement array of the perforations in the infill plate. The ultimate strength, ductility ratio and initial stiffness of the perforated SPSWs have been reduced to 28, 29 and 33.5% compared to the reference specimen, respectively. Also, the values of normalized CHE and LHE and equivalent viscous damping ratio in perforated specimens reduced to about 28, 26 and 10%, respectively.

This paper investigates the influence of an opening in the infill steel plate on the behavior of steel trapezoidal corrugated infill panels. Two specimens of steel trapezoidal corrugated shear walls were constructed and tested under cyclic loading. One specimen had a single rectangular opening, while the other one had two rectangular openings. In addition, the percentage of opening in both specimens was 18%. The initial stiffness, ultimate strength, ductility ratio and energy dissipation capacity of the two tested specimens are compared to a specimen without opening. The experimental results indicate that the existence of an opening has the greatest effect on the initial stiffness of the corrugated steel infill panels. In addition, the experimental results reveal that the structural performance of the specimen with two openings is improved in some areas compared to the specimen with one opening. To that end, the energy dissipation capacity of the specimen with two openings is obtained larger than the specimen with one opening. Furthermore, a number of numerical analyses were performed. The numerical results show that with increasing the thickness of the infill plate or using stiffeners around the opening, the ultimate strength of a corrugated steel infill panel with an opening can be equal to or even more than the ultimate strength of that panel without an opening.

As steel plate shear walls are typically used in the building central cores around the elevators and stairs, introduction of an opening as door seems to be inevitable in steel plate shear wall spans. Due to the weakening of the steel plate shear walls’ performance caused by this particular type of opening, the use of stiffeners around the opening is necessary. Nevertheless, introduction of stiffeners around all sides of the opening, which does continue to boundary elements, is very expensive and inefficient. Therefore, the study on the effect of different arrangements of stiffeners on the behavior of steel plate shear walls is significant. In this research, a number of steel plate shear walls with different characteristics in terms of the plate aspect ratio, location of openings, arrangement of stiffeners around the openings, and number of stories are designed, and also a series of nonlinear static analyses are performed. Then, the optimum locations of openings along with the arrangement of stiffeners for each case are identified based on the structural and economic criteria. Finally, a modified model, which is more efficient in terms of cost and performance in comparison with the similar unmodified model, is proposed.

This paper aims to examine flexural vibrations of fully saturated poroelastic structures on an elastic bed subjected to moving point loads via an analytical solution. Using a flexural beam model in conjunction with the Biot’s poro-elasticity theory, the equations of motion of the porous structure are derived. Using assumed mode method and Laplace transform, the explicit expressions of displacement and pore pressure are obtained carefully. For a particular case, the predicted results are also compared with those of another work and a reasonably good agreement is achieved. The influences of the moving load velocity, permeability ratio, transverse stiffness of the foundation, viscosity of the pore fluid, and porosity on the maximum elasto-dynamic fields and pore pressure are conclusively discussed. The velocity pertinent to the maximum possible dynamic response is graphically determined and the roles of influential parameters on this crucial factor are displayed. The present model could be easily extended to multi-layered poroelastic structures under moving loads.

In this research, the combination of Fourier sine series and Fourier cosine series is employed to develop an analytical method for free vibration analysis of an Euler-Bernoulli beam of varying cross- section, fully or partially supported by a variable elastic foundation. The foundation stiffness and cross section of the beam are considered as arbitrary functions in the beam length direction. The idea of the proposed method is to superpose Fourier sine and Fourier cosine series to satisfy general elastically end constraints and therefore no auxiliary functions are required to supplement the Fourier series. This method provides a simple, accurate and flexible solution for various beam problems and is also able to be extended to other cases whose governing differential equations are nonlinear. Moreover, this method is applicable for plate problems with different boundary conditions if two-dimensional Fourier sine and cosine series are taken as displacement function.Numerical examples are carried out illustrating the accuracy and efficiency of the presented approach.

Double web angle connection is one of the most rudimentary connections in simple structural systems such as braced frame system. Essentially, it is presumed in conventional designs, which actually double web angle connection behaves as a hinge connection. However, in braced frames, due to existence of braces in some bays, in specified locations where gusset plates of brace placed with beam to column connection in one joint, this contemplation may not be accurate. This is due to the restraining of the beam from rotation by gusset plates that is placed on top and bottom of the beam or only on one side. In such cases, the simple beam to column connection may be transformed into a semi-hinge or fixed connection. In this paper, double web angle connection is investigated in the mentioned locations using the FEM method along with the calculating moment rotation behavior of connection and subsequently type, as well as the rigidity of connection. Furthermore, an analytical model is proposed to predict the characteristics of the double web angle connection in the view of the relevant case.

Summary: Studies on corrugated steel shear walls (CSSWs) generally indicate noticeable increase of energy absorption, as well as increasing shear buckling capacity of corrugated plates being more likely rather than the flat plates. In this paper, the effect of variation in the angle of trapezoidal plate on the behavior of CSSWs has extensively been investigated. Three specimens of CSSW with 1 story and single bay in half scale are tested under cyclic load. The observations of experiment do indicate that stress concentration has been increased in the corner of subpanels, by increasing of the corrugation angle. Development of the tensile field and wall yield and damage depends on the geometry of the plate. By increasing the corrugation angle, the stiffness and energy dissipation decrease; in addition, large loss of strength takes place. Comparing the numerical and experimental results indicates that for a closer look at behavior of trapezoidal CSSWs, fracture mechanics, fatigue, and damping of materials should be considered by numerical analysis.

The National Iranian Gas Company (NIGC) is one of the top ten gas companies in the gas industry in the Middle East and is comprised of 7 gas refineries. So this company needs to apply the most optimum time management methods to achieve its goals. Custom scheduling calculation of project planning uses the Critical Path Method (CPM) as a tool for Planning Projects activities. CPM is now widely used in planning and managing projects but in spite of its wide application, this method has a critical weak point of not taking into account the uncertainties in scheduling calculation. This article aims to present a precise method based on the application of Fuzzy Expert Systems in order to improve the Time Estimation Method in construction projects and in this regard, reviews the results of the implementation of this method in construction projects of Iranian Gas Refineries. The results show that the proposed method increases the accuracy of time estimation about 7 to 22 percent.