• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2003.10a
• /
• pp.169-176
• /
• 2003

In the present study, a shape design optimization scheme in shell structures is implemented based on the integrated framework of geometric modeling and analysis. The common representation of B-spline surface patch is used for geometric modeling. A geometrically-exact shell finite element is implemented. Control points or the surface are employed as design variables. In the computation of shape sensitivity, semi-analytical method is employed. Sequential linear programming is applied to the shape optimization of surfaces. The developed integrated framework should serve as a powerful tool to design and analysis of surfaces.

• Structural Engineering and Mechanics
• /
• v.43 no.1
• /
• pp.71-87
• /
• 2012

This paper extends a single equation, semi-analytical approach for three-span bridges to multi-span ones for the rapid and precise determination of natural frequencies and natural mode shapes of an orthotropic, multi-span plate. This method can be used to study the dynamic interaction between bridges and vehicles. It is based on the modal superposition method taking into account intermodal coupling to determine natural frequencies and mode shapes of a bridge deck. In this paper, a four- and a five-span orthotropic roadway bridge deck are compared in the first 10 modes with a finite element method analysis using ANSYS software. This simplified implementation matches numerical modeling within 2% in all cases. This paper verifies that applicability of a single formula approach as a simpler alternative to finite element modeling.

• Structural Engineering and Mechanics
• /
• v.51 no.5
• /
• pp.809-821
• /
• 2014

The truss based steel bridge structures usually consists of gusset plates which lose their load carrying capacity and rigidity under the effect of repeated and dynamics loads. This paper is focused on modeling the nonlinear material behavior of the gusset plates of the Truss Based Bridges subjected to dynamics loads. The nonlinear behavior of material is characterized by a damage coupled elsto-plastic material models. A truss bridge finite element model is established in Abaqus with the details of the gusset plates and their connections. The nonlinear finite element analyses are performed to calculate stress and strain states in the gusset plates under different loading conditions. The study indicates that damage initiation occurred in the plastic deformation localized region of the gusset plates where all, diagonal, horizontal and vertical, truss member met and are critical for shear type of failure due tension and compression interaction. These findings are agreed with the analytical and experimental results obtained for the stress distribution of this kind gusset plate.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.8 s.113
• /
• pp.840-847
• /
• 2006

Dynamic modelingand active vibration control of smart hull structure using Macro Fiber Composite (MFC) actuators are conducted. Finite element modeling is used to obtain equations of motion and boundary effects of smart hull structure. Modal analysis is carried out to investigate the dynamic characteristics of the smart hull structure, and compared to the results of experimental investigation. Negative velocity feedback control algorithm is employed to investigate active damping of hull structure. It is observed that non-resonant vibration of hull structure is suppressed effectively by the MFC actuators.

• Structural Engineering and Mechanics
• /
• v.73 no.1
• /
• pp.27-35
• /
• 2020

In rail industry, noise reduction is a concern to decrease environmental pollution. The current study focuses on rail damper modeling and improvement of the model through validation with experimental results. Accurate modeling and simulation of rail dampers, specifically tuned rail dampers with layers interconnected by bolt joints, shall enable objective-oriented improvement of their design. In this work, to improve the damper model cone pressure theory is applied in the FE model and the sensitivity analysis is then applied to gradually improve the FE model. The improved model yields higher Modal Assurance Criterion (MAC) values and lower frequencies deviation.

• Computers and Concrete
• /
• v.29 no.5
• /
• pp.279-283
• /
• 2022

The seismic analytic collapse fragility of soil nail wall structures with a shotcrete concrete covering is investigated in this paper. The finite element modeling process has been well described. The fragility function evaluates the link between ground motion intensities and the likelihood of reaching a specific level of damage. The soil nail wall has been subjected to incremental dynamic analysis (IDA) from medium to strong ground vibrations. The nonlinear dynamic analysis of the soil nail wall uses a set of 20 earthquake ground motions with varying PGAs. PGD is utilized as an intensity measure, the numerical findings demonstrate that the soil nailing wall reaction is particularly sensitive to earthquake intensity measure (IM).

• Computers and Concrete
• /
• v.14 no.1
• /
• pp.73-90
• /
• 2014

The traditional destructive tests in damage detection require high cost, long consuming time, repairing of damaged members, etc. In addition to these, powerful equipments with advanced technology have motivated development of global vibration based damage detection methods. These methods base on observation of the changes in the structural dynamic properties and updating finite element models. The existence, location, severity and effect on the structural behavior of the damages can be identified by using these methods. The main idea in these methods is to minimize the differences between analytical and experimental natural frequencies. In this study, an application of damage detection using model updating method was presented on a one storey reinforced concrete (RC) building model. The model was designed to be 1/2 scale of a real building. The measurements on the model were performed by using ten uni-axial seismic accelerometers which were placed to the floor level. The presented damage identification procedure mainly consists of five steps: initial finite element modeling, testing of the undamaged model, finite element model calibration, testing of the damaged model, and damage detection with model updating. The elasticity modulus was selected as variable parameter for model calibration, while the inertia moment of section was selected for model updating. The first three modes were taken into consideration. The possible damaged members were estimated by considering the change ratio in the inertia moment. It was concluded that the finite element model calibration was required for structures to later evaluations such as damage, fatigue, etc. The presented model updating based procedure was very effective and useful for RC structures in the damage identification.

• Smart Structures and Systems
• /
• v.31 no.3
• /
• pp.275-281
• /
• 2023

In recent years, technological developments have rapidly increased the number of complex structures and equipment in the industrial. Accordingly, the prognostics and health monitoring (PHM) technology has become significant. The safety assessment of industrial sites requires data obtained by installing a number of sensors in the structure. Therefore, digital twin technology, which forms the core of the Fourth Industrial Revolution, is attracting attention in the safety field. The research on digital twin technology of structures subjected to seismic loads has been conducted recently. Hence, this study proposes a digital twin system that estimates the responses and arbitrary load in real time by utilizing the minimum sensor to a pipe that receives a seismic and arbitrary load. To construct the digital twin system, a finite-element model was created considering the dynamic characteristics of the pipe system, and then updating the finite-element model. In addition, the calculation speed was improved using a finite-element model that applied the reduced-order modeling (ROM) technology to achieve real-time performance. The constructed digital twin system successfully and rapidly estimated the load and the point where the sensor was not attached. The accuracy of the constructed digital twin system was verified by comparing the response of the digital twin model with that derived by using the load estimated from the digital twin model as input in the finite-element model.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.10
• /
• pp.990-998
• /
• 2004

There have been lots of efforts to analyze the dynamic characteristics of mechanical systems. However, it is difficult the know the dynamic characteristics of mechanical systems composed of many parts with joints. Specially, in case of a bolted Joint structure, no effective modeling method has been defined to acquire dynamic characteristics of the structure using the finite element (FE) analysis. In this research, a linear dynamic model is developed for bolted feints and large interfaces using con frusta method and linear spring elements, respectively. The developed modeling method for bolted joints is verified based on the experimental result.

• Computers and Concrete
• /
• v.22 no.2
• /
• pp.167-182
• /
• 2018

The modeling of loss of bond between reinforcing bars (rebars) and concrete due to corrosion is useful in studying the behavior and prediction of residual load bearing capacity of corroded reinforced concrete (RC) members. In the present work, first the possibility of using different methods to simulate the rebars-concrete bonding, which is used in three-dimensional (3D) finite element (FE) modeling of corroded RC beams, was explored. The cohesive surface interaction method was found to be most suitable for simulating the bond between rebars and concrete. Secondly, using the cohesive surface interaction approach, the 3D FE modeling of the behavior of non-corroded and corroded RC beams was carried out in an ABAQUS environment. Experimental data, reported in literature, were used to validate the models. Then using the developed models, a parametric study was conducted to examine the effects of some parameters, such as degree and location of the corrosion, on the behavior and residual capacity of the corroded beams. The results obtained from the parametric analysis using the developed model showed that corrosion in top compression rebars has very small effect on the flexural behaviors of beams with small flexural reinforcement ratio that is less than the maximum ratio specified in ACI-318-14 (singly RC beam). In addition, the reduction of steel yield strength in tension reinforcement due to corrosion is the main source of reducing the load bearing capacity of corroded RC beams. The most critical corrosion-induced damage is the complete loss of bond between rebars and the concrete as it causes sudden failure and the beam acts as un-reinforced beam.