• Advances in nano research
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• v.10 no.1
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• pp.1-14
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• 2021

In the present computational approach, thermal buckling and frequency characteristics of a doubly curved laminated nanopanel with the aid of Two-Dimensional Generalized Differential Quadrature Method (2D-GDQM) and Nonlocal Strain Gradient Theory (NSGT) are investigated. Additionally, the temperature changes along the thickness direction nonlinearly. The novelty of the current study is in considering the effects of laminated composite and thermal in addition of size effect on frequency, thermal buckling, and dynamic deflections of the laminated nanopanel. The acquired numerical and analytical results are compared by each other to validate the results. The results demonstrate that some geometrical and physical parameters, have noticeable effects on the frequency and pre-thermal buckling behavior of the doubly curved open cylindrical laminated nanopanel. The favorable suggestion of this survey is that for designing the laminated nano-sized structure should pay special attention to size-dependent parameters because nonlocal and length scale parameters have an important role in the static and dynamic behaviors of the laminated nanopanel.

• Structural Engineering and Mechanics
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• v.9 no.4
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• pp.397-416
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• 2000

The present study deals with the nonlinear dynamics and stability of autonomous dissipative either imperfect potential (limit point) systems or perfect (bifurcational) non-potential ones. Through a fully nonlinear dynamic analysis, performed on two simple 2-DOF models corresponding to the classes of systems mentioned above, and with the aid of basic definitions of the theory of nonlinear dynamical systems, new important phenomena are revealed. For the first class of systems a third possibility of postbuckling dynamic response is offered, associated with a point attractor on the prebuckling primary path, while for the second one the new findings are chaos-like (most likely chaotic) motions, consecutive regions of point and periodic attractors, series of global bifurcations and point attractor response of always existing complementary equilibrium configurations, regardless of the value of the nonconservativeness parameter.

• Smart Structures and Systems
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• v.26 no.2
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• pp.213-226
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• 2020

In this manuscript, static and dynamic behaviors of geometrically imperfect carbon nanotubes (CNTs) subject to different types of end conditions are investigated. The Doublet Mechanics (DM) theory, which is length scale dependent theory, is used in the analysis. The Euler-Bernoulli kinematic and nonlinear mid-plane stretching effect are considered through analysis. The governing equation of imperfect CNTs is a sixth order nonlinear integro-partial-differential equation. The buckling problem is discretized via the differential-integral-quadrature method (DIQM) and then it is solved using Newton's method. The equation of linear vibration problem is discretized using DIQM and then solved as a linear eigenvalue problem to get natural frequencies and corresponding mode shapes. The DIQM results are compared with analytical ones available in the literature and excellent agreement is obtained. The numerical results are depicted to illustrate the influence of length scale parameter, imperfection amplitude and shear foundation constant on critical buckling load, post-buckling configuration and linear vibration behavior. The current model is effective in designing of NEMS, nano-sensor and nano-actuator manufactured by CNTs.

• Steel and Composite Structures
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• v.2 no.3
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• pp.161-170
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• 2002

The problem of the elastic buckling of a cylindrical liquid-storage tank subject to horizontal earthquake loading is considered. An equivalent static loading is used to represent the dynamic effect. A theoretical solution based on the nonlinear Fl$\ddot{u}$gge shell equations is developed, and numerical results are found using the new differential quadrature method. A second solution is obtained using the finite element package ADINA. A major motivation of the study was to show that the new method can serve to verify finite element solutions for cylindrical shell buckling problems. For this purpose the paper concludes with a comparison of buckling results for a number of cases covering a wide range in tank geometry.

• Structural Engineering and Mechanics
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• v.86 no.2
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• pp.277-290
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• 2023

A supplementary reinforced concrete wall can be used to improve the seismic behavior of a buckling restrained braced frame as a mixed system. In such a novel system, the total lateral force is resisted by the combination of the RC wall system and the BRBF. There is not enough research on the response modification factor of such a mixed system. This paper investigates the response modification factor, and such relevant factors as ductility reduction factor and over strength factor for a system consisting of reinforced concrete wall and buckling restrained braced frame. To this purpose, nonlinear incremental dynamic analysis as well as static push over analysis are used for 6- to 14-story sample structures. The results show that for mixed considered systems, the mean value of response modification factor varies approximately from 7 to 9.

• Earthquakes and Structures
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• v.22 no.2
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• pp.169-184
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• 2022

The importance of seismicity in developing countries and the strengthening of buildings is a topic of major importance. Therefore, the study of several solutions with the development of new technologies is of great importance to investigate the damage on retrofitted structures by using probabilistic methods. The Federal Emergency Management Agency considers three types of performance levels by considering different scenarios, intensity and duration. The selection and scaling of ground motions mainly depends on the aim of the study. Intensity-based assessments are the most common and compute the response of buildings for a specified seismic intensity. Assessments based on scenarios estimate the response of buildings to different earthquake scenarios. A risk-based assessment is considered as one of the most effective. This research represents a practical method for developing countries where exists many active faults, tall buildings and lack of good implementable approaches. Therefore, to achieve the main goal, two high-rise steel buildings have been modeled and assessed. The contribution of buckling-restrained braces in the elastic design of both buildings is firstly verified. In the nonlinear static range, both buildings presented repairable damage at the central top part and some life safety hinges at the bottom. The nonlinear incremental dynamic analysis was applied by 15 representative/scaled accelerograms to obtain levels of performance and fragility curves. The results shown that by using probabilistic methods, it is possible to estimate the probability of collapse of retrofitted buildings by buckling-restrained braces and tuned mass dampers, which are practical retrofitting options to protect existing structures against earthquakes.

• Structural Engineering and Mechanics
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• v.50 no.1
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• pp.1-17
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• 2014

In this paper, overstrength, ductility and response modification factors are calculated for frames braced with a different type of buckling restrained braces, called reduced yielding segment BRB (Buckling Restrained Brace) in which the length of its yielding part is reduced and placed in one end of the brace element in comparison with conventional BRBs. Forthermore, these factors are calculated for ordinary BRBF and the results are compared. In this regard incremental dynamic analysis (IDA) method is used for studying 17 records of the most known earthquakes happened in the world. To do that, the considered buildings have different stories and two bracing configurations: diagonal and inverted V chevron, the most ordinary configurations of BRBFs. Static pushover analysis, nonlinear incremental dynamic analysis and linear dynamic analysis have been performed using OpenSees software. Considering the results, it can be seen that, overstrength, ductility and response modification factors of this type of BRBF(Buckling Restrained Braced Frame) is greater than those of conventional types and it shows better seismic performance and also eliminates some of conventional BRBF's disadvantages such as low post-yield stiffness.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.277-283
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• 2005

Inelastic model of Second Jindo Bridge is investigated to perform nonlinear dynamic analyses with various earthquake ground motions. The modal analysis is performed to obtain dynamic characteristics of the bridge and verify the model. It proves that the model has an appropriate dynamic characteristic and its natural frequency is relatively low. Four ground motions are chosen for time history dynamic analyses; El Centro, Kobe, Taft, and Mexico earthquake. Each ground motion multiplied by specified factors to investigate damages of the structure. The analyses prove that responses of the bridge depend on the duration time and the frequency characteristics of ground motion, not only peak acceleration. Static push-over analysis of steel pylon shows that the dynamic analysis over-estimates the seismic behavior of steel pylon definitely. Nonlinear spring hinge model is suggest to improve the shortage of the inelastic model could not deliberate local buckling damage. According to the time history analysis of nonlinear spring hinge model, it is proved that the inelastic beam element analysis overestimate the seismic capacity of steel pylon unquestionably with a large amount of errors.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.2
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• pp.83-90
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• 2023

The recent increase in earthquake activities has highlighted the importance of seismic performance evaluation for civil infrastructures. In particular, the container crane essential to maintaining the national logistics system with port operation requires an exact evaluation of its seismic response. Thus, this study aims to assess the seismic vulnerability of container cranes considering their seismic characteristics. The seismic response of the container crane should account for the structural members' yielding and buckling, as well as the crane wheel's uplifting derailment in operation. The crane's yielding and buckling limit states were defined using the stress of crane members based on the load and displacement curve obtained from nonlinear static analysis. The derailment limit state was based on the height of the rail, and nonlinear dynamic analysis was performed to obtain the seismic fragility curves considering defined limit states and seismic characteristics. The yield and derailment probabilities of the crane in the near-fault ground motion were approximately 1.5 to 4.7 and 2.8 to 6.8 times higher, respectively, than those in the far-fault ground motion.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.85-96
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• 2003

In the present investigation, the nonlinear dynamic buckling of a curved plate subjected to sinusoidal loading is examined. By the theoretical analyses, a highly nonlinear snap-through motion of a clamped-free-clamped-free plate and its effect on the overall vibration response are investigated. The problem is reduced to that of a single degree of freedom system with the Rayleigh-Ritz procedure. The resulting nonlinear governing equation is solved using Runge-Kutta (RK-4) numerical integration method. The snap-through boundaries, which vary with different damping coefficient and linear circular frequency of the flat plate are studied and given in terms of force and displacement. The relationships between static and dynamic responses at the start of a snap-through motion are also predicted. The analysis brings out various characteristic features of the phenomenon, i.e. 1) small oscillation about the buckled position-softening spring type motion, 2) chaotic motion of intermittent snap-through, and 3) large oscillation of continuous snap-through motion crossing the two buckled positions-hardening spring type. The responses of buckled plate were found to be greatly affected by the snap-through motion. Therefore, better understanding of the snap-through motion is needed to predict the full dynamic response of a curved plate.