• Steel and Composite Structures
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• 제24권1호
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• pp.79-91
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• 2017

Free vibrations of steel-concrete composite beams are analyzed by using the dynamic stiffness approach. The coupled equations of motion of the composite beams are derived with help of the Hamilton's principle. The effects of the shear deformation and rotary inertia of the two beams as well as the transverse and axial deformations of the stud connectors are included in the formulation. The dynamic stiffness matrix is developed on the basis of the exact general solutions of the homogeneous governing differential equations of the composite beams. The use of the dynamic stiffness method to determine the natural frequencies and mode shapes of a particular steel-concrete composite beam with various boundary conditions is demonstrated. The accuracy and effectiveness of the present model and formulation are validated by comparison of the present results with the available solutions in literature.

• 한국포장학회지
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• 제5권1호
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• pp.13-20
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• 1999

Not only is it important that the physical properties of the paperboards be appropriate for the intended end use, but the proper arrangement of the component in the built-up board is essential for attaining the optimum moment of inertia and the maximum load-carrying ability in a box. It is known to be impossible to estimate the stress distribution and deflection pattern by experiments or theoretical analysis when the corrugated fiberboard get the bending force. This study was tried theoretical and finite element analysis to analyze structural strength characteristics of corrugated fiberboards. If the linerboard and corrugating medium of every corrugated fiberboards is made from the same material, the location of neutral axis comes close to inside liner in order of DMA, DM, DMB, SW and DW, and moment of inertia of area decreases in order of DMA, DMB, DW, DM and SW. With the finite element analysis, deflection of applied loads represented SW, DM, DMA, and TW in the order of their value.

• Structural Engineering and Mechanics
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• 제88권3호
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• pp.221-238
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• 2023

This paper developed and examined a novel passive vibration isolator (i.e., "X-inerter") motivated by combining a bio-inspired structure and a rack-pinion inerter. The bio-inspired structure provided nonlinear stiffness and damping owing to its geometric nonlinearity. In addition, the behavior was further enhanced by a gear inerter that produced a special nonlinear inertia effect; thus, an X-inerter was developed. As a result, the X-inerter can achieve both high-static-low-dynamic stiffness (HSLDS) and quasi-zero stiffness (QZS), obtaining ultra-low frequency isolation. Furthermore, the installed inerter can produce a coupled nonlinear inertia and damping effect, leading to an anti-resonance frequency near the resonance, wide isolation region, and low resonance peak. Both static and dynamic analyses of the proposed isolator were conducted and the structural parameters' influence was comprehensively investigated. The X-inerter was proven to be comparatively more stable in the ultra-low frequency than the benchmarking QZS isolator due to the nonlinear damping and inertia properties. Moreover, the inertia effect could suppress the bio-inspired structure's super- and sub-harmonic resonance. Therefore, the X-inerter isolator generally possesses desirable nonlinear stiffness, nonlinear damping, and unique nonlinear inertia, designed to achieve the ultra-low natural frequency, the anti-resonance property, and a wide isolation region with a low resonance peak.

• Earthquakes and Structures
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• 제7권6호
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• pp.955-967
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• 2014

Storage racks are used worldwide in industries and commercial outlets due to the advantage of lighter, faster erection and easy alteration of pallet level as required. The studies to understand the behaviour of cold formed steel pallet racks, under seismic action is one of the emerging area of research. The rack consists of perforated uprights and beams with hook-in end connector, which enables the floor height adjustments. The dynamic characteristics of these racks are not well established. This paper presents the dynamic characteristics of 3-D single bay two storey pallet rack system with hook-in end connectors, which is tested on shake table. The sweep sine test and El Centro earthquake acceleration is used to evaluate the seismic performance of the cold formed steel pallet racks. Also an attempt is made to evaluate the realistic dynamic characteristics by using STAAD Pro software. Modal analysis is performed by incorporating the effective moment of inertia of the upright, which considers the effect of presence of perforations and rotational stiffness of the beam-to-upright connection to determine the realistic fundamental frequency of pallet racks, which is required for carrying out the seismic design. Finite element model of the perforated upright section has been developed as a cantilever beam through which effective moment of inertia is evaluated. The stiffness of the hook-in connector is taken from the previous study by Prabha et al. (2010). The results from modal analysis are in good agreement with the respective experimental results.

• Structural Engineering and Mechanics
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• 제26권1호
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• pp.1-14
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• 2007

Because of complexity, the literature regarding the free vibration analysis of a Timoshenko beam carrying "multiple" spring-mass systems is rare, particular that regarding the "exact" solutions. As to the "exact" solutions by further considering the joint terms of shear deformation and rotary inertia in the differential equation of motion of a Timoshenko beam carrying multiple concentrated attachments, the information concerned is not found yet. This is the reason why this paper aims at studying the natural frequencies and mode shapes of a uniform Timoshenko beam carrying multiple intermediate spring-mass systems using an exact as well as a numerical assembly method. Since the shear deformation and rotary inertia terms are dependent on the slenderness ratio of the beam, the shear coefficient of the cross-section, the total number of attachments and the support conditions of the beam, the individual and/or combined effects of these factors on the result are investigated in details. Numerical results reveal that the effect of the shear deformation and rotary inertia joint terms on the lowest five natural frequencies of the combined vibrating system is somehow complicated.

• 국제초고층학회논문집
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• 제10권2호
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• pp.149-164
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• 2021

Most of high-rise buildings in Japan^*1 are structure with damping systems recently. The design procedure is performance-based design (PBD), which is based on the nonlinear response history procedure (NRHP) using 2 or 3-dimentional frame model. In addition, hysteretic property of steel plates or velocity-dependent property of viscous dampers are common practice for the damping system. However, for the selection of damping system, the easy dynamic analysis of recent date may lead the most of engineers to focus attention on the maximum response only without thinking how it shakes. By nature, the seismic design shall be to figure out the action of inertia forces by complex & dynamic loads including periodic and pulse-like characteristics, what we call seismic ground motion. And it shall be done under the dynamic condition. On the contrary, we engineers engineers have constructed the easy-to-use static loads and devoted ourselves to handle them. The structures with damping system shall be designed considering how the stiffness & damping to be applied to the structures against the inertia forces with the viewpoint of dynamic aspect. In this paper we reconsider the role of damping in vibration and give much thought to the basic of shake with damping from a standpoint of structural design. Then, we present some design examples based on them.

• Computational Structural Engineering : An International Journal
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• 제1권2호
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• pp.89-96
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• 2001

A study on the topology optimization of a Hard-Disk-Driver(HDD) actuator arm is presented. The purpose of the present wert is to increase the natural frequency of tole first lateral mode of the HDD actuator arm under the constraint of total moment of inertia, so as to facilitate the position control of the high speed actuator arm. The first lateral mode is an important factor in the position control process. Thus the topology optimization for 2-D model of the HDD actuator arm is considered. A new objective function corresponding to multieigenvalue optimization is suggested to improve the solution of the eigenvalue optimization problem. The material density of the structure is treated as the design variable and the intermediate density is penalized. The effects of different element types and material property functions on the final topology are studied. When the problem is discretized using 8-node element of a uniform density, tole smoothly-varying density field is obtained without checker-board patterns incurred. AS a result of 7he study, an improved design of the HDD actuator arm is suggested. Dynamic characteristics of the suggested design are compared computationally with those of the old design. With the same amount of the moment of inertia, the natural frequency of the first lateral mode of the suggested design is subsequently increased over the existing one.

• Computers and Concrete
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• 제21권5호
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• pp.495-504
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• 2018

The possibility of earthquakes in vulnerable regions indicates that efficient technique is required for seismic protection of buildings. During the recent decades, the concept is moving towards the insertion of base isolation on seismic prone buildings. So, investigation of structural behavior is a burning topic for buildings to be isolated in base level by bearing device. This study deals with the incorporation of base isolation system and focuses the changes of structural responses for different types of Lead Rubber Bearing (LRB) isolators. A number of sixteen model buildings have been simulated selecting twelve types of bearing systems as well as conventional fixed-base (FB) scheme. The superstructures of the high-rise buildings are represented by finite element assemblage adopting multi-degree of freedoms. Static and dynamic analyses are carried out for FB and base isolated (BI) buildings. The dynamic analysis in finite element package has been performed by the nonlinear time history analysis (THA) based on the site-specific seismic excitation and compared employing eminent earthquakes. The influence of the model type and the alteration in superstructure behavior of the isolated buildings have been duly assessed. The results of the 3D multistory structures show that the lateral forces, displacement, inertia and story accelerations of the superstructure of the seismic prone buildings are significantly reduced due to bearing insertion. The nonlinear dynamic analysis shows 12 to 40% lessening in base shear when LRB is incorporated leading to substantial allowance of horizontal displacement. It is revealed that the LRB isolators might be potential options to diminish the respective floor accelerations, inertia, displacements and base shear whatever the condition coincides. The isolators with lower force intercept but higher isolation period is found to be better for decreasing base shear, floor acceleration and inertia force leading to reduction of structural and non-structural damage. However, LRB with lower isolator period seems to be more effective in dropping displacement at bearing interface aimed at reducing horizontal shift of building structure.

• Structural Engineering and Mechanics
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• 제2권4호
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• pp.345-357
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• 1994

The differential equations governing free, in-plane vibrations of linearly elastic circular arches with variable cross-sections are derived and solve numerically for quadratic arches with three types of rectangular cross sections. Frequencies, mode shapes, cross-sectional load distributions, and the effects of rotatory inertia on frequencies are reported. Experimental measurements of frequencies and their corresponding mode shapes agree closely with those predicted by theory. The numerical methods presented here for computing frequencies and mode shapes are efficient and reliable.

• Structural Engineering and Mechanics
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• 제24권5호
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• pp.601-620
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• 2006

The paper presents an effective stiffness model for deformational analysis of reinforced concrete cracked members in bending throughout the short-term loading up to the near failure. The method generally involves the analytical derivation of an effective moment of inertia based on the smeared crack technique. The method, in a simplified way, enables us to take into account the non linear properties of concrete, the effects of cracking and tension stiffening. A statistical analysis has shown that proposed technique is of adequate accuracy of calculated and experimental deflections data provided for beams with small, average and normal reinforcement ratios.