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Published Articles

The Volume 16, No 1, March 2011

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Thermally Induced Oscillations of an Inflatable Space Structure with a Repeated Element Pattern

Armaghan Salehian, Daniel J. Inman


Presented here is the analysis of thermally induced vibration of an inflatable space structure using the homogenization method. It is shown that this technique can effectively be used to quantify the thermal oscillations in such structures.

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Technical Note: Measurement of Background Noise Level and Prediction of Reverberation Time in University Classrooms

Parvin Nassiri, Pedram Jafari Shalkouhi


A study was conducted to measure background noise levels and to predict reverberation times in university classrooms. Twenty-five classrooms were selected due to the dimensions and location. Background noise level in all classrooms exceeds the recommendations in ANSI S12.60-2002. Calculated reverberation times based on the Sabine equation indicate that none of the classrooms have reverberation times below the recommendations in ANSI S12.60-2002, as well as the Building Bulletin 93. It is concluded that interior noise sources, such as classrooms' HVACs, students from other classrooms or corridors, and corridors' HVACs, must be taken into consideration rather than exterior noise sources because all eight buildings were located far from any environmental noise sources. The classrooms' doors (due to the openings) are more responsible for sound transmission than are the walls.

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Sound Pattern of the Panel Saws Family

Marcos D. Fernandez, Jose A. Ballesteros, Ivan Suarez, Samuel Quintana, Isabel Gonzalez and Laura Rodr?guez


"A type of machines" can be understood as a set of machines that have some part in common, and are generally used for the same function. Therefore, it seems logical to think that they should usually share the same working philosophy, which often includes a similar noise emission. This reasoning will be proved by the comparison of the different factors that characterize a machine, that is, the measurement of sound power level and sound quality. All of this should be done for a number of machines to guarantee enough heterogeneity in the test samples so as to probe the existence of a trend in the acoustical characteristics of the machines of the same family. This will lead to the existence of a sound pattern. It has been possible, for the panel saws family, to determine that emission pattern. The knowledge of this sound pattern offers a wide set of possibilities that permit emission reductions and protection of workers.

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Seismic-Resistant Investigation of Multi-Storey Building by Response Spectrum Method

Shankha Pratim Bhattacharya, Swapan Kumar Chakraborty


The present article attempts to evaluate the earthquake resistance of a four-storey building frame. It also compares the performance of buildings with soft ground floors and different infill parameters, such as brick wall and shear wall. The Indian standard code (IS-code) of practice (IS: 1893, Part-1:2002) guidelines and methodology are used to analyze the problem. Response spectrum method, involving various modal participations, is employed to evaluate the nodal forces in the typical beam-column junctions. The frame members, infill walls and floors are tackled as rigid end joints, panel element, and diaphragms rigid in-plane, respectively. Linear elastic analysis is performed with individual floor mass and stiffness, taking into account the building as a multiple degrees of freedom system. The effect of damping and the soil criteria are also studied as per the provision of IS-code. The investigation concludes that the proper mass and stiffness distribution in multi-storied buildings will minimize the hazardous effects of seismic excitation. The mathematical model of the building finally recognized the hazardous features of Indian reinforced concrete buildings and recommends some measures to improve the seismic performance.

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Parametric Instability of a Sandwich Beam with an Electrorheological Fluid Core Subjected to Various Boundary Conditions

Sukesh C. Mohanty


In the present study, the parametric instability of a three layer sandwich beam with an embedded electrorheological (ER) fluid core has been studied under various boundary conditions, namely fixed-fixed, pinned-pinned, fixed-free, and fixed-pinned. The beam has been modeled using finite elements and the regions of instability have been established using Saito and Otomi conditions. The ER core model is based on the pre-yield rheological properties and is represented by the complex shear modulus. The sandwich model is based on shear configuration. The effects of the electric field, shear parameter, and core thickness parameter on the fundamental frequency, fundamental buckling load, and fundamental system loss factor have been investigated. The effects of different parameters, such as the electric field, shear parameter, thickness parameter, and static load factor on the stability behavior of the beam have been investigated. Increasing the electric field strength, core thickness ratio, and shear parameter has a stabilizing effect for all the boundary conditions; by contrast, increasing the static load factor has a destabilizing effect for these support conditions.

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Estimation and Simulation of the Nonlinear Dynamic Properties of a Boring Bar

Henrik Akesson, Tatiana Smirnova, Lars Hakansson, Ingvar Claesson, Thomas T. Lago


In this paper, an initial investigation of the nonlinear dynamic properties of clamped boring bars is carried out. Two nonlinear, single-degree-of-freedom models with different softening spring nonlinearities are introduced for modeling the nonlinear dynamic behavior of the fundamental bending mode in the cutting speed direction of a boring bar. Also, two different methods for the simulation of nonlinear models are used. The dynamic behavior in terms of frequency response function estimates for the nonlinear models and the experimental modal analysis of the clamped boring bar is compared. Similar resonance frequency shift behavior for varying excitation force levels is observed for both the nonlinear models and the actual boring bar.

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