scholarly journals Effect of architectural components on the dynamic properties of a long-span floor system

1987 ◽  
Vol 14 (4) ◽  
pp. 461-467 ◽  
Author(s):  
G. Pernica
Keyword(s):  
Fundamental Mode ◽  
Composite Structures ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Long Span ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Vibration Tests ◽  
Comparison Of The Results ◽  
Floor System

Vibration measurements were taken to determine the effects of architectural components on the dynamic properties (modal frequency, modal damping ratio, and mode shape) of a long-span floor system. The floor was located above a two-storey gymnasium in a recently constructed three-storey elementary school. The dynamic properties of the bare floor system were measured during the construction phase, immediately after the main structural components and the exterior masonry walls were in place. Six months later, with construction completed and the school ready for occupancy, the properties of the finished floor system, complete with internal partitions, mechanical ducts, furnishings, and carpeting, were again obtained.A comparison of the results of the two test series indicated that the dynamic properties of the floor system were altered by the addition of the architectural components. The fundamental frequency rose by 3% and the frequencies of the higher modes by 23%, even though the static load on the floor increased by about 26%. The substantial stiffening of the floor system necessary to precipitate these increases in frequency was linked to the presence of the internal partitions. A full-span partition was also found to behave as a floor support, creating an additional set of modes which were not previously present. Except for the fundamental mode, damping ratios increased by about 2% of critical, from 1.5% to 3.5% of critical. For the fundamental mode, the negligible increase in damping from 4.1 to 4.2% of critical could not be explained. Key words: floors, composite structures, vibration tests, spectrum analysis, resonant frequency, vibration damping.

scholarly journals Experimental and numerical studies on the vibration serviceability of fanshaped prestressed concrete floor

2018 ◽  
Vol 14 (8) ◽  
pp. 155014771879574 ◽  
Author(s):  
Liang Cao ◽  
Hongtuo Qi ◽  
Jiang Li
Keyword(s):  
Prestressed Concrete ◽  
Damping Ratio ◽  
Impact Excitation ◽  
Concrete Floor ◽  
Long Span ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Study Results ◽  
Vibration Serviceability ◽  
Floor System

An extensive experimental and numerical research was undertaken to study the vibration serviceability of a long-span fanshaped prestressed concrete floor system to be used in the lounge of a major airport. Specifically heel-drop and jumping impact tests were conducted to obtain the natural frequencies and modal damping ratios of the floor system, followed by the discussion on the distribution of peak accelerations. Running tests and simulation were also performed to capture the acceleration responses. Moreover, the finite element method was used to evaluate the dynamic characteristics. The floor system is found to have a low fundamental frequency (≈6.00 Hz) and the corresponding modal damping ratio (average ≈2.20%). The comparison of the experimental results with the published American institute of steel construction (AISC) design guide indicates that the prestressed concrete floor system exhibits satisfactory vibration perceptibility overall. The study results also show that the intensity and the location of impact excitation have a significant influence on the rate of acceleration decay. A crest factor βrp is proposed based on the test results to calculate the maximum root mean square acceleration for running for convenience.

Operational Modal Analysis of Broaching Machine

2012 ◽  
Vol 159 ◽  
pp. 170-175
Author(s):  
Lv Gao Lin ◽  
Shen Shun Ying ◽  
Shu Qiong Chen ◽  
Xiao Tian Lv
Keyword(s):  
Cutting Force ◽  
Natural Frequency ◽  
Fundamental Frequency ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Modal Parameters ◽  
Modal Shape ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Cutting Velocity

Modal parameters for LG51SH broaching machine from operational responses are studied to examine the dynamic properties of mechanical structure. The operational modal is analyzed using PolyMAX method with responsive data of key point in broaching machine, which is excited in practical broaching operation and tested by LMS SCADAIII-105 system. The identified steady state modal, representative modal shape, modal damping ratio and natural frequency in broaching are presented. The test and analysis result shows that there are natural frequency of 38Hz and 192Hz, which are close to multiple of the fundamental frequency of cutting force in broaching, 6Hz, therefore, reasonable cutting velocity should be adopted to void producing fundamental frequency of cutting force in broaching.

scholarly journals Dynamic behaviour of a gymnasium floor

1986 ◽  
Vol 13 (3) ◽  
pp. 270-277 ◽  
Author(s):  
J. H. Rainer ◽  
J. C. Swallow
Keyword(s):  
Concrete Slab ◽  
Damping Ratio ◽  
Mode Shapes ◽  
Resonant Frequencies ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Load Factors ◽  
Resonance Frequencies ◽  
Floor Vibrations ◽  
Vibration Tests

Ten mode shapes, natural frequencies, and modal damping values have been measured for a steel-joist concrete-slab floor spanning 32.1 m. From ambient vibrations and steady-state shaker tests the frequency of the fundamental mode was determined to be 3.5 Hz, and the modal damping ratio to be approximately 1% of critical. A comparison of vibration criteria in Appendix G of CAN3-S16.1-M84 confirms satisfactory performance for walking, but for other rhythmic exercises disturbing vibrations developed. These occurred primarily at the forcing frequency of the exercises and not at floor resonance frequencies. Values of dynamic load factors, α, for rhythmic loadings of this floor were evaluated in accordance with the guidelines on floor vibrations in the Commentary to the National Building Code of Canada 1985. Key words: floors, gymnasiums, vibration tests, resonant frequencies, mode shapes, dynamic loads, dynamic response.

EFFECTS OF HUMAN-STRUCTURE INTERACTIONS ON THE DYNAMIC PROPERTIES OF BUILDING FLOORS SUSCEPTIBLE TO VIBRATIONS

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Mehdi Setareh ◽  
Stephanie Renard
Keyword(s):  
Dynamic System ◽  
Dynamic Models ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Human Movements ◽  
Vibration Serviceability ◽  
Dimensional Parameters ◽  
Vibration Tests ◽  
Floor System ◽  
Two Degree Of Freedom

Excessive vibrations of building floors due to human movements have become an important vibration serviceability problem for building designers and owners. A series of vibration tests on a full-scale laboratory floor with different numbers of humans in various postures were conducted. Using this data, the dynamic properties of a two-degree-of-freedom (2-DOF) dynamic system representing groups of people in different postures were computed. A 3-DOF model representing the floor and humans was developed and its dynamic properties were defined in terms of non-dimensional parameters. The dynamic properties of the floor were measured when occupied by groups of people in different postures and compared to those predicted using the 3-DOF dynamic model considering the identified human models. The results showed that the predicted properties were within the range of those found from the measurements, which validated the identified human dynamic models. This study also showed how the presence of humans can affect the natural frequency and damping ratio of a floor system.

Effect of Crack Orientation on Laminated CFRP Composites Using Vibration and Numerical Analysis

2021 ◽  
Vol 79 (11) ◽  
pp. 1081-1093
Author(s):  
Essam Moustafa ◽  
Khalid Almitani ◽  
Hossameldin Hussein
Keyword(s):  
Composite Structures ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Composite Plates ◽  
Mode Shapes ◽  
Crack Orientation ◽  
Test Plate ◽  
Cfrp Composites ◽  
Cfrp Composite ◽  
Vibration Tests

Crack orientation, a critical parameter, significantly affects the dynamic properties of composite structures. Experimental free vibration tests were conducted on carbon fiber–reinforced polymer (CFRP) composite plates at room temperature with different crack orientations. Dynamic properties such as damping ratio, natural frequency, and storage modulus were measured using a four-channel dynamic pulse analyzer. Multi-sensors were mounted on the test plate to pick up the vibration signals. Experimental modal analysis was performed to identify the first three mode shapes of the defective plates. A numerical model using ANSYS software was developed via parametric investigation to predict the correlation between crack orientation and resonant frequencies with corresponding mode shapes. The orientation of the introduced cracks had a significant effect on the dynamic properties of CFRP composites. Vertical cracks had the most significant influence on the eigenvalues of the mode shape frequencies. Furthermore, the damping ratio was an effective method to detect the cracks in CFRP composites.

Dynamic Characteristics of a Wood Frame Structure: (II) the Effect of Artificial Damage

2013 ◽  
Vol 671-674 ◽  
pp. 921-926
Author(s):  
Hai Ling Xing ◽  
Dong Sheng Yao ◽  
Song Tao Xue
Keyword(s):  
Dynamic Properties ◽  
Damping Ratio ◽  
Frame Structure ◽  
Modal Parameter ◽  
Hilbert Huang Transform ◽  
Artificial Damage ◽  
Identification Technique ◽  
Wood Frame ◽  
Frequency Changes ◽  
Vibration Tests

A full-scale, three-storey wood frame structure had been tested in-situ to investigate the changes of dynamic properties due to artificial damage. Beams and braces of the test structure were removed, to simulate damage, and then reassembled, to simulate rehabilitation. Free vibration tests were performed during every stage of the tests. The natural frequencies and damping ratios were obtained using modal parameter identification technique based on the Hilbert-Huang Transform. It is shown that, when the structure is damaged or rehabilitated, the natural frequency changes in accord with the structural stiffness in general while the damping ratio varies irregularly.

Modal damping ratio analysis of dynamical system with non-stationary responses

2016 ◽  
Vol 59 ◽  
pp. 138-146 ◽  
Author(s):  
Da Tang ◽  
Ran Ju ◽  
Qianjin Yue ◽  
Shisheng Wang
Keyword(s):  
Dynamical System ◽  
Damping Ratio ◽  
Ratio Analysis ◽  
Modal Damping Ratio ◽  
Modal Damping

scholarly journals Coupling of Flexural and Longitudinal Damped Vibration in a Two-Layered Beam

1998 ◽  
Vol 5 (5-6) ◽  
pp. 337-341
Author(s):  
F. Pourroy ◽  
S. Shakhesi ◽  
P. Trompette
Keyword(s):  
Damping Ratio ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Resonance Frequencies ◽  
Layered Beam ◽  
Flexural Vibrations

In dynamics, the effect of varying the constitutive materials’ thickness of a two-layered beam is investigated. Resonance frequencies and damping variations are determined. It is shown that for specific thicknesses the coupling of longitudinal and flexural vibrations influences the global modal damping ratio significantly.

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