scholarly journals Damping Assessment of Lightweight Timber Floors Under Human Walking Excitations

2019 ◽  
Vol 9 (18) ◽  
pp. 3759 ◽  
Author(s):  
Alexander Opazo-Vega ◽  
Francisco Muñoz-Valdebenito ◽  
Claudio Oyarzo-Vera
Keyword(s):  
Social Housing ◽  
Damping Ratio ◽  
Human Walking ◽  
Structural Elements ◽  
Housing Projects ◽  
Frequency Decomposition ◽  
Modal Damping ◽  
Vibration Tests ◽  
Stochastic Identification

Vibrations on timber floors are among the most common serviceability problems in social housing projects. The presence of low damping levels on these floors could cause excessive vibrations in a range of frequency and amplitude that generate discomfort in users. This study focuses on the influence of the damping ratio in the dynamic serviceability of social housing timber floors due to walking excitations. More than 60 human-walking vibration tests were conducted on both laboratory and in-situ timber floors. The floors were instrumented with accelerometers, and fundamental modal damping ratios were estimated by applying Enhanced Frequency Decomposition Domain (EFDD) and Subspace Stochastic Identification (SSI) methods. The vibration dose value (VDV) was used to estimate the dynamic serviceability of floors. The results indicated that timber floors had an impulsive-type vibration response, with fundamental damping ratios between 1.9% and 14.8%, depending on their constructive characteristics. The in-situ floors had damping ratios between two to three times greater than the laboratory floors due to the presence of non-structural elements. Finally, it was possible to demonstrate that the floors with the highest damping ratios reached lower vibration dose values and, therefore, a better dynamic serviceability performance.

Damping in LMFBR Pipe Systems

1985 ◽  
Vol 107 (4) ◽  
pp. 366-372 ◽  
Author(s):  
M. J. Anderson ◽  
D. A. Barta ◽  
M. R. Lindquist ◽  
E. J. Renkey ◽  
J. A. Ryan
Keyword(s):  
Excitation Amplitude ◽  
Test Facility ◽  
Seismic Events ◽  
Seismic Loads ◽  
Modal Damping ◽  
Water Plant ◽  
Pipe Systems ◽  
Vibration Tests ◽  
Recent Laboratory

Liquid Metal Fast Breeder Reactor pipe systems typically utilize a thicker insulation package than that used on water plant pipe systems. They are supported with special insulated pipe clamps. Mechanical snubbers are employed to resist seismic loads. Recent laboratory testing has indicated that these features provide significantly more damping than presently allowed by Regulatory Guide 1.61 for water plant pipe systems. This paper presents results of additional in-situ vibration tests conducted on Fast Flux Test Facility pipe systems. Pipe damping values obtained at various excitation levels are presented. Effects of filtering data to provide damping values at discrete frequencies and the alternate use of a single equivalent modal damping value are discussed. These tests further confirm that damping in typical LMFBR pipe systems is larger than presently used in pipe design. Although some increase in damping occurred with increased excitation amplitude, the effect was not significant. Recommendations are made to use increased damping values for seismic events in design of heavily insulated pipe systems.

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.

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.

A validated robust and automatic procedure for vibration analysis of bridge structures using MEMS accelerometers

2020 ◽  
Vol 14 (3) ◽  
pp. 327-354
Author(s):  
Mohammad Omidalizarandi ◽  
Ralf Herrmann ◽  
Boris Kargoll ◽  
Steffen Marx ◽  
Jens-André Paffenholz ◽  
...  
Keyword(s):  
Vibration Analysis ◽  
Damping Ratio ◽  
Fem Analysis ◽  
Cost Effective ◽  
Analysis Procedure ◽  
Modal Parameters ◽  
Bridge Structure ◽  
Modal Damping ◽  
Mems Accelerometers ◽  
Better Than

AbstractToday, short- and long-term structural health monitoring (SHM) of bridge infrastructures and their safe, reliable and cost-effective maintenance has received considerable attention. From a surveying or civil engineer’s point of view, vibration-based SHM can be conducted by inspecting the changes in the global dynamic behaviour of a structure, such as natural frequencies (i. e. eigenfrequencies), mode shapes (i. e. eigenforms) and modal damping, which are known as modal parameters. This research work aims to propose a robust and automatic vibration analysis procedure that is so-called robust time domain modal parameter identification (RT-MPI) technique. It is novel in the sense of automatic and reliable identification of initial eigenfrequencies even closely spaced ones as well as robustly and accurately estimating the modal parameters of a bridge structure using low numbers of cost-effective micro-electro-mechanical systems (MEMS) accelerometers. To estimate amplitude, frequency, phase shift and damping ratio coefficients, an observation model consisting of: (1) a damped harmonic oscillation model, (2) an autoregressive model of coloured measurement noise and (3) a stochastic model in the form of the heavy-tailed family of scaled t-distributions is employed and jointly adjusted by means of a generalised expectation maximisation algorithm. Multiple MEMS as part of a geo-sensor network were mounted at different positions of a bridge structure which is precalculated by means of a finite element model (FEM) analysis. At the end, the estimated eigenfrequencies and eigenforms are compared and validated by the estimated parameters obtained from acceleration measurements of high-end accelerometers of type PCB ICP quartz, velocity measurements from a geophone and the FEM analysis. Additionally, the estimated eigenfrequencies and modal damping are compared with a well-known covariance driven stochastic subspace identification approach, which reveals the superiority of our proposed approach. We performed an experiment in two case studies with simulated data and real applications of a footbridge structure and a synthetic bridge. The results show that MEMS accelerometers are suitable for detecting all occurring eigenfrequencies depending on a sampling frequency specified. Moreover, the vibration analysis procedure demonstrates that amplitudes can be estimated in submillimetre range accuracy, frequencies with an accuracy better than 0.1 Hz and damping ratio coefficients with an accuracy better than 0.1 and 0.2 % for modal and system damping, respectively.

‘Excavating’ Pruitt-Igoe using space syntax

2021 ◽  
Vol 25 (1) ◽  
pp. 55-68
Author(s):  
Mark David Major
Keyword(s):  
United States ◽  
Twentieth Century ◽  
Public Housing ◽  
Social Housing ◽  
Space Syntax ◽  
Modern Architecture ◽  
Housing Authority ◽  
Housing Project ◽  
Housing Projects ◽  
Charles Jencks

Pruitt-Igoe, in St Louis, Missouri, United States, was one of the most notorious social housing projects of the twentieth century. Charles Jencks argued opening his book The Language of Post-Modern Architecture, ‘Modern Architecture died in St Louis, Missouri on July 15, 1972 at 3.32 pm (or thereabouts) when the infamous Pruitt-Igoe scheme, or rather several of its slab blocks, were given the final coup de grâce by dynamite.’ However, the magazine Architectural Forum had heralded the project as ‘the best high apartment’ of the year in 1951. Indeed, one of its first residents in 1957 described Pruitt-Igoe as ‘like an oasis in a desert, all of this newness’. But a later resident derided the housing project as ‘Hell on Earth’ in 1967. Only eighteen years after opening, the St Louis Public Housing Authority (PHA) began demolishing Pruitt-Igoe in 1972 [1]. It remains commonly cited for the failures of modernist design and planning.

The Membrane Skeleton of Pseudomicrothorax

1991 ◽  
Vol 100 (4) ◽  
pp. 707-715 ◽  
Author(s):  
IRM HUTTENLAUCH ◽  
ROBERT K. PECK
Keyword(s):  
Spatial Organization ◽  
Membrane Skeleton ◽  
Basal Bodies ◽  
Structural Elements ◽  
Or Groups ◽  
Positive Immunoreactivity ◽  
Cortical Membranes ◽  
Cytoskeletal Elements

The membrane skeleton, or epiplasm, is part of the structurally complex ciliate cortex. It is thought to have skeletal functions concerning the spatial organization of cortical elements such as the basal bodies. Here we report the biochemical and immunological characterization of some components of the purified epiplasm of Pseudomicrothorax dubius. The epiplasm proteins consist of two quantitatively major groups of proteins, one of 76–80x103Mr, the other of 11–13x103Mr, which appear to be the principal structural elements of the epiplasm, and a series of minor components of 62–18x103Mr. Based upon lectin labeling and glycosidase treatment, some of the latter have been identified as glycoproteins. Using affinity-purified antibodies specific for individual glycoproteins or groups of glycoproteins, we were able to localize them in situ by immunoelectron microscopical methods. This in situ localization demonstrates that the glycosylated epitopes, unlike the glycoresidues of membrane proteins, are distributed throughout the entire epiplasmic layer rather than being restricted to regions adjacent to the cortical membranes. Thus, these proteins represent glycosylated, cytoskeletal elements. At least one of these glycoproteins (Mr 62x103) shows positive immunoreactivity with a monoclonal antibody (Pruss anti-IFA) recognizing most intermediate filament (IF) proteins, indicating that IF proteins might be present in protozoan cytoskeletons.

Experimental Validation of an Identification Procedure of Soil Profile Characteristics from Free Field Acceleration Records

2012 ◽  
Vol 3 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Z. Harichane ◽  
H. Afra ◽  
R. Bahar
Keyword(s):  
Soil Profile ◽  
Damping Ratio ◽  
Linear Optimization ◽  
Free Field ◽  
Unit Weight ◽  
New Approach ◽  
Theoretical Function ◽  
Minimization Technique ◽  
Profile Characteristics

In this paper, a new approach for soil profile characterization is validated. The soil characteristics are calculated by fitting the theoretical amplification functions to those obtained experimentally. The identified characteristics have been observed to agree well with those obtained by in situ and laboratory tests. This new approach uses system identification theory and free field records. It is based on formulation of theoretical soil amplification function for two sites in terms of the different parameters of the soil profile layers (thickness, damping ratio, shear wave velocity and unit weight). The theoretical function is smoothed according to the experimental data (spectral ratios) by means of the least squares minimization technique. The function parameters are determined by solving, numerically, a non linear optimization problem. In this approach, soil profile characteristics of two sites can be identified simultaneously, from only a single soil acceleration record at free surface of each site without need of bedrock or outcropping acceleration records. Strong ground motions data recorded during the Boumerdes earthquake (Algeria) of May 21, 2003, are used for the validation.

scholarly journals Use of a card game tool to capture end users' preferences and add sustainability value to social housing projects

2020 ◽  
Vol 20 (1) ◽  
pp. 7-20
Author(s):  
Adrieli Cristina Vieira de Carvalho ◽  
Ariovaldo Denis Granja ◽  
Vanessa Gomes da Silva
Keyword(s):  
Social Housing ◽  
Health And Safety ◽  
Real Estate Market ◽  
End Users ◽  
Sustainable Construction ◽  
Card Game ◽  
Housing Projects ◽  
Sustainable Products ◽  
Sustainable Value ◽  
Safety Parameters

Abstract The construction industry is increasingly adopting sustainable strategies to reduce environmental impacts. Despite this increase, some barriers are still perceived in the real estate market for sustainable buildings. One of them is the delivery of products that are not aligned with the needs and values of end users. This paper investigates the aspired sustainability values in housing projects based on the concept of stated preferences. A card game tool was developed based on the AQUA - HQE(tm) rating system and applied to ask a 164-respondent sample, assembled from four social housing projects to identify their preferences regarding sustainable construction. Responses were statistically analyzed based on bootstrap confidence values and on the index of general significance (IGS) of each sustainable value attribute. Results show a sustainable value hierarchy, in which the health and safety parameters were the most valued. This study confirms the validity of using a set of illustrated cards as a potential tool for identifying sustainability values end users bear and consequently improving decision-making process within sustainable products development.

A novel energy dissipation outrigger system with rotational inertia damper

2018 ◽  
Vol 21 (12) ◽  
pp. 1865-1878 ◽  
Author(s):  
Liangkun Liu ◽  
Ping Tan ◽  
Haitao Ma ◽  
Weiming Yan ◽  
Fulin Zhou
Keyword(s):  
Damping Ratio ◽  
Mass Parameter ◽  
Inertial Force ◽  
Rotational Inertia ◽  
Analysis Model ◽  
Damping Force ◽  
Damped System ◽  
Modal Damping ◽  
Assembly Technique ◽  
Excellent Control

Rotational inertia damper, a novel damper, possessing the advantage of displacement amplification, has been employed in outrigger system for seismic mitigation. The equivalent analysis model composed by a uniform cantilever beam and an equivalent spring was proposed to simulate the rotational inertia damper outrigger system, by which the corresponding dynamic characteristic equation was derived based on numerical assembly technique. To gain the response of the damped system, finite element method and state space method have been utilized. Finally, the results show that the pseudo-undamped natural frequency ratios and system modal damping ratios are significantly influenced by stiffness parameter of the exterior column, while the mass parameter of the rotational inertia damper has little effect on them. The optimal damping ratio can be acquired for one mode, but it may be worse for the other mode in the same position equipping rotational inertia damper. Furthermore, numerical simulation results for the typical earthquake records have verified that the rotational inertia damper outrigger has excellent control performance in displacement as well as acceleration. A good agreement between damping force and equivalent force also suggests that the damping force of rotational inertia damper is predominant and the inertial force has no significant effect on the structure.

In-Situ Static and Dynamic Testing and Numerical Modelling of the Dome of the Siena Cathedral (Italy)

2015 ◽  
pp. 85-114
Author(s):  
Gianni Bartoli ◽  
Michele Betti ◽  
Saverio Giordano ◽  
Maurizio Orlando
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
13Th Century ◽  
Structural Behaviour ◽  
Destructive Testing ◽  
Dynamic Vibration ◽  
Heritage Buildings ◽  
Siena Cathedral ◽  
Vibration Tests

The chapter reports on the in-situ experimental campaign and the numerical modelling that were performed to assess the static and dynamic behaviour of the Cupola of the Siena Cathedral in Italy: an irregular polygonal masonry structure built in the 13th century and composed of two domes. The research was motivated by the failure of some of the stone-trusses which connect the two masonry domes and consists of: a) single and double flat-jack tests in the internal dome, b) dynamic vibration tests on the Cupola under environmental (wind) and artificial (vibrodyne) loads and c) dynamic vibration tests on the double colonnade located below the Cupola (hammer impact tests). Results of tests were employed to identify a numerical model of the Cupola, which allowed to simulate its structural behaviour and to account for the failure of the stone-trusses between the two domes. The numerical model was later extended to the whole Cathedral. Through the discussion of an emblematic case study, the chapter shows a careful application of non-destructive testing (NDT) and numerical modelling in the field of assessment (and rehabilitation) of heritage buildings.

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