Comparison of Modal Parameters of a Concrete Slab Floor from EMA and OMA

This study addressed delamination detection of concrete slabs by analyzing global dynamic responses of structures. Both numerical and experimental studies are presented. In the numerical examples, delaminations with different sizes and locations were introduced into a concrete slab; the effects of presence, sizes, and locations of delaminations on the modal frequencies and mode shapes of the concrete slab under various support conditions were studied. In the experimental study, four concrete deck specimens with different delamination sizes were constructed, and experimental tests were conducted. Traditional peak-picking, frequency domain decomposition, and stochastic subspace identification methods were applied to the modal identification from dynamic response measurements. The modal parameters identified by these three methods correlated well. The changes in modal frequencies, damping ratios, and mode shapes that were extracted from the dynamic measurements were investigated and correlated to the actual delaminations and can indicate presence and severity of delamination. Finite element (FE) models of reinforced concrete decks with different delamination sizes and locations were established. The modal parameters computed from the FE models were compared to those obtained from the laboratory specimens, and the FE models were validated. The delamination detection approach was proved to be effective for concrete decks on beams.

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Vibration Monitoring of Two Long-Span Floors Equipped with Tuned Mass Dampers

International Journal of Structural Stability and Dynamics ◽

10.1142/s0219455419501013 ◽

2019 ◽

Vol 19 (09) ◽

pp. 1950101 ◽

Cited By ~ 1

Author(s):

Pei Liu ◽

Hai-Xin Zhu ◽

Babak Moaveni ◽

Wei-Guo Yang ◽

Shu-Qiang Huang

Keyword(s):

Natural Frequency ◽

Dynamic Properties ◽

Concrete Slab ◽

Vibration Monitoring ◽

Ambient Vibration ◽

Mode Shapes ◽

Modal Parameters ◽

Tuned Mass Dampers ◽

Long Span ◽

Wood Flooring

This paper presents the field tests and vibration performance assessment of two long-span floors with tuned mass dampers (TMDs). The floors considered are made of steel beams and concrete slabs, as part of a gymnasium with composite floors spanning 36 m in each direction and equipped with 30 TMDs. Operational modal analysis based on ambient acceleration measurements is performed to extract the modal parameters of the floors. Ambient vibration tests were conducted at three stages of construction for each floor, namely (i) after the concrete slab was completed, (ii) after one layer over the concrete slab was added, and (iii) after the flooring (surfacing) was fully finished. The effects of the layers making up the flooring system and of the TMDs on the dynamic properties of the floors are studied. The finite element models of the floors are validated using the identified modal parameters. The effects of natural frequency of TMDs on the dynamic properties of the floors are investigated using the validated model. Finally, the effects of flooring on the vibration serviceability of the two floors are studied with TMDs in operation, when the floors were subjected to crowd-induced rhythmic loading, from which the efficiency of TMDs is assessed numerically. The results show that the coupled vibrations of the two floors with TMDs turned off occur in the first two modes, while the natural frequencies of the floors decrease with the addition of layers. The TMDs in operation break the first mode of the floor into two modes with similar mode shapes, resulting in smaller vibration response and larger damping ratios, which vary with the natural frequency of TMDs. Also, the wood flooring significantly increases the human-induced vibration of the floor, while the plastic flooring shows basically no effect.

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Theoretical and experimental research on slip and uplift of the timber-concrete composite beam

BioResources ◽

10.15376/biores.15.3.7079-7099 ◽

2020 ◽

Vol 15 (3) ◽

pp. 7079-7099

Author(s):

Jianying Chen ◽

Guojing He ◽

Xiaodong (Alice) Wang ◽

Jiejun Wang ◽

Jin Yi ◽

...

Keyword(s):

Differential Equations ◽

Deformation Theory ◽

Concrete Slab ◽

Theoretical Calculations ◽

Structural Element ◽

Structural Efficiency ◽

Theoretical Investigations ◽

New Type ◽

Interlayer Slip ◽

Good Agreement

Timber-concrete composite beams are a new type of structural element that is environmentally friendly. The structural efficiency of this kind of beam highly depends on the stiffness of the interlayer connection. The structural efficiency of the composite was evaluated by experimental and theoretical investigations performed on the relative horizontal slip and vertical uplift along the interlayer between composite’s timber and concrete slab. Differential equations were established based on a theoretical analysis of combination effects of interlayer slip and vertical uplift, by using deformation theory of elastics. Subsequently, the differential equations were solved and the magnitude of uplift force at the interlayer was obtained. It was concluded that the theoretical calculations were in good agreement with the results of experimentation.

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Impact Resistance Performance Of Waste Long Drink Cans Fibres Reinforced Concrete Slab

10.15405/epsbs.2018.07.02.103 ◽

2018 ◽

Cited By ~ 1

Author(s):

Agusril Syamsir

Keyword(s):

Reinforced Concrete ◽

Concrete Slab ◽

Impact Resistance ◽

Reinforced Concrete Slab ◽

Resistance Performance

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Bending Strength of Steel Fibre Reinforced Concrete Ribbed Slab Panel

Scientific Research Journal ◽

10.24191/srj.v15i1.4165 ◽

2018 ◽

Vol 15 (1) ◽

pp. 15

Author(s):

AMIR SYAFIQ SAMSUDIN ◽

MOHD HISBANY MOHD HASHIM ◽

SITI HAWA HAMZAH ◽

AFIDAH ABU BAKAR

Keyword(s):

Reinforced Concrete ◽

Bending Strength ◽

Steel Fibre ◽

Concrete Slab ◽

Future Application ◽

Fibre Reinforcement ◽

Fibre Reinforced Concrete ◽

Conventional Concrete ◽

Steel Fibre Reinforced Concrete ◽

Bending Load

Nowadays, demands in the application of fibre in concrete increase gradually as an engineering material. Rapid cost increment of material causes the increase in demand of new technology that provides safe, efficient and economical design for the present and future application. The introduction of ribbed slab reduces concrete materials and thus the cost, but the strength of the structure also reduces due to the reducing of material. Steel fibre reinforced concrete (SFRC) has the ability to maintain a part of its tensile strength prior to crack in order to resist more loading compared to conventional concrete. Meanwhile, the ribbed slab can help in material reduction. This research investigated on the bending strength of 2-ribbed and 3-ribbed concrete slab with steel fibre reinforcement under static loading with a span of 1500 mm and 1000 mm x 75 mm in cross section. An amount of 40 kg/m steel fibre of all total concrete volume was used as reinforcement instead of conventional bars with concrete grade 30 N/mm2. The slab was tested under three-point bending. Load versus deflection curve was plotted to illustrate the result and to compare the deflection between control and ribbed slab. This research shows that SFRC Ribbed Slab capable to withstand the same amount of load as normal slab structure, although the concrete volume reduces up to 20%.

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Issues on Design of Piled Raft Foundation

JOURNAL OF ADVANCES IN CHEMISTRY ◽

10.24297/jac.v14i1.5905 ◽

2018 ◽

Vol 14 (1) ◽

pp. 6057-6061 ◽

Cited By ~ 1

Author(s):

Padmanaban M S ◽

J Sreerambabu

Keyword(s):

Contact Area ◽

Concrete Slab ◽

Design Procedure ◽

Bending Moment ◽

Foundation Design ◽

Detailed Review ◽

Piled Raft ◽

Piled Raft Foundation ◽

Raft Foundation ◽

Influencing Parameters

A piled raft foundation consists of a thick concrete slab reinforced with steel which covers the entire contact area of the structure, in which the raft is supported by a group of piles or a number of individual piles. Bending moment on raft, differential and average settlement, pile and raft geometries are the influencing parameters of the piled raft foundation system. In this paper, a detailed review has been carried out on the issues on the raft foundation design. Also, the existing design procedure was explained.

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Effect of Bass Bar Tension on Modal Parameters of a Violin's Top Plate

Archives of Acoustics ◽

10.2478/aoa-2014-0015 ◽

2015 ◽

Vol 39 (1) ◽

pp. 145-149 ◽

Cited By ~ 3

Author(s):

Ewa B. Skrodzka ◽

Bogumił B.J. Linde ◽

Antoni Krupa

Keyword(s):

Modal Analysis ◽

Experimental Modal Analysis ◽

Mode Shapes ◽

Modal Parameters ◽

Normal Value ◽

Modal Damping

Abstract Experimental modal analysis of a violin with three different tensions of a bass bar has been performed. The bass bar tension is the only intentionally introduced modification of the instrument. The aim of the study was to find differences and similarities between top plate modal parameters determined by a bass bar perfectly fitting the shape of the top plate, the bass bar with a tension usually applied by luthiers (normal), and the tension higher than the normal value. In the modal analysis four signature modes are taken into account. Bass bar tension does not change the sequence of mode shapes. Changes in modal damping are insignificant. An increase in bass bar tension causes an increase in modal frequencies A0 and B(1+) and does not change the frequencies of modes CBR and B(1-).

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