scholarly journals Experimental Investigations and Numerical Simulations of the Vibrational Performance of Wood Truss Joist Floors with Strongbacks

Forests ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1493
Author(s):  
Yinlan Shen ◽  
Haibin Zhou ◽  
Shuo Xue ◽  
Xingchen Yan ◽  
Jiahao Si ◽  
...  
Keyword(s):  
Full Scale ◽  
Experimental Investigations ◽  
Reduction Peak ◽  
Acceleration Response ◽  
Maximum Deformation ◽  
Vibration Behavior ◽  
Modeling Analysis ◽  
Single Person ◽  
Vibration Serviceability ◽  
Vibration Performance

This paper provides an experimental study and computer modeling analysis of vibration performance of full-scale wood truss joist floors, related to the static deflection and vibration mode/frequency and single-person-induced vibration. The vibration behavior of full-scale truss joist floors was investigated and the influences of the strongbacks on the vibration behavior were assessed. The results showed that the simulated predictions agreed well with the measured results. Strongbacks do not significantly affect the fundamental frequency of the truss joist floors but influence the second and third modal frequencies. The use of strongback rows at mid-span effectively decreased the maximum deformation of point loading at floor center. The effect of adding strongbacks at one-third of each span on decreasing maximum deformation at the floor center was minimal. The case of walking parallel to the joist produced higher acceleration response at the floor center than that of walking perpendicular to the joist. The closer the placements of strongbacks were to the mid-span, the more significant reduction of the vibration at floor center was. Two strongback rows at mid-span performed the best effect on reduction of vibration response at floor center. However, the use of strongbacks had limits of reduction peak acceleration of the sheathing between the joists. The study provides a valuable guide for future vibration serviceability study and design optimization of wood truss joist floors.

scholarly journals Vibration serviceability assessment of office floors for realistic walking and floor layout scenarios: Literature review

2019 ◽  
Vol 23 (6) ◽  
pp. 1238-1255
Author(s):  
Márcio S Gonçalves ◽  
Aleksandar Pavic ◽  
Roberto L Pimentel
Keyword(s):  
Design Guidelines ◽  
Design Criterion ◽  
Embodied Energy ◽  
Human Gait ◽  
Vibration Source ◽  
Structural Elements ◽  
Single Person ◽  
Vibration Serviceability ◽  
Floor Vibration ◽  
Vibration Performance

Over the last two decades, office floors have been built progressively lightweight with increasing spans and slenderness. Therefore, vibration performance of office floors due to walking dynamic loads is becoming their governing design criterion, determining their size and shape, and therefore overall weight and embodied energy of the building. To date, floor design guidelines around the world recommend walking load scenarios in offices featuring some or all of the following standard characteristics: (a) walking loads are assumed to be periodic dynamic excitation represented by the Fourier series, including harmonics corresponding to up to the first four integer multiples of the pacing frequency of which at least one is exciting the floor at a resonant frequency and (b) single person walking. However, the literature surveyed provides evidence that such assessment methodology is potentially an over-simplification which does not reflect real walking load scenarios, since crucial features of the floor vibration source, path and receiver are missing. First, in terms of vibration source, realistic scenarios need to feature (a) moving rather than stationary walking forces, (b) stochastic nature of human gait, (c) simultaneous multi-person walking and (d) human–structure interaction. Second, for the transmission path (i.e. office floor structure), two features are needed to consider: (a) realistic office floor layouts and (b) presence, or absence, of non-structural elements. Finally, for the vibration receivers (i.e. floor occupants), (a) vibrations calculated at floor locations occupied by users (instead of at the potential highest response location which may not be occupied), (b) actual period over which occupants feel vibration due to such excitation and (c) assessment of vibration levels based on their probability of occurrence. This study therefore addresses these seldom considered but increasingly important features and discusses realistic approaches to floor design for vibration serviceability.

Prediction of floor responses to crowd bouncing loads by response reduction factor and spectrum method

2020 ◽  
pp. 136943322097556
Author(s):  
Jun Chen ◽  
Jingya Ren ◽  
Vitomir Racic
Keyword(s):  
Structural Damage ◽  
Response Spectrum ◽  
Field Measurements ◽  
Reduction Factor ◽  
Response Reduction Factor ◽  
Long Span ◽  
Single Person ◽  
Vibration Serviceability ◽  
Concert Halls ◽  
Structural Responses

Bouncing is a typical rhythmic crowd activity in entertaining venues, such as concert halls and stadia. When the activity’s frequency is close to the natural frequency of the occupied structure, the corresponding bouncing loads can cause intense structural vibrations resulting in vibration serviceability problems, even structural damage. This study suggests a method for prediction of vibration response due to crowd bouncing by a response reduction factor (RRF) in conjunction with a previously established response spectrum approach pertinent to a single person bouncing. The RRF is defined as a ratio between structural responses with and without taking into account synchronization of body movements of individuals in a bouncing crowd. The variations of RRF with number of persons, structural frequency, bouncing frequency and structural damping ratios have been studied using experimental records of crowd bouncing loads. Based on the findings a practical design curve for RRF has been proposed. Application of the proposed method has been validated on numerical simulations and field measurements of a long-span floor subjected to crowd bouncing loads.

Experimental Investigations of Single and Multi-Fault in Rotor System

2014 ◽  
Vol 541-542 ◽  
pp. 628-634
Author(s):  
S.P. Mogal ◽  
D.I. Lalwani
Keyword(s):  
Fourier Transform ◽  
Fast Fourier Transform ◽  
Real Life ◽  
Rotor System ◽  
Vibration Response ◽  
Experimental Investigations ◽  
Multiple Faults ◽  
Single Fault ◽  
Vibration Behavior ◽  
Combined Action

Many researchers dealt with single fault but in real life situations, combined action of two or more single faults are usually present. Multi-faults (two and three combinations) were studied by few researchers. Researchers have mostly studied the vibration behavior of a rotor with misalignment, unbalance and rub separately. This paper presents one such case, where multiple faults are considered together in a rotor system, i.e. misalignment, unbalance and rub. The objective of this paper is to experimentally investigate the vibration response of combined of three faults misalignment, unbalance and rub using Fast Fourier Transform (FFT). FFT spectrum of combination of three faults misalignment, unbalance and rub show 1 X and 2 X are predominant and many sub harmonics are generated.1X peak represent unbalance, 2X peak represents misalignment and sub harmonics shows rub fault.

Modeling, Analysis, and Suppression of the Impact of Full-Scale Wind-Power Converters on Subsynchronous Damping

2013 ◽  
Vol 7 (4) ◽  
pp. 700-712 ◽  
Author(s):  
Khaled Mohammad Alawasa ◽  
Yasser Abdel-Rady I. Mohamed ◽  
Wilsun Xu
Keyword(s):  
Wind Power ◽  
Power Converters ◽  
Full Scale ◽  
Modeling Analysis ◽  
The Impact

Numerical and Experimental Study on the Dynamic Behavior of an Innovative Steel-Concrete Composite Hollow Waffle Floor

2020 ◽  
Vol 20 (08) ◽  
pp. 2050087
Author(s):  
Xi Zhang ◽  
Qing Li ◽  
Yousan Wang ◽  
Qiming Wang
Keyword(s):  
Experimental Study ◽  
Structural Parameters ◽  
Design Guidelines ◽  
Element Analysis ◽  
Long Span ◽  
Vibration Serviceability ◽  
Floor Vibration ◽  
Walking Tests ◽  
Vibration Performance ◽  
Hollow Beams

The U-shaped steel-concrete composite hollow waffle (CHW) floor is an innovative slender large-span floor composed of a thin slab and bidirectional orthogonal steel-concrete composite hollow beams. Large vibrations may occur under human excitations, and vibration guidelines for CHW floors are still lacking. Thus, this paper undertook a parametric and experimental study to explore the vibration performance of the CHW floors. First, the modal properties and vibration response under walking tests considering the varying frequencies and routes were obtained from the measurements, which validated the accuracy of the finite element analysis (FEA). Then, the influence of the structural parameters on the floor vibration was investigated by numerical modeling. The parametric study shows that the medium-sized long-span (MLS) (28[Formula: see text]m) CHW floors present the best vibration serviceability, the small-sized long-span (SLS) (14[Formula: see text]m) CHW floors vibrate substantially under walking excitation, and the large-sized long-span (LLS) (42[Formula: see text]m) CHW floors are vulnerable to resonance. Finally, this paper provides recommendations for design guidelines for CHW floors and indicates that controlling the span-to-height (SH) value and beam spacing (BS) at a small value are the most effective methods of vibration control.

Evaluating Vibration Performance of a Subsea Pump Module by Full-Scale Testing and Numerical Modelling

2016 ◽  
Author(s):  
Pieter J. G. van Beek ◽  
Hajo P. Pereboom ◽  
Harmen J. Slot
Keyword(s):  
Evaluation Criteria ◽  
Full Scale ◽  
Operating Conditions ◽  
Piping System ◽  
Vibration Modes ◽  
Surrounding Water ◽  
Pipe System ◽  
Vibration Performance ◽  
Submerged Conditions ◽  
Pipe Vibration

Prior to subsea installation, a subsea system has to be tested to verify whether it performs in accordance with specifications and component specific performance evaluation criteria. It is important to verify that the assembled components work in accordance with the assumptions and design criteria used in the detailed engineering. These criteria also cover the vibration performance. In the current study, the pump module within the Åsgard subsea compression station has been subjected to such system evaluation test, including its vibration performance. Vibrations may be caused by internal and external flow through a complex process that is affected by numerous factors such as the piping geometry, flow and operating conditions and also the fluid properties. When severe, mechanical vibrations can lead to fatigue failure of the equipment components. One of the major parameters that affects the vibration response of the subsea piping is the surrounding water. It is generally known that surrounding water does participate in some vibration modes by adding mass to the total, dynamic mass participating in the vibration. Therefore, resonant frequencies of a piping system will have different values for non-submerged and submerged cases. In addition, the surrounding water can also lead to higher damping of the vibration modes. In this paper the effect of submerging a pipe system in water is quantified, by analyzing the changes in damping coefficient and the characteristics of measured pipe vibration in-situ. This is achieved by analysis of full-scale frequency response tests performed on a subsea pipe system within the pump module in both non-submerged and submerged conditions. The results are used for validation of numerical techniques that are used to quantify pipe vibration in submerged conditions. Different modeling techniques for the submerged case are investigated. It is shown that the effects from the surrounding water on pipe vibrations are different for small-bore piping than that for main piping. Furthermore the different modeling approaches and general observations and trends in damping coefficients are discussed and compared with the measurements.

scholarly journals Full-scale experimental testing of dump-point safety berms in surface mining

2015 ◽  
Vol 52 (11) ◽  
pp. 1791-1810 ◽  
Author(s):  
Anna Giacomini ◽  
Klaus Thoeni
Keyword(s):  
Current Knowledge ◽  
Experimental Testing ◽  
Construction Materials ◽  
Surface Mining ◽  
Full Scale ◽  
Waste Rock ◽  
Experimental Investigations ◽  
Rules Of Thumb ◽  
Australian Coal ◽  
Experimental Findings

Waste rock (muck) piles are used as energy absorption barriers in many surface mining applications, such as berms at dumping points and at the crest of slopes, and in windrows as traffic separators or edge barriers on haul roads. The height of safety berms and windrows is currently designed using rules of thumb, such as height equal to half the maximum wheel diameter. However, over the last few decades, the dimensions of haul trucks have increased, and it is unclear if such rules of thumb are still applicable. This study, funded by the Australian Coal Association Research Program (ACARP), was carried out with the objective of improving the current knowledge on design and construction of dump-point safety berms in mining environments. Through full-scale experimental investigations on the dynamic impact of haul trucks on dump-point safety berms, significant data on berm design, construction materials, as well as principal berm characteristics were collected for the first time. The experimental findings suggested that the current rule of thumb might only be suitable for dump points where trucks travel at velocities lower than 10 km/h. The studies also showed that safety berms should be built using fresh, blocky, nonslaking waste rock materials and well maintained over their lifespan.

scholarly journals Vibration Behavior and Reinforcement Effect Analysis of the Slab Track-Subgrade with Mud Pumping under Cyclic Dynamic Loading: Full-Scale Model Tests

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Junjie Huang ◽  
Qian Su ◽  
Wei Wang ◽  
Xun Wang ◽  
Huiqin Guo
Keyword(s):  
Epoxy Resin ◽  
Normal Condition ◽  
Full Scale ◽  
Scale Model ◽  
Reinforcement Effect ◽  
Slab Track ◽  
Vibration Behavior ◽  
Low Viscosity ◽  
Concrete Base ◽  
Mud Pumping

Mud pumping occurring in the subgrade bed can gradually deteriorate the performance of the slab track-subgrade, negatively affecting the comfort and safety of high-speed railway. In this paper, a full-scale model of the slab track-subgrade was established to analyze the vibration behavior of the model in normal condition and before and after mud pumping reinforced, as well as the reinforcement effect of mud pumping using low-viscosity epoxy resin. The research results show that the vibration acceleration and displacement and the settlement of the model in normal condition stabilize gradually with the increasing number of loading cycles. Under the upper layer of the subgrade bed saturated by water, mud pumping occurs in the subgrade bed as soon as the second loading stage reaches to 3.0 × 104 cycles, and the deterioration of mud pumping increases gradually with the increasing number of loading cycles. Moreover, a large volume of slurry composed of water and fine particles is squeezed out of the subgrade bed after the model is subjected to the second cyclic loading stage of 2.0 × 106 cycles, causing contact loss between the concrete base and the subgrade bed, which makes the acceleration and displacement of the concrete base increase abnormally compared with the model in normal condition, as well as the cumulative settlement of the subgrade bed. The model with significant mud pumping in the upper layer of the subgrade bed was reinforced by using low-viscosity epoxy resin. This effectively controlled the abnormal acceleration and displacement of the concrete base and restored the support capability of the subgrade bed for the concrete base of the slab track structure.

Mathematical Modeling of Energy Distribution in Entering a Beam into the Workpiece Material in the Course of Electron Beam Welding

Vestnik MEI ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 88-95
Author(s):  
Sergey O. Kurashkin ◽  
◽  
Vadim S. Tynchenko ◽  
Aleksandr V. Murygin ◽  
◽  
...  
Keyword(s):  
Electron Beam ◽  
Energy Distribution ◽  
Mathematical Models ◽  
Electron Beam Welding ◽  
Welding Process ◽  
Full Scale ◽  
Temperature Fields ◽  
Experimental Investigations ◽  
Technological Parameters ◽  
Welding Processes

Modeling of electron beam welding processes is one of the most important parts of applied research, because full-scale experimental investigations are either expensive or highly labor intensive. The problem of modeling the temperature fields at the electron beam entering stage during welding is considered. The aim of the study is to simplify the adjustment of the electron beam welding process technological parameters and to elaborate and develop more efficient control algorithms through replacing full-scale experiments by model ones. The mathematical body of the proposed solutions is constructed using the theories of thermal and welding processes, based on which the energy distribution mathematical models are developed. For practically implementing the computations, an algorithmic support is presented that allows the mathematical models to be applied in modern modeling systems, such as Matlab, Comsol Multiphysics, and Ansys. Apart from supplementing the set of existing mathematical models of the electron beam welding process, the obtained models for calculating the temperature in the beam entering area widen their application for calculating and optimizing the welding process, taking into account the workpiece temperature in the electron beam entering area. By using the proposed solutions, several numerical experiments were carried out for a workpiece made of VT-14 titanium alloy and two pieces of different thickness made of AMg-6 aluminum alloy. The obtained temperature fields and the rms values of process parameters are almost identical with the results of previously conducted full-scale studies.

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