Vibration Criteria Research Articles

Sustainability Design Considerations for Timber-Concrete Composite Floor Systems

Over the last few decades, there has been growing interest in the use of low-carbon materials to reduce the environmental impacts of the construction industry. The advent of mass timber panels (MTP), such as cross laminated timber (CLT), has allowed structural engineers to specify a low-carbon material for a variety of floor design considerations. However, serviceability issues such as vibration and deflection are limiting the construction of longer span timber-only floor systems and have encouraged the development of timber-concrete composite (TCC) systems. The use of concrete would negatively impact on the carbon footprint of the TCC floor system and should be minimized. The purpose of this study was to study the impact on embodied carbon in the TCC system, when the ratio of timber and concrete was varied for specific floor spans. Two MTP products were considered, CLT and glued laminated timber (GLT). The floors were designed to satisfy structural, acoustic, and vibration criteria, and the results were presented in the form of span tables. It was found that using thicker MTP instead of adding concrete thickness to meet a specific span requirement can lead to lower embodied carbon values. Increasing concrete thickness for long-span floor systems led to a reduction in allowable floor span due to the vibration criterion being the controlling design parameter. Increasing timber thickness also resulted in higher strength and stiffness to weight ratios, which would contribute toward reducing the size of lateral load resisting systems and foundations, resulting in further reductions in the embodied carbon of the entire structure.

Vibration Assessment on Various Distance to Demolition Works

Abstract: Vibration has been a serious problem to be discussed over the past years. Vibration has caused cosmetic damages to buildings and annoyance to the occupants of the building. Sources of vibration are usually produced by construction work, traffic, seismic effect and human activities. In this paper, the amplitude of vibration caused by demolition has been analyzed and the level of vibration and level of damage caused have been determined. Besides, the effect of the vibration strength due to distance from the source has also been studied. The vibration data due to demolition work was obtained and analyzed by using MATLAB software. The analyzed data in graphical form were compared with the Gordon vibration criteria to obtain the vibration limit and the level of vibration damage according to DOE (Malaysia) standard as well. The results indicated that the vibration at 1m distance and 10m distance from the vibration source will cause minor damage to the building whereas the vibration at 25m distance from the source is at the caution level. By comparing the Gordon vibration criteria curve, the vibration from 1m, 10m and 25m distance from the demolition vibration source are not suitable for sensitive equipment. This study also proved that the vibration strength will decrease as the distance from the source increases due to the loss of vibration energy during the propagation of vibration waves. Hence, the further the distance from the source, the weaker the strength of the vibration and lower level of damage on surrounding buildings.

Degree and nature of shaft misalignments in pumping units assessed against vibration criteria

The paper shows that the degree and type of shaft misalignments, along with imbalances, have a decisive impact on vibration levels in centrifugal pumps. An accurate assessment is impossible without a unit shutdown to measure shaft alignments with special devices. A method for determining misalignments is proposed to assess the degree of misalignment against vibration spectra, the so-called rotational harmonics.

Heuristics for chemical species identification in dense systems.

A new approach to identify chemical species from molecular dynamics (MD) simulations of reacting materials under extreme temperatures and pressures is presented. The approach is based on bond-distance and vibrational criteria, derived from the examination of atomic behavior during a density functional theory MD simulation of an overdriven shock of the explosive pentaerythritol tetranitrate. For comparison, the trajectory was analyzed using popular bonding criteria commonly used in analysis of reactive MD simulations, including distance, distance-time, and bond-order criteria. Cluster analyses using the new time-dependent bond definition approach presented here and a bond-order approach revealed that species and their corresponding lifetimes were strongly dependent on the chosen approach, indicating significant implications for the development of chemical mechanisms and chemical kinetics models using the results of reactive MD simulations.

Control of Metro Train-Induced Vibrations in a Laboratory Using Periodic Piles

Laboratories with sensitive instruments need a low-vibration environment. It is a challenge to control the train-induced vibration impact on these instruments when a newly planned metro line is adjacent to a laboratory building. An alternative method of mitigating train-induced ground vibrations involves installing measures along the transmission path. Recent research has highlighted the potential of periodic pile barriers with specifically designed band gaps for controlling environmental vibrations. This study performed in-situ measurements of ambient vibrations inside and outside a laboratory containing various types of sensitive instruments and located adjacent to a newly designed metro line. The vibration transfer function of the laboratory was then obtained. To help design and optimize the band gaps of periodic piles, a novel band gap performance evaluation function was proposed. Finally, numerical analysis was conducted to validate the mitigation effect of the designed periodic piles. The results showed that the band gap performance evaluation function can be used to optimize the mitigation effect of periodic piles. The proposed periodic piles clearly attenuated vibrations between 52.4 and 74.3 Hz, especially those at 63 Hz. A comparison of general vibration criteria (VC) curves revealed that vibration attenuation of one level can be obtained by the designed periodic piles.

Assessment of tool platform micro vibrations induced by moving vehicles in hi-tech factories

This study explores the micro vibrations of floors and tool platforms induced by internal moving automated guided vehicles (AGVs) in hi-tech factories. The equation of motion of a simplified multi-span floor (or beam) system installed with a tool platform under AGV moving forces generated by a modified Kanai-Tajimi power spectral density (MKT-PSD) function is derived. Dynamic time history analyses of the continuous beam model travelled by different AGV weights are performed. The corresponding root-mean-square (RMS) floor and platform vibration spectra are obtained by using a one-third octave band spectrum analysis and in turn used to compare with the micro vibration criterion. Simulated results indicated that the floor and platform vibrations increase with the AGV weight. For the maximum AGV weight considered, the floor vibration exceeds VC-A, while under the minimum AGV weight, the floor vibration reaches VC-B which is required by the vibration-sensitive tools. Moreover, the platform vibrations are far more than VC-A regardless of the AGV weight. Therefore, the introduction of a proper vibration control scheme is recommended to suppress the excessive micro vibrations of the floors and taller tool platforms.

Analysis of the influence of aerodynamic qualities of the components of mixtures on separation in power-saving vortex vehicles

The object of research is gas-dynamic vortex processes in heterogeneous polydisperse flows. One of the most problematic issues is the determination of the aerodynamic characteristics of the components of a heterogeneous polydisperse medium, which are necessary to create a mathematical model of the separation process. The study used methods of mathematical modeling based on the theory of similarity. A technique has been developed for assessing the aerodynamic parameters of mixture components, on the basis of which a number of aerodynamic similarities have been compiled. The coefficients of lift, aerodynamic drag, lateral force, longitudinal, transverse and rotational moments of the components of the grain mixture are obtained. This is necessary for theoretical studies of gas-dynamic processes in vortex separators in unsteady three-dimensional flow with variable flow density, concentration and flow rate of the separated mixture components and the carried fractions. The Reynolds vibration criterion is obtained, based on which the trajectories and energy of the vortex motion of individual components and the separation degree of heterogeneous mixtures are determined. This allows to improve the mathematical model of the distribution process of heterogeneous polydisperse mixtures in the proposed energy-saving vortex separators. The obtained results provide the basis for improving the general theory of heterogeneous vortex flows by introducing an external disturbance criterion that takes into account the drag of the vortex force field and the amplitude-frequency energy level. Thanks to this, it is possible to evaluate the influence of any argument in the desired function. The research results make it possible to automate the analysis of process characteristics and compare them by parameters with experimental data. And also to evaluate the correspondence of dynamic, kinematic and gas-dynamic functions calculated from the given geometric parameters of the vortex devices with the functions obtained from the averaged values. These data makes it possible to work out a range of variations in the parameters of the geometric design of vortex apparatuses by zones, parameters at the inlet, outlet, and degrees of separation, minimize the number of manufactured laboratory and semi-industrial vortex apparatuses, and unify a number of units. Compared with similar known separators, vortex apparatuses are proposed that reduce the cost of preparing raw materials in the grain mill area by a factor of tens due to the elimination of moving working parts, assemblies and screens.

Vibration Control of Scanning Electron Microscopes with Experimental Approaches for Performance Enhancement.

A vibration isolator embedded in precision equipment, such as a scanning electron microscope (SEM), wafer inspection equipment, and nanoimprint lithography equipment, play a critical role in achieving the maximum performance of the equipment during the fabrication of nano/micro-electro-mechanical systems. In this study, the factors that degrade the performance of SEM equipment with isolation devices are classified and discussed, and improvement measures are proposed from the viewpoints of the measured image patterns and vibrations in comparison with the relevant vibration criteria. In particular, this study quantifies the image patterns measured using SEMs, and the results are discussed along with the measured vibration. A guide for the selection of mounting equipment is presented by performing vibration analysis on the lower mount of the dual elastic mount configuration applied to the SEM, as well as the image patterns analyzed with that configuration. In addition, design modifications for the mount and its arrangement are suggested based on impact tests and numerical simulations.

Vibration Criteria Analysis on Floor due to Human Walking

The development of concrete material technology and modern structural design pattern in Malaysia may not consider the effect of vibration from seismic and other sources. Floor vibration may affect the serviceability of the structural and also provide uncomfortable environment to occupants. The main purpose of this study is to investigate the dynamic analysis on floor at the first floor of Faculty of Technology Management and Business (FPTP) building. The analyses are compared with the vibration criteria guidelines by Gordon (1991) to identify the vibration sensitivity of the floor. The investigation on floor vibration due to people walking is using Finite Element Modelling (FEM) in ANSYS software in order to perform modal analysis and transient analysis. Modal analysis shows the result of the natural frequency of the floor and different mode shapes react with subjected various frequency. The time history of the vibration signal will be performed by transient analysis. Furthermore, the results are transferred to MATLAB software (e.g. VSATs) to assess the vibration criteria curve. The results of the vibration plot show the middle of floor panel and laboratory room are categorized under ISO level. Therefore, it can be concluded that this room is not suitable to accommodate the sensitive equipment particularly at the middle of the floor.

Інтегральні показники зміни вібрації бурильної колони — критерій оцінки зношеності шарошкового долота

Інтегральні показники зміни вібрації бурильної колони — критерій оцінки зношеності шарошкового долота

Isolation solution for extreme environmental vibrations for quantum-enabling cryogenic setups installed on raised frames.

Cryogenic quantum sensing techniques are developing alongside the ever-increasing requirements for noiseless experimental environments. For instance, several groups have isolated internal system vibrations from cold heads in closed-cycle dilution refrigerators. However, these solutions often do not account for external vibrations, necessitating novel strategies to isolate the entire cryogenic systems from their environments in a particular set of raised cryostats. Here, we introduce a dual-stage external active vibration-isolation solution in conjunction with a closed-cycle dilution refrigerator that isolates it from the environment. This dual stage includes two sets of active attenuators and a customized steel tower for supporting experimental probes at heights of 3 m from the floor. Both stages achieve 20-40 dB of attenuation with the active systems engaged, corresponding to levels of vibration in the VC-G range (a standardized Vibration Criterion appropriate for extremely quiet research spaces) on the cryostat's room temperature baseplate and the steel tower. Our unique vibration isolation solution therefore expands the applications of modern cryogenic equipment beyond exclusively quiet specialty buildings, rendering such equipment suitable for interdisciplinary, open-floor research centers.

Assessment of Floor Micro-Vibrations Induced by Moving Vehicles in High Technology Factories Using a Fragility-Based Method

This study presents assessment of floor micro-vibrations induced by moving vehicles in high technology factories by using a fragility-based method. A series of time history analysis of a simplified three-span continuous beam model under moving loads simulated by a modified Kanai-Tajimi power spectral density (PSD) function considering various vehicle weights and moving speeds is performed. The best-fitting surface in terms of the maximum root mean square (RMS) velocity responses and their corresponding pair of the vehicle weight and moving speed is obtained by using the least square regression method. With the regression surface denoting the mean values and the standard deviation obtained, the fragility surfaces for each vibration criterion or limit are further constructed. The assessment of the floor micro-vibration in terms of probability of exceeding a given vibration limit for various pairs of vehicle weight and moving speed can be read accordingly from the fragility surfaces.

Comprehensive investigation of embodied carbon emissions, costs, design parameters, and serviceability in optimum green construction of two-way slabs in buildings

This paper presents an optimum design model for the green construction of reinforced concrete two-way slabs in buildings. The model was applied to various design cases of two-way slabs in residential, office, and commercial buildings to derive designs that minimize environmental impact. The sustainability and economic feasibility of the derived designs were extensively compared with those of the conventional design method in relation to the material composition of concrete and steel in slabs, design parameters, and dominant design factors. As compared to the conventional design method, the optimum sustainable design method achieved average CO2 emission reductions of 4.94%, 11.40%, and 19.96% for residential, office, and commercial buildings, respectively, for all design cases considered in this study. Moreover, a multi-objective optimum design method that could simultaneously minimize embodied carbon emissions, cost, and vibration responses was created to consider the serviceability for vibrations induced by human activity in buildings. The design method was applied for the design cases of slabs in residential and office buildings, which are sensitive to human-induced vibrations. A design with increased concrete strength was derived to satisfy vibration criteria in the case of a residential building. This resulted in an increase of 8.89% in embodied carbon emissions compared with the conventional design method. On the contrary, in the case of an office building, the derived design showed a reduction of 15.79% in embodied carbon emissions while satisfying vibration criteria.

Prevention of structural shorts in highly engineered noise and vibration isolation systems

Noise and vibration isolation in structures is becoming more and more common as the world we live in becomes noisier and noisier. The increase in noise coupled with people’s desire for lower background noise and vibration criteria results in the need for higher performing isolation systems. In order to achieve these performance levels, the system needs to be properly designed and engineered. One of the most common culprits for a system not providing the expected performance calculated during the design process is a short or sound bridge . A short typically occurs during the installation of the system by rigidly connecting the structure or machine that is being isolated to an unisolated element. This causes noise and vibration from sources such as subway, transit, and mechanical equipment to transfer with ease into the structure intended for isolation, rendering the highly engineered system useless or highly degraded. This paper will examine a multitude of ways to eliminate the possibility of a short and elaborate on the importance of the installation process of isolated systems. It will also review how the process differs when isolating for vibration compared to noise and the importance of each.

Vibration criteria analysis on floor at laboratory room

Engineer is now facing a significant challenge related to the vibration problem in the structure. Building is subjected to the significant dynamic load induced by people will generate the dynamic forces. The objectives of this study are to model a three storey building by using Finite Element Modelling (FEM) and perform the vibration criteria plot on floor at laboratory building due to people walking. A vibration excitation source is generated by people walking at four different points. The Finite Element (FE) analyses such as modal analysis and transient analysis are carried out in ANSYS and the data are further generated via MATLAB (VSATs) software to assess the vibration criteria plot (VC). After evaluation, the vibration criterion of survey laboratory fell under VC-E which contributed to the highest percentage plot which is 40 percent of vibration criterion at the certain points. The maximum Root Mean Square (RMS) curve for survey laboratory is 10 micrometers/sec which fell under VC-C at the certain points. VC-C criterion is the good standard for most lithography and inspection equipment up to 1 micron detail size. Thus, survey laboratory has fulfilled the vibration requirements based on the Gordon standard since the VC-E (less severe) criterion is more suitable to allocate the survey equipment for the certain location. The floor vibration performance is analyzed and compared with the guideline and standard such as Generic Vibration Criteria by Gordon in which the vibration level is under minimum permissible level for sensitive equipment.

Vibration isolation of buildings housed with sensitive equipment using open trenches – Case study and numerical simulations

The vibration isolation of buildings housed with sensitive equipment is always a challenging one due to the stringent vibration criteria imposed on them. The paper presents a case study on the vibration isolation scheme adopted for an important building of space research agency. The vibration levels in the building had to follow the vibration criterion which is in the form of a set of one – third octave band velocity spectra, expressed as vibration criterion curves. Various sources that can generate vibrations in the building were identified and assessed. The external sources and the internal sources of vibration were analyzed and the possible limits of vibrations were evaluated. The selection procedure of design frequency, which is the significant step in the design of vibration isolation trench under the passive isolation scheme, is explained. Numerical simulations were developed to evaluate the influence of trench parameters on the amplitude reduction of Rayleigh waves propagating across the trench. Based on the results from numerical simulations, the vibration isolation trench was designed to reduce the amplitudes of vibrations produced from external and internal sources.

The application of new noise and vibration standards onboard ships

The ship represents a very complex system of noise and vibration sources determined by the operation of numerous onboard installations and specific activities of crew and passengers. Shipboard noise can cause discomfort to passengers and hearing damage to the crew and in this regard the need for a safe work environment is growing. Due to these effects, it is necessary to strictly observe the noise and vibration criteria by noise and vibration analysis in the design phase and their adequate control. In this paper are discussed the aspects regarding the latest standards of noise and vibration for ships. It is well known that changes made in regulations are not easy to be implemented on board old ships. The authors made a careful analysis of these changes and made a few recommendations for the shipbuilding companies and naval operators.

Vibration Analysis of Beam and Block Precast Slab System due to Human Vibrations

Beam and block precast slabs system are very efficient which generally give maximum structural performance where their voids based on the design of the unit soffit block allow a significant reduction of the whole slab self-weight. Initially for some combinations of components or the joint connection of the structural slab, this structural system may be susceptible to excessive vibrations that could effects the performance and also serviceability. Dynamic forces are excited from people walking and jumping which produced vibrations to the slab system in the buildings. Few studies concluded that human induced vibration on precast slabs system may be harmful to structural performance and mitigate the human comfort level. This study will investigate the vibration analysis of beam and block precast slab by using finite element method at the school building. Human activities which are excited from jumping and walking will induce the vibrations signal to the building. Laser Doppler Vibrometer (LDV) was used to measure the dynamic responses of slab towards the vibration sources. Five different points were assigned specifically where each of location will determine the behaviour of the entire slabs. The finite element analyses were developed in ABAQUS software and the data was further processed in MATLAB ModalV to assess the vibration criteria. The results indicated that the beam and block precast systems adequate enough to the vibration serviceability and human comfort criteria. The overall vibration level obtained was fell under VC-E curve which it is generally under the maximum permissible level of vibrations. The vibration level on the slab is acceptable within the limit that have been used by Gordon.

Dynamic Analysis of an Office Building due to Vibration from Road Construction Activities

Construction activities are widely known as one of the predominant sources of man-made vibrations that able to create nuisance towards any adjacent building, and this includes the road construction operations. Few studies conclude the construction-induced vibration may be harmful directly and indirectly towards the neighbouring building. This lead to the awareness of study the building vibration response of concrete masonry load bearing system and its vibrational performance towards the road construction activities. This study will simulate multi-storey office building of Sekolah Menengah Kebangsaan (SMK) Bandar Enstek at Negeri Sembilan by using finite element vibration analyses. The excitation of transient loads from ground borne vibrations which triggered by the road construction activities are modelled into the building. The vibration response was recorded during in-situ ambient vibration test by using Laser Doppler Vibrometer (LDV), which specifically performed on four different locations. The finite element simulation process was developed in the commercial FEA software ABAQUS. Then, the experimental data was processed and evaluated in MATLAB ModalV to assess the vibration criteria of the floor in building. As a result, the vibration level of floor in building is fall under VC-E curve which was under the maximum permissible level for office building (VC-ISO). The vibration level on floor is acceptable within the limit that have been referred.

Controlling construction-induced vibrations in healthcare facilities

Controlling excessive floor vibrations is critical in modern healthcare facilities where high-resolution imaging and diagnostic equipment are often used. These types of equipment have stringent floor vibration criteria to ensure the accuracy of their results. Controlling floor vibrations is further complicated as existing healthcare facilities are being renovated and upgraded to meet current healthcare demands, while remaining in operation. This paper presents a case study of an existing hospital which is undergoing extensive renovations. This hospital houses a variety of diagnostic imaging equipment including Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) equipment, as well as mass spectrometers. To determine the extent of the vibration mitigation required such that the equipment can remain operational during construction, vibration tests simulating the future construction activities were conducted. The vibration tests consisted of striking the ground with an excavator, while accelerometers were placed at strategic locations throughout the hospital to capture the excitation.