Vibration Performance Of Floors Research Articles

Measurement and documentation recommendations for reporting footfall floor vibration performance in mass timber buildings

Construction methods utilizing mass timber are increasingly offering more sustainable and eco-friendly solutions for vibration sensitive buildings that have traditionally used only concrete or concrete and steel materials. Regardless of the building material, it is important to consider vibration serviceability with respect to occupants or sensitive equipment as part of the design process. Several references are now available to help with the footfall vibration design of mass timber floors. These references borrow heavily from established methods outlined in American and European design guides for steel and concrete construction. What cannot be borrowed from these guides is the wealth of empirical validation data that has been obtained from measurements in steel buildings. As more mass timber buildings are built, it will benefit the community to have floor vibration performance measurements to further inform and validate prediction and design methods. This paper discusses measurement methods and documentation items to report floor vibration performance in existing mass timber buildings. The consistent reporting of the collected empirical data will help standardize future design prediction methods and validations with these structures.

Human-induced vibrations of floors: A probabilistic approach

The current design guidelines for assessing floor vibration performance rely on a simplified approach that considers a single pedestrian as a fixed load with multiple harmonic components applied to the anti-nodes of the floor mode shapes. However, these guidelines do not account for the influence of variability in the walking path on the dynamic response of floors. Moreover, the deterministic approaches used in these guidelines may yield unreliable estimates of vibration response due to the stochastic nature of pedestrian walking force. The aim of this paper is to investigate the dynamic response of floors under a single pedestrian walking load while considering the randomness of the walking path and the walking load itself. A probabilistic perspective is adopted to analyze the dynamic response under different random loading scenarios. Furthermore, the effectiveness of the current guidelines in predicting the dynamic response of floors is critically assessed. The importance of incorporating probabilistic approaches is emphasized to achieve a more comprehensive understanding of the vibration serviceability of floors and to enhance design practices in this context.

New approaches for floor vibrations of steel–polymer–steel sandwich floor systems

Diverse sandwich floor systems have recently been developed owing to their significant features, such as high strength and low weight. Because sandwich floor systems generally have a high bond strength between the face and core materials, they exhibit fully composite behaviors under large deformations. The main feature of sandwich floor systems is that face materials primarily resist bending moments, whereas core materials resist shear forces under flexural loading. Thus, the flexural behavior of the sandwich floor systems should consider shear deformations owing to relatively weak and soft core materials compared with face materials. However, current publications, such as guides and recommendations, for evaluating or designing floor vibration propose estimation equations derived from a uniform section beam, commonly known as the Euler–Bernoulli beam theory, which is governed by pure bending behavior. This approach should be developed when evaluating or designing floor vibrations of sandwich floor systems, which simultaneously exhibit bending and shear behavior under flexural loading. Therefore, this paper proposes new approaches, which include shear and bending deformations, for the floor vibration performance of the sandwich floor system, particularly the steel–polymer–steel sandwich floor system. New approaches are derived from the sandwich beam theory and deformation-based approach with a single-degree-of-freedom model; they were validated through a comparison with laboratory-scale and full-scale tests in an actual building. For full-scale tests in an actual building, the two conditions, with and without finishings, were considered to conduct the floor vibration tests. Furthermore, a more efficient and simple approach derived from the deformation-based approach is highly recommended for practical design.

Vibration serviceability evaluation of lightweight cold-formed steel floor systems

Featured by lightweight and high strength-to-weight ratio, cold-formed steel framing has been increasingly used in floor systems of low-rise and mid-rise residential and commercial building constructions. The high stiffness-to-weight ratio and low damping of such floor systems may result in potential risk for annoying floor vibrations and then bring forth a serviceability issue, particularly in an attempt to achieve longer floor spans. Several design methods have been published to enable engineers to ensure human comfort on wood-framed and structural steel-framed floors. However, although significant advancement has been attained in cold-formed steel framing, a practical and efficient design method of evaluation vibration serviceability for cold-formed steel floor systems is yet available. This paper presents a simplified design method for vibration serviceability of lightweight cold-formed steel floor systems, in which a new acceptance criterion for vibration serviceability was proposed by using binary logistic regression to correlate human prediction on floor vibration performance with vibration characteristics of the floor systems based on available test data. The procedure and corresponding equations for computing design parameters which signify the vibration characteristics of the floor system are presented. Two examples are provided to demonstrate efficiency of the proposed design method.

A Comparison on Numerical Simulation Models for Vibrational Performances of the Wood Truss Joist Floor System

Wood truss joist floors are increasingly used to replace traditional solid timber joist floors in low‐rise timber houses. An understanding of the vibration performance of wood truss joist floors is critical for the design and serviceability of the floors. It is difficult to model wood truss joist floors accurately because of the complicated boundary conditions and numerous sophisticated flexible connections. This paper discusses three simplified modeling methods for the wood truss joist floor system. The modeling results were validated by a series of static deflection tests and vibration modes and frequencies tests of a full‐size floor. And predictive analysis of human‐induced vibration of the floor was also conducted. The vibration characteristics of the wood truss joist floor were investigated. The examination of the applicability of these modeling methods was provided. The results indicate that the point loading deflection more easily affects the deflection of the adjacent joist. However, the deflection influence on other joists that are three spaces away is minimal. Walking on the wood truss joist floor produces steep vibration acceleration fluctuations at the floor center for a relatively long time period. The sheathing‐to‐joist connections and the metal plate connections of the joists have significant influences on the vibration response of the wood truss joist floor. The modeling method, which considers the flexible metal plate connections and flexible sheathing‐to‐joist connections, performs best for predicting the vibration performance of the floor.

Floor Vibration Experiment and Serviceability Test of iFLASH System.

Studies on novel composite structures that can decrease floor height and improve constructional efficiency in order to increase spatial efficiency and lease revenue have been actively conducted. An innovative fire-proof, lightweight, absorbed, shallow, and hybrid (iFLASH) system was developed to solve construction site issues, such as improving constructability, reducing construction time, and attaining structural efficiency by reducing the weight of the building structure. This system can shorten the construction duration and decrease the floor height and structural weight, owing to features such as a low thickness and light weight. However, studies on the vibration characteristics of this new floor system have not been performed yet. As the general thickness of the iFLASH system ranges from 25 to 30 mm, it must have a sufficient floor vibration performance in order to be utilized. To evaluate the floor vibration performance of the iFLASH system, an experiment was performed in two buildings where the system was applied. This paper presents the results of the dynamic characteristics and serviceability testing as basic data for the vibration characteristics of the iFLASH system.

Ambient Vibration Response of Precast Hollow Core Flooring System

Prestressed precast hollow core is known as a long span slab with a void along its length. The void has a big influence on the weight of the slab. In vibration theory, a lightweight slab with a long span is very sensitive to vibration. In this study, the ambient vibration response of precast hollow core is investigated using the finite element method and modal analysis. Numerical analysis is used to predict the floor vibration and modal testing is used to test the vibration performance of floors on the actual site. The prediction data is obtained by using SAP2000 to determine the vibration behaviour and compared with the modal testing result of the floor located in Kuala Lumpur. The 1st mode shape appeared for 12 natural frequencies between 8.36 Hz to 9.29Hz in the prediction analysis. For modal testing, the vibration behaviour of the actual hollow core floor is determined using an ambient test. The data was obtained using an accelerometer and analysed using Artermis software to determine natural frequencies, damping ratio and mode shape. The 1st mode of natural frequencies for floor area A and area B were 8.45Hz and 9.34Hz. The results from the analysis show that the range of natural frequency between the predicted analysis and that of the modal testing is acceptable. The limitation stated that 10Hz is the cut-off frequency to determine the class of the floor. From the analysis, it is shown that the prediction and the modal testing results are accepted where both floors are classified as low-frequency floors.

Car body floor vibration of high-speed railway vehicles and its reduction

An on-site test has been performed to address the problem of feet numbness caused by the floor vibration of high-speed railway vehicles. Analysis of the floor vibration performance indicates that the vibration of the car body chassis transmitted to the floor by the elastic supports is significantly amplified in the frequency range of 20–50 Hz. This overlaps with the frequency range in which human lower extremities are most sensitive, leading to feet numbness. A refined finite element model of the car body, including the floor panels is developed to further study the vibration mechanism of the floor. Results show that due to the inappropriate design of the elastic support stiffness, the deformations of the floor above the bogie centre for several typical modes in the frequency range of 20–50 Hz are significantly amplified. When the excitation frequencies transmitted from the car body chassis were close to the eigenfrequencies of the floor, the local resonance of the floor will occur, which is the root cause of human feet numbness. The dynamic stiffness of the elastic support is further optimised, and the experimental verification shows that the vibration transmissibility from the car body chassis to the floor in the frequency range of 20–50 Hz has been significantly reduced, and the problem of feet numbness has been solved.

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.

철골 조립식주택 바닥판 진동 평가에 관한 연구

최근 연구개발이 활발히 이루어지고 있는 철골 조립식주택은 공장에서 생산되고 현장에서 조립되는 건설방식의 특성으로 인해 일반 건축물의 철근콘크리트 바닥판과 같이 일체타설 시공되지 못하게 되며 부재 단면크기 감소 및 경량화 등으로 인해 거주자의 활동에 의한 바닥판의 수직진동 및 처짐이 사용성 평가 측면에서 중요한 문제가 될 수 있다. 따라서 이 연구에서는 대상 조립식주택에서 장변방향 보 중앙에 샛기둥이 설치된 모듈과 설치되지 않은 모듈을 대상으로 실무에서 일반적으로 사용되고 있는 AISC 설계지침서 11의 계산식(이하 AISC 계산식)을 이용하여 바닥판의 진동성능을 평가하고 범용해석프로그램을 이용한 해석결과와 비교를 통해 AISC 계산식의 적용성을 고찰하였다. 이를 토대로 샛기둥이 설치된 모듈의 바닥판에서 AISC 계산식과 해석결과의 오차가 크게 발생되는 구조적 원인을 분석하고 이를 고려하는 방안을 제시하였다. 또한 대상 조립식주택 바닥판에 대한 진동성능 향상방안을 변수로 해석모델을 수립하고 진동응답해석 및 경제성평가를 통해 진동성능과 경제성이 우수한 방안을 제시하였다. The steel frame modular housing of which the research and development has been actively carried out recently cannot be constructed through monolithic placement like the reinforced concrete deck of general structure due to the characteristics of construction method of production in the factory and assembly on the site. And floor vertical vibration and deflection caused by inhabitants' activities may become an important issue in the aspect of usability evaluation due to a decrease in the section size of member, a decrease in weight, and so on. Therefore, this study evaluated the vibration performance of deck by using formula of AISC Design Guide 11(hereinafter AISC formula) which was practically used in general for modules where a stud was and wasn't installed at the center of beam in the longitudinal direction in the modular housing to be studied, and examined the applicability of AISC formula through comparison with the results of analysis using a general-purpose analysis program. On the basis of this, a structural cause for an error to occur between analysis result and AISC formula in the deck of module in which a stud was installed was analysed, and measures for considering this were suggested. Besides, an analysis model with the variables of measures for improving the floor vibration performance of modular housing to be studied was established. And measures having excellent vibration performance and economic feasibility were suggested through vibration response analysis and economic evaluation.

Potential Use of Deformed Shank Nails as a Solution to Annoying Vibrations in Wood Floor Systems

Abstract In the United States, modern designs of wood floor systems rarely directly account for annoying floor vibration criteria, because it is not a required design criterion in the International Building Code or the International Residential Code. However, adhesives are sometimes used to supplement traditional subfloor fasteners in an effort to improve the floor vibration performance, but they are mainly used to reduce or eliminate homebuilder “callbacks” due to floor squeaks. This article addresses using high performance deformed shank fasteners rather than adhesives to minimize common annoying floor vibration problems.

Modal testing and FE model correlation and updating of a long-span prestressed concrete floor

There is a lack of information on as-built vibration properties and performance of slender prestressed post-tensioned (PT) concrete floors in buildings. To improve this situation, this paper describes modal testing, finite element (FE) modelling, and model correlation and updating of one such prototype floor. Advanced testing, correlation and updating technologies demonstrated in this paper were successfully transferred from mechanical and aerospace engineering disciplines where they are nowadays used as a standard design tool. Two structural configurations of the full-scale floor were examined: the bare floor in the unclad building, and the same bare floor but in the clad building with services attached underneath. Modal testing showed a considerable increase in stiffness in the latter case. The FE model correlation and updating exercise quantified this contribution and also demonstrated that bending of in situ cast concrete columns supporting the in situ cast concrete floor contributed significantly to the floor bending stiffness and, therefore, should not be modelled as pin-supports. Finally, wide and shallow band-beams, which often feature in PT floors, were shown to have considerable lateral stiffness. This feature has the potential to improve the floor's vibration performance, and was successfully modelled using orthotropic shell elements.

Modal testing and FE model correlation and updating of a long-span prestressed concrete floor

There is a lack of information on as-built vibration properties and performance of slender prestressed post-tensioned (PT) concrete floors in buildings. To improve this situation, this paper describes modal testing, finite element (FE) modelling, and model correlation and updating of one such prototype floor. Advanced testing, correlation and updating technologies demonstrated in this paper were successfully transferred from mechanical and aerospace engineering disciplines where they are nowadays used as a standard design tool. Two structural configurations of the full-scale floor were examined: the bare floor in the unclad building, and the same bare floor but in the clad building with services attached underneath. Modal testing showed a considerable increase in stiffness in the latter case. The FE model correlation and updating exercise quantified this contribution and also demonstrated that bending of in situ cast concrete columns supporting the in situ cast concrete floor contributed significantly to the floor bending stiffness and, therefore, should not be modelled as pin-supports. Finally, wide and shallow band-beams, which often feature in PT floors, were shown to have considerable lateral stiffness. This feature has the potential to improve the floor's vibration performance, and was successfully modelled using orthotropic shell elements.