Building Vibration Research Articles

Generalized Damped Outrigger Systems for Suppressing Multimode Vibrations of Tall Buildings

Damped outrigger is a viable means for reducing dynamic responses of tall buildings. This study focuses on generalized damped outrigger (GDO) systems. A GDO is composed of a damper for energy dissipation, a negative stiffness device and an inerter for damping enhancement. The GDO system incorporates GDOs at different floors of the tall building optimized to varied structural modes. Frequency equation of a tall building simplified as a cantilever beam with multiple GDOs is first derived by complex modal analysis. A finite different model of such a system is used for verification. Parametric analyses are then performed to compare damping effects of different GDO systems. It is found that a negative stiffness damped outrigger (NSDO) or inerter damped outrigger (IDO) needs to be optimized for maximizing damping of a specific mode. GDOs, respectively, tuned to different modes can largely improve the multimode damping effects. The optimal parameters of the GDOs are slightly different from those in the case when they are installed separately. With both negative stiffness and nonzero inertance, a GDO still needs to be tuned to a specific mode because multimode damping is sensitive to the damper coefficient. The combination of an NSDO optimized to the first mode and an IDO tuned to a higher mode seems the best solution. The IDO additionally improves the first mode damping provided by the NSDO and the two-mode damping is not sensitive to the damper coefficient of the NSDO. The findings are confirmed through seismic response analyses of a tall building with different GDO systems.

Linear Oscillations of the High-Rise Buildings

Seismic calculations are based on the hypothesis that maximum seismic horizontal displacements of inelastic systems are equal to displacements of elastic systems of equivalent frequencies.Analysis of strong earthquakes of recent years (San Francisco, USA, 1971, Spitak, Armenia, 1988, Kobe, Japan, 1995 and others) led scientists to the conclusion that this hypothesis cannot be recognized as acceptable. In a number of cases, the maximum horizontal displacements turned out to be 2–3 orders of magnitude higher than the maximum displacements of elastic systems. For example, a displacement graph based on the 1985 Mexico City earthquake shows that the actual plastic displacements are 100 times the expected plastic displacements. In the case of other earthquakes, there are hundreds of subtle inconsistencies. The quantitative results concluded that the intensity of building vibrations exceeded 1.5 times the 9-point design seismic intensity 2.5 and that a special approach, including the need to consider impact effects, is needed and is particularly serious in such zones. This should also be taken into account. Inelastic deformations are indicated. The new calculation is used to study non-linear oscillations caused by impulsive actions of a continuous system. In the case of elastic vibration, changing the mass gives very different results. Reducing the lower mass by a factor of 3 reduces the displacement by a factor of 2.2 for the upper mass and 2.4 for the second mass. The same impact was applied to a 16-story building and the stiffness distribution of the rods was studied in different ways. The stiffness was constant everywhere, constant within 4 stories, where it varied linearly and parabolically with height. Displacements during the course of the pulse shock were greater in the stiffer buildings. Furthermore, the vibration decreases in amplitude by a factor of 3 or more for the upper mass and by a factor of 4 for the lower mass. The force on the upper rod is reduced by a factor of 4 and the force on the lower rod is reduced by a factor of 6. This will make it possible to perform calculations for a small time scale, which is necessary to take into account high-frequency oscillations that occur in the epicentric zone.

Building vibration measurements induced by train operation on concrete floor

Buildings located near subway lines and railway lines are usually subject to train-induced vibrations. The rest and work of people in residential and office buildings, as well as the use of vibration-sensitive equipment in laboratories and precision manufacturing facilities are impacted by the vibrations. To explore the impact of train-induced vibration on over-track buildings, the measurements were conducted at Guangzhou Baiyun railway station, where the passenger and cargo trains operate on the concrete floor within the building. The vibration transmission law of the building height and the distance to the track was obtained. The vibrations induced by passenger and cargo trains were compared. It is found that the vertical vibration mainly attenuates with the increase of the distance from the source, while the horizontal vibration attenuates with different floors due to the propagation wave of vertical vibration in the floor slab and horizontal vibration in the column in terms of the bending wave. The vibrations caused by trains running on concrete floors decay more slowly than those caused by trains running on the soil. The results provide useful pre-construction vibration level estimation for designing similar buildings over the railway.

Train-induced vibration mitigation based on foundation improvement

The distance between railway systems and buildings has been significantly reduced due to the rapid development of public transportation. Environmental vibration is increasingly influencing human health and comfort as well as vibration-sensitive equipment. To alleviate the issue, amplifying the coupling loss between soil and building using foundation improvement techniques, is an effective way to mitigate building vibration from external sources. In this study, a 4-story building need to be built over the railway was used to study the vibration mitigation by foundation improvement. The vibration mitigation performance of foundation design parameters, including foundation type, shear wave velocity of soil, distance from the source, pile diameter, pile length, dimension of the pile cap, and pile group, were studied by a finite element method model. A guideline for optimizing foundation design, which can effectively improve the coupling loss between soil and foundation, has been proposed and applied to the construction of a 4-story building. The train-track dynamic model and the full-scale track-ground-building finite element method model were built to predict the proposed building vibration with the designed foundation. The measurement was conducted before and after the building construction to validate the accuracy of model and the feasibility of the foundation improvement design. The soil-foundation coupling loss is significant from 10 to 80 Hz, which indicates the foundation improvement for vibration mitigation by amplifying the coupling loss is feasible.

Uncertainty quantification of wood floor system modal frequencies resulting from variable densities in members

Low-frequency vibration in a multi-story wood building is of concern because failure in mitigation of such vibration may lead to occupant discomfort. Ultimately, it may cause damage to their health. Variability in material properties of the members of a wooden floor system significantly influences vibration response characteristics such as eigenfrequencies and mode shapes. In this study, we investigate the uncertainty in low-frequency characteristics of a selected wood floor system, resulting from uncertainty in the members’ material properties. We use a surrogate model developed using polynomial chaos expansion, based on a few training samples computed using a finite element model of an experimental-scale structure comprised of seven load-bearing joists of spruce. We estimate the hyperparameters needed for accurate surrogate model development and, with these, we predict probability distributions for each of the floor-system modal frequencies. Also, we perform local and global sensitivity analyses to assess how material property variation affects the modal frequencies. Results confirm the accuracy and efficiency of the developed surrogate models in prediction of the modal frequencies, resulting from uncertainty in wood material properties. The accuracy of the results is comparable to those based on more expensive Monte Carlo simulation.

Structural Engineering of Nanocarbons Comprising Graphene Frameworks via High-Temperature Annealing

Abstract High-temperature annealing is an effective way to heal the defects of graphene-based nanocarbons and enhance their crystallinity. However, the thermally induced vibration of the graphene building blocks often leads to unfavorable micro-, nano-structural evolution including layer stacking. Herein, the key structural factors to achieve highly crystalline graphene frameworks with desired microstructures upon annealing at 1800 °C is revealed. The structural changes of fullerenes, single-walled carbon nanotubes, and graphene-based porous frameworks are precisely analyzed by their structural parameters, such as the total number of graphene edge sites and precise graphene stacking structures, using a novel advanced vacuum temperature-programmed desorption technique up to 1800 °C. The stacked structure is differentiated into loose and tightly stacking, where the loosely stacked structure is found to induce further stacking at high-temperature. Moreover, a graphene framework with an inner space size of greater than 4–7 nm is beneficial to avoid structural change upon high-temperature annealing. These findings offer both a fundamental understanding of the solid-state chemistry of nanocarbons under high temperatures and a viable strategy for engineering edge-site free graphene frameworks with pre-designed microstructures.

Energy sink outrigger control of a tall building under wind loads

The ability of the nonlinear energy sink (NES) device to suppress unwanted wind-induced vibrations in a tall building is investigated in this paper. This controller is an additional energy dissipation embedded within the inner surface of the perimeter column and the end boundary of the outrigger. The Timoshenko theory based on partial differential equations is used to model the dynamic response of the core-tube type structure. The root-mean-square (RMS) response of the structure, defined as the objective function, is used to evaluate the optimal placement of the damped outrigger. Subsequently, a detailed algorithm is proposed to better understand the numerical selection procedure of the suitable location. The effectiveness of the NES on the dynamics of the structural system is investigated through a comprehensive parametric study and compared to a TMD (Tuned Mass Damper) system. According to the results, it is found that the use of appropriate intrinsic parameters of the NES device improves its dynamic response to a considerable level. The presence of this control device is beneficial for the mechanical system and can minimize more than 79 % of the effects of wind-induced vibrations at the top of the structure.

Practical back-analysis methodology to predict underground train-induced building vibrations.

The vehicle-track interaction leads to the vibrating source for the prediction of train-induced building vibrations. To prevent modeling difficulties in the source part, this study proposes a practical back-analysis methodology for calculating underground train-induced building vibrations. The methodology combines the advantages of field measurements and numerical simulations. The fundamental concept of the hybrid methodology is to first create a virtualized moving source at the rail surface and subsequently modify it until the numerical predictions are consistent with the field measurements at the same locations. These locations are frequently selected at the ground surface or near the building foundation. Finally, this imaginary force can be used to predict the vibrations of buildings. The practicality of the hybrid methodology is verified by comparing the predicted vibrations of buildings with field test results. As an application of the proposed method, the transmission laws and characteristics of the vibrations in buildings are analyzed.

Transmission characteristics of train-induced vibration in buildings based on wave propagation analysis

Various studies have focused on predicting, evaluating, and controlling train-induced building vibrations and radiated noise. This study aimed to clarify the theory of building vibration transmission by investigating the transmission characteristics of vibrations in buildings using wave propagation analysis. First, the building was modelled as a periodic structure, as each floor was similar in layout. Based on the wave propagation method, a periodic structure model was established in which the dynamic stiffness matrix of the cell structure could be derived using the spectral element method. Second, a response transfer function (RTF) database of 140 simplified typical residential buildings was established by wave analysis method. Finally, the transmission laws of train-induced vibration were studied. The results indicated that the vibration transmission laws were related to the mode shapes of structures and the participation of modes, which was affected by the spectral characteristics of the input excitation. With an increase in building height, the natural frequency decreased, which influenced the participation of each mode, and this would cause the transmission characteristics of the total vibration energy to change.

Comparative Studies on Nonlinear Structures with Multiple Tuned Mass Damper and Multiple Tuned Impact Damper

This study proposes integrating the particle damping technology into multiple tuned mass damper (MTMD) to form a multiple tuned impact damper (MTID) system for suppressing the vibrations of nonlinear high-rise buildings under earthquakes. A systematic performance comparison comprising vibration damping effects and working strokes between the optimal MTMD and optimally designed MTID with a distinct multi-objective optimization strategy is addressed. The energy-based analysis is also conducted to essentially reveal the difference in damping mechanisms of the two dampers. Furthermore, due to the parameter deviations of engineering structures in practice, the robustness of MTID and MTMD is evaluated involving structural mass, damping and stiffness. The results show that MTID is capable of transferring more energy to the damper and reducing structural energy to a greater extent, thus presenting superiority in controlling structural root mean square (RMS) responses and nonlinear indicators comprising joint curvature and the number of plastic hinges compared with MTMD. Through parametric evaluation, greater robustness is validated in MTID under deviations of various structural parameters with downgraded performance fluctuation in both range and degree, and the efficient operating range of MTID under the deviation of structural parameters is given. Furthermore, a smaller working stroke of the optimal MTID system is required compared with MTMD, permitting the improved applicability of the MTID system and better space utilization in the practical building.

Investigation of the elliptical resonant vibration of high-rise buildings induced by the oblique-downwind interference effects

ABSTRACT The interference effect is one of the difficult topics in wind engineering research themes. Enormous publications have been made to understand its whole picture qualitatively and quantitatively in the past several decades. However, rare results focused on the interference effects of the neighboring building located downstream. This study intends to investigate several mentioned downstream interference effects based on the high-frequency-force-balance tests. Four different cross-sections are selected to understand how the adjacent building’s appearance interferes with the square principal building. Results show that the interference effects induced by the downstream neighboring buildings can be categorized into two locations – the oblique-downwind location and the downwind location. The oblique-downwind interference effect generates two different motion shapes of the principal building, including the inclined hollow elliptical motion from the two-directional resonant vibration and the standing elliptical motion from the one-directional resonance. The downwind interference effect generates a similar one-directional resonance. Several force spectrum examples are given in this study to illustrate how the oblique-downwind interference effect mechanism forms at a specific distance and reduced velocity. In addition, the results from the augmented experiment with more combinations of two buildings suggest more efforts are necessary for inspiring the phenomenon of an inclined hollow elliptical motion.

Characterisation of time-varying structure-borne sound sources using a reception plate to predict maximum Fast time-weighted levels in heavyweight buildings

Structure-borne excitation from many mechanical appliances leads to structural vibration which can be transmitted to nearby rooms and cause annoyance for building occupants. The reception plate method provides a simplified characterisation procedure to obtain the power input for SEA prediction models. Empirical corrections based on the relationship between Leq and LFmax are introduced to predict sound transmission from time-varying source vibrations in buildings. For this purpose, the reception plate method is used to capture the maximum power input. Using different ramped noise signals as idealised versions of time-varying signals from machinery has allowed empirical corrections to be identified such that short Leq measurements can be used with the reception plate. When using SEA or EN12354 it is shown that LFmax in a room can be predicted for a time-varying structure-borne sound source with one-third octave band errors within ±3 dB. Similar results occurred for predicted LAFmax levels calculated from frequency-dependent A-weighted LFmax. A case study with a toilet flush was performed on the reception plate to replicate the empirical corrections derived from ramped noise signals which resulted in close agreement.

A prediction method for indoor vibration over metro depot throat area based on coupled interactions of wheel-rail

Environmental vibration pollution is the primary environmental problem faced by the superstructure of metro depots. The throat area is especially prone to high wheel-rail impact vibration due to multiple joints and turnouts, which may cause high annoyance to the residents in the superstructures both on the upper cover and surrounding areas. In this paper, based on the coupled dynamic analysis of wheel-turnout, a prediction method to evaluate the indoor vibration of over-track building is established. Firstly, subway turnout with variable sections on switch, connection part and frog and vehicle models are established, and wheel-rail force is obtained through multibody dynamics calculation. Secondly, the track-foundation-structure finite element numerical model was built, loading the wheel-rail force excitation, then the indoor vibration could be obtained. The accuracy of this method is verified taking a 32 story residential superstructure in North China as an example. The vertical vibration accelerations were measured on every other floor when a A-type train travelled on a 7-turnout. The error between the measured data and the calculated results was within 5%, indicating that this prediction method has certain accuracy. The research results have certain guiding significance for the prediction and control of vibration in metro depot.

Analysis on seismic control strategies for structural control device: A comparative study

The paper explores various control strategies proposed by researchers from decades ago in controlling the building structural system. It focuses on hybrid mass dampers used by many researchers in their previous work because the implementation of this device needs an excellent control strategy to provide a better performance in suppressing building vibration. The suitable choice of control strategy in structural control is important in giving the best structure response to withstand an earthquake or strong wind. Based on previous structure and control strategies, a simulation for a two-storey building structure system equipped with a hybrid mass damper at the top building has been conducted. Fuzzy logic controller (FLC), Sliding mode controller (SMC) and fuzzy sliding mode controller (FSMC) are used to suppress the building structure vibration during an earthquake by giving input from seismic excitation taken from El Centro earthquake. The simulation result shows that FSMC technique provides better performance compared to FLC and SMC in suppressing the building vibration based on the displacement response and frequency response. This paper concludes with the problems left and recommendations for structural control improvement.

The Influence of Chamfered and Rounded Corners on Vortex-Induced Vibration of Super-Tall Buildings

In order to study the influence of chamfered and rounded corners on vortex-induced vibration of super-tall buildings, a series of multi-degree-of-freedom (MDOF, in short) aeroelastic models were made, including chamfered-corner models with chamfer ratios of 0%, 2.5%, 5.0%, 7.5%, and 12.5%, and rounded-corner models with rounded ratios of 0%, 12.5%, 15%, and 17.5%. The crosswind displacement response of each aeroelastic model was measured by a laser displacement meter in a wind tunnel. The test results indicate that the crosswind displacement response is significantly reduced when the chamfer ratio increases to 5% or the rounded ratio increases to 12.5%; in particular, the vortex-induced vibration (VIV, in short) response can be reduced by more than 60%, which indicates that the chamfered corner and rounded corner play a good role in restraining the VIV of super high-rise buildings. When the reduced wind speed is small, the reduction of the crosswind response of chamfered and rounded models is mainly caused by the reduction of wind load; when the reduced wind speed approaches the VIV wind speed, the negative aerodynamic damping phenomenon of the model with a proper chamfer ratio and rounded ratio disappears, which shows that the VIV is suppressed not only because the cut corner reduces the wind load but also because the cut corner weakens the aeroelastic effect. Generally speaking, a chamfer ratio of about 7.5% and rounded ratio of about 15% can achieve a good reduction effect on the VIV of super high-rise buildings.

Train-induced vibration attenuation measurements and prediction from ground soil to building column.

The investigation of the influence of soil-structure coupling on the vibration propagation pattern is the key to ensuring the reliability of the prediction of train-induced building vibration. This study selects different metro depots with over-track buildings as the research objects based on the existing engineering examples. It analyzes the general laws of vibration propagation from the ground soil to the building columns. The study provides valuable references for predicting vibration and designing vibration isolation measures for over-track buildings. Additionally, this study proposes a vibration prediction method for over-track buildings above metro depots based on the back propagation (BP) neural network model in machine learning. This model considers the soil-structure coupling loss in a data-driven manner based on the rich data samples, which avoids the problems of complex numerical simulation calculations and parameter uncertainties to some extent. This prediction method has a good balance of efficiency and convenience and also meets the accuracy requirements. It was judged to be a promising prediction method for the preliminary design stage of the over-track buildings above metro depots.

Influence of the thermomechanical behavior of NiTi wires embedded in a damper on its damping capacity: Application to a bridge cable

<abstract><p>Thanks to high dissipation properties, embedding NiTi Shape Memory Alloys in passive damping devices is effective to mitigate vibrations in building and cable structures. These devices can inconceivably be tested directly on full-scale experimental structures or on structures in service. To predict their effectiveness and optimize the set-up parameters, numerical tools are more and more developed. Most of them consist of Finite Element models representing the structure equipped with the damping device, embedding parts associated with a superelastic behavior. Generally, the implemented behavior laws do not include all the phenomena at the origin of strain energy dissipation, but stress-induced martensitic transformation only. This article presents a thermomechanical behavior law including the following phenomena: (i) intermediate R-phase transformation, (ii) thermal effects and (iii) strain localization. This law was implemented in a commercial Finite Element code to study the dynamic response of a bridge cable equipped with a NiTi wire-based damping device. The numerical results were compared to full-scale experimental ones, by considering the above-mentioned phenomena taken coupled or isolated: it has been shown that it is necessary to take all of these phenomena into account in order to successfully predict the damping capacity of the device.</p></abstract>

Vibration measurement of KIUT building by MEMS accelerometer

This paper describes the measurements of structure small vibration in buildings of Yeoju Technical Institute in Tashkent (YTIT) in the use of MEMS accelerometer. The natural frequencies of main 6-story building were about 1.55Hz in both directions. In additions, the frequencies were measured for 10-story curve building under construction.

A Machine Learning Enabled Hall-Effect IoT-System for Monitoring Building Vibrations

Vibration monitoring of civil infrastructures is a fundamental task to assess their structural health, which can be nowadays carried on at reduced costs thanks to new sensing devices and embedded hardware platforms. In this work, we present a system for monitoring vibrations in buildings based on a novel, cheap, Hall-effect vibration sensor that is interfaced with a commercially available embedded hardware platform, in order to support communication toward cloud based services by means of IoT communication protocols. Two deep learning neural networks have been implemented and tested to demonstrate the capability of performing nontrivial prediction tasks directly on board of the embedded platform, an important feature to conceive dynamical policies for deciding whether to perform a recognition task on the final (resource constrained) device, or delegate it to the cloud according to specific energy, latency, accuracy requirements. Experimental evaluation on two use cases, namely the detection of a seismic event and the count of steps made by people transiting in a public building highlight the potential of the adopted solution; for instance, recognition of walking-induced vibrations can be achieved with an accuracy of 96% in real-time within time windows of 500ms. Overall, the results of the empirical investigation show the flexibility of the proposed solution as a promising alternative for the design of vibration monitoring systems in built environments.

To the solution of the problem of longitudinal vibrations of multi-storey buildings on the basis of the plate model

The article is devoted to the development of a continual spatial plate model of a multi-story building, developed in the framework of the bimoment theory of thick plates. A technique for dynamic spatial calculation for the seismic resistance of buildings under longitudinal seismic impacts is proposed. Formulas are given for determining the reduced moduli of elasticity. Numerical results of eigenfrequencies and displacements are obtained.