Floor Response Research Articles

Measurement of the Vaginal Pressure Profile with the Femfit® and Leakage Events Using a Newly Developed Pad Test during Selected Sports Activities: A Pilot Study.

Measuring changes in the vaginal pressure profile (VPP) with the Femfit® by JUNOFEM during various sports will help improve understanding of the magnitude of pressures generated during such activities and the pelvic floor's response to those pressures. This could aid in selecting safe exercises for women with pelvic floor dysfunction. The primary aim of this study was to measure intravaginal pressure changes using a novel pressure sensor array (Femfit®) during high-risk sports activities in elite female athletes with and without stress urinary incontinence (SUI). The secondary aim was to quantify the amount of urine leakage during these activities using a newly developed innovative pad weighing test (iPWT). We used the International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form (ICIQ-UI SF) to assess participants and measured the VPP using the Femfit® device during ground jumps, trampoline jumps, weightlifting, slow running and fast running. Urine leakage was assessed using the iPWT during the five sports activities. The highest VPP (53.7 ± 21.6mmHg) was recorded during ground jumps, followed by trampoline jumps. The second-highest values (24.7 ± 8.1mmHg) were measured during fast and slow running, while the lowest values were observed during weightlifting (11.6 ± 4.0mmHg). Measurements of VPP during sporting activities revealed lower pressure values in elite female athletes with SUI than in those without SUI. The overall mean urine leakage in the SUI group during the five activities was 6.6 ± 1.8g. On the basis of the VPP and the newly developed iPWT, sports involving jumps and lunges have been identified as revealing SUI and should therefore be included in testing female athletes. The iPWT may prove suitable for measuring SUI in elite female athletes but requires further testing and validation. gov Registration: NCT06224335.

Device topology optimization for an inerter-based structural dynamic vibration absorber

A tuned viscous mass damper (TVMD) and a tuned inerter damper (TID) have been proposed as devices that can achieve weight reduction by replacing the mass element of a structural dynamic vibration absorber (DVA) with an inerter. In the TID, the damping element is arranged in parallel with the spring, making its device topology the same as conventional dynamic vibration absorbers. In contrast, in the TVMD the damping element is arranged in parallel with the inerter. This parallel mechanism of inerter and damping element can be realized in a single device, and the member of the building that supports the device can be used as the spring element, making the TVMD highly practical. In fact, TVMDs with a mass effect equivalent to thousands of tons have been commercialized and applied to high-rise buildings in Japan. This paper aims to clarify the effects of the choice of objective functions and damping element arrangement on the seismic response control effectiveness of inerter-based structural DVAs, providing guidelines for structural engineers in selecting suitable devices to achieve desired control effects. The method of investigation considers a model that encompasses both TVMD and TID configurations and formulates a multi-objective optimization problem to simultaneously minimize the displacement amplification factor and floor response acceleration amplification factor. The results of the multi-objective optimization reveal that the TVMD is optimal when the focus is on controlling displacement response, while the TID is optimal when prioritizing the control of floor response acceleration. It was found that the floor response acceleration amplification factor of a structure containing TVMD could be significantly improved by slightly compromising the displacement response amplification factor, leading to the recommendation of adopting the TVMD configuration as an inerter-based structural DVA.

Vibration in Floors Induced for Human Walking: Comparison of Two Design Guidelines

The design of floors must fulfill not only the requirements for the Ultimate Limit State but the Serviceability Limit State, which affects, among other factors, the comfort of the users. Due to the modern design of floors and changes in the use of buildings, the effect of human walking and the vibrations induced by this activity can be a determinant factor in the correct design of a floor. National codes are mainly focused on the Ultimate Limit State and give brief recommendations for the Serviceability Limit Sate. In parallel, several design guidelines have been published to assist in the design phase of floors. In this work, we compute the dynamic response of floors excited by human walking using two guidelines, The American Institute of Steel Construction Design Guide (AISC) and the European Guidelines on Human-Induced Vibration of Steel Structures (JRC-ECCS). To compare both design guidelines, we transform the maximum acceleration obtained with the AISC guidelines in velocity and then compare the maximum velocities for different values of natural frequencies, modal masses and damping ratios of the floor under evaluation. The similarities and differences in the response of the floors are studied, as well as the tolerance limits imposed by the guidelines that indicate if the floor design is correct for the comfort of the users.

Optimal properties of hysteretic dampers to minimize peak floor accelerations in multi-story buildings subjected to earthquakes

In this study, the optimal reduction of seismic peak floor accelerations in buildings equipped with hysteretic dampers is investigated. The structures are modeled as linear elastic shear buildings, and the seismic demand is modeled as a stochastic process. The optimal properties and height-wise distribution of the hysteretic dampers are found using a pattern search optimization algorithm. The objective function is defined in terms of the stochastic non-stationary response of the structure, which is obtained using the Explicit Time Domain Method in combination with statistical linearization. Possible influence of the fundamental period of the structure, the frequency content of the excitation, and the number of stories, on the optimal properties of the hysteretic dampers are analyzed. The effects of the optimal solutions on other response quantities, such as inter-story drifts, ductility demand on the hysteretic dampers, energy dissipation, and floor response spectra, are also assessed. Findings of this study are validated by a case study that considers a real building model subjected to actual ground motion acceleration records. The main findings are: a) optimally designed hysteretic dampers are indeed effective in reducing the seismic peak floor acceleration response; and b) optimal non-uniform height-wise distributions of hysteretic dampers are essentially equal to or at most somewhat better (but not by a wide margin) than optimal uniform height-wise distributions.

Inductive graph‐based long short‐term memory network for the prediction of nonlinear floor responses and member forces of steel buildings subjected to orthogonal horizontal ground motions

AbstractThis paper introduces a novel hierarchical graph‐based long short‐term memory network designed for predicting the nonlinear seismic responses of building structures. We represent buildings as graphs with nodes and edges and utilize graph neural network (GNN) and long short‐term memory (LSTM) technology to predict their responses when subjected to orthogonal horizontal ground motions. The model was trained using the results of nonlinear response‐history analyses using 2000 sample 4–7‐story steel moment resisting frames and 88 pairs of ground‐motion records from earthquakes with a moment magnitude greater than 6.0 and closest site‐to‐fault distance shorter than 20 km. The results demonstrate the model's great performance in predicting floor acceleration, velocity, and displacement, as well as shear force, bending moment, and plastic hinges in beams and columns. Furthermore, the model has learned to recognize the significance of the first mode period of a building. The model's robust generalizability across diverse building geometry and its comprehensive predictions of floor responses and member forces position it as a potential surrogate model for the response‐history analysis of buildings.

Shaking table test and numerical simulation of rocking wall frame structure considering dynamic soil-structure interaction

This study investigates the seismic response of a rocking wall frame structure considering dynamic soil-structure interaction (DSSI) through shaking table tests. A comparison with conventional frame structures and structures with fixed-base foundations is made to examine the influence of DSSI effects on various aspects including structural damage distribution, dynamic characteristics, and floor responses. Test results indicate that the presence of a rocking wall reduces structural responses across different site conditions, although the reduction is less significant under soft soil conditions compared to fixed-base foundation conditions. Overall, DSSI diminishes the mitigating effect of the rocking wall on the maximum structural response. Furthermore, a three-dimensional finite element model of the shaking table test is established. The numerical model employs the equivalent linear method to simulate the soil's nonlinear behavior and incorporates the concept of the rocking wall. Comparative analysis between experimental and simulated results demonstrates that the model effectively predicts the dynamic response of the rocking wall frame structure in DSSI systems.

Towards situation dependent radiation efficiency

Designing buildings to protect inhabitants against ground-borne noise from railway lines or other outdoor ground vibration sources has become a subject of importance. Prediction methods to tackle such a problem are under discussion within a European task group (CEN/TC126/WG2/TG1). From velocity response of floors and walls, the structure-borne sound level has to be evaluated; the linking quantity is the radiation efficiency. In the frequency range of interest, i.e. covering the one-third octave bands from 16 to 250 Hz, rooms modes exist for standard size living spaces in building. A parametric investigation is carried out to evaluate the effect of the room modes on the radiation efficiency. In a first step, a modal approach is used to estimate the radiation efficiency for different room sizes, heavy floor and light wall types. Randomly positioned forces are considered as excitation on these structural elements. From these results, the situation dependent radiation efficiencies are investigated and discussed.

How does the pelvic floor respond to modulations in trunk pressure induced by a variety of voicing tasks? A cross-sectional, observational study.

The pelvic floor responds to changes in trunk pressure, elevating during low-pressure exhale and descending during high-pressure exhale. Voicing occurs during exhalation, spanning low-to-high trunk-pressure, yet it is unknown how voicing affects the pelvic floor. The aim of this study was to quantify pelvic floor response to voicing and identify if there are differences for women with stress urinary incontinence. We hypothesized that shouting would cause pelvic floor descent, with greater magnitude for incontinent women. Sixty women (38 incontinent, 22 continent) performed four voicing tasks (counting to "4" in speaking/shouting/low-pitch/high-pitch voice) while transperineal ultrasound measured changes in pelvic floor morphology. ANOVA compared variance of responses to voicing and t-tests compared groups. Bladder neck height shortened, levator plate length increased and levator plate angle decreased more during shouting compared to speaking; consistent with pelvic floor straining. There were no differences for high versus low pitch-voicing and small group differences based on continence status. Voicing causes pelvic floor muscles to strain, with greater strain during shouting. Changing vocal pitch does not affect pelvic floor morphology and incontinent women had slight differences from continent women. Voicing may be a safe way to lengthen the pelvic floor without provoking incontinence.

A novel deep learning-based method for generating floor response spectra of building structures

Accurately and efficiently generating floor response spectra is crucial for the seismic design and analysis of nonstructural components, and seismic analysis of equipment placed on floors. In this article, a direct spectra-to-spectra method for generating floor response spectra is designed based on deep learning algorithms. The dataset was developed using the records of 102 building observation arrays in the Center for Engineering Strong Motion Data, which included 48 concrete structures, 44 steel structures and 10 masonry structures. The procedure involves training a deep learning model (FRSNet) with the ground response spectra and easily obtained structural parameters as inputs and the floor response spectra as outputs. Analysis results show that the prediction performance of the model is good on concrete structures, steel structures and masonry structures. The proposed model has sufficient accuracy, and the prediction performance is better than that of other models compared in this article. Finally, the proposed model is validated through two numerical models, a shaking table model structure and an actual structure. Convincing results confirm the accurate prediction capabilities of the proposed method.

Novel rod-sprung-mass model to investigate characteristics of building structural vibration induced by railways

Railway-induced vibrations in building structures require predictions to assess the serviceability. Fundamental properties such as the predominant modes of railway-induced vibrations are critical in structural design and mitigation approaches. However, the existing numerical models are customised to specific buildings. This renders these models unsuitable for broader mechanistic investigations. To address this, this study proposes a rod-sprung-mass (RSM) model to investigate the dynamic behaviour of structures under vertical ground excitations induced by railways. The columns were modelled as axial vibration rods, with each floor suspended on the rod as a sprung mass. The model was validated using a three-story steel frame structure and a five-story concrete structure. Subsequently, the dynamic characteristics of the structures and railway-induced responses were discussed. The structural vertical modes are attributed to the interaction between the columns and slabs, and the structural natural frequencies are outside the frequency range of the individual components. Parametric studies revealed that lower-order structural modes are generally predominant. Under such circumstances, the floor response tends to first decrease and subsequently increase with the floor height. As a result, low-rise buildings exhibit the maximum amplitude on the top floor, whereas the maximum amplitude is on the ground floor for high-rise buildings. Meanwhile, when structural high-order modes become predominant owing to a high-frequency input, the responses of the middle floors intensify, and the peak responses can be altered to the middle floors. This study emphasises the necessity of considering vertical global modes, whereas existing studies have focused mainly on mode shapes on particular floors. The RSM model is an efficient tool for structural design and vibration control.

Investigating the Influence of Dynamic Interaction Between Primary and Secondary Structures on Elastic Floor Response Spectra During Near- and Far-Field Earthquakes: A Comparative Analysis with EC8 Formulation

Investigating the Influence of Dynamic Interaction Between Primary and Secondary Structures on Elastic Floor Response Spectra During Near- and Far-Field Earthquakes: A Comparative Analysis with EC8 Formulation

Seismic correlation coefficient evaluation for the application of separation of variables approach in fragility assessment

Seismic correlation can affect seismic probabilistic risk assessment results when components within the system have similar dynamic characteristics. While the fragility assessment methodology is well established, researches to evaluate and apply seismic correlation in fragility are still in progress. In this study, the seismic correlation coefficient (SCC) was quantitatively analyzed based on fragility assessment methods. In order to evaluate the SCC of several random variables associated with structure response in fragility assessment, a numerical analysis model of the structure was constructed and statistical analysis of the numerical results was performed. The SCC of the floor responses of the structural model considering random variables was evaluated from two perspectives. The first perspective involved applying variables individually or simultaneously when performing probabilistic structural analysis. The second perspective aimed to assess whether simplification of the structural analysis model affects the SCC. For this purpose, SCCs were calculated for each method and applied to a simplified failure sequence model to compare the combined fragility curves. The results of this study demonstrate the applicability of separation of variables method to the evaluation and generalization of the SCC for random variables of the fragility curve.

Comparison of evaluations of human-induced floor vibration based on different design guidelines

This paper presents a comparative study on the evaluation of human-induced floor vibrations based on different design guidelines, including AISC DG11, ISO 10137:2007, SCI P354, and JGJT441–2019. Dynamic responses of floors are captured using FEM (Finite Element Method) simulations, with respect to varying thicknesses under different walking patterns and frequencies. The same single-step walking force model is applied across all scenarios to mitigate differences in floor comfort evaluation results due to varying walking force models, with a target to identify the differences induced by floor thicknesses, and walking patterns and frequencies. The dynamic responses are evaluated with respect to different evaluation indices in terms of floor comfort based on the adopted design guidelines. The findings reveal that resonance can occur even when the fundamental frequency of the floor is not equal to the walking frequency, but equal to (or very close to) an integral multiple of the walking frequency. The findings also reveal that walking patterns can affect the evaluation results of floor comfort, and walking at a fixed location may not give the worst evaluation scenario. Statistical analyses revealing the relationship between peak acceleration and floor thickness for walking at a fixed location can be mimicked using an exponential function, while for walking along fixed routes, a fifth-order polynomial function is more appropriate in depicting the relationship between peak acceleration and landing location. Comparison of the evaluation results indicates that different guidelines may give inconsistent or conflicting conclusions in terms of floor comfort, and among the adopted guidelines, ISO 10137:2007 imposes the strictest comfort requirements, while SCI P354 (VDV approach) offers the loosest criteria.

Seismic Fragility Assessment of Equipment in Nuclear Power Plant Structures Considering Nonlinear Hysteretic Behavior of Squat Walls

Accurate seismic risk assessment of structures necessitates precise fragility analysis. This study focuses on the seismic fragility assessment of equipment in nuclear power plant structures, particularly emphasizing the influence of nonlinear hysteretic behavior exhibited by squat walls. By developing and comparing linear and nonlinear models of reactor containment and auxiliary buildings within a nuclear power plant, this research elucidates the significant impact of nonlinear behaviors on the seismic response and subsequent fragility curves of associated equipment and systems. Utilizing a lumped-mass stick model, the study efficiently captures the characteristics of squat shear walls, facilitating the calculation of floor response spectra and fragility for nuclear facility structures. The impacts of pinching and degradation, inherent characteristics of a squat wall’s hysteresis under cyclic loading, were identified as significant. These include the shift and change in amplitude of the floor response’s peak, along with amplification in high-frequency domains. Fragility assessments, informed by seismic response analysis, indicate significant variations in fragility curve parameters based on equipment location and frequency. The findings question the effectiveness of traditional response factor methods and general regression techniques in accurately addressing the complex probabilistic seismic demands of equipment, thus highlighting the importance of using direct analysis for calculating fragility in situations with significant nonlinearity.

Experimental implementation of the nonstructural element simulator on shake table (NEST) for an archetype tall building

AbstractNonstructural damage, usually predominates in buildings subjected to low to moderate seismic intensities and contributes significantly to business interruption and economic losses. It promotes a rapidly growing need for experimental research and qualification of various types of nonstructural elements in buildings in the recent decades. To provide a novel option of experimentally simulating the realistic boundary conditions for various nonstructural elements in labs, we developed the Nonstructural Element Simulator on Shake Table (NEST), a passively controlled three‐layer substructural testbed driven by existing shake tables. This paper presents the first experimental implementation of NEST on a challenging 42‐story archetype tall building. The dynamic properties of the substructure were tuned to adapt the archetype building and the required shake table motions were solved as a reverse problem by an open‐loop control algorithm. The test results proved the capability of NEST to replicate the history responses of the target floors in the archetype building under either recorded earthquake ground motion or artificial loading protocols for qualification purposes. In all cases, the synthetic relative error in the floor accelerations and the inter‐story drift within the frequency range of interest was less than 5% in the numerical domain and less than 30% in the physical realization. The seismic responses of a variety of nonstructural elements to the substructural motions show that, in the mid‐story of the archetype tall building, the ceiling sustained minimum damage because of the small floor acceleration while the indoor contents slid significantly and even overturned.

Resilience-based seismic design for nuclear island building: An innovative hybrid passive control system

The Fukushima nuclear incident has heightened global concerns about the safety of nuclear facilities, the imperative to enhance the seismic resilience of nuclear power plants (NPPs) has become a pivotal aspect of nuclear safety. This study introduces an innovative hybrid passive control system that integrates three-dimensional (3D) base isolation technology with periodic isolation walls, aiming to bolster the seismic resilience of NPPs against very rare earthquakes. Furthermore, a complete and viable computational procedure was developed to study the nonlinear soil-structure interaction effects with high-precision wave motion analysis. Finally, the efficacy of the innovative control system to improve the seismic resilience of large-scale nuclear island buildings situated on non-rocky sites was assessed. The findings reveal that the system significantly mitigates the distribution of damage to NPPs during very rare earthquake scenarios. Compared to non-isolated NPP, the adoption of a hybrid passive control system reduces structural damage dissipation energy by 97.73 %. The system augments the effectiveness of 3D base isolation technology in reducing dynamic responses; specifically, the floor response spectra at the top position of the nuclear island building in the X, Y, and Z directions were lowered by 62.33 %, 52.03 %, and 84.12 %, respectively. Moreover, the system considerably reduces the deformation of the 3D isolation bearings. The innovative hybrid passive control system helps to enhance the seismic resilience of NPPs.

Seismic response of irregular RC buildings designed for gravity and seismic loads

Irregular reinforced concrete framed buildings are peculiar and their seismic response is difficult to predict using simplified approaches. The irregularity in structural configuration is characterized by cross-sectional area reduction of the columns along the height, in-elevation and in-plan irregular distribution of the masses, complex floor geometry or floor geometry variation along the height. This study analyses the seismic response of several four-storey buildings with different types of irregularities, namely in-elevation floor height and floor geometry variation. Additionally, responses of both seismically designed and gravity load designed structures are compared for each geometry considered. A numerical model accounting for non-linear flexural and shear response of the structure is developed, aimed at conducting non-linear incremental dynamic analyses. The results are discussed in terms of inter-storey drift, floor acceleration profiles, fragility functions and floor response spectra. A significant influence of the irregularity on floor accelerations and displacements was observed, as well as on the spectral acceleration at collapse, mainly caused by mass and stiffness variation along the height. On the other hand, no significant influence was detected on failure modes.

Estimation of consistent absolute acceleration and relative displacement floor response spectra in existing masonry-infilled reinforced concrete buildings

Estimation of consistent absolute acceleration and relative displacement floor response spectra in existing masonry-infilled reinforced concrete buildings

Correlating the seismic acceleration of reinforced concrete moment-resisting-frames with structural and earthquake characteristics

Nonstructural components (NSCs) are elements within the building unrelated to the lateral load-carrying system. Failure of NSCs during earthquakes can result in casualties, significant economic losses, disabled critical infrastructures, and loss of building functionality. The NSCs can be categorized into two primary groups: deformation-sensitive and acceleration-sensitive. Thanks to well-established seismic design guidelines and standards, buildings may suffer minor seismic deformations – resulting in lesser damage to deformation-sensitive components. However, planning under the peak floor response or peak floor acceleration (PFA) is getting much less attention – exposing the acceleration-sensitive components to greater risk. This manuscript develops equations for moment-resisting reinforced concrete frames (MRRCFs) that estimate the total floor acceleration. The data is gathered based on 984 inelastic response simulations, elaborated to create an idealized equation based on the earthquake characteristics. The developed equation offers engineers a quantitative approach to understanding the inertial forces applied to the NSCs within the building during earthquakes, allowing them to plan for potential risks due to earthquakes.

A Low-Cost Sensing Solution for SHM, Exploiting a Dedicated Approach for Signal Recognition.

Health assessment and preventive maintenance of structures are mandatory to predict injuries and to schedule required interventions, especially in seismic areas. Structural health monitoring aims to provide a robust and effective approach to obtaining valuable information on structural conditions of buildings and civil infrastructures, in conjunction with methodologies for the identification and, sometimes, localization of potential risks. In this paper a low-cost solution for structural health monitoring is proposed, exploiting a customized embedded system for the acquisition and storing of measurement signals. Experimental surveys for the assessment of the sensing node have also been performed. The obtained results confirmed the expected performances, especially in terms of resolution in acceleration and tilt measurement, which are 0.55 mg and 0.020°, respectively. Moreover, we used a dedicated algorithm for the classification of recorded signals in the following three classes: noise floor (being mainly related to intrinsic noise of the sensing system), exogenous sources (not correlated to the dynamic behavior of the structure), and structural responses (the response of the structure to external stimuli, such as seismic events, artificially forced and/or environmental solicitations). The latter is of main interest for the investigation of structures' health, while other signals need to be recognized and filtered out. The algorithm, which has been tested against real data, demonstrates relevant features in performing the above-mentioned classification task.