Acceleration Demands Research Articles

Machine learning for reducing noise in RF control signals at industrial accelerators

Industrial particle accelerators typically operate in dirtier environments than research accelerators, leading to increased noise in RF and electronic systems. Furthermore, given that industrial accelerators are mass produced, less attention is given to optimizing the performance of individual systems. As a result, industrial accelerators tend to underperform their own hardware capabilities. Improving signal processing for these machines will improve cost and time margins for deployment, helping to meet the growing demand for accelerators for medical sterilization, food irradiation, cancer treatment, and imaging. Our work focuses on using machine learning techniques to reduce noise in RF signals used for pulse-to-pulse feedback in industrial accelerators. Here we review our algorithms and observed results for simulated RF systems, and discuss next steps with the ultimate goal of deployment on industrial systems.

Ratio of accelerations to decelerations in Women’s division I lacrosse

This study analyzed the differences by position in acceleration, deceleration, and the ratio of accelerations to decelerations in drills and quarters of games (Q1-Q4). Data were collected in 23 female collegiate lacrosse athletes (20.8 ± 1.5 years, 168.3 ± 6.1 cm), consisting of ten midfielders, five defenders, and eight attackers. Drills were categorized as: stickwork (SW), small-sided games (SSG), warm-up (WU), active recovery (AR), individual skills (IS), scrimmage, and conditioning. AR (0.31 ± 0.09 accelerations/min) and WU (0.47 ± 0.07 accelerations/min) showed the lowest number of accelerations, and conditioning and SW were the highest (>1.0 accelerations/min). Conditioning showed the highest demand for decelerations (0.37 ± 0.14 decelerations/min) and AR and WU had the fewest (0.10 ± 0.04 decelerations/min). AR, IS, SW, and WU all had higher acceleration/deceleration ratios (4:1 to 5.7:1) than the remaining drill types (p = .000 - .050, 3:1-4:1). Q1 had a higher acceleration demand (0.72 ± 0.52 accelerations/minute) than the remaining three quarters (0.57 - 0.67 accelerations/min). The game demand in decelerations was approximately 0.20 decelerations/minute across all quarters and the acceleration/deceleration ratio was approximately 4:1, with the exception of defenders in Q1 who had 6:1 ratio. There is a large demand for accelerations in field lacrosse with no positional differences, and training should be devoted towards this skill.

Seismic assessment of SSSI effects between adjacent Cross-Laminated Timber (CLT) buildings

Urban building designs have been performed considering the behaviour of individual structures in isolation, neglecting potential seismic interactions with neighbouring buildings. In densely populated metropolitan areas, the Structure–Soil–Structure Interaction (SSSI) becomes a significant factor, capable of either amplifying or reducing the seismic response of buildings. This suggests that there is an unquantified seismic risk in densely packed urban areas, which will need to be estimated to obtain designs for more resilient infrastructure. Despite the increasing popularity of CLT as a structurally competitive material, limited attention has been given to investigating dynamic interactions between timber structures. The reduced weight of CLT structures compared to traditional materials necessitates a focused examination of the effects imposed by nearby buildings under varying soil conditions, challenging the fixed-base assumptions commonly applied in seismic analyses. This study investigates the impact of SSSI between pairs of cross-laminated timber (CLT) buildings. Three distinct building heights are considered, exploring differences in storey ratios, under five different ground motions to evaluate seismic performance comprehensively. Sixty detailed high-order three-dimensional models, treating soil and buildings as unified systems, are developed as numerical dynamic simulations. Results reveal that SSSI can significantly influence the displacement and acceleration demands of buildings, with a more pronounced effect observed in loose soil conditions. Particularly, the presence of adjacent higher buildings leads to an increase in the seismic response of the smaller structure, showing amplification effects in peak values but maintaining similar dynamic behaviour. There has been observed a clear trend of increase in the roof displacements of the smaller structure when the storey ratio of neighbouring structures increases; however, the trend of behaviour is not clear in the maximum accelerations. The study underscores the importance of understanding how nearby buildings, particularly those with more storeys, can impact the seismic response on CLT structures.

Probabilistic evaluation of spectral acceleration demands on light secondary systems supported by partially self-centering structures

Partially self-centering structures are promising seismic resilient structural systems by reducing residual inter-story drifts with low initial construction costs. Comprehensive studies focused on structural design and performance evaluation, but no research was conducted to investigate the design of nonstructural components in partially self-centering structures. This research focuses on developing the probabilistic spectral acceleration demands for the nonstructural design in partial self-centering structures. 320 near-fault recorded ground motions were adopted for considering the uncertainties of seismic excitations. The spectral accelerations of the light nonstructural component were obtained through comprehensive dynamic analyses. The logarithmic normal distribution can be used for describing the probabilistic distribution of floor spectra for partially self-centering structures under earthquakes, validating through the Anderson-Darling test. The influences of design parameters (including structural period, hysteretic parameters, structural damping, the ratio of the structural period to the nonstructural period, and nonstructural damping) on the probabilistic distribution of floor spectra were investigated through parametric dynamic analysis results. Artificial neural network (ANN) models were developed for predicting the probabilistic floor spectra for partially self-centering structures. The analysis results indicate that ANN models can achieve excellent accuracy with a coefficient of determination larger than 0.99. Comparative analysis results reveal that the ASCE method may underestimate the acceleration demand of light secondary systems supported by partially self-centering structures. The developed ANN models were interpreted using the shapely additive explanations. It has been found that the fundamental periods of the main structure and nonstructural components and the response modification factor show significant effects on the median and deviation of the probabilistic floor spectra for partially self-centering structures. The software FloorSpecPS was established to predict the probabilistic floor spectra for partially self-centering structures using the developed ANN models in practical application.

Response spectrum and modal dynamic analyses of gravity dams using ground motion accelerations modified to account for hydrodynamic effects

This research proposes simplified methods for response spectrum and modal dynamic analyses of gravity dams using time-history and spectral seismic accelerations modified to directly account for hydrodynamic effects. The developed methods waive the need for specialized fluid-structure interaction software. They also lead to more accurate assessment of coupled structural flexibility and hydrodynamic effects due to each vibration mode than the static correction method commonly used in traditional simplified methods. The methodology utilizes analytical formulations of hydrodynamic pressure or simplified added masses to obtain the contributions of the selected vibration modes to the total seismic response. A hydrodynamic modification factor characterizing the amplification/de-amplification of acceleration seismic demands due to earthquake-induced hydrodynamic effects is also introduced. The application of the proposed methods is illustrated numerically through examples of two typical gravity dam-reservoir systems subjected to four earthquakes. The obtained results are in excellent agreement with the classical reference solutions. Time-history and spectral seismic acceleration demands modified by hydrodynamic effects as well as selected key response indicators, such as relative displacements and stresses within the studied gravity dams, are discussed.

Seismic life-cycle cost evaluation of steel-braced frames: Comparing conventional BRBF with emerging SCVDF and HBF systems

In the past two decades, various self-centering bracing systems have been developed to enhance structural seismic resilience. However, compared to conventional bracing systems, their high initial cost and lower efficiency in controlling peak floor accelerations have reduced their economic benefits and limited their application in engineering projects. Accordingly, the self-centering viscous energy-dissipative brace (SCVDB) and the hybrid bracing system (HB), the synergistic combination of the SCVDB and buckling-restrained brace (BRB), have emerged as innovative approaches with exceptional capabilities in passive control over peak floor acceleration demand. Despite their promise, a comprehensive understanding of the life-cycle economic benefits of structures equipped with these bracing systems remains limited. This study aims to comprehensively highlight the life-cycle economic benefits associated with self-centering viscous energy-dissipative braced frames (SCVDFs) and hybrid braced frames (HBFs) compared to traditional buckling-restrained braced frames (BRBFs) across various structural heights using the improved HAZUS assessment methodology. Focusing on 4-, 8-, and 12-story buildings designed with BRBFs, SCVDFs, and HBFs, each maintaining identical peak inter-story drift ratios, the research conducts dynamic analyses combined with Monte Carlo simulations. Critical parameters such as residual inter-story drift (RID) limits defined for demolition, initial construction costs of the SCVDBs, and discount rates are considered. The analyses reveal that the expected annual earthquake-induced loss (EAL) for mid- and high-rise structures is more sensitive to RID limits than those of low-rise structures. The SCVDFs and HBFs exhibit lower EAL than BRBFs, even without considering the demolition situation. The RID limit, initial construction cost of SCVDBs, and discount rates significantly influence the relative economic benefits of SCVDFs and HBFs compared to BRBFs. In most scenarios, HBFs demonstrate superior economic benefits over SCVDFs. The HBF effectively utilizes the synergistic effects of SCVDBs and BRBs, substantially lowering initial construction costs and achieving favorable economic benefits across various structural heights within the considered parameter range.

In-plan distribution of peak floor acceleration demands in torsionally irregular buildings

The precise estimation of peak floor acceleration demands is essential to ensure the seismic safety of building contents and attachments. The present study aims to investigate the distribution of the peak floor acceleration demands across the floor plan in torsionally irregular buildings. To achieve this objective, 28 mid-rise reinforced concrete buildings with torsional irregularities are analyzed under 5600 bidirectional earthquake excitations, considering various strength ratios in buildings. A total of 2,59,200 in-structure amplification factors are estimated at multiple locations within the building plan and also at different floors. It is observed that current seismic design codes tend to underestimate the in-structure amplification factor for torsionally irregular buildings, particularly at locations distant from the center of rigidity (towards flexible frames), by up to 137 % for elastic buildings, and up to 54 % for moderately inelastic buildings. Even in the case of frames closer to the stiff frames, the seismic design codes underestimated the in-structure amplification factor by up to 68 % for elastic buildings. It is observed that a strong relationship exists between the torsional amplification of the peak floor acceleration and displacement amplification due to building torsion at the floor of interest. The torsional amplification of peak floor acceleration is found to be approximately equal to torsional displacement amplification for the flexible frames at the floor of interest. Simplified equations are developed for their integration with existing building codes to precisely estimate the in-plan distribution of peak floor acceleration demands in torsionally irregular buildings.

The influence of torsion on acceleration demands in low-rise RC buildings

AbstractThis paper presents a study of acceleration demands in low-rise reinforced concrete (RC) buildings with torsion, evaluated by quantifying peak floor accelerations (PFAs) and floor response (acceleration) spectra (FRS). The study was performed with the aim to provide simple empirical formulas to quantify the amplification effects due to torsion, which can occur in most of the existing and new RC buildings. With this goal in mind, a set of eight archetype buildings was selected, characterized by an increasing floor eccentricity obtained by moving the centre of rigidity (CR) away from the centre of mass (CM). Numerical models of the proposed set of archetype RC buildings were considered in both linear elastic and nonlinear configurations. For the latter, the properties of models were widely varied, by systematically modifying parameters of plastic hinges, in order to obtain a sample of 1000 models. Non-structural components (NSCs) were considered linear elastic in all cases. To investigate acceleration demands, a set of forty Eurocode 8 spectrum-compatible ground motion records were used as input. For linear elastic building models, it was observed that the change of demands depends on the position of the NSC (in-plan and in-height), and on the distance between CR and CM. On the other hand, for nonlinear models, additional parameters must be considered, such as the building ductility (μ) and yielding force (Vy). New regression models were proposed for quantifying the observed differences in PFAs and FRS when torsion occurs. The efficiency of the proposed models was assessed by testing the new formulas on an existing case study building, as well as on the well-known SPEAR building.

Reinforcement Learning-Driven Bit-Width Optimization for the High-Level Synthesis of Transformer Designs on Field-Programmable Gate Arrays

With the rapid development of deep-learning models, especially the widespread adoption of transformer architectures, the demand for efficient hardware accelerators with field-programmable gate arrays (FPGAs) has increased owing to their flexibility and performance advantages. Although high-level synthesis can shorten the hardware design cycle, determining the optimal bit-width for various transformer designs remains challenging. Therefore, this paper proposes a novel technique based on a predesigned transformer hardware architecture tailored for various types of FPGAs. The proposed method leverages a reinforcement learning-driven mechanism to automatically adapt and optimize bit-width settings based on user-provided transformer variants during inference on an FPGA, significantly alleviating the challenges related to bit-width optimization. The effect of bit-width settings on resource utilization and performance across different FPGA types was analyzed. The efficacy of the proposed method was demonstrated by optimizing the bit-width settings for users’ transformer-based model inferences on an FPGA. The use of the predesigned hardware architecture significantly enhanced the performance. Overall, the proposed method enables effective and optimized implementations of user-provided transformer-based models on an FPGA, paving the way for edge FPGA-based deep-learning accelerators while reducing the time and effort typically required in fine-tuning bit-width settings.

Investigation on floor response spectra of a three-story building exposed to near- and far-field earthquakes

Historical earthquakes highlighted structural collapses and non-structural component (NSC) failures. This study aims to analyze NSC behavior during near and far-field earthquakes in a three-story building by studying elastic and inelastic acceleration responses. The investigation delves into floor response spectra and analyzes how NSCs affect floor acceleration responses, aiming to understand the performance of these components. The findings from the analysis indicated that the Floor Response Spectra (FRS) consistently align peaks with elastic and inelastic modal periods. Inelastic FRS notably show reduced floor spectral accelerations compared to elastic FRS. Near-field earthquakes induce 25-30% higher floor acceleration demands in NSCs compared to far-field earthquakes. Peak Component Acceleration (PCA) values differ significantly between near and far field earthquakes, with near-field ones exhibiting notably higher values across all floors. Higher damping ratios in NSCs lead to decreased peaks in the Component Dynamic Amplification Factor (CDAF) spectrum. The inelastic model notably reduces peak values of CDAF by approximately 49.53% to 69.3% for near-field and 51.81% to 64.47% for far-field earthquakes compared to the elastic model. In summary, the examination of peak floor responses against the formulation based on building codes highlights variations, with instances where the formulation either underestimates or overestimates the peak response demands.

Elastic and inelastic acceleration amplification of nonstructural components characterized using recorded building responses

This paper presents a comprehensive study of the acceleration (or force) amplification behavior of building nonstructural components characterized using a large set of recorded building responses available in the Center for Engineering Strong Motion Data (CESMD) repository. The elastic acceleration amplification demands of nonstructural components are analyzed statistically and subsequently compared with the corresponding inelastic demands characterized by the constant-ductility floor response spectra. Different simplified hysteretic rules are adopted for evaluating the inelastic acceleration responses of nonstructural components. The numerical study demonstrates that the elastic acceleration amplification characteristics of the nonstructural components are highly dependent on their natural periods relative to the specific vibration modes of the supporting structures as well as their attachment locations relative to the building height. The presence of component ductility effectively reduces their seismic acceleration demands, particularly in period ranges tuned with their supporting structures. Furthermore, the hysteretic behavior of nonstructural components may moderately modify their acceleration amplification effects. Findings from this study substantiate current seismic design provisions of nonstructural components with evidence derived from building floor responses recorded during real earthquakes.

Linear accelerator maintenance cost analysis.

Medical linear accelerators are the most costly standard equipment used in radiation oncology, however the service costs for these machines are not well understood. With an increasing demand for linear accelerators due to a global increase in cancer incidence, it is important to understand the expected maintenance costs of a larger global installed base so that these costs can be incorporated into budgeting. The purpose of this investigation is to analyze the costs for medical linear accelerator service and maintenance at our institution, in order to estimate the service cost ratio. We collected the costs of parts used for all service work done on 32 medical linear accelerators over a two year period. The data was segregated by center, machine, linear accelerator type, and failure area in the machine. We found the service cost ratio (excluding software support expenses) to be 3.13% [2.74%, 3.52%,]. We observed a variability of parts costs, and overall variability of the service cost ratio to be between 2.14% and 5.25%. This result is lower than other estimates for service costs for medical equipment in general and medical linear accelerators specifically. Two-thirds of the service costs were due to labor costs, which indicate the importance of a well-trained service technician workforce. We estimated the service cost ratio for medical linear accelerators to be 3.13% [3.52%, 2.74%] of the initial capital cost. This result was lower than other estimates of the service cost ratio.

Peak floor acceleration demands in torsionally irregular buildings

AbstractAccurate estimation of the peak floor acceleration (PFA) plays a crucial role in ensuring the seismic safety of a building, its contents, and attachments. This study investigates amplification in PFA due to building torsion. Torsionally irregular reinforced‐concrete moment‐resisting frame buildings are analyzed under bidirectional earthquake excitations for five levels of ductility demands. A total of 5600 nonlinear dynamic analyses are conducted on the considered buildings while subjected to the far‐field ground motions suite. It is shown that the existing code provisions significantly underpredict the PFA demands at the flexible edge of elastic and moderately inelastic torsionally irregular buildings. The torsional amplification factors for PFA demands depend on the building's torsional and strength characteristics. Further, these torsional amplification factors are correlated well with the building's elastic floor displacement‐based torsional irregularity indices. Practice‐oriented equations are proposed to predict the torsional amplification factors for PFA demands in torsionally irregular buildings. The proposed equations can be easily used after estimating the elastic floor displacement‐based torsional irregularity indices using the modal superposition method. When applied with the latest ASCE 7 provisions, the proposed equations provide reasonably accurate estimates of the PFA demands in torsionally irregular buildings.

Equipment response spectra for wind turbines considering the baseline control system

As more and more wind turbines are installed in areas with high seismic intensity, various published works have studied the seismic performance of wind turbines. However, these studies usually focus on the wind turbine, and less attention is paid to the electrical equipment mounted on the wind turbine. Electrical equipment is a non-structural component on wind turbine, which is prone to failure and damage, resulting in the loss of function of the wind turbine. Therefore, it is necessary to study the seismic performance of the electrical equipment installed on the wind turbine. This study focuses on evaluating and quantifying the dependence of equipment spectrum accelerations on the location of the electrical equipment in the structure, the damping ratio of the equipment, and the baseline control system. The baseline control system is used to control the output power by adjusting the rotor speed and the blade pitch angle, which affects the equipment spectrum of the wind turbines. There is a stronger relationship between the equipment response spectrum and the peak floor acceleration. Therefore, the equipment spectral amplification function is calculated as the ratio of the equipment spectral acceleration to the peak floor acceleration for different height. The equipment spectra amplification function is proposed and validated to estimate peak acceleration demands on the design of electrical equipment placed on wind turbines. The results indicate that current seismic code provisions will not always provide an adequate characterization of equipment accelerations. And the effect of wind turbine baseline control and equipment damping is more pronounced in the range of the structural tuning period than in the non-tuning range.

A 24.3 μJ/Image SNN Accelerator for DVS-Gesture With WS-LOS Dataflow and Sparse Methods

Spiking Neural Networks (SNNs), inspired by the biological brain, attract extensive attention for their simplified computation and the ability to process spatiotemporal data. With the development of retina-like sensors, there is a growing demand for edge SNN accelerators. The structural dataflow and great spiking sparsity of SNNs provide much exploration space for energy-efficient accelerators. However, current SNN accelerators did not co-optimize the two features together. This work proposes an energy-efficient edge accelerator architecture to support typical spiking neural networks. We propose a Weight Stationary-Local Output Stationary (WS-LOS) dataflow for SNNs and maximize the data reuse with a hierarchical memory structure. Three methods, including address skipping (AS), dynamic workload scheduling (DWS), and reconfigurable adder tree (RAT), are proposed to exploit the spiking sparsity. The accelerator is synthesized under 65nm technology, running at 250MHz. We prove our accelerator’s ability to process spatiotemporal data based on the DVS-Gesture dataset, achieving 92.7% accuracy and 24.3μJ/image energy. This design achieves 349.6KFPS recognition throughput on the MNIST dataset and 0.52 μJ/image energy, which realizes top performance among edge SNN accelerators.

Seismic acceleration demands in tall CLT buildings, predictive models and intensity measures

An accurate prediction of floor accelerations is crucial for estimating damage to contents and non-structural components in a building. Oversimplifying the nature of acceleration demands might result in biased estimates of building damage and consequently bias in the calculation of economic losses. However, given the relative novelty of multi-storey tall timber buildings, dedicated studies and models of their seismic acceleration demands are lacking. The need for these is stressed further when we recognise that the behaviour of walled timber structures is decidedly different from that of other conventional structural types. In this study, we apply modern data-driven approaches to evaluate efficient intensity measures (IMs) and develop regression models for predicting the peak floor acceleration (PFA) of multi-storey cross-laminated timber (CLT) buildings. Twenty-four IMs are evaluated and their prediction performance is compared. The sensitivity of acceleration demands to different IMs over a wide range of CLT buildings is investigated. We perform a systematic feature selection process using three different data-driven techniques. The selected features are then used to develop nine regression models to estimate PFA. Various modelling techniques, consisting of conventional (Linear and Polynomial regressions) as well as machine learning algorithms (Decision trees, Random forest, K-nearest neighbour, and Support vector regression) are used. The dataset used to train the models is obtained from numerical results of 69 CLT building models with variations in building height, panel fragmentation levels, and q-factors (ductility levels) subjected to a large set of strong earthquakes. After assessing the accuracy of our model predictions, their PFA estimates obtained are compared against previous research and design codes. Finally, simplified expressions for estimating peak floor accelerations in CLT structures are provided for practical purposes.

Seismic response analysis of single-degree-of-freedom systems with superelastic monocrystalline CuAlBe SMAs

Although the potential of shape memory alloys (SMAs) in seismic applications has been well recognized, the majority of the past research was directed to NiTi SMAs. This study aims to investigate the feasibility of using a novel type of SMA, termed superelastic monocrystalline CuAlBe SMA, in seismic vibration control. According to prior loading tests, CuAlBe SMAs had an excellent superelasticity behavior with the largest recoverable strain over 25%. Within the superelastic range, CuAlBe SMAs shown unloading behavior which was dependent on the strain amplitude in the present cycle, which could not be captured by current constitutive models. Hence, a new constitutive model was firstly proposed to simulate the hysteretic behavior of CuAlBe SMAs, and a good agreement is found between the experimental data and numerical simulations. And then, to explore the characteristics and advantages in terms of seismic applications, case studies on single-degree-of-freedom (SDOF) systems with NiTi and CuAlBe SMAs were carried out. Finally, two design methods were used to size the NiTi and CuAlBe SMAs, and the corresponding SDOF systems were subjected to two ensembles of earthquakes associated with frequently occurred and design basis seismic hazard levels. The simulation results indicated that, compared with NiTi SMAs, CuAlBe SMAs could more effectively control the displacement and acceleration demands, if their ductility capacity was fully utilized in the design procedure.

Numerical investigation of a proposed multidimensional isolator applied to large-scale domes subjected to earthquakes

A three-dimensional seismic isolation device that is effective in isolating both horizontal and vertical earthquake components has drawn the interest of researchers in recent years. This paper proposes a new three-dimensional isolator for large-scale dome structures, which is composed of a quintuple friction pendulum component and a stacked disc spring component in series in the vertical direction. The complex working characteristics of these components are investigated in detail. Numerical modeling methods are proposed to simulate this isolator for engineering application purposes, and the model accuracy is validated based on theory and experiments. Thus, the isolator is applied to a large-scale dome structure subjected to near- and far-fault ground motions. Numerical analysis shows that the proposed modeling methods can efficiently analyze the isolation performance of the isolator in a large-scale structure. The numerical results demonstrate that the isolator has excellent isolation performance not only for displacement and axial force demands but also for velocity and acceleration demands in all three directions. In addition, according to the comparative study of this paper, the isolation performance of the proposed isolator is better than that of other types of isolators under major earthquakes due to the adaptive sliding characteristics of the quintuple friction pendulum component and the flexibility of the stacked disc spring component prolonging the structural periods.

Seismic retrofit of Italian pre-‘70 case-study RC buildings by solving shear failures: code-compliant assessment and economic effort

Existing reinforced concrete (RC) buildings designed for gravity loads only (GLD) are widespread worldwide even in seismic prone areas, including Italy, showing a significant vulnerability to shear failures under seismic shaking.This work focuses on the seismic upgrading of pre-70 GLD buildings, by means of solving tensile shear failures of primary elements. Its technical effectiveness, depending on building height and seismic hazard throughout the Italian country, is also evaluated.RC GLD moment resisting frames case-study buildings, with the same floorplan, and a number of stories ranging from 2 to 6 are considered. Seismic assessment is performed using nonlinear static analyses, according to the current Italian technical code. Then, strengthening interventions, based on fibre reinforced polymers wrapping for beams/columns and pre-stressed steel strips for beam-column joints, are designed aiming at solving the detected tensile shear failures at Severe Damage Limit State. Post-strengthening seismic capacity is compared with seismic demand throughout the Italian country, finding that 2- and 3-storey buildings can always reach 100% of safety level of a newly designed building. This condition is attained, on average, also for 4- to 6-storey buildings only in sites where the peak ground acceleration demand is lower than 0.15 g. In the other sites, the 60% of the safety level of a newly designed building can be achieved, on average.Lastly, the economically feasibility of the adopted strengthening strategy is examined through its comparison with the most recent grant opportunities to mitigate seismic risk of buildings funded by Italian government.

Vertical floor acceleration spectra for regular steel frame structures

The scope of this contribution is the assessment of the vertical peak component acceleration of single-degree-of-freedom (SDOF) oscillators attached to elastic moment-resisting steel frames subjected to recorded ground motions. These SDOF oscillators represent nonstructural components (NSCs) flexibly attached to the load-bearing structure whose acceleration demands correlate with their maximum strength demands. The results in terms of floor acceleration spectra show that the interaction between a vertically oscillating NSC and the structure is much more pronounced than for horizontally oscillating NSC of the same mass and natural frequency. This means that even for vertical NSCs with very small mass (in the case of the investigated eight-story frame 0.01% of the frame mass depending on the number of stories) a coupled analysis is required for a realistic prediction of the NSC acceleration demand. In a parametric study of vertical NSCs attached to steel frame structures of different number of stories, a median vertical peak component acceleration was observed up to 5.5 times larger than the vertical peak floor acceleration of the attachment node of the load-bearing structure and up to 20 times larger than the vertical peak ground acceleration. The amplification of the vertical acceleration response is thus of the same order of magnitude as for horizontal NSCs. This means that the vertical dynamic response of flexible NSCs cannot be neglected and should therefore be studied in more detail in the future.