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& This paper provides an overview of the response of grandstands to dynamic crowd loading. It summarizes the guidance which is currently available in the UK and how it has been developed. The interaction between structures and crowds is then considered for both jumping and station- ary crowds. A model for jumping loads is given, and the frequency r...
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... Only one stand had a vertical mode below 8´4 Hz (at 7´9 Hz). Table 2 shows the distribution of horizontal natural frequencies (to the nearest 0´1 Hz). The mea- sured damping values for the fundamental sway modes were in the range 1´5±4´5% critical; those for the fundamental FtoB modes were in the range 2´2±6´0% critical, with one exception, where a value of about 17% critical was obtained. ...
Citations
... On one hand, the presence of people can act as a form of distributed damping due to energy dissipation through body movements and interactions with the stand, which can lead to a mitigation of vibration amplitudes. On the other hand, synchronized actions, such as rhythmic jumping or bobbing, can amplify vibrations, especially if these actions resonate with the natural frequencies of the structure [6]. The effect of crowd configuration on the dynamic behaviour of Bradford stadium in the UK is studied in [7]. ...
... This second concert is shown here to provide an example of a different type of concert, since the set list comprised downtempo songs and ballads, resulting in a more subdued audience response. For this case too, the same stands are considered and, as it is possible to see, the ratio a pk /RMS is almost always scattered around 2.5, only occasionally dropping toward values of 2 (see, for example, the events at time 10,000 s in the graph related to stand [3][4][5][6][7][8]. This indicates that in this concert, the phenomenon of synchronized jumping of the crowd at a frequency close to one of the natural frequencies of the stand is not taking place. ...
The dynamic behaviour and serviceability of stadium grandstands during events are critical concerns, especially for aging structures and modern lightweight designs. This paper presents a comprehensive study of the real-time and long-term vibration monitoring system implemented at the Giuseppe Meazza Stadium in Milan. The primary objectives of this work are twofold: first, to describe the real-time monitoring system capable of providing immediate assessments during events such as concerts and football matches; and second, to explore the extensive database of vibration data collected during 41 concerts held in the Meazza Stadium during the last years. Recently, the system has been updated to include an online component that checks in real-time the vibration levels achieved during concerts or football matches. This allows to evaluate the grandstand behaviour also in case of short-term and extreme events. In the first part of the paper, particular emphasis is on the challenges related to the data acquisition strategies, distributed processing, data synchronization and transfer. In addition, the study delves into the long-term analysis of the extensive vibration data database, employing synthetic representation techniques to identify critical events and trends related to various types of excitations. This dual approach not only demonstrates the effectiveness of the monitoring system in capturing real-time data but also showcases its capability in distinguishing between different excitation sources and pinpointing significant events over the long term, in a large and always-growing database.
... Thus, based on the Brazilian concrete code NBR 6118 [10] recommendations (see section 23.3 and Table 23.1 presented in reference [10]), excessive vibrations could be perceived by users. It is also noteworthy that the floor fundamental frequency (f 01 = 7.89Hz) and the other five natural frequencies are in the dynamic excitation frequency range (human rhythmic activities), of the second and the third harmonics, according to the ranges defined by Faisca [7] (5.66 Hz to 8.57 Hz), and Littler and Ellis [11] (4.50 Hz to 8.40 Hz), respectively. Therefore, initially, it can be concluded that the investigated floor can be susceptible to excessive vibration and human discomfort. ...
... Nevertheless, the modal response directly affects the investigated reinforced concrete floor dynamic structural response (see Tables 4 to 6). In sequence of the investigation, Table 7 presents the recommended human comfort criteria limits when the human rhythmic activities are considered, based on the criteria defined by: Setareh [33], Littler and Ellis [11], AISC [3] and SCI [6], and Table 8 presents the studied floor dynamic response maximum values. 16), it can be concluded that the "only force" models [3], [6], [7] have produced higher dynamic responses when compared to the dynamic effects related to the utilisation of the biodynamic systems [1], as shown in Tables 4 to 6. ...
This work aims the assessment of the dynamic structural response of reinforced concrete floors subjected to rhythmic human activities, based on the use of biodynamic models, in order to consider the people-structure interaction effect. Initially, an experimental modal analysis on the investigated floor , with dimensions of 16m x 35m, was performed, in order to identify and assess the global dynamic behaviour of the structure. In sequence, a finite element model was developed and calibrated through experimental results. After that, based on forced vibration analyses, the floor dynamic response was determined (displacements and accelerations). It is concluded that the biodynamic systems modelling induced significant attenuations on the structural response when compared to those calculated based on the use of traditional “only force” models.
... An important issue is the mutual effect of people movement and structure response; it has been shown [2] that the human body does not simply represent a mass, but can adsorb and release energy due to its flexibility. Consequently, it will interact with the structure depending on its response. ...
... Furthermore, as [2] report, the achievable frequency for a jumping crowd is between 1.5 Hz -3.5 Hz; jumping at frequency equal to 4.39 Hz is unrealistic for a group of people. This implies that the vertical mode can be actually excited when the activity matches a submultiple of the vertical mode (e.g., 1.46 Hz). ...
Reports from all over the world highlight that several stadiums with cantilever grandstand have shown problems due to excessive vibrations during soccer matches, requiring a more detailed and careful evaluation of the actual structural performances with the aim of assessing both human comfort and structural safety. As a matter of fact, many of the stadiums currently used have been designed and built neglecting some phenomena (e.g., dynamic load of spectators), because of the limited knowledge and computational resources. This work intends to examine the San Siro Meazza reinforced concrete Stadium, located in Milan; in particular, the analysis focuses on the study of a portion of the second sector, for which observed acceleration values could disturb the spectators according to literature’s reference. The dynamic behavior of the structure has been evaluated under different conditions of dynamic loads in terms of frequency and synchronous/asynchronous motion of people through a linear finite element model (FEM). The model has been calibrated on experimental dynamic data.The studies have highlighted the importance of the dynamic characterization of the structure for both human comfort and structural safety; under certain load conditions, numerical results are consistent with those obtained experimentally.
... The importance of these topics has pushed researchers to investigate people's behavior when jumping or bouncing on civil structures [2], [3], [4]. Although the load model has been well understood in the case of a single individual [5], [6] or small groups [7], [8], the generalization to a large crowd is not straightforward. ...
The prediction of the dynamic loads produced by groups of people is a crucial aspect for the design of stadiums or entertaining venues. This is because the coordinated motion of lively crowds may induce severe vibration levels in the structure, which can become critical for both human comfort and structural safety. However, the available information on this topic are very limited. Human loads often rely on deterministic models which do not consider the interaction and the coordination achieved by the participants or try to account for them through empirical assumptions. Therefore, they could find very little correspondence in realistic scenarios. This paper aims to close this gap by introducing a vision-based technique able to directly measure the crowd loading and quantify the synchronization level between the individuals. Starting from a sequence of images of a jumping crowd, Digital Image Correlation (DIC) is used extract the vertical velocity of different regions occupied by the participants; then, the vertical force time record is estimated. Finally, the comparison between the actual force signals and their envelopes allows to estimate the crowd synchronization over time. The method has been successfully validated with two field tests on the grandstands of the Giuseppe Meazza stadium in Milan, demonstrating its ability to reliably estimate the synchronization level reached by the participants.
... These researches are focused on the estimation of jumping and bobbing activities since these are the most critical cases to be considered for stadiums. A first approach uses a direct mathematical representation based on combinations of Fourier series, whose amplitude coefficients are commonly known as dynamic loading factors (DLF) [1], [2]. This results in a perfectly periodic signal, where the effect of spectral leakage associated to non-stationary jump variations is neglected. ...
... In case of a real stadium event, where many people are included in the framed stand portion, it is difficult to estimate the jumping motion of each person separately. Therefore, a possible solution is to pass through an average computation, like the one expressed in (1). Here, the time history of the crowd relative displacement ds c (t) is calculated as the average of all the subset displacements belonging to the framed area occupied by the crowd: ...
Stadium grandstands may experience high vibration levels due to the crowd action. Existing codes and guidelines used for the design and the assessment of grandstands highlight the need of an already ongoing revision, since there is a lack of information about the real nature of the crowd excitation and its accurate evaluation. This paper describes a highly improved computer vision method, based on the use of Digital Image Correlation (DIC), able to provide reliable estimates of the crowd induced loads on stadium grandstands. The effectiveness and the applicability of DIC is validated through a series of experimental tests held at the G. Meazza stadium in Milan. A first study with 27 jumping volunteers is carried out to assess the performance of DIC in a real environment. Then, the procedure is extended to the case of a larger crowd made of 108 individuals. In both cases, the forces estimated through image processing have been used in conjunction with the impulse response function of the stand to determine the resulting structural vibrations. The comparison between measured and computed vibrations provides a good agreement both in the time and the frequency domain.
... The riskiest actions will be caused by live human force in a resonant mode with the structure. The recommended frequency ranges for loads caused by rhythmic jumping, which are of interest to us, according to [3] are: • 1.2-2.8 Hz, when only one person jumps, • 1.5-2.5 Hz, when a small group of people jumps synchronously (at aerobics), • 1.8-2.3 ...
... The recommendation [4] gives a frequency range of 1.5-3.5 Hz in the case when one person jumps. The study [3] concludes that a larger human group cannot maintain its synchronized jumping at higher frequencies, so a more realistic upper frequency limit, for example, 2.8 Hz, should certainly be taken. Synchronized lateral action of people on the structure is especially discussed in [5]. ...
... In addition, this action is synchronized (rhythmic). The mathematical model of a vertical synchronized periodic load by an individual person on a support structure can be presented by the Fourier series, [3], as: ...
This paper contributes to the research of rhythmic behavior of a group of people, which, more or less synchronized, moves or jumps on a thin and elastic plate, thus performing a dynamically variable load. The analysis of the rhythmic behaviour of the crowd carried out on the basis of the experimental testing on the special steel test platform. The experiment consisted of sixteen measurements of live force and acceleration of the test platform. The dynamic loads caused by the mass of the human crowd and individuals had different intensities. The measurements of acceleration of the carrying platform were performed in order to estimate how the live human force influences on vibrations of machine structures. This research allows us to gain a picture of how serious the threats are from some human actions on the support structure of machines that are handled when performing works in industry, construction or mining. On the basis of these experiments, the mathematical models of the equivalent excitation forces were developed. The measured accelerations of the test platform tread surface and calculated dynamic coefficients of human force indicate that similar actions can seriously endanger balance of the support structure of some machine, and even, for example, can cause the main girder of the bridge crane to fall out. This and similar experiments allow us to formulate appropriate models of excitation loads by human force, which can then be used in simulation analyses in order to develop future systems of electronic protection of machines structures from adverse events.
... [1][2][3][4][5][6][7] It means that, on the one hand, the development of the strength of materials, which has allowed the use of long spans, lightweight, and slender structures, is advantageous in terms of aesthetic and design costs; on the other hand, the proximity between the frequency of human-induced forces and the structural frequencies can lead to resonant states which may compromise the vibration serviceability. [8][9][10][11] Concerning buildings' floors submitted to human rhythmic excitations, Lee et al. 12 presented a global resonance phenomenon case occurred in a 39-storey steel building. The experimental tests and the corresponding numerical model revealed that the floors have the global vertical vibration mode equal to 2.7 Hz and damping factor of 0.3%. ...
The study of the human‐structure interaction (HSI) using biodynamics models has gained attention lately. Several studies have demonstrated that the passive (standing still) and active (bobbing/bouncing or walking) persons can act for the benefit of the structural system by considering their body dynamic properties. Nevertheless, little concern has been addressed regarding the HSI during jumping loads on floors. This kind of human load is often considered as a “force‐only” model by design guides, and the body dynamics is disregarded. Therefore, aiming at filling this gap, this work investigates experimental and numerically an individual jumping on a vibrating (flexible) floor mounted in the laboratory. The active HSI was evaluated considering both single and two degree of freedom models in time and frequency domains. Besides, the assessment of the human body dynamic parameters (spring, mass and damper) was carried out based on optimisation techniques. The results show the potential benefit of taking into account the active HSI in near‐resonant cases to the detriment of a force‐only model.
... It should also be added that steel grandstand vibrations act strongly on human perception and comfort [14]. It is therefore necessary to verify also the level of comfort under human-induced vibrations of structures [15]. ...
... The aim of the analysis has been related to the determination of peak values of acceleration of the structure equipped with different bracing systems which is exposed to dynamic load due to jumping of spectators. In the analysis, the dynamic load has been assumed to be consisted of synchronous repetitive impacts, as expressed by Fourier series (see [15]): ...
... where ( ) -dynamic load; -weight; -Fourier coefficient (or dynamic load factor) of the th term; -number of Fourier terms; -period of the jumps; and -phase lag of the th term. The full load, as given by Eq. (1) with parameters described in [15], has been applied in the vertical direction assuming that the structure is fully filled by spectators with average mass of each person equal to 100 kg. Additionally, 6 % of the load has also been applied in the horizontal (sway) direction, as recommended by the Polish Standard PN-EN 1991-2: 2003 [16]. ...
Grandstands are structures which are regularly subjected to dynamic loads generated by crowd motions. It is a dangerous situation when spectators induce rhythmic jumping, dancing, stamping, etc. If the synchronized movement of spectators excites a natural frequency of the structure, resonant response might occur. To avoid such situations, temporary steel grandstands are commonly strengthened using additional elements that create bracing system which is selected depending on the size of the structure, type of the event, acting load, etc. It was proved that not only the use but also the arrangement of such structural members is crucial for the dynamic structural resistance. The aim of the present study is to determine the most effective arrangement of bracing system for a typical example of the temporary steel grandstand which is exposed to dynamic load induced by spectators. Three different arrangements of bracing systems have been analysed using five criteria recommended in the literature. The results of the study clearly show that the dynamic parameters of the grandstand are substantially different for various types of bracing systems. The largest improvement in the structural behaviour has been obtained for the grandstand equipped with the bracing system satisfying all proposed criteria. The peak accelerations for this case have been found to be nearly twice as low as for structures with other bracing arrangements. The application of such a system for the grandstand which is exposed to human-induced vibrations allows for safe use of the structure as well as improves comfort of spectators.
... However, this excitation force model does not consider the dynamic contributions from humans, such as body mass or damping. A few structural measurements [8][9][10] have shown that humans can change dynamic structural properties such as damping or natural frequency. In addition, biomechanical measurement [11] has shown that the human body possesses a relatively larger damping capacity and elastic stiffness. ...
Walking crowd-induced lateral vibrations on slender structures have attracted considerable attention. The improper vibration of a structure adversely affects human comfort. To explore the effects of crowds on lateral structural properties, a pedestrian from a crowd is simulated by a walking bipedal robot. A simplified theory for structural vibration is proposed based on the assumptions of uniform distribution and synchronized walking of pedestrians. This theory can be used to describe the effect of the change in crowd size on lateral structural damping and the frequency of the structure. The method can estimate the variations in structural properties in the case of a certain crowd for engineering design. The results show that the increase in crowd size results in decrease in structural natural frequency in the lateral direction, but increases structural damping. The influence of the crowd on structural properties agrees well with the non-simplified model. Change in walking frequency has little influence on the structural properties. However, the continuous increase in crowd size on structure top causes a non-convergent amplification of dynamic response under a resonant walking excitation. This research provides a quantitative assessment on the effect of crowd size on the change in structural properties for structural design or serviceability evaluation.
... Besides the significant magnitude of dynamic loads that can be induced by crowds, the human-structure interactions can also change the dynamic properties of the structure itself. As a consequence, especially for the design of stadium structures, it is highly recommended to consider the dynamic nature of moving loads induced by lively spectators [7]. Despite the extensive literature research documents focused on the dynamic performance of existing stadium structures, the available knowledge on the topic is still not yet sufficiently advanced, and currently not recognised in most of the design codes. ...
This paper reports on the dynamic characterisation of a Reinforced Concrete (RC) stadium grandstand module for the Sporting Stadium in Lisbon. To this aim, a three-dimensional (3D) Finite-Element (FE) numerical model, implemented according to the technical drawings of the structure, is first presented to provide preliminary estimates of the expected modal characteristics for the examined structural system. Ambient vibration tests are then carried out on the same grandstand, and used to extract the natural frequencies and vibration modes of the system, according to conventional state-of-the-art output-only modal parameter identification techniques. A sensitivity investigation and FE model updating study is hence presented for the grandstand, giving evidence of the major influencing parameters and key input data for the numerical fitting of the experimental modal testing results.
