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Response of cantilever grandstands to crowd loads. Part I: Serviceability evaluation
Proceedings of the Institution of Civil Engineers - Structures and Buildings
Abstract
This paper considers the problem of human acceptance of vibration in grandstands. It adopts the BS frequency weighting methodology and uses the vibration dose value (VDV) as an indication of when adverse comments may be expected. Measurements were taken on a number of cantilever grandstands during concerts and football matches. These were analysed to determine peak accelerations and VDVs and some empirical relationships were derived. As human reaction at these events relates more to vibration tolerance than perception, it has been necessary to consider a logical extrapolation based on current BS guidance to suggest VDVs that are appropriate for grandstand vibration. The reactions and VDVs recorded on the grandstands appear to support this suggestion. The calculation of VDVs is also considered, but this depends to a great extent on the calculation of peak accelerations, which is considered in another paper. Finally a number of key points arising from this work are discussed.
... Nowadays, stadiums and grandstands are used for hosting events like pop concerts, various sporting events, and other entertainment activities. [12][13][14][15][16] The dynamic properties of these structures change due to the mass, stiffness, and damping properties of humans during various rhythmic activities. [17][18][19] Being the venues for live events, these structures experience dynamic loading resulting from the spectator's body movement. ...
... Using Eqs. (15) and (4), the restoring force of the oscillator can be described by Eq. (16), which expresses the bouncing load produced during the bouncing motion: Fig. 13. The pattern of the force-time plot for the proposed oscillator is identical to the observed data. ...
... ω 1 is the natural angular velocity of the oscillator expressed by Eq. (15). Now, the following relationships exist: ...
This paper proposed a single-degree-of-freedom self-sustained nonlinear oscillator capable of precisely predicting the bouncing force induced by a person during bouncing activity on a flat and rigid surface. A bouncing person produces essential internal energy required to maintain its motion, so it can be modeled as a self-sustained oscillator that can generate (i) the stable limit cycle, (ii) the periodic bouncing force signal, and (iii) the self-sustained motion. A hybrid Van der Pol–Rayleigh oscillator added with two quadratic and one cubic nonlinear terms has been derived to yield desired softening and hardening effects as well as even and odd harmonics, as observed from the analysis of experimental bouncing force data. The force applied on the surface corresponds to its restoring force. The stability analysis of the oscillator has been performed using the energy balance and perturbation methods. The model parameters are extracted from the experimental bouncing force data resulting from a bouncing test on a group of seven subjects with shoe insoles at six different frequencies guided by a metronome. The bootstrapping method has been performed to examine the convergence of mean values of each model parameter by increasing the cardinality of the experimental set. The bouncing force signals produced by the proposed model and experimental results demonstrate an excellent agreement.
... As a result, the ERTSE 2020 IOP Conf. Series: Materials Science and Engineering 989 (2020) 012006 IOP Publishing doi: 10.1088/1757-899X/989/1/012006 2 natural frequency of the structure will be equal or close to frequency of jumpers, resonant or near-resonant vibrations will happen. The resonance imparts serious structural problems [15]. ...
... Moreover, it is desirable to measure and analyze the dynamic loads of spectator activities like jumping, bobbing, swaying etc. because these dynamic loads cannot be easily expressed in a numerical formula. Even though many kinds of literature [8,9,10,11] and code [2] have adopted a numerical formula for calculation of load function due to individual jumping are mentioned below. ...
... It can be related to the comfort level of occupants. The comfort level of an individual to the corresponding vibration level is calculated using the specifications listed in Table 3 as given by [10] for structures like grandstands with frequency less than 10 Hz. ...
Constructions industry’s novel design and technological development have resulted in an enhanced use of slender structures having low natural frequency. The overwhelming happiness in concert, shows, sporting events etc., potentialize enthusiastic behaviour of people causes dynamic crowd load i.e., synchronized rhythmic movements may excite supporting slender structures such as stadium, grandstands, auditorium, bridges, malls and convention centre. The combination of slender structures with dynamic crowd load makes the structure easily vulnerable to excessive vibrations and dangerously affects the safety and comfort of occupants. Hence the vibration problems due to increased structural slenderness and dynamic crowd excitation have become more common. So studies regarding the behaviour of dynamic crowd load are mandatory. The present work aims to find out the behaviour of permanent grandstand structure under dynamic crowd load. Here we investigate the behaviour of grandstand structure considering load at different frequency of jumpers in the range of 1.5 Hz to 3.5Hz, different types of activity such as normal jumping, high aerobics and low aerobics and various percentage of active crowd with total crowd, also the effects of rake angle on the structure to reduce the vibration. Active dynamic crowd load was analytically developed as taken from BS 6399-Part 1 and generated as time history and applied to the structure. The passive live load as taken 5kN/m ² specified in IS 875 (Part II). A three dimensional finite element model is used to model the grandstand structure. For modelling the grandstand structure and dynamic analysis finite element software, SAP2000 was used. The results obtained are compared in form of horizontal frequency, vertical frequency, acceleration, displacement, shear force and bending moment.
... The structural dynamic response of the structural model is obtained and it must be emphasised that the random nature of the human rhythmic activities was considered since the investigated floor structural system present very close natural frequencies and a multimodal behaviour. Besides, the floor dynamic response in terms of peak accelerations was obtained by numerical simulations and compared to the limiting values proposed by several authors, technical recommendations and design codes [3,4,9,11], including a comparison among three different human comfort criteria, i.e. peak accelerations, RMS accelerations and VDV (vibration dose values). ...
... The results of the dynamic analysis were obtained from an extensive parametric analysis, based on the finite element method using the ANSYS program [10]. Aiming at evaluating quantitative and qualitatively the results obtained according to the proposed methodology, the steel-concrete composite floor accelerations were calculated and compared to several design recommendations limiting values [3,4,9,11]. This comparison was made to assess a possible occurrence of excessive vibration levels and human discomfort. ...
... Concerning the human comfort analysis, it is worth noting that there is no generally agreed acceptance criterion for human rhythmic activities. In others words, several authors [3,4,9,11] have established comfort limits in function of acceleration assessment methods. This way, the human comfort of the floors of the composite building was evaluated in terms of unweighted peak accelerations (a p ), RMS-weighted accelerations (a w , RMS ) and vibration dose values, VDV. ...
The main objective of this research work is to investigate the dynamic structural response of floors, when subjected to rhythmic human activities (aerobics), based on experimental tests and numerical modelling. The focus of this investigation is to assess the human comfort of floors, initially, simulating the individuals by traditional “force only” models and after that the effect of the people–structure dynamic interaction is considered based on the modelling of SDOF biodynamic models (mass–spring–damper systems). This way, the analysed structural model is related to a steel–concrete composite building, which is composed of three floors, with dimensions of 20 × 20 m, total area of 1200 m² (3 × 400 m²) and a ceiling height of 4 m. The numerical modelling of the structure was performed based on the use of the ANSYS computational program and utilising the Finite Element Method (FEM) simulations. Aiming to evaluate the human comfort of the investigated composite floors, the dynamic characteristics of the individuals (mass, damping and stiffness) were experimentally obtained to introduce them into the developed biodynamic modelling. Thus, the dynamic response of the investigated composite floors was evaluated in terms of the peak accelerations, RMS and VDV values, based on current human comfort criteria. The results found along this investigation have indicated significant reductions of the peak accelerations values, when the biodynamic systems were considered in comparison with the results provided by the “force only” models.
... multimodal behaviour. Besides, the floor dynamic response in terms of accelerations was obtained by numerical simulations and compared to the limiting values proposed by several authors and design codes [3,[8][9][10][11], including a comparison among three different human comfort criteria, i.e. peak accelerations, RMS accelerations and VDV (vibration dose values). ...
... Several investigations [2,3,9,10] have described the loading generated by human activities as a Fourier series, which consider a static part due to the individual weight and another part due to the dynamic load. The dynamic analysis is performed equating one of the activity harmonics to the floor fundamental frequency, leading to resonance. ...
... Aiming at evaluating quantitative and qualitatively the results obtained according to the proposed methodology, the steel-concrete composite floor accelerations were calculated and compared to several design recommendations limiting values [2,3,[9][10][11]. This comparison was made to assess a possible occurrence of unwanted excessive vibration levels and human discomfort. ...
The main objective of this paper is to investigate the dynamic behaviour of building steel–concrete composite floors when submitted to human rhythmic activities. The investigated structural model was based on a real building steel–concrete composite floor spanning 40 m by 40 m with a total area of 1600 m2. The structural system represents a typical interior floor of a commercial building for gym purposes, and designed according to the usual ULS and SLS Eurocode provisions. The human comfort evaluation methods used in the analysis indicated that the composite floor presented excessive vibrations. Hence, it was detected that this type of structure can reach high vibration levels that can compromise the user’s comfort. In addition, the use of multiple tuned mass damper systems (TMDs) was simulated to provide a multimode vibration control aiming to improve the human comfort.
... Regardless, these two standards are also referenced for consideration of the vibration serviceability limit state. [2,3] Each standard specifies methods for quantifying vibration and repeated shocks. The recommended methods exhibit several general similarities but also some distinct differences that influence the eventual measurement quantity. ...
... However, current research is suggesting that such quantification measures are applicable and the preliminary results are being considered to develop new guidance and serviceability assessment limits. [3] Because of the uncertainty associated with the time period to be considered, each measurement channel was analyzed for each method with a range of time periods from 1 second to 10 minutes. Each channel was analyzed using a series of consecutive analysis periods of the each time length. ...
... VDV range which is described as disturbing but did not have any events with a VDV greater than 2.38. [3] Channels 3, 7, and 8 also had numerous 5 minute events in the 0.66-2.38 VDV or disturbing range. ...
Today's stadium facilities are more frequently subjected to a crowd induced rhythmic loading when they host rock or pop concerts. The motion generated by such rhythmic loading has the potential to be disturbing or even alarming to the occupants of the stand and this vibration serviceability limit state needs to be considered. Design procedures for such serviceability limit states are often developed from experimental test data. Currently, numerous processing techniques are available for evaluating the vibration response of the structure. For example, ISO-2631 specifies a weighting procedure to be used with one of three assessment schemes: RMS, VDV and MTVV while BS6841 specifies a different weighting procedure and recommends the use of vibration dose values to assess vibration levels. Other measurement evaluations involving absorbed power and DRI weighting have also been employed. An investigation into several evaluation techniques and how each is affected by certain vibrational characteristics is discussed. Experimental results from a rock concert at Manchester Stadium are used to illustrate the use of these different measures and to compare their results.
... An attempt has also been made to specify limits of vibration response in terms of VDV (Ellis and Littler 2004). The limiting values of VDV were derived from the linear relations between VDV and peak response given in equations 4 and 5 applied to Kasperski's limits summarised in Table 2, resulting in the VDV limits specified in Table 3. ...
... This assessment of vibration response agrees with the subjective observations of the test personnel during the in-service monitoring, where there was no indication of problematic levels of vibration. Comparing the measured VDV for the whole event (Table 1) with the limits proposed by Ellis and Littler (2004) (Table 3), it can be seen that the measured VDV also lies in the range of "reasonable for passive persons". ...
... Using the very limited available guidance on assessment of vibration serviceability of stadia (Kasperski 1996;Ellis and Littler 2004), the stand was assessed as "suitable for a passive crowd" using both peak accelerations and measured VDV for the whole event. However, as this paper has demonstrated that the methodology by which the VDV limits were obtained may be susceptible to varying data acquisition and analysis methodologies, the authors therefore have higher confidence in the original limits specified by Kasperski (1996). ...
Vibration problems in stadia are becoming more common due to increased structural slen- derness and more lively dynamic crowd excitation. Unfortunately, there is very little guidance available to design engineers dealing with the assessment and design of stadia structures. This paper presents unique data from a programme of modal testing and in-service monitoring of a large contemporary cantilever grandstand in the UK. The in-service monitoring was carried out during an international football match, during which the stadium was full to capacity. Modal properties obtained from the testing on the empty structure are presented and the results from in-service monitoring are described. It is found that crowd occupation can significantly alter the modal properties of a stadium, and that the changes can vary according to the crowd con- figuration. Additionally, previously proposed methods for assessment of vibration serviceability have been applied and it has been shown that they can lead to inconsistent results, which is a result of their sensitivity to the data acquisition and analysis techniques used. It is concluded that it is very important that consistent methods of data acquisition, analysis and vibration serviceability assessment are utilised by future researchers and practitioners. Also, further re- search is required to define vibration serviceability limits using the state-of-the-art vibration dose approach.
... The steel-concrete composite floor accelerations were calculated based on the four dynamic loading models described in Section 2. The total time in which the aerobic activity was performed on the floor was equal to 10s and the dynamic response of the structure was obtained from its central node. Table 5 shows the human comfort acceptance criteria [3,15,16] and Tables 6 and 7 present the results related to the two investigated loading cases (Fig. 7). ...
... It must be emphasized that these acceleration values have indicated extremely uncomfortable vibration levels to the persons who practice the aerobic activity according to design standards and technical recommendations [2,3,15,16]. Furthermore, based on the found results and in the author's opinion, it was also verified that the Faisca [6] dynamic loading model have presented an economical design recommendation in comparison with the others investigated dynamic loading models. ...
The structural problems related with excessive vibrations of steel-concrete composite floors due to human rhythmic activities is the main motivation for the development of an analysis methodology supported by design guides and several researches aiming to obtain the dynamic response of a typical steel-concrete composite floor spanning 10 by 10 m when subjected to human rhythmic dynamic loadings. Therefore, this research develops an extensive study based on the use of four different mathematical formulations used for modelling of the human rhythmic actions. Furthermore, it was observed that high levels of annoying vibrations were reached on the investigated floor during the rhythmic activities. Besides, it was verified that the analysed composite floor may be leaded to a very conservative design depending on the choice of the used dynamic loading model. Finally, design considerations related to a more reasonable and economical dynamic loading models used to evaluate the human comfort of composite floors are discussed.
... Peak accelerations are used in these thresholds. Table 4 also shows a criterion in terms of VDV that is recommended by Ellis and Littler (2004) for stadia. Four levels of human response are considered. ...
... The linear relationship between VDV and peak weighted acceleration was first reported in Ellis and Littler (2004). The empirical relationship is useful for directly calculating VDVs when required. ...
The vibration serviceability of an as-built long-span concrete floor was assessed using field measurements taken during the structure's daily use and under controlled human activities including a group of people walking and jumping at specific frequencies. The floor serves as the waiting hall of a railway station and has a unique external prestressing system. The measured natural frequencies and recorded accelerations were compared with threshold values specified in design guidelines. The fundamental frequency of the floor was estimated to be approximately 2.2 Hz, which does not satisfy the requirements of current Chinese design codes for concrete structures and PCI design guidelines. The recorded vibrations were much lower than the vibration amplitude thresholds specified in several design codes for similar types of structures. This positive result is consistent with interview results from users stating that there have been no complaints from passengers or station staff relating to the floor's vibration performance since the station was open to the public three years ago. Unless the external prestressing system is changed, numerical analysis demonstrates that it is too expensive and in some cases technically impossible to increase the natural frequency of a floor to 3 Hz to satisfy the recommended threshold value. The authors conclude that the frequency threshold value given in the current Chinese code and PCI design guideline is too strict for this floor. An approach that sets a vibration amplitude threshold seems more appropriate for assessing the vibration serviceability of this kind of long-span concrete floors. A multiplication factor of 30 to the ISO vibration baseline curve is recommended as an appropriate assessment criterion for floors serving as waiting halls in railway stations. Vibrations of the floor under different volumes of users were recorded and analyzed to capture the influence of crowd configurations on the vibration. Observations revealed that the vibration induced did not show much dependence on crowd configurations. Besides, floor vibrations under various group sizes were investigated. Even though they were found to be dependent on group size, the floor vibrations did not change linearly with group size as a result of imperfect synchronization.
... Moreover in the case of a stadium like the Giuseppe Meazza, in which two important teams share the same structure, a different kind of public occupies the same stand. One of the stand considered in this paper is occupied by the "ULTRAS", the hottest supporters, while Proceedings of the IMAC-XXVII February [9][10][11][12]2009 Orlando, Florida USA ©2009 Society for Experimental Mechanics Inc. ...
... These limits are reported in Table 1. [11]. Table 2 summarizes the limits expressed in that paper. ...
Stadia structures, like the G. Meazza in Milano, nowadays host many events that they were not originally designed for. Apart from the traditional football matches many live rock concerts and other public happenings are hosted. In this paper a comparison is made in order to classify the different kind of events in terms of vibration serviceability assessment measurements. The reached vibration levels must be evaluated against the serviceability levels given in existing guidance in order to prevent dangerous situations, such as panic or other uncontrollable phenomena in the crowd. Standards exist to evaluate vibration levels, among them the most widely used are ISO2631-1, ISO2631-2 and BS6841, which differ in the frequency weighting used and in the quantities used to identify the vibration, even though the starting point is the same measured acceleration time histories. More than a comparison of the two standards, already discussed in other papers, this paper investigates the level reached during different events and the influence of all choices left free to the technician performing measurements. Standards are applied to a set of vibration measurements taken on different events on different parts of the G. Meazza stadium. Results are then compared to the reference values suggested in the standards and to the limits found in literature. The effect of the dynamic response of the different sub-structures of the stadium on the reached vibration levels is analyzed and a set of results are given in order to asses the validity of limits given both in the standards and in literature.
... Although ISO-2631 does not provide references to levels of perception ranges based on VDV, recent research has suggested ranges for the VDV measurements based on level of perception as shown in Table 2 [48]. These levels of perception were used to determine aircrew perception based on the VDV calculated for the flight tests data. ...
Many systems deal with the problem of undesired vibration transmitted to the occupant through the seat. It is an important issue related to the health and comfort of the occupant. In helicopters, it is a crucial problem regarding exposure of helicopter pilots to high vibration level. The seat as the main interface part plays a key role in order to reduce the vibration transmitted to the occupant body. Therefore, evaluation of the effect of the seat and its auxiliary equipment on the vibration reduction transmitted to the occupant is necessary. In this paper, a comprehensive evaluation is done concerning on the impact of the seat accessories (such as the suspension system and cushion) and attached equipment onto the helmet (such as the Night Vision Goggle and helmet-mounted display systems) on the vibration transmitted to the pilot’s body parts, especially the head, in order to determine contribution of seat design parameters in the vibration transmissibility reduction. Evaluations are performed based on ISO-2631 and conventional criteria using two distinctive model of occupant’s body. In addition, a beneficial mathematical relation is derived between the SEAT value and cushion characteristics. Accordingly, the characteristics of optimal cushion and the optimal seat suspension are derived from the results of the evaluations. Also in a scarce study, the impact of the seat parameters and attached equipment onto helmet on the neck stretch of pilot are evaluated under flight situation. In order to reach realistic results, the simulations are performed based on the measured vibration data of a Bell-412 helicopter. The results reveal that the optimal cushion and seat suspension system can decrease pilot vibration level up to 20% individually, but utilizing both of them together has not significant impact on more reduction of the vibration transmissibility.
... Level of comfort (International Standard ISO 2631-1, 1997) and perception(Ellis and Littler, 2004) for occupant. ...
One of the most important issues for the helicopter pilots is the health risk due to the vibration transmitted to the pilot through the seat. In this article, a seat suspension based on negative stiffness structure is presented to decrease the vibration transmitted to the pilot in both vertical and lateral directions without losing the loading capacity of the system. Here, an integrated model of the suspension–cushion–occupant is derived. To generalize the results of system analysis and its usability in other applications, the impact of parameters on the system performance is studied in dimensionless form. Despite coupling between the lateral and vertical directions, the design parameters of the seat suspension are determined in such a way that the system responds simultaneously as a negative stiffness structure in both directions. The system efficiency in vibration damping is assessed by seat effective amplitude transmissibility and transmissibility criteria. In addition, the whole body vibration and impact of the vibration on the pilot body are evaluated using ISO-2631. To verify the system efficiency in more realistic situation, the simulations are performed using the measured vibration data of a Bell-412 helicopter. The results indicate that the vibration amplitude is decreased by about 45% and 48% in the lateral and vertical directions, respectively. The frequency spectrum comparison of the seat and cabin floor reveals 80% reduction of amplitude in fundamental frequency in the vertical direction, whereas it is about 93% in the lateral direction. Furthermore, the level of pilot’s comfort and perception is improved that demonstrates better riding quality and reduced vibration environment.
... Table 1 also shows the experimental dynamic response of the floor in terms of maximum peak acceleration (a p ), RMS weighted acceleration (a w,rms ), 65 and VDV values 65 in the vertical direction. According to the human comfort criteria based on the last two for grandstands 66,67 (see Table 2), these values were found in the range classified as "probably causing panic" for the near-resonant case (1.89 Hz, a w,rms = 2.86 m s −2 and VDV = 11.10 m s -1.75 ) and as "disturbing/unacceptable" for the out-of-resonance cases (2.00 Hz, 2.27 Hz and 2.86 Hz; see Table 1). However, the participant was aware of the purpose of the trial and did not panic, which might not occur in situations outside the laboratory environment. ...
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.
... Recommendations were made by Ellis and Littler and refined by other researcher, as listed in Table 1. [11] 660-2380 Salyards, Hanagan and Trethrwey [12] 1400-4800 Casagrande, Giongo, Pederzolli, et al. [13] 400 Setareh [14] 1200 ...
Human-induced vibration has become a serious serviceability problem due to the larger opening of girder, lighter floor systems and longer spans designed and used in practice. Vibration tests were undertaken in laboratory to research the vibrational characteristics of the arch pre-stressed concrete truss (APT) system spanning 16.0 m. Results from ambient vibration, impulse excitations (heel-drop and jumping) and steady-state incentives (walking and running) were presented. Dynamic characteristics such as natural frequencies, damping ratios, mode shapes and acceleration responses were studied and checked against the existing codes. Experimental results show that the investigated APT girder possesses high fundamental frequency and low damping ratio. Moreover, the perception factors based on the root-mean-square acceleration, vibration dose value (VDV) and psychological comfort data were obtained. Lastly, the threshold accelerations and VDVs were suggested for evaluating the human-induced vibration.
... BS 6399-1:1996 [7], BRE Digest 426 [8], the User's Guide to the National Building Codes of Canada [9] Commentary D (Part 4 of Division B) and ISO 10137:2007 [10] were shown to be over-conservative based upon observations of real structures [11]. The Institution of Structural Engineers (IStructE), Department for Communities and Local Government (DCLG), Department for Transport, Local Government and the Regions (DTLGR) and Department for Culture, Media and Sport (DCMS) have been closely involved with a number of UK research projects designed to address the problem [12][13][14][15][16][17][18] and the results have been fed into two world leading design recommendations [19,20]. Their latest design guidance on crowd dynamic loading of grandstands [20] is a step in the right direction but still not perceived as the final version. ...
Contemporary design guideline pertinent to vibration serviceability of entertaining venues describes bouncing forces as a deterministic and periodic process presentable via Fourier series. However, fitting the Fourier harmonics to a comprehensive database of individual bouncing force records established in this study showed that such a simplification is far too radical, thus leading to a significant loss of information. Building on the conventional Fourier force model, this study makes the harmonics specific to each individual and takes into account imperfections in the bouncing process. The result is a numerical generator of stochastic bouncing force time histories which represent reliably the experimentally recorded bouncing force signals.
... Tables II, III, IV and V show the results obtained using the four load cases, based on the dynamic load models I [6] and II [7], [8] and Table VI shows the human comfort acceptance criteria [8], [10], [11]. The modal damping ratio of 1% was chosen according to ISO 10137 [2] and lies in the extreme range of 0.5% to 8.0% for fully composite steel beams with shear connectors to concrete slab. ...
A growing number of structural problems associated with excessive vibrations of steel-concrete composite floors due to human rhythmic activities is the main motivation for the development of an analysis methodology supported by design guides and several researches to obtain the dynamic response of a steel-concrete composite floor spanning 40 by 40 m when subjected to human rhythmic dynamic loads.
Therefore, this research develops a study based on the use of two different mathematical formulations used for modelling human rhythmic actions (aerobics). Furthermore, it was observed that high levels of annoying vibrations were reached during the aerobic activity.
... BS 6399-1:1996 [7], BRE Digest 426 [8], the User's Guide to the National Building Codes of Canada [9] Commentary D (Part 4 of Division B) and ISO 10137:2007 [10] were shown to be over-conservative based upon observations of real structures [11]. The Institution of Structural Engineers (IStructE), Department for Communities and Local Government (DCLG), Department for Transport, Local Government and the Regions (DTLGR) and Department for Culture, Media and Sport (DCMS) have been closely involved with a number of UK research projects designed to address the problem [12][13][14][15][16][17][18] and the results have been fed into two world leading design recommendations [19,20]. Their latest design guidance on crowd dynamic loading of grandstands [20] is a step in the right direction but still not perceived as the final version. ...
... VDV uses fourth power instead of the second power of the weighted acceleration time history (Equation 2). Vibration dose values are calculated through Equation 2 and the decision on comfort level is made by comparing the resultant with the values suggested by Ellis and Littler (2004) (Table 3). Figure 5 shows the processed data from Game 1 and the resultant RMS values after human comfort and perception analysis. ...
Stadium structures may suffer from vibration serviceability problems due to light weight and rapid constructions as well as considerations such as improved line of sight and increased capacity. In this context, Structural Health Monitoring (SHM) data can be implemented to track and evaluate performance of such structures during different events. This paper presents findings from a Structural Identification (St-Id) implementation to a football stadium to evaluate the structural performance by means of a detailed Finite Element (FE) model validated using experimental data. The stadium was monitored for three years to determine the vibration levels during different games and different events, e.g. goals, interceptions and playing a particular song. It is observed that certain events and long periods of playing particular songs generate vibration levels that create uncomfortable situations for the spectators based on the design codes. Laboratory studies were conducted to determine the forcing functions experimentally due to jumping with the rhythm of a song that was often played in the stadium. The FE model of the stadium was developed and validated using the modal analysis results from the ambient vibration data. The experimentally obtained loading functions were used with the FE model to simulate the behavior under spectators' loading.
... However an evaluation approach based on peak accelerations is not a universal measure of vibration exposure because it does not take into account the duration of exposure. In 2004, Ellis and Littler [8] promoted the use of vibration dose values (VDV) as a way of assessing vibrations in grandstands. The VDV measure incorporates a time variable and a root mean square (RMS) value of the acceleration. ...
This paper reports a controlled laboratory investigation on the evolution of human vibration-perception and comfort states as a result of a change in the vibration levels of an occupied grandstand structure. Our structural dynamics laboratory is equipped with a fully instrumented real-life grandstand whose motion could be controlled to simulate a vibrating structure. Students were recruited to participate as a seated and a standing audience and to provide feedback on the state of their comfort and vibration perception during exposure to different vibration levels. After applying frequency weighting filters specified in different standards to each vibration level, charts are presented to describe vibration perception and comfort levels of the audience given a prescribed movement of the structure. The charts indicate that the perception variable takes on its extreme state sooner than the comfort variable, confirming that vibrations are felt long before they are generally deemed uncomfortable. This makes the assessment of human perception of vibrations to be of primary importance in establishing safety criteria. Finally, the results were compared with recommendations of several international standards and design guidelines in the same area of research. The results of the comparison showed serviceability data obtained from our grandstand study to be lying significantly below the recommended limits for transportation structures (BS6841) but significantly above the recommended limits for most classes of buildings (BS6472). This implies a serviceability limit state for grandstand-design lying somewhere between the recommended limits of the two standards. These results are an important contribution to the establishment of serviceability requirements for grandstand structures.
... Kasperski recommended the RMS acceleration or MTVV levels shown in Table 1. [2] Ellis and Littler recommended the VDV limits shown in Table 2. [3] Probably causing panic ...
A stadium, when serving its intended purpose, attracts a crowd to participate in a common event. Whether the performers are athletes or musicians, crowd enthusiasm is an integral part of the event. Crowd enthusiasm can often result in stadium vibration. The more coordinated the crowd, the greater the motion. Using vibration monitoring, this study examines the implications of generating crowd enthusiasm by deliberately coordinating crowd movement. Several locations in a large football stadium were measured for vibration during several football games. Throughout these games, a portion of a popular song with a very enticing beat was played on the loudspeakers while the scoreboard flashed the word "BOUNCE." These particular incidences show a marked increase in vibration levels over the remaining typical activity. The experimental monitoring procedure and results will be discussed to draw attention to the potential for crowd-induced rhythmic motion during events other than concerts.
... This is a significantly more complex calculation than the natural frequency approach and requires the anticipated dynamic loading due to crowd motions to be identified for a given event and applied to an appropriate model of the structure. The resulting maximum dynamic response level is calculated and compared to vibration thresholds, from a suitable code or guidance document ͑Bachmann et al. 1995;BRE 2004;BSI 1987BSI , 1992Culley and Pascoe 2005;Ellis and Littler 2004;ISO 1997;NRC 1995͒, that are considered acceptable for humans. Unlike the natural frequency approach, which is recognized as a coarse grained and indirect method for limiting levels of vibration response ͑IStructE 2001͒, a performance-based calculation takes the nature of the loading into account as well as the damping within the structure and as such is a potentially more valuable tool to the engineer when attempting to refine and reduce costs in design. ...
The behavior of humans jumping and bobbing on flexible structures has become a matter of some concern for both structural integrity and human tolerance. The issue is of great importance for a number of structure types including stadia terraces. A unique test rig has been developed for exploring the forces, accelerations, and displacements that occur when a human subject jumps or bobs on a flexible structure where motion can be perceived. In tests reported earlier, it was found that the subject is able to generate near resonant structural response but it is extremely difficult, if not impossible, to jump or bob at or very near to the natural frequency of the structure when its vertical motion is significant. Also, under such near-resonant conditions, the force developed by the subject was found to drop significantly. In this paper, the effect of altering the subject-to-structure mass ratio and the damping ratio of the structure on these phenomena is presented. As would be expected, it is shown that as the structure becomes more massive and more highly damped it moves less for nominally the same excitation. In this situation, it becomes easier to jump and bob near to resonance and the degree of force dropout reduces, although it is still significant for even the most massive and highly damped case considered. A method for including these effects of human-structure interaction in a load model for dynamic response calculations is then proposed.
... At the moment, the only available strategy is related to vibration measurement. 7 This approach, however, is only related to the structural vibration monitoring, without considering crowd movement, which is the cause of the oscillation. This is because in the past no techniques were available to estimate crowd behavior. ...
An image-based measurement technique, the DCI technique, of crowd motion is described to study the people-induced vibrations of civil structures. The measurement technique is based on the analysis of an image sequence grabbed using a common digital camera and depicting the crowd on grandstands. The proposed validation procedure of this technique is based on computer-generated images of a moving crowd, allowing one to know people movements a priori. The estimated velocity time histories of each ROI have been compared to the real and known ones, defined during the image generation task, to evaluate the uncertainty of the measurement. The results show that the measurement method performances decrease when the ROI size in pixels is too small. The accelerometer signals can be effectively adopted for a quantitative comparison with the DIC outcomes, although the uncertainty associated with accelerometer measurements cannot be neglected.
In the last decades, several excessive vibrations problems in buildings floors have been observed, due to human activities. Therefore, this research work investigates the dynamic structural behaviour of a steel‐concrete composite floor with total area of 315 m2, when subjected to rhythmic human actions, based on the use of different mathematical formulations in order to define the dynamic loadings. The floor numerical modelling was implemented in the finite element program ANSYS, aiming the dynamic structural response analysis. The results indicate important levels for peak accelerations values, resulting in excessive vibrations and discomfort to the building users.
Excessive vibration of temporary grandstand by the crowd has lateral rhythmic motions, which attracted increasing attention in the recent years. This paper focuses on experiments where a temporary grandstand occupied by 20 participants is oscillated by a shaking table with a series of random waves and the crowd-induced rhythmic swaying motions at lateral direction, respectively. The dynamic forces that were induced by participants who have swayed at 0.5–1.8 Hz are recorded by a tri-axial human biomechanics force plate. A new relationship between the annoyance rate and structural acceleration at logarithmic coordinate is investigated and proposed, and the swaying load model is given. Based on these experimental results, a simplified three-degree-of-freedom lumped dynamic model of the joint human–structure system is reinterpreted. Afterwards, combined with a feasible range of crowd/structural dynamic parameters, a series of interaction models are analyzed, the vibration dose value (VDV) of the structure is obtained and discussed, and the notable parameters for interaction model are predicted. The experimental results show that the lateral serviceability limit is 1.29 m/s1.75 and the upper boundary is 2.32 m/s1.75. The dynamic response of model indicated that the VDV of structure will be decreased with increasing the mass of static crowd and damping ratio of the dynamic crowd. The max response of the model is α ≤ 0.6, f2 = 1.8 Hz or α > 0.6, f2 = 1.5 Hz or f1 = 2.5–3.5 Hz. It may be used as a reference value in vibration safety and serviceability assessment of TDGs, to estimate realistically the vibration response on the occasions when the crowds are swaying.
Background
The performances of composite steel-concrete slabs are strongly influenced by the connection between the concrete and the steel decking, which is essentially assured by bonding, interlocking, and adhesion. The connection can be continuous or localized by means of connectors. In order to increase the bonding between steel and concrete elements and to allow their collaboration, typically, a continuous connection with indentations or embossings is realized.
Objective
In this study, the simulation of the concrete-steel bond interaction of a typical composite decking is analyzed. In particular, the objective is the investigation of the role of the main geometric parameters of the indentations or embossings that determine the effective functionality of the connection.
Methods
To this scope, the results of four-point bending tests on five specimens of a typical layout of a composite floor are reported and discussed. Then, the obtained results are used to determine the shear bond strength according to the partial interaction method, by following the procedure provided by the Eurocode 4. Successively, the experimental results are exploited in order to calibrate a FE model in Abaqus software to be able to account for the basic effects involved in the shear bonding mechanism, i.e . interlocking, friction, and adhesion.
Results & Conclusion
Finally, the obtained results are discussed, and the FE model is used to evaluate the geometrical and mechanical parameters influencing the longitudinal shear bonding resistance.
Annoying vibrations in grandstand structures have been receiving more attention due to the increasing slenderness of the architectural components and the complexity of the crowd loading for engineers. The vibration serviceability checks under these conditions become a challenge in the design and operation stages. Regarding human comfort, excessive vibrations due to occupant activities may affect comfort and/or cause panic, especially for passive occupants who do not participate in generating excitations. Although durations of excessive vibrations have been considered as one of the most important factors affecting occupant comfort, incorporating the vibration duration in the occupant comfort analysis has not been addressed yet. In addition, the currently available approaches using raw acceleration, weighted RMS acceleration, vibration dose values (VDV), and so on may not always be sufficient for serviceability assessment due to the lack of guided procedure for calculating the integration time and implementing the duration of vibration into the process. Therefore this study proposes a new parameter and framework for assessing human comfort which incorporates the duration of vibration with conventional data processing. The aim is to better examine vibration levels and the corresponding occupant response focusing on grandstand structures. A new parameter, the area of RMS (ARMS), is introduced using the running RMS values of acceleration weighted by the frequency weighting functions. Furthermore, perception ranges for human comfort levels based on the proposed parameter are presented. The experimental study reveals that the proposed framework can successfully address the impact of duration time on determining the levels of vibrations and comfort using the proposed parameter.
This work aims is to investigate the structural dynamic response of steel-concrete composite floors, when subjected to rhythmic human activities, based on experimental tests and numerical modelling, from the point of view of human comfort. The main focus of this paper is to study the effect of the dynamic interaction between the occupants and the floors, representing these people by SDOF biodynamic models (mass-spring-damper systems), in order to better evaluate the dynamic response and the vibration serviceability states. This way, the investigated structural model is related to a steel-concrete composite building which is composed of three floors used for aerobics classes, with dimensions of 20m × 20m, a total area of 1200m² (3 × 400m²) and a ceiling height of 4m. The numerical modelling of the structure was performed by ANSYS program and was based on the finite element method (FEM). In order to evaluate the dynamic response of the investigated steel-concrete composite building, accelerations associated with 32 individuals practicing rhythmic activities were experimentally obtained to introduce them into the finite element model. Thus, the dynamic response of the building floors was evaluated in terms of the peak accelerations, RMS and VDV values, according to human comfort criteria and considering situations of the design practice.
The dynamic characteristics of multi-panel floors, primarily to provide information for calculating their response to human loading are examined. The design concern arises from the possibility of resonance being generated by rhythmic human loading if the floor's principal frequency coincides with the load frequency or with two or three times its value. One of the strategies to provide a simple minimum frequency is determining the floor response to various dynamic loads and assessing its acceptability. It requires an evaluation of the floor's dynamic characteristics, primarily the frequency, mode shape, stiffness and damping of the principal mode. The natural frequencies of the modes, the mode shapes and the modal stiffness are determined by using finite element evaluation. Modal stiffness may not be given as the standard output from the finite element (FE) program but they can be derived. Damping, or the ability to dissipate energy, is an important component of any dynamic system as it limits the amplification of motion in a resonant situation.
Vibration serviceability due to rhythmic loading generated by a crowd is a widely acknowledged design consideration for assembly-type structures such as stadium grandstands. However, guidance for serviceability design is rarely incorporated into a governing code. To aid designers in the process of designing for serviceability due to rhythmic crowd loading, the current state of knowledge is summarized. Topics to be presented are organized based on the various components contributing to vibration serviceability assessment: 1) excitation, 2) structural response, and 3) assessment/design. The excitation component will speak to a crowd loading to be used for design and the many factors that influence the crowd loading including the synchronization effects of a crowd, the number of harmonic components to be included, and the effects that the motion of the structure has on the crowd motion. The structural response component will focus on the estimation of the dynamic properties of a structure and how these properties are affected by human-structure interaction. The final component, assessment and design, will explain the current assessment measures for vibration serviceability including vibration dose values and RMS acceleration. The acceptable limits for these measures will be discussed as well as the various design approaches to prevent serviceability issues.
Annoying levels of vibration on long-cantilevered structures owing to crowd movements during musical concerts, sporting events, aerobics exercises and so on, have become more common in recent years. There are still a number of issues related to excessive floor vibrations owing to human activities that need to be addressed such as: guidelines for more accurate analytical representation of structural parameters to predict floor dynamic response, better definition of forcing functions to simulate human activities in a computer model and finally more consistent methods of evaluation and assessment of vibrations. This paper focuses on the requirements and guidelines for the evaluation and assessment of vibrations as related to acceptability for human exposure. It briefly reviews the provision of several current standards and design guides for the evaluation and assessment of building vibrations owing to human rhythmic activities. Using the measured vibrations generated by crowd activities on a large cantilevered structure during several rock concerts, collected by way of a remote vibration monitoring system, this paper compares these provisions with each other and draws conclusions on their applicability. New relationships between the current vibration evaluation parameters along with guidance for the assessment of human exposure to vibration owing to rhythmic activities are proposed.
The reinforced concrete terrace units were positioned and tested on a specially manufactured steel frame resting on the strong floor in the Civil Engineering laboratories at Coventry University. In parallel, a finite element model was developed and set to free vibration. Natural frequencies and mode shapes were recorded and compared with those obtained experimentally. As correlation was not deemed to be satisfactory, an updating process was initiated and a series of parameters, starting with the concrete material properties were revised to improve links with the experimental results. Boundary conditions built-in the code were not adequate to model the real behaviour of the structure. Best results were achieved when supports conditions were modelled with a stiffness matrix. Correlation between experimental and computer predicted results improved further with the introduction of more advanced modelling techniques and gradual lifting of the limitations of the model, hence assisting the validation process, while verification did not provide the expected degree of confidence. It was concluded that it is possible to extract the natural frequencies and mode shapes of a complex, non-symmetric structure accurately, by using relatively low-cost, basic modal testing equipment and the finite element method of analysis, hence avoiding the risk of not detecting any mode shapes. This can be more apparent in complex modes (e.g. coupled, flexural/torsional) as they depend greatly on the number, position, direction, type and quality of the transducers and data logging and processing equipment used. Emphasis is placed on the experience built up in interpreting modal analysis results in order to be used for similar future work.
Nowadays the new architecture tendencies and construction market demands are leading the structural engineers to search for increasingly daring solutions. These new structural systems are intrinsically associated to the recent evolution of building construction methods, i.e. fast erection and assembly, with minimum weight, being capable of supporting large spans with few columns enabling greater constructed space flexibility. A direct consequence of this new design trend is the increasing incidence of building vibration problems due to human activities. This was the main motivation for the development of a design methodology centred on the modelling of the dynamic behaviour of steel–concrete composite floors submitted to loads due to human rhythmic activities for the evaluation of human comfort. Thus, three dynamic loading models were utilised to simulate human rhythmic activities such as jumping and aerobics. The dynamic loads were obtained through experimental tests and were based on international design codes and recommendations. The investigated structural model was based on a real steel–concrete composite floor spanning 40 m by 40 m, with a total area of 1600 m2. The structural system consisted of a typical composite floor of a commercial building. The peak accelerations values found in the present investigation indicated that human rhythmic activities could induce the composite floors to reach unacceptable vibration levels leading to a violation of the current human comfort criteria.
The equations governing crowd-structure interaction dynamics are derived from first principles. No assumptions are made about structural support conditions, crowd or beam displacements or crowd-induced forces in this derivation. The general equations of motion are shown to exist in pairs of two degree of freedom systems, for every ith beam-crowd mode. Numerical optimisation of the system response functions is preferred to both classical undamped eigenvalue analysis and a damped complex eigenvalue analysis using a state space formulation. Single parameter continuation of optima of frequency response functions is employed. In addition, two parameter continuations of folds of these optima are used. As a result, a fold loci plot in parameter space defines the region where multiple beam optima exist. This results in the possibility of complicated response behaviour. Increases in predominant frequency of the structure with increasing crowd mass are observed. In other cases, sudden drops in predominant frequency with increasing crowd mass are observed.
This paper considers the crowd loads encountered on cantilever grandstands and estimates these loads from response measurements. It considers two forms of loading: rhythmic loading which is usually encountered at pop concerts and non-rhythmic loading, usually encountered at football matches. The responses of several grandstands were monitored during pop concerts and the songs that produced the peak responses were identified. For two cantilever tiers at one stadium, the peak responses to four songs were considered. The measurements were processed to determine the accelerations corresponding to the first four Fourier coefficients (FCs) of the rhythmic load. These accelerations were used to determine the FCs of the load. The load model was then used for calculations on two other grandstands. The results were compared with measurements and a reasonable correlation obtained. For non-rhythmic loading the peak responses measured on three grandstands during seven football matches were considered. To represent a crowd jumping to its feet in response to a goal, a simple load model based on the instantaneous removal of the weight of the crowd was considered. Although the calculated displacements were reasonable, the peak accelerations were significantly underestimated on two grandstands.
This paper explores the current recommended measures for assessing vibration serviceability in building structures and the recommendations for relating these vibration measures to levels of perception and expected occupant reactions. Two of these assessment measures, the maximum transient vibration value and vibration dose value, are discussed with respect to serviceability in stadium structures. The results of the monitoring and assessment of three stadium structures during several events are presented and these results indicate that the current recommendations are overly conservative in assessing occupant perception. Recommendations for vibration dose levels that are more consistent with the evaluation of events monitored in stadium structures are proposed.
Nowadays large civil structures such as stadia and basketball fields host many events that they were not originally designed for. In particular, live rock concerts are the ones raising problems linked to the higher level of vibrations reached and sometimes maintained for a significant duration. These vibration levels must be evaluated against the serviceability levels given in existing guidance in order to prevent dangerous situations, such as panic or other uncontrollable phenomena in the crowd. Standards exist to evaluate vibration levels, among them the most widely used are ISO2631 and BS6841, which differ in the frequency weighting used and in the quantities used to identify the vibration, even though the starting point is the same measured time histories. In this paper the two standards are compared in different situations to evaluate their efficiency in detecting anomalous vibration levels. The comparison is performed considering different events in the same structure (G. Meazza Stadium in Milano) and comparing the same event in two different structures (Red Hot Chili Peppers in the Milano and Manchester Stadium). The obtained results are a good starting base for the evaluation of the performance of the standards and also to evaluate the performance in terms of vibration serviceability of the different structures.
Vibration serviceability in large assembly-type structures such as stadiums and grandstands has become a design and management
concern as crowds continue to impose significant dynamic loads on a structure through synchronized movement. However, there
is little guidance on the appropriate dynamic design loading to be anticipated for the design of new structures or the assessment
of existing structures. The guidance currently available for human-induced dynamic loading is limited to laboratory experiments
and numerical models that fail to take into account the effects that many factors of the event atmosphere may have on the
loading models. Because measurement of the forces exerted by a crowd under true event conditions is next to impossible, this
project investigates the ability to estimate the dynamic loading with consideration of only the more reasonably obtainable
acceleration response of the structure during the event. Experimental testing was performed on a simple floor structure subjected
to dynamic forces generated by small groups to investigate the accuracy and sensitivity of the load estimation method for
consideration when applying this method to large scale structures.
This paper is a critical review of information pertinent to the behaviour of stadia structures subjected to dynamic crowd loading. It is intended to introduce and explain key concepts in the field as well as summarise the development of current guidance and methods for modelling and assessing crowd occupancy.The review is structured by presenting a field overview and then rationalising the materials found into a standard vibration serviceability problem defined by the vibration source, path and receiver. After briefly introducing the problems associated with dynamic crowd loading, the loads generated by various actions of occupants are discussed. This leads into methods for modelling these activities. The derivation of relevant dynamic structural properties, through both FE modelling and field dynamic testing, is briefly investigated. The concept of human–structure interaction, the merging of dynamic properties of occupants and structure, is considered in depth.Finally, methods for assessing vibration levels are discussed and currently available codes and guidance are appraised in the context of the issues outlined.Further work is required at all stages of the excitation/source (crowd load models which account for flexible structures and large, distributed crowds), system/path (methods for accounting for the effects of occupancy upon system dynamic properties) and response/receiver (occupant tolerance levels) serviceability assessment approach in order to be able to understand and model the outlined phenomena accurately.
& 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 range for jumping and the dynamic crowd eÄect are discussed. Numerical modelling of grand- stands and the determination of structural response are considered, together with possible structural modifications to improve dynamic behaviour. Next, the testing of structures is examined and the results from tests on a range of grand- stands summarized, including the charac- teristics of empty structures and response to crowd loading during concerts and sports events. Finally, vibration service- ability levels are considered and some other design considerations discussed.
This paper considers the problem of human acceptance of floor vibrations induced by walking loads. It defines the parameters used in the assessment of this serviceability issue, including vibration dose values (VDVs) and the frequency weighting that should be applied to vertical vibrations. The relevant guidance given in British Standards is discussed and an example provided to illustrate the analysis procedures. The paper then considers the analysis of measurements of vibration induced by walking, examining first a range of walking frequencies and then deriving some empirical links between measured peak acceleration and VDV. To determine human reaction, VDVs need to be measured for a complete day or night. As this may not always be possible, it is necessary to consider ways of estimating daily VDVs. Therefore, the number of walking periods that should be considered during a day is examined and its influence on the estimated VDVs determined. This provides a relationship between the peak accelerations that can be measured during tests and the VDVs used to assess serviceability. The calculation of VDV is then examined, and calculated VDVs for a range of floors presented. Crowd loading is illustrated using measurements made on two floors. Although the use of VDVs does not seem to have been adopted widely, they appear to provide a sensible method for serviceability evaluation of floor vibrations.