An Experimental Study Focused on Spectators' Behavior and Induced

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X International Conference on Structural Dynamics, EURODYN 2017 An Experimental Study Focused on Spectators’ Behavior and Induced Vibrations of a Reinforced Concrete Grandstand on a Football Stadium

Tomáš Plachýa, Michal Poláka, Martin Vernera,*

aCzech Technical University in Prague, Faculty of Civil Engineering, Thákurova 7, CZ-166 29 Prague, Czech Republic

Abstract

A series of experiments focused on spectators’ behavior and induced grandstand vibrations during some football matches were carried out at the Eden stadium in Prague the home stadium of the SK Slavia Prague football club from the Czech Republic. The experiments were carried out as the experimental basis for specification, improvement and verification of developed spectator’s crowd load models which are based on stochastic approaches. The paper is concentrated on one particular match between home team and FC Banik Ostrava. The different types of spectators’ behavior were investigated based on the continuous camera records. The grandstand vibrations were measured simultaneously in three spots on the lower surface of the grandstand structure. The basic experimental results obtained from observed behavior of spectators and examined grandstand vibrations are stated in the paper. As it was expected, the largest evaluated vibrations were connected with the spectators’ behavior types as Jumping, in which all fans in the grandstand sector were involved actively and high degree of their synchronization was achieved. © 2017 The Authors. Published by Elsevier Ltd. © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the organizing committee of EURODYN 2017. Peer-review under responsibility of the organizing committee of EURODYN 2017. Keywords: Spectators’ behaviour; vibrations; grandstand; stadium; reinforced concrete; crowd load model; dynamic analysis;

1. Introduction

At present time, the dynamic load of stadium grandstands is not described in any standard with acceptable precision. However, new spectator’s crowd dynamic load models have been currently developed which are based on stochastic approaches [1, 2, 3]. There is a shortage of appropriate in situ experiments that could be used as a basis for

* Corresponding author. Tel.: +420-224-354-476; fax: +420-224-310-775. E-mail address: [email protected]

10.1016/j.proeng.2017.09.574 1877-7058 2872 Tomáš Plachý et al. / Procedia Engineering 199 (2017) 2871–2876 2 Tomáš Plachý, Michal Polák, Martin Verner / Procedia Engineering 00 (2017) 000–000 improvement or verification of the models [4, 5, 6], and moreover, these experiments are focused only on football matches [5, 6] or concerts [6]. A series of experiments focused on spectators’ behavior and induced grandstand vibrations during some football matches were carried out at the Eden stadium in Prague the home stadium of the SK Slavia Prague football club from the Czech Republic which followed similar experiments performed on a steel cantilever grandstand structure at the AC Sparta football stadium in Prague [7, 8, 9] and on a reinforced concrete frame grandstand structure at the ice hockey stadium in Pilsen [10]. The basic objective of the experiments was to study football spectators in a selected stadium area where the most active fans of the home team (also called “Ultras”) were gathered, their behavior and simultaneously grandstand vibrations induced by them. The experiments were primarily performed as the experimental basis for specification, improvement and verification of developed spectator’s crowd load models which are based on stochastic approaches as the filtered Gaussian white noise processes for example [2]. The paper is concentrated on one particular match between SK Slavia Prague and FC Banik Ostrava played on February 28th 2016 that home team won 3:1.

A B

Fig. 1. The overall view on the studied stadium part (left); the bottom view on the load bearing structure in the closely observed sector and the location and orientation of the accelerometers used by the experiment (right).

Fig. 2. The overall view on spectators in the studied north part of the stadium (left) and in the closely observed grandstand sector (right).

2. The brief description of the stadium, the studied grandstand structure and the observed football match

Eden Arena is the home stadium of SK Slavia Prague football club. It was put into operation in May 2008 and it is the most modern and with a capacity of 20 617 spectators also the largest football stadium in the Czech Republic. The cantilever steel roof is constructed that the views from the stands are not restricted by any columns (see Fig. 1). The observed part of the grandstand is built as the reinforced concrete structure assembled from prefabricated elements. The basic structure members of grandstand in the observed area are noticeable in Fig. 1. The L-shaped reinforced concrete horizontal beams that create the walking area of the grandstand are simply supported on the Tomáš Plachý et al. / Procedia Engineering 199 (2017) 2871–2876 2873 2 Tomáš Plachý, Michal Polák, Martin Verner / Procedia Engineering 00 (2017) 000–000 Tomáš Plachý, Michal Polák, Martin Verner/ Procedia Engineering 00 (2017) 000–000 3 improvement or verification of the models [4, 5, 6], and moreover, these experiments are focused only on football inclined main beams and these ones are simply supported too but on the vertical columns. The observed football matches [5, 6] or concerts [6]. A series of experiments focused on spectators’ behavior and induced grandstand match was played between SK Slavia Prague and FC Banik Ostrava on February 28th 2016 in the 19th round of the vibrations during some football matches were carried out at the Eden stadium in Prague the home stadium of the SK Czech first football league. The home team won the game 3:1. However, the first goal was scored in the 27th minute Slavia Prague football club from the Czech Republic which followed similar experiments performed on a steel by FC Banik Ostrava (0:1). SK Slavia Prague subsequently scored in the 32nd minute (1:1), in the 37th minute (2:1) cantilever grandstand structure at the AC Sparta football stadium in Prague [7, 8, 9] and on a reinforced concrete and in the 65th minute (3:1). SK Slavia player Soucek scored all three goals of the home team and it means that he frame grandstand structure at the ice hockey stadium in Pilsen [10]. achieved hat-trick. The basic objective of the experiments was to study football spectators in a selected stadium area where the most active fans of the home team (also called “Ultras”) were gathered, their behavior and simultaneously grandstand 3. The experiment arrangement vibrations induced by them. The experiments were primarily performed as the experimental basis for specification, improvement and verification of developed spectator’s crowd load models which are based on stochastic approaches The experiment described in the paper was focused on the part of the stadium where the most active fans of the as the filtered Gaussian white noise processes for example [2]. The paper is concentrated on one particular match home team (also called “Ultras”) were assembled. This group of spectators is generally gathered in the stadium between SK Slavia Prague and FC Banik Ostrava played on February 28th 2016 that home team won 3:1. sector behind the north football gate as it is shown in Fig. 2. The fans in this sector are standing in the majority of time (see Fig. 2) despite the fact that permanent seats are installed on the grandstand structure (see Fig. 1). The vibrations of the grandstand structure were investigated on the bottom surface of the grandstand (see Fig. 1) in three spots. The four piezoelectric sensors Brüel&Kjær of type 4507 B005 were used for the described experiment. The two acceleration transducers were placed in the middle of the L-shaped reinforced concrete B horizontal beam on that the highest concentration of the core of fans was assumed (the spot B in Fig. 1). The first A sensor measured the vertical vibrations and the second one horizontal transversal vibrations. The remaining two transducers were situated on the two inclined main beams in positions close to the supports of the observed L- shaped horizontal beam (the spot A (see Fig. 1) and the spot C). They both recorded acceleration in the vertical direction. The measurement system Pulse and Front-end 3050-B-040 Brüel&Kjær were used for data acquisition. The evaluated results gave us the information about the induced grandstand accelerations and how particular types of spectators’ behavior influenced the level and features of the grandstand structure vibrations. For this purpose, it was also important to determine the cause of the observed vibrations. The studied sector of the grandstand was continuously monitored by camera situated on the other part of the stadium. The photos from the obtained records are shown in Fig. 2. Fig. 1. The overall view on the studied stadium part (left); the bottom view on the load bearing structure in the closely observed sector and the location and orientation of the accelerometers used by the experiment (right). 4. The types of spectators’ behavior identified during the experiment

The indications of the spectators’ behavior types used in the paper were mainly adopted from the article [5]. However, some types were taken from reference [8]. Static state: All spectators sit or stand statically and watch the game passively only. Walking: This type of spectators’ behavior happens mostly outside the play. Bouncing: This case of cheering is similar to Jumping of the 1st type that is mentioned below. However, the basic distinction between these types is the feet of fans remain in contact with the surface of the grandstand by bouncing. Swaying: This type of spectators’ behavior develops most often by cooperation with fans in two nearby stadium sectors by shouting of a united slogan. For example, the spectators on the observed grandstand area cry the initial part of the slogan at first and then the spectators in the nearby stadium sector respond the slogan final part. Fans in both sectors sway forward to support the shouted slogan and whole movement is improved by arm motion besides. Jumping is the type of the spectators’ behavior that caused usually the most intensive dynamic excitation of the Fig. 2. The overall view on spectators in the studied north part of the stadium (left) and in the closely observed grandstand sector (right). grandstand and its largest dynamic response as seen in Table 2. The four different types of fan jumping were observed in the examined grandstand area. st 2. The brief description of the stadium, the studied grandstand structure and the observed football match Jumping of the 1 type: The spectators are jumping together during this type of behavior. However, they are jumping spontaneously independently on each other. nd rd Eden Arena is the home stadium of SK Slavia Prague football club. It was put into operation in May 2008 and it Jumping of the 2 and the 3 type: These two types of jumping are similar to each other. In separates lines, the is the most modern and with a capacity of 20 617 spectators also the largest football stadium in the Czech Republic. fans join together with arms around their shoulders and they begin to jump synchronously on the spot in vertical nd The cantilever steel roof is constructed that the views from the stands are not restricted by any columns (see Fig. 1). direction (the 2 type) or the united spectators in lines move horizontally by synchronous jumping from left to right rd The observed part of the grandstand is built as the reinforced concrete structure assembled from prefabricated and back again generally in revers directions in adjacent lines (the 3 type). th elements. The basic structure members of grandstand in the observed area are noticeable in Fig. 1. The L-shaped Jumping of the 4 type: This type of jumping could be described as “Sit and Jump”. First, all fans in the entire reinforced concrete horizontal beams that create the walking area of the grandstand are simply supported on the sector sit down. Next, they jump up concurrently on a signal of their leader and start continuous jumping at once. 2874 Tomáš Plachý et al. / Procedia Engineering 199 (2017) 2871–2876 4 Tomáš Plachý, Michal Polák, Martin Verner / Procedia Engineering 00 (2017) 000–000

The SK Slavia Prague fans used three basic particular types of hand-clapping. Hand-clapping of the 1st type: The spectators clap their hands constantly at the level of their chest. Hand-clapping of the 2nd type: The fans clap their hands constantly above their heads. Hand-clapping of the 3rd type: The spectators clap their hands at chest level at first and then they throw up their arms above their heads in the V-shape. These two parts are repeated periodically. The other two specific types of spectators’ behavior were identified during observed match that cannot be classified to above mentioned cheering types. Goal scoring: This type of spectators’ behavior appears in the moment when the supported team scores the goal. It represents the type laying somewhere between jumping of the 1st type, swaying and hand-clapping of the 1st type. Mexican wave: The sitting spectators stood briefly up and thrown temporary up their arms round the whole stadium subsequently. The fans in the observed grandstand sector were standing for whole match practically therefore they made Mexican wave using a temporary lift of their arms only.

Table 2. The comparison of the maximum peak values of the acceleration and deflection evaluated by the selected particular spectator behavior types in the observed spots. Type of spectator behavior Spot: A Spot: B Spot: B Spot: C Spot: B Spot: B vertical vertical horizontal vertical vertical horizontal acceleration acceleration acceleration acceleration deflection deflection [m·s-2] [m·s-2] [m·s-2] [m·s-2] [mm] [mm] Jumping of the 1st type 0.24 1.06 0.42 0.23 - - Jumping of the 2nd type 0.45 2.73 1.17 0.56 3.6 1.2 Jumping of the 3th type 0.37 2.45 0.92 0.45 3.9 1.6 Jumping of the 4th type 0.18 0.92 0.48 0.30 - - Goal scoring 0.31 2.17 0.61 0.34 0.8 0.5

5. The description of the experiment results

The described experiment was performed practically during the whole analyzed football match from the entrance of players to the pitch to the exit of fans from the grandstand at the end of the game. About 200 fans were gathered Tomáš Plachý et al. / Procedia Engineering 199 (2017) 2871–2876 2875 4 Tomáš Plachý, Michal Polák, Martin Verner / Procedia Engineering 00 (2017) 000–000 Tomáš Plachý, Michal Polák, Martin Verner/ Procedia Engineering 00 (2017) 000–000 5

The SK Slavia Prague fans used three basic particular types of hand-clapping. in the closely observed grandstand sector. The total number of spectators presented at the stadium was nearly Hand-clapping of the 1st type: The spectators clap their hands constantly at the level of their chest. thirteen thousand. Hand-clapping of the 2nd type: The fans clap their hands constantly above their heads. Hand-clapping of the 3rd type: The spectators clap their hands at chest level at first and then they throw up their arms above their heads in the V-shape. These two parts are repeated periodically. The other two specific types of spectators’ behavior were identified during observed match that cannot be classified to above mentioned cheering types. Goal scoring: This type of spectators’ behavior appears in the moment when the supported team scores the goal. It represents the type laying somewhere between jumping of the 1st type, swaying and hand-clapping of the 1st type. Mexican wave: The sitting spectators stood briefly up and thrown temporary up their arms round the whole stadium subsequently. The fans in the observed grandstand sector were standing for whole match practically therefore they made Mexican wave using a temporary lift of their arms only.

Table 1. The time duration of the particular types of spectator behavior that was evaluated during the observed football match. Type of spectator behavior Minimum First First Second Second Other Other Total Total proportion half half half half time time time time of active fans [min] [%] [min] [%] [min] [%] [min] [%] [%] Fig. 3. The frequency spectrum of the acceleration measured in vertical (red line) and horizontal (blue line) direction in the spot B situated on the horizontal beam during the half-time (type of spectator behavior - Walking) (left) and Goal scoring (the winning second goal) (right). Static state 85 16:14 37.0 17:48 44.0 1:57 7.9 35:59 33.0 Walking 50 - 0.0 - 0.0 15:37 62.9 15:37 14.3 Bouncing 40 3:13 7.3 1:51 4.6 - 0.0 5:04 4.7 Swaying 50 5:51 13.3 2:49 7.0 0:33 2.2 9:13 8.4 Jumping of the 1st type 60 4:42 10.7 4:25 10.9 1:44 7.0 10:51 9.9 Jumping of the 2nd type 100 - 0.0 1:01 2.5 - 0.0 1:01 0.9 Jumping of the 3th type 100 0:32 1.2 - 0.0 - 0.0 0:32 0.5 Jumping of the 4th type 100 - 0.0 0:46 1.9 0:43 2.9 1:29 1.4 Goal scoring 100 0:10 0.4 0:18 0.7 - 0.0 0:28 0.4 Mexican wave 95 0:37 1.4 1:10 2.9 - 0.0 1:47 1.6 Hand-clapping of the 1st type 40 6:07 13.9 5:35 13.8 2:34 10.3 14:16 13.1 Hand-clapping of the 2nd type 90 3:49 8.7 3:18 8.2 0:39 2.6 7:46 7.1 Hand-clapping of the 3rd type 90 2:40 6.1 1:24 3.5 1:02 4.2 5:06 4.7 Fig. 4. The frequency spectrum of the acceleration measured in vertical (red line) and horizontal (blue line) direction in the spot B situated on the horizontal beam during Jumping of the 2nd type (left) and Jumping of the 3rd type (right). Table 2. The comparison of the maximum peak values of the acceleration and deflection evaluated by the selected particular spectator behavior types in the observed spots. The detailed analysis of participation of the particular spectators’ behavior types during the whole studied match Type of spectator behavior Spot: A Spot: B Spot: B Spot: C Spot: B Spot: B and also its parts is summarized in Table 1. In some moments, all fans present in the observed grandstand sector vertical vertical horizontal vertical vertical horizontal acceleration acceleration acceleration acceleration deflection deflection were participated in all types stated in Table 1. However, the ratio of active fans to passive ones for the separate [m·s-2] [m·s-2] [m·s-2] [m·s-2] [mm] [mm] types varied during the game in the interval from the minimum proportion that is stated in Table 1, to 100 %. Jumping of the 1st type 0.24 1.06 0.42 0.23 - - The maximum peak values of the measured acceleration for selected types of spectators’ behavior with most intensive dynamic excitation are summarized in Table 2. The maximum peak values of deflection that were Jumping of the 2nd type 0.45 2.73 1.17 0.56 3.6 1.2 determined using double integration of the measured acceleration in the time domain are also stated in the Table 2. th Jumping of the 3 type 0.37 2.45 0.92 0.45 3.9 1.6 Some interesting and also significant frequency spectra of the acceleration measured in the spot B are shown in Jumping of the 4th type 0.18 0.92 0.48 0.30 - - Fig. 3 and Fig. 4. Goal scoring 0.31 2.17 0.61 0.34 0.8 0.5 6. Conclusions 5. The description of the experiment results The largest evaluated vibration (see Table 2) are especially connected with the spectators’ behavior types as nd rd The described experiment was performed practically during the whole analyzed football match from the entrance Jumping of the 2 and 3 type, in which all fans in the grandstand sector were involved actively (the proportion of of players to the pitch to the exit of fans from the grandstand at the end of the game. About 200 fans were gathered active spectators was 100 %) and high degree of their synchronization was achieved. 2876 Tomáš Plachý et al. / Procedia Engineering 199 (2017) 2871–2876 6 Tomáš Plachý, Michal Polák, Martin Verner / Procedia Engineering 00 (2017) 000–000

The organization of cheering by the leader in the stadium sector where the most active fans are gathered caused almost always the involvement of all of the spectators present at the sector. It happens mainly for Jumping of the 2nd, 3rd and 4th type, Mexican wave and Goal scoring. The most active fans repeated mostly two or three types of behavior within one cheering choreography continuing usually about three or five minutes. For example, Hand-clapping of the 2nd type passed into Jumping of the 1st type and this sequence was repeated every fourteen seconds on average. The ratio of the active fans decreased with increasing time of the duration of the choreography from 100 % at its start to 60% on average at its end. The fundamental frequency of the jumping of the spectators is about 2.1 Hz (see Fig. 4). However, the dynamic response of the grandstand structure to the excitation caused by this behavior type contains also the integer multiples of the fundamental frequency (see Fig. 4) that are different from the natural frequencies of the grandstand structure. The two significant grandstand natural frequencies, that usually appear recognizably in the dynamic response, are 9.56 Hz and 11.05 Hz (see Fig. 3 for example). These harmonics are demonstrated in Jumping of the 2nd, 3rd and 4th type and also in Bouncing when the spectators are more or less synchronized and their movement is substantial. But seven harmonic parts (2.17 Hz, 4.31 Hz, 6.47 Hz, 8.63 Hz, 10.81 Hz, 12.91 Hz and 15.13 Hz) were found only in the Jumping of 2nd type. Nevertheless, it means, this type of jumping can potentially induce resonance vibration at a grandstand natural frequency higher than 6 Hz. On the other hand, distinguishable harmonics did not appear in other observed behavior types as is Goal scoring for example (see Fig. 3). The largest measured acceleration of the grandstand mentioned in the paper could be considered by some siting or passively staying spectators as a little uncomfortable.

Acknowledgements

This paper has been supported by the Czech Science Foundation project No. GA15-15728S.

References

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