Crowd Induced Deflection of Dow's Lake Ice Cover During Winterlude Festival 1985 Sinha, N
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NRC Publications Archive Archives des publications du CNRC Crowd induced deflection of Dow's Lake ice cover during Winterlude Festival 1985 Sinha, N. K. This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur. Publisher’s version / Version de l'éditeur: Proceedings of the 9th International Conference on Offshore Mechanics and Arctic Engineering (OMAE '90), 4, pp. 161-167, 1990 NRC Publications Archive Record / Notice des Archives des publications du CNRC : https://nrc-publications.canada.ca/eng/view/object/?id=f7539289-86fd-4c7a-b226-c94f57be8b78 https://publications-cnrc.canada.ca/fra/voir/objet/?id=f7539289-86fd-4c7a-b226-c94f57be8b78 Access and use of this website and the material on it are subject to the Terms and Conditions set forth at https://nrc-publications.canada.ca/eng/copyright READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE. L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site https://publications-cnrc.canada.ca/fra/droits LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB. Questions? Contact the NRC Publications Archive team at [email protected]. If you wish to email the authors directly, please see the first page of the publication for their contact information. Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à [email protected]. Ser - - TH1 National Research Conseil national R 2 1d *I Council Canada de recherches Canada no. 1678 c, 2 I Institute for lnstitut de BLDG Research in recherche en - -- Construction construction Crowd Induced Deflection of Dow's Lake Ice Cover During Winterlude Festival - 1985 by N.K. Sinha r* E *I- F* +\\ %:" : -ED Reprinted from Proceedings of The Ninth International Conference of Offshore Mechanics and Arctic Engineering 1990 OMAE Volume IV, p. 161-167 (IRC Paper No. 1678) NRC - ClSTl LIBRARY JAR; !s9! NRCC 32348 ~IBLI~TH~QUE IRC CNRC - ICIST I 1I Ce document decrit la rbponse de la couche de glace flottante de 0,6 m d'6paisseur qui recouvrait un petit lac lorsque 60 000 spectateurs se sont rassemblb pour assister a un concert sur des estrades montk sur la glace. Afin de contraler et d'kvaluer la securite, on a enregistre en permanence le flechissement et la deformation superficielle de la couverture de glace devant les estrades. Les donnks illustrent l'effet du mouvement d'une foule sur la deformation de la couche de glace et montrent combien il importe que les organisateurs preparent minutieusement les evbnements et assurent la maitrise de la foule. Cet aspect de la question, pourtant extremement important, est souvent neglig6 dans les documents techniques. Reprinted From Proceedings of The Ninth International Conference of Offshore Mechanics and Arctic Engineering @ The American society of Editors: 0. A. Ayorinde, N. K. Sinha, and D. S. Sodhi Mechanical Engineers Book No. 10296F - 1990 .- - - CROWD INDUCED DEFLECTION OF DOW'S LAKE ICE COVER DURING WINTERLUDE FESTIVAL - 1985 N. K. Sinha National Research Council of Canada Ottawa, Ontario, Canada Abstract Background The response of a 0.6 m thick floating ice cover in a small The National Capital Commission (NCC) is responsible for lake is described, when 60,000 spectators gathe:ed to witness a the maintenance of Canada's Federal Government properties in the concert on stages built on the ice. To monitor and evaluate safety, nation's capital. The Commission also manages and maintains the deflection and surface strain of the ice cover were recorded Rideau Canal, which flows through the core of the city, under a continuously in front of the stages. The data illustrates the effect of program for the development and improvement of the National crowd movement on the deformation of the ice cover and Capital Region of Ottawa-Hull. For the last 12 years, a 7.8 km long emphasizes the importance of careful planning of events, as well as and 30-70 m wide section of the canal has been used by the NCC crowd control by the organizers. This side of the story, in spite of to make a public ice skating rink. This rink has become the centre its extreme importance, is often neglected in a technical paper. of public activities in Ottawa for about two months every winter. Introduction The success of the rink and the popularity of the area led NCC to organize - since the winter of 1979 - a ten day long annual 'Wlnterlude weaves Its maglc br 80,000" was the front page festival known as "Winterlude". It is held in the first two weeks of headllne of Ottawa's newspaper The Citizen" on Saturday, February. An important part of this festival is the snow sculpture Fsbruaty 2, 1985. This headline was fol!owed by a paragraph: competition and the exhibition of the sculptures on the floating ice "Skating, dancing, slnging and clapping, an estimated 60,050 people cover of Dow's Lake which was originally constructed as a reservoir celebrated the openlng of the seventh annual Wlnterluda Friday night for the canal. This lake is about 800 m bng and 300 m wide. On {Rb.1) at hw's Lake. Stretching out along the Rideau Canal, the average the water depth is maintained at about 3 m during the filling the terrace of the Dow's Lake Pavilion, standing on picnic summer. Experience taught the organizers to limit the size, shape tables, crouchng around camp Rres, they cheered brightly-wloured and the mass of the sculptures, and to distribute these loads on the tireworks leaving clouds of smoke in the clear sub-zero air." ice cover. The result was a physically safe and artistically pleasant Dow's Lake ice complex containing the sculpture exhibition area, "Ice It was the largest crowd ever on the ice cover of Dow's Lake Dream", public skating path, and a number of ice hockey and figure for the opening night ceremony of the tenday long annual winter skating rinks shown in Fig. 2 representing a small section of the festival in Ottawa called "Winterlude". It was a family night - babies complex. were snugly wrapped up in sleighs; children skating hand-in-hand with their brothers, sisters, friends, parents and grandparents. They The study to be reported here was undertaken in 1985 with danced around the 101 snow sculptures and clapped in rhythm to one week's notice when the Winterlude organizers expressed their i the tunes coming from huge and powerful speakers beside the two concern about the safety of the ice cover on Dow's Lake, particularly C grandstands (Fig. 1) built on the ice cover - and the ice cover when a very large crowd was anticipated for opening night. responded in harmony with the mass motion. Opening Night Ceremony - Location 1- In the midst of the crowd there was a number of people i- whose duly it was to patrol the ice cover and monitor the condition It was decided by the authorities to celebrate the Winterlude- t of the ice in case it failed. One of the most strategic and vulnerable 1985 opening night ceremony in the 100 m x 100 m area in front of spots was the area in front of the grandstands where the load of the newly constructed Dow's Lake Pavilion and adjacent to the "Ice spectators was maximum. At this site the deflection and surface Dream", as can be seen on the left-hand side of Fig. 2. strain of the ice cover was monitored continuously. This paper describes several aspects of the monitoring programs, the severe Two stages, each with dimensions of 20 m x 30 m were constraints of carrying out such investigations, and the results of the constructed on the ice cover (Fig. 2). Two scaffolded towers, with obsenrations. The study brings out several factors on the response a base of 3 m x 3 m, were constructed 20 rn in front of each of of an ice cover when it is used by a crowd, without any control of these stages for mounting the stage lights. These structures were their movements, which is different from when it is used for about 5 m high and contained a platform for the operators of the transportation (1) or for parking cars under full control of the load lights and television camera. The spaces below these platforms distribution, as described by Meneley (2). were thought to be ideal for instrumenting the ice because the Figure 1 Crowd on Dow's Lake ice cover during the Winterlude opening night ceremony, Feb. 1, 1985 (Courtesy of Ottawa Citizen) scaffolding could provide the necessary protection from the crowd. These two positions were designated as the measuring stations 1 and 2 as indicated in Fig. 2. The tower associated with Station 1 can be seen on the right hand side in Fig. 1. Instrumentation It was decided to record continuousiy the surface straln of the Ice cover at the two stations. This choke was prompted by the fact at straln gauges designed earlier for ice (31, Invohing d~rect- current displacement hansducers (DCDT), were available and at the operational peopfe were reluctant to allow anything, such as drllling holes, that might affect generar use of the ice mver.