b'Technical Articlepredeterminedcriterion.Basically,in the analysis. Another advantage of thepost-processorscansthecon- wind tunnels is the option to install tinuoustimehistoryandsearchesa significant number of pressure taps for wind speed peaks greater than 30(many more than is possible in field Pressure sensormph (13.4 m/s), then segments of 10studies). By increasing the pressure minutes of data (five minutes beforetap density, there are more chances and after each wind speed peak) areto capture the critical peak pressures extractedtogeneratethedatabaseon the roof. It should be recalled that required for further analysis. Fig. 3athe wind load on the roof is not uni-shows a typical example of a windform, with a great gradient close to time history (24 hours) and the seg- corners and roof edges.mentationprocess.Fig.3bshowsThewindtunnellaboratories the concatenation of all the segmentsthatparticipatedinthisresearch collected for this specific day. Duringusedtheirowncriteriatoevaluate monitoring of the IOWA building,theIOWAbuilding.Forexample, 92 segments of data were collectedthegeometriclengthscaleswere Transducer box and used for the completion of the1:250 and 1:200 for the Concordia project. These instrumentation andand Western tests, respectively. Con-Referencemeasurement techniques have beencordiainstalled194pressuretaps, pressureDAQsuccessfully applied in the previouswhereas Western installed 534 taps. NRC-SIGDERSfieldmonitoringThe roof-height velocities were 9.1 programs (Ottawa site, 8,9Rialto site 9 m/s (20.4 mph), with a turbulence and Vancouver site 10,11 ). intensityof14percent,and5.12 m/s (11.5 mph), with a turbulence Wind Tunnel Experiments intensity of 19.5 per cent, for Con-In addition to field monitoring,cordiaandWestern,respectively. datawerealsocollectedusingtheNotethatturbulenceintensityis conventional wind tunnel approach.theratioofthefluctuatingwind Scaledwindtunnelmodelsofthevelocity over the mean wind speed. IOWA building were tested by theFig.4presentstheexperimental Building Aerodynamics Laboratorysetup,close-uppicturesandpres-ofConcordiaUniversityinMon- sure models.treal,Quebec,andtheBoundaryItisimportanttounderstand Layer Wind Tunnel Laboratory ofthat even though wind tunnel simu-Western University in London, Ont. lations have proven to be an effec-Themajoradvantageofwindtivetooltoinvestigatewindloads tunnelmodelsistheopportunityonroofs,theyremainsimulations, to evaluate the effect of wind for allwithseveralassumptionsandap-wind directions. This is possible be- proximations. This is why the tan-cause the model is installed on a turn- demfieldandwindtunnelevalu-table, which allows investigators toation is observed as a powerful and change the approaching wind direc- promising approach to advance the tion as desired by rotating the model.credibility of design loading. Details In this study, the wind was evaluatedof the comparisons of wind tunnel Figure 2: Details of the pressure sensor developed by National Research Council of Canada to evaluate wind load on the roof. Note: DAQdata with field measurements can be Figure 2. Details of the pressure sensor developed by the National Research Council of Canada tofor all wind azimuths to ensure that = data acquisition system. the critical wind direction is includedfound in Chavez et al. 12evaluate wind load on the roof. Note: DAQ = data acquisition system.a) Think Safe,Work Safe,since 1988b) Top-Line Roofing & Sheet-Metal Inc specializes in the installation, repair, and maintenance of industrial roofs throughout Southern Ontario. OUR SERVICES:Commercial roofing Re-roofingRoof maintenance Skylight installationRoof inspection,Sheet metal flashing evaluation & report fabrication & installationHistorical restoration Retro-fit curb installationEmergency roof repairsOne 10-minute segment (peak 30 mph [13.4 m/s]) (905) 602-07601325 Fewster DrMississauga, ONL4W 1A2 Figure 3: Data from field monitoring: (a) typical wind speed time history; (b) example of data toplineroofing.ca Figure 3. (a) typical wind speed time history and (b) example of data segmentation into 10 minute segmentation into 10-minute records (November 19, 2016). Note: 1 mph = 0.447 m/s.records (November 19th, 2016). 16ONTARIO ROOFING NEWSISSUE 4 2022/23 THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ORN'