Croatian Building Regulations Concerning Wind Loading

»With the contribution of the Civil Protection Financial Instrument of the European Union« Croatian building regulations concerning wind loading

Vladimir Divić, Ph.D. Faculty of civil engineering, architecture and geodesy University of Split Historical overview

Croatian codes: European codes:  JUS – Yugoslovenian norms • 1st generaton 1985. based on German DIN • 2nd generation 1989. ENV codes standards (CEN)  HRN – First Croatian norms, only difference from JUS is • 3rd generation 2007. EN codes nomenclature  HRN ENV – Croatian translation of European building codes  HRN EN – Final form of Croatian building norms  National Annex – characteristics of local winds in Croatia concerning wind loads on buildings WindRisk Workshop 10.09.2015. Croatian wind climate

 Bora and sirrocco wind – dominant and very different winds  First exploration of Bora – team of Japanese scientist observes similarity between Japan local winds and Bora (1960)  Downslope wind type – terrain plays important role

WindRisk Workshop 10.09.2015. Croatian wind climate

 Unofficial highest recorded speed 307 km/h 24.12.2003. on highway A1 between Sv. Rok and Maslenica bridge  Official highest speed 248 km/h on Maslenica bridge 21.12.1998.  High turbulence winds

WindRisk Workshop 10.09.2015. Croatian wind climate

WindRisk Workshop 10.09.2015. Basic concepts of wind loading in EN

 Basic wind speed  Basic wind speed modifiers  Surrounding terrain  Wind dynamics  Construction dynamics

WindRisk Workshop 10.09.2015. Basic concepts of wind loading in EN

 Simplified calculations – low rise buildings, unsensitive to wind dynamics  Detailed calculations – sensitive and tall buildings

WindRisk Workshop 10.09.2015. Basic wind speed  Statistical value of speed of wind  10 m A.G.L.  10-minutes averaged  Above class II terrain (grass and low vegetation)  50 years return period

WindRisk Workshop 10.09.2015. Croatian basic wind chart

WindRisk Workshop 10.09.2015. Basic wind speed modifiers

 Modifier concerning wind direction  Croatian NA defines cdir as 1.0  Modifier concerning season  Croatian NA defines cseason as 1.0

WindRisk Workshop 10.09.2015. Influence of surrounding terrain

 Vertical distribution of wind speed

 Factor of surface roughness Cr  5 classes of terrain  Procedure for determination is clear  Croatian NA accepts proposed EN method

WindRisk Workshop 10.09.2015. Influence of surrounding terrain

 Orography factor Co  Takes in account vertical terrain profile in wind direction  Croatian NA accepts proposed EN method

WindRisk Workshop 10.09.2015. Wind dynamics

 Wind turbulence  Irregular changes in wind speed and direction – relies on statistical description  Simplest description is standard deviation of wind speed  More detailed description: wind fluctuation spectra, vortex size, spatial cross-covariance etc.  In EN norms included as increase of mean pressure on construction

WindRisk Workshop 10.09.2015. Wind dynamics

 It is convenient to describe it as ratio between standard deviation and mean of wind speed named turbulence intensity – as is case in EN

 In EN it relies on only one coefficient ki – turbulence factor for structures insensitive to dynamic wind loading  In Croatian NA ki = 1.0  Peak velocity pressure – a static approach to dynamic loading

WindRisk Workshop 10.09.2015. Wind dynamics

 For sensitive constructions wind dynamics are described with turbulence length and wind speed spectral density function  Wind turbulence length depends only on terrain roughness  Spectral density function depends on wind mean speed, wind speed variance and turbulence length

WindRisk Workshop 10.09.2015. Construction dynamics factor

 Factor regarding nonuniformity of wind loads Cs  Factor regarding amplicifation of dynamics displacments due to resonance with construction Cd  Detail method requires exhausting calculation of construction dynamics  Wind dynamics are included as turbulence length and wind spectra

WindRisk Workshop 10.09.2015. Shape factors

 Shape and dimension of construction defines it  Values for pressure distriburion and integral force  Represents ratio of forces induced at element of construction to forces over unobstructed infinite flat plate of same reference area

WindRisk Workshop 10.09.2015. Wind forces on construction

 Including previously described parameters

 Main input for civil engineers to calculate wind effect on construction

WindRisk Workshop 10.09.2015. Open questions / further research

 Influence of wind time-scale  Wind direction influence – bora and sirroco  Better description of wind dynamic properties  Group of constructions – interaction wind-construction  Climate change  Scientist researching climate change are predicting:  Lower mean wind speed  More frequent situations with high wind speeds  Stronger wind gusts

WindRisk Workshop 10.09.2015. References

 Bajić, A. Bora wind load upon structures. Croat. Meteorol. J. 48/49, 3–17 (2014).  Bajić, A., Prostorna raspodjela očekivanih maksimalnih brzina vjetra na složenom terenu Hrvatske kao podloga za ocjenu opterećenja vjetrom (University of Zagreb, 2011)  Divić, V. Simulacije krajnjih graničnih stanja pod djelovanjem vjetar metodom konačno-diskretnih elemenata. (University of Split, 2014).  Holmes, J. D. Impact of Climate Change on Design Wind Speeds in Cyclonic Regions Impact of Climate Change on. (2011).  Wang, C. H. & Wang, X. Hazard of Extreme Wind Gusts in Australia and Its Sensitivity to Climate Change. in 18th world IMACS/ MODSIM Congress 2576–2582 (2009).  Rockel, B. & Woth, K. Extremes of near-surface wind speed over Europe and their future changes as estimated from an ensemble of RCM simulations. Clim. Change 81, 267–280 (2007).  Bajić, A., Peroš, B., Vučetić, V. & Žibrat, Z. Opterećenje vjetrom – meteorološka podloga za hrvatske norme. Građevinar 53, 495–505 (2001).  Peroš, B., Pouzdanost konstrukcija s dominantnim djelovanjem vjetra, Doktorska disertacija, (University of Zagreb, 1995)  Peroš, B., Boko, I., Divić, V., Wind shear characteristics of local winds, Proceedings of Seventh Asia-Pacific Conference on Wind Engineering, Chinese Taiwan Association for Wind Engineering, 649-652, 2009  Peroš, B., Boko, I., Investigations of the effects of the Bora wind load upon transmission line pylons, 3. International Congress of the Croatian Society for Mechanics, Proceedings, 587-594, 2000  Peroš, B., Constructional steel design for structures with a dominant wind Bora load, Journal of Constructional Steel Research 46, 321-322, 1998  EN 1991-1-4:2005, Eurokod 1 – Djelovanja na konstrukcije, Dio 1-4: Opća djelovanja – Djelovanja vjetra, 2005  nHRN EN 1991-1-4:2012/NA, Eurokod 1 – Djelovanja na konstrukcije, Dio 1-4: Opća djelovanja – Djelovanja vjetra- Nacionalni dodatak, 2012

WindRisk Workshop 10.09.2015. Thank you!

Vladimir Divić, PhD [email protected]

WindRisk Workshop 10.09.2015.