{{update|date=April 2021}} {{Infobox Bridge |bridge_name=Mirna Bridge |image=Mirna bridge from east.jpg |caption= |official_name=Most Mirna |carries= 2 lanes of A9 motorway |crosses=Mirna River |locale=Istria, Croatia |maint=BINA Istra |design=Girder bridge |mainspan=70.1 m |length=1,378 m |width=10.1 m |clearance= |below= |traffic= |open=2005 |closed= |toll=yes |map_cue= |map_image= |map_text= |map_width= |coordinates={{coord|45.329461|N|13.626652|E|region:HR_type:landmark|display=inline,title}} }}
The '''Mirna Bridge''' is located between the Nova Vas and Višnjan interchanges of the A9 motorway in Istria, Croatia, spanning the Mirna River and the wide Mirna River valley. It is {{convert|1378|m}} long and comprises two traffic lanes. The bridge has been open for traffic since June 2005. The bridge is one of the most significant structures on the motorway.<ref name="BINA-Mirna">{{cite web | publisher = BINA Istra |url=http://www.bina-istra.com/Default.aspx?sid=1156# | title = The Most Important Road Structures | accessdate = September 24, 2010 }}{{Dead link|date=April 2020 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="Građevinar-Mirna">{{cite news|newspaper=Građevinar |language=Croatian |url=http://www.casopis-gradjevinar.hr/dokumenti/200407/6.pdf |title=Zapadni krak 'istarskog ipsilona' i most preko Mirne |trans-title=Western arm of Istrian Y and the Mirna Bridge |author=Tanja Vrančić, Branko Nadilo |date=August 10, 2004 |accessdate=September 24, 2010 |url-status=dead |archiveurl=https://web.archive.org/web/20110718202924/http://www.casopis-gradjevinar.hr/dokumenti/200407/6.pdf |archivedate=July 18, 2011 }}</ref> The bridge was designed by Zlatko Šavor.<ref name="Gradimo-Mirna">{{cite web | publisher = Gradimo | url=http://www.gradimo.hr/Vijadukt-preko-Mirne-na-istarskoj-brzoj-cesti/hr-HR/13049.aspx | language= Croatian | title= Vijadukt preko Mirne na istarskoj brzoj cesti |trans-title=Viaduct across Mirna on the Istrian expressway | accessdate = September 24, 2010}}</ref><ref name="Nacional-Šavor">{{cite news|newspaper=Nacional |url=http://www.nacional.hr/clanak/22890/tvorac-najvecih-hrvatskih-mostova |language=Croatian |title=Tvorac najvećih hrvatskih mostova |trans-title=Creator of the largest Croatian bridges |author=Eduard Šoštarić |date=30 January 2006 |accessdate=27 September 2010 |archivedate=18 July 2012 |url-status=live |archiveurl=https://web.archive.org/web/20120718102738/http://www.nacional.hr/clanak/22890/tvorac-najvecih-hrvatskih-mostova }}</ref>
The A9 route between Umag and Kanfanar, where the Mirna Bridge is located, was upgraded to motorway standards in June 2011.<ref name="Expansion of A9/B9">{{cite news | newspaper = Novi List | language = Croatian | url=http://novine.novilist.hr/default.asp?WCI=Rubrike&WCU=2859285C2863285E2863285A2858285928592863289628942898289428632863285D285E28582858285E285D28632863286328592863G | author = Darko Pajić | title = Ipsilon postaje autocesta |trans-title=The Y becomes a motorway | date = June 14, 2011 | accessdate = June 26, 2011}}</ref><ref name="A9 sections under construction">{{cite web | publisher = BINA Istra | url= http://www.bina-istra.com/Default.aspx?sid=1838 | title = Full profile motorway construction plan | accessdate = September 24, 2010 }}{{Dead link|date=April 2020 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> However, the works did not include construction of a parallel structure across the Mirna River which would carry the additional carriageway. Expansion of the bridge to a full motorway is planned to start in 2013 and be completed by 2015.<ref name="Expansion of Mirna">{{cite news | newspaper = Jutarnji list | language = Croatian |url = http://www.jutarnji.hr/istra-dobila-prve-kilometre-autoceste-i-prvu-naplatu-cestarine/840609/ | title = Istra dobila prve kilometre autoceste. I cestarinu također |trans-title=Istria gets the first kilometers of motorway. And the toll too. | author= Silvana Fable | date = June 20, 2010 | accessdate= September 24, 2010}}</ref>
==Description== thumb|left|250px|A view of the Mirna Bridge from the A9 motorwayThe deck structure stretches across 22 spans: {{convert|51.07|m|abbr=on}} + 15 x {{convert|66.5|m|abbr=on}} + {{convert|70.1|m|abbr=on}} + 2 x {{convert|50.01|m|abbr=on}} + {{convert|61.1|m|abbr=on}} + {{convert|42.6|m|abbr=on}} + {{convert|30.5|m|abbr=on}}. The design of the bridge was initially in {{convert|66.5|m|adj=on}} spans, but the final layout was imposed by the particular soil conditions and the arrangement of the river bed and canals below the bridge. Since the soil supporting the bridge foundations has exceptionally low load carrying capacity, it was important to reduce weight of the structure as much as possible. Therefore, the design employs two weight-reducing elements: longitudinal steel girders and piers with cap beams at varying heights. The latter reduces volume of concrete used for construction of the piers thereby reducing weight of the structure while giving the bridge a curved, concave deck.<ref name="Gradimo-Mirna"/>
The design of the pier foundations was further affected by the fact that the valley is a high quality agricultural area that had to be preserved as much as possible. The height of the reinforced concrete piers ranges from {{convert|13.45|m}} to {{convert|40.03|m}} and each of the piers is topped by a cap beam. The piers comprise an I-cross section with the webs aligned with the bridge axis. Peripheral piers (P1, P2, P20, P21) are executed on shallow foundations, while the remaining piers are executed on driven piles. The superstructure consists of two longitudinal prefabricated girders of constant depth set {{convert|550|cm}} apart made composite with the deck slab and cross-girders. Structurally, the superstructure is a {{convert|1354.86|m|adj=on}} long continuous girder across 22 spans, tracing a horizontal and a vertical curve. The cross section of the superstructure consists of two solid I-section steel girders of constant depth.<ref name="Građevinar-Mirna"/><ref name="Gradimo-Mirna"/><ref name="HAC-Monografijaautocesta">{{cite web | publisher = Hrvatske autoceste |url = http://www.hac.hr/brosure/monografija/virtualMagazine.html | title = Croatian Motorways, pp.409-410 | accessdate = May 17, 2010 | url-status = dead | archiveurl = https://web.archive.org/web/20100818140354/http://www.hac.hr/brosure/monografija/virtualMagazine.html | archivedate = August 18, 2010 }}</ref>
==Traffic volume== Traffic is regularly counted and reported by BINA Istra, the operator of the bridge and the A9 motorway where the bridge is located, and published by Hrvatske ceste.<ref name="HC-promet">{{cite web|publisher=Hrvatske ceste |url=http://www.hrvatske-ceste.hr/WEB%20-%20Legislativa/brojenje-prometa/CroDig2009.pdf |title=Traffic counting on the roadways of Croatia in 2009 - digest |date=May 1, 2010 |accessdate=September 24, 2010 |url-status=dead |archiveurl=https://web.archive.org/web/20110721100545/http://www.hrvatske-ceste.hr/WEB%20-%20Legislativa/brojenje-prometa/CroDig2009.pdf |archivedate=July 21, 2011 }}</ref> Substantial variations between annual (AADT) and summer (ASDT) traffic volumes are attributed to the fact that the bridge carries much tourist traffic to the Istrian Adriatic resorts. The traffic count is performed using analysis of motorway toll ticket sales.
{| class="wikitable" |- | colspan="5" style="text-align:center; background:#f2f2f2; margin-top:15;"| '''Mirna Bridge traffic volume''' |- style="text-align:center; background:#f2f2f2;" || '''Road''' || '''Counting site''' || '''AADT''' || '''ASDT''' || '''Notes''' |- | 25px A9 | 2722 Mirna toll plaza | align=center | 4,659 | align=center | 10,821 | Between Nova Vas and Višnjan interchanges; from 2009. |}
==See also== *List of bridges by length *A9 motorway
==References== {{Reflist}}
==External links== * {{Structurae|id=20008332|title=Mirna Bridge}}
Category:Plate girder bridges Category:Bridges completed in 2005 Category:Toll bridges in Croatia Category:Buildings and structures in Istria County