Seismic analysis of a district heating pipeline

ScienceDi ec A ailable online a www.sciencedi ec .com A ailable online a www.sciencedi ec .com ScienceDi ec Ene gy P ocedia 00 (2017) 000–000 www.else ie .com/loca e/p ocedia 1876-6102 © 2017The Au ho s. Published by Else ie L d. Pee - e iew unde esponsibili y o he Scien i ic Commi ee o The 15 h In e na ional Symposium on Dis ic Hea ing and Cooling. The 15 h In e na ional Symposium on Dis ic Hea ing and Cooling Assessing he easibili y o using he hea demand-ou doo empe a u e unc ion o a long- e m dis ic hea demand o ecas I. And ića,b,c*, A. Pinaa, P. Fe ãoa, J. Fou nie b., B. Laca iè ec, O. Le Co ec aIN+ Cen e o Inno a ion, Technology and Policy Resea ch -Ins i u o Supe io Técnico,A . Ro isco Pais 1, 1049-001 Lisbon, Po ugal bVeolia Reche che & Inno a ion,291 A enue D ey ous Daniel, 78520 Limay, F ance cDépa emen Sys èmes Éne gé iques e En i onnemen -IMT A lan ique, 4 ue Al ed Kas le , 44300 Nan es, F ance Abs ac Dis ic hea ing ne wo ks a e commonly add essed in he li e a u e as one o he mos e ec i e solu ions o dec easing he g eenhouse gas emissions om he building sec o . These sys ems equi e high in es men s which a e e u ned h ough he hea sales. Due o he changed clima e condi ions and building eno a ion policies, hea demand in he u u e could dec ease, p olonging he in es men e u n pe iod. The main scope o his pape is o assess he easibili y o using he hea demand –ou doo empe a u e unc ion o hea demand o ecas . The dis ic o Al alade, loca ed in Lisbon (Po ugal), was used as a case s udy. The dis ic is consis ed o 665 buildings ha a y in bo h cons uc ion pe iod and ypology. Th ee wea he scena ios (low, medium, high) and h ee dis ic eno a ion scena ios we e de eloped (shallow, in e media e, deep). To es ima e he e o , ob ained hea demand alues we e compa ed wi h esul s om a dynamic hea demand model, p e iously de eloped and alida ed by he au ho s. The esul s showed ha when only wea he change is conside ed, he ma gin o e o could be accep able o some applica ions ( he e o in annual demand was lowe han 20% o all wea he scena ios conside ed). Howe e , a e in oducing eno a ion scena ios, he e o alue inc eased up o 59.5% (depending on he wea he and eno a ion scena ios combina ion conside ed). The alue o slope coe icien inc eased on a e age wi hin he ange o 3.8% up o 8% pe decade, ha co esponds o he dec ease in he numbe o hea ing hou s o 22-139h du ing he hea ing season (depending on he combina ion o wea he and eno a ion scena ios conside ed). On he o he hand, unc ion in e cep inc eased o 7.8-12.7% pe decade (depending on he coupled scena ios). The alues sugges ed could be used o modi y he unc ion pa ame e s o he scena ios conside ed, and imp o e he accu acy o hea demand es ima ions. © 2017 The Au ho s. Published by Else ie L d. Pee - e iew unde esponsibili y o he Scien i ic Commi ee o The 15 h In e na ional Symposium on Dis ic Hea ing and Cooling. Keywo ds: Hea demand; Fo ecas ; Clima e change Ene gy P ocedia 149 (2018) 216–225 1876-6102 © 2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/) Selec ion and pee - e iew unde esponsibili y o he scien i ic commi ee o he 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018. 10.1016/j.egyp o.2018.08.186 10.1016/j.egyp o.2018.08.186 © 2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/) Selec ion and pee - e iew unde esponsibili y o he scien i ic commi ee o he 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018. 1876-6102 A ailable online a www.sciencedi ec .com ScienceDi ec Ene gy P ocedia 00 (2018) 000–000 www.else ie .com/loca e/p ocedia 1876-6102 © 2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/) Selec ion and pee - e iew unde esponsibili y o he scien i ic commi ee o he 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018. 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018, 9–12 Sep embe 2018, Hambu g, Ge many Seismic analysis o a dis ic hea ing pipeline Ge sena Banushia*, Ingo Weidlicha aHa enCi y Uni e si y, Übe seesallee 16, Hambu g, 20457, Ge many Abs ac The e ec o seismic loading is no con empla ed in any o he cu en design s anda ds o Dis ic Hea ing and Cooling (DHC) ne wo ks, since his echnology has been o iginally adop ed in no he n Eu ope, cha ac e ized by low ea hquake ulne abili y. Ne e heless, an inc easing numbe o coun ies, including hose in seismic a eas like I aly, Tu key, China, Japan, and Chile a e using DHC solu ions due o he highe ene gy e iciency, compa ed o indi idual hea ing sys ems. Seismic egions a e one o he mos hos ile en i onmen s o bu ied pipelines due o he e ec s o T ansien G ound De o ma ion (TGD) caused by seismic wa e p opaga ion, and Pe manen G ound De o ma ion (PGD), like aul ing, landsliding, la e al sp eading and buoyancy due o lique ac ion. Mos o esea ch publica ions on he seismic analysis and design o bu ied s eel pipelines ha e been mo i a ed by he need o sa egua ding he in eg i y o hyd oca bon pipelines, and he e a e no ac ual s udies on he seismic ulne abili y o DHC pipelines. This highligh s he need o ca e ully e alua e he seismic pe o mance o DHC pipelines, conside ing hei ypical composi e c oss-sec ion and soil-pipe in e ac ion unde se ice loading. The p esen pape analyses he e ec o di e se ea hquake haza ds on an ope a ing Dis ic Hea ing (DH) pipe bend, usually suscep ible o s ess concen a ions due o he g ea e lexibili y, as well as he abili y o accommoda e he mal expansions, and abso b o he ex e nally-induced loading. The esponse o he ope a ing DH pipeline subjec ed o di e en seismic loading is e alua ed aking in o accoun he geome ic and mechanical p ope ies o he sys em, including he soil-pipeline in e ac ion. In conclusion, he ob ained esul s gi e a be e unde s anding on he seismic beha io o DH pipelines, highligh ing impo an esea ch g ound o assessing hei ea hquake pe o mance in ope a ing condi ions. © 2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/) Selec ion and pee - e iew unde esponsibili y o he scien i ic commi ee o he 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018. Keywo ds: Seismic analysis; T ansien G ound De o ma ion; Pe manen G ound De o ma ion; Dis ic Hea ing Pipeline * Co esponding au ho E-mail add ess: [email p o ec ed] A ailable online a www.sciencedi ec .com ScienceDi ec Ene gy P ocedia 00 (2018) 000–000 www.else ie .com/loca e/p ocedia 1876-6102 © 2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/) Selec ion and pee - e iew unde esponsibili y o he scien i ic commi ee o he 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018. 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018, 9–12 Sep embe 2018, Hambu g, Ge many Seismic analysis o a dis ic hea ing pipeline Ge sena Banushia*, Ingo Weidlicha aHa enCi y Uni e si y, Übe seesallee 16, Hambu g, 20457, Ge many Abs ac The e ec o seismic loading is no con empla ed in any o he cu en design s anda ds o Dis ic Hea ing and Cooling (DHC) ne wo ks, since his echnology has been o iginally adop ed in no he n Eu ope, cha ac e ized by low ea hquake ulne abili y. Ne e heless, an inc easing numbe o coun ies, including hose in seismic a eas like I aly, Tu key, China, Japan, and Chile a e using DHC solu ions due o he highe ene gy e iciency, compa ed o indi idual hea ing sys ems. Seismic egions a e one o he mos hos ile en i onmen s o bu ied pipelines due o he e ec s o T ansien G ound De o ma ion (TGD) caused by seismic wa e p opaga ion, and Pe manen G ound De o ma ion (PGD), like aul ing, landsliding, la e al sp eading and buoyancy due o lique ac ion. Mos o esea ch publica ions on he seismic analysis and design o bu ied s eel pipelines ha e been mo i a ed by he need o sa egua ding he in eg i y o hyd oca bon pipelines, and he e a e no ac ual s udies on he seismic ulne abili y o DHC pipelines. This highligh s he need o ca e ully e alua e he seismic pe o mance o DHC pipelines, conside ing hei ypical composi e c oss-sec ion and soil-pipe in e ac ion unde se ice loading. The p esen pape analyses he e ec o di e se ea hquake haza ds on an ope a ing Dis ic Hea ing (DH) pipe bend, usually suscep ible o s ess concen a ions due o he g ea e lexibili y, as well as he abili y o accommoda e he mal expansions, and abso b o he ex e nally-induced loading. The esponse o he ope a ing DH pipeline subjec ed o di e en seismic loading is e alua ed aking in o accoun he geome ic and mechanical p ope ies o he sys em, including he soil-pipeline in e ac ion. In conclusion, he ob ained esul s gi e a be e unde s anding on he seismic beha io o DH pipelines, highligh ing impo an esea ch g ound o assessing hei ea hquake pe o mance in ope a ing condi ions. © 2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/) Selec ion and pee - e iew unde esponsibili y o he scien i ic commi ee o he 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018. Keywo ds: Seismic analysis; T ansien G ound De o ma ion; Pe manen G ound De o ma ion; Dis ic Hea ing Pipeline * Co esponding au ho E-mail add ess: ge [email protected] 2 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 1. In oduc ion Dis ic Hea ing and Cooling (DHC) consis o an unde g ound pipe ne wo k connec ing buildings in an u ban a ea o cen alized plan s o a numbe o dis ibu ed hea p oducing uni s, allowing o hea ecycling and enewable ene gy supply. Due o he highe ene gy e iciency, an inc easing numbe o coun ies including hose in seismic a eas like I aly, Tu key, China, Japan, a e adop ing dis ic hea ing solu ions. The e ec o seismic loading is no con empla ed in any o he cu en design s anda ds o DH ne wo ks, since his echnology has been o iginally adop ed in no he n Eu opean coun ies, cha ac e ized by low ea hquake ulne abili y. Seismic egions a e one o he mos hos ile en i onmen s o bu ied pipelines due o he e ec s o T ansien G ound De o ma ion (TGD) caused by seismic wa e p opaga ion, and Pe manen G ound De o ma ion (PGD), like aul ing, landsliding, la e al sp eading and buoyancy due o lique ac ion [1]. Mos o esea ch publica ions on he seismic analysis and design o bu ied s eel pipelines ha e been mo i a ed by he need o sa egua ding he in eg i y o hyd oca bon pipelines [2], and he e a e no ac ual s udies on he seismic ulne abili y o DHC pipelines. This highligh s he need o ca e ully e alua e he seismic pe o mance o DHC pipelines, conside ing hei ypical composi e c oss-sec ion and soil-pipe in e ac ion unde se ice loading. To minimize hea losses, DHC pipes ha e a composi e c oss-sec ion o h ee di e en ma e ial laye s, including he s eel pipe o he wa e supply, he insula ion oam o polyu e hane (PUR), and an ou e coa ing o High Densi y Polye hylene (HDPE), in e ac ing wi h he su ounding soil. The s i ness o he PUR oam and i s cons an adhesion o he s eel pipe a e essen ial o p ope ly ansmi a he HDPE coa ing he ic ion s esses om he su ounding soil. The axial expansion o he ope a ing pipeline, is coun e ac ed by he soil ic ion a he ou e HDPE coa ing in e ace, un il he o al ic ion eac ion equilib a es he pipe axial o ce a he ancho poin , whe e he he mal expansion is ully es ained. Mo eo e , he he mal expansion is coun e ac ed a he bend by he la e al soil eac ion, inducing high s ess le els in his c i ical egion, as schema ically illus a ed in Fig. 1. Addi ionally, he PUR insula ion is e y sensi i e o axial shea s ess and la e al p essu es, inducing high s esses associa ed wi h ma e ial ailu e and loss o he bond; in a wo se case, i can lose i s insula ion e ec i he s eel se ice pipe c acks and he oam is mois u ed. [3]. Fig. 1. De o ma ion o bu ied ope a ing DH pipeline a he bend (adap ed om [4] and [5]) The e o e, a co ec design o DHC pipelines equi es an accu a e conside a ion o he ele a ed s esses and de o ma ions due o he ope a ing loads like in e nal p essu e and empe a u e, as well as he e alua ion o he soil- pipeline in e ac ion. Ge sena Banushi e al. / Ene gy P ocedia 149 (2018) 216–225 217 A ailable online a www.sciencedi ec .com ScienceDi ec Ene gy P ocedia 00 (2018) 000–000 www.else ie .com/loca e/p ocedia 1876-6102 © 2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/) Selec ion and pee - e iew unde esponsibili y o he scien i ic commi ee o he 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018. 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018, 9–12 Sep embe 2018, Hambu g, Ge many Seismic analysis o a dis ic hea ing pipeline Ge sena Banushia*, Ingo Weidlicha aHa enCi y Uni e si y, Übe seesallee 16, Hambu g, 20457, Ge many Abs ac The e ec o seismic loading is no con empla ed in any o he cu en design s anda ds o Dis ic Hea ing and Cooling (DHC) ne wo ks, since his echnology has been o iginally adop ed in no he n Eu ope, cha ac e ized by low ea hquake ulne abili y. Ne e heless, an inc easing numbe o coun ies, including hose in seismic a eas like I aly, Tu key, China, Japan, and Chile a e using DHC solu ions due o he highe ene gy e iciency, compa ed o indi idual hea ing sys ems. Seismic egions a e one o he mos hos ile en i onmen s o bu ied pipelines due o he e ec s o T ansien G ound De o ma ion (TGD) caused by seismic wa e p opaga ion, and Pe manen G ound De o ma ion (PGD), like aul ing, landsliding, la e al sp eading and buoyancy due o lique ac ion. Mos o esea ch publica ions on he seismic analysis and design o bu ied s eel pipelines ha e been mo i a ed by he need o sa egua ding he in eg i y o hyd oca bon pipelines, and he e a e no ac ual s udies on he seismic ulne abili y o DHC pipelines. This highligh s he need o ca e ully e alua e he seismic pe o mance o DHC pipelines, conside ing hei ypical composi e c oss-sec ion and soil-pipe in e ac ion unde se ice loading. The p esen pape analyses he e ec o di e se ea hquake haza ds on an ope a ing Dis ic Hea ing (DH) pipe bend, usually suscep ible o s ess concen a ions due o he g ea e lexibili y, as well as he abili y o accommoda e he mal expansions, and abso b o he ex e nally-induced loading. The esponse o he ope a ing DH pipeline subjec ed o di e en seismic loading is e alua ed aking in o accoun he geome ic and mechanical p ope ies o he sys em, including he soil-pipeline in e ac ion. In conclusion, he ob ained esul s gi e a be e unde s anding on he seismic beha io o DH pipelines, highligh ing impo an esea ch g ound o assessing hei ea hquake pe o mance in ope a ing condi ions. © 2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/) Selec ion and pee - e iew unde esponsibili y o he scien i ic commi ee o he 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018. Keywo ds: Seismic analysis; T ansien G ound De o ma ion; Pe manen G ound De o ma ion; Dis ic Hea ing Pipeline * Co esponding au ho E-mail add ess: [email p o ec ed] A ailable online a www.sciencedi ec .com ScienceDi ec Ene gy P ocedia 00 (2018) 000–000 www.else ie .com/loca e/p ocedia 1876-6102 © 2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/) Selec ion and pee - e iew unde esponsibili y o he scien i ic commi ee o he 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018. 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018, 9–12 Sep embe 2018, Hambu g, Ge many Seismic analysis o a dis ic hea ing pipeline Ge sena Banushia*, Ingo Weidlicha aHa enCi y Uni e si y, Übe seesallee 16, Hambu g, 20457, Ge many Abs ac The e ec o seismic loading is no con empla ed in any o he cu en design s anda ds o Dis ic Hea ing and Cooling (DHC) ne wo ks, since his echnology has been o iginally adop ed in no he n Eu ope, cha ac e ized by low ea hquake ulne abili y. Ne e heless, an inc easing numbe o coun ies, including hose in seismic a eas like I aly, Tu key, China, Japan, and Chile a e using DHC solu ions due o he highe ene gy e iciency, compa ed o indi idual hea ing sys ems. Seismic egions a e one o he mos hos ile en i onmen s o bu ied pipelines due o he e ec s o T ansien G ound De o ma ion (TGD) caused by seismic wa e p opaga ion, and Pe manen G ound De o ma ion (PGD), like aul ing, landsliding, la e al sp eading and buoyancy due o lique ac ion. Mos o esea ch publica ions on he seismic analysis and design o bu ied s eel pipelines ha e been mo i a ed by he need o sa egua ding he in eg i y o hyd oca bon pipelines, and he e a e no ac ual s udies on he seismic ulne abili y o DHC pipelines. This highligh s he need o ca e ully e alua e he seismic pe o mance o DHC pipelines, conside ing hei ypical composi e c oss-sec ion and soil-pipe in e ac ion unde se ice loading. The p esen pape analyses he e ec o di e se ea hquake haza ds on an ope a ing Dis ic Hea ing (DH) pipe bend, usually suscep ible o s ess concen a ions due o he g ea e lexibili y, as well as he abili y o accommoda e he mal expansions, and abso b o he ex e nally-induced loading. The esponse o he ope a ing DH pipeline subjec ed o di e en seismic loading is e alua ed aking in o accoun he geome ic and mechanical p ope ies o he sys em, including he soil-pipeline in e ac ion. In conclusion, he ob ained esul s gi e a be e unde s anding on he seismic beha io o DH pipelines, highligh ing impo an esea ch g ound o assessing hei ea hquake pe o mance in ope a ing condi ions. © 2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY-NC-ND license (h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/) Selec ion and pee - e iew unde esponsibili y o he scien i ic commi ee o he 16 h In e na ional Symposium on Dis ic Hea ing and Cooling, DHC2018. Keywo ds: Seismic analysis; T ansien G ound De o ma ion; Pe manen G ound De o ma ion; Dis ic Hea ing Pipeline * Co esponding au ho E-mail add ess: ge [email protected] 2 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 1. In oduc ion Dis ic Hea ing and Cooling (DHC) consis o an unde g ound pipe ne wo k connec ing buildings in an u ban a ea o cen alized plan s o a numbe o dis ibu ed hea p oducing uni s, allowing o hea ecycling and enewable ene gy supply. Due o he highe ene gy e iciency, an inc easing numbe o coun ies including hose in seismic a eas like I aly, Tu key, China, Japan, a e adop ing dis ic hea ing solu ions. The e ec o seismic loading is no con empla ed in any o he cu en design s anda ds o DH ne wo ks, since his echnology has been o iginally adop ed in no he n Eu opean coun ies, cha ac e ized by low ea hquake ulne abili y. Seismic egions a e one o he mos hos ile en i onmen s o bu ied pipelines due o he e ec s o T ansien G ound De o ma ion (TGD) caused by seismic wa e p opaga ion, and Pe manen G ound De o ma ion (PGD), like aul ing, landsliding, la e al sp eading and buoyancy due o lique ac ion [1]. Mos o esea ch publica ions on he seismic analysis and design o bu ied s eel pipelines ha e been mo i a ed by he need o sa egua ding he in eg i y o hyd oca bon pipelines [2], and he e a e no ac ual s udies on he seismic ulne abili y o DHC pipelines. This highligh s he need o ca e ully e alua e he seismic pe o mance o DHC pipelines, conside ing hei ypical composi e c oss-sec ion and soil-pipe in e ac ion unde se ice loading. To minimize hea losses, DHC pipes ha e a composi e c oss-sec ion o h ee di e en ma e ial laye s, including he s eel pipe o he wa e supply, he insula ion oam o polyu e hane (PUR), and an ou e coa ing o High Densi y Polye hylene (HDPE), in e ac ing wi h he su ounding soil. The s i ness o he PUR oam and i s cons an adhesion o he s eel pipe a e essen ial o p ope ly ansmi a he HDPE coa ing he ic ion s esses om he su ounding soil. The axial expansion o he ope a ing pipeline, is coun e ac ed by he soil ic ion a he ou e HDPE coa ing in e ace, un il he o al ic ion eac ion equilib a es he pipe axial o ce a he ancho poin , whe e he he mal expansion is ully es ained. Mo eo e , he he mal expansion is coun e ac ed a he bend by he la e al soil eac ion, inducing high s ess le els in his c i ical egion, as schema ically illus a ed in Fig. 1. Addi ionally, he PUR insula ion is e y sensi i e o axial shea s ess and la e al p essu es, inducing high s esses associa ed wi h ma e ial ailu e and loss o he bond; in a wo se case, i can lose i s insula ion e ec i he s eel se ice pipe c acks and he oam is mois u ed. [3]. Fig. 1. De o ma ion o bu ied ope a ing DH pipeline a he bend (adap ed om [4] and [5]) The e o e, a co ec design o DHC pipelines equi es an accu a e conside a ion o he ele a ed s esses and de o ma ions due o he ope a ing loads like in e nal p essu e and empe a u e, as well as he e alua ion o he soil- pipeline in e ac ion. 218 Ge sena Banushi e al. / Ene gy P ocedia 149 (2018) 216–225 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 3 Repo ed expe imen al esea ch on he esponse o bu ied DH pipe sys ems subjec ed o g ound mo emen is e y limi ed, equi ing u he analysis o he soil-pipe in e ac ion o bu ied DH pipes, while aking in o accoun eal ope a ing condi ions and mode n pipe laying echnologies [6-10]. On he o he hand, he seismic esponse o bu ied pipelines has been in es iga ed by many esea che s in he las 50 yea s, using expe imen al in es iga ions as well as simple analy ical o mo e complex nume ical app oaches [11-17]. Du ing ex eme e en s like ea hquakes, he pipeline needs o plas ically s e ch, bend and comp ess in o de o accommoda e local o global mo emen o he su ounding soil, equi ing s ain-based pe o mance c i e ia o a sa e and cos -e ec i e pipeline design [18-19]. E iden ly, s ess-based pe o mance limi s a es, like hose ecommended in Eu opean s anda d EN 13941 [20] o in he Eu ocode 3 - Pa 4-3 [21] a e o e conse a i e o pipelines cons uc ed in ha sh en i onmen s, like seismic egions. The p esen pape analyses he e ec o seismic induced g ound mo emen on an ope a ing Dis ic Hea ing (DH) pipe bend, ypically suscep ible o highes momen s and s ess concen a ions due o he g ea e lexibili y, as well as he abili y o accommoda e he mal expansions, and abso b o he ex e nally-induced loading. [22]. The esponse o he ope a ing DH pipeline subjec ed o seismic loading is e alua ed aking in o accoun he geome ic and mechanical p ope ies o he sys em, including he soil-pipeline in e ac ion. In conclusion, he ob ained esul s gi e a be e unde s anding on he seismic beha iou o DH pipelines, highligh ing impo an esea ch g ound o assessing hei ea hquake pe o mance in ope a ing condi ions. Nomencla u e Ds ou e diame e o he s eel pipe s hickness o he s eel pipe D ou e diame e o ex e nal HDPE coa ing PUR hickness o he PUR insula ion Rbend adius o he pipe bend L leng h o he pipe legs Lc leng h o he expansion cushion a each bend leg H soil co e dep h E elas ici y modulus o he s eel pipe ν Poisson's a io o he s eel pipe σ y yield s eng h he s eel pipe α linea he mal expansion coe icien o he s eel pipe φ soil ic ion angle γ soil densi y Ti, T ins alla ion and ope a ing empe a u e Pi, ope a ing in e nal p essu e in he s eel pipe Ug, ε g, λ g ea hquake induced g ound displacemen , g ound s ain, and seismic wa e leng h FR soil ic ion eac ion Pu maximum la e al soil eac ion k elas ic la e al soil s i ness kc equi alen la e al s i ness in he pipe co ne wi h expansion cushion My yielding momen o he s eel pipe sec ion 2. Me hodology This pape in es iga es he pe o mance o p einsula ed bonded DH pipelines, subjec ed o TGD due o seismic wa e p opaga ion. Clea ly, his haza d a ec s DH ne wo ks, conside ably mo e han does PGD, h ea ening mainly ansmission hyd oca bon pipelines. 4 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 The in es iga ed pipe bend DN 150/250 is composed o a cen al P235GH s eel pipe o ex e nal diame e Ds = 168.3 mm and hickness s = 4 mm, a oam insula ion o hickness PUR = 37 mm, and ex e nal plas ic man le wi h ou e diame e D = 250 mm. The adius o he pipe bend is Rbend = 1 m, he leng h o he expansion cushion a he co ne is Lc = 2 m, while he leng h o bo h bend legs is L = 40 m, ancho ed a he ends. The pipe is assumed bu ied in loose sand soil wi h a co e dep h H = 0.8 m, as schema ically illus a ed in Fig. 1. The soil-pipeline sys em subjec ed o seismic loading has been analyzed nume ically wi hin beam on Winkle ounda ion heo y, using he ini e elemen so wa e ABAQUS/S anda d [23]. The pipeline is modeled using he PIPE31 beam elemen ype, allowing he possibili y o speci y ex e nal o in e nal p essu e. The soil-pipeline in e ac ion is modeled wi h he sp ing-like pipe-soil in e ac ion elemen s PSI34, ep esen ing he soil eac ion o he soil mo emen in he axial, la e al, and e ical di ec ion. One edge o he elemen sha es nodes wi h he unde lying pipe elemen while he nodes on he o he edge a e assigned he a - ield g ound mo ion h ough he bounda y condi ions. The P235GH s eel pipe ma e ial model is de ined wi hin he on Mises plas ici y heo y wi h nonlinea ha dening. The ma e ial pa ame e s a e de e mined as a unc ion o he ope a ing empe a u e T, acco ding o EN 13941 [19]. The elas ici y modulus, yield s eng h, and he linea he mal expansion coe icien a he ope a ing empe a u e T = 90°C a e E = 208857 MPa , σ y = 215.8 MPa and α = 12.098 10-06 1/K espec i ely, while he Poisson's a io is ν = 0.3. A loose sand ma e ial is assumed as soil back ill, wi h he same p ope ies epo ed in he calcula ion example o he Ge man s anda d FW 401 [4], cha ac e ized by a ic ion angle φ = 32.5°, and a soil densi y γ = 18 kN/m3. The o ce-displacemen ela ionship is conside ed bilinea elas o-plas ic, and e alua ed acco ding o FW 401 [5]. Speci ically, he calcula ed soil ic ion eac ion is FR = 3944 N/m, while he maximum la e al soil eac ion is Pu = 49750 N/m, wi h an elas ic la e al soil s i ness k = 35 MPa beyond he expansion cushion, whe e he equi alen elas ic la e al s i ness is kc = 0.247 MPa [5]. The seismic-induced g ound mo emen is applied a he ee nodes o he pipe-soil in e ac ion elemen s, as a sinusoidal wa e p opaga ing ho izon ally in he di ec ion o he longi udinal leg. The nume ical analysis o assessing he seismic pe o mance o he ope a ing DH pipeline a e conduc ed in wo consecu i e s eps. A i s , a s a ic analysis is pe o med o es ablish he s ess and s ain s a e in he soil-pipeline sys em in ope a ing condi ions wi h in e nal p essu e Pi = 12 Ba , ins alla ion and se ice empe a u e Ti = 10°C and T = 90°C, espec i ely. In he second s ep, a ho izon al displacemen is applied quasi-s a ically a he ee nodes ends o he pipe-soil in e ac ion elemen s, ma ching he sinusoidal pa e n de ined by: ( ) ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = λ π π λ ε y xU g gg 2 sin 2 (1) whe e εg = 0.0041 is he soil s ain and λ = 500 m is he seismic wa e leng h. Thus, he maximum alue o he g ound displacemen esul s Ug = 0.33 m On each loading s ep, he global equilib ium equa ions a e sol ed i e a i ely by he New on-Raphson me hod pe mi ing o assess he pipe and soil de o ma ion s a e a each inc emen . 3. Resul s and discussion This sec ion p esen s he s uc u al esponse o he bu ied DH pipeline e alua ed using he p oposed me hodology. Fi s ly, he pipeline esponse is in es iga ed in ope a ing condi ions, unde he e ec o in e nal p essu e and empe a u e a ia ion. Then he seismic pe o mance o he pipeline is analyzed in e ms o loading and de o ma ions, o di e en alues o he maximum seismic-induced g ound displacemen Ug, as discussed u he in his sec ion. 3.1. S uc u al esponse o he pipeline in ope a ing condi ions The expansion o he ope a ing pipeline is coun e ac ed by he bene icial e ec o he soil ic ion, and he bea ing o ce on he ans e se leg (Fig. 1). The maximum axial elonga ion o he pipeline in ope a ion condi ions, Ge sena Banushi e al. / Ene gy P ocedia 149 (2018) 216–225 219 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 3 Repo ed expe imen al esea ch on he esponse o bu ied DH pipe sys ems subjec ed o g ound mo emen is e y limi ed, equi ing u he analysis o he soil-pipe in e ac ion o bu ied DH pipes, while aking in o accoun eal ope a ing condi ions and mode n pipe laying echnologies [6-10]. On he o he hand, he seismic esponse o bu ied pipelines has been in es iga ed by many esea che s in he las 50 yea s, using expe imen al in es iga ions as well as simple analy ical o mo e complex nume ical app oaches [11-17]. Du ing ex eme e en s like ea hquakes, he pipeline needs o plas ically s e ch, bend and comp ess in o de o accommoda e local o global mo emen o he su ounding soil, equi ing s ain-based pe o mance c i e ia o a sa e and cos -e ec i e pipeline design [18-19]. E iden ly, s ess-based pe o mance limi s a es, like hose ecommended in Eu opean s anda d EN 13941 [20] o in he Eu ocode 3 - Pa 4-3 [21] a e o e conse a i e o pipelines cons uc ed in ha sh en i onmen s, like seismic egions. The p esen pape analyses he e ec o seismic induced g ound mo emen on an ope a ing Dis ic Hea ing (DH) pipe bend, ypically suscep ible o highes momen s and s ess concen a ions due o he g ea e lexibili y, as well as he abili y o accommoda e he mal expansions, and abso b o he ex e nally-induced loading. [22]. The esponse o he ope a ing DH pipeline subjec ed o seismic loading is e alua ed aking in o accoun he geome ic and mechanical p ope ies o he sys em, including he soil-pipeline in e ac ion. In conclusion, he ob ained esul s gi e a be e unde s anding on he seismic beha iou o DH pipelines, highligh ing impo an esea ch g ound o assessing hei ea hquake pe o mance in ope a ing condi ions. Nomencla u e Ds ou e diame e o he s eel pipe s hickness o he s eel pipe D ou e diame e o ex e nal HDPE coa ing PUR hickness o he PUR insula ion Rbend adius o he pipe bend L leng h o he pipe legs Lc leng h o he expansion cushion a each bend leg H soil co e dep h E elas ici y modulus o he s eel pipe ν Poisson's a io o he s eel pipe σ y yield s eng h he s eel pipe α linea he mal expansion coe icien o he s eel pipe φ soil ic ion angle γ soil densi y Ti, T ins alla ion and ope a ing empe a u e Pi, ope a ing in e nal p essu e in he s eel pipe Ug, ε g, λ g ea hquake induced g ound displacemen , g ound s ain, and seismic wa e leng h FR soil ic ion eac ion Pu maximum la e al soil eac ion k elas ic la e al soil s i ness kc equi alen la e al s i ness in he pipe co ne wi h expansion cushion My yielding momen o he s eel pipe sec ion 2. Me hodology This pape in es iga es he pe o mance o p einsula ed bonded DH pipelines, subjec ed o TGD due o seismic wa e p opaga ion. Clea ly, his haza d a ec s DH ne wo ks, conside ably mo e han does PGD, h ea ening mainly ansmission hyd oca bon pipelines. 4 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 The in es iga ed pipe bend DN 150/250 is composed o a cen al P235GH s eel pipe o ex e nal diame e Ds = 168.3 mm and hickness s = 4 mm, a oam insula ion o hickness PUR = 37 mm, and ex e nal plas ic man le wi h ou e diame e D = 250 mm. The adius o he pipe bend is Rbend = 1 m, he leng h o he expansion cushion a he co ne is Lc = 2 m, while he leng h o bo h bend legs is L = 40 m, ancho ed a he ends. The pipe is assumed bu ied in loose sand soil wi h a co e dep h H = 0.8 m, as schema ically illus a ed in Fig. 1. The soil-pipeline sys em subjec ed o seismic loading has been analyzed nume ically wi hin beam on Winkle ounda ion heo y, using he ini e elemen so wa e ABAQUS/S anda d [23]. The pipeline is modeled using he PIPE31 beam elemen ype, allowing he possibili y o speci y ex e nal o in e nal p essu e. The soil-pipeline in e ac ion is modeled wi h he sp ing-like pipe-soil in e ac ion elemen s PSI34, ep esen ing he soil eac ion o he soil mo emen in he axial, la e al, and e ical di ec ion. One edge o he elemen sha es nodes wi h he unde lying pipe elemen while he nodes on he o he edge a e assigned he a - ield g ound mo ion h ough he bounda y condi ions. The P235GH s eel pipe ma e ial model is de ined wi hin he on Mises plas ici y heo y wi h nonlinea ha dening. The ma e ial pa ame e s a e de e mined as a unc ion o he ope a ing empe a u e T, acco ding o EN 13941 [19]. The elas ici y modulus, yield s eng h, and he linea he mal expansion coe icien a he ope a ing empe a u e T = 90°C a e E = 208857 MPa , σ y = 215.8 MPa and α = 12.098 10-06 1/K espec i ely, while he Poisson's a io is ν = 0.3. A loose sand ma e ial is assumed as soil back ill, wi h he same p ope ies epo ed in he calcula ion example o he Ge man s anda d FW 401 [4], cha ac e ized by a ic ion angle φ = 32.5°, and a soil densi y γ = 18 kN/m3. The o ce-displacemen ela ionship is conside ed bilinea elas o-plas ic, and e alua ed acco ding o FW 401 [5]. Speci ically, he calcula ed soil ic ion eac ion is FR = 3944 N/m, while he maximum la e al soil eac ion is Pu = 49750 N/m, wi h an elas ic la e al soil s i ness k = 35 MPa beyond he expansion cushion, whe e he equi alen elas ic la e al s i ness is kc = 0.247 MPa [5]. The seismic-induced g ound mo emen is applied a he ee nodes o he pipe-soil in e ac ion elemen s, as a sinusoidal wa e p opaga ing ho izon ally in he di ec ion o he longi udinal leg. The nume ical analysis o assessing he seismic pe o mance o he ope a ing DH pipeline a e conduc ed in wo consecu i e s eps. A i s , a s a ic analysis is pe o med o es ablish he s ess and s ain s a e in he soil-pipeline sys em in ope a ing condi ions wi h in e nal p essu e Pi = 12 Ba , ins alla ion and se ice empe a u e Ti = 10°C and T = 90°C, espec i ely. In he second s ep, a ho izon al displacemen is applied quasi-s a ically a he ee nodes ends o he pipe-soil in e ac ion elemen s, ma ching he sinusoidal pa e n de ined by: ( ) ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = λ π π λ ε y xU g gg 2 sin 2 (1) whe e εg = 0.0041 is he soil s ain and λ = 500 m is he seismic wa e leng h. Thus, he maximum alue o he g ound displacemen esul s Ug = 0.33 m On each loading s ep, he global equilib ium equa ions a e sol ed i e a i ely by he New on-Raphson me hod pe mi ing o assess he pipe and soil de o ma ion s a e a each inc emen . 3. Resul s and discussion This sec ion p esen s he s uc u al esponse o he bu ied DH pipeline e alua ed using he p oposed me hodology. Fi s ly, he pipeline esponse is in es iga ed in ope a ing condi ions, unde he e ec o in e nal p essu e and empe a u e a ia ion. Then he seismic pe o mance o he pipeline is analyzed in e ms o loading and de o ma ions, o di e en alues o he maximum seismic-induced g ound displacemen Ug, as discussed u he in his sec ion. 3.1. S uc u al esponse o he pipeline in ope a ing condi ions The expansion o he ope a ing pipeline is coun e ac ed by he bene icial e ec o he soil ic ion, and he bea ing o ce on he ans e se leg (Fig. 1). The maximum axial elonga ion o he pipeline in ope a ion condi ions, 220 Ge sena Banushi e al. / Ene gy P ocedia 149 (2018) 216–225 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 5 calcula ed nume ically (31.1 mm) is consis en wi h he heo e ical alue o he maximum axial elonga ion umax, acco ding o he o mula epo ed in he s anda ds FW 401 [5] and EN 13941 [20]: mmL EA F L DP EA Tu s R s si s T29.4 10 7 4 )21( 2 max ≈⋅ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛⋅−⋅ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛− +Δ= ν α (2) Clea ly, he i s addend in Eq. (2) indica es he pipeline expansion due o he posi i e empe a u e a ia ion Δ T = 80°C, and in e nal p essu e Pi = 12 Ba , while he second nega i e e m ep esen s he pipeline con ac ion due o he soil esis ance a he ou e HDPE coa ing. The a o emen ioned alues o he maximum axial elonga ion a e consis en wi h he es ima ions using he me hod p oposed in [22, 24-26], conside ing he bend ei he igid (30.8 mm) o lexible (31.4 mm). The pipeline esponse in e ms o longi udinal de o ma ions does depend on he geome ical and mechanical pa ame e s o he sys em, like he ope a ing empe a u e T , he pipe leng h L, and he bend adius Rbend. Clea ly, he maximum longi udinal s ain in ope a ing condi ions occu s a he elbow ( ε max = 0.42%, o T = 90°C, L = 40 m and Rbend = 1 m). A small pa ame ic s udy has shown ha he pipeline de o ma ion is accen ua ed o g ea e ope a ing empe a u es ( ε max = 1.03%, o T = 130°C), la ge pipe leng h ( ε max = 0.91%, L = 80 m), smalle bending adius ( ε max = 0.68%, o Rbend = 0.5 m), all o he pa ame e s emaining he same, as shown in Fig. 2. These c i ical ac o s need o be ca e ully e alua ed in he design phase in o de o a oid excessi e s ess-s ain concen a ion in he ope a ing pipeline, associa ed wi h ma e ial damage. Fig. 2. Longi udinal s ain con ou and de o med shape o pipeline a he bend egion, unde ope a ing condi ions, o di e en alues o he sys em pa ame e s: a) T = 90°C, L = 40 m, Rbend = 1 m; b) T = 130°C, L = 40 m, Rbend = 1 m; c) T = 90°C, L = 80 m, Rbend = 1 m; d) T = 90°C, L = 40 m, Rbend = 0.5 m. E iden ly, he axial o ce in ope a ing condi ions is comp essi e and in he elas ic ange, wi h i s magni ude inc easing linea ly along he pipeline om he bend egion owa ds he ancho poin s, whe e i eaches i s maximum 6 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 alue (162507 N). The obse ed linea a ia ion o he axial o ce beyond he bend egion is caused by he cons an soil ic ion (FR = 3944 N/m) opposing he he mal expansion. Ins ead, close o he bend, he pipe axial o ce dec eases due o he bea ing o ce on he ans e se leg (Fig. 3a). Con e sely, he bending momen unde se ice loads is maximum a he bend (22163 Nm), exceeding he yielding momen o he pipe sec ion (My = 18804 Nm), associa ed wi h plas ic bending s ains (Fig. 4), leading o comp essi e plas ic longi udinal s ains (-0.3%). The la e mus be ca e ully e i ied in o de o p e en he onse o local buckling limi s a e in he ope a ing pipeline. Fig. 3 Va ia ion o he loads along he pipeline axis o di e en alues o he g ound displacemen Ug: a) axial o ce; b) shea o ce; c) bending momen . Ge sena Banushi e al. / Ene gy P ocedia 149 (2018) 216–225 221 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 5 calcula ed nume ically (31.1 mm) is consis en wi h he heo e ical alue o he maximum axial elonga ion umax, acco ding o he o mula epo ed in he s anda ds FW 401 [5] and EN 13941 [20]: mmL EA F L DP EA Tu s R s si s T29.4 10 7 4 )21( 2 max ≈⋅ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛⋅−⋅ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛− +Δ= ν α (2) Clea ly, he i s addend in Eq. (2) indica es he pipeline expansion due o he posi i e empe a u e a ia ion Δ T = 80°C, and in e nal p essu e Pi = 12 Ba , while he second nega i e e m ep esen s he pipeline con ac ion due o he soil esis ance a he ou e HDPE coa ing. The a o emen ioned alues o he maximum axial elonga ion a e consis en wi h he es ima ions using he me hod p oposed in [22, 24-26], conside ing he bend ei he igid (30.8 mm) o lexible (31.4 mm). The pipeline esponse in e ms o longi udinal de o ma ions does depend on he geome ical and mechanical pa ame e s o he sys em, like he ope a ing empe a u e T , he pipe leng h L, and he bend adius Rbend. Clea ly, he maximum longi udinal s ain in ope a ing condi ions occu s a he elbow ( ε max = 0.42%, o T = 90°C, L = 40 m and Rbend = 1 m). A small pa ame ic s udy has shown ha he pipeline de o ma ion is accen ua ed o g ea e ope a ing empe a u es ( ε max = 1.03%, o T = 130°C), la ge pipe leng h ( ε max = 0.91%, L = 80 m), smalle bending adius ( ε max = 0.68%, o Rbend = 0.5 m), all o he pa ame e s emaining he same, as shown in Fig. 2. These c i ical ac o s need o be ca e ully e alua ed in he design phase in o de o a oid excessi e s ess-s ain concen a ion in he ope a ing pipeline, associa ed wi h ma e ial damage. Fig. 2. Longi udinal s ain con ou and de o med shape o pipeline a he bend egion, unde ope a ing condi ions, o di e en alues o he sys em pa ame e s: a) T = 90°C, L = 40 m, Rbend = 1 m; b) T = 130°C, L = 40 m, Rbend = 1 m; c) T = 90°C, L = 80 m, Rbend = 1 m; d) T = 90°C, L = 40 m, Rbend = 0.5 m. E iden ly, he axial o ce in ope a ing condi ions is comp essi e and in he elas ic ange, wi h i s magni ude inc easing linea ly along he pipeline om he bend egion owa ds he ancho poin s, whe e i eaches i s maximum 6 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 alue (162507 N). The obse ed linea a ia ion o he axial o ce beyond he bend egion is caused by he cons an soil ic ion (FR = 3944 N/m) opposing he he mal expansion. Ins ead, close o he bend, he pipe axial o ce dec eases due o he bea ing o ce on he ans e se leg (Fig. 3a). Con e sely, he bending momen unde se ice loads is maximum a he bend (22163 Nm), exceeding he yielding momen o he pipe sec ion (My = 18804 Nm), associa ed wi h plas ic bending s ains (Fig. 4), leading o comp essi e plas ic longi udinal s ains (-0.3%). The la e mus be ca e ully e i ied in o de o p e en he onse o local buckling limi s a e in he ope a ing pipeline. Fig. 3 Va ia ion o he loads along he pipeline axis o di e en alues o he g ound displacemen Ug: a) axial o ce; b) shea o ce; c) bending momen . 222 Ge sena Banushi e al. / Ene gy P ocedia 149 (2018) 216–225 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 7 The bending momen dec eases mono onically beyond he bend, in e ing i s di ec ion un il eaching wo local peaks (17981 Nm) in he elas ic ange, loca ed symme ically a a dis ance o 2.5 m om he bend. A e wa ds, he magni ude o he bending momen dec eases apidly o ze o, so ha beyond a dis ance o 5m om he bend, he pipeline unde goes only axial loading (Fig. 4). Fig. 4 Va ia ion o he s ains along he mos s essed gene a o o he pipeline o di e en alues o he g ound displacemen Ug: a) longi udinal s ain; b) axial s ain; c) bending s ain. 8 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 3.2. S uc u al esponse o he pipeline in ope a ing condi ions The seismic wa e p opaga ing pa allel o one longi udinal leg, e e ses he di ec ion o he ac i a ed soil ic ion unde se ice loads (Fig. 5), subjec ing he pipeline o inc easing ensile o ces, as shown in Fig. 4 (a). E iden ly, pipe axial o ce a ies linea ly along he pipeline axis beyond he bend egion, due o he soil ic ion eac ion (FR = 3944 N/m), ha is assumed cons an h oughou he analysis, despi e he cyclic loading. The pipe axial o ce is maximum a he ancho poin in he longi udinal leg, pa allel o he di ec ion o he seismic wa e p opaga ion, dec easing linea ly he eupon, un il he bend egion whe e i inc eases sligh ly, due o he la e al soil eac ion in ans e se leg. The linea a ia ion o he axial o ce along he pipe axis is due o he soil ic ion eac ion (FR = 3944 N/m), ha is assumed cons an h oughou he analysis, despi e he cyclic loading. Fig. 5. Con ou o he soil ic ion eac ion along he pipeline (N/m): a) in ope a ing condi ions; b) unde seismic loading. The bending momen along he pipeline in e s i s di ec ion wi h espec o he ope a ing condi ions (Fig. 4), exceeding he elas ic limi (My = 18804 Nm), a he bending poin in he ans e se leg, loca ed a 2.4 m om he bend. Consequen ly, wo plas ic hinges de elop a hese bending poin s du ing seismic loading, cha ac e ized by a localiza ion o excessi e bending and longi udinal s ains, as shown in Fig. 4 and Fig. 6. Fig. 6 Longi udinal s ain con ou and de o med shape o he pipeline a he bend egion: a) in ope a ing condi ions; b) unde seismic loading. Ge sena Banushi e al. / Ene gy P ocedia 149 (2018) 216–225 223 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 7 The bending momen dec eases mono onically beyond he bend, in e ing i s di ec ion un il eaching wo local peaks (17981 Nm) in he elas ic ange, loca ed symme ically a a dis ance o 2.5 m om he bend. A e wa ds, he magni ude o he bending momen dec eases apidly o ze o, so ha beyond a dis ance o 5m om he bend, he pipeline unde goes only axial loading (Fig. 4). Fig. 4 Va ia ion o he s ains along he mos s essed gene a o o he pipeline o di e en alues o he g ound displacemen Ug: a) longi udinal s ain; b) axial s ain; c) bending s ain. 8 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 3.2. S uc u al esponse o he pipeline in ope a ing condi ions The seismic wa e p opaga ing pa allel o one longi udinal leg, e e ses he di ec ion o he ac i a ed soil ic ion unde se ice loads (Fig. 5), subjec ing he pipeline o inc easing ensile o ces, as shown in Fig. 4 (a). E iden ly, pipe axial o ce a ies linea ly along he pipeline axis beyond he bend egion, due o he soil ic ion eac ion (FR = 3944 N/m), ha is assumed cons an h oughou he analysis, despi e he cyclic loading. The pipe axial o ce is maximum a he ancho poin in he longi udinal leg, pa allel o he di ec ion o he seismic wa e p opaga ion, dec easing linea ly he eupon, un il he bend egion whe e i inc eases sligh ly, due o he la e al soil eac ion in ans e se leg. The linea a ia ion o he axial o ce along he pipe axis is due o he soil ic ion eac ion (FR = 3944 N/m), ha is assumed cons an h oughou he analysis, despi e he cyclic loading. Fig. 5. Con ou o he soil ic ion eac ion along he pipeline (N/m): a) in ope a ing condi ions; b) unde seismic loading. The bending momen along he pipeline in e s i s di ec ion wi h espec o he ope a ing condi ions (Fig. 4), exceeding he elas ic limi (My = 18804 Nm), a he bending poin in he ans e se leg, loca ed a 2.4 m om he bend. Consequen ly, wo plas ic hinges de elop a hese bending poin s du ing seismic loading, cha ac e ized by a localiza ion o excessi e bending and longi udinal s ains, as shown in Fig. 4 and Fig. 6. Fig. 6 Longi udinal s ain con ou and de o med shape o he pipeline a he bend egion: a) in ope a ing condi ions; b) unde seismic loading. 224 Ge sena Banushi e al. / Ene gy P ocedia 149 (2018) 216–225 Ge sena Banushi / Ene gy P ocedia 00 (2018) 000–000 9 Pa icula ly, he la ge comp essi e s ains a he plas ic hinges may lead o local buckling and consequen pipe ailu e, equi ing p ope mi iga ion measu es in he design phase. Fu he mo e, he axial s ains a y linea ly along he pipeline in he elas ic ange, apa wo local peaks de eloping a he bending poin s (Fig. 4). The la e a e p oduced by he in e ac ion be ween bending and axial s ains as a esul o he elas oplas ic esponse o he pipe sec ion [27, 28]. Once he maximum longi udinal s ain exceeds he yielding limi , axial s ains inc ease locally so ha he in eg al o he co esponding longi udinal s esses is equal o he con inuously inc easing axial o ce due o he g ound displacemen . E iden ly, he c i ical pipe egion unde going excessi e plas ic de o ma ions is de e mined by he la ge bending momen , dissipa ing wi hin a ew pipe diame e s a ound he bend (5 m), while beyond i he pipeline is subjec ed only o axial loading in he elas ic ange. 4. Conclusions The p esen pape analyses he pe o mance o an ope a ing DH pipeline subjec ed o seismic loading wi hin he ini e elemen me hodology, aking in o accoun he geome ic and mechanical p ope ies o he sys em, including he soil-pipeline in e ac ion. The analyzed pipeline bend su e ed plas ic s ains due o p edominan bending induced by he imposed seismic g ound displacemen , leading o la ge comp essi e s ains associa ed wi h local buckling in a b i le ailu e mode. The pipeline pe o mance depends on he geome ical and mechanical p ope ies o he sys em, like he ope a ing empe a u e, he pipe leng h, and he bend adius, equi ing accu a e e alua ion in he design phase, in o de o p e en ma e ial damage, unde se ice and seismic loading. Mo eo e , despi e he simplis ic assump ions ega ding he adop ed nume ical model, including he ep esen a ion o seismic loading as a sinusoidal wa e, he ob ained esul s gi e a be e unde s anding on he ea hquake esponse o ope a ing DH pipelines. The la e is cha ac e ized by a cyclic soil-pipe in e ac ion du ing seismic wa e p opaga ion (Fig. 7), equi ing p ope conside a ion in he enginee ing design p ac ice. Fig. 7 Pipeline beha iou du ing: a) ope a ing condi ions; b) seismic g ound de o ma ion. 5. Re e ences [1] O’Rou ke M.J. and Liu X. "Seismic design o bu ied and o sho e pipelines". Monog aph MCEER-12-MN04, Mul idisciplina y Cen e o Ea hquake Enginee ing Resea ch, MCEER (2012). [2] Ka amanos, S. A., Sa anis, G. C., Keil, B. D., and Ca d, R. J. "Analysis and Design o Bu ied S eel Wa e Pipelines in Seismic A eas". Jou nal o Pipeline Sys ems Enginee ing and P ac ice 8(4) (2017). [3] Weidlich I., Illgu h M., Banushi G. 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