Citation for published version (APA): De Vos, L., & Frigaard, P. (2005). Wave Run-Up Offshore Windturbine Foundations.

Transcription

1 Aalborg Universitet Wave Run-Up Offshore Windturbine Foundations De Vos, Leen; Frigaard, Peter Bak Publication date: 25 Document Version Early version, also known as pre-print Link to publication from Aalborg University Citation for published version (APA): De Vos, L., & Frigaard, P. (25). Wave Run-Up Offshore Windturbine Foundations. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.? Users may download and print one copy of any publication from the public portal for the purpose of private study or research.? You may not further distribute the material or use it for any profit-making activity or commercial gain? You may freely distribute the URL identifying the publication in the public portal? Take down policy If you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from vbn.aau.dk on: november 23, 217

2 (4. AALBORG UNIVERSITY Wave Forces on Offshore Windturbine Foundations on Borkum Riff Part C: Summary

3 DEPARTMENT OF CIVIL ENGINEERING AALBORG UNIVERSITY SOHNGAARDSHOLMSVEJ 57 DK-9 AALBORG DENMARK TELEPHONE TELEFA SS Hydraulics and Coastal Engineering No. 5 ISSN December 24 Wave Forces on Offshore Windturbine Foundations on Borku m Riff Part C: Summary By Brian Juul Larsen, Thomas Lykke Andersen & Peter Frigaard Aalborg University

4 Contents Page Introduction 4 Tests 5 Results 6 References 9 Appendix 1 1 3

5 Wave Forces on Offshore Windturbine Foundations- Part C Introduction The present report is a summary of the reports by Juul Larsen and Frigaard (24) and Lykke Andersen and Frigaard (November 24). It also contains some additional force measurements on a cone shaped structure and some new force measurements on the concrete tripod. For further information on the conducted test programme contact Brian Juul Larsen (phone: , i5bjl@civil.aau.dk), Thomas Lykke Andesen (phone: , i5tla@civil.aau.dk) or Peter Frigaard (phone: , peter.frigaard@civil.aau.dk). All measures given in this report is in prototype values unless otherwise is stated. 4

6 Tests The overall test setup in the new tests are similar to the setup used in Juul Larsen and Frigaard (24) and Lykke Andersen and Frigaard (November 24). The water depth is 25 meters in all tests. At a water depth of 25 meters the models have the following eigenfrequencies: Cone.53 Hz Concrete tri. 39 Hz Table 1. Eigenfrequencies with a water depth of25 m. The JONSW AP wave spectrum has been used with a peak enhancement factor of 3.3. The concrete tripod is placed with two legs in the direction facing the waves and one directly backward. A description of the models can be found on page 47 and 48 in the report by Juul Larsen, De V os and Frigaard (November 24). As in Lykke Andersen and Frigaard (November 24) the data analysis has been performed by use of Wavelab using the same methods and techniques. 5

7 Results The largest positive and negative forces and moments measured during the tests are listed in table 2. Structure H!/3 Tp Fmax Fmin Mmax Mm in Test [m] [s] [kn] [kn] [knm] [knm] 1 Monopile Monopile Monopile Monopile Monopile Monopile Monopile Monopile Monopile Monopile Monopile Monopile Monopile Monopile Monopile Monopile Monopile Monopile Steel Steel Steel Steel Steel Steel Steel Steel TLA1 Monopile TLA3 Concrete TB1 Cone TB2 Cone TB3 Cone TB4 Cone TB5 Cone TB6 Concrete TB7 Concrete TB8 Concrete TB9 Concrete TB1 Concrete Table 2. Largest positive and negative forces and moments measured during the tests. 6

8 ti::..,() /V y a >t-'*' Wave Forces on Offshore Windturbine Foundations - Part C As a reasonable representative for the maximum and minimum forces of the tests the 1/25 values are compared in figure 1. 1 Concrete tripod 9 Steel tripod -1 :}xx 8 Monopile Cone z ll" 7-3 )( g g <:! u.- 4 u.- " ' 3 < 11-7 l6< 2-8 Concrete tripod Steel tripod 1 "f:x -9 Monopile Cone H,[m] H, (m] 1' 1' 15 Concrete tripod Steettripod Monopile Cone )( 1-5 'E 'E z! - 'x g 1:; ;[ 5-1 )( r(' B. Concrete tripod Steel tripod ><. i( Monopile H 5 (m] H, [m] Figure 1. Comparison of measured 1/25 forces and moments. Cone x x 7

9 (!{/::2 "o V v -J 't Wave Forces on Offshore Windturbine Foundations - Part C A summary of the works by Aalborg University on the Borkum Riffgrund project gives the following result plots: 1 Concrete tripod 9 Steel tripod -1 )f' Monopile 8 Cone, xx ", 5-5 u. u. 4-6 *'< 3-7 x 2-8 Concrete tripod " Steel tripod 1 'S.scx -9 Monopile Cone H [m] H [m] 5 5 x Concrete tripod Steel tripod Monopile xx Cone ' 1-5 x ' x '!'x ' "' a 'E 'I< 'E z ::;: E )< 5-1 '( ::;: x x Concrete tripod Steel tripod "'< Mono pile Cone H 5 [m] H 5 [m] Figure 2. Comparison of largest measured forces and moments. 8

10 25. "E o!l. ""' l " Mono pile Monopile Boussinesq calcultaions Figure 3. Comparison of measured attack point of largest forces with some Boussinesq calculations. H,[m] I References Juul Larsen, B. and Frigaard, P. (24): Wave Forces on Offshore Windturbine Foundations on Borkurn Riff. Department of Civil Engineering, Aalborg University, Hydraulic and Coastal Engineering No. 5, ISSN Lykke Andersen, T. and Frigaard, P. (November 24): Wave Forces on Offshore Windturbine Foundations on Borkum Riff- Part B: Verification Tests. Department of Civil Engineering, Aalborg University, Hydraulic and Coastal Engineering No. 5, ISSN Juul Larsen, B., De V os, L. and Frigaard, P. (November 24): Scour around Offshore Windturbine Foundations on Borkum Riffgrund. Department of Civil Engineering, Aalborg University, Hydraulic and Coastal Engineering No. 9, ISSN

11 Wave Forces on Offshore Windturbine Foundations- Part C Appendix 1 - Result Plots Test TBOl With a cone structure H 1, 3 = 3.56 m, Tp = 9.5 s ====c=== -- e1-. 1o 7 (m] -- F 1(N] --- M (Nm] Maximum force: 4345 kn Minimum force: 415 kn Maximum moment: 5681 knm Minimum moment: 761 knm x )( L Time (s] 5, xx F"'ce(NJ x 1 8 I 2 "" Force (N] , , 1 7 s.-----c-, " ' 1 2 Ex. Prob. (%] OL , , Ex. Prob. (%] 25 Incident wave spectrum at structure Incident wave height distribution at structure :: ,... NE 2 ;: 15 ] 1 u <J) ;!...:i 1' Frequency (Hz] 1"' L ''--'-'<---" 4 1

12 Test TB2 With a cone structure H 113 = 4.23 m, Tp = 9.5 s --Eta 1 1' [m] --PtO[N] --M(Nm] Maximum force: 5328 kn Minimum force: 56 kn Maximum moment: 739 knm Minimum moment: -561 knm tooo t 2 t4 t6 t8 ttoo Time(s] & 2 " 4 3 I 2 c Q. to i!...e L-----._ Force (N] x to -to 2 Force [N] x Ex. Prob. [%] Incident wave spectrum at structure r--, , L " 2 1" Ex. Prob. [%] to' --'"-e-nt_w_a_verh_e_h_ld i_ s tr_ib_u_lion-at_s_tru_u_r, 35 to'.5 O.t O.t Frequency [Hz] to ' " _--"':-.,..,_...5 t (HIH/ to j 11

13 Test TB3 With a cone structure H 113 = 6.86 m, Tp = 12.1 s Maximum force: 8436 kn Minimum force: kn Maximum moment: 117 knm Minimum moment: knm _, --Eta;1 7 (m) P1(NJ --M(NmJ 1\Nfft Tome(s) 4,jJ 'E 3 6 j 4 I 2 :g "' < I ::; Force (NJ 1 6 x1 7 2 " xn -6 1" 2-6 1" 1 1 1' 1' Ex. Prob. (%) Ex. Prob. (% 'E 4 ;: 2 " E ::; -6 x... InCident wave spectrum at structure 15 1' Incident wave height distribution at structure N 1() " i 5 "' ' Q_ l:. e J --- 1' Frequency (Hz} (HIH/ 12

14 Test TB4 With a cone structure H L'3 = 7.51 m, Tp = 13.9 s ;=====,-, ---- Eta;1o 7 (m( ---- F"1 (N) - - M(Nm] Maximum force: 8665 kn Minimum force: kn Maximum moment: 1131 knm Minimum moment: knm Time(s) 'E 6 E 4 * I a. j -1 xx' -L Force (N) x 1e -1 Fa<ce (N) )( ,._. ;[ 2 8 'E 4 2 ::t " Ex. Prob. (%] Incident wave spectrum at structure 15 r " 2 1 ' Ex. Prob. (%] 1 2 Incident wave height distribution at structure D e a..li ) Frequency (Hz) (HIH/ 13

15 Test TBOS With a cone structure H 113 = 8.71 m, Tp = 13.9 s 1e: 1. 5, r=====:::;l --Eta 1 *1 7 [m) --F"1(NJ --M(Nm] Maximum force: 8745 kn Minimum force: -688 kn Maximum moment: 1234 knm Minimum moment: knm 1 1 o'=" oo=---...,.1 ::':2:-::o---:1":'4-:o-...,.--1:-::6'::-o::---...,.18---:1.J1 T1me (s] x , r---r---r---., 2 c. 1 g Force (N) 1 Force (N) r , r-:c._ , '!: e.5! Ex. Prob. (%] ' 1 2 Ex. Prob. (%] 25 Incident wave spectfum at structure 1' Incident wave height distribution at structure 2 ;;; NE ;: 15.., 1!l. "' 5 ) Frequency (Hz) 1' x y (HIH,)' 14

16 Test TB6 With a concrete tripod structure H 113 = 3.67 m, Tp = 9.5 s Maximum force: 3413 kn Minimum force: kn 5 x to' 2 --Eta;"1 7 (m) - -F"1 (N) --M(Nm) Maximum moment: 4788 knm 3 Minimum moment: knm Tlme(s) '!< 4 'E 3 z 3 'E 2 I :ll 1 "iii < c = -1 ::; 2.J Force (NJ 1 6 Force [N) x x 'E 1 8 c "- 1 ::; J 2 < "' 1 1' ' 1 2 Ex. Prob. [%) Ex. Prob. [%) 35 Incident wave spectrum at structure 1 2 InCident wave height distribution at structure 3 ';j' 25 N.s f 2 " 7 15,:j 1 br 1 J 1" 1 "' 1 1,, Frequency [Hz) IHIH/ 15

17 Test TB7 With a concrete tripod structure H 1,3 = 4.6 m, Tp = 9.3 s Maximum force: 3511 kn Minimum force: kn Maximum moment: 519 knm Minimum moment: -375 knm 1 1 sr ====c=== --Eta 1 "1 7 [m[ --P1[N) --M(Nm) : ' Time [s) 5 4 E ;;. 3 E i 2 1 i 1 ::; 1i I ;: '15 "- i!.!! < Force [NJ Force [NJ 1 5,, lic )( '">< -1 L " 2 1' Ex. Prob. (%] -1 -J L " Ex. Prob. {%) 35 Incident wave spectrum at structure Incident wave height distribution at structure 3 ';j' 25 N.. 2," 15 j 1 1' D e "- "'-< / Frequency [Hz) (HIH/ 16

18 Test TB8 With a concrete tripod structure H 1, 3 = 6.5 m, Tp = 12.5 s Maximum force: 544 kn Minimum force: 91 kn Maximum moment: 6787 knm Minimum moment: 872 knm.el ' Time (s] )()( Force(NJ 2 Force (N) "' Ex. Prob. (%] InCident wave spectrum at structure 12 r , Incident wave height distribution at structure r ' 2 } --< J Frequency (Hz) 1'' ' " ' (HIH/ 17

19 TestTB9 With a concrete tripod structure Wave Forces on Offshore Windturbine Foundations - Part C H 113 = 7.27 m, TP = 12.9 s 6 Maximum force: 6416 kn Minimum force: 92 kn 1 1 to r======= --Eta 1 to 7 {m] --F'tO{N] --M (Nm] Maximum moment: 937 knm -6 tooo t2 t4 t6 t6 ttoo Minimum moment: -512 knm Time (s] I 2 "E c; "- to j 2-6 Force (N] 1 1' 6 r to 17 6.< y 2 u e L to ' 1 1,, Ex. Prob. {%] Ex. Prob. {%] t2 Incident wave spectrum at structure lncjdent wave height distribution at structure too... N.E. 6 f 6 tl c. "' 4 2 D e "- to' \!le 1" t Frequency {Hz] (HIH/ 18

20 Wave Forces on Offshore Windturbine Foundations-Part C Test TBlO With a concrete tripod structure R t. 3 = 8.53 m, TP = 14.5 s r r===== --Eta,"1 7 (m] --F"1 (N] - - M(Nm) Maximum force: 7196 kn Minimum force: -584 kn Maximum moment: 956 knm Minimum moment: knm ) Time(s] I 2 "E "i5.. to tl -1 Force (N) 1 1 Forte (N] JI. 6 E 4 "E , :f Ex. Prob. j%).l)l Ex. Prob. (%) Incident wave spectrum at structure 18 r---,---r , N 12 f 1 8 6! 4 2 J '""' Frequency (Hz) 1'' --:"::------::-----:'":------:": (H/H/ 19