Global Structural Strength Analysis Methodology of a Typical TLP

Abstract

Abstract:

We focus on the global structure strength analysis of a typical tension leg platform (TLP). The objective of the TLP global structural analysis is to check the hull global structural integrity under design environmental conditions. Firstly, a global finite element model of the entire TLP is established, the hull structure is modeled in detail, whilst the deck structure is represented through a simplified deck beam model. A hydrodynamic analysis for operation and extreme conditions is conducted to get the design wave parameters for critical wave loads. After that, wave loads are mapped to the global structure finite element model, and the tendons are modeled as spring element which represents 6 degrees of freedom and rotations. Finally, the maximum stress and its distribution trends, together with the control elements, are obtained by finite element analysis according to critical wave heading, wave periods, wave heights and wave positions. Results and the TLP analysis method proposed can be used as reference for strength analysis of other offshore platforms.

Key words: tension leg platform, global structural strength analysis, extreme conditions, finite element model, wave heading

CLC Number:

TE951

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Yang LI, Zhong-min SHI, Bin XIE, Wen-hui XIE. Global Structural Strength Analysis Methodology of a Typical TLP[J]. Ocean Engineering Equipment and Technology, 2014, 1(1): 3-13.

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Figures/Tables 24

Fig. 1

Schematic of a typical TLP

Fig. 1

Fig. 2

Typical TLP motion nomenclature

Fig. 2

Fig.3

Plate thickness of TLP hull

Fig.3

Fig.4

Global structural model

Fig.4

Fig.5

Global TLP finite element model

Fig.5

Table 1

Tension leg spring element stiffnessN/m

X	Y	Z
1.230×10⁴	1.230×10⁴	2.030×10⁴

Table 1

Fig.6

Boundary conditions of tendon porch location

Fig.6

Table 2

Weight summary for drilling normal condition

结构划分	分组	基础质量 /t	裕度 /t	相对裕度 /%	设计质量 /t	X_CG/m	Y_CG/m	Z_CG/m
平台主结构	船体结构	14 958	1 496	10.0	16 454	0	0	20.66
	轮机系统	500	50	10.0	550	0	0	35.00
	舾装	2 441	314	12.9	2 756	-0.95	-0.53	36.34
	储物舱	1 500	150	10.0	1 650	-24.32	2.88	52.45
上部模块	甲板结构	5 644	1 129	20.0	6 773	0.14	-0.32	66.88
	上部模块设备 (干重)	5 433	543	10.0	5 976	13.39	-3.24	70.14
	上部模块设备 (可变)	1 420	142	10.0	1 562	9.50	-0.13	70.51
	钻井系统(干重)	3 000	300	10.0	3 300	-10.59	4.66	80.75
	钻井系统(可变)	2 500	182	7.3	2 682	-7.90	3.48	94.12
垂向载荷	张力腿垂向载荷	19 269	0	0	19 269	0	0	1.50
	TTR垂向载荷	2 181	327	15.0	2 508	2.34	-2.34	60.20
	SCR垂向载荷	1 702	232	13.6	1 934	-13.13	-1.49	6.90
压载水舱	Trim压载	660	0	0	660	34.18	3.78	0.93
压载水舱	预留压载	6 360	0	0	6 360	0.01	0.01	3.90
预留	公司预留	1 000	0	0	1 000	0	0	67.70
小计	平台主结构	19 399	2 010	10.4	21 410	-2.00	0.15	25.50
	上部模块	17 996	2 296	12.8	20 293	1.96	0.15	73.97
	垂向载荷	23 152	559	2.4	23 711	-0.82	-0.37	8.15
	压载水舱	7 020	0	0	7 020	3.22	0.36	3.62
	预留	1 000	0	0	1 000	0	0	67.70
总计	质量与载荷	68 567	4 865	7.1	73 432	0	0	31.77
总计	质量	45 415	4 306	9.5	49 722	0.39	0.18	43.04

Table 2

Table 3

Weight summary for drilling extreme condition

结构划分	分组	基础质量 /t	余量 /t	余量系数 /%	设计质量 /t	X_CG/m	Y_CG/m	Z_CG/m
平台主结构	船体结构	14 958	1496	10.0	16 454	0	0	20.66
	轮机系统	500	50	10.0	550	0	0	35.00
	舾装	2 441	314	12.9	2 756	-0.95	-0.53	36.34
	储物舱	1 050	105	10.0	1 155	-24.32	2.88	52.45
上部模块	甲板结构	5 644	1 129	20.0	6 773	0.14	-0.32	66.88
	上部模块设备 (干重)	5 433	543	10.0	5 976	13.39	-3.24	70.14
	上部模块设备 (可变)	994	99	10.0	1 094	9.50	-0.13	70.49
	钻井系统(干重)	3 000	300	10.0	3 300	-10.59	4.66	80.75
	钻井系统(可变)	1 274	127	10.0	1 401	-10.59	4.66	80.75
垂向载荷	张力腿垂向载荷	19 269	0	0	19 269	0	0	1.50
	TTR垂向载荷	2 181	327	15.0	2 508	2.34	-2.34	60.20
	SCR垂向载荷	1 702	232	13.6	1 934	-13.13	-1.49	6.90
压载水舱	Trim压载	259	0	0	259	33.23	25.73	0.70
压载水舱	预留压载	9 005	0	0	9 005	0.01	0	4.47
预留	公司预留	1 000	0	0	1 000	0	0	67.70
小计	平台主结构	18 949	1 965	10.4	20 915	-1.47	0.09	24.86
	上部模块	16 344	2 199	13.5	18 543	2.24	0.01	71.66
	垂向载荷	23 152	559	2.4	23 711	-0.82	-0.37	8.15
	压载水舱	9 264	0	0	9 264	0.93	0.72	4.36
	预留	1 000	0	0	1 000	0	0	67.70
总计	质量与载荷	68 710	4 723	6.9	73 432	0	0	29.28
总计	质量	45 558	4 164	9.1	49 722	0.39	0.18	39.35

Table 3

Table 4

Weight calibration of drilling extreme condition

分组		计算重心位置				调整后有限元模型重心位置
分组		质量/t	X_CG/m	Y_CG/m	Z_CG/m	质量/t	X_CG/m	Y_CG/m	Z_CG/m
组1	主结构	20 915	-1.468	0.089	24.859
组2	上部模块公司预留	19 544	2.130	0.012	71.458	19 544	2.130	0.012	71.46
组3	压载舱	9 264	0.934	0.729	4.365
组4	垂向载荷	23 711	-0.824	-0.369	8.149
组1+组3		30 179	-0.730	0.286	18.568	30 178.9	-0.730	0.286	18.566
总质量(1+2+3)		49 723	0.394	0.178	39.357	49 722.9	0.394	0.178	39.356
总质量与载荷 (1+2+3+4)		73 434	0.001	0.001	29.280

Table 4

Table 5

Weight calibration of drilling normal condition

分组		计算重心位置				调整后有限元模型重心位置
分组		质量/t	X_CG/m	Y_CG/m	Z_CG/m	质量/t	X_CG/m	Y_CG/m	Z_CG/m
组1	主结构	21 410	-1.997	0.154	25.497
组2	上部模块	21 293	1.863	0.140	73.680	21 293	1.863	0.140	73.681
组2	公司预留	21 293	1.863	0.140	73.680	21 293	1.863	0.140	73.681
组3	压载舱	7 020	3.223	0.364	3.621
组4	垂向载荷	23 711	-0.823	-0.369	8.149
组1+组3		28 430	-0.708	0.206	20.095	28 429.9	-0.708	0.206	20.091
总质量(1+2+3)		49 723	0.393	0.178	43.042	49 722.3	0.393	0.178	43.040
总质量与载荷 (1+2+3+4)		73 434	0	0.001	31.776

Table 5

Fig.7

Control groups position

Fig.7

Table 6

Selected control element groups

控制单元组	结构成分	控制单元组	结构成分
CG01	浮箱底内侧肘板	CG19	节点船底板(中心)
CG02	浮箱底外侧肘板	CG20	节点船底板(外环)
CG03	节点顶部水平内侧肘板	CG21	节点船顶板(外环)
CG04	节点顶部水平外侧肘板	CG22	节点外板(中圈)
CG05	节点顶部垂向内侧肘板	CG23	立柱底部舷侧外板(中部内侧)
CG06	节点顶部垂向外侧肘板	CG24	立柱底部舷侧外板(中部外侧)
CG07	浮箱底部板(外侧)	CG25	立柱上部舷侧外板(板厚过渡处)
CG08	浮箱底部板(中部)	CG26	立柱中部舷侧外板(中部内侧)
CG09	浮箱底部板(外侧贯穿水密舱壁)	CG27	立柱中部舷侧外板(中部外侧)
CG10	浮箱顶部板(外侧)	CG28	立柱上部舷侧外板(中部内侧)
CG11	浮箱顶部板(中部)	CG29	立柱上部舷侧外板(中部外侧)
CG12	浮箱顶部板(外侧贯穿水密舱壁)	CG30	立柱上部舷侧外板(板厚过渡处)
CG13	浮箱内侧板(上部)	CG31	立柱与Post连接处
CG14	浮箱内侧板(下部)	CG32	Post底部舷侧外板
CG15	浮箱内侧板(中部)	CG33	立柱内侧板(底部)
CG16	浮箱外侧板(上部)	CG34	立柱内侧板(中部)
CG17	浮箱外侧板(下部)	CG35	立柱内侧板(上部)
CG18	浮箱外侧板(中部)

Table 6

Table 7

Summary for design wave cases

工况	载荷参数	设计波				对应编号
工况	载荷参数	波高/m		周期/s	L/H	浪向/(°)
100年一遇台风	甲板重心处水平加速度	13.78	9	9.18	0~360 (间隔45°)	A1~A8
	中拱/中垂	16.76	10	9.32		B1~B8
	水平剪切/扭转	20.03	10	7.8		C1~C9
	垂向剪切	26.07	15	13.48		D1~D9
一年一遇台风	甲板重心处水平加速度	10.86	9	11.65	0~360 (间隔45°)	A1~A8
	中拱/中垂	12.02	10	12.99		B1~B8
	水平剪切/扭转	14.01	10	11.43		C1~C9
	垂向剪切	13.76	14	22.25		D1~D9

Table 7

Table 8

Summary for global wave casesm

工况	高度				平均吃水
工况	9 s周期		10 s周期	14 s周期	15 s周期
一年一遇台风	10.86	14.01	13.76	--	31.82
100年一遇台风	13.78	20.03	--	26.07	34.56

Table 8

Fig.8

Typical wave loads to the TLP (0°)

Fig.8

Fig.9

Von Mises stress distribution of hull for 100-year load case

Fig.9

Fig.10

Maximum Von Mises stress distribution of hull for 100-year load case

Fig.10

Fig.11

Von Mises stress of pontoon gussets for 100-year load case

Fig.11

Fig.12

Von Mises stress of column at upper post of 100-year load case

Fig.12

Table 9

Control element stresses for 1-year condition with maximum unity ratios

组号	单元号	等效应力/MPa		安全因子	相位角/(°)	编号
组号	单元号	计算值		安全因子	相位角/(°)	允许值
CG01	64288	68.7	241.5	0.284	16	C4
CG02	6 697	50.5	241.5	0.209	4	C8
CG03	64 032	73.9	241.5	0.306	28	C4
CG04	6 716	62.7	241.5	0.260	40	C4
CG05	71 515	214.2	241.5	0.887	36	C3
CG06	55 155	204.7	241.5	0.848	34	C5
CG07	11 277	63.8	241.5	0.264	178	C2
CG08	93 946	99.7	241.5	0.413	0	C8
CG09	42 307	75.4	241.5	0.312	28	C4
CG10	11 336	97.1	241.5	0.402	40	C4
CG11	31 017	81.3	241.5	0.337	30	C7
CG12	42 310	123	241.5	0.509	26	C7
CG13	43 600	80.7	241.5	0.334	30	C7
CG14	71 534	58.5	241.5	0.242	28	C4
CG15	43 578	123.4	241.5	0.511	36	C3
CG16	8 836	88.4	241.5	0.366	44	C4
CG17	55 159	58.0	241.5	0.240	8	C8
CG18	56 077	150.7	241.5	0.624	56	C6
CG19	21 980	230.2	241.5	0.953	16	C4
CG20	9 186	50.5	241.5	0.209	14	C8
CG21	49 040	50.9	241.5	0.211	44	C6
CG22	2 502	108.5	241.5	0.449	30	D3
CG23	69 427	89.3	241.5	0.370	32	C5
CG24	110 028	61.6	241.5	0.255	36	C3
CG25	78 811	108.3	241.5	0.448	48	C5
CG26	67 144	93.4	241.5	0.387	56	C3
CG27	102 149	44.3	241.5	0.183	52	C3
CG28	72 587	97.3	241.5	0.403	38	C5
CG29	107 496	25.2	241.5	0.104	44	C3
CG30	81 025	116.1	241.5	0.481	56	C5
CG31	61 956	358.3	241.5	1.484	40	C3
CG32	82 456	229.3	241.5	0.949	42	C5
CG33	76 615	64.6	241.5	0.267	28	C3
CG34	77 746	52.4	241.5	0.217	40	C7
CG35	81 730	52.4	241.5	0.217	40	C7

Table 9

Table 10

Control element stresses for 100-year condition with maximum unity ratios

组号	单元号	等效应力/MPa		安全因子	相位角/(°)	编号
组号	单元号	计算值		安全因子	相位角/(°)	允许值
CG01	64 288	93.6	310.5	0.301	12	C4
CG02	6 697	65.7	310.5	0.212	2	C8
CG03	64 032	113.4	310.5	0.365	28	C4
CG04	6 716	95.4	310.5	0.307	38	C4
CG05	71 515	310.3	310.5	0.999	30	C8
CG06	55 155	271.0	310.5	0.873	32	C5
CG07	9 558	92.4	310.5	0.298	178	C8
CG08	93 948	121.2	310.5	0.390	14	C4
CG09	42 307	83.6	310.5	0.269	20	C4
CG10	11 336	128.5	310.5	0.414	38	C4
CG11	31 017	106.4	310.5	0.343	28	C7
CG12	42 310	149.0	310.5	0.480	26	C7
CG13	43 570	100.7	310.5	0.324	32	C7
CG14	71 534	68.4	310.5	0.220	14	C8
CG15	43 579	138.1	310.5	0.445	32	C7
CG16	8 836	117.0	310.5	0.377	42	C4
CG17	55 159	75.5	310.5	0.243	178	C2
CG18	56 077	167.5	310.5	0.539	50	C6
CG19	21 980	266.8	310.5	0.859	16	C4
CG20	9 186	70.0	310.5	0.225	178	C2
CG21	49 040	74.2	310.5	0.239	42	C6
CG22	111 404	88.3	310.5	0.284	32	C3
CG23	68 508	101.9	310.5	0.328	32	C5
CG24	110 028	78.1	310.5	0.252	32	C3
CG25	78 811	118.7	310.5	0.382	44	C5
CG26	67 144	92.3	310.5	0.297	126	D4
CG27	102 149	62.3	310.5	0.201	46	C3
CG28	72 587	114.5	310.5	0.369	36	C5
CG29	107 496	34.5	310.5	0.111	40	C3
CG30	81 025	124.0	310.5	0.399	42	C8
CG31	61 956	477.8	310.5	1.539	36	C3
CG32	82 456	300.0	310.5	0.966	40	C5
CG33	76 615	76.8	310.5	0.247	26	C7
CG34	77 746	57.8	310.5	0.186	36	C5
CG35	93 271	61.2	310.5	0.197	38	C5

Table 10

Table 11

Stresses of major components for 1-year condition with maximum unity ratios

结构名称	等效应力/MPa		安全因子
结构名称	计算值		允许值
立柱与浮箱肘板	214.2	241.5	0.887
浮箱底板	106.3	241.5	0.440
浮箱顶板	123.0	241.5	0.509
浮箱内侧板	123.1	241.5	0.510
浮箱外侧板	173.9	241.5	0.720
节点底板	230.2	241.5	0.953
节点顶板	113.6	241.5	0.470
节点侧板	130.4	241.5	0.540
立柱外板	175.5	241.5	0.727
立柱顶板	202.1	241.5	0.837
Deck Post	229.3	241.5	0.949
立柱内板	156.0	241.5	0.646

Table 11

Table 12

Stresses of major components for 100-year condition with maximum unity ratios

结构名称	等效应力/MPa		安全因子
结构名称	计算值		允许值
立柱与浮箱肘板	310.3	310.5	0.999
浮箱底板	126.8	310.5	0.408
浮箱顶板	149.0	310.5	0.480
浮箱内侧板	145.3	310.5	0.468
浮箱外侧板	190.0	310.5	0.612
节点底板	266.8	310.5	0.859
节点顶板	153.8	310.5	0.495
节点侧板	126.1	310.5	0.406
立柱外板	200.6	310.5	0.646
立柱顶板	276.7	310.5	0.891
Deck Post	300.0	310.5	0.966
立柱内板	166.2	310.5	0.535

Table 12

References 3

[1]	American Petroleum Institute.API RP 2T. Recommended practice for lanning, designing and constructing tension leg platforms[S]. Washington: American Petroleum Institute, 2010.
[2]	American Petroleum Institute.API RP 2FPS. Planning, designing, and constructing floating production system[S]. Washington: American Petroleum Institute, 2010.
[3]	American Bureau of Shipping. Guide for building and classing floating production, storage, and offloading systems[M]. Houston: American Bureau of Shipping, 1996.

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