Offshore Compliant Platforms. Srinivasan Chandrasekaran

      1 Chapter 1Figure 1.1 A typical tension leg platform.Figure 1.2 TLP mechanics.Figure 1.3 Active control strategy.Figure 1.4 Semi‐active control strategy.Figure 1.5 Block diagram for passive control strategy.Figure 1.6 Pall friction damper.Figure 1.7 Metallic yield damper.Figure 1.8 Viscous fluid damper.Figure 1.9 Tuned liquid damper: (a) circular; (b) rectangular.Figure 1.10 Tuned liquid column damper.Figure 1.11 Tuned mass damper.Figure 1.12 Schematic diagram of an idealized system.Figure 1.13 Schematic diagram of a spring‐mass system with a TMD.Figure 1.14 Mass used in the TMD.Figure 1.15 Response of a TLP and TMD (μ = 1.5%).Figure 1.16 Response of a TLP and TMD (μ = 3.0%).Figure 1.17 Surge RAO of a TMD.Figure 1.18 Comparison of surge response (H_S = 8 m; T_P = 12 seconds).Figure 1.19 Comparison of surge response (H_S = 8 m; T_P = 16 seconds).Figure 1.20 Comparison of surge response (H_S = 8 m; T_P = 20 seconds).Figure 1.21 Comparison of surge response (H_S = 8 m; T_P = 32.5 seconds).Figure 1.22 Comparison of pitch response (H_S = 8 m; T_P = 12 seconds).Figure 1.23 Comparison of pitch response (H_S = 8 m; T_P = 16 seconds).Figure 1.24 Comparison of pitch response (H_S = 8 m; T_P = 20 seconds).Figure 1.25 Comparison of pitch response (H_S = 8 m; T_P = 32.5 seconds).Figure 1.26 Articulated tower.Figure 1.27 Analytical model.Figure 1.28 Variation of responses for different frequency ratios.Figure 1.29 Variation of responses for different frequency ratios with a TMD...Figure 1.30 Variation of responses for different frequency and mass ratios w...Figure 1.31 Geometric details of the model.Figure 1.32 Model of a TMD.Figure 1.33 Free‐vibration time history.Figure 1.34 Surge response of a MLAT without a TMD.Figure 1.35 Surge RAO for TMD‐1.Figure 1.36 Surge RAO for TMD‐2.Figure 1.37 Surge RAO for TMD‐3.Figure 1.38 Comparison of RAOs for 3 cm wave height.Figure 1.39 Comparison of RAOs for 5 cm wave height.Figure 1.40 Comparison of RAOs for 7 cm wave height.

      2 Chapter 2Figure 2.1 Schematic diagram of the BLSRP installed in a wave flume.Figure 2.2 Experimental setup and arrangements: (a) side view; (b) hinged jo...Figure 2.3 Orientation of the BLSRP for the wave heading angle.Figure 2.4 Response of the BLSRP (0°, 0.1 m wave height).Figure 2.5 Numerical model of the BLSRP.Figure 2.6 Response of the BLSRP (30°, 15 m).Figure 2.7 Tether tension variations in mooring lines.Figure 2.8 Power spectral density plots of buoyant leg 1 (0°, 6 m, 10 second...Figure 2.9 Power spectral density plots of the deck (0°, 6 m, 10 seconds).Figure 2.10 Numerical model of the BLSRP (normal case).Figure 2.11 Numerical model of the BLSRP with postulated failure.Figure 2.12 Dynamic tether tension variation in postulated failure cases.Figure 2.13 Mathieu stability for the BLSRP in postulated failure cases.

      3 Chapter 3Figure 3.1 Typical regular wave profile (H = 2 m, T = 5 s).Figure 3.2 PM spectrum for different sea conditions.Figure 3.3 Two‐dimensional random wave profile (Wang and Isberg 2015).Figure 3.4 API spectrum plot for different wind velocities.Figure 3.5 Wind‐generated current velocity profile.Figure 3.6 Service life estimation methodology.Figure 3.7 Triceratops model.Figure 3.8 Experimental model of a stiffened triceratops.Figure 3.9 Plan of the triceratops.Figure 3.10 RAOs of the deck and buoyant legs with regular waves.Figure 3.11 Deck response given different wave heading angles.Figure 3.12 Tether tension variation in rough sea conditions.Figure 3.13 Deck surge and heave PSD plots in very high sea conditions.Figure 3.14 Pitch response of the deck and buoyant legs in very high sea con...Figure 3.15 Maximum deck response in very high sea conditions.Figure 3.16 Tether tension spectrum with very high sea conditions.Figure 3.17 Maximum tether tension in very high sea conditions.Figure 3.18 Deck response with high sea conditions (w – waves, w + w – waves...Figure 3.19 Phase plots in the surge DOF with very high sea conditions.Figure 3.20 Buoyant leg response with high sea conditions.Figure 3.21 Tension spectrum with very high sea conditions.

      4 Chapter 4Figure 4.1 Random ice force and vibration of the structure.Figure 4.2 True stress–strain curve of AH36 grade steel.Figure 4.3 Different shapes of indenters.Figure 4.4 Time–temperature curves for different fire conditions.Figure 4.5 Reduction factors for yield strength, proportional limits, and li...Figure 4.6 Variations in the thermal conductivity of carbon steel.Figure 4.7 Variations in the specific heat of carbon steel.Figure 4.8 Variations in the thermal strain of carbon steel.Figure 4.9 Spectral density plot given different ice velocities.Figure 4.10 Spectral density plot given different ice forces.Figure 4.11 Ice force–time history.Figure 4.12 PSD plots for normal ice sea conditions with ice load on two buo...Figure 4.13 PSD plots of tether tension variation in normal sea conditions....Figure 4.14 Total deck response for different ice thicknesses.Figure 4.15 Total deck response for different ice crushing strengths.Figure 4.16 Total deck response for different ice velocities.Figure 4.17 PSD plots of the deck in open water and ice‐covered load cases....Figure 4.18 Methodology of impact analysis.Figure 4.19 Numerical model of buoyant legs and indenters.Figure 4.20 Force versus nondimensional deformation curve.Figure 4.21 Deck surge responses for impact loads on buoyant leg 1.Figure 4.22 Force–deformation curves for different indenter sizes.Figure 4.23 Force–deformation curves for different impact locations.Figure 4.24 Force–deformation curves for different indenter shapes.Figure 4.25 Force–deformation curves for different numbers of stringers.Figure 4.26 Force–deformation curve of buoyant legs at different temperature...Figure 4.27 Deck plate of a triceratops.Figure 4.28 Scale deck plate model.Figure 4.29 Hydrocarbon fire cases.Figure 4.30 Temperature variations in plates and stiffeners.

      5 Chapter 5Figure 5.1 Numerical model of a triceratops with a wind turbine.Figure 5.2 Pitch RAO of the triceratops.Figure 5.3 PSD plot of the surge free‐decay response.Figure 5.4 PSD plot of the roll free‐decay response.Figure 5.5 Frequency response to operable and parked conditions.Figure 5.6 PSD plots for different DOF.Figure 5.7 Dynamic tether tension variation.Figure 5.8 Plan and elevation of a stiffened buoyant leg.Figure 5.9 Fabricated model of a stiffened buoyant leg.Figure 5.10 Fabricated model of a ball joint.Figure 5.11 Surge, heave, and pitch RAOs of the deck and buoyant legs with 0...Figure 5.12 Surge, heave, and pitch RAOs of the deck and buoyant legs with 9...Figure 5.13 Surge, heave, and pitch RAOs of the deck and buoyant legs with 1...Figure 5.14 Effect of wave direction on the stiffened triceratops.Figure 5.15 Cross section of the buoyant legs.Figure 5.16 Plan view of the triceratops with circular and elliptical buoyan...Figure 5.17 Total force–time history, given high sea conditions.

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