Jürgen Grünberg, Joachim Göhlmann. Concrete Structures. for Wind Turbines. Brnst&Sohn. A Wiley Brand

Transcription

1 Jürgen Grünberg, Joachim Göhlmann Concrete Structures for Wind Turbines Brnst&Sohn A Wiley Brand

2 Contents Editorial IX 1 Introduction 1 2 Actions ori wind turbines permanent actions Turbine Operation (rotor and nacelle) Wind loads Wind loads for onshore wind turbines Wind loads according to the DlBt guideline Checking the susceptibility to Vibration E x ampl e of application Wind loads for offshore wind turbines Classification of wind turbines peterrnining the wind conditions (wind climate) Normal wind conditions Extreme wind conditions Wind farm influence Height of sea level Hydrodynamic environmental conditions Seacurrents Natural se a state Harmonie primary wav e Waves of finite steepness Statistical description of the sea State Short-term statistics for the sea State Long-term statistics for the sea State E x trem e sea State values Breaking waves Hydrodynamic analysis General Morison formula Potential theory method - linear motion behaviour Integral equation method (singularity method) Vertical cylinders (MacCamy and Fuchs) Higher-order Potential theory Wave loads on large-volume offshore struetures Thermal actions Seaice leing-up of structural members 83

3 VI Contents 3 Non-Iinear material behaviour General Material laws for reinforced and prestressed concrete Non-Iinear stress-strain curve for concrete Non-Iinear stress-strain curve for reinforcing steel Non-Iinear stress-strain curve for prestressing steel Bending moment-curvature relationships Reinforced concrete cross-sections in general Prestressed concrete cross-sections in general Annular reinforced concrete cross-sections Deformations and bending moments according to second-order theory Design of cross-section for ultimate limit State Material resistance of concrete Material resistance of reinforcement Three-dimensional mechanical models for concrete Failure envelopes and stress invariants Common failure models for concrete Three-phase model Constitutive models Loadbearirtg structures and detailed design Basis for design Structural model for tower shaft Rotation of the foundation Stability of towers on soft subsoils Investigating vibrations Mass-spring Systems with single/multiple degrees of freedom The energy method Practical Vibration analysis Example of application Natural frequency analysis of loadbearing structure Prestressing Prestressing with grouted post-tensioned tendons External prestressing with unbonded tendons Design of onshore wind turbine support structures Total dynamic analysis Simplified analysis Sensitivity to Vibration Vibration damping Design load cases according to DlBt guideline (onshore) Critical design load cases Partial safety factors according to DIBt guideline Design of offshore wind turbine structures Control and safety Systems Design situations and load cases 127

4 Contents VII Fundamental considerations regarding the safety concept Safety analysis Combined sea State and wind Design load cases according to GL guideline Commentary to Table Partial safety factors according to GL guideline Ultimate limit State Deformation calculations according to second-order theory Linear analysis of internal forces Analysis of stresses in tower shaft Special characteristics of prefabricated construction Terminology Shear force transfer across opening joints Detailed design Transferring prestressing forces Erecting and prestressing precast concrete elements Design of openings Analysis of serviceability limit State Action effects in tower shaft due to external actions Limiting the deformations Limiting the stresses Limiting crack widths and decompression limit State Restraint stresses acting on shaft wall Special aspects of construction with precast concrete elements Fatigue limit State Fatigue-inducing actions on wind turbine support structures Actions due to wind and turbine Operation Actions due to waves and sea state Fatigue analyses according to DIBt wind turbine guideline Simplified analyses for concrete Direct analysis according to DIBt guideline Multi-stage fatigue loads Numbers of fatigue cycles to failure for multi-axial fatigue loads Procedure Derivation of damage variables KJ?" and K fat t Failure envelope for fatigue load Failure curves for biaxial fatigue loads Design proposal for multi-axial fatigue Procedure for designing on the basis of the linear accumulation hypothesis Derivation of modification factor A. c3 (N, r) for fatigue loads on compression meridian Derivation of modification factors X c2 (N, a) for biaxial fatigue loads Design of construction nodes Loads on nodes 180

5 VIII Contents Composition of forces at the ultimate limit State Characteristic values for loads Example of calculation Load on circular ring beam at ultimate limit State Design of circular ring beam U Foundation design Calculating the internal forces Construction of prestressed concrete towers Introduction Hybrid structures of steel and prestressed concrete prestressed concrete towers with precast concrete segments Examples of design and construction Further developments in precast concrete construction Offshore substructures in concrete Compact substructures with ice cones Middelgrunden offshore wind farm Sequence of Operations on site Design, construction, transport and erection of concrete substructures Special design criteria Construction Transport and erection Spread and deep foundations Innovations 207 References 209 Index 217 l