1	Pushover Analysis
2	Assessment Types Pushover is typically part of a platform assessment 1. Metocean Assessment - US GOM API Ultimate strength criteria - 100 year environment 2. Seismic Assessment - 1,000 year earthquake 3. Ice Assessment - Design ice levels
3	Initiators Assessment Initiators: 1. Change in Life safety category 2. Change of Consequence of Failure category 3. Significant increase in loading 4. Inadequate deck height (metocean only) 5. Significant damage 6. Decrease in net capacity
4	Category Change Life Safety Category Consequence of Failure Category
5	Increased Loading Operational Loading: 1. Addition of packages and/or equipment 2. Addition of decks and/or extensions Environmental Loading: 1. Addition of conductors 2. Addition of risers
6	Deck Height Inadequate Deck Height: 1. Deck inundated by design wave (increase in loading)
7	Damage Primary Framing 1. Significant damage Minor Framing 2. Cumulative effects of damage
8	Decreased Capacity Net Capacity Change 1. Decrease capacity due to damage 2. Increase in loading
9	Non-Linear Pushover Global inelastic ultimate strength analysis (push-over analysis) is part of the metocean reassessment procedure. It determines a Reserve Strength Ratio (RSR) for the design or ultimate strength environment.
10	Surveys and Soil Data Topside 1. Level I survey (walk around) 2. Drawings 3. Equipment layout Jacket 1. Level II underwater survey 2. Drawings Soil 1. On-site or near-site data
11	Modeling General 1. Use mean yield stress (instead of nominal) if allowed 2. Declare secondary elements as “Elastic”. Avoid: 1. Stiffened, corrugated & membrane plates (isotropic OK) 2. Special cross section types (ie. dented, stiffened, etc.) 3. Shell or solid elements 4. User defined stiffness properties
12	Topside Model Framing 1. Include main framing 2. Declare deck members and groups as elastic Deck Loading 1. Equipment weight 2. Live loading
13	Jacket Model Framing 1. Include all main framing 2. Include boatlanding & barge bumpers as dummy structures Conductors 1. Include as “Elastic” elements 2. Use wishbones at conductor guides (instead of releases) 3. Make guide dummy members “Elastic”
14	Jacket Model (cont’d) Simulate Damage 1. Corrosion - Use effective thickness 2. Break – Divide member & use dummy structure 3. Dent – Use effective thickness
15	Jacket Model (cont’d) Damage (cont’d) 4. Vent Hole – Flood member, use effective thickness 5. Joint Break – Use member releases 6. Buckling – Add new joint
16	Jacket Model (cont’d) Complex Connections 1. Include stiffness overrides (may require FE study)
17	Jacket Model (cont’d) Complex Connections (cont’d)
18	Foundation Model Soil Properties Refine old data using current techniques Create ‘worst case’ soil if on-site unavailable Use T-Z instead of adhesion data Include scour Conductors Include conductors, may need to linearize
19	Analysis Parameters General Options Strain Hardening Joint Flexibility Joint Strength Local Buckling Pile Plasticity Overrides Secondary and deck members as elastic Joint strength parameters (RSFAC, RSFACO lines)
20	Load Sequence Dead Load and Weights Apply dead load and weights first Apply appropriate live loads Use combinations if possible (requires “CMB” option) Design Environmental Load Increment design environmental load* 2. May need to refine increment size near capacity
21	Reserve Strength Reserve Strength Ratio (RSR) 1. The load factor applied to the design environmental load prior to collapse or prior to obtaining maximum displacement. 2. The overall RSR is lowest reserve strength ratio for all directions considered.
22	Mitigation Reduce Load Remove non-producing conductors Change Life Safety or Failure Consequence category Increase Strength Add framing Repair damage Grout legs Grout or stiffen connections