PSE: PETROLEUM STRUCTURAL ENGINEERING
SOLUTIONS FOR ONSHORE & OFFSHORE STRUCTURES
PETROLEUM STRUCTURAL ENGINEERING ®
INTEGRATED STRUCTURAL ANALYSIS, DESIGN AND EVALUATION OF OFFSHORE/ONSHORE STRUCTURES ACCORDING TO THE API 4F (4th EDITION).
SAFI™ TECHNOLOGIES: YOUR SOURCE FOR STRUCTURAL ENGINEERING SOLUTIONS
The PSE Petroleum Structural Engineering® Software is a tool for offshore and onshore structures. The PSE Software is being used by several notable international companies in production work for building innovative offshore and onshore derricks, masts and substructures.
The software accounts for wind loads, vessel dynamic motions, wave and current loads.
ABS American Bureau of Shipping has approved the PSE Petroleum Structural Engineering® Software for the analysis and design of offshore derricks and structures.
The PSE Petroleum Structural Engineering® Software is based on the API 4F (4th edition) specification for drilling and well servicing structures.
The API 4F specifications for wind loads based on the velocity component approach is integrated into the PSE Petroleum Structural Engineering software. Accordingly, drilling structures are classified based on their Structural Safety Level (SSL) and their offshore or onshore location.
The design reference wind velocity value represents a 3-second gust wind measured in knots at an elevation of 10 m (33 ft) in open water, with an associated return period of 100 years.
The API 4F specifications are applicable to the following wind environments:
- Operational wind
- Erection wind
- Transportation wind
- Unexpected wind
- Expected wind
The PSE software allows different configurations of the drilling structure models according to a given wind environment. The program requires the input of the rated design wind velocity, Vdes, and accounts for the design reference wind velocity and wind velocity multiplier. The program computes the local wind velocity, Vz, by scaling the rated design wind velocity by the appropriate elevation factor, ß, in order to obtain the velocity for estimating the wind forces.
A wind profile in a selected direction provides the wind intensity that generates the wind loads to structural members and surface areas. As many as required wind directions can be defined through different basic loads.
MEMBER SELECTION PROCEDURES
Member selection procedures allow the application of the wind profile to the entire structure or to specific zones and excluding members behind or in front of wind walls. It is possible to apply the API 4F wind loads directly to elements such as equipment, wind walls and other objects attached to the drilling structures.
AUTOMATED SHAPE FACTOR
The shape factor is automated in the PSE software for various section shapes. The program accounts for the gust factor and the reduction factor for shielding by members and appurtenances.
OFFSHORE VESSEL DYNAMIC MOTIONS
In various production wells, the offshore drilling structures are located on top decks of vessels, semisubmersible or floating hulls. Vessel motion includes roll, pitch and yaw rotations and heave, sway and surge translations.
The PSE software computes the inertial forces due to the vessel dynamic motion as well as radial, tangential and translational forces due to the acceleration of masses attached to the drilling structures. These forces have a significant influence on the structural design and reliability of offshore structures.
The PSE software accepts three types of user input in order to estimate the inertial forces induced by the vessel dynamic motions:
- Linear displacements, angular rotations and time periods
- Linear and angular velocities and accelerations
- Linear accelerations at two points in the vessel which are converted to linear and angular accelerations by the program.
High pressure mud piping, electrical cable trays, junction boxes, racking boards, tong counterweights, turning sheaves, deadline anchors, crown accessories, casing stabbing baskets and other outfitting items add weight to the derrick. Weight data is converted to masses applied at the correct locations on the derrick.
WAVE & CURRENT LOADS
The PSE software computes wave and current forces applied on the structural members. The wave kinematics can be established using either Airy’s linear theory or Fenton’s nonlinear theory.
NONLINEAR KINEMATIC THEORY
The linear kinematic theory is valid where the wave height is small compared to the water depth. On the other hand, the nonlinear kinematic theory, proposed by J.D. Fenton, solves the motion equations by representing the velocity potential and surface elevation with a Fourier series. The later method minimizes the error of each parameter governing the wave motion equations and is valid over the entire spectrum.
The PSE software accounts for the following wave profiles and kinematic parameters:
- Wave period
- Incidence angle
- Elevation of the sea bed
- Elevation of the still water line (SWL)
- Kinematic reduction factor
- Crest position criterion
A preview of the wave surface profiles, velocities and accelerations at any point is readily available.
With the PSE software, the current profile is described with respect to the sea bed. The current speed is defined by a set of elevation-velocity-angle triplets and the reduction of the current speed in the vicinity of the structure or the blockage factor is accounted for.
In order to combine the current with the wave profile, the current needs to be stretched, or compressed, to the local wave surface. Two stretching methods are available:
- The linear stretching method, also known as the Wheeler stretching
- The non linear method or hyperbolic stretching
According to commentary C.3.2.1 of the design code API RP-2A- 2003, the Doppler effect is accounted for by calculating an apparent period defined as the wave period as seen by an observer moving with the current.
EFFECT OF MARINE GROWTH ON MEMBERS
Marine growth increases the cross section diameter and surface roughness of the members, and it is defined by a set of elevation-thickness pairs.
MEMBER WAVE LOADS
The input for the member wave loads consists of the following six parameters:
- Current profile
- Wave profile
- Marine growth profile
- Drag coefficient
- Inertia coefficient
- Shielding factor
The member forces, calculated using Morison equation, vary according to the position of the waves with respect to the structure. In order to obtain the maximum forces in the members, the critical position of the wave crest is determined by the program.
Other loads such as seismic, snow and ice loads for far northern extreme weather are also considered for the design of masts, derricks, platforms and substructures.
The PSE Petroleum Structural Engineering® Software can directly import models (geometry, loads and design parameters) from the StruCAD*3D program and the SACS program.
DOWNLOAD THE PDF TECHNICAL BROCHURE OF THE PSE PETROLEUM STRUCTURAL ENGINEERING SOFTWARE