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Volume 2
M
e c h a n
i c a l
E n
g i n e e r i n g
N e w s
FOR THE POWER,
PETROCHEMICAL AND
RELATED INDUSTRIES
The COADE Mechanical Engineering
News Bulletin is published periodicallyfrom the COADE offices in Houston,Texas. The Bulletin is intended to provideinformation about software applicationsand development for MechanicalEngineers serving the power, petrochemi-cal and related industries. Additionally, theBulletin serves as the official notificationvehicle for software errors discovered inthose Mechanical Engineering programsoffered by COADE. (Please note, thisbulletin is published only two to threetimes per year.)
©1999 COADE, Inc. All rights reserved.
I N T H I S I S S U E :
V O L U M E 2 8 J A N U A R Y 2 0 0 0
What’s New at COADE
CAESAR II Version 4.20 New Features ......... 2
PVElite Version 3.60 New Features ............... 2
CODECALC Version 6.20 New Features ....... 3
Shows and Exhibitions ................................... 3
Technology You Can Use
Modeling Sway Brace Assemblies in
CAESAR II ................................................. 3
Hydrodynamic Loading of Piping Systems .... 5A Comparison of Wind Load Calculations
per ASCE 93 and ASCE 95 ..................... 10
Layouts in AutoCAD 2000 and
CADWorx/PIPE........................................ 13
PC Hardware for the Engineering User
(Part 28) ................................................... 17
Program Specifications
CAESAR II Notices ...................................... 18
TANK Notices ............................................... 19
CODECALC Notices .................................... 19
PVElite Notices ............................................ 20
Hydrodynamic
Loading ofPiping Systems
> see story page 5
Layouts inAutoCAD 2000 &
CADWorx/PIPE
> see story page 13
CAESAR II
Version 4.20New Features
> see story page 2
CAESAR II Receives TD12 Approvalby Transco
On November 30, 1999, following a long and rigorous validation process,
the Stress Analysis Workgroup of Transco officially approved CAESAR II
for use on projects requiring the IGE/TD/12 piping code, “Pipework
Stress Analysis for Gas Industry Plant”. Transco is the Gas Transportation
arm of the British Gas Group. CAESAR II thus becomes the first and
only commercially available pipe stress analysis program so accepted by
Transco. Note that only CAESAR II Version 4.10 Build 991201
(December 1, 1999) and later is covered by this acceptance.
ATTENTION:Users of Green External Software Locks!
All new COADE products released after July 2000 will no longer support
the old SSI (Software Security, Inc.) ESLs since this company is no longer
in business. Any users who are current on their maintenance and are now
using one of these ESLs (identified by their green color) should contact
COADE to arrange for a replacement ESL.
All COADE products released after January 2000 will remind any users
who still have green ESLs of this situation. Please contact COADE as per
the instruction on the screen so that this transition can be accomplished with
a minimum of effort.
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CAESAR II Version 4.20
New FeaturesBy: Richard Ay
CAESAR II Version 4.20 is nearing completion. Some of the
major new features of this release are listed in the table below.
CAESAR II Version 4.20 Features
New Input Graphics - utilizes a true 3D library, enabling graphic element selection
Completely revised material data base, including Code updates.
Hydrodynamic loading for offshore applications. This includes the Airy, Stokes 5th
, and
Stream Function wave theories, as well as Linear and Power Law current profiles.
Wind analysis expanded to handle up to 4 wind load cases
New piping codes: B31.4 Chapter IX, B31.8 Chapter VIII, and DNV (ASD)
A wave scratchpad - see the recommended theory graphically, or plot the particle data for
the specified wave.
Updated piping codes: B31.3, B31.4
Automatic Dynamic DLF Plotting
Hydra expansion joint data bases
PCF Interface
The new input graphics provide a much faster drawing response,
noticeably speeding up the graphics operations. The default drawing
mode will be a 3D rendered view. New capabilities of this graphics
library will allow the user to click on an element and pull up the
associated input spreadsheet. Additionally, the graphic can be
annotated with user defined notes for printing purposes. A sample
input graphic generated from this new library is shown in the figure
below. The new input graphics are provided alongside the old ones,
since all functions have not be provided in this environment yet.
Details of the hydrodynamic (wave and current) capabilities are
discussed in a later article in this newsletter. Several piping codes
have been added for the offshore implementation of hydrodynamic
loads (B31.4 Chapter XI, B31.8 Chapter VIII, and DNV). In
addition, the load case editor has been modified to accommodate up
to four wave/current cases and up to four wind cases.
For users of the “force spectrum dynamics”, Version 4.20 w
provide automatic plotting of the computed DLF curve. T
plotting occurs automatically once the time pulse has been enter
The resulting numeric DLF data and its plot are shown side by si
as depicted in the figure below.
The PCF interface was actually first distributed in the 990617 bu
of Version 4.10. We don’t normally include new capabilitiesfeatures in intermediate builds, but we felt this one was wo
distributing before the next major release. The PCF interface rea
a PCF neutral file and creates a CAESAR II model. Any CA
package which can create a PCF file, can be used to cre
CAESAR II piping geometries.
PVElite Version 3.60 New FeaturesBy: Scott Maye
PVElite Version 3.60 will be ready to ship before the end of 199
A number of new capabilities have been added for this version,
addition to the ASME code updates. These new features are lis
in the table below.
PVElite Version 3.60 Features
A-99 addenda changes have been incorporated, including the higher allowable stresses
for Div. 1
The pre 99 addenda is available as an option (uses the 98 addenda material database, etc
Other FVC nozzles such as types F, V1, V2, and V3 are now included (with or without
nut relief)
Nozzle calculations in ANSI blind flanges can now be performed (full area replacement
An ANSI flange dimension lookup feature has been added
Required flange thickness calculations based on Rigidity considerations are included
A saddle copy feature has been incorporated
The program’s documentation is now available on-line in PDF format
Several enhancements to the user interface have been made
Dimensional Solutions Foundation 3-D interface has been addedMAWP and MAPnc can now be manually defined
The 3/32 min. thickness requirement based on the Service type (Unfired Steam) is
accounted for
The Maximum hydrotest pressure is computed in the case of overstressed geometries
The ESL will automatically be updated for current users (obviating the need for the pho
call)
An option for the pneumatic hydrotest type has been added
The material database editor can select materials from the database for editing purposes
Additional changes and updates have also been made to t
component modules of PVElite, which are also included
CODECALC Version 6.20.
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CODECALC Version 6.20
New FeaturesBy: Scott Mayeux
CODECALC Version 6.20 will be ready to ship before the end of
1999. A number of new capabilities have been added for thisversion, in addition to the ASME code updates. These new features
are listed in the table below.
CODEC ALC V ers ion 6 .20 Features
A-99 adden da changes have b een incorporated, including the higher al lowable stresses
for Div. 1
The pre 99 addenda is available as an option (uses the 98 addenda material database,
etc.)
Required flange thickness calculations based on Rigidity considerations
TEM A Eighth edit ion changes are included
Code Case 2260 has been added
The Cod eCalc User interface has been re-writ ten and now has lower m emory
requirements
Calculations per WRC 297 have been added
Appendix Y calculations are now a lso included
The m aterial database editor can select materials from the database for edit ing
pu rp os es
The E SL will automatically be updated for current users (obviating the need for the
ph on e ca ll)
Thick Wa lled Cylinder and Sphere equations are implemented per Appen dix 1
The output processor has been re-worked and streamlined
Shows and ExhibitionsBy: Richard Ay
COADE attends industry trade shows and exhibitions as a normal
business activity. The benefits of attending these events are: contact
with existing customers, introduction of the software to prospective
users, introduction of new features to the industry. Recently COADEattended two shows, hosted by our local dealers in the regions.
The Offshore Europe show was held in Aberdeen, Scotland from
September 7 through September 10, 1999. COADE’s Tom Van
Laan helped staff Fern Computer Consultancy’s booth for this
event. At this show, COADE demonstrated the new offshore
features of CAESAR II. The four day show attracted over 25,000
attendees, including many long-time COADE customers.
The Arab Oil and Gas show was held in Dubai, U.A.E. from
October 16 through October 19, 1999. COADE’s Richard Ay
helped staff ImageGrafix’s booth for this event. At this show, two
presentations were made. The first presentation detailed the newhydrodynamic (offshore) features of CAESAR II Version 4.20.
The second presentation was an “all product” demonstration,
covering the complete line of COADE software products.
The ImageGrafix Booth at the Arab Oil & Gas Show,
Dubai, U.A.E.
COADE has also attended a number of CAD-centric shows, in
order to showcase CADWorx, our piping design and drafting
software. Among others, Vornel Walker and Robert Wheat have
attended AEC Systems, the Autodesk “One Team” Conferences (in
Los Angeles and Nice, France), and the World Wide Food Expo
this year.
Visitors to these exhibitions have the opportunity to discuss software
issues, concerns, and needs first hand with the local dealer offering
support in the region, as well as the developers of the software
These exhibitions provide an excellent forum for information
exchange and education. A list of the exhibitions at which COADE
personnel will be present is maintained on the COADE web site
These events are well worth attending.
Modeling Sway Brace Assemblies
in CAESAR IIBy: Griselda Man
Vibration in a piping system is an undesirable movement that a
designer must often consider. Vibration from equipment such a
pumps, turbines and vessels can usually be anticipated and prevented
However, periodic motion or rapid oscillations of piping components
cannot always be anticipated; it may cause serious failure in a short
period of time or fatigue failure if of long duration. A recommendedsolution for controlling this type of vibration in a piping system is
the use of a sway brace assembly.
The sway brace is commonly used to allow unrestrained thermal
movements while “tuning” the system dynamically to eliminate
vibration. In this respect, the sway brace resembles a spring: it may
be pre-loaded in the cold (installed) position, so that after therma
pipe growth it reaches the neutral position and the load on the
system in the operating condition is zero or negligible.
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• Model the sway brace
Assume the following parameters:
Sway Brace Spring Rate = 150 lb./in.
Sway Brace Initial Loading = 150 lb.
Sway Brace Allowed Movement in Either Direction =
3 in.
Restraints:
Node: 10 CNode: 101
Type: X2 K2: 150 lb./in.
K1: F: 150 lb.
Node: 10 CNode: 101
Type: X Gap: 3.0 in.
Stiff:
Displacements:
Node: 101
DX2: 0.5 in.
• Include the applied displacement D2 (vector 2) in both the
SUS and OPE load cases.
Typically as shown:
Load Case 1 - W+P1+T1+D1+F1+D2 (OPE)
Load Case 2 - W+P1+F1+D2 (SUS)
Load Case 3 - DS1-DS2 (EXP)
In the SUS case the displacement D2 (vector 2) represents the pre-
load in cold position. Under shutdown conditions, the pipe returns
to its cold position and the brace exerts a force as previously
described.
Sustained case restraint loads on sway brace = Pre-Load + Hot
Deflection * Spring Rate
In OPE the displacement allows thermal expansion and the sway
assumes neutral position exerting zero or negligible load on the
pipe.
Operating case restraint loads on sway brace =~ 0.0 (does not
restrain thermal expansion)
Engineers and designers in search of solutions to vibration problems
readily recognize the importance and functions of the sway brace.
The assembly is easy to handle, select and adjust, and now, easy to
model in CAESAR II.
Hydrodynamic Loading of
Piping SystemsBy: Richard Ay
Ocean waves are generated by wind and propagate out of the
generating area. The generation of ocean waves is dependent on thewind speed, the duration of the wind, the water depth, and the
distance over which the wind blows. This distance over which the
wind blows is referred to as the fetch length. There are a variety o
two dimensional wave theories proposed by various researchers
but the three most widely used are the Airy (linear) wave theory
Stokes 5th Order wave theory, and Dean’s Stream Function wave
theory. The later two theories are non-linear wave theories and
provide a better description of the near-surface effects of the wave
(The term “two dimensional ” refers to the “uni-directional ” wave
One dimension is the direction the wave travels, and the other
dimension is vertical through the water column. Two dimensiona
waves are not found in the marine environment, but are somewha
easy to define and determine properties for, in a deterministic sense
In actuality, waves undergo spreading, in the third dimension. This
can be easily understood by visualizing a stone dropped in a pond
As the wave spreads, the diameter of the circle increases. In
addition to wave spreading, a real sea state includes waves of
various periods, heights, and lengths. In order to address these
actual conditions, a deterministic approach cannot be used. Instead
a sea spectrum is utilized, which may also include a spreading
function. As there are various wave theories, there are various sea
spectra definitions. The definition and implementation of sea spectra
are usually employed in dynamic analysis. Sea Spectra and dynamic
analysis, which has been left for a future implementation ofCAESAR II , will not be discussed in this article.)
The linear or Airy wave theory assumes the free surface is symmetric
about the mean water level. Furthermore, the water particle motion
is a closed circular orbit, the diameter of which decays with depth
(The term circular should be taken loosely here, the orbit varies
from circular to elliptical based on whether the wave is in shallow or
deep water.) Additionally, for shallow water waves, the wave
height to depth ratio (H/D) is limited to 0.78, to avoid breaking
(None of the wave theories address breaking waves!) The figure
below shows a typical wave and associated hydrodynamic
parameters.
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SWL - The still water level.
L - The wave length, the horizontal distance between
successive crests or troughs
H - The wave height, the vertical distance between the
crest and trough.
D - The water depth, the vertical distance from the bottom
to the still water level.
η - The surface elevation measured from the still water level.
Ocean Wave Particulars
The Airy wave theory provides a good first approximation to the
water particle behavior. The nonlinear theories provide a better
description of particle motion, over a wider range depths and wave
heights. The Stokes 5th wave theory is based on a power series.
This wave theory does not apply the symmetric free surface
restriction. Additionally, the particle paths are no longer closed
orbits, which means there is a gradual drift of the fluid particles, i.e.
a mass transport.
Stokes 5th order wave theory however, does not adequately address
steeper waves over a complete range of depths. Dean’s Stream
Function wave theory attempts to address this deficiency. This
wave theory employs an iterative numerical technique to solve the
stream function equation. The stream function describes not only
the geometry of a two dimensional flow, but also the components of
the velocity vector at any point, and the flow rate between any two
streamlines.
The most suitable wave theory is dependent on the wave height, the
wave period, and the water depth. Based on these parameters, the
applicable wave theory can be determined from the figure below
(from API-RP2A, American Petroleum Institute - Recommended
Practice 2A).
Applicable Wave Theory Determination
The limiting wave steepness for most deep water waves is usua
determined by the Miche Limit:
H / L = 0.142 * tanh( kd )
where: H is the wave height
L is the wave length
k is the wave number (2π/L)d is the water depth
Pseudo-Static Hydrodynamic Loading
CAESAR II allows individual pipe elements to experience loadi
due to hydrodynamic effects. These fluid effects can impose
substantial load on the piping elements in a manner similar to, b
more complex than wind loading.
The various wave theories incorporated into CAESAR II as well
the various types of current profiles are discussed below. The wa
theories and the current profile are used to compute the wa
particle velocities and accelerations at the node points. Once th
parameters are available, the force on the element can be compu
using Morrison’s equation:
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F = 1/2 * ρ * Cd * D * U * |U| + π/4 * ρ * C
m * D2 * A
where ρ - is the fluid densityC
d- is the drag coefficient
D - is the pipe diameter
U - is the particle velocity
Cm - is the inertial coefficientA - is the particle acceleration
The particle velocities and accelerations are vector quantities which
include the effects of any applied waves or currents. In addition to
the force imposed by Morrison’s equation, piping elements are also
subjected to a lift force and a buoyancy force. The lift force is
defined as the force acting normal to the plane formed by the
velocity vector and the element’s axis. The lift force is defined as:
Fl = 1/2 * ρ * Cl * D * U2
where ρ - is the fluid densityCl - is the lift coefficientD - is the pipe diameter
U - is the particle velocity
The buoyancy force acts upward, and is equal to the weight of the
fluid volume displaced by the element. The buoyancy effect is
automatically included in all load cases which include weight.
Once the force on a particular element is available, it is placed in the
system load vector just as any other load is. A standard solution is
performed on the system of equations which describe the piping
system. (The piping system can be described by the standard finite
element equation:
[K] {x} = {f}
where [K] - is the global stiffness matrix for the
entire system
{x} - is the displacement / rotation vector
to solve for
{f} - is global load vector
The element loads generated by the hydrodynamic effects are placed
in their proper locations in {f}, similar to weight, pressure, and
temperature. Once [K] and {f} are finalized, a standard finite
element solution is performed on this system of equations. Theresulting displacement vector {x} is then used to compute element
forces, and these forces are then used to compute the element
stresses.)
Except for the buoyancy force, all other hydrodynamic forces acting
on the element are a function of the particle velocities and
accelerations.
AIRY Wave Theory Implementation
Airy wave theory is also known as “linear” wave theory, due to the
assumption that the wave profile is symmetric about the mean water
level. Standard Airy wave theory allows for the computation of the
water particle velocities and accelerations between the mean surface
elevation and the bottom. The Modified Airy wave theory allowfor the consideration of the actual free surface elevation in the
computation of the particle data. CAESAR II includes both the
standard and modified forms of the Airy wave theory.
To apply the Airy wave theory, several descriptive parameters
about the wave must be given. These values are then used to solve
for the wave length, which is a characteristic parameter of each
unique wave. CAESAR II uses Newton-Raphson iteration to
determine the wave length by solving the dispersion relation, shown
below:
L = (gT2 / 2π) * tanh(2πD / L)
where g - is the acceleration of gravityT - is the wave period
D - is the mean water depth
L - is the wave length to be solved for
Once the wave length (L) is known, the other wave particulars of
interest may be easily determined. The parameters determined and
used by CAESAR II are: the horizontal and vertical particle
velocities ( UX and UY ), the horizontal and vertical particle
acceleration ( AX and AY ), and the surface elevation (ETA) above
(or below) the mean water level. The equations for these parameters
can be found in any standard text (such as those listed at the end of
this section) which discusses ocean wave theories, and thereforewill not be repeated here.
STOKES Wave Theory Implementation
The Stokes wave is a 5th order gravity wave, and hence non-linear
in nature. The solution technique employed by CAESAR II is
described in a paper published by Skjelbreia and Hendrickson of
the National Engineering Science Company of Pasadena California
in 1960. The standard formulation as well as a modified formulation
(to the free surface) are available in CAESAR II.
The solution follows a procedure very similar to that used in the
Airy wave; characteristic parameters of the wave are determined by
using Newton-Raphson iteration, followed by the determination of
the water particle values of interest.
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The Newton-Raphson iteration procedure solves two non-linear
equations for the constants beta and lambda. Once these values are
available, the other twenty constants can be computed. After all of
the constants are known, CAESAR II can compute: the horizontal
and vertical particle velocities (UX and UY), the horizontal and
vertical particle acceleration (AX and AY), and the surface elevation
(ETA) above the mean water level.
Stream Function Wave Theory Implementation
The solution to Dean’s Stream Function Wave Theory employed by
CAESAR II is described in the text by Sarpkaya and Isaacson. As
previously mentioned, this is a numerical technique to solve the
stream function. The solution subsequently obtained, provides the
horizontal and vertical particle velocities (UX and UY), the horizontal
and vertical particle acceleration (AX and AY), and the surface
elevation (ETA) above the mean water level.
Ocean Currents
In addition to the forces imposed by ocean waves, piping elements
may also be subjected to forces imposed by ocean currents. There
are three different ocean current models in CAESAR II; linear,
piece-wise, and a power law profile.
The linear current profile assumes that the current velocity through
the water column varies linearly from the specified surface velocity
(at the surface) to zero (at the bottom). The piece-wise linear
profile employs linear interpolation between specific “depth/
velocity” points specified by the user. The power law profile
decays the surface velocity to the 1/7 power.
While waves produce unsteady flow, where the particle velocitiesand accelerations at a point constantly change, current produces a
steady, non-varying flow.
Technical Notes on CAESAR II Hydrodynamic Loading
The input parameters necessary to define the fluid loading are
described in detail in the next section. The basic parameters
describe the wave height and period, and the current velocity. The
most difficult to obtain, and also the most important parameters, are
the drag, inertia, and lift coefficients, Cd, C
m, and C
l. Based on the
recommendations of API RP2A and DNV (Det Norske Veritas),
values for Cd
range from 0.6 to 1.2, values for Cm
range from 1.5 to
2.0. Values for Cl show a wide range of scatter, but the approximate
mean value is 0.7.
The inertia coefficient Cm is equal to one plus the added mass
coefficient Ca. This added mass value accounts for the mass of the
fluid assumed to be entrained with the piping element.
In actuality, these coefficients are a function of the fluid partic
velocity, which varies over the water column. In general practi
two dimensionless parameters are computed which are used
obtain the Cd, Cm, and Cl values from published charts. The fi
dimensionless parameter is the Keulegan-Carpenter Number, K.
is defined as:
K = Um * T / D
where: Um
- is the maximum fluid particle veloc
T - is the wave period
D - is the characteristic diameter of the
element.
The second dimensionless parameter is the Reynolds number,
R e is defined as
R e = U
m * D / ν
where Um - is the maximum fluid particle velocD - is the characteristic diameter of the
element
ν - is the kinematic viscosity of the flui(1.26e-5 ft2/sec for sea water).
Once K and R e are available, charts are used to obtain C
d, C
m, a
Cl. (See Mechanics of Wave Forces on Offshore Structures by
Sarpkaya, Figures 3.21, 3.22, and 3.25 for example charts, whi
are shown in the figures below.)
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In order to determine these coefficients, the fluid particle velocity
(at the location of interest) must be determined. The appropriate
wave theory is solved, and these particle velocities are readily
obtained.
Of the wave theories discussed, the modified Airy and Stokes
5th theories include a modification of the depth-decay function.
The standard theories use a depth-decay function equal to
cosh(kz) / sinh(kd), where:
k - is the wave number, 2π /LL - is the wave length
d - is the water depth
z - is the elevation in the water column
where the data is to be determined
The modified theories include an additional term in the numerator of this depth-decay function. The modified depth-decay function
is equal to cosh(k αd) / sinh(kd), where:
α - is equal to z / (d + η)
The term αd represents the effective height of the point at which the particle velocity and acceleration are to be computed. The use of
this term keeps the effective height below the still water level. This
means that the velocity and acceleration computed are convergen
for actual heights above the still water level.
As previously stated, the drag, inertia, and lift coefficients are afunction of the fluid velocity and the diameter of the element in
question. Note that the fluid particle velocities vary with both depth
and position in the wave train (as determined by the applied wave
theory). Therefore, these coefficients are in fact not constants
However, from a practical engineering point of view, varying these
coefficients as a function of location in the fluid field is usually no
implemented. This practice can be justified when one considers the
inaccuracies involved in specifying the instantaneous wave height
and period. According to Sarpkaya, these values are insufficient to
accurately predict wave forces, a consideration of the previous fluid
particle history is necessary. In light of these uncertainties, constan
values for Cd, C
m, and C
l are recommended by API and many other
references.
The effects of marine growth must also be considered. Marine
growth has the following effects on the system loading: the increased
pipe diameters increase the hydrodynamic loading; the increased
roughness causes an increase in Cd, and therefore the hydrodynamic
loading; the increase in mass and added mass cause reduced natura
frequencies and increase the dynamic amplification factor; it causes
an increase in the structural weight; and possibly causes
hydrodynamic instabilities, such as vortex shedding.
Finally, Morrison’s force equation is based the “small body”
assumption. The term “small” refers to the “diameter to wave
length” ratio. If this ratio exceeds 0.2, the inertial force is no longein phase with the acceleration of the fluid particles and diffraction
effects must be considered. In such cases, the fluid loading a
typically implemented by CAESAR II is no longer applicable.
Additional discussions on hydrodynamic loads and wave theories
can be found in the references at the end of this article.
Input: Specifying Hydrodynamic Parameters in CAESAR II
The hydrodynamic load analysis requires the specification of severa
measurable parameters which quantify the physical aspects of the
environmental phenomenon in question. The necessary
hydrodynamic parameters are shown in the following CAESAR II
hydrodynamic loading.
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Details of this input screen can be found in the program
documentation. Once the wave parameters have been defined, the“plot” button on the tool bar (the far right button in the figure above)
will activate the Wave Wizard . This module will plot the
“Recommended Wave Theory” diagram, including the location of
the specific wave just defined. This diagram shows exactly where
the specified wave falls on the chart, as shown in the figure below.
The Wave Wizard can produce other plots of the data for this
specific wave, as well as display the numeric data tables which
correspond to these plots. The “View Data Table” button at the
bottom of the screen brings up the numeric data in tabular form.
This data includes the free surface elevation as a function of wave
phase, and tables of horizontal and vert ical velocit ies and
accelerations as a function of wave phase and water depth. An
example plot (obtained by selecting from the drop list in the figure
above) shown below.
A Comparison of Wind Load
Calculations per ASCE 93
and ASCE 95By: Scott Maye
Frequently in the design of vertical and horizontal pressure vesse
the need for computing loads on these and other structures due
the effects of wind is a necessity. Air can be thought of as a fluid
low viscosity. When air moves around an obstacle, its kine
energy is given up to the structure that is resisting the wind. Becauof this transfer of momentum and energy, forces are placed on
structure that cause bending and other loads to arise. It is th
loads that we must account for in the design of pressure vesse
most notably vertical pressure vessels. In this article we w
explore the equations that are used in the computation of wind loa
according to the ASCE 95 and 93 design codes. Of course there
many wind design codes that are in use world wide, but the ASC
codes are commonly used in the United States and we will concentr
on how these codes develop loads due wind and compare the
The discussion of the ASCE 95 code will be followed by t
discussion of the ASCE 93 code.
From physics, the kinetic energy of a moving particle is express by the following equation:
Ke = 1/2 M V2
Where M is the mass of the particle and V is the velocity. In U
customary units the mass is expressed in units of lb. and velocity
expressed in units of feet per second. Please note that in this syst
of units the gravitational acceleration constant of 32.2 must
properly applied to the mass M.
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Obtaining the kinetic energy term is step 1 in the determination of
the wind pressure at a given elevation. The term is as follows:
Constant = 00256.03600
5280
2.320765.0
2
1 22
=
×
s
hr
mi
ft
hr
mi
ft
s
ft cu
lb
The constant that uses the value of 0.0765, reflects the mass density
of air at standard atmospheric pressure and a temperature of 59
degrees F. This constant is used in the following equation of qz,
which is the wind pressure at an arbitrary elevation (z). qz is
expressed by the following equation:
qz = 0.00256(Kz)(Kzt)(V2)(I) units: Pound per square foot (psf)
Where Kz - velocity pressure coefficient,
Kzt - topographic factor,
V - basic wind speed
I - importance factor.
The term Kz in turn is defined by the following equation(s):
For elevations below 15 feet, Kz = 2.01*( 15/zg)2/alpha. For elevations
above 15 feet, Kz = 2.01*(z/zg) 2/alpha. Values of alpha and zg are
shown in the table below:
Exposure Category Constants
Exp. Category alpha Zg(ft)
A 5.0 1500
B 7.0 1200
C 9.5 900D 11.5 700
The exposure categories in the ASCE code are explained in paragraph
6.5.3. The exposure category pertains to the amount of obstruction
the structure is shielded from. For example, a vertical structure that
lies along a flat unobstructed plain will feel the full effect of the
wind. While a structure in the middle of a large city center with
plenty of shielding will not feel the full effect of the wind. An
exposure D is the most conservative while A is the least conservative.
The topographic factor Kzt involves computing the speed up effect
of the wind blowing over a hill or some other type of escarpment.
For most computations in this industry, Kzt is taken to be 1.0.
V is defined as the basic wind speed. The minimum value of V is 70
miles per hour. Along hurricane oceanlines V increases substantially
to 120 mph or higher. Note that since this term is squared, it has a
big impact on the final wind pressure qz.
The final term in the equation of qz is I. I is the importance factor.
It accounts for the degree of loss of life and damage to property. I
can vary between 0.87 to values of 1.15 or greater.
Now that we are familiar with all of the terms needed to compute qz
lets look at a sample calculation.
Given: Exposure C, V = 100 mph, I = 1.15, z = 50 ft.
From the table alpha is 9.5 and zg is 900 ft. Consequently kz =
2.01*(50/900) 2/9.5
. kz is therefore equal to 1.098. qz =0.00256(1.0938)(1)(100 * 100)(1.15). Thusly at an elevation of 50
feet the computed wind pressure is 32.2 lbs/sq ft. Once the wind
pressure at the target elevation has been computed the relation
Force = pressure * area is used to determine a single concentrated
force F at this elevation.
PVElite uses this methodology to compute loads at the wind centroid
of each element (shell course). There are two more terms that are
involved in the final computation of the force. These terms are the
Gust Response Factor and the shape factor. Vertical pressure
vessels are typically round and smooth and have a shape factor of
0.6 to 0.8. The other term is the gust response factor G. The gus
response factor accounts for the fact that the wind “gusts” or speedsup periodically. This factor is a computed constant for the entire
structure and depends on its dynamic sensitivity. Gust effect factors
are discussed in paragraph 6.6 of ASCE 95.
After the wind pressure at each elevation has been computed, the
area of each element must also be computed. The wind pressure
times the area results in a force at elevation z. This force times a
distance to the support point results in a bending moment. The
stress on the cross section due to this moment should also be
investigated.
The following sample shows a PVElite sample model with a wind
loading and shear and bending report.
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PVElite 3.5 Licensee: COADE, Inc.
FileName : WindLoad —————————————————————————————————————— Page 1
Wind Load Calculation STEP: 8 9:42a Nov 2,1999
Wind Analysis Results
User Entered Importance Factor is 1.150
ASCE-7 95 Gust Effect Factor (Ope)(G or Gf) Dynamic 0.979
User entered Beta Value ( Operating Case ) 0.0100
ASCE-7 95 Shape Factor (Cf) 0.601
User Entered Basic Wind Speed 100.0 mile/hr
Wind Vibration Calculations
—————————————————————————————————————————————————————————————————————————
This evaluation is based on work by Kanti Mahajan and Ed Zorilla
Nomenclature
Cf - Correction factor for natural frequency
D - Average internal diameter of vessel ft.
Df - Damping Factor
Dr - Average internal diameter of top half of vessel ft.
f - Natural frequency of vibration (Hertz)
f1 - Natural frequency of bare vessel based on a unit value of (D/L^2)(10^4
L - Total height of structure ft.
Lc - Total length of conical section(s) of vessel ft.
tb - Uncorroded plate thickness at bottom of vessel in.
V30 - Wind Velocity at 30 feet mile/hr
Vc - Critical wind velocity mile/hr
Vw - Maximum wind speed at top of structure mile/hr
W - Total corroded weight of structure lb.
Ws - Cor. vessel weight excl. weight of parts which do not effect stiff. lb Z - Maximum amplitude of vibration at top of vessel in.
Dl - Logarithmic decrement ( taken as 0.03 for Welded Structures )
Vp - Vibration Possibility, 25.00000 no possibility.
Vp = W / ( L * Dr^2 )
Vp = 108779 / ( 55.50 * 8.000^2 ) = 30.625
Since Vp is > 25.0000 no further vibration analysis is required !
Wind Load Calculation
| | Wind | Wind | Wind | Height | Element |
From| To | Height | Diameter | Area | Factor | Wind Load |
| | ft. | ft. | sq.in. | psf | lb. |
10| 20| 2.50000 | 9.80000 | 7056.00 | 24.9911 | 720.260 |
20| 30| 5.12500 | 9.80000 | 352.800 | 24.9911 | 36.0130 |
30| 40| 10.2500 | 9.80000 | 14112.0 | 24.9911 | 1440.52 |
40| 50| 20.2500 | 9.80000 | 14112.0 | 26.6210 | 1534.47 |
50| 60| 30.2500 | 9.80000 | 14112.0 | 28.9681 | 1669.75 |
60| 70| 40.2500 | 9.80000 | 14112.0 | 30.7633 | 1773.23 |
70| 80| 50.2500 | 9.80000 | 14112.0 | 3 2 . 2 3 4 6 | 1858.04 | 80| 90| 56.2504 | 9.80000 | 2277.03 | 33.0092 | 307.007 |
PVElite Version 3.5, (c)1995-99 by COADE Engineering Software
Notice that in this report the wind height is the value z used in the
above formulas. The element wind load is multiplied by the wind
height to determine the moment at the base and at the bottom of
each section of the vessel. Also note that the wind pressure increases
as a function of the wind height as one would expect. The following
report illustrates the wind shear and bending for all of the elements.
PVElite 3.5 Licensee: COADE, Inc.
FileName : WindLoad —————————————————————————————————————— Page 1
Wind/Earthquake Shear, Bending STEP: 10 9:42a Nov 2,1999
The following table is for the Operating Case.
——————————————————————————————————————————————————————————————————————————
Wind/Earthquake Shear, Bending
| | Elevation | Cummulative| Earthquake | Wind | Earthquake |
From| To | of To Node | Wind Shear| Shear | Bending | Bending |
| | ft. | lb. | lb. | ft.lb. | ft.lb. |
10| 20| 2.50000 | 9339.29 | 0.00000 | 280342. | 0.00000 |
20| 30| 5.12500 | 8619.03 | 0.00000 | 235446. | 0.00000 |
30| 40| 10.2500 | 8583.02 | 0.00000 | 233296. | 0.00000 |
40| 50| 20.2500 | 7142.50 | 0.00000 | 154668. | 0.00000 |
50| 60| 30.2500 | 5608.03 | 0.00000 | 90915.6 | 0.00000 |
60| 70| 40.2500 | 3938.28 | 0.00000 | 43184.0 | 0.00000 |
70| 80| 50.2500 | 2165.05 | 0.00000 | 12667.4 | 0.00000 |
80| 90| 55.3750 | 307.007 | 0.00000 | 307.141 | 0.00000 |
PVElite Version 3.5, (c)1995-99 by COADE Engineering Software
Once the moments have been resolved at each point of interest,
stress on that cross section can be obtained by using the standa
stress equation; stress = Moment * Fiber Distance / (Moment
Inertia). These stresses are added algebraically to other longitudin
stresses to obtain the total stress on both the tensile and compress
side of the vessel. These resulting stresses can then be compared
appropriate allowables.
ASCE 93
Prior to the publication of ASCE 95, the wind design code
general use was its predecessor ASCE 93. This wind code w
essentially the American National Standard Institute Code 58
There are a few key differences between these two wind lo
specifications. We will now explore these differences.
First of all the basic equation for the wind pressure qz is differe
In the 93 edition it is as follows:
qz = 0.00256(Kz)( I V) 2 units: Pound per square foot (psf)
Note that the importance factor I is now squared along with t
design wind velocity and the factor Kzt is absent from the equatio
Other differences include changes to values of alpha in Table C
The values are reduced in comparison to those in the later editi
causing higher values of Kz to result.
Analyzing our tower model under the older code with the sam
parameters produces the following results:
PVElite 3.5 Licensee: COADE, Inc.
FileName : WindLoad —————————————————————————————————————— Page 1
Wind Load Calculation STEP: 8 9:24a Nov 8,1999
Wind Analysis Results
User Entered Importance Factor is 1.150
ASCE-7 Gust Factor (Gh, Gbar) Dynamic 1.217
ASCE-7 Shape Factor (Cf) for the Vessel is 0.601
User Entered Basic Wind Speed 100.0 mile/hr
Wind Vibration Calculations
—————————————————————————————————————————————————————————————————————————
This evaluation is based on work by Kanti Mahajan and Ed Zorilla
Nomenclature
Cf - Correction factor for natural frequency
D - Average internal diameter of vessel ft.
Df - Damping Factor
Dr - Average internal diameter of top half of vessel ft.
f - Natural frequency of vibration (Hertz)
f1 - Natural frequency of bare vessel based on a unit value of (D/L^2)(10^4 L - Total height of structure ft.
Lc - Total length of conical section(s) of vessel ft.
tb - Uncorroded plate thickness at bottom of vessel in.
V30 - Wind Velocity at 30 feet mile/hr
Vc - Critical wind velocity mile/hr
Vw - Maximum wind speed at top of structure mile/hr
W - Total corroded weight of structure lb.
Ws - Cor. vessel weight excl. weight of parts which do not effect stiff. lb
Z - Maximum amplitude of vibration at top of vessel in.
Dl - Logarithmic decrement ( taken as 0.03 for Welded Structures )
Vp - Vibration Possibility, 25.00000 no possibility.
Vp = W / ( L * Dr^2 )
Vp = 108779 / ( 55.50 * 8.000^2 ) = 30.625
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Since Vp is > 25.0000 no further vibration analysis is required !
Wind Load Calculation
PVElite 3.5 Licensee: COADE, Inc.
FileName : WindLoad —————————————————————————————————————— Page 2
Wind Load Calculation STEP: 8 9:24a Nov 8,1999
| | Wind | Wind | Wind | Height | Element |
From| To | Height | Diameter | Area | Factor | Wind Load |
| | ft. | ft. | sq.in. | psf | lb. |
10| 20| 2.50000 | 9.80000 | 7056.00 | 27.1152 | 971.392 |
20| 30| 5.12500 | 9.80000 | 352.800 | 27.1152 | 48.5696 |
30| 40| 10.2500 | 9.80000 | 14112.0 | 27.1152 | 1942.78 |
40| 50| 20.2500 | 9.80000 | 14112.0 | 29.5427 | 2116.72 |
50| 60| 30.2500 | 9.80000 | 14112.0 | 33.1322 | 2373.90 |
60| 70| 40.2500 | 9.80000 | 14112.0 | 35.9493 | 2575.75 |
70| 80| 50.2500 | 9.80000 | 14112.0 | 38.3023 | 3177.61 |
80| 90| 56.2504 | 9.80000 | 2277.03 | 39.5569 | 457.313 |
PVElite Version 3.5, (c)1995-99 by COADE Engineering Software
It can be seen that the wind pressure at each corresponding elevation
is greater than in the 95 edition causing the element loads (in
conjunction with the gust factor) to produce larger loads and moments
on this process tower model.
In conclusion, we note that the 93 edition is more conservative than
the newer 95 edition. However please understand that the guidelinesin the 95 edition are based on newer findings and reflect the effort of
a great deal of research in the area of actual wind dynamics and
behavior.
Layouts in AutoCAD 2000
and CADWorx/PIPEBy: Robert Wheat
With the release of AutoCAD 2000, Autodesk has made another
strong step towards the Windows look and feel. The new features in
the AutoCAD 2000 when combined with CADWorx version 3.0
makes these products even more robust. Ease of use was the main
reason CADWorx was designed and with this new AutoCAD
release, many of the functions used are even simpler to operate due
to this totally integrated Windows environment.
Autodesk has added an object property manager (OPM), real-time
shading, multiple document interface (MDI), and has made extensive
changes to the functionality of Paperspace. The new OPM allows
modification to the properties of any entity from within a simple
dialog. With this facility, layers, colors, and line types are easily
changed. Hyperlinks can be attached from this simple list type
dialog. The real time shading can make your CAD station seem likea tinker toy set. Purchase a $300-$600 video card and your monitor
will come to life in a whole new dimension. CADWorx/PIPE
functionality has been modified to work with the new shaded images
in many ways. For example, CEDIT has been improved to allow
the user to pick the graphic outlines instead of having to pick
centerlines of the component. This allows the user to work and
build piping systems in this new real time shaded mode. The new
multiple document interface allows the user to open multiple
drawings within a single AutoCAD session. This is really powerful,
allowing drag and drops of entities from drawing to drawing
CADWorx/PIPE has utilized this functionality in every way. Sizes
and specifications are unique in each drawing while in this single
session of AutoCAD. CADWorx/P&ID allows items to be dropped
from other drawings and then it automatically updates the database
as needed. All these new features make AutoCAD 2000 and
CADWorx an unbeatable pair.
To us, the development staff at COADE, Inc., the new Paperspace –
Modelspace layout features are probably the most exciting. With
the addition of the multiple layouts in Paperspace, all those tha
have not used Paperspace and three-dimensional models will have
to take another look. This environment has become a very valuable
asset. Users of CADWorx/PIPE are creating single models and
populating the environment with up to 50 different layouts. These
layouts consist of the plans, elevation, various sections and any
details that might be required for the job. Layouts can have differen
scales and even different borders. They can be isometrics or simple
orthographics. With CADWorx/PIPE’s view clipping
(VIEWCLIP), sections can be set up from any of these differenlayouts. Now, the magic of these new layouts is when one change is
made to the model, all the different drawings will be updated
Modify dimensions, text and other annotation – but don’t worry
about the model – change it once.
Our support staff is always providing ideas and suggestions for
making Paperspace work. We believe that Paperspace is very
useful tool. Within this article, we would like to supply some
secrets that will make all of this quite simple. Many people try to
make Paperspace-Modelspace modeling much more difficult than it
really is.
What do we do first? Well, the user must start with a 3D modelBuilding a three dimensional model within CADWorx/PIPE is
simple and easy. Take the time to build something simple and see
just how easy it is. Most resistance to 3D models is the time facto
needed to create a true model versus the time factor needed to create
all the plans and elevations in pure 2D layouts. In all reality, the
time factor is just about the same with the exception of changes
When computers first became useful in engineering departments
around the mid-80s, we found that things were easier to change.
Therefore, changes are much more prevalent than they were in the
days prior to CAD. Changes are easier to deal with in a model
Things change within a project, and to be able to change one item
on a model and have it update 50 layouts (with borders, titles
annotation, etc.) would be incredible. This would also be a huge
time saving both for the customer and the engineering group.
To make this simpler, start with a 2D plan view of the project. Lay
everything out as though it was a 2D drawing. Think of it as only
the working X-Y layout. Forget about the vertical information –
valves in down comers or what elevations need to look like (this is
the Z information which will be added later). If this was a
maintenance job, elevations might not be known, but for now jus
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draw the piping flat on the piece of paper. Most new jobs will
require the designer to set elevations based on some type of intelligent
decision after the job becomes more organized. But this is not done
at the beginning of the job. We can apply elevations to the piping
anytime in a very simple manner with the CHANGEELEV command
within CADWorx/PIPE. Use the 2D drawing capabilities of
CADWorx/PIPE and create a 2D drawing.
Once the 2D drawing is created, elevate the components as mentioned
above with the CHANGEELEV command. This will seem to be
one of those steps
that was not
required in the 2D
world but the
sections and
elevation created in
the 2D world is not
one of those
required for the 3D
model. At this po int, mode
convert everything
to either 3D solids
or to an isometric
mode. This is
accomplished with
t h e
CONVERTSOLID
or CONVERTISO
commands within
CADWorx/PIPE.
Solids will be the
finished productand should be used
whenever possible.
Isometrics are good
for layout purposes
when things get crowded. Now, we have the beginning of a true 3D
model. There will be vertical information missing but that is what
you develop sections and elevations for with the Mviews that will
be discussed later.
Models are not restricted to just one drawing either. Many designers
can work on different parts of the model and they can all be Xref’ed
(external reference) together to create one model. With this Xref’ed
model, it to can be created with multiple layouts as with a single
model in a single drawing.
Next, develop some plan views in Paperspace. Make sure that the
UCS is set to World and run the Plan command using the world
option while in Model space. This should show you a plan view of
the model. In AutoCAD 2000, pick the Layout tab at the bottom
right above the command prompt. When you enter this space, a plot
dialog appears which requires a plotter to be selected before you
can continue. If a plotter configuration is not set up, go to the
named “Plot Device” and under the plotter configuration, pick t
plotter named “None”. Then pick the “Plot Settings” tab and p
the paper size desired. If you have a plotter already set up, use
There are some very useful and needed features in the new plotti
menu in AutoCAD 2000. Autodesk supplied some needed au
clips that help in the setup of a plotter and it is our suggestion view and listen to these clips for all the new details involved w
this new plotting method. In the Options dialog, under the
named “Display”, there is a toggle that allows the automatic creati
of an Mvi
whenever a layout
created. We fou
that this automatica
created Mview w
usually deleted
make room for on
that are really need
therefore we togg
it off in oconfiguration.
Prior to making
Mview, it was eas
to choose the vi
desired fro
Modelspace. This
accomplished w
the AutoCAD Vi
command a
choosing one of t
preset views from t
“Orthographic aIsometric View” t
If you need to clip t
view, wait till t
Mview is create
Then use the AutoCAD 3DCLIP command or CADWorx/PIP
VIEWCLIP command (note, the AutoCAD 3DCLIP command w
take some time for it to rotate the view in the clipping viewer if i
a relatively large model).
Create an Mview that shows the desired part of the piping pl
needed in the first layout. This is real easy. Run the Mvi
command and cut a hole in the Paperspace of any size. When thi
done the whole model immediately shows up in the Mview. Th
from the CADWorx/PIPE pulldown menu, chose the Util
pulldown and notice that the “Zoom Factors” item on the menu
accessible. Here, zooming to any scale is accommodated. Pic
scale and then pick the focal or center point within the desir
piping plan. Note that an Mview must be active for this comma
to work properly (toggle the Paper button on the status line
Model). Now, readjustment of the Mview might be requir
Toggle the Model button on the status line to Paper and then g
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the Mview (the hole in the paper) and stretch it as required. This
hole in the paper (Mview) is just like another AutoCAD entity. The
layer can be changed and it can be turned off in the Layer dialog
(move it or create it on the VIEWL layer – this is the purpose of this
layer).
Use the SETUP command within CADWorx/PIPE for setting up a border. Run the setup command and then chose the Border button
on the main dialog. Here options are available for placing the
border in Paperspace and choosing the correct border. As with
most of CADWorx/
PIPE, customizing
the borders or adding
a new border is
always possible.
Renaming the
“Layout1” tab at the
bo ttom of the
AutoCAD screen will be requ ired to
indicate what all the
different layouts will
be. Right click on
the tab and presented
are options for
renaming, deleting,
creating new layouts,
etc. “Plan 0.0-10.0”
would be appropriate
for the first layout
created above which
might show a planfrom the 0’ level to
the 10’ level. Others
might need “North
Elevation”, “Sections
A-E”. Others might be 3D isometrics field assembly drawings like
“Assembly Southeast”. Imagine that, an assembly view from the
southeast. You cannot easily create that with a 2D drawing.
To make a section, go to the model and choose the correct view that
the section needs to appear in. Next place the UCS location on the
point where the section needs to take place. It might be easier to
change the viewpoint with one of the isometric views listed above in
the AutoCAD VIEW command dialog. Use the CADWorx/PIPE
point and shoot UCS feature to place the UCS at the desired
location and make sure the X-Y plane of the UCS is actually the
plane needed for the section. Next create or go to the layout that
this section needs to appear. Cut an Mview and follow the procedure
for scaling and positioning as outline above. Do not move the UCS
once positioned in the model. Then, once the total view has been
created, run the CADWorx/PIPE VIEWCLIP command and clip
the view in the Mview (do this while in the Mview). This command
has an option that allows the front and rear clipping distances to be
set. You might need to change to these distances several times
before the right piping components are displayed.
Now that all the sections are developed, the user can go into each
one and create any vertical components required. This can be
accomplished from the model also. Many designers are used tomanipulating the drawing or design from a flat view. This probably
is the easiest place to change or alter anything within the model and
it also completes the design just like the user would if he were
working with a 2D
drawing or layout
As mentioned
above, it is our
estimate that each
job, 2D or 3D, wil
take the same
amount of time on
the front end. Once
the model iscreated, there is al
the free information
that comes with it –
a u t o m a t i c
isometrics, stress
analysis, accurate
bill of material and
d a t a b a s e s
automatic elevation
and plan updates
etc.
Once the Mviewsfor the entire job
have been created
it is best to lock
each Mview. This
is accomplished with the Mview command and its lock option. This
locks the Mview where the zoom factor cannot be changed. Very
simply, zoom in an Mview and AutoCAD switches the environmen
to Paperspace. Once the zoom command has completed, it re
enters the Mview. CADWorx/PIPE has a similar function
introduced in AutoCAD Release 14 called ZOOMLOCK. It is used
primarily by our Paperspace-Modelspace isometric. CADWorx
PIPE automatically turns this feature on in an automatic isometric
at the very end. It prohibits the zoom factor from being changed
When working with multiple layouts such as described here, it is
best to use the AutoCAD Mview command’s lock option. This
particular zoom lock is saved with the drawing whereas the
CADWorx/PIPE equivalent is turned off as the drawing is ended
Please note, we have tried to change the zoom factor many times
within an Mview only to find that the zoom lock was on. This can
be very frustrating, so make sure that the zoom lock in the Mview is
off while trying to scale or zoom an Mview.
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After the layouts are finished, annotation and dimensions can be
placed. Dimensioning can be placed in either Modelspace or
Paperspace. If they are placed in Modelspace, they must be placed
on separate layers such as “Dim1”, “Dim2”, or “DimPlanTopRight”.
Once a layer is used within an Mview, it must be frozen in all view
ports except the current one. The layers dialog can accommodate
this. Make sure the setvar DIMSCALE is set to 0. This forces allthe dimensioning routines in AutoCAD and CADWorx/PIPE to
scale the dimensioning to the proper size based on the size of the
Mview. In CADWorx/PIPE, the setvar DIMSCALE will also
affect the annotation
routines as well as
the elevation
annotation and the
line numbering
annotation.
When the
dimensions are
pl aced inPaperspace, the
setvar DIMSCALE
should also be set to
0. Also, since the
Mview is scaled to a
relative size of the
current Paperspace,
the dimensioning
setvar DIMLFAC
should be adjusted.
From the Dimension
Style Manager,
accessing the“Modify” button and
then the “Primary
Units” tab can set
this variable in the
“Scale Measurement” section. The dialog does not give the user
any help with the value that it needs to be set but there is an “Apply
to Paperspace Only” toggle which is real useful (I’m sure there is
some setvar which controls this one also). To figure what this value
should be is not difficult. For example 3/8” = 1’-0” would be 32.
Divided 12”(1’-0”) by 3/8” – make sure both values are of equal
units – inches vs. inches, millimeter vs. millimeter. The reciprocal
of this value is the same for zooming.
Annotation can be placed in Paperspace or Modelspace also. When
placed in Paperspace, it can be placed on a single layer. When
placing the annotation in Modelspace, you must place it on separate
layers just like the dimensioning. Currently, the automatic annotation
routines such as line numbering, elevation and component labeling
will only work in Modelspace. This will change in the next release
(Version 3.1) of CADWorx/PIPE. As with the dimensioning, the
setvar DIMSCALE should be set to 0 whenever the annotation
routines are used in an active Mview. The routines were design
to operate just like the dimensioning where the size of the text
automatically set according to the view port size.
Plotting is now as simple as opening a layout and picking the pr
button. There is a really neat preview button now inside of AutoCA
2000 that allows you to look at any plot prior to actual plottinAlso there is a setvar, HIDEPRECISION, which will improve t
actual plotted images greatly. This setvar increases the precis
used by the hiding algorithm inside of AutoCAD and helps pl
that have proble
such as pipe outlin
not appearing. W
have also notic
that when a pipi
design layout is a
very high elevatio
this problem see
to increase. W
advise not to uninozzle to vessel a
equipment until t
job is finished. T
way the user c
move or re-orient
nozzle at wi
Although, when th
have not be
unioned with t
equipment, plotti
looks incorrect. W
suggest doing t
union toward the eof the jo
Equipment is t
perfect example
Xrefs (place ea
piece of equipment in a drawing of its own – then Xref it into
layout or plan).
There are a couple of commands that need to be mentioned he
The SOLPROF command is excellent for creating profiles of
solids. This can be used for equipment creation and also pipi
systems that might roll out of plane. This will create a perfect
block of the solid’s profile. This command can only be used wh
in an Mview. The other commands that can be used to make flat
drawings from the 3D models are the Drawing Exchange Bina
format (DXB) and the Window metafile (WMF) format. The DX
format can be accessed from the plotting dialog and can plot t
model from Paperspace or Modelspace. The DXBIN command c
then import the DXB file into the drawing as a flat 2D drawing. T
WMF format is good for selecting item from the Modelspace on
When re-imported, it comes back as a block that will require scali
by the user.
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There are some issues with this method of 3D modeling that are a
little aggravating. There are some things that don’t work or appear
correctly according to the standards we used to produce 2D drawings.
Ball and globe valves don’t appear correctly. Centerlines disappear
into the solid of a component. There is not a good way of breaking
a pipe over another system with pipe breaks as we did in a 2D
environment. But there are ways around these problems. The problem with ball and globe valves is they both look the same.
However, you can place a circle in Paperspace over the globe valve
then place a solid hatch within the circle. Breaking pipe over
another system might not be needed since that system below can be
clipped out and shown somewhere else. It’s not like having to
redraw it. It’s all part of the model. The centerline problem is one
that we don’t have a solution for. Losing centerlines versus getting
a model that automatically updates all the drawings would be well
worth it to me.
The next generation of CADWorx/PIPE will handle the problems
as mentioned above. The components in our next generation system
will allow centerline viewing. Breaking will be allowed on pipetype components and globe valve when viewed in a plan or elevation
will appear as they have for the last 100 years. When the view is
changed back to 3D, things will look as they are in our present
CADWorx/PIPE. Hopefully completed within the next year, this
system will truly leap beyond the traditional 2D drafting techniques
and give us a tool where there will be no comparison.
PC Hardware/Software for the
Engineering User [Part 28]By: Richard Ay
Q: How can I improve I/O performance?
A: If your system is fairly I/O intensive, you may benefit from raising
the I/O Page Lock Limit, which can increase the effective rate the
operating system reads or writes data to the hard disks.
First, benchmark your common tasks. See how long it takes to load
and save large files, how long it takes to search a database or run a
common program; just do your normal tasks, timing them to record
how fast they are. Then follow these steps:
1. Start the registry editor (regedit.exe)
2. Move to HKEY_LOCAL_MACHINE\SYSTEM
\CurrentControlSet\Control\Session Manager\Memory
Management
3. Double click IoPageLockLimit
4. Enter a new value.
This value is the maximum bytes you can lock for I/O
operations. A value of 0 defaults to 512KB. Raise this value
by 512KB increments (enter “512”, “1024”, etc.), then exi
regedit and benchmark your system after each adjustment
When an increase does not give you a significant performance
boost, go back and undo the last increment.
Caution: There is a limit to this. Do not set this value (in bytes) beyond the number of megabytes of RAM times 128
That is, if you have 16 MB RAM, do not set IoPageLockLimi
over 2048 bytes; for 32MB RAM, do not exceed 4096
bytes, and so on.
5. Click OK.
6. Close the registry editor
Unless you do little I/O, this should give you a significant boost in
performance.
Q: My machine has a “constant” connection to the internet. Is my
machine secure?
A: Check out the link http://www.grc.com/, which will load a web
page designed to test the security of your computer. (Click on the
“ShieldsUp” icon.) This web site contains all the details you need
to check out the security of your system, including explanations of
security details. A related article can be found on Ziff Davis’s site
at http://cgi.zdnet.com/slink?10862:1590013
Basically, you don’t want to bind TCP/IP to Microsoft Networking
Protocols (NetBIOS or NetBEUI). If binding occurs, this opens up
the local ports to perusal via TCP/IP, which is a security breach. On
Windows NT systems, you can check and disable this binding byright clicking on “Network Neighborhood” and selecting
“Properties”. Next click on the “Bindings” tab, and finally click on
the “NetBIOS” interface. Insure the “WINS Client” is disabled
You can disable this by highlighting this option and using the
buttons at the bottom, as shown in the figure below.
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For Windows 95/98, the procedure is slightly different. Right click
on “Network Neighborhood”, then select “Properties” as before.
Next select TCP/IP form the list. After selecting TCP/IP, click on
the “Properties” button in the middle of the screen. Select the
“Bindings” tab from the resulting dialog box. Insure neither “Client
for Microsoft Networks” or “File and printer sharing for Microsoft
Networks” is checked. These two dialogs are shown in the figures below.
Q: Where can the latest, up to date information on operating
systems be obtained?
A: Check out these web sites:
JSI, Inc. - Windows NT Resource at http://www.jsinc.com/
Windows Magazine PC Tips at http://www.winmag.com/
Windows NT FAQ at http://www.ntfaq.com/
CAESAR II Notices
Listed below are those errors & omissions in the CAESAR II
program that have been identified since the last newsletter. These
corrections are available for download from our WEB site. Unless
otherwise stated, all of these changes and corrections are contained
in the 990918 build.
1) Piping Input Module: Corrected a problem inserting an
element at the front of a job, which caused the element’s data to
be lost. This problem was corrected in the 990617 build.
• Corrected the “node renumbering” option to handle negative
increments, user defined coordinates, and nozzle node
numbers.
• Corrected a problem addressing non-CADWorx valve/flange
data bases
• Corrected the acquisition of allowable stress data for the T
12 piping code
• Corrected a problem where “inserting an element at the st
of a job” lost the data for the first element. Corrected in
990617 build.
• Corrected a problem with the input echo which occurred whthe data path exceeded 64 characters. Corrected in the 9912
build.
2) Analysis Setup Module: Corrected the static load case che
routine which prevented algebraic load cases greater than 2
• Corrected the fatigue stress identifier for TD/12 cases wh
recommended by the software.
• Corrected the dynamic input module to properly interp
input specified in exponential notation. Corrected in
991201 build.
3) Miscellaneous Analysis Module: Corrected the pass/fail sta
in the expansion joint rating module on failures. This probl
was corrected in the 991201 build.
• Corrected the static output data acquisition routine to addr
more than 20 load cases. This problem was corrected in
991201 build.
• Corrected a WRC297 curve interpolation problem.
• Corrected the flange material selection routine to acqu
allowables properly when using metric units.
4) Equipment Module: Corrected the static output data acquisitiroutine to address more than 20 load cases. This problem w
corrected in the 991201 build.
• Corrected the initialization of the API661 outlet diame
value when read from an existing data file.
• Corrected the coordinate transformation (from global to loc
of the inlet MX value for API617 and NEMA23.
5) Dynamic Output Processor: Corrected the “included m
report” to list the spectrum names properly following the fi
line.
• Corrected a data conversion problem in the input echo for
through P9. Corrected in the 990617 build.
6) Static Output Processor: Corrected a problem with the inp
echo which occurred when the data directory path exceeded
characters.
• Corrected the tracking of hangers (predefined and design
in the job to allow proper load case and report selection.
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• Corrected a data conversion problem in the input echo for P3
through P9. Corrected in the 990617 build.
7) Material Data Base Editor: Corrected a problem when editing
user materials which caused the material to be added again,
instead of modified.
8) Piping Error Checker: Corrected the allowable stress
acquisition routine to handle the case where a user checked the
“allowable stress check box”, but didn’t enter any data. Corrected
in the 991201 build.
• Corrected the acquisition of allowable stress data for the TD/
12 piping code.
• Corrected an error which copied force vector #7 into vectors
#8 and #9. Corrected in the 990617 build.
• Modified necessary TD/12 calculations as per Transco's
validation project. Corrected in the 991201 build.
9) Dynamic Stress Computation Module: Corrected an error
processing the cyclic reduction factors to temperatures 4 through
9 when determining the allowable dynamic stress. Corrected in
the 990617 build.
• Modified necessary TD/12 calculations as per Transco's
validation project. Corrected in the 991201 build.
10) Static Stress Computation Module: Corrected the computation
of the allowable stress for the Z662 code, for the “from” end of
elements in tension. Corrected in the 990617 build.
• Modified necessary TD/12 calculations as per Transco's
validation project. Corrected in the 991201 build.
11) Element Generator: Modified Bourdon Pressure calculations.
Corrected in the 991201 build.
TANK Notices
Listed below are those errors & omissions in the TANK program
that have been identified since the last newsletter. These correctionsare available for download from our WEB site. Unless otherwise
stated, all of these changes and corrections are contained in the
990811 build.
1) Input Module: Corrected the acquisition of stainless steel
allowables from the material data base when using non-English
units.
• Corrected the units conversion constant for the girder ring
radius.
• Corrected several resource ID values which caused incorrec
text labels on some dialog boxes. Corrected in the 991005
build.
• Corrected the shell course material input so users can changematerials once the job is defined. Corrected in the 991005
build.
2) Error Check Module: Corrected the units conversion constan
for the girder ring radius.
3) Solution Module: Corrected a variable misspelling which
caused the value of “maximum pressure limited by uplift in
inches of H2O” to be reported as zero.
4) Output Module: Corrected a variable misspelling which
caused the number of user defined anchor bolts to be reported as
zero.
CODECALC Notices
Listed below are those errors & omissions in the CODECALC
program that have been identified since the last newsletter. These
corrections are available for download from our WEB site.
1) In WRC 297, there were a few unit conversion problems in the
results and an import function units conversion error when the
units were not English. Also a curve interpolation problem wascorrected. Also a check box for the use of ASME Section VII
Division 2 stress indices was added. To maintain compatibility
with previous results, this box must be checked. The defaul
setting is not checked.
2) For the ASME fixed tubesheet, the factor J was not properly
computed when there was no expansion joint. This was an
unconservative error. This problem has been resolved.
3) Some other fixes/enhancements were made to the U-tube required
thickness calculation when the elastic/plastic iteration was being
performed.
4) In the flange routine, circular blind flanges were being treated as
non-circular resulting in a higher than required thickness.
5) The conical discontinuity stress calculations were slightly
modified. The new results may vary slightly with the previou
results, depending on the input and the magnitude of the forces
on the top and bottom of the cone.
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6) Small nozzles on flat heads were being computed regardless of
how small the finished opening was.
7) In the shell and head module the minimum thickness has been set
to 1/16 of an inch. Additionally, some other cosmetic changes
were made to the printout.
8) The merge button in the ASME tubesheet, Tema Tubesheet and
horizontal vessel was not properly accounting for the diameter
basis.
9) In the rectangular vessel program, the Membrane stress MAWP
for figure A3 was in error and has been corrected.
PVElite Notices
Listed below are those errors & omissions in the PVElite programthat have been identified since the last newsletter. These corrections
are available for download from our web site.
1) The vortex shedding routines were obtaining results that were
extremely conservative due to a units conversion error. This
problem has been corrected.
2) The conical discontinuity stress calculations were slightly
modified. The new results may vary slightly with the previous
results, depending on the input and the magnitude of the forces
and moments on the top and bottom of the cone.
3) The BS-5500 head thickness routine failed to obtain the correctresult in one known case. The routine was re-written to solve the
problem. Also the MAWP computation for heads was reworked
at the same time and now gives correct results. This problem
occurred on elliptical and torispherical heads. Also, some of the
nomenclature was updated in the BS-5500 nozzle analysis and
some conservative error checks were resolved.
4) There was an error in the CodeCase 2260/2261 calculations for
some geometries that caused the thickness to be more conservative
than the regular ASME equations.
5) The thickness limit for hub type nozzles using Division 1 was
conservative in some cases. This problem has been fixed.
12777 Jones Rd. Suite 480 Tel: 281-890-4566 Web: www.coade.com
Houston, Texas 77070 Fax: 281-890-3301 E-Mail: [email protected]
COADE Engineering Software