Mech Eng News Jan 00

8/16/2019 Mech Eng News Jan 00

1/20

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.


2/20

COADE Mechanical Engineering News January 20

2

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.


3/20

January 2000 COADE Mechanical Engineering News

3

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.


4/20


5/20


5

• 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.


6/20


6

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:


7/20


7

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.


8/20


8

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.)


9/20


9

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.


10/20


10

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.


11/20


11

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.


12/20


12

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.



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 |


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:




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


13/20


13

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 | 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 |


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


14/20


14

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


15/20


15

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.


16/20


16

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.


17/20


17

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.


18/20


18

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.


19/20


19

• 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.



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.



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.


20/20


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

Documents

Mech Eng News Jan 00