apett engineering the association of professional...

APETT Engineering

Magazine June 2018

June 2016 Edition

June 2018

Edition

The Association of

Professional Engineers of

Trinidad and Tobago

APETT’s Mission:

The Association of

Professional Engi-

neers of Trinidad and

Tobago is a learned

society of profession-

al engineers dedicat-

ed to the develop-

ment of engineers

and the engineering

profession. The asso-

ciation promotes the

highest standards of

professional practice

and stimulates

awareness of tech-

nology and the role

of the engineer in

society.

ISSUE 5

June 2018 Edition

APETT Engineering Magazine June 2018

TABLE OF CONTENTS

Pipeline Hydraulic (Line Pack)

By: Vicard Gibbings

Article References

DISCLAIMER: Statements made and information presented by contributors to this Newsletter do not necessarily reflect

the views of APETT, and no responsibility can be assumed for them by APETT or its Executive Members and Editors.

Increasing Impact of Corrosion Control due to Change in Global Climate

By: Jerome Marshall

Page 6

Page 10

Application of Organic Communication Channels

By: Aaron Roopnarine and Dr. Sean Rocke Page 13

Hybridization of the Direct Stiffness and Macaulay Methods of Structural

Analysis

By: Jovon Jacob

Page 16

The Environmental Impacts of the Cement Manufacture Process

By: Jonathan V. Juman and Saara Sultan

Page 19

Page 26

Misunderstandings about Building Codes and T&T

By: Richard Clarke

Page 21

Page 23

Editor’s Message

Eng. Julio Bissessar

Eng. Julio Bissessar is cur-

rently a Management Trainee

and Technical Analyst for the

Senior Advisor at Massy Energy

& Industrial Gases Business

Unit. He is involved on a full-

time basis in the construction

and commissioning of the

CGCL Plant in La Brea. He has

over two years experience in

Process Engineering both at

Atlantic LNG and Petrotrin.

Julio holds a Masters of Engi-

neering in Process Engineering

from UTT and has won numer-

ous engineering competitions

solely and as a team including

BP’s UFT and the Prime Minis-

ter’s Awards for Scientific Inge-

nuity. Julio has avid interests and experience in Energy, Plant

Optimization and Design Engi-

neering as well as Mathematical

Modelling and Simulation De-

velopment.

Hello and welcome to another edition of APETT’s Engineering Magazine!

In this edition, we have a number of articles ranging from a beautiful fluids

problem in the upstream sector to the technical aspects of building foundations

and structures.

We continue to see the addition of value to the energy sector by our extremely

skilled and competent local engineers. Just by observation of the articles, it is

apparent of the level of technicality required which we engineers sometimes

take for granted. We must always take a step back and look at how our impact

affects the grander scheme of things.

As we head towards new local developments in the areas of renewables and

green energy, some of the articles featured touches on some of these factors

such as global warming impacts and the use of organic communication chan-

nels. It is extremely exciting to see what the future holds for us here in T&T.

I would like to thank all of my fellow editors who assisted greatly with the de-

velopment of this magazine. I would also like to give a special thanks to Eng.

Anna Warner and Eng. Vicard Gibbings for their continued support in ensur-

ing that this magazine is published to the highest standards and quality on

time.

Cheers!

Julio

Ms. S. Valerie Kelsick has an

extensive and diverse background covering over thirty (30) years com-bined experience in project manage-

ment, project finance, banking, finan-cial and management consulting, facility maintenance and consulting

engineering.

Ms. Kelsick holds an MBA in Finance & International Business, from Co-lumbia Business School (USA), a Bachelor of Science degree in Civil

Engineering from the University of Southampton (UK) and the PMI’s Project Management Professional

(PMP) (USA) credential. She is a Registered Engineer with the Board of Engineering as well as a Fellow of

the Association of Professional Engi-neers of Trinidad & Tobago. She also possesses various professional

credentials having completed cours-es including Chartered Director Programme from Caribbean Corpo-rate Governance Institute (TT),

public private sector partnerships, mediation and construction con-

tracts.

She is a project manager at Republic

Bank Limited managing construction and bank related projects. Ms Kel-sick is the current President of the

Association of Professional Engi-neers of Trinidad & Tobago (APETT) and also serves on the

Board of the Fondes Amandes Reaforestation Community Project

(FACRP).

Message from APETT’s President

We are living in the best of times and the worst of times. Rapidly changing

technologies and new innovations lead to enhanced and deeper knowledge

whilst also causing some uncertainty and disruption. Engineers are faced

with the task of designing and implementing resilient systems and infra-

structure which will withstand adverse effects of climate change and increased

frequency and forces of natural disasters. Competing demands on limited

available financial, human and economic resources also demands of the Engi-

neer to continue to discover alternative viable options. We must commit to the

mandate for continuous professional development.

We applaud our contributors in their quest to produce worthy articles based on

sound research, analyses and practical applications. We also express our heart-

felt thanks to our Magazine Editor Eng. Julio Bissessar and the rest of his

hardworking team for their outstanding commitment to deliver this publication

which covers the full range of the core engineering disciplines. We are notably

impressed by the extent of the critiques. Future contributors, take note!

I would like to remind all members as well as inform the rest of the readership

that APETT will be hosting our annual Honors and Awards function as well as

our Technical Conference entitled “Engineering for Competitiveness: Re-

Booting Our Economy”, successively in September 2018. We too must observe

frugality.

Finally, we encourage us all to continue to support the APETT Magazine by

submitting articles for publication.

Valerie Kelsick


Pipeline Hydraulic (Line Pack)

By: Vicard Gibbings, B.Sc., AMAPETT, AMIChemE

Line Pack A pipeline, particularly in the oil and gas industry is used to transport natural gas from production well head to consumers

(few to several hundred miles in-between) and can also be used to store that gas before and during transportation to con-

sumers. Noteworthy, the compressibility of the gas allows the storing of gas in pipelines to be performed, temporarily. This

technique is called Line Packing, i.e., a method used for providing short-term gas storage in which natural gas is compressed

in transmission lines, providing additional amounts of gas to meet limited peak demand. Therefore, by using the line packing

technique, sustainability of gas supply to consumers can be ensured if there is an increase for gas demand or a problem

encountered by an upstream producer.

Generally, in a natural gas transfer pipeline, gas flows from point ‘A’ to point ‘B’. Main properties such as pressures and

temperatures vary along the pipeline length. In a single-phase line (Gas only or Liquid only), the volume of the respective

fluid contained in a given length of pipeline is simply the physical volume of the pipe segment. For example, consider a 1-

mile Nominal Pipe Size (NPS) 16-inch natural gas pipeline. The physical volume of the gas in this pipeline will be 7000 ft3.

This pipeline volume will represent the volume of gas in this 1-mile section at the actual gas temperature and pressure.

This also applies for single-phase liquid pipelines, for example in condensate transfer pipelines. The quantity of gas con-

tained within the pipeline under pressure, measured at standard conditions (generally 14.7 psia and 60°F), is termed the

line pack volume whereas for single-phase liquid pipeline, the ‘pack volume’ is simply the physical volume of the pipeline

since liquid is incompressible. However, there are some instances where the fluid in the pipeline can experience two phase

phenomena – a particular example of multiphase flow. This will be explained in the Line Pack Calculation (Multiphase Meth-

od).

Line Pack Calculation (Single-Phase Method)

Consider pipe segment, of length L and inside diameter D, with upstream pressure (P1) and temperature (T1) and down-

stream pressure (P2) and temperature (T2), then the physical volume (Vp) of the pipe section is given by equation (1):

…Equation (1) (E. Shashi Menon, 2005)

This volume is the gas volume (assuming single-phase vapour) at pressures and temperatures ranging from P1, T1 (at the

upstream end) to P2, T2 (at the downstream end) of the pipe length L with internal diameter D. The gas volume calculated

is at actual conditions and thus needs to be converted to standard conditions of pressure (Pb) and temperature (Tb). We

apply the gas law in equation (2):

…Equation (2) (E. Shashi Menon, 2005)

Where Pavg = average gas pressure in pipe segment, Tavg = average gas temperature in pipe segment, Zavg = average gas com-

pressibility factor at Tavg and Pavg, Zb = compressibility factor at base conditions ~1.00 and Vb = line pack volume in pipe

segment at standard conditions. The average pressure (Pavg) is calculated from the upstream and downstream pressures, P1

and P2 respectively, using equation (3) below. This equation was utilized since at larger pressure drops, the percentage er-

ror increases.

In addition, pressure drop vary non-linearly and the equation used can be the best representative of calculating Pavg. The

average temperature (Tf) can be taken as the arithmetic mean of the upstream and downstream temperatures T1 and T2

respectively. This approach for average temperature will be accurate only if we consider short segments of pipe. Finally, the

compressibility factor, Z can be calculated using equation (4). It is important to note that this compressibility factor is valid

when the average gas pressure is greater than 100 psig. For average pressures less than or equal to 100 psig, Z is approxi-

mately equal to 1.00. Alternatively, we can use an engineering software such as Aspen HYSYS to get the Z-value.

…Equation (3 ) (E. Shashi Menon, 2005)

…Equation (4) (E. Shashi Menon, 2005) Where G is the gas gravity (air =1)

From Equation (2), solving for line pack Vb at standard conditions, we get

…Equation (5) (E. Shashi Menon, 2005) Substituting Vp from equation (1) into equation (5) into yields

…Equation (6) (E. Shashi Menon, 2005) Where Vb = line pack in pipe segment in standard ft3, D = pipe inside diameter in ft, L = pipe segment length in ft. Since the pressure and temperature in a gas pipeline vary along the length, to improve the accuracy of calculations, the line

pack volume Vb is calculated for short segments of pipe and summed to obtain the line pack of the entire pipeline . It can be noted that the above calculation method is done for single-phase vapour. If liquid only is present in a pipeline, the

physical volume of the pipe will give you the volume of liquid in the pipeline as this fluid is incompressible. Refer to Equa-

tion (1).

Two-Phase Phenomena

In this discussion, before calculating the ‘Gas or Liquid Only’ Line Pack Volume in a multiphase pipeline, we need to under-

stand the phase behavior of two-phase fluid (multiphase) pipeline. Phase Behavior sometimes called Pressure-Volume-

Temperature (P-V-T) data is an important aspect for engineering designs especially in pipelines. Therefore, we need to have

accurate models to predict the accuracy of the P-V-T properties, especially in a gas as this is critical for pipeline design, gas

storage and gas measurement. It is necessary to distinguish between the transportation of ‘dry gases’ (no liquid, only va-

pour) and ‘wetter gases’ (multiphase conditions experience due to condensate dropout) as these can affect the cost and/or

supply expectations of the producer and consumer.

When gas flows through a pipeline, pressure and temperature changes (P-T trace) and this may cause formation of a liquid

phase owing to partial condensation of the gaseous medium. Retrograde phenomenon — typically found in multi-

component hydrocarbon systems — takes place by allowing condensation of the gas phase and liquid appearance even un-

der expansion of the flowing stream. The same phenomenon may also cause vapourization of the liquid phase such that it

re-enters the gas phase. Liquid and gas phase composition are continuously changing throughout the pipeline due to the

unceasing mass transfer between the phases. Generally, the amount of heavies in the stream determines the extent of the

retrograde behavior and liquid appearance.

For a given compositional analysis, the prevailing pressure and temperature conditions will always determine if the fluid

state is all liquid (single-phase), all gas (single-phase) or gas-liquid (two-phase). If a richer gas comes into the system, it will

show a single-phase condition at the inlet, but after a certain distance the pressure and temperature conditions will be

within the two-phase region. If the system is transporting a wetter gas, it would encounter two-phase conditions both at

the inlet and at the outlet of the pipeline.

In summary, the liquid presence and/or formation in a pipeline is ultimately dictated by the properties of the gas that is

being transported and vice versa.

Line Pack Calculation (Multiphase Method)

As explained above, gas pipelines can experience liquid drop-out depending on the properties of gas or simply the gas

being ‘wet’ at the inlet of the pipeline. When we need to estimate the line pack volume, we need to consider the total

volume of liquid in the pipeline in order to arrive to a suitable solution. A simple and easy way for a suitable ‘ball-park’

estimation is using Aspen HYSYS where we can determine the stream properties and other properties such as liquid hold

-up (with slip) at each pipeline segment interval (5 is usually suitable). Figure (1) below illustrates the liquid hold-up frac-

tions at different pipeline lengths obtained from Aspen HYSYS by simulation of an oil and gas production stream. It is

necessary to find the total liquid inventory in the pipeline by using the equation (7) below:

…Equation (7)

Where VL is the liquid volume, HL is the liquid-holdup fraction and Vp is the pipe segment volume

Figure 1: Liquid Hold-Up Fraction along the pipeline.

After the total volume of liquid is obtained in the pipeline, the vapour space volume is calculated by subtracting the total

volume of liquid from the physical volume of the pipeline. This vapour volume is then used to determine the volume of

the gas in the pipeline at standard conditions by modifying equation (6) by substituting equation (8) into equation (6) to

yield equation (9):

…Equation (8)

… Equation (9)

Conclusion

As discussed, by using line packing technique, the assurance of

gas supply can be achieved if there is an increase in gas demand

or problems with producers. Consequently, if the line is single-

phase liquid, the physical volume of the pipeline will represent

the volume of liquid inventory in the pipeline and can be consid-

ered the ‘pack volume’ since liquid is incompressible. With respect to multiphase line, an easy method of finding the total

liquid hold-up inventory can be determined using Aspen HYSYS and hence vapour space volume can be calculated and the

line pack equation can be used to determine the pack volume of gas in the multiphase pipeline. It is recommended that de-

tailed modeling of multiphase pipelines in OLGA should be done to give a more accurate representation of the packed vol-

ume of gas and liquid hold-up inventory within the pipelines.

Vicard Gibbings is currently a Junior

Process Engineer at Massy Wood Group

(MWG). Vicard has approximately one (1)

year’s experience in brownfield engineering

in the oil and gas industry, all at MWG. He

holds a B.Sc. in Chemical and Process

Engineering (Hons.) at the University of

West Indies, St. Augustine (U.W.I) in which

he graduated in 2017. He was the Class

Representative for his tenure at U.W.I and

he has also won awards such as the EOG

Resources Trinidad Ltd. award for producing the best Chemical and Process

Engineering Research Project together with his accomplishment of being

placed in the Dean’s Honour Role.

Moreover, in his spare time, Vicard is a Personal Tutor where he tutors

children (ages 11 until). He started his private tutoring services late 2017. In

addition, Vicard loves to play sports, mainly football and currently plays for a

team called Central A Renegades.


Increasing Impact of Corrosion Control

due to Change in Global Climate

By: Jerome Marshall, M.Sc Project Management,

B.Sc Mechanical Engineering, PMP

Existing Situation of Climate Change One of the key topics on everyone’s lips in the scientific and

global community has been the growing concern around the

incremental increase in global temperatures. As human in-

dustrialization has increased, there has been a significant

rate of increase (shown below) in the global ambient tem-

perature (currently approximated at 0.90oC/year), with

many new historic highs being reached. As a tropical coun-

try, these changes hold the potential for significant cata-

strophic outcomes in the longer term, but can have subtle

and unexpected effects in the short term.

Figure 1. Source: NASA Vital Signs: Shaftel, H. (2018). Global Tem-

perature

Trends in Global Corrosion Cost

One of those subtle and unexpected areas of impact is in

the area of corrosion control. Corrosion control is a signifi-

cant on a global basis, with economic losses being reported

on global basis by most estimates. According to the Nation-

al Association of Corrosion Engineers’ (NACE) Internation-

al Measures of Prevention, Application and Economics of

Corrosion Technology (IMPACT) study, completed in 2013,

corrosion is believed to have a global cost of 2.5 trillion

United States dollars, or 3.4% of the global GDP. This cost

is an estimation of the direct impact of repair and replace-

ment costs, but corrosion can have significant unaccounted

cost. The risk of equipment failure and lost opportunity cost

as a result of corrosion is not quantified for example, nei-

ther is the cost to human life and welfare (e.g. corrosion of

water piping leading to decrease water quality and health)

or the cost of increased unsafe working condition controls

that can be introduced as a result.

Types of Corrosion The impacts of corrosion can literally be seen in any space

where metal exists. There are eight main corrosion types

listed by NACE, which can all lead to the failure of equip-

ment or any other metallic object. The types of corrosion

are shown below, with brief explanation of each.

Figure 2. Source: NACE – Corrosion 101: Fontana & Greene

(1967). Eight Forms of Corrosion

Estimate of Impact in Trinidad and Tobago The NACE IMPACT Study categorized the economic im-

pact of corrosion in the groupings of ‘Services’, ‘Industry’

and ‘Agriculture & Allied Activities’. Services are thought to

include elements such as accommodation, food service,

transportation, storage, recreation and more. Industry in-

cludes items such as mining/quarrying, manufacturing, con-

struction, utilities, and more. Agriculture & Allied Activities

are thought to include agriculture, forestry and fishing. As-

suming that the cost of corrosion in Trinidad and Tobago

follows global norms of 3.4% GDP, based on Trinidad and

Tobago’s 2016 GDP of US$20.99 billion (Source: tradingec-

onomics.com, https://tradingeconomics.com/trinidad-and-

tobago/gdp), corrosion can be assumed to be a problem

worth US$713.66 million across all sectors.

Change in Climate of Trinidad and Tobago

Trinidad and Tobago whilst perhaps not severely impacted

as yet has not been immune to the phenomenon of climate

change. The graph below was constructed from World Bank

Data, which shows a steady increase in the local tempera-

ture. (Source: Climate Change Knowledge Portal, 2018). It is

also notable that a prominent feature of climate change is

increased rainfall in affected areas, which can possibly be

manifest in the future.

Figure 3. Climate Change Knowledge Portal, 2018

Likely Impact on the Cost of Corrosion A question to be answered however, is the impact that cli-

mate change will have on corrosion control. There are sev-

eral issues which can impact the economic future of corro-

sion as a result of global warming. One element which has

changed as a result of greenhouse gas emissions is the in-

creased incidence of acid rain and dissolved carbon dioxide.

Carbon Dioxide (CO2) is known to form carbonic acid

(H2CO3) when dissolved in water, leading to the leaching of

iron from steel and degradation of it. Another known ele-

ment is the acceleration of corrosion due to metallic creep

(potentially likely in areas with existing significant tempera-

ture fluctuations, such as industrial plants or areas with

heavy machinery), as a result of greater extremes of temper-

ature as a result of global warming and the potential for in-

creased rainfall. These all have the potential to lead to addi-

tional costs in replacement of equipment, equipment/

infrastructure failures and additional lost opportunity costs

in the future.

Future Solutions: Design for Corrosion Control

Within the realm of mechanical engineering, the potential

exists to mitigate the impact that this phenomenon will have

on Trinidad and Tobago. With a knowledge of the potential

impact that global warming will have on a global scale to a

significant cost, mechanical and structural engineers have a

responsibility to include a Design for Maintenance philoso-

phy (DfM) and Design against Corrosion Damage philosophy

into the project design process. Careful process must be

implemented, including the selection of materials (to avoid

galvanic corrosion as far as reasonably possible), the minimi-

zation of irregular connections and spaces which collect

corrosive fluids (to minimize crevice corrosion), and imple-

ments which allow for regular inspection of metallic surfac-

es. The design of machines, plant fabric and structures which

lend themselves to predictive maintenance should be consid-

ered, as well as initial protective measures such as the use of

sacrificial metals, cathodic protection, the application of pro-

tective coatings and much more. Efforts should also be made

to remain abreast of the newest materials and protection

systems that may arise. Given the increasing relevance of

global and local climate change to us as a collective and as

individuals, we should continue to remain educated and dili-

gent to avoid this silently growing threat to profitability and

safety in each industry.

Eng. Jerome Marshall graduated from the University of the West Indies in 2010

with a B.Sc in Mechanical Engineering. He further went on to complete a M.Sc in

Project Management and is a certified PMP. He started his professional career

working in Anti-Corrosion Technical Services Limited and is now a Project

Engineer for Business Development for the Massy Energy and Industrial Gases

Business Unit, responsible for the development and evaluation of new business

models and technologies. He is also a contributor in Massy Energy’s drive to ensure

realize its vision of being a ‘Force for Good’ by evaluating socially responsible

energy projects in various parts of the Caribbean.


Application of Organic Communication

Channels

By: Aaron Roopnarine, B. Sc. Electrical and Computer Engineering,

UWI and Dr. Sean Rocke , Electrical Engineering

Abstract

Organic Communication Channels (OCCs) show great poten-

tial when considering what has been accomplished with Hu-

man Body Communication (HBC). For example, improvement

in the efficiency of rescue operations, harvesting operations

and surveillance. However, not much work has been done in

extending HBC to other OCCs. Consequently, this paper

investigates the current work done on OCCs, proposes com-

munication techniques to apply to all OCCs and suggests pos-

sible use cases for this area. Consequently, based on these

preliminary findings, the feasibility of the use of OCCs is plau-

sible.

Introduction

Organic Communication Channels (OCCs) consist of any pe-

troleum-based media e.g. animals, vegetation and soil. The

interest in this area stems from the tremendous accomplish-

ments made thus far for Human Body Communication in Body

Area Networks (BANs). Body Area Networks (BANs) allow

for the systematic monitoring of heath and so reduces the

reliance on medical personnel.

BANs consist of three communication modes: Narrowband,

Ultra-wideband (UWB), and Human body communication

(HBC) PHY. The IEEE 802.15.6 regulate communication in

these modes. NB and UWB use RF based propagation tech-

niques whilst HBC uses a non-RF based technique that uses

the human body as the transmission medium [1]. HBC recent-

ly emerged as an alternative to short range RF communication

as it achieves higher data rates, greater spectral efficiency,

better security- as the communication is localized to the hu-

man body- and better power efficiency.

HBC is well researched covering areas such as channel charac-

terization, transceiver design, standardization of different lay-

ers of communication and proposals for improvement upon

the format of these communication layers [2-4]. However, not

much research has been done on the other OCCs. Soil based

communication has been investigated in the literature. Howev-

er, no standardization exists for soil based communication

from literature surveyed. To the best of the authors’

knowledge, no work has been done on vegetation based and

oil based OCCs.

Consequently, this article will focus on the possible use cas-

es for OCCs and the communication techniques proposed

for this area. This will provide insight into the feasibility us-

ing OCCs.

Communication techniques for OCCs

To the extent of the literature surveyed, soil based communica-

tion and HBC are the only OCCs that have been researched.

Since HBC is standardized, higher data rates are achieved when

compared to soil based communication [3, 5, 6]. Hence, HBC

communication techniques should be used with other OCCs.

HBC communication techniques are divided into 2 categories:

electric HBC (eHBC) and magnetic HBC (mHBC).

eHBC involves the use of electric fields [3]. It is the usual tech-

nique employed in HBC systems.The signal generated- modulat-

ed with the data to be sent- by the transmitter is electrically

coupled to the receiver through electrodes. The transmitted

signal is captured by the receiver using similar electrodes at

another part of the body. eHBC could be further classified into

two types: capacitive coupling and galvanic coupling[2]. In gal-

vanic coupling, the induced signal is controlled by current flow.

An alternating current (AC) is coupled into the body which is

considered as the transmission line. A differential electrical sig-

nal is applied between the two electrodes at the transmitter

and induces galvanic currents [7]. Figure 1 (a) shows this for

another OCC.

However, galvanic coupling only works with small distances-

approximately 15cm- between electrodes. In capacitive cou-

pling, the induced signal is controlled by an electric potential

caused by leaving 1 electrode from the transmitter and 1 from

the receiver floating. Hence, a return path is created. Figure 1

Figure 1: Galvanic (a) and Capacitive (b) Coupling

mHBC involves the use of magnetoquasistatic fields through

magnetic induction. This technique is typically used in soil

based communication[5]. In this system the transmitter and

receiver both have conducting loops. The principle of

mHBC is similar to a transformer: where the current in the

transmit coil induces a changing magnetic field which is cou-

pled to the receive coil, inducing a current there. Figure 2

shows this applied to another OCC. This current is modu-

lated with the data to be sent. Therefore, there is magnetic

coupling between the transmitter and receiver coils form

the communication channel. Since the magnetic permeability

of most surrounding materials are the same, an mHBC will

be more channel resilient when compared to eHBC tech-

niques [8].

Thus, eHBC and mHBC techniques can be applied to OCCs

for feasible communication. Magnetic induction shows most

promise as it may contribute to channel resilience. The

standardization of HBC communication through the IEEE

802.15.6 document facilitates interoperability amongst de-

vices and higher data rates compared to a non-standardized

method. Hence, this standard should be modified for other

OCCs to achieve a universal standard for OCC communica-

tion.

Use Cases The possible applications of OCCs are endless. OCC com-

munication techniques can be leveraged to develop cyber-

physical systems that can be applied to the Internet of

Things (IoT). Through HBC, BANs present the possibility of

averting medical crises such us heart attacks and strokes [9].

BANs could be applied to the field of sport through real-

time physiological monitoring of athletes to maximize player

performance by preventing injuries and burnouts [10]. Thus,

BANs reduce the strain imposed on healthcare personnel

and hence serve to as mechanism to deal with the increase

in demand for healthcare services. Now consider expanding

to other OCCs. Figure 1 shows how these OCCs can be

utilized for cyber-physical systems.

Furthermore, OCCs can be used in IoT technology to de-

velop a natural resources management system which moni-

tors climate, soil health, land use and plant health which will

mitigate food insecurity for countries [11]. Clearly, the po-

tential for OCCs is seen.

Conclusion

OCCs show great potential as seen in its use cases. Based

on the literature surveyed, HBC techniques can be applied

to other OCCs to achieve feasible communication. A modi-

fied version of the IEEE 802.15.6 standard is proposed for

specification of the different communication layers for all

OCCs to achieve reasonable data rates and interoperability.

Figure 2: Magnetic Coupling Figure 3: Use cases for OCCs

Aaron Roopnarine received his BSc.

degree in Electrical and Computer Engineer-

ing in 2017 at the University of the West

Indies with First Class Honours. He is cur-

rently pursuing his Master of Philosophy

degree in Electrical & Computer Engineering

at the University of the West Indies. He co-

authored two other publications in the

International Journal of Signal Processing, Image

Processing and Pattern Recognition. His current

research interests include areas include

areas where the principles of Electrical and

Computer Engineering can be expanded to

other domains, as with OCCs.

Sean Rocke received his BSc in Electrical & Comput-

er Engineering from The University of the West Indies

in 2002, his Masters in Communications Management

and Operational Communications from Coventry

University in 2004, and his Ph.D. in Electrical & Com-

puter Engineering from Worcester Polytechnic Insti-

tute in 2013. His areas of interest include signal pro-

cessing and optimization techniques relating to wire-

less communications and energy systems, statistical

signal processing, biosensor development and biologi-

cal data mining.


Hybridization of the Direct Stiffness and

Macaulay Methods of Structural Analysis

It is in the designer's best interest to validate the output of programs they have used for structural analyses. Occasionally,

they may not do so due to their confidence in the reliability of certain programs out of many years of use and/or due to

doubts in their capability to successfully perform such checks. Furthermore, from longevity in practice one often develops

a keen eye to detect errors intuitively. Supervisors are cognizant that less experienced engineers usually do not possess

these skills and depending on the complexity of the design, may encourage their junior colleagues to perform calculations

themselves i.e. without the use of structural analysis software. The latter is also used as a means to assess whether trainees

have understood a particular topic at the degree level.

Though conducive to hand calculations, classical methods of structural analysis such as Clapeyron's Theorem of Three Mo-

ments (Hearn 2000), the Slope-Deflection Method (Hibbeler 2012), and the Moment Distribution Method (Williams 2009)

can be daunting especially if used for preliminary designs or to double-check intermediate work, in which cases these calcu-

lations may be irrelevant at the final design stage. The aforesaid methods can also be restrictive according to the type of

structure, its support conditions and indeterminacy, even if implemented in spreadsheets which are ubiquitous nowadays.

For instance, the applicability of the Theorem of Three Moments is limited to beams which have at least two spans, or sys-

tems which can be modelled as such. Due to the simultaneous equations involved in the Slope-Deflection Method, it be-

comes cumbersome when the number of unknown displacements are large. Likewise, the Moment Distribution Method

inherently assumes members are axially rigid, it is a numerical method—thus its accuracy is reliant on the number of itera-

tions performed—and the method can become laborious for frames where sway is uninhibited as well as for non-prismatic

members.

Matrix methods are perhaps the most versatile techniques for structural analysis and are readily adaptable to features

which are complicated to model when using classical procedures. Examples of these are: hinges for Gerber beams and

springs, used in the analysis of beams on elastic foundations (Bowles 1996). Matrix methods gained prominence in the

1950s with the advent of digital computers (Hearn 2000) and are used within the vast majority of structural analysis pro-

grams (Hibbeler 2012). One form of these matrix methods is the Direct Stiffness Method (DSM), which can be used to

calculate nodal forces as well as displacements (Megson 2005).

The first use of singularity functions in structural analyses is most often credited to William Herrick Macaulay, hence, such

techniques are referred to as Macaulay’s Method (Megson 2005, Hearn 2000). This Method is convenient and simplifies the

determination of deflections along a beam (Beer, et al. 2012, Williams 2009). A typical singularity function is shown in Ta-

ble 1 below, and for values of the exponent (n) greater than or equal to unity, these functions can be simplified algorithmi-

cally using the maximum function.

Comprehensive explanations of the DSM and Macaulay Methods are outside the scope of this article. However, the two

can be hybridised to produce an innovative technique which can be used for structural analysis as follows: reactions and

displacements at extreme nodes are calculated using DSM; Beams, more so those with up to three spans are fundamental

structural design elements since they can be used to model systems with larger numbers of spans. This is because load ap-

plied to adjacent spans has a reducing effect the further it is from the span being analysed (McCormac and Brown 2014).

By: Jovon Jacob, B.Sc Civil Engineering

Table 1. Singularity Functions

Additionally, some structural elements may be modelled as a continuous member with three geometrically distinct sec-

tions, these include: gently tapered cantilevers, beams with stepped haunches or a span of a slab with drop panels (Portland

Cement Association 2013). The hybridised Direct Stiffness and Macaulay Methods have been set up for the analysis of the

aforesaid structures in a spreadsheet, “3Span_v1.xlsm” which is available for download at https://goo.gl/ffxtTd.

A screenshot of the file is shown in Figure 1 hereafter. It is anticipated that such applications of a spreadsheet would re-

sult in cost saving from not having to purchase licenses for more expensive programs, especially if the structural analyses

to be performed are relatively simple. Additionally, time should be saved, as this is intrinsic of automated calculation but

also because spreadsheets typically require minimal computer resources to run optimally.

The determination of fixed-end reactions are prerequisite to the use of DSM. Generic equations for linearly-distributed

loads were derived using Macaulay’s Method and are stated in Table 2 since these have not been seen in any other litera-

ture. Such equations for point loads and couples are published in most structural analysis text books as well as design ta-

bles, however are included here for completeness. To avoid confusion with the bending moment equation presented here-

after, couples with the symbol “c” were chosen over the traditional nomenclature of “M” for applied moments.

Figure 1. Screenshot of 3Span_v1.xlsm


Equations in Table 2 are based on the sign convention

of upward forces and anticlockwise moments being

positive, which is typical for matrix methods. Once the

vertical reaction (Ryn), moment (Rzn), slope (θn) and

deflection (un) at the near node (left end) of the mem-

ber have determined from DSM, the deflection (u) at all

points along the member (0 ≤ x ≤ L) can be obtained

using Equation 1 below.

The above uw, up and uc are functions also derived

from Macaulay’s Method which model the effect of line-

arly-distributed, point and couple loads respectively

(see Equations 2-4). For elastic systems, individual

load effects can be superposed (Williams 2009) hence,

the summation. It should be noted that the near-node vertical reaction, Ryn is a sum consisting of components (Rynw, Rynp

and/or Rync) for the load types applied; Rzn, θn and un are similarly aggregated.

Equation 1 is differentiable, and the Euler-Bernoulli theory is

used to obtain bending moments and shears. Due to the load-

ing sign convention already applied, in order for bending mo-

ments (M) and shears (V) to be consistent with their tradition-

al sign conventions (Hibbeler 2012) shown in Figure 2 below, the relations hereunder are utilised.

Advantages of using the hybrid approach opposed to DSM exclusively for structural analyses are best illustrated with an ex-

ample. If DSM only is used for the analysis of the discretized simply supported beam in Figure 3, the size of assembled stiff-

ness matrix would be 20x20 before it is condensed to 18x18 to solve for unknown degrees of freedom (DOFs). Once all 18

DOFS are solved, they can be used to determine the moments and shears at all 10 nodes, however, the slopes obtained for

the 8 intermediate nodes may not be useful beyond that.

From analysing the simple span above with the hybrid method, the typical

4x4 beam stiffness matrix will be used—this is much smaller thus faster to

process. The stiffness matrix will then be condensed to 2x2 for determi-

nation of the slopes at nodes 1 and 10. After the reactions have been

solved, they can be plugged into the Macaulay equations for deflection,

moment and shear. All of these equations are functions of “x,” so one can

accurately locate points of contra-flexure, maximum moment etc. easily,

by expanding the range of x; or running the relevant equation through a

solver; without having to redo the matrix analysis, as would be the case

with the DSM only approach if the member is insufficiently discretised.

Additionally, with the hybrid approach, fewer fixed end loads would have

to be calculated for the force vector while slopes for the intermediate

nodes can be solved only if necessary, as these are not generally used for

design. The hybridised Direct Stiffness and Macaulay Methods can also be

used for the analysis of frames as will be shown in a document to be re-

leased in future, as part of the Civil Division Council’s Peer-Reviewed

Spreadsheet (PReSs) initiative.

Eng. Jovon Jacob is a graduate civil

engineer who assists professional design engineers in the preparation

of reports, spreadsheets and CAD drawings. Jovon believes that with

clever programming, spreadsheets can become invaluable design aids

for practitioners and, revolutionary teaching tools for students. His

article, ‘Microsoft Excel as a Ge-otechnical Engineering Teaching

Tool’ is being considered for publica-tion in the European Journal of

Engineering Education. Jovon holds a B.Sc. in Civil Engineering, from UWI

St. Augustine, has over 9 years of experience in AutoCAD drafting. He

was also awarded a GoRTT National Scholarship in 2011 and member of

the winning team for in IStructE’s Young Structural Engineers Design

and Build Competition that year.

Table 2. Equations for Fixed End Reactions.


The Environmental Impacts of the

Cement Manufacture Process

By: Jonathan V. Juman, Yr 2 B.A.Sc. Civil Engineering, UTT

Saara Sultan, Yr 2 B.A.Sc. Civil Engineering, UTT

The vast and rapidly expanding industry of construction and

infrastructural development over time has required a stable

and cheap yet strong alternative to the construction of old

that once used timber and raw materials for their infrastruc-

ture. It sought for many years to find a suitable material that

can be moulded, formed, capable of a wide variety of uses

and most importantly cheap. The introduction of concrete as

a mainstream and easily accessible building material has revo-

lutionized the construction market and with new and ever

improving machinery and processes, the ease of access and

availability for this man made wonder has never been greater.

Early and mid-1900’s saw the exponential growth of the use

of concrete; from buildings, roads, sidewalks, bridges, pipes,

electrical poles, man-made waterways and dams, and even

missile silos are made of concrete either in part or as a

whole. Concrete has overtaken the market in terms of mate-

rials with a high demand and an even higher use spectrum;

anywhere that there is development, there is concrete.

Amidst all this expansion, the 21st century brought along cli-

mate change and deforestation that sparked the call for envi-

ronmental awareness above all else. Many factories and man-

ufacturers have reinvented their manufacturing processes in

an effort to reduce their carbon footprint and facilitate the re

-growth of the environment. Concrete however, has two

processes to production that has not changed from its incep-

tion. The wet and dry processes both require blasted raw

material, a crushing and burning process to create the fin-

ished product. In an effort to help the environment, this re-

port is done on the environmental impacts of concrete; from

production to end of life.

Cement Manufacture Process

Cement, also known as Portland cement, is one of the three

core components that formulate concrete along with aggre-

gate and water. Its main purpose serves as the binder in the

concrete and gives the concrete its strength when dry as it

holds and hardens the mixture together. There are several

processes that take place before cement reaches its final

state.

Stage one of the manufacture process is the quarrying for

all raw materials needed.

This may be done either by machine quarrying an open pit

mine or by Blasting which requires the use of explosive

charges and creates severe dust clouds that cause severe air

pollution and pollute nearby waterways when it settles. Dust

in the air can contaminate nearby vegetation depending on

meteorological conditions and has the potential to cause

damage. Chemical changes to soil composition may occur

due to the chemical composition of the dust. Limestone pro-

duces dust that is highly alkaline and although it has been

used before to influence crop sensitivity, the dust would not

be near the quality needed and may cause more damage than

good. Flyrock, formed due to the energy produced from

blasting may endanger employees and nearby personnel.

Blasting also produces high amounts of waste energy that is

converted to seismic vibration, noise, heat and light. This may

not only disturb neighbouring structures due to its loudness

but may also cause damage to their infrastructure and com-

promise their structural integrity to an extent. The effects of

this excess energy may also disturb coastal and marine envi-

ronments, historic landmarks and nature reserves.

Machinery in the quarrying industry increases productivity

with increasing the rate the job is performed due to large

scale movement by the equipment. Crawler tractors are used

to strip surfaces and mine softer raw material such as sand or

clay.

Figure 1. Basic Process Flow of Cement Manufacturing Process.

Wheel loaders take the mined raw material to load them

onto the trucks for transportation to the crushing and

washing equipment. They have large buckets that can hold

up to 35 tonnes of material. Smaller scale loaders are used

to load the finished material onto smaller, road legal trucks.

Off-highway trucks carry the extracted material from the

open pit to the crushing and washing equipment. These

trucks have a maximum capacity of 3600 tonnes and ex-

tremely powerful diesel engines making the time for

transport of material relatively short in comparison to reg-

ular dump trucks. These equipment are all diesel powered

and emit carbon monoxide that affect concentrations of

other greenhouse gases such as methane, tropospheric

ozone and carbon dioxide. The carbon monoxide readily

reacts with the hydroxyl radical to form carbon dioxide,

increasing the concentration of methane as methane is re-

moved by the hydroxyl radical in the atmosphere.

Stage two is a fairly simple and short step where the ma-

terials are mixed together. This is where both dry and wet

processes become distinct. The dry process has the materi-

als mixed without any addition whereas the wet process

adds water. This water is used to create a paste-like tex-

ture in the mixture. This liquid mix does not differ much in

process and result from the dry mixture but it does have a

positive impact environmentally. This comes in the form of

a reduction of carbon footprint. Due to the liquid state, the

mixture can be transported from the quarry to the cement

manufacturing plant without the use of trucks or fuel pow-

ered vehicles. Instead, it is transported by means of large

pipes that are on a constant gradient so it flows from the

quarry to the plant. This reduces the use of fuel, the

amount of carbon monoxide, carbon dioxide and methane,

and overall increases the plant’s productivity because there

is not only a constant flow of material but also a faster in-

flow of it when compared to dump truck transport.

Stage three is the heating process. The mixture falls

through a pre-heat tower and becomes heated partially

heated before entering the kiln. Once in the kiln it is fully

heated to 1500°C. This heating process however is not

completely environmentally friendly. Oxides of sulphur are

formed from the combustion of fuels containing sulphur

and the burning of raw material containing sulphur. All the

materials that is used to produce the clinker contains sul-

phur. Once the sulphur oxides are exposed to water va-

pour in the atmosphere with the presence of sunlight, it

becomes sulphuric acid that would mix together with the

water droplets in the air as condensation and eventually

precipitate as what is known as acid rain. This affects soil

pH causing imbalance in the soil’s composition which can

result in deformed and underperforming crop harvests and

can also impact on humans as respiratory illnesses are

closely linked to higher sulphur oxide levels.

The heating and burning process of the rotary kiln also pro-

duces high Carbon oxides from its fuel and the decarboni-

sation of the raw materials, with particular attention drawn

to limestone. Burning of fossil fuels and the process of ther-

mal oxidisation occurs at between 1200oC-1600oC. This

involuntary process creates oxides of nitrogen that are also

released into the atmosphere and can cause serious health

and environmental issues due to the various compounds of

nitrogen including nitrogen dioxide, nitric acid and nitrates.

These compounds react with water to form various acidic

compounds and can cause imbalance to several water bod-

ies such as lakes, making their pH more acidic. Plant and

animal life may also be dependent on the pH balance and

the change may create difficulty for them to survive. Ni-

trous oxide is also a greenhouse gas that collects in the

earth’s atmosphere and gradually causes atmospheric tem-

perature rise.

Stage four is the final stage of the manufacturing process.

The material that comes out of the kiln, known as clinker,

is the agglomerated form of cement powder. This is taken

from the kiln and cooled before being ground into fine

powder. This step is executed with the use of a ball mill.

The milling process generates heat and as a result needs to

be cooled by spraying water onto the outside of the mill.

Environmental impacts of the milling process is minimal

other than the dust that is produced by the mill grinding

the clinker into powder form. The ball mill would also pro-

duce exhaust fume emissions similar to all other machinery

that would pollute the atmosphere and as a result, cause

some production of greenhouse gases. A positive take-away

from this process can see the exhausted heat be rerouted

to the pre-heater to raise its temperature therefore using

less fuel and lowering total emissions.

The use of concrete as the most easily accessible building

material for construction has been in use for years and will

continue to be the most highly preferred material for the

provision of a reliable standing foundation. The manufacture

of cement is a complex topic when it comes to identifying

its environmental impacts, some effects are harmful where-

as some are beneficial. Cement being the major component

of concrete has its environmental impacts which are thor-

oughly discussed in its manufacturing process above. Work-

ing with cement has numerous concerns therefore different

measures are to be considered and variation in methods

are to be implemented to reduce the likelihood of addition-

al environmental issues and to prevent ongoing issues from

worsening.

Jonathan V. Juman is a 2nd year student at the University of Trinidad &

Tobago, currently pursuing his Bachelors of Applied Science Degree in the

field of Civil Engineering. In 2016 he completed his National Technician’s

Diploma in Civil Engineering also from UTT and hopes one day to further

his studies in the field of Structural Engineering with specific focus on

mitigation systems for buildings against seismic activity. He also hopes to

bring awareness to the engineering community about the vast effects that

construction practices can have on the environment to one day help these

processes become more eco-friendly and preserve the eco-system while

expanding the human infrastructure.

Saara Sultan is a 2nd year student at the University of Trinidad &

Tobago, currently pursuing her Bachelors of Applied Science

Degree in the field of Civil Engineering Systems. Prior to her

pursuit of the engineering degree, her occupation saw her become

a maintenance technician at the Ministry of Works and Transport

and this peaked her interest which gave her a passion to pursue

Civil Engineering. She hopes to one day become a project manager

as well as a lead site/construction engineer and run a management

firm that operates throughout the Caribbean.

Misunderstandings about Building Codes

and T&T

By: Dr. Richard Clarke, Technical Committee Member of the ASCE 41-17

Technical Committee Member of the TTBS Small Building Guide

Senior Lecturer, Department of Civil Engineering, UWI

Former Chair of the BOE/APETT/TTBS Structures Codes Committee

Right now, unless you are in an open field, your safety is dependent on a structural engineer (or civil engineer depending on

the employer) since gravity is trying to collapse the building you are in, or if an earthquake or hurricane were to occur right

now, the associated forces will also conspire to cause the building to collapse. The engineer is protecting you by ensuring

the structure is built based on her or his implementation of an appropriate building code.

Upon attending the JCC meeting at the Hyatt Regency yesterday, it is clear that we continue to harbour significant misun-

derstandings about the building codes in terms of their intent and roles and our capacity to properly implement them. The

need to clarify the matter has become more pressing given the apparent increase in the frequency of the natural hazards of

hurricanes and earthquakes within the past months throughout the Caribbean, and the anticipated increase in the near fu-

ture. Furthermore, there is the need for decision-makers to invest in risk reduction in the correct distribution hence based

on a correct order of priority of the national risk factors. This topic is therefore so important that the author will mention

the names of the critical documents so that they may enter the discourse of the nonprofessional T&T citizenry as least so

that they can begin to empower their own safety. The principal misunderstandings are: (1) not having a T&T building code

increases the risk to the public, (2) to derive a T&T building code by adopting a building code used elsewhere is a simple

task, and (3) lack of enforcement of a building code is a major source of risk to the public.

The demands on a building due to an earthquake are higher both in terms of determining what an earthquake will do to a

building, and how the material is to be arranged, compared to the demands due to a hurricane. However in selecting a

building code or set of codes as a model or basis for T&T, that selection must cater for both earthquakes and hurricanes.

As regards the first misunderstanding, this is simply false. All that is needed is for the engineer to base their calculations on

a seismic building code, and knowledge of the extent of ground shaking to be expected during the service life of the build-

ing. Such a code has been available and used in T&T since 1970, when the Seismic Committee of the Association of Profes-

sional Engineers of T&T (APETT) recommended the seismic code then in use in California, U.S.A – the Structural Engineers

Association of California (SEAOC) seismic code, for use in T&T. Use of this code was supplemented by studies by a num-

ber of seismologists within the period 1970 to 1978 to provide the required information on the levels of ground shaking for

the Caribbean territories. At the present point in time, the Designs Engineering Branch (DEB) of the Ministry of Works

and Transport (MOW) will approve a building design if based on the American Society of Civil Engineers/Structural Engi-

neering Institute (ASCE/SEI) document called the ASCE 7-05 (2005), and the seismic maps published by the Seismic Re-

search Centre of the University of the West Indies, St. Augustine. In keeping with the original 1970 decision, the U.S.A

codes are the preferred choice. As regards hurricanes, again the ASCE 7-05 caters for this, but information on the extent

of the wind speed to be expected during the service life of the building is required. This information is also provided by the

DEB based on studies of the Caribbean by world-renowned expert Dr. Peter Vickery. One may have heard of the Interna-

tional Building Code (IBC), but this code is largely dependent on the ASCE 7.

However, referring to the ASCE 7 is not sufficient. Note that when mentioning the ASCE 7 code above, it is the 7-05

(2005) that is cited. Since that time, the ASCE 7 has evolved to the ASCE 7-10, then to the ASCE 7-16. However, our

engineers cannot use any of these codes without taking the personal risk of specifying what the level of earthquake should

be. This is because these codes require a type of seismic map that does not as yet exist for the Caribbean territories. This

is a big problem and is causing engineers to be unable to make consistent and proper use of the latest knowledge available

in these codes.

The need for this type of map (called a risk-targeted map) became necessary in the U.S.A in order to remove certain in-

consistencies. But in doing so, this has now required engineers, for the first time ever, to be knowledgeable of more ad-

vanced technology. A similar quantum leap in the knowledge required by the engineer to properly implement the code

took place in the period from 2010 to 2016. This is due to the adoption of a new design paradigm and associated tech-

nology called “performance-based design” which has been embodied in the ASCE 7-16. Also for the first time, the ASCE

7 refers substantially to the document which is the source of new paradigm - the ASCE 41. The ASCE 41-17 is the most

advanced code document derived by any organization worldwide to date and as codes evolve, it will become the main

building code. Unless a local engineer invests in receiving the training in these developments (i.e. the risk basis and per-

formance-based design) these codes cannot be properly applied and the engineer is not motivated to do this since T&T

does not as yet have an effective Continuing Professional Development (CPD) programme which will make such training

mandatory.

As regards the second misunderstanding, though a local building code can be derived by adopting a U.S.A code, such

codes nowadays are strict as regards the intellectual property requirements. If one selects say the Los Angeles building

code for earthquake-resistant design and the Florida building code for hurricane-resistant design, those codes adopt the

IBC. The International Code Council, who publishes the IBC, requires special contractual arrangements and so-called

“application documents” for territories external to the U.S.A.. Another misconception is that payment must be made to

participants in the code development process. The international practice is that the input of technical professionals is

done on a pro bono basis hence no such individual should be paid and providing service to one’s country on a technical

committee should be regarded as an honour and privilege and not a job, especially in this period of austerity.

The third aforesaid misunderstanding is so because it misses the point by putting the cart before the horse. A code must

be made mandatory before it can be enforced. In T&T by far the highest risk to the public is housing because in the vast

majority of cases the roof is supported on 100 mm (i.e. 4 inch) block walls. This applies to single-storey houses and the

top-storey of most 2-storey houses. Extensive state-of-the-art studies have shown the inadequacy of this form of con-

struction hence exposure to the national economy. Collectively, this means that approximately seventy percent of all

buildings in T&T do not comply with code requirements. This situation exists because the Small Building Guide, published

by the T&T Bureau of Standards, and which has the correct methods, is not mandatory. This must be done before it can

be enforced and implies the need for a very large retrofitting effort in order to reduce the risk to acceptable levels.

In the author’s view, the most significant factors negatively impacting the risk to the public due to earthquakes and hurri-

canes in T&T are (in descending order) – that the Small Building Guide is not mandatory; lack of risk-consistent seismic

maps, and lack of training and an effective CPD program for structural and civil engineers in T&T to ensure they are up-to

-date with the most recent codes.

Dr. Richard P. Clarke is a structural and quality engineer with extensive indus-

trial experience and has authored papers in leading international journals and sym-

posia in the areas of seismic retrofitting, hysteresis modeling, seismic nonlinear

structural dynamics, and vulnerability analysis. His research interests are in the

areas of earthquake resistant seismic design and assessment, structural cementi-

tious composite materials, sustainable affordable and multi-hazard resistant hous-

ing, and computer-based education.


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apett engineering the association of professional...

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