Civil Engineering Materials (eBook)

Peter A. Claisse (Autor)

eBook Download: PDF | EPUB

2015 | 1. Auflage
528 Seiten
Elsevier Science (Verlag)
978-0-12-802751-6 (ISBN)

Infos

Civil Engineering Materials explains why construction materials behave the way they do. It covers the construction materials content for undergraduate courses in civil engineering and related subjects and serves as a valuable reference for professionals working in the construction industry. The book concentrates on demonstrating methods to obtain, analyse and use information rather than focusing on presenting large amounts of data. Beginning with basic properties of materials, it moves on to more complex areas such as the theory of concrete durability and corrosion of steel.

• Discusses the broad scope of traditional, emerging, and non-structural materials
• Explains what material properties such as specific heat, thermal conductivity and electrical resistivity are and how they can be used to calculate the performance of construction materials.
• Contains numerous worked examples with detailed solutions that provide precise references to the relevant equations in the text.
• Includes a detailed section on how to write reports as well as a full section on how to use and interpret publications, giving students and early career professionals valuable practical guidance.

Peter A. Claisse is a professor at Coventry University and the author of more than 100 publications on construction and materials.

Textauszug

Chapter 1

Units

Abstract

This is an introductory chapter, which introduces units and methods that will be used later in the book. The main part of the chapter is expressed in MKS SI Units, but separate sections give common US customary and CGS units and their conversion factors. Scientific notation is described, and common errors in its use are discussed. Unit prefixes for the MKS system are presented. Guidance is given on the use of logarithms, and the conventions used to show natural logs, and logs to base 10. Unit analysis is introduced with a simple example.

Keywords

scientific notation

unit prefixes

MKS SI units

US customary units

Chapter outline

1.1 Introduction 1

1.2 Symbols 2

1.3 Scientific Notation 3

1.4 Unit Prefixes 3

1.5 Logs 4

1.5.1 Logs to Base 10 4

1.5.2 Logs to Base e 4

1.6 Accuracy 4

1.7 Unit Analysis 5

1.8 MKS SI Units 5

1.9 US Customary Units 5

1.10 CGS Units 6

1.11 Properties of Water in Different Units 6

1.12 Summary 7

Notation

e

Mathematical constant = 2.718

L

Length (m)

m

Mass (kg)

ρ

Density (kg/m3)

1.1. Introduction

This chapter provides an overview of some mathematical notation and methods that are essential to engineering. All students should read through it, and many will be able to confirm that they have covered it all in previous studies. It is essential that any students who are not familiar with this material should study it further because, if it is not fully understood, many section of this book and many other aspects of a degree in engineering will be impossible to understand.

The main discussion uses metre–kilogramme–second (MKS) units; but the use of Imperial (US customary), and centimetre–gramme–second (CGS) units is also described. The purpose of this is not that students in Europe should read one section, and students in the United States should read the other. When searching for values for material properties on the Internet, they may be found in any units. All students should be fully familiar with all these types of units, and able to recognize them, and convert between them. Unit conversion macros are found easily online. The important concept is to recognize which system of units the data is in, and make sure that all data in an equation or calculation is in the same system.

1.2. Symbols

This book is about the properties of construction materials. Where possible, these properties are measured quantitatively; this means that values are assigned to them. For example, if a large block of concrete is considered which has one side 10-m long, this may be represented by equation (1.1):

 = 10m

(1.1)

where L is the variable we are using for the length of that side.

If the length of the block in other directions is considered and these are 8 and 12 m, this may be represented by equation (1.2):

1 = 10m   L2 = 8m   L3 = 12m

(1.2)

To calculate the mass of the block, the density must be known. This could be given by the equation (1.3):

 = 2400 kg/m3

(1.3)

where ρ is the Greek letter rho that is often used as a variable for density. Greek letters are used because there are insufficient letters in the English alphabet (correctly called the Roman alphabet) for the different properties that are commonly measured.

The Greek letters that are commonly used are in Table 1.1.

Table 1.1

Greek Letters in Common Use in Engineering

Lower Case

Upper Case

Name

α

Alpha

β

Beta

γ

Gamma

δ

∆

Delta

ɛ

Epsilon

η

Eta

θ

Theta

λ

Lambda

μ

Mu

ν

Nu

π

Pi

ρ

Rho

σ

Σ

Sigma

τ

Tau

ϕ

Phi

ω

Ω

Omega

1.3. Scientific notation

The mass of the block is given by equation (1.4):

 = L1 × L2×L3 × ρ = 2,304,000kg

(1.4)

The result has been given in kilogrammes. It may be seen that the number is large, and not easy to visualize or use. In order to make the number easier to use, it is expressed commonly in scientific notation as 2.304 × 106 kg.

It is important to express numbers correctly in scientific notation. The 2.304 should normally be between 1 and 10. To express this number as 0.2304 × 107 or 23.04 × 105 is mathematically the same, but should not normally be used. The number raised to a power must be 10, for example, 86 or 76 should not appear in this notation. The power must be a positive or negative integer, for example, numbers such as 104.5 or 106.3 should not appear, but negative powers such as 10−4 may be used.

Because many computer printers could not at one time print superscripts, an alternative notation is often used: 2.304 × 106 is written as 2.304E6. This notation may be found in books and papers, but it is not recommended for use in formal reports. It is, however, a convenient notation, and is used in spreadsheets. The E is represented by the “EXP” key on some calculators. Note that, for example, 108 is entered into a calculator as 1 EXP 8 not 10 EXP 8. 10 EXP 8 is 10 × 108, which is 109.

1.4. Unit prefixes

The alternative way of making the number easier to use is to change the units. For all metric units, the prefixes in Table 1.2 are used.

Table 1.2

Metric Prefixes

P

Peta

1015

T

Tera

1012

G

Giga

109

M

Mega

106

k

Kilo

103

m

milli

10−3

μ

micro

10−6

n

nano

10−9

p

pico

10−12

Thus 2,304,000 kg = 2,304 Mg (Megagramme). It would be technically correct, but very unusual to express it as 2.304 Gg. One Mg is equal to a metric tonne, so the mass would commonly be expressed as 2304 tonnes.

1.5. Logs

Another method of expressing large numbers is the use of logarithms, called commonly logs. These are particularly useful on graphs because both small and large numbers can be represented on the same graph (see, e.g., Fig 15.1). The log function is available on many calculators, and in all spreadsheets.

Logs are always relative to a given base, and the log of a number x to a base a is written as loga(x), and is defined from equation (1.5):

loga(x) = x

(1.5)

Some useful relationships with logs are:

a(xy)=loga(x)+loga(y)

(1.6)

axy=loga(x)−loga(y)

(1.7)

a(xy)=y×loga(x)

(1.8)

1.5.1. Logs to base 10

Logs to base are the logs that were used for calculations before calculators were invented. The procedure for multiplying two numbers together was to obtain the log of each, and then add these together (as in equation (1.6)), and obtain the inverse log (shown as 10x on calculators) of the result.

It may be seen...

Produkt-Details

• Erscheint lt. Verlag: 3.9.2015
• Sprache: englisch
• Themenwelt: Technik ► Architektur
• Themenwelt: Technik ► Bauwesen
• Themenwelt: Technik ► Maschinenbau
• Themenwelt: Wirtschaft
• ISBN-10: 0-12-802751-7 / 0128027517
• ISBN-13: 978-0-12-802751-6 / 9780128027516