MECHANICAL PROPERTIES OF ALUMINIUM AND ALUMINIUM ALLOYS

The compositional specifications for wrought aluminium alloys are now internationally agreed throughout Europe, Australia, Japan and the USA. The system involves a four-digit description of the alloy and is now specified in the UK as BS EN 573, 1995.

Registration of wrought alloys is administered by the Aluminum Association in Washington, DC. International agreement on temper designations has been achieved, and the standards agreed for the European Union, the Euro-Norms, are replacing the former British Standards.

Thus BS EN 515. 1995 specifies in more detail the temper designations to be used for wrought alloys in the UK. At present, there is no Euro-Norm for cast alloys and the old temper designations are still used for cast alloys.

In the following tables the four-digit system is used, wherever possible, for wrought materials.

Alloy designation system for wrought aluminium

The first of the four digits in the designation indicates the alloy group according to the major alloying elements, as follow:

1XXX aluminium of 99.0% minimum purity and higher

2XXX copper

3XXX manganese

4XXX silicon

5XXX magnesium

6XXX magnesium and silicon

7XXX zinc

8XXX other element, incl. lithium

9XXX unused

1XXX Group:

In this group the last two digits indicate the minimum aluminium percentage.

Thus 1099 indicates aluminium with a minimum purity of 99.99%. The second digit indicates modifications in impurity or alloying element limits. 0 signifies unalloyed aluminium and integers 1 to 9 are allocated to specific additions.

2XXX-8XXX Groups:

In these groups the last two digits are simply used to identify the different alloys in the groups and have no special significance. The second digit indicates alloy modifications, zero being allotted to the original alloy.

National variations of existing compositions are indicated by a letter after the numerical designation, allotted in alphabetical sequence, starting with A for the first national variation registered.

SOURCES OF ESTIMATING INFORMATION FOR CIVIL ENGINEERING PROJECTS

For matters relevant to estimating and costs, the best source of information is your historical data. These figures allow for the pricing of the project to match how the company actually performs its construction.

This information takes into account the talent and training of the craft personnel and the management abilities of the field staff personnel. In addition, it integrates the construction companies’ practices and methodologies.

This is why a careful, accurate accounting system combined with accuracy in field reports is so important. If all of the information relating to the job is tracked and analyzed, it will be available for future reference.

Computerized cost accounting systems are very helpful in gathering this information and making it readily available for future reference. See Construction Accounting and Financial Management by Steven J. Peterson for more information on managing construction accounting systems.

There are several “guides to construction cost” manuals available; however, a word of extreme caution is offered regarding the use of these manuals. They are only guides; the figures should rarely be used to prepare an actual estimate.

The manuals may be used as a guide in checking current prices and should enable the estimator to follow a more uniform system and save valuable time. The actual pricing in the manuals is most appropriately used in helping architects check approximate current prices and facilitate their preliminary estimate.

In addition to these printed guides, many of these companies provide electronic databases that can be utilized by estimating software packages. However, the same caution needs to be observed as with the printed version.

These databases represent an average of the methodologies of a few contractors. There is no simple way to convert this generalized information to match the specifics of the construction companies’ methodologies.