Text 25. Design of welded joints

1 Listen to the text and render it either in English or in Russian.

The most economical choice of weld to use for a given condition depends on several factors. It should be born in mind that members to be connected by welding must be firmly clamped or held rigidly in position during the welding process. In riveting a beam to a column, it is necessary to provide a seat angle as a support to keep the beam in position for riveting the connecting angles. The seat angle is not considered as adding strength to the connection. Similarly, with welded connections, seat angles are commonly used. The designer must have in mind the actual conditions during erection and must provide for economy and ease in working the welds. Seat angles or similar members used to facilitate erection are shop welded before the material is sent to the site. The welding done during erection is called field welding. The designer in preparing welding details indicates on the drawings which are shop and which are field welds. Some designers consider field welding to be less effective than shop welding and, therefore, reduce the working stress in field welds. Reductions up to 25 % are sometimes used. Conventional welding symbols are used to indicate the type, size, and position of the various welds. Only engineers or architects experienced in the design of welded connections should design or supervise welded construction. It is apparent that a wide variety of connections is possible; experience is the best aid in determining the most economical and practical.

Vocabulary:

to weld – сваривать

clamped – скрепленный, зажатый

to rivet – клепать, заклепывать

seat angle – угол основания, опорной поверхности, подставки

erection – сборка, установка, монтаж

field welding – сварка на месте

shop welding – сварка в цеху

to supervise – наблюдать (за чем-л.), заведовать

2 Answer the questions.

1 What factors influence the most economical choice of weld?

2 What is necessary to do in riveting a beam to a column?

3 What is called field welding?

4 Why do some designers consider field welding to be less effective than shop welding?

5 What can conventional welding symbols indicate? Why are they used for?

3 Define tense forms of the underlined words.

4 Make up your own sentences with the modal verbs should and must + Infinitive: Indefinite Active or Passive.

Text 26. Piles

1 Read and translate the text.

Where and how piles are used. Where the subsoil consists of mud, river-bed silt, and other unstable materials, the use of piling has to be resorted to. Piles were used in the earliest ages but their types and the methods of driving them have undergone great change since the advent of modern engineering. The original form of the pile was a moderate − sized three trunks with its branches removed and one and pointed to facilitate driving it into the soil.

This was set up in position and driven by dropping on its upper end a heavy weight or by striking it with a heavy hammer. Very likely this method was used by some of the earliest races of mankind, for such piles have been used since prehistoric times. Even today the same system is used where loads are small, such as in building a small pier or a little footbridge. As soon as piles of any substantial size have to be used, the hand method becomes inadequate and power must be applied to the driving system. Hence, today we have pile-drivers ranging up to some very large sizes and using weights of several thousand tones, which are lifted into the dropping position by means of power. Sometimes steam is used and in some cases electric motor or gasoline-engine drives are applied to work of raising the heavy weight.

Within the last several decades, great improvements took place also in design of the piles themselves.

Now large piles are generally made of concrete which has been reinforced by use of steel rods. Some concrete piles are cast in moulds and allowed to harden thoroughly, after which they are driven like wooden piles. Others are made in place by first driving into position a removable interior form. This form is then withdrawn and the inside of the hollow shell is filled with concrete. In some cases, steel piers are used. After they are driven into place, all muck is removed from the inside and the interiors are filled with concrete.

Vocabulary:

pile – свая, столб, кол

subsoil – подпочва

silt – ил, осадок

to resort – прибегать (к чему-л.)

advent – приход, прибытие

moderate – средний, небольшой

pier – пирс, дамба, бык (моста)

footbridge – пешеходный мостик

steel rod – стальной прут, брус

cast – отливать, лить (металлы)

mould – (литейная) форма

withdraw – удалять, извлекать

hollow – пустой, полый

shell – обшивка

muck – грязь

2 Answer the questions.

1 Why do the engineers have to resort to the use of piling?

2 What was the original form of the pile?

3 Where is the hand method of piling used today? And in what case is it inadequate?

4 How can the engineers cope with work of raising the heavy weight?

5 What improvements took place in design of the piles today?

3 Define forms of the verbs in each sentence and explain their use.