Question

A bridge to be fabricated of steel girders is designed to be 500 m long and 12 m wide at ambient temperature (assumed 20°C). Expansion joints will be provided to compensate for the change in length in the girders as the temperature varies. Each expansion joint can compensate for a maximum of 20 mm of change in length. From historical records it is estimated that the minimum and maximum temperatures in the region will be -35°C and 40°C, respectively. Determine (a) the minimum number of expansion joints required and (b) the length that each bridge section should be fabricated.

Answer 1

a) 22.5number

b) 22.22 m length

Step-by-step explanation:

Given data:

Bridge length = 500 m

width of bridge = 12 m

Maximum temperature = 40 degree C

minimum temperature = - 35 degree C

Maximum expansion can be determined as

`\Delta L = L \alpha (T_(max) - T_(min))`

where , \alpha is expansion coefficient
`= 12* 10^(-6)` degree C

SO,
`\Delta L = 500* 12* 10^(-6)* ( 40 - (-35))`

`\Delta L = 0.45 m = 450 mm`

number of minimum expansion joints is calculated as

`n = (450)/(20) = 22.5`

b) length of each bridge

`Length = (500)/(22.5) = 22.22 m`