Examples and Applications

A continuous steel bridge superstructure has an expansion length of $L = 80\text{ m}$ measured from the fixed bearing to the expansion joint at the abutment. The bridge is located in a region where the design temperature range is from a minimum of $T_{min} = -30^\circ\text{C}$ to a maximum of $T_{max} = 50^\circ\text{C}$. The installation temperature is assumed to be $T_{inst} = 15^\circ\text{C}$.

The coefficient of thermal expansion for steel is $\alpha = 11.7 \times 10^{-6}\text{ /}^\circ\text{C}$.

Calculate the total design movement range ($\Delta L_{total}$) the expansion joint must accommodate, and determine the maximum expansion and maximum contraction relative to the installation state.

A simply supported concrete pedestrian bridge with a $15\text{ m}$ span is being designed. The anticipated vertical loads (dead + live) at each support are relatively light ($150\text{ kN}$). The anticipated longitudinal thermal movement is very small (less than $10\text{ mm}$).

Evaluate three bearing options: Steel Pot Bearings, Roller Bearings, and Plain Elastomeric Pads. Recommend the most appropriate bearing type for this structure.

A continuous three-span steel girder bridge spans across a river. The span arrangement is $30\text{ m} - 45\text{ m} - 30\text{ m}$. The bridge is supported by two abutments (Abutment 1 and Abutment 2) and two river piers (Pier 1 and Pier 2).

The river is prone to heavy debris flow, meaning Pier 1 and Pier 2 must be relatively slender to avoid trapping debris, but this makes them flexible and less capable of taking massive horizontal loads. Abutment 1 is founded on solid bedrock, while Abutment 2 is on softer soil with pile foundations.

Determine an appropriate articulation strategy (which supports should have Fixed, Guided Expansion, or Free Expansion bearings) to manage longitudinal thermal expansion and braking forces.