H$1\mathrm{.}2$ Structural Systems and their Behaviour

Consider the two bridges as described below:

$(1)$ A bridge is to be built between two crests of a $200m$ high plateau separated by a $500m$ wide canyon in Leh, a rocky terrain $($Figure H$1\mathrm{.}2($a$)).$ The canyon is located in a hot and dry climatic condition where the temperature falls drastically at night during winters; and

$(2)$ A bridge is to be built to connect two islands of Andaman and Nicobar Islands, whose shores are $20km$ apart $($Figure H$1\mathrm{.}2($b$)).$ The ocean salt spray is severe with hot and humid tropical climatic condition. The maximum depth of water between the islands is $5m$ and the rock level is at $100m$ of depth.

As a structural engineer, propose suitable structural systems for the two bridges with appropriate choices of bridge components and their materials. Write logical arguments in favour of your choices.

$($v$)$

Figure H$1\mathrm{.}2$: Locations of bridges to be built: $($a$)$ over a canyon, and $($b$)$ between two islands