When a component is subjected to a downward load, the entire beam will bend downward: the upper part of the beam is compressed and pressed, and the lower part is stretched and pulled.
Concrete has an extremely strong natural ability to withstand compression and crack when pulled, so it is directly placed in the compression zone to fully utilize its strengths; The concrete slab serves as both the bridge deck and floor slab, directly bearing vehicle and live loads, and also restraining the upper flange of the steel beam to prevent local buckling and instability of the thin steel plate under compression.
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