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why do we stagger reinforcement overlapping?

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First, we should know that steel rebar comes in standard length such as 12m. using very long reinforcement is impractical because it will result in difficulties in handling reinforcement by steel fabricators. Also, longer rebar is heavier and difficult to lift and move. So for a long structure such as a slab, we require a reinforcement length that is more than the standard reinforcement. We can't use a single piece of rebar for a specific length for such a structure, so we use two or more steel rebars to cover the entire length of the structure.
Figure no:1


The zone of overlapping between reinforcement will be considered as a weak zone. Therefore, it is a good practice to stagger the reinforcement overlapping. Staggering is done by overlapping the reinforcement at a different location. Staggering reinforcement overlapping will reduce the number of rebars overlapped at the same point, which will be beneficial in two ways. Firstly, it will reduce the discontinuity of rebar at the same location, minimizing the impact of overlapping at the same zone and improving stress transfer and resistance. Additionally, staggering rebar overlapping will reduce the reinforcement congestion. Congesting reinforcement at the same zone can result in difficulties in placing concrete, which can cause concrete honeycombes and impair structure integrity and strength.  

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My name is Mohammad Hamdan, and I am a Civil/bridge Engineer with extensive professional background and experience in the field of construction. I have 10+ years of experience in the construction field. During my professional career, my emphasis has been placed on structural projects, mainly bridges, infrastructure and roads. Reading and practicing the design of structures is my passion.i was lucky to be a part of a big team that executed major highway interchanges. I believe in spreading the knowledge, thus, i compose these courses to share my experience and knowledge. My course focuses on the practical side of construction field. On other word, i am sharing some of what new engineers need to know about construction field. Beside working on construction field, i love writing some articles on my website ( curious civil engineer) Moreover, i wrote some engineering papers, you can check them  by searching my name on Google (Mohammad mamon Hamdan)