The first stage: small and exquisite M.
The first stage of the beam is a small and exquisite M, with concrete and steel bars dancing hand in hand at the top of the flexible work. With the end of the dance steps, the concrete in the pull area gently touches the boundary of ft, and a cracked smile blooms.
The second stage: M gradually emerges.
In the second stage of the beam, M gradually emerged, and the smile of concrete in the pulling area became more and more obvious. The neutralization axis moves up quietly, and the concrete in the compression area presents plastic charm, and the compressive strain is like silk. At this time, the stress of the steel bar just touched the edge of yield. Dealing with cracks in beams reveals the secrets of deformation and crack width in the limit state of normal use.
The third stage: after the steel bar yields.
In the third stage of the beam, after the steel bars yield, the stress no longer rises, and the strain runs like a runaway wild horse. The concrete cracks spread upward, the neutralization axis moved up rapidly, and the height of the concrete compression zone gradually became thinner. The deflection of the beam soared like a roller coaster. When the concrete reaches the ultimate compressive strain, it breaks and the beam comes to an end. At this moment, we realize the charm of calculating the ultimate state bearing capacity.