👉The failure of the concrete staircase is primarily caused by 
improper or insufficient steel reinforcement and poor structural design and execution at the connection point with the upper floor slab. 

🚧Details of the Failure

💫Lack of Proper Anchorag:

⏺The image and associated information indicate a critical mistake where the main reinforcement bars of the staircase were not properly anchored into the landing beam or slab above with adequate development length or proper bends (hooks). Instead, they appear to have been cut short or installed incorrectly.

💫Missing or Incorrect Negative Reinforcement:

⏺The diagrams in the image highlight the need for "top" or negative reinforcement bars extending from the top of the stair into the upper slab to handle the tension forces that occur at this connection point when the stair is loaded.
This was likely omitted or installed incorrectly in the failed structure.

💫Structural Weakness:

⏺A staircase is a major structural element that carries significant loads.
⏺Without correct and continuous reinforcement into the supporting structure, the connection point becomes a weak link, leading to a bond failure and collapse as seen in the image.

💫Substandard Workmanship:

⏺This type of failure often results from trying to cut costs, using unqualified labor, or failing to follow approved engineering drawings and building codes. 

@etconp