When the size of a column is reduced above a floor, the handling of its main reinforcement bars depends on the specific design requirements and detailing practices.

Column Reduction Scenarios

A reduction in column size typically occurs at floor levels or between stories. The main bars from the lower, larger column section must transition smoothly and safely into the upper, smaller column section.

Analysis of Main Bar Behavior

Let's analyze how the main bars might be treated in each scenario:

• Option 1: Continues up
  In cases where the size reduction is minimal, or the detailing allows, the main bars might continue upwards directly into the reduced column section. This requires careful arrangement and potentially reduced concrete cover to fit the bars within the smaller dimensions.
• Option 2: Bend inwards at the floor level
  Sometimes, the design might necessitate bending the main bars inwards at the floor level. This could be a specific detailing strategy to manage load transfer into the reduced section or to align with the geometry of adjacent structural elements.
• Option 3: Stops below floor level and lap bars provided
  This is a very common construction practice. The main bars from the lower section are terminated at a calculated distance (development length) below the floor level. New bars (lap bars) are then introduced starting from the floor level upwards, overlapping with the terminated bars to ensure continuity of reinforcement strength across the floor joint.

Conclusion on Column Bars

Since all three scenarios described represent plausible methods for detailing main reinforcement bars when a column size is reduced above a floor, depending on structural design and site conditions, all the given options can be correct.

Therefore, the most appropriate answer acknowledges that any of these methods might be employed.