- Strength: A higher span to effective depth ratio can result in a lower strength capacity of the beam. As the span length increases relative to the effective depth, the beam becomes more susceptible to bending and deflection. Limiting the span to effective depth ratio helps ensure that the beam can resist the applied loads without excessive deflection or failure.

- Stability: A higher span to effective depth ratio can lead to stability issues in the beam. As the span length increases, the beam becomes more prone to buckling and lateral instability. By limiting the span to effective depth ratio, the beam's stability can be maintained.

- Serviceability: A higher span to effective depth ratio can result in excessive deflections, which can affect the serviceability of the beam. Limiting the span to effective depth ratio helps control the deflection of the beam, ensuring that it meets the required serviceability criteria.

- Economy: Limiting the span to effective depth ratio helps optimize the design and material usage, leading to a more economical solution. By keeping the ratio within the specified limits, the beam can be designed to efficiently utilize the available materials.

In conclusion, the span to effective depth ratio for a continuous beam with a steel grade of Fe 415 should not be more than 26. This limitation is necessary to ensure the strength, stability, serviceability, and economy of the beam design.