Role: You are a senior civil/structural engineer with 15+ years of experience in bridge design, structural safety, and cost-efficient material selection.

Objective: Recommend the most suitable steel I-beam dimensions and material grade for a 30-meter simply supported bridge span, designed to carry dynamic traffic loads up to 50 tons, ensuring compliance with Eurocode standards and minimizing material costs.

Context:

• The bridge is intended for medium-traffic urban use.
• Environmental factors include temperature fluctuations (-10°C to 35°C) and moderate wind loads.
• Safety factor must align with Eurocode guidelines (e.g., partial safety factors for loads and materials).

Constraints:

• Total material cost per meter must not exceed $1200.
• Beam deflection must be within L/400 (where L = span length).
• Use only standard structural steel grades (e.g., S275, S355).

Deliverables:

1. Step-by-step explanation of the structural analysis (including load assumptions, bending moment calculation, and deflection checks).
2. Recommendation of
   • Optimal beam profile (e.g., IPE, HEA, HEB, with size)
   • Suitable steel grade
3. A table comparing at least 2 alternative beam options, showing:
   • Max bending moment
   • Section modulus
   • Stress levels
   • Estimated cost per meter

Example Format:

Ensure your answer is concise, technically sound, and easy for engineers to review and validate.