Design Guide for Steel Pedestrian Bridges: A Systematic Approach from Parameter Planning to Structural Selection

I. Core Design Elements of Overall Layout

The design of steel pedestrian bridges must focus on functionality, safety, and applicability. The overall layout covers six key dimensions, all interrelated and strictly constrained by industry standards:

II. Access and Safety Design: Traffic Standards and Protection Specifications

1. Width Design Criteria
   • Minimum width for conventional pedestrian bridges ≥ 2 meters (exceptions for railway station connecting bridges);
   • For mixed pedestrian-cyclist traffic, bridge width ≥ 3.5 meters, separated by isolation lines, different pavement materials, or contrast colors.
2. Guardrail Height SpecificationsScenarioGuardrail Height RequirementAbove railway lines1.5 metersAbove ordinary roads1.15 metersVulnerable areas1.8 meters
3. Accessibility Design
   • Consider passage needs for wheelchair users and cyclists, e.g., ramp slopes must comply with ergonomic standards.

III. Span Planning: Obstacle Avoidance and Safety Redundancy Design

1. Basic Span Determination
   • Minimum span is determined by obstacle width. For moving vehicles (railways, roadways), additional safety distances are required to avoid collisions:
     • Distance between roadway edge and bridge support structure ≥ 4.5 meters;
     • In railway scenarios, if the support is < 4.5 meters from the track, the bridge must withstand single-support failure without collapse.
2. Support Arrangement Principles
   • Support structures are prohibited between road lanes to reduce vehicle impact risks.

IV. Clearance Height Design: Scenario Adaptation and Structural Selection

1. Standard Clearance Parameters
   • Minimum clearance height for highway pedestrian bridges: 5.7 meters;
   • Railway clearance heights vary by train type and line category, with no unified standard.
2. Special Scenario Handling
   • If the entrance is at track level (ground level), both clearance height and superstructure depth must be considered. Prefer shallow-depth through-girder construction to avoid excessively long ramps or oversized support components.

V. Service Facilities Arrangement: Concealment and Maintenance Convenience

1. Installation Principles
   • Facilities like cables and water pipes should be hidden between main girders;
   • Water and gas pipes are forbidden inside box girders. Other facilities must be placed in dedicated ducts for maintenance without contacting the box girder.

VI. Construction Types and Span Matching: Selection Basis and Application Ranges

Different structural forms of steel pedestrian bridges correspond to specific span ranges, requiring integration of span requirements with cost-effectiveness:

VII. Design Process and Key Logic

The design of steel pedestrian bridges follows the principle of “parameters first, systematic collaboration”:

1. Determine basic span and clearance height based on obstacle types (traffic flow, natural barriers);
2. Define width and safety standards according to user groups (pedestrians/cyclists);
3. Adjust structural details based on service facility requirements and installation codes;
4. Finally, match the optimal construction type to the span range, e.g.:
   • 10-25 meters: Double steel beams or composite beams;
   • ≥ 40 meters: Cable-stayed or suspension bridges for visual effect and structural rationality.

The design of steel pedestrian bridges is an art of balancing functional needs and technical standards. From millimeter-level guardrail heights to tens-of-meters span planning, each parameter must be precisely controlled based on scenario characteristics and code requirements. Rational construction type selection is the core to achieving unity of safety, economy, and aesthetics.