Bridge construction demands precision, especially for hatch bridge deck spans where overlooked errors can compromise structural integrity and longevity. Below are critical mistakes to avoid:
Design & Planning Phase
- Inadequate Load Modeling: Failing to accurately account for dynamic loads, impact factors, anticipated heavy vehicle traffic, or concentrated loads from equipment can lead to undersized members and premature fatigue.
- Ignoring Differential Deflection: Insufficient consideration of deflection differences between the main longitudinal girders and cross beams can cause deck cracking, ponding water, and accelerated deterioration.
- Poor Connection Design: Specifying connections with high stress concentrations or inadequate fatigue resistance, particularly at hatches, cross beam-to-girder connections, and bracing points.
- Insufficient Drainage Planning: Omitting or undersizing scuppers, pipes, and positive slope on the deck surface leads to water accumulation, corrosion, and ice hazards.
Fabrication & Construction Control
- Tolerance Non-Compliance: Allowing excessive deviations in girder camber, cross beam levelness, or connection hole alignments during fabrication creates fit-up problems and unintended stresses during erection.
- Improper Weld Procedures/Execution: Using incorrect welding parameters, sequence, or technique introduces defects like undercut, porosity, or excessive heat-affected zones, compromising fatigue life. Inadequate pre/post-weld treatments are common oversights.
- Poor Fit-Up Forcing: Using excessive force to connect misaligned members induces locked-in stresses that significantly reduce fatigue resistance and structural performance.
- Defective Decking Placement: Incorrect installation of deck panels (grid, plate, etc.), including poor welding/bolting to supports, insufficient bearing, or gaps, creates vulnerable points susceptible to cracking and loosening.
Materials & Corrosion Protection
- Material Specification Oversights: Selecting grades of steel inappropriate for the anticipated service environment (low toughness in cold climates) or fatigue requirements. Using mismatched filler metals.
- Inadequate Corrosion Protection: Underestimating exposure conditions, leading to insufficient coating systems (e.g., poor surface preparation, inadequate DFT) or omission of critical details in drain paths, crevices, and weld zones.
- Ignoring Fatigue Details: Failing to adhere strictly to designated fatigue detail categories during fabrication (e.g., weld toe grinding, back-gouging, avoiding attachments on tension flanges).
Proactive mitigation involves rigorous design reviews focusing on fatigue and constructability, strict adherence to fabrication tolerances and welding codes, comprehensive inspections (especially of connections), and selecting durable materials with robust corrosion protection tailored to the specific environmental exposure.
