Structural Steel, Connections & Prestressed/Post-Tensioned/Precast Concrete

Structures work built from fabricated steel and precast or prestressed concrete arrives on site largely finished, the inspection burden shifts from "is this being built correctly" to "is this fabricated element being erected, connected, and stressed correctly." That shift doesn't lower the stakes: a bad bolt pattern, a missed weld inspection, or a mis-recorded post-tensioning elongation can compromise a structure that looks complete from the outside.

Structural Steel Erection

Steel members are erected following an approved erection plan and sequence, with temporary bracing and guys kept in place until enough permanent connections are complete for the structure to stand on its own, particularly under wind loading during construction. The inspector verifies members against shop drawings and piece marks (the fabricator's identification tags), confirms correct orientation, and checks that camber and plumbness fall within the tolerances of the AISC Code of Standard Practice.

Bolted Connections

Highway steel connections use high-strength bolts (commonly ASTM F3125 Grade A325 or A490, or their legacy designations) in one of three joint types: snug-tight, pretensioned, or slip-critical, depending on what the connection needs to resist. Pretensioned and slip-critical joints require a verified, documented tensioning method, turn-of-nut, calibrated wrench, direct tension indicator (DTI) washers, or twist-off tension-control (TC) bolts, and the inspector records which method was used and confirms it was executed correctly. Slip-critical faying surfaces (the mating steel surfaces) must meet the specified surface-preparation class, free of oil and loose mill scale, or the connection cannot develop its design slip resistance.

Welded Connections

Welding is performed under an approved Welding Procedure Specification (WPS) by welders qualified for the specific process and position, following AWS D1.5 for bridge steel. Every weld gets a visual inspection; complete-penetration or otherwise critical welds identified in the specification also require nondestructive testing, ultrasonic testing (UT) or magnetic particle testing (MT), to detect internal flaws a visual check can't catch. The inspector confirms weld size and type match the plan detail, not just that a weld is present.

Precast and Prestressed Concrete

Precast and prestressed members, girders, deck panels, box beams, are fabricated at an approved plant under the plant's own quality control program and arrive with material certifications. On delivery, the field inspector checks for cracks, chips, or handling damage. The single most important field-handling rule: members are lifted and supported only at the pick points shown on the shop drawings, a beam is designed for its final support condition, and lifting or blocking it anywhere else can induce cracking the beam was never designed to resist. Members are stored on padded dunnage aligned with the eventual bearing points and set on elastomeric bearing pads exactly as detailed.

Post-Tensioning

Where a member is post-tensioned in the field, tendons are stressed after the concrete reaches a specified strength, using calibrated hydraulic jacks in the sequence shown on the shop drawings. The inspector witnesses the stressing operation and records both the jack pressure (gauge reading) and the measured tendon elongation, comparing the field measurement to the engineer's calculated theoretical elongation.

A measured elongation outside the expected tolerance signals a problem, excess friction in the duct, a partial blockage, or a broken strand, and must be investigated before the tendon is accepted. After stressing, ducts are grouted promptly to bond the tendon to the surrounding concrete and, just as important, to seal the strand away from moisture; incomplete grouting, confirmed by checking that grout emerges at every vent, is a leading cause of long-term tendon corrosion failures.

Pretensioned vs. Post-Tensioned, at a Glance

Pretensioned members (most precast plant beams) have their strands stressed before the concrete is cast, with the strand bonded directly to the surrounding concrete as it cures. Post-tensioned members are cast first, with ducts left open, and the strands are stressed and anchored after the concrete gains strength, the method used for most field-assembled or segmental structures, and the one that requires the inspector's direct witnessing of the stressing operation.

Demolition of Existing Structures

Where a project requires removing an existing bridge or structure element, the inspector confirms work follows an approved demolition plan: sequencing that keeps the remaining structure stable throughout, protection of adjacent structures and utilities that must stay in service, containment or capture of demolition debris (particularly over traffic or waterways), and proper handling of any hazardous materials, such as lead paint on older steel, identified before work begins. Demolition sequencing errors, removing a member that was still carrying load, are among the more serious field failures on a structures project, so the approved sequence is followed exactly rather than adjusted in the field for convenience.