Mississippi Structural Steel

Key Concepts

Principles of Post-Tensioned Prestressed Concrete Post-tensioning applies compressive force to concrete after it has hardened, counteracting tensile stresses from applied loads. Unlike pre-tensioning, strands are stressed on-site using hydraulic jacks. Key advantages: reduced member depth, crack control, longer spans, and camber control.

Tendon Components - Strand: High-strength steel (typically 7-wire, Grade 270) - Sheathing: Plastic (HDPE) tube encasing the strand, prevents bond with concrete - P/T Coating: Corrosion-inhibiting grease injected inside the sheathing; also reduces friction during stressing - Anchorages: Cast-iron or ductile iron assemblies that transfer prestress force to concrete via wedges seated in the anchor cavity

Anchorage Types - Stressing-End (Live-End): Field-stressed using a hydraulic jack; includes pocket former, bearing plate, and anchor casting - Fixed-End (Dead-End Anchorage): Pre-installed at the factory end; not used for field stressing - Intermediate Anchorage: Located along the tendon length; allows stressing of a segment without cutting the tendon — commonly used at pour breaks for early formwork removal - Anchorage Zone Reinforcement: Includes bursting steel (controls tensile bursting forces spreading from the anchor) and back-up bars (controls splitting forces from concentrated anchor load)

Encapsulated System: A fully watertight system required in corrosive environments. All connections — stressing end, fixed end, and intermediate anchorages — must be watertight. The anchor cavity cap is filled with P/T coating material.

Key Concepts

Bar Sizes & Identification Markings

• Deformed bars are designated by number: #3 through #11, #14, and #18 (also #20 in larger applications). Bar number approximates diameter in eighths of an inch (e.g., #4 = 4/8" = ½" diameter).
• Every deformed bar carries four line symbols rolled into the surface: (1) producing mill mark, (2) bar size number, (3) steel type/grade, (4) for Grade 60+, additional marks indicate yield strength.
• Grade 40 = one line or no grade mark; Grade 60 = one continuous line or the number "4"; Grade 75 = two lines or the number "5." ASTM A615 (billet steel) is most common; A706 is used where weldability or ductility is critical.

Concrete Cover Requirements

• Concrete cover protects steel from corrosion and fire. Minimum cover varies by exposure:
• Footings/concrete cast against earth: 3 inches minimum
• Exposed to weather (#6–#18 bars): 2 inches; #5 and smaller: 1½ inches
• Interior slabs/beams (#6–#18): 1½ inches; #5 and smaller: ¾ inch
• Columns: 1½ inches minimum to ties/spirals
• Placement tolerances: ±⅜ inch for members ≤8" deep; ±½ inch for members >8" deep; ±1 inch for members >24" deep.

Key Concepts

Fall Protection – §1926.760 - General trigger height for fall protection in steel erection: 15 feet (not the standard 6-foot construction threshold) - Connectors working between 15–30 feet above a lower level must have fall protection; those working above 30 feet must use fall arrest or restraint systems - Controlled Decking Zone (CDZ): Permitted up to 90 feet from the leading edge; limited to 3,000 sq ft per zone; workers must be trained and visually identifiable (e.g., hard hat color) - Safety deck attachments: The first two rows of decking must be connected before unhooked from the hoisting line

Hoisting & Rigging – §1926.753 - A qualified rigger must rig all loads - Cranes must be inspected by a competent person prior to each shift; critical lifts require additional inspection - No workers allowed under a suspended load — workers must be kept clear of the load path - Multiple lift rigging ("Christmas tree" lifts): Maximum 5 members per lift; members must be rigged to prevent uncontrolled rotation; must be done with a qualified rigger - Tag lines must be used to control loads unless using them would create a greater hazard

6 Questions | 10% of Exam | Reference: 29 CFR 1926

Key Concepts

Fall Protection (Subpart M)

• Trigger height for fall protection in construction: 6 feet above a lower level
• Three accepted systems: guardrail, safety net, personal fall arrest system (PFAS)
• Guardrail top rail height: 42 inches (±3 inches) — must withstand 200 lbs of outward/downward force
• Safety nets must be installed as close as practical below the walking surface, no more than 30 feet below
• PFAS components: anchor, body harness, lanyard/deceleration device — must limit free fall to 6 feet and arrest forces to 1,800 lbs

PPE (§1926.95 / §1926.20(f))

• Employer must provide and pay for required PPE — failure to provide PPE to each individual employee is a separate violation per employee
• PPE must be selected based on the specific hazard present
• Hard hats, safety glasses, gloves, and foot protection are standard on structural steel sites
• Respirators required when engineering controls are insufficient (Subpart E)

Topic Weight: 7 questions, 12% of exam | Reference: SDI Manual of Construction with Steel Deck (MOC3-2016)

Key Concepts

Product Types and Profiles

• Composite Floor Deck: Contains shear connector devices (embossments, lugs, holes, or welded wires) that mechanically interlock concrete and steel so they act together under load. Finishes are either galvanized or bare/painted (bare top surface contacts concrete; bottom has primer coat).
• Roof Deck: Supports roofing materials; no composite action required.
• Form Deck: Acts as a concrete form only — no shear connectors; does not structurally reinforce the slab.
• Cellular Deck: Consists of a form deck sheet welded to a flat sheet, creating enclosed cells; used for electrical/data routing and composite or non-composite applications.
• Acoustic Deck: Roof deck with perforations on the flute surfaces to absorb sound; typically used in exposed ceiling applications.
• Standard deck lengths typically ≤ 40' due to shipping limitations. Standard widths: 12", 18", 24", 30", or 36".

Deck Fastening Methods (Deck-to-Frame)

• Arc spot welds (puddle welds): Most common method; fuse deck directly to structural steel supports.
• Self-drilling screws: Mechanical alternative to welding, especially where welding is restricted.
• Powder-actuated fasteners (PAF): Driven by explosive charge; used where welding is impractical.
• Air-driven (pneumatic) pins: Similar application to PAF; faster installation in some conditions.

Key Concepts

Product Types & Designation Systems

• K-Series: Depths 10"–30" (2" increments), spans 10–60 ft, standard bearing depth 2½", top bearing (underslung) typical, Warren or modified Warren web
• LH-Series: Depths 18"–48", spans up to 96 ft, standard bearing depth 5", can be underslung or square-ended, chords can be parallel, single, or double pitched
• DLH-Series: Depths 52"–120", spans up to 240 ft, bearing depth 5" (chord designations 10–17) or 7½" (chord designations 18–25)
• Joist Girders: Primary members, bear on columns, depths 20"–120", spans up to 120 ft, standard bearing depth 7½", designation format: 36G9N6K = 36" deep, 9 joist spaces, 6-kip panel point load
• CJ-Series: Composite joists; governed by separate SJI Standard Specification

Designation decoding example: - 18K7 → 18" depth, K-Series, chord #7 - 40LH13 → 40" depth at mid-span, LH-Series, chord #13 - 56DLH15 → 56" depth at mid-span, DLH-Series, chord #15

Erection Bridging Requirements

• Bridging must be installed before hoisting cables are released
• Load table shading zones dictate bridging requirements:
• Red zone: Highest bridging demand — erection bridging required, joist may not be used as bridging anchor
• Blue zone: Intermediate bridging requirements
• Gray zone: Least restrictive; standard erection bridging applies
• Bridging rows must be anchored at walls or to structural framing at terminus points — bridging is never left floating