South Carolina Marine

6 questions | 12% of exam weight

Key Concepts

Marine Operations Safety (OSHA 1926 Subpart O)

• Subpart O covers motor vehicles, mechanized equipment, and marine operations on construction sites
• All equipment used over or near water must have adequate flotation and stability provisions
• Workers on or near water require U.S. Coast Guard-approved personal flotation devices (PFDs); ring buoys with ≥90 ft of line must be immediately available

Floating Cranes & Cranes on Barges

• Before lifting, a stability and list assessment must be performed — the barge/vessel must be on an even keel or within acceptable list limits
• Free surface effect: liquid in partially filled tanks reduces effective stability — tanks should be full, empty, or compartmentalized to minimize this
• Trim = fore-aft tilt; List = side-to-side tilt — both must be accounted for in load calculations before any lift
• Rated crane capacity is reduced when operating on a floating platform due to dynamic motion

Marine Hoisted Personnel Transfer & Hoisting Over Water

• Personnel transfers over water require approved personnel transfer baskets meeting applicable crane and rigging standards
• A competent person must inspect all rigging prior to each transfer
• Employees being transferred must wear PFDs at all times during hoisting over water
• Tag lines must be used to control basket movement

Cofferdams

• Controlled flooding: cofferdam design must allow for controlled flooding in emergencies; flooding procedures must be pre-planned and workers trained
• Guardrails required on all open sides/edges where workers could fall into water or into the cofferdam
• Evacuation warnings: audible alarm systems required; workers must be able to evacuate quickly — design must account for rapid water rise
• Cofferdams near navigation channels must be marked with lights/signals per U.S. Coast Guard requirements and must not obstruct navigation without permits

Key Concepts

Pile Types and Classifications

• Timber piles: Used in marine environments; must be treated (creosote or CCA); subject to marine borer attack below waterline; relatively low load capacity
• Concrete piles: Precast (prestressed or reinforced) or cast-in-place; excellent corrosion resistance; high capacity; heavy and require careful handling
• Steel piles: H-piles (end bearing) or pipe piles (friction or end bearing); can be spliced; susceptible to corrosion in marine environments; good for hard driving
• Sheet piles: Steel, concrete, or vinyl; used for earth retention, cofferdams, and bulkheads; interlock at joints; not primary load-bearing members

Pile Load Transfer Mechanisms

• Friction (skin friction) piles: Load transferred along pile shaft through soil-pile interface friction; used in soft soils with no firm bearing stratum; capacity = unit skin friction × surface area
• End-bearing piles: Load transferred through pile tip to firm stratum (rock or dense soil); shaft resistance is minimal; used when competent bearing layer exists at depth
• Combination piles: Both friction and end bearing contribute; most common in practice

Pile-Driving Hammer Types

• Single-acting steam/air hammer: Ram raised by air or steam pressure; falls by gravity; lower blow rate (35–60 BPM); good energy control
• Double-acting hammer: Air/steam raises AND accelerates the ram downward; higher blow rate (90–150 BPM); lower stroke; suitable for sheet piles
• Diesel hammer: Self-contained; open-end (single-acting) or closed-end (double-acting); fuel ignition drives ram; rate varies with soil resistance; unreliable energy in soft soils
• Hydraulic hammer: Precise energy control; environmentally cleaner; preferred for sensitive sites and noise-restricted areas
• Vibratory hammer: Uses eccentric weights to vibrate pile into soil; fast installation; does NOT provide a blow count for bearing capacity verification; best in granular soils and for sheet piles

Key Concepts

Mix Design & Water-Cementitious Materials (w/cm) Ratio

• Lower w/cm ratio = higher strength, lower permeability, better durability. Typical structural concrete: 0.40–0.50. Exposure to sulfates or freeze-thaw: 0.45 max. Severe sulfate exposure: 0.40 max.
• Aggregate sizing: maximum size should not exceed 1/5 of the narrowest form dimension, 1/3 of slab depth, or 3/4 of minimum clear spacing between reinforcing bars.
• Common admixtures: water reducers (increase workability without adding water), air-entraining agents (freeze-thaw resistance), accelerators (cold weather), retarders (hot weather/long hauls).

Fresh Concrete Properties

• Slump test measures workability/consistency. Typical range: 3–5 inches for most structural concrete.
• Bleeding: water rises to surface; finishing too early on bleed water causes weak surface layer (dusting).
• Air content: for freeze-thaw exposure, 5–7% entrained air is required depending on aggregate size and exposure severity.

Batching, Mixing & Transport

• Two types: transit-mixed (mixed in drum en route) and central-mixed (mixed at plant, transported by agitator truck).
• Ready-mixed concrete must be discharged within 90 minutes or before 300 drum revolutions after water is added — whichever comes first (ASTM C94).
• Concrete should not be re-tempered (adding water on-site to restore slump) — it reduces strength.

Subgrade, Formwork & Placement

• Subgrade must be moistened (not saturated) before placement to prevent dry soil from absorbing mix water.
• Formwork (per §1926.700): includes all molds, shores, reshores, braces, and hardware. Must be designed by or reviewed by a qualified structural person before construction loads are applied (§1926.701(a)).
• Concrete should be placed in horizontal layers, consolidated immediately; cold joints form if layers are not placed before the prior layer stiffens.
• Consolidation: internal vibrators should not be used to move concrete horizontally; insert at 18–24 inch spacing, withdraw slowly.

Key Concepts

Bar Types & ASTM Specifications - ASTM A615 – Deformed and plain carbon-steel bars (most common); available in Grades 40, 60, 75, 80 - ASTM A706 – Low-alloy steel bars; Grade 60 is the standard weldable rebar; must comply with AWS D1.4 for welding - Grade 60 is the most common: minimum yield strength 60,000 psi (420 MPa), minimum tensile strength 90,000 psi (620 MPa) - A706 Grade 60 max yield is 540 MPa (78,000 psi); tensile must be ≥ 1.25× actual yield

Bar Identification Markings (deformed bars carry 3–4 marks): 1. Producer's mill mark 2. Bar size number 3. Steel type (S = A615 carbon steel; W = A706 low-alloy; SS = stainless) 4. Grade mark (one line = Grade 60; two lines = Grade 75; or the number 4 for Grade 40, 6 for Grade 60, etc.)

Bar Sizes – Designated by number; the number = bar diameter in eighths of an inch (e.g., #4 = 4/8" = 0.5" diameter). Standard sizes range from #3 through #18.

Concrete Cover Requirements (ACI 318): - Cast against and permanently exposed to earth: 3 in. - Exposed to earth/weather (#6–#18): 2 in.; (#3–#5): 1.5 in. - Not exposed to weather – slabs/walls (#14, #18): 1.5 in.; (#11 and smaller): 0.75 in. - Beams/columns (ties, stirrups, spirals): 1.5 in.

Placement Tolerances (ACI 117): - Effective depth (d) for members ≤ 8 in. deep: ±3/8 in. - Effective depth (d) for members > 8 in. deep: ±1/2 in. - Longitudinal location of bends and ends: ±2 in. - Cover tolerance: −3/8 in. (cover may not be reduced more than 3/8 in. from specified)

Bar Splices: - Lap splices – Most common; bars overlap a calculated length; Class A or Class B based on % of bars spliced at one location and reinforcement ratio - Mechanical splices – Sleeve/coupler devices; must develop 125% of the specified yield strength of the bar - Welded splices – Must also develop 125% of yield; use only A706 bars for reliable welding; follow AWS D1.4