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Essential hull structural stresses

2nd Mate
UK Management
MEO Class 2
MEO Class 4
UK EOOW

times asked: 30; times asked
questions: 11; questions
last asked: 2026; last asked

The slides, written out

AI-drawn illustration. Simplified to explain the idea, not to scale.

Slide 1 · LEARN

LEARN PRACTICE EXCEL AT SEA HULL STRUCTURE SERIES ESSENTIAL HULL STRUCTURAL STRESSES Understand the forces that shape a stronger, safer ship KEY CONCEPTS EVERY MARINER SHOULD KNOW

Slide 2 · Hull Structure Series

Hull Structure Series Essential Hull Structural Stresses RACKING STRESSES Transverse distortion of the hull When a ship rolls in a seaway or is subjected to beam waves, unequal transverse loading can distort the hull cross section. The normally rectangular cross section tends to deform toward a parallelogram. This distortion is called racking. Normal Section Under Racking Higher pressure on this side Lower pressure on this side Rectangular cross section Distorted to a parallelogram What Resists Racking? Transverse bulkheads Transverse framing Deep web frames Associated structural members Key Survey Point Racking stresses are particularly significant at the corners of the box section and around structural discontinuities. Pay special attention to: Corner brackets Beam knees Structural connections Areas around openings EXAM KEYWORD Racking = Transverse distortion of hull cross section LEARN PRACTICE EXCEL AT SEA

Slide 3 · Hull Structure Series

Hull Structure Series Essential Hull Structural Stresses PANTING & POUNDING Two important end region stresses PANTING POUNDING Rhythmic in-and-out movement Sudden impact loading Fluctuating water pressure causes shell plating at the bow and stern to flex in and out. It is particularly severe at the forward end, especially when the ship is making headway into a seaway. When the bow pitches clear of the water and then comes down heavily onto the sea, a severe shock load is produced. Pounding is primarily a forward-end loading problem, particularly in the forward bottom region, and the structure is strengthened accordingly. Panting action at forward end Pounding (slamming) at forward end Resisted by Structural measures Panting beams Panting stringers Breast hooks Deep floors Closer frame spacing Increased structural strength Increased plate thickness where required REMEMBER Panting = Repeated flexing Pounding = Impact / Slamming LEARN PRACTICE EXCEL AT SEA

Slide 4 · Hull Structure Series

Hull Structure Series Essential Hull Structural Stresses FLOOR PLATE A structural member of the double bottom A floor plate is a structural transverse plate forming part of the double-bottom structure. It supports the bottom structure and inner bottom and connects with the longitudinal girders. Main Functions Common Arrangements Supports the bottom structure Supports the inner bottom (tank top) Connects with longitudinal girders Provides transverse strength and rigidity Solid Plate Floor Continuous transverse structural plate. Bracket Floor Transverse bracketed structural arrangement, depending on the double-bottom framing system. Typical Double-Bottom Section Inner Bottom (Tank Top) Floor Plate (transverse) EXAM SKETCH TIP Show a section with: outer bottom shell, inner bottom, a solid floor plate spanning between them, with a vertical web and stiffeners. Outer Bottom Shell Longitudinal Girders EXAM KEYWORD Floor plate = Transverse structural member of the double bottom LEARN PRACTICE EXCEL AT SEA

Slide 5 · Hull Structure Series

Hull Structure Series Essential Hull Structural Stresses SHEAR STRAKE Uppermost strake of side shell plating The shear strake is the uppermost continuous strake of side shell plating, adjoining the strength deck. It forms an important part of the longitudinal strength of the hull. Why is it Important? • Hull-girder bending produces high longitudinal stresses toward the extreme top and bottom of the hull girder. • The shear strake therefore carries significant longitudinal loads, particularly in the strength-deck region. Works With The shear strake works together with the stringer plate. • Stringer plate = outboard strake of deck plating. • They are joined at the deck edge, which is a highly stressed zone on the vessel. Survey Attention • The deck-edge connection between shear strake and stringer plate is a significant structural detail. • Stress concentrations can occur in this region, so it receives special attention during surveys. Material Consideration Depending on: • Design temperature • Structural location • Material thickness • Applicable classification requirements the steel in critical hull structural regions such as the shear strake may require specified impact toughness. Deck Stringer Plate (outboard deck strake) Shear Strake (uppermost side shell strake) Side Shell Plating EXAM KEYWORD Shear strake = Uppermost side shell strake adjoining the strength deck. LEARN PRACTICE EXCEL AT SEA

In exams

Asked 30 times across 11 different questions, most recently in 2026. Asked most in 2nd Mate (17), UK Management (5), MEO Class 2 (4), MEO Class 4 (3).

Drafted by SailR from our daily lessons. AI-drawn illustration. Simplified to explain the idea, not to scale. Last updated 19 Oct 2026.

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