Materials, Loads and Concrete
Nine videos on force, pressure, stress and strain, and how steel and concrete behave under load. Module 2 of the CSWIP 3.1u syllabus. I did not make them. I picked them, put them in teaching order, and wrote under each one what the exam wants you to take from it.
Video by video, with the exam angle
Each video teaches the concept. The line under it tells you how that concept turns up in the exam and where divers lose the mark.
Force, pressure and stress
Exam angle. Stress is force divided by area. That one formula is the reason every thickness reading you take has engineering value. Less area, same load, more stress. Say it that way in the exam.
Exam angle. Force is the push. Pressure, or stress in steel, is the push spread over an area. A corroded member carries the same force on less steel, so the stress goes up. That is the whole point of corrosion monitoring.
Loads and the stresses they cause
Exam angle. Tension stretches, compression squashes, shear slides, bending does both. On a beam loaded downward the top is in compression and the bottom is in tension. Cracks grow under tension, not compression.
Exam angle. Torsion and bending are the two divers forget. Then remember the offshore extras: drag rises with the square of velocity, and vortex shedding behind a cylinder gives a cyclic side force. Cyclic load is what causes fatigue, the most common in-service failure on offshore steel.
How steel behaves
Exam angle. Yield is where permanent deformation begins. Below it the steel springs back. Above it the steel stays bent. Residual stress at a weld toe sits near yield with no load applied, which is why cracks start there.
Exam angle. Yield and UTS are not the same number. UTS is the maximum stress before break and is always above yield. Ductile steel gives warning by stretching. Brittle failure gives none. The exam asks for the stress where permanent deformation starts. Answer yield.
Concrete
Exam angle. Three ingredients: cement, water, aggregate. Strong in compression, weak in tension. Fresh concrete is very alkaline, about pH 12.5, and that forms the passive film that protects the rebar. Chlorides from seawater attack that film. That is the offshore corrosion driver.
Exam angle. Rebar carries the tensile load the concrete cannot. Prestressing goes one step further and tensions the tendons first so the concrete stays in compression in service. Know both words. And know the minimum cover offshore is 60 mm.
Exam angle. Name them and sort them. Honeycombing is voids from poor compaction. Blowholes are trapped air against the formwork. Spalling is a piece breaking away. A pop-out is a small cone pushed out by internal pressure. Freeze-thaw cracks from inside as water expands about nine percent.
The course is the exam practice
These videos explain the science. The NDTPrep 3.1u Interactive Theory course puts it in the order the syllabus uses, with the diagrams, the plain-English explanations, and a quiz at the end of every module. Then the Q&A and Flashcards drill it until it sticks.
The videos on this page belong to their creators. I have not edited them. My notes are my own reading of the CSWIP syllabus and are not endorsed by the video makers.