Pancyprian Mechanics & Construction flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Static equilibrium equations

For a planar rigid body, ΣFx = 0, ΣFy = 0 and ΣM = 0 about any chosen point. These three independent equations allow solution of up to three unknown reactions.

Moment of a force

The product M = F × d, where d is the perpendicular distance from the reference point to the line of action of the force. Units are newton-metres and the sign depends on rotation direction.

Coefficient of friction

Ratio of limiting friction force to normal reaction. The static coefficient applies at impending motion and exceeds the kinetic coefficient, which applies once sliding has begun.

Constant acceleration kinematics

Three relations link velocity, displacement and time when acceleration is uniform: v = u + at, s = ut + ½at², and v² = u² + 2as. They fail for varying acceleration.

Axial stress and strain

Normal stress equals axial force divided by cross-sectional area. Strain is change in length divided by original length, and Hooke's law links them through the elastic modulus.

Section modulus

The ratio W = I/c of second moment of area to distance from the neutral axis to the extreme fibre. Maximum bending stress in a section equals bending moment divided by section modulus.

Parallel axis theorem

Second moment of area about any axis equals the value about the parallel centroidal axis plus area times the square of the distance between the axes.

Euler buckling load

Critical load for a slender pin-ended column is π²EI divided by the square of its length. Other end fixities are handled by an effective length factor applied to the actual length.

Characteristic concrete strength

The 28-day strength below which no more than five percent of standard cube test results should fall. Design calculations apply partial safety factors to this characteristic value.

Water-cement ratio

Mass of water divided by mass of cement in a mix. Lowering it raises strength and durability but reduces workability, so admixtures or adjusted aggregate grading may be needed.

Nominal concrete cover

Distance from the outer concrete surface to the nearest reinforcement surface. It is set by exposure class for durability and by fire resistance requirements, not chosen freely.

Steel grade S355

Designation for structural steel with a specified minimum yield strength of 355 MPa for the relevant thickness range. Higher grades permit smaller sections for the same applied load.

First-angle projection

A drawing convention in which the object sits between observer and projection plane, so the view from above appears below the front view. The projection symbol identifies the system used.

Drawing scale 1:50

One unit on the paper represents fifty units on site. A 20 mm measured length on such a drawing corresponds to one metre of actual construction.

Cutting plane line

A chain line with thick ends and arrows showing the direction of viewing, labelled to match the section drawing it produces. It marks where the object is notionally cut.

Bar bending schedule

A table listing each reinforcement bar mark with diameter, shape code, number of bars, cut length and total weight, used for fabrication and for checking steel delivered to site.

Height of collimation method

Levelling reduction in which a collimation height is computed as known reduced level plus backsight, then each new level is that height minus its foresight reading.

Traverse angular misclosure

Difference between the sum of measured interior angles and the theoretical (n−2)×180 degrees for an n-sided closed traverse. It is distributed equally among the measured angles.

Bearing and coordinate change

For a line of length d on bearing θ measured clockwise from north, the easting change is d·sinθ and the northing change is d·cosθ.

Prismoidal volume formula

Volume of a segment equals length divided by six, multiplied by the sum of the two end areas plus four times the mid-section area. It is more accurate than the mean end-area method.

Residual current device

A protective device that trips when the difference between live and neutral currents exceeds its rated sensitivity, typically 30 mA for socket and wet-area circuits.

Trap seal depth

The vertical water depth retained in a sanitary fitting trap, nominally at least 50 mm, which blocks foul air from the drainage stack entering the room.

Cooling load components

Total cooling load combines fabric and glazing transmission, solar gain, internal gains from people, lighting and equipment, plus the latent load of moisture.

Earthing system TT

An installation whose exposed conductive parts connect to a local earth electrode independent of the supply neutral earth. It normally requires residual current protection for fault disconnection.

Hierarchy of control

Order of risk reduction: eliminate the hazard, substitute, apply engineering controls, then administrative controls, with personal protective equipment last because it protects only the wearer.

Scaffold inspection interval

Scaffolds must be inspected by a competent person before first use, after alteration or adverse weather, and at intervals not exceeding seven days while in service.

Excavation inspection

Sides and supports of an excavation must be inspected at the start of each shift and after any event such as heavy rain or ground movement that could affect stability.

Lifting plan

A documented method prepared by a competent person covering load weight, crane capacity and radius, rigging, ground conditions and the exclusion zone beneath the load.

Lump-sum contract

An agreement for a fixed price to complete defined works. Quantity risk generally rests with the contractor, who is paid the stated sum regardless of actual measured quantities.

Retention in construction contracts

A percentage withheld from interim payments as security for performance. It is usually released in two parts, at practical completion and after the defects liability period.

Liquidated damages

A pre-agreed sum per day of culpable delay beyond the completion date, representing the employer's estimated loss. It must be a genuine estimate, not a penalty.

Earned value cost index

Cost performance index equals earned value divided by actual cost. A value below one means the work completed has cost more than budgeted for that progress.