week 5 Flashcards
(20 cards)
What are the typical load types that buildings are subjected to?
Buildings experience dead loads, live loads, wind loads, earthquake loads, soil pressure loads, and hydrostatic pressure loads.
What is the difference between dead loads and live loads?
Dead loads are permanent, such as the self-weight of structural elements; live loads vary over time, like people and furniture on a floor slab
How are wind loads treated differently from dead and live loads?
Wind loads are dynamic (vary with time and intensity) while dead and live loads are static. Engineers convert dynamic wind loads into equivalent static loads for calculations or use finite element models with wind tunnel simulations.
How do structural frames transfer loads from floors and roofs to the foundation?
Loads from slabs and roofs transfer to beams, then to structural columns, and finally to the foundation and sub-soil via pad footings.
What are the three axes of a structural element like a beam?
The longitudinal axis (along the beam length), and two cross-sectional axes: major (parallel to the shorter side) and minor (parallel to the longer side).
What stresses are induced by axial and transverse loads on structural members?
Axial loads cause compressive or tensile stresses along the longitudinal axis; transverse loads induce bending and shear stresses
What is the difference between pinned (simply supported) and fixed (rigid) beam connections?
Pinned connections allow rotation and have zero moment at supports; fixed connections restrain rotation, reducing deflection but inducing moments at supports.
Where are compressive and tensile stresses located in a simply supported beam under bending?
Compression occurs at the top fibers, tension at the bottom fibers, and zero stress at the neutral axis.
Why are reinforcement bars provided at both top and bottom of beams?
Reinforcements resist tensile stresses from bending and help minimize shrinkage cracks in concrete.
What is the purpose of pad footings in load transfer?
Pad footings increase the area over which loads are transferred to the soil, reducing soil stress and preventing foundation failure.
What is the primary function of a suspended floor?
To span between structural beams or load-bearing walls and safely carry dead, superimposed dead, and live loads.
What types of loads must a suspended floor resist?
Dead loads (self-weight), superimposed dead loads (floor finishes), and live loads (furniture and occupants).
What kinds of stresses act on suspended floors?
Bending, shear, and rotating stresses.
Why is fire resistance important in suspended floors?
To delay collapse and fire spread, allowing safe evacuation; specified by Fire Resistance Levels (FRL) in the NCC
How do suspended floors help with sound insulation?
Heavy materials like concrete reduce airborne noise, while impact noise resistance depends on floor toppings (e.g., carpet improves it).
Is thermal insulation necessary for all suspended floors?
Not always, but floors with in-slab heating/cooling must be insulated underneath and around edges with at least R1.0
What is the difference between one-way and two-way slab action?
One-way slabs transfer loads mainly in one direction (supported on two edges), while two-way slabs transfer loads in both directions (supported on four edges).
What are the benefits of continuous mid-span supports versus discontinuous supports?
Continuous supports reduce mid-span sagging, allowing thinner slabs but require tension reinforcement at the support (hogging moment).
What are the advantages of concrete floors over timber floors?
Concrete floors are more durable, stiffer, energy efficient (thermal mass), better at noise reduction, and quicker to construct with precast elements.
What are the main types of concrete suspended floors?
In situ concrete floors, composite concrete/steel floors (with permanent steel decking), and precast concrete floors (beams, planks, panels).
