Lectures W1

Lectures_ Week 1 07 January 2014 16:57

Five types of primary structures 1. 2. 3. 4. 5.

Tension structures Compression Structures Trusses Shear structures Bending structures Real trusses connects members using "gusset plates" Kassamali

"A structure refers to a system of connected parts used to support a load. Important examples related to civil engineering include buildings, bridges, and towers; and in other branches of engineering, ship and aircraft frames, tanks, pressure vessels, mechanical systems, and electrical supporting structures are important." - Hibbele

Imagine a view without the bridge

The pedestrian bridge suppose to be 1. Safe 2. Aesthetically pleasing 3. Serviceable - makes sense from the world, stays within the sound usable state (balance is criticized) Also, you will consider 4. Economic factor 5. Environmental considerations ( glass brick is criticized)

(Zubizuri bridge, Bilbao, Spain)

Loads on Structures 1. 2. 3. 4. 5. 6. 7.

Dead Loads Live loads / Action loads Wind loads Snow loads Bridge loads (also action loads) Impact loads Earthquake loads

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Eurocode I Reference BS EN 1991-1-1 BS EN 1991-1-2 BS EN 1991-1-3 BS EN 1991-1-4 BS EN 1991-1-5 BS EN 1991-1-6 BS EN 1991-1-7 BS EN 1991-2 BS EN 1-3 BS EN 1-4

Title Densities, self-weight and imposed loads Actions on structures exposed to fire Snow loads Wind actions Thermal actions Actions during execution Accidental actions due to impact and explosions Traffic loads on bridges Actions induced by cranes and machinery Actions in silos and tanks

Reference

Australian code: AS/NZS 1170

Problems! (Hibbeler, 2012) A two-story office building shown in the photo has interior columns that are spaced 22m apart in two perpendicular directions. If the (flat) roof loading is 2kN/m 2 determine the live load supported by a typical interior column located at ground level (assume action load for office building is 3kN/m 2).

Find the components of the force F in the directions of Ox and Oy shown in Figure.

The floor system of a gymnasium consists of a 130-mm-thick concrete slab resting on four steel beams (A = 9,100 mm 2), that, in turn, are supported by two steel girders (A= 25,600 mm2), as shown in Fig.3. Determine the dead loads acting on beam BF and girder AD. (Assume steel density of 7.8g/cm 3)

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Note: Eurocode increased bulk density of concrete from 2.4g/m3 to 2.5 g/m3

Statically determinate and indeterminate Determinate structure means it can be solved by equilibrium equations Determinacy or indeterminacy of a structure can be external or internal External indeterminacy: total number of support reactions > number of equilibrium equations. Internal indeterminacy total number of unknown member forces > number of the equilibrium equations (when look at the relevant internal FBD)

m + r = 2j m + r > 2j m + r < 2j

or m = 2j - r determinate or m > 2j – r indeterminate or m < 2j – r unstable

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