Week 1 Challenge

1. Truss type reasoning

Out of the two through type truss systems shown below, which is the most efficient in carrying gravity load? Reason it out.

AIM: To find out which truss system is best for carrying out gravity load.

OBSERVATION: Truss A is having vertical & inclined member forming a "N" shape & is known as Pratt truss.

• It is the most common form of truss used
• compression forces is generated only in the vertical member while the inclined member only take tension.
• Pratt truss have more unloaded member as compared to the howe truss.

Truss B is opposite of pratt truss & is known as howe truss

• Compression forces is generated in inclined members while vertical member takes the tension
• The structure generates less 0 force member as compared to Pratt truss

CONCLUSION: As Pratt truss distributes loads more evenly and has more 0 force member as compared to Howe

truss we can clearly say that TRUSS A is more efficient in carrying Gravity load as compared to

TRUSS B.

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2. Deflection shape & Bending Moment Drawing (Qualitative approach)

For the beam & Frame below draw deflected shape and bending moment drawing. (Qualitative approach). E & I are constants.

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3. Determine MOI, Weight, C/S area of sections below

A)

MOI ALONG Ixx=18360000 mm4

MOI ALONG Iyy=1987000 mm4

Cross sec area=3040mm2

Weight per meter= 23.8kg/m

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B)

MOI ALONG Ixx=5470000000 mm4

MOI ALONG Iyy=135000000 mm4

Cross sec area=26000mm2

Weight per meter= 204.1kg/m

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C)

MOI ALONG Ixx=185000000 mm4

MOI ALONG Iyy=14200000 mm4

Cross sec area=9651mm2

Weight per meter= 75.8kg/m

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D)

MOI ALONG Ixx=671000000 mm4

MOI ALONG Iyy=89800000 mm4

Cross sec area=1677.4mm2

Weight per meter= 132kg/m

( Calculation sheet for above is attached)

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4. Load calculation problem

For the floor framing below, Calculate the load on interior beam, Exterior beam, Interior Girder and exterior girder having Floor Load of 10kN/m²

Soln: Interior beam=20KN/m(-)

Enterior beam=10KN/m(-)

Interior Girder=22.5KN/m(-)

Enterior Girder=20KN/m(-)

( Calculation sheet for above is attached)

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5. Expansion joint size determination for temperature stated problem

Assuming a bridge, made of steel, with an initial total length of 2000 m at -20 ºC, calculate the length difference at 40 ºC and its total length.

Coefficient of Thermal expansion of steel = 12x10^-6/°C

Soln: Length of Bridge at-20 ºC =2000m,

Coefficient of Thermal expansion of steel = 12x10^-6/°C

we know that Length difference at 40ºC= 2000 x 40 x 12x10^-6

^{= 0.96m}

^{Hence the length differene at 40 ºC =0.96m}

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