fundamental concepts tutorial 1 to answer just click on the button or image related to the answer

Fundamental Concepts

Tutorial 1

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A. FUNDAMENTAL CONCEPTS

what is their weight (in kN) on earth ?

(on Earth g = 10 m/s2 approx)

a person has a mass of 70 kgs.

Question A1

700 kNa

0.7 kNb

70 kNc

what is their weight (in kN) on a roller coaster ?

(on roller coaster grc = 3 x g m/s2 approx)


Question A2

2.1 kNa

210 kNb

21 kNc

what is their weight (in kN) on the moon ?

(on the moon gm = 0.17 x g m/s2 approx)


Question A3

1.2 kNa

120 kNb

0.12 kNc

what is the force acting down on surface S ?

given two blocks A, and Bon a surface S.

Question A4a

200 kNa

3 kNb

300 kgc

ABS

mass (A) = 100kg

mass (B) = 200kg

what is the force acting up on block B ?

given two blocks A, and Bon a surface S.

Question A4b

2 kNa

3 kNb

1 kNc

ABS

mass (A) = 100kg

mass (B) = 200kg

what is the pressure on surface S ?

given two blocks A, and Bon a surface S and that block B is 200 x 150 mm

Question A4c

66.6 Paa

1000 kPab

100 kPac

ABS

mass (A) = 100kg

mass (B) = 200kg

what is the moment at A ?

given the force of 2kNacting as shown

Question A5a

5 kNma

10 kN/mb

10 kNmc

B

A

C

5m

2kN3m

what is the moment at B ?


Question A5b

6 kNma

3 kN/mb

1.5 kNmc

B

A

C

5m

2kN3m

what is the moment at C ?


Question A5c

2 kNma

2 kN/mb

0 kNmc

B

A

C

5m

2kN3m

what have we learnt ?

so in general, if a point lies on the line of action of a force

Question A5d

nothinga

the moment of a force about a point lying on the line of action of the force is zero

b

which system of forces will provide equilibrium?

given the system shown

Question A6

a b

10kN

10kN

10kN

10kN

10kN

10kN

10kN

10kN

14.1kN

either a or bc

find forces F2 and R1 so as to provide equilibrium?

given the system shown

Question A7F2= ? kN F1= 12kN

A B C3m 1mR1= ? kN

F2 = 4 kNm and R1 = 16 kNma

F2 = 4 kN and R1 = 16 kNb

F2 = 36 kN and R1 = 48 kNc

B. GENERAL PRINCIPLES

what is the purpose of structure in buildings?

Question B1

to provide the fabric of the space enclosurea

to organize the elements of the buildingb

to resist all the forces acting on the building and transfer them to supports (the ground)

c

all of the aboved

a and ce

what are the three main considerations when dealing with structure?

Question B2

aesthetics, spaces and materialsa

stability, strength and stiffnessb

dead loads, live loads and supports c

Question B3

show answera

finishb

given the post-and beam arrangement as shown, and assuming pin-joints,describe three ways of stabilising it.

draw and name them

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Weight is a force. Weight = Mass x g where g = 10 m/s2 on earth1kg of mass = 10N of force on earth. 100kg of mass = 1kN weight on earth

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Weight is a force. Weight = Mass x g where g = 10 m/s2 on earth1kg of mass = 10N of force on earth. 100kg of mass = 1kN weight on earth

0.7 kNso on Earth (g = 10 m/s2) Weight = 70 x 10 /1000 =

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Weight is a force. Weight = Mass x g where g = 10 m/s2 on earth

and 30 m/s2 on a roller coaster1kg of mass = 30 N of force on roller coaster. 100kg of mass = 3 kN weight on roller coaster

2.1 kNso on roller coaster (g = 30 m/s2) Weight = 70 x 30 /1000 =

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and 30 m/s2 on a roller coaster1kg of mass = 30 N of force on roller coaster. 100kg of mass = 3 kN weight on roller coaster

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and 1.7 m/s2 on the moon1kg of mass = 1.7N of force on the moon. 100kg of mass = 0.17kN weight on the moon

0.12 kNso on the moon (g = 1.7 m/s2) Weight = 70 x 1.7 /1000 =

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and 1.7 m/s2 on the moon1kg of mass = 1.7N of force on the moon. 100kg of mass = 0.17kN weight on the moon

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both blocks A and B are acting on surface S

3000 Nso the total weight on surface S (on earth) = (100 +200) x 10 =

3 kN =

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both blocks A and B are acting on surface S

don’t forget that it’s force we are after, not massyou must convert the total mass to a force

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for every force there is an equal and opposite reaction

since the total force acting down is 3 kN, the force acting up, i.e. the reaction must be 3kN

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remember:for every force there is an equal and opposite reaction

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pressure = force / area, P = F / A

so, working in kNs and metres, P = 3 / (0.2 x 0.15) = 100 kN/m2

since 1 kN/m2 = 1 kPa, 100 kN/m2 = 100 kPa

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pressure = force / area, P = F / A

so think about what the total force down is and what the area is.work in kNs and metres

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moment = force x distance, M = F x D

yep! moment is force x distance, so the moment is 2 x 5 = 10 kNmsince it is force x (multiplied by) distance the units are kN x m, i.e kNm

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so think what the force is and what the distance is.The distance is the perpendicular distance from the point to the force

work in kNs and metres


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so think what the units areforce multiplied by – not divided by distance


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Think of the units. Work in kNs and metres


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Think of the units. Work in kNs and metres


THINK !!

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so if the point lies on the line of action of the force, the distance from the point to the force must be 0and hence the moment must be 0

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so think what the distance is when the point lies on the line of action of the force.


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in a) the vertical forces are equal and opposite and the horizontal forces are equal and oppositein b) the resultant force of the horizontal and vertical forces would be 14.1 kN, so the equilibrant force (the force providing equilibrium) would be 14.1 kN (equal and opposite to the resultant force)

both systems are in equilibrium

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the vertical forces are equal and opposite and the horizontal force are equal and opposite

so it is in equilibrium but this is not quite the right answer

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the equilibrant force is equal and opposite to the resultant force of the horizontal and vertical forces

so it is in equilibrium but this is not quite the right answer

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clockwise moments about B = 12 x 1 = 12 kN anti-clockwise moments about B = F2 x 3so F2 x 3 = 12 kN F2 = 4 kNsince ΣV = 0, R1 = 4 + 12 = 16 kN

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THINK !!what are the units for forces?

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take clockwise moments about B , then take anti-clockwise moments about B

then use the equation ΣM = 0 (sum of clockwise = sum of anti-clockwise)

How did you get this?

Don’t guess!!

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enough !

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that’s part of the answer – what else is there?

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in general terms, structure does deal with the organization of complex objects but we are concerned with structure in the domain of forces

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How did you get this?

Don’t guess!!

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Stability - equilibrium building must not move - up, sideways or overturn all forces and moments must balance

Strength building & elements must not break / collapse

Stiffness / functionality building & elements must continue to serve their purpose, must not deform too much

the three Ss

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we are concerned with structure in the domain of forces not with architectural form or spaces

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these are concerns - but they are not the main general concerns

a) cross-bracing

b) knee-bracing

c) rigid joints

d) solid infill (shear panels)

e) build-in posts

any of these will do

that’s it

fundamental concepts tutorial 1 to answer just click on the button or image related to the answer

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