Rubrics of Exams

Rubrics and grading Rubrics of exams

Prestressed concrete questions Questions Type 1

They got 2 QUESTIONS of 10 points

AT TRANSFER in a prestressed concrete design, what loads are on the beam? What are the three primary differences between TRANSFER and SERVICE in prestressed concrete design? AT SERVICE in a prestressed concrete beam how does the prestressing FORCE compare to the FORCE at transfer?

If you design a prestresed concrete beam that is okay at Decrease live load or Decrease Pc, increase compression stress of concrete TRANSFER, but fails in SERVICE, what should you change (f'c) any of those 10 points. If only says increase inertia, increase heigth of about the design? the beam 8 points, anything less precise but making some sense 5 points

If you design a prestresed concrete beam that is okay in Increase Inertia, increase heigth of the beam, decrease e, Decrease Pi, SERVICE, but fails at TRANSFER, what should you change increase compression stress of concrete (f'ci) any of those 10 points, anything about the design? less precise but making some sense 5 points

Grading out of 10 EACH

Only self load 10 points, if they say only dead 5 points, if they put live load 0 points

Transfer: Only self load, Pi is applied, F'ci. Service: Self load+Dead+%live load, Pc is less than Pi,we consider F'c which is greater than F'ci. Three differences

10 points, Two differences 7 points, 1 difference 5 points

Pc< Pi, Prestressed force at service Pc is less than the one in transfer Pi - 10 points If they say another difference true regarding transfer vs service, example: service considers live load and transfer no give 5 points, another thing somewhat half sensible up to 2 points

Calculation Dead and live loads Choose material Advantages and disadvantage Questions Type 2

They got 6 QUESTIONS of 5 points

When trying to estimate the depth of concrete beams – what is a good estimate for a 25 ft long concrete beam (spaced every 8 ft with office live loads). When you find the area of steel required for a concrete beam, you then check that the bars will fit and then you also check the strain in the steel. Why is it important to check the strain in the steel? When you check if steel bars will fit into your cross section, list the three things you have to take into account? Describe the difference between live load and dead load When we factor loads to design a piece of a structure, dead load takes a lower factor than live load does, why? Your first boss in your first architecture firm proposes building an ordinary reinforced concrete beam that is 80 ft long, what do you say? Name two advantages to pre-stressed concrete as a structural material List two advantages of concrete as a structural material List 2 disadvantages of concrete as a structural material Grading out of 5 EACH

L/10 to L/15 so, from 20 to 30 in - any in this range 5 points. If they say L/20 so, 15 to 19 in - any in this range: 4 points. If they say above 30: 2 points, any

Reinforced When you find an Area of steel required, what is the concrete design next step in designing a concrete beam

other value 0 points

Cause we want the steel to fail first, so it gives a warning sing. If the concrete fails first then it would collapse instantly, not allowing time to evacuate. Anything revolving that 5 points. If they say cause the strain in the steel at failure should be larger that the yield strain, or if they say the strain has to be less than 0.002 3 points, anything less precise 2 points

Go to the chart and find a rebar combination that has equal or greater the Area of steel required. Anything revolving that 5 points, anything less precise 2 points

Spacing, diameter of the bars, concrete cover. Those three things 5 points,

Only two things : 3 points. Only one thing: 2 points

Dead load: permanent, stationary, can not be moved, predictable. Live load: Can move, can change, less predictable. Anything revolving that 5 points,

anything less precise 2 points

live is less certain/predicable/controllable - 5 points otherwise up to 2 points

if you think they said something halfway sensible No, we have to change to prestress concrete or steel. 5 Points. No, ordinary reinforced concrete can not spam that much 4 points. Only no without justification 3 points

Limited or less cracking, Greater spam, Smaller cross section, less self load than conventional reinforced concrete, can carry greater loads, less construction time on site any other true - Mentions two advantages 5

points, Mentions one advantage: 3 points

Good at compression, Durability, low mantainance, fire resistance, good sound absorption, thermal mass, allows fix connections easily, any other true

- Mentions two advantages 5 points, Mentions one advantage: 3 points

Bad at tension, Large self load, Bigger cross section, has cracking, formwork is required, needs time to acquire its final strength, any other true disadvantage - Mentions two disadvantages 5 points, Mentions one advantage: 3 points