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CVEN 444: STRUCTURAL CONCRETE DESIGN

CLASS PROJECT

The structural floor plan of a three-story (ground floor, two suspended floors, and a roof) office

building is shown on the next page. The roof covers the hole used for the elevator shaft andstairwells. The new building will be located in Houston, Texas. The floor systems consist of one-way pan joists slabs supported in one direction by beams located on column lines A through F. Inaddition, beams are located on column lines 1 and 4 as part of the lateral force resisting system.

The design loads for the floor (in addition to the self-weight) include a superimposed dead load(SDL) of 20 psf to account for moveable partitions, ceiling panels, etc. and a superimposed liveload (LL) to be determined from ASCE 7-95. In addition, a 0.5 kip/ft. wall load is applied aroundthe building perimeter. The design loads for the roof (in addition to the self-weight) include asuperimposed dead load (SDL) of 10 psf.

Overview of Required Design:

A. Design the continuous beams of the first floor on column lines D and E of the secondsuspended floor assuming that they support the one-way pan joist floor system (3 parts).

B. Design the slab of the second suspended floor as a one-way pan joist system supported in

one direction on column lines A through F (3 parts).

C. Design and detail the columns for all three stories for the location where column lines Eand 2 intersect (1 part).

D. Design the roof system as a two-way slab without beams (1 part).

E. Design the footing for the column on column lines E and 2 (1 part).

Follow detailed instructions on separate assignment sheets!!!

Dimension Assignments by Groups

Parameter Group Number

1 2 3 4 5 6L 35 35 40 40 45 45

fc 4 ksi 4 ksi 4 ksi 4 ksi 4 ksi 4 ksify 60 ksi 60 ksi 60 ksi 60 ksi 60 ksi 60 ksi

bw 4 6 6 7 7 6Sw 20 30 30 53 53 66

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2

t = 5

10-20*

bw Sw

Section 1-1(Joists)

0.75L

0.75L

0.75L

0.75L

L0.85LL

A

D

E

1 2 3 4

1 1

Pan joist - ribdirection (typ)

C2

2

Plan View

B

F

0.75L

Hole forElevator shaftsand stairwells

12-24

Section 2-2

(Beams)

t = 5

10-27

L = _______fc = _______fy = _______bw = _______

Sw = _______

2 2

* Use standard pan joistdimensions.

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ASSIGNMENT #A1

Design the continuous beams on column lines D and E of the second suspended floor assumingthat they support the one-way pan joist floor slab system.

The design loads for the floor (in addition to the self-weight) include a superimposed dead load(SDL) of 20 psf to account for moveable partitions, ceiling panels, etc. and a superimposed liveload (LL) to be determined from ASCE 7-95 for an office building. In addition, a 0.5 kip/ft. wallload is applied around the building perimeter. The design loads for the roof (in addition to theself-weight) include a superimposed dead load (SDL) of 10 psf. Use a factored load case of U =1.4(DL) + 1.7(LL).

Requirements:

1. Establish team goals and expectations for your group. List these goals and expectationsand sign them. Everyone in the group should keep a copy for themselves and a copyshould be turned in with this assignment.

2. Estimate the total depth of the slab, joists, and column line beams using ACI Table 9.5 (a)and then use these dimensions to estimate the dead weight. Normal weight concrete isused for all members. Assume a web thickness for the column line beams (between 12and 24).

3. Estimate the loading on the beams using the "tributary area method".

4. Determine the design moment and shear envelopes for the beams on column line D usingan elastic analysis (SAP 2000 or equivalent). Use the appropriate load patterns tomaximize the member forces due to the live load. Turn in a hard copy of the input andoutput files for your analysis, along with plots of the moment and shear envelopes for allbeams along column line D.

Assume the column cross sections are 24" square, story heights are 14 ft., and all beamsare identical to the beam selected in step 2. For the effective second moment of area instiffness computations, use 70% and 35% of the gross section properties for the columnsand beams, respectively. Note the beam stiffnesses are based on the slab flange widthspecified by the ACI Code (Sec. 8.10).

5. Determine the design moment and shear envelopes for the beams on column line Eaccording to the approximate method using the ACI moment coefficients (ACI 8.3.3).Verify that these coefficients may be used for this structural layout.

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ASSIGNMENT #A2


Using the data from Assignment #A1, design the continuous beams of column lines D and E ofthe second suspended floor assuming that they support the one-way pan joist floor system. Thecolumns, beams, and joist slabs are poured monolithically.

Requirements:

1. Determine the beam cross-sectional dimensions and reinforcement required for bendingon column lines D and E. Consider all beams to have T-sections or inverted L-sections.

2. Determine the lengths of the reinforcement for proper development (bond) based on themoment envelopes.

3. Show the reinforcement on a sketch with all the required details - bars and cross sections.A portion of your grade will be based upon the neatness of your calculations and sketches.A computer-generated drawing showing your details is encouraged.

Reminder: The cover sheet of each project assignment must identify the calculator(s) and

checker(s). In addition, the calculator(s) and checker(s) must initial each sheet within theassignment to indicate their final approval of the project documents.

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ASSIGNMENT #A3


Using the data from Assignments #A1 and #A2, design the continuous beams of column lines Dand E of the second suspended floor assuming that they support the one-way pan joist floorsystem. The columns, beams, and joist slabs are poured monolithically.

Requirements:

1. Determine the shear reinforcement required for the beams on column lines D and E.

2. Determine the specific dimensions and details (hooks, etc.) of the shear reinforcement.

3. Provide sketches detailing the shear reinforcement. The sketches should show thedistribution of shear reinforcement along the length of the beams plus cross-sections withall the required details for each stirrup type. The information for the longitudinalreinforcement determined for Assignment #A2 should also be shown.

A portion of your grade will be based upon the neatness of your calculations and sketches.A computer-generated drawing showing your details is encouraged.

Reminder: The cover sheet of each project assignment must identify the calculator(s) andchecker(s). In addition, the calculator(s) and checker(s) must initial each sheet within theassignment to indicate their final approval of the project documents.

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ASSIGNMENT #B1

Design the slab of the second suspended floor as a one-way pan joist system supported in onedirection on column lines A through F.

Requirements:

1. Determine moment and shear envelopes for the pan joist slab using the ACI coefficientmethod or a more rigorous elastic analysis (SAP 2000 or equivalent) and momentredistribution for the load combination of 1.4 DL + 1.7 LL.

2. Determine the reinforcement required in the ribs for moment resistance.

3. Determine the required development based on the "shifted" moment envelopes.

4. Verify the shear resistance near the interior supports. If necessary, design the shearreinforcement using stirrups or by widening the longitudinal ribs.

5. Sketch a plan of the floor and the reinforcement required for construction. Specify thelength and the number of bars (including stirrups).




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ASSIGNMENT #B2


Requirements:

1. Evaluate the deflection for a typical joist spanning between column lines A and B. Whenchoosing the permissible deflection criteria in the ACI Code, assume that glass partitionwalls will be used on this floor. Assume the SDL of 10 psf is applied after the glasspartitions are in place and 50% of the live load will be sustained for at least 6 months.

Use any reasonable analysis procedure(s) to determine the deflections. Explain your workand state all assumptions made in your analysis. When computing the average effectivemoment of inertia for the span, it will be acceptable to use the same effective moment of

inertia for each of the joist ends.

2. Check the ACI Code crack width provisions at midspan of a typical joist between columnlines A and B.


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ASSIGNMENT #B3


Requirements:

1. Using assignments #A1-#A3 and #B1, determine quantities of reinforcing bars requiredper floor. For example, find the total number of a particular stirrup type (assume you canorder stirrups directly) and the total number of longitudinal reinforcing bars at a givenlength (assume that bar lengths can only be purchased at 20, 30, 40, and 50 and can becut to the appropriate length in the field). Assume that the beam and rib reinforcementcalculated previously is the same for all beams on the given floor.

2. Determine the total weight of reinforcement and volume of concrete per sq ft of floor area(divide the calculated reinforcement weight and concrete volume by the plan dimensionsof the building).

3. Estimate the materials cost per floor area assuming that the concrete costs $100 per yd3

and reinforcement costs $0.25 per lb.

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ASSIGNMENT #C1

Design and detail the columns for all three stories for the location where column lines E and 2intersect.

Requirements:

1. Develop a spreadsheet that calculates the interaction diagram for a generic four-layeredreinforced concrete short column. Display the variables (see below) and the finalinteraction diagram at the top of the spreadsheet for ease of use and visibility by the user.

2. Determine the axial loads on each column of column line E (E1, E2, E3, E4) at each levelof the building using the tributary area method. Show all factored axial loads in a table.Determine approximate dimensions for these columns using Eq. 11-18a (MacGregor,1997) with a 2% reinforcement ratio. Calculate the required longitudinal reinforcementassuming short column behavior with no bending.

3. Determine the design forces (P and M) for column E2 at each level of the building usingelastic analysis (SAP 2000). Find design demands for gravity loading only(U=1.4DL+1.7LL). Consider two cases: (1) maximize Pu and Mu, and (2) maximize theeccentricity due to the Mu divided by Pu. Show all critical combinations of the factoredforces for each story in a table.

4. For column E2, determine whether short column behavior or slender column behaviormust be considered for each story level, based on the approximate dimensions selected inpart 2 of this assignment. If the column segments turn out to be slender, assume for this

project only that they are short columns.

Continued on next page.


ASSIGNMENT #C1 (cont.)

9

h

As,1

d1

b

d3

d4

d2

As,2

As,3

As,4

fc=

fy =

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5. Using the forces found in step 3, determine the size and reinforcement for column E2 atall story levels and verify that the strength provided is adequate using axial load-bendingmoment interaction diagrams generated using your spreadsheet from part 1 of thisassignment and the PCACOL software (assume bending in only one direction).

6. Show a view of the column from the foundation to the roof and detail the reinforcementincluding ties and lap splices. Show typical cross-sections wherever there is a change inreinforcement or column dimensions.



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ASSIGNMENT #D1

Design the roof system as a two-way slab without beams.

Design the slab of the roof supported by columns (assume 24" x 24") without beams (flat plateconstruction). There is no need to increase the load for the panel which covers the elevator shaftdue to the elevator's own weight. Limit your design to the frames along column lines 2 and E.Neglect wind loads in this analysis.

Requirements:

1. Divide the slab into frames suitable for design using the direct design method (columnlines 2 and E).

2. Determine the required slab thickness from ACI Table 9.5a (make uniform throughout).

3. Determine the positive and negative moments on the frames using the coefficients fromthe direct design method.

4. Divide the frames into column and middle strips and distribute the longitudinal momentsto these strips.

5. Determine the reinforcement for each strip.

6. Show the floor plan and display the reinforcement for each strip along each frame in twodifferent plans. Show the lengths and bends of the bars based on ACI requirements.



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ASSIGNMENT #E1

Design the footing for the column on column lines E and 2.

Design and detail a spread footing for column E2 of the office building. Assume that theunfactoreddemands (dead + live loads) on this footing from the column are given as: P = 350kips; M2-2 axis = 150 kip-ft; and ME-E axis = 0 kip-ft. Thefactoreddemands (1.4 DL + 1.7 LL) onthis footing from the column are given as: Pu = 550 kips; Mu2-2 axis = 220 kip-ft; and MuE-E axis = 0kip-ft. Use fc = 3 ksi and fy = 60 ksi.

Requirements:

1. Estimate the size and thickness of a square footing by limiting the unfactored bearing

stresses from the column on the soil to 5.0 ksf. Note that there are no adjacent buildingsor property lines to limit the size or geometry of the footing. Neglect any overburden soilthat may exist on the footing

2. Determine actual thickness of footing to satisfy one-way and two-way shear requirementsaccording to ACI 318 such that transverse shear reinforcement would not be required inthe footing.

3. Determine flexural steel reinforcement for both directions 2-2 and E-E according to thefactored demands. Note that the steel in each direction will not be the same. Also detailthe reinforcement for proper embedment length.

4. Assuming 8-#9 bars will be used as dowel reinforcement, detail for proper embedmentlength.

5. Show plan and elevation views of the footing as well as required reinforcement.



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