CVEN 444: STRUCTURAL CONCRETE DESIGN CLASS PROJECT

Transcription

1 CLASS PROJECT The structural floor plan of a three-story (ground plus 3 floors) office building is shown on the next page. The roof covers the hole used for the elevator shaft and stairwells. The new building will be located in Houston, Texas. Story floor systems consist of one-way pan joists supported on column lines A through F. The design loads for the floor (in addition to the self-weight) include a superimposed dead load of 20 psf to account for partitions, plumbing, etc and a design live load to be determined from ASCE 7-05, plus a 0.25 kip/ft wall load around the building perimeter. The dimensional variables for the project are defined as: L = 30 ft; f c = 4,000 psi; fy = 60,000 psi; Bw = 12 in.; Sw = 48. Design Required: A. Design the continuous beams of the first floor on column lines B and C assuming that they support the one-way pan joist floor system (4 parts). B. Design the slab of the first floor as a pan joist system supported in one direction on column lines A through F (3 parts). C. Design and detail the columns on all stories intersecting column lines B and 3 (1 part). D. Design the slab of the roof as a two-way slab without beams (1 part). E. Design the footing for the column on column lines B and 3 (1 part). Follow detailed instructions from separate sheets!!! 1

2 A L B 0.85L C 2 2 Hole for Elevator shafts and stairwells 0.85L D Pan joist - rib direction (typ) 0.85L E 0.85L F L 0.85L Plan View L tw = 12 -? t = 5 tw = 12 -? t = 5 L = 30 ft fc = 4,000 psi fy = 60,000 psi Bw = 12 in. Sw = 48 in. Bw Sw 12 -? Section 1-1 Section 2-2 2

3 ASSIGNMENT #A1 Design the continuous beams of the first floor on column lines B and C assuming that they support the one-way pan joist floor system. The columns, beams, and slabs are poured monolithically. Required: 1. Estimate the total depth of the slab, slab joists, and column line beams using ACI Table 9.5a and estimate their dead weight. 2. Estimate the loading on the beams using the "tributary area method". 3. Determine the design moment and shear envelopes for the beam on column line B according to the approximate ACI method. Verify assumptions in code. Assume that no lateral loading exists (gravity loads only). 4. Determine the moment and shear envelopes for the beam on column line C using an elastic analysis (ETABS). Assume the column cross sections are 30"x30" squares, story heights are 13', and all beams are identical to the beam selected here. For the effective second moment of area in stiffness computations, use 70% and 50% of the gross section properties for the columns and beams, respectively. Note the beam stiffnesses are based on the slab flange width specified by the code. Identify all load cases and load combinations required to find maximum stresses in all sections of the beam due to dead and live loads only (gravity loads). Turn in hard copies of input and output files for your analysis, along with plots of the moment and shear envelopes for all beams along column line C. 5. Make a photocopy of your work for this assignment before you turn it in because you will need it for future assignments. 3

4 ASSIGNMENT #A2 Using the data from assignment #A1, design the continuous beams of the first floor on column lines B and C assuming that they support the one-way pan joint floor system. The columns, beams, and slabs are poured monolithically. 1. Determine the beam cross section dimensions and reinforcement required for bending on column lines B and C. Consider all beams to have T or inverted L sections. 2. For the span between column lines 1 and 2 only, determine the lengths of the reinforcement based on the moment envelopes and detailing requirements in ACI Show the reinforcement on a sketch with all the required details - bars and cross sections. 4. Make a photocopy of your work for this assignment before you turn it in because you will need it for future assignments. 4

5 ASSIGNMENT #A3 Using the data from assignments #A1 and #A2, design the continuous beams of the second floor on column lines B and C assuming that they support the one-way pan joist floor system. The columns, beams, and slabs are poured monolithically. 1. Determine the shear reinforcement required for the beams on column lines B and C. For this assignment, the shear reinforcement for any span of column lines B and C should be determined based on the critical shear loading for any span. 2. Determine the specific dimensions and details (hooks, etc.) of the shear reinforcement. 3. Show this additional reinforcement on the sketch with all the required details - bars and cross sections. 5

6 ASSIGNMENT #A4 You will be assigned into groups of either 3 or 4 students. In this assignment, you are asked to compare the work of each individual member of your group for assignments A1, A2 and A3. As a group, you are to explain the strengths and weaknesses of each design and then select the most appropriate design (i.e. the one that the group considers as most correct). If deficiencies exist in the best design, then these deficiencies should be identified, discussed, and rectified. 6

7 ASSIGNMENT #B1 Design the slab of the first floor as a pan joist system supported by beams along column lines A through F. Required: 1. Determine moment and shear envelopes for the joists using the ACI coefficient method for the load combination of 1.2 DL LL. 2. Determine the reinforcement required in the joists for moment resistance. 3. For a typical interior span only, determine the lengths of this reinforcement based on the moment envelope and the detailing requirements in ACI For a typical interior span only, verify the shear resistance. If necessary, design the shear reinforcement using stirrups or by widening the longitudinal ribs. 5. Sketch a plan of the floor and the reinforcement required for construction. Specify the length and the number of bars (including stirrups if necessary). 7

8 ASSIGNMENT #B2 Design the slab of the first floor as a pan joist system supported by beams along column lines A through F. 1. Verify the instantaneous deflections in the span between column lines A and B of the ribbed slab (joint) using the ACI deflection approach in Section 9.5 by averaging the moments of inertia of the joist at the ends and midspan. Explain all work and state all assumptions made in your analysis. 2. Check the ACI Code crack width provisions at midspan of a typical joist between column lines A and B. 8

9 ASSIGNMENT #B3 Design the slab of the second floor as a pan joist supported by beams along column lines A through F. 1. Using assignments #A1-#A3 and #B1, determine quantities of reinforcing bars required per floor. For example, find the total number of a certain shape stirrup (assume you can order stirrups directly) and the total number of longitudinal reinforcing bars at a given length (assume that bar lengths can only be purchased at 20, 30, 40, and 50 and can be cut to the appropriate length in the field). Assume that the beam and rib reinforcement calculated 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 dimensions of the building). 3. Estimate the materials cost per floor area assuming that the concrete costs $100 per yd 3 and reinforcement costs $0.25 per lb. 9

10 ASSIGNMENT #C1 Develop a spreadsheet to find the interaction diagram for a generic short column and design the flexural reinforcement for column B3. Required: 1. Develop a spreadsheet that calculates the interaction diagram for a generic four-layed reinforced concrete short column. Display the variables (see below) and the final interaction diagram at the top of the spreadsheet for ease of use and visibility by the user. 2. For column B3, determine if short column behavior or slender column behavior must be considered (kl/r < 22). 3. For assignment A1, show factored loads for column B3 at each story level of the building. 4. Determine the size and reinforcement for column B3 at all story levels and verify its strength on axial load-bending moment interaction diagrams using the spreadsheet from part 1 above and PCACOL (assume bending in only one direction). 5. Show a view of the column from the foundation to the roof and detail the reinforcement including ties and lap splices. Show typical cross-sections wherever there is a change in reinforcement or column size. d 3 d 2 d 1 A s,1 f c = d 4 A s,2 h fy = A s,3 A s,4 b 10

11 ASSIGNMENT #D1 Design the slab of the roof supported by columns (assume 30" x 30") without beams (flat plate construction). There is no need to increase the load for the panel which covers the elevator shaft due to the elevator's own weight. Limit your design to the frames along column lines 2. Neglect wind loads in this analysis. Required: 1. Divide the slab into frames suitable for design using the direct design method (column line 2 for this assignment). 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 from the direct design method. 4. Divide the frames into column and middle strips and distribute the longitudinal moments to these strips. 5. Determine the reinforcement for each strip. 6. Show the floor plan and display the reinforcement for each strip. Show the lengths and bends of the bars based on ACI requirements. 11

12 ASSIGNMENT #E1 Design and detail a spread footing for column C1 of the office building. Assume that the unfactored demands (dead + live loads) on this footing from the column are given as: P = 250 kips; M 1-1 axis = 75 kip-ft; and M C-C axis = 0 kip-ft. The factored demands (1.2D + 1.6L) on this footing from the column are given as: P = 400 kips; M 1-1 axis = 120 kip-ft; and M C-C axis = 0 kipft. Use fc = 3 ksi and fy = 60 ksi. Required: 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 buildings or property lines to limit the size or geometry of the footing. Neglect any overburden soil that may exist on the footing 2. Determine actual thickness of footing to satisfy one-way and two-way shear requirements according to ACI 318 such that transverse shear reinforcement would not be required in the footing. 3. Determine flexural steel reinforcement for both directions 1-1 and C-C according to the factored demands. Note that the steel in each direction will not be the same. Also detail the reinforcement for proper embedment length. 4. Assuming 8 #8 bars will be used as dowel reinforcement, detail for proper embedment length. 5. Show plan and elevation views of the footing as well as required reinforcement. 12