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CVEN 444 Structural Concrete Design Structural System Overview

CVEN 444 Structural Concrete Design Structural System Overview. Dr. E. Sandt Fall 2002 Semester. Presentation Overview. Building system primary functions Types of load RC structural systems RC structural members. 1. Basic Building System Functions.

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CVEN 444 Structural Concrete Design Structural System Overview

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  1. CVEN 444 Structural Concrete DesignStructural System Overview Dr. E. Sandt Fall 2002 Semester

  2. Presentation Overview • Building system primary functions • Types of load • RC structural systems • RC structural members CVEN 444 Structural Concrete Design

  3. 1. Basic Building System Functions Support gravity loads for strength and serviceability during: • Normal use (service) conditions • Maximum considered use conditions • Environmental loading of varying intensities CVEN 444 Structural Concrete Design

  4. Vertical deflection (sag) Lateral deflection (sway) Wind or earthquakes Dead, Live, etc. Performance-Based Design: Control displacements within acceptable limits during service loading, factored loaded, and varying intensities of environmental loading CVEN 444 Structural Concrete Design

  5. Gravity: Dead Live Impact Snow Rain/floods Lateral Wind Earthquake Soil lateral pressure Thermal Centrifugal 2. Types of Load CVEN 444 Structural Concrete Design

  6. 3. RC Structural Systems • Floor Systems • Lateral Load Systems CVEN 444 Structural Concrete Design

  7. A. Floor Systems • Flat plate • Flat slab (w/ drop panels and/or capitals) • One-way joist system • Two-way waffle system CVEN 444 Structural Concrete Design

  8. Flat Plate Floor System Slab-column frame system in two-way bending Elevation Plan CVEN 444 Structural Concrete Design

  9. Flat Plate Floor System Advantages: • Simple construction • Flat ceilings (reduced finishing costs) • Low story heights due to shallow floors Typical Applications: • Short-to-medium spans with light loading • For LL=50 psi, 15’ - 30’ spans • For LL=100 psi, 15’ – 25’ spans CVEN 444 Structural Concrete Design

  10. Flat Plate w/Spandrel Beam System Elevation Plan CVEN 444 Structural Concrete Design

  11. Flat Plate w/Spandrel Beam System Advantages: • Same as flat plate system, plus • Increased gravity and lateral load resistance • Increased torsional resistance • Decreased slab edge displacements Typical Applications: • Same as flat plate systems CVEN 444 Structural Concrete Design

  12. Flat Plate w/Beams Floor System Two-way bending Gravity and lateral load frames CVEN 444 Structural Concrete Design

  13. Flat Plate w/Beams Floor System Advantages: • Increased gravity and lateral load resistance • Simple construction • Flat ceilings (reduced finishing costs) Typical Applications: • Medium spans with light loading • For LL=50 psi, 25’ - 30’ spans • For LL=100 psi, 20’ – 30’ spans CVEN 444 Structural Concrete Design

  14. Flat Slab Floor System Flat plate with drop panels,shear capitals, and/or column capitals Elevation Plan CVEN 444 Structural Concrete Design

  15. Flat Slab Floor System Advantages: • Reduced slab displacements • Increased slab shear resistance • Relatively flat ceilings (reduced finishing costs) • Low story heights due to shallow floors Typical Applications: • Medium spans with moderate to heavy loading • For LL=50 psi, 30’ – 35’ spans • For LL=100 psi, 25’ – 35’ spans CVEN 444 Structural Concrete Design

  16. One-Way Joist Floor System Rib (joist) slab : (One-way bending) 2D gravity or lateral frames 2D lateral frames Floor joists, type CVEN 444 Structural Concrete Design

  17. One-Way Joist Floor System Rib (joist) slab with beams: (One-way bending) Lateral space frame Floor joists, type CVEN 444 Structural Concrete Design

  18. One-Way Joist Floor System Typical Joist Top of Slab 8-24” for 30” Modules 16-24” for 53” Modules 14-24” for 66” Modules . 1:12 Slope, type Width varies 4”, 6” or larger • 2’ or 3’ cc. – Joists • 4’ or 6’ cc. – Skip joists • 5’ or 6’ cc – Wide-module joists CVEN 444 Structural Concrete Design

  19. One-Way Joist Floor System Advantages: • Longer spans with heavy loads • Reduced dead load due to voids • Electrical, mechanical etc. can be placed between voids • Good vibration resistance Typical Applications: • Medium-to-long spans with heavy loading • For 30” modules, 35’ – 40’ spans • For 53” & 66” modules, 35’ – 50’ spans CVEN 444 Structural Concrete Design

  20. Two-Way Joist Floor System Waffle slab : (Two-way bending) 2D lateral frames Waffle pans, type CVEN 444 Structural Concrete Design

  21. Two-Way Joist Floor System Advantages: • Longer spans with heavy loads • Reduced dead load due to voids • Electrical, mechanical etc. can be placed in voids • Good vibration resistance • Attractive Ceiling Typical Applications: • Long spans with heavy loading • For 3’, 4’, and 5’ modules, 40’ – 50’ spans and beyond CVEN 444 Structural Concrete Design

  22. Floor System Effective Cost(PCA 2000) 100 Flat Plate Flat Slab One-way joist Live Load, psf 50 25 30 35 50 Bay Spacing, ft CVEN 444 Structural Concrete Design

  23. B. Lateral Load Systems • Frame Overview • Flat plate (& slab)-column (w/ and w/o drop panels and/or capitals) frame systems • Beam-column frame systems • Shear wall systems (building frame and bearing wall) • Dual systems (frames and shear walls) CVEN 444 Structural Concrete Design

  24. Frame: Coplanar system of beam (or slab) and column elements dominated by flexural deformation Planar (2D) Space (3D) CVEN 444 Structural Concrete Design

  25. Basic Behavior Gravity Load Lateral Loading CVEN 444 Structural Concrete Design

  26. 2D vs. 3D Frames (Plan) 2 or 4 frames , 2 frames 4 frames , 4 frames Floor joists, type Planar Space CVEN 444 Structural Concrete Design

  27. Frame Advantages • Optimum use of floor space, ie. optimal for office buildings, retail, parking structures where open space is required. • Relatively simple and experienced construction process • Generally economical for low-to mid-rise construction (less than about 20 stories) • In Houston, most frames are made of reinforced concrete. CVEN 444 Structural Concrete Design

  28. Frame Disadvantages • Generally, frames are flexible structures and lateral deflections generally control the design process for buildings with greater than about 4 stories. Note that concrete frames are about 8 times stiffer than steel frames of the same strength. • Span lengths are limited when using normal reinforced concrete (generally less than about 40 ft, but up to about 50 ft). Span lengths can be increased by using pre-stressed concrete. CVEN 444 Structural Concrete Design

  29. Frame Lateral Load Systems Flat plate-column frame: Effective slab width Elevation Plan CVEN 444 Structural Concrete Design

  30. Frame Lateral Load Systems Beam-column frame: Elevation CVEN 444 Structural Concrete Design

  31. Frame Lateral Load Systems Diaphragm (shear) element: Carries lateral loading to the lateral load resisting system Lateral load frame, type. Plate element Deformed shape -Lateral load distributes to frames proportional to tributary area CVEN 444 Structural Concrete Design

  32. Frame Lateral Load Systems For relatively square plans, diaphragms are generally considered rigid Space frame with square plan Deformed shape has constant lateral displacement - No diaphragm flexibility, ie. lateral load distributes to frame proportional to frame stiffness CVEN 444 Structural Concrete Design

  33. Shear Wall Lateral Load Systems Shear deformations generally govern Shear wall Edge column Elevation Interior gravity frames CVEN 444 Structural Concrete Design

  34. Shear Wall Lateral Load Systems Elevator shaft configuration Gravity frames Shear walls Hole Coupling beams CVEN 444 Structural Concrete Design

  35. Dual Lateral Load Systems Wall-Frame Dual System: Lateral frames – 25% of lateral load, minimum Hole Shear walls CVEN 444 Structural Concrete Design

  36. 4. Structural Members • Beams • Columns • Slabs/plates/shells/folded plates • Walls/diaphragms CVEN 444 Structural Concrete Design

  37. Defn: Members subject to bending and shear L V M M V E,I,A Beam Elements d2,Q2 d1,Q1 • Elastic Properties: • kb = f ( EI/Ln) (bending) s = My/I (normal stress) • ks = GA/L (shear) v = VQ/Ib (shear stress) • db = f (load, support conditions, L, E, I) (bending) CVEN 444 Structural Concrete Design

  38. Defn: Members subject to bending, shear, and axial Column Elements L V d3 F F V E,I,A d2,Q2 d1,Q1 M M • Elastic Properties: • ka = EA/L (axial) sa = F/A (normal stress) • kb = f ( EI/Ln) (bending) sb = My/I (normal stress) • ks = GA/L (shear) v = VQ/Ib (shear stress) • db = f (load, support conditions, L, E, I, A) (normal) CVEN 444 Structural Concrete Design

  39. Defn: Members subject to bi-directional bending & shear Slab/Plate Elements z y Mx, My, and Vz Qx, Qy, and dz x CVEN 444 Structural Concrete Design

  40. Defn: Members subject to shear Wall/Diaphragm Elements y Vx and Vx dx and dy x CVEN 444 Structural Concrete Design

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