Lecture 2  Structural System Overview

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Lecture 2 Structural System Overview

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1. Lecture 2 Structural System Overview CVEN 444 -Structural Concrete Design January 15, 2003

2. CVEN 444 Structural Concrete Design 2 Presentation Overview RC structural systems RC structural members Advantages and disadvantages of concrete structures

3. CVEN 444 Structural Concrete Design 3 One-Way Joist Floor System

4. CVEN 444 Structural Concrete Design 4 One-Way Joist Floor System

5. CVEN 444 Structural Concrete Design 5 One-Way Joist Floor System

6. CVEN 444 Structural Concrete Design 6 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

7. CVEN 444 Structural Concrete Design 7 Two-Way Joist Floor System

8. CVEN 444 Structural Concrete Design 8 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

9. CVEN 444 Structural Concrete Design 9 Floor System Effective Cost (PCA 2000)

10. CVEN 444 Structural Concrete Design 10 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)

11. CVEN 444 Structural Concrete Design 11 Frame: Coplanar system of beam (or slab) and column elements dominated by flexural deformation

12. CVEN 444 Structural Concrete Design 12 Basic Behavior

13. CVEN 444 Structural Concrete Design 13 2D vs. 3D Frames (Plan)

14. CVEN 444 Structural Concrete Design 14 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.

15. CVEN 444 Structural Concrete Design 15 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.

16. CVEN 444 Structural Concrete Design 16 Frame Lateral Load Systems

17. CVEN 444 Structural Concrete Design 17 Frame Lateral Load Systems

18. CVEN 444 Structural Concrete Design 18 Frame Lateral Load Systems

19. CVEN 444 Structural Concrete Design 19 Frame Lateral Load Systems

20. CVEN 444 Structural Concrete Design 20 Shear Wall Lateral Load Systems

21. CVEN 444 Structural Concrete Design 21 Shear Wall Lateral Load Systems

22. CVEN 444 Structural Concrete Design 22 Dual Lateral Load Systems

23. CVEN 444 Structural Concrete Design 23 4. Structural Members Beams Columns Slabs/plates/shells/folded plates Walls/diaphragms

24. CVEN 444 Structural Concrete Design 24 Beam Elements Defn: Members subject to bending and shear

25. CVEN 444 Structural Concrete Design 25 Column Elements Defn: Members subject to bending, shear, and axial

26. CVEN 444 Structural Concrete Design 26 Slab/Plate Elements Defn: Members subject to bi-directional bending & shear

27. CVEN 444 Structural Concrete Design 27 Wall/Diaphragm Elements Defn: Members subject to shear

28. CVEN 444 Structural Concrete Design 28 Advantages of Concrete Structures Economical Thinner floor systems Reduced Building Height Lower wind loads (< A) Saving in Cladding Materials widely available

29. CVEN 444 Structural Concrete Design 29 Advantages of Concrete Structures Suitability of material for architectural and structural function Concrete place in plastic condition - desired shape & texture can be obtained with forms and finishing techniques Designer can choose shape and size

30. CVEN 444 Structural Concrete Design 30 Advantages of Concrete Structures Fire Resistance Concrete building have 1-3 hour fire rating with no fire proofing (steel and timber require fireproofing to obtain this rating) Rigidity Greater stiffness & mass reduces oscillations (wind), floor vibrations (walking)

31. CVEN 444 Structural Concrete Design 31 Advantages of Concrete Structures Low Maintenance Availability of Materials Sand, gravel, cement, H20 & concrete mixing facilities widely available Reinforcement - easy to transport as compared to structural steel

32. CVEN 444 Structural Concrete Design 32 Disadvantages of Concrete Structures Low tensile strength - ~ 0.1 fc cracking if not properly reinforced

33. CVEN 444 Structural Concrete Design 33 Disadvantages of Concrete Structures Forms and Shoring (additional steps) Construction of forms Removal of forms Prepping (or shoring) the new concrete to support weight until strength is adequate. Labor/Materials cost not required for other types of materials

34. CVEN 444 Structural Concrete Design 34 Disadvantages of Concrete Structures Strength per unit volume is relatively low. fc ~ (5-10% of steel) greater volume required long spans typical built with steel

35. CVEN 444 Structural Concrete Design 35 Disadvantages of Concrete Structures Time-dependent volume changes Concrete & steel undergo similar expansion and contraction. Concrete undergoes drying shrinkage, which may cause deflections and cracking. Creep of concrete under sustained loads causes an increase in deflection with time.

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