Unit 1 lesson 01 (introduction to reinforced concrete design)
- 3. COVER the amount of concrete required to protect steel reinforcement from fire and corrosion, measured from the surface of the reinforcement to outer surface of the concrete section
- 4. 75 mm for concrete cast and permanently exposed to earth such as footings 40-50 mm for concrete members exposed to weather 40 mm concrete cover of pipes, conduits or fittings and exposed to weather 40 mm for beams and columns 20 mm for concrete not exposed to weather or in contact with ground, such as slabs, walls and joists
- 5. EFFECTIVE LENGTH the depth of concrete section measured from the compression face to the centroid of the tension reinforcement BOND STRESS the adhesive force per unit area of contact between reinforcing bar and the surrounding concrete developed at any section of a flexural member.
- 6. HOOK a bend or curve given to develop an equivalent embedment length, used where there is insufficient room to develop in adequate embedment length STANDARD HOOK a 90º, 135º, 180º bend made at the end of a reinforcing bar according to standards ANCHORAGE any of various means, as embedment length or hooked bars, for developing tension or compression in a reinforcing bar on each side of critical section in order to prevent bond failure or splitting
- 8. OVERREINFORCED SECTION a concrete section in which the concrete in compression reaches its assumed ultimate strain before the tension reinforcement reaches its specified yield strength. This is a dangerous condition since failure of the section could occur instantaneously without warning UNDERREINFORCED SECTION a concrete section in which the tension reinforcement reaches its specified yield strength before the concrete in compression reaches its assumed ultimate strain. This is desirable condition since failure of the section would be preceded by large deformations giving prior warning of impending collapse
- 11. EMBEDMENT LENGTH length of embedded reinforcement provided beyond a critical section JACKING FORCE in pre-stressed concrete, temporary force exerted into pre-stressing tendons
- 12. KINDS OF LOADS CONCENTRATED LOADS - is a force applied at a single point on a beam or structure.
- 13. UNIFORM LOADS - a series of uniform concentrated loads, but for 5 or more uniformly spaced concentrated loads.
- 14. TYPES OF SUPPORT
- 15. TYPES OF BEAMS SIMPLY SUPPORTED BEAM SIMPLY SUPPORTED W/ OVER HANG
- 16. CANTILEVER BEAM - is a beam anchored at only one end. The beam carries the load to the support where it is forced against by a moment and shear stress.
- 17. CONTINOUS BEAM - are those that rest over three or more supports, thereby having one or more redundant support reactions.
- 18. TYPES OF INTERNAL FORCES COMPRESSION - pushes towards joint. TENSION - pulls away from joint. SHEAR - arises from the force vector component parallel to the cross section
- 19. STRESS- STRAIN DIAGRAM - graphic representation of the relationship between unit stress values and the corresponding unit strains for a specific material.
- 20. PROPORTIONAL LIMIT - maximum stress which the material springs back to the original length when the load is released.
- 21. ELASTIC LIMIT - maximum stress below which the material does not return to its original length but has incurred a permanent deformation we call permanent set.
- 22. YIELD POINT - the stress wherein the deformation increases without any increase in the load. The material at some portion shows a decrease in its cross section.
- 23. ULTIMATE STRENGTH - the maximum stress that can be attained immediately before actual failure or rupture.
- 24. RUPTURE STRENGTH - stress at which material specimen breaks.
- 25. Dead load, DL……………………………………….. 1.40 Live load, LL…………………….…………….……… 1.70 Wind load, WL………...………………………….….. 1.70 Earthquake, E………………………………….…..…. 1.87 Earth or water pressure, H………………………..… 1.70 LOAD FACTORS
- 26. Flexure w/o axial load…………………………………………….….. 0.90 Axial tension & axial tension w/ flexure…………….………….…. 0.90 Shear and torsion ……………………………………………………. 0.85 Axial compression & axial compression w/ flexure a. Spiral Reinforcement ………….……………………… 0.75 b. Tie Reinforcement ………………………….…………. 0.70 Bearing on concrete ………………………………………..……….. 0.70 STRENGTH REDUCTION FACTOR Ø
- 27. Required strength U to resist dead load DL and live load LL is U= 1.4DL + 1.7LL Wind load W are included in design U= 0.75 (1.4DL + 1.7LL + 1.7W) Earthquake loads or forces are included in design U= 0.75 (1.4DL + 1.7LL + 1.87E) Where structural effect T of differential settlement, creep, shrinkage or temperature change are significant in design U= 0.75 (1.4DL + 1.4T + 1.7LL) but required strength U shall not be less than U= 1.4 (DL + T) REQUIRED STRENGTH, U or Pu
- 28. LIVE LOADS
- 29. WIND LOAD
- 32. 180º bend plus 4db extension but not less than 65 mm at free end 90º bend plus 12db extension, at free end of bar for stirrups and tie hooks: 16 mm bar and smaller, 90º bend plus 6db extension at free end of bar or 20 mm and 25 mm bar, 90º bend plus 6db extension at free end of bar or 25 mm bar and smaller, 135º bend plus 6db extension at free end of bar STANDARD HOOKS
- 33. MINIMUM DIAMETERS OF BEND The diameter of bend measured on the inside of the bar shall not be less than the following: 6db for 10 mm to 25 mm bar 8db for 28 mm to 36 mm bar 10db for 42 mm to 58 mm bar 4db minimum inside diameter of bend of stirrups and ties for 16 mm bar and smaller in diameter
- 34. FOR BUNDLED BARS • Groups of parallel reinforcing bars bundled in contact as a unit shall be limited to 4 in any one bundle • Bundled bars shall be enclosed within stirrups or ties • Bars larger than 32mm shall not be bundled in beams • Individual bars within a bundle terminated within the span of flexural members should terminate at a different points at least 40db stagger
- 35. FOR BUNDLED BARS The minimum concrete cover for bundled bars shall be: Equal to the equivalent diameter of the bundle but not exceeding 50 mm 75 mm - for concrete cast against and permanently exposed to earth
- 36. STEEL BARS TABLE
- 37. BEAM SPAN the extent of space between two supports of a structure CLEAR SPAN the distance between inner faces of the support of a span EFFECTIVE SPAN the center to center distance between the supports of a span
- 38. BEAM
- 39. Coarse Aggregate
- 40. Aggregates Fine aggregates- sand are those that passes through a No.4 sieve (about 6mm in size) Coarse aggregate - gravel or crushed stone
- 41. Mixing
- 43. COLUMN COLUMN - a relatively slender structural member designed primarily to support axial, compressive loads, applied at the member ends. POST - a stiff vertical support especially a wooden column in timber framing
- 44. COLUMN BUCKLING the sudden lateral or torsional instability of a slender structural member induced by the action of a compressive load. Buckling can occur well before the yield stress of the material is reached. BUCKLING the axial load at which a column begins to deflect laterally and becomes unsuitable.
- 45. COLUMN LONG COLUMN a slender column subject to failure by buckling rather than by crushing SHORT COLUMN a thick column subject to failure by crushing rather than by buckling. Failure occurs when the direct stress from an axial load exceeds the compressive strength of the material available in the cross section. An eccentric load, however, can produce bending and result in uneven stress distribution in the section INTERMEDIATE COLUMN a column having a mode of failure between that a short column and a long column, often party inelastic by crushing and partly elastic by buckling
- 46. FOUNDATION DESIGN Footings are structural members used to support columns and walls and to transmit and distribute their loads to the soil in such a way that the load bearing capacity of the soil is not exceeded, excessive settlement, differential settlement, or rotation are prevented and adequate safety against overturning or sliding is maintained.
- 47. TYPES OF FOOTINGS Wall footings are used to support structural walls that carry loads for other floors or to support nonstructural walls.
- 48. TYPES OF FOOTINGS Isolated or single footings are used to support single columns. This is one of the most economical types of footings and is used when columns are spaced at relatively long distances.
- 49. TYPES OF FOOTINGS Combined footings usually support two columns, or three columns not in a row. Combined footings are used when two columns are so close that single footings cannot be used or when one column is located at or near a property line.
- 50. TYPES OF FOOTINGS Cantilever or strap footings consist of two single footings connected with a beam or a strap and support two single columns. This type replaces a combined footing and is more economical.
- 51. TYPES OF FOOTINGS Continuous footings support a row of three or more columns. They have limited width and continue under all columns.
- 52. TYPES OF FOOTINGS Rafted or mat foundation consists of one footing usually placed under the entire building area. They are used, when soil bearing capacity is low, column loads are heavy single footings cannot be used, piles are not used and differential settlement must be reduced.
- 53. TYPES OF FOOTINGS Pile caps are thick slabs used to tie a group of piles together to support and transmit column loads to the piles.
- 54. Minimum Requirements for Foundations
- 55. ONE-WAY SLAB A one-way slab is considered as wide shallow rectangular beam. The reinforcing steel is usually spaced uniformly over its width. The flexural reinforcement of a one-way slab extends in one direction only. Maximum flexural reinforcement spacing: 3 times the slab thickness or 450 mm
- 56. ONE-WAY SLAB Minimum thickness of one-way slab: Solid one-way slab L/20 - simply supported L/24 - one end continuous L/28 - both end continuous L/10 - cantilever * Span length L is in millimeter
- 57. SIZE AND SPACING OF MAIN BARS & TIES Clear distance between longitudinal bars shall be not less than 1.5 db nor 40 mm Use 10 mm diameter ties for 32 mm bars or smaller and at least 12 mm in size for 36 mm and bundled longitudinal bars Vertical spacing of ties shall be the smallest of the following: 16 x db (db = longitudinal bar diameter) 48 x tie diameter least dimension of columns
- 58. MINIMUM REQUIREMENT FOR DEVELOPMENT OF REINFORCEMNT not less than 12 db not less than 1/16 clear span not less than d whichever is greater
- 59. THE END