1. CONCRETE CONSTRUCTION “ Concrete is a plastic material susceptible to the impressions of the imagination.” Frank Lloyd Wright
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6. Meditation Center for UNESCO Paris, France 1995 Tadao Ando, Architect “ a space of prayer for world peace” “ A rchitecture, to me , is an endless search of one’s engagement with oneself and with society From the construction of an abstract concept to its realization.” TADAO ANDO AIA Gold Medal 2003
Course Aggregate approx. 3/4 of volume Structural strength heavily dependent on MUST BE: Strong, clean Resistant to freeze-thaw Chemically stable Properly Graded - Through SIEVES For proper “packing” of materials Largest must fit between Reinforcing Generally < 3/4 of clear distance or 1/3 of slab thickness Fine Aggregate Portland Cement Water Admixtures (optional)
Course Aggregate approx. 3/4 of volume Structural strength heavily dependent on MUST BE: Strong, clean Resistant to freeze-thaw Chemically stable Properly Graded - Through SIEVES For proper “packing” of materials Largest must fit between Reinforcing Generally < 3/4 of clear distance or 1/3 of slab thickness Fine Aggregate Portland Cement Water Admixtures (optional)
Specified by 28 Day Compressive Strength (psi) POUNDS PER SQUARE INCH CONCRETE IN THEORY CONTINUES TO HARDEN - TYPICALL 28 STRENGTH Primarily Determined By: STRENGTH PRIMARILY DETERMINED BY Amount of Cement PROPORTION/ AMOUNT OF CEMENT Water-Cement Ratio WEIGHT OF H2O / WEIGHT OF WATER NEED MORE WATER THAN WHAT IS NEEDED FOR HYDRATION - PLACEMENT AND FINISHING TOO MUCH WATER EXTRA WATER EVAPORATES LEAVES VOIDS - REDUCE STRENGTH CAN REDUCE WATER AND STILL GET WORKABILITY WITH ADMIXTURES (AIR, WATER REDUCING AGENTS) Proper Aggregate & Gradation FINE AND COARSE AGGREGATE Strength Ranges: 2000 - 19,000+ psi COMMON - 3000, 4000, 5000, 6000psi
No Useful Tensile Strength GREAT IN COMPRESSION - LITTLE IN TENSION MOST STRUCTURAL MEMBERS IN BOTH NEED A MATERIAL FOR TENSION Reinforcing Steel - Tensile Strength Similar Coefficient of thermal expansion EXPAND AND CONTRACT SAME AMOUNT IF NOT, BREAK BOND Chemical Compatibility WON’T REACT W/ EACH OTHER & PROTECTS STEEL FROM CORROSION Adhesion Of Concrete To Steel ADHERES WELL Theory of Steel Location “ Place reinforcing steel where the concrete is in tension” SIMPLE BEAM - IN BOTTOM MULTIPLE SPAN OVER SUPPORT @ TOP
Reinforcing Support Chairs or bolsters WIRE OR PLASTIC SOME WITH PROTECTIVE COATINGS ON FEET - SOME MADE OF SS Properly position the steel VARIOUS HEIGHTS POSITION REINFORCING OFF FORMWORK FOR DESIGN LOCATION AND MINIMUM CONCRETE POTECTION FOR FIRE RATINGS Special Coatings Galvanized or Epoxy Coated Exposure to Salts or Sea Water
Type of Reinforcing Grid of “wires” spaced 2-12 inches apart STEEL WIRE Specified by wire gauge and spacing Typical Use - Horizontal Surfaces ELEVATED SLABS SOG USED IN SOME WALLS Comes in Mats or Rolls MATS FOR LARGER GAUGE WIRE Advantage - Labor Savings BUT CAN’T HANDLE LARGE LOADINGS
Location of Tension Forces Changes Midspan - Bottom in Tension At Beam Supports - Top in Tension NOTE; SLAB REINFORCING PRINCIPALS SIMILAR LIKE A LARGE/WIDE BEAM EXCEPT OFTEN ADD TEMPERATURE STEEL
Reinforced Concrete Members AT ANY LOCATION IN THE MEMBER Part of the member in compression Part of the member in tension Over half of the concrete Not carrying any load, it’s: “ Holding” reinforcing in position & Providing protective cover NOT GETTING THE FULL / EFFECTIVE USE OF THE MEMBER
Theory; “Place all the concrete of the member in compression” (take advantage of concrete’s compressive strength of the entire member) Advantages Increase the load carrying capacity or Reduce the member’s size
Stressing high strength steel stands either before or after concrete placement HIGH LOADS - 30,000 POUNDS/ STRAND Pretensioning Prior to concrete placement Generally performed at a “plant” HIGH LOADS - 30,000 POUNDS/ STRAND NEED SOMETHING TO JACK AGAINST Posttensioning After concrete placement (& curing) Generally performed at the jobsite JACK AGAINST THE POURED/CURED CONCRETE
“ Level surface of concrete supported on the ground” Loading; Carries little or no structural stress except: Transmission of superimposed loads LIVE LOADS - TRAFIC, EQUIPMENT, STORAGE Thickness & Reinforcing determined by: Continuity & Capacity of the soil STRENGHT / BEARING CAPACITY CONTINUITY OF SOIL CAPACITY Loads imposed
Materials Custom Built of Lumber & Plywood 2x & PLYWOOD BUILT FOR LOCATION/USE/PROJECT “ STICK” BUILT” Prefabricated steel, fiberglass PARTICULAR PROJECT/USE HIGH REUSE - SHEARWALLS Standardized prefabricated panels ASSEMBLE FOR USE / STANDARD SIZES COMBINATION GANG FROMS MAY INCORPORATE SEVERAL Choice Depends on : Number of uses, Irregularity of wall HIGH USE - STEEL/FIBERGLAS/MDO Wall finish & tie spacing, HIGH FINISH EXPOSED VS STRUCTURAL Availability & Cost
Layout, Install one side, anchor, & brace ANCHOR AND PLUMB Coat w/ Form Release EASE OF STRIPPING Install Reinforcing (or after form ties)
Install Form Ties “ Small diameter metal rods which hold the forms together (remain in the wall) MANY DIFFERENT TYPES HYDROSTATIC LOAD
One-Way Slab System “ Spans across parallel lines of support furnished by walls and/or beams” Limited Span Length One-Way Joist System Span Greater Distances, “Less Dead Load” DEAD LOAD OF SLAB / “TENSILE” CONCRETE Spaced ribs or joists w/ a thin top slab 3-5” SLAB Utilizes “pans” (metal, plastic, fiberglass) HIGH NUMBER OF REUSES Wide-Module or “Skip-Joist” System
Bay Spacing - Square or Irregular SQUARE - TWO WAY Span Length GREATER - JOIST VS FLAT SLAB Loading HIGHER LOADS - DEEPER SECTION Ceiling Treatment EXPOSED - FLAT SLAB Lateral Stability HIGH STABILITY - DEEPER SECTION
Prior to Formwork Construction Prepare, submit, & approve Engineered Shop Drawings MAY TAKE WEEKS FORMWORK DESIGN FORMWORK SUPPORT RESHORE AMOUNT & PLACEMENT ALL HAVE SOME IMPACT ON REQUIRED AMOUNT OF FORMWORK ALSO AFFECTED BY CONCRETE DESIGN & SCHEDULE FRPS supporting walls/columns
Set Beam Bottoms (if required) Erect Beam Sides Form Slab OPTIONS SCAFFOLD - SINGLE / GANGED TABLES LARGE COST - MINIMZE LABOR Install MPE sleeves, block outs, “Cast in” electrical roughin PENETRATIONS THROUGH SLAB OTHER OPTION - CORE Clean “Deck” & apply form release
Place Reinforcing Generally START FROM THE BOTTOM UP Beam reinforcing Slab bottom & then top reinforcing
Strip Formwork Re-shore May Extend 3-4 Floors Below Re-shore Purpose Support Construction Load Support the Weight of the next Floor
Can be used with any framing system Reduce member size and/or Extend span capacity
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