CONST METH & MAT I
CONST METH & MAT I CM 313
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This 119 page Class Notes was uploaded by Ibrahim Crona on Wednesday September 9, 2015. The Class Notes belongs to CM 313 at University of Washington taught by Staff in Fall. Since its upload, it has received 21 views. For similar materials see /class/192190/cm-313-university-of-washington in Construction Management at University of Washington.
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Date Created: 09/09/15
quot39uggm Jim Parkins PE Sales Manager Pier and Parking Structurs What is Precast Concrete a Concrete NOT cast in its final position in a structure a Can be cast off to the sie of the structure Most commonly refers to plant casting v Shipped by truck barge or rail Requires crane atjobsite for erection 1amp1 p a 239 What is Prestressed Concrete r Concrete with embedded steel strands a Strands are used to induce stresses opposite to what the product will see in its final position in the structure a Almost always made at a specialized plant CTC Quick History i J Founded by Alt amp Tom Anderson in 1951 Industry pioneers The first prestressed plant in the United States Our components can be found in thousands of projects in the Pacific Northwest Alaska and Hawaii including bridges buildings tanks piers and floats T V A 1 1 u 1 1 u xkta 9 milEN y Concrete Raw Materials EA Composed of cement aggregate water r Liquid admixtures and other solid compounds can be used for higher performance concrete Concrete strength 2 Compression strength measured in pounds per square inch Convention is to measure strength at 28 da s a Driven by amount of Cement quality of aggregate and water to cement ratio a Break standard cylinders Reinforced Concrete Concrete almost always has steel reinforcement Concrete is great in comression weak in tension gt Over ten times stronger in compression as a comparison for steel the strength is the same for both load conditions Steel is excellent in tension Combining these materials provides efficient eCOnomical structural members 141 g 9 3 JJMttl f 39 VWWWWW i H NHWW QWffWquot iif s 1 v is f WW 4 v If i771 m iv quot v Reinforced Concrete z Concrete is a brittle material sudden failure a Steel is ductile warning before failure Steel reinforcement allows us to design concrete with ductile behavior Where are compression and tension forces at a Deflecled shape Cracks a Moment diagram a Dallected shape b Moment dlaglam c Relnfarcemenl location Beam Load Test Region shown In Flg 4 3 Heinforcemen 1 Slralns Sttesses p a Stage A Before cracklng f 1 Compfsslve 7 44Lr LJPLLFLILILXEL J7 Tenslls 39 l p S rams 5085588 F b Stage cAnev cracking beiore yleld service load P p l Crushed concieta l shearcracks Emmpmmm E l P Slrains Suesses 1c Stags E Fallure Figure 475 Cracks strains and stresses in test beam Beam Load Test Crushmg 39 39 Cracks Ht 476 39l beam after failure Phoxogruph courtesy ul39JG Mchregor Reinforced Concrete EA Cracking is inherent a Rebar does not pick up tension loads until concrete begins cracking a Rebar contols crack widlh a Not a sh39uctural concern m Slight sagging under loads is inherent e Consh39uction codes specify maximum allowed sag Prestressed Concrete Prestressing induces stresses opposite in direction to the stresses imposed on the element in the finished structure Cracks gtlt Prestress Concept We effectively eliminate tension or keep it under the limit for cracking Apply compression force below centroid of crosssection Creates upward deflection called cambel Camber range 12 to 4 depends on prestress force and product length Iqmlwmn i uuuuuuu Prestressing Strand Prestress Process Stretch strand POLII Concrete and cure Release stra nd Prestressing Strand 4 times stronger than rebar 12 amp 06 diameter common 06 strand can hold 59000 lbs before breaking Strand continuously bonded to concrete When tension is released concrete around strand compresses Prestress Production Issues a Prestress induces large internal stresses in the member so high strength concrete is requ39red e Nonpreslj essed concrete 4000 psi zadays we are s00010000 psi To release strand at the plant we often required 6000 8000 psi OVERNIGHT to handle internal stresses a Type III Cement highear e Low water to cement ratio a Admixtures e Wellprotected environment e Controlled curing with application of external heat We attain these high strengths through ly Plant Production Cycle EA Almost all products are built cured and stripped on a daily basis car This requires crews working almost 24 hours a day a Typical day begins at 400 AM The setup crew Removes product from yesterday s cast and cleans forms Pulls the strands to the right amount of tension 3 Kit a megs S d n a r t S d n U 0 r a Tie rebar n O S e M S m r 0 F e C b P Pour Concrete Cure Overnight Removes product from yesterday s cast and cleans forms PostTension wag 39 39 KW 39 I A Wyypfb I i L WIN 1 39w a Select Projects Mass Transit Buildings 1 ng mi LL t V quotbiIx Via F r ar 39l39h 7V 839 7 11 139 71zquot 139 l114quot on 4 Vxquot H ARPED STRANDS 39Lcc 4 14quot HARPED STRANDS SECTION MIDSPAN Bridges gm C 35 illa wx nu ll Eagle vw h 2 A Elnmfal a 4 g 5 CT C s most popular section Single pieces can span up to 180 feet x Castinplace deck poured over temporaryforming between girders Available depths are 4250587483 and 95 inches Deck Bulb Tee Similar to I Beam with deck integrated into member Large spans attainable over 160 ft to date Available depths are 354153 and 65 inches or custom depths available with custom form filler Trap Girder Piers 1amp1 p a 239 n quot 33 5 31 Mi Parking Garage BeamColumn Frame Prestrssed Inverted Tee Beam Floor ElementsDouble Tees Depths available are 12 to 36 in increments of Can be cast up to 10quot wide w Spams u to 80 feet with standaii live load Hybrid Garage Precast Columns amp Beams with PT Deck HV39 9 El N 39 1 gm E m Humans 1 igijillillv I Fl Beams and Girders Transfer Girder v n 51cm I D Standard Beam Interior Elevations may 9D n xg 3mg mlnxm why B sgnu mum 521mng a lift 1 2quot u m w munANA 3 1w ExteriorSpandrels mvmou an a HV39 9 El N 39 1 gm E m Humans 1 igijillillv I Fl HollowcoreDetention Vaults Floating Structure r39 39 7m J 39 w r m u u Q r i4 Port Orchard Intermodal Terminal PrecastPrestressed Concrete s Attributes Advantages over Steel Lower Maintenance 6 An attractive finish can be attained without topical coating a Oxidation not a concern ascast surface will not deteriorate More Economical a a i Lulllywcd u Fire Resistance a Concrete does not require topical coatings for fire resistance Greater Flexibility in Aesthetic Design a A variety of shapes can be attained only limited by cost of forms Advantages over CastinPlace Concrete Increased Construction Speed omponenls can be fabricated concurrently with sitework and 39 Hecaster 39 on contractor AllWeather Construction Higher Quality Concrete Prestressing Increases Span Capability a More open floor plans for tenant flexibility Special Considerations V Transportation 2 Must factor in cosis for transportation and erection a Does affect member size and shape Camber a How does this affect interfacing with other materials c There are ways to alleviate camber Economy Through Repetition 2 Excessive form changes can be costly ConnectionsSimple L ax3xx039 6quot w 2 4 x 239 oquot TYPA CONNECTION 39W 111d N W v MW 39L39 W 39313
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