covenin 444 structural systems

CVEN 444 Structural Concrete Design

Structural System Overview

Dr. E. SandtSpring 2002 Semester

CVEN 444 Structural Concrete Design*Presentation OverviewBuilding system primary functionsTypes of loadRC structural systemsRC structural members


CVEN 444 Structural Concrete Design*1. Basic Building System FunctionsSupport gravity loads for strength and serviceability during:Normal use (service) conditionsMaximum considered use conditionsEnvironmental loading of varying intensities


CVEN 444 Structural Concrete Design*Lateral deflection (sway)Wind or earthquakesVertical deflection (sag)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*2. Types of LoadGravity:DeadLiveImpactSnowRain/floodsLateralWindEarthquakeSoil lateral pressureThermalCentrifugal


CVEN 444 Structural Concrete Design*3. RC Structural SystemsFloor SystemsLateral Load Systems


CVEN 444 Structural Concrete Design*A. Floor SystemsFlat plateFlat slab (w/ drop panels and/or capitals)One-way joist systemTwo-way waffle system


CVEN 444 Structural Concrete Design*Flat Plate Floor System Slab-column frame system in two-way bendingPlanElevation


CVEN 444 Structural Concrete Design*Flat Plate Floor SystemAdvantages:Simple constructionFlat ceilings (reduced finishing costs)Low story heights due to shallow floors

Typical Applications:Short-to-medium spans with light loadingFor LL=50 psi, 15 - 30 spansFor LL=100 psi, 15 25 spans


CVEN 444 Structural Concrete Design*Flat Plate w/Spandrel Beam SystemPlanElevation


CVEN 444 Structural Concrete Design*Flat Plate w/Spandrel Beam SystemAdvantages:Same as flat plate system, plus Increased gravity and lateral load resistanceIncreased torsional resistanceDecreased slab edge displacements

Typical Applications:Same as flat plate systems


CVEN 444 Structural Concrete Design*Flat Plate w/Beams Floor SystemGravity and lateral load framesTwo-way bending


CVEN 444 Structural Concrete Design*Flat Plate w/Beams Floor SystemAdvantages:Increased gravity and lateral load resistanceSimple constructionFlat ceilings (reduced finishing costs)

Typical Applications:Medium spans with light loadingFor LL=50 psi, 25 - 30 spansFor LL=100 psi, 20 30 spans


CVEN 444 Structural Concrete Design*Flat Slab Floor SystemFlat plate with drop panels,shear capitals, and/or column capitalsPlanElevation


CVEN 444 Structural Concrete Design*Flat Slab Floor SystemAdvantages:Reduced slab displacementsIncreased slab shear resistanceRelatively flat ceilings (reduced finishing costs)Low story heights due to shallow floors

Typical Applications:Medium spans with moderate to heavy loadingFor LL=50 psi, 30 35 spansFor LL=100 psi, 25 35 spans


CVEN 444 Structural Concrete Design*One-Way Joist Floor System2D lateral framesFloor joists, typeRib (joist) slab : (One-way bending)2D gravity or lateral frames


CVEN 444 Structural Concrete Design*One-Way Joist Floor SystemLateral space frameFloor joists, typeRib (joist) slab with beams: (One-way bending)


CVEN 444 Structural Concrete Design*One-Way Joist Floor System 2 or 3 cc. Joists 4 or 6 cc. Skip joists 5 or 6 cc Wide-module joistsTop of Slab1:12 Slope, type8-24 for 30 Modules16-24 for 53 Modules14-24 for 66 Modules .Width varies4, 6 or largerTypical Joist


CVEN 444 Structural Concrete Design*One-Way Joist Floor SystemAdvantages:Longer spans with heavy loadsReduced dead load due to voidsElectrical, mechanical etc. can be placed between voidsGood vibration resistance

Typical Applications:Medium-to-long spans with heavy loadingFor 30 modules, 35 40 spansFor 53 & 66 modules, 35 50 spans


CVEN 444 Structural Concrete Design*Two-Way Joist Floor System2D lateral framesWaffle pans, typeWaffle slab : (Two-way bending)


CVEN 444 Structural Concrete Design*Two-Way Joist Floor SystemAdvantages:Longer spans with heavy loadsReduced dead load due to voidsElectrical, mechanical etc. can be placed in voidsGood vibration resistanceAttractive Ceiling

Typical Applications:Long spans with heavy loadingFor 3, 4, and 5 modules, 40 50 spans and beyond


CVEN 444 Structural Concrete Design*Floor System Effective Cost(PCA 2000)Bay Spacing, ftLive Load, psf1005025303550One-way joistFlat SlabFlat Plate


CVEN 444 Structural Concrete Design*B. Lateral Load SystemsFrame OverviewFlat plate (& slab)-column (w/ and w/o drop panels and/or capitals) frame systemsBeam-column frame systemsShear wall systems (building frame and bearing wall)Dual systems (frames and shear walls)


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


CVEN 444 Structural Concrete Design*Basic BehaviorGravity LoadLateral Loading


CVEN 444 Structural Concrete Design*2D vs. 3D Frames (Plan)PlanarSpaceFloor joists, type2 or 4 frames , 2 frames4 frames , 4 frames


CVEN 444 Structural Concrete Design*Frame AdvantagesOptimum use of floor space, ie. optimal for office buildings, retail, parking structures where open space is required.Relatively simple and experienced construction processGenerally 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*Frame DisadvantagesGenerally, 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*Frame Lateral Load SystemsFlat plate-column frame:PlanElevationEffective slab width


CVEN 444 Structural Concrete Design*Frame Lateral Load SystemsBeam-column frame:Elevation


CVEN 444 Structural Concrete Design*Frame Lateral Load SystemsDiaphragm (shear) element: Carries lateral loading to the lateral load resisting systemLateral load frame, type.Plate elementDeformed shape -Lateral load distributes to frames proportional to tributary area


CVEN 444 Structural Concrete Design*Frame Lateral Load SystemsFor relatively square plans, diaphragms are generally considered rigidSpace frame with square planDeformed shape has constant lateral displacement - No diaphragm flexibility, ie. lateral load distributes to frame proportional to frame stiffness


CVEN 444 Structural Concrete Design*Shear Wall Lateral Load SystemsShear wallElevationEdge columnInterior gravity framesShear deformations generally govern


CVEN 444 Structural Concrete Design*Shear Wall Lateral Load SystemsGravity framesShear wallsCoupling beamsElevator shaft configurationHole


CVEN 444 Structural Concrete Design*Dual Lateral Load SystemsLateral frames 25% of lateral load, minimumShear wallsWall-Frame Dual System:Hole


CVEN 444 Structural Concrete Design*4. Structural MembersBeamsColumnsSlabs/plates/shells/folded platesWalls/diaphragms


CVEN 444 Structural Concrete Design*Beam ElementsDefn: Members subject to bending and shear

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)d2,Q2d1,Q1


CVEN 444 Structural Concrete Design*Column ElementsDefn: Members subject to bending, shear, and axial

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)VVLE,I,AMMFFd2,Q2d1,Q1d3


CVEN 444 Structural Concrete Design*Slab/Plate ElementsDefn: Members subject to bi-directional bending & shear

xyzMx, My, and VzQx, Qy, and dz


CVEN 444 Structural Concrete Design*Wall/Diaphragm ElementsDefn: Members subject to shear

xyVx and Vxdx and dy


*****

covenin 444 structural systems

Documents

structural concrete

flat plate systemscven

performancebased design

spansfor ll

light loadingfor ll

heavy loadingfor ll

medium spans

lateral deflection swaywind