ch03 - CHAPTER 3 Ski The acivantagos Oi “strength design...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: CHAPTER 3 Ski The acivantagos Oi “strength design as comparcd to WED inciiide the following: {a} Better estimates of the least—carrying abilities of structures. ‘ l {b} it more consistent theory for the different types of members as say beams , anti cciumns {c} The use of more rsaiistic load factors for the different types of loads. {d} More uhiform safety factors throughout structures. {a} Better advantage taken of high strength reinforcing. {i} More flexible designs with varying percentages of reinforcing. 3.2 Strength reduction factors are used to account for the uncertainties in material strengths, variations in structural anaiysis. imperfect field dimensions and other workmanship items. The factors specified for columns are lower than they are far beams for the following reasons: V (a) if a column fails in a building a larger part of the huiiding wili probably faii than it a beam fails. “ (b) it is more difficult to piacc concrete compactly in columns than in beams. (c) The failure strengths of reinforced concrete columns are primarily based on the: concrete‘s ultimate strength - a property which is quite variable. On the other hand the faiiure strengths of concrete beams are primarily derived from the steers yield strength ~ 3 property which is accurately known. (d) The strengths of columns are drastically affected by their lengths (or that is their slendemess ratios) and by minor flaws in their construction. Such is generally not the case with beams. 33 The assumptions used for the . strength design theory include: (a) Strains vary in proportion to distances from neutral axes. (b) Concretes are assumed to crush when compressive strains equal 0.003. {c} The actual curved stress block is replaced with an equivalent rsctangular one. (cl) Only underreinforceci flexural members are to be used. 3.4 The ACE Code specifies a certain minimum percentage of reinforcing in members to make sure that the ultimate resisting moments of those members are iarger than their cracking moments thus preventing sudden failures without warning. 3.5 (a) A beam which has a balanced steel ratio is one for which this-tensile steel will theoretically start to yield at the same time the concrete crushes on the compression side. (b) An underreinforccd beam has isss ster than is rcqulrsci for a balanced design and as a result the tensile steel wit: yield before the compression concrete fails by crushing. * (c) An cverrsinicrcsci beam is one which has more reinforcing than is required for a balanced design. For such a member ths steel wiii not yieki before failure. As a rssuit failure will occur suddenly without warning. 3.6 The reinforcing steel provided for concrete members must be protected from the surrounding environment. in other words firs anti corrosion crotscticn must be provided. in addition the covering concrete will improve the bonding between the concrete and the reinforcing steel. {WW 3, 7 21+" 27” W? . 3“ Cufpomfi ~~~~ w CL: m2 q'wybflmn sssmem. ‘QJR‘SEZ‘LB QWBGWQ 8‘: 0.99 gem Lg-GCDQ 95°: 66?}QV633T'Q 0* 5389., . C’ :3” B x (3 95 3‘ m. 3 Gt :2: < 4: \(0500352 .WBLalmg 33 M?- Oaaag emu! 4530.510 43mm “3% CM %\a©«q%éwnm\LW24- : "i‘gtfgjinpéa Macmg 6"; A “L!” O Mafia? A’s? L?.7‘2\(75\) . 2 A. 1W2. .5345 . a. 0‘95 fig}; (Q’gstQmQX 4 m A. w __ {3‘ - twee) W 4,360 “4000) PI ..... m-AW (0K3wa O;85~W<0355§ 5-? 0.75 0.... m 4.545 W ' CL; ‘9! m Wm WM at: .3 ac (a.oc>’3\ :( QHB \(Gnm‘3\ 2:: 0500972. ‘5? @005 .‘L Ii+s c£m¢lvgaia (max 4; 1:; 0,610 MW 4) M,“ :2 c{> As Q3 L fig) :éyflojfianqvjswgm ’MifirgB d, .2 11-020.“! “mfg: 33%.2 fink /%aml» 1+1 W a?» 0495 90th @0095? camavajve 0L. ' thciéai ‘ a W '3: M2 ,8 , Q ..,. B 0‘95 5 3a m gt :2, (:i—éi\(03003\2 i2;:::fX(o,w§\ : 0.3mm <. 0.00 L} g“. gec‘mém mag WGKF‘ be. used as “C gear" . mum-“WWW ...
View Full Document

Page1 / 4

ch03 - CHAPTER 3 Ski The acivantagos Oi “strength design...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online