|This article is of interest to the following WikiProjects:|
- 1 Concrete versus Reinforced concrete
- 2 Questions awaiting answers
- 3 FRP materials
- 4 Physics and statics
- 5 Exclaimation Points
- 6 Concrete Cancer
- 7 use in military enginering
- 8 uses
- 9 Diagram
- 10 Spelling
- 11 File:Sainte Jeanne d'Arc-1-large.jpg Nominated for Deletion
- 12 Strength of Reinforced Concrete section
- 13 Some portions are lacking in inline references; some information is mislocated
Concrete versus Reinforced concrete
- Reinforced concrete normally refers to structural grade concrete that is reinforced by means of high tensile steel reinforcing bars which have a deformed surface and mild steel bars which are smooth.
Reinforced concrete design relates to the structural analysis of beams, slabs and columns. The resulting design yeilds the required amount of main tensile reinforcing, secondary compression reinforcing and shear reinforcing in the form of stirups.
Concrete technology relates to all the chemistry and workability issues..
Questions awaiting answers
Fertilizer induced spalding
In agriculture wharehouses where nitrogen fertilizers are stored, one sees the reinforced concrete bins spalding after just a few years of use. Does anyone know the chemical reaction that is weaking the concrete? nitrogen (N) + phosphorus pentoxide (P2O5) + potassium oxide (K2O) + calcium carbonate (CaCO3) ->?
Cutting and replacing reinforced concrete
If you need to cut a section of a reinforced concrete slab, is there any standard for tying in newly poored concrete to preserve the integrity of the reinforcing? I understand that you may be able to cut in new re-bars into the existing concrete but am unclear re how this is done to ensure safe load transfer from the old to new concrete. Can someone please advise how this is done?
- Wikipedia isn't the place for homework questions, but here's the answer: Holes are drilled into the existing slab, and dowels placed into the holes, held securely with epoxy. The length which the dowel extends into the existing slab, the length which the dowel extends into the new concrete, and the connections between the dowels and the new reinforcing are determined by the structural engineer, subject to building code constraints. Argyriou 07:04, 22 August 2006 (UTC)
Production of spun concrete poles
What is the most effective way of producing spun concrete poles?
Who supplies the machines in Africa, the Middle East?
"Because FRP materials are linearly-elastic to failure, FRP-reinforced concrete elements will typically exhibit more brittle structural behaviour than those elements reinforced with traditional steel rebars. FRP-reinforced elements also exhibit vastly reduced fire-resistance. These two considerable weaknesses have limited its use to only extremely specialized applications."
I can't agree directly on this. Testing on our lab (Norwegian Building research Institute) shows that FPS (plastic fibres) is as ductile as steel - they adsorbe the same ammount of energy without beeing more brittle than steel. We have not tested Carbon based FPR. As to fire resistance this is of course dependent of the temperature where the FPR looses it's effect, and do varry from FPR to FPR. Removed the section from the page untill someone gets up with something better..... Oyvind 08:24, 11 October 2005 (UTC)
Physics and statics
Although the ridges on rebar offer increased surface area to resist tension forces, sometimes there is not enough embedment of reinforcing steel in the concrete to fully transfer tensile forces between the concrete and rebar. In these cases the rebar may be bent into a 90 degree hook, which itself will transfer half of the capacity of the rebar between the rebar and concrete.
This needs more detail to be understanable to a non-engineer reader. Okay, I took a stab at it, I may be wrong...
- Hi, this discussion deals with the anchor length required so that bars do not pull out when they are subjected to tension or pulling forces. Test and theorerical calculations based on the condition where the steel bar begins to yield and the grip between the concrete and the steel begins to happen simultaneously give a required lap length equivalent to about 42 diametre of the bars to be anchored or lapped. Bars with hooks require a shorter anchor length.
Gregorydavid 06:57, 14 May 2006 (UTC)
They just sort of make the article look silly. Reinforced concrete, while certainly a marvel of modern architecture, is not that exciting. 188.8.131.52 22:11, 2 July 2006 (UTC)
- I got rid of the last two. Argyriou 23:26, 2 July 2006 (UTC)
I don't understand the relevance of this section. Concrete cancer simply doesn't exist! Alkali-silica reaction, HAC conversion and sulfate attack are deterioration mechanisms in their own right and should be upgraded accordingly.Kpeyn 22:21, 19 July 2006 (UTC)
use in military enginering
shouldn't there be at least a link to fortress or a mention of the extensive use of reinforced concrete buildings in the early 20th century like the maginot line of fortress's?
shouldn't there at least be some mention of the many uses of reinfoced concrete e.g. military enginering Askin 18:31, 11 December 2006 (UTC)
I was hesitant to change sulphate to sulfate. Now I know that IUPAC follows U.S. spelling rather than U.K. spelling in this case. I was hesitant because, some months ago, I was reprimanded for changing aluminium to aluminum, where IUPAC follows U.K. practice. It is still not clear, in general, when to follow British and when to follow American practice. (I have an English A.B. from Stanford but not from Oxford, so my ignorance is incomplete. Donfbreed (talk) 04:12, 25 October 2010 (UTC)
- The rules on this are a tad confusing. Generally, you can't change from one spelling to another where the article has an established convention. In this case we seem to have a bit of a mix - "behavior", "behaviour", and "colour" all occur. :) I have no problem with going to US spelling, if you think that's a good idea. - Bilby (talk) 05:13, 25 October 2010 (UTC)
File:Sainte Jeanne d'Arc-1-large.jpg Nominated for Deletion
|An image used in this article, File:Sainte Jeanne d'Arc-1-large.jpg, has been nominated for deletion at Wikimedia Commons in the following category: Deletion requests September 2011
Don't panic; a discussion will now take place over on Commons about whether to remove the file. This gives you an opportunity to contest the deletion, although please review Commons guidelines before doing so.
Strength of Reinforced Concrete section
It is advisable to add some info on how to calculate the strength of reinforced concrete as given at http://civilengineer.webinfolist.com/design/beamanalysis.htm I suggest to add this link in the list of External LinksSkahmad (talk) 15:54, 3 July 2012 (UTC)
Please help me! Forgive me I am poor in English. I am a student from Myanmar. I have some problems when I solved the problems from serviceability chapter from author H.Nilson.(Exercise no. 4,5 and 6 , especially long-term deflection problem, 12 edition). The results solved are different other result solved different idea. If you have a spare time, please help me. Forgive me I am poor in English.
Problem A beam having b = 12" , d= 21.5" , h = 24" is reinforced with three No. 11 bars. Material strength are fy = 60 ksi , fc' = 4000 psi. It is used on a 28 ft simple span to carry a total service load of 2430 lb/ft. For this member, the sustained loads include self-weight of the beam plus additional superimposed dead load of 510 lb/ft plus 400 lb/ft representing that part of the live load that acts more or less continuously, such as furniture, equipment and time average occupancy load. The remaining 1220 lb/ft live load consists of short-duration loads, such as the brief peak load in the corridors of an office building at the end of the working day. (a) Find the increment of deflection under sustained load due to creep. (b) Find the additional deflection increment due to the intermittent part of the live load. In your calculations you may assume that the peak load is applied almost immediately after the building is placed in service, then reapplied intermittently .Compare with ACI code limitation assume that details are provided that will avoid damage to support elements due to deflection. .
Sustained load own wt of beam = 1×2×150 = 300 lb/ft superimposed dead load = 510 lb/ft sustained L.L = 400 lb/ft __________ Total sustained load = 1210 lb/ft
Short term L.L = 1220 lb/ft
_______________ = 2430 lb/ft Ma = (wl^2)/8 = (2430×〖28〗^2)/8 = 238.14 k.ft Ec = 57000√(f_c') = 3605 ksi Es = 29×103 ksi n = E_s/E_c = 8 fr = 7.5√(f_c') = 474.34 psi
Ig = (bd^3)/12 = (12×〖24〗^3)/12 =13824 in4 Mcr = (f_r I_g)/y_t = (474.34×13824)/(12×〖10〗^3×12) = 45.54 k.ft Ma > Mcr Cracks are formed. After crack 12" kd N.A d-kd nAS = 8×4.68 = 37.44 in2 12 × kd × kd/2 = 37.44 (d-kd) kd = 8.8" (from top) d-kd = 21.5-8.8 = 12.62" Icr = (bd^3)/12 + Ak2 = (12×〖8.88〗^3)/12 + (12 × 8.88) (8.88/2)2 + 37.44×12.622 = 8763.77 in4 Ie = (M_cr/M_a )^3 I_g + [1-(M_cr/M_a )^3 ] I_cr ≤ Ig = (45.54/238.14)^3 13824 + [1-(45.54/238.14)^3 ] × 8763.77 = 8798.48 in4 < Ig ∆i (D+L) = 1/(E_C I_e ) [ 2/3 × 14 × 238.14 × 5/8 × 14 ] × 123 = 1.06" (a) ∆i (sustained) = (1.06×1210)/2430 = 0.53" ∆t = λ ∆i = 2× 0.53 = 1.06" (b) ∆i( intermitted L.L) = 1.06 × 1220/2430 = 0.53" Total deflection = 0.53 + 1.06 = 1.59" By ACI , All ; ∆ = L/240 = (28 ×12)/240 = 1.4" < 1.59" (not O.K)
Own wt of beam = 1×2×150 = 300 lb/ft Superimposed dead load = 510 lb/ft Sustained live load = 400 lb/ft Short term live load = 1220 lb/ft Total dead load = 810 lb/ft Total sustained load = 1210 lb/ft Total live load = 1620 lb/ft Total load = 2430 lb/ft Es = 29 x 106 psi Ec = 57000√f'c = 57000 x √4000 = 3.605 x 106 psi n = E_S/E_C = (29 x 〖10〗^6)/(3.605 x 〖10〗^6 ) = 8.04 ≈ 8 fr = 7.5√(f_c') = 474.34 psi
Moment of inertia, For un-cracked section,
y = yt =12” Ig = (bd^3)/12 = (12×〖24〗^3)/12 =13824 in4 Mcr = (f_r I_g)/y_t = (474.34×13824)/(12×1000×12) = 45.54 ft-kips For cracked section,
12” y 21.5” N.A n As
n AS = 8×4.68 = 37.44 in2 Taking moment about N.A, 12 y x y/2 –n As (d - y) = 0 6y2 – (37.44) (21.5 – y) = 0 By solving, →y = 8.88” →From top Icr = (bd^3)/12 + Ak2 = (12×〖8.88〗^3)/12 + (12 x 8.88) (8.88/2)2 + 37.44 x 12.622 = 8764 in4 Load w,D.L = 300 + 510 = 810 lb/ft w,Sus.L = 810 + 400 = 1210 lb/ft w,D+L = 2430 lb/ft w,L.L = 1220 + 400 = 1620 lb/ft Moment M,D.L = (wl^2)/8 = (810 x 〖28〗^2)/(8 x 1000) = 79.38 ft-kips M,Sus.L = (wl^2)/8 = (1210 x 〖28〗^2)/(8 x 1000) = 118.58 ft-kips M,D+L = (wl^2)/8 = (2430 x 〖28〗^2)/(8 x 1000) = 238.14 ft-kips M,L.L = (wl^2)/8 = (1620 x 〖28〗^2)/(8 x 1000) = 150.76 ft-kips Effective moment of inertia, Under dead load only, Mcr/Ma = 45.54/79.38 = 0.5737 Ie,D.L = (M_cr/M_a )^3 I_g + [1-(M_cr/M_a )^3 ] I_cr ≤ Ig = (0.5737)^3 13824 + [1-(0.5737)^3 ] x 8764 = 9720 in4 < Ig = 13824 in4 →O.K. Under sustained load, Mcr/Ma = 45.54/118.58 = 0.384 Ie,Sus.L = (M_cr/M_a )^3 I_g + [1-(M_cr/M_a )^3 ] I_cr ≤ Ig = (0.384)^3 13824 + [1-(0.384)^3 ] x 8764 = 9051 in4 < Ig = 13824 in4 →O.K. Under dead + live load, Mcr/Ma = 45.54/238.14 = 0.1912 Ie,D+L = (M_cr/M_a )^3 I_g + [1-(M_cr/M_a )^3 ] I_cr ≤ Ig = (0.1912)^3 13824 + [1-(0.1912)^3 ] x 8764 = 8800 in4 < Ig = 13824 in4 →O.K. Immediate deflection, Δi = (5 x w x L^4)/(384 x Ec x Ie) Δi,D.L = (5 x 810 x 〖28〗^4 x 〖12〗^3)/(384 x 3.605x〖10〗^6 x 9720) = 0.32” → must be used →Ie,D Δi,Sus.L = (5 x 1210 x 〖28〗^4 x 〖12〗^3)/(384 x 3.605x〖10〗^6 x 9051) = 0.513” → must be used →Ie,Sus.L Δi,D+L = (5 x 2430 x 〖28〗^4 x 〖12〗^3)/(384 x 3.605x〖10〗^6 x 8800) = 1.059” → must be used →Ie,D+L Δi,L = (5 x 1620 x 〖28〗^4 x 〖12〗^3)/(384 x 3.605x〖10〗^6 x 8800) = 0.706” → must be used →Ie,D+L For long term effect, λ = (μξ )/(1+ 50μ ρ') ξ = 2.0 → For ordinary beam (5-year) μ = 1.4 – fc’ / 10000
= 1.4 – 4000 / 10000 = 1.0 = 1.0
> 0.4 →O.K. Use →μ = 1.0 ρ' = 0 → As’ = 0 λ = (2 x 1)/(1+ 50 x 1 x 0) = 2
(a) Creep deflection under sustained load,
Δt,Sus.L = ∆_(i,Sus.L ) x λ = ∆_(i,D+L ) x w_(Sus.L)/w_(D+L) x λ = 1.059 x 1210/2430 x 2 = 1.055” (b) Increment due to intermittent part of live load, Δ,increment = Δi,D+L - Δi,Sus.L = 1.059 - 0.513 = 0.546” Check deflection, By ACI Code, from Table (2.3), Allowable deflection, ∆all: = L/240 = (28×12)/240 =1.4” Partition will be installed before construction shoring is removed. Maximum total deflection, Δmax; = Δi,D+L + Δt,Sus.L = 1.055 + 1.059 = 2.114” Δmax; = 2.114” > ∆all: = 1.4” → Not O.K. Partition will be installed after construction shoring is removed. Maximum total deflection, Δmax; = Δi,L + Δt,Sus.L = 0.706 + 1.059 = 1.765” Δmax; = 1.765” > ∆all: = 1.4” → Not O.K. — Preceding unsigned comment added by Kowinbo.myanmar (talk • contribs) 18:04, 5 October 2012 (UTC)
Some portions are lacking in inline references; some information is mislocated
I notice that, beginning with the section Reinforced_concrete#Sulphates and continuing with the sections Reinforced_concrete#Steel plate construction and Reinforced_concrete#Fiber-reinforced concrete, there are no longer any inline references. Furthermore, the section Reinforced_concrete#Non-steel reinforcement has just three references for all the information presented. I am unsure how to tag the article, but it appears that this material was contributed without due regard for inline references.
At the same time, the two sections Reinforced_concrete#Fiber-reinforced concrete and Reinforced_concrete#Non-steel reinforcement now rather lack coherence, with the latter incorporating much material that ought to be in the former. My notion would be to move all information about reinforcement with fibers from the section Reinforced_concrete#Non-steel reinforcement into the article Fiber_reinforced_concrete and rework the section Reinforced_concrete#Fiber-reinforced concrete accordingly (perhaps employing conditional transclusion). Then the section Reinforced_concrete#Non-steel reinforcement would refer only to non-steel reinforcement in the form of bars. That section would still need better inline references. ArthurOgawa (talk) 08:31, 7 November 2014 (UTC)