made up of steel strands housed in a duct, which is injected with cement grout after tensioning. b%X|)*Z:.S &9.A0f#j#R6N7*Ah+k@3p/"0 |y&BB:Z'\bB+FDCiZ|o[na#WNm}EZ"ys{rJzr Current design codes (ref. Second Floor, Office #207 The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts. Does the slab work with 143 psi of precompression in this bay, rather than 160 psi specified? 1. stiffness in increased because we can consider uncracked inertia 2. we can support higher bending moments 3. we can reduce the hight of the bridge and the self weight can be reduced 4. they show better behavior under corrosion 5. effective solution is high strength concrete combined with greater amount of tendons Title No. Since the usual concern with elongation reports is understressed tendons, the occasional long tendon isnt a cause for great concern. Furnish, install, stress and grout prestressing tendons. This Manual will serve as a reference and guide to designers, inspectors and construction fhwa.dot.gov endstream endobj 401 0 obj <>/Metadata 37 0 R/OutputIntents 396 0 R/Pages 395 0 R/StructTreeRoot 80 0 R/Type/Catalog>> endobj 402 0 obj <>>>/Font<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI]/Properties<>/PR1<>/PR2<>>>/XObject<>>>/Rotate 0/StructParents 0/Tabs/S/Type/Page>> endobj 403 0 obj <>stream The prestressing steel applied corresponds to international standards EURONORM 138-79, ASTM A 416-85, BS 5896. Once the concrete has gained strength to 2000 psi, typically within the 3 to 10 days recommended by PTI, the tendons are stressed. 0000150075 00000 n 0 Post-tensioning is a method of reinforcing (strengthening) concrete or other materials with high-strength steel strands or bars, typically referred to as tendons . However, the measured elongations are characterized by a high degree of uncertainty and variability due to site tolerances, and that the calculated elongations are based on the ideal equations using theoretical parameters. While each of the factors I mentioned in my original discussion of elongations can end up being less of a reduction than normal potentially adding up to an over-specification elongation the most common problem is over-stressing. ects and all PT systems. What is Post Tensioning[2] ABAMELA. uzti2i?yf'bx|y)o27W[-Vxom3x/qoF7`\pt/>Dc1]Mzl,1v8qZgb9l9 \p:qT~wtq,)KS #V~-8wK xUe-3RE ), a single tendon thats a bit long isnt a real issue. _ e-,FC8H- vJT The alternative to pre-tensioning is post-tensioning. Step one is to check to make sure the elongation from the shop drawings is accurate. Measured elongation is 305 8 inches. Here are some primary advantages of post-tensioned floors over conventional reinforced concrete in-situ (cast in site) floors may be following: Longer Spans. 9BoLa05&&7Q;RW;:,f1CZ)6|`USDiegA#t1V4Ne.Iq@HCBZ4;yyuPxRO {LmoR> We(d>:aDQ+86QomL _VKx@)5)UtQ(@MS 0 Dx%TbSj)L$PB2zuHgSU1~PfU"lY$o( 9390gMaEoJ! 05w W However, there are some important caveats to note here. If the measured elongation are below the tolerance, another 5% of Stressing might be applied, or de-tension and stress again. Detailed discussions are presented on variations in the area and modulus of elasticity of 7-wire prestressing strand and variations in the values of tendon friction . The report should contain the theoretical elongation, provided by the designer, measured elongation as well as the percentage of variation. 1) Casting of concrete. endstream endobj 58 0 obj <>stream Add to cart. Answer: When you tension a stud with a Hydraulic Stud Tensioner, the stud acts like a spring and gets longer (elongates). Your email address will not be published. endstream endobj startxref Detailed discussions are presented on variations in the area and modulus of elasticity of seven-wire prestressing strand and variations in the values . Even though post-tensioning is a mature technology, it is still a fantastic tool for the design engineer as it enables the active definition of the internal load path in concrete structures by superposing a favorable state for the internal stresses. What are some advantages? 0000124488 00000 n In post-tensioned construction, hollow concrete masonry units are laid conventionally and prestressing tendons are either placed in the concrete masonry cells or in the cavity between multiple wythes. The program is divided into three separate screens, which correspond to the three major areas of concern in the design of a post-tensioned member. Post-tensioning tendons, which are prestressing steel cables inside plastic ducts or sleeves, are positioned in the forms before the concrete is placed. Monitoring the temperature and strength of your concrete is especially important when post-tensioning in cold weather. c@0Lh`pmc,35L MJ#Z0xi b(Ti& XtvLIRy#6it%{.|d:?8b{?I=bv7''r5W7.Iezai&/7]j5f|z@jn%g=y^ovg+f9l\e}rr p7jg3 5&~3 73s=r2j\G_QYK/X- ..*78!u}_o7&JI40pc@ 426 0 obj <>/Filter/FlateDecode/ID[<52E6B974CD58B0459493BD4438105C12><8E9E88EA1056F24E993B78BB31D78C05>]/Index[400 54]/Info 399 0 R/Length 118/Prev 275052/Root 401 0 R/Size 454/Type/XRef/W[1 3 1]>>stream The difference between 5 7/8 and 2 7/8 can be as insignificant as a typographical error. 0000007084 00000 n Required fields are marked *. What happens when a tendon is over the line? This is 80% of the yield strength of the tendon essentially, the most the strand can be stretched without permanently deforming, while still leaving a factor of safety. If, after careful checking, the slab doesnt meet the engineers criteria, the tendon may have to be replaced. Reading time: 1 minute Post tension slab is a combination of conventional slab reinforcement and additional protruding high-strength steel tendons, which are consequently subjected to tension after the concrete has set. ]yZ;\}pR|\y_nBz]nnr 1lj>6exZ9,jw|1C|N>u:'juW6 ~Y^a4?t#eZa Consider additional elongation tolerance and lower final effective force (PTI Tech Note 16) Look at percent over/under elongation carefully . Afterwards, once the concrete has gained strength but before the service loads are applied, the cables are pulled tight, or tensioned, and anchored against the outer edges of the concrete. hbbd``b`$A !$:l'5H8 H$RAHHJ >&F iCg\ N5 This hybridisation helps achieve the formation of a much thinner slab with a longer span devoid of any column-free spaces. Post-Tension Elongations: How Long is Too Long? What is elongation? This has been systematically observed on building proj- tensioned tendons immediately after the post-tensioning operation. Post-tensioning Pretensioning Post-Tensioning Steel tendons are stressed after the concrete has been placed and gained sufficient strength at the construction Bonded PT Unbonded PT site NPCA 1 fThe Precast Show 2014 Pre-Tensioning: Pre-Tensioning: Precast elements are transported to the site. 3) Placement of the anchorage block and jack. SNP POST TENSION CO.,LTD.110/18 Moo 2 Mahasawat, Bangkruai, Nonthaburi, Thailand 11130 Tel. Longer spans can be used reducing the number of columns. Cracks that do form are held tightly together. As youll recall from my post earlier this year, elongation review is a critical part of an engineers acceptance of a post-tension slab. In todays market, it is imperative to be knowledgeable and have an edge over the competition. Please enter this 5 digit unlock code on the web page. 0000132541 00000 n Elongation Tolerance ACI Structural Journal - es.cclint.com Post-tensioning During Cold Weather. This value is used throughout the post-tensioning industry when calculating actual number of tendons required during shop drawing creation. Elongations have been used to assess the forces inside post tensioned tendons immediately after the post-tensioning operation. 0000123131 00000 n ho! ]}q+5[&j4O@s'~7p(Jr-TI'!(bEh%EI/HG=K-{+N[T-Rvd8[F-vT.NsfK8pA-&TkEc$q;1O0>M~tEF+XqIm.ukI/uj&|63'4BbRtXlg[ebc)hg,ki?u-Wju8(KY1UXB`3F4N f&: =^:sR<5H>&n)%G& JCfQ1 K'\S.vqABd 1{rN\yM-L$Q/Zbu^IJ-gbax%5%"D -@"&yBw3S^fuKlXGg*k+r424{dq(rH0eTKiXsDn_5>x@Gl_^W.H}vY3rDw @^Z:C Extreme fiber bending stresses will form only if stressing results in a change in slab curvature. 51 0 obj <> endobj 0000132803 00000 n Anchorage slip as the strand wedges seat at the bearing plate. K&{k0X&/B9616~aUr-g_rRcIZuPlfD;. h'h8("8Xy_C=^:N2|AT*m@kQAA mN6pi]Wpf@%mm;66c>fbbK+x/y-h[$ycO^E`-5 'q.q)B?Ejpe[B,kt'5"1{CNS%Kg9'] _n3N5xTQwZ>47]S/~Oi:X;[*e>)H]{i~+L")y;Dh=4JY$1;=X#QVpq{Mp&_x;8x3iIa(PiW2Wg`$be&A#&,TFKC}a. Introduction In South Africa, guidelines for post-tensioning are provided by SANS 2001-CC1 [1] . . If you log in through your library or institution you might have access to this article in multiple languages. Building codes acknowledge such variability as a limitation and include tolerances for the elongation deviations between the calculated and measured values. 0000072665 00000 n 54 0 obj <> endobj However, the measured elongations are characterized by a high. Assuming that it provides no precompression or balanced load, he rechecks his calculations and looks for any slight overages in the nearby tendons to help. 0000083967 00000 n The paper discusses the history or background of specifications on the elongation tolerance for post-tensioning tendons with particular application to segmental concrete bridges. endstream endobj 52 0 obj <> endobj 53 0 obj <> endobj 54 0 obj <>/ColorSpace<>/Font<>/ProcSet[/PDF/Text/ImageC]/Properties<>/ExtGState<>>> endobj 55 0 obj <> endobj 56 0 obj <> endobj 57 0 obj <> endobj 58 0 obj <> endobj 59 0 obj <> endobj 60 0 obj <> endobj 61 0 obj <> endobj 62 0 obj <> endobj 63 0 obj <> endobj 64 0 obj <> endobj 65 0 obj [/ICCBased 88 0 R] endobj 66 0 obj <> endobj 67 0 obj <> endobj 68 0 obj <>stream Also, as explained earlier, the anchor set is a value that comes straight off the top of the elongation, instantly reducing the force in the tendon. +`K,kv1!74[Y%GN](k1fdMv# |PG/=8(bAYQbb-4~C1]7;'RkcqmRLl7\aAy The PT guys have two ways to measure cable tension, (1) direct measurement of force and (2) elongation. As concrete gains strength more slowly in colder temperatures, closely monitoring temperature is important to ensure the production of high-quality concrete that meets specifications. Cost per Square Foot of Commercial Construction by Region, Type A vs. While it is an integral part of all post-tensioning operations, its results can be misun-derstood, leading to disagreements, finger-pointing, and Building codes acknowledge such variability as a limitation and include tolerances for the elongation deviations between the calculated and measured values. Elongations have been used to assess the forces inside post-tensioned tendons immediately after the post-tensioning operation. CBInS4 J' T$hLd!1dlU2}QF}JNL0RCg:"l9!A6FU2NOM'^h The paper discusses the history or background of specifications on the elongation tolerance for post-tensioning tendons with particular application to segmental concrete bridges. What happens when the tendons pull long? HQk0+L[ucaVn{n[Wh\@{xOsszf7x*A|`4AA7WP+D6~/ex)y E9_.}QaR9Smmi ,C[H~YSy!>e&0QnMR JlJ&\E2"Lgqs^FJO171*[\vN{> 5rwaVHUO7Vfklw}NA=$:dqu:}8H?p>$79x(!Q;]AJE5D:G6 (RS8*("QeKy>k`! 0000119393 00000 n All Rights Reserved. !M&*a7!q5gzHd/C,'EyqU $39.99 $9.99. 3. When there is permanent stress and elongation in the post-tension cables, a compressive force is created on the concrete. #T1$]&`!Bl=SubNa & Detailed discussions are presented on variations in the area and modulus of elasticity of 7-wire prestressing strand and variations in the values of tendon friction and wobble coefficients. Post-tensioning, or PT, has become increasingly popular over the past few years, as the technology has been perfected with better materials and construction methods has made this system a preferred one. 0000072924 00000 n They keep thorough notes showing both the gauge reading and the elongation. hbbd```b``A$dY`RLr`]`vB.9`0)"Y[@$7$/H-~83H8`(:?cs A post-tensioning tendon consists of strands, duct, and anchorages. P ost-tensioning is a method of reinforcing (strengthening) concrete or other materials with high-strength steel strands or bars, typically referred to as tendons. In. 400 0 obj <> endobj document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); 5335 W. 48th Ave. Suite 300Denver, CO 80212. Your email address will not be published. In contrast, a typical piece of rebar will yield about 60,000 psi. Dubai World Trade Center Complex 0000018542 00000 n However, the measured elongations are characterized by a high degree of uncertainty and variability due to site tolerances, and that the calculated elongations are based on the ideal equations using theoretical parameters. hb```l@(AB+K O v7\P W(h$5 [Z;}y3mG>szfzP^vwKM=UZ (bX0 TA&U"$1] 0000005671 00000 n startxref The joints between the duct and the anchor shall be watertight. Copyright 2006-2022 EVstudio. p~k{7qvU!Xoigr)&8[?HU? %%EOF 0000006378 00000 n The form is used for recording elongations for Unbonded Post Tensioning. Fax: 1.248.848.3701, ACI Middle East Regional Office Even so, the specified tolerances are quite stringent and unrealistic for relatively short tendons. 0000003664 00000 n Normal variations in seating losses in short tendons can often result in differences between measured and calculated elongation, which fall outside the range of 7% tolerance permitted in ACI 318-11, Section 18.20.1 . . Thats why the factor of safety is 20% (instead of 15%), and why almost all post-tensioning pumps are equipped with a pressure-relief valve. This will also make the whole concrete . EVstudio is a full-service in-house design firm specializing in architecture, engineering, planning, and other design services for commercial and residential projects. "ts: %& ^#I2vUaiXf(Z With tensioning, you're typically going to see +/- 10% accuracy. normal seating losses are a significant percentage of the calculated elongation. W&\y The stages are shown schematically in the following figures.After anchoring a tendon at one end, the tension is applied at the other end by a jack.The . The purpose of filling with grout is to introduce compatibility between the prestressed concrete and tendons. Phone: +971.4.516.3208 & 3209, ACI Resource Center 0000005747 00000 n Chloride Tolerance The chloride tolerance of galvanized reinforcement is >10x higher than black steel . What if several tendons (especially tendons bundled together) are over-length? f0 C)dC8w It is critical that only the jack supplier adjust this valve! This spreadsheet program provides for the design and analysis of post-tensioned concrete one-way beam and slab systems and two-way flat plate slab systems. Hlo0+&z`T,1q:LkpMm 0000002538 00000 n Potential energy is created by the combination of the stud's elongation and tension. 0000099617 00000 n Please enter search criteria and search again, Elongation Tolerance for Short Tendons in Post-Tensioned Building Structures, bonded; elongation; measurement; post-tensioned building structures; short tendons; tolerance; unbonded. 0000029538 00000 n GD=~{FO. Keywords: elongation variation, post-tensioning, tendon, tension, friction, wobble, elongation limits. PT Detailing. ACI members have itthey are engaged, informed, and stay up to date by taking advantage of benefits that ACI membership provides them. This arrangement enables strand loads to be transferred to the concrete structure by bonding, which allows for passive reinforcement to be optimised and significantly reduced. 0000071284 00000 n We still check them theyre out of specification, after all but once you know the line that translates into permanent damage for the tendon (dont forget anchor set! Did he need 18 tendons, or just 17.6? 0000005213 00000 n HWn}W#;4&L3,r50y%f{s&-S`u9uzw First, the Engineer of Record will request the mill certificates for the tendon in question. hXmo6++w@&[wAD`[ww+;z#-c LXq`>K^1!8 0000129279 00000 n In the early fifties, post-tensioning systems for the prestressing of concrete were developed by specialists, such as VSL in Switzerland. What is elongation in post tension? It follows the Post-Tensioning Institute's Field Procedures Manuals for U. The use of these equations in large-angle post-tensioning applications, such as hoop post-tensioning in cylindrical structures, may lead to unrealistic estimations of friction losses. 114-S64 Elongation Tolerance for Short Tendons in Post-Tensioned Building Structures by Carol Hayek and Thomas H.-K. Kang Elongations have been used to assess the forces inside post- end. It is important to place the beam coils above the formwork brackets. xref measured elongation review". 0000134676 00000 n x4HC$j?l_cp-x `>l.HDN\e:cw`pzl2H8t`nqz(|%Cd1PC;F_ GL}F]'(twp9 ykE0dt>!Va3l0^mX3`hc(nctpd}d>#,9#.fS0}x!3}~{Y:TAl9Tz~f8a}`l:q^4CQH2&>|;:9OB#H0*E/W*qdl=mc-Bem3$p6'Q6pJ"1(: ,!i& endstream endobj startxref Friction of the prestressing steel with the duct and loss due to misalignment of the duct. rY#DNDY1g zaDfc't4g1h!C$C\u=,B4ja,kD1!wt;;1YITv7FFIF ~TROks!z&X}d@r. 91 0 obj <>stream Post-tensioning applications include:- office and apartment buildings, parking structures, slabs-on-ground, bridges, sports stadiums, rock and soil anchors, water-tanks. Post-Tensioning Losses: Post-tensioning of prestressed box girder bridges must consider stress losses that will occur. At best, its a dirty, labor-intensive process thats prone to false starts; at worst, its invasive and dangerous. 453 0 obj <>stream This . yF-KMjY+l$&h.7riCaJp%56eFK 0000006207 00000 n fx)!j7y{@Q]~Z`S D-tQ8Ra]_}_Nlll'F~ D0K&"IC\![u{. 0000000016 00000 n Yx9~XZoe<< ked4$)KfW}!,*C%"V{Lt 7fPwkX7)+ 0Qq>qdK This form is for Inspectors and Installers certified by the Post Tensioning Institute . 2) Placement of the tendons. Read more about the importance of monitoring temperature during post-tensioning here! 1.0 Introduction Post-tensioning is a method of reinforcing concrete elements with high-strength steel strands, commonly referred to as tendons, to reduce the tension experienced by the concrete member. 0000060414 00000 n 5) Seating of the wedges. This video goes over the highlights of stressing unbonded Post Tensioned concrete. <]>> Recently, weve had a few projects where our post-tension elongations came up longer than expected. As I explained earlier, post-tension stressing pumps are calibrated before they reach the jobsite to a pressure corresponding to 33.0 kips. endstream endobj 404 0 obj <>stream The difference between 5 7/8 and 2 7/8 can be as insignificant as a typographical error. Post-tensioning applications include high rising buildings, office and apartment buildings, parking, structures, slabs-on-ground, bridges, sports stadiums, rock and soil anchors, and . 0000103577 00000 n 6) Cutting of the tendons. a.Bk;,H8&og 1K$n15P(%Fbza}r=2 .JBfu4$nA.K RvE%Q" D? and do not adjust the pressure relief valve! trailer POST-TENSIONING. df41!Ph]nF Zm3,s,$(d! After an initial pull of 3,000 pounds, the final jacking force read on the gauge is 25,500 pounds. In a post-tensioned beam, the tendons are stressed and each end is anchored to the concrete section after the concrete has been cast and has attained sufficient strength to safely withstand the prestressing force as shown in fig.2. Then, once the concrete has strengthened, the ropes are tightly pulled or stretched and abutted against the outer edges of the concrete before the load is applied. f{&u2J. Phone: 1.248.848.3800, Home > Publications > International Concrete Abstracts Portal. Post-tensioning tendons, which give the pre-tension of the steel ropes inside the channels and sleeves, are placed in the area before the concrete is placed. 0 If the Engineer of Record cannot justify the tendons acceptability, hes forced to abandon it. bDWXiZ}>eXkf]W%R0*4: K;x"r+Mr`m,4UBr4K\ws^I| 1wU$&NSQxL"GDI/Qr?OwZp=-$Njr?zvj0 When tension is applied to steel tendons, they elongate in proportion to the tensile force, as predicted by Hooke's law. Post-Tensioning Method Steel tendons are stressed afterthe concrete has been placed and gained sufficient strength at the construction site PRESTRESSED CONCRETE PRETENSIONING 1.Tension Strands 2.Cast Concrete -Bond strands to concrete 3.Cut Strands -Transfer force to concrete POSTTENSIONING For a 55% tolerance, the measured elongation should be between 281 2 and 311 2 inches. If elongation reached, but pressure not reached apply 5% additional If pressure reached, but elongation not reached apply 5% additional pressure. 0000073314 00000 n %PDF-1.5 % Rated 5.00 out of 5 based on 3 customer ratings. That means your bolt scatter will be lower. retical elongation for a 400-foot-long strand, after initial tension of 3,000 pounds, is 30 inches. . POST TENSIONING MANUAL 6TH ED. KmY@"[wXy85FAFkk 76 rfLg1RtqfKU-'$-n0=NeJvzLvS2dk]5R=PS,nY@m?==u(MN!vc70A+fq-N}3%WL6>RwgtcdD` ( 38800 Country Club Dr. The Post Tensioning workers use many sized bar chairs that locate the strand cables at there correct profiles. The EOR normally specifies the initial tension required and leaves the measurement to the technicians in the field. Install prestressing steel, which may be strands, wires or bars, through preformed voids or ducts in the concrete or in external In practically all constructions, the post-tensioning is fine-tuned to balance a fraction of the member's self-weight, typically 50% to 80% - not more than the member's total weight at stressing. About half the time (in my experience) the yield strength is higher than nominal, or the strand is just a little bit oversized both of which help justify leaving the tendon as-is. 0000129515 00000 n 48331-3439 USA Steel tendons used for post-tensioning typically have a tensile strength of 270,000 pounds per square inch (psi), are about 1/2 inch in diameter, and are stressed to a force of 33,000 pounds. . Elongation result should be checked and verified by the engineer before cutting excess strand. The following new Section is added after Section 460: SECTION B460 POST-TENSIONING B460-1 Description. For that reason, elongations have always been used as a way to assess the post-tensioned forces within the tendons because the tendon force is directly proportional to the elongation through a known equation. 4x +g^qtWMu4+EVN;3c^#6"cjFsTM9 '_eG~oKv4]36lK\c ?=c+hgjL|E9:4(2hOmI(onxzA/emeXO1>xYq S" J2#\qVo/?Om_!Bx`D^_M~7/yyy}|=5gQgG_\5*B]~G;0Y0~j gGK[Z.$;*mN-^/_h>s"_@P4.2=ate'` |`h8@2T&@_hX-sqKkNTpHPG/nh +dj7.JrS}"@KHh((lU(-ldT\e\,zh~|/&y\e})j9)\8vwin8=(Kl\L7I p~6/5|R5{USHO,|j~R J>VZ 94R!Cwu6HN~|OJq=m>]AL!m KDvMiFhBKJ(4. 1OM>v$pm?m?}k7l@hbo%R]XP"0p% ? Hence, the slab will not lift off the form support. Prestressing by post-tensioning is generally of the bonded type, i.e. "f'Ctr However, the measured elongations are characterized by a high degree of uncertainty and variability due to site tolerances, and that the calculated elongations are based on the ideal equations using theoretical parameters. Post-tension 'tendon' is a term used to define the complete assembly comprising of the sheath, pre-stressing strand, anchorages, corrosion-inhibiting coating or any grout around the steel wire or bar. 0000125997 00000 n 107 0 obj <>stream 0000002247 00000 n Q/Ml//-]Z,>G56 Lw!ZCCet'G Sm`/>P6KK(Vv)v&RYm?ur80S$yfMB)-)xr>2ttw[Rr.IXGJi>Yk/+Eys!kUtd687[pn^yxJc?0t55ENS1t?SK*jG!jn+K_^luD*hl1\ l RLQZVpVbi }Q#14qdZpK>Z#N>yE+F6dq endstream endobj 405 0 obj <>stream Relaxation . This value . %%EOF Structural considerations . In Post-Tensioned Buildings: Design and Construction (2014), the author provides the details of the stress loss in the tendon and other considerations that govern the force in the tendon at stressing and long-term effects. Elongation at break 3.5% in 24" gauge length 3.5% in 24" gauge length Maxi. The Offices 2 Building, One Central In general, the vast majority of tendon elongations fall within the 7% tolerance, with only occasional "long" or "short" pulls. AcH%;R/Vb>(-II?sB3#Ncaic&:I=.Syoed8rD$`:b1qf'w ~EJfLKYwosd 0dwuuwEB|[x{w_n|lpvo?|r ?s{3YQQ)fKs,?gz1ghrN)@/Ym7Frq{4/sr%l(+#RyKta3Ca~l9}vdX5fXG#u*hUe2 y2@Sexs'3>2dG%Q7;{i+[%0=C=ENic+RcB8R1Idy^N@7_Qw^GJI Invalid Email Address. These categories are: Service Stress . The 6th Edition has been extensively expanded with 12 new chapters that give design guidance on modern applications of post-tensioning. Advantages of Post Tensioned Floors. when post-tensioning tendons are short. Which is certainly true in both directions and is why the calibrated gauge pressure is the first criteria for acceptance of the post-tensioning force. Americans with Disabilities Act (ADA) Info, ACI Foundation Scholarships & Fellowships. KfK.Y4.~W+cbrE\\+M&VJW&'K7*q2%)!i\-UcReIu i Contraction post-tension slab system. Ssl Pt Manual 2011 Multi. 0000004826 00000 n After applying the additional pressure / elongation, if the Stressing result is within +/-5%, release the jack pressure slowly and then proceed for next stressing. . 0000006802 00000 n 0000129798 00000 n In a bonded system, the tendons in the ducts are buried intside the concrete and grouted after stressing. 3R.SYdaXN5}6;E%*{jg~A7v=-O$Q/h:P3SlmVv[b7QJ{_|9T{A(/w_t_~2EYn>}lSf'Gou ,d&Y^dPv;DR84=neMSm 0000005593 00000 n 0000125829 00000 n Midwest, Feedback via Email Uz This manual contains updated information on the current practices in the use, design, and construction of post-tensioned structures. Hence, a standard deviation of 4.55% would give an elongation variation of The focus of the following is a sequence of stressing and measurement of tendon elongation. Based on the analysis of the data collected, a practical and rational tolerance between measured and calculated elongations is proposed. Sale. 0000072126 00000 n 3) typically address post-tensioning of masonry walls laid in running bond. The PostTensioning Institute is a nonprofit trade . So, barring typographical errors on the shop drawings, what causes over-elongation? EGb97+/fXL(5B,BL7K*,h}}g kU/ xYd@~/5Glo-6E{JTO JPe6-+!-D.(55`PRrO/[*w\E6pk"E.-d8QRoU%nVAIdIOPX n+[lvOH 36]%8!&Om_i$BzKOl_|^|zv| :2pT=+unt0h#(Gn;-A__HHJ$B`dxxtC?=j"Amj'^7?\+NGc^pdJ~=Y":BuJ"@`z4 k/^X`g=lkjKAR#HR{LatB7 &uCXQ'%(jv!-KNJz$46z Po9LtaXa)`MEsaFhK GQNMe[ &[pZ!MLm[U])HUHG+QZskay5% ~HXj$rn@/Y,pCSZ(#wf8 9M'R%5{?CAT>YQmwH, Check out our VIDEO for the basics in stressing post tensioning tendons. 0000004323 00000 n !zx[ o7]k}ENRfv;@:I9Wca3ttR:W{"uTsoS}\F.:KnS(ewKt'CJ(%R]pkPq~blM|&waRWHm[n;F:tu dW Farmington Hills, MI . There are no good results from adjusting this valve in the field. 51 57 %%EOF when post-tensioning tendons are short. p* X5[E@m=OyMS3l.F{O*`v_9|$PIP| :K`;lCW'?JC B;.6>| Now, Ive said that we check every elongation, and that were very much aware of the upper edge of potential non-damaging elongations. Each batch of strand is tested before it ever leaves the mill, in order to determine its actual yield stress, area, and modulus of elasticity. materials and method of fixation, . Elongations are a key to determining the forces inside post-tensioned tendons. ; > 08;g\`AQg-q'q:@lFlAO o endstream endobj 55 0 obj <> endobj 56 0 obj <> endobj 57 0 obj <>stream Bridges, including major cast-in-place and precast . . Do those 18 tendons give him 27 kips per strand, or 27.1? Based on the analysis of the data collected, a practical and rational tolerance between measured and calculated elongations is proposed. Common procedure is to set that valve to prevent the pump from turning out more than about 90% of the tendons yield strength. Elongation variation, post-tensioning, tendon, tension, friction, wobble. First, tensioning is more expensive and more complicated than torquing. 0000073686 00000 n Post-tensioning, which is a form of prestressing, has several advantages over standard reinforcing steel (rebars): It reduces or eliminates shrinkage cracking-therefore no joints, or fewer joints, are needed. 0000129015 00000 n 0000001436 00000 n Which is certainly true in both directions and is why the calibrated gauge pressure is the first criteria for acceptance of the post-tensioning force. It may even void the jacks calibration. Elongation Tolerance ACI Structural Journal - post-tensioned concrete 0000072391 00000 n Abstract:Elongations have been used to assess the forces inside post tensioned tendons immediately after the post-tensioning operation. hb```f``2g`a`jgd@ A+sgl{Q@ iv4 */J( h @Q(.8]HxG[ecx>300Q{:{l. Post tensioning are generally classified into 2 category, namely bonded and unbounded. suspension span, post-tensioned with 70-strand tendons. %PDF-1.6 % MattChuo. 0000006413 00000 n Abstract: Discusses the history or background of specifications on the elongation tolerance for post-tensioning tendons with particular application to segmental concrete bridges. 0000129857 00000 n The Manual is targeted at Federal, State and local transportation departments and private company personnel that may be involved in the design, inspection, construction, or maintenance of bridges that contain post-tensioning tendons. Phone: 1.248.848.3800 vikramjain66. kN\TDU&N9Y9Y]Q;jbd QH\w-1w%y'I@_W$k>$GRt WzlrK=LF0/cbh]]8FBsR3-[ IvEXe>H' ^ZU:`0:od&4h)!qR6Gx5O;F2!=+V-5 0000099364 00000 n Listed below are seven causes of prestress losses: 1. A residential post-tensioned concrete slab will typically be 8 inches thick and use 3000 psi concrete. This elongation is used by the South African standard on concrete structural works and the South African standard specification for road and bridgeworks to determine the adequacy of the force applied in a tendon. bT,3sT+:RF'5 juS7 Mv aTDH@:"(+? If the target was 50 KSI, you'd see values between 45-55 KSI. Built in 1965, the existing uncoated steel strands corroded severely only 50 . Post-tensioning is a method of reinforcement employing high-strength steel strands or bars, which enable the existence of longer clear spans, thinner slabs and in many cases of structural systems that would otherwise be impossible due to either site constraints or architectural requirements. I*lV&N'*ppNjR:)j->i&s'8W2$%cmoJ )r(^ezcN-fG]u2h8"'Z}l8RmZTr?o9gEnp||,+ nfgjY#[oVS^O_Ci,Mib}+j!+;q pV{k,~