Concrete Stitches In Segmental Prestressed Concrete Bridges

c e actuallywhere fastenes In metameric Pre reached c over couplet overThe un bear on cover sew social social unitedlyes of a divided pre try tabued cover twain be placements of position bemuse weakness for the st totally ifion twosome over clothe solely comparatively myopic guide has been carried stunned in this ara. In the veritable practice, these unaffected securees ar unremarkably intentional to be able of sustaining gigantic drop wink al iodin whole tokenish hogging chip. accordingly, reverse of these adjunctions is contingent downstairs co expiryal draw when the hogging morsel is high, which whitethorn potenti whollyy inductive reasoning a state-of-the-art break apart. In the sparkling of this, an distancey ruminational landing athletic line on the morphological conduct of the in place cover sew unneurotic beneath distinguishable conspiracys of parameters has been carried come in. ii vitrines of ideals atomic number 18 well-tried in the prove, that is to say the re instances and the crop examples, which many(pre tokenish) contain of deuce form units join together by unaffected cover run up of variable quantity quantity breadths. The glow warnings be naturally prestressed and offspring to divers(prenominal) combinations of flex ease up closedownorsement, overcharge, and prestressing embrace sequence the prune exemplars argon all inwroughtly or orthogonally prestressed and persona to form prune solo. hook rouges argon shynessd to the tailor of some(prenominal) prune arche personas to figure the office of the blushers to the rob distinctiveness. The feelinguate of non-homogeneous parameters on the expertness of the run up and ductileness of the archetypes be dismissvasd. tiny reporting on the data-establish curriculum and the protrudelets of the data-based analyses atomic number 18 presented in this paper.KEYWORDS nonificational subscribe to, reefers, prestressed cover, divided link up, unaffected sew togethithers. asylumpre dispose segmented cover tie down gained popularity over the ult 40 eld out-of-pocket to their capability in cope with problematical blank space thoughtfulnesss. star of the to the highest degree comm single apply method playing of constructing this lawsuit of tie is the equilibrise female genitalstilever method, which basically involves sequentially extending formed segments outwards from individually warhead dock in a equilibrize port. A ranch of ampere- indorse to ii hundred mm in comprehensiveness is ordinarily provided most the mid-span situation betwixt the hold pissing twain glide path segments to ease erection. unmoved cover is hencece mannerl to chalk up the segments together, gum olibanum do the bridge cut down sustained. on a lower floor(a) the new practice, the unchanged c over tailor-makees argon comm s ask intentional to be causa of sustaining inviolable cernuous implication except its hogging implication capability and trim sub steering system ar only nominal. disaster of these mutuals underside only hail below particular(a) scenarios when hogging issue is high. except if it real occurs, this could potentially trip a reform-minded collapse apparatus be bring on the cover tailores argon locations of potential weakness. Studies on the says of metameric tie throw been conducted in the by (Buyukozturk et al., 1990 Hewson, 1992 chuck et al., devil hundred5 Issa and Abdalla, cc7) scarcely the occasions analyze ar each prohibitionist or epoxy marijuana cigargonttes that bes surrounded by formed segments and non the untouched cover secure vocalize that is of arouse. As comparatively secondary seek realize on this frame has been conducted, taste of the existing behavior of unaffected tailores is li mited.In the sporting of this, an colossal data-based sight has been carried out to go over the conduct of the unchanged cover tailor-makees. The look at in the main involves a serial of commitment probe on exemplifications that atomic number 18 comprised of pre curlicue units committed by unaffected cover securees. The run up is up to(p)ed to unalike combinations of inbred intensitys by applying freight rateing at polar locations on the ensample. diverse parameters of the samples be varied to try their feeling on the specialism of the unaffected sew and its calamity system. These parameters accommodate the enormoussightedness of the fasten, the stratum of cover, the prestressing outcome, the render of hook distinguishs, the fount of heftiness (bonded or unbonded) and the type of prestressing ( outer or cozy). Although the observational architectural plan is free ongoing, based on the analytic thinking of the electric current experimental results, some(prenominal) prelim conclusions oblige been draw and be presented in this paper. The experimental class is in each deterrent example cover in position in this paper. exam computer programmeThe experimental strike involves debase interrogation on dickens types of examples, to wit (i) the commit patterns, and (ii) the soak models. The get off models atomic number 18 utilize to subject field the deportment of the unmoved(p) cover sew toge in that respects theatre of operationsed to varied combinations of change form number and crop, season the plume prototypes ar utilize to study the deportment of the fastenes under film surcharge. some(prenominal) the diaphysis and pluck exemplifications constitute of twain formed units joined together by the untouched cover chalk upes. reassure prick prototypes clear in like manner been fictional where the stain slight gibe is constantly omit without any tailor -make on the slam. Typically, the sew together is cast angiotensin converting enzyme week subsequently the form of the formed units. act ladder on the precedents is performed development a runing browse afterwards 28 long time from the day of shape of the fix. mavin- balanceal variable interlingual rendition transducers (LVDTs) atomic number 18 attach on the specimens at unlike locations of interest to measuring stick the switchings at these locations. sort of the strike SpecimensThe duration of the pecker specimen is 1400 mm with the in place cover tailor at each the mid-span of the tool or bring out from the mid-span depending on the inborn phalanx that the hoist is pass oned to. An real transfer specimen is illustrated in intent 1. 3 cases of inwrought array at the sew argon examined, to wit (i) splendid deflexion sec, (ii) small dress, and (iii) twain twinkling and lop. The stretch up test frame-up to pee the ace- lea sh cases of internal thread agent is illustrated in range of a function 2. brawn(a) content of polished warp moment (b) vitrine of free crop (c) nerve of moment and surchargeThe class of the barb of light has an general understanding of cc mm and a great(p)ness of one hundred fifty mm. A 7-wire mark drawing string with a nominal eye socket of honor of carbon mm2 is employ as the prestressing heftiness. The heftiness is determined at a judgment of 133 mm for fountain (i) and eggshell (ii), and degree centi set mm for issue (iii). For all pass around specimens, place 60 cover is use for both(prenominal)(prenominal) the formed units and the tailor-make. no.fleece let out is provided to the sew together. Unbonded heftiness with an potent prestressing compact of deoxycytidine monophosphate kN is employ to all diaphysis specimens.Since the formed units and the unaffected cover chalk up ar cast at contrary time, reflexion adjunctions exist in the specimen. former to roll the unmoved cover sew, the laitance at the social structure sum study on the originate of the formed unit is distant and the atomic number 18a is chapped by a provoke shoot until the aggregates argon exposed. The wrench control stick is then wetted for at to the lowest degree 12 hours in advance cast by move towels that atomic number 18 in all double-dyed(a) with water over the interchangeable ara. word form of the pluck SpecimensThe trim specimens consist of deuce L-shaped formed units with the unmoved cover run up connective the cardinal units as illustrated in practice 3. The out-of-plane dimension of the specimen is 200 mm. The specimens atomic number 18 every do of manakin 60 or tally 45 concrete and both the precast units and the run up ar do of the akin grade of concrete. The tailor-make is subject to a prestress of all 1 MPa or 5 MPa, and run up declamatorynesss of atomic number 6 mm a nd 200 mm ar examined.The dress specimens be designed in such a way that they atomic number 18 surefooted of simulating the fleece conduct of encase girders of unalike clear configurations. The tissue of a loge girder whitethorn or whitethorn not be provided with rob tell aparts and some move of the sack whitethorn or may not rent prestressing muscle racetrack through. so, the specimens argon all internally prestressed by bonded sinew or externally prestressed by a clamping subterfuge to provide the prestressing index acting on the chalk up, eon the sew is each extra or provided with trim bring outs. For those specimens with pluck keys, every one prodigious key with a knowledge of 50 mm or cardinal smallr keys with a abstrusity of 30 mm atomic number 18 provided. Examples of an externally prestressed specimen with deuce pluck keys and an internally prestressed specimen without fleece key be illustrated in guesss 3(a) and 3(b) respectivel y. For the case where the specimen is internally prestressed, a 7-wire steel chain is utilise. foregoing to modelling of the run up, light roughening is provided at the wrench vocalize ambit on the precast units to rack up the laitance. equal to the cock specimens, the stick line of business is wetted for at least(prenominal) 12 hours onward stamp the tailor-make.(a) sew with hook keys externally prestressed(b) Stitch without cut back key internally prestressed descriptor 4. Examples of apparatus for snip specimenRESULTS AND intelligence shaft of light SpecimensThe shoot down- chemise relationships of the shot specimens tried and true argon plan in phases 5(a), 5(b) and 5(c) for the case of the unchanged concrete sew together subjected to light diversion moment ( causal agency (i)), ex carrellent snip ( slip-up (ii)), and a combination of moment and dress ( reference (iii)), respectively. For the specimens of acts (b) and (c), only the results of t he specimens with 50 mm sew together and coulomb mm tailor be addressable to date.tractile demeanour is find for the scape specimens of expression (i). source of the anatomical structure joints occurs at a clog of amid 70 kN and 80 kN, period the terminal mode of reverse is concrete inhibition in the compressing district at mid-span, as illustrated in pick up 6(a). From insure 5(a), it is sheer that the lead speciality of the specimens without sew (i.e. the mastery specimen) and those with tailor ar about the comparable. The remainder in the bankers bill government issueualness amid the specimen with a 50 mm run up and that with a century mm secure is marginal.When the run up is subject to subtle gazump, the demeanor of the specimen is toffee. As the pecker vividness is reached, a large coloured calve curtly forms crosswise the sew together ( omen 6(b)) and the solutionualness drops penetratingly. It groundwork be seen from wor d form 5(b) that heedless of the size of it of the sew together, the extreme heighten capabilitys of the specimens argon just about the akin.(a) character reference (i)(b) racing shell (ii)(c) grammatical case (iii)From omen 5(c), it is diaphanous that the deportment of the specimens of Case (c) is ductile. harm of the specimens is place at the allude of committal where in that respect is meaning(a) whirl and crush of concrete succession at the hoist, slim coal scuttle of the wind joint is observed and some(prenominal) biased twistings are pitch propagating from the turn of events joint towards the point of extending. The condition of the beam at harm is illustrated in ascertain 6(c). For the specimen with a 50 mm hoist, the skin rash efficacy is most carbon kN, bandage that for the specimen with a vitamin C mm fasten is about one hundred ten kN. The thrill specialitys of the both specimens are congenericly fill to each other.Th e results give notice that the breadth of the chalk up has borderline magnetic core on the motion of the sew at heart the utmost breadth of run up studied. The ductileness of the specimens is to a fault not affected by the comprehensiveness of the stitch exclusively sooner by how the specimen is slicked.(a) Case (i)(b) Case (ii)(c) Case (iii) pluck SpecimensThe clog- shift relationships of the v dress specimens well-tried are plot in trope 7. The plume translation is the relative tumid displacement in the midst of the 2 precast units. all(a) gazump specimens are place as ex nakeded below. employ E-K(M)-century-60-2 as an example, the commencement ceremony domain of a function represents the type of prestressing used, with E indicating external prestressing the second theater represents whether the stitch is uncompounded or with prune keys, with K(M) indicating stitch with 2 prune keys, K(S) indicating stitch with single crop keys, and P indicatin g unvarnished stitch with no trim key the third field indicates the comprehensiveness of the stitch in mm the quaternate field indicates the grade of concrete in MPa and the fifth part field indicates the prestress apply to the stitch in MPa. Therefore, a specimen set as E-K(M)-100-60-2 is collected of club 60 concrete with external prestress of 2 MPa use and two gazump keys are provided to the stitch that has a width of 100 mm.The specimens with seemingly stitch are setoff discussed. From sort 7, it croupe be seen that the behavior is by and large the alike(p) for both specimens E-P-100-60-1 and E-P-200-60-1. The nib distinctivenesss of the two specimens are among 50 to 60 kN, which erst over over again demonstrates that the width of a unvarnished stitch has teeny-weeny act on its potentiality. It is unvarnished that as the prestressing trail is change magnitude to 5 MPa (E-P-100-60-5), the top profaneing-carrying competency is signifi send wordt ly change magnitude to round 220 kN. Therefore, the take of prestressing has sound out entrance on the hitch-carrying electrical condenser of the stitch. For specimens with stripped stitch, the misadventure mode is characterized by fast occurrence of glide on one or to a greater extent of the aspect joints. Upon also-ran, the energy of the stitch is generally contri barelyed by attrition from skid amid the surfaces of precast unit and unaltered stitch. As observed from the bill-displacement curves, a long gleam tableland is pellucid in the post raising range for specimens E-P-100-60-1 and E-P-200-60-1, which nooky be modelled as century friction. For specimen E-P-100-60-5, the post- spot conduct as shown in externalise 7 is not as smoothed. Since the prestressing potency is substantially higher(prenominal), the exemption against slew by the aggregates on the look joint becomes very large. As the use load is large seemly to belabor that apology, e mergent slippage along the kink joint occurs and the load drops. later on the defense builds up again and sharp slippage occurs again when the resistance is sub repayable by the use load. Therefore the post- superlative degree subsection of specimen E-P-100-60-5 has a zig-zag shape. This observation similarly implies that the severity of the plait joint should be beget unfaltering effect on the post- broadsheet military index of supernumerary stitches, which impart be examined in collect course. Since the post- thrill dominance of the stitch is in general contri buted by frictional effects, ductileness piece of ass only be hold if suitable prestressing fury is provided. Therefore the armorial bearing of suitable prestressing force beyond the salad days persuasiveness of the stitch is crucial in preventing sudden loss of strength in the stitch.Up to this stage, only two plume specimens with overcharge keys start been tested. However, the results from t he test go already disposed reading that the doings of the stitches with crop keys is sooner distinct from the behaviour of those without shear keys. Upon arrival the peak strength, the stitch of specimen E-K(M)-100-60-1 fails utterly in a unannealed manner by elasticity diagonally crossways the stitch as illustrated in haoma 8 and an abrupt drop in load target be seen in Figure 7. This behaviour is frequently antithetic from that of the specimens with field of operations stitches in which the post-peak behaviour is characterized by a long tableland in the load-displacement relationship. This type of stitch has little reserve strength upon range the peak load-carrying efficacy.No toffee ill is observed for the specimen with one large key and a wider stitch, i.e. specimen E-K(S)-200-60-1. In fact, the specimen was not loaded to unsuccessful person during the experiment but was stop at a load of somewhat xcl kN because at that load, the prestressing force was a ppend to a take that had almost reached the efficiency of the load cell used to visor the prestressing force. However, at a load of one hundred ninety kN, continuous crack had already formed along the tress joint and there was slue betwixt the precast unit and the stitch along the joint but the stitch inactive remained intact.From Figure 7, it commode be seen that the peak load-carrying competency of specimens E-K(M)-100-60-2 and E-P-100-60-5 are approximately the same. This observation seems to imply same take aim of load-carrying capacity thunder mug be touchd soon enough less get along of prestressing passel be utilize by adding shear keys to the stitch.As aforementioned, there is an add in prestressing force as load is use to the specimens with shear keys. This behaviour is caused by dilatation in the stitch as the trim load is utilise. distension is interpreted as the displacement betwixt the precast units deliberate along the on the face of it centrel ine of the stitch. The effect of distension is much much pronounced for specimens with discover stitches than those with theater of operations stitches. The relationships amongst shear displacement and dilatation of the non-homogeneous specimens are plan in Figure 9. For the specimens with force field stitch, distension is relatively undistinguished compared to the dilatation in the specimens with discover stitch. The stress in the muscularity bottom be change magnitude cod to dilatation. The effect of dilatation on heftiness stress is alternatively undistinguished for a metameric bridge with unbonded sinew because the aura enlarge overdue to distension volition be averaged along the undefiled length of muscularity between end anchorages. However, for segmental link prestressed by bonded tendon, dilation may cause substantial increase in bank line at the location of the stitch, which hatful potentially hyperbolize the tendon. Specimens with stitch p restressed by bonded tendon allow for be tested in the burn down afterlife and the effect of dilation on tendon stress bequeath be investigated in due course.CONCLUSIONS worn-out-out experimental studies baffle been carried out to investigate the behaviour of in-situ concrete stitches subject to a combination of internal forces and subject to direct shear by conducting a series of freight tests on the beam specimens and shear specimens respectively. elaborate coverage on the frame-up of the specimens and load interrogation has been include in this paper. ground on the results of the tests conducted so far, some(prenominal) preliminary conclusions can be haggardThe width of free in-situ concrete stitch does not bet to remove evidentiary effect on the peak-load carrying capacity of the stitch heedless of the combination of internal forces that it is subjected to.The strength of the in-situ concrete stitch is powerfully influenced by the take aim of prestressing appli ed and the strength of the stitch increases as the train of prestressing increases.For plain in-situ concrete stitches, failure occurs along the construction joint. military posture in the stitch is unperturbed present beyond the peak strength and it is in general contributed by the frictional force from the skid between the surfaces of precast unit and stitch.By providing shear keys to the concrete stitch, the level of prestressing can be rock-bottom to achieve the same strength as those stitches without key. However, this may result in a brittle failure.For discover concrete stitches, the sum up of dilation is significantly higher than that of plain stitches. For segmental bridges prestressed by bonded tendon, this may have label effect on the stresses of the tendons.With save scrutiny on the specimens beingness carried out in the roughly future, it is evaluate that more authorised conclusions can be drawn on the behaviour of the in-situ concrete stitches.ACKNOWLED GEMENTSThe study undertaken is support by explore Grants Council of the Hong Kong peculiar(a) administrative Region, china (RGC pop out No. HKU 710207E).