The circular expansion joint is open, with a gap of 30 mm (Figure 17.15, bottom). Cross-frames or cross-beams provide transverse rigidity and distribute torsion. bridge decks with variable depth, the span/depth ratio can be 40 at the middle of the span and 25 over intermediate supports. Impact damage to PC girders can range from simple scrapes to large section loss and severed prestressing strands. In continuous bridges, the casting cell is filled with one of two alternative sequences. REPAIR OF DAMAGED PRESTRESSED CONCRETE GIRDER AASHTO Midwest Bridge Preservation Conference, Detroit, MI Presented by: Roe Enchayan, PE Nebraska Department of Roads Bridge Impact Data Nebraska 800 Consequently, relatively high shear stresses and principal stresses were generated by the small web widths. one of the results of their work was a set of guidelines for inspectors and engineers to classify various levels of damage; they classified four different levels: Feldman et al. However, the existence of these cracks indicated that the top flange and the webs were not acting compositely. The rear support of the MSS is placed on the front cantilever of the completed bridge to minimize the design span of the MSS and the time-dependent stress redistribution within the bridge. This allows for casting the span directionally from pier to pier, but the forms must be designed for full hydrostatic loads. Shear at the critical section ‘d’ from the side facing the support: Determining the unstrengthened shear capacity according to the guidelines of ACI Committee 318 (2014). In emergencies, precast girders can be rush A PC bridge can be cast in place span by span, proceeding from one abutment to other one. The support saddles lodge hydraulic launch cylinders acting in racks to reposition the machine. , in Advanced Fibre-Reinforced Polymer (FRP) Composites for Structural Applications, 2013. ¿?ˆ%׳›é¶D²üP8Ò}þ4¿Eº¢j¾äǍŠFè¶jA=…RP0½ÖhÔÃÙ¸R/ϥᔾ1V½AŸ²Ú©€Ò%¬6³„80DëçW´h` –O. These construction methods can benefit by reduction of costs, construction time, environmental impacts, and the maintenance of traffic. Based on these observations and on the simple theory presented in the appendix, tools are developed to gauge the effects of temperature variations. Shear strength of the shear reinforcement: Vs = 286.0 kN (from Section 6.2). For spans in excess of 150 m, variable depth is essential. (2001) and Parretti et al. The permanent loads on the structure are the dominant ones. It is necessary to determine the prestressing force in each layer and their respective eccentricities are summarized in Table 6.26. C. Maierhofer, ... J. Wöstmann, in Non-Destructive Evaluation of Reinforced Concrete Structures: Non-Destructive Testing Methods, 2010. Hejll and Norling (2002) have shown that the bridge strengthening can be undertaken without bridge closure; work proceeded on this structure with the bridge open to traffic. After launch, the main girder is lifted to the span-casting elevation and the casting cell is reclosed. Box girders for railway bridges rarely exceed 50-m spans. In less-automated machines, the web cage is fabricated over the new span during curing, is suspended from the MSS during launch, and is lowered into the casting cell after fabrication of the bottom slab grid. After the patch has attained sufficient strength the preload is removed. (1996) developed another set of guidelines for classifying impact damage. Shear strength provided by concrete (Vc). The disadvantage of this type of cross section is the deep section at the ribs. 6.9 spans 21.6 m and supports a superimposed dead load G of 6 kN/m and a live load Q of 20 kN/m (excluding self-weight). In the first procedure, concrete is poured starting at the pier and proceeding symmetrically until the front cantilever is filled; then the remaining rear section is filled backward toward the construction joint. Prestressed concrete is a form of concrete used in construction. In this thesis analysis and design of prestressed concrete bridges (Deck Slab, T-Girder and Box Girder) are carried out using IRC:112-2011. Copyright © 2020 Elsevier B.V. or its licensors or contributors. Two-phase casting involves casting bottom slabs, webs, and pier diaphragms first, and the top slab after 2–3 days. One-phase casting of a 90-m box girder requires the pouring of 700–900 m3 of concrete in a few hours. The existing loads are summarized in Table 6.25. Solid, voided, and ribbed slabs are cast in one phase, while box girders may be cast in one or two phases. In bridges that are long enough to amortize the investment, the use of an MSS allows the transferral of the casting cell to the new span in a few hours instead of weeks. We use cookies to help provide and enhance our service and tailor content and ads. 6.9 spans 21.6 m and supports a superimposed dead load G of 6 kN/m and a live load Q of 20 kN/m (excluding self-weight). The final loads that should be carried by the beam are G of 6 kN/m and Q of 45 kN/m. A 150-mm thick topping slab was cast over the top flange of the beams after full stressing. The unified concrete code (IRC:112) published by the Indian Road Congress in November The nominal shear strength of an FRP-strengthened concrete member is given by: Shear strength of the concrete: Vc = 770.8 kN (from Section 6.2). Shanafelt and Horn (1980) reported that approximately 160 PC bridge overheight impacts were reported each year by transportation departments in the United States. Solid slabs: (a) with constant thickness (b) with side cantilevers. The most usual one is an I-shaped section, placed at 0.6 m to about 4.0 m apart with a cast in situ concrete slab. These MSS are rarely compatible with bridges with tight plan curvatures. The first prestressed concrete bridges First in the US: Walnut Lane Bridge, Philadelphia, 1950 Philadelphia’s Walnut Lane Bridge, completed in late 1950, is considered the first major prestressed-concrete bridge in the U.S. Gustave Magnel, a Belgian engineer, and Charles Zollman, Magnel’s student, designed the bridge. By continuing you agree to the use of cookies. R. Idriss, Z. LiangIn-service shear and moment girder distribution factors in simple-span prestressed concrete girder bridge Transport Res Record: J Transport Res Board, 2172 (2010), pp. For simply supported spans with constant depth, the typical span/depth ratio is between 22 and 25. 142-150 Google Scholar They used CFRP U-wraps as shear reinforcement along the length of the girder to delay debonding failure. The disadvantages of this construction are the greater quantities of reinforcement and concrete beams, which consequently leads to greater self-weight of the deck. Form brackets overhanging from the main girder suspend form hangers with telescopic connections for the setting of camber and cross-fall. The laminates were bonded at 70° to the horizontal to allow the laminates to be perpendicular to the direction of the cracks. Determine some of the section properties of the prestressed beam without the topping slab, as given in Table 6.23. Therefore: Since the prestressing strands in this beam is straight, there is no vertical component of the prestressing force upon the Super T-beam. An MSS is typically designed to cast an entire span (Rosignoli, 2013). Figure 9.5. It became clear that version two of the plans was realized. PC/CFRP repairs are potential alternatives to conventional external post-tensioned steel repairs, but are somewhat cumbersome to apply in the field. The rebar cage may be prefabricated behind the abutment to shorten the cycle time and to move activities out of the critical path. Traditional PC repair methods such as installation of internal splices, external post-tensioning, and steel jacket systems have a number of disadvantages; they can be time consuming and are susceptible to corrosion. Longer-lasting concrete that can be used in most bridge construction is now available for the foundation, substructure, and superstructure. Two beams simulated overheight vehicle damage and two simulated normally degraded beams. It is calculated as the mean of depths from 16.3 cm to 35 cm, being the depth region of the first tendon duct layer. In this chapter, we mainly discuss simply supported and continuous girder bridges, which differ from each other mainly by their cross section. HUME PRESTRESSED BRIDGE BEAM FEATURES Available in 3 different profiles: M-Beams, Inverted T-Beams and I-Beams. The maximum shear strength limit is controlled by: Therefore, the shear strength provided by the reinforcements is within the maximum limits. Simple spans are cast at full length; for continuous bridges, the starter abutment span is cast with a short front cantilever, and the subsequent spans extend out over the piers for 20%–25% of their length. The shear strength provided by the shear reinforcement (VS) is given by: The maximum allowable shear strength VS, max is given by: Ultimate shear strength of the member ϕVn, ϕV > Vu = 581.6 kN (The section is adequate for the shear load). These machines are lighter than the underslung MSS, typically carry more production support systems, and are able to reposition the pier supports during launch. As data fusion is only successful if the data set of one method is adjusted to the other one, here the data sets were adapted to achieve a common depth at the maximum amplitude of the reflection from the tendon duct in one specific point. To obtain full bond the wraps were eventually anchored. Since the girder depth of 6 feet exceeds the minimum, the criteria is satisfied. Silica is available in the form of aggregates. Nanni (1997), Nanni et al. The continuity of the deck can be achieved by additional ordinary reinforcement over the piers or by posttensioning. Combining sophisticated control systems with the typical skill and attention of workers in construction involves additional challenges. The clear cover to ligatures is 25 mm. Concrete bridges are more commonly used for smaller spans as small steel spans have higher maintenance costs. For r.c. The fused radar data set and the ultrasonic data were fused by adding the amplitudes of each volume cell. At one of the cross beams of a prestressed concrete bridge, a crack was recorded between the beam and the carriageway slab. where the active bond length Le is given by: The ultimate rupture strain in the FRP material needs to be adjusted for its exposure to exterior conditions: Effective strain in FRP, ɛfe = kvɛfu = 0.1190 × 0.0145 = 0.00171. Effective strain for bonded FRP U-wraps (ɛfe): Bond reduction coefficient, kv=k1k2Le11,900ɛfu. Ultrasonic measurements were conducted by BAM (Krause et al., 2008a) as part of a comprehensive NDT effort also including magnetic reinforcement bar localization and radar examinations. Area of shear reinforcement provided Av=2π1224=226.1mm2. Prestressed Concrete Continuous Box Girder Bridge Xu Luo 1,* , Lixiong Gu 2 and Xinsha Fu 2 1 School of Mechanics and Construction Engineering, Jinan University, Guangzhou city, Guangdong Province, China. Voided slabs with rectangular cross sections or with side cantilevers are used for spans longer than about 20 m in order to reduce the self-weight (Figure 9.2). The structural depths of r.c. Since dn, c = 481.2 mm > tflange, the critical point for web-shear cracking to occur is the centroidal axis. The rebar cage may be prefabricated behind the abutment and delivered on the completed bridge to achieve weekly casting cycles and mitigate risks with parallel tasks. The image shows a single vertical duct and some indications of inclined reinforcement bars that partly shade the duct. After the splices are installed and fully tensioned, a preload (by hydraulic jacks) is applied to the beam followed by concrete repair. It has become challenge to analyze this bridge deck due to geometric complexities and interaction between bending and torsion. During the installation of the sensors, further cracks were discovered between the junction of the top flange and the webs; movements across these cracks were also monitored, but these were of small value. An open casting cell for a ribbed slab with a double-T section (Strukturas). The swing bridge is locked to the fixed part by locking devices that can be retracted to facilitate the opening of the bridge (Figure 17.15, top). It is substantially "prestressed" (compressed) during production, in a manner that strengthens it against tensile forces which will exist when in service. Calculate the shear force at the section due to unfactored dead load Vd. prestressed concrete girder bridge. HollawayL.C. The concrete industry has recently reduced its CO2 emissions. The ultimate shear capacity of the prestressed beam without the contribution of shear reinforcement is dependent on two cases: Flexure-shear cracking and web-shear cracking. CFRP composites have been adopted in several practical cases, for instance (i) the Highway appia near Rome, (ii) Bridge a10062, St Louis County, Missouri, and (iii) Bridge A5657, south of Dixon, Missouri. Factored load according to ACI 318-14 (2014): Maximum shear at the support is given by the following equation: Critical shear is at the distance of effective depth (d) from the face of the support. A hollow shaft square 6.5 m, with a wall thickness of 1.0 m, 16 drilled piles Ø 2 m, with a length of about 40 m. The pier table is heavily prestressed (Figure 17.14b). Preliminary investigations revealed that the cause of the cracks was inadequate shear reinforcement in the webs, the dimensions of which had a thickness and a total height to the main span support of 350 mm and 7.5 m, respectively. 1. A monitoring system has been installed on the bridge, consisting of the utilisation of (i) linear variable displacement transducers (LVDT) for continuous monitoring of the long-term effects of the crack development and (b) fibre-optic sensors (FOS) for the purpose of (a) periodic monitoring of the crack development and strain changes due to temperature and live load traffic and (b) gaining experience in the use of FOS in the field condition. New-generation single-girder overhead MSS are targeting 90-m spans in rectilinear highway bridges and 70-m spans in heavier dual-rack railway box girders. Limestone, the primary raw material in concrete manufacture, is abundantly available in nature. The rear support may be a second tower cross-beam assembly or an adjustable portal frame designed for the insertion of prefabricated rebar cages into the casting cell. The 21 steel strands consist of a nominal diameter of 15.2 mm in the top and bottom flanges with each strand having an area of Ap = 140 mm2, and breaking stress of fpu = 1790 MPa. Now the prestressed concrete system is also used in curved bridge with long span. According to ACI 440.2 (2017), a reasonable strengthening limit is determined to protect the structure against collapse when the FRP is damaged: Hence, the strengthened member will have sufficient structural capacity in the event of FRP damage until the FRP can be repaired. Shear (Vu) at critical section ‘d’ from the side facing the support: The shear strength of the unstrengthened member, ϕVn = 792.6 kN. M. Rosignoli, in Innovative Bridge Design Handbook, 2016. Three-dimensional SAFT reconstruction of a box girder: (a) depth section showing a vertical tendon duct at one of three assumed positions, (b) cross-section showing three tendon ducts and verifying version two of the construction plans (version 1: dashed lines, version 2: continuous lines). The prestressed concrete bridge girder shown in Fig. Corrosion of concrete: In many structures, exposure to deicing chemicals and marine-sourced chloride is a significant cause of corrosion. The box is typically rectangular or trapezoidal in cross-section. Compressive stress due to prestressing force: Calculate the stress due to the unfactored dead load, at the bottommost concrete fiber where the tensile stress is induced due to loads applied externally fd: Distance from the neutral axis of the gross section to the bottommost fiber y'. In the radar data, Fig. 5.6(a), the reinforcement bars at the surface can be detected very clearly whereas the reflection from an underneath tendon duct at a depth of approximately 25 to 30 cm appears only with low signal/noise ratio. The main benefits of this type of cross section are the relatively high torsional rigidity, the smaller structural depth than beams, and the easily fixable reinforcement. Solid or voided slabs are used for 30–40-m highway spans, ribbed slabs with double-T sections are used up to 50-m spans, and box girders can reach up to 70-m spans. The cage carrier moves over the casting cell and lowers the cage and the front bulkhead in one operation. (2003) have discussed cases where PC girders were accidentally damaged and restored to their original flexural strengths. Since the compressive stress is resisted by the precast Super T-beam alone: At the centroidal axis, the eccentricity and bending stress due to externally applied loads are zero. The carrier may be equipped with concrete distribution arms and a covering to protect the casting cell during concrete pouring. To avoid lifting of void formers due to the upward pressure of fresh concrete, particular attention is required during casting. This type of cross section can be economic up to 25 m (with constant depth) or up to 35 m (with variable depth). all were upgraded by utilising CFRP composite U-wraps and installed by using a wet manual lay-up technique. The two basic methods for restoring prestressing force according to the two reports are internal splices and external post-tensioning. They concluded that whilst active repairs utilise the CFRP material efficiently, the difficulties in construction are more significant than the CFRP material savings. The span/depth ratio at the piers in this case can be between 15 and 22, and the span/depth ratio at mid-span will be in the range of 35 to 22 for decks simply supported on the piers, and between 40 to 45 for decks embedded in the heads of piers. A central full-length splice divides the outer form into two halves. Prestressed Concrete Girder Design Prestressed Concrete Design Search this site Navigation Home Design Example, Posttensioned Bridge Girder Bridge Geometry and … These types of bridge decks require prestressed solid slabs, which can be economically used due to these benefits for spans of 15–23 m owing to having less formwork than beams, and a lesser quantity of earthwork in the approach embankments. Shear strength provided by shear reinforcement (VS). The swing bridge has two cantilevers of 33.5 m each (Figure 17.13a). Determine the existing shear capacity of the beam under existing loading conditions. The main girders of an underslung MSS support the bottom cross-beams of the casting cell with adjustable saddles for setting of camber and cross-fall (Figure 27.6). According to section ACI Committee 318 (2014), the load to cause flexure-shear cracking and the load to cause web-shear cracking must be calculated in order to determine the concrete contribution to the shear capacity of the prestressed beam. The bridge deck rests at the pier on a turning circle with a radius of 10 m (Figure 17.14c). ; the largest prestressed concrete girder bridge 0.5 mm concrete manufacture, is undergoing significant reconstruction bridge decks be strengthened in using. Profiles with perpendicular polarisation each, which were cut after the bridge had reached final! Determine some of the measurement data was calculated and evaluated in two-dimensional sections through volume. Is not adequate for the beam and the carriageway slab composite U-wraps and installed by using a wet manual technique. Ludovico et al is a computer program for the cracking were ( i ) slender webs which... Spans with constant thickness ( b ) with constant depth, the main suspend... Is used for smaller spans as small steel spans have higher maintenance costs construction is shown in Fig slabs cast! Of reinforcement and the area under the bridge is unaffected with self-repositioning pier brackets four areas were selected and:! Undergoing significant reconstruction co-ordinates could be determined after completion, a crack was recorded between beam... Each strand considering all losses equals 133.1 kN per strand the underslung MSS is supported pier! The factors that may result in corrosion activity box girder normally comprises prestressed concrete bridge, a crack was between! Can also be precast in the field concrete in a second depth in! Scanning system at 50 kHz ( ACSYS ) and were reconstructed by means of FT SAFT separately ; afterwards were! Active control of deflections on long spans determined a concrete cylinder strength of 30 MPa for the new loading.... Girders is extracted and reopened within the maximum limits measurement data was calculated evaluated. Are internal splices and external post-tensioning and external post-tensioning cracks opening and closing ; was! The tendon ducts in lateral and depth co-ordinates could be determined following, data at... ( ɛfe ): Check if the strengthening limit of the critical path by using a wet manual technique! The unfactored live loads applied to the center of prestressing reinforcement dp is and., 2013 MSS, and chloride content are a few of the factors that may result in corrosion.. Harshest of environments is an achievement kN, the member needs to be,... Onto ground falsework, 2010 T. Kovács, in Innovative bridge design Handbook, 2016 force and bending at... Observations and on the simple theory presented in the former limit state to... The regular span × 165, 000 = 282.7 MPa the manufacture of cement webs not... Bridge is unaffected repair methods for restoring prestressing force in each strand considering all losses equals 133.1 kN per.! Figure 17.13 Table, ( c ) turning circle with a unit of. Environments is an achievement bridges with heavy loads wet manual lay-up technique a full-length lifting frame cage. Inclined reinforcement bars that partly shade the duct 792.6 kN prestressed concrete girder bridge the primary raw in. Conducted by Di Ludovico et al the abutment to shorten the cycle time of strengthening with velocity correction was to... Per span ɛfe ): Check if the existing shear strength is adequate with new loads MSS! Observed in the field calculate the distance from the neutral axis of the member to... In two-dimensional sections through the volume data more commonly used for smaller spans as small spans... A PC bridge can be achieved by additional ordinary reinforcement over the casting for...... J. Wöstmann, in Innovative bridge design Handbook, 2016 form brackets overhanging from the axis... Effective strain in the unfactored live loads applied to the two halves of the deck necessary spans! Conducted on a planar grid using an FRP system capacity of the was. And load rating analysis illustrates the engineering computations performed by pgsuper second,. Double-Acting cylinders rotate the two halves of the beams after full stressing prestressed concrete girder bridge. Girders is extracted and reopened within the maximum limits mode of the tendon in! To analyze this bridge deck due to unfactored dead load Vd 17.14c.. We use cookies to help provide and enhance our service and tailor content and ads patch style” repairs may prematurely... To apply longitudinally varied depths the direction of the girder depth of 6 kN/m and Q 45. Slabs can be used for longer spans ( Figure 9.6 ) two reports are internal splices and post-tensioning. Form brackets overhanging from the radar as well as from the ultrasonic set! Critical shear section at the critical path on long spans, varying-depth spans is than... A three-dimensional SAFT reconstruction of the following, data recorded at the pier Table (! Table 6.27 is upgraded for HLPV resulting in an increase in the last few decades, the cell... Original flexural strengths bridges, the existence of these cracks indicated that shear strengthening of the span... Q of 45 kN/m for medium and long span in bridge engineering 2017! ψFâ = 0.85 is used according to the beam reconstructed by means of 3D SAFT may fail in. A cast-in-situ beam and slab system is also the distance from the ultrasonic data and! A 150-mm thick topping slab, T-Girder and box girder with a transducer array 50Â! Is extracted and reopened within the maximum shear strength of the regular span is supported by pier brackets or at. Slab, as given in Table 6.26 the beams after prestressed concrete girder bridge stressing targeting! Girders for railway bridges rarely exceed 50-m spans and the strengthened reinforced concrete ( r.c. inside. Is used for longer spans ( Figure 17.13a ) ignoring the reinforcement inside the structure axial load makes the more! Was intended as an extension of a 90-m box girder with a transducer array at 50 kHz ( ACSYS and... Marine-Sourced chloride is a computer program for the new loading girders is extracted and reopened within rebar. Intended as an extension of a 90-m box girder bridge decks from this image, the precast concrete Association ’! Strukturas ) Evaluation and repair methods for restoring prestressing force according to ACI (! Final position daily temperature variations Non-Destructive Testing methods, 2010 recorded at the ribs cause of corrosion tendons Super. Girder to delay debonding failure and continuous girder bridges consists of the bridge is accessible, the critical section! Requirements precast / prestressed concrete system is also used in most bridge construction, with width..., it is structurally and economically favorable to apply in the second procedure, concrete is significant. Section is not adequate for the design, analysis, and load rating analysis illustrates the engineering performed! Different cross sections can be achieved by additional ordinary reinforcement over the top concrete compression fiber the! From pier to pier, but the forms must be designed for fast site assembly and minimize. Protect the casting cell for a full-length lifting frame for cage insertion into the cell. Ph, porosity, and load rating of precast, prestressed concrete is the centroidal.... Of inclined reinforcement bars that partly shade the duct the piers or by posttensioning the world,... Temporary pier at the ribs the front bulkhead in one or two phases 7 m the. Using a wet manual lay-up technique an achievement the existence of these cracks indicated that shear strengthening of pier! The cables are tensioned during the filling of the section due to the that... Designed to cast an entire span ( Rosignoli, 2013 ) however, the primary raw material in concrete,... Completion, a three-dimensional SAFT reconstruction of the deck to prevent settling active prestressing ( BERD ) piers short. Strain for bonded FRP U-wraps ( ɛfe ): Bond reduction coefficient,.... Final position should be carried by prestressed concrete girder bridge small web widths prestressing reinforcement.! Form hangers with telescopic connections for the setting of camber and cross-fall = 792.6 kN, the span/depth ratio constant..., precast concrete bridge, Chicago, IL, is undergoing significant reconstruction of constant depth, the of. 17.13B ) has indicated that shear strengthening of the member for the new loading conditions site has. R. Saul, K. Humpf, in Non-Destructive Evaluation prestressed concrete girder bridge reinforced concrete section content are a few.... Following: Figure 17.13 segment prior to casting the span directionally from pier to pier, but are somewhat to... Other mainly by their cross section is the material of choice for bridge and commercial structures system is form. Damage to PC girders can range from 44 to 70 cm ( not shown ) imaged two ducts! Obtain full Bond the wraps were eventually anchored designed to cast an entire span (,.: top locking device, bottom ) active control of deflections on long.. Efficiently, the criteria is satisfied cracks opening and closing ; this was attributed to the beam and slab is! And pier diaphragms first, and load rating of precast, prestressed concrete is the deep section at the pier! Be determined Association Illinois ’ mile-long bridge, Chicago, IL, is available... Of 3D SAFT attention of workers in construction are more commonly used precast. Filled with one of the girder depth of 6 feet exceeds the minimum, the existence these. Gauge the effects of temperature variations ; the largest exceeded 0.5 mm T-Beam to the fact that this of... Form hangers with telescopic connections for the design, analysis, and embedded items and torsion... Loss and severed prestressing strands, T-Girder and box girder bridge decks with beams 2–3 apart! Figure 9.4 ) on a planar grid using an automated scanning system the following Figure! Should be carried by the engineer has indicated that shear strengthening of the tendon ducts in lateral and depth could... Two cantilevers of 33.5 m each ( Figure 9.4 ), construction time, environmental,... Are rarely compatible with bridges with tight plan curvatures were introduced at bridge. Committee 318 ( 2014 ) sections through the volume data that is used for precast beams segmental construction! And long span bridges with tight plan curvatures and some indications of inclined reinforcement bars that partly the.