Segmental Post-tensioned Concrete Bridges

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S E G M E N T A L P O S T - T E N S I O N E D C O N C R E T E B R I D G E S

By Dumitru Cecan Student Number: 200659800, Civil Engineering Erasmus

Architectural Engineering Studies, CIVE 5976M November 2011

1. INTRODUCTION

Prestressed concrete segmental bridge is one of the most widely used methods for the construction of large bridges around the world. As its name implies, a segmental post-tensioned concrete bridge is built consecutively in short segments either cast-in-place or precast concrete. This category of bridge combines the concepts of prestressing, box girder design, and generally the cantilever method for construction. Muller and Podolny (1982, p.vii) emphasised that this construction ‘arose from a need to overcome construction difficulties in spanning deep valleys and river crossing without the use of conventional falsework, which in some instances may be impractical, economically prohibitive, or detrimental to environment and ecology.’ However, nowadays with the development of public railway transport systems, this type of structure is employed amply in highly urbanized cities for long elevated railway lanes like metro or rail shuttles (see figure 1.1). The relatively short construction time, the adaptability to almost any conceivable site condition, reduced urban environment and waste site pollution are the key advantages of this method.

Figure 1.1: Bangkok Mass Transit System, (Egis, Jean Muller International)

1.1 Evolution of Segmental Construction The idea to use precast segmental construction for prestressed concrete bridges was developed just after the World War II in Europe. ‘The urgent need to reconstruct bombed-out bridges quickly and efficiently, and with steel production capacity debilitated by war efforts, European designers and builders turned out to prestressed concrete.’ (Libby and Denney Pate, 1976)

Eugene Freyssinet, in 1945 to 1948 was the first to use precast segmental construction for the pre-stressed bridge over the Marne River. Shortly thereafter, German engineers applied cast-in-place segmental pre-stressed construction in a balanced cantilever fashion of construction. Muller and Podolny (1982, p.11) highlights that ‘more than 300 such structures, with spans in excess of 250 ft (76 m), were constructed between 1950 and 1965 in Europe. Since then the concept has spread throughout the world.’

The next innovation was the introduction of a launching gantry of which the Oleron Viaduct in France, see figure 1.1.1, is a good example.

Figure 1.1.1: Oleron Viaduct (France) built by incremental launching method; fr.structurae.de

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2. DESCRIPTION OF SEGMENTAL CONCRETE BRIDGES

Segmental concrete bridge constructions are completely based on prestressed concrete considerations. The understanding of the morphology of this type of structure and its behaviour indicates knowledge about the post-tensioned concrete.

2.1 Overview of Post-tensioned Concrete The tensile strength of concrete is only about 10% of its compressive strength. By placing the concrete members in compression the mechanical efficiency of concrete members increases considerably as all the material sections resist loads. Therefore, compressive forces are induced in concrete structure by installing cables, which are stressed by proprietary jacks reacting against the concrete. The cables are then locked to the concrete by anchors and consequently provide compressive force. The total compression of the concrete must be below a reasonable value in order to avoid any risk of longitudinal cracking. A prestressed concrete structure is subjected to a system of artificially created effort to generate permanent constraints which composed with the stresses due to external loads, provide total stress between the limits concrete can withstand indefinitely and safely. (SETRA, 2003) ‘The self-weight deflections of the member may be cancelled, and, in continuous beams, manipulation of the prestress secondary moments allows a degree of optimisation of the ratio of support and span moments. Prestressing also frequently allows a reduction in the depth and in the cross-section area of beams and a reduction in the thickness of slabs as compared with reinforced concrete.’ (Benaim, 2008)

There are two categories of post-tension: a) internal is when the prestressed cables are implanted in steel ducts that are embedded in the formwork before the concrete is cast as shown in the figure 2.1.1.

In order to ensure the corrosion protection cement grout is injected in the ducts;

Figure 2.1.2.1 : Example of intern post-tension montage ; Cimbéton

b) external method means that the ducts are generally high-density polyethylene and placed outside the concrete. The steel cables inside the ducts are protected by injecting cement grout or soft produce like wax or grease. The major difference between the two methods is that in the first case the steel pipes are in contact with the concrete throughout the cable path and apply a reactive force at each point. In regard to external method of applying prestressing, the path of cables is plotted using deflection cross-beams. In this case, the prestressed cables apply a reactive force only at the deflection cross-beams as shown in the figure 2.1.2.

Figure 2.1.2.2: Extern post-tensioned cables in the core of a box-girder bridge; SETRA

Both methods are used in segmental post-tensioned concrete constructions. Usually, for spans below 35 meters only internal prestressing is used, while for longer spans a combination of internal and external prestressing is fairly common.

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2.2 Post-Tensioning Technology Many proprietary post-tensioning systems are available but the most common systems for bridge construction are multiple strand systems for permanent post-tensioning tendons and bar systems for both temporary and permanent use. Key features of the multiple strand system and bar system are illustrated in figures 2.2.1 - 2.2.4 (U.S Departament of Transportation, Federal Highway Administration, 2004)

Figure 2.2.1 : Typical Post-Tensioning Anchorage Hardware for Strand Tendons. (U.S Departament of Transportation, Federal Highway Administration, 2004)

Figure 2.2.2: Example of Post-Tensioning operations for concrete slab deck bridge by multiple strand system. Paul. Tensa M 4800 kN [online] Available from: www.paul.eu

Figure 2.2.3: Typical Post-Tensioned Bar System Hardware. (U.S Departament of Transportation, Federal Highway Administration, 2004)

Figure 2.2.4: Example of Post-Tensioning System using Bars. DYWIDAG. DYWIDAG Bars. [online] Available from: www.dsiamerica.com

2.3 Various Type of Structure Segmental post-tensioned bridge construction is applied to single span bridges as well multi spans bridges. In the case of continuous multi span bridge, the path of cables is of paramount importance and the designer should have extensive knowledge and experience about prestressing in multi-spans bridges. A multitude of cross deck sections and methods of construction are used in the segmental post-tensioned concrete bridges, which makes this field very broad and complex.

2.3.1 Nature of deck Generally, there are two categories of segmental post-tensioned concrete bridges according to the type of cross-section:

Segmental Post-tensioned Concrete Slab Deck Bridges; Segmental Box-Girder Bridges.

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2.3.2 Segmental post-tensioned concrete slab deck bridges

The post-tensioned prestressed slab deck bridges constitute widely applied samples of road bridges. In the case of road loading, a span length of 50 meters could be reached while an economical span of slab deck bridges is about 30 meters.

There are three main types of slab deck:

Solid Slab (see figure 2.3.2.1)– is the most common solution for short spans;

Figure 2.3.2.1 : Cross section of solid slab deck bridge; Roulex45. 2008. Pont-Dalle-BA [online] Available from: commons.wikimedia.org

Ribbed Slab (see figure 2.3.2.2);

Figure 2.3.2.2: Cross section of ribbed slab deck bridge; Design Agency Egis Jean Muller International Lyon (France). 2011. Preliminary Study Rennes Metro Project

Hollow Core Slab (see figure 2.3.2.3).

Figure 2.3.2.3: Cross section of Hollow core slab deck bridge; Design Agency Egis Jean Muller International Lyon (France). 2011. Preliminary Study Rennes Metro Project

The common point between these three decks is that their height is generally below one meter and the internal method of prestressing is always applied.

2.3.3 Segmental post-tensioned concrete box-girder bridges

If the conditions, such as topographic, loading etc., require longer or much longer spans, a box-girder bridge is commonly used. Typical cross sections of concrete

box-girder bridges commonly used are shown in figures 2.3.3.1 - 2.3.3.3:

Figure 2.3.3.1: Cross section of a simple box girder. (SETRA, 2003)

Figure 2.3.3.2: Cross section of a braced box-girder. (SETRA, 2003)

Figure 2.3.3.3: Cross section of two sections transversely joined box-girder. (SETRA, 2003)

There are two categories of box-girder bridges according to the construction technique:

Incremental Launching or Push-out Construction – common span length is comprised between 35 and 65 meters;

Balanced Cantilever Construction – the preferred field of application of this type of structure built by successive cantilevers is between 80 and 150 meters. But this technique can be used without major problems up to 200 meters for common widths. Beyond this value, the quantities of material increases rapidly which limits the competitiveness of the method. The world record of the balanced cantilever bridge is held by the Stolma

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Bridge, Norway with a 301 meters length span. (SETRA, 2003)

‘The structural simplicity of the box-girder bridge, particularly in continuous structures of medium to long spans, has been well demonstrated. The efficiency of the cross section for positive and negative longitudinal bending moments as well as for torsional moments is apparent even to

the casual observer.’ (Libby and Perkins. 1976, p.57)

The box-girder bridges could be prestressed by internal method for medium span lengths, as well by external method for long spans or a combination of two. Figure 2.3.3.4 offers a perspective showing various features of a typical precast cantilever segment, tendon locations and anchors.

3. ADVANTAGES, DISADVANTAGES and COSTS

As mentioned before, the segmental prestressed concrete bridges quickly became widespread. Its popularity was and is still due to its numerous advantages. In reference to its disadvantages, it took several decades for engineers to discover its problems related to its sustainability.

3.1 Advantages Quality Control. Precasting under plant control conditions offers more favourable conditions for forming, placement of reinforcement and placing and curing of concrete; Speed of Construction. This advantage makes the segmental method very useful for long viaducts;

Minimization of Falsework – precast concrete girders may be erected without falsework over existing highways, railroads, waterways and any other construction where erection of falsework is impractical. Longer spans may be erected by the progressive cantilever method or cantilever-suspended span scheme; Economy. Labour and equipment may be utilized with maximum efficiency and take advantage of mechanization in manufacture; Control of Creep and Shrinkage. Creep and shrinkage may be greatly reduced by using higher strength concretes with a lower water-cement ratio.

(ACI Committee 343, 1981) High Structural Efficiency (for box-girder bridges). Thus, the prestress required to carry out the dead and live loads is reduced.

Figure 2.3.4.4 : Typical Balanced Cantilever Segment, also called voussoir. (U.S Departament of Transportation, Federal Highway Administration, 2004)

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Great Torsional Strength (for box-girder bridges). This aspect allows greater curvatures in plan and eccentric live loads.

3.2 Disadvantages High Dead Weight. This issue leads to greater support and foundations; Dynamic Behaviour. The designer should take special precautions when the bridge is located in a seismic zone; Aesthetical Considerations. Usually, the box-girder is thick, which can cause aesthetic problems at some sites. The division into small pieces and multiple phases of concrete also promotes differences in colour between two successive segments.

(SETRA, 2003) Security Considerations. The post-tension is a complicated and high risked procedure. Special precautions need to be taken during tensioning tendons. Sustainability Considerations. ‘Some of the earliest bridges have exhibited evidence of serious defects, particularily corrosion of the prestressing steel. Indeed a few have actually collapsed in service, sometimes with loss of life, thereby making this type of construction a subject of concern around the world.’ (Highways Agency; SETRA; LCPC, 1999)

3.3 Costs Comparisons Benaim (2008) states that ‘typical installed costs in the UK for reinforcement and prestressing steel are £700 per ton and £2,000 per ton respectively, a ratio of approximately three, whereas the ratio of the ultimate strengths is approximately four. When the weight of steel is governed by the ULS (Ultimate Limit State), the prestressed version would show a saving of some 30 per cent. More than 50 per cent of the cost of prestressing consists of site labour, of which a large part is due to the operations of stressing and then grouting the tendons.’

4. CONSTRUCTION TECHNOLOGIES

Segmental construction offers another advantage in the choice of numerous methods of construction that can be adapted for site constraints. Prestressed concrete segmental bridges may be categorized by its method of construction: such as balanced cantilever, span-by-span, progressive placement or incremental launching.

4.1 Segmental Balanced Cantilever Segmental balanced cantilever construction involves the symmetrical erection of either cast-in-place or precast segments about a supporting pier. Cantilever longitudinal tendons are placed in the top slab as the construction advances in order to resist to negative bending moments as illustrated in figure 5.2.2.2. The cast-in-place construction ‘becomes economical for bridges with a main span of 60 m and above’. (Benaim, 2008) An example of cast-in-place balanced cantilever construction is shown in figure 4.1.1. Form travellers support the concrete until it has reached a satisfactory strength for post-tensioning. Therefore, the cast-in-place method requires more construction time than precast technique.

Figure 4.1.1 : Cast-in-Place Segmental Construction using Form Travelers (U.S Departament of Transportation, Federal Highway Administration, 2004)

Regarding precast segmental construction; it is ‘adaptable to spans from 25 m to about 150 m, and can cope with virtually any

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succession of span lengths and deck alignments’. (Benaim, 2008) Precast successive segments (see figure 4.2.1) are built cantilevered over the one preceding it. When a segment is lifted into position, ‘adjoining match-cast faces are coated with epoxy and temporary post-tensioning bars are installed and stressed to attach the segment to the cantilever. Typically, after a new, balancing segment, is in place on each end of the cantilever, post-tensioning tendons are installed and stressed from one segment on one end of the cantilever to its counter-part on the other.’ (U.S Departament of Transportation, Federal Highway Administration, 2004) Thus constituting a self-supporting console that is used to support the sequence of operations.

There are two typical methods of placing precast segments in balanced cantilever, as shown if figure 4.1.2; using cranes if the site conditions allow it, or using an overhead launching gantry. When all segments have been erected, permanent continuity post-tensioning tendons are installed and stressed through the closure to make the cantilevers continuous.

Figure 4.1.2: Precast Segmental Balanced Cantilever Construction. (U.S Departament of Transportation, Federal Highway Administration, 2004)

4.2 Span-by-Span Construction Span-by-span construction involves the erection of all segments of a span on a temporary support system as shown in the figure 4.2.1. In the next step, tendons are

installed and stressed from the pier segment at one end of the span to that at the other. The tendons from one span overlap with the tendons of the next in the top of the pier segement in order to achieve continuity with the next span. (U.S Departament of Transportation, Federal Highway Administration, 2004)

As in the balanced cantilever method of construction, the concrete can be cast-in-place or precast in a plant and transported to the site. The cast-in-place construction is applicable to decks with spans that generally lie between 20m and 45m, while the precast method is well adapted to long viaducts with spans that generally do not exceed 50m. (Benaim, 2008)

The support system, consisting of steel superstructures, which is moved from the completed portion of the structure to the next span. Muller and Podolny (1982) states that typical construction time for a 100ft (30m) span superstructure using precast method is five to eight working days.

Figure 4.2.1: Span-by-Span Construction. (U.S Departament of Transportation, Federal Highway Administration, 2004)

4.3 Progressive Placement Construction Progressive placement derives from the balanced cantilever method. In progressive placement the precast segments are placed from one end of the structure to the other in successive cantilevers so the

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construction starts at one end proceeds continuously to the other end. Segments are transported over the deck, where they are positioned by a swivel crane that proceeds from one segment to the next. Only one-third of the span from the pier may be erected by the free cantilever method, the segments being held in position by exterior temporary ties and final prestressing tendons. For the remaining two-thirds of the span, external ties and stays are used to support the cantilever span. (Muller and Podolny, 1982) Figure 4.3.1 shows typical phases for progressive placement construction.

Figure 4.3.1: Progressive Placement Construction. (Muller, Podolny, 1982)

4.4 Incremental launching Incremental launching bridge construction involves the erection of the deck in segments either cast-in-place or precast ‘behind one of the abutments and pushed or pulled forwards out of the mould by hydraulic jacks’. (Benaim, 2008) In order to reduce the bending moments in the cantilever part of the bridge while launching, the deck is equipped with a steel launching nose. Benaim (2008) suggests that this method is only used for box-girders bridges with spans between 30m and 55m. ‘Rates of construction are typically one 15m – 25m segments per

week’. (Benaim, 2008). The figure 4.4.1 illustrates the incremental launching process.

Figure 4.4.1 : Incremental launching sequence. (Muller and Podolny. 1982)

5. PRELIMINARY DESIGN

‘Engineering design is thus driven by the simultaneous consideration of rationality, economy and appearance.’ (Benaim, 2008) To achieve the best choice, both on the technical, economic and aesthetic, the designer should know the range of possible solutions with their constraints, their limitations and costs. In the first step of bridge design, the items to be finalized as early as practical are: a) typical section and alignment (vertical and horizontal); b) span length composition (same or varying); c) structure type and depth-span ratios-including type of materials; d) other major considerations.(ACI Committee 343, 1981)

5.1 Span Length Considerations The first point in the design process of a bridge determines the maximum distance to span as it could be the key factor choosing the type of the structure. The total or the maximum span length is established by the typical traffic under the structure. The figure 5.1.1 summarizes the practicable span lengths of different segmental post-tensioned concrete bridges. (Calgaro, Bernard-Gely; Muller, Podolny 1982)

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There are environments where the span length is not dictated by the obstacles to be crossed, in this case, the choice of the most economical span is not straightforward, as each deck type and method of construction has its own internal logic. (Benaim, 2008) Choosing the most economical span implies a global cost analysis, ‘one must consider the costs of both the deck and the substructure.’ Benaim (2008, p.249) emphasised that the choice of most economical span ‘it is very much a matter of experience and intuition’. Benaim (2008) states that for a viaduct that is crossing reasonably level ground with unexceptional foundation conditions, the most economical span length for a box section deck (box-girder deck) of constant depth it is likely to lie between 30 m and 45 m.

5.2 Structure Type, Depth-Span Ratio and Other Major Considerations

In this section the general characteristics of the common types of segmental post-tensioned concrete bridges, especially depth-span ratios, are indicated for reference in preliminary studies. Benaim (2008, p.234) highlights that ‘the dimensions may be the result of analysis, or governed by considerations of buildability; they should never be the result of preconceived ideas.’

5.2.1 Segmental post-tensioned concrete slab deck bridge preliminary design The depth-span ratios for segmental post-tensioned concrete slab deck bridges, for highway usage are summarized in the following table (Table 5.2.1.1).

Table 5.2.1.1: Elements of preliminary design for post-tensioned concrete slab deck bridges for highway usage (Calgaro and Bernard-Gely):

Nature of deck Span composition Depth-span

ratio

Solid Slab Deck

Single span deck 1/25 Two-span deck 1/28

Three-span deck, or more

1/33 for central spans

1/38 for side spans

Ribbed Slab or Hollow Core Slab

Single span deck 1/22 Two-span deck of constant thickness 1/25

Two-span deck of variable thickness

1/20 at supports

1/30 at middle span

Three-span deck, or more, of constant thickness

1/30

Three-span deck, or more, of variable thickness

1/24 at supports

1/42 at middle span

Benaim (2008) suggests ‘when the maximum bending stress on the bottom fibre of a solid slab deck is below the allowable limit, it is possible to remove material without increasing the depth of the deck, leaving a shallow ribbed slab.’

Benaim (2008) also suggests that ‘the principal benefits of voided slab are greater deck efficiency and lower weight, leading economies in the quantitiy of prestress, and savings in the foundations.’ On the other hand he insists that the cost of voided slab ‘will increase due to the greater intricacy, and hence to the greater labour required. Also, the quantity of passive reinforcement will be significantly increased, probably exceeding 110 kg/m3 of concrete.’

Figure 5.1.1 : Practical Span Length of Segmental Post-Tensioned Concrete Bridges

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5.2.2 Segmental post-tensioned concrete box-girder bridges preliminary design This section will explain the preliminary aspect of box-girder bridge design built by cantilever method as this method is one of the most used for segmental post-tensioned concrete bridges throughout the world.

Span Lengths Distribution In most common cases, the structures built according to this process consist of equal intermediate length spans and of side spans, which lengths are slightly more than half of that of the intermediate spans, in order to avoid the lifting of the deck under the live loads in the most unfavourable configuration. (Calgaro, Bernard-Gely)

The deck height can be designed as constant or variable. Beyond 70 meters, varying the deck height becomes more economical and, in general, more aesthetic. When the height of the deck is variable and all intermediate span lengths are equal to L, the optimal length of side spans is in the range of 0.58 to 0.60 L. If the height of the deck is constant, the optimal length is rather in the range of 0.68 to 0.70 L. (Calgaro, Bernard-Gely)

If the intermediate span lengths are different and the deck height is variable, which can be the case to cross an elongated obstacle, figure 5.2.2.1 shows the distribution of span lengths following Calgaro and Bernard-Gely.

Figure 5.2.2.1 : Span Lengths Distribution for a Cantilever Variable Height Deck Bridge. (Calgaro, Bernard-Gely)

Post-Tension Tendons Design A cantilevered post-tensioned bridge comprises mainly two kinds of cables: - Cantilever tendons as shown in figure 5.2.2.2, implemented during the construction of the cantilever arm within the top slab ‘usually spaced in a single

layer over each web’ (U.S Departament of Transportation, Federal Highway Administration, 2004) The cantilever tendons are used to allow the construction operations but also to resist the permanent tensile forces in the top fibre due to the negative bending moments at lever of the piers;

Figure 5.2.2.2: Cantilever Tendons. (SETRA) - Continuity Tendons (see figure 5.2.2.3) are placed and then tensioned once those cantilever arms are joined (once the erection of entire span or spans are finished). The structural function of these cables is to provide compressive forces where required. In order to achieve the optimal effectiveness of prestressing, the tendons deviate to the top of the deck, the right of intermediate supports, and to the bottom in the mid-spans as shown in figure 5.2.2.3.

Figure 5.2.2.3 : Continuity Tendons. (SETRA)

In traditional cantilever prestressing, all the tendons are embedded in the concrete, while in the modern cabling, only the cantilever tendons and some internal continuity tendons, as shown in figure 5.2.2.4, are placed inside the concrete. Most continuity tendons are placed outside the concrete as shown in the figure 2.1.2.2.

Figure 5.2.2.4 : Internal Continuity Tendons. (SETRA)

Box-Girder Preliminary Design Calgaro and Bernard-Gely, for a preliminary box-girder cross section design, whose width does not exceed 15 meters, and post-tension tendons design,

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suggest the following principles using the notations from the figure 5.2.2.5:

Figure 5.2.2.5 : Data for the design of a single cell box. (Calgaro, Bernard-Gely)

Hc : deck height at mid-span Hp : deck height at supports

Internal cables

External cables

Span-depth ratio, simply supported deck (L main span)

LHp

=16+0,25 �L

100�

4

LHp

=0,16 L+22-7,5

(L / 50)3

Span-depth ratio, deck embedded into piers at supports (L main span)

LHp

=16+0,25 �L

100�

4

LHp

=0,2 L+25-12,5

(L / 50)3

b = B / 2; e'(cm) ≥ 20 or 25; b'(cm)

7≤ e''(cm) ≤

b'(cm)7

;

es (cm) = b (cm) / 25 ei (cm) (Ø post-tensioned cables ducs diameter)

≥ max [18 cm; 3 Ø; es /3]

at mid span

≥ max [18cm; es/3] at mid span

ea (cm)

26 + L (m) / 5

≥ 36 (12T13) ≥ 44 (12T15) ≥ 59 (19T15)

L (m) / 2,75 + 125 B/L –

12,5

5.3 Typical Reinforcement Ratios Benaim (2008, p.243) states that ‘each type of deck has a typical rate of reinforcement per m3 of concrete.’ He also gives the ‘typical rates of reinforcement for the various prestressed concrete deck types subjected to 45 units of HB loading in accordance with the UK code of practice are as follows:’

Solid slab Ribbed slab Hollow core slab Concrete box-girders;

span < 80 m Concrete box-girders;

span < 80 m

45-60 110 120

150-180

110-130

kg/m3

kg/m3

kg/m3

kg/m3

kg/m3

5.4 Typical Prestress Ratios For decks of constant depth up to 50 m span, the rate of prestress will vary from about 30 kg/m3 to 80 kg/m3, for most projects varying from 35 to 55 kg/m3. Variable depth decks with spans up to about 120 m would be expected to have prestressinng rates of 45 to 55 kg/m3. (Benaim, 2008)

5.5 Post-tensioning - Special Considerations

ACI Committee 343 (1981, p.343R-74) insists that ‘prestressed concrete bridges should be investigated for stresses and deformations for each load that may be critical during construction, stressing, handling, transportation, erection, and the service life of the bridge.’ 5.5.1 Precast concrete system The design of a precast concrete system implies that all deck sections need to be in compression for all types and positions of loading. It means, that any tension is not allowed as there is no continuity between the concrete segments. 5.5.2 Corrosion Protection Highways Agency, SETRA and LCPC (1999) concludes that the corrosion of tendons is a main problem for post-tensioned concrete structures and the failures of corrosion protection can be related to: inadequate protection of the tendons; poor design details; ineffective grouting methods and materials and poor workmanship. It means that the designer should pay special attention to this aspect by considering the replacement of tendons in circumstances in which they need to be changed.

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LIST OF FIGURES and TABLES

Figure 1.1 Bangkok Mass Transit System, (Egis, Jean Muller International) 1 Figure 1.1.1 Oleron Viaduct (France) built by incremental launching method; fr.structurae.de 1 Figure 2.1.2.1 Example of intern post-tension montage ; Cimbéton 2 Figure 2.1.2.2 Extern post-tensioned cables in the core of a box-girder bridge; SETRA 2 Figure 2.2.1 Typical Post-Tensioning Anchorage Hardware for Strand Tendons 3 Figure 2.2.2 Example of Post-Tensioning operations for concrete slab deck bridge by multiple

strand system. Paul. Tensa M 4800 kN [online] Available from: www.paul.eu 3

Figure 2.2.3 Typical Post-Tensioned Bar System Hardware. 3 Figure 2.2.4 Example of Post-Tensioning System using Bars 3 Figure 2.3.2.1 Cross section of solid slab deck bridge 4 Figure 2.3.2.2 Cross section of ribbed slab deck bridge 4 Figure 2.3.2.3 Cross section of Hollow core slab deck bridge 4 Figure 2.3.3.1 Cross section of a simple box girder. (SETRA, 2003) 4 Figure 2.3.3.2 Cross section of a braced box-girder. (SETRA, 2003) 4 Figure 2.3.3.3 Cross section of two sections transversely keyed box-girder. (SETRA, 2003) 4 Figure 2.3.4.4 Typical Balanced Cantilever Segment, also called voussoir. 5 Figure 4.1.1 Cast-in-Place Segmental Construction using Form Travelers 6 Figure 4.1.2 Precast Segmental Balanced Cantilever Construction. 7 Figure 4.2.1 Span-by-Span Construction. 7 Figure 4.3.1 Progressive Placement Construction. (Muller, Podolny, 1982) 8 Figure 4.4.1 Incremental launching sequence. (Muller and Podolny. 1982) 8 Figure 5.1.1 Practical Span Length of Segmental Post-Tensioned Concrete Bridges 9 Figure 5.2.2.1 Span Lengths Distribution for a Cantilever Variable Height Deck Bridge. 10 Figure 5.2.2.2 Cantilever Tendons. (SETRA) 10 Figure 5.2.2.3 Continuity Tendons. (SETRA) 10 Figure 5.2.2.4 Internal Continuity Tendons. (SETRA) 10 Figure 5.2.2.5 Data for the design of a single cell box. (Calgaro, Bernard-Gely) 11 Table 5.2.1.1 Elements of preliminary design for post-tensioned concrete slab deck bridges for

highway usage (Calgaro and Bernard-Gely): 9

BIBLIOGRAPHY

ACI Committee 343. 1981. Analysis and Design of Reinforced Concrete Bridge Structures. 1981. Benaim, R. 2008. The Design of Prestressed Concrete Bridges, Concepts and Principles. London and New York : Taylor & Francis, 2008. ISBN: 0-203-96205-2. Calgaro J-A, Bernard-Gely A. Conception des ponts, Démarche de conception. s.l. : Techniques de l'Ingénieur. C4496-1. Egis, Jean Muller International. Experience and Innovation in Designing Structures for Urban Mass Transit Systems. Figg L, Denney Pate W. 2004. Precast Concrete Segmental Bridges - America's Beautiful and Affordable Icons. PCI Journal. 2004. Highways Agency; SETRA; LCPC. 1999. Post-Tensioned Concrete Bridges. London : Thomas Tolford Publishing, 1999. ISBN: 978-0-7277-2760-2. Libby, H and Perkins, N. 1976. Modern Prestressed Concrete, Highway Bridge Superstructures, Design Principles and Construction Methods. San Diego : Grantville Publishing Company, 1976. Muller J, Podolny W. 1982. Construction and Design of Prestressed Concrete Segmental Bridges. New York : John Wiley & Sons, 1982. ISBN: 0471056588 9780471056584. SETRA. 2003. Guide de conception: Ponts en béton précontraint construit par encorbellements successifs. s.l. : Ministère de l'Equipement des Transports du Logement du Tourisme et de la Mer, France, 2003. —. Prestressed Concrete Bridges built by the Cantilever Method, Design and Stability During Erection. New Delhi : s.n. fib Symposium on Segmental construction in concrete. Thonier, H. 1985. Le Béton Précontraint aux Etats-Limites. Paris : Presses de l'Ecole Nationale des Ponts et Chaussées, 1985. ISBN: 2-85978-082-3. U.S Departament of Transportation, Federal Highway Administration. 2004. Post-Tensioning Tendon Installation and Grouting Manual. 2004.