Structural Engineering International 1/2014 Technical Report 105

Viaduct over Guadalhorce River and A-92 Highway, Málaga, SpainÓscar Ramón Ramos Gutiérrez, PhD (c), Civil Eng., Head of Structures Division, APIA XXI – Louis Berger DCE, PCTCAN,

Santander, Cantabria, Spain; Assoc. Prof. of Steel Structures, Cantabria Univ., Spain; Marcos J. Pantaleón Prieto, PhD, Civil Eng.,

President, APIA XXI – Louis Berger DCE, PCTCAN, Santander, Cantabria, Spain; Full Prof. of Steel Structures, Cantabria Univ.,

Spain; Guillermo Ortega Carreras, Civil Eng.; Cristina Gaite González, Civil Eng.; José Manuel Martínez García, PhD (c),

Civil Eng., Structures Division, APIA XXI – Louis Berger DCE, PCTCAN, Santander, Cantabria, Spain; Rubén Magán Ocaña, Civil Eng., Owner Technical Site Manager, INECO – ADIF, Antequera, Málaga, Spain. Contact: oramos@apiaxxi.es

DOI: 10.2749/101686614X13830788505838

The main obstacles for the viaduct to overcome were bridging the A-92 Highway that crosses underneath one of its spans and the effects of the hori-zontal forces due to the large length. To resolve these issues, a steel tied arch and a post-tensioned concrete delta-shaped pier were designed and incor-porated into the structure (Fig. 1).

The bridge has a constant slope of 2,5% in the vertical alignment, whereas the plan view shows that the spans lie inside a 3100-m radius with leftward circular alignment, followed by two clothoid alignments, and ending with a 2200-m radius rightward circular alignment.

The deck houses a double-track rail-way platform containing 10,10-m width of ballast, service sidewalks, and several devices for the installation of the railway at both sides, resulting in a total deck width of 14 m, that is normal in the high-speed Spanish railways.1

Two section types are present in the bridge: a post-tensioned concrete box-

girder and a steel–concrete composite box-girder, both with a constant depth of 3,40 m. Both sections are continuous throughout the entire viaduct (Fig. 2).

Typical Post-Tensioned Spans

The Guadalhorce Viaduct presents some singularities due to both its length (2525,50 m) and the need to have a long-length span over the A-92 Highway. Consequently, two different superstructure types may be found: one used to span the highway and another used to resolve the rest of the viaduct.

The total number of spans is 49, each 51,25 m long, except for the one that crosses the highway, which has a length of 90 m.

The typical span consists of a continu-ous single-cell post-tensioned box-girder of 3,40 m depth. This yields a depth:length ratio of 1:15, which is common for this type of bridges.2–4 The

Abstract

The Guadalhorce Viaduct, built as part of the high-speed line Antequera-Peña de los Enamorados (south Spain), has a length of 2525,50 m and consists of 49 spans of 51,25 m length each. It is one of the longest bridges of its type in the country and is situated in a medium-risk seismic zone. The superstructure consists of a continuous single-cell post-tensioned box-girder of 3,40 m depth. The main span, which crosses the A-92 Highway, is 90 m long and is reinforced by two steel tied arches. This span, along with its backward and for-ward spans, was resolved with a steel–concrete composite box-girder with a constant depth of 3,40 m. A point of fixity is materialized in a delta-shaped post-tensioned concrete pier located in an intermediate area of the bridge in order to meet the friction, braking, and seismic longitudinal forces induced by the large length of the viaduct. Hence, expansion joints are placed at both abutments. Span-by-span erection is being followed by means of two self-launching formwork gantries work-ing simultaneously, starting from each abutment, and moving toward the delta-shaped pier. Temporary fixed points were required during the erec-tion process and set at the piers placed just before the gantry. The viaduct is currently under construction.

Keywords: post-tensioned box-girder; steel tied arch; temporary fix point; self-launching gantry; delta-shaped pier.

Introduction

The need for the Guadalhorce Viaduct project arises from the necessity to give way to the Antequera–Granada high-speed railway line. The bridge is located in the Guadalhorce River floodplain, and thereby requires such a large length.

Fig. 1: General view of the bridgeAuthors

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106 Technical Report Structural Engineering International 1/2014

duct is placed in a flat valley and all the piers are of similar height.

The typical pier consists of a con-stant elliptical section shaft, with 4,50 m transversal axis and 3 m longitudi-nal axis. A variable elliptical section pier cap, which progressively widens throughout the 4 m height in order to house the deck-bearing devices, is placed above the shaft.

The piers that support the arches consist of two frames, located at each side of the longest span, made of two reinforced concrete shafts topped by a

The section is completed by two lon-gitudinal steel ties of 1,95 m width. Placed on each side of the deck, they act as tension ties of the arch and are connected to the arch truss. Anchorage ribs are placed every 20 m at the junc-tion between the triangular diagonals and the longitudinal ties, connecting them with the steel box-girder (Fig. 3).

Piers

The deck is supported by 48 reinforced concrete piers. The maximum regis-tered height is 27 m, although the via-

post-tensioning arrangement consists of four families of four tendons per family. Each tendon is compounded of 27 strands of 15,2 mm diameter and the tensile strength is equal to 1860 N/mm2. The four families follow a verti-cal alignment that adapts to the flex-ural bending moment acting on the superstructure.

Arch Span

The longest span of the viaduct is resolved with two steel tied arches. The sag is 17 m long, which yields a sag:length ratio of 1:5. The position of both arches as well as their truss geometry respects the skew angle formed by the viaduct alignment and the highway, improving the aesthetics. The transversal distance between arch axes is 16 m and they com-prise a 1,50 × 1,50 m2 section with slots at the sides. The truss diagonals consist of six tubular shapes per arch of 1 m diam-eter and 20 to 30 mm depth that creates a triangular structure.

The deck type used for the span over the highway, along with its backward and forward spans, is a steel–concrete composite box-girder design with a constant depth of 3,40 m measured at the axis of the bridge. The section comprises a bottom flange of 5,50 m width, sloped webs at both sides 7 m apart at the top slab, and lateral over-hang flanges of 3,50 m length. The top reinforced concrete slab is 0,45 m deep at the axis, decreasing to 0,375 m when reaching the webs and 0,20 m at the tip of the overhang flanges. Double composite action has been designed at the pier section in order to guarantee the stability of the bottom flange and decrease the steel plate thickness. This kind of section has already been suc-cessfully used in other bridges.5

Fig. 2: Elevation view of the Guadalhorce Viaduct: (a) complete viaduct, (b) steel–concrete composite superstructure spans (Units: m)

PK 301+502,50Rail expansion device

PK 304+028,00Rail expansion device

RioGuadalhorce

39,00

15,16

E1 P124×51,25

1269,00

2525,50

1256,50

18×51,2590,00

A-92Minimum clearance V = 14,18

A-92 Minimum clearance

V = 14,18Steel-concrete composite box girder

4×51,25

90,00 51,2551,2539,25 39,25

Fix point

P29P25

P28

(a)

(b) P29 P30 P31

P30 P48E239,00

15,39

Post-tensioned concrete box girder Steel concrete composite box girder

Steel-concrete composite box girder with steel tied-arches

5,50

14,00

14,00

3,40

5,5018,40

17,0

0 m

ax.

φ1,00

14,00

5,50

1,50

1,50

3,40

18,40

3,40

Fig. 3: Typical sections: (a) concrete box-girder, (b) steel–concrete composite box-girder, (c) steel–concrete composite box-girder with steel tied arches (Units: m)

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lifetime, such as thermal expansion and contraction, concrete shrinkage, and creep and braking of the train passing over the deck.

Once the fixity point is defined, the pier design is created by the effect of the longitudinal earthquake forces acting on the deck. In the transversal direc-tion, as most of the piers have similar height and considering the length of the structure, each pier absorbs noticeably a proportional fraction of the force cor-responding to its tributary length.

Deep foundations are needed for the pier. Measuring 16,5 × 21,0 × 5,0 m, each of them houses 18 drilled shafts of 1,80 m diameter spaced 4,50 m between axes (Fig. 5).

Bearings and Rail Expansion Devices: Monitoring

The bearing devices used on the via-duct consist of sliding bearings that incorporate a PTFE (PolyTetraFluoroEthylene, Teflon) surface and have suitable guides that restrict the move-ments. Two bearing devices are placed on each abutment and pier. One of them is a free bearing allowing move-ment in all directions, while the other one is a guided bearing that allows movement only in the longitudinal direction to accommodate thermal expansion/contraction of the deck.

Two rail expansion devices, with maxi-mum opening of 1200 mm, are located at both abutments. To adjust the movement of the expansion devices, a monitoring system that continuously assesses structure integrity is installed in the bridge. It tracks movements and measures temperature of the concrete wherever sensors are embedded.

The monitoring system records the real gap between the abutment and the superstructure, which depends on

the bridge, materialized in a delta-shaped pier. It consists of two sloped post-tensioned concrete shafts joint at the basement by a horizontal beam. The two shafts (2,85 m along the lon-gitudinal axis and 5,50 m along the transversal axis) converge at the deck creating the fixity point of the viaduct for the nonaccidental horizontal forces induced in the bridge deck during its

horizontal post-tensioned bent cap that confers transversal stiffness and pro-vides support for the steel box-girder. The four shafts are approximately 23 m high and form a rectangular section whose dimension decreases from the basement to the top. At the top, the piers are only 4 m wide along the lon-gitudinal axis and 3 m wide along the transversal axis, whereas at the bottom the longitudinal dimension is about 6,35 m and the transverse dimension about 4,55 m.

The foundations of the piers support-ing the span over the A-92 Highway consist of 12 × 12 m2 spread footings, with 3,50 m depth. Each of them houses eight drilled shafts of 1,80 m diameter, placed along three rows spaced 4,50 m apart in both directions (Fig. 4).

Delta-Shaped Pier

The large length of the viaduct has led to the introduction of a fixity point, located in an intermediate area of

4,50

AA

4,50

12,00

Typical pier

Arch pier

3,00

4,00

3,50

3,50

4,53 4,53 6,30

12,00 12,00 12,00

8 Pilesφ1,80

8 pilesφ1,80

8 Pilesφ1,80

8 Pilesφ1,80

4,00

H3,

50

3,00

1,60

4,00

3,504,

003,00

23,0

0

2,50

A-A

Fig. 4: Pier geometry: (a) typical pier, (b) arch pier (Units: m)

2,852,85

28,1

46

2×18 Piles φ1,8018 Piles φ1,80

Delta shaped pier

16,50 16,50 21,00

5,00

5,50

5,00

Fig. 5: Delta-shaped pier geometry (Units: m)

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108 Technical Report Structural Engineering International 1/2014

thermal and time-dependent move-ments. Recorded gap–temperature graph (Fig. 6a) shows that both vari-ables are in the same phase. The gap can be expressed in terms of the recorded temperature and a time-dependent function by means of the empirical for-mula (1). Recorded gap–expected gap graph (Fig. 6b) shows good correlation between both variables:

g = gini − α·T·L + β·rhe(n, r, t)·L (1)

where g, expected gap at a given time; gini, initial gap; α·T·L, movement caused by the thermal action; α, thermal expansion coefficient of concrete; T, temperature of the concrete at a given time; L, distance from abutment to the center of mass of the deck; β·rhe(n, r, t) ·L, movement caused by the time-dependent action; β, long-term strain caused by shrinkage and creep of con-crete; rhe(n, r, t), time evolution coef-ficient of shrinkage and creep (0 at the beginning; 1 at the end); n, end time of shrinkage and creep (in years); r, time when shrinkage and creep are initially considered; and t, age of concrete at the time when shrinkage and creep are initially considered (in years).

Empirical formula (1) is obtained by linear correlation between the recorded gap g and the recorded tem-perature T and the time evolution coefficient of shrinkage and creep rhe(n, r, t). With this formula, it is pos-sible to determine the real values of α and β coefficients for the concrete used in the deck.

The real value of the thermal expan-sion coefficient of concrete α used in the viaduct is 10 to 20% smaller than the usual values of the codes in force.6,7 As is well known, the presence of lime-stone aggregate in the concrete may lower the thermal coefficient value.6,8

The theoretical time-dependent move-ment at the gap is known by means of a step-by-step analysis model that counts the real concrete ages according to the erection procedure. The comparison of the theoretical time-dependent move-ment and the time-dependent term of the empirical formula (1) reveal that the real time-dependent movement is about 90% of the theoretical movement.

Construction Procedure

The spans of the entire bridge, except for the one over the A-92 Highway, will be assembled by means of a self-launching formwork gantry, as per the sequence described below:

• Construction of substructure com-ponents (piers and abutments).

• Installation and assembly of the aux-iliary equipment for the deck con-struction (self-launching formwork).

• Casting of concrete deck in subse-quent phases; construction to begin from the abutments and advance toward the fi xity point.

• Finishes: superstructure (ballast, sleepers, rails, culverts, parapets, bar-riers, etc.).

To fulfill the construction deadline, two self-launching formwork gantries are

employed simultaneously in the via-duct, and so two different gantry suppli-ers were required. For the construction of the first segment (spans located prior to the steel arch), an upper self-launch-ing formwork is used consisting of a gantry placed above the deck, while for the second segment, a lower self-launching formwork is used and the gantry is placed below the deck.

Temporary shoring towers will be installed for the assembling of the steel tied arch. The composite deck segments, previously assembled at the worksite, will be erected by cranes and supported by the towers.

Temporary Longitudinal Fix Points

Temporary fix points are needed dur-ing the construction stage in order to absorb the longitudinal effects until the connection between all the compo-nents and the delta-shaped pier takes place.

The usual way of controlling these effects consists of fixing the deck to the abutment during the construction stage. However, placing the temporary fix point at the abutment in this long via-duct could lead to high relative move-ments during the concrete hardening between the previous and the currently cast span. It was then decided that the temporary fix points would be placed in the pier(s) of the previous cast spans.

To this purpose, the actions consid-ered during each construction stage

Fig. 6: (a) Recorded movements vs. temperature at abutment two. (b) Recorded movements vs. expected movements at abutment two (Units: m)

36,6

33,9

31,2

28,5

25,8

Tem

pera

ture

(°C

)

23,1

20,4

17,7

15,0

12,3

9,6

782,2

772,2

762,2

752,2

742,2

Rec

orde

d ga

p (a

butm

ent-

deck

) (m

m)

Rec

orde

d ga

p (a

butm

ent-

deck

) (m

m)

732,2

722,2

712,2

702,2

692,2

682,2

782,2

772,3

762,4

752,6

742,7

732,8

723,0

713,1

703,2

693,4

683,5

Exp

ecte

d ga

p (a

butm

ent-

deck

)

782

772

762

752

742

732

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712

702

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68226/03/13 14:30

Time

X: time, Y: c14 «section 4. bottom slab. thermometer T17» (°C)X: time, Y: c23 «abutment E2. recorded gap. láser L2» (mm)

X: time, Y: c23 «abutment E2. recorded gap. laser L2» (mm)X: time, Y: mod02 «abutment E2. expected gap. (mm)

23/08/13 14:40 26/03/13 14:30Time

Viaduct over Gudalhorce Riverstructure 2. history record

Viaduct over Gudalhorce Riverstructure 2. history record

(a) (b)

23/08/13 14:40

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Structural Engineering International 1/2014 Technical Report 109

in a medium-risk seismic zone. The seismic design was made according to the Spanish seismic code for bridges NCSP-07,9 which is quite similar to the Eurocode 8.10 The basic ground accel-eration of the site is 0,09g, whereas the considered design ground acceleration was 0,113g. As per Eurocode 8, ground type C is found in the first 10 m and type A in the following 20 m. The seis-mic effects were determined by means of a modal response spectrum analysis, using a linear elastic model of the struc-ture and the design spectrum given by the Spanish standard NCSP-07.

When obtaining the natural period of vibration in the longitudinal direction, the axial flexibility of the superstruc-ture (due to large length of the viaduct) comes into play, as well as the bending

Fig. 8: Shell FE-modeled connection nodes: (a) stress distribution diagrams, (b) adopted solution: double longitudinal exterior gussets

Step: step-1Increment 1: step time = 1,000Primary var: S, MisesDeformed var: U Deformation scale factor: +1,000e+00

Max: +3,160e+008

Y N4

N1

N2

Q3N3

Q4

XZ

(a) (b)

Z

X

Y

S, MisesEnvelope (max abs)(Avg: 75%)

Max: +3,160e+08 Elem: NUDO–1,17936 Node: 94Min: +4,803e+06 Elem: NUDO–1,1105 Node: 350

Min: +4,803e+006+3,220e+08+2,956e+08+2,691e+08+2,427e+08+2,163e+08+1,898e+08+1,634e+08+1,370e+08+1,105e+08+8,410e+07+5,767e+07+3,124e+07+4,803e+06

to be acting on the piers, apart from the self-weight of the components, are the first-order longitudinal acciden-tal eccentricity at the pier head, lon-gitudinal force due to friction of the sliding bearings, second-order effects, superimposed deformations due to thermal and shrinkage/creep effects, and earthquake forces assuming a ten-year return period.

The number of temporary fixed piers in every phase depends on the superstruc-ture length previously cast and, con-sequently, on the friction forces of the sliding bearings. The number of fixed piers increases from one to four, the big-gest number being the worst scenario.

The special device designed to fix the pier(s) consists of a group of steel

structures embedded on the deck and the pier. The sizes of the steel structures have been determined in accordance to the maximum longitudinal force that acts on the pier. The longitudinal lock force acting on the deck is transmitted by means of hydraulic jacks.

Structural Analysis

A unique three-dimensional (3D) beam model for the entire viaduct was cre-ated, including a step-by-step analysis of each construction stage. This model allows an in-depth study of the time-dependent effects, the thermal behav-ior between concrete and steel, and the seismic response of the structure.

Seismic effects are considered in the model because the viaduct is situated

Fig. 7: First longitudinal vibration mode

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110 Technical Report Structural Engineering International 1/2014

the tubes and the arch and tie girder, and improves the fatigue behavior.

Conclusion

The Guadalhorce Viaduct has excelled in establishing itself as one of the lon-gest bridges of its type in the country. A post-tensioned concrete box-girder sec-tion spans 2,5 km with a delta-shaped pier as a unique fixity point. An accu-rate analysis of the thermal and time-dependent coefficients of the concrete could increase the length of this type of bridge, since a smaller value of con-crete strain would lead to a larger max-imum length of viaduct for the same rail expansion device opening.

References

[1] Reguero Martínez A. Tipologías de Viaductos en L.A.V. Madrid-Barcelona-Frontera Francesa. Revista de Obras Públicas 2004; 3445: 91–102.

[2] Pantaleón M, Ramos OR, Ortega G, Martínez JM. Viaductos sobre río Deza y Anzo 2. V Congreso de ACHE 2011; 1: 420.

[3] Manterola J, Astiz MA, Martínez A. Puentes de Ferrocarril de Alta Velocidad. Revista de Obras Públicas 1999; 3386: 43–77.

[4] Sobrino JA, Gómez MD. Aspectos Significativos de Cálculo en el Proyecto de Puentes de Ferrocarril. Revista de Obras Públicas 2004; 3445: 7–18.

[5] Pantaleón M, Ramos OR, Martínez JM, Ortega G. Viaducto sobre rego das Lamas. V Congreso de ACHE 2011; 1: 410.

[6] Instrucción de Hormigón Estructural (EHE- 08). Gobierno de España, Ministerio de Fomento; July 2008.

stiffness of the delta-shaped pier foun-dation. Periods of 2,17 and 2,04 s for the longitudinal vibration modes of the left and right semi-viaduct, respectively, are obtained, which are placed in the long-period portion of the response spec-trum. As these values are quite close, the Square Root of the Sum of the Squares (SRSS) combination method is not considered accurate enough; hence the Complete Quadratic Combination (CQC) combination method was used instead.10 The deformation of the delta-shaped pier foundation was studied. The maximum longitudinal seismic force obtained in the delta-shaped pier is 72 500 kN (Fig. 7).

Several options were studied when designing the connection nodes of the truss diagonals with both the longi-tudinal ties and the steel arches. The fatigue effects due to the railway traf-fic (highly important in high-speed line bridges) and the stress concentrations at the connection nodes were analyzed.

Various finite element (FE) models by shell elements were made, covering the following variables: intersection of tubes, gap between tubes, single or double gusset, and longitudinal or transversal gussets. According to the analysis of the several solutions the double longitudinal exterior gus-sets was the best solution, as shown in Fig. 8. This solution allows a better distribution of stress, offers better and direct transmission of forces between

SEI Data Block

Owner:ADIF, Ministerio de Fomento, Spain

Contractor:ACCIONA, SpainTorres Cámara, Spain

Site supervision:GETINSA, SpainGUIA, Spain

Structural design:APIA XXI - Louis Berger DCE, Santander, Spain

Concrete (m3): 64530Reinforcing steel (t): 14308Prestressing steel (t): 1280Structural steel (t): 1590Total cost (EUR million): 65

Service date: September 2015 (expected)

[7] Eurocode 2: Design of concrete structures. European Committee for Stan dardization; December 2004.

[8] AASHTO LRFD Bridge Design Specifications, 6th ed. American Association of State Highway and Transportation; 2012.

[9] Norma de Construcción Sismorresistente: Puentes (NCSP-07). Gobierno de España, Ministerio de Fomento; May 2007.

[10] Eurocode 8: Design of Structures for Earthquake Resistance. European Committee for Standardization; December 2003.

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