Viaduct over River Almonte, Spain

The High Speed Rail between Madrid and Extremadura crosses over River Almonte through a 996 m long viaduct with a great 384 m concrete arch, which make it the largest HSR arch bridge built to date. The bridge forms part of the section conceived to connect Madrid and Lisbon through High Speed, planned for a mixed traffic of freights and passengers with a maximum speed of 350 km/h. Both design and definition of the erection procedure (which conditions the design itself), have sought to combine the technical feasibility and the optimization of resources and costs of such a singular structure.

The bridge construction began in July 2011 and its completion was reached at the end of 2016. The cantilever construction of the arch required the creation of very complex travelling formworks that permit the variation of every single dimension of the section to adapt their selves to the variable arch shapes. The formworks are two for each cantilever, one on every inclined foot at springers, combining their selves and forming a unique travelling formwork at the central part of the arch. The first segments provisional cablestays get anchored to the pier over arch’s springers, but once reached a certain cantilever length its height becomes incapable, making necessary the installation of a temporary steel tower. This temporary steel tower, constitutes a structure itself with a height of over 50 m above the deck and pinned in its base. Its placement was carried out rotating and rising the tower from its horizontal position thank to this articulated support. Execution process is being monitored with a continuous measurement instrumentation composed by inclinometers, accelerometers, straingauges, load cells in the retaining hangers, automated topographical computation and weather condition measurements. Recording all these values enables their evaluation to detect displacements or changes in the structure’s vibration frequencies that warn of any change or anomaly in its behaviour.

The command of current up to date technology and construction techniques has allowed the execution of this engineering challenge. Among them it should be highlighted the high performance 80 MPa concrete allowing to adopt more slender arch section, the four legged arch configuration, the nonlinear and evolving calculation software and techniques, the aeroelastic wind tunnel modelling, and the semiprobabilistic normative treatments, as key elements for the design and structural guarantee validation of the Viaduct over River Almonte. Their intensive use as a whole, has allowed to overpass the established span lengths for high speed rail bridges, emphasizing the importance of greater loads, the influence of the amplified dynamic effects and the nonlinear behaviour, both geometric and material, to accurately assess the security levels with which this structure is dimensioned and constructed.

(Spanish HSR Infrastructure Administrator)
Designer: DJV Arenas & Asociados - Idom
Contractor: CJV FCC Construcción - Conduril
Length (m): 996
Main Span (m): 384
Arch Concrete C80/95 (m3): 9.748
Rest of the structure Concrete (m3): 44.351
Reinforcement Steel B500 (t): 7.255
Post-Tension Steel (t): 541
Temporary cable-stays Steel (t): 857
Temporary Tower Steel (t): 894
Retaining ground Anchors (m): 6.032
Cement injected in rock (ton): 529
Cost (EUR million): 41
Service Date: November 2016