Highlights of the design and construction of a 12 km elevated APM bridge project in Saudi Arabia

Abstract

The automated people mover (APM) bridge project constructed at Princess Nora University (PNU) IntroductionPrecast prestressed beams have been increasingly used in recent decades for the construction of simple and multispan bridges as well as in buildings such as multi-storey car parks, factories, etc. The main advantages of precast beams can be summarized as the considerable savings in costs, labour and construction time. Moreover, the precast beam alternative offers a solution in congested areas where formwork is unacceptable due to traffic requirements. However, in the general case, the precast multigirder deck solution has the disadvantages of exhibiting inferior aesthetics and lower torsion stiffness capacity compared with box girder bridge solutions. In the light of this, the optimum solution -combining good aesthetics and high torsion stiffness capacity -is the use of precast box girder bridges. In most cases the precast box girders, with their considerable weight, require special lifting equipment, transport and handling which may not be readily available on the construction site. Therefore, splitting the box girder into two or more precast beams and then using stitching concrete can be the answer for a simplified box girder construction. The precast beams required for the box girder construction can be unsymmetrical in one or both directions. Further, precast segmental techniques can represent another solution for the construction of box girder bridges.Many publications are found in the literature dealing with precast prestressed beams. Rodriguez et al. [1] presented the design of a precast concrete light rail system for JFK international airport using precast prestressed concrete segments with symmetrical sections. Yee [2] discussed the structural and economic benefits of precast/ prestressed concrete construction. He, too, was dealing with precast symmetrical sections. Tadros and Sun [3] discuss the behaviour and advantages of unsymmetrical precast beams used for box girder construction but do not emphasize the effect of the beam's self-weight and the pretensioning strand arrangement on the distortion that may occur at transfer due to the doubly unsymmetrical section behaviour.This article presents the design and construction of the major elevated automated people mover (APM) bridge at Princess Nora University (PNU) in Saudi Arabia, which is based on precast concrete techniques. Fig. 1 shows the layout of the APM project, which in terms of geometry can be divided into straight parts, curves and bifurcations, whereas from the structural point of view the bridge project combines simply supported systems for straight and bifurcation parts, with a maximum span of 36 m (pier to pier), continuous systems for curved parts, with a maximum span of 36 m, and straight parts spanning 42.5 m. The total length of the current elevated APM is 12 km; it has 400 piers founded on shallow footings. A box girder deck with 2.25 m total depth was adopted for all parts of the project.

Dynamic response assessment in compliance with the Eurocodes for the elevated viaducts of the Doha Metro Green Line

“…The three segments comprise simply supported precast and in situ bridges with spans of 32 and 23 m (typical span lengths extensively adopted) and a two‐span in situ continuous bridge with 39.5 and 57 m adjacent spans. Most of the simply supported decks of the project consist of precast units in order to accelerate significantly the construction of the bridge superstructure . As shown in Figure , the simply supported segments have a posttensioned U‐shape section carrying two tracks and resting on four elastomeric bearings (two at each end) and with depths of 2.2 and 2 m at support and mid‐span, respectively.…”

“…Most of the simply supported decks of the project consist of precast units in order to accelerate significantly the construction of the bridge superstructure. 8,9 As shown in Figure 2, the simply supported segments have a posttensioned U-shape section carrying two tracks and resting on four elastomeric bearings (two at each end) and with depths of 2.2 and 2 m at support and mid-span, respectively. At mid-span, the web and slab thicknesses are 35 cm, while at the support the web and slab thicknesses are 60 and 50 cm, respectively.…”