A Composite Arch Bridge, Iceland

Procedia Engineering, 2011

The search for new architectural shapes may lead to schemes of bridges which cannot be traced back to known and tested typologies. In these cases, a new aesthetics requires new static views. The novelty of the De Gasperi Bridge, located in Milan, consists of two steel arches diverging towards the lateral sides of the deck. Such a choice involved particular structural problems as regards to both the vertical loads and the lateral ones due to wind and earthquake. Another delicate issue was posed by the array of joints connecting the tubular hangers and the arches, for which cardan joints have been employed in order to avoid any flexural stresses. The paper illustrates the criteria which led to the conception of a structural system which, while respecting the shape determined by architectural choices, activates an effective and natural force path. A synthesis of the analyses and of the experimental tests performed on the cardan joint are presented.

Using arch form to span deep gorges with steep rocky banks is not new. However, in recent times other types of construction due to high costs of formwork and construction time have eclipsed the arch bridge. This has prompted a new bridge system being proposed. Called the ‘prestressed steel arch bridge’, its main load bearing members are steel arch ribs that are prestressed with high tensile rock anchors embedded in the banks. The prestressing aims to achieve material economy by relieving the arch rib bending moments induced under self-weight and non-uniform load. The principle design criteria are design of arch rib as tensile arch under prestressing load during self-weight condition and as a conventional arch bridge under live load and temperature variation. The key elements of design and construction are discussed. An example illustrates the effectiveness of the new design.

Structure and Infrastructure Engineering, 2015

The study presents a new strengthening methodology in bridges over river beds affected by scour and erosion at piers. The proposal is part of an innovative concept, implementing a structural change of the original bridge, without the need to strengthen the substructure, thanks to the construction of an upper arch with network and vertical hangers. The vertical hangers are responsible to lift the deck from the piers, generating a single span (simply supported tied arch). The study describes the construction phases, considering the conditions and difficulties in their implementation due to multi-objective targets and additional boundary conditions and requirements. Additionally, it gives a description of the structural behaviour and a layout of each element, to use as criteria or guideline for future applications of the method. Finally, a validation is made through a comparative analysis in a Chilean bridge, between a traditional method of strengthening by additional piling in the foundations and the proposal here presented. Additionally to the feasibility of application, the example shows that the new solution is cheaper.

2017

This doctoral thesis deals with the design evolution of long span bridges and the corresponding technical improvement which has led to change the role of deck stiffened system through centuries. All typologies (suspension bridges, cable –stayed bridges, deck arch bridges, bowstring arch bridges) usually adopted to cover long distances, have been taken into account, reading in the same perspective the process which allows their structural optimization. Through the back analysis of about 100 existing bridges, this work investigates on main changes occurred for deck stiffened system, underling the corresponding effects on long span bridge structural behaviour. The central thread of this dissertation is to underline that to cover 150m longer spans, it has been necessary to pass form flexural regime of structures having shorter spans, which act like simple beam-bridges, to the extensional regime of slender long span bridges, whose strict succession of deck cross sections guarantee them t...

Transportation Research Record, 1988

The results of a structural analysis of elliptical-shaped precast concrete arch structures and circular-shaped arches being considered by the Minnesota Department of Transportation are summarized in this paper. These arch structures were analyzed to compare the effect of geometry on structural performance. They were analyzed using the finite element method by placing identical load conditions on each arch. Half of each arch was modeled, based on symmetry, with no rotation allowed at the arch crown. The effects of cracking, critical stresses, and displacements were tabulated. Temperature stresses and shrinkage of the concrete were also introduced into the shape comparisons. Conclusions are included which indicate the optimum geometric shape and considerations for further analysis of different loading combinations. The application of arch structures in transportation systems is not new. Nevertheless, many aspects of the structures' behavior are not well understood, and therefore studies are being conducted by several researchers to enhance knowledge in this area. In April 1987, an analytical study was initiated to review the differences between an elliptical-shaped arch and several proposed arches being developed by the Minnesota Department of Transportation (Mn/DOT). The circular shapes chosen have rise-span ratios of approximately 1:3 to 1:4 and radii less than 25 ft. The structures were compared by subjecting finite element models of each arch to identical loads and reviewing the resulting stresses and deflections. This study and its conclusions were based on a computer analysis and did not include field testing. However, the results of this study will be used as a basis for the development of future field testing. The arches vary in span from 24 to 44 ft and have vertical openings from 8 to 14 ft high. They have a constant thickness of 10 in. and support an HS20 loading. The circular shapes were designed for use over small rivers or streams and were not intended for traffic passage through the arch opening. The arches are generally manufactured in 6-ft-wide panels that are placed side by side to form the required roadway width. The circular shapes are presently being designed, but have not yet been built.

2012

Proceedings of the ICE - Bridge Engineering, 2013

Masonry arches are strong, durable, aesthetically pleasing and largely maintenance free, yet since 1900 there has been a dramatic decline in their use. However, designers, contractors and clients now have access to a new method of constructing arches incorporating precast concrete voussoirs interconnected via polymeric reinforcement and a concrete screed. No centring is necessary, as the FlexiArch, when it is lifted, transforms under the forces of gravity into the desired arch shape. After discussing general aspects of innovation, the basic concept of the arch bridge system is presented along with technological advances since it was patented. Experiences gained from building over 40 FlexiArch bridges in the UK and Ireland and from model and full-scale tests carried out to validate the system during installation and in service are described. Thus under load the system behaves like a traditional masonry arch and existing analysis methods can be used for design and assessment.

The advent of modern precast concrete technology has revolutionised conventional construction of masonry arch bridge with astonishing beauty and durability. Precast concrete arch segments of single, double and triple-leaf were introduced since 1960’s to construct short span bridges using closed spandrel arch bridge system. For ease of moulding and manufacturing of precast panels, simple solid rectangular reinforced concrete sections are designed to suit the specific arch profiles. These sections are bulky and heavy to handle and have limited their current applications to only less than 25.6 m span. This paper presents the development of a new folded plate section in “corrugated” form with substantial weight reduction but increased stiffness as a better alternative for the short span arch bridge market segments. Capitalizing on soil-concrete interactions with granular overfills, thin reinforced concrete with structurally efficient sections are designed to provide a cost competitive concrete arch bridge solution. This paper describes the development, planning, design and construction of the pilot project over a canal in Malaysia. The arch bridge was designed in accordance to BS 5400 for HA and HB loadings for a span of 20m with 5.6m rise. The challenges of mould fabrication, product manufacturing and installation are also highlighted.