The network arch bridge (NAB) is a new structural form of arch bridge that was devised 60 years ago by the Norwegian engineer Per Tveit, who is now prof. dr. docent emeritus at the University of Agder, Norway. The network arch is a tied-arch (also known as a bowstring-arch) bridge that combines the benefits of tied-arch bridges and trusses in a single system. While in a classical tied arch, the hangers are vertical, in a network arch, the suspension of the deck to the arch is ensured through a network of inclined hangers that intersect each other at least twice. Thus, the core of the NAB is the hanger arrangement that minimizes the bending moment in the arch to very small values, leading to compression in the arch. Compression with only small bending leads to very slender cross-sections for the elements of the bridge, and deep reductions in terms of materials used and economic and environmental costs. This paper reviews the research into the structural form proposed by Per Tveit and extended by researchers and engineers worldwide. The research methodology included bibliometric literature research, obtained by interrogating the ISI Web of Science (WoS) database and the cited references from the articles on WoS. While the first structural form of a network arch is still in use today and it has proven to be a good idea for spans around 100–120 m, engineers worldwide devised new bridge cross-sections. A brief view of the types of bridge cross-section in use today is given, with details about the bridges chosen as representative. Using analysis of Prof. Tveit’s map, Structurae database and literature review, a database of the network arches around the world was created, emphasizing the development of network arches from the perspectives of continental distribution, opening year, number of structures in different structural forms, and bridge purposes. The structural form was assessed from the perspective of materials used for the arch and the tie, span, purpose and number of lanes, the presence/absence of upper wind-bracings and arch disposition in the vertical plane. In the last part of this review, the newest research into the development of the network arch is discussed. In the past 15 years we have seen an acceleration in network arch development from multiple perspectives: new materials used, such as glulam for the arch or carbon fiber-reinforced plastic for the hangers; span lengths of 250 m and 380 m for large bridge widths; architectural constraints that lead to the outward inclination of the arch, that is pleasing to the eye, but difficult to address from an engineering perspective; the most slender arch bridge in the world, with very slender cross-sections for the arch and the tie.

To ensure the crossing of the Someş River in the city of Cluj-Napoca, a new footbridge was designed in order to replace the old one using a trapezoidal composite steel-concrete box girder solution. For architectural reasons, the depth of the girder was chosen relatively small and constant, so the ratio depth/span is of 1/30 approximately.The footbridge has a span of 58.00 m, with a width of 6.00m and a depth of 2.00 m and the deck includes two pedestrian lanes of 1.60 m each and a cyclist lane in the central part of the deck of 2.50 m.Due to the fact that there is a high power line above the river, the constructive solutions of suspension, cable stayed or an arch bridge were not viable.The paper presents the solution adopted for the footbridge and a number of design problems faced during the design stage, like the calculation of the shear lag at the ultimate limit state, the evaluation of the concrete shrinkage stresses and the stresses induced by the vertical component of temperature differences. As well, the issue of the comfort level is addressed. The variation of the temperature field along the depth of the composite girder cross section modifies the internal state of stresses both in the concrete slab and in the steel part. The stresses overlap those produced from permanent and live loads having an important effect upon the overall state of stresses

A new bridge was required in the city of Sibiu, to ensure the crossing of Cibin River, in Sibiu, in the Cibin square, due to the fact that the old bridge, with only two traffic lanes, was having both a weight and height restriction and was also strangling the traffic in the area. The streets connected by the bridge are all with four lanes.This paper presents aspects regarding the design and the erection of the new bridge. The new bridge, designed with four vehicle lanes and two lateral pedestrian and cyclist lanes, is an arch bridge with arches having a circular cross-section section Ø508x40mm. The main arches are connected to two secondary inclined arches in order to prevent their lateral buckling. The span of the arches is 34.0 m and their rise 8.1m.The curvature of the arches was achieved by hot bending of the sections, through the electromagnetic induction phenomenon, at a factory from the field of extractive industry from another Romanian city, Ploiesti.The bridge deck is a composite structure consisting in cross girders and a reinforced slab. The slab loading is transmitted to the main arches through hangers made from solid circular steel bars of steel S460M.Some special issues that arisen during the design and execution of the bridge are addressed: prevention of the lateral buckling phenomenon and the adjustment of the execution of the steel deck to actual manufacturing conditions