# A Review of the Network Arch Bridge
## 4 Research on Network Arch Bridges
### Other Research on Network Arch Bridges  
Asymmetric NABs were studied in ref. [79], where the asymmetry was defined as an arch not symmetric to its center plane. A 100 m long asymmetric road arch bridge with a concrete tie/deck was chosen for the study. The principal difference seen was in the value of the compressive force, smaller on the steep side of the arch and larger where the shape of the arch was less curved. Even in the case of asymmetric arches, the overall behavior of an NAB in terms of bending moment distribution remains unchanged. An interesting idea proposed by [PERSON] and [PERSON] [80] was to use network arches to strengthen existing old beam bridges on multiple spans, where the piers are affected by scour and erosion. By changing the structural system, the intermediate infrastructures were eliminated; therefore, the erosion of piers is no longer a problem. The paper describes the steps needed to modify the superstructure and the design criteria. A series of papers described the construction of German network arch bridges [81; 82]. In ref. [81], the experience with the construction of a series of railroad NABs across Germany is presented: Rosenbachtal Bridge, opened in 2008, is an 89 m arch bridge that carries one railway track and has a hanger net of 36 flat steel hangers; Oder River Bridge, also known as the Frankfurt Railroad Bridge, also opened in 2008, has a span of 104 m, carries two railway tracks, and was designed with 26 flat steel hangers; the B6 Railroad Overpass, opened in 2009, has a span of 79 m, carries one railway track and has 24 flat hangers on each arch; Flora Bridge, opened in 2010, is a network arch with a span of 132.60 m and 30 flat steel hangers that carries one railway track. Brieselang Bridge is a highway network arch bridge completed in 2011, with a span of 106 m and a radial arrangement of the hangers. Brieslang Bridge comprises two independent NABs, one for each motorway direction. In ref. [82], aspects regarding the design and construction work are presented. In refs. [83; 84; 85], a series of network arch road overpasses in Poland are presented, with the arch ribs made of hot-rolled profiles and the deck a longitudinally prestressed concrete slab. The four overpasses have spans varying from 62 m to 75 m and were opened to traffic in 2008 and 2009. Based on the experience gained at that time, a new overpass with a span of 120 m was constructed over the Lyna River, with the arches made of HD 400 \(\times\) 744 and HD 400 \(\times\) 1086 hot rolled profiles in steel grade S460 [85]. In 2018, a railroad NAB with a span of 116 m was erected in Krakow, using as the arch cross-section HD 400 \(\times\) 1299 profiles. The two network arches that are part of the Vienna Central Railway Station Bridge, both supporting a double-track railway with spans of 88.5 m and 112.5 m, are presented in [86; 87]. Structural considerations, the form of the arch and the hanger arrangement, together with the bending moment and axial force diagrams, are given in ref. [86], and details from the builder in relation to the construction method used are given in ref. [87]. River Irwell Crossing, the first NAB built in the United Kingdom, is introduced in [88]. The bridge was designed with a weathering steel box section, the arch axis is circular, and the plate thickness of the cross-section varies from 40 mm to 60 mm. The form of the bridge was dictated by esthetic requirements; the arch on the main span has an apparent continuation of the approach span. The technical report [88] gives insight into all stages of the bridge's construction, from the overall concept to the stressing of the hangers. In another technical report [89], the international award-winning design of the Perry Bridge Network Arch over the Waikato River in New Zealand is presented. Perry Bridge spans 130 m with two inclined steel tube arches that are braced together.