# A Review of the Network Arch Bridge
## 3 Network Arch Bridges of Different Structural Systems around the World
### Network Arch Bridges in Numbers  
Through this research, the authors also looked at the development of NABs around the world. A total of 184 network arch bridge structures were identified using the map of the network arches [3], the Structurae database [7], literature references on NABs, and street views from Google Maps. While the total number of NABs is undoubtedly higher than those identified, we feel certain that most of the structures were found. In assessing whether a structure is an NAB or not, the definition stated at the beginning was taken into consideration, namely that \"some of the hangers cross at least twice\". From the point of view of continental distribution, Figure 17a, almost half of the world's network arches are in Europe, with 47%, followed by Asia with 37% and North America with only 8%. The leading development of NABs in Europe is due to Prof. [PERSON], who gave lectures on his idea for a bridge in more than 50 countries [2] and worked with students and colleagues from different universities in Europe to understand and improve the network arch bridge through several diploma, master's and PhD theses [8; 9; 10; 11; 12; 13; 14; 15]. As Prof. [PERSON] states in [1], Prof. [PERSON] saw a test model of the Fehmarn Sound Bridge in Hannover in 1960. He took the idea to Japan, where it flourished. Most of the NABs in Asia are located in Japan. The Japanese call these bridges Nielsen-Lohse bridges, but they are in fact network arches. The distribution of the 184 structures according to the opening years is shown in Figure 17b. Most of the structures were opened to traffic between 2000 and 2020, more than  
Figure 17: NABs in numbers: (**a**) Continental distribution; (**b**) opening year; (**c**) number of structures in different systems; (**d**) types of bridges. twice as many as in the years the idea of a network arch was developed and started to be popularized. Without question, in the next 20 years, the NAB will show exponential growth as the idea spreads across the globe and engineers find improved solutions both in term of structural response and sustainable features [31; 32; 33; 34; 35; 36] compared to other structural systems. Figure 16(c) provides insight into the different structural systems used for NABs. Only 29 structures in the form proposed by Prof. [PERSON] have been built across the world. The vast majority are composite structures for the tie/deck. Such systems are chosen usually due to the simpler execution compared to the prestressed concrete deck. A very small number of arches were built in concrete, usually for architectural reasons, and four other bridges were built using wood as the arch material. All wooden arches are in Norway. The next chapter will have a subsection dedicated to research in gulam use for network arches. Figure 16(d) shows the distribution of NABs for different purposes. Most network arches, a total number of 141, have been built as road bridges, 21 NABs are railway bridges, and seven structures are combined bridges for road, railway or road, railway, and pedestrian use. The seven structures designed as combined bridges are large spans, 177 m to 248 m in length, for bridges already used for traffic; larger spans of network arches, 280 m to 420 m in length, were identified for a bridge in China under construction at the time with three NAB spans [43; 44]. The large spans of the combined NABs prove the reliability of the system for any type of load. Of the identified structures, 15 are footbridges. The span range for pedestrian bridges varies from 40 m to 182 m. The largest pedestrian network arch is the George C. King Bridge in Calgary, Canada.