Footbridges, pedestrian and cycle bridges

Walkways, pedestrian and cycle-pedestrian bridges are elements of union between spaces, they enrich the environment and often characterize it and charge it with symbolic and cultural values. They serve to overcome fractures, to restore the continuities of a body, such as those generated by a fault that interrupts a rock mass, but they also serve to unite spaces and places built by man.

Bridges and walkways connect and become, therefore, in the green paths or in the city, something particularly pleasant to see and cross. Suspension bridges were those that existed between the medieval towers such as those of San Gimignano, and, thinking of the suspended paths between the buildings, the city of Perugia comes to mind, whose historic center is characterized by the ancient Etruscan-Roman aqueduct, reused as a connection at altitude between the houses, while one of the most interesting bike rides in nature is that of the old route of the Apulian Aqueduct, which becomes a very interesting greenway.

Bridges unite, they serve to overcome obstacles, respecting their nature and conformation. They often bring the city and nature together in an extraordinary way, leading users to walk in the greenery, offering new and suggestive views, service spaces, parking and observation. Crossing a stream with a bridge means not interrupting its course, respecting its flow, on the contrary, diverting it, burying it, in essence denying it, only serves to increase environmental problems.
Thinking about the possibility of uniting spaces is an extraordinary ambition, which allows us to bring environments closer together, to unite places.
Bridges and cycle/pedestrian walkways can also be used to cross, at a different height, a railway line or a busy road.

Modern cities are increasingly characterized by the design of spaces on a human scale, which respect the environment and which think of self-sufficient urban spaces where the model refers to a ratio of a quarter of an hour, that is, in a quarter of an hour all citizens must be able to find, in a normal cycle-pedestrian path, all the essential services. The possibility of redesigning the city therefore allows to connect and unite the fractures with systems at altitude that can facilitate the use of services and infrastructures. Also in this case, the example of the city of Perugia comes to the rescue, where urban infrastructures have been built with the insertion of parking lots on the edge of the ancient city and, with modern connection systems, they have privileged pedestrian access to the impervious medieval fortress, also using an integrated system of new bridges and walkways, in addition to escalators and elevators.

Solutions for bridges and walkways

Today, to build bridges and pedestrian walkways, there are many prefabricated solutions that use innovative technologies and materials, which are based on the observation and study of ancient examples and the contribution of modern production processes. They maintain the seduction of Japanese bridges and the slenderness of wooden walkways that soar between the mountains; respecting nature they give us the idea of ​​freedom, allowing us to overcome obstacles. These are systems of walkways, crossings and connections that can integrate and adapt to any context, bringing parts of the city closer together, connecting city and nature in a virtuous relationship.

Spectacular pedestrian walkways leave their mark on the landscape, sometimes suspended in the void, inserted in urban contexts, in naturalistic or archaeological areas, they represent elements that offer great suggestions, such as the Swiss pedestrian crossing of the Zermatt Valley or the Ponte alla Luna near Potenza. There are spectacular bridges such as the glass bridge in the Grand Canyon of Zhangjajie and the pedestrian walkways that for 19 km cross the woods of the Jinniushan hill. There are many examples abroad, from Canada to Denmark, but there are also in Italy, such as the one in the archaeological area of ​​the Valley of the Temples in Agrigento.

Bridges suspended in the void are extraordinary and futuristic, often with effects of extreme lightness, made with glass walkways that allow you to see the wonders of nature. Therefore, walking on them, it seems to hover in the void. Memorable are the bridges that serve to unite parts of the city, such as the Ponte della Costituzione in Venice designed by Calatrava.
Bridges, walkways, can be built with specific and unique projects, or using prefabricated modules and elements.

Walkway and bridge structures – Some typologies

Aluminium alloy
The cycle-pedestrian overpasses in aluminium alloy meet the requirements of functionality and aesthetics, presenting themselves with low visual impact and versatility of use, with a limited and often very pleasant visual impact.
The products in aluminum alloy are designed and installed with stainless steel fixings, with the possibility of using different materials for the walking surface, such as metal grates, wood, transparent shatterproof glass structures, or polyurethane layers to have an anti-slip and soundproofing effect. Useful loads of 500 kg/mXNUMX can be obtained, which allow us to imagine dynamic and punctual loads supported in almost all cycle/pedestrian paths. An advantage of aluminum structures is that they allow the surfaces to be colored in a color scale (RAL) to obtain a camouflage or distinctive effect with respect to the surrounding environment and, if you are not satisfied, you can make a covering with wood or any other material.

Wood
Wooden walkways have always been used, since ancient times, often preceding the construction of stable bridges, then built in masonry, reinforced concrete or iron. Today the materials mainly used are solid Nordic pine or larch wood, laminated fir wood. These are materials that, through autoclave treatments carried out with alternating phases in vacuum with high-pressure impregnators, allow the materials to be guaranteed from fungi and insect attack. The advantage is that it is a natural material, which integrates perfectly into naturalistic contexts. It is certainly a material for which greater maintenance must be planned compared to other materials, because they are more subject to wear, the effects of atmospheric agents and biological attacks.

Steel
Steel is a very effective material that can guarantee the creation of light and flexible structures, resistant over time, economical and with a reduced environmental impact. In particular, COR-TEN steel is a material characterized by chromatic differences, which allows it to be inserted into the landscape, integrating perfectly. COR-TEN steel combines high mechanical resistance characteristics with good resistance to corrosion because, exposed to the atmosphere, it is covered with a uniform patina of oxides that slow the internal propagation of corrosion, protecting the material and giving it a pleasant aesthetic appearance; the color varies, in completing its oxidation process, within a range of reds. Support elements can also be made with steel cables that give the idea of ​​extraordinary lightness, such as the bridge over the Aare in the city of Solothurn that allows you to cross the river suspended on ropes that enhance the technique and, in the meantime, to feel immersed in nature.

Reinforced Concrete
The use of reinforced concrete is less suitable for insertion in naturalistic contexts, it is mainly used for road crossings or to build bridges over rivers. Sometimes mixed systems can be used in which concrete slabs can be integrated with tension cables, as happens in the structures of road bridges.

Walking surfaces
In walkways, the walking surface can be made of various materials; continuous gratings in galvanized steel can be used, which guarantee static characteristics in relation to the load-bearing capacity and, at the same time, allow the transparency necessary to let light reach the ground below.
The gratings can also be coated with polyurethane layers to have an anti-slip and soundproofing effect. You can use walking surfaces in wooden slats of various types, which are fixed to the frame with stainless steel screws. Interesting solutions include extruded aluminum platforms, which are anti-heel, anti-slip, anti-vertigo, and demonstrate excellent drainage capacity. There are COR-TEN steel walking surfaces, with special micro-holes and embossing that stiffen the structure, prevent slips and falls and ensure good drainage. The use of glass sheets is more complex, because to ensure safe accessibility, it is necessary to take into account Ministerial Decree no. 236/1989 and, therefore, guarantee the anti-slip and anti-slip characteristics.
Furthermore, for heavy loads, even when using stratified slabs, it is necessary to carefully size the type of support and the resistance to static and dynamic loads.

Regulations
In addition to building permits, verification of coherence with urban planning tools, therefore verification of which building permits best suit the requirements of the type of work proposed, verification of hydrogeological and landscape constraints, walkways must comply with a series of standards. Those between buildings are assimilated to road and railway bridges and must be protected by protective parapets which, also to ensure safety for the roads below, should be effective barriers both to avoid going over it and to avoid throwing objects.
All pedestrian walkways, even temporary ones used on construction sites, must comply with Presidential Decree 547/1955, which concerns compliance with the regulations on footboards and handrails and Law no. 13/1989 and subsequent amendments, in terms of architectural barriers. The minimum support at both ends must have minimum bases of 30 mm. from each end with a maximum slope of 5%, while Ministerial Decree 236/1989 sets the maximum slope value of the paths at 8%. In Legislative Decree 81/2008 (Consolidated Law on Safety) it is necessary to take into account art. 130 “walkways and walkways” and art. 126 “parapets”.

All walkways, even temporary and mobile ones, must be sized according to the rules of the art, because they must resist the maximum loads resulting from crowding; on the open sides they must have parapets and be equipped with adequate handrails.
Pedestrian walkways are assimilated to third category bridges, pursuant to the New Technical Standards for Construction, Ministerial Decree 14/01/2008, and the related update, Ministerial Decree 17/01/2018, being subject to chapter 5 of the Standards. They must, therefore, respect the isolated and dynamic loads, those determined by the presence of the crowd and take into account the seismic regulations, the regulations regarding the investigations on the soil and rocks, the general stability of the soil for the calculation of the adequate foundations (L.64/1974). Obviously, when projects are carried out within areas subject to constraints, the competent Superintendencies must authorize the interventions, pursuant to the Cultural Heritage Code and the Public Procurement Code must always be taken into account, if the client is a public body.
Footbridges also intended for cycling purposes, in addition to the specific decree (DM 557/1999), must comply with the regulations regarding the Highway Code (Legislative Decree 285/1992 “New Highway Code” and subsequent amendments), and those regarding roads (DM 5/11/2001; DM 19/04/2006).