Bridges, walkways, elements of union between spaces, enrich the environment, often characterize it and load it with symbolic and cultural values. They are used to overcome fractures, to restore the continuity 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 unite and become, therefore, in the paths in the green or in the city, something particularly pleasant to see and cross. Suspended bridges were those that existed between medieval towers such as those of San Gimignano, and, thinking of the hanging paths between the buildings, the city of Perugia comes to mind, whose historic center is characterized by the ancient Etruscan-Roman aqueduct, reused as high-altitude connection between the houses, while one of the most interesting rides in nature is that of the old route of the Apulian Aqueduct, which becomes a very interesting green road.
Bridges unite, serve to overcome obstacles
, respecting their nature and conformation. Often they bring the city and nature together in an extraordinary way, leading users to walk in the green, offering new and suggestive views, service spaces, parking and observation. Crossing a stream with a bridge means not interrupting its course, respecting its course, on the contrary, diverting it, burying it, essentially denying it, only serves to increase environmental problems.
Thinking about the possibility of joining spaces is an extraordinary ambition, which allows you to bring environments closer together, to unite places.
Bridges and cycle-pedestrian walkways can also be used to cross a railway line or a busy road at a different altitude.
Modern cities are increasingly characterizing themselves with the design of spaces on a human scale, which respect the environment and think of self-sufficient urban spaces where the model refers to a relationship of a quarter of an hour, i.e. in a quarter from now on all citizens must be able to find all essential services in a normal cycle / pedestrian path. The possibility of redesigning the city allows, therefore, to connect and join the fractures with high-altitude systems 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 inclusion of parking lots on the edge of the ancient city and, with modern connection systems, have privileged pedestrian access to the impervious medieval fortress. , including using an integrated system of new bridges and walkways, in addition to escalators and elevators.
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 the wooden walkways that hover 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 manage to 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 at the landscape level, sometimes they are suspended in the void, inserted in urban contexts, in naturalistic or archaeological areas, they represent elements that give great suggestions, such as the Swiss pedestrian crossing of the Zermatt Valley or the nearby Ponte alla Luna in Potenza. There are spectacular bridges such as the glass bridge in the Grand Canyon of Zhangjajie and the footbridges that for 19 km cross the woods of 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. It therefore seems, walking along them, to hover in the void. Memorable are the bridges that serve to unite parts of the city, such as the Constitution Bridge in Venice based on a Calatrava project.
Bridges, walkways, can be built with specific and unique projects, or using prefabricated modules and elements.
Walkways and bridge structures - Some types
The cycle-pedestrian overpasses in aluminum alloy meet functional and aesthetic requirements, presenting a low visual impact and versatility of use, with a limited and often very pleasant visual impact.
The aluminum alloy products are designed and installed with stainless steel fixings, with the possibility of using different materials for the walking surface, such as metal gratings, wood, transparent structures in shatterproof glass, or polyurethane layers to have an effect. non-slip and soundproofing. Payloads of 500 kg / m2 can be obtained, which allow you to imagine dynamic and punctual loads borne in almost all cycle and pedestrian paths. An advantage of aluminum structures is that due to the possibility of being able to color the surfaces 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 coating with wood or with any other material.
Wooden walkways have always been used, since ancient times, often preceding the construction of stable bridges, later built in masonry, reinforced concrete or iron. Today the materials mainly used are solid wood of Nordic pine or larch, laminated fir wood. These are materials which, through autoclave treatments carried out with alternating phases in vacuum with high pressure impregnating agents, allow to guarantee the materials from the attack of fungi and insects. The advantage is that of being a natural material, which integrates perfectly into naturalistic contexts. It is certainly a material for which greater maintenance must be provided than other materials, because they are more subject to wear, the effects of atmospheric agents and biological attacks.
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 strength characteristics with good corrosion resistance since, when exposed to the atmosphere, it is covered with a uniform patina of oxides that inhibit the internal propagation of corrosion, defending the material and giving it a pleasant aesthetic appearance; the color varies, in carrying out its oxidation process, within a range of reds. Support elements can also be made with steel cables that give an 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.
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 platbands can be integrated with pretension ropes, as happens in road bridge structures.
In the 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 lift and, at the same time, allow the transparency necessary to let the light reach the ground below.
The gratings can also be coated with polyurethane layers to have an anti-slip and soundproofing effect. It is possible to use walking surfaces in wooden slats of various essences, which are fixed to the frame with stainless steel screws. The solutions of extruded aluminum platforms are interesting, which are anti-heel, anti-slip, anti-vertigo, and demonstrate excellent draining capacity. There are walkable surfaces in COR-TEN steel, with special micro-holes and embossing that stiffen the structure, prevent slips and falls and guarantee good drainage. The use of glass sheets is more complex, because to ensure safe accessibility, Ministerial Decree n. 236/1989 and, therefore, guarantee the anti-slip and anti-slip characteristics.
Furthermore, for demanding loads, even if using stratified sheets, the type of support and the resistance to static and dynamic loads must be carefully dimensioned.
In addition to building permits, the verification of consistency with urban planning tools, then the verification of which building permits are best suited to the requests of the type of work proposed, the verification of hydrogeological and landscape constraints, the walkways must comply with a series of rules . Those between the buildings are assimilated to road and railway bridges and must be protected by protective parapets which, also to ensure safety for the streets below, should be effective barriers both to avoid crossing it and throwing objects. All pedestrian walkways, even the temporary ones used on site, must comply with the D.P.R. 547/1955, which concerns compliance with the rules on toeboards and handrails and the law n.13 / 1989 and subsequent amendments, in terms of architectural barriers. The minimum support at both ends must have a minimum base of 30 mm. from each end with a maximum slope of 5%, while the Ministerial Decree 236/1989 sets the maximum slope of the paths at 8%. In the Legislative Decree 81/2008 (Consolidated Law on security), art. 130 "walkways and walkways" and art. 126 "parapets".
All walkways, even those of the temporary and mobile type, must be sized in a workmanlike manner, because they must withstand 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, D.M. 14/01/2008, and its update, D.M. 17/01/2018, being subjected to chapter 5 of the Regulations. Therefore, they must respect the isolated and dynamic loads, those determined by the presence of the crowd and take into account the seismic regulations, the rules concerning the investigations on soils and rocks, the stability of the land in general for the calculation of adequate foundations ( L.64 / 1974). Obviously, when projects are carried out within restricted areas, the competent Superintendencies must authorize the interventions, pursuant to the Code of Cultural Heritage and the Public Procurement Code must always be taken into account, if the client is a public body.
The footbridges also intended for cycling functions, in addition to the specific decree (DM 557/1999), must comply with the rules concerning the highway code (Legislative Decree 285/1992 "New Highway Code" and subsequent amendments) , those of the roads (DM 5/11/2001; DM 04/19/2006).
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