The Single-Span Bridges
Da Vinci Bridge in Norway
Leonardo designed many bridges, including the rotating arched bridge, the horizontal retractable bridge to allow boats to pass through, and the temporary rotating bridge that is easy and quick to build.
At the time of Leonardo bridges played an important role in military logistics to move troops and supplies and were often a determining factor in the outcome of battles. This is why in Leonardo’s various codes bridges are often part of the repertoire of drawings dedicated to war machines. They were usually designed to be built from wood and were intended to be temporary and only used when necessary. In 1502 Leonardo made an unsuccessful pitch to Sultan Bayezid II of Turkey for the so-called Galata bridge, a single-span structure that was designed to reach a length of 350 m. The design was characterised by a double support for the bridgeheads in the form of a swallowtail, which is better at withstanding transversal loads, in this case made from solid stone. Based on drawings that specialists of the time considered impossible to build, the bridge was meant to cross the Golden Horn and connect Galata to Constantinople.
The bridge was built 500 years later in Ås, a city in Norway to the south of Oslo. In 1994, while visiting an exhibition, the artist Vebjørn Sand was struck by the modernity of the lines of a bridge designed by Leonardo and managed to convince the Norwegian highways authority to build it. At the end of 2001 the bridge, the first ever example of a public work built according to a design by Leonardo, was inaugurated and was named Da Vinci bridge. Even though the original design was followed as closely as possible in terms of structure and form, the bridge, designed for pedestrians and cyclists, differs for its size and the materials used. It is 67 m long, the structure is made from wood rather than stone and it sits on three arched pylons, also made from wood. Mapei also took part in the construction of the bridge by supplying admixtures for the concrete.
Florence City Walls
The Atlantic Codex contains the “curriculum vitae” sent by Leonardo to Duke Ludovico Il Moro which, amongst other things, highlights his ability as a military architect and engineer.
Amongst Leonardo’s numerous interests, his study of cities and city defences certainly couldn’t be left out. A number of sketches, drawn during the period he was called to Milan by Duke Ludovico il Moro, document his research into innovations for civil architecture and fortresses: in two drawings, which are now conserved in Paris, he designed two particularly high lookout towers for the Sforza Castle in Milan.
In 1502 Leonardo was on the payroll of the military leader and politician Cesare Borgia as a military architect and engineer and, when he arrived in Cesena (Central Italy), his various tasks included measuring and updating the fortifications of the cities in the Romagna region (Central Italy) that had been conquered.
The history of many Italian cities is closely connected to their defence systems and fortifications. One of the many examples is the city of Florence. In 2005 restoration work was carried out on the remains of the city walls built in Florence in 1312 and 1325. This intervention was carried out on the stretch of wall running from Porta San Frediano to Torrino di Verzaia (75 m).
The entire zone is now under the protection of the Local Heritage Authority. Because of the poor condition of the walls the restoration work was not easy and consisted mainly in consolidating the structure. According to methods used at the time, the construction involved a combination of stones, gravel and sand from the rivers Arno and Mugnone to create a type of dry wall; the original binder was made from very fine, crumbly off-white mortar. After cleaning and preparing the substrates, the mixed stonework making up the walls was repointed.
Mapei successfully proposed Mape-Antique, a line of products including cement-free rendering mortars and binders, specifically formulated for use in dehumidifying work, including on walls of significant historical value.
The Atlantic Codex contains a description of lock gates.
The opening system for the gate and sluices, which is described in detail in his drawings and notes, was carried out from dry land.
The numerous designs contained in Leonardo’s codes are a testimony of his interest in hydraulic works. He carried out important studies on basins during the first few years of his stay in Milan while visiting the nearby city of Pavia and the Bereguardo Canal.
He also designed several improvements, such as the steps and the insertion of a lower gate to be included in the corner gates.
After many centuries lock systems are still being used in important projects, such as the major construction works for the Panama Canal. Based on a lock system, the Canal (81.1 km long) was built between 1907 and 1920 to facilitate the passage of ships from the Pacific Ocean to the Atlantic Ocean and avoid having to circumnavigate South America.
Operation of the canal is based on a system of 6 locks with 16 gigantic steel sluice gates which are able to open or close off the water chambers the ships use to climb around 27 m in just a few minutes.
Construction work on the new Canal started in 2009 so that even larger ships would be able to pass through. It was handed over in 2016 and, in terms of complexity and figures, the Canal is the most important feat of engineering achieved in recent decades. The project introduced a system of large communicating basins to save 60% of the water needed for every operation of the locks whereas, with the old canal, all the water used when ships pass through would have been discharged into the ocean.
The Mapei Group took part in this site by supplying admixtures for the concrete used to construct the locks for the new Canal and to restore the existing locks, as well as supplying membranes to waterproof the auxiliary basins (see the dedicated articles inRealtà Mapei International No. 38, Realtà Mapei International No. 40, Realtà Mapei International 42, Realtà Mapei International 56).
Three Gorges Dam in China
In the Leicester Codex, water is a very important theme and is developed along various lines: hydraulics, geology, physics and cosmology.
In 1500 Leonardo left Milan during the French occupation and, after a brief stay in Mantua (Northern Italy), moved to Venice where he was commissioned to design a system of defences against the Turkish threat. Using his studies of water, Leonardo came up with the idea for a mobile dam to be installed at the confluence between the River Isonzo and the River Vipacco that would be able to flood the defences of an enemy on dry land.
Over the course of the centuries dams have completely changed the economy and landscape of many countries. One of the most recent examples is the spectacular Three Gorges Dam in China. In 2009 the River Yangtze, was sealed off with a dam system, creating a 600 km long lake extending over an area of more than 1,000 km2 with a capacity of 39 billion m³. It is known as the Three Gorges Dam, which takes its name from three gorges the river flows through - the Qutang Gorge, the Wuxia Gorge and the Xiling Gorge - and it is also the most powerful hydroelectric power station in the world, with an installed capacity of 22,500 megawatts.
According to the Chinese government, construction of the dam was necessary to reduce the risk of flooding, to make the upper part of the Yangtze navigable and to produce electricity, indispensable for the development of local industry. The dam itself is 185 m tall and its overall length is more than 2,000 m. Mapei took part in the construction of the spillways by supplying admixtures for concrete. The contractor asked for concrete with high mechanical properties and limited risk of cracks formation and the solution was found with the use of the first nanostructural superplasticiser, the forefather of the Dynamon line of admixtures launched by Mapei (see Realtà Mapei International No. 20).
Navigli Canal Network in Milan
Leonardo often used the Navigli Canals to travel around the city and testimony of his interest for the canal system can be found in drawings and research work contained in the Atlantic Code.
The Navigli canal network in Milan was started in the 12th century, the idea being to create a system of man-made canals for defence purposes, to supply water and to transport goods. Leonardo developed them and proposed a series of expansion projects and new inventions; between 1506 and 1513 he was particularly interested in the basin of the S. Marco Canal. The aim was to connect Naviglio Martesana to the inner network of canals through two locks, one at S. Marco and one at Incoronata. In so doing, it would then have been possible to cross the city on water and then, at a later date, connect the River Adda to the River Ticino. Amongst all Leonardo’s ideas the ones that deserve to be highlighted here more than most are those connected to the basins, including the lower sluice that can be manoeuvred by the towpath, to decrease or increase the flow-rate of the water. Of the original Navigli system, the only ones that can still be seen are Naviglio Martesana, Naviglio Pavese and Naviglio Grande.
A pilot site was started on Naviglio Grande in 2004 to find more reliable non-destructive techniques to successfully intervene on the static functionality of the walls of the canal banks. As for the masonry wall worked on, Mapei supplied the Mape-Antique System, a complete range of cement-free products for restoring damp or deteriorated masonry. The results of this test campaign were satisfactory and, in 2006, a site was set up for the static consolidation and conservative restoration of the banks of Naviglio Grande (see Realtà Mapei International No. 21).