Structure review Saint Isaac's Cathedral General Info 📚 Location: Saint Isaac's Square 4, Saint Petersburg, Russia, 🇷🇺 Style: Late Neoclassical, Byzantine and Greek Years of construction: 1818 to 1858, 40 years Construction cost: 1 000 000 gold rubles Total height: 101.52 m Entrance to the cathedral: 250 rubles (it’s free for children under 7 years old, while children and young people from 7 to 18 years old must pay 50 rubles). Design 🏗 It is the largest Orthodox cathedral in St. Petersburg – and the 4th largest in the world! (The tallest one is the People's Salvation Cathedral in Bucharest, Romania.) The temple has a volume of 260 000 m3 and dimensions of 111.3 m x 97.6 m. Designed and constructed by a French classicist architect Auguste de Montferrand. Emperor Nicholas, I personally oversaw its construction, showing the importance of this grand project. During the construction, Montferrand almost got killed (in November 1837), when the workers were lifting 64-ton dome columns to their full height. The architect fell from the scaffolds, but, luckily, nearby workers managed to catch him. The scaffolding was made by Spanish engineer Agustin de Betancourt and the works were extended until 1858. Auguste de Montferrand died just one month after the construction was completed. That was his last and, probably, the greatest creation... During the construction in 1818, to ensure that the cathedral's structure will not sink and collapse into the fenland of Saint Petersburg, 25,000 piles were driven to strengthen the foundations of the structure. The costs of the foundations rose to 2.5 million rubles, which at the time made the cathedral the most expensive temple in Europe. The cathedral's interior, on the other hand, was decorated with about 400kg of gold. History 📑 Under the Soviet government, the building was stripped of religious trappings. In 1931, it was turned into the Museum of the History of Religion and Atheism, the dove sculpture was removed, and replaced by a Foucault pendulum. In 1937, the museum was transformed into the museum of the cathedral that you visit nowadays. During World War II, the dome was painted over in grey to avoid attracting attention from enemy aircraft. On its top, in the skylight, a geodesical intersection point was placed, to determine the positions of German artillery batteries. SOURCE russiable , TravMedia

General Information ℹ️ Location: Batalha, Portugal, 🌎 39°39′33″N 8°49′34″W Architect: Afonso Domingues Style: Late gothic, Manueline architecture Construction Dates: 1386-1530 (completely finished in 1907) Batalha Monastery was to be the Portuguese monarchy's main building project for the next two centuries. Here a highly original, national Gothic style evolved, profoundly influenced by Manueline art, as demonstrated by its masterpiece, the Royal Cloister. King John, ordered the construction to begin in 1386 and it continued for more than 100 years until the 1530s when King John III decided to focus efforts on the construction of the Jeronimos Monastery, built to commemorate Portugal’s role during the Age of Discoveries. Left practically abandoned, it was then nearly ruined during the Napoleonic Wars of the 1800s. Only in 1840 did Portugal’s King Fernando II decide to restore and complete the monastery, which was finally finished in 1907. The Royal Cloister is cloister was not part of the original project. It was built under the architect Fernão de Évora between 1448 and 1477. Its sober outward appearance is in stark contrast with the Flamboyant Gothic style of the church Buy a Poster of the ROYAL CLOISTER on Amazon here Many architects had their hands in the design and structure of the Batalha Monastery and it is considered a precious Gothic treasure showcasing various styles. It is also one of the most significant examples of Manueline architecture, a Portuguese style developed during the Age of Discoveries. The Royal Cluster is one of the most prominent examples in the monastery of this latter style. "MOSTEIRO DA BATALHA floor plan. Portugal mapa - 1913 - old antique vintage map - printed map s of Portugal" RECCOMENDED VIDEO FOR YOU...

🏆 SI's STRUCTURE OF THE YEAR 2020 🏆 General Info📚 Location: Daxing, Beijing&Guangyang, Langfang(Hebei) 🇨🇳 Construction Period: 26 December 2014 - 25 September 2019 Total Passenger capacity: 3,138,000 🧍‍♂️🧍‍♂️ Airport Master Plan: NACO (Netherlands Airport Consultants) Architects: Zaha Hadid Architects 🇬🇧 & Planner ADPI 🇫🇷 Facade Designer: XinShan Curtainwall and Beijing Institute of Architectural Design Project cost: US$17 billion 💵 ‼️ Construction chief engineer: Guo Yanchi 👷🏻‍♂️ Building Area: 700.000m² Technologies implemented: The entire airport has 5G access and uses facial recognition technology for check-ins 👉 Visit Structures Insider's homepage for more stories.👈 As per AD : "The terminal layouts minimize the walking distances between check-in and gate, and also the distances between gates for transferring passengers, to a maximum of eight minutes by foot," says Cristiano Ceccato, ZHA's project director for the Beijing Daxing airport. A project to create the world’s largest airport terminal. A series of key technologies were proposed during the design to realise a fantastic architectural effect. These included a supporting system mainly composed of C-shaped columns, seismic-isolation system of a gigantic planar structure, and vibration control techniques for the high-speed railway passing through the terminal. The rooftop, which allows in ample natural sunlight, also has supporting beams that move constantly through space, acting like lines toward the central courtyard. This, once more, was intentionally done to assist passengers in their navigation of the busy airport. International and domestic passengers are stacked on different levels hence spreading the areas vertically making the airport more crowd efficient and enable a more congestion-free space for passengers. "Transferring passengers only need to walk a short distance to the center of the airport, then quickly and efficiently funnel themselves to any other of the four legs in the airport. How many runways does Daxing airport have? For the time being, Daxing Airport has four runways and 79 airport stands. The 4 runways’ size is impressive while the airport stands are suitable both for one twin-aisle and two single-aisle planes. Eventually, the airport will have 7 runways in total and will be able to serve about 620.000 flights annually. How much did the Daxing Airport Cost? Built-in less than five years at a cost of 120 billion yuan ($17 billion), the airport is roughly the size of 100 football fields. How big is Daxing airport? The gigantic Daxing airport, with the impressive shape which has given it the nickname “Starfish”, has enormous dimensions. There are currently 4 runways (with the prospect of becoming 7 in the future) and a vast terminal building covering a 700.000m² area while the ground transportation centre extends to 80.000m². Sources: daxing-pkx-airport.com, istructe.org, archdaily

General Info 📚 Location: Prague, 🇨🇿 Construction dates: 1992-1996 Architects: Croatian-Czech architect Vlado Milunić in cooperation with Canadian-American architect Frank Gehry on a vacant riverfront plot. Awards: The Dancing House won Time Magazine's design contest in 1997. The Dancing House was also named one of the 5 most important buildings in the 1990s by Architekt Magazine. For more stories visit Structure’s Insider HomePage Design 🏗 The inspirations for the design were the dancers Fred Astaire and Ginger Rogers, Astaire is represented by a concrete cylinder with pop-out windows topped with a bird’s nest-shaped mesh sculpture. Rogers is represented by a billowing glass structure that curves away from Astaire with spindly concrete legs fixed to the pavement. The "Dancing House" is set on a property of great historical significance. Its site was the location of a house destroyed by the U.S. bombing of Prague in 1945 The style is known as deconstructivist ("new-baroque" to the designers) architecture due to its unusual shape. The "dancing" shape is supported by 99 concrete panels, each a different shape and dimension. On the top of the building is a large twisted structure of metal nicknamed Mary'. The Ultimate tour guide for Prague Available to buy on Amazon for only £5.16 In the middle of a square of buildings from the eighteenth and nineteenth century, the Dancing House has two main parts. The first is a glass tower that narrows at half its height and is supported by carved pillars; the second runs parallel to the river and is characterized by undulating mouldings and unaligned windows. This design was driven mainly by aesthetic considerations: aligned windows would make evident that the building has two more floors, although it is the same height as the two adjacent nineteenth-century buildings. The windows have protruding frames, such as those of paintings, as the designer intended for them to have a three-dimensional effect. The winding mouldings on the façade also serve to confuse perspective and diminish contrast with the surrounding buildings. Drop us a question in Quora What is Quora?: Quora is a question-and-answer website where questions are asked, answered, and edited by Internet users, either factually, or in the form of opinions.

The way I know it, there are 3 methods to perform seismic analysis of buildings depending on basic factors like building height and shape. The 3 methods are: Equivalent Static Load method - also known as Simplified Modal Response Spectrum This is the simplest method and happens to be the most commonly used. Its concept is to represent the seismic forces by horizontal static forces acting on the building. However, there are some criteria that must be satisfied in order to use this method; the building must not be higher than 60 meters, the ratio of length to breadth should not exceed 4 and the building should be fairly uniform in shape and in its static system. 2. Multi-Modal Response Spectrum method This method takes into consideration the displacement of the structure due to the impact of the seismic forces. The reference, in this case, is a commonly used graph known as ‘the response spectrum curve’. 3. Time History Analysis This method relies on calculating the internal elements’ response to the dynamic seismic forces. The dynamic properties of the building must also be known and accounted for. It is a complex method requiring laboratory-grade investigation and analysis. Post by: Sherif Issa

General Info📚 Design: stone arch bridge Width: 22.90 metres (75.1 ft) Height: 7.32 metres (24.0 ft) Construction dates: 1588 - 1591 Engineer: Nicolò Barattieri 👉 Visit Structures Insider's homepage for more stories.👈 In The World of Venice, Jan Morris paints an affectionate picture of the Rialto Bridge: "Structurally, it was a complete success--during rioting in 1797 they even fired cannon from its steps, to dispel the mobs; and for myself, I would not change a stone of it. I love the quaint old figures of St. Mark and St. Theodore, on the station side of the bridge. I love the Annunciation on the other side, angel at one end, Virgin at the other, Holy Ghost serenely aloft in the middle. I love the queer whale-back of the bridge, humped above the markets, and its cramped little shops, facing resolutely inwards. I think one of the great moments of the Grand Canal occurs when you swing around the bend beside the fish market and see the Rialto there before you, precisely as you have imagined it all your life, one of the household images of the world, and one of the few Venetian monuments to possess the quality of geniality." History 📑 of Engineering 🏗 Maintenance was vital for the timber bridge. It was partly burnt in the revolt led by Bajamonte Tiepolo in 1310. In 1444, it collapsed under the weight of a crowd watching a boat parade and it collapsed again in 1524. The idea of rebuilding the bridge in stone was first proposed in 1503. Several projects were considered over the following decades. In 1551, the authorities requested proposals for the renewal of the Rialto Bridge, among other things. The present stone bridge, a single span designed by Antonio da Ponte, was finally completed in 1591. It is similar to the wooden bridge it succeeded. The engineering of the bridge was considered so audacious that architect Vincenzo Scamozzi predicted future ruin. The bridge has defied its critics to become one of the architectural icons of Venice. 2020 Travelling Essentials Amazon's Choice You May Also Like: Worth £630 million is the new stadium for AC Milan and Inter planned to open in 2022 The 5 Greatest Engineers of All Times "Triangle shaped building New York"

General Info📚 Architects: Frank Williams & Associates; M.M.Posokhin Structural Engineer: Rosenwasser/Grossman Consulting Engineers P.C. Cost: US$1 billion Location: Moscow Russia Main contractor: Rasen Construction Space usage: offices, apartments, retail, fitness centres 👉 Visit Structures Insider's homepage for more stories👈 Design 🏗 Mercury City Tower is 29m higher than the Shard in London, UK, Mercury City Tower is 29m higher than the Shard in London, UK, and it was the tallest tower in Europe between 2012-2014 before being overtaken by several competitors. Currently Lakhta Center in St Petersburg, Russia holds the record at 462m height. The skyscrapers its copper-coloured cladding is what makes it unique. The building was originally designed to be surfaced in reflective silver glass in order to mirror the buildings surrounding but eventually came to be wrapped in equally reflective bronze-tinted glass. Thanks to its inimitable façade, the tower exhibits a constant glow that makes it appear as though it is continually immersed in the light of the sun on the horizon. A media facade made of 2 million LEDs was installed on the exterior of the 67th and 68th floors of the building. Thus, the Mercury City Tower has the tallest media facade in Europe. Sustainability Futures 🌿 The building is claimed by architect Frank Williams as the first environmentally friendly building in Russia since it was designed to collect melting snow water, as well as provide 70% of the workplaces with access to daylight. The building also features a smart “energy cycle” system that regulates energy usage, ambient temperatures, and hot water distribution throughout the development. Materials ⚒️ Materials used for the construction include heat-resistant reinforced concrete. Approximately 130,000m³ of concrete and 35,000t of reinforcement was used for the construction. For greater reliability, two independent reinforced concrete skeletons were provided to make the Mercury City Tower resistant against a 6.0 magnitude earthquake. This, as a result, gives the building a futuristic and high-tech look, fitting it in the Structural Expressionist architectural style. Facade The façade is built of steel and glass with aluminium glazing, with approximately 1,500t of foreign steel used for the façade cladding. It is the first Russian building constructed using environment-friendly methods. Source: designbuild-network You May Also Like: What's the most impressive ancient structure in the world? New York City is planning to expand Manhattan into East River to battle climate change Dracula's luxurious residence has 57 rooms and has its own private wooden church

General Information Total area: 468.19 sq mi (1,212.60 km2) Land: 300.37 sq mi (777.95 km2) Water: 167.82 sq mi (434.65 km2) Metro: 13,318 sq mi (34,490 km2) Population: 8,399,000 GDP (City, 2018): $842.3 billion New York City comprises 5 boroughs sitting where the Hudson River meets the Atlantic Ocean. At its core is Manhattan, a densely populated borough that’s among the world’s major commercial, financial and cultural centres. Its iconic sites include skyscrapers such as the Empire State Building and sprawling Central Park. Pics of the week 5. 4. 3. 2. 1.

Engineering has been transforming our world and bringing innovation.Here are the 5 greatest engineers in the industry of Civil, Computing, Mechanical, Automotive and Aerospace engineering of ALL TIMES 5. Civil Engineering Isambard Kingdom Brunel 🇬🇧 Isambard Kingdom Brunel (9 April 1806 – 15 September 1859), was an English civil engineer who is considered "one of the most ingenious and prolific figures in engineering history", "one of the 19th-century engineering giants", and "one of the greatest figures of the Industrial Revolution, who changed the face of the English landscape with his groundbreaking designs and ingenious constructions". Brunel is known for a project such as: Great Western Railway Clifton Suspension Bridge SS Great Britain 4. Mechanical Engineering Nikola Tesla 🇷🇸 Nikola Tesla was an engineer and scientist known for designing the alternating-current (AC) electric system, which is the predominant electrical system used across the world today. He also created the "Tesla coil," which is still used in radio technology. Tesla obtained around 300 patents worldwide for his inventions. 3. Computer Science Alan Turing 🇬🇧 Alan Turing was an English mathematician and pioneer of theoretical computer science and artificial intelligence. During WW2, he was instrumental in breaking the German Enigma code, leading to Allied victory over Nazi Germany. Alan Turing is known for : Cryptanalysis of the Enigma, Turing's proof, Turing machine, Turing test, Unorganised machine, Turing pattern, Turing reduction. Cause of death is speculated to be suicide by cyanide poisoning. 2. Automotive Engineering Henry Ford 🇺🇸 Henry Ford (July 30, 1863 – April 7, 1947) was an American industrialist, the founder of the Ford Motor Company, and the sponsor of the development of the assembly line technique of mass production. Although Ford did not invent the automobile or the assembly line, he developed and manufactured the first automobile that many middle-class Americans could afford. In doing so, Ford converted the automobile from an expensive curiosity into a practical conveyance that would profoundly impact the landscape of the 20th century. 1. Aerospace Engineering Sergei Korolev 🇺🇦 Sergei Korolev was the lead Soviet rocket engineer for the Soviet Union in the 1950s and 1960s. Regarded as the father of practical astronautics by many, he played a key role in the Space Race between the United States and the Soviet Union as the lead rocket engineer and spacecraft designer. He also played a crucial role in launching the first human being into space. Source: MNB

After nearly two decades of rejecting Sacha Baron Cohen’s satirical depiction of Kazakhstan in Borat Sagdiyev, the country’s tourism board has finally given in and embraced the ‘Very Nice!’ publicity he brings. The first film’s version of the Kazakhstan national anthem begins with the words: “Kazakhstan greatest country in the world, all other countries run by little girls.” (The true anthem begins: “Sky of golden sun, steppe of golden seed”.) However, following the release of Borat Subsequent Moviefilm on Friday, October 23, the tourism board has finally given in to the ‘any publicity is good publicity’ mentality. The idea for the campaign came from American Dennis Keen, who travelled to the country on a high school exchange, then studied with a Kazakh professor at Stanford University. He now lives in Almaty, where he gives walking tours, the New York Times reported. 👇 Watch the movie now on Amazon Prime Video👇 "Great Success" Sources: UNILAD, TheGuardian Nur-Sultan Tour Guide Emerald Towers, the tallest skyscrapers are located in the youngest capital of the world, Nur Sultan Nur-Sultan as known between 1998 and 2019 as Astana is the capital city of Kazakhstan. In March 2019, it was renamed Nur-Sultan in honour of the departing Kazakh president, Nursultan Nazarbayev. It stands on the banks of the Ishim River in the northern part of Kazakhstan, within the Akmola Region. In 2018, Nur-Sultan attracted more than three trillion tenges (US$7.91 billion) in foreign direct investments, a record amount for the city. The growth was achieved due to a large number of construction projects. Tourism becomes one of the factors that drive economic growth in the city. 👉 Visit Structures Insider's homepage for more stories.👈 Architecture 🏛 Design Thinking: Located in the heart of the developing historic city, the Emerald Towers consist of three buildings, two of which are 37-storeys and one is 54. As the tallest buildings in Kazakhstan, the Towers have become a tourist attraction and an elegant icon on the skyline of Astana. The Towers gracefully integrate itself into the rapidly developing urban texture and compliment the historic grand boulevard. Working in harmony with the surrounding landscape and architecture, the Towers form an architectural interpretation of indigenous prairie grass swaying gently in the wind. Key Features: The first two phases contain primarily office space, while the third phase will be a mixed-use hotel and condominium. At the tower’s base, the 2,000 car parking podium includes pedestrian-friendly retail, as well as a large conference centre and health spa. Source: Zeidler A bit about Astana, the youngest capital metropolis on the planet. Astana also is known as Nur-Sultan became the capital of Kazakhstan in 1997. A 2017 official estimate reported a population of 1,029,556 within the city limits, making it the second-largest city in Kazakhstan, behind Almaty, the capital from 1991 to 1997. The Japanese architect Kisho Kurokawa designed the master plan of Astana Founded in 1830 as a settlement of Akmoly or Akmolinsky prikaz, it served as a defensive fortification for the Siberian Cossacks. In 1832, the settlement was granted town status and renamed Akmolinsk. On 23 March 2019, following a unanimous vote in Kazakhstan's parliament, the city was renamed Nur-Sultan from Astana, after former Kazakhstan President Nursultan Nazarbayev. Read more: Visit Structures Insider's homepage for more stories. 5 books you NEED to own if you are a 1st-year civil engineering student Top 5 engineering consulting firms 2019 What's the most impressive ancient structure in the world?

The Torre Cepsa is a skyscraper located in the Cuatro Torres Business Area in Madrid, Spain. With a height of 248.3 m (815 ft) and 45 floors, It is the second tallest building in Spain and the 5th tallest building in the European Union. Designed by Lord Foster, it was first known as Torre Repsol and would have served as headquarters for Repsol YPF oil and gas company. In August 2007 the building was purchased from Caja Madrid for €815 million. Awarded the best Large Structural Project, awarded by the Structural Engineers Association of Illinois Foster + Partners Architects Torre Cepsa was originally built as a landmark headquarters for Caja Madrid, Spain’s oldest savings bank – its subsequent transfer to the oil company, Cepsa demonstrates the flexibility of its office accommodation. The tower’s design continues the practice’s investigations into the environmentally sensitive, uplifting workplace, which can be traced through the design of a family of office towers, most notably for the Commerzbank, Swiss Re and the Hearst Corporation. Design ⚒️ Owner • CurrentPontegadea Inmobiliaria • PastBankia; Khadem al-Qubaisi; Repsol YPFDeveloperRepsol YPFArchitect Design Foster + Partners; Gonzalo Martínez-Pita Copello Structural Engineer • DesignGilsanz Murray Steficek; Halvorson and Partners Steel Supplier • ArcelorMittal Structural Material Composite design: Core: Reinforced Concrete, Columns: Steel, Floor Spanning: Steel The fifty-five-storey tower is located on the site of the former Real Madrid training grounds, where the Madrid city council assigned sites for four new towers, to be designed by leading international architects. Torre Cepsa is the tallest of this group. It marks a curve in the wide boulevard of the Paseo de la Castellana – the ‘backbone’ of Madrid – and is carefully positioned to maximise the exceptional qualities of its site. Compositionally, the building can be thought of as a tall arch, with the services and circulation cores framing the office floors. At ground level, a 22-metre-high glazed atrium provides the transition from the street and accommodates a ‘floating’ glass-walled auditorium set into a mezzanine. At the top of the building, the void beneath the uppermost section of the ‘portal’ frame is designed to house wind turbines, which are capable of providing a significant proportion of the building’s power supply. Although the building was conceived as a corporate headquarters, it also has the flexibility to be partly sub-let if required, enabling Cepsa to expand or contract its accommodation easily in the future. This degree of adaptability results in part from pushing the service cores to the edges of the plan – a strategy pioneered in the design of the Hongkong and Shanghai Bank – to create 1,200-square-metre floor plates. You may also like: Commerzbank Tower | World's first ecological high-rise building | Frankfurt At fifty-three storeys and a height of 300m, the Commerzbank in Frankfurt is the world’s first ecological office tower structure. Designed by Fosters+Partners and structurally engineered by ARUP. Read more... The north-south orientation maximises natural shade by directing the low-angle sunlight towards the cores, a move that has the added benefit of framing spectacular views of the hills of Sierra de Guadarrama to the north and the centre of Madrid to the south. Strategies such as triple-glazing the office facades further improve the building’s energy efficiency. Air Solutions Used developed LG Key Video Notes: 12 technical plants are present in the structure that contains all the facilities that provide different services to the building. This structure had rooms that were in extremely high-density usage that needed air conditioning requirements that are not present in the supply industry except LG Products. Concept In terms of composition, the building can be thought of as a high arch, with services and circulation cores framing the body offices. Designed by Foster + Partners, its floating rectangular arc angle is one of the most ecological visionary designs throughout the project. The open space on the roof leaves opens the possibility of future installation of wind turbines. Structural System The structural system for all floors above ground is composed of I-section steel beams supporting concrete slabs of 75mm thickness at each floor. All Floor steel racks are K2G3 S355 / G4. Thicker slabs are used in levels were service floors are located with a 150mm thickness to minimise the noise transmissions of the engine rooms. Vierendeel truss structures The Vierendeel frames and truss members take into account the creep and shrinkage of the two concrete cores (red&yellow) of the building so the vertical movement of the two structural components can be allowed. The Vierendeel framework in the perimeter of each floor office has columns that are adjacent to the central wall that provides shear resistance to the steel frame. Images from: Wikiarquitectura Source: Foster + Partners Architects , wikiarquitectura Read more: 5 books you NEED to own if you are a 1st-year civil engineering student Top 5 engineering consulting firms 2019 What's the most impressive ancient structure in the world?

Facts📐📚 Type: Residential Location: Lower Parel, Mumbai Construction started: 2011 Cost: US$321 million Owner: Anup Mandal (owner of government company) Height: 442 m (1,450 ft) Floor count: 117 Area: 750,000 m2(8,072,933 sq ft) Lifts/elevators : 12 Design and construction Architect: Pei Cobb Freed & Partners Structural Engineer: Leslie E. Robertson Associates, Jay L. Berman, AIA, Lead Designer Main contractor: Simplex and Muscovite Group Material: Composite ( Reinforced Concrete) CTBUH 2011 Seoul Conference - Jay L. Berman & William J. Faschan, "World One Tower" Read more: Orthodox Church of Saint Sava in Belgrade used as a tank's parking in WW2 |Read to learn more Reims Cathedral visit tour Guide Everything you need to know about the iconic Norte-Dame de Paris before in burned to ashes About World One🏙 Composed of 3 towers, uniquely curvilinear in shape, The World Towers forms a stunning sculpture of glass and steel. A powerful symbol of Mumbai’s unfettered aspirations and unstoppable drive, The World Towers soar and redefine the city’s skyline. A magnificent 17-acre estate ensconced in the Golden Mile, the glittering stretch that comprises some of Mumbai’s finest residences, business spaces and luxury hotels, The World Towers embodies global standards in luxury. The Avenue, an elegant boulevard lined with palm trees, boasting some of the finest gourmet restaurants, ushers you into a grand landscaped entrance courtyard extending over almost 100,000 sq. ft. Here, on a 5-acre podium, amidst gardens and serene water bodies, The World Towers soar into the sky. Source: Wikipedia, pcf-p.com PHOTOS