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Sebara Dildiy ( Amharic : ሰበረ ድልድይ seberi dilidī , "Broken Bridge"), also commonly known as the Portuguese Bridge or the Fasil Bridge , is a 17th century arch bridge built during Gondarine period , constructed across the Blue Nile , which is locally referred to as Abay River in Ethiopia . It is located to the north east of Mota in Misraq Gojjam Zone of the Amhara Region . The bridge is 60 meters in length and 4 meters in width. The bridge was built by Emperor Fasilides during 17th century, likely in between 1600–1660, and it was partially destroyed during World War II .

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144-406: It is reported that no significant repairs have been successful since its partial destruction during World War II. In February 2002, a truss bridge supported by the original superstructure was installed to functionally repair Sebara Dildiy, making it traversable. It was designed and installed by an American nonprofit organization, Bridges to Prosperity and it reportedly lasted until 2005. In 2009,

288-466: A Parker truss or Pratt truss than a true arch . In the Brown truss all vertical elements are under tension, with exception of the end posts. This type of truss is particularly suited for timber structures that use iron rods as tension members. See Lenticular truss below. This combines an arch with a truss to form a structure both strong and rigid. Most trusses have the lower chord under tension and

432-598: A cable suspension bridge for pedestrians was built nearby to connect to the country's existing road network. According to Ethiopian legend, Emperor Fasilides was said to have been in possession of many beautiful concubines, but none dared to admonish him openly as the clergy wished to retain their privileges. An austere and religious monk, finding this to be unacceptable, made his way to the Emperor's palace in Gondar whereupon he openly condemned Fasilides. The furious Emperor then had

576-628: A 1,200 mi (1,900 km) frontier with the AOI. Platt had 21 companies (4,500 men) of the Sudan Defence Force (SDF) of which five (later six) were organised as motor machine-gun companies. There was no artillery, but the Sudan Horse was converting to a 3.7-inch mountain howitzer battery. The 1st Battalion Worcestershire Regiment , 1st Battalion Essex Regiment and the 2nd Battalion West Yorkshire Regiment , were, in mid-September, incorporated into

720-544: A Parker truss vary from near vertical in the center of the span to diagonal near each end, similar to a Warren truss. George H. Pegram , while the chief engineer of Edge Moor Iron Company in Wilmington, Delaware , patented this truss design in 1885. The Pegram truss consists of a Parker type design with the vertical posts leaning towards the center at an angle between 60 and 75°. The variable post angle and constant chord length allowed steel in existing bridges to be recycled into

864-632: A base to attack Germany through eastern and south-eastern Europe. The conquest of Italian East Africa came second only to the defence of Egypt and the Suez Canal. In August, Wavell ordered for plans to be made quickly to gain control of the Red Sea. He specified a concept of offensive operations from Djibouti to Harar and then Addis Ababa or Kassala to Asmara then Massawa, preferably on both lines simultaneously. Wavell reconnoitred East Africa in January 1940 and

1008-576: A common truss design during this time, with their arched top chords. Companies like the Massillon Bridge Company of Massillon, Ohio , and the King Bridge Company of Cleveland , became well-known, as they marketed their designs to cities and townships. The bowstring truss design fell out of favor due to a lack of durability, and gave way to the Pratt truss design, which was stronger. Again,

1152-615: A conference in Khartoum at the end of October 1940 with Selassie, South African Prime Minister Jan Smuts (an advisor to Churchill), Wavell, Lieutenant-General William Platt and Lieutenant-General Alan Cunningham . A plan to attack Ethiopia, including support for Ethiopian irregular forces, was agreed. In November 1940, the British gained an intelligence advantage when the Government Code and Cypher School (GC & CS) at Bletchley Park broke

1296-435: A conventional truss into place or by building it in place using a "traveling support". In another method of construction, one outboard half of each balanced truss is built upon temporary falsework. When the outboard halves are completed and anchored the inboard halves may then be constructed and the center section completed as described above. The Fink truss was designed by Albert Fink of Germany in 1854. This type of bridge

1440-540: A few miles north of Kassala. The same aircraft then proceeded to machine-gun from low level the nearby positions of the Italian Blackshirts and colonial infantry. A few days later, the aircraft bombed the Italian base at Keru , fifty miles east of Kassala. The Commonwealth pilots had the satisfaction of seeing supply dumps, stores and transport enveloped in flame and smoke as they flew away. One morning in mid-December,

1584-509: A force of Italian fighters strafed a Rhodesian landing-strip at Wajir near Kassala, where two Hardys were caught on the ground and destroyed; 5,000 US gal (19,000 L; 4,200 imp gal) of fuel were set alight and four Africans were killed and eleven injured fighting the fire. The approaches to the Red Sea through the Gulf of Aden and the Bab-el-Mandeb (Gate of Tears Strait)

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1728-895: A further advance. After the conquest of British Somaliland the Italians adopted a more defensive posture. In late 1940, Italian forces suffered defeats in the Mediterranean Campaign , the Operation Compass in the Western Desert, the Battle of Britain and in the Greco-Italian War . This prompted General Ugo Cavallero , the new Italian Chief of the Chief of the General Staff in Rome, to adopt

1872-484: A hill overlooking the fort as a flank guard. The troops on the hill covered the advance at 6:40 a.m. of the 3rd Royal Garwhal Rifles followed by the tanks. The Indians reached Gallabat and fought hand-to-hand with the 65th Infantry Division "Granatieri di Savoia" and some Eritrean troops in the fort. At 8:00 a.m. the 25th and 77th Colonial battalions counter-attacked and were repulsed but three British tanks were knocked out by mines and six by mechanical failure caused by

2016-471: A limited number of truss bridges were built. The truss may carry its roadbed on top, in the middle, or at the bottom of the truss. Bridges with the roadbed at the top or the bottom are the most common as this allows both the top and bottom to be stiffened, forming a box truss . When the roadbed is atop the truss, it is a deck truss; an example of this was the I-35W Mississippi River bridge . When

2160-477: A lower chord (functioning as a suspension cable) that curves down and then up to meet at the same end points. Where the arches extend above and below the roadbed, it is called a lenticular pony truss bridge . The Pauli truss bridge is a specific variant of the lenticular truss, but the terms are not interchangeable. One type of lenticular truss consists of arcuate upper compression chords and lower eyebar chain tension links. Brunel 's Royal Albert Bridge over

2304-760: A new span using the Pegram truss design. This design also facilitated reassembly and permitted a bridge to be adjusted to fit different span lengths. There are twelve known remaining Pegram span bridges in the United States with seven in Idaho , two in Kansas , and one each in California , Washington , and Utah . The Pennsylvania (Petit) truss is a variation on the Pratt truss . The Pratt truss includes braced diagonal members in all panels;

2448-576: A new strategy in East Africa. In December 1940, Cavallero thought that Italian forces in East Africa should abandon offensive actions against the Sudan and the Suez Canal and concentrate on the defence of the AOI. After Cavallero and Aosta requested permission to withdraw from the Sudanese frontier, the army high command in Rome ordered Italian forces in East Africa to withdraw to better defensive positions. Frusci

2592-459: A pin-jointed structure, one where the only forces on the truss members are tension or compression, not bending. This is used in the teaching of statics, by the building of model bridges from spaghetti . Spaghetti is brittle and although it can carry a modest tension force, it breaks easily if bent. A model spaghetti bridge thus demonstrates the use of a truss structure to produce a usefully strong complete structure from individually weak elements. In

2736-487: A railway junction at Kassala. The Italians forced the British garrison of 320 men of the SDF and some local police to retire after inflicting casualties of 43 killed and 114 wounded for ten casualties of their own. The Italians also drove a platoon of No 3 Company, Eastern Arab Corps (EAC) of the SDF, from the small fort at Gallabat, just over the border from Metemma , about 200 mi (320 km) south of Kassala and took

2880-537: A shoal and suffered severe damage; the wreck was salvaged later. Documents recovered from Galileo Galilei were used to intercept and damage Torricelli on 21 June. The submarine headed for home but was caught off Perim Island and sunk by Kandahar , Kingston , Khartoum and the sloop Shoreham . Several hours afterwards, a torpedo on Khartoum , damaged by a shell from Torricelli , exploded and caused an uncontrollable fire. Khartoum tried to reach Perim Harbour about 7 nmi (13 km; 8.1 mi) distant but

3024-772: A short way across the Ethiopian border, beyond the Boundary Khor, a dry riverbed with steep banks covered by long grass. Both places were surrounded by field fortifications and Gallabat was held by a colonial infantry battalion. Metemma had two colonial battalions and a banda formation, all under the command of Lieutenant-Colonel Castagnola. The 10th Indian Infantry Brigade, a field artillery regiment and B Squadron, 6th RTR with seven Cruiser Mk I (A9) tanks and seven Light Tank Mk VI , attacked Gallabat on 6 November at 5:30 a.m. An RAF contingent of six Wellesley bombers and nine Gloster Gladiator fighters, were thought sufficient to overcome

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3168-454: A squadron of five first world war Motoscafo Armato Silurante (MAS, motor torpedo boats ). The Flotilla had eight modern submarines ( Archimede , Galileo Ferraris , Galileo Galilei , Torricelli , Galvani , Guglielmotti , Macallé and Perla ). The flotilla was based at Massawa in Eritrea on the Red Sea. The port linked Axis-occupied Europe and the naval facilities in

3312-532: A variant of the lenticular truss, "with the top chord carefully shaped so that it has a constant force along the entire length of the truss." It is named after Friedrich Augustus von Pauli  [ de ] , whose 1857 railway bridge (the Großhesseloher Brücke  [ de ] ) spanned the Isar near Munich . ( See also Grosshesselohe Isartal station .) The term Pauli truss is not interchangeable with

3456-564: A war of about six months' duration, the submarines denying the Red Sea route to the British. The British had based forces in Egypt since 1882 but these were greatly reduced by the terms of the Anglo-Egyptian Treaty of 1936 . A small British and Commonwealth force garrisoned the Suez Canal and the Red Sea route, which was vital to British communications with its Indian Ocean and Far Eastern territories. In mid-1939, General Archibald Wavell

3600-630: Is 15 nmi (28 km; 17 mi) wide. With the Italian declaration of war on 10 June and the loss of French naval support in the Mediterranean after the Armistice of 22 June, the 1,200 nmi (2,200 km; 1,400 mi)-long Red Sea passage to Suez became the main British sea route to the Middle East. South of Suez the British-held Port Sudan, about halfway down on the Sudan coast and

3744-406: Is a bridge whose load-bearing superstructure is composed of a truss , a structure of connected elements, usually forming triangular units. The connected elements, typically straight, may be stressed from tension , compression , or sometimes both in response to dynamic loads. There are several types of truss bridges, including some with simple designs that were among the first bridges designed in

3888-677: Is a Pratt truss design with a polygonal upper chord. A "camelback" is a subset of the Parker type, where the upper chord consists of exactly five segments. An example of a Parker truss is the Traffic Bridge in Saskatoon , Canada. An example of a camelback truss is the Woolsey Bridge near Woolsey, Arkansas . Designed and patented in 1872 by Reuben Partridge , after local bridge designs proved ineffective against road traffic and heavy rains. It became

4032-507: Is a hybrid between a Warren truss and a double-intersection Pratt truss. Invented in 1863 by Simeon S. Post, it is occasionally referred to as a Post patent truss although he never received a patent for it. The Ponakin Bridge and the Bell Ford Bridge are two examples of this truss. A Pratt truss includes vertical members and diagonals that slope down towards the center, the opposite of

4176-499: Is dangerous, build a bridge, and issue a decree that everyone who cross the bridge say 'God save the soul of Fasilides!' The Almighty will surely grant this prayer repeated by an entire people!" The Emperor followed the slave's advice and constructed the stone bridge across the Abay river in Gojjam . Italian scholar Alberto Pollera, while visiting the bridge in 1930, almost three centuries after it

4320-798: Is named after the K formed in each panel by the vertical member and two oblique members. Examples include the Südbrücke rail bridge over the River Rhine, Mainz, Germany, the bridge on I-895 (Baltimore Harbor Tunnel Thruway) in Baltimore, Maryland, the Long–Allen Bridge in Morgan City, Louisiana (Morgan City Bridge) with three 600-foot-long spans, and the Wax Lake Outlet bridge in Calumet, Louisiana One of

4464-555: Is partly based on the Howe truss . The first Allan truss was completed on 13 August 1894 over Glennies Creek at Camberwell, New South Wales and the last Allan truss bridge was built over Mill Creek near Wisemans Ferry in 1929. Completed in March 1895, the Tharwa Bridge located at Tharwa, Australian Capital Territory , was the second Allan truss bridge to be built, the oldest surviving bridge in

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4608-671: Is practical for use with spans up to 250 feet (76 m) and was a common configuration for railroad bridges as truss bridges moved from wood to metal. They are statically determinate bridges, which lend themselves well to long spans. They were common in the United States between 1844 and the early 20th century. Examples of Pratt truss bridges are the Governor's Bridge in Maryland ; the Hayden RR Bridge in Springfield, Oregon , built in 1882;

4752-427: Is sufficiently stiff then this vertical element may be eliminated. If the lower chord (a horizontal member of a truss) is sufficiently resistant to bending and shear, the outer vertical elements may be eliminated, but with additional strength added to other members in compensation. The ability to distribute the forces in various ways has led to a large variety of truss bridge types. Some types may be more advantageous when

4896-407: Is supported only at the ends and is fully independent of any adjacent spans. Each span must fully support the weight of any vehicles traveling over it (the live load ). In contrast, a continuous truss functions as a single rigid structure over multiple supports. This means that the live load on one span is partially supported by the other spans, and consequently it is possible to use less material in

5040-463: Is the Victoria Bridge on Prince Street, Picton, New South Wales . Also constructed of ironbark, the bridge is still in use today for pedestrian and light traffic. The Bailey truss was designed by the British in 1940–1941 for military uses during World War II. A short selection of prefabricated modular components could be easily and speedily combined on land in various configurations to adapt to

5184-467: Is thought the unit was guilty of severe over-claiming . From November 1940 to early January 1941, Platt put pressure on the Italians along the Ethiopia–Sudan border with patrols and raids by ground troops and aircraft. Hurricanes and more Gladiators began to replace some of the older models. On 6 December, a large concentration of Italian motor transport was bombed and strafed by Commonwealth aircraft

5328-715: The Regio Corpo Truppe Coloniali (Royal Corps of Colonial Troops), led by Italian officers and NCOs . With Britain in control of the Suez Canal , the Italian forces were cut off from supplies and reinforcement once hostilities began. On 13 June 1940, an Italian air raid took place on the RAF base at Wajir in Kenya and the air war continued until Italian forces had been pushed back from Kenya and Sudan, through Somaliland, Eritrea and Ethiopia in 1940 and early 1941. The remnants of

5472-865: The Regia Aeronautica . On the Italian declaration of war on 10 June 1940, East Africa Force (Lieutenant-General Douglas Dickinson) comprised two East African brigades of the King's African Rifles organised as a Northern Brigade and a Southern Brigade with a reconnaissance regiment, a light artillery battery and the 22nd Mountain Battery Royal Indian Artillery (RIA). By March 1940, the KAR strength had reached 883 officers, 1,374 non-commissioned officers and 20,026 African other ranks. Wavell ordered Dickinson to defend Kenya and to pin down as many Italian troops as possible. Dickinson planned to defend Mombasa with

5616-566: The Regia Marina (Italian Royal Navy) laid plans for an ocean-going "escape fleet" ( Flotta d'evasione ) equipped for service in the tropics. The plans varied from three battleships, an aircraft carrier, twelve cruisers, 36 destroyers and 30 submarines to a more realistic two cruisers, eight destroyers and twelve submarines. Even the lower establishment proved too expensive and in 1940 the Red Sea Flotilla had seven older fleet destroyers ,

5760-782: The Arbegnoch ( Amharic for Patriots). Italian reinforcements arrived in October and patrolled more frequently, just as dissensions among local potentates were reconciled by Sandford's diplomacy. The Frontier Battalion of the Sudan Defence Force, set up in May 1940, was joined at Khartoum by the 2nd Ethiopian and 4th Eritrean battalions, which were raised from émigré volunteers in Kenya. Operational Centres consisting of an officer, five NCOs and several picked Ethiopians were formed and trained in guerrilla warfare to provide leadership cadres and £1 million

5904-445: The 17 Italian fighters and 32 bombers believed to be in range. The infantry assembled 1–2 mi (1.6–3.2 km) from Gallabat, whose garrison was unaware that an attack was coming, until the RAF bombed the fort and put the wireless out of action. The field artillery began a simultaneous bombardment; after an hour the gunners changed targets and bombarded Metemma. The previous night, the 4th Battalion 10th Baluch Regiment occupied

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6048-399: The 1st South African Division was formed and by the end of 1940, about 27,000 South Africans were in East Africa, in the 1st South African Division, the 11th (African) Division and the 12th (African) Division. Each South African brigade group consisted of three rifle battalions, an armoured car company and signal, engineer and medical units. By July, under the terms of a war contingency plan,

6192-510: The 28th Destroyer Flotilla comprising HMS  Khartoum , Kimberley , Kingston and Kandahar and three sloops from the Mediterranean. The force was to conduct a blockade Italian East Africa ( Operation Begum ), attack the Red Sea Flotilla and protect the sea route from Aden to Suez. On 6 June, the Azio-class minelayer Ostia used 470 mines to lay eight barrages off Massawa and

6336-505: The 29th Indian Infantry Brigade , 10th Indian Infantry Brigade and 9th Indian Infantry Brigade respectively of the 5th Indian Infantry Division (Major-General Lewis Heath ) when it arrived. The 4th Indian Infantry Division (Major-General Noel Beresford-Peirse ) was transferred from Egypt in December. The British had an assortment of armoured cars and B Squadron 4th Royal Tank Regiment (4th RTR) with Matilda infantry tanks joined

6480-579: The 2nd (West Africa) Infantry Brigade , from the Gold Coast ( Ghana ) and the 1st (West Africa) Infantry Brigade from Nigeria , were provided for service in Kenya by the Royal West African Frontier Force (RWAFF). The 1st (West African) Brigade, the two KAR brigades and some South African units, formed the 11th (African) Division. The 12th (African) Division had a similar formation with the 2nd (West African) Brigade. At dawn on 17 June,

6624-542: The Abay river and the debris in the water made it difficult for us to cross. Nevertheless, since we had surmounted the biggest difficulty, the destruction of the Abay bridge could in no way prevent us from continuing our journey. No significant repairs were undertaken afterwards; temporary crossing was on wooden logs or by ropes. The lack of safety caused five deaths every year. The bridge was repaired in February 2002 by engineers from

6768-759: The Abyssinian campaign ) was fought in East Africa during the Second World War by Allies of World War II , mainly from the British Empire , against Italy and its colony of Italian East Africa , between June 1940 and November 1941. The British Middle East Command with troops from the United Kingdom , South Africa , British India , Uganda Protectorate , Kenya , Somaliland , West Africa , Northern and Southern Rhodesia , Sudan and Nyasaland participated in

6912-427: The Arbegnoch north of Lake Tana to spring several ambushes on the Metemma–Gondar road, and the Italian garrison at Wolkait was withdrawn in February 1941. On 3 August 1940, the Italians invaded with two colonial brigades, four cavalry squadrons, 24 M11/39 medium tanks and L3/35 tankettes, several armoured cars, 21 howitzer batteries, pack artillery and air support. The British had a garrison of two companies of

7056-458: The Australian Capital Territory and the oldest, longest continuously used Allan truss bridge. Completed in November 1895, the Hampden Bridge in Wagga Wagga, New South Wales , Australia, the first of the Allan truss bridges with overhead bracing, was originally designed as a steel bridge but was constructed with timber to reduce cost. In his design, Allan used Australian ironbark for its strength. A similar bridge also designed by Percy Allen

7200-401: The Commander-in-Chief, East Indies , Vice-Admiral Ralph Leatham , the Commander-in-Chief India , General Robert Cassels , the Inspector General, African Colonial Forces, Major-General Douglas Dickinson and the Air Officer Commanding-in-Chief Middle East , Air Chief Marshal William Mitchell . (French divisions in Tunisia faced the Italian 5th Army on the western Libyan border, until

7344-420: The Dearborn River High Bridge near Augusta, Montana, built in 1897; and the Fair Oaks Bridge in Fair Oaks, California , built 1907–09. The Scenic Bridge near Tarkio, Montana , is an example of a Pratt deck truss bridge, where the roadway is on top of the truss. The queenpost truss , sometimes called "queen post" or queenspost, is similar to a king post truss in that the outer supports are angled towards

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7488-418: The Fort Wayne Street Bridge in Goshen, Indiana , the Schell Bridge in Northfield, Massachusetts , the Inclined Plane Bridge in Johnstown, Pennsylvania , the Easton–Phillipsburg Toll Bridge in Easton, Pennsylvania , the Connecticut River Bridge in Brattleboro, Vermont , the Metropolis Bridge in Metropolis, Illinois , and the Healdsburg Memorial Bridge in Healdsburg, California . A Post truss

7632-414: The Gideon Force attacked the Italian garrison at Bahir Dar , Colonel Saverio Maraventano and his garrison of 8,000 men were forced to retreat. After crossing the Abay River, they then demolished the stone bridge that served as a crossing. The destruction of the bridge was mentioned in Haile Selassie 's (Emperor of Ethiopia from 1930 to 1974) autobiography: The Italians had also destroyed the bridge over

7776-405: The Gulf of Aden , the Red Sea and the Suez Canal. (The Kingdom of Egypt remained neutral during the Second World War but the terms of the Anglo-Egyptian treaty of 1936 allowed the British to occupy Egypt and Anglo-Egyptian Sudan.) Egypt, the Suez Canal, French Somaliland and British Somaliland were also vulnerable to invasion but the Italian General Staff had planned for a war after 1942; in

7920-445: The Howe truss . The interior diagonals are under tension under balanced loading and vertical elements under compression. If pure tension elements (such as eyebars ) are used in the diagonals, then crossing elements may be needed near the center to accept concentrated live loads as they traverse the span. It can be subdivided, creating Y- and K-shaped patterns. The Pratt truss was invented in 1844 by Thomas and Caleb Pratt. This truss

8064-488: The Indian Ocean were brought to Somali ports but their cargoes were not always of much use to the Italian war effort. On 22 November 1940 the Yugoslav steamer Durmitor , captured by the German auxiliary cruiser Atlantis , put in at Warsheikh with a cargo of salt and several hundred prisoners. The Comando Aeronautica Africa Orientale Italiana (CAAOI) of the Regia Aeronautica (General Pietro Pinna) based in Addis Ababa, had three sector commands corresponding to

8208-455: The Italian concession zone at Tientsin in China. There were limited port facilities at Assab , in Eritrea and at Mogadishu in Italian Somaliland. When the Mediterranean route was closed to Allied merchant ships in April 1940, the Italian naval bases in East Africa were well placed for attacks on convoys en route to Suez up the east coast of Africa and through the Red Sea. The finite resources in Italian East Africa were intended to last for

8352-511: The June debacle in France , Wavell had to follow a defensive strategy. After Italian operations in Sudan at Kassala and Gallabat in June, Winston Churchill blamed Wavell for a "static policy". Anthony Eden , the Secretary of State for War , communicated to Wavell that an Italian advance towards Khartoum should be destroyed. Wavell replied that the Italian attacks were not serious but went to Sudan and Kenya to see for himself and met Ethiopian Emperor Haile Selassie at Khartoum. Eden convened

8496-422: The River Tamar between Devon and Cornwall uses a single tubular upper chord. As the horizontal tension and compression forces are balanced these horizontal forces are not transferred to the supporting pylons (as is the case with most arch types). This in turn enables the truss to be fabricated on the ground and then to be raised by jacking as supporting masonry pylons are constructed. This truss has been used in

8640-437: The United States , because wood was in abundance, early truss bridges would typically use carefully fitted timbers for members taking compression and iron rods for tension members , usually constructed as a covered bridge to protect the structure. In 1820, a simple form of truss, Town's lattice truss , was patented, and had the advantage of requiring neither high labor skills nor much metal. Few iron truss bridges were built in

8784-461: The 19th and early 20th centuries. A truss bridge is economical to construct primarily because it uses materials efficiently. The nature of a truss allows the analysis of its structure using a few assumptions and the application of Newton's laws of motion according to the branch of physics known as statics . For purposes of analysis, trusses are assumed to be pin jointed where the straight components meet, meaning that taken alone, every joint on

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8928-563: The 1st East African Infantry Brigade and to deny a crossing of the Tana River and the fresh water at Wajir with the 2nd East African Infantry Brigade. Detachments were to be placed at Marsabit , Moyale and at Turkana near Lake Rudolf (now Lake Turkana ), an arc 850 mi (1,370 km) long. The Italians were thought to have troops at Kismayo , Mogadishu, Dolo , Moyale and Yavello , which turned out to be colonial troops and bande , with two brigades at Jimma , ready to reinforce Moyale or attack Lake Rudolf and then invade Uganda . By

9072-400: The 1st East African Light Battery (3.7-inch howitzers) came from Kenya, raising the total to 4,000 troops, in the first week of August. In the Aden Protectorate , British Forces Aden (Air Vice-Marshal George Reid ) had a garrison of the two Indian infantry battalions until they were transferred to British Somaliland in August. In August 1939, Wavell had ordered a covert plan to encourage

9216-427: The 4th Indian Division in January 1941. On the outbreak of hostilities, Lieutenant-Colonel Arthur Reginald Chater in British Somaliland had about 1,754 troops comprising the Somaliland Camel Corps (SCC) and a battalion of the 1st Battalion Northern Rhodesia Regiment. By August, the 1/2nd Punjab and 3/5th Punjab regiments had been transferred from Aden and the 2nd Battalion of the King's African Rifles (KAR) with

9360-436: The 5th Destroyer Division with the Leone-class destroyers Pantera , Tigre and Leone and the 3rd Destroyer Division with the Sauro-class torpedo boats (a class of ships between the size of small, fast motor torpedo boats and destroyers, not found in the Royal Navy) Francesco Nullo , Nazario Sauro , Cesare Battisti and Daniele Manin . There were Orsini and Acerbi two old local defence torpedo boats and

9504-524: The AOC-in-C Middle East, had 14 Squadron , 47 Squadron and 223 Squadron (Wellesley bombers). A flight of Vincent biplanes from 47 Squadron performed Army Co-operation duties and were later reinforced from Egypt by 45 squadron ( Blenheims ). Six Gladiator biplane fighters were based in Port Sudan for trade protection and anti-submarine patrols over the Red Sea, the air defence of Port Sudan, Atbara and Khartoum and for army support. In May, 1 (Fighter) Squadron South African Air Force (SAAF) arrived,

9648-463: The AOI would remove the land threat to supplies and reinforcements coming from Australia, New Zealand, India, South Africa and British East Africa via the Suez Canal for the Western Desert campaign and re-open the land route from Cape Town to Cairo . On 10 June 1940, East Africa Force (Major-General Douglas Dickinson) was established for North-East Africa, East Africa and British Central Africa . In Sudan about 8,500 troops and 80 aircraft guarded

9792-420: The Air Force), Aosta had about 290,476 local and metropolitan troops (including naval and air force personnel). By 1 August, mobilisation had increased the number to 371,053 troops. On 10 June, the Italian army was organised in three corps and one division commands, Aosta had two metropolitan divisions, the 40th Infantry Division "Cacciatori d'Africa" and the 65th Infantry Division "Granatieri di Savoia" ,

9936-431: The Alpini Battalion "Uork Amba" of the 7th Alpini Regiment Alpini (elite mountain troops), a Bersaglieri battalion of motorised infantry, several Blackshirt Milizia Coloniale battalions and smaller units. About 70 per cent of Italian troops were locally recruited Askari . The regular Eritrean battalions and the Regio Corpo Truppe Coloniali (RCTC Royal Corps of Somali Colonial Troops ) were among

10080-399: The American philanthropic organization Bridges to Prosperity . The repairs to the Sebara Dildiy bridge reportedly lasted until 2005. After this, a modern bridge that was connected to the country's road network was constructed nearby in 2009. 11°13′04″N 37°52′36″E  /  11.21767°N 37.87667°E  / 11.21767; 37.87667 Truss bridge A truss bridge

10224-515: The British recognised Selassie as emperor and in August, Mission 101 entered Gojjam province to reconnoitre. Sandford requested that supply routes be established before the rains ended, to the area north of Lake Tana and that Selassie should return in October, as a catalyst for the uprising. Gaining control of Gojjam required the Italian garrisons to be isolated along the main road from Bahir Dar Giorgis south of Lake Tana, to Dangila , Debre Markos and Addis Ababa to prevent them concentrating against

10368-454: The Emperor went in with humble clothes and knelt before her. He explained the reason for his arrival and begged her absolution. The slave was greatly confused at the sight of her Emperor bowing before her, saying, "Why O' Emperor do you thus humiliate yourself before me, your slave? Only the Almighty condemns and absolves, but if you please, listen to my advice: there where the road across the river

10512-618: The Franco-Axis Armistice of 22 June 1940 .) In Libya, the Regio Esercito Italiana (Royal Italian Army) had about 215,000 men and in Egypt, the British had about 36,000 troops, with another 27,500 men training in Palestine. Wavell had about 86,000 troops at his disposal for Libya, Iraq , Syria , Iran and East Africa. Middle East Command was established before the war to control land operations and co-ordinate with

10656-631: The Italian defeat greatly eased the flow of supplies through the Red Sea to Egypt. Most of the Commonwealth forces were transferred to North Africa to participate in the Western Desert campaign . On 9 May 1936, the Italian dictator, Benito Mussolini , proclaimed the formation of Italian East Africa ( Africa Orientale Italiana , AOI), from Ethiopia after the Second Italo-Abyssinian War and

10800-684: The Italian forces in the region surrendered after the Battle of Gondar in November 1941, except for small groups that fought a guerrilla war in Ethiopia against the British until the Armistice of Cassibile in September 1943, which ended the war between Italy and the Allies. The East African campaign was the first Allied strategic victory in the war; few Italian forces escaped the region to be used in other campaigns and

10944-589: The Italians began the Battle of Tug Argan ( tug , a dry, sandy riverbed), where the road from Hargeisa crosses the Assa hills and by 14 August, the British were at risk of defeat in detail by the larger Italian force and its greater quantity of artillery. Close to being cut off and with only one battalion left in reserve, Godwin-Austen contacted Henry Maitland Wilson , commander of the British Troops in Egypt in Cairo (Wavell

11088-433: The Italians entered Berbera on the evening of 19 August. In the final four days, the RAF flew twelve reconnaissance and 19 reconnaissance-bombing sorties, with 72 attacks on Italian transport and troop columns; 36 fighter sorties were flown over Berbera. The British suffered casualties of 38 killed and 222 wounded; the Italians suffered 2,052 casualties; fuel and ammunition expenditure and wear and tear on vehicles

11232-656: The Pennsylvania truss adds to this design half-length struts or ties in the top, bottom, or both parts of the panels. It is named after the Pennsylvania Railroad , which pioneered this design. It was once used for hundreds of bridges in the United States, but fell out of favor in the 1930s and very few examples of this design remain. Examples of this truss type include the Lower Trenton Bridge in Trenton, New Jersey ,

11376-509: The Red Sea coast to protect Port Sudan , the 9th Indian Infantry Brigade was based south-west of Kassala and the 10th Indian Infantry Brigade ( William Slim ) were sent to Gedaref , with the divisional headquarters, to block an Italian attack on Khartoum from Goz Regeb to Gallabat, on a front of 200 mi (320 km). Gazelle Force (Colonel Frank Messervy ) was formed on 16 October, as a mobile unit to raid Italian territory and delay an Italian advance. Gallabat fort lay in Sudan and Metemma

11520-457: The Red Sea coast to their base at Gedaref. Information on the Italian withdrawal plan was quickly decrypted by the British and Platt was able to begin his offensive into Eritrea on 18 January 1941, three weeks ahead of schedule. In Sudan, the Royal Air Force (RAF) Air Headquarters Sudan (Headquarters 203 Group from 17 August, Air Headquarters East Africa from 19 October), subordinate to

11664-524: The Rhodesians supported a raid by the SDF on the Italian desert outpost of El Wak in Italian Somaliland about 90 mi (140 km) north-east of Wajir. The Rhodesians bombed and burnt down thatched mud huts and generally harassed Italian troops. Since the main fighting at that time was against Italian advances towards Moyale in Kenya, the Rhodesians concentrated there. On 1 July, an Italian attack on

11808-461: The South Africans even pressing an old Valentia biplane into service as a bomber. The South Africans faced experienced Italian pilots, including a cadre of Spanish Civil War veterans. Despite its lack of experience, 1 Squadron claimed 48 enemy aircraft destroyed and 57 damaged in the skies over East Africa. A further 57 were claimed destroyed on the ground. all for the loss of six pilots. It

11952-407: The Sudan Defence Force, two motor machine-gun companies and a mounted infantry company. Kassala was bombed and then attacked, the British retiring slowly. On 4 August, the Italians advanced with a western column towards Zeila , a central column (Lieutenant-General Carlo De Simone) towards Hargeisa and an eastern column towards Odweina in the south. The SCC skirmished with the advancing Italians as

12096-468: The United States before 1850. Truss bridges became a common type of bridge built from the 1870s through the 1930s. Examples of these bridges still remain across the US, but their numbers are dropping rapidly as they are demolished and replaced with new structures. As metal slowly started to replace timber, wrought iron bridges in the US started being built on a large scale in the 1870s. Bowstring truss bridges were

12240-473: The army and air force in East Africa. Merchant traffic was stopped by the British on 24 May, pending the introduction of a convoy system. The Red Sea Force (Senior Naval Officer Red Sea, Rear-Admiral Arthur Murray ), operational at Aden since April with the light cruisers HMS  Liverpool and HMAS Hobart ( Liverpool was replaced by HMS  Leander ), was reinforced by the anti-aircraft cruiser HMS  Carlisle , which sailed south with Convoy BS 4,

12384-461: The availability of machinery, and the cost of labor. In other cases, the appearance of the structure may take on greater importance and so influence the design decisions beyond mere matters of economics. Modern materials such as prestressed concrete and fabrication methods, such as automated welding , and the changing price of steel relative to that of labor have significantly influenced the design of modern bridges. A pure truss can be represented as

12528-729: The base at Aden, 100 nmi (190 km; 120 mi) east of Bab-el-Mandeb on the Arabian Peninsula . The principal Italian naval force ( Contrammiraglio [Rear-Admiral] Mario Bonetti ) was based at Massawa in Eritrea, about 350 nmi (650 km; 400 mi) north of the Bab-el-Mandeb, well placed for the Red Sea Flotilla to attack Allied convoys. British code-breakers of the Government Code and Cypher School (GC&CS) at Bletchley Park in England, deciphered Italian orders of 19 May, coded using C38m machines, secretly to mobilise

12672-512: The best Italian units in the AOI and included Eritrean cavalry Penne di Falco (Falcon Feathers). (On one occasion a squadron of horse charged British and Commonwealth troops, throwing small hand grenades from the saddle.) Most colonial troops were recruited, trained and equipped for colonial repression, although the Somali Dubats from the borderlands were useful light infantry and skirmishers. Irregular bande were hardy and mobile, knew

12816-511: The border town of Moyale, on the edge of the Ethiopian escarpment, where the tracks towards Wajir and Marsabit meet, was repulsed by a company of the 1st KAR and reinforcements were moved up. The Italians carried out a larger attack by about four battalions on 10 July, after a considerable artillery bombardment and after three days the British withdrew unopposed. The Italians eventually advanced to water holes at Dabel and Buna , nearly 62 mi (100 km) inside Kenya but lack of supplies prevented

12960-702: The bridge companies marketed their designs, with the Wrought Iron Bridge Company in the lead. As the 1880s and 1890s progressed, steel began to replace wrought iron as the preferred material. Other truss designs were used during this time, including the camel-back. By the 1910s, many states developed standard plan truss bridges, including steel Warren pony truss bridges. In the 1920s and 1930s, Pennsylvania and several states continued to build steel truss bridges, using massive steel through-truss bridges for long spans. Other states, such as Michigan , used standard plan concrete girder and beam bridges, and only

13104-406: The bridge deck, they are susceptible to being hit by overheight loads when used on highways. The I-5 Skagit River bridge collapsed after such a strike; before the collapse, similar incidents had been common and had necessitated frequent repairs. Truss bridges consisting of more than one span may be either a continuous truss or a series of simple trusses. In the simple truss design, each span

13248-694: The campaign. These were joined by the Allied Force Publique of Belgian Congo , Imperial Ethiopian Arbegnoch (resistance forces) and a small unit of Free French Forces . Italian East Africa was defended by the Comando Forze Armate dell'Africa Orientale Italiana (Italian East African Armed Forces Command), with units from the Regio Esercito (Royal Army), Regia Aeronautica (Royal Air Force) and Regia Marina (Royal Navy). The Italian forces included about 250,000 soldiers of

13392-699: The center of the structure. The primary difference is the horizontal extension at the center which relies on beam action to provide mechanical stability. This truss style is only suitable for relatively short spans. The Smith truss , patented by Robert W Smith on July 16, 1867, has mostly diagonal criss-crossed supports. Smith's company used many variations of this pattern in the wooden covered bridges it built. East African campaign (World War II) [REDACTED]   Free France [REDACTED]   Italy Associated articles Asia-Pacific Mediterranean and Middle East Other campaigns Coups The East African campaign (also known as

13536-707: The center, the opposite of the Pratt truss . In contrast to the Pratt truss, the diagonal web members are in compression and the vertical web members are in tension. Few of these bridges remain standing. Examples include Jay Bridge in Jay, New York ; McConnell's Mill Covered Bridge in Slippery Rock Township, Lawrence County, Pennsylvania ; Sandy Creek Covered Bridge in Jefferson County, Missouri ; and Westham Island Bridge in Delta, British Columbia , Canada. The K-truss

13680-490: The center. Many cantilever bridges, like the Quebec Bridge shown below, have two cantilever spans supporting a simple truss in the center. The bridge would remain standing if the simple truss section were removed. Bridges are the most widely known examples of truss use. There are many types, some of them dating back hundreds of years. Below are some of the more common designs. The Allan truss , designed by Percy Allan ,

13824-456: The colonies of Italian Eritrea and Italian Somaliland . On 10 June 1940, Mussolini declared war on Britain and France , which made Italian military forces in Libya a threat to Egypt and those in the AOI a danger to the British and French colonies in East Africa. Italian belligerence also closed the Mediterranean to Allied merchant ships and endangered British sea lanes along the coast of East Africa,

13968-414: The compression members and to control deflection. It is mainly used for rail bridges, showing off a simple and very strong design. In the Pratt truss the intersection of the verticals and the lower horizontal tension members are used to anchor the supports for the short-span girders under the tracks (among other things). With the Baltimore truss, there are almost twice as many points for this to happen because

14112-576: The construction of a stadium, with the upper chords of parallel trusses supporting a roof that may be rolled back. The Smithfield Street Bridge in Pittsburgh, Pennsylvania , is another example of this type. An example of a lenticular pony truss bridge that uses regular spans of iron is the Turn-of-River Bridge designed and manufactured by the Berlin Iron Bridge Co. The Pauli truss is

14256-751: The country and were effective scouts and saboteurs, although sometimes confused with Shifta , marauders who plundered and murdered at will. Once Italy entered the war, a 100-strong company was formed from German residents of East Africa and stranded German sailors. Italian forces in East Africa were equipped with about 3,313 heavy machine-guns, 5,313 machine-guns, 24 M11/39 medium tanks, 39 L3/35 tankettes, 126 armoured cars and 824 guns, twenty-four 20 mm anti-aircraft guns, seventy-one 81 mm mortars and 672,800 rifles. The Italians had little opportunity for reinforcement or supply, leading to severe shortages, especially of ammunition. On occasion, foreign merchant vessels captured by German merchant raiders in

14400-446: The destroyer Pantera dropped 110 mines in two barrages off Assab the day after. When Italy declared war on 10 June, Galileo Ferraris sailed for French Somaliland (Djibouti), Galileo Galilei to Aden, Galvani to the Gulf of Oman and Mecallé to Port Sudan. On 14 June Torricelli put to sea to relieve Galileo Ferraris whose crew had been incapacitated by chloromethane poisoning from

14544-475: The earliest examples is the Old Blenheim Bridge , which with a span of 210 feet (64 m) and a total length of 232 feet (71 m) long was the second-longest covered bridge in the United States, until its destruction from flooding in 2011. The Busching bridge, often erroneously used as an example of a Long truss, is an example of a Howe truss, as the verticals are metal rods. A Parker truss bridge

14688-401: The elements, as in a Vierendeel truss . In the bridge illustrated in the infobox at the top, vertical members are in tension, lower horizontal members in tension, shear , and bending, outer diagonal and top members are in compression, while the inner diagonals are in tension. The central vertical member stabilizes the upper compression member, preventing it from buckling . If the top member

14832-465: The end of July, the 3rd East African Infantry Brigade and the 6th East African Infantry Brigade had been formed. A Coastal Division and a Northern Frontier District Division had been planned but then the 11th (African) Division and the 12th (African) Division were created instead. On 1 June, the first South African unit arrived at the port of Mombasa in Kenya and by the end of July, the 1st South African Infantry Brigade Group had arrived. On 13 August,

14976-405: The fort to the Italians and on 9 November, two Baluch companies attacked and held the fort during the day and retired in the evening. During the night an Italian counter-attack was repulsed by artillery-fire and next morning the British re-occupied the fort unopposed. Ambushes were laid and prevented Italian reinforcements from occupying the fort or the hills on the flanks, despite frequent bombing by

15120-531: The high grade cypher of the Italian Army in East Africa. Later that month, the replacement cypher for the Regia Aeronautica was broken by the Combined Bureau, Middle East (CBME). In September 1940, Wavell ordered the commanders in Sudan and Kenya to make limited attacks once the rainy season had ended. On the northern front, Platt was to attack Gallabat and the vicinity; on the southern front, Cunningham

15264-499: The infantry had no cover. An ammunition lorry was set on fire by burning grass and the sound was taken to be an Italian counter-attack from behind. When a platoon advanced towards the sound with fixed bayonets, some troops thought that they were retreating. Part of the 1st Battalion, Essex Regiment at the fort broke and ran, taking some of the Gahrwalis with them. Many of the British fugitives mounted their transport and drove off, spreading

15408-651: The land fronts, In June 1940, there were 323 aircraft in the AOI, in 23 bomber squadrons with 138 aircraft, comprising 14 squadrons with six aircraft each, six Caproni Ca.133 light bomber squadrons, seven Savoia-Marchetti SM.81 squadrons and two squadrons of Savoia-Marchetti SM.79s . Four fighter squadrons had 36 aircraft , comprising two nine-aircraft Fiat CR.32 squadrons and two nine-aircraft Fiat CR.42 Falco squadrons; CAAOI had one reconnaissance squadron with nine IMAM Ro.37 aircraft. There were 183 first line aircraft and another 140 in reserve, of which 59 were operational and 81 were unserviceable. On

15552-595: The main British force slowly retired. On 5 August, the towns of Zeila and Hargeisa were captured, cutting off the British from French Somaliland. Odweina fell the following day and the Italian central and eastern columns joined. On 11 August, Major-General Alfred Reade Godwin-Austen was diverted to Berbera , en route to Kenya to take command as reinforcements increased the British garrison to five battalions. (From 5 to 19 August, RAF squadrons based at Aden flew 184 sorties, dropped 60 long tons (61 t) of bombs, lost seven aircraft destroyed and ten damaged.) On 11 August,

15696-574: The manufacture of lime in Gujarat . The value of this innovation was recognized, Almeida says, by both the Emperor and the local stonemasons, who "valued it greatly". The establishment of Gondar and the beginning of the Gondarine period would be accompanied by the building of a number of bridges, greatly facilitated by the introduction of lime mortar, as Ethiopian stonemasons regularly struggled in finding cement to make mortar . The innovation of bridge building

15840-459: The monk executed in the public square. Immediately after the execution, many of the clergymen claimed to have seen the victim's head with wings fly into heaven and decided to excommunicate the Emperor; they, too, were sentenced to death. The Emperor was said to have deeply regretted his actions, but could not find a monk to absolve him of his sins. Fasilides then learned in his dreams that a very holy elderly hermit, who never leaves her cave, existed in

15984-431: The mountains of Simien . Dressed as a pilgrim, Fasilides undertook the long journey to her refuge and begged her absolution. The old woman refused to pardon him and instead gave some advice, telling the monarch to return to Gondar and find a young slave woman who carries extra jugs for the poor. Fasilides made his way back to Gondar , where he identified the slave and the hut she lived in. There, to her great surprise,

16128-458: The naval and air commands in the Mediterranean and Middle East. Wavell was allowed only five staff officers for plans and command of an area of 3,500,000 sq mi (9,100,000 km ). From 1940 to 1941, operations took place in the Western Desert of Egypt, East Africa, Greece and the Middle East . In July 1939, Wavell devised a strategy to defend and then to dominate the Mediterranean as

16272-412: The needs at the site and allow rapid deployment of completed trusses. In the image, note the use of pairs of doubled trusses to adapt to the span and load requirements. In other applications the trusses may be stacked vertically, and doubled as necessary. The Baltimore truss is a subclass of the Pratt truss. A Baltimore truss has additional bracing in the lower section of the truss to prevent buckling in

16416-496: The open space, they manage to pass with their merchandise from one side to the other, without entering, the stream." In 1908, Emperor Menelik II ordered its reconstruction and also added an imposing gateway on the southern side of the bridge, which featured a cement panel commemorating his work. The bridge was destroyed on April 29, 1941, by retreating Italian soldiers during the East African Campaign . In early April 1941,

16560-727: The outbreak of war, the CAAOI had 10,700 t (10,500 long tons) of aviation fuel, 5,300 t (5,200 long tons) of bombs and 8,620,000 rounds of ammunition. Aircraft and engine maintenance was conducted at the main air bases and at the Caproni and Piaggio workshops, which could repair about fifteen seriously-damaged aircraft and engines each month, along with some moderately and lightly damaged aircraft and could also recycle scarce materials. The Italians had reserves for 75 per cent of their front-line strength but lacked spare parts and many aircraft were cannibalised to keep others operational. The quality of

16704-554: The panic and some of the runaways reached Doka before being stopped. The Italian bombers returned next morning and Slim ordered a withdrawal from Gallabat Ridge 3 mi (4.8 km) west to less exposed ground that evening. Sappers from the 21st Field Company remained behind to demolish the remaining buildings and stores in the fort. The artillery bombarded Gallabat and Metemma and set off Italian ammunition dumps full of pyrotechnics. British casualties since 6 November were 42 men killed and 125 wounded. The brigade patrolled to deny

16848-588: The rebellion in the western Ethiopian province of Gojjam , which the Italians had never been able to repress. In September, Colonel Daniel Sandford arrived to run the project, but until the Italian declaration of war, the conspiracy was held back by the government's policy of appeasement. Mission 101 was formed to co-ordinate the activities of the Ethiopian resistance. In June 1940, Selassie arrived in Egypt and in July, went to Sudan to meet Platt and discuss plans to recapture Ethiopia, despite Platt's reservations. In July,

16992-561: The refrigeration system. The crew of Macallé was also afflicted; the boat was run aground and lost on 15 June. On 18 June, Galileo Galilei boarded and released the neutral Yugoslav steamship Dravo and the next day engaged the armed trawler HMS  Moonstone off Aden. All but one officer was killed by shell-fire and Galileo Galilei was captured along with many documents including operational orders for four other Italian submarines. Archimede , Perla and Guglielmotti sailed from 19 to 21 June. On 26 June, Guglielmotti ran onto

17136-425: The rocky ground. The defenders at Boundary Khor were dug in behind fields of barbed wire and Castagnola had contacted Gondar for air support. Italian bombers and fighters attacked all day, shot down seven Gladiators for a loss of five Fiat CR-42s and destroyed the lorry carrying spare parts for the tanks. The ground was so hard and rocky that there were no trenches and when Italian bombers made their biggest attack,

17280-559: The short verticals will also be used to anchor the supports. Thus the short-span girders can be made lighter because their span is shorter. A good example of the Baltimore truss is the Amtrak Old Saybrook – Old Lyme Bridge in Connecticut , United States. The Bollman Truss Railroad Bridge at Savage, Maryland , United States is the only surviving example of a revolutionary design in the history of American bridge engineering. The type

17424-451: The simplest truss styles to implement, the king post consists of two angled supports leaning into a common vertical support. This type of bridge uses a substantial number of lightweight elements, easing the task of construction. Truss elements are usually of wood, iron, or steel. A lenticular truss bridge includes a lens-shape truss, with trusses between an upper chord functioning as an arch that curves up and then down to end points, and

17568-450: The standard for covered bridges built in central Ohio in the late 1800s and early 1900s. The Pegram truss is a hybrid between the Warren and Parker trusses where the upper chords are all of equal length and the lower chords are longer than the corresponding upper chord. Because of the difference in upper and lower chord length, each panel is not square. The members which would be vertical in

17712-464: The structure is functionally considered to be a flexible joint as opposed to a rigid joint with the strength to maintain its shape, and the resulting shape and strength of the structure are only maintained by the interlocking of the components. This assumption means that members of the truss (chords, verticals, and diagonals) will act only in tension or compression. A more complex analysis is required where rigid joints impose significant bending loads upon

17856-517: The summer of 1940 Italy was far from ready for a long war or for the occupation of large areas of Africa . Amedeo, Duke of Aosta , was appointed Viceroy and Governor-General of the AOI in November 1937, with a headquarters in Addis Ababa , the Ethiopian capital. On 1 June 1940, as the commander in chief of Comando Forze Armate dell'Africa Orientale Italiana (Italian East African Armed Forces Command) and Generale d'Armata Aerea (General of

18000-472: The term lenticular truss and, according to Thomas Boothby, the casual use of the term has clouded the literature. The Long truss was designed by Stephen H. Long in 1830. The design resembles a Howe truss , but is entirely made of wood instead of a combination of wood and metal. The longest surviving example is the Eldean Covered Bridge north of Troy, Ohio , spanning 224 feet (68 m). One of

18144-462: The theatre was formally added to his responsibilities. He expected that the Somalilands could be defended with minor reinforcement. If Italy joined the war, Ethiopia would be invaded as soon as there were sufficient troops. Wavell also co-ordinated plans with South Africa in March. On 1 May 1940, Wavell ordered British Troops Egypt to mobilise discreetly for military operations in western Egypt but after

18288-545: The truss members are both above and below the roadbed it is called a through truss; an example of this is the Pulaski Skyway , and where the sides extend above the roadbed but are not connected, a pony truss or half-through truss. Sometimes both the upper and lower chords support roadbeds, forming a double-decked truss . This can be used to separate rail from road traffic or to separate the two directions of road traffic. Since through truss bridges have supports located over

18432-471: The truss. Continuous truss bridges were not very common before the mid-20th century because they are statically indeterminate , which makes them difficult to design without the use of computers . A multi-span truss bridge may also be constructed using cantilever spans, which are supported at only one end rather than both ends like other types of trusses. Unlike a continuous truss, a cantilever truss does not need to be connected rigidly, or indeed at all, at

18576-570: The units varied. The SM.79 was the only modern bomber and the CR.32 fighter was obsolete but the Regia Aeronautica in East Africa had a cadre of highly experienced Spanish Civil War veterans. There was the nucleus of a transport fleet, with nine Savoia-Marchetti S.73 , nine Ca.133, six Ca.148 (a lengthened version of the Ca.133) and a Fokker F.VII , which maintained internal communications and carried urgent items and personnel between sectors. From 1935 to 1940

18720-428: The upper chord under compression. In a cantilever truss the situation is reversed, at least over a portion of the span. The typical cantilever truss bridge is a "balanced cantilever", which enables the construction to proceed outward from a central vertical spar in each direction. Usually these are built in pairs until the outer sections may be anchored to footings. A central gap, if present, can then be filled by lifting

18864-550: The villages of Qaysān , Kurmuk and Dumbode on the Blue Nile . From there the Italians ventured no further into Sudan owing to a lack of fuel and fortified Kassala with anti-tank defences, machine-gun posts and strongpoints, later establishing a brigade-strong garrison. The Italians were disappointed to find little anti-British sentiment among the Sudanese population. The 5th Indian Division began to arrive in Sudan in early September 1940. The 29th Indian Infantry Brigade were placed on

19008-430: The wood is employed for compression elements while other types may be easier to erect in particular site conditions, or when the balance between labor, machinery, and material costs has certain favorable proportions. The inclusion of the elements shown is largely an engineering decision based upon economics, being a balance between the costs of raw materials, off-site fabrication, component transportation, on-site erection,

19152-414: Was also easy to assemble. Wells Creek Bollman Bridge is the only other bridge designed by Wendel Bollman still in existence, but it is a Warren truss configuration. The bowstring truss bridge was patented in 1841 by Squire Whipple . While similar in appearance to a tied-arch bridge , a bowstring truss has diagonal load-bearing members: these diagonals result in a structure that more closely matches

19296-664: Was appointed General Officer Commanding-in-Chief (GOC-in-C) of the new Middle East Command, over the Mediterranean and Middle East theatres. Wavell was responsible for the defence of Egypt through the General Officer Commanding-in-Chief, British Troops Egypt, to train the Egyptian Army and co-ordinate military operations with the Commander-in-Chief Mediterranean, Admiral Andrew Cunningham ,

19440-452: Was built, claimed to have personally witnessed caravanners and merchants who, upon crossing the bridge, cried out, "God save the soul of Fasilides!" The introduction of lime mortar to Ethiopia is attributed to an artisan from India imported by the Portuguese in 1621, who, according to Manuel de Almeida , "discovered a kind of fine, light as it were worm eaten stone", similar to that used in

19584-421: Was difficult to remedy, which forced the Italians to return to the defensive. Churchill criticised Wavell for abandoning the colony without enough fighting but Wavell called it a textbook withdrawal in the face of superior numbers. Anglo-Egyptian Sudan shared a 1,000 mi (1,600 km) border with the AOI and on 4 July 1940, was invaded by an Italian force of about 6,500 men from Eritrea, which advanced on

19728-521: Was in London) and received permission to withdraw from the colony. The 2nd Battalion, Black Watch , supported by two companies of the 2nd King's African Rifles and parties of the 1st/2nd Punjab Regiment covered the retreat of the British contingent to Berbera. By 2:00 p.m. on 18 August, most of the contingent had been evacuated to Aden but HMAS  Hobart and the HQ stayed behind until morning before sailing and

19872-405: Was named after its inventor, Wendel Bollman , a self-educated Baltimore engineer. It was the first successful all-metal bridge design (patented in 1852) to be adopted and consistently used on a railroad. The design employs wrought iron tension members and cast iron compression members. The use of multiple independent tension elements reduces the likelihood of catastrophic failure. The structure

20016-549: Was ordered to withdraw from Kassala and Metemma in the lowlands along the Eritrea–Sudan border and hold the mountain passes on the Kassala– Agordat and Metemma–Gondar roads. Frusci chose not to withdraw from the lowlands, because withdrawal would involve too great a loss of prestige and because Kassala was an important railway junction; holding it prevented the British from using the railway to carry supplies from Port Sudan on

20160-659: Was popular with the Baltimore and Ohio Railroad . The Appomattox High Bridge on the Norfolk and Western Railway included 21 Fink deck truss spans from 1869 until their replacement in 1886. There are also inverted Fink truss bridges such as the Moody Pedestrian Bridge in Austin, Texas. The Howe truss , patented in 1840 by Massachusetts millwright William Howe , includes vertical members and diagonals that slope up towards

20304-501: Was set aside to finance operations. Major Orde Wingate was sent to Khartoum with an assistant to join the headquarters of the SDF. On 20 November, Wingate was flown to Sakhala to meet Sandford, and the RAF managed to bomb Dangila, drop propaganda leaflets and supply Mission 101, which raised Ethiopian morale, which had suffered much from Italian air power since the Second Italo-Abyssinian War. Mission 101 managed to persuade

20448-565: Was taken under the reign of Emperor Fasilides , who built seven stone bridges throughout his reign, the most notable one being the Sebara Dildiy. Geographer C.T. Beke was told that the central arch of this bridge was removed during the Zemene Mesafint (1769–1855) by the orders of a local warlord to stop an impending invasion. Despite the damage, Beke reports that it was still used by native merchants, who "by means of ropes stretched across

20592-596: Was to advance northwards from Kenya through Italian Somaliland into Ethiopia. In early November 1940, Cunningham had taken over the East African Force from Dickinson, who was in poor health. While Platt advanced from the north and Cunningham from the south, Wavell planned for a third force to be landed in British Somaliland by amphibious assault to re-take the colony, prior to advancing into Ethiopia. The three forces were to rendezvous at Addis Ababa. The conquest of

20736-458: Was transferred to Egypt to convert to Gladiators and returned to Khartoum in August. The SAAF in Kenya comprised 12 Squadron ( Junkers Ju 86 bombers), 11 Squadron ( Battle bombers), 40 Squadron ( Hart light bombers), 2 Squadron ( Fury fighters) and 237 (Rhodesia) Squadron RAF ( Hardy general-purpose aircraft). Better aircraft became available later but the first aircraft were old and slow,

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