Signs and symptoms.

The most common signs of jaundice in adults are a yellowish discoloration of the white area of the eye (sclera) and skin with scleral icterus presence indicating a serum bilirubin of at least 3 mg/dL. Other common signs include dark urine (bilirubinuria) and pale, fatty stool (steatorrhea). Because bilirubin is a skin irritant, jaundice is commonly associated with severe itchiness.  Eye conjunctiva have a particularly high affinity for bilirubin deposition due to high elastin content. Slight increases in serum bilirubin can therefore be detected early on by observing yellowing of sclerae. Traditionally referred to as "scleral icterus," this term is actually a misnomer because bilirubin deposition technically occurs in the conjunctival membranes overlying the avascular sclera. Thus, the proper term for the yellowing of "white of the eyes" is "conjunctival icterus".  A much less common sign of jaundice specifically during childhood is yellowish or greenish teeth. In developing children, hyperbilirubinemia may cause a yellow or green discoloration of teeth due to bilirubin deposition during the process of teeth calcification. While this may occur in children with hyperbilirubinemia, teeth discoloration due to hyperbilirubinemia is not observed in individuals with adult-onset liver disease. Disorders associated with a rise in serum levels of conjugated bilirubin during early development can also cause dental hypoplasia.

Causes.

Jaundice is a sign indicating the presence of an underlying diseases involving abnormal bilirubin metabolism, liver dysfunction, or biliary tract obstruction. In general, jaundice is present when blood levels of bilirubin exceed 3 mg/dL. Jaundice is classified into three categories, depending on which part of the physiological mechanism the pathology affects. The three categories are:

Pre-hepatic Causes.

Pre-hepatic jaundice is most commonly caused by a pathological increased rate of red blood cell (erythrocyte) hemolysis. The increased breakdown of erythrocytes → increased unconjugated serum bilirubin → increased deposition of unconjugated bilirubin into mucosal tissue. The following diseases may cause jaundice due to increased erythrocyte hemolysis:

Hepatic Causes.

Hepatic jaundice is caused by abnormal liver metabolism of bilirubin. The major causes of hepatic jaundice are significant damage to hepatocytes — due to infectious, drug/medication-induced, auto-immune etiology — or, less commonly, due to inheritable genetic diseases. The following is a non-exhaustive list of hepatic causes to jaundice:

Post-hepatic Causes.

Post-hepatic jaundice (obstructive jaundice), is caused by a blockage of bile ducts which transport bile containing conjugated bilirubin out of the liver for excretion. The following is a list of conditions that can cause post-hepatic jaundice:

Pathophysiology.

Jaundice is typically caused by an underlying pathological process that occurs at some point along the normal physiological pathway heme metabolism. A deeper understanding of the anatomical flow of normal heme metabolism is essential to appreciate the importance of pre-hepatic, hepatic, and post-hepatic categories. Thus, an anatomical approach to heme metabolism precedes a discussion of the pathophysiology of jaundice.

Normal Heme Metabolism.

Pre-hepatic Metabolism.

When red blood cells complete their life span of approximately 120 days, or if they are damaged, they rupture as they pass through the reticuloendothelial system and cell content including hemoglobin is released into circulation. Macrophages phagocytose free hemoglobin and split them into heme and globin. Two reactions then take place with the heme molecule. The first oxidation reaction is catalyzed by the microsomal enzyme heme oxygenase and results in biliverdin (green color pigment), iron, and carbon monoxide. The next step is the reduction of biliverdin to a yellow color tetrapyrrole pigment called bilirubin by cytosolic enzyme biliverdin reductase. This bilirubin is "unconjugated," "free" or "indirect" bilirubin. Approximately 4 milligrams of bilirubin per kilogram of blood is produced each day. The majority of this bilirubin comes from the breakdown of heme from expired red blood cells in the process just described. Approximately twenty percent comes from other heme sources, however, including ineffective erythropoiesis, and the breakdown of other heme-containing proteins, such as muscle myoglobin and cytochromes. The unconjugated bilirubin then travels to the liver through the bloodstream. Because this bilirubin is not soluble, it is transported through the blood bound to serum albumin.

Hepatic Metabolism.

Once unconjugated bilirubin arrives in the liver, a liver enzyme UDP-glucuronyl transferase conjugates bilirubin + glucuronic acid → bilirubin diglucuronide (conjugated bilirubin). Bilirubin that has been conjugated by the liver is water-soluble and excreted into the gallbladder.

Post-hepatic Metabolism.

Bilirubin enters the intestinal tract via bile. In the intestinal tract, bilirubin is converted into urobilinogen by symbiotic intestinal bacteria. Most urobilinogen is converted into stercobilinogen and further oxidized into stercobilin. Stercobilin is excreted via feces, giving stool its characteristic brown coloration. A small portion of urobilinogen is reabsorbed back into the gastrointestinal cells. Most reabsorbed urobilinogen undergoes hepatobiliary recirculation. A smaller portion of reabsorbed urobilinogen is filtrated into the kidneys. In the urine, urobilinogen is converted to urobilin, which gives urine its characteristic yellow color.

Abnormalities in Heme Metabolism and Excretion.

One way to understand jaundice pathophysiology is to organize it into disorders that cause increased bilirubin production (abnormal heme metabolism) or decreased bilirubin excretion (abnormal heme excretion).

Pre-hepatic Pathophysiology.

Pre-hepatic jaundice is attributed to a pathologic increase in bilirubin production. The pathophysiology is quite simple: an increased rate of erythrocyte hemolysis → increased bilirubin production → increased deposition of bilirubin in mucosal tissue → appearance of yellow hue.

Hepatic Pathophysiology.

Hepatic jaundice (hepatocellular jaundice) is due to significant damage to liver function → hepatic cell death and necrosis occur → impaired bilirubin transport across hepatocytes. Bilirubin transport across hepatocytes may be impaired at any point between hepatocellular uptake of unconjugated bilirubin and hepatocellular transport of conjugated bilirubin into the gallbladder. In addition, subsequent cellular edema due to inflammation causes mechanical obstruction of intrahepatic biliary tract. Most commonly, interferences in all three major steps of bilirubin metabolism — uptake, conjugation, and excretion — usually occur in hepatocellular jaundice. Thus, an abnormal rise in both unconjugated and conjugated bilirubin will be present. Because excretion (the rate-limiting step) is usually impaired to the greatest extent, conjugated hyperbilirubinemia predominates.  The unconjugated bilirubin still enters the liver cells and becomes conjugated in the usual way. This conjugated bilirubin is then returned to the blood, probably by rupture of the congested bile canaliculi and direct emptying of the bile into the lymph leaving the liver. Thus, most of the bilirubin in the plasma becomes the conjugated type rather than the unconjugated type, and this conjugated bilirubin, which did not go to intestine to become urobilinogen, gives the urine the dark color.  Bilirubinuria is due to excess conjugated bilirubin excreted in the urine.

Post-hepatic Pathophysiology.

Post-hepatic jaundice (obstructive jaundice) is due to a blockage of bile excretion from the biliary tract → increased conjugated bilirubin and bile salts. In complete obstruction of the bile duct, conjugated bilirubin cannot access the intestinal tract → no further bilirubin conversion to urobilinogen → no stercobilin or urobilin. Instead, excess conjugated bilirubin is filtrated into the urine without urobilinogen in obstructive jaundice. Conjugated bilirubin in urine (bilirubinuria) gives urine an abnormally dark brown color. Thus, the presence of pale stool (stercobilin absent from feces) and dark urine (conjugated bilirubin present in urine) suggest an obstructive cause of jaundice. Because these associated signs are also positive in many hepatic jaundice conditions, they cannot be a reliable clinical feature to distinguish obstruction versus hepatocellular jaundice causes.

Diagnosis.

Most people presenting with jaundice will have various predictable patterns of liver panel abnormalities, though significant variation does exist. The typical liver panel will include blood levels of enzymes found primarily from the liver, such as the aminotransferases (ALT, AST), and alkaline phosphatase (ALP); bilirubin (which causes the jaundice); and protein levels, specifically, total protein and albumin. Other primary lab tests for liver function include gamma glutamyl transpeptidase (GGT) and prothrombin time (PT). No single test can differentiate between various classifications of jaundice. A combination of liver function tests as well as other physical exam findings is essential to arrive at a diagnosis.

Labs.

Some bone and heart disorders can lead to an increase in ALP and the aminotransferases, so the first step in differentiating these from liver problems is to compare the levels of GGT, which will only be elevated in liver-specific conditions. The second step is distinguishing from biliary (cholestatic) or liver causes of jaundice and altered laboratory results. ALP and GGT levels will typically rise with one pattern while aspartate aminotransferase (AST) and alanine aminotransferase (ALT) rise in a separate pattern. If the ALP (10–45 IU/L) and GGT (18–85 IU/L) levels rise proportionately as high as the AST (12–38 IU/L) and ALT (10–45 IU/L) levels, this indicates a cholestatic problem. On the other hand, if the AST and ALT rise is significantly higher than the ALP and GGT rise, this indicates a liver problem. Finally, distinguishing between liver causes of jaundice, comparing levels of AST and ALT can prove useful. AST levels will typically be higher than ALT. This remains the case in most liver disorders except for hepatitis (viral or hepatotoxic). Alcoholic liver damage may see fairly normal ALT levels, with AST 10 times higher than ALT. On the other hand, if ALT is higher than AST, this is indicative of hepatitis. Levels of ALT and AST are not well correlated to the extent of liver damage, although rapid drops in these levels from very high levels can indicate severe necrosis. Low levels of albumin tend to indicate a chronic condition, while it is normal in hepatitis and cholestasis.  Lab results for liver panels are frequently compared by the magnitude of their differences, not the pure number, as well as by their ratios. The AST:ALT ratio can be a good indicator of whether the disorder is alcoholic liver damage (above 10), some other form of liver damage (above 1), or hepatitis (less than 1). Bilirubin levels greater than 10 times normal could indicate neoplastic or intrahepatic cholestasis. Levels lower than this tend to indicate hepatocellular causes. AST levels greater than 15 times normal tend to indicate acute hepatocellular damage. Less than this tend to indicate obstructive causes. ALP levels greater than 5 times normal tend to indicate obstruction, while levels greater than 10 times normal can indicate drug (toxin) induced cholestatic hepatitis or cytomegalovirus infection. Both of these conditions can also have ALT and AST greater than 20 times normal. GGT levels greater than 10 times normal typically indicate cholestasis. Levels 5–10 times tend to indicate viral hepatitis. Levels less than 5 times normal tend to indicate drug toxicity. Acute hepatitis will typically have ALT and AST levels rising 20–30 times normal (above 1000), and may remain significantly elevated for several weeks. Acetaminophen toxicity can result in ALT and AST levels greater than 50 times normal.  Laboratory findings depend on the cause of jaundice.  Unconjugated bilirubin is hydrophobic and therefore cannot be excreted in urine. Thus, the finding of increased urobilinogen in the urine without the presence of bilirubin in the urine (due to its unconjugated state) suggests hemolytic jaundice as the underlying disease process. Urobilinogen will be greater than 2 units (i.e., hemolytic anemia causes increased heme metabolism; exception: infants where gut flora has not developed). Conversely, conjugated bilirubin is hydrophilic and thus can be detected as present in the urine — bilirubinuria — in contrast to unconjugated bilirubin which is absent in the urine.

Imaging.

Medical imaging such as ultrasound, CT scan, and HIDA scans are useful for detecting bile duct blockage.

Differential diagnosis.

Yellow discoloration of the skin, especially on the palms and the soles, but not of the sclera or inside the mouth is due to carotenemia—a harmless condition.

Treatment.

Treatment of jaundice will vary depending on the underlying cause. If a bile duct blockage is present, surgery is typically required; otherwise, management will be medical. Surgery in patients with obstructive jaundice are associated with significantly higher rates of complications (69% vs 38%, P=0.002) and mortality. Medical management may involve treating infectious causes and stopping medication that could be contributing to the jaundice. The itchiness may be helped by draining the gallbladder or ursodeoxycholic acid.

Complications.

Hyperbilirubinemia, more precisely hyperbilirubinemia due to the unconjugated fraction, may cause bilirubin to accumulate in the gray matter of the central nervous system, potentially causing irreversible neurological damage leading to a condition known as kernicterus. Depending on the level of exposure, the effects range from unnoticeable to severe brain damage and even death. Newborns are especially vulnerable to hyperbilirubinemia-induced neurological damage and therefore must be carefully monitored for alterations in their serum bilirubin levels.  Individuals with parenchymal liver disease who have impaired hemostasis may develop bleeding problems.

Epidemiology.

Jaundice in adults is rare. Under the five year DISCOVERY programme in the UK, annual incidence of jaundice was 0.74 per 1000 individuals over age 45, although this rate may be slightly inflated due to the main goal of the programme collecting and analyzing cancer data in the population. Jaundice is commonly associated with severity of disease with an incidence of up to 40% of patients requiring intensive care in ICU experiencing jaundice. The causes of jaundice in the intensive care setting is both due to jaundice as the primary reason for ICU stay or as a morbidity to an underlying disease (i.e. sepsis).  In the developed world, the most common causes of jaundice are blockage of the bile duct or medication-induced. In the developing world, the most common cause of jaundice is infectious such as viral hepatitis, leptospirosis, schistosomiasis, or malaria.

Risk factors.

Risk factors associated with high serum bilirubin levels include male gender, white ethnicities, and active smoking. Mean serum total bilirubin levels in adults were found to be higher in men (0.72 ± 0.004 mg/dL) than women (0.52 ± 0.003 mg/dL). Higher bilirubin levels in adults are found also in non-Hispanic white population (0.63 ± 0.004 mg/dL) and Mexican American population (0.61 ± 0.005 mg/dL) while lower in non-Hispanic black population (0.55 ± 0.005 mg/dL). Bilirubin levels are higher in active smokers.

Special Populations.

Neonatal Jaundice.

Symptoms.

Jaundice in infants presents with yellowed skin and icteral sclerae. Neonatal jaundice spreads in a cephalo-caudal pattern, affecting the face and neck before spreading down to the trunk and lower extremities in more severe cases. Other symptoms may include drowsiness, poor feeding, and in severe cases, unconjugated bilirubin can cross the blood-brain barrier and cause permanent neurological damage (kernicterus).

Causes.

The most common cause of jaundice in infants is normal physiologic jaundice. Pathologic causes of neonatal jaundice include the following:

Pathophysiology.

Transient neonatal jaundice is one of the most common conditions occurring in newborns (children under 28 days of age) with more than eighty percent affected during their first week of life. Jaundice in infants, like adults, is characterized by increased bilirubin levels (total serum bilirubin greater than 5 mg/dL).  Normal physiological neonatal jaundice is due to immaturity of liver enzymes involved in bilirubin metabolism, immature gut microbiota, and increased breakdown of fetal hemoglobin (HbF). Breastmilk jaundice is caused by an increased concentration of β-glucuronidase in breast milk → ↑ deconjugation and reabsorption of bilirubin → persistence of physiologic jaundice with unconjugated hyperbilirubinemia. Onset of breastmilk jaundice is within 2 weeks after birth and lasts for 4–13 weeks.  While most cases of newborn jaundice are not harmful, if bilirubin levels are very high, brain damage — kernicterus — may occur leading to significant disability. Kernicterus is associated with increased unconjugated bilirubin (which is not carried by albumin). Newborns are especially vulnerable to this due to increased permeability of the blood–brain barrier and increased unconjugated bilirubin given fetal hemoglobin breakdown and immature gut flora. This condition has been rising in recent years due to less time spent outdoors.

Treatment.

Jaundice in newborns is usually transient and dissipates without medical intervention. In cases when serum bilirubin levels are greater than 4–21 mg/dL (68-360 μmol/L), infant may be treated with phototherapy or exchanged transfusion depending on the infant's age and prematurity status. A Bili light is often the tool used for early treatment, which often consists of exposing the baby to intensive phototherapy. Sunbathing is effective treatment, and has the advantage of ultra-violet-B, which promotes vitamin D production. Bilirubin count is also lowered through excretion — bowel movements and urination —so frequent and effective feedings are vital measures to decrease jaundice in infants.

Etymology.

Jaundice comes from the French "jaune", meaning yellow, "jaunisse" meaning "yellow disease". The medical term for it is icterus from the Greek word "ikteros". The origin of the word icterus is quite bizarre, coming from an ancient belief that jaundice could be cured from looking at the yellow bird "icteria". The term "icterus" is sometimes incorrectly used to refer to jaundice specifically of sclera.

Jaundice, also known as icterus, is a yellowish or greenish pigmentation of the skin and whites of the eyes due to high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of an underlying diseases involving abnormal heme metabolism, liver dysfunction, or biliary tract obstruction. The prevalence of jaundice in adults is rare, while jaundice in babies is common with an estimated eighty percent affected during their first week of life. The most common associated symptoms of jaundice are itchiness, pale feces, and dark urine. Normal levels of bilirubin in blood are below 1.0 mg/dL (17 μmol/L), while levels over 2–3 mg/dL (34-51 μmol/L) typically result in jaundice. High blood bilirubin is divided into two types: unconjugated bilirubin and conjugated bilirubin. Causes of jaundice vary from non-serious to potentially fatal. High unconjugated bilirubin may be due to excess red blood cell breakdown, large bruises, genetic conditions such as Gilbert's syndrome, not eating for a prolonged period of time, newborn jaundice, or thyroid problems. High conjugated bilirubin may be due to liver diseases such as cirrhosis or hepatitis, infections, medications, or blockage of the bile duct. Blockage of the bile duct may occur due to gallstones, cancer, or pancreatitis. Other conditions can also cause yellowish skin, but are not jaundice, including carotenemia — which can develop from eating large amounts of foods containing carotene — or medications like rifampin. Treatment of jaundice is typically determined by the underlying cause. If a bile duct blockage is present, surgery is typically required; otherwise, management is medical. Medical management may involve treating infectious causes and stopping medication that could be contributing to the jaundice. Jaundice in newborns may be treated with phototherapy or exchanged transfusion depending on age and prematurity when the bilirubin is greater than 4–21 mg/dL (68-360 μmol/L). The itchiness may be helped by draining the gallbladder or ursodeoxycholic acid. The word "jaundice" is from the French "jaunisse", meaning "yellow disease".

Der Ikterus (früher auch "Icterus"; von, "íkteros", „Gelbsucht“), auch Gelbsucht (von mittelhochdeutsch "gëlsuht"; veraltet auch "Gallsucht") genannt, ist eine Gelbfärbung von Haut, Schleimhäuten sowie der Lederhäute der Augen durch eine erhöhte Konzentration von Bilirubin im Blut. Es handelt sich um ein bereits im Altertum in Vorderasien beschriebenes Symptom, das bei unterschiedlichen Erkrankungen auftreten kann.


Geographical extent.

Inside Europe.

Germany.

It has been estimated that Low German has approximately 2 to 5 million speakers (depending on the definition of 'native speaker') in Germany, primarily in Northern Germany,  Variants of Low German are spoken in most parts of Northern Germany, for instance in the states of Lower Saxony, North Rhine-Westphalia, Hamburg, Bremen, Schleswig-Holstein, Mecklenburg-Vorpommern, Saxony-Anhalt, and Brandenburg. Small portions of northern Hesse and northern Thuringia are traditionally Low Saxon-speaking too. Historically, Low German was also spoken in formerly German parts of Poland as well as in East Prussia and the Baltic provinces (modern Estonia and Latvia). The Baltic Germans spoke a distinct Low German dialect, which has influenced the vocabulary and phonetics of both Estonian and Latvian. The historical of Low German also included contemporary northern Poland, East Prussia (the modern Kaliningrad Oblast of Russia), a part of western Lithuania, and the German communities in Estonia and Latvia, most notably their Hanseatic cities. German speakers in this area fled the Red Army or were forcibly expelled after the border changes at the end of World War II.  The language was also formerly spoken in the outer areas of what is now the city-state of Berlin, but in the course of urbanisation and national centralisation in that city, the language has vanished (the Berlin dialect itself is a northern outpost of High German, though it has some Low German features).  Today, there are still speakers outside Germany to be found in the coastal areas of present-day Poland (minority of ethnic German East Pomeranian speakers who were not expelled from Pomerania, as well as the regions around Braniewo). In the Southern Jutland region of Denmark there may still be some Low German speakers in some German minority communities, but the Low German and North Frisian dialects of Denmark can be considered moribund at this time.

The Netherlands.

Dialects of Low German are spoken in the northeastern area of the Netherlands (Dutch Low Saxon) and are written there with an unstandardized orthography based on Standard Dutch orthography. The position of the language is, according to UNESCO, vulnerable. Between 1995 and 2011 the numbers of parent speakers dropped from 34% in 1995 to 15% in 2011. Numbers of child speakers dropped from 8% to 2% in the same period. The total number of speakers is estimated at 1.7 million speakers. There are speakers in the Dutch north and eastern provinces of Groningen, Drenthe, Stellingwerf (part of Friesland), Overijssel, Gelderland, Utrecht and Flevoland, in several dialect groups per province.

Outside Europe and the Mennonites.

There are also immigrant communities where Low German is spoken in the Western hemisphere, including Canada, the United States, Mexico, Belize, Venezuela, Bolivia, Argentina, Brazil, Paraguay and Uruguay. In some of these countries, the language is part of the Mennonite religion and culture. There are Mennonite communities in Ontario, Saskatchewan, Alberta, British Columbia, Manitoba, Kansas and Minnesota which use Low German in their religious services and communities. These Mennonites are descended from primarily Dutch settlers that had initially settled in the Vistula delta region of Prussia in the 16th and 17th centuries before moving to newly-acquired Russian territories in Ukraine in the late 18th and early 19th centuries, and then to the Americas in the 19th and early 20th centuries. The types of Low German spoken in these communities and in the Midwest region of the United States have diverged since emigration. The survival of the language is tenuous in many places, and has died out in many places where assimilation has occurred. Members and friends of the Historical Society of North German Settlements in Western New York (Bergholz, NY), a community of Lutherans who trace their immigration from Pomerania in the 1840s, hold quarterly "Plattdeutsch lunch" events, where remaining speakers of the language gather to share and preserve the dialect. Mennonite colonies in Paraguay, Belize, and Chihuahua, Mexico have made Low German a "co-official language" of the community.  East Pomeranian is also spoken in parts of Southern and Southeastern Brazil, in the latter especially in the state of, being official in five municipalities, and spoken among its ethnically European migrants elsewhere, primarily in the states of Rio de Janeiro and. East Pomeranian-speaking regions of Southern Brazil are often assimilated into the general German Brazilian population and culture, for example celebrating the, and there can even be a language shift from it to in some areas. In, nevertheless, Pomeranian Brazilians are more often proud of their language, and particular religious traditions and culture, and not uncommonly inheriting the nationalism of their ancestors, being more likely to accept marriages of its members with Brazilians of origins other than a Germanic Central European one than to assimilate with Brazilians of Swiss, Austrian, Czech, and non-East Pomeranian-speaking German and Prussian heritage – that were much more numerous immigrants to both Brazilian regions (and whose language almost faded out in the latter, due to assimilation and internal migration), by themselves less numerous than the Italian ones (with only Venetian communities in areas of highly Venetian presence conserving Talian, and other Italian languages and dialects fading out elsewhere).

Nomenclature.

There are different uses of the term "Low German":  In Germany, native speakers of Low German call their language,,,,, (South-Westphalian), (Eastphalian), (Prussian), or. In the Netherlands, native speakers refer to their language as,,, or the name of their village, town or district.  Officially, Low German is called or (Nether or Low German language), or (Nether or Low German) in High German by the German authorities, (Nether or Low German language), or (Nether or Low German) in Low German by the German authorities and (Nether or Low Saxon) by the Dutch authorities., and, are seen in linguistic texts from the German and Dutch linguistic communities respectively.  In Danish it is called, or, rarely,. Mennonite Low German is called.  "Low" refers to the flat plains and coastal area of the northern European lowlands, contrasted with the mountainous areas of central and southern Germany, Switzerland, and Austria, where High German (Highland German) is spoken. Etymologically however, "Platt" meant "clear" in the sense of a language the simple people could understand. In Dutch and German, the word can also mean "improper", "rude" or "too simple" which is why the term is not popular in the Netherlands.  The colloquial term denotes both Low German dialects and any non-standard Western variety of German; this use is chiefly found in northern and Western Germany and is not considered to be linguistically correct.  The ISO 639-2 language code for Low German (Low Saxon) has been nds ( or ) since May 2000.

Classification.

Low German is a part of the continental West Germanic dialect continuum. To the West, it blends into the Low Franconian languages, including Dutch. A distinguishing feature between the Southern Low Franconian varieties and Low German varieties is the plural of the verbs. Low German varieties have a common verbal plural ending, whereas Low Franconian varieties have a different form for the second person plural. This is complicated in that in most Low Franconian varieties, including standard Dutch, the original second-person plural form has replaced the singular. Some dialects, including again standard Dutch, innovated a new second-person plural form in the last few centuries, using the other plural forms as the source.  To the South, Low German blends into the High German dialects of Central German that have been affected by the High German consonant shift. The division is usually drawn at the Benrath line that traces the " – " isogloss.  To the East, it abuts the Kashubian language (the only remnant of the Pomeranian language) and, since the expulsion of nearly all Germans from the Polish part of Pomerania following the Second World War, also by the Polish language. East Pomeranian and Central Pomeranian are dialects of Low German.  To the North and Northwest, it abuts the Danish and the Frisian languages. Note that in Germany, Low German has replaced the Frisian languages in many regions. Saterland Frisian is the only remnant of East Frisian language and is surrounded by Low German, as are the few remaining North Frisian varieties, and the Low German dialects of those regions have influences from Frisian substrates.  Most linguists classify the dialects of Low German together with English and Frisian as the "North Sea Germanic" or "Ingvaeonic" languages. However, most exclude Low German from the group often called Anglo-Frisian languages because some distinctive features of that group of languages are only partially observed in Low German, for instance the Ingvaeonic nasal spirant law (some dialects have "us", for "us" whereas others have, ), and because other distinctive features do not occur in Low German at all, for instance the palatalization of /k/ (compare palatalized forms such as English "cheese", Frisian to non-palatalized forms such as Low German or, Dutch, German ).

Language or dialect?

The question of whether today's Low German should be considered a separate language or a dialect of German or even Dutch has been a point of contention. Linguistics offers no simple, generally accepted criterion to decide the question.  Scholarly arguments have been put forward for classifying Low German as a German dialect. As stated above, the arguments are not linguistic but rather sociopolitical and revolve mainly around the fact that Low German has no official standard form or use in sophisticated media. The situation of Low German may thus be considered a "pseudo-dialectized abstand language" ("scheindialektisierte Abstandsprache"). In contrast, Old Saxon and Middle Low German are generally considered separate languages in their own rights. Since Low German has strongly declined since the 18th century, the perceived similarities with High German or Dutch may often be direct adaptations from the dominating standard language, resulting in a growing inability by speakers to speak correctly what was once Low German proper.  Others have argued for the independence of today's Low German dialects, taken as continuous outflow of the Old Saxon and Middle Low German tradition. "Glottolog" classifies six varieties of Low German as distinct languages, based on a low degree of mutual intelligibility.

Legal status.

Low German has been recognized by the Netherlands and by Germany (since 1999) as a regional language according to the European Charter for Regional or Minority Languages. Within the official terminology defined in the charter, this status would not be available to a dialect of an official language (as per article 1a), and hence not to Low German in Germany if it were considered a dialect of German. Advocates of the promotion of Low German have expressed considerable hope that this political development will at once lend legitimacy to their claim that Low German is a separate language, and help mitigate the functional limits of the language that may still be cited as objective criteria for a mere dialect (such as the virtually complete absence from legal and administrative contexts, schools, the media, etc.).  At the request of Schleswig-Holstein, the German government has declared Low German as a regional language. German offices in Schleswig-Holstein are obliged to accept and handle applications in Low German on the same footing as Standard High German applications. The ruled in a case that this was even to be done at the patent office in Munich, in a non–Low German region, when the applicant then had to pay the charge for a translator, because applications in Low German are considered "" (not written in the German language).

Varieties of Low German.

In the Netherlands.

The Dutch Low Saxon varieties, which are also defined as Dutch dialects, consist of:

History.

Old Saxon.

Old Saxon, also known as Old Low German, is a West Germanic language. It is documented from the 9th century until the 12th century, when it evolved into Middle Low German. It was spoken on the north-west coast of Germany and in Denmark (Schleswig-Holstein) by Saxon peoples. It is closely related to Old Anglo-Frisian (Old Frisian, Old English), partially participating in the Ingvaeonic nasal spirant law.  Only a few texts survive, predominantly in baptismal vows the Saxons were required to perform at the behest of Charlemagne. The only literary texts preserved are "Heliand" and the Old Saxon Genesis.

Middle Low German.

The Middle Low German language is an ancestor of modern Low German. It was spoken from about 1100 to 1600. The neighbouring languages within the dialect continuum of the West Germanic languages were Middle Dutch in the West and Middle High German in the South, later substituted by Early New High German. Middle Low German was the lingua franca of the Hanseatic League, spoken all around the North Sea and the Baltic Sea. It had a significant influence on the Scandinavian languages. Based on the language of Lübeck, a standardized written language was developing, though it was never codified.

Contemporary.

There is a distinction between the German and the Dutch Low Saxon/Low German situation.

Germany.

After mass education in Germany in the 19th and 20th centuries, the slow decline which Low German had been experiencing since the end of the Hanseatic League turned into a free fall. The decision to exclude Low German in formal education was not without controversy, however. On one hand, proponents of Low German advocated that since it had a strong cultural and historical value and was the native language of students in northern Germany, it had a place in the classroom. On the other hand, High German was considered the language of education, science, and national unity, and since schools promoted these values, High German was seen as the best candidate for the language of instruction.  Initially, regional languages and dialects were thought to limit the intellectual ability of their speakers. When historical linguists illustrated the archaic character of certain features and constructions of Low German, this was seen as a sign of its "backwardness." It wasn't until the efforts of proponents such as Klaus Groth that this impression changed. Groth's publications demonstrated that Low German was a valuable language in its own right, and he was able to convince others that Low German was suitable for literary arts and was a national treasure worth keeping.  Through the works of advocates like Groth, both proponents and opponents of Low German in formal education saw the language's innate value as the cultural and historical language of northern Germany. Nevertheless, opponents claimed that it should simply remain a spoken and informal language to be used on the street and in the home, but not in formal schooling. In their opinion, it simply did not match the nationally unifying power of High German. As a result, while Low German literature was deemed worthy of being taught in school, High German was chosen as the language of scholarly instruction. With High German the language of education and Low German the language of the home and daily life, a stable diglossia developed in Northern Germany. Various Low German dialects are understood by 10 million people, but many fewer are native speakers. Total users in all countries are 301,000.  The KDE project supports Low German (nds) as a language for its computer desktop environment, as does the GNOME Desktop Project. Open-source software has been translated into Low German; this used to be coordinated via a page on Sourceforge, but as of 2015, the most active project is that of KDE.

Netherlands.

In the early 20th century, scholars in the Netherlands argued that speaking dialects hindered language acquisition, and it was therefore strongly discouraged. As education improved, and mass communication became more widespread, the Low Saxon dialects further declined, although decline has been greater in urban centres of the Low Saxon regions. When in 1975 dialect folk and rock bands such as Normaal and became successful with their overt disapproval of what they experienced as "misplaced Dutch snobbery" and the Western Dutch contempt for (speakers of) Low Saxon dialects, they gained a following among the more rurally oriented inhabitants, launching Low Saxon as a sub-culture. They inspired contemporary dialect artists and rock bands, such as,,, Nonetheless, the position of the language is vulnerable according to UNESCO. Low Saxon is still spoken more widely than in Northern Germany. A 2005 study showed that 29,2% spoke exclusively Low Saxon and 47,9% spoke both Dutch as Low Saxon at home. 70,9% percent said that they could speak Low Saxon. This is a significant higher number than the 2011 study. Efforts are made in Germany and in the Netherlands to protect Low German as a regional language.

Sound change.

As with the Anglo-Frisian languages and the North Germanic languages, Low German has not been influenced by the High German consonant shift except for old having shifted to. Therefore, a lot of Low German words sound similar to their English counterparts. One feature that does distinguish Low German from English generally is final devoicing of obstruents, as exemplified by the words 'good' and 'wind' below. This is a characteristic of Dutch and German as well and involves positional neutralization of voicing contrast in the coda position for obstruents (i.e. t = d at the end of a syllable.) This is not used in English except in the Yorkshire dialect, where there is a process known as "Yorkshire assimilation".  For instance: "water", "later", "bit", "dish", "ship", "pull", "good", "clock", "sail", "he", "storm", "wind", "grass", "hold", "old".  The table below shows the relationship between Low German consonants which were unaffected by this chain shift and their equivalents in other West Germanic languages. Contemporary Swedish and Icelandic shown for comparison; Eastern and Western North Germanic languages, respectively.  "Notes":

Grammar.

Generally speaking, Low German grammar shows similarities with the grammars of Dutch, Frisian, English, and Scots, but the dialects of Northern Germany share some features (especially lexical and syntactic features) with German dialects.

Nouns.

Low German declension has only two morphologically marked noun cases, where accusative and dative together constitute an oblique case, and the genitive case has been lost.

Dative den/dän.

In most modern dialects, the nominative and oblique cases are primarily distinguished only in the singular of masculine nouns. In some Low German dialects, the genitive case is distinguished as well (e.g. varieties of Mennonite Low German.) It is marked in the masculine gender by changing the masculine definite determiner 'de' from "de" to "den/dän". By contrast, German distinguishes four cases: nominative, accusative, genitive, and dative. So, for example, the definite article of the masculine singular has the forms: der (nom), den (acc), des (gen), and dem (dat.) Thus case marking in Low German is simpler than in German.

Verbs.

In Low German verbs are conjugated for person, number, and tense. Verb conjugation for person is only differentiated in the singular. There are five tenses in Low German: present tense, preterite, perfect, and pluperfect, and in Mennonite Low German the present perfect which signifies a remaining effect from a past finished action. For example, "Ekj sie jekomen", "I am come", means that the speaker came and he is still at the place to which he came as a result of his completed action.  Unlike Dutch, German, and southern Low German, the northern dialects form the participle without the prefix "ge-", like the Scandinavian languages, Frisian and English. Compare to the German past participle geschlafen. This past participle is formed with the auxiliary verbs "hebben" "to have" and "wesen/sien" "to be". When the past participle ends with "-en" or in a few oft-used words like "west" (been).  The reason for the two conjugations shown in the plural is regional: dialects in the central area use -t while the dialects in East Frisia and the dialects in Mecklenburg and further east use -en. The -en suffix is of Dutch influence. The -t ending is however more often encountered, even in areas where -en endings were prominent due to the fact that these -t endings are seen as "kennzeichnend Niederdeutsch", that is to say "a well-known feature of Low German".  There are 26 verb affixes.  There is also a progressive form of verbs in present, corresponding to the same in the Dutch language. It is formed with "wesen" (to be), the preposition "an" (at) and "dat" (the/it).

Adjectives.

The forms of Low German's adjectives are distinct from other closely related languages such as German and English. These forms fall somewhere in between these two languages. As in German, the adjectives in Low German may make a distinction between singular and plural to agree with the nouns that they modify, as well as between the three genders, between the nominative and oblique cases and between indefinite (weak) and definite (strong) forms. However, there is a lot of variation in that respect and some or all of these distinctions may also be absent, so that a single undeclined form of the adjective can occur in all cases, as in English. This is especially common in the neuter. If the adjective is declined, the pattern tends to be as follows:  As mentioned above, alternative undeclined forms such as "dat lütt Land", "de lütt Lannen", "en stark Kerl", "de stark Kerl", "stark Kerls", "de stark Kerls" etc. can occur.

Personal pronouns.

Like German, Low German maintains the historical Germanic distinction between the second person singular and second person plural. In English and German, this distinction would translate to “thou” and “du” referring to one person, and “ye” and “ihr” referring to more than one person. The second person pronouns for each case are given below to further illustrate this distinction.  In the genitive (possessive) case, the pronoun functions in the same way as an adjective and so it may take an ending if needed to match the singular or plural status of the noun it is modifying. So, for example, if “you” possess multiple books, then [dinen] would be used to express that the singular second person possesses multiple objects: the books. If several people in the second person (“you all”) possessed multiple books, then [jug’] would be used instead.

Writing system.

Low German is written using the Latin alphabet. There is no true standard orthography, only several locally more or less accepted orthographic guidelines, those in the Netherlands mostly based on Dutch orthography, and those in Germany mostly based on German orthography. To the latter group belongs the orthography devised by Johannes Sass. It is mostly used by modern official publications and internet sites, especially the Low German Wikipedia. This diversity, a result of centuries of official neglect and suppression, has a very fragmenting and thus weakening effect on the language as a whole, since it has created barriers that do not exist on the spoken level. Interregional and international communication is severely hampered by this. Most of these systems aim at representing the phonetic (allophonic) output rather than underlying (phonemic) representations, but trying to conserve many etymological spellings. Furthermore, many writers follow guidelines only roughly. This adds numerous idiosyncratic and often inconsistent ways of spelling to the already existing great orthographic diversity.  In 2011, writers of the Dutch Low Saxon Wikipedia developed a spelling that would be suitable and applicable to all varieties of Low Saxon in the Netherlands, although the semi-official dialect institutes have not picked up on this, or indicated that they believed that yet another writing system will only further confuse dialect writers rather than suit them. The new spelling was introduced to the Dutch Low Saxon Wikipedia to unify the spelling of categories, templates and comparable source code writings.  In 2018, a team of writers from both the Dutch and the German Low Saxon Wikipedia completed the New Saxon Spelling, which aims to unite the different spelling systems of the Netherlands and Germany. Unlike traditional spelling systems, this spelling does not focus on correct display of pronunciation, but instead seeks mutual legibility for both German and Dutch readers of Low Saxon, based on etymology. Readers may apply their own pronunciation. As such, it can be seen as an extension of the Algemeyne Schrievwies' by Reinhard Franz Hahn.

Notable Low German writers and performers.

Middle Low German authors:  Plautdietsch authors:

Low German or Low Saxon is a West Germanic language spoken mainly in Northern Germany and the northeastern part of the Netherlands. It is also spoken to a lesser extent in the German diaspora worldwide (e.g. Plautdietsch).

Als nieder- oder plattdeutsche Sprache wird eine hauptsächlich im Norden Deutschlands (vgl. West- und Ostniederdeutsch) verbreitete westgermanische Sprache bezeichnet, die auch in den angrenzenden Regionen sowie im Osten der Niederlande beheimatet ist.


Etymology.

The "Oxford English Dictionary" traces the origin of the word "bridge" to an Old English word "brycg", of the same meaning. The word can be traced directly back to Proto-Indo-European "*bhrēw-." The word for the card game of the same name has a different origin.

History.

The simplest type of a bridge is stepping stones, so this may have been one of the earliest types. Neolithic people also built a form of boardwalk across marshes, of which the Sweet Track and the Post Track, are examples from England that are around 6000 years old. Undoubtedly ancient peoples would also have used log bridges; that is a timber bridge that fall naturally or are intentionally felled or placed across streams. Some of the first man-made bridges with significant span were probably intentionally felled trees.  Among the oldest timber bridges is the Holzbrücke Rapperswil-Hurden crossing upper Lake Zürich in Switzerland; the prehistoric timber piles discovered to the west of the Seedamm date back to 1523 BC. The first wooden footbridge led across Lake Zürich, followed by several reconstructions at least until the late 2nd century AD, when the Roman Empire built a wooden bridge. Between 1358 and 1360, Rudolf IV, Duke of Austria, built a 'new' wooden bridge across the lake that has been used to 1878 – measuring approximately in length and wide. On April 6, 2001, the reconstructed wooden footbridge was opened, being the longest wooden bridge in Switzerland.  The Arkadiko Bridge is one of four Mycenaean corbel arch bridges part of a former network of roads, designed to accommodate chariots, between the fort of Tiryns and town of Epidauros in the Peloponnese, in southern Greece. Dating to the Greek Bronze Age (13th century BC), it is one of the oldest arch bridges still in existence and use. Several intact arched stone bridges from the Hellenistic era can be found in the Peloponnese.  The greatest bridge builders of antiquity were the ancient Romans. The Romans built arch bridges and aqueducts that could stand in conditions that would damage or destroy earlier designs. Some stand today. An example is the Alcántara Bridge, built over the river Tagus, in Spain. The Romans also used cement, which reduced the variation of strength found in natural stone. One type of cement, called pozzolana, consisted of water, lime, sand, and volcanic rock. Brick and mortar bridges were built after the Roman era, as the technology for cement was lost (then later rediscovered).  In India, the "Arthashastra" treatise by Kautilya mentions the construction of dams and bridges. A Mauryan bridge near Girnar was surveyed by James Princep. The bridge was swept away during a flood, and later repaired by Puspagupta, the chief architect of emperor Chandragupta I. The use of stronger bridges using plaited bamboo and iron chain was visible in India by about the 4th century. A number of bridges, both for military and commercial purposes, were constructed by the Mughal administration in India.  Although large Chinese bridges of wooden construction existed at the time of the Warring States period, the oldest surviving stone bridge in China is the Zhaozhou Bridge, built from 595 to 605 AD during the Sui dynasty. This bridge is also historically significant as it is the world's oldest open-spandrel stone segmental arch bridge. European segmental arch bridges date back to at least the Alconétar Bridge (approximately 2nd century AD), while the enormous Roman era Trajan's Bridge (105 AD) featured open-spandrel segmental arches in wooden construction.  Rope bridges, a simple type of suspension bridge, were used by the Inca civilization in the Andes mountains of South America, just prior to European colonization in the 16th century.  During the 18th century there were many innovations in the design of timber bridges by Hans Ulrich Grubenmann, Johannes Grubenmann, and others. The first book on bridge engineering was written by Hubert Gautier in 1716.  A major breakthrough in bridge technology came with the erection of the Iron Bridge in Shropshire, England in 1779. It used cast iron for the first time as arches to cross the river Severn. With the Industrial Revolution in the 19th century, truss systems of wrought iron were developed for larger bridges, but iron does not have the tensile strength to support large loads. With the advent of steel, which has a high tensile strength, much larger bridges were built, many using the ideas of Gustave Eiffel. In Canada and the United States, numerous timber covered bridges were built in the late 1700s to the late 1800s, reminiscent of earlier designs in Germany and Switzerland. Some covered bridges were also built in Asia. In later years, some were partly made of stone or metal but the trusses were usually still made of wood; in the United States, there were three styles of trusses, the Queen Post, the Burr Arch and the Town Lattice. Hundreds of these structures still stand in North America. They were brought to the attention of the general public in the 1990s by the novel, movie, and play "The Bridges of Madison County".  In 1927 welding pioneer Stefan Bryła designed the first welded road bridge in the world, the Maurzyce Bridge which was later built across the river Słudwia at Maurzyce near Łowicz, Poland in 1929. In 1995, the American Welding Society presented the Historic Welded Structure Award for the bridge to Poland.

Types of bridges.

Bridges can be categorized in several different ways. Common categories include the type of structural elements used, by what they carry, whether they are fixed or movable, and by the materials used.

Structure types.

Bridges may be classified by how the actions of tension, compression, bending, torsion and shear are distributed through their structure. Most bridges will employ all of these to some degree, but only a few will predominate. The separation of forces and moments may be quite clear. In a suspension or cable-stayed bridge, the elements in tension are distinct in shape and placement. In other cases the forces may be distributed among a large number of members, as in a truss. Some Engineers sub-divide 'beam' bridges into slab, beam-and-slab and box girder on the basis of their cross-section. A slab can be solid or voided (though this is no longer favored for inspectability reasons) while beam-and-slab consists of concrete or steel girders connected by a concrete slab. A box-girder cross-section consists of a single-cell or multi-cellular box. In recent years, integral bridge construction has also become popular.

Fixed or movable bridges.

Most bridges are fixed bridges, meaning they have no moving parts and stay in one place until they fail or are demolished. Temporary bridges, such as Bailey bridges, are designed to be assembled, and taken apart, transported to a different site, and re-used. They are important in military engineering, and are also used to carry traffic while an old bridge is being rebuilt. Movable bridges are designed to move out of the way of boats or other kinds of traffic, which would otherwise be too tall to fit. These are generally electrically powered.

Double-decked bridges.

Double-decked (or double-decker) bridges have two levels, such as the George Washington Bridge, connecting New York City to Bergen County, New Jersey, US, as the world's busiest bridge, carrying 102 million vehicles annually; truss work between the roadway levels provided stiffness to the roadways and reduced movement of the upper level when the lower level was installed three decades after the upper level. The Tsing Ma Bridge and Kap Shui Mun Bridge in Hong Kong have six lanes on their upper decks, and on their lower decks there are two lanes and a pair of tracks for MTR metro trains. Some double-decked bridges only use one level for street traffic; the Washington Avenue Bridge in Minneapolis reserves its lower level for automobile and light rail traffic and its upper level for pedestrian and bicycle traffic (predominantly students at the University of Minnesota). Likewise, in Toronto, the Prince Edward Viaduct has five lanes of motor traffic, bicycle lanes, and sidewalks on its upper deck; and a pair of tracks for the Bloor–Danforth subway line on its lower deck. The western span of the San Francisco–Oakland Bay Bridge also has two levels.  Robert Stephenson's High Level Bridge across the River Tyne in Newcastle upon Tyne, completed in 1849, is an early example of a double-decked bridge. The upper level carries a railway, and the lower level is used for road traffic. Other examples include Britannia Bridge over the Menai Strait and Craigavon Bridge in Derry, Northern Ireland. The Oresund Bridge between Copenhagen and Malmö consists of a four-lane highway on the upper level and a pair of railway tracks at the lower level. Tower Bridge in London is different example of a double-decked bridge, with the central section consisting of a low-level bascule span and a high-level footbridge.

Viaducts.

A viaduct is made up of multiple bridges connected into one longer structure. The longest and some of the highest bridges are viaducts, such as the Lake Pontchartrain Causeway and Millau Viaduct.

Multi-way bridge.

A multi-way bridge has three or more separate spans which meet near the center of the bridge. Multi-way bridges with only three spans appear as a "T" or "Y" when viewed from above. Multi-way bridges are extremely rare. The Tridge, Margaret Bridge, and Zanesville Y-Bridge are examples.

Bridge types by use.

A bridge can be categorized by what it is designed to carry, such as trains, pedestrian or road traffic (road bridge), a pipeline or waterway for water transport or barge traffic. An aqueduct is a bridge that carries water, resembling a viaduct, which is a bridge that connects points of equal height. A road-rail bridge carries both road and rail traffic. Overway is a term for a bridge that separates incompatible intersecting traffic, especially road and rail. A bridge can carry overhead power lines as does the Storstrøm Bridge.  Some bridges accommodate other purposes, such as the tower of Nový Most Bridge in Bratislava, which features a restaurant, or a bridge-restaurant which is a bridge built to serve as a restaurant. Other suspension bridge towers carry transmission antennas.  Conservationists use wildlife overpasses to stop habitat fragmentation and animal-vehicle collisions. The first animal bridges sprung up in France in the 1950s, and these types of bridges are now used worldwide to protect both large and small wildlife.  Bridges are subject to unplanned uses as well. The areas underneath some bridges have become makeshift shelters and homes to homeless people, and the undertimbers of bridges all around the world are spots of prevalent graffiti. Some bridges attract people attempting suicide, and become known as suicide bridges.

Bridge types by material.

The materials used to build the structure are also used to categorize bridges. Until the end of the 18th century, bridges were made out of timber, stone and masonry. Modern bridges are currently built in concrete, steel, fiber reinforced polymers (FRP), stainless steel or combinations of those materials. Living bridges have been constructed of live plants such as "Ficus elastica" tree roots in India and wisteria vines in Japan.

Military bridge.

The Tank bridge transporter (TBT) has the same cross-country performance as a tank even when fully loaded. It can deploy, drop off and load bridges independently, but it cannot recover them.

Analysis and design.

Unlike buildings whose design is led by architects, bridges are usually designed by engineers. This follows from the importance of the engineering requirements; namely spanning the obstacle and having the durability to survive, with minimal maintenance, in an aggressive outdoor environment. Bridges are first analysed; the bending moment and shear force distributions are calculated due to the applied loads. For this, the finite element method is the most popular. The analysis can be one, two or three-dimensional. For the majority of bridges, a two-dimensional plate model (often with stiffening beams) is sufficient or an upstand finite element model. On completion of the analysis, the bridge is designed to resist the applied bending moments and shear forces, section sizes are selected with sufficient capacity to resist the stresses. Many bridges are made of prestressed concrete which has good durability properties, either by pre-tensioning of beams prior to installation or post-tensioning on site.  In most countries, bridges, like other structures, are designed according to Load and Resistance Factor Design (LRFD) principles. In simple terms, this means that the load is factored up by a factor greater than unity, while the resistance or capacity of the structure is factored down, by a factor less than unity. The effect of the factored load (stress, bending moment) should be less than the factored resistance to that effect. Both of these factors allow for uncertainty and are greater when the uncertainty is greater.

Aesthetics.

Most bridges are utilitarian in appearance, but in some cases, the appearance of the bridge can have great importance. Often, this is the case with a large bridge that serves as an entrance to a city, or crosses over a main harbor entrance. These are sometimes known as signature bridges. Designers of bridges in parks and along parkways often place more importance to aesthetics, as well. Examples include the stone-faced bridges along the Taconic State Parkway in New York. To create a beautiful image, some bridges are built much taller than necessary. This type, often found in east-Asian style gardens, is called a Moon bridge, evoking a rising full moon. Other garden bridges may cross only a dry bed of stream washed pebbles, intended only to convey an impression of a stream. Often in palaces a bridge will be built over an artificial waterway as symbolic of a passage to an important place or state of mind. A set of five bridges cross a sinuous waterway in an important courtyard of the Forbidden City in Beijing, China. The central bridge was reserved exclusively for the use of the Emperor and Empress, with their attendants.

Bridge maintenance.

Bridge maintenance consisting of a combination of structural health monitoring and testing. This is regulated in country-specific engineer standards and includes an ongoing monitoring every three to six months, a simple test or inspection every two to three years and a major inspection every six to ten years. In Europe, the cost of maintenance is considerable and is higher in some countries than spending on new bridges. The lifetime of welded steel bridges can be significantly extended by aftertreatment of the weld transitions. This results in a potential high benefit, using existing bridges far beyond the planned lifetime.

Bridge traffic loading.

While the response of a bridge to the applied loading is well understood, the applied traffic loading itself is still the subject of research. This is a statistical problem as loading is highly variable, particularly for road bridges. Load Effects in bridges (stresses, bending moments) are designed for using the principles of Load and Resistance Factor Design. Before factoring to allow for uncertainty, the load effect is generally considered to be the maximum characteristic value in a specified return period. Notably, in Europe, it is the maximum value expected in 1000 years.  Bridge standards generally include a load model, deemed to represent the characteristic maximum load to be expected in the return period. In the past, these load models were agreed by standard drafting committees of experts but today, this situation is changing. It is now possible to measure the components of bridge traffic load, to weigh trucks, using weigh-in-motion (WIM) technologies. With extensive WIM databases, it is possible to calculate the maximum expected load effect in the specified return period. This is an active area of research, addressing issues of opposing direction lanes, side-by-side (same direction) lanes, traffic growth, permit/non-permit vehicles and long-span bridges (see below). Rather than repeat this complex process every time a bridge is to be designed, standards authorities specify simplified notional load models, notably HL-93, intended to give the same load effects as the characteristic maximum values. The Eurocode is an example of a standard for bridge traffic loading that was developed in this way.

Traffic loading on long span bridges.

Most bridge standards are only applicable for short and medium spans - for example, the Eurocode is only applicable for loaded lengths up to 200 m. Longer spans are dealt with on a case by case basis. It is generally accepted that the intensity of load reduces as span increases because the probability of many trucks being closely spaced and extremely heavy reduces as the number of trucks involved increases. It is also generally assumed that short spans are governed by a small number of trucks traveling at high speed, with an allowance for dynamics. Longer spans on the other hand, are governed by congested traffic and no allowance for dynamics is needed. Calculating the loading due to congested traffic remains a challenge as there is a paucity of data on inter-vehicle gaps, both within-lane and inter-lane, in congested conditions. Weigh-in-Motion (WIM) systems provide data on inter-vehicle gaps but only operate well in free flowing traffic conditions. Some authors have used cameras to measure gaps and vehicle lengths in jammed situations and have inferred weights from lengths using WIM data. Others have used microsimulation to generate typical clusters of vehicles on the bridge.

Bridge vibration.

Bridges vibrate under load and this contributes, to a greater or lesser extent, to the stresses. Vibration and dynamics are generally more significant for slender structures such as pedestrian bridges and long-span road or rail bridges. One of the most famous examples is the Tacoma Narrows Bridge that collapsed shortly after being constructed due to excessive vibration. More recently, the Millennium Bridge in London vibrated excessively under pedestrian loading and was closed and retrofitted with a system of dampers. For smaller bridges, dynamics is not catastrophic but can contribute an added amplification to the stresses due to static effects. For example, the Eurocode for bridge loading specifies amplifications of between 10% and 70%, depending on the span, the number of traffic lanes and the type of stress (bending moment or shear force).

Vehicle-bridge dynamic interaction.

There have been many studies of the dynamic interaction between vehicles and bridges during vehicle crossing events. Fryba did pioneering work on the interaction of a moving load and an Euler-Bernoulli beam. With increased computing power, vehicle-bridge interaction (VBI) models have become ever more sophisticated. The concern is that one of the many natural frequencies associated with the vehicle will resonate with the bridge first natural frequency. The vehicle-related frequencies include body bounce and axle hop but there are also pseudo-frequencies associated with the vehicle's speed of crossing and there are many frequencies associated with the surface profile. Given the wide variety of heavy vehicles on road bridges, a statistical approach has been suggested, with VBI analyses carried out for many statically extreme loading events.

Bridge failures.

The failure of bridges is of special concern for structural engineers in trying to learn lessons vital to bridge design, construction and maintenance. The failure of bridges first assumed national interest during the Victorian era when many new designs were being built, often using new materials.  In the United States, the National Bridge Inventory tracks the structural evaluations of all bridges, including designations such as "structurally deficient" and "functionally obsolete".

Bridge health monitoring.

There are several methods used to monitor the condition of large structures like bridges. Many long-span bridges are now routinely monitored with a range of sensors. Many types of sensors are used, including strain transducers, accelerometers, tiltmeters, and GPS. Accelerometers have the advantage that they are inertial, i.e., they do not require a reference point to measure from. This is often a problem for distance or deflection measurement, especially if the bridge is over water.  An option for structural-integrity monitoring is "non-contact monitoring", which uses the Doppler effect (Doppler shift). A laser beam from a Laser Doppler Vibrometer is directed at the point of interest, and the vibration amplitude and frequency are extracted from the Doppler shift of the laser beam frequency due to the motion of the surface. The advantage of this method is that the setup time for the equipment is faster and, unlike an accelerometer, this makes measurements possible on multiple structures in as short a time as possible. Additionally, this method can measure specific points on a bridge that might be difficult to access. However, vibrometers are relatively expensive and have the disadvantage that a reference point is needed to measure from.  Snapshots in time of the external condition of a bridge can be recorded using Lidar to aid bridge inspection. This can provide measurement of the bridge geometry (to facilitate the building of a computer model) but the accuracy is generally insufficient to measure bridge deflections under load.  While larger modern bridges are routinely monitored electronically, smaller bridges are generally inspected visually by trained inspectors. There is considerable research interest in the challenge of smaller bridges as they are often remote and do not have electrical power on site. Possible solutions are the installation of sensors on a specialist inspection vehicle and the use of its measurements as it drives over the bridge to infer information about the bridge condition. These vehicles can be equipped with accelerometers, gyrometers, Laser Doppler Vibrometers and some even have the capability to apply a resonant force to the road surface in order to dynamically excite the bridge at its resonant frequency.

A bridge is a structure built to span a physical obstacle, such as a body of water, valley, or road, without closing the way underneath. It is constructed for the purpose of providing passage over the obstacle, usually something that can be detrimental to cross otherwise. There are many different designs that each serve a particular purpose and apply to different situations. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, the material used to make it, and the funds available to build it.

Eine Brücke ist ein Bauwerk, das Verkehrswege (Straßen, Geh- und Radwege, Eisenbahnstrecken, Wasserstraßen u. a.) oder Versorgungseinrichtungen (wie Rohrleitungen, Kabel-Leitungen, Transportbänder u. a.) über natürliche Hindernisse (Bäche, Flüsse, Schluchten u. a.) oder andere Verkehrswege hinwegführt.


History.

On 7 February 1990, the "Neue Forum" (“New Forum”), the "Initiative Frieden und Menschenrechte" (“Peace and Human Rights Initiative”) and "Demokratie Jetzt" (“Democracy Now”) groups agreed upon the creation of the strategic partnership "Bündnis 90" (“Alliance ’90”) for the German "Volkskammer" elections. On 18 March 1990, in the next and final free election of the former East Germany, the electoral alliance received 2.9% of the vote, thus securing 12 seats. By far the best result for Alliance ’90 was in constituency of Berlin with 6.3%. In the remaining constituencies results ranged from 1.6% in Neubrandenburg to 3.8% in Potsdam. Together with the eight electees from the “Green Party in the GDR”, they created the "Fraktion Bündnis 90/Grüne" (“Alliance ’90/Greens Party”).  In the East German Landtag election on 14 October 1990 the differently-comprised electoral alliances made their entry into every Landtag except Mecklenburg-Vorpommern, where the "Neue Forum" did not participate in the alliance. In Brandenburg, the three civic groups of the "Bündnis 90" took office alone. In other states, the Greens also successfully took part in the electoral alliances. In Brandenburg from 1990 until 1994, "Bündnis 90" formed part of a traffic light coalition with the Social Democrats and Free Democrats.  In the 12th Bundestag election on 2 December 1990, the first after the German reunification, 6.1% of voters in the Eastern electoral area (1.2% across Germany) cast their "Zweitstimme" (the vote for a party, as opposed to for a person) for the group "Bündnis 90/Grüne – BürgerInnenbewegung" (“Alliance ’90/Greens – Citizens' Movement”), that entered into the German Bundestag with eight East German electees: Klaus-Dieter Feige, Ingrid Köppe, Gerd Poppe, Christina Schenk, Werner Schulz, Wolfgang Ullmann, Konrad Weiß and Vera Wollenberger. Werner Schultz took over the function of Speaker of the Bundestag group, which he held for the entirety of the legislative period. Its West German partners, the Greens, fell short of election to the parliament.  On 21 September 1991, the party "Bündnis 90" was founded, which brought together parts of the "Neue Forum", "Demokratie Jetzt" and the "Initiative Frieden und Menschenrechte". On 14 May 1993 came the agreement create the union of "Bündnis 90/Die Grünen" with the Greens which had been a cross-German party since the end of 1990.  One part of the Brandenburg state alliance advocated against a unification with the Greens, including Matthias Platzeck, Günter Nooke, Ute Platzeck, Peter Schüler, Manfred Kruczek and Gerd Gebhardt. However, they were unsuccessful in their case and founded the "BürgerBündnis" (“Citizens’ Alliance”), headed by Günter Nooke, Matthias Platzeck und Wolfgang Pohl.  The party "Bündnis 90/Die Grünen" in Saxony had already been established on 27 September 1991, one and a half years before the unification at federal level.

Alliance 90 () was an alliance of three non-communist political groups in East Germany. It was formed in February 1990 by the New Forum ("Neues Forum"), Democracy Now ("Demokratie Jetzt") and the Initiative for Peace and Human Rights ("Initiative Frieden und Menschenrechte"). It received 2.9% of the vote in the 1990 Volkskammer elections. For the first all-German elections it formed a joint list with the East German Green Party. It was this coalition that merged with the West German Green Party in 1993 to form Alliance 90/The Greens.

Das Bündnis 90 war ein Zusammenschluss von Bürgerbewegungen und Oppositionsgruppen in der DDR, der während der Zeit der Wende und friedlichen Revolution im Februar 1990 entstand und im September 1991 in eine politische Partei umgewandelt wurde. Im Mai 1993 ging Bündnis 90 gemeinsam mit Die Grünen in der heutigen Partei Bündnis 90/Die Grünen auf.