The earliest gatehouse architecture dates back to ancient Egyptian times, when hinged wooden panels were placed on the opposite side of the door by means of ropes. In relatively early India, the gatehouse building is mostly made of stone, and usually and saloon door open the same way. The Greeks and Romans used stone, concrete, and sandstone in the construction of their gatehouse buildings.
The outline of the doorway of Kulangsu gatehouse architecture is related to the architectural style. This time, the doorway of Kulangsu architecture is classified according to the outline of the hole, and is organized and analyzed retrospectively. The doorway outlines are classified into six basic styles based on their basic forms: domed, segmental, square, Tudor, domed shawl, and Ogee. Their development and dissemination are traced in a general way, and corresponding cases are found on the gatehouse architecture of Kulangsu Island. The paper also analyzes the outline proportions of the six common styles of gatehouses and dismantles their outlines and rising arches in geometric composition. From the basic principles of geometric composition, the starting arches are disassembled and sorted out in detail, with R as the basic standard for step-by-step sorting and organizing.
1.1 circular gatehouse building
The domed portcullis originated from the domed arch and was first used in Mesopotamia, Greece, Persia and ancient Italy along the Mediterranean coast. The earliest use was for underground tunnels and drainage systems, supported and reinforced by the gravity of the domed arch type. The Romans learned how to use arches from the Etruscans. Romans in the 3rd century B.C. discovered how to use domed arches to construct bridges, fords and buildings. The domed arch allowed for the rapid formation and expansion of the Roman Empire's infrastructure and became a fundamental motif of Western architecture, creating a new building system throughout Europe.
The basic structure and proportions of the cupola are very simple. The distance from the opening of the doorway is the diameter, the midpoint is the center of the circle, and R is the radius of the arc drawn to form a complete semicircle. Generally, the arches of the semicircle are covered with gables and mountain flower decoration to form a complete doorway. (Figure 1)
The style of dome-shaped gatehouse is not common in Kulangsu architecture, more or less possessing smaller gatehouses in more or less cases. Most of its gatehouses are based on water-brushed stone and mirage ash work, often in the form of plain surfaces. The architectural language of some gatehouses is mixed, and there will be many architectural features where many styles coexist. The domed arch style is simpler and therefore often accompanies the segmental style. Ogee style and tent style appear together. Among the gatehouse buildings on Kulangsu Island, No. 35 Fujian Road and No. 457 Nei Chu Ao Road (Figure 2) use this style of arch.
The arc of an architectural arch is generally constructed and designed based on the craftsman's skills
1.2 Segmental gatehouse building
Segmented gatehouse architecture is a type of gatehouse architecture with an inner arc of less than 180 degrees. The segmental arch is one of the strongest arches because it is able to resist thrust by its own gravity. Each segmental arch must have an upper gable arc greater than or equal to one-eighth the width of the doorway. The segmental arc of the upper gable to less than one-eighth of the span width must have an additional permanent support or frame under the doorway to prevent collapse.
The structural composition of the segmental doorway has two forms, 1) the size of the doorway opening as the diameter (2R), where the point is the center of the circle to its reverse arc intersected by a vertical line down the point of the circle, connecting the intersection with the other side of the end point to get √2R radius. With √2R as the radius of both sides of the doorway endpoints as the beginning and end of the arc, to get the first segmental arch. 2) the size of the doorway opening as the diameter (2R), take half of its 1/2R as the radius, the midpoint as the center of the circle to draw a quarter of the arc below to get the new center of the circle. The new center of the circle and the door opening a section of the endpoint line to get the radius R, and do arc intersection with the two sides of the endpoint, and thus get a new arc.The above is the determination of the proportional relationship between the two segmented doorways (Figure 3).
The ancient Romans were the first to use segmental arches. The closed St. Martin's Bridge built in 25 B.C. in the Aosta Valley, Italy. The first large span segmental arch bridge was the Anji Bridge in Hebei Province, China. Segmental arches were most commonly used in the 20th century in residential buildings with doorways, fireplaces and windows, and in the Kulangsu Island doorway buildings No. 62 Fuzhou Road, No. 121 Fujian Road
In Kulangsu Island, gatehouse styles such as No. 62 Fuzhou Road and No. 121 Fujian Road all used segmental arching gatehouses. This type of arch accounts for more than 30% of the buildings on Kulangsu Island.
1.3 Tudor Gatehouse Architecture
The Tudor arch, also known as the four-center arch and the Persian arch, is a style of doorway with a lower starting arch, a wider opening, and a pointed roof. Its structure is achieved by depicting two arcs of the 1/2R, which draws a quarter arc upward from the 1/4 point of the doorway as a round point. With the end of the small arc and 1/4 circle center as the two endpoints to draw an extension line to three-quarters out as the origin, R as the radius of the arc downward to intersect with the extension line to form the second circle center. To this point as the center of the circle quarter arc end point for the other side of the starting point to draw the arc, forming a four-center arch for a single side. Repeat the appeal operation on the other side to form a complete four-center arch. This type of arch is more efficient and decorative when used in doorways. It is also used in wall decoration where the outline of the arches and window openings form part of the surface decoration. This type of decoration was common in Persian architecture and was gradually introduced to England as the prototype of the Tudor style doorway. In English architecture the four central arches became flatter. Another variant, the ogee, was also formed, with the middle part of the arch being straight rather than curved. This type developed rapidly in the architecture of Queen Anna's time [1].
The Tudor style spread rapidly in England, and its rise and development occurred between 1485 and 1558, mainly in building entrances and windows. The style is a transposition of Renaissance decorative elements to the vertical Gothic style. The Tudor architectural style coincides chronologically with the first phase of Tudor rule, beginning with the accession of Henry VII in 1485 and the death of Elizabeth I in 1558. The appearance of the Tudor style used in the gatehouse architecture of Kulangsu Island is generally characterized by the use of wooden doors with rectangular squares; intricate carved decorations at the location of the hill walls; and gatehouse materials dominated by rouge brick, mirage ashlar, and water-brushed stone. Tudor-style gatehouses use a large amount of plaster to decorate the pediments, cornices and walls, often in direct imitation of Renaissance decorative motifs. This approach is used in the buildings of Kulangsu Island, such as No. 42 Nei Chuao Road, No. 44 Anhai Road, and the entrance gate of the Xiehe Hospital. (Figure 6)
1.4 Pointed trefoil gatehouse building
The name trifolium, or cloverleaf, is derived from the Latin trifolium, which consists of three overlapping semicircles or leaf shapes. It is widely used in churches, gatehouses and Gothic architecture because of its trinity significance in Christian architecture. The trefoil doorway is common in Gothic and Renaissance architecture and is used for window and door decoration and mountain flower decoration. The trefoil arch was developed in Egypt around the 12th to 16th centuries, and the arch is also the main feature of the decorative doorway decoration in late Egyptian architecture[2].
The trefoil structure is formed by the overlapping of three circular arcs. With the opening of the doorway as the diameter (2R), a square with R as the side length is drawn on the left side and connected to its diagonal. With 3/2R as the radius to draw a one-sixth arc, the endpoint line and the square diagonal intersection with a point, the point for the small circle center O. Square side of the end point and 3/2R at the two vertices to draw a straight line L, the line as the axis of symmetry to get the small circle center O1. do the reverse extension of the straight line L, the length of R to get another circle center O2, O2 as the center of the circle R as the radius to draw 1/12 arc to get the three-leaf The structure of one side of the formula. The other side is outlined in reverse symmetry as described above (Figure 7).
In Kulangsu gatehouse architecture, the trefoil-style gatehouse is less decorated and is mostly the overall structure of the building. It is often used in combination with square door arches and segmental door arches. The outer decoration of the material of the three-leaf gatehouse is mostly based on water-brushed stone and mirrored ash workmanship, and white stone carving and rouge brick stacking rarely appear. Kulangsu Island gatehouse buildings in the side door of Jingualou and No. 8 building of Naicuo Ao Road are from the use of this type of decoration.
1.5 Ogee gatehouse building
Ogee style is also called willow leaf style, three-stage arc style, etc. Ogee style gatehouse architecture originated in India in the 3rd century BC. The entrance form of Buddhist caves in India is similar to it. This form is similar to the outer outline of the leaves of the Bodhi tree and to the prayer posture prevalent in India. But it may also be a purely aesthetically pure form of architectural expression. Orgian architecture appeared in Islamic architecture in the 1100s, then spread to Persian and Egyptian architecture, and emerged for use in late Gothic architecture from the 13th to the 14th centuries. In Gothic architecture, especially in the later Gothic style, they became the most visible and characteristic element, giving a sense of verticality. Ogee arches are usually used in arcades, windows, doorways, etc. In the Late Gothic style Ogee arches are mostly used in façade decoration.
Its structure is composed of four segments of circular arc symmetrically, with the opening width of the doorway as 2R, the end point as the center of the circle 2R as the radius to draw a 45 degree arc. With the end of the arc end point and the center of the circle as two fixed points, draw its reverse extension line. In the extension line to go up 2R for the distance to draw a circular arc, the arc will intersect in the midline of the vertical line, forming an S-shaped curve. This S-shaped curve in the Kulangsu architectural doorway decoration has "convex" type and "concave" type two. Convex Auggie-style buildings are more common in Kulangsu's gatehouse decoration. In the late thirteenth century, the Auggie arch became a characteristic feature of English Gothic architecture, especially in the late fourteenth and fifteenth centuries, when it was a decorative element of the Gothic style. [3](Figure 9).
1.6 Basket-handle gatehouse building
The Carrycentric arch is also known as the tri-centric arch. It differs markedly from the double-centred (segmental) and four-centred (Tudor) arches in that it has no distinct S-curve or peak point. The latter is often found in the Gothic and Romantic periods, while the former was used in another style - colonial architecture - for its basic shape, which resembles the ellipse. The emergence of the basket arch was later, after the appearance of the four-centered arch in the Gothic period, due to the improvement of the skill of the builders and the secularization of people's aesthetics, the basket arch gradually came into view.Its basic structure is composed of three circular arcs. Taking the length of the doorway opening as the diameter 2R.
From one side, draw one-sixth arc with 1/2R as radius. And the two starting points as the end point down to draw the reverse extension line, the length of R. Connect 1/2R and R as the radius, the end point of the extension line as the center of the circle to draw one-sixth of the arc. Repeat the above on the other side. This form of architecture usually appears adjusted according to the craftsmanship of the craftsman and the aesthetics of the house owner. Most of the materials used in the architecture of Kulangsu Island for the building of the Tikuan-style gatehouse are based on mirrored ash work and water-brushed stone work, and the type of rouge brick decoration is rarely found.
[1] Bloom,Jonathan M.(2017-05-15).Early Islamic Art and Architecture.Routledge. ISBN 9781351942584.
[2] Papadopoulo, Alexandre (1979). Islam and Muslim Art. p. 242. ISBN 9780810906419.
[3] Gosh, A. (1964). Indian Archaeology: A review 1961-62. New Delhi: Archaeological survey of India. pp. 50–52