Compound-mode crack propagation law of PMMA semicircular-arch roadway specimens under impact loading

An underground roadway usually contains defects of various types, and when the roadway is subjected to external loading, the locations of those defects influence the roadway by differing degrees. In this study, to study how the locations of defects affect crack propagation in a roadway, specimens with tunnel-type voids were made using polymethyl methacrylate, and the stress wave produced by a bullet impacting an incident rod was used as the impact load. Meanwhile, the variations in crack speed, displacement, and dynamic stress intensity factor during crack propagation were obtained using an experimental system of digital laser dynamic caustics, and the commercial software ABAQUS was used for numerical simulations. From the experiments and numerical simulations, the crack propagation path was verified and the impact fracture behavior of a semicircular-arch roadway with different defect positions was presented. The results show that when the pre-fabricated crack is on the central axis of the sample, the crack propagation is purely mode I; when the pre-fabricated crack is 5 mm from the central axis, the crack propagation alternates between mode I and a mixture of modes I and II; when the pre-fabricated crack is at the edge of the semicircular-arch roadway, the crack propagation follows the I–II mixed mode.

The Catholicon of the Monastery of Agios Panteleimon on the Island of Ioannina, Greece

The monastery is located at the SE end of the settlement of the Island and became widely known in modern history, as Ali Pasha was assassinated in its cells in 1822. The catholicon today is a three-aisled basilica with a quadruple roof and in its present size was probably built at late 17th or early 18th century. The aisles are separated by wooden colonnades. The W and N walls, probably most of the E, were rebuilt after their destruction in the early 19th century by falling rocks. In the E there is a semicircular arch. The original church was supposed to be a small one-aisled with a semicircular arch, traces of which were discovered on the SE side of the modern church.The monastery is located at the SE end of the settlement of the Island and became widely known in modern history, as Ali Pasha was assassinated in its cells in 1822. The catholicon today is a three-aisled basilica with a quadruple roof and in its present size was probably built at late 17th or early 18th century. The aisles are separated by wooden colonnades. The W and N walls, probably most of the E, were rebuilt after their destruction in the early 19th century by falling rocks. In the E there is a semicircular arch. The original church was supposed to be a small one-aisled with a semicircular arch, traces of which were discovered on the SE side of the modern church.From the early building phase the modern church has incorporated part of the S wall, which dates to the early 15th century. On the W side was added a late 19th-century loggia, which is roofed with a sloping roof lower than that of the church and possibly replaced an older one. The column of the loggia comes from an earlier building phase of the church. On the W side is raised a rectangular narthex, possibly of the same date as the loggia, which is roofed with a quadruple roof. The present entrance door to the main church is located at the W end of the S wall, while the original door was opened in the middle of the same wall and has been walled today. There is a small conch above the walled door.The church is built of stone with irregularly placed stones. More elaborate construction on the arch with carved stones in the pseudo-isodomic system. On the S wall between the stones are inserted bricks. Brick arched frame is formed above the walled gate. The fresco decoration of the catholicon is confined to the outer front of the S wall and the lower parts of the main church. It is of particular importance, as we distinguish five post-Byzantine phases, the first of which at the end of the 15th century. The first is located in the E part of the outer front of the S wall. The rest continue to the W on the outer front of the same wall and on the lower parts inside the main church.In the initial phase of the frescoes belong the Deisis with the Christ and the Virgin, as well as the frontal St. Nicholas, behind the Virgin. The upper parts of the scene have been repainted. The next phase, which can be dated to the 16th century, involves the half-bodied Christ above the conch of the S wall, who blesses with open arms and two full-length archangels on either side of the conch, who have also been repainted. In the third phase of the painting belongs the enthroned Virgin holding the Child amid two angels, pictured behind her massive wooden throne. The composition is to the right of the entrance door to the church. This layer is precisely dated by a dedicatory inscription bearing the date ZΡKϚ (= 1617/18). The penultimate phase is found only in the interior of the catholicon, in the lower parts of the sanctuary, and on the N and S walls of the main church, where a decorative zone is distinguished. The feet of at least two saints are visible on the N wall, another figure of saint next to the iconostasis on the S wall and to the right of the doorway to the church the lower part of the body of a frontal archangel, who steps on a cloud. Above the door there should have been the inscription, mentioned by Aravantinos, but not preserved today, and bearing the date ΑΨΖ (= 1707). During the late 19th century, the outer conch of the S wall was painted with St. Panteleimon, who is depicted half-bodied and holding a vessel and a scalpel.The building phases of the catholicon and the multiple layers of its decoration make it one of the most important monuments of the Ioannina area, as it locates the oldest known frescoes on the Island and throughout the Ioannina basin. At the same time, after reading of one of the dedicatory inscriptions, it was possible to distinguish more clearly the painting layers and to make more effective use of the older reading, by Aravantinos, of the inscription in the interior of the catholicon.

Basket-Handle Arch and Its Optimum Symmetry Generation as a Structural Element and Keeping the Aesthetic Point of View

The arches were a great advance in construction with respect to the rigid Greek linteled architecture. Its development came from the hand of the great Roman constructions, especially with the semicircular arch. In successive historical periods, different types of arches have been emerging, which in addition to their structural function was taking aesthetic characteristics that are used today to define the architectural style. When, in the construction of a bow, the rise is less than half the springing line, the semicircular arch is no longer used and the segmental arch is used, and then on to another more efficient and aesthetic arch, the basket-handle arch. This study examines the classic geometry of the basket-handle arch also called the three-centered arch. A solution is proposed from a constructive and aesthetic point of view, and this is approached both geometrically and analytically, where the relationship between the radius of the central arch and the radius of the lateral arch is minimized. The solution achieved allows the maximum springing line or clear span to be saved with the minimum rise that preserves the aesthetic point of view, since the horizontal thrust of a bow is greater than the relationship between the springing line of the arch and the rise. This solution has been programmed and the resulting software has made it possible to analyse existing arches in historic buildings or constructions to check if their solutions were close or not from both points of view. Thus, it has been possible to verify that in most of the existing arches analyzed, the proposed solution is reached.

textos inscritos en la Foncalada de Oviedo

La Foncalada de Oviedo es una fuente monumental, datada generalmente en el siglo IX, durante el período del reino asturiano (718-910). En la fachada del lado este, donde se abre un arco de medio punto, se grabaron algunas inscripciones latinas. Era conocido el contenido de las situadas sobre el arco. Son similares a algunos epígrafes regios de la época. Del texto de las demás solamente se conservan pequeños fragmentos. En este artículo ofrecemos una reconstrucción, lograda gracias a haberse detectado el modelo en que se basan: una oración de santificación del agua, empleada, aunque no exclusivamente, en el ritual hispánico, y contenida en los Libri Ordinum. The Foncalada of Oviedo is a monumental fountain commonly dated in the 9th century, at the time of the Asturian Kingdom (718-910). On the façade of the east side, where a semicircular arch opens, some Latin inscriptions were engraved. The content of those situated on the arch is well-known, since they are similar to some royal epigraphs of the period, while only small text fragments have been preserved from the rest of inscriptions. In this work we offer a reconstruction of the latter, based on a finding that what we consider the model or source used for the creation of these epigraphs: a prayer form for the sanctification of water, used, though not exclusively, in the Hispanic rite, and contained in the Libri Ordinum.

Buckling and post-buckling behaviour of semicircular functionally graded material arches: a theoretical study

In this study, behaviour of a thin semicircular arch made of functionally graded material subjected to radial and tangential follower forces, as well as thermal loading, based on the theory of large deformation of the arches and critical buckling load and post-buckling of structures is investigated. Assuming thin arch, governing equations of the arch behaviour are derived using kinematics and static equilibrium. Resulting equations including different support conditions form a set of highly coupled and non-linear boundary value differential equations. To solve the problem, the well-known numerical boundary value problems of shooting method are employed. By gradual increase of loading, the buckling and post-buckling behaviour is closely monitored. Several examples corresponding to different combinations of support conditions/loadings/non-homogeneity/slenderness ratio to illustrate the performance of the proposed algorithm are presented.

Islam and the West: The Early Use of the Pointed Arch Revisited

As this is a valedictory rather than an inaugural lecture, it seemed legitimate to be a little self-indulgent in the choice of theme. Every medievalist at some time or other has to take an interest in the role of the pointed arch in the transformation of medieval architecture from Romanesque to Gothic and in the ways that the pointed arch form was subsequently manipulated through the later Middle Ages. It is only a short step, but one that has been taken less often than you might expect, to pursue that interest back into the early use of the pointed arch in Islamic architecture: to ask how it came to replace the semicircular arch of classical architecture and why it was used.