Lateral Thrusts Research Articles

Bayesian Updating for Random Tensile Force Identification of Ancient Tie Rods Using Modal Data

Tie rods play a crucial role in civil engineering, particularly in controlling lateral thrusts in arches and vaults, and enhancing the structural integrity of masonry buildings, both historic and contemporary. Accurately assessing the tensile axial forces in tie rods is challenging due to the limitations of existing methodologies. These methodologies often rely on indirect measurements, computational models, and optimization procedures, resulting in single-point solutions and neglecting both modeling and measurement uncertainties. This study introduces a novel Bayesian updating framework to effectively address these limitations. The framework aims to accurately identify the structural parameters influencing tie rod behavior and estimate uncertainties using natural frequencies as references. A key innovation lies in the mathematical formulation of Bayesian updating, which is founded upon the definition of computational models integrating uncertain updating parameters and latent random variables derived from a rigorous sensitivity analysis aimed at quantifying the impact of the updating parameters on the natural frequencies. Notably, the application of Bayesian updating to the structural identification problem of ancient tie rods represents a significant advancement. The framework provides a comprehensive description of the uncertainties associated with computational models, offering valuable insights for practitioners and researchers alike. Moreover, the results of the sensitivity analysis serve as a valuable tool for setting up inverse problems geared towards accurately identifying tensile axial forces.

Soft dorsal/anal fins pairs for roll and yaw motion in robotic fish

Fish has primarily served as a model for many bio-inspired underwater robots. However, most of the work on fish-inspired robots is focused on propulsion and turning in the horizontal plane. In this paper, we present our work on the 3D motion of bio-inspired underwater robots. A pair of actuated soft fins, mimicking the soft dorsal and anal fins of a live fish, have been designed and tested to generate lateral thrusts that aim to produce both roll and yaw motions. Furthermore, they can be used to provide vertical stabilization of the forward motion in the robot. These fins comprise shape memory alloy wires embedded in silicone. We demonstrate that these fins can provide a means for 3D maneuvering. In this work, we focus on roll and yaw motions. A key feature of the proposed design is that it is lightweight, compact, and waterproof.

The Modification and the Application of Ground Pressure Calculation Model for the Shallow Tunnels under Seismic Scenario

The traditional simplified model for ground pressure calculation is widely used in the anti-seismic design of shallow tunnels. However, it presents two obvious deficiencies, which are related to the block equilibrium and the additional seismic load respectively. A modified calculation model is proposed in this article by introducing the concept of slip angle, so that the deflection of potential slip planes and the distribution of ground pressure can be considered and further discussed. By combining the horizontal slice method and graphical method, a series of explicit formulas for calculating ground pressure are presented so that the vertical ground pressure, the rupture angle, and the lateral thrust can be calculated more accurately. The proposed modified model is compared with the existing model to validate the correctness of calculation results. The results show that the explicit formula of modified model could be reduced to Liu's formula when the potential slip planes are assumed to be vertical. Additionally, the sensitivity analyses on the vertical ground pressure, block volume, and distribution pattern of the lateral thrust are carefully investigated. The lateral thrusts acting on the left and right wedges distribute logarithmically and exponentially respectively, which implies that the distribution pattern is mainly affected by the direction of earthquake inertia force, while the cohesion and the friction angle merely influence the magnitude of lateral thrust to some extent.

Lessons from Structural Analysis of a Great Gothic Cathedral: Canterbury Cathedral as a Case Study

ABSTRACT Damage in Gothic cathedrals can occur due to single extreme events or long-term processes, often associated with large deformations and cracking. This paper presents the damage survey and structural assessment of a UNESCO world heritage site and one of the oldest, most visited and most known Christian temples in the UK: Canterbury Cathedral, in Kent. Inspection and damage survey showed repetitive crack patterns on the vault’s intrados, with more severity in the south aisle, including outward rotating movement and cracking in the south flying buttresses. Ambient vibration tests were carried out to identify the structure modal properties. An FE model of a typical transversal section of the nave and lateral aisles was prepared, and calibrated based on the tests. Nonlinear static analyses were performed, considering the main parameters of influence to the structure, as the construction process, the infill volume, the presence of lateral thrusts from the nave’s roof and differential settlements. A validated FE model, presenting sufficient correlation with the existing damage was used to determine the safety factors for lateral and vertical loading, which according to the local hazard are considered adequate. A comparison with limit analysis, based on the static approach, was also carried out.

Evaluation of the Structural Stability of an Octagonal Dome with Meridional Cracks. Case Study: Temple of Santa Lucia, Ambalema, Colombia

This work performed a comparative analysis between the construction process carried out when building the dome at the Temple of Santa Lucía, in Ambalema-Colombia and the typical process of an octagonal dome. Additionally, the structural stability is assessed of the dome of the case study against service and dynamic loads. To compare with the case study, known domes were taken as examples from structures in Italy and Spain. The analysis includes a study on the dome’s geometry and the constructive errors found. Methodology: The dome’s stability was evaluated through structural analysis software for which the dome was simplified into a system of four articulated arches. Conclusions: As a result, it was found that the dome of the temple of Santa Lucía does not have a system to counteract lateral thrusts (a drum or its similar), which permitted the appearance and widening of meridional cracks. These cracks propagate from the base to the crown, but do not compromise the structure’s stability for service loads. The analysis for seismic loads indicates that the dome is at risk of collapse upon seismic events, even of moderate magnitudes. Originality: The study is aimed at architects and engineers interested in the theme of restoration of historical structures.

Thin-folded Shell for the Renewal of Existing Wooden Roofs

ABSTRACTIn this article, a technique for the renewal of historic building wooden roofs is presented. The solution can be used for the strengthening of existing wooden roofs against excessive lateral thrusts on the peripheral wall or for the recovery of the attics, as it allows removing the existing structural elements, such as possible wooden truss-works of no artistic value. With minor adaptations, the solution can be addressed to enhance the building seismic performance. The technique is minimally impairing on existing buildings and can be applied also in new constructions.The technique is based on the construction of a thin folded shell, overlaying the existing pitches. Emphasis is given to lightweight folded shells, obtained by overlaying thin plywood panels on the existing roof rafters and planks, without modifying the overall architectural layout.The technique conceptual design is discussed and a simplified analytical method is proposed, which allows for the clarification of the role of each structural component and can be adopted for the folded shell proportioning and design. The analytical results are validated against numerical results obtained with reference to some case studies. Ultimately, emphasis is given to the detailing, whose correct execution is mandatory for the success of the proposed structural intervention.

Shake table lateral earth pressure testing with dense c-ϕ backfill

Dynamic lateral earth pressure is recorded during ten shake table testing events. In these tests, peak input acceleration at the base of the retaining wall varied in the wide range of 0.13–1.20g in order to include scenarios of relevance to recently observed strong earthquake excitations. The results shed light on the influence of soil cohesion and the effect of small wall movements on the magnitude and distribution of earth pressure. In accordance with field practice, a commonly encountered dense sand backfill with a small percentage of fines (SP-SM) is used. Inside a large soil container, earth pressure is measured against a rigid wall (backfill height H=1.7m) that is allowed to undergo limited translation/rotation due to the imparted dynamic excitation (up to 10mm or 0.006H at 1.2g base acceleration). In this particular series of experiments, favorably low dynamic pressures were recorded at backfill accelerations of up to about 0.7g in light of: (i) the relatively high soil strength (including cohesion) that precluded a limit equilibrium type failure in the backfill, and (ii) the high soil stiffness coupled with the small value of observed wall translation/rotation (as much as 3mm or 0.0018H at ground surface). In tests with instants of very high acceleration (in the range of 1g), the corresponding dynamic earth pressure is found to be of much significance for practical applications. Lateral thrusts recorded during these instants of strong shaking compare well with limit equilibrium predictions that include the soil cohesion intercept. Exclusion of the cohesion intercept results in substantial over-prediction of the measured lateral forces.

The stability of gabion walls for earth retaining structures

The stability of earth retaining structures in flood prone areas has become a serious problem in many countries. The two most basic causes of failure arising from flooding are scouring and erosion of the foundation of the superstructure. Hence, a number of structures like bridges employ scour-arresting devices, e.g., gabions to acting on the piers and abutments during flooding. Research was therefore undertaken to improve gabion resistance against lateral movement by means of an interlocking configuration instead of the conventional stack-and-pair system. This involved simulating lateral thrusts against two dimensionally identical retaining wall systems configured according to the rectangular and hexagonal gabion type. The evolution of deformation observed suggested that the interlocking design exhibits better structural integrity than the conventional box gabion-based wall in resisting lateral movement and therefore warrants consideration for use as an appropriate scour-arresting device for earth retaining structures.

The Vaults of St. John the Theologian at Ephesos

E ver since the first excavation of the remains of the church of St. John the Theologian on the hill of Ayasoluk, the reconstruction of the vaulted, sixth-century phase of the monument has been a major challenge in the field of early Byzantine architecture. This is partly due to the historic significance of the building. According to the contemporary account of Procopius, the church, rebuilt and enlarged under the auspices of Justinian, constituted the Ephesian counterpart to the Constantinopolitan church of the Holy Apostles.1 It was later to become the heart of medieval Ephesos and one of the most important pilgrimage churches in Asia Minor.2 Besides its historical interest, the reconstruction of St. John’s has a great significance for the study of early Byzantine vaulting technology. Indeed, reconstruction offers the only opportunity to recapture the form of the enormous brick vaults of the church, which are now lost. These sophisticated vaults, which seem to have survived in an earthquake-prone area for more than eight centuries, constitute a remarkable feat of structural engineering.3 They must have been a highly innovative structure, erected at a time when most churches were timber-roofed. The task of accurate and reasoned reconstruction through the scrutiny of archaeological evidence is more demanding than it may initially appear, in spite of the systematic exploration of the monument since its discovery in 1921. Eight decades of excavation and survey have made the ground plan of the aisled cruciform church as well as the footprint of its atrium, baptistery and skeuophylakion mostly clear (Figure 1).4 Some parts have even become the object of full-scale physical reconstruction (Figure 2). In addition to this, Hans Hormann, Mustafa Buyukkolanci, and Andreas Thiel have shed light on the building phases that preceded Justinian’s vaulted church.5 Still, in spite …

Lateral versus anterior thoracic thrusts in the generation of airway pressure in anaesthetised pigs

ObjectiveAnterior chest thrusts (with the subject sitting or standing and thrusts applied to the lower sternum) are recommended by the Australian Resuscitation Council as part of the sequence for clearing upper airway obstruction by a foreign body. Lateral chest thrusts (with the victim lying on their side) are no longer recommended due to a lack of evidence. We compared anterior, lateral chest and abdominal thrusts in the generation of airway pressures using a suitable animal model. MethodsThis was a repeated-measures, cross-over, clinical trial of eight anaesthetised, intubated, adult pigs. For each animal, ten trials of each technique were undertaken with the upper airway obstructed. A chest/abdominal pressure transducer, a pneumotachograph and an intra-oesophageal balloon catheter recorded chest/abdominal thrust, expiratory air flows, airway and intrapleural pressures, respectively. ResultsThe mean (SD) thrust pressures generated for the anterior, lateral and abdominal techniques were 120.9 (11.0), 135.2 (20.0), and 142.4 (27.3)cmH2O, respectively (p<0.0001). The mean (SD) peak expiratory airway pressures were 6.5 (3.0), 18.0 (5.5) and 13.8 (6.7)cmH2O, respectively (p<0.0001). The mean (SD) peak expiratory intrapleural pressures were 5.4 (2.7), 13.5 (6.2) and 10.3 (8.5)cmH2O, respectively (p<0.0001). At autopsy, no rib, intra-abdominal or intra-thoracic injury was observed. ConclusionLateral chest and abdominal thrust techniques generated significantly greater airway and pleural pressures than the anterior thrust technique. We recommend further research to provide additional evidence that may inform management guidelines for clearing foreign body upper airway obstruction.

Case Study of the Failure of a Cross Vault: Church of Holyrood Abbey

The church of Holyrood Abbey, in Edinburgh, collapsed in 1768 after an inappropriate intervention in the nave vaults. This resulted in excessive lateral thrusts, which could not be contained by the existing buttressing systems, causing progressive instability of the lateral walls. This effect was studied on a lateral cross vault of the church. A replica in 1:4 scale was built and tested initially under service loads and subsequently until collapse due to movement of the two front abutments. Analysis of the model was carried out with the finite-element program ABAQUS. The resulting behavior demonstrated the significant load-bearing capacity of the structure under service conditions and its high sensitivity to imposed changes of the geometry. Although the tensile stresses exceeded the flexural strength at the vertices and the abutments, the collapse was dominated by the membrane tensile failure at the groins, hence both the geometry and condition of this area are critical for the safety of the vault. The results of this study can improve the assessment and thus help in the preservation of many important Gothic and neo-Gothic churches.

Comparative study of courtship in twelve phycitine moths (Lepidoptera: Pyralidae)

The courtship behavior of 12 phycitine moths (Lepidoptera: Pyralidae) was studied using frame-by-frame analysis of video recordings. Behavioral transitions during courtship were quantified for selected species and kinematic diagrams of courtship sequences were constructed. Interspecific similarities in courtship behaviors were measured by calculating Euclidean distances between species based on 12 courtship characters and by clustering species according to UPGMA (unweighted pair-group method using arithmetic averages). The resulting phenogram revealed two major behavioral patterns in courtship: (1) interactive and (2) simple. The former was characterized by a complex sequence in which, typically, a male approached a pheromoneemitting female, engaged in a head- to- head posture with the female, and then brought his abdomen over his head and struck the female on the head and thorax. This action brought male abdominal scent structures into close proximity with the female antennae. The male then attempted copulation from the head- to- head position by a dorsolateral thrust of the abdomen toward the female genitalia. Males of these species possessed scent structures located either on the eighth abdominal segment, or in a costal fold of the forewing, or both. Courtship in the second group was much more prosaic. After locating the female by response to her sex pheromone, the male simply attempted copulation by lateral abdominal thrusts under the female wing, without behavioral embellishments. Males of species exhibiting simple courtship had either no scent structures or structures that appeared vestigial. The grouping of species based on courtship characters was poorly correlated with taxonomic relationships, suggesting that the selective pressures governing the evolution and maintenance of courtship and male pheromones were distinct from those involved in the evolution of other morphological characters. While we argue that the primary force molding the evolution of courtship was an adaptive response to interspecific mating mistakes, we do not believe that isolation is brought about by the sequence of courtship behaviors themselves, due to the striking similarity in the sequence across several diverse species. Rather, these behaviors act to deliver more efficiently the male pheromonal message, which mayhave evolved for reproductive isolation.

The temporomandibular-maxillary relationship

<h2>Abstract</h2> Equilibrium is the terminus of all closing motion of the mandible. It represents a centered balanced position of the mandible at a fixed vertical height. The method of using time as an element of measure for determining the vertical height has been very successful, and is extremely sensitive to slight variations. The secondary or reverse motion of the mandible, with its axis on the occlusal surfaces of the first bicuspid teeth, permits normal apposition of the teeth, closing of the temporomandibular articulation, and avoids lateral and anterior thrusts which would result from pivoting on the distal margins of the lower molar teeth. The closing of the joint avoids pressure, soreness of the mylohyoid ridge, and a "searching bite." This intermaxillary record as a whole produces a comfortable, efficient, pressure-free set of dentures.