The goal of the current investigation is to determine the dynamic behaviour of double-arch systems: the system is made of two arches reinforced by three different functionally graded patterns of ...carbon nanotubes and connected with an elastic layer of spring bed. The carbon-nanotube functionally graded patterns considered are uniformly distributed, FG-X and FG-O. Two different boundary conditions of movable and immovable simply supported (named SS1 and SS2) are studied for the reinforced double-arches, where the displacements along the curve-line are constrained for the ends of SS2 arches. Both the Hamilton principle and force-moment technique are utilised to formulate the coupled equations of motion. A series expansion technique is then used to solve the equations. A validation is performed and consistent agreement between the proposed methodology and simplified version of the double-arch system is achieved. One prominent observation arising from this study is that an increase in the opening angle of the double-arch system results in a decline in both the series for the transverse natural frequencies for SS1. Conversely, the systems with SS2 boundary conditions exhibit an initial rise in both the series of natural frequencies as the opening angle increases, followed by a gradual decrease. A thicker carbon-nanotube reinforced functionally graded double-arch system demonstrates an increased natural-frequency sensitivity to variation in opening angles. Lastly, increasing the elastic layer coefficient of stiffness causes an increment in the second series natural frequency of the system.
This study investigated the structural behavior of an arch system composed of segmental precast concrete panels and steel outrigger ribs, with respect to the cross-sectional geometries of the ...structural members. Thus, a three-dimensional finite element (3D FE) analysis of the proposed arch system was conducted at each construction step, and the cross-sectional geometries of the structural members were varied. From the results of the FE analysis regarding the structural-member cross-sectional configurations and geometries, the changes in stress and deformation were identified with respect to the changes in the thickness of the precast panels, thickness of the outrigger ribs, and height of the V-strip. Stresses and displacements of structural members in the proposed arch system were affected up to 48% by the height of the V-strip and the thickness of the outrigger ribs. The thickness of the precast panel affected relatively small on its structural behaviors. Therefore, the height of the V-strip and thickness of the outrigger ribs should be considered as the major design parameters for the design of the proposed arch system.
A characteristic engineering example of the model presented in this paper, which consists of a viscoelastically and nonlinearly coupled beam-arch system, can be found in the physical model of a ...bridge. Here, the beam analogue of von Kármán's nonlinear strain-displacement relationships is used. After that the p-version of the finite element method is employed for the coupled system's geometrically nonlinear responses. In order to investigate the features of the arch's curvatures, a nonlinear analysis is performed in the time domain by the Newmark method and in the frequency domain by harmonic balance and continuation methods. The main contribution of the work is the discovery that the upper excited beam (in a double-beam model) goes back to the amplitude-symmetric vibration regime (as in the case of an excited single beam model) only if the lower beam is curved for the same excited scenario. That phenomenon comes from the nonlinear couplings in the beam-arch system and cannot be detected in the linear regime, while its existence is not evident without the analysis presented in this paper. Therefore, the non-symmetric higher amplitude deviations in the steady state regime of vibrations of the upper beam are transferred to the lower beam, only if the latter is curved. The paper shows that this nonlinear phenomenon is a consequence of 1:3 and 1:5 internal resonances where the first and the third/fifth modes become coupled. The most important purpose of the study lies in the clear physical insight into the nonlinear stabilizing benefits and the appearance of the nonlinear dynamic absorption or decrease in the excited beam amplitudes with determined amplitude-frequency responses, time histories, phase plots and deformed shapes for each particular case. In addition, by applying the Richardson extrapolation method within the standard Newmark procedure, an improvement is also explained and presented. The results of all these analyses are very valuable and have a wider application in vibrations.
This study aims to assess the seismic response of a newly developed buried arch bridge system. The proposed buried arch bridge system is comprised of precast concrete panels, external steel ...outriggers, and steel V-strips to solve the limitation encountered in the storage, transportation, and construction of traditional buried arch structures. The three-dimensional finite element analysis of this arch system is conducted under dynamic analysis emphasizing the frequency content of earthquakes. Then, the fragility curves are suggested for this arch system based on two damage states defined via incremental dynamic analysis. The results show that this proposed arch system is significantly affected under a high frequency content earthquake compared to the low and intermediate ones. Additionally, the arch system deflects the most at the mid-high position rather than at the arch crown. The deflection at the arch crown or at the mid-high position can be used for establishing the fragility curves as they both connect with the failure mechanism of the arch structure.
A segmented precast panel arch system with a steel outrigger rib was proposed to efficiently exploit material characteristics and a structural section, which resists the internal and external forces ...caused by arch effects. This study was conducted lifting and installation tests of this arch system and flexural loading tests for precast panels to validate and examine its structural behavior. The load-bearing capacity of a precast panel was experimentally evaluated against the flexural loading that occurred during the lifting process in the flexural loading test. In the lifting experiments for the fabricated arch specimen with a span length and height of 6.2 m and 2.5 m, respectively, the structural behavior of the precast panels and outrigger ribs during lifting were compared with the structural deformations and stresses of the system components after final installation. From the lifting and installation tests conducted in this study, the structural response and behaviors of the proposed arch system and its components were validated and evaluated.
The construction of mountain roads often promotes the occurrence of landslides, and poses a serious threat to the safety of driving and the geological environment. This paper introduces a new type of ...road landslide area anti-sliding structure based on thermal factors. The type door rigid frame-pile arch system, it is mainly composed of three parts: the gate type anti-slide pile, the reinforced concrete arch plate, and the mouth shaped guard pier. Its characteristics are: door-type anti-slide pile role is to resist the landslide thrust and the main road as a support structure; reinforced concrete arch between the plate as the door-type anti-slide pile and pile retaining force transmission member, active play arch structure compression high strength, can change the mechanical properties of stress paths, so that the lateral landslide sliding force to reduce; shaped mouth guard pier to control the deformation and solid slope, and enhance the overall stability of the system. The FLAC3D simulation results show that the stress distribution of arch plate is more uniform, with the increase of the sliding force, the stress in the arch foot and the lower part of the arch plate increases rapidly, which accords with the principle of soil arching. At the same time, the contact beam gradually works, The landslide thrust is transmitted to the front row of piles. The stress of the rear row of piles increases more than that of the front row of piles. The stress of the upper part of the beam increases more than that of the lower part of the beam. The overall trend is more and more gentle.
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Four methods of conducting overall and anterior Bolton tooth-size analyses were compared using 22 (11 pretreatment and 11 posttreatment) sets of models. No more than 3 mm of crowding existed in any ...of the models, and all were in good condition. An analysis employing vernier calipers was completed 3 times to set a standard. Pearson correlation coefficients revealed a high degree of intra-operator reliability with mean R values of 0.930 and 0.843 for the overall and anterior discrepancies, respectively. The mean Vernier caliper results were compared with each of the following computerized methods: QuickCeph, Hamilton Arch Tooth System (HATS), and OrthoCad. No statistically significant error was present for any of the methods using repeated-measures analysis of variance testing and paired t-tests (p < .05). Clinically significant differences (>1.5 mm) were present for each method. Absolute differences were calculated, and linear regression and R values were determined. The HATS analysis had the highest degree of correlation (R = 0.885 for overall and 0.825 for anterior), followed by OrthoCad (R = 0.715, 0.574), and QuickCeph (R = 0.432, 0.439). Each method also was compared based on the time required to complete each analysis. The QuickCeph was the fastest (1.85 minutes) followed by HATS (3.40 minutes), OrthoCad (5.37 minutes), and Vernier caliper (8.06 min).
We reviewed the cases of 33 patients from our clinic and 142 patients from the literature with congenital bronchopulmonary vascular malformations (BPVM), systematically analyzed the bronchopulmonary ...airways, pulmonary arterial supplies, and pulmonary venous drainages, and classified these patients by pulmonary malinosculation (PM).
From January 1990 to January 2007, a total of 33 patients (17 men or boys and 16 women or girls), aged 1 day to 24 years (median, 2.5 months), with congenital BPVM were included in this study. Profiles of clinical manifestations, chest radiographs, echocardiographs, esophagographs, computer tomography (CT), magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), cardiac catheterizations with angiography, contrast bronchographs, bronchoscopies, chromosomal studies, surgeries, and autopsies of these patients were analyzed to confirm the diagnosis of congenital BPVM. A total of 142 cases from the literature were also reviewed and classified similarly.
The malformations of our 33 patients can be classified as type A isolated bronchial PM in 13 patients, type B isolated arterial PM in three, type C isolated venous PM in two, type D mixed bronchoarterial PM in five, type F mixed arteriovenous PM in one, and type G mixed bronchoarteriovenous PM in nine.
Dysmorphogeneses of the primitive foregut system and the primitive aortic arch system may lead to haphazard malinosculations of the airways, arteries, and veins of the lung. A systematic classification of patients with congenital BPVM is clinically feasible by assessing the three basic bronchovascular systems of the lung independently.
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