Abutment Displacement Research Articles

Research on construction monitoring of curvilinear continuous beam bridge jacking and horizontal moving construction

This article investigates the issue of beam misalignment in continuous curved beam bridges. Taking the D0–D6 spans of the Gongbin Road elevated bridge as a basis, real-time monitoring of the stress and displacement of the beams is carried out during the jacking and shifting construction process. At the same time, the reaction forces of each support are monitored. The jacking force of the hydraulic jacks is controlled to ensure the stability and safety of the beam during the construction process. Finally, the jacking and shifting monitoring data is organized and compared with theoretical values. It is found that the stress values generated during the jacking phase of the bridge are below the stress control standard. No uplift phenomenon occurs at the supports, and the jacking height is controlled within a reasonable range. The construction process does not cause damage to the beams, and it is safe and reliable. During the shifting construction, the whole bridge was displaced using the jacking method, and the three working conditions were monitored throughout the process. The stress increment at the 2# and 4# sections was relatively small, and the measured stress increments for the entire bridge were all below the stress control standard. The displacement of the bridge abutment during the jacking process was minimal, with no contact with the abutment blocks, and no significant elastic deformation occurred. The jacking displacement was successfully achieved.

Longevity of different abutments placed on narrow diameter implants: Assessment of structural damage and loosening

ObjectivesTo evaluate structural damage and loosening of abutments placed on narrow diameter implants after cyclic fatigue. MethodsSixty Morse taper narrow diameter implants (Neodent, Brazil) received two types of abutments (1PA- one-piece abutment or 2PA- two-piece abutment), which were randomly divided into 3 fatigue experiments (n = 10). The implants were placed into a customized supporting holder and a software-assisted digital torque wrench secured the manufacturer recommended torque for each abutment. Cone beam computed tomography (CBCT) scans were acquired, before and after fatigue, and post-processed (software e-Vol DX) to assess damage and abutment displacement. The boundary fatigue method was adapted to use 2 × 106 cycles, 2 Hz of frequency and constant peak load of 80 N (first experiment) that varied according to the failure rate of previous specimens (second and third experiments). Failure was evaluated using CBCT scans and removal torque values. Data were used to estimate long-term torque degradation, probability of failure and Weibull modulus (software ALTA PRO9). ResultsAll 2PA specimens became loosen independently of the applied fatigue load, and structural bending was observed in 14 abutments. Eight 1PA got loosen during the fatigue experiment. The Weibull analysis showed a lower modulus (m = 1.0; 0.7, 1.4) for 1PA than for 2PA (m = 2.6; 2, 3.4) resulting in longer predicted lifetimes and slower torque degradation for 1PA than for 2PA specimens. Significance1PA showed greater long-term survival probability than 2PA. Predicting the lifetime and mechanical behavior of implant-abutment systems are useful information to clinicians during the decision-making process of oral rehabilitations.

In vitro assessment of internal implant-abutment connections with different cone angles under static loading using synchrotron-based radiation

BackgroundThe stability of implant-abutment connection is crucial to minimize mechanical and biological complications. Therefore, an assessment of the microgap behavior and abutment displacement in different implant-abutment designs was performed.MethodsFour implant systems were tested, three with a conical implant-abutment connection based on friction fit and a cone angle < 12 ° (Medentika, Medentis, NobelActive) and a system with an angulated connection (< 40°) (Semados). In different static loading conditions (30 N − 90º, 100 N − 90º, 200 N − 30º) the microgap and abutment displacement was evaluated using synchrotron-based microtomography and phase-contrast radioscopy with numerical forward simulation of the optical Fresnel propagation yielding an accuracy down to 0.1 μm.ResultsMicrogaps were present in all implant systems prior to loading (0.15–9 μm). Values increased with mounting force and angle up to 40.5 μm at an off axis loading of 100 N in a 90° angle.ConclusionsIn contrast to the implant-abutment connection with a large cone angle (45°), the conical connections based on a friction fit (small cone angles with < 12°) demonstrated an abutment displacement which resulted in a deformation of the outer implant wall. The design of the implant-abutment connection seems to be crucial for the force distribution on the implant wall which might influence peri-implant bone stability.

Finite Element Analysis of the Influence of Implant Tilting and the Direction of Loading on the Displacement and Micromotion of Immediately Loaded Implants

ABSTRACT Objectives: To investigate the outcome of the loading direction and implant tilting on the micromotion and displacement of immediately placed implants with finite element analysis (FEA). Materials and Method: Eight blocks of synthetic bone were created. Eight screw-type implants were inserted, four axially and four slanted, each measuring 11 mm in length and 4.5 mm in diameter. The axial implants and the tilted implants were distally inclined by 30°. The top of the abutment was subjected to 180 N vertical and mesiodistal oblique (45° angle) loads, and the displacement of the abutment was measured. The abutment displacement and micromotion were estimated, and nonlinear finite element models simulating the in vitro experiment were built. In vitro studies and FEA data on abutment displacement were compared, and the reliability of the finite element model was assessed. Result: Under oblique stress, abutment displacement was larger than under axial loading, and it was also greater for tilted implants than for axial implants. The consistency of the in vitro and FEA data was satisfactory. Under vertical stress, the highest micromotion values in the axial and tilted implants were extremely near Conclusion: Under mesiodistal oblique stress, tilted implants may have a smaller maximum amount of micromotion than axial implants. The loading direction had a significant impact on the highest micromotion values. The abutment displacement values were not reflected in the maximum micromotion measurements.

Exploring the Effect of Near-Field Ground Motions on the Fragility Curves of Multi-Span Simply Supported Concrete Girder Bridges

Investigating the impact of near-field ground motions on the fragility curves of multi-span simply supported concrete girder bridges is the main goal of this paper. Fragility curves are valuable tools for evaluating seismic risks and vulnerabilities of bridges. Numerous studies have investigated the impact of ground motions on the fragility curves of bridges. Ground motions are commonly categorized into two sets, based on the distance of the recorded station from the seismic source: far-field and near-field. Studies examining the influence of near-field records on bridge fragility curves vary depending on the specific bridge type and type of fragility curve being analyzed. Due to the widespread use of multi-span simply supported concrete girder bridges in the Central and Southeastern United States, this study makes use of this bridge type. This research investigates the component fragility curves for column curvatures, bearing deformations, and abutment displacements by employing 3-D analytical models and conducting nonlinear time history analysis. These curves illustrate the impact of near-field ground motions on different components. The component fragility curves for two sets of records, 91 near-field ground motions and 78 far-field ground motions, were obtained and compared. These findings demonstrate that near-field ground motions have a greater damaging effect on columns and abutments than far-field earthquakes. When it comes to bearing deformations, the far-field earthquake impact is more severe at lower intensities, whereas the impact of the near-field ground motion is stronger at higher intensities.

SEM Analysis and Micro-CT Evaluation of Four Dental Implants after Three Different Mechanical Requests-In Vitro Study.

Implant-supported rehabilitations are an increasingly frequent practice to replace lost teeth. Before clinical application, all implant components should demonstrate suitable durability in laboratory studies, through fatigue tests. The purpose of this in vitro study was to evaluate the integrity and wear of implant components using SEM, and to assess the axial displacement of the implant-abutment assembly by Micro-CT, in different implant connections, after three distinct mechanical requests. Four KLOCKNER implants (external connection SK2 and KL; and internal connection VEGA and ESSENTIAL) were submitted to three different mechanical requests: single tightening, multiple tightening, and multiple tightening and cyclic loading (500 N × 100 cycles). A total of 16 samples were evaluated by SEM, by the X-ray Bragg-Brentano method to obtain residual stresses, and scratch tests were realized for each surface and Micro-CT (4 control samples; 4 single tightening; 4 multiple tightening; 4 multiple tightening and cyclic loading). All dental implants were fabricated with commercially pure titanium (grade 3 titanium). Surface topography and axial displacement of abutment into the implant, from each group, were evaluated by SEM and Micro-CT. In the manufacturing state, implants and abutments revealed minor structural changes and minimal damage from the machining process. The application of the tightening torque and loading was decisive in the appearance and increase in contact marks on the faces of the hexagon of the abutment and the implant. Vega has the maximum compressive residual stress and, as a consequence, higher scratch force. The abutment-implant distances in SK2 and KL samples did not show statistically significant differences, for any of the mechanical demands analyzed. In contrast, statistically significant differences were observed in abutment-implant distance in the internal connection implants Vega and Essential. The application of mechanical compression loads caused deformation and contact marks in all models tested. Only internal connection implants revealed an axial displacement of the abutment into the implant, but at a general level, a clear intrusion of the abutment into the implant could only be confirmed in the Essential model, which obtained its maximal axial displacement with cyclic loading.

Effects of Soil–Structure Interaction on Performance of Bridges During Earthquakes. Case Study: Integral Abutment Bridge in Pennsylvania, USA

Bridges are among the most important transportation elements that may be damaged by earthquakes. An integral abutment bridge (IAB) is a bridge linking the superstructure directly to the substructure. As soil piles, abutments, and superstructures act as a combined system to resist lateral loading on the bridge, soil stiffness has a major impact on load distribution. This research attempts to determine how the structure and soil parameters affect the IABs. The parametric study consists of four variables, namely bridge span (short, medium, and large spans were 18.3, 35.4, and 64.5 m, respectively), backfill height/pressure (3.1, 4.6, and 6.1 m, respectively), stiffness of soil mixture backfills (high, intermediate, and low), and soil density around the piles (high, intermediate, and low). Because of the small width–length ratio of the bridge, a 2D model of an IAB with soil springs around the piles and abutments was developed with finite element software. Findings show that the value of the backfill pressure affects girder axial forces and girder bending moments at the IAB. Also, the stiffness of soil mixture backfills is an important factor to change lateral displacements, while less movement is related to high stiffness of soil mixture backfills with intermediate clay around the pile. It is clear that the maximum axial girder moments at the superstructure generally decrease when the stiffness of the soil mixture behind the abutments and around piles increases, similar to pile deflection and abutment displacements. In addition to maximum abutment, the head moment decreases when abutment backfill is dense and increases when piles are located in hard clay, similar to pile moments. Lastly, dense sand backfill behind abutments is recommended since it decreases pile deflections, pile lateral forces, abutment displacements, abutment head moments, and particularly pile bending moments.

Effect of inclined pile on seismic response of bridge abutments undergoing liquefaction—Induced lateral displacement: Case study of Nishikawa bridge in the 2011 Great East Japan earthquake

It is reported that the inclined pile could be either beneficial or detrimental for the abutment they support in the condition of liquefaction—induced lateral displacement. To clarify the effect of inclined pile on seismic response of bridge abutments undergoing liquefaction—induced lateral displacement, numerical analyses were carried out on the damaged abutment that was supported by inclined piles and that was displaced riverwards 100 mm–150 mm due to soil liquefaction during 2011 Great East Japan earthquake. Accordingly, a fully coupled dynamic effective stress finite element model was developed for the soil—pile—superstructure system. It was found that the shear failure of the bridge abutment was initialized from the inclined piles and then followed by the middle vertical pile. Moreover, the earthquake—induced liquefaction caused substantial lateral displacement of soils around the piles and thus dominated the backward rotation of the abutments supported by inclined piles. Additionally, the exclusion of the deck pinning effect may lead to a marked increase in the lateral displacement and rotation of abutments. If the abutment were supported by vertical piles, a much larger lateral displacement was expected and the promotion of the earth pressure behind the abutment was the main cause of the forward rotation of the piled abutment.

Effects of Geogrid Reinforcement on the Backfill of Integral Bridge Abutments

The construction of integral bridges is one of the most effective methods to reduce bridges’ construction and in-service costs. However, there are associated geotechnical problems with their abutments backfill due to the integrated abutments. The main goal of this study is to evaluate and quantify the benefits of geogrid reinforcement for reducing the backfill’s geotechnical problems. For this purpose, using small-scale physical modeling, the benefits of geogrid reinforcing of the backfill of an integral abutment bridge subjected to cyclic movements are evaluated. The results are then compared with a previous study performed on unreinforced backfill and two types of geocells. In this study, 120 loading cycles are applied to geogrid-reinforced soil to simulate the cyclic loadings on integral abutment backfill due to seasonal abutment displacement. The horizontal reaction load at the top of the wall, changes in pressure behind the wall, and deformation in backfill soil are measured during the test. Then the results are discussed in terms of equivalent peak lateral soil coefficient (Kpeak), lateral earth pressure coefficient (K*), and normalized settlement behind the wall (Sg/H). The derived lateral soil coefficients and settlement behind the abutment show that geogrid substantially reduces pressure and settlements after 120 cyclic loads. Based on the results, Kpeak and K* of the geogrid-reinforced backfill decrease by up to 36%, and Sg/H behind the wall decreases by 62%. In addition, the comparison of the results for geogrid with two geocell types shows that geogrid is more efficient in terms of lateral soil coefficients.

Centrifugal Model Test and Simulation of Geogrid Reinforced Backfill and EPS Interlayer on Bridge Abutment

In this paper, the use of geotechnical centrifuge and numerical modeling techniques to investigate the influence of geogrid reinforcement and EPS interlayer on the lateral earth pressure and the backfill surface settlements behind gravity abutment and pile-supported abutment is reported. According to the principle of equal strain, the abutment back structure, foundation, backfill material, grid and interlayer material were simulated, and the centrifugal model test for two types of abutments was carried out with a model scale of n = 62.5, 40, respectively. The tests showed that the reinforcement of the geogrid could reduce the surface settlement of backfill and the lateral earth pressure of the backfill on the back of abutment. After setting the EPS interlayer, the influence of abutment displacement on earth pressure could be eliminated, and the earth pressure of the backfill material on the abutment back was significantly reduced. The “interlayer + geogrid” structure further reduced the earth pressure of backfill material on the abutment back. The existence of the EPS interlayer adjusted the strain distribution of the reinforced material, significantly increasing the strain of the reinforced material near the abutment, which was conducive to the reinforcement effect. The above research conclusions could provide a basis for the design and practical application of abutment backfill materials.

Axial displacement of the suprastructures at the conical implant — abutment interface

BACKGROUND: The inconsistency of the congruence of the surface of the implantabutment interface leads to the impaired communication of the implant shaft with the oral cavity, breakdown of the structure, including the implant, and changes in the occlusal relationships because of axial displacement.&#x0D; AIM: This study aimed to investigate the degree of axial displacement of abutments made relative to implants and analogs. Specific tasks were as follows: (1) to make various abutments for implants with a conical connection obtained from MIS, (2) to study the value of axial displacement of abutments of each type relative to the implant with load modeling, and (3) to examine the value of the axial displacement of abutments of each type relative to the analog of the implant from the tightening force of the screw.&#x0D; MATERIALS AND METHODS: Axial displacements were tested using implants and analogs of MIS implants with conical joints. Original and non-original abutments were chosen as suprastructures. The original abutment was presented by CS-CPK62. Abutments for the conical connection C1 were made by milling, laser sintering, and casting according to burned models. The fastening of implant analogs and implants was made in a block of plaster of the 4th class. The study was conducted in a simulation complex we have developed, which creates a cyclic load within 30 kg. The study was divided into two stages. In the first stage, axial displacements on analogs from the force of screw tightening were examined. Abutments were attached with various forces: 7 Ncm (tightening force with a simple screwdriver), 15 Ncm, and 30 Ncm. After each screw tightening, vertical measurements were made with a micrometer. In the second stage, axial displacements on implants under load in the original simulation complex were assessed. The screw was tightened with a force of 30 Ncm, as recommended by the manufacturer, and load simulation was performed. Measurements were made both before and after the load simulation.&#x0D; RESULTS: The original abutments and those made by milling showed the greatest deviation (0.056 mm and 0.066 mm, respectively), and abutments obtained by casting had deviations of 0.047 mm. The smallest deviation was found in the abutment made by laser sintering (0.032 mm). The values obtained in the second stage were as follows. Original abutments and abutments obtained by milling showed the smallest axial displacement when modeling the load (0.00167 mm each). Moreover, the abutments obtained by casting and laser melting showed significant displacements (0.007 mm and 0.004 mm, respectively).&#x0D; CONCLUSIONS: A pattern was revealed: the smoother the surface of the conical parts, the stronger the axial displacement on the analog implants in the range of 730 Ncm, whereas an uneven surface gives the smallest axial displacement, and fixation according to the protocol provided resistance to chewing loads on the implants in the original and milled abutments. The use of a platform with a conical system to create high-precision orthopedic structures has certain limitations because an error in the height of the restoration is created in laboratory conditions. The use of non-original suprastructures leads to the accumulation of errors. Thus, it is necessary to further evaluate conical systems from other manufacturers and improve the accuracy of restorations based on dental implants.

Comparing loosening between cement retained and screw retained implant supported crowns: a dynamic non-linear finite element analysis

Titanium root form implants are widely accepted because of the advantages of their mechanical properties. This study compared the screw loosening between two types of implant supported crowns (cement retained and screw retained) at the location of left lower first molar, using finite element method in a nonlinear analysis. The Dentis system was used for modeling of the implant, abutment and suprastructure. The amount of preload displacement was almost the same for both types of abutments. Applying force in any direction reduced the amount of downward preload displacement and decreased abutment-implant stability. In the cement retained crown, the amount of inner abutment displacement was always less than the screw head displacement by applying vertical, oblique and vertical-horizontal loads, so the stability of the abutment-implant complex was maintained. In the screw retained crowns under vertical-horizontal load the amount of displacement at the screw head and inner side of abutment was close to each other and this put the screw on the verge of loosening. However, under oblique pressure of 100 N, the inner abutment displacement exceeded the screw head displacement and the screw was loosened. Under vertical loading of 100 and 150 N, the stability of implant abutment was maintained. Screw loosening is less likely to occur under vertical load compared with oblique load. The cemented retained crowns have a higher biomechanical stability than screw retained crowns.

Displacement and performance of abutments in narrow-diameter implants with different internal connections

Statement of problemDisplacement of abutments into conical connection implants during screw tightening may also occur during functional loading, creating unsettling forces that may cause loss of preload. A recent conical-hexagon connection with double friction fit (conical-hexagon connection) could prevent this axial displacement. PurposeThe purpose of this in vitro study was to measure the 3D axial displacement of abutments with a conical-hexagon connection or conical connection in narrow-diameter implants. Removal torque values (RTVs), preload efficiency, and survival after cyclic loading were also compared. Material and methodsNarrow-diameter implants with a conical connection (Osseospeed EV, 3.0×13 mm-AST) and narrow-diameter implants with a conical-hexagon connection (Eztetic, 3.1×13 mm) were embedded in resin rods (G10) (n=6). Six titanium abutments per system were used, and their spatial relationship to the implant platforms after hand tightening was determined by using 3D digital image correlation. The abutments were tightened to the manufacturers’ specified values, and the abutments’ relative position was recorded again. The displacement of the abutment after tightening was calculated. The implants were subjected to cyclic loading (5×106 cycles at 2 Hz) under 200-N loads at a 30-degree angle. After cyclic loading, the RTVs of screws were measured and compared with those specified by the manufacturers to calculate preload efficiency. ANOVA was used to compare the differences in displacements after tightening and to compare differences in RTVs after cyclic loading across the groups (α=.05). ResultsThe mean displacement in the U direction (X-axis) for the AST was −0.7 μm and −4.7 μm for ZIM, with no statistical difference (P=.73). The mean displacement in the V direction (Y-axis) for AST was −37.0 μm, and −150.0 μm for ZIM, with significant statistical difference (P<.001). The mean displacement in the W direction (Z-axis) for AST was −0.9 μm, and −23.0 μm for ZIM, with no statistical difference (P=.35). The survival of groups was similar (P=.058). During cyclic loading, 3 AST specimens fractured. After cyclic loading, mean RTV for AST was −8.77 Ncm, and −14.24 Ncm for ZIM, and these values were significantly different (P=.04). Preload efficiency was 28.1% for AST and 41.5% for ZIM. ConclusionsGreater abutment displacements were observed with the conical-hexagon connection, which required a higher torque, as specified by its manufacturer. The abutments displaced more in the V-axis in both implants. Only the conical connection implant (Ti Grade 4, commercially pure) had failures during cyclic loading, but the survival of the implants was similar. After cyclic loading, the abutment screws in both systems lost some of their torque value. The abutment screws of the conical-hexagon connection implant maintained preload more efficiently during cyclic loading than those of the conical connection implant.

Prediction equations for estimating maximum lateral displacement and settlement of geosynthetic reinforced soil abutments

Abstract The Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS), which consists of closely-spaced layers of geosynthetic reinforcement and compacted granular fill material, is a fast, sustainable and cost-effective method for bridge support. The in-service performance of this innovative bridge support system is largely evaluated through the vertical and horizontal deformations of the GRS abutments. This paper presents the development of nonlinear equations for estimating the maximum lateral displacement and settlement of GRS abutments. The parameters that are considered in the prediction equations include abutment geometry (height, facing batter and foundation width), backfill friction angle, reinforcement characteristics (stiffness, spacing, and length), and applied static loads from 50 to 400 kPa. In the development of the prediction equations, a parametric study was first conducted using a validated finite difference numerical model. The results of the parametric study were then used to conduct a regression analysis to develop the equations for estimating the maximum lateral displacement and settlement of GRS abutments under service loads. The equations were validated using three case studies. The developed prediction equations can contribute to a better understanding and enable simple calculations in designing these structures.

The Influence of a Positioning Hex on Abutment Rotation in Tapered Internal Implants: A 3D Finite Element Model Study

The purpose of this study was to investigate the resistance against rotation of a two-piece abutment with or without the presence of a positioning hex in tapered internal connection implant systems. A tapered internal connection implant with an 11-degree internal oblique angle was placed into a constructed three-dimensional (3D) bone model. Two types of abutments were compared: hex-type abutments with a positioning hex and two-piece round-type nonhex abutments. Vertical compressions equivalent to the screw tightening torque of 30 Ncm and 40 Ncm were applied to the abutment screws. A horizontal load of 150 N was applied to the superstructure to create moments. The contact area between the implant and abutment was compared and analyzed. The rotational displacement of the abutments was investigated as well. When a preload equivalent to 40 Ncm of tightening torque was applied, the round-type abutment exhibited a larger contact area than the hex-type abutment by approximately 2.5% to 3.5% in contrast to the internal surface area of the implant. When the screw tightening torque of 30 Ncm was applied, the rotational displacement of the hex-type abutment was approximately 0.54 degrees and the round-type was approximately 1.16 degrees under clockwise moment loading. Within the limitations of this study, it can be assumed that the hexagonal design of the abutment acts as rotational resistance against moments.

WITHDRAWN: Synchrotron-based Radiography of Conical- vs. Butt-joint Implant Abutment Connections.

Ahead of Print article withdrawn by publisher.

Abutment screw withdrawal after conical abutment settlement: A pilot study.

This study investigated the effects of abutment screw withdrawal after conical abutment settlement on the stability of the implant-abutment connection. Twenty implants of a conical connection system were used. Two two-piece abutment designs were used: cone only (n=10; NI) and cone plus octagonal index design (n=10; I); for each design, five samples were used with (S) and without (NS) abutment screw withdrawal before a cyclic test. Finally, four groups, namely Gr S(NI), Gr S(I), Gr NS(NI), and Gr NS(I), were included. The cyclic test included cyclic loading of 20-200N, 30°, and 4-mm off-axis to implant axis at 10Hz for 106 cycles, simulating a clinical time interval of 40months. The fatigue cycles were recorded. The axial displacement of the conical abutments during abutment settlement, screw withdrawal, and cyclic loading were measured. Abutment morphology was examined through scanning electron microscopy (SEM). Only Gr NS(NI) failed the test, indicating that without the index design and abutment screw withdrawal, and connection stability seriously deteriorated. Gr NS(I) exhibited significantly higher axial displacement into the implant after abutment settlement than did Gr NS(NI). It also exhibited continuous axial displacement into the implant after cyclic loading. SEM after cyclic testing in Gr NS(I) revealed marked burnishing on lateral edges of the index, indicating that the index design provides an antitorsional ability. Although this study has few limitations, abutment screw withdrawal is feasible in this conical implant-abutment connection system with index design.

Displacement of Customized Abutments Designed on a Working Cast and in the Oral Cavity: A Comparative In Vivo Study.

To compare abutment displacement between the virtual, customized abutment that was designed on a cast and the customized abutment prepared in the oral cavity. Eleven patients were selected for a single posterior implant prosthetic treatment. The impression was obtained using the closed tray impression method with a vinyl polysiloxane material using a custom tray. The standard tessellation language files of the customized abutment that was designed using the computer-aided design system and acquired with an intraoral scanner in the oral cavity were superimposed and analyzed for distance and angle displacement using the three-dimensional inspection analysis program (Geomagic Control X). In the statistical analysis, distance and angle displacement values were analyzed with the Kruskal-Wallis H test (α = 0.05), and a post hoc comparison was performed using the Mann-Whitney U-test and Bonferroni correction method. The mean distance and angle displacement of the 15 customized abutments were 89.52 ± 66.86 µm and 0.83 ± 1.21°, respectively. There were significant differences in distance displacement (p < 0.001), and angle displacement (p < 0.001) among the 15 customized abutments, and there were no significant differences in angle displacement along the 4 directions (p = 0.735). The displacement values of the customized abutments evaluated in the oral cavity differed significantly from patient to patient.

Experimental Study on the Global Stability of the xiaowan Arch Dam Using a 3D Geo-mechanical Model Test

In this paper, a three-dimensional geo-mechanical model test for the Xiaowan high arch dam was studied and the topographical and geological features, the distribution of weak structural planes, the shallow relaxation unloading phenomena were simulated. Furthermore, a type of model material known as the temperature analogous material, whose strength varies with temperature throughout the experiment, was used to simulate the decrease in shear strength of the weak structural planes. The deformation characteristics and failure mechanism of the dam foundation and abutments were obtained by using comprehensive test method, which considered both the overloading and strength-reduction techniques. Through data analysis, the strength reserve coefficient, the overloading and the global safety factor were obtained. Synthetic analysis of the test results indicates that the displacement of the mid-upper abutment was reduced and the failure zone become smaller due to the significant reinforcement effects of concrete displacement plugs on the faults and alteration zones. The failure pattern shown in the model test indicates that reinforcements should be installed at faults F11 and F10 above an elevation of 1245 m in the right abutment and the rock above the thrust block in the left abutment.

Experimental Study and Simulation of Film Tension Measurement by Apex Method

In order to ensure the normal use of the tensioned membrane structure, it is necessary to effectively detect the tension applied to the tensioned membrane surface. In this paper, a top-projection membrane surface tension measuring instrument with fixed boundary was designed. During the measure process, the force and the apex displacement were measured simultaneously to obtain the calibration curve group of force and abutment displacement. Compared with the traditional apex method, the measuring instrument eliminates the influence of the membrane structure boundary on the measurement results, and the measurement results were accurate and reliable. The correctness of the device is verified by numerical simulation and experimental results. Theoretically solved the technical problem of rapid measurement of membrane surface tension, and obtained stable results in actual measurement, thus providing a new method for membrane surface tension measurement.