Main Arch Research Articles

Research on the cross-sectional geometric parameters and rigid skeleton length of reinforced concrete arch bridges: A case study of Yelanghu Bridge

To investigate the influence of cross-sectional parameters and the rigid skeleton length on the structural mechanics behavior of reinforced concrete arch bridges, this study focused on the Yelanghu Bridge with a span of 210 m. The sensitivity of the main arch rib's instability mode to cross-sectional parameters such as width, spacing between adjacent webs, height, and concrete thickness was examined by combining the finite element method and the theoretical derivation. Subsequently, research was conducted on the impact of the rigid skeleton length during construction on the static and dynamic performance of the structure relying on the Midas Civil software. The findings indicate that for the Yelanghu Bridge, the risk of in-plane instability is greater than that of out-of-plane and local instabilities. In-plane instability is most sensitive to the section height and the out-plane instability is most sensitive to the thickness of the roof and floor concrete. Under ultimate load-bearing conditions, the axial force in the critical sections of the bridge increases with the length of the rigid skeleton. The fundamental frequency of the Yelanghu Bridge is approximately 0.32, which is significantly lower than that of more rigid arch bridges but higher than those of structurally softer structures such as cable-stayed or suspension bridges. This indicates that large-span reinforced concrete arch bridges exhibit unique dynamic characteristics and belong to moderately flexible structures.

Impacts of the mechanical connectors on seismic performance of the restored masonry Plaka Bridge using experimental and numerical studies

The use of clamp and dowel materials in the arch of the masonry bridges holds pivotal significance in enhancing the seismic resilience of these structures, as these elements contribute crucially to the structural integrity and dynamic response of these venerable structures. For this reason, the seismic performance of the restored historic Plaka Bridge, originally constructed in 1866 in Arta, Greece, and later restored in 2015 after flooding, was investigated considering the dowels and clamps in the arch section of this study. A combination of experimental and numerical analyses was conducted and verified to understand the in-situ interface behavior of the arch stones. In the first phase of the study, the mechanical properties of the dowels and clamps were characterized by the experimental tests. Compression and tension tests were conducted on the stone samples containing dowel bars and clamps respectively to determine the mechanical properties, The experimental outcomes were subsequently validated through Three-Dimensional (3D) Finite Difference Models (FDM). It was obtained that the dowels and clamps represent the bi-linear material model at the interfaces. Finally, the idealized interface behavior was constructed with normal and tangential spring stiffness properties in 3D-FD Models. These springs successfully simulate the interface delamination failure of the stones in all directions. In the final phase of the study, a 3D-FD model of the Plaka Bridge was constructed employing the previously validated normal and tangential stiffness elements in the arch of the bridge. A free-field non-reflecting boundary condition was imposed on the base and lateral boundaries of the bridge model. Seismic analyses were conducted utilizing the significant seismic events including 2023 Kahramanmaraş earthquakes. The results revealed significant alterations in the structural behavior of the bridge under considered earthquakes. Furthermore, the displacements, principal stresses and tensile-compressive damages in the main arch significantly reduced with the adopted stiffness values. This study proposes the undeniably realistic and efficient implementation of interface material modeling for the mechanical connections as opposed to the traditionally assumed mortar properties in literature. Furthermore, the combined behavior of the dowel, clamp, and Khorasan mortar proposes non-linear interface material model to the existing literature by invalidating commonly assumed linear interface behavior in masonry structures.

Sliding connectors for cyclic construction of steel-UHPC composite truss arch bridges: design method and feasibility study

To break through the three major technical bottlenecks of traditional long-span arch bridges, which are excessive self-weight, high cost and difficult construction, a new steel-ultra high performance concrete (UHPC) composite truss arch bridge scheme and a matching cyclic construction method were proposed. The main arch can be divided into several times for closure from the inside out. Special transverse connection devices need to be installed between the arch ribs constructed with successive closures by step. The devices can not only ensure the stability of the arch ribs constructed subsequently, but also do not cause serious stress superposition on the already closed arch ribs. Therefore, sliding connectors for the cyclic construction of new arch bridges and the corresponding simplified modeling method were proposed in this paper. Subsequently, the working mechanism was analyzed, and the design method was proposed. Finally, the feasibility of sliding connectors and the correctness of the corresponding design method were verified by the experiment. The results indicate that it is necessary to install a transverse sleeve structure in the sliding connector, which plays a key role in transverse adjustment. The design of key dimensions in sliding connectors is controlled by the maximum vertical and longitudinal displacements of the inner arch. The outer arch could slide freely under the premise of ensuring stability, and the mechanical superposition response of the inner arch was relatively small. For the inner arch, the vertical displacement at the crown only increased by 10.94 %, and the maximum compressive stress in the UHPC arch ribs only increased by 16.3 %. The sliding connector also has the potential for further optimization to achieve smaller stress superposition.

Convergence of Literature and History: 'The Bridge on the Drina' in the Context of Historiographic Metafiction

While the boundary between the disciplines of literature and history has come into question due to the problematization of their ontological natures, their textuality and similar narrative technics stand out as two main elements among the other intersections. As the criticisms of objectivity directed at history have echoed in literary studies, literary works where historical facts and fiction cluster have taken it one step further and rendered it possible to discuss the matter more broadly with cultural aspects. In The Bridge on the Drina, it is seen that the main arch of the narration proceeds along the historical realities, and yet Ivo Andrić’s sole aim is not to put forward a classic historical novel. In fact, rather than foregrounding the realities in question and erasing the fictive elements, he presents a kind of alternative history by palpably bringing together the historical and the fictional. Hence, the aim of this study is to argue that in The Bridge on the Drina, the boundary between history and literature gets blurred and their conventional characteristics get problematised. Presenting views from both historical and literary studies, the primary theoretical frame will be based on the notion of historiographic metafiction.

Analysis of the Temperature Effect During the Lifting Stage of The Main Arch Ring of The Strong Skeleton

In this paper, a finite element model of the main arch ring of the strong skeleton is developed in order to analyse the stress and deflection response of the strong skeleton under the action of uniform temperature during the lifting stage. Uniform temperature action was found to have a significant effect on the stresses and deflections of rigid skeletal stringers. The effect of the huddle on the stress and deflection of the skeleton at the non-design reference temperature was further investigated, and the results showed that the changes of the stress and deflection of the skeleton were directly proportional to the relative temperature difference (the difference between the huddle temperature and the design reference temperature).In addition, a reasonable value for the jointing temperature was analysed, and it was suggested that a value of 2℃slightly lower than the average annual temperature be used as the jointing temperature.

Simulation analysis of the entire construction process of the sunflower shaped continuous arch bridge

At present, there is a lot of research on the structural system of the completion stage of the Kuihua arch bridge in China, but there is a lack of research on the risks existing in each stage of the construction of the Kuihua arch bridge. Therefore, it is necessary to conduct a full process simulation analysis of the construction process of the sunflower shaped continuous arch bridge. The following conclusions were drawn from this study: (1) After analysis, the construction method of first removing the support below the main arch ring and then pouring the main beam can ensure the safety of construction. (2) The maximum axial force of the support pole below the main arch is -17.67kN, located in rows 10 and 50. The maximum vertical displacement of the main arch is -4.998mm, which is much smaller than the allowable deflection. Therefore, the shape of the main arch is within the safe range. (3) The tensile stress of the main arch and continuous longitudinal beam are both less than the design value of C40 concrete tensile strength of 1.71MPa, so the main arch and continuous longitudinal beam have not cracked, and are in a safe state throughout the construction process.

Harnessing the joint effect of approach bridges in arch bridge construction: an analytical study on thrust stiffness and elevation error mitigation

Achieving full equilibrium for the horizontal component force of the backstay in cable-stayed arch bridges is challenging, and the stiffness of the buckle tower has a notable influence on the overall shape of the main arch structure. Increased stiffness in the buckle tower leads to reduced construction complexity. Therefore, this study proposed a method of enhancing the longitudinal thrust stiffness of the buckle tower using the joint effect of approach bridges. A sensitivity analysis was conducted on the approach bridge–composite buckle tower structure to determine the optimal combination method, resulting in the formulation of an analytical expression for the thrust stiffness of this structure. In this study, numerical analysis was performed to explore the composition mechanism of the thrust stiffness influenced by the pier–girder connection, and we discussed the applicability of the joint effect of approach bridges during the cantilever assembly process of arch ribs. The following conclusions were obtained: 1) prior to installing the main girder of the approach bridge, when the steel buckle tower and the junction pier have already been secured, the most effective approach is to form a “T” rigid structure by firmly connecting the main girder of the approach bridge with the composite buckle tower. This configuration provides self-weight deflection and pier–girder rotation restriction effects. 2) The study presents analytical formulas for the completely rigid pier–girder connection of the approach bridge–composite buckle tower structure, partially rigid pier–girder connection, and pre-deviation. Combined with the calculation program, this can guide structural design. 3) When a large downward elevation error of the arch ribs occurs in the middle and later stages, the cable force needed to install new arch segments becomes overly large. Therefore, the joint effect of approach bridges can be utilized to substitute for a portion of the cable force, effectively reducing potential elevation errors that might arise in subsequent arch ribs in the absence of this joint effect.

Study and application of joint assessment model for construction risk of Xiangxi Yangtze River Bridge

Closure of main arch rib is the key process of steel box girder arch bridge construction. The way to achieve quantitative and accurate prediction of closure error risk remains to be studied in depth. Taking the construction risk model of closure of main arch rib of Xiangxi Yangtze River Bridge as an example, firstly, the causal relationship between prior data and closure error of main arch rib is considered to construct Bayesian network topology; Further, the central limit theorem (CLT) is used to update the prior distribution of the parent nodes in the network using dynamic multi-source monitoring data; Then the finite element analysis and BP neural network are combined to reproduce the corresponding relationship between the arch rib closure error and the influencing factors. Finally, the probability distribution is determined by the Monte Carlo method, and the quantitative prediction of the joint construction risk error is realized. The analysis data shows that the risk probability of arch rib vertical error of Xiangxi Yangtze River Bridge is transmissible, and the risk level of arch rib closure error reaches Grade IV when it is 75∼125mm. Therefore, the prestress of anchor cable, tower buckle offset and local temperature should be closely monitored during construction. The calculated value of the joint prediction model of construction risk is consistent with the actual closure control error trend of the project, which can provide reference for the prediction and regulation of related bridge construction risks.

Optimization method for the length of the outsourcing concrete working plane on the main arch rib of a rigid-frame arch bridge based on the NSGA-II algorithm

In addressing the challenges of determining the length of the outsourcing concrete working planes on the main arch rib of rigid-frame arch bridges—a process often reliant on extensive engineering experience, large-scale manual calculations and lack of multi-objective control. This paper employs the NSGA-II multi-objective optimization algorithm, where the objective functions are set to minimize the maximum compressive stress, tensile stress, and vertical deformation of the arch crown after the bridge was built. Optimization studies of the outsourcing concrete working plane length were conducted in different pouring schemes. Based on the case study of a main arch rib specimen with a span of 60 m, the optimal results for different construction schemes were derived. The uneven stress distribution coefficient of key sections was used as the evaluation index to filter the Pareto-optimized solutions from the NSGA-II optimization results. The experimental results indicated that: (1) Compared with the original pouring scheme, the optimized scheme respectively reduced the structure's maximum compressive stress, tensile stress, and vertical deformation of the arch crown by 4.19 MPa, 0.12 MPa, and 1.74 mm, showing a decline of 24.19%, 19.67%, and 2.82%. (2) Seven distinct outsourcing concrete pouring schemes were devised by altering the number of working planes, segments per working plane, and concrete pouring direction. All schemes achieved favorable optimization results through length optimization, demonstrating the broad applicability of the NSGA-II algorithm. (3) The stress distribution coefficients non-uniformity for the outsourcing concrete of the main arch rib are mostly located in the range of [0.7, 0.8], surpassing the original scheme's 0.69. Therefore, the NSGA-II algorithm not only ameliorates the primary arch rib's stress condition and diminishes the arch crown's vertical deformation, but also elevates the post-construction stress distribution state of the bridge's outsourcing concrete.

Evolution Law of Concrete Interface Stress of Rigid-Frame Arch under Construction and Its Impact on Ultimate Load-Bearing Capacity.

To study the evolution of stress on the ring and segment interfaces during the construction process of the concrete encapsulation of the main arch ring in a rigid-frame arch bridge, alongside its impact on the ultimate load-bearing capacity of the main arch ring, a 1:10 scale model experiment was conducted by taking the 600 m Tian'e Longtan Bridge as the prototype. The key cross-section concrete strain data were collected during the entire construction process of the main arch ring via fiber-optic strain sensors, which were used to investigate the stress evolution at ring and segment interfaces. ANSYS APDL was employed to simulate the ultimate bearing capacity under various loading conditions of two different finite element models, which were, respectively, formed segmentally and by single pouring. The results revealed that (1) after the closure of the concrete encapsulation of the main arch ring, the concrete stress in the cross-section exhibits significant stress disparities. At the same cross-section, the level of the web concrete stress can reach 76% of the floor concrete stress, while the roof concrete stress level is less than 20% of the floor concrete stress. (2) At the junction of two adjacent work planes, there are considerable differences in the stress levels of the concrete on both sides. After the closure of the main arch ring, the intersegment stress ratios of the floor, web, and roof concrete are 60~70%, 40~60%, and 0~5%, respectively. (3) Loading conditions remarkably affected the ultimate bearing capacity of the main arch ring. Under mid-span loading and 1/4 span symmetrical loading conditions, compared to single-pour concrete encapsulation, the ultimate bearing capacity of the main arch ring with concrete encapsulated by segmented and ring-divided pouring decreased by 19.16% and 5.23%, respectively, compared to single-pour concrete encapsulation. This suggests that the non-uniformity of stress distribution in the concrete sheath can lead to reductions in the ultimate bearing capacity of the arch ring.

Construction-Monitoring Analysis of a Symmetrical Rigid Frame Tied Steel Box Arch Bridge in Southwest China Based on Segmental Assembly Technique

Tied steel box arch bridges are increasingly being used due to their attractive appearance, high load-bearing capacity, and good stress performance. Their construction involves multiple processes and factors. Construction monitoring can ensure that such a bridge remains in its intended stress and linear states during and after construction. This helps to minimize deviations from the design state at every stage of construction. Using the segmental assembly construction technique, this study conducted construction monitoring of the alignment and force at each stage of the reconstruction of bridges using MIDAS Civil software. The construction monitoring analysis indicated that the arch rib and lattice beam were correctly placed, thereby meeting the specified requirements for arch rib closure. Displacement errors between the measured and theoretical values at each stage of construction fell within an allowable range, resulting in overall smooth bridge alignment. The measured stress in the main arch and the lattice beam generally corresponded to the theoretical stress derived from the control section stress of the entire bridge. The deviation between the cable force of the suspender and the tie rod and theoretical value fell within 10%, indicating good stress reserve. The symmetrical monitoring points in the analyzed rigid-frame tied steel box arch bridges exhibited symmetrical displacement, stress, and cable force results under various working conditions. This observation further confirms the effectiveness of construction monitoring using the segmental assembly technique.

Improvement in the Seismic Performance of a Super-Long-Span Concrete-Filled Steel-Tube-Arch Bridge

The applicability of current seismic-performance-improvement technologies needs to be studied. This research took a super-long-span CFST arch bridge with a total length of 788 m as the object on which to perform a non-linear time-history analysis and a seismic-check calculation according to the seismic response, so as to reveal the seismic weak points of the arch bridge. After the completion of the bridge’s construction, we arranged and utilized the stayed buckle cables (SBCs) reasonably. The seismic performance of the super-long-span CFST arch bridge was improved through friction-pendulum bearings (FPBs) and SBCs. The research shows that FPBs can solve the problem of the insufficient shear resistance of bearings, and SBCs can address the problem whereby the compressive stress of the transverse connection of the main arch exceeds the allowable stress. Moreover, SBCs can increase the transverse stiffness of arch bridges and reduce their seismic responses. Finally, a combination of FPBs and SBCs was adopted to improve the overall seismic performance of the arch bridge and obtain the best seismic-performance-improvement effect.

Research on Loading Scheme for Large-Scale Model Tests of Super-Long-Span Arch Bridge

A reasonable and efficient loading scheme is needed to guarantee the success of large-scale bridge tests. In this study, an array-type, self-balancing pulley-group loading system was designed based on the world’s largest spanning arch bridge using a 1:10 scale model test. Automatic statistics of the required load at each loading point were realized using ANSYS, and a load optimization algorithm for loading points at different construction stages was proposed. Tests were carried out separately for the loading system using a single set of pulley groups and an array-type pulley group. Finite element models of the model bridge and the original bridge were established separately using ANSYS, and the stress results of different components during different construction stages of the main arch ring were compared. The research results show the following: (1) The load magnification factor of the single-pulley-group loading device is approximately 6.6 times, with a mechanical efficiency of 94.26%. (2) In the array-type loading system, the actual load at each loading point can reach the design value. The self-balancing characteristic of this system can eliminate the impact of vertical deformation of the structure on loading accuracy, verifying the reliability of the system. (3) The simulation results of the original bridge and the model bridge coincide well, and the stress of each component during the construction process has the same trend. At key construction stages, the maximum relative errors of the stress results of the rigid steel frame and the concrete inside the pipe of the two bridges are 8.33% and 9.34%, respectively, and the maximum absolute error of the bottom plate concrete is 0.66 MPa, verifying the correctness of the counterweight-optimization method. The loading scheme proposed in this paper can provide a reference for the design of loading systems with the same type of scale model test.

Symmetrically Construction Monitoring Analysis and Completed State Evaluation of a Tied Steel Box Arch Bridge Based on Finite Element Method

Because of their beautiful appearance, strong crossing ability, and reasonable stress performance, the application of tied steel box arch bridges is becoming more and more extensive. Bridge construction monitoring can control and adjust the deviation state to ensure the stress and linear state of the bridge after completion. This study carried out a symmetrical construction monitoring analysis and completed state evaluation of the newly built Dafeng River Bridge in Guangxi Province based on the finite element method. MIDAS Civil finite element software is used for simulation analysis to calculate the deformation and stress of the tied steel box arch bridge at the construction and completion stages. The tensile and compressive stress of the main arch and transverse brace, as well as the cumulative displacements of the main arch and lattice beam, are symmetrically distributed. The maximum tensile and compressive stresses are 15.1 MPa and 74.6 MPa, respectively, less than the specification’s allowable value. Meanwhile, for the completed bridge under the loading combinations of serviceability limit state and bearing capacity ultimate limit state, the stress of the main arch, transverse brace, and lattice beam meets the specification requirements. The maximum cable forces of the suspender and tie rod under the bearing capacity ultimate limit state are 2189.4 kN and 2991.2 kN, and their corresponding minimum safety factors are 3.2 and 2.7. In addition, the deviations between the on-site monitoring and the finite element theoretical values are within the specification allowable range for the cable force of the suspender and tie rod and the bridge deck alignment. It indicates that the bridge construction monitoring effect is reasonable and ideal, and the symmetrically finite element simulation analysis can provide a theoretical basis for construction monitoring.

Analysis of Seismic Response of the Arch Bridge across Reservoir considering Fluid-Solid Coupling Effect

Most of the deep-water bridges in Chinese reservoirs are concentrated on rivers in the southwest region. The unique structural characteristics of arch bridges are more in line with the geological topography requirements of deep reservoir areas, making them the bridge type of choice for bridges in deep reservoir areas. While the southwest region is an earthquake-prone area, in order to study the safety of arch bridges across deep water in the reservoir area, it is necessary to analyze the effect of water under seismic behavior on the box section arch ring and explore the effect of arch inundation depth on the dynamic response of arch bridges in the reservoir area. In this study, the effect of fluid-solid coupling is considered, the modified Morison equation is used to calculate the hydrodynamic pressure, and the effect of arch bridge inundation depth on the dynamic response is analyzed based on the Midas/civil finite element model of the arch bridge in the Yunnan reservoir area. The results show that the seismic response of the arch bridge across the reservoir is greatly influenced by the submergence depth of the arch bridge due to the fluid-solid coupling effect, and the influence of the hydrodynamic pressure on the longitudinal moment (My) and transverse moment (Mz) of the arch bridge increases with the increase of the submergence depth. There is a threshold value of the submergence depth. When the submergence depth is less than the threshold, the effect of fluid-solid coupling is negligible, and when the submergence depth is greater than the threshold, the fluid-solid coupling effect is significant. The thresholds for different parts of the main arch ring are different. The most unfavorable water depth in different parts of the main arch ring is not necessarily the water depth when the arch ring is completely submerged. Based on this result, for reservoir arch bridges in high intensity areas, it is recommended that the inundation depth of arch bridges crossing deep water reservoirs should be h/f less than or equal to 5/8 f.

Development and Application of a Crossed Multi-Arch Greenhouse in Tropical China

Deep analysis and demonstration of the developed crossed multi-arch greenhouse were conducted from the perspectives of conceptual design, architectural and structural design, functional design, loading parameters, and structural internal forces. The results show that the crossed multi-arch greenhouse combines the ventilation area between the floor-standing round-arch greenhouse and the unsuitable operation area under the arch bars into one to form a multi-span crossed arch structure with good ventilation and heat dissipation, land savings, and fine mechanical behaviors. The main arch structure uses 32.4% less steel and 25% less foundation volume than the control greenhouse under the same load, which can save about CNY 10,184.00/667m2 of investment according to the current cost level. In the meantime, ventilation simulation analysis of the developed crossed multi-arch greenhouse was carried out using the software Design Builder. A comparison shows that, under the condition of no wind and breeze (1 m/s) in summer, the setting of the ventilation channel has obvious advantages for the heat dissipation of the greenhouse, and the average temperature is about 2 °C lower than that of the greenhouse without a ventilation channel; under the breeze condition, the temperature in the crossed multi-arch greenhouse is more evenly distributed than that of an ordinary round-arch greenhouse with ventilation channels. Considering the greenhouse function, building cost, using effect, and other evaluation factors, the crossed multi-arch greenhouse can meet the production environment requirements of tropical coastal areas (rain protection, sunshade, and ventilation), with obvious structural advantages, good typhoon resistance, and low construction costs, which is a preferable choice of greenhouse type.

Active Bearing Technology of Foot Steel Pipe Applied in Controlling the Large Deformation of Tunnels: A Case Study

Foot steel pipe was the main arch foot supporting structure to control large deformation of loess tunnels, but the supporting effect was not ideal. Taking Yulinzi Tunnel in Qingyang, Gansu Province, as the engineering background, the design concept and implementation scheme of a foot steel pipe active bearing was put forward. The purpose was to solve the problem that it was difficult to control the surrounding rock settlement with the foot steel pipe. Numerical simulation and field experiments were used to verify the effect of the active bearing technology of the foot steel pipe. The main conclusions were as follows: (1) The effect of increasing the diameter of the foot steel pipe is better than that of increasing the number of foot steel pipes. (2) The active bearing mode of exerting its bearing capacity in advance by prepressing the foot steel pipe can effectively reduce the settlement of the vault. The settlement rate of the vault can be reduced by about 70% in 1–2 days and more than 50% in 1–3 days. (3) At the initial stage of surrounding rock deformation, this technology can provide a large bearing capacity, thereby reducing the overall deformation of the surrounding rock, slowing down the release of the surrounding rock pressure, and playing a positive role in the settlement control of the vault.

Research on the Method of Temporary Prestressing to Regulate the Stress in the Section during the Construction of the Main Arch Ring of the Cantilever Cast Arch Bridge

To control the level of tensile stress in the section of reinforced concrete arch cantilever construction, a construction control method of temporary prestressing reinforcement is proposed in this study. The influence law of temporary prestressing on the arch ring section stress is revealed based on the engineering background (Shatuo Special Bridge in Guizhou). Meanwhile, a temporary prestressing test is carried out on the ring section of the main arch to verify the effectiveness of the method. The results show that the prestressing configuration during the construction of the main arch ring of the suspension arch bridge has obvious influence on the control of tensile stress. The method can also effectively improve the force uniformity of the buckle cables, reduce the variation range of cable forces during construction, and improve the safety of arch ring construction.

Surgical Orthodontic Treatment of Class II Malocclusion with Facial Asymmetry

This case report describes a successful surgical orthodontic treatment of a Class II malocclusion with facial asymmetry. An 18-year-old female visited our dental clinic due to proclined anterior teeth and facial asymmetry. Straight facial profile and skeletal Class II was observed. The frontal cephalometric analysis showed that the left ramus length was longer and the left ramal angle was greater than the right. After extraction of the maxillary and mandibular second premolars, dental arch was decompensated. After presurgical orthodontic treatment, bilateral sagittal split ramus osteotomy (BSSRO) was performed. Facial asymmetry was improved, but posterior open bite on the right was occurred by insufficient dental decompensation. To prevent recurrence of the mandible, a bite stop was made by bonding resin on the lingual side of the right maxillary canine. This prevented the recurrence of the mandibular rolling and yawing with the use of bilateral intermaxillary elastics. The right mandibular posterior part with open bite was segmented from the main arch wire and was extruded with intermaxillary elastic. Fast occlusal stabilization was achieved by using the rapid tooth movement after surgery. Since intermaxillary elastic was used while applying an intrusion force with a micro-implant to the left posterior region, it was possible to stabilize the mandible while prevent tooth extrusion. After treatment, facial symmetry and good occlusal relationship were achieved.

Research on Hanger Force and Main Arch Stability of Long-Span Concrete-Filled Steel Tube Arch Bridge

In recent years, the construction of a CFST arch bridge has developed rapidly; however, as a kind of structural system dominated by compression, with the increase of material strength and span, the stability of the main arch of the CFST arch bridge has become more and more important. In this paper, the finite element method is used to analyze the hanger force and the main arch stability of the long-span CFST arch bridge. Combined with the Shenzhen Rainbow Bridge project, the axial force of the hanger, the internal force, and stability of the main arch of the arch bridge are studied. In the establishment of the finite element model, considering the actual operation of the arch bridge, the model simulates the interaction between steel pipe and concrete, it studies the large deformation of CFST arch bridges, and the stress distribution and overall stability of the arch bridge are analyzed. The results show that the main deformation of the CFST arch bridge is the vertical displacement of the deck, and the axial force of most members of the upper arch ribs is greater than that of the lower arch ribs. The axial force and bending moment of the lower arch rib near the arch foot are larger, and the compressive stress of the arch foot is greater than that of other positions. The axial force of the suspender of the arch bridge is the largest at both ends of the hanger and the middle hanger, and the axial force of the other hanger is close to each other, and the axial force changes little under the same case. The buckling modes of the arch are mainly the lateral buckling or flexural buckling of the arch rib outside the plane, which indicates that the vertical stiffness of the arch bridge structure is larger than that of the transverse stiffness. The research results make the load-bearing mechanism of the CFST arch bridge more clear and also provide a certain reference for the design and construction of the CFST arch bridge.