Longitudinal Connection Research Articles

Beyond the CLAIM: A comprehensive needs assessment strategy for creating an Advanced Medical Education Research Training Program (ARMED-MedEd).

The health professions education (HPE) landscape has shifted substantively with increasing professionalization of research and scholarship. Clinician educators seeking to become competitive in this domain often pursue fellowships and master's degrees in HPE, but there are few resources for the continuing professional development (CPD) of those who seek to continue developing their scholarly practice within HPE. Acknowledging the multiple players in this landscape, the authors sought to design a new "beyond beginners" HPE research program using a novel needs assessment planning process. The authors developed and conducted a new three-phase, five-step process that sets forth a programmatic approach to conducting a needs assessment for a CPD course in HPE research. The five steps of the CLAIM method are: Competitive analysis, Literature review with thematic analysis, Ask stakeholders, Internal review by experts, and Mapping of a curriculum. These steps are organized into three phases (Discovery, Convergence, and Synthesis). Over a 12-month period, the authors completed a comprehensive needs assessment. The CLAIM process revealed that longitudinal digital connection, diverse and in depth exposure to HPE research methods, skills around scholarly publishing, and leadership and management of research would be beneficial to our design. The CLAIM method provided scaffolding to help the authors create a robust curriculum that adopts a scholarly approach for developing a HPE research course. This needs assessment methodology may be useful in other CPD contexts.

Longitudinal connection effect on initial support steel frames in tunnels—Take the traffic tunnels as examples

Most tunnel projects are designed with cross-sectional loads, and the inhomogeneity of the longitudinal forces is ignored. In theory, such a support structure can resist large loads, but in practice, large deformation, concrete cracking, steel frame distortion, and other phenomena often occur in tunnels under poor surrounding rock conditions. Hence, the longitudinal stability of the tunnel must be considered. In this study, the mechanism of longitudinal connecting ribs (LCRs) of tunnels was investigated through element tests, theoretical analyses, and numerical simulations, and the effect of the LCRs was evaluated experimentally. The applicability of the constitutive relations and boundary conditions of the numerical model was verified. The instability mode of the steel frame reflecting the longitudinal stress gradient of the tunnel was analyzed, and the longitudinal surrounding rock pressure and the verified numerical model were applied to analyze the LCR using the load structure method. The results indicate the following: (1) LCRs can effectively improve the ultimate bearing capacity and stability of a structure and reduce the area and degree of damage; (2) Two types of instability modes occur in tunnel steel frames, and the main factor is bending failure caused by the axial force; (3) The distance sensitivity of the LCR in the tunnel is higher than the stiffness sensitivity. For large deformations of tunnels, double rows of rebars with a spacing of less than 1.5 m should be used as longitudinal connections.

Rigid pavement planning in traffic: Case study in Ciherang road and Pemuda road, Bogor Regency, Indonesia

Rd Ciherang and Rd Pemuda, Dramaga Subdistrict, Bogor Regency, are located in a densely populated area which connects Rd Raya Dramaga and Rd Dramaga Ring. The existing condition of the road is in the form of flexible pavement or asphalt, but there are several points that have been damaged. Damage is in the form of longitudinal cracking, cracks and holes. The purpose of planning rigid pavement is to improve the surface layer of the road smoother and provide comfort, smoothness for road users. The method used is to calculate the thickness of the plate and geometric analysis of the road. The basis for choosing rigid pavement is due to its location in the mountains and poor subgrade conditions. The basic condition of rigid pavement strongly supports the movement of heavy vehicles in locations which are planned for the outer ring road. Because the geometric conditions of the road are winding and up and down, Spiral-Circle-Spiral and Full-Cyrcle planning is highly recommended. Fatik and erosion damage must be less than 100%. This is to get the results of the calculations that have been done. Rigid Pavement is planned and geometric analysis to provide comfort and smoothness for road users. In this study, a pavement thickness of 18.5cm was produced from the results of calculations using Bina Marga Method. Transverse connection using dowel diameter 25mm, length 450mm, spacing 300mm. Longitudinal connection using tie bars with a diameter of 16mm, a length of 700mm and a distance of 600mm. The results of the geometric analysis obtained five horizontal alignment forms, namely the spiral-circle-spiral (SCS) PI-1 bend with a bend length of 153.35m. The PI-2 bend is spiral-circle-spiral (SCS) with a bend length of 233.21m. The PI-3 bend is full circle (FC) type with a bend length of 174.19m. The PI-4 bend is full circle (FC) type with a bend length of 68.11m. Full circle (FC) type PI-5 bend with a bend length of 66.47m.

Design of Cold-formed Steel Built-Up Closed Section Columns using Direct Strength Method

Structural behavior of Cold-formed Steel (CFS) face-to-face connected built-up closed cross-section columns is investigated in the present study. The CFS built-up columns are designed as long (L > 20r) and locally slender (λl > 1) to verify the influence of intermediate longitudinal connection spacing and check the appropriateness of the current AISI’s Direct Strength Method (DSM) design. A total of 31 axial compression tests were carried out with fixed–fixed end conditions, the design parameters such as local slenderness (λl), global slenderness (λc), intermediate longitudinal fastener spacing (a), and length of the column (L) are varied. The failure modes of the column are summarized and the reason for them is elucidated. The influence of intermediate longitudinal connection spacing was observed in the failure modes and ultimate loading capacity. The test results including ultimate load and failure modes were compared with the current direct strength method design predictions. As a preliminary work towards improving the current AISI design approach, a modified local slenderness (λlm) expression is suggested to consider the influence of intermediate longitudinal fastener spacing in the design strength of cold-formed steel built-up closed cross-section columns.

Association Between Sarcopenia and Depressive Symptoms in Chinese Older Adults: Evidence From the China Health and Retirement Longitudinal Study.

Background: Little is known about whether sarcopenia predicts incident depressive symptoms in older adults. Using the nationally representative data from the China Health and Retirement Longitudinal Study (CHARLS), we conducted cross-sectional and longitudinal analyses to estimate the association between sarcopenia and depressive symptoms among older adults.Methods: The sample comprised 7,706 participants aged at least 60 years (50.6% women; mean age 68.0 ± 6.5) from the CHARLS 2015. Based on the Asian Working Group for Sarcopenia 2019 (AWGS 2019) criteria, sarcopenia status was classified into three types: no-sarcopenia, possible sarcopenia, and sarcopenia. Depressive symptoms were assessed using the validated 10-items of the Center for Epidemiologic Studies Depression Scale. A cross-sectional analysis was used to examine the relationship between sarcopenia status and depressive symptoms. A total of 4,652 participants without depressive symptoms were recruited from the same cohort in 2015 and were followed up in 2018. Cox proportional hazards regression models were conducted to examine the effect of sarcopenia status on subsequent depressive symptoms with the report of hazard ratio (HR).Results: The prevalence of depressive symptoms in total populations, no-sarcopenia, possible sarcopenia, and sarcopenia individuals were 27.1% (2085/7706), 21.5% (927/4310), 33.6% (882/2627), and 35.9% (276/769), respectively. Both possible sarcopenia (OR: 1.75, 95% CI: 1.46–2.10) and sarcopenia (OR: 1.64, 95% CI: 1.23–2.19) were positively associated with higher odds of depressive symptoms (all p < 0.01). During the 3.7 years of follow-up, 956 cases (20.6%) with incident depressive symptoms were identified. In the longitudinal analysis, individuals with the diagnosed possible sarcopenia (HR: 1.27, 95% CI: 1.01–1.58) and sarcopenia participants (HR: 1.49, 95% CI: 1.06–2.09) were more likely to have new onset depressive symptoms than no-sarcopenia peers.Conclusions: Both possible sarcopenia and sarcopenia, assessed using the AWGS 2019 criteria, were independent predictors for the occurrence of depressive symptoms among Chinese older adults. Our findings provided new evidence supporting the longitudinal connection between sarcopenia and mental health problems, it also provides further justification for timely identification and management of both possible sarcopenia and sarcopenia as part of comprehensive strategies to fight against depressive symptoms.

Influence of longitudinal structural connectivity on seismic performance of three-hinged precast arch culverts

The hinge type of precast concrete arch culvert was introduced to Japan from France in the 1990s in consideration of the saving of labor, shortening of the construction period, and high quality control of the concrete members. However, due to the 2011 off the Pacific Coast of Tohoku Earthquake (March 11, 2011), the three-hinged precast arch culverts that had been constructed in Japan at the beginning of the period when precast arch culverts were firstly introduced, suffered damage, which spoiled their serviceability. According to the extent of the damage and the type of culverts that were damaged, the longitudinal structural connectivity of the culverts was assumed to be one of the possible reasons for the reported damage mechanism. Therefore, the objective of this paper was to clarify how strongly the longitudinal structural connectivity influenced the longitudinal seismic behavior of the three-hinged arch culverts. To achieve this objective, an elasto-plastic finite element analysis was conducted with an analytical model that could capture the characteristics of the damaged culverts. Simultaneously, a penalty method with the bi-linear spring model was applied as a solution to the contact-impact problems of the precast segmental arch members. As a result, it was found that the weaker longitudinal structural connectivity in the damaged culverts allowed the torsional displacements of the arch members to induce critical damage to the arch members, namely, edge defects in the arch crown and concrete foundation. The numerical results proved the unignorable influence of the longitudinal structural connection on the possible damage to three-hinged arch culverts.

Longitudinal neural connection detection using a ferritin‐encoding adeno‐associated virus vector and in vivo MRI method

The investigation of neural circuits is important for interpreting both healthy brain function and psychiatric disorders. Currently, the architecture of neural circuits is always investigated with fluorescent protein encoding neurotropic virus and ex vivo fluorescent imaging technology. However, it is difficult to obtain a whole‐brain neural circuit connection in living animals, due to the limited fluorescent imaging depth. Herein, the noninvasive, whole‐brain imaging technique of MRI and the hypotoxicity virus vector AAV (adeno‐associated virus) were combined to investigate the whole‐brain neural circuits in vivo. AAV2‐retro are an artificially‐evolved virus vector that permits access to the terminal of neurons and retrograde transport to their cell bodies. By expressing the ferritin protein which could accumulate iron ions and influence the MRI contrast, the neurotropic virus can cause MRI signal changes in the infected regions. For mice injected with the ferritin‐encoding virus vector (rAAV2‐retro‐CAG‐Ferritin) in the caudate putamen (CPu), several regions showed significant changes in MRI contrasts, such as PFC (prefrontal cortex), HIP (hippocampus), Ins (insular cortex) and BLA (basolateral amygdala). The expression of ferritin in those regions was also verified with ex vivo fluorescence imaging. In addition, we demonstrated that changes in T2 relaxation time could be used to identify the spread area of the virus in the brain over time. Thus, the neural connections could be longitudinally detected with the in vivo MRI method. This novel technique could be utilized to observe the viral infection process and detect the neural circuits in a living animal.

Clarifying the connection between parental conditional regard and contingent self-esteem: An examination of cross-lagged relations in early adolescence.

Relations between parental conditional regard (PCR) and children's motivational and emotional functioning have been demonstrated by past research. However, most available studies relied on cross-sectional correlational data, leaving open the causal direction of these relations. In the present article, we sought to contribute to this topic and examined the longitudinal connection between PCR and adolescents' contingent self-esteem (CSE) over time. Hypotheses were tested in two longitudinal studies with differently gifted samples of German high school students (N=188 and N=202 students, respectively). Data were gathered at three time points in Study 1 and at two time points in Study 2. In both studies, adolescents answered questionnaires regarding positive and negative PCR in the academic domain as well as general CSE (and additionally academic CSE in Study 2). Cross-lagged analyses revealed several significant paths from CSE to PCR, and some paths from PCR to CSE, indicating the presumed reciprocal relationship between these constructs. Our findings suggest that children high in CSE may lead their parents to engage in PCR and that these effects may be more pronounced than vice versa. Possible reasons for these findings and their implications are discussed.

Support Measures to Prevent the Deformation and Failure of a Carbonaceous Mudstone Tunnel

A carbonaceous mudstone tunnel is a type of soft rock tunnel. There is little research on the prevention and control measures for the deformation and failure of carbonaceous mudstone tunnels. In this article, we investigated the construction of the Qiguding carbonaceous mudstone tunnel in Meizhou City, Guangdong Province, China. We monitored and analyzed the deformation and stress characteristics of a section under the original support scheme. The monitoring data showed that this section had large peripheral convergence, vault subsidence, steel arch strain, and concrete strain. The deformations exhibited significant differences in the horizontal and vertical directions, eventually resulting in concrete cracking, steel arch bulging, and distortion in the section. The analysis showed that the primary mechanisms for the failure were the softening characteristics of the carbonaceous mudstone, the plastic rheology, and the shear slip of the rock stratum. Based on a comparative analysis and numerical simulation, we proposed a new support measure called the longitudinal rigid enlarged foundation that consists of a steel arch longitudinal connection system and a locking foot anchor pipe system. Several comparative tests were performed at the tunnel site. The results demonstrated the excellent performance and reliability of the proposed support scheme for the deformation control of the carbonaceous mudstone, providing a reference for similar projects.

Prefabricated Urban Underground Utility Tunnels: A Case Study on Mechanical Behaviour with Strain Monitoring and Numerical Simulation

The prefabricated urban utility tunnels (UUTs) have many advantages such as short construction period, low cost, high quality, and small land occupation. However, there is still a lack of in‐depth analysis of the mechanical performance of the prefabricated urban utility tunnel (UUT) structure with bolted connections under different working conditions. In this paper, the force performance of a prefabricated UUT in Tongzhou District, Beijing, was studied under different working conditions using two methods: field monitoring and numerical simulation. The multichannel strain monitor was used for monitoring, and the internal wall concrete and bolt strain change data under the two conditions of installation and backfill were obtained. Combined with the construction process of the UUTs, a three‐dimensional numerical model was established by COMSOL, where the build‐in bolt assembly was used to simulate the longitudinal connection of the tunnel. The simulation results were compared with the measured data to verify the rationality of the computational model. The simulation results showed that the concrete and bolts on the inner wall of the tunnel work well under the two conditions of installation and backfilling; The deformation of the top plate of the prefabricated tunnel was approximately parabolic, with the largest vertical displacement (0.37 mm) in the middle and the most sensitive to the vertical load in the central part of the roof. The central portion of the side wall had the largest displacement (0.17 mm) in the inner concave. The tensile stress of bolt 3 increased the most (30.75 MPa) but was still much smaller than the yield strength of the bolt. The concrete and bolts of the UUT were found to work well through force analysis under operating conditions. In conclusion, analysis of structural forces and deformation failure modes will help design engineers understand the basic mechanisms and select the appropriate UUT structure.

Cross-Sectional and Longitudinal Associations Between Sarcopenia and Depressive Symptoms of the Aged

Background: Using the nationally representative data from the China Health and Retirement Longitudinal Study (CHARLS), we conducted cross-sectional and longitudinal analyses to estimate the association between sarcopenia and depressive symptoms among older adults. Methods: In the cross-sectional analysis, the sample comprised 7706 participants aged ≥ 60 years (50.6% women; mean age 68.0 ± 6.5). A total of 4652 participants without depressive symptoms were recruited from the same cohort and were followed up in 2018. Findings: The prevalence of depressive symptoms in total populations, no-sarcopenia, possible sarcopenia and sarcopenia individuals were 27.1% (2085/7706), 21.5% (927/4310), 33.6% (882/2627), 35.9% (276/769), respectively. Both possible sarcopenia and sarcopenia were positively associated with higher odds of depressive symptoms (P < 0.01). 956 cases (20.6%) with incident depressive symptoms were identified. In the longitudinal analysis, individuals with the diagnosed possible sarcopenia (HR:1.27, 95% CI: 1.01–1.58, P = 0.040) and sarcopenia participants (HR:1.49, 95% CI: 1.06–2.09, P = 0.021) were more likely to have new onset depressive symptoms than no-sarcopenia peers. Compared with the individuals without any sarcopenia components, those having low muscle mass alone were not significantly associated with higher odds of depressive symptoms or increased risk of depressive symptoms ( P＞0.05). Interpretation: Both possible sarcopenia and sarcopenia were independent predictors for the occurrence of depressive symptoms among Chinese older adults. Our findings supports the longitudinal connection between sarcopenia and mental health problems, timely identification and management of both possible sarcopenia and sarcopenia as part of comprehensive strategies to fight against depressive symptoms. Funding; None to declare. Declaration of Interest: None to declare. Ethical Approval: This study was approved by the Ethical Review Committee of Peking University (approval number: IR1052-11015).

Effects of differential subgrade settlement on damage distribution and mechanical properties of CRTS II slab track

Differential subgrade settlement adversely affects the slab track. In this study, a three-dimensional model of a slab track based on damage mechanics theory was established for analysing the effects of differential subgrade settlement on the damage distribution and mechanical properties of the slab track. The prestressed steel bars and ordinary steel bars in the precast slab of the slab track were refined. The rail supporting forces were employed as the train loads. The damage distribution, deformation, and longitudinal stress of the track under differential subgrade settlement cases were calculated using the model. The results indicated that with the increasing of settlement amplitude, the concrete base is damaged first. If the settlement amplitude continues to increase, the precast slab is damaged. The critical subgrade settlement amplitude of the initial damage of the track structure increases with the increasing of settlement wavelength. Under differential subgrade settlement, the steel bars in the precast slab were subjected to additional loads. However, the precast slab may also crack. Damage to the precast slab and concrete base destroys the integrity of the longitudinal connection system of the CRTS II slab track. Subgrade with differential settlement should be repaired in time to avoid serious damage to the track structure.

Applicability of finger jointing to circular laminated veneer hollow sections for temporary soil nailing

This paper investigates the strength properties of circular laminated veneer lumber hollow sections made of beech wood and loaded in tension. These tubular, hollow wooden poles are intended for an innovative geotechnical approach, which utilizes the high tensile strength of beech wood and its limited durability as soil nails for temporary geotechnical slope stabilisation. Due to the standardized design approaches of soil nail walls that prevent a rigid soil body from sliding by using nails as reinforcement elements, primary tension loads will be aligned to the structural elements. Depending on the height of the soil nail wall, nails with a length up to 10 m may be necessary, demanding for high-performance longitudinal section joints due to the natural length limitations of the wood veneer. This paper discusses the applicability of finger jointing to tubular, laminated beech wood veneer poles and presents the results of large-scale tensile tests. Depending on the joint arrangement, the median tensile strength is reduced by 37–43% compared to the unjointed sections of a similar geometry. Thus, finger jointing has been found to be an efficient method of a longitudinal load-carrying connection in combination with a minimized cross section reduction at the joint. However, due to the low sample size of the tests, further improvements are necessary.

Public Transport as a Public Place: Urban Insertion Strategies of the Coquimbo – La Serena Light Rail Project

The public transport systems, as much for its infrastructure magnitude as for the importance of its services, have been addressed from the urban design theory and practice as potential structure elements of the contemporary urban experience. They are presented as privileged meeting points, and as possible protagonists of the form, culture and identity of a city. The Coquimbo-La Serena light rail project arises as an alternative to improve the connectivity through public transportation of this conurbation, a new metropolitan area of almost half million inhabitants, which has undergone far-reaching changes in its mobility habits in the last decades. The use of private cars has doubled in detriment of the use of public transport and walking, which consequently produces congestion and pollution problems. This project proposes a new longitudinal connection, a clean, efficient and interconnected backbone of public transport, which links isolated residential sectors with the city town areas and the main public infrastructure of both cities. It is presented as a “complete street” project that unites important elements of history, geography and city life, being a new urban landmark that conveys the will of diverse actors accomplished as a public-private project through the MOP (Acronym for Ministry of Public Works) concession system.This article, which is the first academic work about the project, highlights the role of the public transport infrastructure as a central element of the sustainable construction and development of the city, and it discusses the light rail suitability in this sense, particularly compared to the BRT option. Through the presentation of the urban insertion strategies of the Coquimbo–La Serena light rail project, it is stated that a public transportation infrastructure constitutes “place” when it is integrated to the structure, landscape and urban public spaces in a sustainable way.

Effects of oxygen adsorption on spin transport properties of single anthracene molecular devices

With the miniaturization of molecular devices, high-performance nano devices can be fabricated by controlling the spin states of electrons. Because of their advantages such as low energy consumption, easy integration and long decoherence time, more and more attention has been paid to them. So far, the spin filtration efficiency of molecular device with graphene electrode is not very stable, which will decrease with the increase of voltage, and thus affecting its applications. Therefore, how to enhance the spin filtration efficiency of molecular device with graphene electrode becomes a scientific research problem. Using the first principle calculations based on density functional theory combined with non-equilibrium Green’s function, the physical mechanism of regulating the spin polarization transport properties of single anthracene molecule device with graphene nanoribon as electrode is investigated by molecular oxygen adsorption. In order to explore the effect of the change of the connection mode between single anthracene molecule and zigzag graphene nanoribbon electrode on the spin transport properties of the device, we establish two models. The first model is the model M1, which is the single anthracene molecule longitudinal connection, and the second model is the model M2, which is the single anthracene molecule lateral connection. The adsorption model of single oxygen molecule is denoted by M1O and M2O respectively. The results show that when none of oxygen molecules is adsorbed, the spin filtering effect of single anthracene molecule connecting graphene nanoribbons laterally (M2) is better than that of single anthracene molecule connecting graphene nanoribbons longitudinally (M1). After oxygen molecules are adsorbed on single anthracene molecule, the enhanced localized degree of transport eigenstate will make the spin current of the two kinds of devices decrease by nearly two orders of magnitude. However, molecular oxygen adsorption significantly improves the spin filtering efficiency of the device and enhances the application performance of the device. The maximal spin filtering efficiency of single anthracene molecule connecting graphene nanoribbons longitudinal (M1O) can be increased from 72% to 80%. More importantly, the device with single anthracene molecule connecting graphene nanoribbons laterally (M2) maintains nearly 100% spin filtering efficiency in a bias range from –0.5 V to +0.5 V. These results provide more theoretical guidance for practically fabricating spin molecular devices and regulating their spin transport properties.

2011 개정 교육과정 『고등학교 한국사』 교과서에서 近代 資料의 수록 양상과 脈絡化의 실제

This paper is a review of whether or not to implement contextualization by analyzing the modern historical data of ‘Korean History’ high school textbooks based on 2011 the education ministry revised curriculum. As a result, some items of exploration activity are seen, such as the relationship between the data and the data within the exploration activity, and the consistency between the data and the time-space background, which is weak in longitudinal causality and transverse connection. In particular, there was a considerable gap between data and exploratory questions. This characteristic of materials in textbooks not only constrains students’ contextual understanding, but can also significantly reduce the use of textbooks. It is not just a factor that hinders the growth of historical thought that counts in history education, but it can also disrupt the strategy of learning in contextualization. This is why the mutual infiltration of history and history education to research activities and documents surrounding them is very urgent in the course of textbook writing.

The Explanatory Mechanism of Child Impulsivity in the Bidirectional Associations between Parental Psychological Control and Child Physical Aggression

Parental psychological control is a stressor that may provoke children’s aggression. However, whether there are bidirectional associations between parental psychological control and children’s physical aggression remains unclear, as does the mechanism underlying these associations. Using an autoregressive cross-lagged model, the present study tested (a) the extent to which parental psychological control predicts physical aggression and vice versa, and (b) whether child impulsivity explains this bidirectional association. Data were collected across three time points (fall semester of 4th grade, spring semester of 4th grade, and fall semester of 5th grade). A sample of 689 children (385 boys, 304 girls) completed questionnaires regarding parental psychological control, impulsivity and physical aggression. Gender, age and socioeconomic status were controlled in the analyses. As hypothesized, the findings showed that there was a direct longitudinal connection from parental psychological control to child physical aggression, and the inverse relation was also significant. Moreover, the results demonstrated an indirect link from parental psychological control to physical aggression via child impulsivity, but the inverse effect was not significant. Our findings suggest that there is a reciprocal relationship between parental psychological control and children’s physical aggression, and that the parent-driven component of this bidirectional process is mediated by child impulsivity. The results have potential applied value for prevention and intervention.

Progressive collapse analysis and structural robustness of steel-framed modular buildings

This paper investigated the structural robustness of steel-framed modular buildings based on the alternative load path method using LS-DYNA. The structural responses of a reference structure were first simulated to understand typical building motion, load redistribution mechanisms and failure modes after removal of a base corner module. Based on the reference scenario, a comprehensive parametric study was then carried out to investigate the effects of structural configuration (number of modules of each floor), module posts (wall thickness and number of supporting posts) and other features (inclusion of floor slab, longitudinal wall bracing, connection stiffness and connection capacity) on the structural responses of steel modular buildings. It was found that the collapse resistance of steel modular buildings could be improved with an increase in the number of modules per floor, the number and capacity of supporting posts, higher rotational stiffness and capacity of inter-module connections, and the use of longitudinal wall bracing. Consideration of floor slabs provided a more realistic description of collapse mechanisms, due to the slab-related contact interaction and diaphragm action. Also, the structure was more vulnerable to the removal of modules (or posts) near the end corner of a building.

Study on Bearing Mechanism and Coupling Mechanism of Steel Arch-concrete Composite Structure of Initial Support System of Large Section Tunnel

Fully utilizing and developing underground space is an important direction of future world development. In order to meet the increasing traffic demand, there are more and more super-large section tunnel projects such as two-way eight-lane tunnel. In the initial support system of NATM, “steel arch + concrete shotcrete” is widely used in engineering as one of the most common forms of support. But at present, in the study of supporting system, most researches are based on mechanical analysis of single steel arch, and few of them consider the spatial combination of multi-arch and the influence of concrete shotcrete. Therefore, in order to grasp the spatial combination effect of multi-arch and the influence of concrete shotcrete layer on the bearing mechanism of initial support system, and to establish the analysis and calculation model of initial support system, this paper carries out numerical tests on the mechanical characteristics of three composite steel arch + concrete shotcrete initial support system, and clarifies the spatial combination effect of multi-arch and the effect of concrete shotcrete on initial support. Based on the bearing capacity of the initial support system, the influence of concrete shotcrete strength, arch spacing and longitudinal connection spacing on the mechanical properties of the initial support system is comprehensively analyzed. The research results can provide theoretical basis for the design and application of related engineering.

Research on Bearing Mechanism and Spatial Layout Designing Parameters of Arch Support in Large Section Tunnel

At present, there is no unified support design criterion for the construction of super-large cross-section tunnel. The design of initial supporting components is based on engineering analogy method, lacking theoretical and experimental guidance. The spacing of arch and longitudinal connection strength have significant influence on the bearing capacity of initial support system, so in-depth study in this area is very important. Therefore, based on the typical super-large cross-section tunnel-Letuan Tunnel of Binlai Expressway in China, laboratory test and numerical test are carried out in this paper to study the combinational bearing mechanism of multiple spatial arches in initial supporting system. This paper also clarifies the mechanical characteristics of spatial supporting system and the influence mechanism different designing parameters such as arch spacing, longitudinal connection spacing. The cost performance of each design scheme of the spatial supporting arch system is established. The research results show that the influence of arch spacing and longitudinal connection spacing on arch bearing capacity is remarkable. Strength of combined arch structures is 3.14–3.92 times of single arch frame. The influence of arch spacing is more obvious than that of longitudinal connection spacing. The research results can provide reference for related projects.