Joint Opening Research Articles

Radiographic predictors of lateral translation in patients with residual adolescent idiopathic scoliosis and thoracolumbar/lumbar curves: A focus on L3 lateral translation.

Patients with residual adolescent idiopathic scoliosis (AIS) and thoracolumbar/lumbar (TL/L) curves may present with progression after cessation of growth, with lateral translation as a major risk factor. Nonetheless, radiographic predictors and underlying mechanisms remain indefinite. This study aimed to determine these radiographic predictors and structural mechanisms in patients with residual AIS. Radiographic and clinical data were collected from 45 consecutive patients with preoperative residual AIS and TL/L Cobb angle >40° who subsequently underwent corrective surgery at our institution. Lateral translation was defined as intervertebral slippage ≥6 mm on computed tomography. Statistical analyses included Student's t-test, Pearson's correlation coefficients, receiver operating characteristic (ROC) curve analysis, and multivariate logistic regression analysis. Out of 45 patients, 3 were male, whereas 42 were female, with a mean age of 40.6±17.4 years. L3 slippage was observed in 21 patients, resulting in the categorization into the slippage and non-slippage cohorts. Multivariate logistic regression analysis revealed statistically significant disparities in the bilateral facet angles, facet joint opening, and facet joint vacuum phenomenon between the two cohorts. The ROC analysis determined a 20.5° cut-off value for predicting L3 slippage. In the non-slippage cohort, a strong correlation was particularly observed between L3 slippage and L2-L3 bridging. Facet joint instability, L4 tilt ≥20.5°, and L3 cranial vertebral bridging are predictive radiographic factors for L3 lateral translation in patients with residual AIS. Thus, patients exhibiting these characteristics require consistent follow-up or early surgical intervention before lateral translation occurs.

Experimental Studies of Low-Reinforced Concrete Structures Containing Inter-Bay Construction Joints Strengthened with Prestressed Basalt Composite Reinforcements and External Transverse Reinforcements

During the long-term operation of main run-of-river head powerhouses for hydroelectric power plants, technical changes that deteriorate the operational properties of their reinforced concrete structures can occur. Therefore, in order to substantiate the application of prestressed basalt composite reinforcements to strengthen reinforced concrete hydraulic structures in operation, a set of computational and experimental studies was carried out, taking into account their characteristic features. After 4 years of ageing, the serviceability and reliability of the beams with prestressed basalt composite reinforcements were demonstrated through stabilisation of the prestress losses and the values obtained for bearing capacity, deflection, and the width of the opening of the inter-bay construction joints and the deformations of the metal reinforcements and the basalt composite reinforcements. The bearing capacity of the investigated reinforced concrete beams reinforced with external transverse reinforcements was increased 1.4–2.5 times over that of the variants reinforced with longitudinal prestressed basal composite reinforcements. Furthermore, in this study, the impacts of static loads and seismic effects with a magnitude greater than 8 on the run-of-river hydroelectric power plant powerhouse were calculated based on dynamic design theory. Regarding applications to hydroelectric power plant structures and constructions, for which it is not always possible to determine the location of compressed or tensile zones during their operation nor under seismic action, our research results are suggestive of a reasonably positive effect.

Bridging the gap: enhancing orthopaedic outcomes through qualitative research integration.

The evidence base within trauma and orthopaedics has traditionally favoured quantitative research methodologies. Qualitative research can provide unique insights which illuminate patient experiences and perceptions of care. Qualitative methods reveal the subjective narratives of patients that are not captured by quantitative data, providing a more comprehensive understanding of patient-centred care. The aim of this study is to quantify the level of qualitative research within the orthopaedic literature. A bibliometric search of journals' online archives and multiple databases was undertaken in March 2024, to identify articles using qualitative research methods in the top 12 trauma and orthopaedic journals based on the 2023 impact factor and SCImago rating. The bibliometric search was conducted and reported in accordance with the preliminary guideline for reporting bibliometric reviews of the biomedical literature (BIBLIO). Of the 7,201 papers reviewed, 136 included qualitative methods (0.1%). There was no significant difference between the journals, apart from Bone & Joint Open, which included 21 studies using qualitative methods, equalling 4% of its published articles. This study demonstrates that there is a very low number of qualitative research papers published within trauma and orthopaedic journals. Given the increasing focus on patient outcomes and improving the patient experience, it may be argued that there is a requirement to support both quantitative and qualitative approaches to orthopaedic research. Combining qualitative and quantitative methods may effectively address the complex and personal aspects of patients' care, ensuring that outcomes align with patient values and enhance overall care quality.

Mechanical behaviour of double lining with outer segmental lining and inner fibre reinforced concrete lining under internal water pressure

Double lining with outer segmental lining and inner reinforced concrete lining is extensively used for water conveyance tunnel with internal water pressure. In order to improve the performance of the double lining, the steel rebar and fibre reinforced concrete (R/FRC) is designed for inner lining to enhance the tensile strength of reinforced concrete (RC). Full-scale tests were conducted to compare the mechanical behaviour of double lining with inner RC and R/FRC linings. The test results showed that both types of lining failed in four stages: elastic stage, inner lining cracking stage, crack stabilization and segmental joint damage stage, and failure stage. The cracks firstly occurred in the inner lining near the segmental joints and then propagated to the whole inner lining ring. Finally, the crack width and segmental joint opening successively exceeded the thresholds, and the double lining failed until the breaking of segmental joints. Compared with inner RC lining, R/FRC lining had better performance in terms of the initial cracking load, cracking-control ability, post-cracking stiffness, service limit capacity of inner lining and waterproof capacity of segmental lining. The improvement ratios were 36.3%, 50.3%, 46.3%, 37.2% and 31.1%, respectively. The influences of fibre volume fraction, fibre aspect ratio, and reinforcement ratio of steel rebar on the mechanical performance of R/FRC lining were also investigated based on a previously proposed analytical model. The parametric analysis demonstrated that higher fibre volume fraction and fibre aspect ratio can result in more significant increase of mechanical performance of R/FRC lining. The steel fibres were found to have more significant effects on the post-cracking behaviour of the lining than same amounts of reinforcing bars. Finally, an optimized function was proposed to fulfil a balance of lining performance and economy. The experimental and analytical results indicated that R/FRC lining can substitute RC lining and perform higher mechanical performance in water conveyance tunnels.

Study on the mechanical properties of prefabricated assembled cover arch reinforcements in tunnels

The prefabricated assembled cover arch reinforcement method offers rapid construction and high quality, effectively addressing the challenges of cast-in-place cover arch reinforcement used in tunnel linings in mountainous areas of China. This study investigated the mechanical performance of prefabricated assembled arches in tunnels through model tests and numerical simulations. The results indicate that joint opening and deflection, as well as their change rates, increase with eccentric distance. There is a roughly linear relationship between joint opening and deflection with increasing load. At an eccentric distance of + 0.2 m, the peak stress appears on the outside of the joint, with a valley on the inside, and stress concentration at bolt holes. The application of bolt preloading enhances the joint’s stress performance. Furthermore, the stiffness of the lining and soil significantly impacts the mechanical response of the cover arch, with peak stress mainly observed at the foot of the cover arch and the handhole of the joint.

Effect of Graft Choice for ACL Reconstruction on Clinical Outcomes in Combined ACL and MCL Injuries: Comparison Between Bone-Patellar Tendon-Bone and Hamstring Autografts.

Background/Objectives: The optimal graft, particularly in combined anterior cruciate ligament (ACL) and medial collateral ligament (MCL) injuries, remains controversial. We evaluated the influence of graft choice between bone-patellar tendon-bone (BPTB) and hamstring autografts on clinical outcomes in combined ACL and MCL injuries. Methods: This retrospective analysis included patients with concurrent ACL and MCL injuries who underwent single-bundle ACL reconstruction with BPTB (group B) or hamstring (group H) grafts, between 2010 and 2019, with a ≥2-year follow-up. Patients were classified based on the MCL injury grade (I, II, or III). Clinical outcomes were assessed through knee stability evaluations using valgus stress radiographs and the KT-2000 arthrometer, patient-reported outcomes using the International Knee Documentation Committee (IKDC) subjective score and Lysholm score, and radiologic outcomes using the IKDC radiographic grade. Results: The study included 169 patients (group B, 92; group H, 77). No significant between-group differences in knee stability or functional outcomes were found after follow-up. Within the same MCL injury grade, particularly in high-grade MCL injuries, BPTB grafts resulted in significantly better medial stability (side-to-side difference in medial joint opening on valgus stress radiographs: grade II, p = 0.006; grade III, p = 0.039) and functional outcomes (IKDC subjective score: grade II, p = 0.045; grade III, p = 0.038) than hamstring grafts. In the hamstring group, higher-grade MCL injuries were associated with worse outcomes (Lysholm knee score, p = 0.009; IKDC subjective score, p = 0.015). Conclusions: Graft choice in ACL reconstruction with concomitant MCL injuries may affect clinical outcomes, particularly in high-grade MCL injuries. Although both graft types performed similarly overall, BPTB grafts provided superior medial stability and functional results in higher-grade MCL injuries. However, caution is needed when interpreting these results due to limitations such as the small sample size and the lack of randomization in graft selection.

Failure analysis and deformation characteristics of shield tunnel obliquely crossing ground fissure under earthquake

In order to study the deformation law and failure characteristics of shield tunnel obliquely crossing ground fissure under earthquake action, taking the shield tunnel of Xi ’an Metro Line 8 crossing f3 ground fissure as the engineering background, the 1: 20 shaking table model test method was used to analyze the strain of shield tunnel, the contact pressure with surrounding rock soil, the dislocation of segment and the axial force of bolt in detail, and the seismic damage mechanism and failure characteristics of shield tunnel obliquely crossing ground fissure were obtained. The test results show that under the action of earthquake, the shield tunnel has complex three-dimensional deformation characteristics, among which the vertical deformation is the most obvious. The deformation is mainly concentrated in the location of the ground fissure. The tensile strain and contact pressure of the hanging wall of the tunnel segment are greater than the strain value and contact pressure of the footwall. Because the vertical deformation of the tunnel is the largest, the bolts at the vault and the arch bottom are most obviously pulled. Excavation after the test, it can be seen that the tunnel appeared the phenomenon of ring joint opening, lining cracking and other damage. Under the action of the earthquake, the shield tunnel across the ground fissure is mainly subjected to tensile failure. The failure area is within 10 m from the ground fissure in the hanging wall and footwall, and the total length is 20 m. The closer to the ground fissure, the more serious the damage. The research results provide a scientific and reasonable reference for the subsequent construction and disaster prevention and mitigation design of Xi ’an Metro.

Medial Joint Opening in the Operated Knee After Unilateral High Tibial Osteotomy: Risk of Osteoarthritis and Future Surgery in the Operated and Nonoperated Knee

Background: High tibial osteotomy (HTO) modifies the mechanics of the affected knee but can also affect the nonoperated knee. However, no research has reported on the prognosis and risk factors related to the nonoperated knee after unilateral HTO. Purpose: To assess the radiological parameters associated with osteoarthritis (OA) progression and the need for surgery in the nonoperated knee after unilateral HTO, with concurrent assessment of the operated knee. Study Design: Case series; Level of evidence, 4. Methods: The medical charts of 197 patients with knee OA who underwent unilateral HTO between March 2007 and December 2020 were retrospectively investigated. Radiological parameters such as the Kellgren-Lawrence grade, weightbearing line ratio, joint line convergence angle (JLCA), and joint line obliquity angle were assessed preoperatively and 1 year postoperatively. Results: The mean follow-up length for the 197 patients was 5.9 ± 3.2 years for the operated knee and 5.5 ± 3.2 years for the nonoperated knee. A smaller postoperative JLCA in the operated knee was a significant risk factor for OA progression (P = .027) and undergoing surgery (P = .006) in the nonoperated knee. Conversely, a larger postoperative JLCA in the operated knee was a significant risk factor for OA progression (P = .014) and conversion to arthroplasty (P = .027) in the operated knee. A postoperative JLCA >1.5° (P < .001) and <3.9° (P < .001) was needed to reduce the risk of undergoing surgery in the nonoperated knee and OA progression in the operated knee, respectively. Additionally, a pre- to postoperative change in the JLCA (ΔJLCA) between −5.6° and −1.7° (P = .021 and P = .004, respectively) was needed to reduce the risk of OA progression in both knees. Conclusion: A large medial joint opening (a small postoperative JLCA) in the operated knee after unilateral HTO was associated with a higher risk of OA progression and surgery in the nonoperated knee. Conversely, a small medial joint opening (a large postoperative JLCA) was associated with a higher risk of OA progression and conversion to arthroplasty in the operated knee. For a balanced medial joint opening, if the postoperative JLCA was between 1.5° and 3.9° or the ΔJLCA was between −5.6° and −1.7°, a favorable prognosis in both knees could be anticipated.

Evolving interfaces: A comprehensive review of implant-abutment connections

Studying the implant-abutment connection is crucial, as it primarily determines the strength and stability of an implant-supported restoration, which, in turn, affects prosthetic stability. Traditionally, Brånemark's external hexagon has been used. However, significant complications such as abutment screw loosening, rotational misfit at the implant-abutment interface and microbial penetration have necessitated modifications of the external hexagon and led to the development of internal implant-abutment connection.This review outlines the evolution of various implant-abutment connections from the traditional external hexagon to advanced internal designs. Internal interface designs offer several advantages over the traditional approach. They reduce the vertical height platform for restorative components and distribute lateral loading deep within the implant. These designs also shield the abutment screw and provide long internal wall engagements that create a rigid, unified body resisting joint opening. Additionally, they feature wall engagement with the implant that buffers vibration, offer the potential for a microbial seal, and provide extensive flexibility. Importantly, they allow for the lowering of the restorative interface to the implant level for better aesthetics. These advancements have significantly enhanced the clinical performance and reliability of implant-supported restorations.

Performance-based analysis on fire behavior of shield tunnel joint with DDCI connector

In recent years, there has been significant advancement in large-diameter shield tunnel technology, with the continuous emergence of new joint types. To meet the different requirement of application, numerous studies have been done on the mechanical behavior of the various new joints. In this paper, a new DDCI connector for the shield tunnel joint was proposed. Simultaneously, a thermo-mechanical performance analysis was conducted on the new longitudinal joint combining inclined bolts and the DDCI connector. A refined finite element model of the new joint was established and various working conditions were designed to obtain a full understanding of the thermo-mechanical performance of the structure. This evaluation included the presence of initial loads and exposure to different fire curves, specifically the RABT and RWS fire curves. The validity of the numerical model and the indirect coupling analysis method were verified by physical experiments and previous research, respectively. The temperature distribution, joint opening and internal force of the connectors were analyzed in the study. According to the results, different fire curves and thermo-mechanical sequences both have a great impact on the mechanical response of the new joint under elevated temperature. Moreover, due to the involvement of the DDCI connector, the new joint shows clear advantages in strength and stiffness over the conventional joint. The results contribute to the fire-resistant design of the large-diameter shield tunnels adopting the scheme of the new joint with a DDCI connector.

Experimental Study on the Bending Behavior of Precast Concrete Segmental Bridges with Continuous Rebars at Joints

Longitudinal ordinary rebars are discontinuous at the joints of precast concrete segmental bridges (PCSBs), which can open under tensile stresses induced by bending moments. This will lead to durability issues with the joints. To improve the bending properties of PCSBs, a novel joint type featuring continuous rebars was proposed in the present study. Three specimens were subjected to testing to examine the bending behavior of PCSBs using this new joint design compared to traditional joints. The crack propagation, structural deformation, joint opening width, strain in rebars, failure mode, stiffness, and flexural capacity were comprehensively investigated. The test results reveal that the continuous rebars effectively transferred bending normal stress between joints, ensuring full development of cracks in each beam segment. Effective control of joint opening width was also observed. Compared to traditional joints, the new joints exhibited a 29% to 33% increase in cracking load and a 32% increase in ultimate load. Failure in the continuous rebar joints was characterized by partial anchorage failure of the rebars along with localized concrete crushing in the top compression zone. Based on the test results, a computational method was proposed for calculating the cracking strength and flexural capacity of the new joints.

Disaster mechanism of large-diameter shield tunnel segments under multi-source load coupling: A case study

The deflection squeezing of the shield shell and the eccentric jack thrust significantly impact the segment dislocation and damage. Based on summarizing the derivative relationship between engineering factors and disasters, this study established a 3D numerical calculation model under the multi-source load coupling. Then, this study explored the displacement and dislocation distribution of segments, as well as their derivative relationship with bolt failure. Furthermore, this study analyzed the spatial distribution and evolution characteristics of segment damage. Further revealing the disaster mechanism and proposing the engineering treatment measures. The research results indicate that as the deflection angle increases, the vertical relative compression deformation of the segment that is detaching from the shield tail (segment-DFST) becomes more significant. The plastic strain of the internal bolts inside the two segments in direct contact with the shield shell is mainly related to the radial and longitudinal dislocation. The increase in the deflection angle will lead to a more significant increase in the adjacent dislocation on both sides and the internal dislocation. The plastic strain of the internal bolts of the segment that is completely in the shield shell (segment-CSS) is more influenced by joint opening and longitudinal dislocation under the lower eccentric compression (LEC) state. The plastic strain of the internal bolts in segment-DFST is more influenced by radial dislocation and joint opening under the LEC state. The tension damage of the segments mainly occurs on both sides of the circumferential joint and the lower part of the segment-CSS. The compression damage of the segments is mainly distributed at the top and bottom of the segment-CSS. The eccentric distribution of jack thrust has the most significant impact on the block damage of the lower part of the segment-CSS. With the increase of the deflection angle, the compression damage and distribution range of the blocks at the bottom of the segment-DFST increase sharply. The compression damage and distribution range of the segment-CSS gradually spread from the upper and lower parts to the middle of the segment. The increase in deflection angle will promote the influence of the thrust in LEC state on the compression damage of the lower block of the segment-CSS, and on the tension damage of the upper block of the segment- DFST.

Effect of Extracorporeal Shock Wave on IGF-1, TNF-α, and IL-1in Joint Fluid of Patients with Temporomandibular Joint Disorder Syndrome.

As a new therapeutic method, extracorporeal shock wave (ESW) has shown remarkable efficacy in the treatment of temporomandibular joint disorder syndrome. Numerous studies have shown that it has the advantages of noninvasiveness, short treatment time, etc. It can effectively relieve pain and improve symptoms such as joint mobility and opening degree. In clinical practice, through accurate diagnosis and positioning of different patients, appropriate treatment parameters such as therapeutic transducer, frequency and pressure can be selected to significantly improve the efficacy. At the same time, follow-up evaluation after treatment, including temporomandibular joint disorder index and visual analogue score, is also helpful to fully understand the rehabilitation of patients. Extracorporeal shock wave therapy (ESWT) brings new hope to patients with temporomandibular joint disorder syndrome and has a broad application prospect.

Posterior Cruciate Ligament and Posterolateral Corner Reconstruction: Clinical Outcomes Following Popliteal Tendon Tenodesis and Popliteal Tendon Reconstruction.

Injuries to the posterolateral compartment (PLC) of the knee require special attention, as incorrect diagnosis and treatment may lead to considerable morbidity. However, no gold standard treatment has been established for PLC injuries. 38 patients with concomitant (posterior cruciate ligament (PCL) and PLC injuries were divided into two groups according to surgical treatment of the proximal popliteal tendon injury. They were treated with anatomic popliteal tendon, lateral collateral ligament (LCL), and popliteofibular ligament (PFL) reconstruction (group 1; n = 19) and were treated with popliteal tendon tenodesis, LCL, and PFL reconstruction (group 2; n = 19). The Lysholm score, dial test, and lateral compartment opening on varus stress X-ray were used as outcome measurements evaluated before surgery and at 6, 12, and 24months of follow-up. Overall, there was a progressive improvement in the Lysholm score and the lateral opening on varus stress radiography during the evaluated periods for both groups (p < 0.001). Patients from group 2 recorded better Lysholm scores than those from group 1 at 12- and 24-month follow-up (p = 0.02). Dial test was negative in all patients after 6, 12, and 24months. Patients with popliteal tendon tenodesis were found to have better Lysholm scores than patients with reconstruction after 12 and 24months of follow-up. There was no difference in the lateral joint opening evaluated by stress radiography between groups. These results show that tenodesis could be a viable treatment option for lateral femoral condyle popliteal disruptions in the context of PLC and PCL combined injuries, and should be considered in the surgical planning process.

Seismic characteristics of segmental tunnels considering seal roof blocks arrangement

The position of seal roof block may greatly affect the overall performance of the segmental tunnel. However, a few investigations have been dedicated to evaluating this effect. In the present study, finite element models are established to simulate the ring structure-soil model in order to evaluate the capacity curve of the universal ring structure during progressive failure. Nineteen universal ring structures configurations were analyzed considering different locations of the adjacent seal roof blocks. The models accurately simulated the structural details of the typical handhole for curved bolt in the circumferential and longitudinal joints. The seismic performance of the universal ring structure with different configurations is evaluated and discussed in terms of the moment curve, plastic zone distribution, joint opening angle curve and capacity curve of the universal ring. The results indicate that there are significant differences in the maximum positive and negative moment, plastic zone, and tensile angle of the universal ring structure when the seal roof block is in different positions. At the same time, the development of the performance curve of the ring will also show significant differences, especially in the elastic stage. The structure exhibits best seismic performance when the seal roof block is located at arch shoulder and waist (−67.5° ± 22.5°) because it is less likely to reach the normal function, immediate operational, rectifiable or irreparable damage stages compared to other configurations.

Experimental investigation on the mechanical properties and failure mechanism of key joints in a new-type prefabricated pile-wall composite structure for the open-cut tunnel

To improve the failure resistance of the lining and make use of the retaining structure, this paper proposed a novel method of adding the key joints to connect the lining with the retaining structure. Usually, the joint is the weak point of the whole structure. The failure mechanism of key joints significantly influences the design and safety of the prefabricated structure. In this study, full-scale loading tests were conducted on three types of key joints: sleeve joint, spiral stirrup joint, and U-shaped rebar joint. The joint deformation, failure mechanism, concrete strain, and reinforcement strain are investigated. The results demonstrated that the deformation and failure process of the key joints can be divided into four stages. The flexural-shear failure caused by the joint opening and the sliding of lining is considered as the main failure mode of the key joints. The U-shaped rebar joint exhibited the best mechanical performance. Furthermore, the finite element modes were created to analyze the influence of axial force and the reinforcement diameter. Combining the test and numerical analysis results, the failure mechanism was revealed. In addition, the joints’ loading-carrying capacity was increased with the increase of axial force due to the axial force limiting the joint opening. The research results provide a theoretical basis and reference for the new-type prefabricated pile-wall composite structure (PPCS).

Buckling prediction based on joint opening and safe temperature estimation in jointed plain concrete pavements

Concrete pavement buckling is a significant distress that disrupts traffic flow and results in costly repairs, issues that are increasingly exacerbated by global warming. Addressing these issues, this study develops a systematic framework for assessing jointed plain concrete pavement (JPCP) by integrating temperature and moisture gradients, pavement structures, and material properties into mechanical-based models for predicting buckling potential. Specifically, a two-stage analysis is developed to analyze buckling development based on the slab deformation and the slab-base interface, including joint closure assessment and upheaval buckling prediction. Through the established model, parametric studies are conducted to quantitatively identify key factors influencing buckling. Moreover, the developed models are applied to pavement sections in various climate regions and validated through comparative analysis with field data from the Long-Term Pavement Performance (LTPP) database to confirm model accuracy. Additionally, a case study using pavement buckling data from Wisconsin between 2014 and 2020 demonstrates the model's practical application. As the results, it is found that temperature increase, the percentage of incompressible materials, and the coefficient of thermal expansion are critical for joint opening changes, while the coefficient of thermal expansion, elastic modulus, and slab thickness are crucial to post-buckling performance. Regression equations are provided to estimate safe temperature increases as a recommended buckling temperature limit. Furthermore, the predicted joint opening shows reasonable alignment with joint gauge measurement in the field recordings from the LTPP database. Finally, the predicted buckling events are reasonably compared with field recordings for a Wisconsin pavement section from 2014 to 2020. In summary, by considering pavement structural parameters, material properties, and weather conditions, this comprehensive model provides a reasonable tool for predicting and mitigating JPCP buckling in different climate conditions.

Experimental study on seismic performance of post-tensioned precast segmental piers designed with multiple joint openings

In accelerated bridge construction (ABC), precast segmental piers (PSPs) have shown significant progress in shortening the construction period and reducing the cost. By combining multiple segments with post-tensioned (PT) tendons, the desired self-centering ability can be introduced; however, this may lead to a lower energy dissipation (ED) capacity and concentrated damage. To address this concern, the present study proposes a design concept that promotes multiple joint openings to achieve a better energy dissipation capacity and decentralized damage without compromising the self-centering ability. Two main approaches for this objective are discussed in detail. The first approach incorporates different arrangements of ED rebars at various joints, while the second introduces innovative damage control rubber joints (DCRJs) with varying stiffness beneath each segment. Four scaled specimens designed using these two approaches were quasi-statically tested. The observed damage, final failure mode, energy dissipation capacity, resilience index, and damage decentralization were further examined. The results revealed that for PSPs designed using the first approach, the joint openings were successfully decentralized only up to a certain level, after which they were still predominantly concentrated at a single joint, leading to strength degradation and damage concentration. PSPs designed using the second approach demonstrated decentralized joint openings, improved displacement ductility, and damage mitigation, resulting in both superior seismic and post-seismic performance.

Variation of segment joint opening of underwater shield tunnel during long operational period

Segment joint is the main water leakage channel in underwater shield tunnels, and joint deformation influences tunnel waterproof capacity greatly. Real-time structure health monitoring is a great way to investigate the joint opening and to offer early warnings for abnormality, such as data outlier and joint properties degradation. This study investigated the variation of joint opening, provided early warning indexes and evaluated the joint mechanical properties degradation using the field monitoring data of an underwater shield tunnel over 10 years, which is rarely seen in the literature. Study results show that: (1) Field monitoring data reveals that the distribution of joint opening increments obeys a heavy-tailed distribution rather than the normal distribution. The exponential distribution model and the log normal distribution model can fit the longitudinal joint increments and circumferential joint increments much better. (2) The early warning index is determined based on the statistic theory and 0.999 quantile is set as the warning value. The obtained warning values of the studied underwater tunnel are 0.005 mm and 0.08 mm for the longitudinal and circumferential joint respectively. The small warning value means that small abnormality can be identified and the early warning would be more efficient. (3) A mechanical model is proposed to evaluate the joint mechanical properties degradation based on monitoring data. Results show that normal stiffness of circumferential joint decreases from 18.3 GPa/m to 14.7 GPa/m. Results of this study provides valuable reference for early-warning and joint degradation evaluation of under water shield tunnel.

Prediction on the time-varying behavior of tunnel segment gaskets under compression

The compression force is a critical indicator for assessing the waterproofing capability of ethylene propylene diene monomer (EPDM) rubber gaskets, and the relaxation of EPDM gaskets under compression is a key factor contributing to water leakage in shield tunnels. In this study, detailed accelerated aging tests of gaskets with different precompression openings were conducted. Analytical method and simulation method for predicting the long-term performance of EPDM gaskets considering their different compression states were proposed. First, the compression curve of the gasket was divided into three stages to analyze the mechanism of compression force degradation in depth. Under the action of a compression force, the unrecoverable deformation caused by open holes shortened stage III of the compression curve, which constituted the primary factor influencing gasket compression force relaxation. In addition, the Arrhenius equation was used to establish a conversion relationship between the accelerated aging test conditions and actual service time, and an analytical expression (AE) method for predicting the compression force degradation pattern of gaskets was proposed. Finally, a finite element (FE) method based on the relaxation constitutive model was proposed, enabling simulation of deteriorating tunnel segment gasket performance under complex compression states. Then, the effectiveness and accuracy of the proposed relaxation model were validated by comparing the compression force curves and deformation states obtained from experiments and simulations. Based on the time-varying relaxation constitutive parameters, the variation in the compression force of EPDM gaskets with different joint openings over time was simulated. The results show that the minimum compression force retention rates of gaskets after 100 years of service predicted by the AE method and FE method are 28.5 % and 30.6 %, respectively. This study provides two effective means for predicting the long-term mechanical performance of compressed EPDM gaskets, offering pivotal insights for long-term waterproofing design of shield tunnel joints.