Full-scale testing and modeling of the mechanical behavior of shield TBM tunnel joints

Wen-qi Ding,Yi-cheng Peng,Zhi-guo Yan,Bi-wei Shen,He-hua Zhu,Xin-xin Wei 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.3

For shield TBM (Tunnel Boring Machine) tunnel lining, the segment joint is the most critical component for determining the mechanical response of the complete lining ring. To investigate the mechanical behavior of the segment joint in a water conveyance tunnel, which is different from the vehicle tunnel because of the external loads and the high internal water pressure during the tunnel’s service life, full-scale joint tests were conducted. The main advantage of the joint tests over previous ones was the definiteness of the loads applied to the joints using a unique testing facility and the acquisition of the mechanical behavior of actual joints. Furthermore, based on the test results and the theoretical analysis, a mechanical model of segment joints has been proposed, which consists of all important influencing factors,including the elastic-plastic behavior of concrete, the pre-tightening force of the bolts and the deformations of all joint components, i.e., concrete blocks, bolts and cast iron panels. Finally, the proposed mechanical model of segment joints has been verified by the aforementioned full-scale joint tests.

Full-scale testing and modeling of the mechanical behavior of shield TBM tunnel joints

Ding, Wen-Qi,Peng, Yi-Cheng,Yan, Zhi-Guo,Shen, Bi-Wei,Zhu, He-Hua,Wei, Xin-Xin Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.3

For shield TBM (Tunnel Boring Machine) tunnel lining, the segment joint is the most critical component for determining the mechanical response of the complete lining ring. To investigate the mechanical behavior of the segment joint in a water conveyance tunnel, which is different from the vehicle tunnel because of the external loads and the high internal water pressure during the tunnel's service life, full-scale joint tests were conducted. The main advantage of the joint tests over previous ones was the definiteness of the loads applied to the joints using a unique testing facility and the acquisition of the mechanical behavior of actual joints. Furthermore, based on the test results and the theoretical analysis, a mechanical model of segment joints has been proposed, which consists of all important influencing factors, including the elastic-plastic behavior of concrete, the pre-tightening force of the bolts and the deformations of all joint components, i.e., concrete blocks, bolts and cast iron panels. Finally, the proposed mechanical model of segment joints has been verified by the aforementioned full-scale joint tests.

Effectiveness and safety of acupuncture for angina pectoris: An overview of systematic reviews

Qi Wen-Chuan,Fu Hong-Juan,Sun Rui-Rui,Li Xiang,Cai Ding-Jun,Wang Chao,Liang Fan-Rong 한국한의학연구원 2022 Integrative Medicine Research Vol.11 No.3

Background: The number of systematic reviews or meta-analyses (SRs/MAs) on the effectiveness of acupuncture for angina pectoris (AP) is increasing. Due to the inconsistent conclusions and unknown quality of these SRs/MAs, this overview aimed to systematically evaluate and synthesize the existing SRs/MAs, attempting to provide more reliable evidence for the effectiveness and safety of acupuncture in the treatment of AP. Methods: SRs/MAs were searched via eight databases from inception to March 14, 2022. The risk of bias was evaluated using the Risk of Bias in Systematic reviews (ROBIS) tool. The quality of the methodology, reporting, and evidence were assessed by the Assess Systematic Reviews 2 (AMSTAR-2), the Preferred Reporting Item for Systematic Review and Meta-analysis for Acupuncture (PRISMA-A), and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system, respectively. Results: Sixteen SRs/MAs were included and fifteen SRs/MAs were considered being of critically low quality according to AMSTAR-2. Only three SRs/MAs were rated at low risk of bias. No study reported all the items listed in the PRISMA-A checklist. No high-quality evidence with GRADE assessment was found. With the low-quality evidence, acupuncture combined with other interventions was superior to monotherapy (medications or Chinese medicine) in the angina symptom and electrocardiogram recovery. No adverse effects owing to acupuncture were reported. Conclusions: Owing to the lack of high-quality evidence provided by the current SRs/MAs, the effective-ness of acupuncture for AP still warrants further proof. Further researches with more critical design and methodology are needed for providing more convincing evidence. Background: The number of systematic reviews or meta-analyses (SRs/MAs) on the effectiveness of acupuncture for angina pectoris (AP) is increasing. Due to the inconsistent conclusions and unknown quality of these SRs/MAs, this overview aimed to systematically evaluate and synthesize the existing SRs/MAs, attempting to provide more reliable evidence for the effectiveness and safety of acupuncture in the treatment of AP. Methods: SRs/MAs were searched via eight databases from inception to March 14, 2022. The risk of bias was evaluated using the Risk of Bias in Systematic reviews (ROBIS) tool. The quality of the methodology, reporting, and evidence were assessed by the Assess Systematic Reviews 2 (AMSTAR-2), the Preferred Reporting Item for Systematic Review and Meta-analysis for Acupuncture (PRISMA-A), and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system, respectively. Results: Sixteen SRs/MAs were included and fifteen SRs/MAs were considered being of critically low quality according to AMSTAR-2. Only three SRs/MAs were rated at low risk of bias. No study reported all the items listed in the PRISMA-A checklist. No high-quality evidence with GRADE assessment was found. With the low-quality evidence, acupuncture combined with other interventions was superior to monotherapy (medications or Chinese medicine) in the angina symptom and electrocardiogram recovery. No adverse effects owing to acupuncture were reported. Conclusions: Owing to the lack of high-quality evidence provided by the current SRs/MAs, the effective-ness of acupuncture for AP still warrants further proof. Further researches with more critical design and methodology are needed for providing more convincing evidence.

MODEL PREDICTIVE COORDINATED CONTROL FOR DUAL-MODE POWER-SPLIT HYBRID ELECTRIC VEHICLE

Yunlong Qi,Changle Xiang,Weida Wang,Boxuan Wen,Feng Ding 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.2

Power-split hybrid electric vehicles (HEVs) have great potential fuel efficiency and have attracted extensive research attention with regard to their control system. The coordinated controller in HEV plays an important role in tracking the optimal state reference generated by the energy management strategy (EMS), so as to reach the desired fuel efficiency. Meanwhile, the coordinated controller also has a significant impact on driving performance. To improve its performance, the design of a model predictive control (MPC) based coordinated controller in power-split HEV is presented. First, a non-linear, time-varying constrained control oriented transmission model of a dual-mode power-split HEV is formulated to describe this control problem. Then, to solve this problem, the non-linear part in the transmission model is linearised, and a linear MPC is used to obtain the control signals for the motors and engine at each time step. To meet the requirements of real-time computation, a fast MPC method is also applied to reduce the online computation effort. Simulations and experiments demonstrate the effectiveness of the proposed MPC-based coordinated controller.

Behavior of circular concrete-filled steel tubular columns under pure torsion

Fa-Xing Ding,QIANG FU,Bing Wen,Qi-shi Zhou,Xue-mei Liu 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.4

Concrete-filled steel tubular (CFT) columns are commonly used in engineering structures and always subjected to torsion in practice. This paper is thus devoted to investigate the mechanical behavior of circular CFT columns under pure torsion.3D finite element models based on reasonable material constitutive relation were established for analyzing the load-strain (<i>T-–γ</i>) curves of circular CFT columns under pure torsion. The numerical simulation indicated that local bulking of the steel tube in CFT columns was prevented and the shear strength and ductility of the core concrete were significantly improved due to the confinement effect between the steel tube and the core concrete. Based on the results, formulas to predict the torsional ultimate bearing capacity of circular CFT columns were proposed with satisfactory correspondence with experimental results. Besides, formulas of composite shear stiffness and the overall process of the <i>T-–γ</i> relation of circular CFT columns under pure torsion were proposed.

Experimental investigation of long-term characteristics of greenschist

Zhang, Qing-Zhao,Shen, Ming-Rong,Ding, Wen-Qi,Jang, Hyun-Sic,Jang, Bo-An Techno-Press 2016 Geomechanics & engineering Vol.11 No.4

The greenschist in the Jinping II Hydropower Station in southwest China exhibits continuous creep behaviour because of the geological conditions in the region. This phenomenon illustrates the time-dependent deformation and progressive damage that occurs after excavation. In this study, the responses of greenschist to stress over time were determined in a series of laboratory tests on samples collected from the access tunnel walls at the construction site. The results showed that the greenschist presented time-dependent behaviour under long-term loading. The samples generally experienced two stages: transient creep and steady creep, but no accelerating creep. The periods of transient creep and steady creep increased with increasing stress levels. The long-term strength of the greenschist was identified based on the variation of creep strain and creep rate. The ratio of long-term strength to conventional strength was around 80% and did not vary much with confining pressures. A quantitative method for predicting the failure period of greenschist, based on analysis of the stress-strain curve, is presented and implemented. At a confining pressure of 40 MPa, greenschist was predicted to fail in 5000 days under a stress of 290 MPa and to fail in 85 days under the stress of 320 MPa, indicating that the long-term strength identified by the creep rate and creep strain is a reliable estimate.