Experimental-Numerical Study on the Flexural Ultimate Capacity of Prestressed Concrete Box Girders Subjected to Collision

Precise evaluation for flexural ultimate capacity of bridges which are subjected to the collision of over-height trucks is essential for making decisions on corresponding maintenance, strengthening or replacement. When the span of a cross-line continuous bridge with a double-box girder was hit by an overly high vehicle, the concrete floor of one girder was severely damaged, and part of the prestressed strands and reinforcements in the girder were broken. After the double-box girder was removed and separated into two single box girders, the ultimate flexural capacity of both box girders was studied by destructive tests, and a comparison was made between the damaged and undamaged girders. Moreover, finite element analysis was conducted to simulate the failure process. The results show that the flexural bearing capacity of the damaged box girder decreased by 33%, but it was still 1.07 times greater than the design bearing capacity, which basically meets the design requirements. Also, the damaged box girder showed a desirable serviceable limit state for three-axle vehicles and five-axle vehicles, but showed an undesirable serviceable limit state for six-axle vehicles. This study shows that repairing or strengthening the damaged span may be better than demolishing and rebuilding the whole superstructure bridge.     

四肢开放性骨折使用外固定器的治疗与护理

目的探讨四肢开放性骨折使用外固定器治疗术后护理的措施与对康复的效果。方法 2010-01/2012-01商水县人民医院使用单侧外固定器进行四肢开放性骨折治疗的患者100例,术中术后采取一般性护理的心理护理、环境护理、自体护理;患肢血液灌注护理;预防针孔感染;防止交叉感染;营养支持;功能锻炼等综合护理措施。结果 100例患者骨折均愈合良好,随访2年,患者骨折愈合时间平均为（10.3±5.2）月,未发生感染、骨不连接等并发症。结论四肢开放性骨折使用外固定器治疗术,配合系统护理可有效增进患者的康复。     

Fracture Mode Transition during Assembly of TC4 High-Lock Bolt under Tensile Load: A Combined Experimental Study and Finite Element Analysis

Fracture during the assembly process is an important failure mode for high-lock bolts used in the aviation industry, which greatly increases the potential of unpredictable accidents during service. In the current study, the underlying reasons for fracture during the assembly of a TC4 high-lock bolt was investigated using a tensile test and finite element analysis (FEA). The microstructure of the as-received bolt consisted of a high proportion of α phase, some β phase, and a small amount of α′ phase formed via martensite phase transformation during the rammer process. The experimental force–displacement curves revealed an average yield load of 55.9 kN and a breaking load of 67.65 kN. The corresponding yield strength was calculated to be 0.9 GPa, which was smaller than the standard value of TC4. This was attributed to the preload-induced stress concentration on the thread surface, leading to obvious strain hardening, which can lead to crack initiation. The effect of preload was further confirmed by the fractographies in which the initial crack was observed on the thread surface. The fractographies suggested that hybrid fracture occurred on the tensile loaded bolt. The initial failure was brittle fracture on the thread surface, transforming into ductile fracture in the screw. The results can contribute to understanding the effect of preload on the load carry capacity of high-lock bolts and provide a strategy to design its assembly specification.     

下腰椎骨折并发马尾综合征的手术疗效分析

目的:马尾综合征(CES)包括下腰痛、坐骨神经痛、下肢运动感觉功能障碍、会阴区麻木,以及膀胱直肠功能障碍或丧失,CES的一些认识已经明确,但是临床上采取什么样的治疗最恰当存在争议,有关腰椎间盘突出引起的CES,已经积累了大量的病例资料。但是有关下腰椎骨折引起的马尾综合征临床少有报道。方法:从1998年到2006年,收集17例L2—5腰椎骨折并发马尾综合征的病人,其中车祸伤11例,高处坠落伤6例,脊髓圆锥损伤导致的CES的病例除外,记录所有病例的体征、受伤机制、影像资料、受伤时间、手术方法、神经损伤和恢复情况。结果:所有病例随访至少12个月。所有的病人在出现CES48小时之内进行手术减压治疗,其中14个病人恢复效果满意,另外3个病人虽然在伤后24小时内进行了手术治疗,但是效果不好。双下肢无力在4个月内恢复,膀胱和直肠功能在3个月恢复。总的来看,病人恢复效果的好坏与手术时间的早晚无关。结论根据临床研究,下腰椎骨折引起的CES恢复效果与受伤时马尾损伤的程度密切相关,虽然对于手术的时机存在争议,但是本研究建议在出现CES48小时内施行手术治疗。     

经鼻填充鼻中隔软骨修复眶内侧壁骨折

目的：探讨应用鼻内镜填充鼻中隔软骨,修复眶内侧壁骨折,经鼻做眼部手术的可能性。方法：选取眶内侧壁骨折患者11例（11眼）,术前检查均有不同程度的眼球内陷、复视、视力减退症状,行眼眶CT诊有眶内容物疝入筛窦并伴积液,其中6例内直肌肿胀。手术开始在内镜直视指引下,经鼻腔开放筛窦,摘除筛房,暴露骨折的纸板,将疝入物回纳眶内,鼻中隔软骨覆盖骨折区。结果：患者手术后全部治愈。双眼突出度相差≤1mm,平均0.11mm。视力较术前不改变或者略有改善。鼻内镜检查见筛窦术腔上皮化,填充的鼻中隔软骨无移动,无感染及排斥现象。结论：经鼻填充鼻中隔软骨修复眶内侧壁骨折方法简便,成功率高。自体鼻中隔软骨无排斥反应。     

Numerical Investigation of the Influence of Ultimate-Strength Heterogeneity on Crack Propagation and Fracture Toughness in Welded Joints

The mechanical properties of dissimilar metal-welded joint materials are heterogeneous, which is an obstacle to the safety evaluation of key welded structures. The variation of stress–strain conditions at the crack tip caused by mismatch of material mechanical properties in dissimilar metal-welded joints is an important factor affecting crack propagation behavior. To understand the influence of uneven distribution of ultimate strength of the base metal and the welded metal on the crack propagation path, fracture toughness, as well as the mechanical field at the crack tip in the small-scale yield range, the user-defined field variable subroutine method is used to express continuous variation characteristics of welded joint ultimate strength in finite element software. In addition, the J-integral during crack propagation is calculated, and the effect of the ultimate strength on the J-integral and the stress field at the crack tip are analyzed. The results show that as the crack propagation direction is perpendicular to the direction of ultimate strength, the gradient of ultimate strength increases from |G_y|= 50 to |G_y|= 100 MPa/mm, the crack deflection angle increases by 0.018%, and the crack length increases by 1.46%. The fracture toughness of the material decreased slightly during crack propagation. Under the condition that the crack propagation direction is the same as the direction of ultimate strength, the crack propagation path is a straight line. As the gradient of ultimate strength increases from G_x = 50 to G_x = 100 MPa/mm, the crack propagation length decreases by 5.17%, and the slope of fracture toughness curve increases by 51.63%. On the contrary, as the crack propagates to the low ultimate strength side, the crack propagation resistance decreases, the ultimate strength gradient increases from G_x = −100 to G_x = −50 MPa/mm, and the slope of the fracture toughness curve decreases by 51.01%. It is suggested to consider the relationship between crack growth behavior and ultimate strength when designing and evaluating the structural integrity of cracks at the material interface of dissimilar metal-welded joints.     

A case report on a child with fracture and dislocation of the upper cervical spine accompanied by spinal cord injury

Rationale:This study describes an 8-year-old boy with a C2 fracture and dislocation with a left C2–C3 articular process interlocking and spinal cord injury who underwent open reduction and internal fixation using the posterior cervical approach and achieved satisfactory results.Patient concerns:An 8-year-old boy underwent an emergency transfer from a previous hospital after a car accident.Diagnoses:Axial fracture and dislocation with spinal cord injury (American Spinal Injury Association grade C), traumatic shock, brain contusion, intracranial hemorrhage, mandibular fracture, pulmonary contusion and hemorrhage, left vertebral artery stenosis, and multiple fractures throughout the body. Radiological examination revealed a fracture of the lower edge of the C2 vertebral body, fourth-degree anterior spondylolisthesis of the C2 vertebral body, interlocking of the left C2–C3 articular processes, widening of the C2–C3 vertebral space, and occlusion of the V1 and 2 segments of the left vertebral artery.Interventions:The boy was immediately intubated and transferred to the pediatric intensive care unit for rescue treatment. However, the reduction was unsuccessful with 2 weeks of cranial traction. Thus, an open reduction was performed under general anesthesia. One month after the surgery, the boy was discharged from the hospital on foot after rehabilitation treatment.Outcomes:The boy was discharged from the hospital 1 month after surgery. At the 8-month follow-up, a radiological examination showed that the corrected C2 vertebral body fracture and dislocation were satisfactorily reduced, and the spinal cord was adequately decompressed. The internal fixation position was also good, and the spinal sequence had recovered well. In summary, except for the muscle strength of the right upper limb, which was slightly worse, the other clinical symptoms were significantly improved.Lessons:In treating cervical fracture and dislocation with unilateral facet lock, the posterior open reduction of pedicle screw and lateral mass screw internal fixation achieved satisfactory results. Consequently, treating complex cervical spine injuries in children requires an accurate diagnosis and careful treatment strategy.     

Osteoporosis in COPD patients: Risk factors and pulmonary rehabilitation

ObjectivesTo present a review on the pathogenesis, risk factor and treatment of chronic obstructive pulmonary disease complicated with osteoporosis and provide new ideas for the diagnosis and treatment.Data sourceA systematic search is carried out using keywords as chronic obstructive pulmonary disease, osteoporosis, risk factors, and pulmonary rehabilitation.ResultsPatients with chronic obstructive pulmonary disease have a high prevalence of osteoporosis and a high risk of fracture. The mechanisms of osteoporosis in COPD patients are associated with general risk factors, such as smoking, reduced physical activity, low weight, and disease‐specific risk factors, such as systemic inflammatory, Vitamin D deficiency, use of glucocorticoid, anemia, hypoxemia, and hypercapnia. The treatment of osteoporosis in COPD emphasizes comprehensive intervention, which mainly include basic treatment and anti‐osteoporosis drugs. Noticeably, pulmonary rehabilitation program is an important part of treatment.ConclusionsThis work summarizes the pathogenesis, risk factor, prevention, and treatment of chronic obstructive pulmonary disease complicated with osteoporosis, and the latest progress of studies on chronic obstructive pulmonary disease and osteoporosis is discussed.     

Study on the Initiation of Interface Crack in Rock Joints

The interfacial fracture of rock joints is an important although easily ignored issue in jointed rock engineering. To conduct this study, an interface crack model of rock joints was proposed. By analyzing the ratio of stress intensity factor to fracture toughness, the fracture mode of the interface crack was studied. Based on the Mohr-Coulomb criterion, an interface fracture criterion considering T-stress was established. To verify the proposed fracture criterion, laboratory and numerical tests were conducted. Finally, the effect of relative critical size α, internal friction angle φ and cohesion c on the initiation of an interface crack was comprehensively discussed. It is concluded that the proposed fracture criterion can predit the initiation of the interface cracks properly. With an increase in cohesion c, mode II fracture toughness K_IIC also clearly increases. When the absolute value of K_I is small, the effect of α is much larger than that of φ. In addition, with an increase in the absolute value of the mode I stress intensity factor, the φ of the joint plays a more important role in the initiation of the interface crack.     

CT检查在外伤性腰椎骨折中的诊断价值

目的:探讨外伤性腰椎骨折中采取CT检查的应用价值与优势.方法:本研究抽取2018年6月至2019年8月本院80例外伤性腰椎骨折患者作为研究对象,随机分组后,对照组采取X线检查,观察组采取CT检查,观察两组患者的诊断准确率、外伤性腰椎骨折评分.结果:X线片的准确率是72.50％(29/40),CT诊断准确率为95.00％...