Comparative assessment of impact analysis methods applied to large commercial aircraft crash on reinforced concrete containment.

The precise evaluation of the potential damage caused by large commercial aircraft crash into civil structures, especially nuclear power plants (NPPs), has become essential design consideration. In this study, impact of Boeing 767 against rigid wall and outer containment building (reinforced concrete) of an NPP are simulated in ANSYS/LS-DYNA by using both force time history and missile target interaction methods with impact velocities ranging from 100 m/s to 150 m/s. The results show that impact loads, displacements, stresses for concrete and steel reinforcement, and damaged elements are higher in case of force time history method than missile target interaction method, making the former relatively conservative. It is observed that no perforation or scabbing takes place in case of 100 m/s impact speed, thus preventing any potential leakage. With full mass of Boeing 767 and impact velocity slightly above 100 m/s, the outer containment building can prevent local failure modes. At impact velocity higher than 120 m/s, scabbing and perforations are dominant. This concludes that in design and assessment of NPP structures against aircraft loadings, sufficient thickness or consideration of steel plates are essential to account for local failure modes and overall structural integrity. Furthermore, validation and application of detail 3D finite element and material models to full-scale impact analysis have been carried out to expand the existing database. In rigid wall impact analysis, the impact forces and impulses from FE analysis and Riera's method correspond well, which satisfies the recommendations of relevant standards and further ensure the accuracy of results in full-scale impact analysis. The methodology presented in this paper is extremely effective in simulating structural evaluation of full-scale aircraft impact on important facilities such as NPPs.

Analysis of 46 maxillofacial fracture victims in the 2008 Wenchuan, China earthquake.

PURPOSE: At 14:28 hours on May 12, 2008, a massive earthquake wracked most areas of Sichuan, China, causing catastrophic human loss. The aim of this study was to delineate the characteristics of victims with maxillofacial fractures in this disaster. PATIENTS AND METHODS: A descriptive analysis was conducted based on the medical records of earthquake maxillofacial injuries casualties transferred to West China Hospital of Stomatology, Sichuan University, after the earthquake. Data regarding demographic details, psychological status, patterns, anatomic sites, etiology, concomitant injuries, and management of earthquake maxillofacial fractures were evaluated. RESULTS: A total of 46 maxillofacial fracture patients' records of 28 (60.9%) males and 18 (39.1%) females were included in this study, with peak incidence (32.6%) in the elderly age group (older than 50 years). The most common etiology of earthquake maxillofacial fractures was building collapse (71.7%). The mandible (65.2%) was the most frequent site of the maxillofacial fracture, followed by the zygomatic complex (21.7%) and maxilla (13.0%). The most prevalent of maxillofacial fracture pattern was multiple and/or comminuted fractures (56.5%), which accounted for 72.7% (24/33) in building collapse injury group. There were 9 (19.6%) patients with significant concomitant injuries and the most common site of concomitant injuries was the head (4 cases) and extremity (4 cases). Four (8.7%) patients' maxillofacial fractures were treated conservatively, 16 (34.8%) underwent closed reduction and fixation, and 26 (56.5%) underwent open reduction and rigid internal fixation (RIF). Apart from 3 patients (6.5%) who showed infection, all patients with facial fractures achieved successful bony union with an acceptable occlusion and facial form. Additionally, it is noteworthy that all patients in our study presented the symptoms of posttraumatic stress disorder (PTSD). CONCLUSION: There is a variation of mechanism of injuries, age group, severity, patterns, concomitant injuries, and management of earthquake maxillofacial fractures. Knowledge of these characteristics provides useful strategies for patient care and prevention of further complications. A multidisciplinary and coordinated approach is important for optimum stabilization and ongoing treatment of victims of building collapse injury. The high percentage of PTSD confirms that psychologists should form an integral part of this multidisciplinary team.