Modelling of Crack Propagation in Layered Structures Using Extended Finite Element Method

Crack propagation in structures is an important issue which is engineers and designers should consider. Modeling crack propagation in structures and study the behavior of this phenomenon can give a better insight to engineers and designers for selecting the construction’s materials. Extended finite element method (XFEM) was used successfully in the past few years for simulating crack initiation and propagation in sophisticated and complex geometries in elastic fracture mechanics. In this paper, crack propagation in three-point bending beam including initial crack was modeled based on ABAQUS software. The following consequences were attained through the study of simulation data. First, the effects of young’s modulus and fracture energy on force-displacement curve at three-point bending beam were investigated. It was observed that, by increasing the value of young’s modulus and fracture energy, three-point bending beam was showed more load carrying against initiation. Second, in multi-layer beam, the effect of young’s modulus on force-displacement curve was investigated. In case I (the thin upper layer is harder than the substrate) the value of young’s modulus in substrate was kept constant and the amount of young’s modulus in thin layer was risen in each step rather than the substrate, the peak in force-displacement curve was ascended and three-point bending beam resisted better against crack initiation. Next, similar conditions was considered in case II (the thin upper layer is softer than the substrate), by decreasing the value of young’ modulus in top layer, peak in force-displacement curve was declined and crack initiation was happened in lower loading in each step. Finally, sensitivity analysis for thickness of top layer was conducted and the impact of this parameter was studied

Instrumented undriven steering wheel to illustrate dynamic behavior of vehicles

In this paper, a low-cost dynamometer for undriven, steered wheels is described.  The dynamometer was produced to determine whether such an instrumented mechanism is practical.  Four S-beam load cells and two opto-counters were used to obtain all moments, forces, and points of their application.  Overturning, aligning, and rolling resistance moments besides vertical force are directly measured by the load cells.  The opto-counters detect wheel angular velocity and steering angle.  The dynamometer evaluation results showed significant correlation between expected values and measured data with high accuracy.  Wheel dynamic behavior can be defined according to dynamic and kinematic analysis in which relative calculations have minimum simplifying assumptions.   Keywords: dynamometer, wheel forces and moments, point of force application, load cell, opto-counte

New Active Control Method Based on Using Multiactuators and Sensors Considering Uncertainty of Parameters

New approach is presented for controlling the structural vibrations. The proposed active control method is based on structural dynamics theories in which multiactuators and sensors are utilized. Each actuator force is modeled as an equivalent viscous damper so that several lower vibration modes are damped critically. This subject is achieved by simple mathematical formulation. The proposed method does not depend on the type of dynamic load and it could be applied to control structures with multidegrees of freedom. For numerical verification of proposed method, several criterions such as maximum displacement, maximum kinetic energy, maximum drift, and time history of controlled force and displacement are evaluated in two- , five- , and seven-story shear buildings, subjected to the harmonic load, impact force, and the Elcentro base excitation. This study shows that the proposed method has suitable efficiency for reducing structural vibrations. Moreover, the uncertainty effect of different parameters is investigated here

How Different Seismic Codes Define Torsionally Unbalanced Structure?

Non peer reviewedPublisher PD

Blunt traumatic aortic injury: Initial experience with endovascular repair

ObjectivesEndovascular treatment of traumatic aortic injury (TAI) is an alternative to open repair (OR) in patients with blunt trauma. We report our initial experience after integration of endovascular repair using thoracic devices.MethodsA retrospective review of a prospectively collected institutional trauma registry was performed. Between September 2005 and November 2008, 71 patients with TAI presented to our institution. Based on imaging, TAIs were classified into grade 1-4 in severity. These included: grade 1, intimal tear; grade 2, intramural hematoma; grade 3, aortic pseudoaneurysm; and grade 4, free rupture. Initial management included resuscitation, blood pressure control, and treatment of associated injuries. After stabilization, all patients were considered for thoracic endovascular aortic repair (TEVAR) using a thoracic device. If contraindicated, candidates underwent OR. Outcome measures were mortality, stroke, paraplegia, intensive care unit (ICU), and hospital stay.ResultsThe mean age was 39.8 years, with 50 males. The mean injury severity score (ISS) was 42.6. Nineteen (27%) patients with a mean ISS of 60 died shortly after arrival prior to any vascular intervention. Ten (14%) patients with grade 1 injuries were managed medically. The remaining 42 (59%) patients with grade 2 and 3 injuries underwent repair. Median interval between admission and repair was 4.3 days (range, 0-109 days). Fifteen (21%) patients with a mean ISS of 34.4 underwent OR with no mortality, stroke, or paraplegia. Twenty-seven (38%) patients with a mean ISS of 36.7 underwent TEVAR with no mortality or paraplegia. One TEVAR patient suffered a perioperative stroke. Twenty-two patients had a TAG (W.L. Gore & Associates, Flagstaff, Ariz) device. Four patients had a Talent Thoracic (Medtronic Vascular, Santa Rosa, Calif), and 1 patient had an Excluder (W.L. Gore) device. The left subclavian artery was covered in 13 (48%) patients. Patients who underwent TEVAR were older than those who had OR (47.8 vs 31.1 years, P < .006). The aortic diameter proximal to the injury was larger in the TEVAR group (24.4 vs 19.6 mm, P < .0001). There was no difference in the mean ICU or hospital length of stay between the two groups. Mortality correlated with the ISS score (P < .0001). Median follow-up time was 19.4 months (range, 0-27). Only 56% of the TEVAR patients were fully compliant with their surveillance imaging protocol.ConclusionIn this initial experience, the results of TEVAR did not differ from OR. Long-term follow-up is required to determine the effectiveness of this treatment strategy. Adherence to follow-up imaging protocols is challenging in this patient population. Next generation devices will make TEVAR applicable to a wider range of patients

Discrepancy in Embodied Carbon Calculations for Concrete Materials

Abstract. Accurate assessment of embodied carbon is integral to understanding the environmental impact of building materials and promoting sustainable building practices. This process aids in prioritizing efforts to reduce emissions and mitigate climate change. Existing studies highlight discrepancies across various embodied carbon databases, causing uncertainty in assessments. Our study reveals significant differences in the calculated embodied carbon of materials, depending on whether they are assessed as a singular entity or as composed of individual components. Concrete, a major contributor to embodied carbon in construction projects, serves as our focus. We calculate the embodied carbon of concrete materials in a typical residential building using Life Cycle Assessment (LCA), a comprehensive method to evaluate environmental impacts throughout a building's life cycle. We utilize the Inventory of Carbon and Energy (ICE), one of the most reliable databases, for our assessment. Our findings indicate substantial differences when calculating embodied carbon for concrete as a singular material (first scenario) versus considering its component parts (second scenario). The first scenario results in at least a 20% increase in carbon emissions, with the exact discrepancy depending on the type of concrete materials and whether they are reinforced. Given that approximately 66% of the total quantity of our case study comprises concrete, these differences are substantial. Our study underscores the importance of incorporating embodied carbon factors into a unified database to accurately assess total embodied carbon emissions of buildings. It also highlights the potential for database uncertainty to skew interpretations of embodied carbon if an LCA is conducted for design reduction. Hence, a reliable baseline for calculating embodied carbon is crucial. Keywords: Life Cycle Assessment, Sustainability, Embodied Carbon, Concrete, Discrepanc

Intercostal nerves pulsed radiofrequency for intractable neuralgia treatment in athletes with sport trauma of the chest: A case-series study

Background: Athletes with trauma to the chest could be injured and suffer from an acute disturbing chest wall pain due to intercostal neuralgia. Pulsed radiofrequency (PRF) is an emerging safe therapy in many neurologic pain syndromes. Objectives: This study aimed to determine the effect of PRF on intercostal neuralgic pain in athletes complaining of severe chest pain and limited range of motion. Materials and Methods: This case-series study was conducted on athlete patients who suffered from severe chest pain that has limited their function. Eighteen athletes who were absent from physical training and sports activity due to intercostal neuralgia in their current season were admitted to our pain clinic. Intercostal nerve PRF was used to treat patients. Pain scale and return to sports activity were measured after PRF. Results: The mean time of absence from sports activity was 1.3 ± 0.6 weeks. The mean score of pain severity (numeric rating scale NRS) was 8.46 ± 1.85. In this study, 16 of 18 (88%) patients had effective pain relief (NRS P = 0.001), 2 (P = 0.0015), and 4 (P = 0.0002) weeks following PRF compared to pre-PRF time. Conclusions: Pulsed radiofrequency is a suitable therapy for athletes with intercostal nerve entrapment pain, which provides adequate and quick pain relief, thus enabling them to resume their sport activities

Comparative Analysis of Nanos and Ago Genes Expression in the Germinative Cells Isolated from Germinal Layer and the Neck Region of Echinococcus granulosus

Background: We aimed to evaluate the differential expression of nanos and ago genes in the protoscoleces, germinal layer, the neck, and the sucker regions of adult Echinococcus granulosus. Methods: The study was conducted in 2018 at the Research Center for Hydatid Disease in Iran, Kerman University of Medical Sciences, Kerman, Iran. In the present study E. granulosus protoscoleces were cultured in a di-phasic medium to obtain strobilated worms. The strobilated worms were harvested and using a sterile razor blade, the neck region was separated. In the molecular study the neck sections were compared with the tissues derived from the suckers from the same worm. The primers were specifically designed for RT-qPCR on nanos and ago. The germinative cells were isolated from the cyst germinal layer and cultured in DMEM for further molecular studies. The Immunohistochemical profile was designed to explore the nature of nanos protein in the strobilated worms. Differences between and within groups were statistically assessed relative to the protoscoleces. Results: An increasing nanos gene expressions were found in sucker, neck, cells and germinal layer in comparison to the protoscoleces. The expression of ago gene was decreased in sucker, cell and germinal layer, and increased in the neck region in comparison to the protoscoleces. The results showed that both genes were expressed in all developmental stages of E. granulosus. Conclusion: nanos and ago genes were differentially expressed at different developmental stages of E. granulosus and may contribute to differentiation of the parasite

Whole Life Carbon Assessment of a Typical UK Residential Building Using Different Embodied Carbon Data Sources

The climate crisis in many sectors is driving rapid and substantial changes. Considering the fact that the building sector accounts for 39% of energy related carbon emissions, it is important to take swift actions to reduce these emissions. This study will identify the accuracy and availability of the embodied carbon databases. In this regard, the effect of using different embodied carbon databases on the total emissions during product and end-of-life stages will be compared. The results showed that using the UK Department for Business, Energy, and Industrial Strategy database (BEIS) overestimates the embodied carbon emissions. Additionally, using the Environmental product declarations database (EPDs), compared to the Inventory of Carbon and Energy database (ICE), can reduce embodied carbon for some materials up to 100%. The end-of-life calculation showed a huge difference between the two databases. In addition, Whole Life Carbon Assessment (WLC) has been carried out. The findings revealed that 67% of emissions come from operational carbon and embodied carbon is responsible for 33% of emissions. Using LED lights and installing PV panels can reduce the total CO2 emissions by 24.82 tonCO2. In addition, using recycled metal, less carbon intensive concrete, and recyclable aluminium can reduce the total CO2 emissions by 18.57, 2.07, and 2.3 tonCO2e, respectively