1,721,038 research outputs found
Advanced Seismic Design for Storage Pallet Rack Steel Frames
Full text linkIn the paper, a study on the design of braced and unbraced steel storage pallet racks in seismic zone is summarized. On the basis of a geometric layout of interest for routine design, rack performance has been evaluated via two alternative approaches: the well-established modal response spectrum analysis (MRSA) and an advanced strategy combining non-linear time-history analyses with the measurement of the damage in joints. Reference is made to two recent Italian earthquakes scaled by different values of the peak ground acceleration. Furthermore, cyclic joint behavior has been reproduced by means of a suitable model accounting for joint strength/stiffness degradation, whose excursions in plastic range has been considered to monitor the damage
Modal identification of storage racks for cheese wheels
Full text linkDuring the Emilia-Romagna earthquake (2012), a great number of steel racks used to store cheese wheels collapsed, causing a non-negligible damage to the Italian economy. Therefore, for similar structures that survived and are in service, a deep investigation towards the assessment of their effective safety is required. In the seismic analysis of these frames, the mechanical constraint acting onto the racks due to the reinforced concrete sidewalls, possible nonlinearities exhibited by the base-plate joints and the in-plane restraint provided by wooden boards that connects adjacent columns should be carefully modelled to ensure realistic design results. In the paper, an experimental activity, based on suitable modal identification techniques, is presented to capture the dynamic behaviour of these peculiar structures. The scope is to collect data useful to calibrate numerical finite element models in order to accurately define the aforementioned unknown parameters. Furthermore, a few numerical models based on ideal restraints are herein discussed stressing out non-negligible differences in terms of expected seismic and static response
Characterization of existing steel racks via dynamic identification
Full text linkSteel storage racks are widely used in logistics for storing materials and goods. Rack design is carried out by adopting the so-called design-assisted-by-testing procedure. In particular, experimental analyses must be carried out by rack producers on the key structural components in order to adopt the design approach proposed for the more traditional carpentry frames. For existing racks, i.e., those in-service for decades, it is required to evaluate the load carrying capacity in accordance with the design provisions currently in use. The main problem in several cases should be the appraisal of the key component performance, owing to the impossibility to obtain specimens from in-service racks without reduction or interruption of the logistic flows. To overcome this problem, a quite innovative procedure for the identification of the structural unknowns of existing racks has been proposed in the paper. The method is based on in-situ modal identification tests combined with extensive numerical analyses. To develop the procedure, cheap measurement systems are required, and they could be immediately applied to existing racks. A real case study is discussed, showing the efficiency of the procedure in the evaluation of the effective elastic stiffness of beam-to-column joints and base plate connections, that are parameters which remarkably affect the rack performance. The structural unknowns have been determined based on four sets of modal tests (two configurations on the longitudinal direction and two in the transversal direction) plus 9079 iterative structural analyses. The results obtained were then directly compared with experimental component tests, showing differences lower than 9%
Navigating Uncertainty: the importance of mindfulness for the mental health of volunteer rescuers involved in the Ukrainian humanitarian emergency
No full textVolunteer rescuers provide a crucial support to the population during emergencies. Previous literature demonstrated that the involvement in humanitarian crises, such as the one arising from Russia’s invasion of Ukraine, exposes individuals to emotional and cognitive stressors, leading to detrimental effects on their mental health. Hence, it is of the utmost importance to identify factors that can shield them from developing adverse health-related outcomes. Accordingly, the aim of this study is to investigate whether mindfulness would be related to emotional exhaustion and post-traumatic stress and whether this relationship would be mediated by intolerance of uncertainty. A total of 210 volunteers engaged in the Ukrainian humanitarian crisis completed questionnaires measuring mindfulness, intolerance of uncertainty, emotional exhaustion, and post-traumatic stress. Mediation analyses revealed that mindfulness was negatively related to emotional exhaustion and post-traumatic stress, both directly and indirectly through the mediation of intolerance of uncertainty. By uncovering the protective role of mindfulness, this study makes a valuable contribution to the extant literature on the psychological well-being of volunteers. From a practical standpoint, volunteering associations should provide their volunteers with training, including mindfulness sessions, in addition to offering psychological support services and debriefing sessions following their involvement in emergencies
Evaluation of European approaches applied to design of TWCF steel members
No full textThin-walled cold-formed (TWCF) steel members are widely used in aerospace, automobile and architecture industries. Among the various advantages, mainly associated with the relatively simple and very cheap techniques required for their production and shaping, it is important to mention the relevant high strength to weight ratio. Beside the benefits, it has to be pointed out that the TWCF member response is quite difficult to be predicted because of the significant influence of local, distortional and overall buckling phenomena, owing to the frequent presence of open mono-symmetric cross-sections. The present paper can be intended as a typical technical paper whose results are useful not only for research activities, but, especially, for the routine design. It summarises a study aimed at increasing the safety of two European approaches that should be potentially adoptable for designing TWCF steel members. The grade of reliability of these existing European procedures has been evaluated by predicting the performance of more than 240 TWCF members tested in laboratory, selected in the framework of 13 experimental studies, taken from the literature. Being the assessed load carrying capacity sometimes significantly greater than the characteristic-experimental one, suitable safety factors have been consequently calibrated and proposed for each cross-section type, to be directly adopted in routine design to match the requirements associated with the limit state philosophy. Finally, the strength of additional TWCF beam-column specimens has been predicted to assess the efficiency of the proposed coefficients for practical cases frequently encountered in routine design. A complete benchmark is proposed in Appendix A, where the application of the considered design procedures for one selected case is reported
Non solo stress e malessere per i soccorritori: le risorse psicologiche come fattore di benessere
No full textPost-earthquake damage assessment of moment resisting steel frames
Full text linkThe assessment of damage in structures that have suffered one or more earthquakes is of paramount importance to better understand the post-earthquake effective behaviour, and eventually to define the more appropriate design strategies for retrofitting and repairing. The paper,which is focused on moment-resisting (MR) steel frames, deals with postearthquake assessment after one or more seismic events. A procedure combining non-linear time-history finite element analysis with the low-cyclic fatigue theory have been applied to appraise the damage level of each frame component and then the residual load carrying capacity have been evaluated via the incremental static analysis of the damaged frames. It is worth underlining that, onthe basis of the discussed numerical results, the damage measurement and the residual load carrying capacity, which are often neglected in routine design, appear very useful to increase the knowledge on the effective safety level of the frame after one or more earthquake
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