Numerical investigation of branch plate-to-CHS connection under eccentric shear loading

Circular Hollow Section (CHS) columns are usually used in high-rise buildings. International design specifications usually overestimate the design of the beam-to-CHS column branch plate connections. This paper numerically investigates the behavior and strength of beam-to-CHS column branch plate connections using a finite element (FE) model. The FE model is verified using different experimental results available in previous literature. A parametric study is carried out on specimens subjected to eccentric shear loading on the branch plate with a constant column length and end conditions. The parameters included the CHS column diameter, wall thickness, branch plate length and the effect of load eccentricity. A notable effect of these parameters is observed on the connection capacity. The mode of failure of the studied specimens ranged from chord plastification for small thicknesses followed by chord face punching to excessive column ovalization at the vicinity of the connection followed by either chord punching or tearing out in the weld. For CHS columns with large thicknesses, punching failure in the column face or premature weld failure is observed. Finally, the results of the parametric study indicated a prominent effect of load eccentricity on the in-plane bending capacity. Therefore, a proposed improvement to the current design guidelines for the strength of CHS column branch plate connection subjected to in-plane bending is presented in this paper

Plastic collapse of longitudinal T-type branch plate-to-CHS connections under compression

© 2019 Elsevier Ltd Nowadays, longitudinal branch plates are used as structural members in several engineering applications to connect brace members to Circular Hollow Section (CHS) chord members, which are widely employed due to their aesthetical appeal and efficiency. At ultimate limit state, the failure mechanism of T-type branch plate-to-CHS connections is characterized mainly by the formation of yield lines in the chord. This paper presents an analytical methodology developed using the yield line approach to predict the compressive strength of the longitudinal T-type branch connections. A numerical finite element parametric model was developed and calibrated with experimental work from literature to accurately assess the joint capacity in different configurations. Results obtained from the proposed analytical model show very good agreement with the calibrated FE model. Moreover, a comparison between the results of the parametric FE analysis with both previous studies and current design guidelines is presented. The proposed analytical model takes into consideration the most influential geometrical parameters and the effect of membrane stresses, which was found to be significant in slender chord members. The newly proposed equation also considers the slenderness of chord members which is not considered in the current design equations.status: publishe

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population.The aim of this study was to inform vaccination prioritization by modelling the impact of vaccination on elective inpatient surgery. The study found that patients aged at least 70 years needing elective surgery should be prioritized alongside other high-risk groups during early vaccination programmes. Once vaccines are rolled out to younger populations, prioritizing surgical patients is advantageous