Web Panel Research Articles

When is Perceived Accessibility Over- or Underestimated by Accessibility Indicators?

This study delves into mismatches between accessibility indicators and perceived accessibility across transport modes for the case of grocery shopping. Conducted in Gothenburg, Sweden, the study combines a web panel survey with 1,423 participants and detailed location-based accessibility indicators. Findings reveal mismatches, with analyst’s overestimation (when the accessibility indicator is high, despite low perceived access) and analyst’s underestimation (low indicator, high perceived accessibility) varying across transportation modes. Notably, underestimation is prominent for car accessibility. Multinomial logistic regressions identify key variables influencing these mismatches, such as parenting status, education level and habitual car use.

NEW INSIGHTS INTO THE WEB PANEL COMPONENT

AbstractThe column web panel is a fundamental component of beam‐column joints. This component has been thoroughly studied and codified in the past. In this paper, new insight on its behaviour is obtained using a large amount of high‐quality Finite Element (FE) models, covering a wide range of panel slenderness and aspect ratios. The study shows that the existing models in part 1‐8 of the current and forthcoming Eurocode 3 present a wide scatter in terms of resistance and stiffness, being unconservative in some specific cases.

Change in intention and hesitancy regarding COVID-19 vaccines in a cohort of adults in Quebec during the pandemic

ABSTRACT Although COVID-19 vaccine uptake was high in Quebec for the primary series, vaccine acceptance decreased for the subsequent booster doses. This article presents the evolution of vaccine intention, self-reported vaccination behaviors, and vaccine hesitancy over 2 years. A series of cross-sectional surveys were conducted in Quebec between March 2020 and March 2023, with a representative sample of 3,330 adults recruited biweekly via a Web panel. Panelists could have answered multiple times over the course of the project. A cohort of respondents was created to assess how attitudes and behaviors about COVID-19 vaccines evolved. Descriptive statistics and multivariate logistic regressions were performed. Among the 1,914 individuals with no or low intention of getting vaccinated in Fall 2021 (Period 1), 1,476 (77%) reported having received at least two doses in the Winter 2023 (Period 2). Not believing in conspiracy theory (OR = 2.08, 95% CI: 1.65–2.64), being worried about catching COVID-19 (OR = 2.12, 95% CI: 1.65–2.73) and not living in a rural area (ORs of other areas are 2.27, 95% CI: 1.58–3.28; 1.66, 95% CI: 1.23–2.26; 1.82 95% CI: 1.23–2.73) were the three main factors associated with being vaccinated at Period 2. Among the 11,117 individuals not hesitant at Period 1, 1,335 (12%) became hesitant at Period 2. The three main factors significantly associated with becoming vaccine hesitant were the adherence to conspiracy theories (OR = 2.28, 95% CI: 1.95–2.66), being a female (OR = 1.67, 95% CI: 1.48–1.90) and being younger than 65 years old (the ORs for 18–34, 35–49, and 50–64 compared with 65 and over are 2.82, 95% CI: 2.32–3.44; 2.39, 95% CI: 2.00–2.86 and 1.82, 95% CI: 1.55–2.15 respectively). As the pandemic is over, monitoring the evolution of vaccine attitudes and uptake will be important.

Are Web-Based Valuation Surveys for Preference-Based Measures as Reliable as Face-to-Face Surveys? TTO, DCE and DCE with Duration.

Valuation surveys of preference-based measures are typically conducted face-to-face or on web panels. In this survey, we considered whether face-to-face and online surveys were reliable using three tasks: composite time trade-off (cTTO), discrete choice experiment (DCE), and DCE with duration. Respondents (aged 20-69 years) for both face-to-face (N = 1000, target sample size) and web surveys were selected through quota sampling by sex and age from each panel of the general population in Japan. They were then allocated to one of the three tasks and divided into six groups (two survey modes × three tasks, N = 334 per group). For the cTTO, respondents were asked to rate ten health states described by the EQ-5D-5L. For the DCE and DCE with duration surveys, respondents were asked about 15 health-state pairs. For all participants, as in the second-stage survey, a similar process was repeated two weeks after the first survey. Reliability was evaluated by calculating the percentage of agreement and intraclass correlation coefficients. The cTTO scores of the face-to-face and web surveys were systematically different. Between the face-to-face and web surveys, the agreement of the TTO survey was not good. The intraclass correlation coefficient (ICC) was 0.37 for the face-to-face test-test and 0.59 for the web test-retest. Discrete choice experiment (DCE) and DCE with duration had similarly good agreement (more than 70%), regardless of face-to-face or web surveys. However, between the first and second surveys (test-retest) of DCE and DCE with duration, the agreement depends on whether the positions of the two cards (health states) are identical. If the face-to-face cTTO score is the gold standard, a web-based survey of cTTO is not recommended regardless of the ICC. If a DCE survey is performed, positioning effects should be considered.

Effects of COVID-19 measures on access to HIV/STI testing and condoms among adults in Sweden: a cross-sectional online survey.

To investigate the self-reported impact of COVID-19 measures on access to testing for HIV and other sexually transmitted infections (STIs) and condoms and factors associated with reduced access among adults in Sweden. Cross-sectional data were collected in late 2020 through a web panel with adults (18-49 years) in Sweden as part of the International Sexual Health And REproductive health survey (I-SHARE) (N=1307). The primary outcome was self-reported access to HIV/STI testing and condoms during COVID-19 measures. Logistic regression was used to assess adjusted odds ratios of experiencing reduced access to HIV/STI testing and condoms in relation to sociodemographic characteristics, changes in sexual behaviours and COVID-19-related factors. Of the 1138 sexually active respondents, 17% wanted an HIV/STI test, and of those over half (57%) reported reduced access during the COVID-19 measures in 2020. Compared with cis-women, transgender or non-binary respondents were more likely to experience lower access to testing. Among those who usually used condoms (n=568), 23% reported hampered condom access due to COVID-19 restrictions. Reduced condom access was associated with identifying as non-cis gender and a cis-man compared with cis-woman, non-heterosexual orientation, being foreign-born and financially worried. Findings indicate that access to HIV/STI testing and condoms among sexually active adults of reproductive age in Sweden was disrupted during the COVID-19 pandemic in 2020 with varied impact depending on sexual orientation, gender identity or socioeconomic situation. This signals the importance of ensuring equitable access to sexual and reproductive health services and commodities in future crises response.

Анализ характера течения металла при изготовлении авиационных панелей из различных групп алюминиевых сплавов методами изотермической штамповки

The article discusses the results of studies of the features of the formation of shape defects that occur during the manufacture of aircraft panels, shells and other finned parts from aluminum alloys under conditions of isothermal forging and forging in a state of superplasticity. The formation of defects in the manufacture of panels from various groups of aviation aluminum materials, in particular from alloys based on the Al – Mg system, alloys based on the Al – Mg – Si – Cu system, aluminum alloys of the Al – Zn – Mg – Cu system and alloys of the Al – Mg – Li. The mechanisms of the formation of such shape defects that occur during the production of aircraft panels by isothermal stamping are determined as: a sink on the back side of the panel web in the subcostal space, a rupture of the material of the product in the area of the articulation of the rib and the panel web at the final stages of deformation, the formation of a clamp on the side surface of the rib, the appearance of retracted in the body of the product oxide captivity in the central part of the rib. The dependences of the formation of all the previously mentioned defects on the conditions of the temperature-rate parameters of the deformation process are analyzed. Models of the nature of the metal flow during filling of the die cavity at various temperature-speed parameters of deformation are constructed. It has been established that the nature of the metal flow when filling the die cavity depends on a number of parameters, namely: the thickness of the web of the original slab, the temperature conditions of deformation, the speed conditions of deformation, the ratio of the thickness of the rib and the web of the original slab, the ratio of the height of the rib and the web of the original slab. As a result of the research, the parameters of the processes of deformation of aluminum alloys for the manufacture of defect-free parts of aviation equipment were determined under the conditions of minimizing the consumption rates of basic materials.

Strength of I-Girders with Narrow Panels Subjected to Concentrated Loads

This technical note deals with the strength of web panels under concentrated loads, with emphasis on girders with closely spaced transverse stiffeners (commonly referred to as narrow panels). A review of experimental data and data from simulations suggest that girders with closely spaced panels exhibit substantially higher strength to concentrated loads than that calculated in accordance with the 2016 AISC Specification for Structural Steel Buildings. A simple equation to account for a fraction of the excess in strength is proposed.

Physical Intimate Partner Violence and Emotional Harm in Five U.S. States.

The purpose of this study was to assess the relationship between physical intimate partner violence (IPV) victimization and four related aspects of emotional well-being: threat sensitivity, intolerance of uncertainty, impulse control, and access to resources for emotional regulation. We draw on a transactional model of IPV and emotional regulation to theorize how invalidation and partner threats in relationships can generate harmful emotional outcomes. We used representative data collected for residents living in five U.S. states: Colorado, Minnesota, Mississippi, New Jersey, and Texas. Our analytic sample included individuals who reported having been in a romantic relationship in the past year (N = 2,501). Data were collected using a probability-based web panel, between April 29 and May 15, 2022. Following the presentation of descriptive statistics and bivariate correlations, we developed a series of four multivariate models (ordinary least squares [OLS], negative binomial) to analyze the association between IPV victimization and each emotional outcome. All models adjusted for pertinent demographic and geographic control measures. Physical IPV victimization was associated with increased intolerance of uncertainty and heightened threat sensitivity. IPV victimization also corresponded with poorer impulse control and fewer resources for emotional regulation. Overall, our results demonstrate that experiences of physical IPV victimization are linked to poorer emotional outcomes. These outcomes can be harmful to broader mental health and potentially impact long-term well-being. The findings underscore the importance of mental health screenings that extend beyond assessments of diagnostic-level functions and allocating resources toward alleviating other clinically relevant factors that might arise from or even prompt additional exposure to physical IPV.

Blood Count Scattergrams Are Fingerprints of Blood: Using AI to Inform Health Status

Introduction: Blood count analysers are routinely used to assess health status and for disease monitoring. The major analysers generate more than 300 red cell, leukocyte and platelet parameters. However, in clinical practice, only 10-20 are utilised; a greater number are reviewed by laboratories but some are merely for ensuring instrument stability and quality assurance. Although there are hundreds more measurable parameters available through extended analytical channels, these are not assessed due to the complexity of the numerical analysis and questions as to the clinical utility. However, these extended analytical parameters have potential to be used to generate real-time ‘3-Dimensional (3-D)‘ details of blood cells. Aim: In this study we assessed 312 parameters generated from 5,800 patient samples (of all ages and genders) at a tertiary care hospital (National Institute of Blood Disease, Karachi-Pakistan). These were anonymously outputted and processed by machine learning (ML). Method: The methodology of the present study was based on the waterfall model. The output data from a haematology analyser (Sysmex XN-1000, Kobe Japan) in CSV format, having a total 433 columns, was pre-processed to remove unnecessary features (such as date, analysis details, rack position, receiving time, alerts and others) using Pandas and Numpy libraries, and where required scaling was performed. Data labeling was conducted on conclusions reported on their respective confirmatory tests. The processed data (which included 312 features of the total 433 columns) was labeled (with 67 conclusions on their confirmatory tests). The extracted data was fed to the artificial intelligence Machine Learning models through Python modules and libraries for training, testing, and validation purposes. The web application was developed on modern Python framework (Flask) to automate and provide an option of ‘drag and drop’ the CSV file exported from analyser, we connected pre-processing (data engineering), Machine Learning, and Prediction view by set of different tools (majorly JavaScript libraries). This generated various metrics including accuracy, precision, recall and the mean of precision and recall (F1 score) in relation to the prediction (results) from the CSV file submitted to our system. For each forecast the entire precision report and prediction box were added an optional visualisation on our web panel. Results: Analysis of 1.8 million data points (312 parameters x 5,800 samples) presented promising predictive potential, as, on principal component analysis (PCA) pilot the total variance was remained 41.6% showing that a linear combination of parameters can explain much variability. On a heat map the clustering and visualisation advocated the predictive potential and signatory deviational trends (fingerprints) respectively of these 3-D blood cell features. Examples included separation of myeloid from lymphoid, chronic from acute, bacteria from viral, deficiency of iron from deficiency from vitamin B12 / Folic acid, and differentiation of haemoglobinopathies. The patterns of normal, immature and abnormal blood cells under the title of cell population data was well demonstrated from results of our machine learning models. Of note, we observed an accuracy of 85.6% along with 91.2% precision for one of the ML models used (Random Forest Classifier). Conclusion: The opportunities and challenges of such high dimensional cell population data derived from a complete blood count can provide a novel patient-specific haematological fingerprint. This extended deviational patterning (fingerprint) can provide interpretive diagnostic data with practical disease-specific patterns. This pilot study shows that complete blood count data driven machine learning applications has great potential to uncover disease-associated patterns which could be applied in practice. It also has capacity to provide baseline testing would could assist in sequential health monitoring and potentially the generation of personal reference ranges.

Attitudes and behaviours regarding e-cigarettes in people aged 15–30 years in the UK: a cross-sectional study

BackgroundThe use of e-cigarettes has been rising in the UK, with 7·7% of people aged over 16 years currently vaping daily or occasionally. Young people aged 16–24 years have the highest proportion of vapers at 11·1%. Therefore, this study investigated behaviours, attitudes, and beliefs about e-cigarettes among people aged 15–30 year in the UK. MethodsFor this cross-sectional study, we administered an online survey to a representative sample of people aged 15–30 years in the UK (based on a web panel) between Oct 1, and Nov 30, 2021. Questions related to respondent demographics; use of vaping or smoking products; motivations, attitudes, and behaviours related to vaping; and exposure to e-cigarette advertising. Ever use was described as use even “just once or twice”. We used multivariable logistic regression to identify factors associated with ever e-cigarette use. Findings1009 participants responded to the survey (mean age 23 years, 520 [51·5%] women, 470 [46.6%] men) and were included in the study. 222 (22·3%) participants vaped at least monthly, with one in ten doing it daily. Current smokers were the most likely to use e-cigarettes (453, 44·9%), followed by previous smokers (288, 28·5%) and never smokers (23, 2·3%). Of the 222 participants vaping at least monthly, 199 (89·6%) had used e-cigarettes containing nicotine. The most common reasons for vaping were having friends who used e-cigarettes (103, 46·4%) and quitting or reducing smoking (89, 40·1%). Most participants agreed that e-cigarettes are addictive (698, 75·1%), help people quitting smoking (597, 64·2%), and are bad for health (584, 62·8%). Warning labels on e-cigarettes were seen by 611 (65·7%) participants, and 489 (52·6%) had been exposed to e-cigarette advertising, especially online. Previous or current tobacco smokers were nine and 22 times more likely to use e-cigarettes than never smokers, respectively (odds ratio [OR] 8·5, 95% CI 5·2–14·0 for previous smokers and 22·3, 12·2–40·7 for current smokers). Perceiving e-cigarettes as harmful was associated with a 40% lower likelihood of vaping (OR 0·6, 0·49–0·83). InterpretationVaping seems relatively common among people aged 15–30 years in the UK, mainly among previous and current smokers. Caution should be taken as these findings might not be generalisable to the young UK population, and cross-sectional associations might not be causal. However, perceiving e-cigarettes as harmful might reduce their use, and many users seem unaware of their potential harms, which emphasises the need for further regulation on labelling, marketing, and sales. FundingNational Health and Medical Council.

Elastic local buckling coefficients of I-shaped beams considering flange–web interaction

Since using high–strength and high–performance steels has become a more common structural design practice in building and bridge construction, there is an increased potential for designing extremely thin-walled I-shaped beam members to enhance the efficiency of the steel beam design. For a more accurate design approach for these thin-walled I-beam members, particularly when they are near noncompact limits, it is necessary to explore more rational methods for determining the elastic local buckling strength of I-beams. This study aimed to investigate the local buckling behavior and strength of I-shape structural sections by considering flange-web interactions through three-dimensional finite element analysis. The goal was to provide a more reasonable estimation of local buckling strength under uniform bending. To evaluate the local buckling behavior of flange and web panels and explain it reasonably, this study adopted the ratio of flange-web slenderness (λf/λw) and height-to-width ratio (H/bf) of I-shaped beams which can affect buckling mode shapes and local buckling strength of I-shaped beams induced by flange local and web bend bucklings. Finally, this study presented design equations for both flange local and web-bend buckling coefficients considering λf/λw and H/bf. It was expected that the presented local buckling coefficients (kf) for flanges and webs could lead to a more reasonable design, as compared to the existing AISC design provisions.

COVID-19 vaccination attitudes, values, intentions: US parents for their children, September 2021

ObjectivesTo compare vaccine-related attitudes and values of parents of children 2–17 years old to other adults, examine intentions to vaccinate their children, and identify factors associated with intending to vaccinate children. MethodsA nationally representative survey was conducted in September 2021 (just before the EUA for children 5–11 years old) using Ipsos KnowledgePanel, a probability-based web panel. The survey measured COVID-19 vaccination status, intentions, attitudes, values, and trust in public health authorities among US adults. Scale response options to survey items were dichotomized, and cross-tabulations and logistic regressions were performed. ResultsParents had lower odds of reporting being vaccinated against COVID-19 than other adults even after adjusting for associated sociodemographic characteristics such as age (aOR: 0.66; 95 %CI: 0.50–0.87). The most prevalent parental concerns about COVID-19 vaccines included the speed of their development (88 %), potential side effects (78 %), suspicion of government (77 %), and suspicion of pharmaceutical companies (72 %). Fewer than half (42 %) of parents intended to vaccinate their children 5–11 years old, while 38 % were uncertain and 20 % were unlikely to ever vaccinate their children. Vaccinated parents had higher odds than unvaccinated parents of intending to vaccinate their children (OR: 675.51; 95 %CI: 106.46–4286.12). Discussions with healthcare providers who encouraged COVID-19 vaccination were positively associated with intent to vaccinate children (OR: 11.29; 95 %CI: 2.60–49.02). ConclusionsWe found parental vaccination and conversations with providers were positively associated with intent to vaccinate children. Decisions about childhood vaccination need to be supported by healthcare providers and a public health system that makes vaccine access and related information equitable and accessible. Vaccination-related decision making should be guided by healthcare providers and provide information about safety and risk to children.

Four-Layer QoS Analysis for Multimedia Traffic over Wi-Fi Network at UPNVJ Laboratory

One technique to evaluate and enhance the quality of telecommunications services is to monitor and measure the Quality of Service (QoS) and the user’s Quality of Experience (QoE). This method is suitable to be performed in an area that provides public Wi-Fi for multi-user, such as Wi-Fi at the UPN Veteran Jakarta Electrical Engineering Laboratory. The survey results show that there are still many issues experienced by users regarding the availability, accessibility, retainability, and stability of the network and application services accessed. The multimedia application services analyzed in this study are WhatsApp Desktop Call (voice traffic), Zoom Meeting (video traffic), and the UPNVJ LeADS web (data traffic). The tools used for data collection are Wireshark, PRTG, router admin panel web, and Command Prompt. Based on the monitoring, it was found that: network quality degrades when connected to more than 5 devices at the same time, frequent downtime conditions can reach 54% in a day, and the average data packet traffic speed across one device is 4,34 Mbps. Based on the average calculation of the QoS parameters measured: the highest throughput value is obtained on the UPNVJ LeADS web which reaches 102,09 Kbps, the highest delay value is obtained in the WA Desktop Call which reaches 521,39 ms, the highest jitter value is obtained in the WA Desktop Call which reaches 1,21 ms, and the highest packet loss value is obtained in Zoom Meeting which reaches 2,16%. The most common issue experienced by users is the “no internet” condition on the Wi-Fi network. The solution for network optimization in this condition can be done by administration setting and network management.

Analysis of beam web panels with full length transverse stiffener in compression

The web panels of metal sections subjected to compression have resistances that are often driven by local buckling. Transverse stiffeners are used to increase their resistance. These stiffeners can be arranged at different positions in relation to the edge of the metal section. The strength of the stiffened panel can be compared to that of a compressed element whose cross-section consists of the stiffener and a participating length of the web. To observe the behavior of these stiffened walls and to evaluate the existing analytical calculation methods, an experimental campaign was carried out on two metal sections of different heights, stiffened or not over their entire height of the web. Thus, 33 zones of stiffened or unstiffened panels are tested in double localized compression until failure. The stiffeners are placed near the edge or in the middle of the panel and welded on both sides of the web over its entire height and on the panel flanges. In parallel, a finite element model using shell elements and non-linear calculations considering the plasticity of the materials, the geometrical imperfections and the large displacements is set up. It is validated by comparing its force–displacement curves and modes of ruin with those obtained by tests. The model thus validated makes it possible to enrich the results of the experimental tests to better describe the behavior of stiffened walls subjected to compression. It also allows to discuss the observed failure modes and some analytical formulas which estimate the resistance capacities of the stiffened panels.

Buckling analysis of steel members by extension of EC‐3 methods in bridge girders under Patch Loading

AbstractThe buckling “General Method” of EN 1993‐1‐1 and EN 1993‐1‐5 can be applied to solve problems characterized by non‐uniform geometries and complex stress fields. A typical example occurs during the incremental launching of bridge girders with slender web panel subjected to patch loading. However, this method does not explicitly provide the most critical verification point of a structural element and does not allow to consider the mechanical interaction between instability modes. The objective of the study is the development of a novel methodology that can solve these important special design issues, using a completely automatic process by linear static and linear buckling analyses only. The procedure provides the definition of a slenderness parameter for each point of the structure, in order to avoid the nonlinear analyses with imperfections permutation (as described in Annex C of EN 1993‐1‐5) that require a high computational effort. This pointwise slenderness parameter indicates not only where the slenderness is maximum in each buckling mode, but also the slenderness in other points of the structural elements. This would allow to consider the interaction between global and local buckling, with the definition of an equivalent slenderness parameter for buckling modes coupling.

Seismic behaviour of high‐strength steel welded flange‐bolted web connections

AbstractCyclic loading tests on two groups of welded flange‐bolted web connections employing 690 MPa high‐strength steels were conducted to quantify their plastic deformation and energy dissipation capacities under seismic loading conditions. The Q355 and Q690 beams in the two groups of specimens were designed with Class 1 and Class 3 cross‐sections, respectively; however, the Q690 columns in each group were designed nearly identical except for the thickness of their webs, which varied in order to identify the effect of shear panel strength on the connection seismic performance. Different beam‐to‐column flange welding types in each group were also considered. It was found that welding without backing bars should be used between Q690 beams and columns to accommodate some plastic rotation in the order of 0.01 rad in the beams, while a plastic shear distortion as high as 0.04 rad could be developed in Q690 web panels. This evidenced that those Q690 joint components could still sustain appreciable plastic deformations. In particular, Q690 web panels could be even qualified as high‐ductility class (DCH) in Eurocode 8.

Hysteretic behaviour of welded connections with highly inelastic panel zones

AbstractThe current practice in capacity‐designed steel moment resisting frames (MRFs) worldwide allows for limited shear yielding in the column web panel zone. As such, inelastic deformations concentrate near the beam ends, thereby leading to flexural strength deterioration due to local buckling often at modest lateral drift demands. Experiments on post‐Northridge welded connections suggest that prior to a story drift angle of 5% rad, panel zone kinking does not induce fracture for panel zone shear distortions of up to 10γy. Within such a context, this paper presents an alternative design of a welded moment connection with highly inelastic panel zones. The connection features simplified weld details including a customised beveled backing bar that can be kept in place after the completion of the complete joint penetration welds at the beam flange‐to‐column flange joint. Full scale experiments suggest that the hysteretic response of the connection remains stable up until a story drift angle of 8% rad. The specimen did not exhibit visible structural damage prior to story drift angles of 4% rad, which are characteristic to a maximum considered earthquake. Modest local buckling occurred near the beam ends only after a story drift angle of 5% rad, which is a typical drift threshold in current collapse assessment methodologies. This paper summarises the primary findings of the experimental program for one of the test specimens.

A generalised mechanical model for the characterisation of steel joints

AbstractComponent‐based mechanical models compliant with Eurocode 3 becomes a popular alternative to complex Finite Element (FE) analyses for characterising the behaviour of steel joints. However, several key aspects are not accommodated by the existing spring models, i.e., group mechanisms, component interactions, and the variation of the shear force on the height of the column web panel. This paper introduces an innovative mechanical model suitable for the characterisation of structural joints under generalised loading. The model relies on the principles of the Component Method and incorporates the features systematically disregarded in the classical spring models. This guarantees code‐compliant predictions, and by virtue of its universality, the model can be used for any loading protocol (bending moment ‐ sagging or hogging, axial force, bending moment + axial force). Conclusive evidence given by comparisons with experimental data and analytical results shows the compliance of the proposed model with the Eurocode 3 and proves its accuracy in predicting the actual behaviour of steel joints. The proposed modelling methodology allows integrating the model as a macro‐element in dedicated software, thus presenting promising perspectives for reliable and time efficient structural analyses.

Buckling resistance of stiffened panels subjected to constant transverse compression stresses

AbstractIn a box girder cross‐section with inclined web panel, transverse compression may be introduced into the bottom panel from both sides in addition to constant longitudinal compressive stresses. In EN 1993‐1‐5, the only analytical method for determining the resistance of panels to biaxial compression is the Reduced Stress Method (RSM). However, the current rules were mainly derived for longitudinal stresses. Due to missing rules, in practice the longitudinal stiffeners need being verified according to flexural member buckling considering the transverse updrift forces.Therefore, in order to assess the real behaviour, a large parametric study of stiffened panels with closed longitudinal stiffeners under transverse compressive stresses was carried out using a verified numerical model. LBA and GMNIA are performed for each case. To apply the RSM, all critical buckling stresses were determined considering the torsional stiffness of stiffeners. According to EN 1993‐1‐5, the support of the edges of the panels parallel to the load direction should be set free when determining the critical stress for column‐like behaviour. In the case of a longitudinally stiffened panel under transverse stresses, it is not clear whether the support of the plate and the stiffeners or only the plate should be released. In this paper, these interpretations are discussed and results are compared. Finally, a simplified procedure to determine the global reduction factor of plate buckling for transverse stresses in a single step is proposed.

Full‐Scale Composite Moment‐Resisting Frame with Dissipative Bolted Connections under Monotonic Loads: Experimental versus Numerical Results

AbstractThe detailing of typical semi‐rigid beam‐to‐column joints in Germany was based on the assumption of low seismic actions, thus design could be covered by wind and gravity actions. Given the recent seismic hazard assessment of the national territory, in which the seismic risk was proved to be higher than formerly considered, questions have been raised about the approach to steel and composite joint design and detailing. Answers to the effect of increased seismic demands on semi‐rigid connections and to joint performance are provided in new studies of the authors. The performance (insufficient bending resistance and stiffness, brittle failures) and detailing deficiencies (small weld sizes, weak web panel) require improvements in order for joints to transfer higher bending moments and to conform to prEN 1998‐1‐2. Pre‐test analyses showed that, in comparison with current typical joints, improved solutions have 40% / 70% higher sagging / hogging bending resistance and sustain plastic deformations within connections prior to failure. Thus, the performance of joints designed for moderate‐low seismicity is experimentally assessed through monotonic and cyclic tests on composite frame specimens. The focus of the paper is on the monotonic response.