Impact of corrosion deterioration on the seismic performance of steel frame structures

Steel structures designed before the introduction of modern seismic design codes may be characterised by high seismic vulnerability due to their reduced ductility capacity. Additionally, these structures may be affected by significant corrosion deterioration, as one of the major atmospheric degradation phenomena when built in corrosive environments. Corrosion deterioration leads to a thickness reduction of sections, reduced bearing capacity, stiffness degradation and loss of energy dissipation capacity. Thus, old-corroded steel structures located in seismically active regions could experience a reduction of their seismic performance, significantly increasing the failure probability under earthquake events. The present study investigates the effect of atmospheric corrosion deterioration on steel frames and uses a nonseismically designed three-storey moment-resisting frame for case-study purposes. Atmospheric corrosion models based on the recommendation of ISO 9224:2012 have been adopted considering a 50-years ageing time and modelled as uniform corrosion on steel members. A probabilistic seismic performance assessment of the pristine and ageing steel frames is performed through Incremental Dynamic Analyses (IDAs). IDAs are performed for a set of 43 ground motion records accounting for the influence of the earthquake input’s uncertainty (i.e., the record-to-record variability). The corrosion effects on the seismic performance are evaluated by monitoring both global and local engineering demand parameters (EDPs), allowing the development of seismic fragility functions at components- and system-level

Influence of corrosion on failure modes and lifetime seismic vulnerability assessment of low‐ductility RC frames

Corrosion of reinforced concrete (RC) structures constitutes a critical form of environmental deterioration and may significantly increase the vulnerability of old non‐seismically designed buildings during earthquake events. This study proposes a probabilistic framework to evaluate the influence of corrosion deterioration on the lifetime seismic fragility of low‐ductility RC frame buildings. In contrast to limited past literature on this topic, the proposed framework offers novel contributions. This is one of the first study to consider potential alteration in failure modes of building components (from flexure to flexure‐shear) due to the time‐dependent aging process. Numerical models validated with past experimental test results are utilized to capture these failure modes, which are particularly relevant for low ductility RC frames designed prior to the introduction of modern seismic codes. Secondly, given the gamut of uncertainties associated with the corrosion process, this study develops condition‐dependent seismic fragility functions independent from an assumed exposure scenario, as often done in literature. These functions can be easily adopted by design engineers and stakeholders for prompt fragility assessment, and subsequent decision‐making without the need for computationally expensive finite element (FE) model runs. The proposed framework is demonstrated on a benchmark three‐story RC frame that considers time‐varying seismic demand models and damage state thresholds while accounting for the uncertain corrosion deterioration process and ground motion record‐to‐record variability

Comparative evaluation of efficacy and safety of methyldopa and labetalol in pregnancy‑induced hypertension: A meta‑analysis

Introduction: Methyldopa and labetalol are the drugs that frequently used for the management of pregnancy‑induced hypertension. But fewer data available for the efficacy and safety of their use. So, here we are doing a systemic review for the safety and efficacy of methyldopa in comparison to labetalol.Objectives: Assessment of efficacy and safety of methyldopa versus labetalol in pregnancy‑induced hypertension.Method: A total of 10 randomized controlled trials (RCTs) following PRISMA guidelines (2015) and have included pregnant women who developed hypertension after the 20th week of gestation and receiving methyldopa (100–400 mg/day) or labetalol (250–1000 mg/day). All RCTs with changes in mean arterial pressure (MAP) before and after drug administration was collected. The adverse effects of the respective drugs were also noted. RevMan 5.3 software was used for the calculation of standardized mean difference (SMD). P value less than 0.05 will be considered significant.Result: Data of 1,200 patients were included in our study. Both the drug decreases MAP statistically significantly. In the labetalol group, P value was statistically significant (random effect model P < 0.005 and in the fixed‑effect model <0.001). In methyldopa group, P < 0.001, significant in fixed effect. In the majority of the studies, the difference in the reduction of MAP was higher in labetalol than methyldopa. In labetalol vs methyldopa study using random‑effect model SMD was 1.568 (95% CI, 0.735 to 2.401, P < 0.001). Drowsiness, headache, nausea, vomiting, weakness, and myalgia were associated with drugs. Out of the six adverse effects, there was a significant difference found in drowsiness (P = 0.023) which was seenmore in patients receiving methyldopa. There was no significant difference in the prevalence of the other maternal side effects.Conclusions: Labetalol is more efficacious and safer as compared to methyldopa. Key words: Efficacy; labetalol; methyldopa; pregnancy‑induced hypertension; safety