Development of Features for Early Detection of Defects and Assessment of Bridge Decks

Damage detection is an important area with growing interest in mechanical and structural engineering.One of the critical issues in damage detection is how to determine indices sensitive to the structural damage and insensitive to the surrounding environmental variations.Current damage identification indices commonly focus on structural dynamic characteristics such as natural frequencies,mode shapes,and frequency responses.This study aimed at developing a technique based on energy Curvature Difference,power spectrum density,correlation-based index,load distribution factor,and neutral axis shift to assess the bridge deck condition.In addition to tracking energy and frequency over time using wavelet packet transform,in order to further demonstrate the feasibility and validity of the proposed technique for bridge condition assessment,experimental strain data measured from two stages of a bridge in the different intervals were used.The comparative analysis results of the bridge in first and second stage show changes in the proposed feature values.It is concluded,these changes in the values of the proposed features can be used to assess the bridge deck performance.

Efficacy and safety of systematic corticosteroids among severe COVID-19 patients:a systematic review and meta-analysis of randomized controlled trials

The benefits and harms of corticosteroids for patients with severe coronavirus disease 2019(COVID-19)remain unclear.We systematically searched PubMed,Embase,and Cochrane Central Register of Controlled Trials from December 31,2019 to October 1,2020 to identify randomized controlled trials(RCTs)that evaluated corticosteroids in severe COVID-19 patients.The primary outcome was all-cause mortality at the longest follow-up.Secondary outcomes included a composite disease progression(progression to intubation,ventilation,extracorporeal membrane oxygenation,ICU transfer,or death among those not ventilated at enrollment)and incidence of serious adverse events.A random-effects model was applied to calculate risk ratio(RR)with 95%confidence intervals(Cis).We used the Grading of Recommendations Assessment,Development,and Evaluation approach to evaluate the certainty of the evidence.Seven RCTs involving 6250 patients were included,of which the Randomized Evaluation of COVID-19 Therapy(RECOVERY)trial comprised nearly 78%of all included subjects.Results showed that corticosteroids were associated with a decreased all-cause mortality(27.3 vs.31.1%;RR:0.85;95%CI:0.73-0.99;P=0.04;low-certainty evidence).Trial sequential analysis suggested that more trials were still required to confirm the results.However,such survival benefit was absent if RECOVERY trial was excluded(RR:0.83;95%CI:0.65-1.06;P=0.13).Furthermore,corticosteroids decreased the occurrence of composite disease progression(30.6 vs.33.3%;RR:0.77;95%CI:0.64-0.92;P=0.005),but not increased the incidence of serious'adverse events(3.5 vs.3.4%;RR:1.16;95%CI:0.39-3.43;P=0.79).