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Abstract Our center has observed a substantial increase in the detection rate of fetal left–right(LR) asymmetry disorders between March and May 2023. This finding has raised concerns because these pregnant women experienced the peak outbreak of SARS-CoV-2 in China during their first trimester. To explore the relationship between maternal SARS-CoV-2 infection and fetal LR asymmetry disorders. A retrospective collection of clinical and ultrasound data diagnosed as fetal LR asymmetry disorders was conducted from January 2018 to December 2023. The case–control study involved fetuses with LR asymmetry disorders and normal fetuses in a 1:1 ratio. We evaluated and compared the clinical and fetal ultrasound findings in pregnant women with SARS-CoV-2 infection and pregnant women without infection. The Student t-test was utilized to compare continuous variables, while the chi-squared test was employed for univariable analyses. The incidence rate of LR asymmetry disorders from 2018 to 2023 was as follows: 0.17‰, 0.63‰, 0.61‰, 0.57‰, 0.59‰, and 3.24‰, respectively. A total of 30 fetuses with LR asymmetry disorders and 30 normal fetuses were included. This case–control study found that SARS-CoV-2 infection (96.67% vs 3.33%, P = .026) and infection during the first trimester (96.55% vs 3.45%, P = .008) were identified as risk factors. The odds ratio values were 10.545 (95% CI 1.227, 90.662) and 13.067 (95% CI 1.467, 116.419) respectively. In cases of SARS-CoV-2 infection in the first trimester, the majority of infections (88.1%, 37/42) occurred between 5 and 6 weeks of gestation. We found that 43.7% (66/151) of fetuses with LR asymmetry disorder had associated malformations, 90.9% (60/66) exhibited cardiac malformations. SARS-CoV-2 infection during the first trimester significantly increases the risk of fetal LR asymmetry disorders, particularly when the infection occurs between 5 and 6 gestation weeks. The most common associated malformation is heart malformation.

In order to explore the structural stress characteristics of rocking timber frame in Song Dynasty, the scale model of 1∶2 Song-style four-column four-beam wood frame was tested by horizontal low-cycle reciprocating test. On the basis of the change characteristics of hysteresis curve, skeleton curve, and stiffness degradation curve, the yield stiffness of hysteresis loop, recovery coefficient of displacement, and inter-story displacement concentration factor were used to explore the recoverability of timber frame. The results show that the narrow S-shaped band hysteretic loops are similar, and their equivalent stiffness values degrade significantly. When the horizontal displacement exceeds the yield displacement, the yield stiffness of hysteresis loop approaches overall yield stiffness; The displacement recovery coefficient is between 0.6 and 0.8, and the timber frame has good displacement recovery ability. The inter-story displacement concentration coefficient of the timber frame is between 1.08 and 1.65, and the horizontal deformation is concentrated in the column frame layer, which is the source of timber frame resilience. The research results are the basis of establishing the theoretical analysis model of traditional timber frame, and can provide reference for the current situation evaluation and reinforcement and repair of existing ancient wooden structures.

In order to accurately use numerical analysis results to evaluate seismic performance, a quantitative relationship between the parameters of the ideal finite element model (FEM) and full-scale test model (FTM) of historic timber structures must be established. In this study, a single-story full-scale timber structure with four columns and Dou-gongs that was common during the Song dynasty of China (A.D. 960–1279) was taken as the object, and pseudo-static test (or simulation) analysis was carried out on the FTM and the corresponding FEM. The numerical model was consistent with the test model in terms of the structural deformation pattern and stress characteristics of the key nodes. The key-point loads of the skeleton curves, stiffness ratio, ductility coefficient, and stiffness relationship were quantitatively established for the two models. Accordingly, approximate formulas for the above relationships were proposed. [ABSTRACT FROM AUTHOR]