Durability Assessment Based on Design-value Method for Structure Design

Jitao Yao,Hui Gu 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.4

A significant durability assessment for structure design is devoted to guarantee the necessary service life for its safety andsustainability. A flexible probability assessment method here is improved based on the corrosive cracking life criterion theory modelused in China and improved the design-value method mentioned in ISO2394. It first built an assessment expression consisted ofdesign values and service life, considering limit state function and First Order Reliability Methods (FORM). Then, it took intoaccount the uncertainties and variability about the main random variables in this assessment expression: concrete cover thickness,compressive strength and carbonation depth calculation model uncertainty factor, ignored the secondary variables with littlevariability. Last, by introducing and improving design-value method, it can directly calculate the service life with flexibly reliabilityindex chosen for durability design assessment. This calculation results are easy to contrast with the target index to assess. Withouttraditional reliability calculation, it flexibly evaluated durability design with reliability index of safety results.

Discussion of Sensitivity Factors and Dominating Variable for Design Value Method

Jitao Yao,Kaikai Cheng 대한토목학회 2017 KSCE Journal of Civil Engineering Vol.21 No.1

The partial factor method is considered to be one of the most reliable design methods. However, engineers have examined the shortcomings of the partial factor method, primarily its flexibility and generality in searching for the values of partial factors. In order to improve upon the partial factor method, the design value method has been established on the basis of probability. The design value method is more flexible, general, and represents the developing direction of the reliability design method. However, based on experience, a set of sensitivity factors αi values has been developed. The sum of squares may be greater than 1.0 as a result of conservatism. Although some researchers have revised the values of αi by using the enumeration optimization method, the results are not ideal. This paper focuses on the recommended values of sensitivity factors that are applicable to the safety design as well as the serviceability design. It will be shown that these recommended values can improve the accuracy of the reliability index and present specific ranges of relative errors. This makes it possible to establish a practical design value method based on probability. In addition, a method to determine the dominating parameter is illustrated.

Experimental research on masonry mechanics and failure under biaxial compression

Ren Xin,Jitao Yao,Yan Zhao 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.61 No.1

This study aimed to develop a simple and effective method to facilitate the experimental research on mechanical properties of masonry under biaxial compressive stress. A series of tests on full-scale brick masonry panels under biaxial compression have been performed in limited principal stress ratios oriented at various angles to the bed joints. Failure modes of tested panels were observed and failure features were analyzed to reveal the mechanical behavior of masonry under biaxial compression. Based on the experimental data, the failure curve in terms of two orthotropic principal stresses has been presented and the failure criterion of brick masonry in the form of the tensor polynomial has been established, which indicate that the anisotropy for masonry is closely related to the difference of applied stress as well as the orientation of bed joints. Further, compared with previous failure curves and criteria for masonry, it can be found that the relative strength of mortar and block has a considerable effect on the degree of anisotropy for masonry. The test results demonstrate the validity of the proposed experimental method for the approximation of masonry failure under biaxial compressive stress and provide valuable information used to establish experimentally based methodologies for the improvement of masonry failure criteria.

The Statistical Methods of Membership Function in Structural Serviceability Failure Criterion

Jun Gao,Jitao Yao,Liuzhuo Chen 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.11

The failure criterion of structural serviceability is often fuzzy, which has a direct impact on the results of structural reliability analysis. Membership function is a basic mathematical tool to describe the fuzziness of failure criteria. At present, the fuzzy statistical method for generating the fuzzy set membership function is to take the numerical interval of the fuzzy set as a sample, and directly generate the membership function through statistics. However, this kind of sample will cover the uncertainty of the individual's understanding of fuzzy boundaries to a certain extent, and its statistical results are difficult to truly reflect the characteristics of fuzzy sets. The fuzzy boundary is described by the membership density function, and the numerical interval covering the fuzzy boundary is taken as the sample. The fuzzy statistical method for generating the membership density function is proposed, and the indirect statistical method for generating the membership function is established. The comparative analysis results show that the membership functions generated by the two statistical methods are different. The membership function generated by indirect statistical method can fully reflect the uncertainty of the individual's understanding of the fuzzy boundary, more truly reflect the characteristics of the fuzzy set, and provide a more solid foundation for the fuzzy probability analysis of structural serviceability.

Reliability analysis of Industrial plant reinforced concrete columns

Cheng, Zhengjie,Yao, Jitao,Gao, Jun Techno-Press 2022 Advances in concrete construction Vol.14 No.2

Based on the design of reinforced concrete columns in Chinese design codes, the failure function of reinforced concrete (RC) columns cannot be expressed as a linear function. This makes it difficult to reveal the level of reliability control in Chinese design code. Therefore, the failure function of dimensionless form is established in this paper, and the typical components (Industrial plant columns) are selected for analysis. At last, numerical simulation proves that the proposed model can be used to analysis reliability of columns. The results based on this model indicate that there is a strong difference in the reliability of RC columns designed with different design parameters, and the reliability would be lower when the eccentricity produced by crane load is smaller.

Flexural Properties of Lithium Slag Concrete Beams Subjected to Loading and Thermal-Cold Cycles

Liuzhuo Chen,Jitao Yao,Guangtai Zhang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.2

This paper presents the flexural test results of 10 lithium slag reinforced concrete beams (120 × 200 × 1,100 mm3) subjected to the combined effect of loading and Thermal-Cold (TC) cycles. The parameters include the polypropylene (PP) fibers, number of TC cycles and level of flexural loading. The results show that the cracking load, ultimate load, maximum crack width and deflection improve significantly after 100 TC cycles and deteriorate slightly after 300 TC cycles. As the percentage of the peak moment, which is an experimental value, increases from 0.20 to 0.35, the deflection decreases, the cracking load increases, and there is no noticeable change in the ultimate load. Further, the addition of PP fibers to the concrete beams enhances both the cracking load and the ultimate load, reduces the maximum crack width, and improves the resistance to erosion.

Role of Transcutaneous Electrical Nerve Stimulation in Treating Children With Overactive Bladder From Pooled Analysis of 8 Randomized Controlled Trials

Huanqin Cui,Yi Yao,Zhunan Xu,Zhenli Gao,Jitao Wu,Zhongbao Zhou,Yuanshan Cui 대한배뇨장애요실금학회 2020 International Neurourology Journal Vol.24 No.1

Purpose: Transcutaneous electrical neural stimulation (TENS), as a non-invasive modality, has been clinically used as an alternative treatment for children with overactive bladder (OAB). We conducted a pooled analysis to explore the effect of TENS on OAB. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-analysis guideline was followed in this study. The MEDLINE, Embase, and Cochrane Central Register of Controlled Trials databases, as well as the reference lists of the retrieved studies, were used to find trials relevant for assessing the use of TENS to treat OAB. Results: Of the 246 records identified, 8 publications were analyzed in our study. Our analysis found that TENS resulted in a greater decrease of wet days/wk, daily voiding frequency, daily incontinence episodes, and daily number of voids than was observed in the control group. Furthermore, TENS-treated patients showed similar visual analogue scale (VAS) scores to patients in the control group, demonstrating that the application of TENS did not increase patients’ discomfort and pain. TENS had a relative advantage in the number of partial responses, but no clear differences were found in frequency of no response or a full response compared to the control group. In urodynamic testing, TENS led to obvious improvements in average voided volume and maximum voided volume in children with OAB. Conclusions: TENS had a remarkable effect on the improvement of urodynamic indexes and objective OAB symptoms without a significant increase in VAS scores for children with OAB.