Time-Dependent Reliability Analysis of Corroded Steel Beam

Biao Nie,Shanhua Xu,Youde Wang 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.1

The time-dependent reliability of corroded steel beam was investigated. Nine groups of specimenswere subjected to accelerate corrosion by the outdoor periodic spray test and monotonic tensile test. The surface profile of corroded steel plates and the 3D data of corrosion depth were measured by the three-dimensional non-contact surface topography instrument (PS50 3D). The probability distribution of corrosion depth and nominal yield strength of corroded steel plates were studied. Finally, a probabilistic limit state equation for corroded steel beams was established and the time-dependent failure probability and reliability index of corroded steel beams was calculated by Monte Carlo simulation method (MCS). The results of study show that the corrosion depth on steel plate surface and nominal yield strength of corroded steel plate conformed to the normal distribution. With the increase of corrosion time, the average, the standard deviation of the corrosion depth and relative yield strength increased while the mean of relative yield strength, nominal yield strength, nominal ultimate strength, the elongation decreased. The reliability index decreased rapidly with corrosion time, which shows that the reliability of steel structures under the aggressive environmental should be caused attention.

Experimental and numerical studies on the behaviour of corroded cold-formed steel columns

Nie Biao,Xu Shanhua,Zhang Haijiang,Zhang Zongxing 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.5

Experimental investigation and finite element analysis of corroded cold-formed steel (CFS) columns are presented. 11 tensile coupon specimens and 6 stub columns of corroded CFS that had a channel section of C160x60x20 were subjected to monotonic tensile tests and axial compression tests, respectively. The degradation laws of the mechanical properties of the tensile coupon specimens and stub columns were analysed. An appropriate finite element model for the corroded CFS columns was proposed and the influence of local corrosion on the stability performance of the columns was studied by finite element analysis. Finally, the axial capacity of the experimental results was compared with the predictions obtained from the existing design specifications. The results indicated that with an increasing average thickness loss ratio, the ultimate strength, elastic modulus and yield strength decreased for the tensile coupon specimens. Local buckling deformation was not noticeable until the load reached about 90% of the ultimate load for the non-corroded columns, while local buckling deformation was observed when the load was only 40% of the ultimate load for the corroded columns. The maximum reduction of the ultimate load and critical buckling load was 57% and 81.7%, respectively, compared to those values for the non-corroded columns. The ultimate load of the columns with web thickness reduced by 2 mm was 53% lower than that of the non-corroded columns, which indicates that web corrosion most significantly affects the bearing capacity of the columns with localized corrosion. The results predicted using the design specifications of MOHURD were more accurate than those predicted using the design specifications of AISI.

Study on the Influence and Difference of Taijiquan and Five-animal Exercises on College Students' Ankle Muscle Strength

Nie, ShangQi,Ma, Biao,Song, Jeho The International Promotion Agency of Culture Tech 2020 International Journal of Advanced Culture Technolo Vol.8 No.3

The physique and health status of Chinese college students have received a generous concern in recent years. The physical condition of Chinese college students is not good and this phenomenon is especially obvious among female college students, which has been an disputable fact. This study starts from exercise intervention to study the concrete influence of taijiquan (a kind of traditional Chinese shadow boxing) and five-animal exercises on human body balance ability; the study uses experimental apparatus to measure the specific impact of exercise intervention on human body balance ability; meanwhile, the study also applies data analysis to longitudinally study whether the two studied sports items affect body balance, and whether there is difference in terms of the influence of two sports items on human body balance ability. The conclusions are as follows: firstly, 24-style taijiquan and five-animal exercises can improve ankle muscle strength, and the focus and degree of the improvement are different; secondly, five-animal exercises have a better improvement effect on the flexor and extensor muscles of ankle joint and 24-style taijiquan is in the second place. Moreover, compared with 24-style taijiquan, there is no significant difference in terms of the improvement caused by five-animal exercises; thirdly, 24-style taijiquan has a better effect on the improvement of internal rotation and evertors muscle strength. Compared with 24-style taijiquan, five-animal exercises have no significant difference in terms of the improvement degree.

Random Field Model of Corroded Steel Plate Surface in Neutral Salt Spray Environment

Kong Deliang,Nie Biao,Xu Shanhua 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.7

The random field model of corrosion depth on steel plate surface in neutral salt spray environment was investigated. 10 groups of specimens were subjected to accelerate corrosion by the neutral salt spray test, and the surface profile of corroded steel plates and the 3D data of corrosion depth were measured by three-dimensional non-contact surface topography instrument. The probability characteristics of corrosion depth were studied and the relationship between the average and the standard deviation of corrosion depth and the mass loss rate were analyzed. The corrosion depth were tested for ergodicity and stationarity and the autocorrelation function model of random field model of corrosiondepth was proposed. The results of the study show that the corrosion depth on steel plate surface in neutral salt spray environment conformed to the normal distribution. With the increase of mass loss rate, the average and the standard deviation of the corrosion depth increased. The corrosion depth has ergodicity and stationarity. The random field model of cosine trigonometric function can accurately characterize the distribution of corrosion depth, which prepared the preliminary preparation for the finite element analysis of the corroded steel structure.

Introduction of Functionality, Selection of Topology, and Enhancement of Gas Adsorption in Multivariate Metal–Organic Framework-177

Zhang, Yue-Biao,Furukawa, Hiroyasu,Ko, Nakeun,Nie, Weixuan,Park, Hye Jeong,Okajima, Satoshi,Cordova, Kyle E.,Deng, Hexiang,Kim, Jaheon,Yaghi, Omar M. American Chemical Society 2015 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.137 No.7

<P>Metal-organic framework-177 (MOF-177) is one of the most porous materials whose structure is composed of octahedral Zn4O(-COO)(6) and triangular 1,3,5-benzenetribenzoate (BTB) units to make a three-dimensional extended network based on the qom topology. This topology violates a long-standing thesis where highly symmetric building units are expected to yield highly symmetric networks. In the case of octahedron and triangle combinations, MOFs based on pyrite (pyr) and rutile (rtl) nets were expected instead of qom. In this study, we have made 24 MOF-177 structures with different functional groups on the triangular BTB linker, having one or more functionalities. We find that the position of the functional groups on the BTB unit allows the selection for a specific net (qom, pyr, and rtl), and that mixing of functionalities (-H, -NH2, and -C4H4) is an important strategy for the incorporation of a specific functionality (-NO2) into MOF-177 where otherwise incorporation of such functionality would be difficult. Such mixing of functionalities to make multivariate MOF-177 structures leads to enhancement of hydrogen uptake by 25%.</P>

Seismic performance of steel columns corroded in general atmosphere

Youde Wang,Tao Shi,Biao Nie,Hao Wang,Shanhua Xu 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.2

Steel structures exposed to general atmosphere for a long time are highly susceptible to corrosion damage, which would lead to the degradation of service performance of the components and even structures. This article focuses on the effect of corrosion on the seismic performance of steel column. The accelerated corrosion tests in general atmosphere were conducted on 7 H-shaped steel columns and 20 steel plates. Then the obtained plate specimens were subjected to monotonic tensile tests and cyclic loading tests, and the steel columns were subjected to pseudo-static tests, respectively, to study the effects of corrosion on their mechanical properties and seismic performance. Then, a simplified three-dimensional finite element model (FEM) capable of accurately simulating the hysteretic response of corroded steel columns under low-cycle loading was established. Experimental results indicated that the yield strength, tensile strength, elastic modulus and peak strain of corroded steel plate decreased linearly with the proposed corrosion damage parameter Dn, and the energy dissipations under low-cycle loading were significantly reduced. There is a correlation between the cyclic hardening parameters of corroded steel and the yield-tensile strength difference (SD), and then a simplified formula was proposed. Corrosion could result in the premature entrance of each loading stage of corroded columns and the deterioration of buckling deformation range, bearing capacity and energy dissipation, etc. In addition, a larger axial compression ratio (CR) would further accelerate the failure process of corroded columns. The parametric finite element analysis (FEA) indicated that greater damage was found for steel columns with non-uniform corrosion, and hysteretic performance degraded more significantly when corrosion distributed at flanges or foot zone.

Effect of Pitting Corrosion on the Stress Intensity Factor Magnitude and Distribution

Shan-Hua Xu,Haijiang Zhang,Biao Nie,Zhexun Zhang 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.4

The fracture and fatigue performance of corroded steel components show signifi cant degradation in both the crack initiation and propagation stage. This study is aimed to research the fracture behavior degradation mechanism of corroded steel members through investigating the eff ects of pits on stress intensity factor magnitude and distribution. The numerical simulation method was adopted, and a series of specimens with diff erent sizes and shapes of corrosion pits were modeled. It was found that the pitting-degradation models would show a more intense displacement and stress fi eld. A greater value of stress intensity factor SIF could be observed in model interior when the specimens were attacked by corrosion pits. The SIF distribution characteristic along thickness direction was aff ected by ratios of pit depth to radius. According to SIF numerical results, the premature fracture and shorter fatigue life induced by corrosion pits could be attributed to the higher SIF value compared with non-corrosion one.

Study on the flexural behavior of corroded built-up cold-formed thin-walled steel beams

Zongxing Zhang,Shanhua Xu,Han Li,Rou Li,Biao Nie 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.3

Eight cold-formed thin-walled steel beams were performed to investigate the effect of corrosion damage on the flexural behavior of steel beams. The relationships between failure modes or load-displacement curves and corrosion degree of steel beams were investigated. A series of parametric analysis with more than forty finite element models were also performed with different corrosion degrees, types and locations. The results showed that the reduction of cross-section thickness as well as corrosion pits on the surface would lead to a decline in the stiffness and flexural capacity of steel beams, and gradually intensified with the corrosion degree. The yield load, ultimate load and critical buckling load of the corroded specimen IV-B46-4 decreased by 22.2%, 26% and 45%, respectively. The failure modes of steel beams changed from strength failure to stability failure or brittle fracture with the corrosion degree increasing. In addition, thickness damage and corrosion pits at different locations caused the degradation of flexural capacity, the worst of which was the thickness damage of compression zone. Finally, the method for calculating flexural capacity of corroded cold-formed thin-walled steel beams was also proposed based on experimental investigation and numerical analysis results.