Fracture Prediction of Welded Steel Connections Using Traditional Fracture Mechanics and Calibrated Micromechanics Based Models

Yuanqing Wang,Hui Zhou,Yongjiu Shi,Jun Xiong 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.3

Fracture resistance is of primary concern in the seismic design of beam-to-column connections in steel moment resisting frames (SMRFs). Micromechanics based fracture models such as the void growth model (VGM) and the stress modified critical strain (SMCS) model provide alternative approaches for ductile fracture prediction by relating micro-mechanisms of void nucleation, growth and coalescence to macroscopic stresses and strains. In this study, the VGM and SMCS models were calibrated for Q345 structural steel and the corresponding weld, through smooth notched tensile (SNT) tests and complementary continuum finite element models (FEMs). A series of seven local connections representing beam-to-column connections in SMRFs were tested under monotonic tensile loading and the specimen elongations at fracture critical point were obtained. The traditional J-integral based fracture mechanics and micromechanics based fracture models (VGM and SMCS) were applied to predict fracture in each tested local connection through refined three-dimensional FEM. Comparisons between these numerical approaches and experimental observations in prediction of fracture critical displacement, indicated that the VGM and SMCS models were able to predict fracture of welded connection with good accuracy, while the J-integral based approach resulted in quite conservative fracture prediction. This paper has bridged the gap between small-scale material tests and large-scale structural experiments in fracture evaluations

Bearing Capacity of Non-linear Metallic Spiders Used in Point Supported Glass Facades

Yuanqing Wang,Huanxin Yuan,Yongjiu Shi,Yu Zou 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.2

Experimental and numerical investigations on bearing capacity of non-linear metallic spiders used in glass facades were presented. The non-linear metallic materials adopted in this study included two aluminum alloys (ZL105-T1 and ZL111-T6)and one austenitic stainless steel (AISI 302). A total of 21 spider specimens including three types of configurations were tested. Numerical simulation of the tests was conducted by virtue of sophisticated finite element (FE) models built up with ANSYS software. The test and FE predicted results were used to develop new design proposals for the spiders. Evaluation of the proposed design formulae revealed that a comparatively large safety margin would be appropriate in consideration of brittle glass panels. Finally, safety assessment of the spiders was conducted based upon a practical engineering application-the exhibition greenhouse in Beijing Botanical Garden.

Driving Factors on the Adoption of Low Carbon Production: Evidence from 265 Enterprises Managers in Jiangsu Province of China

Yuanqing Lu,Haiyan Zhao,Fang Huang,Jin Wang 보안공학연구지원센터 2014 International Journal of u- and e- Service, Scienc Vol.7 No.5

It’s the inevitably choice for enterprises to low carbon production, which is the important way to cope with the carbon limitation in the future and to gain competitiveness. Based on factor analysis, present paper developde low carbon production behavior questionnaire and investigated 265 enterprises managers in JiangsuProvince. Results of PLS test shows that: government policies, enterprise development, foreign trade have apparent effects on low carbon production behavior; the role of the public pressure to low carbon production behavior is not found. Through the driving factors analysis, present paper proposed some policy suggestions.

Fracture Behavior Analyses of Welded Beam-to-Column Connections Based on Elastic and Inelastic Fracture Mechanics

Yuanqing Wang,Hui Zhou,Yongjiu Shi,Hong Chen 한국강구조학회 2010 International Journal of Steel Structures Vol.10 No.3

Detailed two-dimensional finite element models are applied to investigate the fracture behavior of welded beam-to-column connections which are widely used in steel structures in China. The elastic stress intensity factor (KI) and inelastic J-integral (JI) around the crack tip are calculated to provide quantitative estimates of fracture toughness requirements in the connections with different configurations. Four types of weld access holes are modeled after the full-scale connection tests. Subsequently,several connection details including weld flaw size and location, weld backing bar, fillet reinforcement and other modifications,are examined in the effectiveness of reducing the toughness demands on the weld. The analyses have confirmed the observations from connection cyclic tests that the fracture is more likely to occur at the beam flange weld heat affected zone (HAZ) which sustains extensive yielding and exhibits relatively low fracture toughness. The weld flaw size and location have shown significant effects on the toughness requirements both by elastic and inelastic analyses. The modification of removing backing bar and reinforcing a fillet weld shows the most effective approach to reduce the toughness demands. By inelastic analyses, the initial weld defect at HAZ (10 mm away from the column face) shows more toughness demands than that at the interface of the column flange and weld. The evaluated moment at column face when crack predicted to propagate, agrees well with the ultimate moment obtained from the connection tests.

Experimental Study of Lateral-torsional Buckling Behavior of Stainless Steel Welded I-section Beams

Yuanqing Wang,Lu Yang,Bo Gao,Yong-Jiu Shi,Huanxin Yuan 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.2

Investigations on lateral-torsional buckling behavior of stainless steel welded I-section beams were carried out through fourpointbending tests. The Chinese austenitic stainless steel adopted in this study contains approximately 17% of Cr, which couldbe graded as EN 1.4401. The non-linear stress-strain relationship of the material, the residual stress distribution of the sectionand the ultimate moment capacity of the welded I-section beams were obtained from the experiments, and they were comparedwith those results predicted by analytical models recommended by several researchers. Besides, a new model is proposed topredict the residual stress distribution of the stainless steel welded I-section beams.

Degradation and damage behaviors of steel frame welded connections

Meng Wang,Yongjiu Shi,Yuanqing Wang,Jun Xiong,Hong Chen 국제구조공학회 2013 Steel and Composite Structures, An International J Vol.15 No.4

In order to study the degradation and damage behavirs of steel frame welded connections, two series of tests in references with different connection constructions were carried out subjected to various cyclic loading patterns. Hysteretic curves, degradation and damage behaviours and fatigue properties of specimens were firstly studied. Typical failure modes and probable damage reasons were discussed. Then, various damage index models with variables of dissipative energy, cumulative displacement and combined energy and displacement were summarized and applied for all experimental specimens. The damage developing curves of ten damage index models for each connection were obtained. Finally, the predicted and evaluated capacities of damage index models were compared in order to describe the degraded performance and failure modes. The characteristics of each damage index model were discussed in depth, and then their distributive laws were summarized. The tests and analysis results showed that the loading histories significantly affected the distributive shapes of damage index models. Different models had their own ranges of application. The selected parameters of damage index models had great effect on the developing trends of damage curves. The model with only displacement variable was recommended because of a more simple form and no integral calculation, which was easier to be formulated and embedded in application programs.

Application of steel equivalent constitutive model for predicting seismic behavior of steel frame

Meng Wang,Yongjiu Shi,Yuanqing Wang 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.19 No.5

In order to investigate the accuracy and applicability of steel equivalent constitutive model, the calculated results were compared with typical tests of steel frames under static and dynamic loading patterns firstly. Secondly, four widely used models for time history analysis of steel frames were compared to discuss the applicability and efficiency of different methods, including shell element model, multi-scale model, equivalent constitutive model (ECM) and traditional beam element model (especially bilinear model). Four-story steel frame models of above-mentioned finite element methods were established. The structural deformation, failure modes and the computational efficiency of different models were compared. Finally, the equivalent constitutive model was applied in seismic incremental dynamic analysis of a ten-floor steel frame and compared with the cyclic hardening model without considering damage and degradation. Meanwhile, the effects of damage and degradation on the seismic performance of steel frame were discussed in depth. The analysis results showed that: damages would lead to larger deformations. Therefore, when the calculated results of steel structures subjected to rare earthquake without considering damage were close to the collapse limit, the actual story drift of structure might already exceed the limit, leading to a certain security risk. ECM could simulate the damage and degradation behaviors of steel structures more accurately, and improve the calculation accuracy of traditional beam element model with acceptable computational efficiency.

Study on the Fracture Properties of the PMMA Structure for the JUNO Central Detector

Zongyi Wang,Yuanqing Wang,Xinxi Du,Tianxiong Zhang,Yuekun Heng 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.6

Polymethyl methacrylate (PMMA) is increasingly used in building structures nowadays. PMMA materials utilized in structures have different fracture property compared with those used in aircrafts or biomedical equipment. Single-edge-notch bending (SENB) tests were firstly carried out at various temperatures (-40°C, -20°C, 0°C, 20°C, and 40°C) to determine the KIC values of base PMMA materials and connected areas. The crack-resisting capacity of PMMA plate is subsequently studied. The fracture property of the PMMA joint for the Jiangmen Underground Neutrino Observatory (JUNO) central detector is investigated. The results show that base PMMA material has higher KIC values than connected area. The KIC of base PMMA material is lowest at 20°C and highest at -20°C, while that of connected area is lowest at 40°C and highest at -40°C. For the PMMA joint of the JUNO detector, the cracks perpendicular to the X axis are more disadvantageous than those perpendicular to the Z axis. The stress intensity factors (SIFs) at the crack front of the embedded crack decrease with the increase of embedded depth. Due to the presence of two parallel surface or embedded cracks, the SIFs at the crack front decrease.

A brain somatic RHEB doublet mutation causes focal cortical dysplasia type II

Shanshan Zhao,Zhenghui Li,Muxian Zhang,Lingliang Zhang,Honghua Zheng,Jinhuan Ning,Yanyan Wang,Feng-Peng Wang,Xiaobin Zhang,Hexia Gan,Yuanqing Wang,Xian Zhang,Hong Luo,Guojun Bu,Huaxi Xu,Yi Yao,Yun-wu 생화학분자생물학회 2019 Experimental and molecular medicine Vol.51 No.-

Focal cortical dysplasia type II (FCDII) is a cerebral cortex malformation characterized by local cortical structure disorganization, neuronal dysmorphology, and refractory epilepsy. Brain somatic mutations in several genes involved in the PI3K/AKT/mTOR pathway are associated with FCDII, but they are only found in a proportion of patients with FCDII. The genetic causes underlying the development FCDII in other patients remain unclear. Here, we carried out whole exome sequencing and targeted sequencing in paired brain–blood DNA from patients with FCDII and identified a brain somatic doublet mutation c.(A104T, C105A) in the Ras homolog, mTORC1 binding (RHEB) gene, which led to the RHEB p.Y35L mutation in one patient with FCDII. This RHEB mutation carrier had a dramatic increase of ribosomal protein S6 phosphorylation, indicating mTOR activation in the region of the brain lesion. The RHEB p.Y35L mutant protein had increased GTPλS-binding activity compared with wild-type RHEB. Overexpression of the RHEB p. Y35L variant in cultured cells also resulted in elevated S6 phosphorylation compared to wild-type RHEB. Importantly, in utero electroporation of the RHEB p.Y35L variant in mice induced S6 phosphorylation, cytomegalic neurons, dysregulated neuron migration, abnormal electroencephalogram, and seizures, all of which are found in patients with FCDII. Rapamycin treatment rescued abnormal electroencephalograms and alleviated seizures in these mice. These results demonstrate that brain somatic mutations in RHEB are also responsible for the pathogenesis of FCDII, indicating that aberrant activation of mTOR signaling is a primary driver and potential drug target for FCDII.

Exponential Stabilization of Takagi–Sugeno Fuzzy Systems With Aperiodic Sampling: An Aperiodic Adaptive Event-Triggered Method

Wang, Yueying,Xia, Yuanqing,Ahn, Choon Ki,Zhu, Yanzheng IEEE 2019 IEEE transactions on systems, man, and cybernetics Vol.49 No.2

<P>In this paper, we study the exponential stabilization problem for continuous-time Takagi–Sugeno fuzzy systems subject to aperiodic sampling. By aiming to transmission reduction, an appropriate aperiodic event-triggered communication scheme with adaptive mechanism is put forward, which covers the existing periodic mechanisms as special cases. For the sake of reduction in design conservativeness, both the available information of sampling behavior and threshold error are fully acquired by constructing a novel time-dependent Lyapunov functional. Then, a new exponential stability criterion is presented to establish the quantitative relationship among the adaptive adjusted event threshold, the decay rate, the upper bound, and the lower bound of variable sampling period, simultaneously. By resorting to a matrix transformation, the corresponding stabilization criterion is further derived by which the sampled-data controller can be obtained. Finally, two illustrative examples are provided to demonstrate the virtue and applicability of proposed design method.</P>