2D and 3D numerical analysis on strut responses due to one-strut failure

Zhang, Wengang,Zhang, Runhong,Fu, Yinrong,Goh, A.T.C.,Zhang, Fan Techno-Press 2018 Geomechanics & engineering Vol.15 No.4

In deep braced excavations, struts and walers play an essential role in the whole supporting system. For multi-level strut systems, accidental strut failure is possible. Once a single strut fails, it is possible for the loads carried from the previous failed strut to be transferred to the adjacent struts and therefore cause one or more struts to fail. Consequently, progressive collapse may occur and cause the whole excavation system to fail. One of the reasons for the Nicoll Highway Collapse was attributed to the failure of the struts and walers. Consequently, for the design of braced excavation systems in Singapore, one of the requirements by the building authorities is to perform one-strut failure analyses, in order to ensure that there is no progressive collapse when one strut was damaged due to a construction accident. Therefore, plane strain 2D and three-dimensional (3D) finite element analyses of one-strut failure of the braced excavation system were carried out in this study to investigate the effects of one-strut failure on the adjacent struts.

Predictive models of ultimate and serviceability performances for underground twin caverns

Zhang, Wengang,Goh, Anthony T.C. Techno-Press 2016 Geomechanics & engineering Vol.10 No.2

The construction of a new cavern modifies the state of stresses and displacements in a zone around the existing cavern. For multiple caverns, the size of this influence zone depends on the ground type, the in situ stress, the cavern span and shape, the width of the pillar separating the caverns, and the excavation sequence. Performances of underground twin caverns can be unsatisfactory as a result of either instability (collapse) or excessive displacements. These two distinct failures should be prevented in design. This study simulated the ultimate and serviceability performances of underground twin rock caverns of various sizes and shapes. The global factor of safety is used as the criterion for determining the ultimate limit state and the calculated maximum displacement around the cavern opening is adopted as the serviceability limit state criterion. Based on the results of a series of numerical simulations, simple regression models were developed for estimating the global factor of safety and the maximum displacement, respectively. It was proposed that a proper pillar width can be determined based on the threshold influence factor value. In addition, design charts with regard to the selection of the pillar width for underground twin rock caverns under similar ground conditions were also developed.

Evaluating seismic liquefaction potential using multivariate adaptive regression splines and logistic regression

Zhang, Wengang,Goh, Anthony T.C. Techno-Press 2016 Geomechanics & engineering Vol.10 No.3

Simplified techniques based on in situ testing methods are commonly used to assess seismic liquefaction potential. Many of these simplified methods were developed by analyzing liquefaction case histories from which the liquefaction boundary (limit state) separating two categories (the occurrence or non-occurrence of liquefaction) is determined. As the liquefaction classification problem is highly nonlinear in nature, it is difficult to develop a comprehensive model using conventional modeling techniques that take into consideration all the independent variables, such as the seismic and soil properties. In this study, a modification of the Multivariate Adaptive Regression Splines (MARS) approach based on Logistic Regression (LR) LR_MARS is used to evaluate seismic liquefaction potential based on actual field records. Three different LR_MARS models were used to analyze three different field liquefaction databases and the results are compared with the neural network approaches. The developed spline functions and the limit state functions obtained reveal that the LR_MARS models can capture and describe the intrinsic, complex relationship between seismic parameters, soil parameters, and the liquefaction potential without having to make any assumptions about the underlying relationship between the various variables. Considering its computational efficiency, simplicity of interpretation, predictive accuracy, its data-driven and adaptive nature and its ability to map the interaction between variables, the use of LR_MARS model in assessing seismic liquefaction potential is promising.

Assessment of flexural and splitting strength of steel fiber reinforced concrete using automated neural network search

Zhang, Zhenhao,Paul, Suvash C.,Panda, Biranchi,Huang, Yuhao,Garg, Ankit,Zhang, Yi,Garg, Akhil,Zhang, Wengang Techno-Press 2020 Advances in concrete construction Vol.10 No.1

Flexural and splitting strength behavior of conventional concrete can significantly be improved by incorporating the fibers in it. A significant number of research studies have been conducted on various types of fibers and their influence on the tensile capacity of concrete. However, as an important property, tensile capacity of fiber reinforced concrete (FRC) is not modelled properly. Therefore, this paper intends to formulate a model based on experiments that show the relationship between the fiber properties such as the aspect ratio (length/diameter), fiber content, compressive strength, flexural strength and splitting strength of FRC. For the purpose of modeling, various FRC mixes only with steel fiber are adopted from the existing research papers. Automated neural network search (ANS) is then developed and used to investigate the effect of input parameters such as fiber content, aspect ratio and compressive strength to the output parameters of flexural and splitting strength of FRC. It is found that the ANS model can be used to predict the flexural and splitting strength of FRC in a sensible precision.

Multivariate adaptive regression splines model for reliability assessment of serviceability limit state of twin caverns

Zhang, Wengang,Goh, Anthony T.C. Techno-Press 2014 Geomechanics & engineering Vol.7 No.4

Construction of a new cavern close to an existing cavern will result in a modification of the state of stresses in a zone around the existing cavern as interaction between the twin caverns takes place. Extensive plane strain finite difference analyses were carried out to examine the deformations induced by excavation of underground twin caverns. From the numerical results, a fairly simple nonparametric regression algorithm known as multivariate adaptive regression splines (MARS) has been used to relate the maximum key point displacement and the percent strain to various parameters including the rock quality, the cavern geometry and the in situ stress. Probabilistic assessments on the serviceability limit state of twin caverns can be performed using the First-order reliability spreadsheet method (FORM) based on the built MARS model. Parametric studies indicate that the probability of failure $P_f$ increases as the coefficient of variation of Q increases, and $P_f$ decreases with the widening of the pillar.

Nonlinear structural modeling using multivariate adaptive regression splines

Wengang Zhang,A.T.C. Goh 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.16 No.4

Various computational tools are available for modeling highly nonlinear structural engineering problems that lack a precise analytical theory or understanding of the phenomena involved. This paper adopts a fairly simple nonparametric adaptive regression algorithm known as multivariate adaptive regression splines (MARS) to model the nonlinear interactions between variables. The MARS method makes no specific assumptions about the underlying functional relationship between the input variables and the response. Details of MARS methodology and its associated procedures are introduced first, followed by a number of examples including three practical structural engineering problems. These examples indicate that accuracy of the MARS prediction approach. Additionally, MARS is able to assess the relative importance of the designed variables. As MARS explicitly defines the intervals for the input variables, the model enables engineers to have an insight and understanding of where significant changes in the data may occur. An example is also presented to demonstrate how the MARS developed model can be used to carry out structural reliability analysis.

Genetic variation and phylogenetic relationships of orchardgrass (Dactylis glomerata L.) as Revealed by SSR markers

Wengang Xie,Xinquan Zhang,Yan Peng 한국초지조사료학회 2009 한국초지조사료학회 학술대회논문집 Vol.2009 No.08

Phylogenetic relationships among 53 accessions of D.glomerata collected from 5 continents were investigated using simple sequence repeat (SSR) markers. 15 SSR primer pairs generated a total of 127 alleles, with an average of 8.5 alleles per locus. The average polymorphic rate (P) was 95.21 %. The genetic similarity (GS) among all accessions ranged from 0.43 to 0.94, with an average of 0.63. Analysis of molecular variance (AMOVA) indicated that larger proportions of variability existed within geographical regions (73.75%). High degree of genetic diversity was observed in Asia (P, 90.55%) and Europe (P, 86.61%) groups. Based on the cluster and principal component analysis, 53 accessions could be divided into five groups (GS=0.64) according to the nearest phylogenetic relationship.

The Research and Application of Multiple Spindle Dynamic Follow to Improve CNC Thread Milling Products Precision

Peng Xiao,Zhiyi Zhang,Wengang Zheng 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.8

In this paper, a new control method is proposed. The SIEMENS 828D control system reads a feed axis machining of any one time processing, calculates the axis displacement data and draws the other two related linkage axis machining data. it through the PLC program of the control system written way R parameter is assigned to the other two related linkage of shaft processing program. Dynamic following effect of forming milling thread machining, reduce the product processing error, improve the product processing precision, technical indicators satisfy the similar foreign products.

SRAP and ISSR Analyses of Genetic Diversity and Relationships in Orchardgrass

Bing Zeng,Xinquan Zhang,Wengang Xie 한국초지조사료학회 2009 한국초지조사료학회 학술대회논문집 Vol.2009 No.08

SRAP (Sequence-related amplified polymorphism) and ISSR (Inter simple sequence repeat) molecualr markers were used to evaluate the levels and patterns of genetic diversity among 45 collections of orchardgrass from four continents. Twenty-one primer combinations were used and 480 bands were produced in SRAP, of which 405(84.38%) were polymorphic. On the other hand, twelve primers were used to generate a total of 116 bands in ISSR, of which 116(87.07%) were polymorphic. The coefficient range of genetic similarity was 0.6248-0.9686 and 0.6116-0.9231 respectively. Based on cluster and principal component analysis on the genetic characteristics, all collections could be divided into four groups and five groups in two markers, respectively. According to the analysis of genetic diversity and relationships, the appropriate strategies for collection and conservation of germplasm resources also were discussed and scientific breeding with far genetic relationship materials in orchardgrass were suggested.

IP-10 Expression in Patients with Chronic HBV Infection and Its Ability to Predict the Decrease in HBsAg Levels after Treatment with Entecavir

Zhao, Kai,Yang, Tao,Sun, Mimi,Zhang, Wei,An, Yong,Chen, Gang,Jin, Lei,Shang, Qinghua,Song, Wengang Korean Society for Molecular and Cellular Biology 2017 Molecules and cells Vol.40 No.6

Interferon-${\gamma}$-inducible protein 10 (IP-10), also known as chemokine C-X-C motif ligand (CXCL) 10, is closely associated with antiviral immunity and the progression of chronic hepatitis B (CHB). However, the value of baseline serological and histological IP-10 expression levels in predicting the efficacy of the antiviral response to nucleoside/nucleotide analogues (NAs) is still unknown. In our research, intrahepatic and peripheral IP-10 expression levels were systemically examined before and after treatment with entecavir (ETV). Baseline serological and histological IP-10 expression levels were significantly increased in patients with CHB, particularly in patients with higher degrees of liver inflammation and liver fibrosis. Moreover, higher baseline intrahepatic IP-10 levels indicated better prognoses in patients with CHB after entecavir therapy. The baseline IP-10 level was also positively associated with several clinical parameters, including baseline levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), hepatitis B virus (HBV) DNA, and hepatitis B surface antigen (HBsAg), and with the decrease in HBsAg levels after treatment. In addition, monocyte-derived IP-10 was expressed at higher levels in patients with CHB than in patients with liver cirrhosis (LC) and healthy controls (HC). According to the results of our in vitro experiments, IP-10 directly promoted hepatocyte apoptosis. Based on these findings, baseline serological and histological IP-10 levels might predict CHB severity and the decrease in HBsAg levels after entecavir therapy.