An efficient approach to structural static reanalysis with added support constraints

Liu, Haifeng,Wu, Baisheng,Li, Zhengguang Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.3

Structural reanalysis is frequently used to reduce the computational cost during the process of design or optimization. The supports can be regarded as the design variables in various types of structural optimization problems. The location, number, and type of supports may be varied in order to yield a more effective design. The paper is focused on structural static reanalysis problem with added supports where some node displacements along axes of the global coordinate system are specified. A new approach is proposed and exact solutions can be provided by the approach. Thus, it belongs to the direct reanalysis methods. The information from the initial analysis has been fully exploited. Numerical examples show that the exact results can be achieved and the computational time can be significantly reduced by the proposed method.

Mechanical Performances of Concrete Produced with Desert Sand After Elevated Temperature

Haifeng Liu,Xiaolong Chen,Jialing Che,Ning Liu,Minghu Zhang 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.4

Currently, fire in building is one of the most serious disasters. With the increase of basic construction items in western China, ordinary medium sand resource no longer met with the need of engineering. Compressive strength experiments of concrete produced with desert sand after elevated temperature were carried out in this paper. The effects of desert sand replacement rate (DSRR), temperature and cooling regime on the mechanical performances of concrete produced with desert sand were analyzed. XRD and SEM experiments were also conducted to study the microstructure of concrete produced with desert sand after elevated temperature. Experimental results showed that the cubic compressive strength of concrete produced with desert sand increased firstly, and then declined with temperature. Whereas, the prismatic compressive strength and elasticity modulus of concrete produced with desert sand under static compression declined with temperature. With the enhancement of DSRR, the elasticity modulus under static compression, cubic compressive strength and prismatic compressive strength of concrete produced with desert sand after elevated temperature increased firstly, and then declined, the maximum value of which was reached when DSRR amounted to 40%. Regression models were established to predict the mechanical performances of concrete produced with desert sand after elevated temperature, which were in good agreement with experimental results.

Efficient Method to Include Joint Zones of Chord Members in Finite Element Model of Tubular Transmission Tower at Linear Elastic Stage

Haifeng Liu,Junke Han,Zhenmao Sun,Jingbo Yang,Fengli Yang,Xiyu Xu 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.4

To include the effects of the joint zones efficiently, firstly a chord member considering the joint zones is seen as a combination of three beams with different sections and its element stiffness matrix is derived; Secondly, based on the statistically geometrical properties of the joint zones and chord members in service, the coefficients in the element stiffness matrix of the varied section beam element related to the moments and shear forces greatly increase more than 70%, while the coefficients related to axial forces only increase less than 2%. Therefore, along with the other two inherent mechanical properties of member structures, it is essential to include the effects of the joint zones. Finally, the results by the finite element models where the chord members and the joint zones are simulated by four methods are compared, which proves the efficiency and the accuracy of the varied section beam element.

Robust Water-Repellent Treatment of Cotton Fabrics with Polysiloxane Modified via Thiol-Ene Click Reaction

Haifeng Liu,Zhu Wang,Chengjun Sun 한국섬유공학회 2018 Fibers and polymers Vol.19 No.3

A facile and inexpensive way to prepare self-crosslinkable poly(dimethylsiloxane) (PDMS) for superhydrophobic treatment of cotton fabrics is reported in the study. Through thiol-ene click reaction between mercaptopropyltrimethoxysilane (MPTMOS) and vinyl-containing poly(dimethylsiloxane) (VPDMS), PDMS-g-TMOS can be simply and quickly synthesized. The trimethoxysilane group of PDMS-g-TMOS can react with hydroxyl group on cotton fabric and other -Si(OCH3)3 groups. The synthesized polysiloxane (PDMS-g-TMOS) was identified by FT-IR and 1H-NMR. The morphology of the treated cotton fabric was observed by SEM and XPS was used to analyze the elemental composition on the surface of cotton fabric. The analysis results indicated that the surface was fully covered with PDMS. Due to the low surface energy of PDMS and the rough surfaces of cotton fabric, the optimized water contact angle (WCA) and sliding angle were respectively 154 o±0.4 o and 14 o±0.5 o, indicating superhydrophobicity. Moreover, water spray test (AATCC Test Method 22-2010) was also applied to evaluate the water repellency of treated cotton fabric and a score of 90 was assigned according to AATCC Test Method 22- 2010. The durability of treated cotton fabric was tested by 50 laundering cycles. The resultant WCA barely decreased and the score of water spray test dropped from 90 to 80, showing the reasonable wash durability.

Consequences of college entrance exams in China and the reform challenges

Haifeng Liu,Qiong Wu 한국교육개발원 2006 KEDI Journal of Educational Policy Vol.3 No.1

College entrance exams(also called gaokao) have been drawing attention from both educators and the society at large in China. The establishment and development of the college admission system, which revolves around the college entrance exams, are closely related to the social and political development in the country as well as the influence of traditional culture. From an educational point of view, gaokao serves as a tool to identify qualified college students and to guide learning and teaching in secondary schools. From the societal point of view, gaokao also promotes social equity and mobility. It should be admitted that the nationally unified gaokao does have some negative impact on education at the elementary and secondary level, but it should also be noted that the unified gaokao protects admission decisions from the interference by many other factors such as political connections among people. Thus, it enhances equity and credibility of college enrollment. The introduction of a western admission system, such as that in the United States, to China would require compatible cultural environment, which is not available in China. One such cultural element that has the greatest impact on gaokao reforms is the traditional strong emphasis on and belief in education. Despite gaokao’s negative consequences, its elimination is not an answer for education in China today.

An efficient method to structural static reanalysis with deleting support constraints

Haifeng Liu,Shigang Yue 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.6

Structural design is usually an optimization process. Numerous parameters such as the member shapes and sizes, the elasticity modulus of material, the locations of nodes and the support constraints can be selected as design variables. These variables are progressively revised in order to obtain a satisfactory structure. Each modification requires a fresh analysis for the displacements and stresses, and reanalysis can be employed to reduce the computational cost. This paper is focused on static reanalysis problem withmodification of deleting some supports. An efficient reanalysis method is proposed. The method makes full use of the initial information and preserves the ease of implementation. Numerical examples show that thecalculated results of the proposed method are the identical as those of the direct analysis, while thecomputational time is remarkably reduced.

An efficient approach to structural static reanalysis with added support constraints

Haifeng Liu,Baisheng Wu,Zhengguang Li 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.3

Structural reanalysis is frequently used to reduce the computational cost during the process of design or optimization. The supports can be regarded as the design variables in various types of structural optimization problems. The location, number, and type of supports may be varied in order to yield a more effective design. The paper is focused on structural static reanalysis problem with added supports where some node displacements along axes of the global coordinate system are specified. A new approach is proposed and exact solutions can be provided by the approach. Thus, it belongs to the direct reanalysis methods. The information from the initial analysis has been fully exploited. Numerical examples show that the exact results can be achieved and the computational time can be significantly reduced by the proposed method.

Epitaxial Growth of Strain-Induced Ferromagnetic LaCoO3 Thin Films by Simple Sol–Gel Technique

Haifeng Liu,Yuqiao Guo,Ruishi Xie,Guohua Ma 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.3

LaCoO3 (LCO) epitaxial films were grown on (001) LaAlO3 (LAO) substrates by the simple sol– gel technique. X-ray diffraction (XRD) and the cross-section transmission electron microscope (TEM) measurements indicate that single-phase (001) oriented LCO epitaxial films with biaxial compressive strain and elongated distortion of CoO6 octahedrons were grown on (001) LAO successfully. The epitaxial relationship between the LCO film and the LAO substrate is confirmed to be (001)LCO||(001)LAO and [100]LCO||[100]LAO. It is also found that LCO grown on LAO has a larger mean Co–O bond length and unit-cell size, compared with those of polycrystalline film. In addition, the magnetic characterization shows that LCO epitaxial film exhibits an obvious ferromagnetic (FM) transition at TC ~ 85 K, which is different from the nonmagnetic ground state of polycrystalline LCO. Combined with the structural analyses, it reveals that the strain-induced ferromagnetism observed in LCO epitaxial film originates from an increase of the mean Co–O bond length and a suppression of the CoO6 octahedral rotations, which can stabilize higher spin state of Co3+ by a decrease of the eg~t2g gap energy.

Investigation of Resistance and Molecular Mechanisms to SDHI Fungicides in Botrytis cinerea Field Strains from Strawberry in Korea

Haifeng Liu,Gahee Lee,Hyunkyu Sang 한국농약과학회 2022 한국농약과학회 학술발표대회 논문집 Vol.2022 No.11

The Cholesky rank-one update/downdate algorithm for static reanalysis with modifications of support constraints

Haifeng Liu,Jihua Zhu,Mingming Li 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.3

Structural reanalysis is frequently utilized to reduce the computational cost so that the process of design or optimization can be accelerated. The supports can be regarded as the design variables and may be modified in various types of structural optimization problems. The location, number, and type of supports can make a great impact on the performance of the structure. This paper presents a unified method for structural static reanalysis with imposition or relaxation of some support constraints. The information from the initial analysis has been fully utilized and the computational time can be significantly reduced. Numerical examples are used to validate the effectiveness of the proposed method.