Experimental Investigation on Fatigue Behavior of Steel Reinforced Concrete Composite Beam-to-Girder Joints

Le-Wei Tong,Qingjun Xian,Liying Zhou,Yiyi Chen,Yunfeng Zhang 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.4

Fatigue behavior and failure mechanism of steel reinforced concrete (SRC) beam-to-girder joints is discussed in this paper,which is intended for use in high-speed railway station structures due to their high stiffness and load capacity. Three identical SRC beam-to-girder joint specimens were designed and tested under static loading and two stages of fatigue loading. In the first stage of fatigue loading, the specimens were subjected to design fatigue load for 2 million cycles, while during the second stage, the specimens were loaded to failure under increased fatigue loading amplitude in order to know its fatigue strength and failure mechanism. The constructional details of SRC beam-to-girder joint specimen and the method of loading and testing are presented. The comparison in structural behavior of the joint is made between under static and fatigue loading. Fatigue failure characteristics of the joint are described in detail. It is found that the SRC beam-to-girder joints remained in their elastic range and the concrete surface crack did not exceed 0.1 mm when subjected to design static loading and 2 million cycles of design fatigue loading. There was no significant difference in structural behavior of each component of SRC composite beam between static and fatigue loading. Fatigue failure occurred after these joints were applied higher-level fatigue loading for another 0.70to 0.91 million cycles. Fatigue crack was initiated at the tension flange of I-shape steel of beam connected by welding to the flange of I-shape steel of girder or at the hole in tension flange of I-shape steel of beam, and then the crack propagated along flange width and web height of the I-shape steel in beam until the I-shape steel lost loading capacity due to lack of enough cross section. The fatigue behavior of constructional detail of the I-shape steel played a key role in the fatigue strength of the SRC beam-to-girder joints. Discussions on improving the fatigue strength of SRC beam-to-girder joints and future research aspects are presented finally.

Fatigue Behavior of Welded Thin-Walled T-joints between Circular and Square Hollow Secitons

Le-Wei Tong,X.L. Zhao,F.R.Mashiri,P.Grundy,Hong-Zhi Zheng 한국강구조학회 2006 International Journal of Steel Structures Vol.6 No.3

The fatigue behaviour of thin-walled CHS-to-SHS T-joints (t < 4 m) under in-plane bending are studied in this paper. Thefailure modes observed in the fatigue tests are described. Surface crack growth was recorded at progressive stages of fatiguelife, from initiation, through-thickness life and end of test failure. The characteristics of fatigue crack initiation and propagationare described. The stress concentration factors (SCFs) along the weld toes at both the circular brace and the square chord are-dimensional joint parameters on SCFs are discussed. The resultant SCFs are compared to both the SCFs from CHS and RHSparametric formulae in IIW guidelines. Both the fatigue tests and FE analyses showed that the hot spot locations of the CHS-to-SHS T-joints were located at the weld toe of the square hollow section chord.

Experimental and Numerical Investigations of High Strength Steel Welded H-section Columns

Feng Zhou,Le-Wei Tong,Yiyi Chen 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.2

This paper reports experimental and numerical investigations of high strength steel columns. A series of tests was performed on different geometries of welded H-sections fabricated from high strength steel sheet with a nominal yield stress of 460 MPa. A non-linear finite element model which includes geometric and material non-linearities was developed and verified against experimental results of high strength steel welded H-section columns. The calibrated model was shown to provide accurate predictions of the experimental ultimate loads and failure modes of the test specimens. Therefore, a parametric study was carried out over a range of cross-section geometries and column lengths. The test and numerical results of stub columns obtained in this study were compared with the nominal section capacities. It is shown that the design provisions specified in the European Code, American Specification and Chinese Code on yield slenderness limits are all conservative. The normalized flange and web slenderness limits for fully effective section codified in European Code are very close to those codified in the American Specification, which are more suitable. Furthermore, the test and numerical results of long columns obtained in this study were compared with the nominal member capacities predicted using the European Code, American Specification and Chinese Code for steel structures. It is shown that the European Code provides the best agreement between the test and numerical data with design strength predictions for high strength steel welded H-section long columns.

Experimental Investigation on Fatigue Strength of Joints between SRC Beams and Concrete-Filled RHS Columns

Qingjun Xian,Le-Wei Tong,Liying Zhou,Yiyi Chen 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.5

Fatigue behavior, failure mechanism and fatigue strength of joints between steel reinforced concrete (SRC) beams and Concrete Filled Rectangular Hollow Section (CFRHS) columns is discussed in this paper. Three identical beam-to-column joint specimens were designed and tested under static loading and two stages of fatigue loading. In the first stage of fatigue loading, the specimens were subjected to design fatigue load for 2 million cycles, while during the second stage, they were loaded to failure under increased fatigue load in order to know failure mechanism and fatigue strength. It is found that the joints satisfied design requirements when subjected to static loading and design fatigue loading. Fatigue failure occurred after these joints were applied higher-level fatigue loading. The crack initiated at the weld toe of stud or stirrup hole in the upper flange of I-shaped steel in certain SRC beam, and then it propagated along flange width in winding trajectory until fatigue fracture occurred. Stress amplitude of tension flange in SRC beam can be regarded as the parameter representing fatigue strength of the joints. S-N curves in related codes are selected to evaluate fatigue strength of the joints. The design method is suggested to consider fatigue design of the joints.

A hemoglobin-based oxygen-carrying biomimetic nanosystem for enhanced chemo-phototherapy and hypoxia alleviation of hepatocellular carcinoma

Jing-Qing Le,Fang Yang,Xun-Huan Song,Ke-Ke Feng,Ling-Wu Tong,Meng-Die Yin,Wen-Zhong Zhang,Ying-Qi Lin,Hui Wu,Jing-Wei Shao 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.123 No.-

Tumor microenvironment is characterized by low pH, high reactive oxygen species and hypoxia, whichprovides a suitable environment for cancer growth. The hypoxia not only elevates tumor angiogenesisand metastasis, but also is responsible for the development of treatment resistance, which graduallybecomes a significant impediment for cancer therapy. Therefore, we developed a biomimetic nanosystemcontaining hemoglobin extracted from red blood cells, chemotherapy drug sorafenib, sensitizer ursolicacid and photosensitizer indocyanine green for enhanced chemo-photo combination therapy of hepatocellularcarcinoma, which could not only enhance the chemotherapy effect of sorafenib bowing to thesensitizing effect of ursolic acid, but also achieved synergetic phototherapy in virtue of indocyaninegreen. Besides, the nanoparticles could effectively delivery exogenous oxygen to tumor site and amelioratethe tumor hypoxic environment with the assistance of hemoglobin. The dual-sensitization drugdelivery system was expected to effectively reduce the resistance of traditional treatment methodsagainst tumor hypoxia, providing a novel prospect for the synergistic hepatocellular carcinomatreatment.