Axial compression ratio limit values for steel reinforced concrete (SRC) special shaped columns

Zongping Chen,Jinjun Xu,Yuliang Chen,Jianyang Xue 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.2

This paper presents the results of experimental investigation, numerical calculation and theoretical analysis on axial compression ratio limit values for steel reinforced concrete (SRC) special shaped columns. 17 specimens were firstly intensively carried out to investigate the hysteretic behavior of SRC special shaped columns subjected to a constant axial load and cyclic reversed loads. Two theories were used to calculate the limits of axial compression ratio for all the specimens, including the balanced failure theory and superposition theory. It was found that the results of balanced failure theory by numerical integration method cannot conform the reality of test results, while the calculation results by employing the superposition theory can agree well with the test results. On the basis of superposition theory, the design limit values of axial compression ratio under different seismic grades were proposed for SRC special shaped columns.

Seismic behavior of T-shaped steel reinforced high strength concrete short-limb shear walls under low cyclic reversed loading

Zongping Chen,Jinjun Xu,Yuliang Chen,Yisheng Su1 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.57 No.4

This paper presents an experimental study of six steel reinforced high strength concrete T-shaped short-limb shear walls configured with T-shaped steel truss under low cyclic reversed loading. Considering different categories of ratios of wall limb height to thickness, shear/span ratios, axial compression ratios and stirrup reinforcement ratios were selected to investigate the seismic behavior (strength, stiffness, energy dissipation capacity, ductility and deformation characteristics) of all the specimens. Two different failure modes were observed during the tests, including the flexural-shear failure for specimens with large shear/span ratio and the shear-diagonal compressive failure for specimens with small shear/span ratio. On the basis of requirement of Chinese seismic code, the deformation performance for all the specimens could not meet the level of ‘three’ fortification goals. Recommendations for improving the structural deformation capacity of T-shaped steel reinforced high strength concrete short-limb shear wall were proposed. Based on the experimental observations, the mechanical analysis models for concrete cracking strength and shear strength were derived using the equivalence principle and superposition theory, respectively. As a result, the proposed method in this paper was verified by the test results, and the experimental results agreed well with the proposed model.

Performance and Calculations of Recycled Aggregate Concrete-filled Steel Tubular (RACFST) Short Columns under Axial Compression

Zongping Chen,Jinjun Xu,Jianyang Xue,Yisheng Su 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.1

This paper describes a series of tests on steel tubular short columns of circular section filled with normal concrete (NA) andrecycled aggregate concrete (RAC). Twenty-two specimens, including 11 small diameter of RAC-filled steel tubular (RACFST)columns named CA series and 11 larger diameter of RACFST columns called CB series, were tested to research the influenceof variations in confinement index and replacement ratio of recycled coarse aggregate (RCA), from 0% to 100% with 10%increasing. The test results show that both types of RACFST columns and normal concrete-filled steel tubular (CFST) columnsfailed due to oblique shear pressure damage with a drum-like. Comparisons are made with predicted bearing capacities ofRACFST columns using the existing theories, such as Unified Strengthen theory (I), Confinement theory (II) and Superpositiontheory (III). The equation for axial compression stress-strain curves of the whole process are proposed in this investigation forRACFST short columns, which can be directly used in theoretical and numerical analysis as well as practical engineering designand evaluation of RACFST structures.

Bond behaviors of shape steel embedded in recycled aggregate concrete and recycled aggregate concrete filled in steel tubes

Zongping Chen,Jinjun Xu,Ying Liang,Yisheng Su 국제구조공학회 2014 Steel and Composite Structures, An International J Vol.17 No.6

Thirty one push-out tests were carried out in order to investigate the bond behavior between shape steel, steel tube (named steels) and recycled aggregate concrete (RAC), including 11 steel reinforced recycled aggregate concrete (SRRAC) columns, 10 recycled aggregate concrete-filled circular steel tube (RACFCST) columns and 10 recycled aggregate concrete-filled square steel tube (RACFSST) columns. Eleven recycled coarse aggregate (RCA) replacement ratios (i.e., 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%) were considered for SRRAC specimens, while five RCA replacement ratios (i.e., 0%, 25%, 50%, 75% and 100%), concrete type and length-diameter ratio for recycled aggregate concretefilled steel tube (RACFST) specimens were designed in this paper. Based on the test results, the influences of all variable parameters on the bond strength between steels and RAC were investigated. It was found that the load-slip curves at the loading end appeared the initial slip earlier than the curves at the free end. In addition, eight practical bond strength models were applied to make checking computations for all the specimens. The theoretical analytical model for interfacial bond shear transmission length in each type of steel-RAC composite columns was established through the mechanical derivation, which can be used to design and evaluate the performance of anchorage zones in steel-RAC composite structures.

Seismic behavior and strength of L-shaped steel reinforced concrete column-concrete beam planar and spatial joints

Zongping Chen,Deyi Xu,Jinjun Xu,Ni Wang 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.3

The study presented experimental and numerical investigation on the seismic performance of steel reinforced concrete (SRC) L-shaped column- reinforced concrete (RC) beam joints. Various parameters described as steel configuration form, axial compressive ratio, loading angle, and the existence of slab were examined through 4 planar joints and 7 spatial joints. The characteristics of the load-displacement response included the bearing capacity, ductility, story drift ratio, energy-dissipating capacity, and stiffness degradation were analyzed. The results showed that shear failure and flexural failure in the beam tip were observed for planar joints and spatial joint, respectively. And RC joint with slab failed with the plastic hinge in the slab and bottom of the beam. The results indicated that hysteretic curves of spatial joints with solid-web steel were plumper than those with hollow-web specimens. The capacity of planar joints was higher than that of space joints, while the opposite was true for energy-dissipation capacity and ductility. The high compression ratio contributed to the increase in capacity and initial stiffness of the joint. The elastic and elastic-plastic story deformation capacity of L-shaped column frame joints satisfied the code requirement. A design formula of joint shear resistance based on the superposition theory and equilibrium plasticity truss model was proposed for engineering application.

Bond Behavior of H-shaped Steel Embedded in Recycled Aggregate Concrete under Push-out Loads

Huahai Zheng,Zongping Chen,Jinjun Xu 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.2

Twenty two push-out tests were carried out in order to investigate the bond behavior between H-shaped steel and recycled aggregate concrete (RAC). Eleven kinds of recycled coarse aggregate (RCA) replacement ratios (i.e., 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100%) were designed in the test, and considering different categories of bond position of H-shaped steel, concrete protective cover thickness, stirrup reinforcement ratio, source and size of RCA were also selected. The load-slip curves at the loading end and free end were obtained; in addition, the distribution of H-shaped steel strain and the bond stress along the embedded length were analyzed. The bond strength in this investigation is related to the RAC cube compressive strength, and as a result, the interface bonding increases with RCA replacement ratio increasing. The bond strengths between different parts of H-shaped steel and RAC can be disparate: (1) the largest bond stress is located at the inside interface of the flange of H-shaped steel; (2) the second one is on the outside interface of the flange of H-shaped steel; (3) the bond stress between web of H-shaped steel and recycled coarse aggregate concrete is the smallest. What’s more, it was found that the ultimate and residual bond stresses can be enlarged due to the stronger grip action with increasing of concrete protective cover thickness and larger constrained effect with expanding the stirrup reinforcement ratio. The RCA serving age has a negative effect on the bonding performance, and when the size of RCA reduces, the ultimate bond strength decreases accordingly. Finally, four calculation models applied to predict the bond strength for all the specimens and the component of bond stress between shape steel and RAC is derived through the law of periodic transmission.

Initial Report on the Oriented-precipitation of T1-Phase in Creep-Aged Al-Cu-Li Single Crystal

Wei Hu,Jiqiang Chen,Shuang Han,Jinjun Xu,Jiale Miao,Ting Xing,Renguo Guan 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.5

In this work, the precipitation behavior of the T1-phase on each {111}Al habit plane was characterized by transmissionelectron microscopy (TEM), which was observed along two < 110 > Al zone axes in an Al-Cu-Li single crystal during creepaging. The results indicate that the oriented-precipitation of T1-phase in the Al-Cu-Li single crystal was originally determinedduring creep aging. The number densities of the T1-phase on the habit planes of (111)Al and (1−11)Al is noticeablyhigher than those of the T1-phase on the habit planes of (−111)Al and (11−1)Al in the same Al-Cu-Li single crystal when theexternal stress is loaded along the direction close to [111]Al orientation. It implies that the T1-phase tends to preferentiallyprecipitate on the habit planes that are perpendicular to the loading direction during creep aging. This work provides theinitial experimental evidence of the oriented-precipitation of the T1-phase in Al-Cu-Li alloy, and proposes the possibilityof regulating the precipitation distribution of the T1-phase.

Culture-Positive Spontaneous Ascitic Infection in Patients with Acute Decompensated Cirrhosis: Multidrug-Resistant Pathogens and Antibiotic Strategies

Jing Liu,Yanhang Gao,Xianbo Wang,Zhiping Qian,Jinjun Chen,Yan Huang,Zhongji Meng,Xiaobo Lu,Guohong Deng,Feng Liu,Zhiguo Zhang,Hai Li,Xin Zheng 연세대학교의과대학 2020 Yonsei medical journal Vol.61 No.2

Purpose: This study investigated multidrug-resistant (MDR) pathogens and antibiotic strategies of culture-positive spontaneousascitic infection (SAI) in patients with acute decompensated cirrhosis. Materials and Methods: We retrospectively analyzed 432 acute decompensated cirrhotic patients with culture-positive SAI from11 teaching hospitals in China (January 2012 to May 2018). A Cox proportional hazards model analysis was conducted to identifyindependent predictors of 28-day mortality. Results: A total of 455 strains were isolated from 432 ascitic culture samples. Gram-negative bacteria (GNB), gram-positive bacteria(GPB), and fungi caused 52.3, 45.5, and 2.2% of all SAI episodes, respectively. Episodes were classified as nosocomial (41.2%), healthcare-related (34.7%), and community-acquired (24.1%). Escherichia coli (13.4%) and Klebsiella pneumoniae (2.4%) were extendedspectrumβ-lactamase producing isolates. The prevalence of methicillin-resistant Staphylococcus aureus was 1.1%. Ceftazidime,cefepime, aztreonam, and amikacin were recommended as first-line antibiotics agents for non-MDR GNB infections; piperacillin/tazobactam and carbapenems for MDR GNB in community-acquired and healthcare-related or nosocomial infections, respectively;and vancomycin or linezolid for GPB infections, regardless of drug-resistance status. Multivariate analysis revealed days ofhospital stay before SAI, upper gastrointestinal bleeding, white blood cell count, alanine aminotransferase, serum creatinine concentration,total bilirubin, and international normalized ratio as key independent predictors of 28-day mortality. Conclusion: MDR pathogens and antibiotic strategies were identified in patients with acute decompensated cirrhosis with culture-positive SAI, which may help optimize therapy and improve clinical outcomes.

Optimal LEACH Protocol with Improved Bat Algorithm in Wireless Sensor Networks

( Xingjuan Cai ),( Youqiang Sun ),( Zhihua Cui ),( Wensheng Zhang ),( Jinjun Chen ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.5

A low-energy adaptive clustering hierarchy (LEACH) protocol is a low-power adaptive cluster routing protocol which was proposed by MIT’s Chandrakasan for sensor networks. In the LEACH protocol, the selection mode of cluster-head nodes is a random selection of cycles, which may result in uneven distribution of nodal energy and reduce the lifetime of the entire network. Hence, we propose a new selection method to enhance the lifetime of network, in this selection function, the energy consumed between nodes in the clusters and the power consumed by the transfer between the cluster head and the base station are considered at the same time. Meanwhile, the improved FTBA algorithm integrating the curve strategy is proposed to enhance local and global search capabilities. Then we combine the improved BA with LEACH, and use the intelligent algorithm to select the cluster head. Experiment results show that the improved BA has stronger optimization ability than other optimization algorithms, which the method we proposed (FTBA-TC-LEACH) is superior than the LEACH and LEACH with standard BA (SBA-LEACH). The FTBA-TC-LEACH can obviously reduce network energy consumption and enhance the lifetime of wireless sensor networks (WSNs).