Mechanical performance of a new I-section weak-axis column bending connection

Linfeng Lu,Yinglu Xu,James B.P. Lim 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.1

This paper reports a novel steel beam-to-column connection suitable for use in the weak axis of I-section column. Monotonic and cyclic loading experimental investigations and numerical analysis of the proposed weak-axis connection were conducted, and the calculation procedure of the beam-column relative rotation angle and plastic rotation angle was developed and described in details. A comparative analysis of mechanical property and steel consumption were employed for the proposed I-section column weak-axis connection and box-section column bending connection. The result showed that no signs of fracturing were observed and the plastic hinge formed reliably in the beam section away from the skin plate under the beam end monotonic loading, and the plastic hinge formed much closer to the skin plate under the beam end cyclic loading. The fracture of welds between diaphragm and skin plate would cause an unstable hysteretic response under the column top horizontal cyclic loading. The proposed weak-axis connection system could not only simplify the design calculation progress when I-section column is adopted in frame structural design but also effectively satisfy the requirements of ‘strong joint and weak member’, as well as lower steel consumption.

Cyclic performance and design recommendations of a novel weak-axis reduced beam section connection

Linfeng Lu,Yinglu Xu,Jie Liu,James B.P. Lim 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.3

In previous weak-axis moment connection tests, brittle fracture always initiated near the edge of the beam flange groove weld due to force flow towards the stiffer column flanges, which is the opposite pattern as strong-axis moment connections. As part of the China NSFC (51278061) study, this paper tested two full-scale novel weak-axis reduced beam section moment connections, including one exterior frame connection specimen SJ-1 under beam end monotonic loading and one interior frame joint specimen SJ-2 under column top cyclic loading. Test results showed that these two specimens were able to satisfy the demands of FEMA-267 (1995) or ANSI/AISC 341-10 (2010) without experiencing brittle fracture. A parametric analysis using the finite element software ABAQUS was carried out to better understand the cyclic performance of the novel weak-axis reduced beam section moment connections, and the influence of the distance between skin plate and reduced beam section, <i>a</i>, the length of the reduced beam section, <i>b</i>, and the cutting depth of the reduced beam section, <i>c</i>, on the cyclic performance was analyzed. It was found that increasing three parametric values reasonably is beneficial to forming beam plastic hinges, and increasing the parameter <i>a</i> is conducive to reducing stress concentration of beam flange groove welds while increasing the parameters <i>b</i> and <i>c</i> can only reduce the peak stress of beam flange groove welds. The rules recommended by FEMA350 (2000) are suitable for designing the proposed weak-axis RBS moment connection, and a proven calculation formulation is given to determine the thickness of skin plate, the key components in the proposed weak-axis connections. Based on the experimental and numerical results, a design procedure for the proposed weak-axis RBS moment connections was developed.

Cyclic response and design procedure of a weak-axis cover-plate moment connection

Linfeng Lu,Yinglu Xu,Huixiao Zheng,James B.P. Lim 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.3

This paper systematically investigated the mechanical performance of the weak-axis cover-plate connection, including a beam end monotonic loading test and a column top cyclic loading test, and a series of parametric studies for exterior and interior joints under cyclic loading using a nonlinear finite element analysis program ABAQUS, focusing on the influences of the shape of top cover-plate, the length and thickness of the cover-plate, the thickness of the skin plate, and the steel material grade. Results showed that the strains at both edges of the beam flange were greater than the middle's, thus it is necessary to take some technical methods to ensure the construction quality of the beam flange groove weld. The plastic rotation of the exterior joint can satisfy the requirement of FEMA-267 (1995) of 0.03 rad, while only one side connection of interior joint satisfied ANSI/AISC 341-10 under the column top cyclic loading. Changing the shape or the thickness or the length of the cover-plate did not significantly affect the mechanical behaviors of frame joints no matter in exterior joints or interior joints. The length and thickness of the cover-plate recommended by FEMA 267 (1995) is also suitable to the weak-axis cover-plate joint. The minimum skin plate thickness and a design procedure for the weak-axis cover-plate connections were proposed finally.

Parametric Study of Weak-Axis Beam-to-Column Composite Connections with Asymmetrical Reduced Beam Section

Yinglu Xu,Linfeng Lu,Hong Zheng 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.2

To evaluate the eff ectiveness of the asymmetrical steel beam section and reduced beam section (RBS), this paper presents a parametric study on weak-axis beam-to-column composite connections with asymmetrical reduced beam section subjected to horizontal cyclic loading. After validating the accuracy of the fi nite element modeling through comparing to the experimental results, a total of 29 refi ned tridimensional models for four series were created for parametric analysis. The load–displacement and moment–rotation relationships, the Mises index, triaxiality index and rupture index distribution across the width of the fl ange welds for each connection were reported. A smaller steel beam top and bottom fl ange width ratio α could alleviate the adverse eff ect of the composite action. The parametric analysis about the geometrical variables of RBS confi rms the need for readjustment of the geometrical characteristics of the RBS in order to apply to the proposed weak-axis profi les. For design purposes, the parameter a , the distance from the skin plate to the reduced region, can be set to (0.65–0.9) b bf ; the parameter b , the length of the reduced region, can be set to b = (0.65–0.90) d b ; the parameter c , the maximum reduction depth of beam bottom fl ange, can be set to 0.20 b bf , where b bf and d b are the beam bottom fl ange width and beam depth respectively.

Investigation of Composite Action on Seismic Performance of Weak-axis Column-tree Moment Connections

Yinglu Xu,Linfeng Lu,Hong Zheng 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.3

This paper presents an experimental study on a developed weak-axis column-tree moment connection subjected to horizontal cyclic loading. In order to study possible positive or negative effect of a composite slab on the seismic performance of the proposed connection, six cruciform specimens were designed and constructed in pairs, where one specimen was bare steel joint and the other involved a composite slab. The standard, cover-plate, and material-changed connection details were considered. The test program is described in detail, and then the structural behavior of test specimens is discussed based on the test data. The tests revealed that although designed with 50% degree of shear connection, the concrete slab still caused obvious upward shift of the neutral axis and increase the strain demand on the bottom flange. But it is clear from the comparison of results that the composite joint specimens performed slightly better than the bare steel counterparts in terms of load-displacement hysteretic curves and energy dissipation capacity, as the concrete slab could effectively enhance the stability of the steel beam and delay the deterioration of the strength and stiffness. The cover-plate connection appears to be one of the more promising moment connection schemes which are able to deliver a much higher level of stability and energy dissipation capacity. The maximum magnitude of slab-steel beam interface slip was less than 0.5 mm, indicating that the concrete floor slab and steel beam could work well together under 50% partial shear connection.

Finite Element Analysis of Weak-Axis Composite Connections Under Cyclic Loading

Yinglu Xu,Linfeng Lu,Hong Zheng 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.1

This paper describes a numerical study on weak-axis composite connection through the nonlinear fi nite element program ABAQUS. After the simulation and validation of experimental results, a total of 16 models were created to investigate the infl uence of the diff erent parameters on the structural performance, and their hysteresis responses, rupture index distribution of beam fl ange welds were discussed in detail. The RBS connection scheme could develop extensive inelastic deformation in RBS region, thus reducing the weld rupture possibility. The thicker the concrete slab, the larger the bending moment under positive bending, and the higher the RI values at the beam bottom fl ange weld and also the neutral axis. The structural behavior was insensitive to the variation of the parameter reinforcement ratio as the reinforcements did not work well, and it is recommended to arrange reinforcements according to the construction requirements. Changing the weld access hole form has a little infl uence on the bearing capacity and rotation capacity, but the PEEQ and RI distributions are sensitive to this parameter. The design option of long access holes could provide a further means to reduce the fracture possibility of beam fl ange groove weld to a reasonable level, thus achieving a favorable performance of weak-axis column bending connections in a composite moment-resisting frame.

Metformin Regulates Gut Microbiota Abundance to Suppress M2 Skewing of Macrophages and Colorectal Tumorigenesis in Mice

Fan Linfeng,Zeng Xiangfu,Xu Guofeng 한국미생물학회 2023 The journal of microbiology Vol.61 No.1

The correlation of imbalanced gut microbiota with the onset and progression of colorectal cancer (CRC) has become clear. This work investigates the effect of metformin on gut microbiota and genesis of CRC in mice. Human fecal samples were collected from healthy control (HC) donors and CRC patients. Compared to HC donors, CRC patients had reduced abundance of gut microbiota; however, they had increased abundance of detrimental Bacteroidetes. Mice were injected with azomethane (AOM) to induce colorectal tumorigenesis models. Treatment of CRC patients-sourced fecal microbiota promoted tumorigenesis, and it increased the expression of Ki67, β-catenin, COX-2, and Cyclin D1 in mouse colon tissues. Further treatment of metformin blocked the colorectal tumorigenesis in mice. Fecal microbiota from the metformin-treated mice was collected, which showed decreased Bacteroidetes abundance and suppressed AOM-induced colorectal tumorigenesis in mice as well. Moreover, the metformin- modified microbiota promoted the M1 macrophage-related markers IL-6 and iNOS but suppressed the M2 macrophage-related markers IL-4R and Arg1 in mouse colon tissues. In conclusion, this study suggests that metformin-mediated gut microbiota alteration suppresses macrophage M2 polarization to block colorectal tumorigenesis.

Adaptive Complex Interpolator for Channel Estimation in Pilot-Aided OFDM System

Guanghui Liu,Liaoyuan Zeng,Hongliang Li,Linfeng Xu,ZhengningWang 한국통신학회 2013 Journal of communications and networks Vol.15 No.5

In an orthogonal frequency division multiplexing system,conventional interpolation techniques cannot correctly balanceperformance and overhead when estimating dynamic longdelaychannels in single frequency networks (SFNs). In this study,classical filter analysis and design methods are employed to derivea complex interpolator for maximizing the resistible echo delay in achannel estimator on the basis of the correlation between frequencydomain interpolating and time domain windowing. The coefficientcomputation of the complex interpolator requires a key parameter,i.e., channel length, which is obtained in the frequency domain witha tentative estimation scheme having low implementation complexity. The proposed complex adaptive interpolator is verified in asimulated digital video broadcasting for terrestrial/handheld receiver. The simulation results indicate that the designed channelestimator can not only handle SFN echoes with more than 200 µsdelay but also achieve a bit-error rate performance close to the optimumminimum mean square error method, which significantlyoutperforms conventional channel estimation methods, while preservinga low implementation cost in a short-delay channel.

High-performance hybrid white organic light-emitting diodes employing p-type interlayers

Baiquan Liu,Hong Tao,Jianhua Zou,Miao Xu,Dongyu Gao,Linfeng Lan,Lei Wang,Honglong Ning,Junbiao Peng 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.27 No.-

A simplified hybrid white organic light-emitting diode (WOLED) employing a p-type interlayer isdesigned, simultaneously realizing high efficiency, high color rendering index (CRI), low efficiency roll-off, low voltage and stable color. The device exhibits maximum total efficiencies of 29.8 cd/A and20.9 lm/W, which slightly decrease to 28.6 cd/A and 16.5 lm/W even at a high luminance of 5000 cd/m2. Besides, a slight color-shift and a CRI of 85 at 100 cd/m2 (3.65 V) are obtained. Such superior resultssystematically demonstrate that the use of p-type interlayer is a new way to realize high-performancehybrid WOLEDs.

Adaptive Complex Interpolator for Channel Estimation in Pilot-Aided OFDM System

Liu, Guanghui,Zeng, Liaoyuan,Li, Hongliang,Xu, Linfeng,Wang, Zhengning The Korea Institute of Information and Commucation 2013 Journal of communications and networks Vol.15 No.5

In an orthogonal frequency division multiplexing system, conventional interpolation techniques cannot correctly balance performance and overhead when estimating dynamic long-delay channels in single frequency networks (SFNs). In this study, classical filter analysis and design methods are employed to derive a complex interpolator for maximizing the resistible echo delay in a channel estimator on the basis of the correlation between frequency domain interpolating and time domain windowing. The coefficient computation of the complex interpolator requires a key parameter, i.e., channel length, which is obtained in the frequency domain with a tentative estimation scheme having low implementation complexity. The proposed complex adaptive interpolator is verified in a simulated digital video broadcasting for terrestrial/handheld receiver. The simulation results indicate that the designed channel estimator can not only handle SFN echoes with more than $200{\mu}s$ delay but also achieve a bit-error rate performance close to the optimum minimum mean square error method, which significantly outperforms conventional channel estimation methods, while preserving a low implementation cost in a short-delay channel.