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Shear behavior and design of an innovative embedded connector with flange for steel–concrete composite girder

Zhang Zhe, Zhang Sheng-Nan, Deng En-Feng, Yu Chen-Yang, Tang Yi, Wang Yan, Sun Dong-Sheng

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e195, 2022

EN

Connectors are crucial for steel–concrete composite girder to insure cooperative work of the two different materials. Flanges in connectors can be used as supports and templates to accelerate construction progress. Embedded connector is a type of connector formed by embedded web with opening holes for arranging reinforcements. However, traditional embedded connector does not include flanges. In this paper, an embedded connector with flanges was proposed. Three full-scale specimens were fabricated and push-out tests were conducted to investigate the shear behavior of the innovative connector. The failure mode and shear performance of the traditional embedded shear connector without flanges and the innovative connector with flanges were compared. Three-dimensional finite-element model (FEM) was developed and validated based on the test results. Furthermore, parametric analysis was conducted to further study the effects of the strength of the concrete, diameter of the hole, diameter of the perforating rebar, embedding depth, and height of the corrugated web on the shear performance of the innovative connector. The results of the parametric study were analyzed to evaluate the shear capacity for the embedded connector with flanges. Finally, an analytical model was proposed to predict the shear strength of the innovative embedded connector, which will provide important guidance for engineering application.

2

Numerical and experimental investigations on Mannesmann effect of nickel‑based superalloy

Zhang Zhe, Liu Dong, Man Tongchi, Li Nan, Yang Yanhui, Pang Yuhua, Wang Jianguo

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e133

EN

The preparation of nickel-based superalloy tubes by rotary tube piercing (RTP) process is still difficult due to the Mannesmann effect (central cracking phenomenon) has not been clarified. The combinations of numerical analysis and experiment verifications method were adopted in the study. The critical parameters for central cracking were determined by experiments. It was found that the evolution process of central cracking for nickel-based superalloy includes voids nucleation, growth and aggregation. Based on the obtained critical parameters, the evolutions of stress, strain, strain rate, temperature and damage were discussed by numerical simulation. By comparing the experiment results and simulation results, the Normalized Cockcroft and Latham (NCL) model was determined as the most suitable model. Considering the influences of temperature and strain rate on the damage threshold, the NCL model of Inconel 718 alloy was established by high-temperature tensile test. Based on the above results, it is found that the maximum shear stress promotes the plastic deformation, which provides necessary conditions for the generation of defects, and the maximum principal stress induces the generation of voids and expansion of micro-cracks, which directly leads to the central cracking. The essence of central cracking is ductile fracture under tensile stress.

3

Experimental study on seismic performance of ultrahigh-strength steel frames with buckling-restrained braces

Pei Sheng, Zhang Zhe, Deng En-Feng, Wang Yan-Bo

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 4

493--506

EN

The application of high-strength steel (HSS) is a significant trend in the development of steel structures. Two main challenges for HSS structures in seismic design (i.e., low energy dissipation capacity and low lateral stiffness) need to be addressed before HSS structures can be widely constructed in practice. To solve those problems, the seismic performance of structures combined of HSS frames and concentric buckling-restrained braces (BRBs) was investigated in this study. Two half-scale experimental specimens with different stiffness ratios between BRB and HSS frame were fabricated and tested under constant vertical load and cyclic increasing horizontal load. The hysteretic response, horizontal bearing capacity, internal force distribution, energy dissipation capacity, and ductility of the dual system were analyzed. The results showed that the specimens exhibited overall ductile performance with high elastic stiffness, significant ductility, and excellent energy dissipation capacity. The characteristics of both specimens in the pseudo-static test can be divided into three typical phases, which were described as overall elastic phase, BRB hardening phase, and failing phase. The BRB hardening phase was characterized by high energy dissipation capacity, and the plastic deformation was limited to the BRB, so the ductile demand of HSS member in HSSF-BRB was reduced. Moreover, the effect of stiffness ratio between BRB and HSS frame on seismic performance was discussed in this paper.

4

Experimental study on seismic performance of double-level yielding buckling-restrained braced concrete frames

Zhang Zhe, Zhang Sheng-Nan, Deng En-Feng, Zhou Tong-Tong, Yi Yu, He Hao, Li Na-Na

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 2

191--206

EN

This paper focused on the seismic performance of buckling-restrained braced concrete frame. Two different systems including the single-level yielding buckling-restrained braced concrete frame (SYBRBCF) and the double-level yielding buckling-restrained braced concrete frame (DYBRBCF) were designed for comparison. Compared with the single-level yielding buckling-restrained braces which are similar to many existing types of buckling-restrained braces, the double-level yielding buckling-restrained braces (DYBRBs) have two different energy absorption mechanisms that are expected to provide energy dissipations under the frequent earthquakes and rare earthquakes. To comparatively investigate the seismic performances of the two systems, cyclic tests were performed on one DYBRBCF specimen and another SYBRBCF specimen. The seismic response including the hysteretic curves, backbone curves, ductility coefficients, equivalent damping ratios, strengths, and stiffness degradations of the two experimental specimens was compared and analyzed. The test results indicate that the properly designed SYBRBCF and DYBRBCF can both exhibit the full hysteretic curves, meet the strong-column–weak-beam design requirement, and achieve the expected seismic performance. However, it was found that the ductility coefficient and energy dissipation capacity of the DYBRBCF were 72.2% and 23.4% higher than those of the SYBRBCF. The present study also provided useful design recommendations, which were beneficial to promote the application of DYBRBs.

5

Experimental and numerical analyses of 45 steel during three dimensional severe plastic deformation (3D-SPD)

Pang Yuhua, Lin Pengcheng, Sun Qi, Zhang Zhe, Liu Dong

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

71--81

EN

Due to the limitation of huge forming load, inhomogeneity of plastic deformation, and small volume of deformation region, it is difficult to prepare bulk ultra-fine grains material (UFGM) with industry size by the existing severe plastic deformation (SPD) methods. In this study, a novel SPD method, namely 3D-SPD, was proposed. By establishing finite element model, the distribution of material flow, restraining to Mannesmann effect, and comparison of load were discussed. Based on the self-developed rolling mill, the corresponding experiments were conducted. The experimental results reveal that the buck ultra-fine grains material of 45 steel was obtained under the condition of feed angle 21°, cross angle 15°, cone angle 5°, reduction rate 50%, and roll speed 30 rpm. The average grain size was refined from 46 to 0.8–4 μm. The tensile test results indicate that the yield strength and tensile strength of the rolled bar were significantly improved.