Axial behavior of RC column strengthened with SM-CFST

Haibo Jiang,Jiahang Li,Quan Cheng,Jie Xiao,Zhenkan Chen 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.43 No.6

This paper aims to investigate the axial compressive behavior of reinforced concrete (RC) columns strengthened with self-compacting and micro-expanding (SM) concrete-filled steel tubes (SM-CFSTs). Nine specimens were tested in total under the local axial compression. The test parameters included steel tube thickness, filling concrete strength, filling concrete type and initial axial preloading. The test results demonstrated that the initial stiffness, ultimate bearing capacity and ductility of original RC columns were improved after being strengthened by SM-CFSTs. The ultimate bearing capacity of the SM-CFST strengthened RC columns was significantly enhanced with the increase of steel tube thickness. The initial stiffness and ultimate bearing capacity of the SM-CFST strengthened RC columns were slightly enhanced with the increase of filling concrete strength. However, the effect of filling concrete type and initial axial preloading of the SM-CFST strengthened RC columns were negligible. Three equations for predicting the ultimate bearing capacity of the SM-CFST strengthened RC columns were compared, and the modified equation based on Chinese code (GB 50936-2014) was more precise.

Impulsive Output Consensus of Networked Passive Systems

Haibo Jiang,Liping Zhang,Jianjiang Yu,Caigen Zhou 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.6

In this paper, we study the problem of impulsive output consensus of multi-agent dynamical systems, where each agent is a passive system. Firstly, an impulsive control protocol is designed for networked passive systems based on the local information of agents. Secondly, sufficient conditions are derived to guarantee the output consensus of the multi-agent dynamical systems for the network with fixed and switching topologies, respectively. Finally numerical simulations are included to show the effectiveness of our theoretical results.

Experimental Study on Shear Behavior of Precast Concrete Segmental Beams with Hybrid Tendons and Dry Joints

Haibo Jiang,Yuhong Li,Airong Liu,Li Chen,Yuanhang Chen,Jie Xiao 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.10

A series of tests were carried out on nine specimens to improve the understanding of the shear behavior of precast concrete segmental beams (PCSBs) with hybrid tendons and dry joints. The influences of the tendon layout (hybrid tendons and external tendons), shear span ratio, and joint type (monolithic joints, and dry joints) on shear behavior of PCSBs were experimentally studied. The test results indicated that hybrid tendons slightly improved the shear strength and stiffness of PCSBs with dry joints compared to external tendons. The shear strengths of PCSBs with hybrid tendons and dry joints reduced with an increasing shear span ratio. Compared to monolithic beams with hybrid tendons, the dry joints slightly decreased the shear strength and enhanced the nonlinear behavior of PCSBs with hybrid tendons. The shear strengths of PCSBs and monolithic beams can be conservatively predicted by the AASHTO, Chinese code, and British Standard. The strut-and-tie model of prestressing force can accurately estimate the shear strengths of all the beams.

Shear strength of match-cast-free dry joint in precast girders

Haibo Jiang,Jiahui Feng,Jie Xiao,Mingzhu Chen,Weibin Liang 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.26 No.2

Shear keys in precast concrete segmental bridges (PCSBs) are usually match-casting which is very labour intensive. In this research, an innovative match-casting-free construction was proposed by leaving small gap between the convex and the concave castellated shear keys in the joints of PCSBs. Specimen experiment, shear strength analysis and numerical simulation were conducted, investigating the loading performance of this new type of dry joints, the gap dry joints. Compared with matchcasting joint specimens, it has been found from experiment that shear capacity of gap joint specimens significantly decreased ranging from 17.75% to 42.43% due to only partially constrained and contacted in case of gap dry joints. Through numerical simulation, the effects of bottom contacting location, the heights of the gap and the shear key base were analyzed to investigate strength reduction and methods to enhance shear capacity of gap joint specimens. Numerical results proved that shear capacity of gap dry joints under full contact condition was higher than that under partial contact. In addition, left contact destroyed the integrity of shear keys, resulting in significant strength reduction. Larger shear key base remarkably increased shear capacity of the gap joint. Experimental tests indicated that AASHTO provision underestimated shear capacity of the match-casting dry joint specimens, while the numerical results for the gap dry joint showed that AASHTO provision underestimated shear capacity of full contact specimens, but overestimated that of left contact specimens.

Consensus of Multi-agent Systems with Dead-zone Nonlinearity

Haibo Jiang,Liping Zhang,Jianjiang Yu,Caigen Zhou 제어·로봇·시스템학회 2012 International Journal of Control, Automation, and Vol.10 No.4

In this paper, we investigate the consensus problem of multi-agent systems with dead-zone nonlinearity over undirected networks. Firstly, a control protocol is designed based on the local infor-mation of agents. Then by LaSalle’s invariance principle for non-smooth systems, we prove that if the undirected graph is connected then the consensus is achieved by the proposed control protocol. Sec-ondly, sufficient conditions are given to guarantee the consensus of multi-agent systems with dead-zone nonlinearity and switching topologies by Lyapunov method. Finally, numerical simulations show the effectiveness of our theoretical results.

Push-out tests on demountable high-strength friction-grip bolt shear connectors in steel–precast UHPC composite beams for accelerated bridge construction

Haibo Jiang,Haozhen Fang,Jinpeng Wu,Zhuangcheng Fang,Shu Fang,Gongfa Chen 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.6

Steel–precast ultra-high-performance concrete (UHPC) composite beams with demountable high-strength frictiongrip bolt (HSFGB) shear connectors can be used for accelerated bridge construction (ABC) and achieve excellent structural performance, which is expected to be dismantled and recycled at the end of the service life. However, no investigation focuses on the demountability and reusability of such composite beams, as well as the installation difficulties during construction. To address this issue, this study conducted twelve push-out tests to investigate the effects of assembly condition, bolt grade, bolt– hole clearance, infilling grout and pretension on the crack pattern, failure mode, load–slip/uplift relationship, and the structural performance in terms of ultimate shear strength, friction resistance, shear stiffness and slip capacity. The experimental results demonstrated that the presented composite beams exhibited favorable demountability and reusability, in which no significant reduction in strength (less than 3%) and stiffness (less than 5%), but a slight improvement in ductility was observed for the reassembled specimens. Employing oversized preformed holes could ease the fabrication and installation process, yet led to a considerable degradation in both strength and stiffness. With filling the oversized holes with grout, an effective enhancement of the strength and stiffness can be achieved, while causing a difficulty in the demounting of shear connectors. On the basis of the experimental results, more accurate formulations, which considered the effect of bolt–hole clearance, were proposed to predict the shear strength as well as the load–slip relationship of HSFGBs in steel–precast UHPC composite beams.

Earth Pressure and Internal Forces of Tunnel Lining in Jet Grouting Reinforced Mud Stratum

Haibo Jiang,Shunhua Zhou,Honggui Di,Weitao Ye,Zhi Liu,Yu Zhao 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.10

In this study, field measurements of the earth pressures and the main reinforcement strains were carried out at three shield tunnel linings in mud stratum reinforced by vertical jet-grouted piles during tunnel construction and post-construction. The measured strains were used to back-calculate the linings' internal forces. The measured earth pressures and the back-calculated internal forces were compared to corresponding design values. The results indicate that the earth pressure and the internal forces increased rapidly, before exhibiting a fluctuating decrease and finally a long-term slow change, after lining assembly. The vertical jet-grouted piles were beneficial to mobilise the soil arching effect and led to the real earth pressure on the lining significantly smaller than the full overburden pressure, even with a relatively shallow buried depth. The vertical jet-grouted piles intensified the influence of backfill grouting on the earth pressure and caused the lining segments near the backfill grouting holes to continuously bear more radial pressure in the long-term. The resultant internal forces during lining assembly were large, and the Conventional Model failed to consider this element of the internal forces. The findings can provide a reference for the design and the construction of similar projects.

Synthesis and characterization of a K/K2CO3-based solid superbase as a catalyst in propylene dimerization

Haibo Jin,Heng Jiang,Qiwei Wang,Suohe Yang,Guohua Luo,Guangxiang He 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.2

A novel solid superbase 3%K/K2CO3 was prepared by loading metallic potassium on K2CO3. The optimized preparation conditions included a loading time of 1.5 h, loading temperature of 150 oC, loading amount of 3wt% and average carrier size of 120 μm. Under the optimum conditions, the conversion of propylene is about 60% with the selectivity of dimers 98.5% and the selectivity of 4MP1 86.3%. In addition, the superbase 3%K/K2CO3 has a base strength of H−≥37, and the concentration of basic sites of H−≥35 is approximately 0.3mmol·g−1 CAT. The microcrystal of metallic potassium was determined using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). It was assumed that the oxygen species, which are adjacent to lattice defects, such as the crystalline corners, edges and vacancies of metallic potassium microcrystals, constituted the superbasic sites.

Effect of Transformation Temperature on the Ferrite–Bainite Microstructures, Mechanical Properties and the Deformation Behavior in a Hot-Rolled Dual Phase Steel

Bo Jiang,Xuewen Hu,Leyu Zhou,Haibo Wang,Yazheng Liu,Fugang Gou 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.2

The ferrite–bainite microstructures and mechanical properties in a hot-rolled dual phase steel with different transformationtemperatures were investigated in this paper. The deformation behavior of bainite and ferrite was analyzed by using in situscanning electron microscope. The results showed that the ferrite and bainite can be refined and the volume fraction of bainitecan be slightly increased by 5% by decreasing the ferrite transformation temperature from 690 to 635 °C and increasing thebainite transformation temperature from 400 to 450 °C. The strengthening mechanism was dislocation difference in polygonaland acicular ferrite and then the grain size difference of ferrite. The hole expansion ratio increased from 52.9 to 83.7% withthe ferrite transformation temperature decreasing. The cracks or voids were smaller in size and also the number in steel withthe lower ferrite transformation temperature after expanding. The microstructure separation along the boundary betweenbainite and ferrite and the slip band in the ferrite appeared at the non-uniform deformation stage. However, fewer appearedin the microstructure of steel with lower ferrite transformation temperature. Cooperative deformation of ferrite and bainiteand finer microstructure in steel with lower ferrite transformation temperature were the mechanisms why the cracks couldnot easily nucleated and propagated, respectively. Thus this was also why there was a better hole expansion ratio.

Microstructural Characterization and Softening Mechanism of Ultra-Low Carbon Steel and the Control Strategy in Compact Strip Production Process

Bo Jiang,Xuewen Hu,Guoning He,Huan Peng,Haibo Wang,Yazheng Liu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.9

In this paper, the microstructures and properties of hot rolled ultra-low carbon steel sheet produced by different compact stripproduction (CSP) processes were investigated. The softening mechanism was also discussed and the control strategy wasproposed in order to obtain optimum properties. Result showed that the average ferrite grain sizes of austenite rolling sheetand multiphase rolling sheet were 31.0 μm and 74.6 μm, respectively. The sheet after austenite rolling had a slightly higheryield and tensile strength while had a 6.3% higher elongation than that of the sheet after multiphase rolling. The higher dislocationin the sheet after multiphase rolling increased the strength while decreased the elongation. The softening mechanismof the sheet after multiphase rolling was the coarsening of ferrite grain. The combined role of {001} and {111} orientationresulted in a slight increase of the r and ̄rvalue in the sheet after multiphase rolling. It was a wise choice to conduct rollingat the Ac1temperature in CSP process to increase the grain size and decrease the dislocation density. Then, the strength ofthe sheets could be further reduced and the elongation could also be improved.