Fluid-structure interaction analysis of heat exchanger with torsional flow in the shell side

Xin Gu,Guan Wang,Qianxin Zhang,Cheng Chen,Ning Li,Weijie Chen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.1

Based on the theory of fluid-structure interaction (FSI), the flow characteristics and mechanical properties of torsional flow heat exchanger (TFHX) and cross torsional flow heat exchanger (CTFHX) were numerically studied. The simulation results were compared with the experimental results to verify the reliability of the numerical simulation. The results show that the pressure drop of CTFHX decrease is 30.31-32.56 % lower than that of TFHX, and the heat transfer coefficient is found to lower by 16.8-18.5 %, but the comprehensive performance h/∆P is increased by 14.8-17.9 %. There is also a higher stress around the baffle holes, and the influence of temperature load on stress is much greater than that of pressure load. Moreover, the linearization results of hazardous locations show that CTFHX has greater stress. This study provides theoretical guidance for the structural optimization and equipment maintenance of heat exchanger.

A 3-D RBSM for simulating the failure process of RC structures

Xingu Zhong,Chao Zhao,Bo Liu,Xiaojuan Shu,Mingyan Shen 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.3

Rigid body spring method (RBSM) is an effective tool to simulate the cracking process of structures, and has been successfully applied to investigate the behavior of reinforced concrete (RC) members. However, the theoretical researches and engineering applications of this method mainly focus on two-dimensional problems as yet, which greatly limits its applications in actual engineering projects. In this study, a three-dimensional (3-D) RBSM for RC structures is proposed. In the proposed model, concrete, reinforcing steels, and their interfaces are represented as discrete entities. Concrete is partitioned into a collection of rigid blocks and a uniform distribution of normal and tangential springs is defined along their boundaries to reflect its material properties. Reinforcement is modeled as a series of bar elements which can be freely positioned in the structural domain and irrespective of the mesh geometry of concrete. The bond-slip characteristics between reinforcing steel and concrete are also considered by introducing special linkage elements. The applicability and effectiveness of the proposed method is firstly confirmed by an elastic T-shape beam, and then it is applied to analyze the failure processes of a Z-type component under direct shear loading and a RC beam under two-point loading.

A fast and simplified crack width quantification method via deep Q learning

Xingu Zhong,Xiong Peng,Kun Zhou,Bingxu Duan,Chao Zhao,Tianyu Zhang 국제구조공학회 2023 Smart Structures and Systems, An International Jou Vol.32 No.4

Crack width is an important indicator to evaluate the health condition of the concrete structure. The crack width is measured by manual using crack width gauge commonly, which is time-consuming and laborious. In this paper, we have proposed a fast and simplified crack width quantification method via deep Q learning and geometric calculation. Firstly, the crack edge is extracted by using U-Net network and edge detection operator. Then, the intelligent decision of is made by the deep Q learning model. Further, the geometric calculation method based on endpoint and curvature extreme point detection is proposed. Finally, a case study is carried out to demonstrate the effectiveness of the proposed method, achieving high precision in the real crack width quantification.

Shear-lag behavior of prestressed concrete box-girder bridges during balanced cantilever construction

Zhong, Xingu,Zhang, Tianyu,Shu, Xiaojuan,Xu, Hongliang Techno-Press 2017 Advances in concrete construction Vol.5 No.5

Balanced cantilever construction is extensively used in the construction of prestressed concrete (PSC) box-girder bridges. Shear-lag effect is usually considered in finished bridges, while the cumulative shear-lag effect in bridges during balanced cantilever construction is considered only rarely. In this paper, based on the balanced cantilever construction sequences of large-span PSC box-girder bridges, the difference method is employed to analyze the cumulative shear-lag effect of box girders with varying depth under the concrete segments' own weight. During cantilever construction, no negative shear-lag effect is generated, and the cumulative shear-lag effect under the balanced construction procedure is greater than the instantaneous shear-lag effect in which the full dead weight is applied to the entire cantilever. Three cross-sections of Jianjiang Bridge were chosen for the experimental observation of shear-lag effect, and the experimental results are in keeping with the theoretical results of cumulative shear-lag effect. The research indicates that only calculating the instantaneous shear-lag effect is not sufficiently safe for practical engineering purposes.

A 3-D RBSM for simulating the failure process of RC structures

Zhong, Xingu,Zhao, Chao,Liu, Bo,Shu, Xiaojuan,Shen, Mingyan Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.3

Rigid body spring method (RBSM) is an effective tool to simulate the cracking process of structures, and has been successfully applied to investigate the behavior of reinforced concrete (RC) members. However, the theoretical researches and engineering applications of this method mainly focus on two-dimensional problems as yet, which greatly limits its applications in actual engineering projects. In this study, a three-dimensional (3-D) RBSM for RC structures is proposed. In the proposed model, concrete, reinforcing steels, and their interfaces are represented as discrete entities. Concrete is partitioned into a collection of rigid blocks and a uniform distribution of normal and tangential springs is defined along their boundaries to reflect its material properties. Reinforcement is modeled as a series of bar elements which can be freely positioned in the structural domain and irrespective of the mesh geometry of concrete. The bond-slip characteristics between reinforcing steel and concrete are also considered by introducing special linkage elements. The applicability and effectiveness of the proposed method is firstly confirmed by an elastic T-shape beam, and then it is applied to analyze the failure processes of a Z-type component under direct shear loading and a RC beam under two-point loading.

A modified RBSM for simulating the failure process of RC structures

Chao Zhao,Xingu Zhong,Bo Liu,Xiaojuan Shu,Mingyan Shen 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.2

In this paper, a modified rigid body spring model (RBSM) is proposed and used to analyze the damage and failure process of reinforced concrete (RC) structures. In the proposed model, the concrete is represented by an assembly of rigid blocks connected with a uniform distribution of normal and tangential springs to simulate the macroscopic mechanical behavior of concrete. Steel bars are evenly dispersed into rigid blocks as a kind of homogeneous axial material, and an additional uniform distribution of axial and dowel springs is defined to consider the axial stiffness and dowel action of steel bars. Perfect bond between the concrete and steel bars is assumed, and tension stiffening effect of steel bars is modeled by adjusting the constitutive relationship for the tensile reinforcement. Adjacent blocks are allowed to separate at the contact interface, which makes it convenient and easy to simulate the cracking process of concrete. The failure of the springs is determined by the Mohr-Coulomb type criterion with the tension and compression caps. The effectiveness of the proposed method is confirmed by elastic analyses of a cantilever beam under different loading conditions and failure analyses of a RC beam under two-point loading.

Feasibility study of buckling-restrained braces with PM-35 steel core

Chao Zhao,Qianqian Chen,Xingu Zhong,Tianyu Zhang,Zhiwen Chen 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.2

The energy dissipation characteristics of core materials greatly influence the working performance of bucklingrestrained braces (BRBs), so it is a vital work to develop more excellent energy dissipation core materials. In this research, a series of experimental studies are conducted, including the mechanical properties of PM-35 steels and the working performance of PM-35 BRB specimens, which serve to investigate the feasibility of PM-35 steel as core materials of BRBs. In addition, the analysis of variance (ANOVA) has been conducted to study the sensitivity factors of energy dissipation of PM-35 BRB specimens, especially the pre-force applied on the BRB specimens. According to the results of this research, it can be concluded that the energy absorption efficiency of PM-35 BRBs specimens is much higher than that of BRB specimens with ordinary core materials; the internal pores greatly weaken the yield strength of PM-35 steel and obviously improve the plastic deformation capacity, which makes that PM-35 core materials are able to absorb energy in a lower stress level; pre-force applied on core materials is the key factor governing the energy absorption, and can significantly improve the working performance of BRB specimens with PM-35 core materials.

2-D meso-scale complex fracture modeling of concrete with embedded cohesive elements

Mingyan Shen,Zheng Shi,Chao Zhao,Xingu Zhong,Bo Liu,Xiaojuan Shu 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.24 No.3

This paper has presented an effective and accurate meso-scale finite element model for simulating the fracture process of concrete under compression-shear loading. In the proposed model, concrete is parted into four important phases: aggregates, cement matrix, interfacial transition zone (ITZ), and the initial defects. Aggregate particles were modelled as randomly distributed polygons with a varying size according to the sieve curve developed by Fuller and Thompson. With regard to initial defects, only voids are considered. Cohesive elements with zero thickness are inserted into the initial mesh of cement matrix and along the interface between aggregate and cement matrix to simulate the cracking process of concrete. The constitutive model provided by ABAQUS is modified based on Wang’s experiment and used to describe the failure behaviour of cohesive elements. User defined programs for aggregate delivery, cohesive element insertion and modified facture constitutive model are developed based on Python language, and embedded into the commercial FEM package ABAQUS. The effectiveness and accuracy of the proposed model are firstly identified by comparing the numerical results with the experimental ones, and then it is used to investigate the effect of meso-structure on the macro behavior of concrete. The shear strength of concrete under different pressures is also involved in this study, which could provide a reference for the macroscopic simulation of concrete component under shear force.

Deformation and Energy Absorption Properties of Porous Metal-Concrete Interpenetrating Phase Composites Filled Thin-Walled Tubes

Zhou Yi,Zhao Chao,Zhong Xingu,Wang Langke,Luo Tianye 한국강구조학회 2024 International Journal of Steel Structures Vol.24 No.1

A fi lled thin-walled tube is an excellent energy absorption device, and its performance is closely related to the fi lled core material. In this paper, a porous metal-high performance concrete interpenetrating phase composites (PMCIPC) fi lling core material is proposed, which takes porous nickel as the matrix and high-performance concrete as the reinforcing element, trying to improve the energy absorption of thin-walled tube. Axial quasi-static compression tests were carried out on empty tube, PMCIPC and fi lled tube. Based on the experimental results, the eff ects of wall thickness and aspect ratio on the deformation and energy absorption performance of the fi lled tube were studied by numerical simulation. The results show that the larger wall thickness increases the energy absorption of the empty tube and the fi lled tube. The PMCIPC fi lling further improves the energy absorption capacity, and for the empty tubes with smaller wall thickness, the PMCIPC signifi cantly increases the crushing force effi ciency. When the aspect ratio (L/D) is 3.7, the deformation mode of the fi lled tube is Euler instability, and the performance begins to decrease sharply. Finally, a theoretical model is established to predict the mean crushing force of the fi lled tubes. The model results are in good agreement with the experimental results. This study provides eff ective guidance for the design of thin-walled structures with high energy absorption effi ciency.