Utilization of Completely Recycled Fine Aggregate for Preparation of Lightweight Concrete Partition Panels

Yibo Yang,Baixi Chen,Weizhen Zeng,Yanjun Li,Qiaohui Chen,Wenying Guo,Hengchang Wang,Yingqin Chen 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.5

To reduce the cost of lightweight concrete (LWC) partition panels and to address recycling concrete waste, this work utilized completely recycled fine aggregate (CRFA) to replace the natural fine aggregate and ceramsite in the preparation of LWC and LWC partition panels. To this end, an autoclave-free curing process and an air-entraining agent were used to prepare the CRFA-LWC. The workability, compressive strength, drying shrinkage, and pore structure of the CRFA-LWC and the performance of the CRFA-LWC partition panels were then investigated. The results show that the optimal ratio of the CRFA to the cement is 2.2 for the lightweight concrete, and the optimal panel cross section is a rounded rectangular one. All the pores in the CRFA-LWC have a diameter of smaller than 0.17 mm, and the diameter of 89% of them is less than 0.05 mm. In order to satisfy the drying shrinkage requirements stipulated by Chinese code JC/T 169-2016, the CRFA-LWC should be cured for at least 10 days. The economic analysis concludes that the material cost of CRFA-LWC is 40% lower than that of the autoclaved ceramsite concrete. In addition, utilizing CRFA in lightweight concrete can ease the shortage of natural aggregate.

Further study on improvement on strain concentration in through-diaphragm connection

Ying Qin,Jing-Chen Zhang,Peng Shi,Yi-Fu Chen,Yao-Han Xu,Zuo-Zheng Shi 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.2

Hollow structural section (HSS) columns have been increasingly popular due to their structural and architectural merits. However, practical difficulty lies in developing proper connections. The through-diaphragm connections are considered as suitable connection type that is widely adopted in Asian countries. However, the stress concentration occurs at the location connecting through-diaphragm and steel beam. Furthermore, the actual load path from the beam flange is not uniformly transferred to the HSS column as conventionally assumed. In this paper, tensile tests were further conducted on three additional specimens with beam flange plate to evaluate the load versus displacement response. The load-displacement curves, yield and ultimate capacity, ductility ratio were obtained. Furthermore, the strain development at different loading levels was discussed comprehensively. It is shown that the studied connection configuration significantly reduces the stress concentration. Meanwhile, simplified trilinear load-displacement analytical model for specimen under tensile load was presented. Good agreement was found between the theoretical and experimental results.

Tensile behavior of bolted through-diaphragm connections to SHS columns

Ying Qin,Jingchen Zhang,Yifu Chen,Peng Shi,Yaohan Xu,Zuozheng Shi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.3

Steel hollow section (SHS) columns have been increasingly popular in structural systems due to high compressive capacity, excellent torsional strength, and symmetric bending stiffness. In moment-resisting frames, the structural performance of connections to SHS columns is important to ensure the ability to carry bending moment. Conventional connections utilize welds to connect the adjacent components to the columns. Brittle fracture often initiates at the welds and reduces the ductility of connections. In this research, bolted connections were proposed to connect the beam to the SHS column through through-diaphragm. Tensile tests were conducted on four specimens to evaluate the structural behavior of connections. Failure mode, load-displacement response, strength, stiffness, and ductility were analyzed. The test results showed that the specimens were failed by the necking down of the flange plate. All specimens had high load-carrying capacity and good ductility. Strain distributions at key locations were investigated to study the force flow path. The application of through-diaphragm was found to deliver the tensile load to larger area and thus reduced the stress concentration at the connecting zone. Moreover, large amount of stress was transferred directly through the diaphragm, and the required stress demand for the SHS column was decreased. Design method was then proposed to predict the yield and the ultimate strength of the bolted connections. Good agreement was found between the experimental results and the theoretical predictions.

Research on Design of Through-Diaphragm Connections between CFRT Columns and HSS Beams

Ying Qin,Zhihua Chen,Ning Han 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.3

The through-diaphragm connection detail has been identified as a good choice for attaching HSS beams to concrete-filledrectangular tube columns in engineering applications. In this research program an analytical study was conducted tocomprehend the behavior of this detail and develop the accompanying design guidelines. The experimental results are presentedelsewhere. In this paper two analytical models were established to predict the shear stiffness and yield shear strength of theHSS beam and panel zone, respectively. Theoretical results based on the proposed model well agreed with the experimentaldata. Finally, design provisions were introduced to check the strength in the connections.

Experimental compressive behavior of novel composite wall with different width-to-thickness ratios

Ying Qin,Xin Chen,Xing-Yu Zhu,Wang Xi,Yuan-Ze Chen 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.2

Double skin composite wall system owns several structural merits in terms of high load-carrying capacity, large axial stiffness, and favorable ductility. A recently proposed form of truss connector was used to bond the steel plates to the concrete core to achieve good composite action. The structural behavior of rectangular high walls under compression and T-shaped high walls under eccentric compression has been investigated by the authors. Furthermore, the influences of the truss spacings, the wall width, and the faceplate thickness have been previously studied by the authors on short walls under uniform compression. This paper experimentally investigated the effect of width-to-thickness ratio on the compressive behavior of short walls. Compressive tests were conducted on three short specimens with different width-to-thickness ratios. Based on the test results, it is found that the composite wall shows high compressive resistance and good ductility. The walls fail by local buckling of steel plates and crushing of concrete core. It is also observed that width-to-thickness ratio has great influence on the compressive resistance, initial stiffness, and strain distribution across the section. Finally, the test results are compared with the predictions by modern codes.

Behavior of improved through-diaphragm connection to square tubular column under tensile loading

Ying Qin,Jing-Chen Zhang,Peng Shi,Yi-Fu Chen,Yao-Han Xu,Zuo-Zheng Shi 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.4

Square tubular columns are commonly used in moment resisting frames, while through-diaphragm connection is the most typical configuration detail to connect the H-shaped beam to the column. However, brittle fracture normally occurs at the complete joint penetration weld between the beam flange and the through-diaphragm due to the stress concentration caused by the geometrical discontinuity. Accordingly, three improved types of through-diaphragm are presented in this paper to provide smooth force flow path comparing to that of conventional connections. Tensile tests were conducted on four specimens and the results were analyzed in terms of failure modes, load-displacement response, yield and ultimate capacity, and initial stiffness. Furthermore, strain distributions on the through-diaphragm, the beam flange plate, and the column face were comprehensively evaluated and discussed. It was found that all the proposed three types of improved through-diaphragm connections were able to reduce the stress concentration in the welds between the beam flange and the through-diaphragm. Furthermore, the stress distribution in connection with longer tapered through-diaphragm was more uniform.

Behavior of L-shaped double-skin composite walls under compression and biaxial bending

Ying Qin,Xin Chen,Wang Xi,Xingyu Zhu,Yuanze Chen 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.4

The application of double-skin composite wall should meet different layout plans. However, most available research focused on the rectangular section with uniform axial compression. In this research, the structural behavior of double-skin composite wall with L section was studied. Due to the unsymmetric geometric characteristics, the considered loading condition combined the axial compression and biaxial bending. Five specimens were designed and tested under eccentric compression. The variables in the test included the width of the web wall, the truss spacing, the thickness of the steel faceplate, and the thickness of the web wall. The test results were discussed in terms of the load-displacement responses, buckling behavior, stiffness, ductility, strength utilization, strain distribution. Two modern codes were employed to predict the interaction between the axial compression and the biaxial bending. The method to calculate the available bending moment along the two directions was proposed. It was found that CECS 159:2004 offers more suitable results than AISC 360.

Eccentric compressive behavior of novel composite walls with T-section

Ying Qin,Xin Chen,Wang Xi,Xingyu Zhu,Yuanze Chen 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.4

Double skin composite walls are alternatives to concrete walls to resist gravity load in structures. The composite action between steel faceplates and concrete core largely depends on the internal mechanical connectors. This paper investigates the structural behavior of novel composite wall system with T section and under combined compressive force and bending moment. The truss connectors are used to bond the steel faceplates to concrete core. Four short specimens were designed and tested under eccentric compression. The influences of the thickness of steel faceplates, the truss spacing, and the thickness of web wall were discussed based on the test results. The N-M interaction curves by AISC 360, Eurocode 4, and CECS 159 were compared with the test data. It was found that AISC 360 provided the most reasonable predictions.

Compressive behavior of rectangular sandwich composite wall with different truss spacings

Ying Qin,Xin Chen,Wang Xi,Xing-Yu Zhu,Yuan-Ze Chen 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.6

Steel-concrete-steel sandwich composite wall is composed of two external steel plates and infilled concrete core. Internal mechanical connectors are used to enhance the composite action between the two materials. In this paper, the compressive behavior of a novel sandwich composite wall was studied. The steel trusses were applied to connect the steel plates to the concrete core. Three short specimens with different truss spacings were tested under compressive loading. The boundary columns were not included. It was found that the failure of walls started from the buckling of steel plates and followed by the crushing of concrete. Global instability was not observed. It was also observed that the truss spacing has great influence on ultimate strength, buckling stress, ductility, strength index, lateral deflection, and strain distribution. Three modern codes were introduced to calculate the capacity of walls. The comparisons between test results and code predictions show that AISC 360 provides significant underestimations while Eurocode 4 and CECS 159 offer overestimated predictions.

Structural behavior of sandwich composite wall with truss connectors under compression

Ying Qin,Xin Chen,Xingyu Zhu,Wang Xi,Yuanze Chen 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.2

Sandwich composite wall consists of concrete core attached by two external steel faceplates. It combines the advantage of steel and concrete. The appropriate composite action between steel faceplate and concrete core is achieved by using adequate mechanical connectors. This research studied the compressive behavior of the sandwich composite walls using steel trusses to bond the steel faceplates to concrete infill. Four short specimens with different wall width and thickness of steel faceplate were designed and tested under axial compression. The test results were comprehensively evaluated in terms of failure modes, load versus axial and lateral deformation responses, resistance, stiffness, ductility, strength index, and strain distribution. The test results showed that all specimens exhibited high resistance and good ductility. Truss connectors offer better restraint to walls with thinner faceplates and smaller wall width. In addition, increasing faceplate thickness is more effective in improving the ultimate resistance and axial stiffness of the wall.