scholarly journals Review of Mechanical Bar Couplers for Splicing Precast Concrete Members

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Seyed Saman Khedmatgozar Dolati
Keyword(s):  
Precast Concrete ◽  
Concrete Members

Case Studies of Seismic Vibration Control of Civil Structures Using Shape Memory Alloys

2011 ◽  
Vol 243-249 ◽  
pp. 5427-5434
Author(s):  
Hui Qian ◽  
Hong Nan Li ◽  
Di Cui ◽  
Huai Chen
Keyword(s):  
Reinforced Concrete ◽  
Energy Dissipation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Vibration Control ◽  
Case Studies ◽  
Precast Concrete ◽  
Reinforced Concrete Beams ◽  
Seismic Vibration ◽  
Concrete Members

Shape memory alloys (SMAs) are unique class materials that have the ability to undergo large deformations, while returning to their undeformed shape through either the applications of heat (SME) or removal of stress (SE). The unique properties lead to their wide applications in the biomedical, mechanical, aerospace, commercial industries, and recently in civil engineering. The paper presents two case studies of structural seismic vibration control using SMAs. The first one is a study of the SMA reinforced RC members. Two innovative applications in RC members, such as SMA-based Precast Concrete Frame Connection (SMA-PCFC), and SMA reinforced RC short column, were proposed. Moreover, the self-rehabilitation properties of SMAs-based Intelligent Reinforced Concrete Beams (SMA-IRCBs) were further experimentally investigated. The results show that SMAs can improve the mechanical properties of concrete members. SMA reinforced RC members have unique seismic performance compared to ordinarily steel reinforced concrete members. The second one is a study of the structural energy dissipation system using SMAs damping device. An innovative hybrid SMAs friction device (HSMAFD) which consists of pre-tensioned superelastic SMA wires and friction devices (FD) was presented. The results of cyclic tensile tests show that the HSMAFD exhibits stable large energy dissipation capacity and re-centering feature. The effectiveness of the HSMAFD in reducing horizontal response of structures subjected to strong seismic excitations was verified through shaking table tests carried out on a reduced-scale symmetric steel frame model with and without the HSMAFD.

Mix Optimization for Precast Concrete Members in Building Industrialization

2014 ◽  
Vol 629-630 ◽  
pp. 382-387
Author(s):  
Jing Li ◽  
Jun Zhang ◽  
Zhao Rong Hou ◽  
Sheng Wei Wu
Keyword(s):  
Precast Concrete ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Concrete Members ◽  
Orthogonal Experiments ◽  
Mix Proportion ◽  
Early Strength ◽  
Cement Strength ◽  
Sand And Gravel ◽  
Good Workability

The traditional mix proportion for concrete used in building field could not meet the requirements for industrialization production any more, and the optimization needs developing to obtain an ideal mix proportion for precast concrete with high early strength and good workability, as well as economy. To achieve the high early strength, Low-Alkalinity Sulphoaluminate Cement was selected, accompanied by Ordinary Portland Cement. The properties of other materials, namely aggregates (medium sand and gravel) and admixtures (polycarboxylate-based superplasticizer and sodium sulfate), were determined through literature review. The parameters of materials, such as the fineness modulus, mud-content of aggregates and cement strength, were determined. Besides, the range of water-cement ratio, admixture content and the ratio of two kinds of cements etc. in a total of 13 preliminary concrete mixes are analyzed. With further analysis, the four dominant factors were chosen, that is, water-cement ratio, cement content, superplasticizer content and sand ratio, leading to a series of orthogonal experiments with 3 levels of each factor. By analysis of test result data and consideration of cost, the optimized mix for precast concrete in building industrialization was carried out, of which the compressive strength in 10 hours reached the required strength and other properties reasonable.

scholarly journals Construction of a Highrise Condominium Building with Precast Concrete Members

1992 ◽  
Vol 30 (8) ◽  
pp. 39-47
Author(s):  
Y. Takenaga ◽  
T. Hitomi ◽  
A. Sumi ◽  
A. Takahata
Keyword(s):  
Precast Concrete ◽  
Concrete Members

scholarly journals Dynamic Optimization Model for Estimating In-Situ Production Quantity of PC Members to Minimize Environmental Loads

2020 ◽  
Vol 12 (19) ◽  
pp. 8202
Author(s):  
Jeeyoung Lim ◽  
Joseph J. Kim
Keyword(s):  
Dynamic Optimization ◽  
Optimization Model ◽  
Co2 Emission ◽  
Precast Concrete ◽  
Environmental Loads ◽  
Concrete Members ◽  
Production Quantity ◽  
Dynamic Optimization Model ◽  
In Situ Production

CO2 emissions account for 80% of greenhouse gases, which lead to the largest contributions to climate change. As the problem of CO2 emission becomes more and more prominent, research on sustainable technologies to reduce CO2 emission among environmental loads is continuously being conducted. In-situ production of precast concrete members has advantages over in-plant production in reducing costs, securing equal or enhanced quality under equal conditions, and reducing CO2 emission. When applying in-situ production to real projects, it is vital to calculate the optimal quantity. This paper presents a dynamic optimization model for estimating in-situ production quantity of precast concrete members subjected to environmental loads. After defining various factors and deriving the objective function, an optimization model is developed using system dynamics. As a result of optimizing the quantity by applying it to the case project, it was confirmed that the optimal case can save 7557 t-CO2 in CO2 emissions and 6,966,000 USD in cost, which resulted in 14.58% and 10.53% for environmental loads and cost, respectively. The model developed here can be used to calculate the quantity of in-situ production quickly and easily in consideration of dynamically changing field conditions.

scholarly journals Ultrasonic Detection Method for Grouted Defects in Grouted Splice Sleeve Connector Based on Wavelet Pack Energy

Sensors ◽  
2019 ◽  
Vol 19 (7) ◽  
pp. 1642 ◽  
Author(s):  
Zuohua Li ◽  
Lilin Zheng ◽  
Chaojun Chen ◽  
Zhili Long ◽  
Ying Wang
Keyword(s):  
Detection System ◽  
Wavelet Packet ◽  
Precast Concrete ◽  
Ultrasonic Method ◽  
Complex Structure ◽  
Ultrasonic Detection ◽  
Concrete Members ◽  
Negative Effect ◽  
Group A ◽  
Ultrasonic Parameters

Grouted splice sleeve (GSS) connectors are mainly used in precast concrete structures. However, errors in manual operation during construction cause grouted defects in the GSS connector, which can lead to a negative effect on the overall mechanical properties of the structures. Owing to the complex structure of precast concrete members with a GSS connector, it is difficult to detect grouted defects effectively using traditional ultrasonic parameters. In this paper, a wavelet packet analysis algorithm was developed to effectively detect grouted defects using the ultrasonic method, and a verified experiment was carried out. Laboratory detection was performed on the concrete specimens with a GSS connector before grouting, in which the grouted defects were mimicked with five sizes in five GSS connectors of each specimen group. A simple and convenient ultrasonic detection system was developed, and the specimens were detected. According to the proposed grouted defect index, the results demonstrated that when the grouted defects reached certain sizes, the proposed method could detect the grouted defects effectively. The proposed method is effective and easy to implement at a construction site with simple instruments, and so provides an innovative method for grouted defects detection of precast concrete members.

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