scholarly journals Experimental Study on Deformation Behavior and Compressive Strength of Concrete Cast in Steel Tube Arches under Low-Temperature Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Tuo Shi ◽  
Nianchun Deng ◽  
Xiao Guo ◽  
Wen Xu ◽  
Shi Wang

Taking the construction of a concrete-filled steel tube (CFST) arch bridge (part of the Sichuan-Tibet Railway) in low temperatures as the test site, firstly the deformation performance test of concrete was carried out. Following this initial testing, measurement of compressive strength and shrinkage performance was conducted in large-diameter CFSTs under a variety of curing conditions. Experimental results showed that the expansion effect of Ca-Mg composite expansive agent in concrete was better than that of other expansive agents at any stage. Under low-temperature curing (0°C), the sampling strength of the large-diameter CFSTs reached 73.5% of the design strength at 28 d in the presence of a nonthermal curing system. The design strength itself was reached, when a curing system involving a thermal insulation film was applied, and use of this film also led to improvements in concrete shrinkage. The results suggested that a Ca-Mg composite expansive agent, combined with an insulation film curing system, should be the technique selected for concrete pumping construction of CFST arch bridges in Tibet.

2013 ◽  
Vol 405-408 ◽  
pp. 2534-2537 ◽  
Author(s):  
Yuan Yuan Wu ◽  
Yuan Peng ◽  
Yong Dao Liu ◽  
Li Li Jia

The expansion of cement mortar mixing expansive agent under standard curing and membrane curing conditions and compressive strength in constrained conditions are studied in this paper. Results show that the early expansion effect of calcium sulphoaluminate hydrate-calcium hydroxide expansive agent is obvious, mid-to late effect of magnesia expansive agent increase clearly. Compare with standard curing, the shrinkage of the basic cement mortar increase and expansion effect of expansive agent reduce under membrane curing. The expansion effect of expansive agent B is good and persistent under membrane curing, its applicable to used in the closed environment, such as concrete filled steel tubes. The compressive strength of mortar with expansion agent is a little more than the basic mortar under the condition of limit.


2019 ◽  
Vol 136 ◽  
pp. 03009
Author(s):  
Yue Tian ◽  
Wanlai Zhang ◽  
Yihang Zhang

Based on the construction characteristics in the Northeast China Region under low temperature conditions, this article studies the influences of admixtures without antifreezing agent of different types and amounts on the low-temperature concrete and characteristics of pore structure. The results show that the amount of the admixtures is stable, the compressive strength of concrete under the curing condition of low temperature naturally varying is higher than the strength under the curing condition of constant low temperature while the porosity of the concrete under the curing condition of low temperature naturally varying is lower than the porosity under the curing condition of constant low temperature; The most appropriate curing method for the concrete used in winter construction is the curing method of low temperature naturally varying.


2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Zhengran Lu ◽  
Chao Guo

Most large-diameter concrete-filled steel tube (CFST) arch bridges adopt spiral-welded steel tubes for technical and economic reasons. However, during the steel tube manufacturing process, the welding temperature and other factors lead to a decreased spiral-welded seam (SWS) strength initially. Furthermore, for the CFST arch bridges using ordinary concrete, the laitance and air void defects inevitably appear, especially 20 years ago when there was no air-entraining agent in China. This paper presents a group of scale model experiments and finite element model analysis of the bearing capacity of a serviced CFST arch bridge rib with decreased SWS strength and concrete air void composite defects, under small eccentric axial compression on ultrasonic scanning field data. Parametric analyses were also performed to investigate the influence of the air void and SWS strength on the bearing capacity of the rib. Finally, a new ultimate strength index of the rib with composite defects was proposed, and a simplified formula was presented to estimate the effects of the air void and SWS strength decrease on the ultimate strength of the CFST arch bridge rib.


2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Tuo Shi ◽  
Nianchun Deng ◽  
Dong Pan ◽  
Shi Wang

To study the construction of concrete-filled steel tubular (CFST) arch bridges in Tibet, China, the hydration-temperature field of nonshrinkage concrete in large-diameter CFST arch ribs was evaluated in a temperature-testing box to simulate a low-temperature environment. A finite element simulation was then conducted to replicate the experimental results. Finally, an improved formula with the parameters related to the diameter, the position, and the retarding time of concrete for predicting the hydration heat generated by non-shrinkage concrete in large-diameter CFST arch ribs cured at low temperatures was proposed. The formula results were shown to be consistent with the experimental results for low-temperature conditions and large diameters. This research method can be extended to predict the hydration heat at all locations in different-diameter CFSTs with different concrete mixes cured at various temperatures.


2014 ◽  
Vol 590 ◽  
pp. 316-320
Author(s):  
Xin Quan Wang ◽  
Shi Min Zhang ◽  
Juan Liao ◽  
Ying Sheng Huang ◽  
Chun Long Wang

The flexural load-bearing performance prototype test has been made on the precast thin-wall steel and spun concrete composite pile with a diameter of 1000 mm (TSC pile). The load deflection curve and pile deflection curve at each loading step have been obtained. The bending test results show that the deformation of large diameter TSC pile experienced elastic, elastic-plastic and plastic three phases under the load of bending moment, the damage of pile was caused by the tension stress of steel in tension zone exceeded the yield strength, which belongs to the ductile damage. As for the TSC pile ultimate flexural bearing capacity, the measured value agreed with the theoretical calculation value, which shows that the existing thin-wall centrifugal concrete filled steel tube structure ultimate flexural bearing capacity calculation theory and method is suitable for large diameter TSC pile. Preface Precast Thin-wall Steel and spun Concrete composite Pile (TSC pile) is in the use of type Q235B or Q345B plate (strip) pouring of concrete filled steel tube made of crimping forming and welding, the centrifugal casting[1]. The compressive strength of concrete is not less than 80MPa, with a new pile products bear large vertical load and horizontal load. Concrete pile has the characteristics of high compressive strength, flexural capacity is weak; While the flexural capacity of steel pipe pile is strong, has good plasticity, But easy buckling occurs when the axial compression, loss of compression capability. TSC pile is a steel - concrete composite structure between steel pile and centrifugal concrete pipe pile, not only can give full play to the advantages of the both, can also overcome the shortcomings of its own when used alone[2]: With the inner wall of the concrete pipe, the outer pipe can enhance its stability ;and the inner concrete pipe with steel " confining effect", by the uniaxial stress state into three dimensional stress state, which greatly improves the compressive strength, With high anti-hammering capability, high penetration, pile sinking speed, good durability, pile quality, materials and low cost[3]. The TSC pile has been successfully applied to industry, electric power, transportation and other areas, commonly used in port engineering pile type of larger diameter, and by the wind, wave and other horizontal load, to put forward higher requirements of flexural performance of pile body. Therefore it is necessary to study the flexural behavior of large diameter pile TSC. Model test is usually the most useful method to study the pile loading behavior[4, 5].In this paper, the diameter 1000mm of TSC pile bending prototype test has been conducted, and the test is a research on the large diameter pile in TSC subjected to pure bending bearing capacity. Experimental Study of Pure Bending of TSC Pile


Buildings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 298
Author(s):  
Tao Ai ◽  
Danni Zhong ◽  
Yao Zhang ◽  
Jingshan Zong ◽  
Xin Yan ◽  
...  

To maximize the utilization of red mud in geopolymers, a red mud–metakaolin (RM-MK) geopolymer and red mud–fly ash (RM-FA) geopolymer were prepared, respectively. The effects of red mud content on the compressive strength and microstructure of the geopolymers were investigated under three different curing conditions. The results showed that the strength of the geopolymer decreased linearly with an increase in the red mud content, whether curing at room temperature or 80 °C. Surprisingly, curing in an autoclave, the appropriate amount of red mud had a favorable impact on the mechanical properties of the geopolymers. When the amount of red mud was 50%, the strength of the RM-MK geopolymer reached its highest compressive strength, 36.3 MPa, and the strength of the RM-FA geopolymer reached its highest at 31.7 MPa. Compared with curing at low temperature, curing the red mud-based geopolymers under a higher temperature and higher pressure can maximize the use of red mud. XRD analysis indicated that zeolite minerals formed. The SEM results showed that the geopolymers cured in an autoclave had a dense structure.


2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yongli Xu ◽  
Guang Yang ◽  
Hongyuan Zhao

For cement-based materials, the curing temperature determines the strength gain rate and the value of compressive strength. In this paper, the 5% cement-stabilized macadam mixture is used. Three indoor controlled temperature curing and one outdoor natural curing scenarios are designed and implemented to study the strength development scenario law of compressive strength, and they are standard temperature curing (20°C), constant low temperature curing (10°C), day interaction temperature curing (varying from 6°C to 16°C), and one outdoor natural temperature curing (in which the air temperature ranges from 4°C to 20°C). Finally, based on the maturity method, the maturity-strength estimation model is obtained by using and analyzing the data collected from the indoor tests. The model is proved with high accuracy based on the validated results obtained from the data of outdoor tests. This research provides technical support for the construction of cement-stabilized macadam in regions with low temperature, which is beneficial in the construction process and quality control.


Machines ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 1
Author(s):  
Jing Wang ◽  
Zhihua Wan ◽  
Zhurong Dong ◽  
Zhengguo Li

The harmonic reducer, with its advantages of high precision, low noise, light weight, and high speed ratio, has been widely used in aerospace solar wing deployment mechanisms, antenna pointing mechanisms, robot joints, and other precision transmission fields. Accurately predicting the performance of the harmonic reducer under various application conditions is of great significance to the high reliability and long life of the harmonic reducer. In this paper, a set of automatic harmonic reducer performance test systems is designed. By using the CANOpen bus interface to control the servo motor as the drive motor, through accurately controlling the motor speed and rotation angle, collecting the angle, torque, and current in real time, the life cycle test of space harmonic reducer was carried out in high vacuum and low temperature environment on the ground. Then, the collected data were automatically analyzed and calculated. The test data of the transmission accuracy, backlash, and transmission efficiency of the space harmonic reducer were obtained. It is proven by experiments that the performance data of the harmonic reducer in space work can be more accurately obtained by using the test system mentioned in this paper, which is convenient for further research on related lubricating materials.


2021 ◽  
Vol 11 (9) ◽  
pp. 4043
Author(s):  
Aleksandar Landović ◽  
Miroslav Bešević

Experimental research on axially compressed columns made from reinforced concrete (RC) and RC columns strengthened with a steel jacket and additional fill concrete is presented in this paper. A premade squared cross-section RC column was placed inside a steel tube, and then the space between the column and the tube was filled with additional concrete. A total of fourteen stub axially compressed columns, including nine strengthened specimens and five plain reinforced concrete specimens, were experimentally tested. The main parameter that was varied in the experiment was the compressive strength of the filler concrete. Three different concrete compression strength classes were used. Test results showed that all three cross-section parts (the core column, the fill, and the steel jacket) worked together in the force-carrying process through all load levels, even if only the basic RC column was loaded. The strengthened columns exhibited pronounced ductile behavior compared to the plain RC columns. The influence of the test parameters on the axial compressive strength was investigated. In addition, the specimen failure modes, strain development, and load vs. deformation relations were registered. The applicability of three different design codes to predict the axial bearing capacity of the strengthened columns was also investigated.


Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2249
Author(s):  
Bei Chen ◽  
Fuqiang Dong ◽  
Xin Yu ◽  
Changjiang Zheng

In order to solve the problems caused by asphalt diseases and prolong the life cycle of asphalt pavement, many studies on the properties of modified asphalt have been conducted, especially polyurethane (PU) modified asphalt. This study is to replace part of the styrene-butadiene-styrene (SBS) modifier with waste polyurethane (WP), for preparing WP/SBS composite modified asphalt, as well as exploring its properties and microstructure. On this basis, this paper studied the basic performance of WP/SBS composite modified asphalt with a conventional performance test, to analyze the high- and low-temperature rheological properties, permanent deformation resistance and storage stability of WP/SBS composite modified asphalt by dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. The microstructure of WP/SBS composite modified asphalt was also observed by fluorescence microscope (FM) and Fourier transform infrared spectroscopy (FTIR), as well as the reaction between WP and asphalt. According to the results of this study, WP can replace SBS as a modifier to prepare WP/SBS composite modified asphalt with good low-temperature resistance, whose high-temperature performance will be lower than that of SBS modified asphalt. After comprehensive consideration, 4% SBS content and 15% WPU content (4 S/15 W) are determined as the suitable types of WPU/SBS composite modified asphalt.


Sign in / Sign up

Export Citation Format

Share Document