scholarly journals Mechanical Behavior of Ultrahigh-Performance Concrete Tunnel Lining Segments

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2378
Author(s):  
Safeer Abbas ◽  
Moncef L. Nehdi
Keyword(s):  
Mechanical Behavior ◽  
Tunnel Lining ◽  
Load Test ◽  
Steel Fibers ◽  
Multiple Cracking ◽  
Cross Sectional ◽  
Mechanical Durability ◽  
Flexural Tests ◽  
Ultimate Load Carrying Capacity ◽  
Thrust Load

Ultrahigh-performance concrete (UHPC) is a novel material demonstrating superior mechanical, durability and sustainability performance. However, its implementation in massive structures is hampered by its high initial cost and the lack of stakeholders’ confidence, especially in developing countries. Therefore, the present study explores, for the first time, a novel application of UHPC, incorporating hybrid steel fibers in precast tunnel lining segments. Reduced scale curved tunnel lining segments were cast using UHPC incorporating hybrid 8 mm and 16 mm steel fibers at dosages of 1%, 2% and 3% by mixture volume. Flexural and thrust load tests were conducted to investigate the mechanical behavior of UHPC tunnel lining segments thus produced. It was observed that the flow of UHPC mixtures decreased due to steel fibers addition, yet steel fibers increased the mechanical and durability properties. Flexural tests on lining segments showed that both the strain hardening (multiple cracking) and strain softening (post-peak behavior) phases were enhanced due to hybrid addition of steel fibers in comparison with the control segments without fibers. Specimens incorporating 3% of hybrid steel fibers achieved 57% increase in ultimate load carrying capacity and exhibited multiple cracking patterns compared to that of identical UHPC segments with 1% fibers. Moreover, segments without fibers incurred excessive cracking and spalling of concrete at the base under the thrust load test. However, more stable behavior was observed for segments incorporating steel fibers under the thrust load, indicating its capability to resist typical thrust loads during tunnel lining field installation. This study highlights the potential use of UHPC with hybrid steel fibers for improved structural behavior. Moreover, the use of UHPC allows producing structural members with reduced cross-sectional dimensions, leading to reduced overall structural weight and increased clear space.

scholarly journals Concrete reinforced with various amounts of steel fibers reclaimed from end-of-life tires

2019 ◽  
Vol 262 ◽  
pp. 06008 ◽  
Author(s):  
Małgorzata Pająk
Keyword(s):  
Compressive Strength ◽  
End Of Life ◽  
Steel Fibers ◽  
Geometrical Characteristic ◽  
Mechanical Parameters ◽  
Fresh State ◽  
Negative Effect ◽  
Flexural Tests ◽  
Concrete Reinforcement

The main objective of the paper was to provide more information about the influence of fibers coming from the end-of-life tires on the behaviour of concrete. Because of their untypical geometrical characteristic they are not eagerly applied as concrete reinforcement. Considering the amount of used tires, the management of this waste would he beneficial for the environment. The paper deals with the typical floor concrete reinforced with three dosages of fibers equal to: 30kg/m3, 40kg/m3 and 60kg/m3. The compressive and flexural mechanical parameters of RSFC were studied. The waste fibers with the shape dissimilar to manufactured fibers did not have a negative effect on the properties of the mix in a fresh state. The compressive strength was slightly affected by the fibers, meanwhile the pronounced influence of RSF on the post-peak flexural parameters was noted. Those parameters increased proportionally with the amount of fibers. However, the scatters in the flexural tests results were increasing with the fibers content. The investigations indicate that the fibers from the end-of-life tires could he applied as a concrete reinforcement. The values of flexural parameters which can be further applied to structural calculations were shown.

scholarly journals Experimental Study on the Behavior of X-Section Pile Subjected to Cyclic Axial Load in Sand

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Yiwei Lu ◽  
Hanlong Liu ◽  
Changjie Zheng ◽  
Xuanming Ding
Keyword(s):  
Axial Load ◽  
Large Scale ◽  
Cross Sectional Area ◽  
Load Test ◽  
Dynamic Responses ◽  
Scale Model ◽  
Loading Frequency ◽  
Sectional Area ◽  
Cross Sectional ◽  
Shaft Friction

X-section cast-in-place concrete pile is a new type of foundation reinforcement technique featured by the X-shaped cross-section. Compared with a traditional circular pile, an X-section pile with the same cross-sectional area has larger side resistance due to its larger cross-sectional perimeter. The behavior of static loaded X-section pile has been extensively reported, while little attention has been paid to the dynamic characteristics of X-section pile. This paper introduced a large-scale model test for an X-section pile and a circular pile with the same cross-sectional area subjected to cyclic axial load in sand. The experimental results demonstrated that cyclic axial load contributed to the degradation of shaft friction and pile head stiffness. The dynamic responses of X-section pile were determined by loading frequency and loading amplitude. Furthermore, comparative analysis between the X-section pile and the circular pile revealed that the X-section pile can improve the shaft friction and reduce the cumulative settlement under cyclic loading. Static load test was carried out prior to the vibration tests to investigate the ultimate bearing capacity of test piles. This study was expected to provide a reasonable reference for further studies on the dynamic responses of X-section piles in practical engineering.

scholarly journals Bearing capacity analysis of helical pile foundation on peat

2018 ◽  
Vol 195 ◽  
pp. 03005
Author(s):  
Ferry Fatnanta ◽  
Andarsin Ongko
Keyword(s):  
Bearing Capacity ◽  
Pile Foundation ◽  
Load Test ◽  
Building Construction ◽  
Capacity Analysis ◽  
Cross Sectional ◽  
Tension Tests ◽  
Constant Rate ◽  
Helical Piles ◽  
The Individual

Peat is a kind of soil with a very low bearing capacity and high compressibility. Generally, a building construction on peat is done by using a wooden pile foundation. However, the length of the wooden piles is sometimes limited and causes the friction strength between the soil and wooden piles to became suboptimal. In order to enhance the bearing capacity of the foundation, the cross-sectional area of the foundation needs to be enlarged. One of the solutions for this problem is through helical piles. There are two methods to determine the helical pile`s bearing capacity, i.e. individual bearing and cylindrical shear methods. In this paper, bearing capacity prediction was discussed. A foundation load test was thoroughly done by a constant rate of penetration. This test consisted of compression and tension tests. The result was analyzed by individual bearing and cylindrical shear methods and next compared to each other. The result of the analysis has shown that the individual bearing method was more suitable in predicting helical piles’ bearing capacity since it produced the lowest error rate, with a magnitude of 21,31%.

Investigation on the Effect of Geometrical Shape of Cold Direct Extrusion on Commercially Pure Aluminum Alloyed by 4% Cu

2015 ◽  
Vol 1105 ◽  
pp. 182-189 ◽  
Author(s):  
Adnan I.O. Zaid ◽  
S.M.A. Al-Qawabah
Keyword(s):  
Mechanical Behavior ◽  
Pure Aluminum ◽  
Extrusion Process ◽  
Control Area ◽  
Geometrical Shape ◽  
Compression Tests ◽  
Maximum Enhancement ◽  
Cross Sectional ◽  
Direct Extrusion ◽  
Cu Alloy

Al-4% Cu alloys are now widely used in many engineering applications especially in robotic, aerospace and vibration control area. The main problem arises from the weakness of their mechanical characteristics. Therefore, this study is directed towards enhancing the mechanical properties through severe plastic deformation, hence it is anticipated that cold direct extrusion process may enhance their mechanical behavior. This was performed through using three different cross sectional dies namely; circular, square, and rectangular that have the same cross sectional area. The general microstructure, microhardness, and compression tests were performed on each specimen produced before and after extrusion for Al and Al-4% Cu alloy. It was found that the maximum enhancement in mechanical behavior was achieved after extrusion through the rectangular shape for both Al and Al-4% Cu alloy at 0.2 strain by 143% for Al and 134.8% for Al-4%Cu wt.; similarly the hardness of both of them was improved where a maximum of 141.8 % was obtained for Al-4% Cu wt. in case of rectangular cross sectional die.

scholarly journals Customer Lifetime Value of Supplementary Health Insurance: An Analytical Model

2021 ◽  
Author(s):  
Roohollah Dehghani Ghale ◽  
Farzad Karimi ◽  
Hassan Ghorbani Dinani
Keyword(s):  
Impact Factor ◽  
Structural Equation ◽  
Deep Understanding ◽  
Customer Lifetime Value ◽  
Load Test ◽  
Insurance Companies ◽  
Structured Interviews ◽  
Cross Sectional ◽  
Customer Lifetime ◽  
Lifetime Value

Background: With the number of insurance customers growing, insurance companies are trying new ways to retain customers and streamline communication channels to avoid loss of revenue. The present study set out to develop a model for a reliable analysis of customer lifetime value. Methods: The present study was exploratory mixed method in design. The study took place in Jundishapur University of Medical Sciences, located in Ahvaz, Iran. A total of 402 insurance experts and university staffers participated in the study. A cross-sectional data collection was done using semi-structured interviews (n = 22) and a questionnaire (n = 380). The latter was validated via a panel of content area experts, criterion-dependent validity (second-order confirmatory factor analysis), and divergent validity (cross-sectional load test and Fornell-Laker). Cronbach's alpha and combined reliability were - 0.8 and 0.8, respectively. A structural equation approach was employed to analyze data using Smart PLS software. Results: Customer loyalty with an impact factor of 0.60 and T-statistic of 5.79, profitability with an impact factor of 0.55 and T-statistic of 3.75, customer co-creation with an impact factor of 0.28, and T-statistic of 2.7 have been identified as dimensions of customer lifetime value. Conclusion: Measuring customer lifetime value to implement various strategies requires a deep understanding of such value dimensions as loyalty, profitability, and value creation.

scholarly journals Steel fiber reinforced concrete pipes: part 1: technological analysis of the mechanical behavior

2012 ◽  
Vol 5 (1) ◽  
pp. 1-11 ◽  
Author(s):  
A. D. de Figueiredo ◽  
A. de la Fuente ◽  
A. Aguado ◽  
C. Molins ◽  
P. J. Chama Neto
Keyword(s):  
Reinforced Concrete ◽  
Mechanical Behavior ◽  
Steel Fiber ◽  
Test Procedure ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Test Procedures ◽  
Concrete Pipes

This paper is the first part of an extensive work focusing the technological development of steel fiber reinforced concrete pipes (FRCP). Here is presented and discussed the experimental campaign focusing the test procedure and the mechanical behavior obtained for each of the dosages of fiber used. In the second part ("Steel fiber reinforced concrete pipes. Part 2: Numerical model to simulate the crushing test"), the aspects of FRCP numerical modeling are presented and analyzed using the same experimental results in order to be validated. This study was carried out trying to reduce some uncertainties related to FRCP performance and provide a better condition to the use of these components. In this respect, an experimental study was carried out using sewage concrete pipes in full scale as specimens. The diameter of the specimens was 600 mm, and they had a length of 2500 mm. The pipes were reinforced with traditional bars and different contents of steel fibers in order to compare their performance through the crushing test. Two test procedures were used in that sense. In the 1st Series, the diameter displacement was monitored by the use of two LVDTs positioned at both extremities of the pipes. In the 2nd Series, just one LVDT is positioned at the spigot. The results shown a more rigidity response of the pipe during tests when the displacements were measured at the enlarged section of the socket. The fiber reinforcement was very effective, especially when low level of displacement was imposed to the FRCP. At this condition, the steel fibers showed an equivalent performance to superior class pipes made with traditional reinforced. The fiber content of 40 kg/m3 provided a hardening behavior for the FRCP, and could be considered as equivalent to the critical volume in this condition.

scholarly journals Prediction of Dilution and Its Impact on the Metallurgical and Mechanical Behavior of a Multipass Steel Weldment

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Y. L. Sun ◽  
C. J. Hamelin ◽  
T. F. Flint ◽  
A. N. Vasileiou ◽  
J. A. Francis ◽  
...  
Keyword(s):  
Weld Metal ◽  
Mechanical Behavior ◽  
Arc Welding ◽  
Measurement Data ◽  
Base Material ◽  
Thermocouple Measurement ◽  
Cross Sectional ◽  
Steel Weldment ◽  
Gas Tungsten Arc ◽  
Compressive Stresses

Abstract A three-pass groove weld made by gas-tungsten arc welding in a 20-mm thick SA508 steel plate is modeled to predict the thermal, metallurgical, and mechanical behavior. The dilution for each pass is estimated as the proportion of base material in the weld metal, based on the predicted cross-sectional areas for the fusion zone (FZ) associated with each individual pass. The temperature predictions are consistent with the thermocouple measurement data and cross-weld macrographs. The predicted microstructures are qualitatively compared with the observed microstructures in cross-weld optical micrographs. The measured hardness is then used to quantitatively validate the predictions for postweld microconstituents (e.g., the ferrite, bainite, and martensite fractions), based on a hardness-microstructure correlation. The predicted residual stresses are compared with those measured by neutron diffraction. The results show that the dilution significantly affects the metallurgical and mechanical properties of weld metal (either as-deposited or reheated), and its consideration notably improves the predictions for microstructure and residual stress in the multipass steel weldment. Furthermore, the increase in dilution promotes the formation of martensite, which enhances the hardness, and leads to lower tensile stresses (or higher compressive stresses) in the weld metal. Such behavior arises due to the higher hardenability of the base material employed in this study, coupled with delayed austenite decomposition on cooling.

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