scholarly journals Effect of Voids behind Lining on the Failure Behavior of Symmetrical Double-Arch Tunnels

Symmetry ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1321 ◽  
Author(s):  
Zhang ◽  
Ye ◽  
Min ◽  
Xu
Keyword(s):  
Service Life ◽  
Earth Pressure ◽  
Internal Force ◽  
Failure Behavior ◽  
Large Section ◽  
Failure Patterns ◽  
Internal Forces ◽  
Tunnel Safety ◽  
Increasing Demand ◽  
The Impact

The presence of voids behind lining seriously affects the safety of the symmetrical double-arch tunnels during service life. It is essential to find out the impact of voids on tunnel safety due to the increasing demand for the construction and maintenance of symmetrical double-arch tunnels. Model tests and numerical analyses were conducted in this research. The results attained were explored including earth pressure, internal force, and lining failure. Results reveal that the presence of voids has a large influence on the internal force in the lining of symmetrical double-arch tunnels, generally in the form of asymmetrical failure patterns of the lining. The failure patterns of the lining are greatly influenced by the size and location of voids with respect to the symmetrical double-arch tunnel circumference. Significant changes in the lining internal forces were found at the areas in the close vicinity of the void whereas a few changes were found at the bottom of the sidewall, the invert, and the central wall far away from the void. The propagation laws of lining cracks of asymmetrical double-arch tunnels are more complicated than symmetrical tunnels with a void behind the central wall. The location of the initial cracking of symmetrical and asymmetrical double-arch tunnels is the same, while the lining failure of the large-section tunnel is the most complicated.

scholarly journals Characterization of track geometric imperfections leading to maximal dynamic amplification of internal forces in railway bridges

2017 ◽  
Vol 10 (4) ◽  
pp. 937-956 ◽  
Author(s):  
P. G. C. Amaral ◽  
C. E. N. Mazzilli
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Internal Force ◽  
Contact Forces ◽  
Beam Model ◽  
Railway Bridges ◽  
Rail Line ◽  
Internal Forces ◽  
Dynamic Amplification ◽  
The Impact

ABSTRACT This paper resorts to a simplified dynamic analysis methodology for the study of vibrations in railway bridges produced by the passage of a typical passenger train, or EUT (Electric Unit Train). It starts from a model with fifteen degrees-of-freedom, namely vertical (bounce) and horizontal displacements (sway) and rotations about the longitudinal (roll), transverse (pitch) and vertical (yaw) axes. In this methodology, dynamic models of the train and the bridge are assumed to be initially uncoupled, yet being bound by the interaction train-bridge forces. Thus, the loads are evaluated for the train running on a rigid and fixed deck, considering geometric irregularities, different for each rail line, in both the vertical and horizontal track planes, as well as in the wheels. The contact forces are statically condensed at the vehicle’s centre of gravity and applied on a simplified 3D beam model. To represent the train passage over the bridge, functions are used to describe the interaction forces at each node of the beam model, as time evolves. Thus, it is possible to identify the dynamic response caused by the geometric irregularities and also evaluate the dynamic amplification obtained for any internal force, which is compared to the impact coefficient proposed by the Brazilian standards for the design of railway bridges (NBR 7187), used in quasi-static analysis. For the sake of an illustration, a thirty-six-metre-span concrete bridge with box girder section was considered. A study was carried out to find out the parameters of the irregularity functions that could potentially lead to maximal amplification of internal forces in the bridge.

scholarly journals Impact of Service Life on the Environmental Performance of Buildings

Buildings ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 9 ◽  
Author(s):  
Shahana Janjua ◽  
Prabir Sarker ◽  
Wahidul Biswas
Keyword(s):  
Life Cycle ◽  
Service Life ◽  
Environmental Performance ◽  
Energy Demand ◽  
Cumulative Energy ◽  
Cumulative Energy Demand ◽  
Building Components ◽  
Environmental Performance Assessment ◽  
Increasing Demand ◽  
The Impact

The environmental performance assessment of the building and construction sector has been in discussion due to the increasing demand of facilities and its impact on the environment. The life cycle studies carried out over the last decade have mostly used an approximate life span of a building without considering the building component replacement requirements and their service life. This limitation results in unreliable outcomes and a huge volume of materials going to landfill. This study was performed to develop a relationship between the service life of a building and building components, and their impact on environmental performance. Twelve building combinations were modelled by considering two types of roof frames, two types of wall and three types of footings. A reference building of a 50-year service life was used in comparisons. Firstly, the service life of the building and building components and the replacement intervals of building components during active service life were estimated. The environmental life cycle assessment (ELCA) was carried out for all the buildings and results are presented on a yearly basis in order to study the impact of service life. The region-specific impact categories of cumulative energy demand, greenhouse gas emissions, water consumption and land use are used to assess the environmental performance of buildings. The analysis shows that the environmental performance of buildings is affected by the service life of a building and the replacement intervals of building components.

Study on Selection of the Length of Reinforced Concrete Segment for Oil and Gas Shield Tunnel with 3D Numerical Analysis

2014 ◽  
Vol 488-489 ◽  
pp. 517-520
Author(s):  
Xiao Feng Wang ◽  
Xiao Jun Zhou ◽  
Hong Yun Hu
Keyword(s):  
Reinforced Concrete ◽  
Oil And Gas ◽  
Earth Pressure ◽  
Internal Force ◽  
Segment Length ◽  
Shield Tunnel ◽  
Element Analysis ◽  
Calculated Stress ◽  
Internal Forces ◽  
Rational Length

3D finite element analysis is utilized to calculate stress and internal forces in three different lengths of reinforced concrete segment for oil and gas shield tunnel subject to water and earth pressure by means of load-structure model. The rational length of concrete segment is determined to be 1.2m long after comparing the calculated stress and internal force in concrete segment with length of 1.0m, 1.2m and 1.5m respectively. Meanwhile, the safety factor is also compared in order to determine the rational length of concrete segment. The analysis shows that segment length for oil and gas shield tunnel with small cross-section should be less than 1.2m so as to facilitate its transportation and erection on construction site.

Interaction Analysis of Infilled Frame Structures under Lateral Loads

2014 ◽  
Vol 578-579 ◽  
pp. 559-567
Author(s):  
Song Gu ◽  
Zhi Zheng ◽  
Xiao Lei Chang ◽  
Zong Kai Wang ◽  
Zhou Ming Liao ◽  
...  
Keyword(s):  
Interaction Analysis ◽  
Internal Force ◽  
Confinement Effect ◽  
Frame Structure ◽  
Equivalent Model ◽  
Lateral Loads ◽  
Specific Analysis ◽  
Internal Forces ◽  
The Impact ◽  
Structure Research

Filler stiffness and confinement effect on the frame structure under horizontal loads, making the earthquake severely damaged in recent years with filler frame structure. Research shows that the actual stiffness frame structure with infill walls and internal force distribution and pure framework significantly different. In this paper, the equivalent model analysis bracing frame structure filler with actual stiffness, elasticity and structure from stage to stage of the internal forces shaping the distribution were analyzed. The results show that the stiffness of the contribution and the confinement effect filler by factors geometry, masonry materials, the impact of the framework is not the same, need to consider the specific analysis and structural design.

THE IMPACT OF UKRAINE'S EXCISE DUTY POLICY ON THE TRANSFORMATION PROCESSES OF THE TOBACCO MARKET

2020 ◽  
Vol 2020 (10) ◽  
pp. 19-33
Author(s):  
Nadiia NOVYTSKA ◽  
◽  
Inna KHLIEBNIKOVA ◽  
Keyword(s):  
Structural Changes ◽  
Tax Avoidance ◽  
Transformation Process ◽  
State Regulation ◽  
Tobacco Products ◽  
Excise Duty ◽  
Increasing Demand ◽  
High Level ◽  
The Impact ◽  
Transformation Processes

The market of tobacco products in Ukraine is one of the most dynamic and competitive. It develops under the influence of certain factors that cause structural changes, therefore, the aim of the article is to conduct a comprehensive analysis of transformation processes in the market of tobacco and their alternatives in Ukraine and identify the factors that cause them. The high level of tax burden and the proliferation of alternative products with a potentially lower risk to human health, including heating tobacco products and e-cigarettes, are key factors in the market’s transformation process. Their presence leads to an increase in illicit turnover of tobacco products, which accounts for 6.37% of the market, and the gradual replacement of cigarettes with alternative products, which account for 12.95%. The presence on the market of products that are not taxed or taxed at lower rates is one of the reasons for the reduction of excise duty revenues. According to the results of 2019, the planned indicators of revenues were not met by 23.5%. Other reasons for non-fulfillment of excise duty revenues include: declining dynamics of the tobacco products market; reduction in the number of smokers; reorientation of «cheap whites» cigarette flows from Ukraine to neighboring countries; tax avoidance. Prospects for further research are identified, namely the need to develop measures for state regulation and optimization of excise duty taxation of tobacco products and their alternatives, taking into account the risks to public health and increasing demand of illegal products.

Strategies to manage stream flow to benefit people and nature: a non-government conservation organisation's perspective

2004 ◽  
Vol 49 (7) ◽  
pp. 89-95
Author(s):  
J. Pittock ◽  
R. Holland
Keyword(s):  
Stream Flow ◽  
Large Scale ◽  
River Basins ◽  
River Basin Management ◽  
Freshwater Biodiversity ◽  
Flow Management ◽  
Stream Flows ◽  
Freshwater Management ◽  
Increasing Demand ◽  
The Impact

More than for any other biome, freshwater biodiversity is increasingly imperiled, particularly due to poor stream flow management and increasing demand for water diversions. The adoption by the world's governments of targets to extend water services to the poor and at the same time to conserve biodiversity increase the need to better direct investments in freshwater management. In this paper WWF draws on examples from its work to identify areas where investment can be focused to assure efficient water use and improve stream flow management, namely:• Prioritize and target those river basins and sub-catchments that are most critical for conservation of freshwater biodiversity to maintain stream flows;• Link strategic field, policy and market interventions at different scales in river basins to maximize the impact of interventions;• Implement the World Commission on Dams guidelines to minimize investment in large scale and costly infrastructure projects;• Apply market mechanisms and incentives for more sustainable production of the world's most water consuming crops;• Enhance statutory river basin management organizations to draw on their regulatory and financial powers;• Implement international agreements, such as the Convention on Wetlands;• Integrate environment and development policies.

Stress-strain curve of paper revisited

2012 ◽  
Vol 27 (2) ◽  
pp. 318-328 ◽  
Author(s):  
Svetlana Borodulina ◽  
Artem Kulachenko ◽  
Mikael Nygårds ◽  
Sylvain Galland
Keyword(s):  
Three Dimensional ◽  
Strain Curve ◽  
Failure Behavior ◽  
Three Dimensional Model ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Fiber Network ◽  
Bonding Parameters ◽  
Particle Level ◽  
The Impact

Abstract We have investigated a relation between micromechanical processes and the stress-strain curve of a dry fiber network during tensile loading. By using a detailed particle-level simulation tool we investigate, among other things, the impact of “non-traditional” bonding parameters, such as compliance of bonding regions, work of separation and the actual number of effective bonds. This is probably the first three-dimensional model which is capable of simulating the fracture process of paper accounting for nonlinearities at the fiber level and bond failures. The failure behavior of the network considered in the study could be changed significantly by relatively small changes in bond strength, as compared to the scatter in bonding data found in the literature. We have identified that compliance of the bonding regions has a significant impact on network strength. By comparing networks with weak and strong bonds, we concluded that large local strains are the precursors of bond failures and not the other way around.

Structural Analysis and Internal Force Calculation of Variable Cross-Section Silo

2012 ◽  
Vol 446-449 ◽  
pp. 429-434
Author(s):  
Rui Ting Ma
Keyword(s):  
Cross Section ◽  
Variable Cross Section ◽  
Internal Force ◽  
Variable Cross ◽  
Axially Symmetric ◽  
Internal Forces ◽  
Differential Element ◽  
Symmetric Load ◽  
Force Calculation ◽  
Constant Section

In this paper, the differential element of constant-section silo wall suffering from axially symmetric load is analyzed. From the results of constant-section silo, the author derives the displacements and internal forces of variable cross-section silo. Through a specific example, this paper compares the displacements , internal forces and concrete consumption of variable cross-section silo with those of constant-section silo, and discusses the merits of variable cross-section silo.

Analysis on the Impact of the Status of the Fresh-Old Concrete Bonding Interface on Dam Safety

2013 ◽  
Vol 405-408 ◽  
pp. 816-823
Author(s):  
Tao Huang ◽  
Guo Xin Zhang ◽  
Bo Yang ◽  
Lei Zhang
Keyword(s):  
Internal Force ◽  
Bonding Interface ◽  
Water Diversion ◽  
Gravity Dam ◽  
Safe Operation ◽  
Concrete Dam ◽  
Concrete Crack ◽  
The Status ◽  
North Water ◽  
The Impact

The bonding problem of interface between the fresh and old concrete is one of the main technological difficulties in the Heightening Project of Danjiangkou Dam in the South-to-North Water Diversion Project. At present, no mature experiences or engineering examples are found in China for concrete dam heightening. Because of the external environmental impacts of temperature change, aging and hydraulic fracturing on the interface between the fresh and old concrete, crack is likely to occur, which brings risks to the safe operation of the dam. In this article, the finite element direct force method was used to calculate the internal force. The safety of No. 1 dam monolith was calculated in accordance with the standard method for gravity dam in three conditions of fresh-old concrete bonding interface, i.e., perfect condition, cracked interface and cracked interface with water seepage. Suggestions for their solutions were also provided.

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