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Register a new userCracks Effects on Tunnels Concrete Linings
دراسة أثر الشقوق في سلوك بطانة الأنفاق البيتونية
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تعد الأنفاق من المنشآت المهمة و ذات الكلفة العالية و لذلك فمن الضروري مراقبتها و تقييم أدائها و تحليل سلوكها الإنشائي من أجل الحفاظ على سلامتها خلال مدة الاستثمار. قمنا في هذه الدراسة بعرض حالة أنفاق السكك الحديدية الموجودة في سورية و التي تقع على محور حلب-اللاذقية، و ذلك من خلال المعاينة الحقلية التي أظهرت وجود تشققات في بطانة هذه الأنفاق. و اعتمدنا في نمذجة و تحليل البطانة المتشققة طريقة النمذجة العددية المعروفة بطريقة العناصر المميزة التي تسمح بدراسة الأوساط غير المستمرة. و ركزنا في دراستنا على نوعية البيتون المستخدم من خلال معامل المرونة و سماكة البطانة البيتونية. و تبين نتيجة التحليل أن وجود الشقوق أدى إلى تغير في توزع الأجهادات و الانتقالات في المقطع المدروس. و هذا التغير يرتبط بمرونة البيتون و الخصائص الميكانيكية للشق.
Tunnels are usually considered as important and costly constructions and therefore it is very necessary to estimate their performance and analyze their structural behavior to maintain their safety in order to ensure their reliability and performance during their hypothetical life. In this issue we reviewed the situation of Syrian railway tunnels on Aleppo – Lattakia axis from the field observations which show that these tunnel linings are cracked. The numerical method, which is known as Distinct Element Method, was used in the analysis of cracked lining. This method performs modeling of discontinuous systems. We focused in this study on the concrete type through elasticity modulus and lining thickness. The result analysis shows that the effects of cracks modify the distribution of stresses and displacements in the lining. This modification is related to concrete elasticity modulus and mechanical crack characteristics.
References used
Bickel, J.; E. King, and T. Kuesel, Tunnel Engineering Handbook, Second Edition, Chapman & Hall, New York, 1996
UIC Code 779-10R, Maintenance of Existing Railway Tunnels, International Union of Railways, 1990
Szechy, Karoly. 'The art of tunneling', the university of technical science, Budapest, 1973
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Cracks are considered important defects in concrete elements, it was noticed after constructing the reinforced concrete walls related to the Foundation, that after a short time after the hardening of concrete and without any overloading on the wall,
there have been vertical cracks of regular distances along each wall we noticed this phenomenon it had happened in many construction projects. We have described the situation, we have also explained, analyzed it by examining its reasons. By a thorough study of three projects carried out in lattakia including scale decanter, building of a tourist hotel and a trade centre, which crack width ranging from 1.25 mm to 3 mm, the height differed in each case studied. Ultimately we have found the practical solutions to avoid this phenomenon including adoption of longitudinal joints for reinforced concrete walls, spacing is about thirty times the wall thickness in order to avoid cracks caused by shrinkage and thermal stress where the depth of joint about 20 mm and the width ranging between 15 mm to 20 mm implemented on both sides of the wall internal and external. After hardening of concrete and lifting the wooden template fill the joints with filler flexible materials.
This paper makes an experimental and analytical investigation of cracks characteristics in Fiber Reinforced Polymer strengthened RC beams under different levels of sustained load and Reinforced ratio.
As the equations available for conventional RC b
eams are inappropriate for the calculation of the short-term crack width in FRP-strengthened RC beams[8], a statistical analysis is carried out on available test data from international sources [6-9-10] and from the test results obtained in the current study (Concrete Labor- Civil engineering Department- Damascus University-2014) to establish a new equation that considers the effect of the FRP laminates. This equation is a correlation of stress in steel bars, concrete surface tension , and effective side cover.
The long-term crack width is then related to the instantaneous crack width by empirical equations which are derived from the test results obtained in the current study.
The research was conducted on hybrid Squash (Nancy F1) at Tishreen University in
the growing season of spring 2013 in order to study the effect of ground covering and low
tunnels on the early production of squash. The study consisted of four experi
mental
treatments: the control (without covering) and three covering treatments (ground covering
using black mulch, ground covering with a low plastic tunnel, and a low plastic tunnel
without ground covering). The completely randomized design was used with three
replications per treatment and ten plants per replication. The results showed that the
covering with a low plastic tunnel was superior to other treatments, resulting in a clear
increase in female flowers, the ratio of female flowers to the total flowers, fruit number,
and plant production. The results also showed a strong positive correlation between the
plant production and the number of female flowers (r=0.999), the number of fruit per plant
(r=0.999), the ratio of female flowers to the total flowers (r=0.990) and the total number of
flowers (0.995). The correlation with male flowers was however negative (r=-0.954).
The extended crack resistance of concrete is necessary in the desisn of nonlinear behavior of structural It can be described through the intensity stress factor and the critical crack opening under maximum
force. The length of the crack is necessary
for calculating intensity stress factor and the critical crack opening under maximum force.
The aim of this work is to conehede the relations between intensity stress factor and the critical crack opening under maximum force with the material properties of concrete such as paste volume, compressive strength and maximum aggregate diameter. The length of crack is calculated using the analytical model of Olesen that depends on bilinear softening, and the parameters of the softening curve were found using inverse analysis. The experimental results of three point bending test for beams with different sizes which are made from concretes with different compressive strengths are used in the inverse analysis.
It is found that intensity stress factor and the critical crack opening under maximum force depend on paste volume and they increase when F'c increases, while they are independent from maximum
aggregate size.
In this paper, ground surface settlement induced by tunneling have been studied
using 2D finite element analysis. By assuming greenfield conditions, which means that
there is no loads on the soil surface above the tunnel.
A FE study was conducted
in which an elasto-plastic constitutive model was adopted
to model the soil behavior (MC,HS).
This paper include Comparison between actual field measurements with (FEM)
results, and parametric study for the most factors that influence ground surface settlement.
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