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CONTENTS
Volume 47, Number 1, July10 2013
 

Abstract
A combined thermal and mechanical action in roller compacted concrete (RCC) dam analysis is carried out using a three-dimensional finite element method. In this work a numerical procedure for the simulation of construction process and service life of RCC dams is presented. It takes into account the more relevant features of the behavior of concrete such as hydration, ageing and creep. A viscoelastic model, including ageing effects and thermal dependent properties is adopted for the concrete. The different isothermal temperature influence on creep and elastic modulus is taken into account by the maturity concept, and the influence of the change of temperature on creep is considered by introducing a transient thermal creep term. Crack index is used to assess the risk of occurrence of crack either at short or long term. This study demonstrates that, the increase of the elastic modulus has been accelerated due to the high temperature of hydration at the initial stage, and consequently stresses are increased.

Key Words
FEM; roller compacted concrete dam; thermal stress; creep; mechanical behavior; crack criterion factor

Address
A.A. Abdulrazeg : Civil Engineering Department, Omar Al Mukhtar University, Libya
J. Noorzaei, T.A. Mohammed, M.S. Jaafar : Civil Engineering Department, Universiti Putra Malaysia, UPM-Serdang, Malaysia

Abstract
A finite element computational procedure for the accurate analysis of quasistatic thermorheological complex structures response is developed. The geometrical nonlinearity, arising from large displacements and rotations (but small strains), is accounted for by the total Lagrangian description of motion. The Schapery\'s nonlinear single-integral viscoelastic constitutive model is modified for a timestress-temperature-dependent behavior. The nonlinear thermo-viscoelastic constitutive equations are incrementalized leading to a recursive relationship and thereby the resulting finite element equations necessitate data storage from the previous time step only, and not the entire deformation history. The Newton-Raphson iterative scheme is employed to obtain a converged solution for the non-linear finite element equations. The developed numerical model is verified with the previously published works and a good agreement with them is found. The applicability of the developed model is demonstrated by analyzing two examples with different thermal/mechanical loading histories.

Key Words
thermo-rheological complex material (TCM); nonlinear Schapery\'s model; geometrical nonlinearity; finite element method (FEM)

Address
Fatin F. Mahmoud, Ahmed G. El-Shafei, Mohamed A. Attia : Department of Mechanical Design and Production Engineering, College of Engineering, Zagazig Univeristy, Zagazig, 44511, Egypt

Abstract
In structural reliability analysis, the response surface method is a powerful method to evaluate the probability of failure. However, the location of experimental points used to form a response surface function must be selected in a judicious way. It is necessary for the highly nonlinear limit state functions to consider the design point and the nonlinear trend of the limit state, because both of them influence the probability of failure. In this paper, in order to approximate the actual limit state more accurately, experimental points are selected close to the design point and the actual limit state, and consider the nonlinear trend of the limit state. Linear, quadratic and cubic polynomials without mixed terms are utilized to approximate the actual limit state. The direct Monte Carlo simulation on the approximated limit state is carried out to determine the probability of failure. Four examples are given to demonstrate the efficiency and the accuracy of the proposed method for both numerical and implicit limit states.

Key Words
response surface method; structural reliability; nonlinear trend of the limit state; adaptive experimental points; probability approach

Address
Weitao Zhao, Yi Yang : Key Laboratory of Liaoning Province for Composite Structural Analysis of Aerocraft and Simulation, School of Aerospace Engineering, Shenyang Aerospace University, 110136 Shenyang, China
Weitao Zhao, Zhiping Qiu : Institute of Solid Mechanics, Beihang University, 100083 Beijing, China

Abstract
The Xiaolan channel super large bridge is unique in style and with greatest span in the world with a total length of 7686.57 m. The main bridge with spans arranged as 100m+220m+100m is a combined structure composed of prestressed concrete V-shape rigid frame and concrete-filled steel tubular flexible arch. First of all, the author compiles APDL command flow program by using the unit birth-death technique and establishes simulation calculation model in the whole construction process. The creep characteristics of concrete are also taken into account. The force ratio of the suspender, arch and beam is discussed. The authors conduct studies on the three-plate webs\'s rule of shear stress distribution, the box girder\'s longitudinal bending normal stress on every construction stage, meanwhile the distribution law of longitudinal bending normal stress and transverse bending normal stress of completed bridge\'s box girder. Results show that, as a new combined bridge, it is featured by: Girder and arch resist forces together; Moment effects of the structure are mainly presented as compressed arch and tensioned girder; The bridge type brings the girder and arch on resisting forces into full play; Great in vertical stiffness and slender in appearance.

Key Words
bridge engineering; long-span V-shape rigid frame composite arch bridge; simulation calculation in the whole construction process; stress distribution law; spatial mechanical behaviors

Address
Hongye Gou, Qianhui Pu, Shiqiang Qin : Department of Bridge Engineering, Southwest Jiaotong University, Chengdu, 610031, P.R. China
Junming Wang : Architecture and Survey Design Institute of Southwest Jiaotong University, Chengdu, 610031, P.R. China
Zeyu Chen : China Railway Siyuan Survey and Design Group Co. Ltd., Wuhan, 430063, P.R. China

Abstract
This study focuses on shear strengthening performance of simply supported reinforced concrete (RC) T-beams bonded by glass fibre reinforced polymer (GFRP) strips in different configuration, orientations and transverse steel reinforcement in different spacing. Eighteen RC T-beams of 2.5 m span are tested. Nine beams are used as control beam. The stirrups are provided in three different spacing such as without stirrups and with stirrups at a spacing of 200 mm and 300 mm. Another nine beams are used as strengthened beams. GFRP strips are bonded in shear zone in U-shape and side shape with two types of orientation of the strip at 45\' and 90\' to the longitudinal axis of the beam for each type of stirrup spacing. The experimental result indicates that the beam strengthened with GFRP strips at 45\' orientation to the longitudinal axis of the beam are much more effective than 90\' orientation. Also as transverse steel increases, the effectiveness of the GFRP strips decreases.

Key Words
glass fibre reinforced polymer (GFRP); reinforced concrete (RC); strengthening; shear strength; T-beams

Address
K.C. Panda : Department of Civil Engineering, ITER, SOA University, Bhubaneswar, 751030, Odisha, India
S.K. Bhattacharyya : CSIR-Central Building Research Institute, Roorkee, 247667, Uttarakhand, India
S.V. Barai : Department of Civil Engineering, IIT Kharagpur, 721302, West Bengal, India

Abstract
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Key Words
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Address
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Abstract
Nonlinear Static Procedures (NSPs) have been developed as a practical tool to estimate the seismic demand of structures. Several researches have accomplished to minimize errors of NSPs, namely pushover procedures, in the Nonlinear Time History Analysis (NTHA), as the most exact method. The most important issue in a typical pushover procedure is the pattern and technique of loading which are extracted based on structural dynamic fundamentals. In this paper, the coefficients of modal force combination is focused involving a meta-heuristic optimization algorithm to find the optimum load pattern which results in a response with minimum amount of errors in comparison to the NTHA counterpart. Other parameters of the problem are based on the FEMA recommendations for pushover analysis of building structures. The proposed approach is implemented on a high-rise 20 storey concrete moment resisting frame under three earthquake records. In order to demonstrate the effectiveness and robustness of the studied procedure the results are presented beside other well-known pushover methods such as MPA and the FEMA procedures, and the results show the efficiency of the proposed load patterns.

Key Words
nonlinear static analysis; pushover; optimization; seismic demand; concrete frame

Address
Mohsen Ali Shayanfar, Mansoor Ashoory, Taha Bakhshpoori and Basir Farhadi : Centre of Excellence for Fundamental Studies in Structural Engineering, Iran University of Science and Technology, Narmak, Tehran 16, Iran

Abstract
In this paper, constraint-based fracture mechanics analyses of hollow cylinders with internal circumferential crack under tensile loading are conducted. Finite element analyses of the cracked cylinders are carried out to determine the fracture parameters including elastic T-stresses, and fully-plastic J-integrals. Linear elastic finite element analysis is conducted to obtain the T-stresses, and elastic-plastic analysis is conducted to obtain the fully plastic J-integrals. A wide range of cylinder geometries are studied, with cylinder radius ratios of ri/ro = 0.2 to 0.8 and crack depth ratio a/t = 0.2 to 0.8. Fully plastic J-integrals are obtained for Ramberg-Osgood power law hardening material of n = 3, 5 and 10. These fracture parameters are then used to construct conventional and constraint-based failure assessment diagrams (FADs) to determine the maximum load carrying capacity of cracked cylinders. It is demonstrated that these tensile loaded cylinders with circumferential cracks are under low constraint conditions, and the load carrying capacity are higher when the low constraint effects are properly accounted for, using constraint-based FADs, comparing to the predictions from the conventional FADs.

Key Words
circumferential crack; cylinder; J-integral; stress intensity factor; T-stress; failure assessment; constraint effect

Address
Michael Bach, Xin Wang : Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, Ontario K1S 5B6, Canada


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