• Structural Engineering and Mechanics
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• v.26 no.4
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• pp.409-426
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• 2007

Following previous work carried out in Building Research Institute in Japan, finite element analyses of conceptual column designs are performed in this paper. The effectiveness of the numerical model is evaluated by experimental tests and parametric studies are conducted to determine influential factors in conceptual column designs. First, three different column designs are analysed: bonded, un-bonded, and un-bonded with additional reinforcing bars. The load-displacement curves and cracking patterns in concrete are obtained and compared with experimental ones. The comparisons indicate that the finite element model is able to reflect the experimental results closely. Both numerical and experimental results show that, the introduction of un-bonded zones in a column end can reduce cracking strains, accordingly reduce the stiffness and strength as well; the addition of extra reinforcement in the un-bonded zones can offset the losses of the stiffness and strength. To decide the proper length of the un-bonded zones and the sufficient amount of the additional reinforcing bars, parametric studies are carried out on their influences. It has been found that the stiffness of un-bonded designs slightly decreases with increasing the length of the un-bonded zones and increases with the size of the additional reinforcing bars.

• Structural Engineering and Mechanics
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• v.61 no.2
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• pp.283-293
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• 2017

The main contribution of the present paper is to propose an intelligent fuzzy inference system approach for modeling the debonding strength of masonry elements retrofitted with Fiber Reinforced Polymer (FRP). To achieve this, the hybrid of meta-heuristic optimization methods and adaptive-network-based fuzzy inference system (ANFIS) is implemented. In this study, particle swarm optimization with passive congregation (PSOPC) and real coded genetic algorithm (RCGA) are used to determine the best parameters of ANFIS from which better bond strength models in terms of modeling accuracy can be generated. To evaluate the accuracy of the proposed PSOPC-ANFIS and RCGA-ANFIS approaches, the numerical results are compared based on a database from laboratory testing results of 109 sub-assemblages. The statistical evaluation results demonstrate that PSOPC-ANFIS in comparison with ANFIS-RCGA considerably enhances the accuracy of the ANFIS approach. Furthermore, the comparison between the proposed approaches and other soft computing methods indicate that the approaches can effectively predict the debonding strength and that their modeling results outperform those based on the other methods.

• Structural Engineering and Mechanics
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• v.67 no.4
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• pp.391-401
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• 2018

Locally available Stainless Steel Wire Mesh (SSWM) bonded on a concrete surface with an epoxy resin is explored as an alternative method for the torsional strengthening of Reinforced Concrete (RC) beam in the present study. An experiment is conducted to understand the behavior of RC beams strengthened with a different configuration of SSWM wrapping subjected to pure torsion. The experimental investigation comprises of testing fourteen RC beams with cross section of $150mm{\times}150mm$ and length 1300 mm. The beams are reinforced with 4-10 mm diameter longitudinal bars and 2 leg-8 mm diameter stirrups at 150 mm c/c. Two beams without SSWM strengthening are used as control specimens and twelve beams are externally strengthened by six different SSWM wrapping configurations. The torsional moment and twist at first crack and at an ultimate stage as well as torque-twist behavior of SSWM strengthened specimens are compared with control specimens. Also the failure modes of the beams are observed. The rectangular beams strengthened with corner and diagonal strip wrapping configuration exhibited better enhancement in torsional capacity compared to other wrapping configurations. The numerical simulation of SSWM strengthened RC beam under pure torsion is carried out using finite element based software ABAQUS. Results of nonlinear finite element analysis are found in good agreement with experimental results.

• Structural Engineering and Mechanics
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• v.20 no.3
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• pp.265-277
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• 2005

This paper is focused on fractal analysis of the surface cracking, a new tool for safety evaluation of corroded reinforced concrete (RC) beams. Comprehensive experimental investigations, including flexural tests, coupon tests on strength evaluation of corroded concrete and rusty rebar, and pullout tests to determine bond strength between concrete and rebar were carried out on nine Corroded Reinforced Concrete Beams (CRCB) exposed to an aggressive environment for more than 10 years. In combination with test results from a previous study on CRCBs fabricated in the laboratory from accelerated methods, it is found that, for both types of beams, the surface cracking distributions are fractal in character at loading and failure stages. Fractal dimension is calculated for all specimens at different corrosion states based on fractal analysis method. Relationships between the fractal dimension and mechanical properties of corroded concrete, rebar corrosion ratio, and ductility of CRCBs are discussed in detail. It is concluded that the fractal dimension can act as a damage index and can be efficiently used to describe the corrosion state of CRCBs.

• Tunnel and Underground Space
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• v.21 no.3
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• pp.216-224
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• 2011

In this study, Class II behavior of rock failure process under uniaxial and biaxial compression has been numerically simulated using bonded particle model. Class II behavior of rock was simulated by radial strain controlled uniaxial and biaxial compression tests using a suggested method of ISRM. Micro-parameters used in the simulation were determined based on the laboratory uniaxial compression tests carried out at ${\"{A}}sp{\"{o}}$ Hard Rock Laboratory, Sweden. Class II behavior of ${\"{A}}sp{\"{o}}$ rock was effectively simulated using newly proposed numerical technique in this study, and the results of numerical simulations show good similarity with the complete stress-strain curves for Class II behavior obtained from the laboratory tests.

• Journal of Welding and Joining
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• v.21 no.5
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• pp.555-560
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• 2003

In automobile industry, it is necessary to reduce the weight from the view point of energy and environmental problems in these days. One of the ways for weight reduction is using adhesive aluminum structures. In this study, ultrasonic signals reflected from the adhesively bonded joint layer are used to evaluate the adhesively bonded joints. FFT is performed to determine bond-layer parameters such as effective thickness and frequency for adhesively bonded joint Al 6061 plates in comparison with the measured and theoretical ratios. And the parameters of ultrasonic wave and the J-integral are investigated to evaluate the adhesively bonded joint strength by DCB specimens.

• Structural Engineering and Mechanics
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• v.53 no.6
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• pp.1083-1104
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• 2015

This paper provides the results of an experimental investigation into the flexural behavior of continuous two-span unbonded post-tensioned high strength concrete (HSC) beams, strengthened by end-anchored CFRP laminates of different configurations in the hogging region. Implementing two different configurations of end-anchorage systems consisting of steel plates and bolts and carefully monitoring the development of strains throughout the load history using sufficiently large number of strain gauges, the response of beams including the observed crack propagations, beam deflection, modes of failure, capacity enhancement at service and ultimate and the amount of moment redistribution are measured, presented and discussed. The study is appropriate in the sense that it covers the more commonly occurring two span beams instead of the simply supported beams investigated by others. The experiments reconfirmed the finding of others that proper installation of composite strengthening system is most important in the quality of the bond which is essential for the internal transfer of forces. It was also found that for the tested two span continuous beams, the capacity enhancement is more pronounced at the serviceability level than the ultimate. This is an important finding as the design of these beams is mostly governed by the serviceability limit state signifying the appropriateness of the suggested strengthening method. The paper provides quantitative data on the amount of this capacity enhancement.

• Structural Engineering and Mechanics
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• v.8 no.1
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• pp.39-51
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• 1999

The dynamic response of buried pipelines has gained considerable importance because these pipelines perform vital role in conducting energy, water, communication and transportation. After realizing the magnitude of damage, and hence, the human uncomfort and the economical losses, researchers have paid sincere attention to this problem. A number of papers have appeared in the past which discuss the different aspects of the problem. This paper presents a theoretical analysis of non-axisymmetric dynamic response of buried orthotropic cylindrical shell subjected to a moving load along the axis of the shell. The orthotropic shell has been buried in a homogeneous, isotropic and elastic medium of infinite extent. A thick shell theory including the effects of rotary inertia and shear deformation has been used. A perfect bond between the shell and the surrounding medium has been assumed. Results have been obtained for very hard (rocky), medium hard and soft soil surrounding the shell. The effects of shell orthotropy have been brought out by varying the non-dimensional orthotropic parameters over a long range. Under these conditions the shell response is studied in axisymmetric mode as well as in the flexural mode. It is observed that the shell response is significantly affected by change in orthotropic parameters and also due to change of response mode. It is observed that axial deformation is large in axisymmetric mode as compared to that in flexural mode.

• Structural Engineering and Mechanics
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• v.74 no.3
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• pp.407-423
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• 2020

The pre-peak cyclic shear mechanism of two-order asperity degradation of rock joints in the direct shear tests with static constant normal loads (CNL) are investigated using experimental and numerical methods. The laboratory testing rock specimens contains the idealized and regular two-order triangular-shaped asperities, which represent the specific geometrical conditions of natural and irregular waviness and unevenness of rock joint surfaces, in the pre-peak cyclic shear tests. Three different shear failure patterns of two-order triangular-shaped rock joints can be found in the experiments at constant horizontal shear velocity and various static constant normal loads in the direct and pre-peak cyclic shear tests. The discrete element method is adopted to simulate the pre-peak shear failure behaviors of rock joints with two-order triangular-shaped asperities. The rock joint interfaces are simulated using a modified smooth joint model, where microscopic scale slip surfaces are applied at contacts between discrete particles in the upper and lower rock blocks. Comparing the discrete numerical results with the experimental results, the microscopic bond particle model parameters are calibrated. Effects of cyclic shear loading amplitude, static constant normal loads and initial waviness asperity angles on the pre-peak cyclic shear failure behaviors of triangular-shaped rock joints are also numerically investigated.

• Structural Engineering and Mechanics
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• v.20 no.1
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• pp.21-43
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• 2005

Masonry is a composite non-homogeneous structural material, whose mechanical properties depend on the properties of and the interaction between the composite components - brick and mortar, their volume ratio, the properties of their bond, and any cracking in the masonry. The mechanical properties of masonry depend on the orientation of the bed joints and the stress state of the joints, and so the values of the shear modulus, as well as the stiffness of masonry structural elements can depend on various factors. An extensive testing programme in several countries addresses the problem of measurement of the stiffness properties of masonry. These testing programs have provided sufficient data to permit a review of the influence of different testing techniques (mono and bi-axial tests), the variations caused by distinct loading conditions (monotonic and cyclic), the impact of the mortar type, as well as influence of the reinforcement. This review considers the impact of the measurement devices used for determining the shear modulus and stiffness of walls on the results. The results clearly indicate a need to re-assess the values stated in almost all national codes for the shear modulus of the masonry, especially for masonry made with lime mortar, where strong anisotropic behaviour is in the stiffness properties.