• Earthquakes and Structures
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• v.11 no.2
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• pp.315-326
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• 2016

This paper presents the results of cyclic loading tests on concrete beams reinforced with various reinforcement, including ordinary steel bars, CFRP bars and CFRP prestressed concrete prisms(PCP). The main variable in the test program was the level of prestress and the cross section of PCP. The seismic performance indexes including hysteretic loops, skeleton curve, ductility, energy dissipation capacity and stiffness degradation were analyzed. The results show that the CFRP prestressed concrete prisms as flexural reinforcement of concrete beams has good seismic performance. And the ductility and the energy dissipation capacity were good, the hysteresis loops were full and had large area.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.96-101
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• 1998

J-R curve tests were performed on 1T compact specimens of SA516 Gr. 70 carbon steels under reverse cyclic loading. A Direct-Current Potential Drop (DCPD) method, one of the nondestructive techniques to detect flaw of structure, is being increasingly used for monitoring crack initiation and stable crack growth in typical fracture mechanics specimens for J-R testing. In many aspects this method is simpler than the unloading compliance method. The objective of this paper is to evaluate the J-R Curve according to the crack length measurement techniques under reverse cyclic loading. In order to prove the reliability and repeatability of the DCPD method, the crack length measured by using DCPD method was compared to one determined from unloading compliance. Consequently, this DCPD method correlated well with J-R curves and crack extension measurements determined from unloading compliance method.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.12
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• pp.44-55
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• 1994

This study is to apply the theory of fatigue fracture to solder joints under thermal cyclic loading and predict life of solder joint to failure. A 62Sn-36Pb-2Ag solder was used in this study. Tensile tests were preformed at temperatures of 15.dec. C, 50.dec. C and 85.dec. C in order to find terms of crack length "a". plastic strain range ""${\Delta}{\varepsilon}_p$" and temperature "T". Solder joint under thermal cyclic loading was analyzed by FEM. this FEM analysis together with the crack growth rate will provide the capability of the fatigue life prediction of solder joints and enhance the reliability od solder joint.

• Structural Engineering and Mechanics
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• v.66 no.3
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• pp.305-315
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• 2018

Interaction of lateral loading, combined with axial force needs to be determined with care in reinforced concrete (RC) one-dimensional structural members (1D SMs) such as beam-columns (BCs) and columns. RC 1D SMs under heavy axial loading are known to fail by brittle mode and small lateral displacements. In this paper, a macro element-based algorithm is proposed to analyze the RC 1D SMs under monotonic or cyclic combined loading. The 1D SMs are discretized into macro-elements (MEs) located between the critical sections and the inflection points. The critical sections are discretized into fixed rectangular finite elements (FRFE). The nonlinear behavior of confined and unconfined concretes and steel elements are considered in the proposed algorithm. The proposed algorithm has been validated by the results of experimental tests carried out on full-scale RC structural members. The evolution of ultimate strain at extreme compression fiber of a rectangular RC section for different orientations of lateral loading shows that the ultimate strain decreases with increasing the axial force. In the examined cases, this ultimate strain ranges from 0.0024 to 0.0038. Therefore, the 0.003 value given by ACI-318 code for ultimate strain, is not conservative and valid for the combined load cases with significant values of axial force (i.e. for the axial forces heavier than 70% of the ultimate axial force).

• Tunnel and Underground Space
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• v.22 no.2
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• pp.77-85
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• 2012

In a material, micro-cracks can be progressively occurred, propagated and finally lead to failure when it is subjected to cyclic or periodic loading less than its ultimate strength. This phenomenon, fatigue, is usually considered in a metal, alloy and structures under repeated loading conditions. In underground structures, a static creep behavior rather than a dynamic fatigue behavior is mostly considered. However, when compressed air is stored in a rock cavern, an inner pressure is periodically changed due to repeated in- and-out process of compressed air. Therefore mechanical properties of surrounding rock mass and an inner lining system under cyclic loading/unloading conditions should be investigated. In this study, considering an underground lined rock cavern for compressed air energy storage (CAES), the mechanical properties of a lining system, that is, concrete lining and plug under periodic loading/unloading conditions were characterized through cyclic bending tests and shear tests. From these tests, the stability of the plug was evaluated and the S-N line of the concrete lining was obtained.

• Steel and Composite Structures
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• v.17 no.5
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• pp.573-599
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• 2014

A new type of connection for steel-concrete composite bridges was developed by the Steel Structures Laboratory of Ecole Poytechinque $F{\acute{e}}d{\acute{e}}rale$ de Lausanne. Resistance to longitudinal shear is based on the development of shear stresses in the confined interfaces which form the connection. Confinement is provided by the reinforced concrete slab which encloses the connection and restrains the uplift (lateral separation) of the interfaces by developing normal stresses. The experimental investigation of the interfaces, under static and cyclic loading, enabled the development of the laws describing the structural behaviour of each interface. Those laws were presented by the authors in previous papers. The current paper focuses on the continuity of the research. It presents the experimental investigation on the new connection by means of push-out tests on specimens submitted to static and cyclic shear loading. Investigation revealed that the damage in the connection, due to cyclic loading, is expressed by the accumulation of a residual slip. A safe fatigue failure criterion is proposed for the connection which enabled the verification of the connection for the fatigue limit state with respect to the limit of fatigue. A numerical model is developed which takes into account the laws describing the interface behaviour and the analytical expressions for the confinement effect, the latter obtained by performing finite element analysis. This numerical model predicts the shear resistance of the connection and enables to assess its fatigue limit which is necessary for the fatigue design proposed.

• Structural Engineering and Mechanics
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• v.76 no.5
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• pp.663-674
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• 2020

In this study, partially restrained beam-column moment joints in the weak-axis direction were examined using three large-scale specimens subject to cyclic loading in order to assess the seismic resistance of the joints of low-rise steel structures and to propose joint details based on the test results. The influence of different number of bolts on the moment joints was thoroughly investigated. It was found that the flexural capacity of the joints in the direction of weak axis was highly dependent on the number of high-tension bolts. In addition, even though the flexural connections subjected to cyclic loading was perfectly designed in accordance with current design codes, severe failure mode such as block shear failure could occur at beam flange. Therefore, to prevent excessive deformation at bolt holes under cyclic loading conditions, the holes in beam flange need to have larger bearing capacity than the required tensile force. In particular, if the thickness of the connecting plate is larger than that of the beam flange, the bearing capacity of the flange should be checked for structural safety.

• 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.

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.71-80
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• 2008

This paper presents the reusults of wide width tensile tests under sustained and cyclic loads with vairous loading rate on geogrids. A seires of modified wide width tensile tests were conducted to investigate the effect of tensile strain rate on the deformation behavior of the geogrids. In addition, residual deformation characteristics of a geogrid under sustained or cyclic tests were also investigated. The results indicated that the residual deformation of a geogrid is strongly related to the viscous behavior of the geogrid, and the residual deformation can be well described by a hyperbolic curve. Also revealed was that residual deformation of a geogrid when subject to sustained or cyclic load should be described with the framework of viscous behavior.

• Geotechnical Engineering
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• v.11 no.1
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• pp.101-112
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• 1995

Deformational characteristics of soils, often expressed in terms of shear modulus and material damping ratios, are important parameters in the design of soil-structure systems subjected to cyclic and dynamic loadings. In this paper, deformational characteristics of dry sand at small to intermediate strains were investigated using resonant column/torsional shear(RC 175) apparatus. Both resonant column(dynamic) and torsional shear (cyclic) tests were performed in a sequential series on the same specimen. With the modification of motion monitoring system, the elastic zone, where the stress strain relationship is independent of loading cycles and strain amplitude, was veri tied and hysteretic damping was found even in this zone. At strains above cyclic threshold, shear modulus increases and damping ratio decreases with increasing number of loading cycles. Moduli and damping ratios of dry sand are independent of loading frequency and values obtained from pseudostatic torsional shear tests are Identical with the values from the dynamic resonant column test, provided the effect of number of loading cycles is considered in the conlparison. Therefore, deformational characteristics determined by RC/TS tests may be applied in both dynamic and static analyses of soil-structure systems.