Results Of Cyclic Loading Tests Research Articles

실대형 실험을 이용한 가진주파수 변화에 따른 콘크리트궤도의 동적평가

호남고속철도에 부설된 동일한 궤도노반시스템을 실제 열차하중이 가능한 실대형 가진시험을 통해 성능을 평가하였다. 실험결 과 Odemark 등가깊이 이론에 의한 노반압력과 매우 유사한 것을 확인하였다. 콘크리트궤도에서 정적하중 330 kN을 재하시 노반 상부의 토압은 50 kPa 이내로 발생하였고, 정적하중시험과 반복하중시험 결과는 비교적 큰 차이가 없었다. HSB의 탄성변위는 증속시험 시 관리기준값 1 mm에 비해 약 1/100 수준이며, 노반의 탄성변위량과 비교해볼 때 1/175 정도로 매우 작은 변위가 발생하였다. 가진주파수의 크기에 따라 궤도노반의 동적거동은 가진주파수가 35 Hz이하에서는 모든 측정값이 거의 선형적으로 증가하였으나, 35 Hz이상에서는 윤중, 변위, 지반가속도 등이 감소하였다. In this study, the full scale model tests were performed with track-roadbed system such as Ho-nam high speed railway. The measured data gives good similar a roadbed pressure with equivalent depth to the Odemark's theory. In the case of earth pressures have a under 50 kPa at upper-subgrade applying 330 kN static loading. Results of cyclic loading tests did not differ significantly from those of static loading test. The elastic displacement at HSB layer has a level of 1/100 compared to the 1 mm that it was evaluation criteria for speed up of High Speed Railway. Elastic displacement at subgrade layer was measured a level of 1/175. The dynamic characteristics of track-roadbed with loading frequency level were linearly increased under 35 Hz, while the wheel loading, displacement and acceleration of roadbed were decreased loading frequency above 35 Hz.

Simple plastic deformation analysis of ballasted track under repeated moving-wheel loads by cumulative damage model

This study examines a simplified and practical prediction method for the cumulative residual settlement of ballasted track under repeated train passages, and the applicability and usefulness of the proposed method are discussed by comparing the experimental results of cyclic loading tests of model ballasted track structures with the analytical results. As the results, this study proposed a new analytical procedure with iterative calculation by linear elastic Finite Element (FE) analysis, which can evaluate the effects of continuous rotation of principal stress axis due to moving-wheel loads by taking into consideration the cumulative strain characteristics of ballast obtained from laboratory element tests such as multi-ring shear tests adopting the moving-wheel loading method in terms of the practical use. In addition, it was revealed that when laboratory element tests with high accuracy was conducted under experimental conditions similar to the actual phenomena in order to grasp the cumulative strain characteristics of ballast and then plastic deformation analysis was performed based on the findings above, the proposed analytical procedure could roughly estimate the cyclic plastic deformation of railroad ballast under repeated moving-wheel loads even with a simple linear elastic FE analysis. These findings confirm sufficient applicability of the proposed analytical procedure to the estimation of the cumulative residual settlement observed at ballasted track structures subjected to repeated train passages.

Theoretical and Experimental Studies on the Resilience of Driven Piles

This paper deals with the resilient condition that may be reached by driven piles, during its installation as well as under static cyclic and monotonic loading tests. During the 1950’s Van Weele observed its effect in the context of a method for the separation of the toe and shaft loads at failure using the results of static cyclic loading tests on driven piles. Under this condition and based on a mathematical model that uses Cambefort’s Relations and takes into account pile compressibility and residual loads, this paper shows that there is a homothetic relation between the loading and the unloading-movement curves at pile head. A graphical construction is presented along with a numerical procedure allowing to improve the understanding of pile behavior and to determine significant parameters of pile-soil interaction under static or driving loadings. Application of the homothetic relations is made to several piles and particularly a new procedure was developed to analyze dynamic loading tests with a single blow record, considering the residual load at the toe.

Welded end‐slot connection and debonding layers for buckling‐restrained braces

SUMMARYThe debonding mechanism has a significant effect on the performance of a buckling‐restrained brace (BRB). In this paper, a method for estimating the compression strength adjustment factor for any given BRB core strain is presented. Experimental investigations were conducted on four BRBs to examine the efficiency of four different debonding materials in reducing the difference between the cyclic peak compression and tension. Test results indicate that chloroprene rubber is very easy to install and very effective in minimizing the difference between the compressive and tensile capacities. The excellent performance of 13 full‐scale welded end‐slot BRBs (WES‐BRBs) is illustrated through experiments. Cyclic loading test results of a 12.5‐m long jumbo WES‐BRB reveal that its peak compressive strength exceeds 16,800 kN and its maximum core strain reaches 0.035. All WES‐BRBs show satisfactory performance with a very stable hysteresis response, modest peak compressive to tensile strength ratio, and very predictable axial stiffness. These specimens sustain a cumulative plastic deformation of greater than 400 times the yield deformation. The hysteresis responses can be satisfactorily predicted by using a two‐surface plasticity analytical model. Advantages of the welded end‐slot connections are also presented through a discussion on the effects of the BRB yield region length ratio on the effective stiffness, the yield story drift, and the core strain level. Copyright © 2014 John Wiley & Sons, Ltd.

Behaviour of concrete beams reinforced with SMA and steel bars under cyclic and monotonic load

This paper presents cyclic and monotonic load test results of concrete flexural members reinforced with shape memory alloy (SMA) and conventional steel bars. The ability of the SMA bars to recover and reduce permanent deformations of concrete flexural members subjected to cyclic load was investigated using reinforced concrete (RC) beam models. Half were control beams, reinforced with conventional steel bars, and the remainder were treated beams, reinforced with both conventional steel and SMA bars. The cyclic load test results showed that there were negligible increments in deflection and the ratio of residual deflection to maximum deflection was almost zero in beams with SMA bars over the whole span. Initially, under lower values of load, the stiffness of the treated beams was slightly higher than that of the control beams, but reduced with an increase in imposed load. The load–deflection behaviours of the treated and control beams were verified using published codes and standards. The results indicate that RC flexural members with SMA and steel provide a better choice for structures subjected to cyclic loads and/or earthquakes.

梁断面寸法と接合詳細が変形能力に及ぼす影響

This paper presents results of full-scale cyclic loading tests of moment connection under constant deformation amplitude conducted to evaluate deformation capacity. The effects of beam section size and of weld access hole are investigated by four type specimens. The relationships between ductility amplitude of beam rotation, cumulative plastic deformation and crack propagation at weld joint are quantitatively obtained from test result. The effects of beam section size and connection detail on crack initiation charactaristic are investigated from stress and strain by FEM analysis.

102 競泳用水着によって生じる股関節トルクの異方性超弾性モデルを用いた解析(OS1-(1),OS1 オーガナイズドセッション《計算力学と数値シミュレーション》)

The calculation using anisotropic hyperelastic model of hip joint torque generated by competitive swimwear was investigated in this paper. An anisotropic hyperelastic model considering cyclic deformation of swimwear fabrics was introduced in order to reproduce the mechanical characteristics of swimwear fabrics on the analysis. The material parameters of the proposed model were approximated using the cyclic tensile loading test results. The stress calculation of swimwear was investigated using this model. Finally, hip joint torque generated by the swimwear was calculated from the calculation results. Therefore, the calculation of hip joint torque generated by swimwear enables the new design of swimwear considering the value of hip joint torque.

二次壁が単層単スパンRC架構の水平耐力に与える影響

This paper reports cyclic loading test results of three one-story, one-bay reinforced concrete moment resisting frame specimens. Two of the specimens have secondary walls which are monolithically constructed or structurally isolated by seismic slits. Consequently, the isolated wall as well as monolithic wall increased the strength of moment resisting frame. This was caused by a small amount of tie bars which were provided for the isolated wall at the wall/frame boundaries. Therefore, a calculation procedure is presented based on the principle of virtual work mainly to evaluate the lateral strength of moment resisting frame with the isolated wall.

완화된 단부 배근상세를 갖는 특수전단벽 구조시스템의 내진성능평가

구조형식별로 구조물의 안정성 확보를 위해 KBC2009에 새로이 도입된 높이제한에 따라, 내진설계범주D에 해당되는 60 m 이상의 RC 구조물을 계획할 경우 특수전단벽을 의무적으로 사용해야 한다. 그러나 특수전단벽의 엄격한 횡보강 배근상세는 시공성 및 경제성에 부정적 영향을 미칠 것으로 예상된다. 그래서 이 연구에서는 현 규준에 따른 특수전단벽보다 완화된 배근 상세를 갖는 특수전단벽을 제안하고, 특수전단벽과의 성능 비교를 위하여 각각 두 개의 실험체를 제작하고 횡방향 반복 하중실험을 실시하였다. 또한 그 실험 결과를 반영한 보통전단벽, 특수전단벽, 완화된 특수전단벽 구조시스템의 해석모델을 설계하여 FEMA P695에 따른 방법론으로 내진성능평가를 실시하였다.

Accumulated Deformation Behavior and Computational Model of Water-Rich Mudstone Under Cyclic Loading

With the rapid development of Chinese railway systems, a large number of railway tracks have been built on or across soft soils and soft rocks, resulting in problems such as accumulated deformation and settlements of the tracks (Zhang et al. 2009) and severe mud pumping in railway tunnels which are built through soft soils (Zhu and Li 2001). Such problems are a big challenge to the safety and efficiency of train operation. Investigations on the characteristics of long-term deformation of geotechnical materials under cyclic train loading are of great interest in engineering practice. Sangrey and Henkel (1969) conducted triaxial cycling tests for saturated soft clay and demonstrated the existence of a critical stress state for soils. Yasuhara and Yamanouchi (1983) performed a triaxial drained test on soft soils under cyclic loading. Muhanna (1994) reported that the permanent deformation of soils was proportional to the cyclic loading number and stress level. Jafari et al. (2004) conducted a systematic study on the fatigue behavior of artificial rock joints that were subjected to cyclic shearing. Bagde and Petros (2005, 2009) analyzed the fatigue behavior of intact sandstones under dry and saturated conditions with dynamic uniaxial cyclic loading. Erarslan and Williams (2012) studied the stress–strain characteristics of Brisbane tuff disc specimens under a diametral compressive sinusoidal cyclic loading with an increasing magnitude. Chinese researchers have also conducted extensive research in this area. Several cyclic triaxial tests have been conducted with different soil types. Systematic studies have been conducted to evaluate the characteristics of cyclic deformation and identify their influencing factors (Cai and Cao 1996; Tang et al. 2003; Gong et al. 2009). Several empirical models based on the results of cyclic loading tests have been developed to describe the cyclic cumulative deformation behaviors of different geotechnical materials. Monismith et al. (1975) proposed an exponential model for the cumulative plastic deformation of clay under cyclic loading. Li and Selig (1996) improved Monismith’s model by adding soil static strength parameters. Based on these models, Chai and Miura (2002) proposed a computational formula to predict the cumulative deformation of road subgrade soil under traffic loading. This formula, which takes into account the original state of soil, is expressed as

In-plane shear behaviour of unreinforced and jacketed brick masonry walls

This paper deals with the results of cyclic load tests on masonry walls performed for the purpose of evaluation of in-plane shear behaviour and identification of shear strength, stiffness and energy dissipation. Eight walls in two series were assembled in laboratory conditions. The first series consisted of four unreinforced masonry walls constructed from solid clay bricks and lime mortar. The walls from the second series were strengthened by application of RC jackets on both sides. These were constructed of the same material and were characterized by the same geometry properties and vertical load levels as those of the walls from the first series. The main goal of the tests was to compare the behaviour of the unreinforced and strengthened walls under cyclic horizontal load. The results from the tests showed that the application of the strengthening method contributed to a significant improvement of the shear resistance of the jacketed walls. Analytical models were used to predict the shear resistance of the walls. Good agreement with the experimental results was obtained with a model based on tensile strength of masonry.

138 3D-CGモデルを用いた競泳用水着の異方性超弾性モデルによる応力解析(生体負荷の変化と軽減)

A new design method for designing competitive swimsuits using 3-dimensional stress calculation was investigated in this paper. An anisotropic hyperelastic modeling of swimwear fabric was developed from the results of tensile loading tests. 3-dimensional stress distributions of swimwear in swimming motions were calculated by the anisotropic hyperelastic model. The displacement fields of 3D-CG human model which reproduce swimming motion of human body were applied to stress calculation. For the material modeling, the uniaxial cyclic tensile loading tests were conducted to obtain the mechanical characteristics of competitive swimsuits. From loading test results, the mechanical characteristics of swimwear fabrics show anisotropy and the stiffness of the fabric shows hardening along with stretching. The cyclic tensile loading test results show stiffness reduction which depended on the maximum deformation. To take the anisotropy and stress reduction into account for the material modeling, a stress softening model for anisotropic hyperelastic model using stiffness ratio of warp or weft was proposed. In this paper, 3-dimensional stress distributions of swimwear were calculated by the proposed anisotropic hyperelastic model. A polygonal model of the swimwear was prepared and deformation of swimwear was adapted to the skin of 3D-CG human model in swimming motions. From the calculated results, stress distributions were possible to be visualized on the 3D-CG swimwear model.

Low cycle fatigue life prediction using a four-bolt extended unstiffened end plate moment connection

The end plate moment connection (EPMC) has been studied using various design concepts. However, after the Northridge, California earthquake in 1994, low cycle fatigue (LCF) analysis became the focus of investigation for EPMCs because the existing design code could not explain the brittle steel moment frame connection failures that occurred in numerous structures as a result of that earthquake. This paper provides a LCF life estimation procedure using a four-bolt extended unstiffened EPMC. In this research, four full-scale experimental tests are conducted to develop the LCF model and to estimate the LCF life of each connection. The experimental test failure mode is LCF fracture in the end plate. The LCF model is developed from three constant peak displacement cyclic load test results, and results from a fourth (and last) test performed with random cyclic loading. From these test results, the life of the structure is predicted using the LCF model. Finite element model (FEM) analysis and theoretical calculations (verified in the companion paper, Preanalysis of the Low Cycle Fatigue Behavior of a Reduced End Plate Moment Connection (T-stub)[1]) are used to predict the structural behavior. The results show reasonable relationships to each other.

Rate-dependent response of superelastic Cu–Al–Mn alloy rods to tensile cyclic loads

We report the results of tensile cyclic loading tests conducted to examine the dependence of constitutive relations for superelastic Cu–Al–Mn alloy rods on loading rates. Recently, Cu–Al–Mn alloy rods with diameters up to 8 mm have been developed by the authors, and it has been demonstrated that these rods have excellent superelastic strains of more than 8%, which is comparable to Ni–Ti alloys and far superior to other Cu-based alloys. No information is available, however, on the rate dependence of constitutive relations for Cu–Al–Mn alloys. In this study, we prepare two Cu–Al–Mn alloy rod specimens, whose lengths and diameters are 150 mm and 8 mm, respectively. Their stress–strain relations are examined under the loading frequencies of 0.001, 0.5, and 1 Hz with constant strain amplitude of 4.5%. It was found from the tests that the maximum stress increase in Cu–Al–Mn alloys due to higher loading rate was less than 5%. Thermo-mechanical analysis predicts that stress increase in Cu–Al–Mn alloys is about 1/4 of that in Ni–Ti alloys, which agrees reasonably well with the experimental observations. Such low stress increase is highly desirable in the design of seismic devices such as dampers and isolators.

Lateral Load: Deflection Response of an Embedded Caisson in Marine Clay

The authors refer to the laboratory testing carried out on model caisson embedded in marine clay collected from the Chennai coast in India. The response of lateral load–ground level deflection of caissons under static and cyclic lateral loading is presented and discussed for the varied parameters such as caisson embedment depth ratio (L/D), load eccentricity ratio (e/D), and undrained strength (su) of clay. The results showed that as the caisson L/D increases, the lateral load required to cause a specified ground level deflection increases. At a given lateral load, the deflection levels are increased as the load eccentricity ratio increases from 0.5 to 2.0. As L/D increases from 2 to 3, the increase in the ultimate lateral capacity is found to be 1.8 to 2.0 times. Similarly, for the change in L/D from 3 to 4, this increase in capacity is found to be 1.6 to 1.8 times at all the undrained strength values and e/D values tested. From the cyclic load test results, it was noticed that the deflections mobilized at the cyclic load ratio (CLR = 0.6) were so small and these are hardly 1% to 2% of the diameter of the caisson. A marked increase in the ground level deflection up to about 900 cycles was observed and thereafter the deflection almost remained the same.

A Proposal of Material Modeling for Swimwear Considering Anisotropy and Viscosity

This paper investigates an engineering approach using numerical analysis on a new constitutive model of the competitive swimwear. First, an anisotropic hyperelastic model was proposed. It reproduces the mechanical characteristics and its material modulus are estimated by the biaxial loading test. From this biaxial loading test, the fabrics for competitive swimwear have shown nonlinear elasticity which is regarded as hyperelasticity like rubber. In addition, they also have shown anisotropic characteristic which is dependent on the directions of warp and weft yarn. An anisotropic model is represented by the power series of invariants of stretch and shear deformation in each yarn. In order to verify the reproducibility, the material parameters of the proposed model were determined by nonlinear least squares approximation and the theoretical value was introduced. Second, from the cyclic loading test results, the materials have shown the viscosity and stress-softening effect. We proposed softening model for cyclic deformation.

Evaluation of vibration control system with U-dampers based on quasi-linear motion mechanism

This paper presents a new vibration control system for protection of steel structures from earthquakes. The proposed system, which uses a quasi-linear motion mechanism, achieves dissipation of seismic energy into the structure through yielding of U-shaped steel dampers. Based on the linear motion mechanism characteristics, the bracing members are subjected only to tensile force. This feature can eliminate the brace-buckling problem for braces, making rod members applicable to bracing members. This paper presents an outline of the vibration control system with subsequent evaluation of the lateral stiffness and strength of the frames with the proposed device. Six cyclic loading tests are conducted using the frame models with the proposed system. The accuracy of the evaluation is discussed by comparing the cyclic loading test results.

Effect of filler material on local and global behaviour of buckling‐restrained braces

AbstractThe nonlinear response of buildings has attracted a tremendous amount of attention in recent years. Braces, as lateral force‐resisting elements of a structure, are designed to not only react in the elastic region, but also to exhibit nonlinear response beyond the elastic limit. However, buckling in compression drastically degrades the performance of braces under earthquake loading. Buckling restrained braces (BRBs) have been evolved into very effective systems for severe seismic applications. They prevent buckling in compression through the encasing of core steel into a steel tube and confining infill concrete.The effect of infill material is investigated in this research through the use of experimental tests. Filler material may be concrete, grout or mortar, as well as granular material such as compacted aggregate. Moreover, lightweight concrete or lean concrete may be utilized as filler to reduce the overall structural weight. Furthermore, the need for unbonding material may not arise when sand and gravel mixture is used. Nevertheless, the strength of the aggregate should be such that no buckling or strength deterioration is observed. Parametric studies on BRB characteristics are carried out in this research. Results of cyclic loading tests are then provided for individual cases to characterize the effect of response parameters of BRB assemblages. Copyright © 2009 John Wiley & Sons, Ltd.

Experimental study on progressive yielding of marble

Cyclic loading experiments were widely used to study the progressive yielding of rock‐like materials. For brittle rocks, around the peak stress or in the post‐peak region, brittle failure occurred as soon as the axial stress was unloaded. In order to conduct the cyclic loading around and after peak stress, a new loading method was proposed based on the elastic–plastic theory. Comparison between the results of conventional triaxial compression tests and cyclic loading tests showed that the new loading method had little influence on the yielding process of marble. Based on the results of cyclic loading tests, a plastic internal variable was defined which took the influence of confining stress on the yielding process into consideration. Then, the variation of elastic parameters was obtained according to the plastic internal variable. The result showed that when the rock underwent plastic deformation, shear modulus progressively decreased while the bulk modulus changed slightly. The efforts of this paper can provide basic data for future study of the mechanical model of brittle rock.

EFFECT OF ULTIMATE FLEXURAL STRENGTH OF BEAM END CONNECTION ON DEFORMATION CAPACITY

This paper presents results of full-scale cyclic loading tests under constant deformation amplitude conducted to evaluate deformation capacity of welded beam-to-column connection adopted in moment frames. Test specimens are designed and fabricated to investigate the influence of flexural strength of beam end connection. The deformation capacity expressed by the relationships between ductility and cumulative plastic deformation is revealed from test results. The relationships between crack growth at welded joint and strength of connection is evaluated regarding deformation amplitude. The initiation of crack is investigated about distribution of stress and strain obtained from FEM analysis.