Results Of Cyclic Loading Tests Research Articles

PLASTIC DESIGN OF STEEL FRAMES WITH VIBRATION CONTROL SYSTEM BASED ON QUASI-LINEAR MOTION MECHANISM

This paper presents a plastic design method of steel frames with a vibration control system with U-shaped steel dampers based on a quasi-linear motion mechanism. Firstly, a plastic collapse load of the damper system is evaluated using the upper bound theorem where the U-shaped dampers are assumed to have three plastic hinges. The accuracy of the evaluation is examined by comparing the cyclic loading test results. Secondly, the plastic design is discussed for steel frames considering some collapse mechanisms. The shear stress in the beam web is also discussed for the beam attached with the U-shaped dampers. Finally, for the sake of introducing the proposed device into the practice, nonlinear finite element analyses are conducted for the three-story three-span steel moment frames with and without the damper system. Relationships between the story shear and story drift obtained from the static pushover analysis are examined. The Von-Mises stress distributions are also examined to reveal the influence of the proposed device on the steel moment frame.

Experimental Investigations on the Behaviour of Pile Groups in Clay Under Lateral Cyclic Loading

This paper presents the results of two-way cyclic lateral load tests carried out on model pile groups embedded in soft marine clay. The tests are conducted on 1 × 2, 2 × 2 and 3 × 3 pile groups having length to diameter ratio (L/D) of 15, 30 and 40 with the spacing to diameter ratio (S/D) of 3, 5, 7 and 9. The experimental results are presented in the form of load–deflection curves and bending moment profiles. Cyclic group efficiency, critical spacing, critical cyclic load level and cyclic p-multipliers are evaluated. It is found that the lateral capacity of the 3 × 3 group reduces by about 42% after 50 cycles of loading. The cyclic p-multipliers of 3 × 3 pile group are found to be 0.41, 0.25 and 0.29 for leading, intermediate and rear rows respectively. The test results are compared with the numerical analysis carried out by p–y method using GROUP program. The analysis carried out with experimentally evaluated p-multipliers predicts load—deflection and bending profiles of pile groups reasonably well, but underestimates the depth to maximum bending moment by about 15%.

Effects of cyclic loading on mechanical properties of Maha Sarakham salt

A series of laboratory testing has been performed to assess the effects of cyclic loading on compressive strength, elasticity and time-dependency of the Maha Sarakham rock salt. Results from the cyclic loading tests indicate that the salt compressive strength decreases with increasing number of loading cycles, which can be best represented by a power equation. The salt elastic modulus decreases slightly during the first few cycles, and tends to remain constant until failure. It seems to be independent of the maximum loads within the range used here. Axial strain–time curves compiled from loci of the maximum load of each cycle apparently show a time-dependent behavior similar to that of creep tests under static loading. In the steady-state creep phase, the visco-plastic coefficients calculated from the cyclic loading test are about an order of magnitude lower than those under static loading. The salt visco-plasticity also decreases with increasing loading frequency. Surface subsidence and cavern closure simulated using parameters calibrated from cyclic loading test results are about 40% greater than those from the static loading results. This suggests that application of the property parameters obtained from the conventional static loading creep test to assess the long-term stability of storage caverns in salt with internal pressure fluctuation may not be conservative.

Strength Behavior of Cemented Marine Clay Subjected to Storm Type Loading

Cyclic loading on offshore structures leads to an increase in long term deformations. These deformations will cause additional stresses in structural members. Overloading of offshore structures may have serious consequences and they must be designed to accommodate the increased deformations. During a storm, there is a surge in the mean sea level causing an increase in stress and they are believed to represent critical conditions for offshore foundations. This program encompasses an experimental investigation for establishing the behavior of soil subjected to storm type varied cyclic loading conditions on Indian East coast marine clay samples. In field situations where cyclic loading is imposed on the soil, it can be considered a stress controlled phenomenon. If the effects of cyclic loading on any soil have to evaluated, it is considered more appropriate if the cyclic load test results are compared with reference static strength results obtained from stress controlled tests. To meet these requirements, a series of triaxial shear tests are conducted by adopting different load durations at each load increment. In order to estimate the effect brought in by storm type cyclic loading, it becomes necessary to conduct reference standard tests under uniform cyclic loading at various cyclic stress ratios (CSR) on identical soil specimens and these stress levels are chosen in such a way that there is no failure taking place during testing. This paper presents the behavior of marine clay subjected to uniform and storm type of varied cyclic loading. The effects of this cyclic loading are brought through the comparisons of the results obtained from testing under both strain and stress controlled monotonic loading.

Displacement-restraint bracing for seismic retrofit of steel moment frames

This paper presents a seismic retrofit method using wire rope (cable) bracing for steel moment-resisting frames. The retrofitted frame using the proposed bracing system exhibits ductile behavior and maintains seismic energy dissipation capacity to the same extent as the original bare frame. The bracing member does not act for small and medium vibration amplitudes. For large vibration amplitudes, the bracing member acts and restrains unacceptably large story drift. This retrofit method prevents an increase in the column compression force resulting from the brace action. Cyclic loading test results of the portal frames reveal fundamental characteristics of the proposed bracing system. Seismic response analyses are also conducted for the three-story moment-resisting frames. The effectiveness of the retrofit method is discussed in light of these test and analysis results.

Seismic performance assessment of steel reinforced concrete members accounting for double pivot stiffness degradation

This paper presents an effective hysteretic model for the prediction and evaluation of steel reinforced concrete member seismic performance. This model adopts the load-deformation relationship acquired from monotonic load tests and incorporates the double-pivot behavior of composite members subjected to cyclic loads. Deterioration in member stiffness was accounted in the analytical model. The composite member performance assessment control parameters were calibrated from the test results. Comparisons between the cyclic load test results and analytical model validated the proposed method's effectiveness.

An Experimental Study on Effectiveness of Reinforcing Methods on L-Shaped Prestressed Concrete Beam-Column Joints

This paper presents experimental results of cyclic loading tests carried out on three L-shaped prestressed concrete beam-column corner joints. Three types of reinforcing methods to enhance the anchorage performance of beam and column longitudinal reinforcing bars were studied based on the experimental results such as the load-displacement relation curves, deformation capacity, prestressing force variation, and strain measurements of the beam and column reinforcing bars. The test specimens were KPCL1 with the column longitudinal reinforcement with 180-degree hooks at their ends, KPCL2 with the column longitudinal reinforcement bent in a U-shape, and KPCL3 with U-shaped column longitudinal reinforcement and additional transverse reinforcement on the beam longitudinal reinforcement. It can be concluded that the anchorage performance was somehow enhanced by the three reinforcing methods in the positive direction of loading (closing direction), while in the negative direction of loading (opening direction) there was no remarkable improvement.

EXPERIMENTAL STUDY ON SHEAR STRENGTH AFFECTED BY SPLITTING BOND FAILURE OF R/C COLUMNS STRENGTHENED LATERALLY WITH EXTERNAL PC RODS

This paper aims to investigate the shear strength, which is affected by splitting both failure of the longitudinal re-bars, of R/C columns laterally strengthened with external PC rods. The results of cyclic loading tests indicate that the shear strength is much higher than that of predictions by an existing method based on the combination of truss and arch mechanisms. The shear strength can be predicted better if the effect of cover concrete on the bond stress of longitudinal re-bars required in the truss mechanism is taken into account.

STUDY ON TORSION PROPERTIES OF CARBON FIBER SHEET STRENGTHENED PC MEMBER WITH ZEBRA-SHAPED

In this research, carbon fiber sheet (CFS) substitute to lateral tie was used for torsional strengthening of PC member. To investigate the mechanical properties of CFS strengthened PC member subjected to torsion and torsional reinforcement effects of CFS, monotonic and cyclic torsional loading tests were carried out with specimens which strengthened by lateral ties and unreinforced specimen for comparison. From both monotonic and cyclic loading test results, it was proved that the CFS can increase the ultimate torsional capacity and cracking torque. And it was also confirmed that the CFS had sufficient reinforcement effect, and for CFS strengthened specimen, the cracks of concrete were dispersed and widths were small. Mechanical properties such as torsional rigidity retention, residual twist, resilience and ductility were excellent. As for three-dimension finite element method analysis, analysis results matched the results of monotonic loading tests well and tracked the cyclic torsional loading tests when both nonlinear properties and hysteresis properties of each material were applied. A calculation concept including torsional effective cross-sectional area and thickness of shearing flow for the torsional capacity of CFS strengthened PC member was proposed.

STUDY ON TORSION PROPERTIES OF CARBON FIBER SHEET STRENGTHENED PC MEMBER WITH ZEBRA-SHAPED

In this research, carbon fiber sheet (CFS) substitute to lateral tie was used for torsional strengthening of PC member. To investigate the mechanical properties of CFS strengthened PC member subjected to torsion and torsional reinforcement effects of CFS, monotonic and cyclic torsional loading tests were carried out with specimens which strengthened by lateral ties and unreinforced specimen for comparison. From both monotonic and cyclic loading test results, it was proved that the CFS can increase the ultimate torsional capacity and cracking torque. And it was also confirmed that the CFS had sufficient reinforcement effect, and for CFS strengthened specimen, the cracks of concrete were dispersed and widths were small. Mechanical properties such as torsional rigidity retention, residual twist, resilience and ductility were excellent. As for three-dimension finite element method analysis, analysis results matched the results of monotonic loading tests well and tracked the cyclic torsional loading tests when both nonlinear properties and hysteresis properties of each material were applied. A calculation concept including torsional effective cross-sectional area and thickness of shearing flow for the torsional capacity of CFS strengthened PC member was proposed.

Unified Elastoplastic–Viscoplastic Bounding Surface Model of Geosynthetics and Its Applications to Geosynthetic Reinforced Soil-Retaining Wall Analysis

The static and dynamic behaviors of reinforced soil structures are possibly subjected to the effects of creep or stress relaxation due to the time-dependent behavior of geosynthetic inclusions and backfill. To simulate the time-dependent monotonic and cyclic behavior of geosynthetics, an isothermal constitutive model is formulated within the framework of elastoplasticity–viscoplasticity. The concept of bounding surface plasticity is first utilized to formulate a time-independent cyclic model of geosynthetics. In order to capture the hardening stiffness of some polyester geosynthetics, an exponential bounding curve is used in simulating the primary loading. The time-independent version of the model was extended into an elastoplastic–viscoplastic model using overstress viscoplasticity with reference to available experimental data. The model was evaluated using creep, stress relaxation, monotonic, and cyclic loading test results obtained for different geosynthetics. It was then incorporated into a finite-ele...

The behavior of welded joint in steel pipe members under monotonic and cyclic loading

Most steel pipe members are joined by welding. The residual stress and weld metal in a welded joint have the influence on the behavior of steel pipes. Therefore, to accurately predict the behavior of steel pipes with a welded joint, the influence of welding residual stress and weld metal on the behavior of steel pipe must be investigated. In this paper, the residual stress of steel pipes with a welded joint was investigated by using a three-dimensional non-steady heat conduction analysis and a three-dimensional thermal elastic–plastic analysis. Based on the results of monotonic and cyclic loading tests, a hysteresis model for weld metal was formulated. The hysteresis model was proposed by the authors and applied to a three-dimensional finite elements analysis. To investigate the influence of a welded joint in steel pipes under monotonic and cyclic loading, three-dimensional finite elements analysis considering the proposed model and residual stress was carried out. The influence of a welded joint on the behavior of steel pipe members was investigated by comparing the analytical result both steel pipe with a welded joint and that without a welded joint.

Cyclic behavior of interior beam-column connections in non-seismic RC frames at different loading rates

This paper provides an insight into the response of non-seismic reinforced concrete (RC) building frames to excitations of different frequencies through experimental investigation. The results of cyclic loading tests of six full-scale RC beam-column sub-assemblies are presented. The tested specimens did not have any transverse reinforcement inside the joint core, and they were subjected to quasi-static and dynamic loading with frequencies as high as 20 Hz. Some important differences between the cyclic responses of non-seismic and ductile RC frames are highlighted. The effect of excitation frequency on the behavior of non-seismic joints is also discussed. In the quasi-static tests, shear deformation of the joint panel accounted for more than 50% of the applied story drift. The test results also showed that higher-frequency excitations are less detrimental than quasi-static cyclic loads, and non-seismic frames can withstand a higher load and a larger deformation when they are applied faster.

SUBSIDENCE PREDICTION OF KANTO LOAM SOIL BASED SUBGRADE USING CYCLIC LOADING EXPERIMENT

In a road excavation to lay a gas distribution pipeline, the re-use of the excavated soil for the subgrade backfill greatly reduces the environmental impact. However, when Kanto loam soil, which is widely distributed in the Kanto region, is employed for the backfill material, the relationship between the amount of the subsidence of the subgrade soil and the cyclic traffic loading is needed. In this study, cyclic loading tests on Kanto loam soil were conducted to investigate the subsidence characteristics. The subsidence prediction method of Kanto loam soil based subgrade under cyclic traffic loading was proposed using the cyclic loading test results. A full scale traffic loading experiments against road beds backfilled with Kanto loam soil were carried out. Consequently, a good correlation was shown to exist between the amount of the predicted subsidence and the measurement results.

3차원 탄소성 유한변위해석을 이용한 고강도(POSTEN60, POSTEN80) 원형강교각의 내진성능에 관한 연구

Recently, as steel structures become higher and more long-spanned, application of high-strength steels is increasing gradually. For seismic design of steel structures using high-strength steels(POSTEN60, POSTEN80), analytical method, can describe the large deformation and inelastic cyclic behavior generated by non-proportional cyclic loading, are required. In this paper, cyclic plasticity model was proposed by results of monotonic loading tests ant cyclic loading tests. Three-dimensional finite element analysis is developed by using proposed model and finite deformation theory and verified as compare with experiment result. Using 3-dimensional elastic-plastic finite deformation analysis, seismic analysis of high-strength steel pipe-section piers are carried out. Also, seismic performance of high-strength steel pipe-section piers in parameter of diameter-thickness ratio was clarified. 缀Ѐ㘰〻ሀ䝥湥牡氠瑥捨湯汯杹

伝統木造建築物柱脚の平面接触モデルに関する実験的研究

This paper reports the results of quasi-static cyclic loading tests conducted for modeling the two-dimensional contact response between a foundation stone and a circular column base of traditional timber frames. Constant axial loads and cyclic forced rotations are applied to three column-base specimens placed on a stone foundation. Three sets of axial load conditions are considered for each specimen. The three specimens are subjected to step-wisely increasing, constant, and step-wisely decreasing amplitudes of cyclic rotations, respectively. In order to obtain the moment-rotation angle relationship at the column base, we estimate the position of the center of mass for the distributed reaction force in the axial direction. We observed from the tests that the magnitudes of the axial load and the differences among the cvclic loading programs have little effect on the relation between the rotation angle and the location of the center of mass, for which an empirical formula is provided.

Cyclic response of axially loaded tapered piles

Instrumented model piles were used to investigate the fundamental behaviour of tapered and cylindrical piles in loose sand due to cyclic loading, using a centrifuge facility. The objectives of this study were to understand and evaluate the cyclic performance of tapered and cylindrical piles and to investigate the degradation in the pile capacity due to cyclic loading. The results of controlled-displacement cyclic loading tests on twelve one tenth-scale model piles with different taper angles in a centrifuge setup were presented and discussed. Six piles were instrumented and six were not. The load-movement curves of tapered and cylindrical piles were measured and compared. The load settlement curves due to axial compressive loading tests before and after cyclic loading tests were compared as well. The comparison showed that cyclic loading led to a change in the load transfer patterns so that a greater portion of the load was carried by toe resistance and a smaller portion by the shaft resistance. The degradation in the axial capacity for both tapered and cylindrical piles was more pronounced for longer piles (1/d = 26, where 1 is the embedded pile length and d is the average pile diameter). The results of this study suggest that the tapered pile response due to cyclic loading is comparable to that of straight-sided piles.

Static and Cyclic Behavior of Wooden Frames with Tenon Joints under Lateral Load

In this paper, the results of static and cyclic lateral load tests on the wooden frames that constitute an ancient Korean commoner’s house are presented. The typical form of beam-column joint used for this type of house is a tenon. Full-scale models of two types of frames are used for testing. The effects of joint type and wooden lattice on the lateral loading capacity and the failure modes of frames are investigated. The tests show a significant nonlinearity and inelasticity in the load-displacement curve. The general failure modes of joints are either shear or bending failure at the mortise branches of a tenon. The nonlinear hysteretic characteristics of the frame are identified and modeled by the so-called modified double target model.

Tests of Welded Beam-Column Subassemblies. I: Global Behavior

This paper describes the results of cyclic loading tests applied to 14 full-scale beam-column subassemblages. First, efforts undertaken in the Japanese steel community in response to damage observed at welded beam-to-column connections in the 1995 Hyogoken-Nanbu (Kobe) Earthquake are introduced. Second, the major test parameters chosen in this study are described: type of steel, type of connection, type of weld access holes, type of weld tabs, and type of loading. Third, the test results are presented in terms of the ductility capacity of the test specimens. Major findings are as follows: (1) All specimens developed plastic rotations and cumulative plastic rotations of 0.03 rad and 0.3 rad, respectively, suggesting that ductility capacity of the specimens was sufficient in light of present Japanese seismic design; (2) dynamic loading had no detrimental effect on ductility capacity; (3) ductility capacity was significantly smaller for specimens with steel weld tabs than for those with flux tabs made of cer...

FEM Analysis for Hysteretic Behavior of Thin-Walled Columns

Thin-walled steel columns composed of stiffened plate elements are often used in Japan as piers for elevated highway bridges in urban areas, because of their small cross-sectional areas and high earthquake resistance. An accurate finite-element-method-based (FEM-based) analysis to predict the ultimate hysteretic behavior of thin-walled steel columns subjected to seismic loading is presented in this paper. For this purpose, a three-surface cyclic metal plasticity model is developed. The three-surface model includes less material parameters and internal variables for the ease of its implementation in the FEM analysis. This model is characterized by a discontinuous surface inserted between the yield surface and the bounding surface. The discontinuous surface is used to express the yield plateau and the change of hardening coefficient. Most material parameters in the three-surface model can be determined by the tensile coupon test. However, three parameters independent of material types are calibrated by the existing cyclic loading test results of thin-walled steel columns. This is to improve the accuracy of this analysis specifically in the simulation of the localized buckling behavior, which accompanies extremely large plastic strains.