Reverse Cyclic Loading Research Articles

역사이클 하중의 하중비 변화가 SA312 TP304 재질의 파괴저항곡선에 미치는 영향

역사이클 하중의 하중비 변화가 SA312 TP304 재질의 파괴저항곡선에 미치는 영향

Improved estimation of the reverse-cyclic behavior of fully-grouted masonry shear walls with unbonded post-tensioning

The use of unbonded post-tensioning to develop fully-grouted masonry shear wall systems that can respond by rocking has recently gained significant momentum. The behavior of these walls has been routinely characterized using monotonic analysis with primary consideration to the rocking mechanism, concentrating the wall deformations at the base. However, experiments have indicated that these walls experience noticeable flexure and shear responses, in addition to rocking, which has been inadequately addressed by previous analysis methods. Moreover, when these walls are subjected to reverse-cyclic loads, their initial post-tensioning forces may reduce significantly due, in part, to masonry degradation at the wall base, producing responses that cannot be captured accurately using monotonic analysis. This paper presents an analysis method that can address these issues by accounting for the reverse-cyclic loading and the three mechanisms of rocking, flexure, and shear. Rocking is estimated using inelastic fiber-element sectional analysis at the wall base, while flexure and shear are modelled as elastic mechanisms, assuming they are small components of the total wall responses. The proposed method is evaluated using experiments and finite element analyses of fully-grouted masonry shear walls with unbonded post-tensioning. The method adequately captures the experimental force-displacement responses, hysteretic energy dissipation, and displacement component responses of the walls. Estimation of the post-tensioning forces experienced by the walls is significantly improved compared to monotonic analyses.

Predicting Displacement Data of Three-Dimensional Reinforced Concrete Frames with Different Strengthening Applications Using ANN

In this study, the artificial neural network (ANN) methodwas used to estimate unavailable displacement data of threedimensional(3D) reinforced concrete (RC) frames with differentstrengthening applications. Four 3D-RC frames wereproduced two storeys and one bay in 1/6 geometric scale withthe deficiencies commonly observed in residential buildingsin Turkey. The first specimen was a bare frame containing nobrick walls and no strengthening. The second specimen wasall brick walls and no strengthening. The third specimen wasstrengthened with an internal steel panel. The fourth specimenwas strengthened with an infilled RC shear wall. The specimenswere tested under reverse cyclic lateral loading and constantvertical loading until failure. This study investigated the estimationof displacement data when the linear variable differentialtransformer of 104 numbers is corrupted and some hystereticloop data are missing. Using the method proposed the unavailableor incorrect displacement data can be predicted by ANNwithout performing any additional experiments. Root meansquared error, coefficient determination, mean absolute error,mean squared error and normalised mean absolute error statisticalvalues were used to compare experimental results withANN model results. These statistical values usually exhibit verylow error rate until a cycle of maximum load is reached.

Experimental Investigation of RC Exterior Beam Column Connection with Eccentric Beam Subjected to Reversible Quasi Static Loads

Insufficiency of the Beam Column Joint (BCJ) caused structures failures particularly in case of the earthquakes. In most of the buildings, the beam center line was not aligned with the column center line. So, the effect of the eccentricity of the beam was studied in this article. Behaviour of reinforced concrete (RC) eccentric beam-column joint under reversible cyclic loading was investigated experimentally. The experimental program is one specimen. The specimen consisted of column and beam. The column divided into symmetry two parts (upper and lower parts). The beam fixed in middle of the column and it was free end. The main parameter was the effect of the eccentricity of the beam center line about the column center on behaviour of RC BCJ. The specimen was tested under reversible ten cycles. The horizontal displacement for the column and the vertical deflection at free end of the beam were recorded at each cycle. The crack pattern of the tested specimen was studied at every cycle in details. It was noticed that the eccentricity of the beam has concentrated more stresses on the joint side close to the eccentricity. The failure took place at the joint due to its weakness.

Effect of Timber Type and Nail Spacing on the Hysteretic Behavior of Timber-Framed Shear Walls with Openings

In scope of the study, behavior of timber-framed shear walls having openings with variable dimensions and locations subjected to reverse cyclic loading is experimentally investigated. Main variables considered in the study are the aspect ratios of timber-framed panel walls, dimensions and locations of the openings on the panel walls, material of the timber frames and spacings of the nails used in the panel connections. Load–displacement relationships, strengths, stiffnesses, displacement ductility ratios, energy dissipation capacities and failure mechanisms of the specimens are determined. The ultimate load capacities of the timber-framed panels are calculated as per Eurocode 5 and presented in comparison to experimental results. Moreover, lateral load-resisting capacities and load–displacement relationships of the test specimens are numerically calculated with finite element analyses. A good agreement was observed between the numerical and experimental results. From the test results, it is observed that the load behavior relationships of the test specimens significantly affected by aspect ratios, location of the openings, material of the timber frames and spacing of the nails used to provide connection between the timber-framed panel elements. Also, the increasing size of the openings decreased the stiffness’ of the test specimens.

Inelastic response prediction of CFST columns and connections subjected to lateral loading

Concrete filled steel tubes (CFST) are composite structural elements which provide an economical and efficient alternative to conventional reinforced concrete and structural steel construction. Under seismic loading, CFSTs undergo reversed cyclic loading, and robust connections capable of sustaining cyclic lateral load demands, while minimizing damage and degradation, are required. Previous research has utilized numerical and experimental methods to demonstrate the performance of an embedded ring (ER) CFST column-to-cap beam/foundation connection in which an annular ring is welded to the end of the steel tube, and embedded in the cap beam/foundation concrete. However, due to the complexities associated with modeling the non-linear cyclic behavior of the ER connection (including the cyclic behavior of the concrete fill and the composite interaction of the materials), prior numerical efforts have focused primarily on monotonic behavior and failure envelopes rather than cyclic behavior. This deficiency is addressed here. A detailed continuum model capable of capturing the non-linear cyclic behavior of the ER connection is introduced and validated using experimental data. The proposed model is shown to predict damage and behavior of the ER connection subjected to reversed-cyclic loading with a reasonable accuracy; failure modes, hysteretic curves, resistance at target drifts, and drifts and steel strains at the initiation of steel tearing compare well with experimental observations.

Performance Evaluation of Exterior Beam–Column Joint with Core Reinforcement Technique Subjected to Reverse Cyclic Loading

The present work aims to study the performance of exterior beam–column joint with core reinforcement technique subjected to reverse cyclic loading. In this experimental study, three sets of one-third scaled exterior beam–column joint specimens using M30 grade concrete were cast and tested. The first set of specimens were detailed as ordinary moment resisting frame (IS:456 and SP:34) and designated as joint BCJ1. The second sets of specimens were detailed as special moment resisting frame (IS:13920) and designated as joint BCJ2. In the third set, the reinforcement detailing followed in joint BCJ1 was integrated with a new type of reinforcement (called “core reinforcement”) proposed in this study and designated as joint BCJ3. Based on the experimental result, the joint BCJ3 gave the better performance considering the strength in terms of load-carrying capacity, energy dissipation capacity, stiffness and ductility factor. The results of reverse cyclic loading tests performed in the exterior beam–column joint models indicate that the additional core reinforcement in the beam–column joint region provide adequate ductility. The stiffness of the joint with additional core reinforcement in the beam–column joint region did not undergo much reduction when compared to other types of joints. In addition, the usage of core reinforcement in the joint region can reduce its installation and difficulties in placing and compacting the concrete. This combination of core reinforcement technique in the beam–column joint region may contribute to reduction in destruction due to earthquakes.

Effects of cyclic vertical loading on bearing and pullout capacities of piles with continuous helix wing

Laboratory and field tests were conducted to investigate the bearing and pullout capacities of steel piles with a continuous helix wing during cyclic loading. Both continuous helix and straight-sided piles were subjected to monotonic compressive, monotonic tensile, and cyclic reversal loading in the laboratory, while only the continuous helix pile was tested in the field. Both the laboratory and the field tests showed that the bearing and pullout capacities of the continuous helix pile under cyclic reversal loading decreased to approximately 60–80% of those of the pile under monotonic loading, with a larger reduction seen in the laboratory tests. The decrease in resistance was mainly due to the reduction in shaft friction, which was likely to be the result of soil disturbance and loosening around the pile with cyclic loading. The laboratory tests also showed that the tip resistance of the straight-sided pile under cyclic reversal loading was reduced, similarly due to the loosening of the soil, particularly underneath the pile tip. The tip resistance of the continuous helix pile, in contrast, did not degrade with cyclic loading, owing to the presence of the wing immediately above the pile tip that inhibited the loosening of the soil. These findings were supported by similar field test observations.

Seismic performance of reinforced concrete squat walls with embedded cold-formed and thin walled steel truss

To investigate the seismic performance of squat reinforced concrete (RC) walls with embedded cold-formed and thin walled (CFTW) steel truss, experimental and analytical studies were conducted. Four one-third scaled composite wall specimens were tested to failure subjected to cyclic load reversals under constant axial load. The experimental behaviors of test specimens including damage development process, load-deformation responses, stiffness degradation, energy dissipation capacity, failure pattern and ductility were discussed. Test results indicate that the embedded CFTW steel truss web braces can effectively avoid web concrete crushing and improve the energy dissipation capacity of shear walls with low aspect ratios, resulting in a more ductile failure pattern due to the failure of boundary elements. Nonlinear finite element analysis (FEA) on test specimens was carried out based on suggested modeling techniques and the accuracy of the numerical method was verified. Influences of critical parameters such as axial load ratio, amounts of embedded CFTW steel truss chord and web braces on the performance of the composite shear walls were further examined through comprehensive parametric analysis. It shows that the axial load ratio has a significant impact on the post-yielding behavior of composite shear walls. Good displacement ductility can be achieved under medium level of axial load ratio. Increasing the amount of embedded truss chord cannot significantly improve the performance of composite walls. The embedded truss web braces are noticeably beneficial to the energy dissipation capacity and ductility behavior of squat composite walls.

Experimental evaluation of the effects of reverse cyclic loading rate on the mechanical behavior of reinforced SCC beams

In this paper, the effects of cyclic loading rate on the mechanical behavior of reinforced SCC beams are investigated experimentally. Based on the results of cyclic loading tests of nine beam specimens, hysteresis loops, stiffness and strength degradation, energy dissipation capacity and equivalent viscous damping of SCC beams were analyzed with various rates before and after the yielding limit. Cyclic loading was displacement-controlled and a uniform loading procedure was selected for this test. Test results indicate that SCC beams demonstrate different behavior before and after the yielding zone among the increase of the loading rate.

Development and Seismic Behavior of Precast Concrete Beam-to-Column Connections

A new precast concrete beam-to-column connection for moment-resisting frames was developed in this study. Both longitudinal bar anchoring and lap splicing were used to achieve beam reinforcement continuity. Three full-scale beam-to-column connections, including a reference monolithic specimen, were investigated under reversal cyclic loading. The difference between the two precast specimens was the consideration of additional lap-splicing bars in the calculation of moment-resisting strength. Seismic performance was evaluated based on hysteretic behavior, strength, ductility, stiffness, and energy dissipation. The plastic hinge length of the specimens is also discussed. The results show that the proposed precast system performs satisfactorily under reversal cyclic loading compared with the monolithic specimen, and the additional lap-splicing bars can be included in the strength calculation using the plane cross-section assumption. Furthermore, the plastic hinge length of the proposed precast beam-to-column connection can be estimated using the models for monolithic specimens.

Out-Of-Plane Behavior of Confined Masonry Walls Subjected to Concentrated Loads (One-Way Bending)

This paper presents the results of a study on the out-of-plane seismic behavior of confined masonry walls. Five confined walls were tested under reverse cyclic loads. The variables studied were the axial stress and the wall aspect ratio. Analytical out-of-plane strength of walls was calculated considering the strengths of the wall panel and the concrete confining elements. The former was determined using the unidirectional strut method and the latter using a plastic analysis. It was observed that for walls with the same aspect ratio, as the axial stress increases, the out-of-plane strength increases. For walls with the same axial stress, as the aspect ratio increases, the strength decreases. Based on comparisons between analytical and experimental results, it was concluded that the models developed in this work predict accurately the out-of-plane strength of the walls.

Behavior of geopolymer and conventional concrete beam column joints under reverse cyclic loading

An experimental investigation was carried out on the strength and behavior plain and fiber reinforced geopolymer concrete beam column joints and the results were compared with plain and steel fiber reinforced conventional concrete beam column joints. The volume fraction of fibers used was 0.5%. A total of six Geopolymer concrete joints and four conventional concrete joints were cast and tested under reversed cyclic loading to evaluate the performance of the joints. First crack load, ultimate load, energy absorption capacity, energy dissipation capacity stiffness degradation and moment-curvature relation were evaluated from the test results. The comparison of test results revealed that the strength and behavior of plain and fiber reinforced geopolymer concrete beam column joints are marginally better than corresponding conventional concrete beam column joints.

Experimental Study on Seismic Performance of New RCS Connection

This paper deals with an experimental study on seismic performance of a new type of exterior RCS connection, in which a steel profile embedded inside RC column is directly welded to the steel beam. A full scale exterior hybrid joint was built and tested under reversed-cyclic loading at the University of Transport and Communications of Vietnam. Seismic performance in term of load bearing capacity, story drift capacity, ductility, energy dissipation and stiffness degradation were evaluated. The test specimen showed a good response to cyclic load reversals. The experimental results indicated that the test specimen performed in a ductile manner and the stiffness degradation during the cycles performed was gradual. It was concluded that the studied RCS joint could be used as dissipative element in the structures of ductility class medium (DCM).

Cyclic Behavior of Lap Splices Strengthened with Ultrahigh Performance Fiber-Reinforced Concrete

The cyclic behavior of six full-scale reinforced concrete (RC) beams with a deficient lap splice strengthened with ultra-high-performance fiber-reinforced concrete (UHPFRC) is experimentally investigated. The experimental program is based on the findings of previous test series carried out in the same research program that demonstrated the ability of UHPFRC to eliminate bond failure in deficient lap splices of beams and wall-type bridge columns. The objective of this experimental work is to determine the efficiency of this strengthening technique on wide flexural elements (beams, slabs, walls, or wall columns) subjected to reverse cyclic loading. Specimen reinforcement consists of two pairs of deformed bars spliced at midspan on both tension and compression faces. The strengthening technique consists of replacing normal concrete around lapped bars in the splice region by UHPFRC, which allows for keeping the original member geometry. One type of fiber, three fiber contents, two bar diameters, and two bar arrangements are considered. For isolating the UHPFRC contribution, the splice regions are free of any confinement. The beam specimens are tested at four points, bending with a constant-moment region along the splice length. The result indicates that UHPFRC with a fiber content of 2 or 3% can significantly increase the bond strength of splice bars without confinement. The levels of ductility reached for the highest fiber content meet the requirements for high ductility demand, such as in seismic design. The results demonstrate that an appropriate casting method combined with a self-compacting UHPFRC with an appropriate fiber content ensure the efficiency of the strengthening technique for providing for the continuity of lapped bars and for enabling a high ductility capacity under monotonic or cyclic loading. The results also confirm the applicability of the method for strengthening lap-spliced regions of wide elements—such as slabs, shear walls, and wall-bridge piers—without having to provide any confinement.

Mechanical properties of concrete beams reinforced with CFRP prestressed prisms under reverse cyclic loading

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.

Experimental study on in-plane cyclic response of partially grouted reinforced concrete masonry shear walls

This article describes the experimental results of ten partially grouted reinforced concrete masonry shear walls (PG-RCMSW) that were subjected to reverse lateral in-plane cyclic loads. The variables analysed in this study were: aspect ratio, shear reinforcement ratio and level of axial pre-compression. The influence of each of these variables on different structural parameters such as degradation of stiffness, shear strength, displacement ductility, dissipation of energy, hysteretic damping and level of drift, was evaluated. In addition, the precision of certain analytical expressions reported in the literature to predict the maximum shear strength of walls was examined and contrasted with the experimental results obtained.The results showed that the evolution of the damage was propagated in a similar way in all the walls tested until reaching the level of maximum strength. From this point, the evolution and extension of the damage depended on the characteristics and loading conditions particular to each wall. Also, a strong interdependence of the variables studied was identified, which became evident in the evaluation of shear strength, dissipation of energy, hysteretic damping, and level of drift. Using a bilinear idealization, displacement ductility values between 2.85 and 7.94 were found to reflect the presence of a moderate level of ductility in the walls tested. The equivalent viscous damping ratio associated with a non-linear response was found to range from 5% to 11%, indicating a moderate level of energy dissipation before the peak load was reached. Finally, the comparison between the predictions of the analytical expressions from the literature and the experimental results showed that those expressions that incorporated some interdependence in their design variables did not possess an appropriate degree of confidence to be applied in assessing the shear strength of PG-RCMSW, while expressions proposed by some international codes seem to be more reliable and conservative.

Coupling elasto-plastic self-consistent crystal plasticity and implicit finite elements: Applications to compression, cyclic tension-compression, and bending to large strains

In this work, we describe a finite element (FE) implementation of an elasto-plastic self-consistent (EPSC) polycrystal plasticity model termed FE-EPSC, which is intended for simulations of metal forming. To this end, we present an analytical Jacobian, which is necessary for the implicit coupling and ensuring a fast convergence. Every FE integration point is a material point that can be represented either by a single crystal or a polycrystalline material. The constituent crystal can deform by a combination of anisotropic elasticity, crystallographic slip, and deformation twinning. The model is validated and applied to a suite of tests, including monotonic compression, cyclic forward loading, unloading and reverse loading and non-monotonic four-point bending, and materials, such as different alloy compositions, crystal structures, and initial microstructures. The same FE-EPSC framework is applied for all these cases with the main differences pertaining to intrinsic properties, such as the available slip and twinning deformation modes, and the material parameters for activating and hardening of these modes. Full characterization for these parameters for high-purity α-Ti is presented here for the first time. Through these examples we show that, in addition to being predictive with great accuracy, the key advantage of this model lies in its versatility. It accounts for the development of backstress aided dislocation glide, thermally activated storage of dislocations, elastic anisotropy, crystallographic slip and deformation twinning via multiple modes, and de-twinning as well as multi-level homogenizations.

Monotonic and cyclic behaviour of lightweight concrete beams with and without steel fiber reinforcement

Experimental tests on four lightweight concrete beams with and without steel fiber reinforcement, subjected to monotonic and reverse cyclic loads, were set-up in order to investigate the influence of the fiber reinforcement on the strength, ductility and energy dissipation. The tests were performed on beams with 200×300mm cross section and clear span of 3000mm. Furthermore, in the framework of the definition of sustainable materials, the cement of the concrete matrix was partially substituted by ashes coming from the combustion of Municipal Solid Waste (MSW), with pozzolanic reaction. The obtained results are presented, discussed and compared.

Monotonic and reverse-cyclic load experiment for plywood and RC slab diaphragms used in timber-concrete hybrid building

In seismically active regions, the use of timber-reinforced concrete (RC) hybrid construction can overcome the structural limitations that occur with timber construction. A series of shake table tests were carried out on RC-timber hybrid systems that used two diaphragms: glulam+plywood system (CN75 @ 50mm nail spacing) and laminated wood+RC slab system. To develop robust analytical models, however, understanding the different components is crucial. In this paper, a series of in-plane monotonic and reverse-cyclic tests were undertaken on two diaphragm systems and their connections. Salient features of each diaphragm (i.e. stiffness, ductility, and energy dissipation) were computed from the monotonic loading test results. With the test results reported, analytical and numerical models can be developed.