Monotonic Lateral Loading Research Articles

Flexural behaviour of RC columns using wire ropes as lateral reinforcement

The use of high-strength, high-flexibility wire ropes for lateral reinforcement in reinforced concrete (RC) columns helps resolve troubles encountered during bending of the high-strength steel bar as well as in the preparation of congested steel bars. Five column specimens were tested to failure under constant axial load and cyclic lateral loads in order to examine the practical application of a spiral-type wire rope for lateral reinforcement in rectangular concrete columns. The main variables investigated were the configuration of spiral wire ropes and the axial load level. The test results were then compared with test results obtained by other researchers for conventional tied columns with rectangular hoops. At a similar lateral reinforcing index level, greater displacement ductility ratios and work damage indicators were observed in the columns containing spiral wire ropes than in conventional tied columns. These results indicate that wire rope is highly effective in enhancing the ductility of columns and preventing the buckling of longitudinal reinforcement. The effect of the configuration of wire rope and the axial load level on the crack propagation and flexural capacity of the columns was similar to the trend commonly observed in tied columns. On the other hand, the flexural capacity and monotonic lateral load–displacement response of RC columns confined with high-strength spiral-type wire ropes could be appropriately predicted by a simple analytical approach derived using the section laminae method and idealised curvature–displacement relationship. Overall, the wire ropes possess great potential for practical applications to lateral reinforcement.

Behavior of Lateral Resistance of Flexible Piles in Layered Soils

This paper presents an experimental investigation on the lateral load carrying capacity of model piles of different flexural stiffness embedded in loose sand between dense sand and dense sand between loose sand layered soil strata. Attempts has been made to study the variation of lateral stiffness, eccentricity and soil layer thickness ratio and the effect of various parameters on the magnitude of Nh. The result of a model tested for the piles embedded in IS grade-II dry Ennore sand under monotonic lateral loadings. Experimental results are used for the load-deflection curves (p-y curves) for laterally loaded piles. The proposed p-y curves were compared to the existing curves with Nh and were evaluated with the experimental data. The ultimate lateral soil resistance and subgrade modulus were investigated and discussed. 0 for dense condition. The tests were conducted in two steps. a) The soil condition is loose sand layer between dense sand layer with H/D ratio of 0.25, 0.50, 0.75, and 0.90. b) The soil condition is dense sand layer between loose sand layer with H/D ratio of 0.25, 0.50, 0.75,and 0.90, where H is the thickness of middle layer and D is the total depth of embedment of the pile(=300mm). In both the cases the eccentricities of 0, 50, 100, 150 and 200mm are conducted in homogeneous loose sand layer and dense sand layer. The outside diameters of the piles are 16mm for solid Steel and Wooden Piles. Hollow Aluminium pile with 16mm outside and 0.3mm thickness. The embedment depths of all the piles are 300mm. The flexural rigidity of steel, wooden and Aluminium piles were 642.106Nm 2 , 506.12Nm 2 and 51.041Nm 2 respectively. The relative stiffness factors for steel, wooden and Aluminium were 0.1192, 0.939 and 0.0094 respectively for Loose sand layer and 0.0263, 0.0207 and 0.0020 for Dense sand layer. The horizontal displacement and rotation of pile cap are recorded by L.V.D.T. and two dial gauges. The stabilized 'Rainfall-Technique' this standard technique is available in standard literature and this technique was used to pour the sand in the testing steel tank. Figure.1 shows schematic sketch of experimental setup.

Nonlinear Finite Element Analysis of an R/C Frame Under Lateral Loading

Recent developments in computer technology have made possible the use of finite element methods for 3D modeling and analysis of reinforced concrete structures. In this study, the failure behavior and crack formation of an R/C frame under monotonic and reversed-cyclic lateral loading are studied by 3D nonlinear finite element analysis using ANSYS software. Modeling the nonlinear behavior of concrete material as well as the reinforcing steel embedded within concrete is a difficult task. Different methodologies and modeling options are considered in the computer model. The application of reversed cyclic displacement loading and the execution of nonlinear analyses are explained in detail. Load-displacement relationships and concrete crack profiles are obtained in order to compare with the experimental data and observed crack profile. The analysis results compared well with the experimental data based on the comparison of load-displacement graphs. The failure mode of the frame is identified by the crack profiles displayed on the structure.

Numerical Assessment of the Lateral Stiffness of Unreinforced Masonry Rectangular Columns

Using an efficient numerical model capable of capturing the cracking and second-order effects, this study investigates the lateral stiffness of unreinforced masonry rectangular columns at uncracked and cracked situations. The columns are modeled as prismatic cantilevers undergoing their own weights, eccentric vertical top loads, and static concentrated lateral top loads having increasing magnitude. The lateral force is considered to perform a monotonic lateral load analysis on the columns. On the basis of the numerically obtained lateral force versus lateral displacement relationships, the behavior of the columns is characterized by two limit states corresponding to the first cracking and the maximum resistance. For a reference column, the lateral stiffness values at these limit states are determined and compared with each other. The results show that the lateral stiffness of a column is related to the displacement level and hence the level of cracking. Implementing parametric analyses, the effects of some parameters are also investigated such as the column slenderness, the magnitude and eccentricity of the vertical top load, the flexibility parameter, and the angle of tilt, if any, on the lateral stiffness of the columns.

Modeling and investigation of elasto-plastic behavior of steel–concrete composite frame systems

This paper presents a mixed finite-element model combining the fibered beam and layered shell elements using the general finite-element program MSC.MARC (2005r2) based on the discussion and comparison of the previous models. The proposed modeling procedure is intended for integrated elasto-plastic analysis of fully connected steel–concrete composite frames subjected to the combined action of gravity and monotonic lateral loads. The model is verified by extensive experiments and examples, and the behavior of composite frames is also investigated intensively. The slab space composite effect and the beam–column semi-rigidity are the two critical factors influencing the structural behavior. These two factors have not been considered simultaneously in some previous models but can be both included in the proposed model. Due to the complex slab space composite effect in composite frames, the previous models with a constant-width effective flange of slab can not trace the actual nonlinear slab behavior, but the proposed model can give accurate results. Since the slip effect between the steel beam and RC slab has negligible influence on the global calculation results of the structural system verified by the calculation examples, the slip effect is neglected in the present study to simplify the modeling procedure and enhance the calculating efficiency. The proposed model possesses good accuracy and broad applicability with simple modeling procedure and high calculation efficiency, and has a great advantage for the large-scale integrated analysis of multistory and high-rise composite frames.

Modelling inelastic hinges using CDM for nonlinear analysis of reinforced concrete frame structures

A new formulation based on lumped plasticity and inelastic hinges is presented in this paper for nonlinear analysis of Reinforced Concrete (RC) frame structures. Inelastic hinge behaviour is described using the principles of Continuum Damage Mechanics (CDM). Member formulation contains provisions to model stiffness degradation due to cracking of concrete and yielding of reinforcing steel. Depending on its nature, cracking is classified as concentrated or distributed. Concentrated cracking is accounted through a damage variable and its growth is defined based on strain energy principles. Presence of distributed flexural cracks in a member is taken care of by modelling it as non-prismatic. Plasticity theory supported by effective stress concept of CDM is applied to describe the post-yield response. Nonlinear quasi-static analysis is carried out on a RC column and a wide two-storey RC frame to verify the formulation. The column is subjected to constant axial load and monotonic lateral load while the frame is subjected to only lateral load. Computed results are compared with those due to experiments or other numerical methods to validate the performance of the formulation and also to highlight the contribution of distributed cracking on global response.

Progressive collapse of a two-story reinforced concrete frame with embedded smartaggregates

This paper reports the experimental and analytical results of a two-story reinforcedconcrete frame instrumented with innovative piezoceramic-based smart aggregates (SAs)and subjected to a monotonic lateral load up to failure. A finite element model of the frameis developed and analyzed using a computer program called Open system for earthquakeengineering simulation (OpenSees). The finite element analysis (FEA) is used to predict theload–deformation curve as well as the development of plastic hinges in the frame. Theload–deformation curve predicted from FEA matched well with the experimental results.The sequence of development of plastic hinges in the frame is also studied from the FEAresults. The locations of the plastic hinges, as obtained from the analysis, weresimilar to those observed during the experiment. An SA-based approach is alsoproposed to evaluate the health status of the concrete frame and identify thedevelopment of plastic hinges during the loading procedure. The results of theFEA are used to validate the SA-based approach for detecting the locations andoccurrence of the plastic hinges leading to the progressive collapse of the frame.The locations and sequential development of the plastic hinges obtained fromthe SA-based approach corresponds well with the FEA results. The proposedSA-based approach, thus validated using FEA and experimental results, has a greatpotential to be applied in the health monitoring of large-scale civil infrastructures.

Cyclic shakedown of piles subjected to two‐dimensional lateral loading

AbstractPile foundations are frequently subjected to cyclic lateral loads. Wave and wind loads on offshore structures will be applied in different directions and times during the design life of a structure. Therefore, the magnitude and direction of these loads in conjunction with the dead loads should be considered. This paper investigates a loading scenario where a monotonic lateral load is applied to a pile, followed by two‐way cycling in a direction perpendicular to the initial loading. This configuration is indicative of the complexity of loading that may be considered and is referred to in the paper as ‘T‐shaped’ loading. The energy‐based numerical model employed considers two‐dimensional lateral loading in an elasto‐plastic soil, with coupled behaviour between the two perpendicular directions by local yield surfaces along the length of the pile. The behaviour of the soil–pile system subjected to different loading combinations has been divided into four categories of shakedown previously proposed for cyclic loading of structures and soils. A design chart has been created to illustrate the type of pile behaviour for a given two‐dimensional loading scenario. Copyright © 2009 John Wiley & Sons, Ltd.

Hysteretic Model for Reinforced Concrete Columns Including the Effect of Shear and Axial Load Failure

Recent strong earthquakes have shown that column failure is the primary cause of collapse in many existing older buildings and bridges. The main objective of this paper is to develop a macromodel to simulate the cyclic lateral load-deformation response of reinforced concrete columns with limited computational effort. Flexural, longitudinal bar slip, and shear deformations are predicted under monotonic lateral loads, including the effects of strength decay and stiffness degradation. Using these monotonic responses as envelopes or primary curves, cyclic responses corresponding to these three deformation components are calculated. The column under consideration is classified into one of five categories considering the potential for flexural, shear, or axial load failure. Individual cyclic responses then are combined to obtain the total lateral response of the column based on its identified failure mode. Comparison of predicted cyclic response and experimental data showed that the proposed model is sufficiently accurate.

A Study on Pushover Analysis of Frame Structure Infilled with Low-Rise Reinforced Concrete Wall

AbstractThis paper focused on the pushover analysis of a frame structure infilled with low-rise reinforced concrete (RC) wall. The softening model of concrete as well as the elastoplastic model of reinforcement was considered in the analysis associated with the equilibrium and compatibility conditions. Accordingly, the shear load-deformation relationship of the wall subjected to monotonic lateral load can be analyzed through the proposed analysis procedure. Based on the relationship obtained, we employed a single equivalent structural strut represented by a nonlinear axial member, acting in the diagonal direction of the frame, in simulating the infilled RC wall to simplify the framed wall model. As a result, the sequential pushover analysis of the whole structure could be performed easily and efficiently based on the realistic procedure proposed.To validate the proposed approach, reported results from the cyclic loading tests of fifteen specimens were adopted for the correlation. Based on the correlation, it is found that this study can provide an acceptable result of the pushover analysis and give an insight into progressive failure consequence of the framed wall structure. The proposed procedure simplifying the structural model helps the practical engineers get a higher efficiency while performing seismic evaluation and retrofit design of the high-redundancy frame structure with numerous infilled low-rise RC walls.

Nonlinear Behavior of Precast Concrete Coupling Beams under Lateral Loads

This paper presents an analytical investigation of the nonlinear behavior of precast concrete coupling beams under monotonic lateral loading. In contrast to conventional monolithic concrete coupling beams, coupling of reinforced concrete wall piers in the proposed system is achieved by posttensioning the beams and the walls together at the floor and roof levels. Under lateral loads, the nonlinear deformations of the coupling beams occur primarily due to the opening of gaps at the beam-to-wall interfaces. The new system offers several advantages over monolithic systems, such as simpler detailing for the beams and the wall piers (no need for diagonal reinforcement crossing the beam-to-wall joints), reduced damage to the structure, and an ability to self-center, thus reducing the residual lateral displacements of the building after a large earthquake. Steel top and seat angles are used at the beam ends to yield and provide energy dissipation during the earthquake. The paper investigates the effects of design parameters, such as the amount of posttensioning, beam and wall properties, and top and seat angle properties, on the lateral strength and displacement characteristics of floor-level coupling beam subassemblies. The results are used to determine how the system behavior can be controlled by design. A procedure to estimate the nonlinear lateral load-deformation relationship of the subassemblies is developed.

Experimental tests and numerical analysis of a real RC structure upgraded by means of C-FRP

The paper presents results of the analysis of the lateral-load response of an existing RC structure seismically upgraded by means of C-FRP. The structure was tested “as-is” under monotonic lateral loading conditions. It failed by a column-type collapse mechanism. The structure was repaired and upgraded by means of C-FRP. The structure has been tested again by a cyclic load test. Results demonstrate the successful implementation of C-FRP with a significant improvement of stiffness, strength and lateral displacement capacity of the upgraded structure. Finally a numerical study has been started with the aim to correctly capture the experimental results.

Finite element modelling and investigation of the behaviour of elastic infilled frames under monotonic loading

In this paper the behaviour of single-storey one-bay infilled frames under monotonic lateral loading is studied and investigated analytically, assuming linearly elastic material laws. To this purpose a precise finite-element micromodel is formulated and used, by considering contact interface conditions between the frame and the infill. The analytical investigation is carried out through an extended comparative parametric study and is focused on the quantitative influence of certain simplified modelling assumptions and several critical modelling parameters on the response of the system. In the analytical investigation, the effects of the alternative modelling of the interface conditions, the density of the discretization mesh, the size of the friction coefficient, the relative beam/column stiffness, the relative frame/infill size and the orthotropy of the infill panel are evaluated, providing a detailed insight and a better quantitative understanding of the basic features of the system response. It is concluded that all these modelling parameters considerably affect the behaviour of the examined infilled frames, except for the parameter describing the infill’s orthotropy. The conclusions obtained can be further extended in the case of multi-storey systems.

Experimental Load–Transfer Curves of Laterally Loaded Piles in Nak-Dong River Sand

This paper describes the results of a model testing of the piles embedded in Nak-Dong River sand, located in south Korea, under monotonic lateral loadings. A number of features were studied, includ...

Monotonic Lateral Loading of Piles in Calcareous Sand

This paper describes the results of a centrifuge modeling study of the response of piles embedded in calcareous sand under monotonic lateral loading. A number of features have been explored, including method of installation, rate of loading, and pile head restraint. The study has led to recommendations for load-transfer curves with the magnitude of lateral resistance linked to the soil strength through the cone resistance. Modification factors have been developed to allow for different methods of installation and for different rates of loading. The proposed load-transfer curves and resulting pile response are shown to provide an excellent match with the experimental data, and are compared with results derived using existing guidelines for terrigenous sands. Significant differences are demonstrated, confirming the need to treat calcareous sediments separately from other soil types with respect to lateral pile response.