RC Walls Research Articles

Numerical investigation of RC structural walls subjected to cyclic loading

This work is based on a nonlinear finite-element model with proven capacity for yieldingrnrealistic predictions of the response of reinforced-concrete structures under static monotonically-increasing loading. In it, the material description relies essentially on the two key properties of triaxiality and brittleness and, thus, is simpler than those of most other material models in use. In this article, the finiteelement program is successfully used in investigating the behaviour of a series of RC walls under static cyclic loading. This type of loading offers a more strenuous test of the validity of the proposed program since cracks continuously form and close during each load cycle. Such a test is considered to be essentialrnbefore attempting to use the program for the analysis of concrete structures under seismic excitation inrnorder to ensure that the solution procedure adopted is numerically stable and can accurately predict thernbehaviour of RC structures under such earthquake-loading conditions. This is achieved through arncomparative study between the numerical predictions obtained presently from the program and availablernexperimental data.

Experimental study on seismic behavior of semi-rigid connection between steel beam and concrete wall

Beam-column or beam-wall connections are an important problem in high-rise buildings. In this study, based on the analysis of an example structure, an analytical model for design of the semi-rigid connections between steel beams and RC walls in high-rise hybrid buildings is proposed. Also, the mechanical characteristics of these connections subjected to low-reversed cyclic loading are investigated through comparison of experimental results from three semi-rigid connections and two rigid connections. Moreover, some latent problems for design of these connections as well as the corresponding solutions are discussed. The results from the experiments and analyses indicate that semi-rigid connections exhibit satisfactory capacity and seismic performance, and the proposed design can be used in practice.

降伏機構分離型鉄筋コンクリート造耐震壁の基本耐震性能

A reinforced concrete shear wall (RC wall) is recognized as an important seismic element due to its high stiffness and strength. In order to use an RC wall more effective in the frame with RC wall, large deformation capacity and stable lateral stiffness at flexural hinge zone are required. This paper proposes a new RC wall with hinge isolated structural system and verifies the lateral force resisting and lateral deformation mechanisms by a horizontal loading test for one-third scale models. The test results show the facts that the RC wall with hinge isolated structural system forms clear isolated flexural hinge mechanism and suffers small damage of concrete in the hinge zone. The larger deformation capacity will be expected by restraining a slip deformation at the wall foot.

Seismic behavior of asymmetric RC wall buildings: principles and new deformation-based design method

The seismic design of multi-story buildings asymmetric in plan yet regular in elevation and stiffened with ductile RC structural walls is addressed. A realistic modeling of the non-linear ductile behavior of the RC walls is considered in combination with the characteristics of the dynamic torsional response of asymmetric buildings. Design criteria such as the determination of the system ductility, taking into account the location and ductility demand of the RC walls, the story-drift demand at the softer (most displaced) edge of the building under the design earthquake, the allowable ductility (ultimate limit state) and the allowable story-drift (performance goals) are discussed. The definition of an eccentricity of the earthquake-equivalent lateral force is proposed and used to determine the effective displacement profile of the building yet not the strength distribution under the design earthquake. Furthermore, an appropriate procedure is proposed to calculate the fundamental frequency and the earthquake-equivalent lateral force. A new deformation-based seismic design method taking into account the characteristics of the dynamic torsional response, the ductility of the RC walls, the system ductility and the story-drift at the softer (most displaced) edge of the building is presented and illustrated with an example of seismic design of a multi-story asymmetric RC wall building. Copyright © 2005 John Wiley & Sons, Ltd.

Implementation of a macro model to predict seismic response of RC structural walls

A relatively simple multiple-vertical-line-element macro model has been incorporated into a standard computer code DRAIN-2D. It was used in blind predictions of seismic response of cantilever RC walls subjected to a series of consequent earthquakes on a shaking table. The model was able to predict predominantly flexural response with relative success. It was able to predict the stiffness and the strength of the pre-cracked specimen and time-history response of the highly nonlinear wall as well as to simulate the shift of the neutral axis and corresponding varying axial force in the cantilever wall. However, failing to identify the rupture of some brittle reinforcement in the third test, the model was not able to predict post-critical, near collapse behaviour during the subsequent response to two stronger earthquakes. The analysed macro model seems to be appropriate for global analyses of complex building structures with RC structural walls subjected to moderate/strong earthquakes. However, it cannot, by definition, be used in refined research analyses monitoring local behaviour in the post critical region.

United States–Japan Cooperative Earthquake Engineering Research Program on Composite and Hybrid Structures

The United States‐Japan Cooperative Earthquake Research Program began in 1979 under the auspices of the UJNR panel on wind and seismic effects. The overall objective of the program was to improve seismic safety practices in both countries through cooperative studies to determine the relationship among fullscale, small-scale, and component tests, as well as related analytical and design implication studies. The first four phases of the program were Reinforced concrete ~RC! structures, steel structures, masonry structures, and precast concrete structures. Research on composite steel RC ~SRC! structures was identified as an important area of concern and recommended in the planning group report. Considering the importance of developing seismic design guidelines and code provisions for typical composite and hybrid structures that have been used in recent practice, and the need for developing new and innovative composite structural elements and hybrid systems using advanced new materials and devices, a 5 year research program on composite and hybrid structures was recommended as the fifth phase of the United States-Japan cooperative earthquake research program. The program contents were based on a number of technical meetings of the United States and Japan planning groups and on the outcome of a joint planning group workshop held in Berkeley, Calif. on September 10‐12, 1992 ~Goel and Yamanouchi 1992!. Because of the diverse and broad scope of the subject area, the research program was organized into the following four groups: concrete-filled tube~CFT! column systems; RC/SRC column systems ~RCS!; RC/SRC hybrid-wall systems ~HWS!; and new materials, elements, and systems ~compiled by Research for Innovation!. The first two systems are moment-resisting frames made of steel beams and either CFT or RC/SRC composite columns, whereas, the HWS systems utilize RC or composite shear walls and steel-beam and column frames. The research work on those three systems aimed at developing practical design guidelines as they represent typical composite and hybrid structural systems used in recent practice. The last group aimed at developing new and innovative composite structural elements and hybrid systems using advanced new materials and devices. A theme structure provided a common focus of the overall research program to facilitate cross-comparison between various system types, and to derive structural elements and subassemblages for detailed studies. The work carried out in the four groups listed previously is briefly described in the following sections.

空間の確保と損傷の防止を目的とした既存ピロティ建築物の地震応答制御

Collapse or severe damage has been observed in many RC residential buildings with soft story at the previous earthquake disasters. Hence development of an effective structural control technology is one of the urgent tasks for residential apartments in the urban area. However, most of the conventional structural control methods for soft story buildings stuff a space with structural elements such as RC walls or response control dampers. This paper proposes a new technique for structural control of RC buildings with soft story by using ductile short columns as response control devices placed beside the existing columns at the soft story. The objective of the response control is upgrading safety as well as reparability for damage mitigation without partitioning off the spaces at the soft story. The main role of these devices are to increase story shear capacity to reduce response drift of the soft story, and to support axial force due to overturning moment in order to reduce axial force acting on the soft story columns. Results of the inelastic earthquake response analysis indicate that yielding of the soft story column can be successfully prevented since the response control devices work effectively.

에너지 소산능력을 고려한 전단벽의 내진설계

최근 능력스펙트럼법, 직접변위기초설계법 등과 같은 성능에 기초한 내진 평가/설계법이 개발되어 사용되고 있다. 이들 방법은 구조물의 비선형 주기거동에 의한 에너지 소산능력을 고려함에 있어 부정확한 경험식에 의존하는 한계를 보이고 있다. 한편, 최근 연구에서 휨지배 철근콘크리트 부재에 대하여 여러 설계변수의 영향을 고려하여 주기거동에 의한 에너지 소산능력을 정확히 평가할 수 있는 방법이 개발되었다. 본 연구에서는 에너지 소산능력을 고려한 내진설계법에 대한 기초적인 연구로서, 최근 연구에서 개발된 에너지 소산능력 산정법을 이용한 철근콘크리트 전단벽 구조의 내진설계법을 개발하여, 기존의 내진설계법과 비교하였다. 제안된 설계법에서는 단면의 크기 및 형상, 축력, 철근비, 배근형태, 연성도 등과 같은 다양한 설계변수에 따른 에너지 소산능력의 변화를 정확히 고려하여 설계할 수 있다. Recently, performance-based analysis/design methods such as the capacity spectrum method and the direct displacement-based design method were developed. In these methods, estimation of energy dissipation capacity of RC structures depends on empirical equations which are not sufficiently accurate, On the other hand, in a recent study, a simplified method for evaluating energy dissipation capacity was developed. In the present study, based on the evaluation method, a new seismic design method for flexure-dominated RC walls was developed. In determination of earthquake load, the proposed design method can address variations of energy dissipation capacity with design parameters such as dimensions and shapes of cross-sections, axial force, and reinforcement ratio and arrangement, The proposed design method was compared with the current performance-based design methods. The applicability of the proposed method was discussed.

Seismic behaviour of multistorey RC wall–frame system versus bare ductile frame system

AbstractThe wall–frame systems have many known advantages, namely increase of the system's lateral strength and stiffness thereby allowing for a good tangential inter‐storey drift control, and the retention of a satisfactory energy dissipation capacity. However, rocking of the wall could occur as a result of uplifting wall base or concentrated plastic hinge deformations. Problems arising from this phenomenon have significant impact on the system behaviour and hence require extended study. This paper focuses on the wall‐rocking phenomenon due to the concentrated plastic hinge rotation at the wall base. To facilitate a comprehensive evaluation, a six‐storey three‐bay RC wall–frame structure is investigated with comparison to a bare ductile frame by means of earthquake simulation tests. The results revealed that, despite a superior performance over the ductile frame under low to moderate seismic actions, the wall–frame structure deteriorated more rapidly than the bare frame during advanced inelastic response. The increasingly significant rocking of the wall resulted in severe material damage at localized critical regions. Mitigating the wall rocking is seen to be a key to the further improvement of the system performance, and the extent to which this may be achieved by incorporating the three‐dimensional effects is explicitly illustrated by an analytical evaluation. Copyright © 2001 John Wiley & Sons, Ltd.

Closure to “Nonlinear Finite‐Element Analysis of RC Shear Panels and Walls” by Amir Ayoub and Filip C. Filippou

Closure to “Nonlinear Finite‐Element Analysis of RC Shear Panels and Walls” by Amir Ayoub and Filip C. Filippou

Experimental shear-dominated response of RC walls. Part II: Discussion of results and design implications

A detailed discussion of the results of the tests presented in Part I (Engng Struct 2000;23(3)229–49), with special emphasis on two main issues is presented: the effect of the tests new boundary conditions, showing that some conclusions from previous tests can not be extrapolated to walls prone to beam behaviour, as is the case in multi-storey buildings; the shear resistance at the plastic hinges, leading to the identification of the corresponding mechanisms of resistance and the evaluation of the respective capacities at the ultimate limit state.

Isolated RC wall subjected to biaxial bending moment and axial force

A numerical study using nonlinear finite element analysis is performed to investigate the behavior of isolated reinforced concrete walls subjected to combined axial force and in-plane and out-of-plane bending moments. For a nonlinear finite element analysis, a computer program addressing material and geometric nonlinearities was developed. Through numerical studies, the internal force distribution in the cross-section is idealized, and then a new design method, different from the existing methods based on the plane section hypothesis was developed. According to the proposed method, variations in the interaction curve of the in-plane bending moment and axial force depends on the range of the permissible axial force per unit length, that is determined by a given amount of out-of-plane bending moment. As the out-of-plane bending moment increases, the interaction curve shrinks, indicating a decrease in the ultimate strength. The proposed method is then compared with an existing method, using the plane section hypothesis. Compared with the proposed method, the existing method overestimates the ultimate strength for the walls subjected to low out-of-plane bending moments, while it underestimates the ultimate strength for walls subject to high out-of-plane bending moments. The proposed method can address the out-of-plane local behavior of the individual wall segments that may govern the ultimate strength of the entire wall.

REPAIR AND RETROFITTING OF RC WALLS USING SELECTIVE TECHNIQUES

In the context of capacity design philosophy, where a desired failure mode exhibiting adequate levels of energy absorption capacity is envisaged, control must be exercised on the member behaviour to safeguard the achievement of the target overall response. Therefore, local repair and retrofitting methods that result in unquantifiable effects on seismic response characteristics should be re-assessed. In contrast, techniques to affect, in a controlled and easy-to-monitor fashion, individual design response parameters, i.e. stiffness, strength and ductility, may provide a new framework for repair and retrofitting earthquake-damaged structures to mirror ‘capacity design’ principles used for new structures. Such an approach is discussed in this paper and possible scenarios where selective intervention may be required are identified. A number of tests on RC walls are also reviewed to confirm the feasibility of the proposed intervention techniques. Finally, extensive parametric studies are carried out, using verified analytical models, leading to the derivation of selective re-design expressions and guidelines.