Infilled Frame Structures Research Articles

Seismic behaviour of infilled and pilotis RC frame structures with beam–column joint degradation effect

The influence of the exterior joints capacity deterioration on the local and global failure mechanisms of reinforced concrete structures with infills is investigated. Exterior beam–column joints with reduced capacity is the common case for the majority of RC structures designed according to older design standards. Nevertheless in common practise the response of these regions is typically assumed as rigid. A key parameter of this investigation is the inclusion of the joints strength and stiffness degradation in the study of the seismic performance of the structures. In this direction, a special-purpose rotational spring element that incorporates a special behaviour model is employed for the simulation of the exterior joints’ local response. The spring element has been incorporated in a well-established general program for nonlinear static and dynamic analysis. The effectiveness of the used joint element model has been demonstrated in a previous paper through comparisons with experimental data reported in literature. In this paper an attempt is presented for the investigation of the influence of the exterior joint damage on the seismic behaviour of bare and infilled RC frame structures. Two types of masonry infilled structures are considered: (a) infilled frame and (b) infilled frame without infills at the base storey (pilotis frame). A parametrical study of the overall seismic response using push over analyses and step-by-step analyses is performed. Results in terms of interstorey drifts, base shear, failure mode, ductility requirements and joints rotational requirements demonstrate that neglecting the possible local damage of the exterior joints may lead to erroneous conclusions and unsafe design or seismic behaviour evaluation that subsequently may become critical in some cases. Furthermore the influence of exterior joints degradation has been proven of vital importance for the overall behaviour of pilotis frames.

Effection of Relevant Parameters of Infilled Frame Wall on its Structural Lateral Stiffness

Statical analysis of infilled frame structure was conducted on 3D finite element models by means of software ANSYS10.0. Analyses on relevant parameters of infilled frame walls with or without openings have been carried out seperately, and it is found that the relevant stiffness of the model gradually increases with the ratio of the wall’s width to its height. However, the effection of the width to height ratio of the wall on its structural lateral stiffness becomes much smaller when the value of the width to height ratio is larger than 1.5. The effection can be basically ignored when the width to height ratio is larger than 1.8. It is investigated that the ratio of posts inertia moment to beams has great influence on model’s relevant stiffness. The relevant stiffness of frame structure decreases with the growth of the ratio of posts inertia moment to beams (I2/I1). For a long time, Filling Wall is widely used in multi-storey buildings and Civil Construction Structures, for its flexible architecture flats and large interior space, etc. However, because of the imperfection in analysis methods and the defects in model, pure- framework design is used in civil architectures, and the weight of filling wall is calculated by converting to the Line Load on the beam. According to the analysis of 5.12 Wenchuan earthquake[1], the early filling wall absorbs a large earthquake because of its stiffness, while its Adhesive Tensile Strength is low, which making the earthquake-damage to the filling wall is more serious than that to the frame structure. By analyzing the parameters in non-opening and opening filling wall and changing a given parameter, while keeping other parameters unchanged. This paper studies the influence on the Lateral Stiffness of Frame Structure, to provide Earthquake Fortifying Areas with reference data in the design process of filling wall.

Experimental and numerical investigations into the composite behaviour of steel frames and precast concrete infill panels with window openings

As an alternative for conventional structures for tall buildings, a hybrid lateral load resisting structure has been designed, enabling the assembly of tall buildings directly from a truck. It consists of steel frames with discretely connected precast concrete infill panels provided with window openings. Besides the stiffening and strengthening effect of the infill panels on the frame structure, economical benefits may be derived from saving costs on materials and labour, and from reducing construction time. In order to develop design rules for this type of structure, the hybrid infilled frame has recently been subjected to experimental and numerical analyses. Ten full-scale tests were performed on one-storey, one-bay, 3 by 3 m infilled frame structures, having different window opening geometries. Subsequently, the response of the full-scale experiments was simulated with the finite element program DIANA. The finite element simulations were performed taking into account non-linear material characteristics and geometrical non-linearity. The experiments show that discretely connected precast concrete panels provided with a window opening, can significantly improve the performance of steel frames. A comparison between the full-scale experiments and simulations shows that the finite element models enable simulating the elastic and plastic behaviour of the hybrid infilled frame.

Modelling and Analysis of Infilled Frame Structures Under Seismic Loads

In-filled frame structures are commonly used in buildings, even in those located in seismically active regions. Precent codes unfortunately, do not have adequate guidance for treating the modelling, analysis and design of in-filled frame structures. This paper addresses this need and first develops an appropriate technique for modelling the infill-frame interface and then uses it to study the seismic response of in-filled frame structures. Finite element time history analyses under different seismic records have been carried out and the influence of infill strength, openings and soft-storey phe- nomenon are investigated. Results in terms of tip deflection, fundamental period, inter-storey drift ratio and stresses are presented and they will be useful in the seismic design of in-filled frame structures. interface condition, friction coefficient, size of the mesh, relative stiffness of beam to column, relative size of infill wall have significant influence on the response of infilled frame, while the effect of orthotropy of infill material was insignificant. When the mesh density was made finer the stress pattern within the infill also improved, with maximum values of stresses at the compressive corners. The existence of friction coefficient at the interface was reported to in- crease the lateral stiffness of the system. However, friction coefficient is dependent on the quality of material and the workmanship CEB 1996 (6) which is difficult to define ac- curately, hence codes do not provide any guidance.

The Analysis of Non-Linear Seismic Response of an Infilled Frame Structure in Yingxiu Town – The Heavy Disaster Areas of Wenchuan 8.0 Earthquake

On 12 May 2008, a magnitude 8.0 earthquake happened in Wenchuan, China .It was the most serious earthquake in china since 1949, causing very huge casualties and engineering damages. The complex building of the Xuankou secondary school in Yingxiu town was designed by the Code for Seismic Design of Buildings of China (GB50011-2001), the seismic fortification intensity of the buildings was 7 degree. In the earthquake, it was destroyed most seriously, and the engineering damage was characteristic. In the paper, the property of material nonlinearity was considered ,the nonlinear analysis model of infilled frame structure was established, the time history analysis and nonlinear static analysis were used during inelastic stage, the main cause of structural destruction was obtained, the influence of the infill wall on the structure was discussed.Therefore ,the results can provide valuable reference for the seismic design of infilled frame structure.

Modelling and Analysis of Infilled Frame Structures Under Seismic Loads

In-filled frame structures are commonly used in buildings, even in those located in seismically active regions. Precent codes unfortunately, do not have adequate guidance for treating the modelling, analysis and design of in-filled frame structures. This paper addresses this need and first develops an appropriate technique for modelling the infill-frame interface and then uses it to study the seismic response of in-filled frame structures. Finite element time history analyses under different seismic records have been carried out and the influence of infill strength, opening and soft-storey phenomenon are investigated. Results in terms of tip deflection, fundamental period, inter-storey drift ratio and stresses are presented and they will be useful in the seismic design of in-filled frame structures.

Analytical Prediction of the Seismic Performance of Masonry Infilled Reinforced Concrete Frames Subjected to Near-Field Earthquakes

In the recent past, a number of ground motions with large velocity pulses have been recorded in the near-field regions of earthquakes. A ground motion recorded in the near-field region of a strike-slip earthquake (i.e., near the fault rupture of the earthquake) exhibits distinctive long-period velocity pulses that are characteristic of near-field earthquakes and are not found in far-field ground motion records. The present study is based on analytical evaluation of the effect of distribution of masonry infill panels over the elevation of planar masonry-infilled RC frames on the seismic response of the frame subjected to near-field earthquakes implementing rational seismic analysis methods within the performance-based framework such as nonlinear dynamic time-history analysis and nonlinear static force-displacement (push-over) analysis using realistic and efficient computational models. Despite intense worldwide research in the area of masonry infilled frame structures during the past few decades, displacement-based nonlinear analyses of masonry infilled frames with explicit consideration of infill panels as structural elements is far from common practice, mostly due to the analytical complexity in modeling the infill panel realistically. The displacements are of particular interest from the viewpoint of performance-based design (PBD), the emerging model for the next generation of standard codes of practice for earthquake-resistant design. One of the objectives of the study is to demonstrate rational displacement-based analysis methodologies within the performance-based framework for accurately and efficiently predicting the global and local seismic demands and related intensity of seismic damage in practical masonry infilled multistory RC framed construction with seismically undesirable vertical layouts of masonry panels under the influence of near-field earthquakes.

Proposed macro-model for the analysis of infilled frame structures

Reinforced concrete frames infilled with masonry panels constitute an important part of the high-risk structures in different regions of high seismicity. In some developing countries, they are still used as main structural system for low to medium rise buildings. Consequently, reliable methods to analyse infilled frames are required in order to reduce the loss of life and property associated with a possible structural failure.
 The equivalent strut model, proposed in the 1960s, is a simple procedure to represent the effect of the masonry panel. Several improvements of the original model have been proposed, as a result of a better understanding of the behaviour of these structures and the development of computer software. This paper presents a new macro-model for the evaluation of the global response of the structure, which is based on a multi-strut formulation,. The model, implemented as 4-node panel element, accounts separately for the compressive and shear behaviour of masonry using a double truss mechanism and a shear spring in each direction. The principal premises in the development of the model are the rational consideration of the particular characteristics of masonry and the adequate representation of the hysteretic response. Furthermore, the model is able to represent different modes of failure in shear observed for masonry infills. The comparison of analytical results with experimental data showed that the proposed model, with a proper calibration, is able to represent adequately the in-plane response of infilled frames.

Mathematical modelling of an infilled RC frame structure based on the results of pseudo‐dynamic tests

AbstractIn this paper, a technique is presented which employs the results of pseudo‐dynamic tests for the development of a mathematical model. This technique, described by means of the mathematical modelling of a three‐storey reinforced concrete frame building with infill in the bottom two storeys, which was tested at ELSA in Ispra, proved to be effective and to lead to a fairly accurate structural model. The results of analyses suggest that the global non‐linear seismic response of reinforced concrete frames with masonry infill can be adequately simulated by a relatively simple mathematical model, which combines beam elements with concentrated plasticity, simple connection elements, and equivalent strut elements representing the infill walls (provided that the infill does not fail out of plane and that no shear sliding failure occurs). Copyright © 2002 John Wiley & Sons, Ltd.

Analytical modelling of infilled frame structures

The analytical modelling of infilled frames is a complex issue because these structures exhibit a highly non- linear inelastic behaviour resulting from the interaction of the masonry infill panel and the surrounding frame. This paper presents a general review of the different procedures used for the analysis of infilled frames, which can be grouped in local or micro-models and simplified or macro-models, depending on the degree of refinement used to represent the structure. The finite element formulation and the equivalent truss mechanism are the typical examples of each group. The advantages and disadvantages of each procedure are pointed out, and practical recommendations for the implementation of the different models are indicated.

Application of the local-to-global approach to the study of infilled frame structures under seismic loading

The seismic performance of civil engineering structures may be estimated by using two levels of modelling. At the local level, each constituent has its own constitutive law and geometric finite element support. The main phenomena such as the cracking and the crushing of concrete and masonry could be reproduced by using the continuous damage or plasticity theories. However the cost of the computations does not allow extensive or dynamic studies and thus the global level — where the constitutive laws based on empirical rules reproduce the behaviour of the structural elements — represents the unique strategy for the analysis of complete civil engineering structures under seismic loading. The present paper aims at presenting the application of these two modelling levels in order to assess the seismic performance of masonry infilled R/C frame structures. The one-bay masonry infilled frames tested at Lisbon under cyclic loading and the four-storey building tested at ELSA have been used for the validation of the modelling approach.

SHAKE-TABLE TESTS OF LARGE-SCALE SHEAR WALL AND INFILLED FRAME MODELS.

In order to evaluate and compare the seismic performance of different types of wall construction, three 1/3 scale four-storey models of structural walls were tested dynamically to ultimate failure by subjecting each of them to a sequence of simulated earthquakes of progressively increasing magnitude on a 5m x 5m shaking table. The three models tested are respectively : a reinforced concrete shear wall structure ; a masonry infilled reinforced-concrete frame structure ; and a concrete infilled frame structure.

Earthquake Resistance of Infilled Frames

The experimental phase consists of quasistatic cyclic load tests on one-third scale model subassemblages of the lower three stories of an 11-story, three-bay frame with infills in the two outer bays: (1)Frame members (particularly the columns) are designed for high rotational ductility and resistance to degradation under reversed cyclic shear loads; (2)gradual panel degradation is achieved using closely spaced infill reinforcement; and (3)panel thickness is limited so that the infill cracking load is less than the available column shear resistance. The analytical phase consists of developing relatively simple, macroscopic mathematical models for predicting the experimentally observed bare and infilled frame behavior. The infilled frame model is found to give excellent predictions of observed response. It is concluded that the model developed and the procedure used can be applied to the analytical prediction of the response of large, engineered infilled frame structures to severe lateral forces.