Effect of Infilled Walls On The Performance of Steel Frame Structures

Today, the subject of a building's resistance to lateral loads is one of the most important concerns of structural engineers. The partitions and infilled walls are non-structural elements that are important due to their effects on the lateral resistance of the building frame. Recently, it has been observed that great damage is occurring to infilled walls, partitions, and buildings in an earthquake-prone area. Infilled walls are effective at increasing the hardness and resistance of building frames, which changes the seismic properties of structures. Therefore, the study of interactions between the structural frame and the infilled walls is essential for a better understanding of structural behaviors. In this paper, the effect of infilled walls is investigated on the behaviour of steel frames using ABAQUS software. Modeling is carried out for different types of infilled materials, including brick and panel, as well as different thicknesses of the infills. It was observed that with an increase in the thickness of infills from 7 to 20 cm, the final capacity and energy absorption increased by 78%. Also, the panel-infilled frames have 18% more capacity and 3.8% more energy absorption than the brick-infilled frame in the same full state. As a result, panel-infilled frames outperform brick-infilled frames in terms of performance.&nbsp

Effect of Infilled Walls On The Performance of Steel Frame Structures

Today, the subject of a building's resistance to lateral loads is one of the most important concerns of structural engineers. The partitions and infilled walls are non-structural elements that are important due to their effects on the lateral resistance of the building frame. Recently, it has been observed that great damage is occurring to infilled walls, partitions, and buildings in an earthquake-prone area. Infilled walls are effective at increasing the hardness and resistance of building frames, which changes the seismic properties of structures. Therefore, the study of interactions between the structural frame and the infilled walls is essential for a better understanding of structural behaviors. In this paper, the effect of infilled walls is investigated on the behaviour of steel frames using ABAQUS software. Modeling is carried out for different types of infilled materials, including brick and panel, as well as different thicknesses of the infills. It was observed that with an increase in the thickness of infills from 7 to 20 cm, the final capacity and energy absorption increased by 78%. Also, the panel-infilled frames have 18% more capacity and 3.8% more energy absorption than the brick-infilled frame in the same full state. As a result, panel-infilled frames outperform brick-infilled frames in terms of performance.&nbsp

STR-913: NON-LINEAR FINITE ELEMENT ANALYSIS OF MODIFIED INFILLED STEEL AND CONCRETE FRAME SYSTEMS

To enhance the resiliency of framed structures under lateral loads, new infilled frame systems have been developed and evaluated using finite element method. The developed frame systems include haunches to reduce stress concentration at the frame’s corners under lateral in-plane loads thus improving the resistance of the infilled frame system. A previously developed and validated three dimensional finite element models based on the simplified micro-modelling technique were adopted in this study to investigate the behaviour of infilled steel and reinforced concrete frames under lateral in-plane loads. The investigated parameters include: the infill wall stiffness, the presence and size of haunches at the beam-column connections. The effect of infill wall stiffness was investigated by analysis of steel and concrete frames infilled with grouted infill walls, which were found to significantly improve the lateral strength and stiffness of the infilled frames. The effect of the size of the haunches on the lateral behaviour of infilled frames was investigated by adding 200 mm, 400 mm, and 600 mm equal-leg haunches at the frame’s beam-column connections. The lateral load resistance of infilled steel and reinforced concrete frames was found to increase by about 60% and 20%, respectively, when 600 mm equal-leg haunches were introduced. The Canadian standard for the design of masonry structures gave conservative estimates for the lateral cracking strength of the studied infilled frames. The accuracy of this standard was found to depend on the lateral stiffness of the bounding frames and the stiffness of the infill wall

Numerical Study of the Force Transfer Mechanism and Seismic Behavior of Masonry Infilled RC Frames with Windows Opening

Masonry infilled walls are widely used in reinforced concrete (RC) frams worldwide. However, infilled RC frame building failure is a common mode in destructive earthquakes. Further researcher is needed to bring insightful understandings into the behaviors of these structures. Therefore, this study investigates seismic parameters, ultimate tensile damage, and force transfer mechanisms in a reinforced concrete structure under in-plan load.  For this purpose, the definitions and the relevant literature were reviewed. Then, an analytical software supporting an infill model was selected and described altogether with a particular modeling approach. Calibrating software results with those presented by Abdulhafez et al. (2014), the researchers designed a series of planer one-story one-bay reinforced concrete frames upon ACI 318M-14 Building Code. The seismic behavior of infilled frames were also studied using finite element method. Force transfer mechanisms in infilled frame with opening, which is one of the important items, was investigated in this study. Comparing the analysis outcomes with the bar frame, it was indicated that the ultimate load, stiffness, and toughness of the full in-filled frame were increased while the ductility was decreased. It was also revealed that the presence of opening in infilled frame decreased the ultimate load, stiffness and toughness corresponding full infilled frame. In addition, the increasing of opening size increased the reduction of the ultimate load, stiffness and toughness

Seismic Performance and Reliability Evaluation of Ductile RC Frame Structures with Infills

Ductile RC frames are often considered to have superior seismic performance even with infills. However, the seismic performance of this type of structure needs to be reassessed considering the additional shear requirements produced by the infills-column interaction and the increased seismic hazard due to the impact of infills on the vibration period of the structure. This paper presents a performance-based earthquake engineering framework aimed at the assessment of the comprehensive seismic performance of ductile RC frames with infills. A series of common configurations are considered in the analysis: bare frame (BF), upper-infilled frame (UIF), all-infilled frame (AIF), and corresponding stirrup-reduction frames with both infills-induced shear failure behavior of column and influence of structural vibration period considered. The results show that infills changed the failure modes and dynamic characteristics of ductile structures and shear failure occurs in all-infilled frame columns. Even though the all-infilled frame meets the shear requirement, its collapse probability is higher than the bare frame due to the high seismic hazard caused by a shorter vibration period

Lateral behavior of steel frames with discretely connected precast concrete infill panels

As an alternative to the conventional structures for tall buildings, a hybrid lateral load resisting structure has been designed at Eindhoven University of Technology. It consists of discretely connected precast concrete panels with window openings in steel frames, and is a new application in infilled frames. Besides the structural advantages of hybrid construction, this structure offers an alternative construction method, improving the constructability of tall buildings. This will result in more economical and high quality buildings. The infilled frame is a type of structure that has proven to be effective and efficient in bracing low-rise and medium-rise buildings to resist in-plane lateral loads. It acts by composite action between the infill and its surrounding frame. Structural interaction between the two components produces a composite structure with a complicated behavior due to the fact that the frame and the infill mutually affect each other. Since the early fifties extensive research has been done into the composite behavior of infilled frames with masonry and cast-in-place concrete infills without openings. However, the application of discretely connected concrete panels with openings as bracing elements in steel frame structures has not been performed yet and represents a new area of research in infilled frames. The main objective of this investigation is to develop practical universally applicable design models for infilled steel frames with discretely connected precast concrete panels, allowing for an accurate prediction of the strength, stiffness and deformation capacity of this type of structure. In order to develop these design models, the structure has been subjected to experimental, numerical and analytical investigation. First, full-scale tests on single-storey, single-bay infilled frame structures were carried out. Objectives of this experimental study were to observe the general behavior of the infilled frame in terms of stiffness, strength and failure modes. In addition, experiments were performed on components of the discrete panel-to-frame connection. Subsequently, finite element models were developed and validated by simulating the experiments. For this purpose, finite element analyses taking non-linear material and structural behavior into account were performed. It has been shown that the finite element model developed for the overall infilled frame behavior can be used to predict the lateral load versus deflection relationship and the ultimate lateral load with good accuracy. Accordingly, the validated finite element model has been used to carry out a parameter study to investigate various configurations of the infilled frame. Four parameters have been studied with respect to their influence on the structural response. These parameters are the frame member dimensions, the rotational stiffness of the frame joints, the infilled frame aspect ratio and the panel opening geometry. From the simulated load-deformation curves, structural characteristics have been derived. These have served as a verification for the developed analytical models for the prediction of the lateral stiffness, the ultimate lateral load and deformation capacity of the structure under consideration. The analytical models are based on the concept of the equivalent diagonal strut, considering the structure as an equivalent braced frame system with a compression diagonal replacing the infill. Finally, a practical method for designing steel frames with discretely connected precast concrete infill panels has been proposed. The aim of this method is to get a good prediction of the internal forces and the lateral deflection in the preliminary phase of the design, without the use of advanced computer simulations. The design method provides a useful guideline that a design engineer can follow, in order to design building structures consisting of steel frames with discretely connected precast concrete infill panels, resulting in a ductile structure, possessing both adequate strength and stiffness

Lateral behavior of steel frames with discretely connected precast concrete infill panels

As an alternative to the conventional structures for tall buildings, a hybrid lateral load resisting structure has been designed at Eindhoven University of Technology. It consists of discretely connected precast concrete panels with window openings in steel frames, and is a new application in infilled frames. Besides the structural advantages of hybrid construction, this structure offers an alternative construction method, improving the constructability of tall buildings. This will result in more economical and high quality buildings. The infilled frame is a type of structure that has proven to be effective and efficient in bracing low-rise and medium-rise buildings to resist in-plane lateral loads. It acts by composite action between the infill and its surrounding frame. Structural interaction between the two components produces a composite structure with a complicated behavior due to the fact that the frame and the infill mutually affect each other. Since the early fifties extensive research has been done into the composite behavior of infilled frames with masonry and cast-in-place concrete infills without openings. However, the application of discretely connected concrete panels with openings as bracing elements in steel frame structures has not been performed yet and represents a new area of research in infilled frames. The main objective of this investigation is to develop practical universally applicable design models for infilled steel frames with discretely connected precast concrete panels, allowing for an accurate prediction of the strength, stiffness and deformation capacity of this type of structure. In order to develop these design models, the structure has been subjected to experimental, numerical and analytical investigation. First, full-scale tests on single-storey, single-bay infilled frame structures were carried out. Objectives of this experimental study were to observe the general behavior of the infilled frame in terms of stiffness, strength and failure modes. In addition, experiments were performed on components of the discrete panel-to-frame connection. Subsequently, finite element models were developed and validated by simulating the experiments. For this purpose, finite element analyses taking non-linear material and structural behavior into account were performed. It has been shown that the finite element model developed for the overall infilled frame behavior can be used to predict the lateral load versus deflection relationship and the ultimate lateral load with good accuracy. Accordingly, the validated finite element model has been used to carry out a parameter study to investigate various configurations of the infilled frame. Four parameters have been studied with respect to their influence on the structural response. These parameters are the frame member dimensions, the rotational stiffness of the frame joints, the infilled frame aspect ratio and the panel opening geometry. From the simulated load-deformation curves, structural characteristics have been derived. These have served as a verification for the developed analytical models for the prediction of the lateral stiffness, the ultimate lateral load and deformation capacity of the structure under consideration. The analytical models are based on the concept of the equivalent diagonal strut, considering the structure as an equivalent braced frame system with a compression diagonal replacing the infill. Finally, a practical method for designing steel frames with discretely connected precast concrete infill panels has been proposed. The aim of this method is to get a good prediction of the internal forces and the lateral deflection in the preliminary phase of the design, without the use of advanced computer simulations. The design method provides a useful guideline that a design engineer can follow, in order to design building structures consisting of steel frames with discretely connected precast concrete infill panels, resulting in a ductile structure, possessing both adequate strength and stiffness

Experimental assessment and retrofit of full-scale models of existing RC frames

PSD tests on two full-scale models of existing non-seismic resisting RC frame structures are described. The testing program covered several aspects, namely assessment of seismic performance of existing frames without and with infill panels, retrofitting of the bare frame using Selective Retrofitting techniques, strengthening of the infill panels using shotcrete and retrofitting of the frame using K-bracing with shear-link dissipators. The main results from the tests are summarized and discussed and the conclusions are drawn. The tests on the bare frame have shown how vulnerable are existing structures constructed in the 60’s and the beneficial effects of infill panels were confirmed from the tests on the infilled frame. Important improvements, in terms of seismic performance, were achieved by the retrofitting of the frames. However, it was also confirmed that strengthening of the existing infill panels in poorly detailed frames may lead to dangerous ‘local’ failures, such as the shear out of the external columns

Effect of Masonry Infill Panels on the Seismic Response of Reinforced Concrete Frame Structures

The present work concerns the numerical investigation of reinforced concrete frame buildings containing masonry infill panel under seismic loading that are widely used even in high seismicity areas. In seismic zones, these frames with masonry infill panels are generally considered as higher earthquake risk buildings. As a result there is a growing need to evaluate their level of seismic performance. The numerical modelling of infilled frames structures is a complex task, as they exhibit highly nonlinear inelastic behaviour, due to the interaction of the masonry infill panel and the surrounding frame. The available modelling approaches for masonry infill can be grouped into two principal types; Micro models and Macro models. A two dimensional model of the structure is used to carry out non-linear static analysis. Beams and columns are modelled as non-linear with lumped plasticity where the hinges are concentrated at both ends of the beams and the columns. This study is based on structures with design and detailing characteristics typical of Algerian construction model. In this regard, a non-linear pushover analysis has been conducted on three considered structures, of two, four and eight stories. Each structure is analysed as a bare frame and with two different infill configurations (totally infilled, and partially infilled). The main results that can be obtained from a pushover analysis are the capacity curves and the distribution of plastic hinges in structures. The addition of infill walls results in an increase in both the rigidity and strength of the structures. The results indicate that the presence of non-structural masonry infills can significantly modify the seismic response of reinforced concrete "frames". The initial rigidity and strength of the fully filled frame are considerably improved and the patterns of the hinges are influenced by structural elements type depending on the dynamic characteristics of the structures. Doi: 10.28991/cej-2021-03091764 Full Text: PD