Masonry infilled walls have been commonly used as interior partitions as well as exterior walls infilled in either steel or reinforced concrete frames in the modern building constructions. In recent years, much research involving both experimentation and numerical modeling has been conducted in an effort to better understand the infill-frame interaction and to provide some rational design approaches. Studies have shown that infill walls can develop a number of possible failure mechanisms, depending on the strength and stiffness of the bounding frames with respect to those of the infills and the geometric configuration of the framing system. Most of models proposed for analysis of infill walls focused on one type of mechanism or the other, and they were not universally applicable to all infilled structures.

Το θέμα της παρούσας εργασίας αφορά την αποτίμηση της απόκρισης των τοιχοπληρωμένων πλαισίων οπλισμένου σκυροδέματος, έναν τομέα που έχει απασχολήσει πληθώρα ερευνητών τις τελευταίες δεκαετίες. Παρότι έχουν προταθεί πολλές διαφορετικές λύσεις για την προσομοίωση των τοιχοπληρώσεων, δεν έχει ακόμη προκύψει ένα ενιαίο και αξιόπιστο προσομοίωμα ικανό να αναπαραστήσει με ακρίβεια τα διαφορετικά χαρακτηριστικά της απόκρισης που εμφανίζονται κατά περίπτωση. Στην παρούσα εργασία προτείνεται ένα νέο απλοποιητικό προσομοίωμα για την ανάλυση των τοιχοπληρώσεων μετά την τροποποίηση του υπάρχοντος προσομοιώματος των Crisafulli and Carr (2007) και διερευνάται η εφαρμογή και η κατάλληλη βαθμονόμηση του για την ανελαστική ανάλυση τοιχοπληρωμένων πλαισίων οπλισμένου σκυροδέματος υπό την δράση πλευρικών ανακυκλιζόμενων φορτίων. Στο προτεινόμενο προσομοίωμα συνδυάζονται μία σειρά από μέλη/ελατήρια προκειμένου να ληφθούν υπόψη ανεξάρτητα η συμπεριφορά της τοιχοπλήρωσης σε διαγώνια θλίψη και διάτμηση. Η αξιοπιστία του προσομοιώματος επαληθεύεται με διαθέσιμα πειραματικά δεδομένα σε τοιχοπληρωμένα πλαίσια, επιδεικνύοντας ικανοποιητικό βαθμό συμφωνίας. Η πολυπλοκότητα των προσομοιωμάτων των τοιχοπληρώσεων έγκειται στην πληθώρα των παραμέτρων που απαιτούνται για τον ορισμό τους. Για το λόγο αυτό η αριθμητική εφαρμογή του προσομοιώματος συνοδεύεται από μία εκτεταμένη παραμετρική μελέτη που στοχεύει στην διερεύνηση της ευαισθησίας του προσομοιώματος σε κάθε μία από τις παραμέτρους που υπεισέρχονται στον ορισμό του επιτρέποντας εν τέλει την ταυτοποίηση των κρίσιμων ποσοτήτων και την καθοδήγηση του μέλλοντα χρήστη σχετικά με την επιλογή τους. / The assessment of the response of masonry infilled RC frame structures has been a major challenge over the last decades. While several modeling approaches have been proposed, none can cover all aspects observed in the tests. The present paper introduces a simplified model built on the approach established by Crisafulli and Carr (2007) and addresses its calibration and implementation in a nonlinear analysis software for the evaluation of the in-plane lateral response of infilled RC frames. The proposed model uses a set of elements/springs to account separately for the compressive and shear behavior of masonry. The efficiency of the modeling approach is validated with available experimental data, yielding satisfactory matching. The most intricate issue encountered when attempting to represent a masonry panel is the plethora of the material parameters involved and the lack of complete and available test results. Thus, the numerical investigation is accompanied by a parametric study on the sensitivity of the model to the various parameters to identify the critical modeling quantities and provide guidance on their selection.

In this dissertation, the seismic behavior and design of AAC-infilled steel moment frames are investigated systematically. The fundamental vehicle for this investigation is the ATC-63 methodology, which is intended for the establishment of seismic design factors for structural systems. The ATC-63 methodology is briefly reviewed, including the concepts of archetypical structures, design rules and mathematical models simulating the behavior of those archetypes. A limited experimental investigation on the hysteretic behavior of an AAC-infilled steel moment frame is developed, conducted, and discussed. Using the experimental results of that investigation, the draft infill design provisions of the Masonry Standards Joint Committee (MSJC) are extended to AAC infills, and a mathematical model is developed and calibrated to simulate the behavior of AAC infills under reversed cyclic loads. Prior to application of ATC-63 methodology to AAC-infilled steel moment frames, the methodology is applied to an example steel moment frame to demonstrate the methodology and verify understanding of it. Then, archetypical infilled frames to be evaluated by the ATC-63 methodology are developed using a series of pushover analyses. Infill configurations whose total lateral strength in a particular story exceeds about 35% of the lateral strength of the bare frame in that story are observed to provoke story mechanisms in the frame. Based on this observation, archetypical infilled frames are selected conforming to two infill configurations: uniformly infilled frames, and open ground story frames. Each infill configuration includes archetypes whose ratio of infill strength to bare-frame strength at each story is less than 35%, and archetypes whose ratio is greater than 35%. The former archetype is typical of steel moment frames infilled with AAC; the latter archetype is typical of steel moment frames infilled with conventional (clay or concrete) masonry. The ATC-63 methodology, specialized for application to infilled frames, is applied to the archetypical infilled frames developed above. The performance of those archetypical infilled frames is evaluated, and seismic design factors are proposed for AAC-infilled steel moment frames. The extension of this work to other types of infilled frames is discussed. / text

Reinforced concrete frames, infilled with brick/concrete block masonry, are the most common type of structures found in multi-storeyed constructions, especially in developing countries. Usually, the infill walls are considered as non-structural elements even though they alter the lateral stiffness and strength of the frame significantly. Approximately 80% of the structural cost from earthquakes is attributable to damage of infill walls and to consequent damages of doors, windows and other installations. Despite the broad application and economical significance, the infill walls are not included in the analysis because of the design complexity and lack of suitable theory. But in seismic areas, ignoring the infill-frame interaction is not safe because the change in the stiffness and the consequent change in seismic demand of the composite structural system is not negligible. The relevant experimental findings shows a considerable reduction in the response of infilled frames under reverse cyclic loading. This behaviour is caused by the rapid degradation of stiffness, strength, and low energy dissipation capacity resulting from the brittle and sudden damage of the unreinforced masonry infill walls. Though various national/international codes of practice have incorporated some of the research outcomes as design guidelines, there is a need and scope for further refinement. In the initial part of this work, a numerical modelling and linear elastic analysis of masonry infilled RC frames has been done. A multi-storey multi-bay frame infilled with masonry panels, is considered for the study. Both macro modelling and micro modelling strategies are adopted. Seismic loading is considered and an equivalent static analysis as suggested in IS 1893, 2002 is done. The results show that the stiffness of the composite structure is increased due to the obvious confinement effects of infill panels on the bounding frame. A parametric study is conducted to investigate the influence of size and location of openings, presence/absence of infill panels in a particular storey and elevation irregularity in terms of floor height. The results show that the interaction of infill panel changes the seismic response of the composite structure significantly. Presence of openings further changes the seismic behaviour. Increase in openings increases the natural period and introduce newer failure mechanisms. Absence of infill in a particular storey (an elevation irregularity) makes it drift more compared to adjacent storeys. Since the structural irregularities influence the seismic behaviour of a building considerably, we should be cautious while construction and renovation of such buildings in order to take the advantage of increased strength and stiffness obtained by the presence of infill walls. A nonlinear dynamic analysis of masonry infilled RC frames is presented next. Material non linearity is considered for the finite element modelling of both masonry and concrete. Concrete damage plasticity model is employed to capture the degradation in stiffness under reverse cyclic loading. A parametric study by varying the same parameters as considered in the linear analysis is conducted. It is seen that the fundamental period calculation of infilled frames by conventional empirical formulae needs to be revisited for a better understanding of the real seismic behaviour of the infilled frames. Enhancement in the lateral stiffness due to the presence of infill panel attracts larger force and causes damage to the composite system during seismic loading. Elevation irregularities included absence of infill panels in a particular storey. Soft storey shows a tendency for the adjacent columns to fail in shear, due to the large drift compared to other storeys. The interstorey drift ratios of soft storeys are found to be larger than the limiting values. However this model could not capture the separation at the interfaces and related failure mechanisms. To improve the nonlinear model, a contact surface at the interface is considered for a qualitative analysis. A one bay one storey infilled frame is selected. The material characteristics were kept the same as those used in the nonlinear model. Contact surface at the interface was given hard contact property with pressure-overclosure relations and suitable values of friction at the interface. This model could simulate the compressive diagonal strut formation and the switching of this compressive strut to the opposite diagonal under reverse cyclic loading. It showed an indication of corner crushing and diagonal cracking failure modes. The frame with central opening showed stress accumulation near the corners of opening. Next, the micro modelling strategy for masonry suggested by Lourenco is studied. This interface element can be used at the masonry panel-concrete frame interface as well as at the expanded masonry block to block interface. Cap plasticity model (modified Drucker – Prager model for geological materials) can be used to describe the behaviour of masonry (in terms of interface cracking, slipping, shearing) under earthquake loading. The blocks can be defined as elastic material with a potential crack at the centre. However, further experimental investigation is needed to calibrate this model. It is required to make use of the beneficial effects and improve upon the ill-effects of the presence of infills. To conclude, infill panels are inevitable for functional aspects such as division of space and envelope for the building. Using the lateral stiffness, strength contribution and energy dissipation capacity, use of infill panels is proposed to be a wiser solution for reducing the seismic vulnerability of multi-storey buildings.

An experimental program was conducted to investigate some aspects of in-plane behaviour of masonry infilled steel frames. Eight concrete masonry infilled steel frames, consisting of three fully grouted and five partially grouted infills, were tested under combined lateral and axial loading. All specimens were constructed using one-third scale concrete masonry units. The in-plane lateral load was gradually increased at the frame top beam level until the failure of the specimen while an axial load was applied to the top beam and held constant. The parameters of the study included axial load, extent of grouting, opening, and aspect ratio of the infill. The experimental results were used, along with other test results from the literature, to evaluate the efficacy of stiffness and strength predictions by some theoretical methods with a focus on Canadian and American design codes. Cracking pattern, stiffness, failure mode, crack strength, and ultimate strength of the specimens were monitored and reported. Presence of axial load was found to increase the ultimate strength of the infilled frame but had no marked effect on its stiffness. Two specimens exhibited “splitting failure” due to axial load. Partially grouted specimens developed extensive diagonal cracking prior to failure whereas fully grouted specimens showed little or no cracking prior to failure. An increase in grouting increased the ultimate strength of the frame system but reduced its ductility. Presence of opening reduced the ultimate strength of the infilled frame and increased its ductility but its effect on the stiffness of the frame system was not significant. A review of current Canadian and American design codes showed that the Canadian code significantly overestimates the stiffness of infilled frames whereas the American code provides improved predictions for stiffness of these frame systems. Both design codes underestimate the strength of masonry infilled steel frames but grossly overestimate the strength of masonry infilled RC frames. / Masonry infilled steel frames tested under combined axial and lateral loading. Behaviour as affected by axial load, grouting, aspect ratio and openings discussed. Correlation between axial load level and the infill lateral resistance examined. Efficacy of the Canadian and American masonry standards on infill design was examined.

A non-linear finite element program to simulate the behaviour of infilled frames and plane stress reinforced concrete members under the action of monotonic and cyclic loading has been developed. Steel is modelled as a strain hardening plastic material, and in the concrete model cracking, yielding and crushing are considered. The separation, sliding, and opening and closing of initial gaps at the interfaces between the frame and the infill panels are accounted for by adjusting the properties of interface elements. The non-linear equations of equilibrium are solved using an incremental-iterative technique performed under load or displacement control. The iterative techniques use the standard and modified Newton-Raphson method or the secant Newton method. An automatic load incrementation scheme, line searches, and restart facilities are included. The capabilities of the program have been examined and demonstrated by analysing five reinforced concrete panels, a deep beam, a shear wall, and eight infilled frames. The accuracy of the analytical results was assessed by comparing them with the experimental results and those obtained analytically by other workers and shown to be good. A study of the effects of some material and numerical parameters on the results of analyses of reinforced concrete deep beam has been carried out. Two techniques have been proposed and used to overcome numerical problems associated with local strain concentrations which occur with the displacement control, when path dependent incremental iterative procedures are used for inelastic materials. The displacement control provided with these modifications has been shown to be more efficient than the load control.

Orientador: Luiz Carlos de Almeida / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-17T14:58:39Z (GMT). No. of bitstreams: 1 Tanaka_EdithSilvanaAmaurydeSouza_M.pdf: 2564170 bytes, checksum: 9c2738bed436807ec3b45b7d32d670ca (MD5) Previous issue date: 2011 / Resumo: Apresenta-se neste trabalho um estudo da influência da alvenaria dotada de aberturas no comportamento estrutural de um edifício em concreto armado de 27 pavimentos. Na análise computacional por elementos finitos através do programa SAP 2000 os painéis de alvenaria são substituídos por escoras diagonais equivalentes. Modela-se também um pórtico isolado por meio da discretização em elementos de chapa e a consideração de molas na interface pórtico-painel. Observa-se neste modelo a formação da biela de compressão, onde se compara a largura da diagonal comprimida com estudos experimentais e analíticos encontrados na literatura. Os pórticos quando interligados com os painéis de alvenaria e submetidos a ações horizontais como ventos e sismos transferem estes esforços através de uma diagonal comprimida que se forma no painel de alvenaria e altera o comportamento estrutural do edifício. Os resultados mostram que a alvenaria contribui na rigidez global do edifício. Esses resultados são apresentados por comparação entre os modelos com e sem a contribuição da alvenaria, sendo que esta pode conter aberturas de portas e janelas / Abstract: It presents in this paper study the influence of masonry provided with openings in the structural behavior of a reinforced concrete building of 27 floors. In finite element analysis computer program SAP 2000 by the masonry panels are replaced by equivalent diagonal struts. Also modeled in a finite element structure consisting of two columns and two beams filled with masonry. Finite element type shells were used in the modeling of masonry and springs were inserted at the interface. Was observed in this model the formation of the compression strut, which compares the width of the strut with experimental and analytical studies in the literature. The frames when interconnected with the masonry panels and subjected to horizontal actions such as winds and earthquakes transfer these efforts through a strut that is formed on the panel of masonry and structural changes the behavior of the building. The results show that masonry contributes to the overall stiffness of the building. These results are presented for comparison between models with and without the contribution of the masonry, and this may contain openings of doors and windows / Mestrado / Estruturas / Mestre em Engenharia Civil

A non-linear finite element program to simulate the behaviour of infilled frames and plane stress reinforced concrete members under the action of monotonic and cyclic loading has been developed. Steel is modelled as a strain hardening plastic material, and in the concrete model cracking, yielding and crushing are considered. The separation, sliding, and opening and closing of initial gaps at the interfaces between the frame and the infill panels are accounted for by adjusting the properties of interface elements. The non-linear equations of equilibrium are solved using an incremental-iterative technique performed under load or displacement control. The iterative techniques use the standard and modified Newton-Raphson method or the secant Newton method. An automatic load incrementation scheme, line searches, and restart facilities are included. The capabilities of the program have been examined and demonstrated by analysing five reinforced concrete panels, a deep beam, a shear wall, and eight infilled frames. The accuracy of the analytical results was assessed by comparing them with the experimental results and those obtained analytically by other workers and shown to be good. A study of the effects of some material and numerical parameters on the results of analyses of reinforced concrete deep beam has been carried out. Two techniques have been proposed and used to overcome numerical problems associated with local strain concentrations which occur with the displacement control, when path dependent incremental iterative procedures are used for inelastic materials. The displacement control provided with these modifications has been shown to be more efficient than the load control. / Iraqi Government

Apresenta-se neste trabalho um estudo sobre o comportamento de estruturas de pórticos preenchidos por painéis de alvenaria submetidos a ações horizontais, considerando a contribuição de alvenaria na rigidez global da estrutura. Este estudo envolveu uma série de ensaios experimentais como protótipos de aço em escala real utilizando-se blocos celular autoclavados; a macromodelagem numérica pelo método dos elementos finitos; a aplicação do conceito da diagonal equivalente; e a realização de um estudo paramétrico, considerando-se pórticos com diferentes relações altura/comprimento, visando à obtenção de recomendações práticas para análise de pórticos preenchidos. Essas recomendações são apresentadas na forma de uma proposta para determinação da carga de ruptura em painéis de pórticos preenchidos com alvenaria, utilizando-se o modelo de bielas e tirantes. Os resultados obtidos com a aplicação desta proposta foram comparados com os dos modelos experimentais e teóricos disponíveis na literatura, comprovando-se a eficiência e praticidade em sua utilização. / This work presents a study of the behavior of masonry infilled frames structures, subjected to horizontal actions, regarding the contribution of the masonry to the structure global stiffening. The study consists of tests, in real size, in steel frames infilled with structural blocks of autoclaved aerated concrete; of the macromodeling using the finite element method; of the application of the concept of equivalnet diagonal struts and of the realization of a parametric study, regarding frames with different ratios height/length, aiming to get design recommendations for the analysis of infilled frames. These recommendations are presented as a proposal for determining the cracking load in panels of infilled frames with masonry. utilizing the strut-and-tie model. The results obtained with this proposal are compared with tests and predictions derived from approximate theoretical analyses, proving the efficiency and practicality in their utilization.

The construction of reinforced concrete buildings with unreinforced infill is common practice even in seismically active country such as Bhutan, which is located in high seismic region of Eastern Himalaya. All buildings constructed prior 1998 were constructed without seismic provisions while those constructed after this period adopted seismic codes of neighbouring country, India. However, the codes have limited information on the design of infilled structures besides having differences in architectural requirements which may compound the structural problems. Although the influence of infill on the reinforced concrete framed structures is known, the present seismic codes do not consider it due to the lack of sufficient information. Time history analyses were performed to study the influence of infill on the performance of concrete framed structures. Important parameters were considered and the results presented in a manner that can be used by practitioners. The results show that the influence of infill on the structural performance is significant. The structural responses such as fundamental period, roof displacement, inter-storey drift ratio, stresses in infill wall and structural member forces of beams and column generally reduce, with incorporation of infill wall. The structures designed and constructed with or without seismic provision perform in a similar manner if the infills of high strength are used.