Bare Frame Research Articles

SEISMIC ANALYSIS OF MULTISTORIED IRREGULAR AND REGULAR BUILDING WITH MASONARY INFILLS

Nowadays, as in the urban areas the space available for the construction of buildings is limited. So in limited space we have to construct such type of buildings which can be used for multiple purposes such as lobbies, car parking etc. To fulfill this demand, high rise buildings is the only option available. The performance of a high rise building during strong earthquake motion depends on the distribution of stiffness, strength and mass along both the vertical and horizontal directions. If there is discontinuity in stiffness, strength and mass between adjoining storeys of a building then such a building is known as irregular building. The present study focuses on the seismic performance of regular and vertical irregular building with and without masonary infills. In the present study G+11 building is considered for the analysis with modelling and analysis done on ETABS software v17.0.1. The earthquake forces are calculated as per IS 1893 (part 1): 2016 for seismic zone III. The width of strut is calculated by using equivalent diagonal strut method. Total five models are considered for the analysis i.e. regular building with bare frame, regular building with masonary infill, soft storey building with open ground storey, mass irregular building with masonary infill and vertical geometric irregular building with masonary infill. The non-linear static analysis (pushover analysis) and linear dynamic analysis (response spectrum analysis) are performed for all the models and thereby compare their results. From analysis, the parameters like performance point, time period, maximum storey displacement, maximum storey drifts, storey shears and overturning moments are determined and also comparative study is done for all the models. From the comparison, it is observed that the vertical geometric irregular building shows better performance under seismic loading and bare frame building shows inferior performance. Moreover, the performance of masonary infilled frame building is f

Experimental and analytical assessment of the influence of masonry façade infills on seismic behavior of RC frame buildings

On May 11, 2011 at 6:47p.m., an M5.1 earthquake took place in Lorca at a depth of 4 km, in the Region of Murcia, south of Spain, which resulted in nine fatalities and 324 injuries and major built environment damage. Approximately 80% of the residential buildings were affected with various degrees of damage, 5% with severe structural damage and 13% with moderate structural damage, in addition to the damage of infrastructure and public buildings. Reconnaissance and expert analyses revealed that one of the main causes of damage during the Lorca earthquake was the interaction between the non-structural elements and the seismic-resisting framing of the buildings. Studies on this interaction, that started in the 1950 s, led to the development of a wide range of macro-models that simulate the stiffness of the masonry infills using one or more equivalent diagonal strut(s). Following an extensive literature review, 12 mathematical expressions have been compiled to estimate the horizontal stiffness of the equivalent strut that simulates the behavior of masonry infills that make up a typical façade of many modern buildings. Two full-scale tests under horizontal cyclic displacement reversals have been carried out on two 5x3m concrete frames: one frame with masonry infill simulating a regular façade; and the other is a bare control frame. The comparison of both tests enabled quantifying the stiffness contribution of the façade infill and identifying the simplified expression that best fits the horizontal stiffness. Using this expression, a realistic seismic design of a prototype building in Lorca, Spain, is conducted under the typical assumption of most modern building codes to consider masonry infills as non-structural elements, and consequently the designed building was seismically assessed considering the influence of the infills. Results of the assessment are in accordance with the real damage patterns observed during the Lorca earthquake reconnaissance.

Inelastic Analysis of Mdof Systems Damaged by Earthquakes, Posteriorly Subjected to Wind Load

This paper deals with the analysis of the inelastic response of buildings originally damaged by earthquakes and subjected to earthquake aftershock and wind loading. The overall aim is to establish the effect of wind actions on structural stability. To that end, one four-story bare frame benchmarked by the European Laboratory for Structural Assessment, is subject to various levels of winds and earthquake joint load while monitoring changes on the ductility demand. In this paper is shown that the combined action of strong winds and earthquakes, however its low probability of occurrence, would cause a decrease of strength reduction factors and considerably increase the ductility demand of damaged infrastructure hence inducing additional risks that would otherwise remain unquantified. The paper examines the non-linear performance of Multi-degree of freedom systems subject to various levels of winds and earthquake load and deals with the estimation of strength reduction factors. This is a relatively unexplored area of research which builds on past developments whereby inelastic performance of buildings has been discussed. It also links to various other paths of development such as structural reliability, forensic and control systems engineering. Doi: 10.28991/cej-2021-03091675 Full Text: PDF

Seismic demands of bare and base-isolated steel frames for real against simulated records of a past earthquake

A challenging task in earthquake engineering is investigation of engineering demand parameters under regional records of large earthquakes due to inherently low frequency of these events. Use of simulated records in such cases is a recent alternative. Ground motion simulations were traditionally performed to model physical processes in earthquake occurrences. Nowadays, simulations are also used for engineering purposes. However, detailed assessment of simulated records against real data including their effect on structural response is necessary. The aim herein is to explore how alternative simulation methods differ in terms of engineering demand parameters for multi-degree-of-freedom models and to find out their efficiency in design and assessment of base isolated structures. For this purpose, bare and base-isolated models of a 6-story steel moment-resisting frame are considered. Force-based, displacement-based and energy-based demands are evaluated due to real and simulated records of 2009 L′Aquila (Italy) event (Mw = 6.3). Ground motion simulation approaches include stochastic finite-fault method and hybrid integral-composite techniques. Analyses show that when seismological misfits between the real and simulated records are smaller, closer matches between their engineering demand parameters are observed. Finally, numerical results reveal that simulated motions validated against real data provide alternative sets particularly for regions with sparse observed records.

In-plane Quasi-static Cyclic Load Tests on Reinforced Concrete Frame Panels with and without Brick Masonry Infill Walls

ABSTRACT In this paper, the influence of brick masonry infill walls on the seismic performance of reinforced concrete (RC) frames is investigated. The presence and the location of a door opening are considered as test variables. Four RC frames were tested: a control specimen (RC bare frame), an infilled RC frame, an infilled RC frame with door opening at the loading end, and an infilled RC frame with door opening in the center. The test specimens were full scale representatives of typical RC frames with brick masonry infill walls. The data from the testing was interpreted in terms of failure modes, hysteresis curves, energy dissipation characteristics, stiffness degradation, and performance levels as established by standards. It was observed that the infill walls improve the RC frame performance in term of strength and stiffness, whereas the addition of a door opening reduces this performance improvement. Shifting the door opening from the side to the center improved the RC frame performance in term of strength and stiffness.

Comprehensive Review of Optimal and Smart Design of Nonlinear Building Structures With and Without Passive Dampers Subjected to Earthquake Loading

The optimal and smart design of nonlinear building structures with and without passive dampers subjected to earthquake loading is of great concern in the structural design of building structures. The research started around 1980 and many investigations have been conducted. A comprehensive review on this subject is made in this article. After the description of essential features of the optimal design problem of nonlinear building structures under earthquake ground motions, analysis types of optimization problems are explained and the significance of the dynamic pushover analysis is discussed from the viewpoint of analysis of limit states under earthquake ground motions of magnitude larger than the code-specified level. Then, the categorization by the response of frames and dampers was made. In this categorization, several subjects are discussed first: 1) Optimal design of bare nonlinear building frames under seismic loading, 2) Optimal design of nonlinear dampers for elastic building frames under seismic loading, 3) Optimal design of linear dampers for nonlinear building frames under seismic loading, 4) Optimal design of nonlinear building frames with specified nonlinear dampers under seismic loading, 5) Optimal design of nonlinear dampers for specified nonlinear building frames under seismic loading, 6) Simultaneous optimization of elastic-plastic building structures and passive dampers. Finally, the classification of researches in view of solution strategies is conducted for providing another viewpoint.

Practitioner-friendly design method to improve the seismic performance of RC frame buildings

Reinforced concrete (RC) frame buildings are a widely used structural system around the world. These buildings are customarily designed through standard code-based procedures, which are well-suited to the workflow of design offices. However, these procedures typically do not aim for or achieve seismic performance higher than code minimum objectives. This article proposes a practical design method that improves the seismic performance of bare RC frame buildings, using only information available from elastic structural analysis conducted in standard code-based design. Four buildings were designed using the proposed method and the prescriptive approach of design codes, and their seismic performance is evaluated using three-dimensional nonlinear (fiber) models. The findings show that the seismic performance is improved with the proposed method, with reductions in the collapse fragility, higher deformation capacity, and greater overstrength. Furthermore, an economic analysis for a six-story building shows that these improvements come with only a 2% increase in the material bill, suggesting that the proposed method is compatible with current project budgets as well as design workflow. The authors also provide mathematical justification of the method.

Strain investigation of infill frames using FEA package MSC NASTRAN

Masonry infill is usually neglected in the design and it is treated as a non-structural element instead of its stiffness and lateral resistance capacity. Their presence in the RC frame could also affect the lateral load resistance. The interaction of infill presence in the RC frame will also depend on the aspect ratio of frame and openings presence in the infill. The infill collapse initiated disaster of RC Framed structures are mainly concerned by the researchers recently. Many researchers considered experimentation up to a single-story single bay frame may be due to constraints in their facilities. A 3-bay 3-Storey Frame is considered in the present study using finite element package using MSC NASTRAN for different frame such as bare frame, Infill frame with different openings provided in it, and meshing was done finally strains were taken at middle third distances on each member of the internal panel of the bare frame, Infill frame, Infill frame with window opening, Infill frame with door opening, Infill frame with window and door openings and a comparison was made with infill frame and presence of openings in the infilled frame.

Concentric versus eccentric strut models in the seismic response of masonry infilled reinforced concrete frame structures using nonlinear dynamic analysis

The influence of masonry infills on the seismic response of reinforced concrete (RC) frame structures is evaluated based on comparative procedure between concentric and eccentric strut models. For this purpose, a four-story reinforced concrete frame structure was selected and designed according to Algerian seismic design code RPA 99/version2003. Comparisons were carried out with the variation in the mechanical characteristics of infills. To this end, three types of masonry infills were considered, defined as weak, intermediate and strong. A series of nonlinear dynamic analyses using a set of three time-history earthquake records were performed with the bare and regular infilled frames structural configurations. Results from nonlinear analyses furnish information on the interaction between the concentric/eccentric strut models and the surrounding structural elements, and their impact on the global and local responses. It is concluded that, at global level, the concentric strut model gives much stiffer response than the eccentric strut model and may be of some practical interest in the design of seismic gaps between adjacent structures; at local level, the concentric strut model is not able to reproduce the increasing of forces in columns due to infills and this increasing phenomenon is particularly relevant in the case of shear force for the strong masonry infill. This paper provides some limitations concerning the number of studied parameters; it can be extended through the consideration of wider set of parameters, such us infill thickness, number of stories, number of bays and irregular infill distribution, in particular soft first story.

Evaluation of seismic torsional response of ductile RC buildings with soft first story

This study investigates the inelastic torsional response of plan asymmetric ductile RC buildings with a soft first story. The buildings of Rectangular, L, T, and U plan shapes are considered for the study. Force-based fiber beam-column elements are modeled for the inelastic response prediction of the buildings. Masonry infill walls are uniformly distributed in the plan and considered for the evaluation of torsional response. The pushover methods, Extended N2 and Extended Capacity Spectrum Method – FEMA 440 are adopted to estimate the inelastic torsional response. Bi-directional nonlinear time history analysis is carried out on the buildings considering near-field and far-field ground motions. Story drift ratio and curvature demand-capacity (D/C) ratio of columns are reported at the stiff, flexible side of buildings. The torsional response of infill wall buildings is compared with that of bare frame buildings. It was observed that the torsionally irregular ductile buildings with soft first story exhibit higher seismic demand on the flexible side corner columns. Infill wall interaction amplifies the torsional response at the bottom story, causing an increase in displacements higher at the flexible side and moderate near the stiff side. This study concludes that the flexible side corner column in plan asymmetric building with a soft first story can be conservatively designed for 1.5 times the design forces obtained from the analysis. This conservative design ensures stable energy dissipation in the corner column under load reversals, without significant strength reduction under higher excitation levels. The designer shall properly distribute lateral load resisting elements in a plan to prevent premature failure of the columns located internally and close to the initial center of rigidity. The designer can avoid the collapse of columns located internally in the buildings with stiff peripheral frames by designing for forces 1.5 times higher than obtained.

Seismic behaviour of masonry infilled hinged steel frames with openings: experimental and numerical studies

This study describes an experimental and numerical investigation on the seismic behaviour of masonry infilled hinged steel frames with openings. Experimental tests of six half-scaled, single-storey and single-bay specimens including one bare hinged steel frame, one solid infilled hinged steel frame, and four masonry infilled hinged steel frames with different opening sizes were carried out under lateral cyclic loading. The cracking patterns, failure modes, hysteretic behaviour, characteristic loads and displacements, stiffness degradation and equivalent viscous damping ratios of these specimens were compared. Furthermore, detailed three-dimensional finite element (FE) models of test specimens were developed in the commercially available FE code ABAQUS, and a series of nonlinear pushover analyses were performed. In particular, the lateral load–displacement relationships of test specimens were numerically simulated and validated against the experimental results. In addition, the mechanical behaviour of infilled walls under lateral loading was investigated.

Dynamic test and numerical simulation on avoiding the weak-story failure mechanism in structures using LSFDs

The structural damage or collapse caused by weak-story failure mechanisms poses a great threat to the safety of human life and property under strong earthquakes. Many researchers have attempted to transform this unexpected failure mechanism into the desired overall failure mechanism by installing various energy dissipation devices on unsafe structures. This paper introduced a lattice-shaped friction device (LSFD), which is a friction device with hardening postyielding stiffness, into a steel frame with a weak-story failure mechanism. Then, shaking table tests of a three types of two-story steel frames—a frame with LSFDs, a frame with traditional friction brace dampers (FBDs), and a bare frame—were carried out. The seismic responses of the hardening postyielding stiffness of the LSFD on the weak-story failure mechanism of the frame were emphatically studied. The results showed that there was little difference in the seismic responses between the two damped structures under moderate and weak earthquakes. The distribution of maximum story drift for the structure with LSFDs was more uniform, which effectively suppressed the weak-story failure under strong earthquakes, whereas the structure with FBDs had serious deformation concentrations. The numerical simulation results of the structure with LSFDs in the shaking table test showed that the simplified model results were basically consistent with the experimental results. Hence, this model could be used to analyze the seismic performance of damped structures with LSFDs.

Effect of Lintel Beam on Seismic Response of Reinforced Concrete Buildings with Semi-Interlocked and Unreinforced Brick Masonry Infills

The primary focus of this study is to evaluate the nonlinear response of reinforced concrete (RC) frames with two types of brick infills viz., unreinforced brick masonry infill (URM) and semi-interlocked brick masonry infill (SIM) together with lintel beams, subjected to seismic loads. The seismic response is quantified in terms of response reduction factor and base shear. Infill walls are modeled using double strut nonlinear cyclic element. Nonlinear static adaptive pushover analysis is performed in the finite element program SeismoStruct. The response reduction factor (R) is computed from adaptive pushover analysis and performance for all models is obtained. The results showed that the average R factor of the RC framed structure with semi-interlocked masonry (SIM) is 1.31 times higher than the RC frame with unreinforced masonry (URM) infill. The R value of the bare frame with the lintel beam is found to be less than the corresponding value recommended in the Indian Standard Code. The results obtained in this study highlight that if the impacts of lintel beams and various brick infill scenarios are considered in the RC frames then the R values used for the design of RC frame buildings with infills would be underestimated (i.e., the evaluated R values are greater than the R values used for the design purpose).

Cyclic response of a reinforced concrete frame: Comparison of experimental results with different hysteretic models

<abstract> <p>An accurate hysteresis model is fundamental to well capture the non-linearity phenomena occurring in structural and non-structural elements in building structures, that are usually made of reinforced concrete or steel materials. In this sense, this paper aims to numerically estimate through simplified non-linear analyses, the cyclic response of a reinforced concrete frame using different hysteretic models present in the literature. A commercial Finite Element Method package is used to carry out most of the simulations using polygonal hysteretic models and a fiber model, and additionally, a MATLAB script is developed to use a smooth hysteresis model. The experimental data is based on the experiments carried out in the Laboratório Nacional de Engenharia Civil, Portugal. The numerical outcomes are further compared with the experimental result to evaluate the accuracy of the simplified analysis based on the lumped plasticity or plastic hinge method for the reinforced concrete bare frame. Results show that the tetralinear Takeda's model fits closely the experimental hysteresis loops. The fiber model can well capture the hysteresis behavior, though it requires knowledge and expertise on parameter calibration. Sivaselvan and Reinhorn's smooth hysteresis model was able to satisfactorily reproduce the actual non-linear cyclic behavior of the RC frame structure in a global way.</p> </abstract>

Evaluating the performance of method to increase the stiffness of structure

The aim of the present research is to increasing the stiffness of the structure against lateral loading. In the present study to increase stiffness of the structure we have four lateral load resisting elements are considered such as shear wall, core wall, bracing system and tube in tube structure and compare all models with bare frame structure. Here an ordinary moment resisting building of G+13 stories located over a medium soil is considered. In the symmetric building the number of bays will be kept as 5 along both direction and the bay size will be kept as 4m with the storey height being 3m. The building will be analysed considering zone V by response spectra method using ETABS 2016 software. The parameters considered as lateral storey displacement, storey drift, storey shear, storey stiffness, base shear and time period.

Dynamic Characteristics Evaluation on Portable Steel Frame due to Mass Irregularities

Application of irregular mass configuration in modern design era of buildings is unavoidable in order to serve various building functionality. The effect of mass irregularities was investigated on 5-storey portable moment resisting steel tower (PostFrame), against its dynamic behaviour. PostFrame was designed at five meter height and assembled on the strong floor in Jamilus Research Centre laboratory, UTHM. The predominant frequencies and mode shapes were determined on bare frame, uniform mass frame and mass irregularities’ frames. A total of four steel blocks at 800 kg were placed in uniform, ascending and alternating orientations on the first to fourth level of the PostFrame. Ambient vibration testing (AVT) was conducted using uni-axial accelerometer sensors. The sensors were aligned in bi-axial horizontal directions with respect to the North-South (NS) and East-West (EW) directions. ARTeMIS processing tool and Frequency Domain Decomposition (FDD) methods were used in the analysis of dynamic behaviour. Comparative findings were made between bare frame and mass action frame. Two translation mode shapes and torsional mode were illustrated by respective three predominant frequencies. Significant reduction of predominant frequency showed up to 37.79% between bare frame and frame with ascending mass orientation.Uniform mass orientation shows at the lowest percentage discrepancy percentage compared to others. Even though some changes have be found in predominant frequencies, but comparable mode shapes illustration were observed from all three predominant frequencies from all frame configurations.

Operational Modal Analysis, Testing and Modelling of Prefabricated Steel Modules with Different LSF Composite Walls.

The modal properties of modular structures, such as their natural frequencies, damping ratios and mode shapes, are different than those of conventional structures, mainly due to different structural systems being used for assembling prefabricated modular units onsite. To study the dynamic characteristics of modular systems and define a dynamic model, both the modal properties of the individual units and their connections need to be considered. This study is focused on the former aspect. A full-scale prefabricated volumetric steel module was experimentally tested using operational modal analysis technique under pure ambient vibrations and randomly generated artificial hammer impacts. It was tested in different situations: [a] bare (frame only) condition, and [b] infilled condition with different configurations of gypsum and cement-boards light-steel framed composite walls. The coupled module-wall system was instrumented with sensitive accelerometers, and its pure and free vibration responses were synchronously recorded through a data acquisition system. The main dynamic characteristics of the module were extracted using output-only algorithms, and the effects of the presence of infill wall panels and their material are discussed. Then, the module’s numerical micromodel for bare and infilled states is generated and calibrated against experimental results. Finally, an equivalent linear strut macro-model is proposed based on the calibrated data. The contribution of this study is assessing the effects of different infill wall materials on the dynamic characteristics of modular steel units, and proposing simple models for macro-analysis of infilled module assemblies.

Experimental Testing and Numerical Modeling of Robust Unreinforced and Reinforced Clay Masonry Infill Walls, With and Without Openings

This paper presents an overview of the experimental results obtained by combined in-plane/out-of-plane (IP/OOP) tests carried out on robust clay masonry infill walls. The combined tests were carried out on eight full-scale one-bay, one-story infilled reinforced concrete (RC) frames, plus one reference RC bare frame. In four cases, the masonry walls fully fill the RC frame: two walls are made of unreinforced masonry (URM), whereas the other two are made of reinforced masonry (RM), with both vertical and horizontal reinforcement. Each pair of specimens was tested up to different levels of IP drift before carrying out the OOP tests. Four other specimens, still made of URM and RM walls, are characterized by the presence of a central opening, and in one case, the effect of a lintel is analyzed. On the basis of the tests carried out, an analytical model was developed for the analysis of the OOP behavior. It was used to calibrate IP damage degradation models based on the experimental results to define limits for the applicability of well-known flexural and arching mechanism models for the evaluation of the OOP capacity of the infill walls and to evaluate the efficiency of vertical reinforcement. In this work, the experimental campaign is presented, and the results of both experimental tests and numerical analyses are discussed.

Progressive collapse behavior of reinforced concrete frame exposed to high temperature

Purpose Technological innovations in the construction field correspond to a wider revolution in metropolitan life and in structural design. With the demand for advanced concrete technology, the introduction of new reinforced materials in concrete, namely, iron, steel and other reinforcing elements. Reinforcement in concrete is developed in the centuries back and several advancements are being stirred to improvise the properties of the concrete through reinforcements. On the basis of this finding from the earlier research studies, a reinforcement methodology is practiced on the current study to investigate the deflection of the M30 mix concrete frame under thermal load conditions. Design/methodology/approach For the examination, corner and the middle frame are considered with the reinforcement provided on four zones with 16-mm diameter for compression and 8-mm diameter is used for the stirrup at 150 mm c/c spacing. The load is applied to the column with live and wall load of 3.5 kN/m and 14.7KN/m. The experimentation is carried out by the finite element analysis strategy in ABAQUS simulation software with five test conditions with the bare frame at single, two and three-bay infill. The model of the frame is developed and meshed with the meshing type of C3D8T under 8-node thermally coupled brick mesh type for the mesh size of 25 mm. Findings From the simulation outcome, the effect of thermal gradient on the reinforced concrete is analyzed and its structural properties are plotted as performance graphs in the result section. Originality/value Under the thermal load condition, the model is simulated for 180 min for five different cases and analyzed the deflection parameters such as deformation, stress and failure rate.

Investigation of Strain in Infill Frames using Nastran Patran

Masonry infill is usually neglected in the design and it is treated as a non-structural element instead of its stiffness and lateral resistance capacity. Their presence in the RC frame could also affect the lateral load resistance. The interaction of infill presence in the RC frame will also depend on the aspect ratio of frame and openings presence in the infill. The infill collapse initiated disaster of RC Framed structures are mainly concerned by the researchers recently. Many researchers considered experimentation up to a single-story single bay frame may be due to constraints in their facilities. A 3-bay 3-Storey Frame is considered in the present study using finite element package using MSC Nastran for different frame such as bare frame, Infill frame with different openings provided in it, and meshing was done finally strains were taken at middle third distances on each member of the internal panel of the bare frame, Infill frame, Infill frame with window opening, Infill frame with door opening, Infill frame with window and door openings and a comparison was made with infill frame and presence of openings in the infilled frame.