Nonlinear Structural Performance of a Historical Brick Masonry Inverted Dome

ABSTRACT

Traditional domes are obtained by double curvature shells, which can be rotationally formed by any curved geometrical plane figure rotating about a central vertical axis. They are self-supported and stabilized by the force of gravity acting on their weight to hold them in compression. However, the behavior of inverted domes is different since the dome is downward and masonry inverted domes and their structural behaviors in the literature received limited attention. This article presents a nonlinear finite element analysis of historical brick masonry inverted domes under static and seismic loads. The brick masonry inverted dome in the tomb of scholar Ahmed-El Cezeri, town of Cizre, Turkey, constructed in 1508 is selected as an application. First, a detailed literature review on the masonry domes is given and the selected inverted dome is described briefly. 3D solid and continuum finite element models of the inverted masonry dome are obtained from the surveys. An isotropic Concrete Damage Plasticity (CDP) material model adjusted to masonry structures with the same tensile strength assumed along the parallel and meridian directions of the inverted dome is considered. The nonlinear static analyses and a parametric study by changing the mechanical properties of the brick unit of the inverted masonry dome are performed under gravity loads. The acceleration records of vertical and horizontal components of May 1, 2003 Bingöl earthquake (Mw = 6.4), Turkey, occurred near the region, are chosen for the nonlinear seismic analyses. Nonlinear step by step seismic analyses of the inverted dome are implemented under the vertical and horizontal components of the earthquake, separately. Static modal and seismic responses of the inverted masonry dome are evaluated using mode shapes, minimum and maximum principal strains and stresses, and damage propagations.     

SEISMIC SAFETY OF AGED CONCRETE GRAVITY DAMS CONSIDERING FLUID-STRUCTURE INTERACTION

It is important to predict the behaviour of an aged concrete gravity dam during an earthquake and to assess its degraded capacity to withstand future earthquakes, so that remedial measures can be taken at the right time. The assessment of operating and ageing dams is more important, since the analyses procedures may become obsolete and state of the art may change since the time of construction. In this paper, an approach to include the time dependent degradation of concrete owing to environmental factors and mechanical loading in terms of isotropic damage index is presented. An effective numerical algorithm for seismic analysis of a concrete dam in the vicinity of an infinite reservoir with the application of damage mechanics considering fluid-structure interaction is presented. The performance of an aged dam with a known percentage of isotropic or orthotropic damage due to seismic excitation is studied.     

Damage Assessment of Unreinforced Stone Masonry Buildings After the 2010–2011 Canterbury Earthquakes

The sequence of earthquakes that has affected Christchurch and Canterbury since September 2010 has caused damage to a great number of buildings of all construction types. Following post-event damage surveys performed between April 2011 and June 2011, an inventory of the stone masonry buildings in Christchurch and surrounding areas was carried out in order to assemble a database containing the characteristic features of the building stock, as a basis for studying the vulnerability factors that might have influenced the seismic performance of the stone masonry building stock during the Canterbury earthquake sequence. The damage suffered by unreinforced stone masonry buildings is reported and different types of observed failures are described using a specific survey procedure currently in use in Italy. The observed performance of seismic retrofit interventions applied to stone masonry buildings is also described, as an understanding of the seismic response of these interventions is of fundamental importance for assessing the utility of such strengthening techniques when applied to unreinforced stone masonry structures.     

Seismic Fragility Assessment of Lightly Reinforced Concrete Structural Walls

Development of fragility functions is a pertinent stage in seismic performance assessment of structures. A database of lightly Reinforced Concrete (RC) walls under simulated seismic loading is compiled from the literature to establish the drift-based seismic fragility functions. To classify the damage states experienced by RC walls, the Park-Ang Damage model is amended in this research. Then, the modified Bouc-Wen-Baber-Noori hysteresis model is implemented in ABAQUS to predict the hysteresis behavior of RC walls. Thereafter, the proposed hysteresis model is employed to develop the seismic fragility curves of low to mid-rise RC walls in Singapore using incremental dynamic analysis approach.     

SEISMIC DESIGN AND RESPONSE OF BARE AND MASONRY-INFILLED REINFORCED CONCRETE BUILDINGS. PART II: INFILLED STRUCTURES

The effects of masonry infills on the global seismic response of reinforced concrete structures is studied through numerical analyses. Response spectra of elastic SDOF frames with nonlinear infills show that, despite their apparent stiffening effect on the system, infills reduce spectral displacements and forces mainly through their high damping in the first large post-cracking excursion. Parametric analyses on a large variety of multi-storey infilled reinforced concrete structures show that, due to the hysteretic energy dissipation in the infills, if the infilling is uniform in all storeys, drifts and structural damage are dramatically reduced, without an increase in the seismic force demands. Soft-storey effects due to the absence of infills in the bottom storey are not so important for seismic motions at the design intensity, but may be very large at higher motion intensities, if the ultimate strength of the infills amounts to a large percentage of the building weight. The Eurocode 8 provisions for designing the weak storey elements against the effects of infill irregularity are found to be quite effective, in general, for the columns, but unnecessary and often counterproductive for the beams.     

Earthquake-Induced Damage Detection in a Monumental Masonry Bell-Tower Using Long-Term Dynamic Monitoring Data

ABSTRACT

This work investigates the use of an advanced long-term vibration-based structural health monitoring tool to automatically detect earthquake-induced damages in heritage structures. Damage produced in a monumental bell-tower at increasing values of the Peak Ground Acceleration (PGA) of the seismic input is predicted by incremental nonlinear dynamic analysis, using a Finite Element model calibrated on the basis of experimentally identified natural modes. Then, predicted damage effects are artificially introduced in the monitoring data to check for their detectability. The results demonstrate that a very small damage, associated to a low intensity and low return period earthquake, is clearly detected by the monitoring system.     

EARTHQUAKE DAMAGE SCENARIOS AND SEISMIC HAZARD OF MESSINA,NORTH-EASTERN SICILY (ITALY) AS INFERRED FROM HISTORICAL DATA

A study aimed at evaluating earthquake damage scenarios and seismic hazard of Messina using historical data, is presented. The analysis of coeval reports allowed us to reconstruct the seismic history of the city and to obtain a homogeneous earthquake site catalogue based on intensity assessed by the European Macroseismic Scale 1998. In the last 1200 years Messina was destroyed once (1908, intensity X-XI EMS) and suffered effects estimated between intensities VII and IX EMS many times (e.g. 853, 1169, 1494, 1509, 1599, 1693, 1783, 1894, 1909). Destruction or severe damage which affected the city are mainly related to earthquakes occurring in the Messina Straits and Southern Calabria, while slighter, moderate effects are usually due to shocks taking place in the seismogenic sources of SE Sicily, Gulf of Patti and Northern Calabria. The damage scenarios of the most relevant events, delineated using coeval urban plans of the city, showed that damage distribution is strongly conditioned by the different soil response. A probabilistic seismic hazard assessment was obtained by using site observed intensities: The expected intensity in a time span of 50 years (i.e. maximum intensity characterised by at least 10% exceedance probability in 50 years) is DC EMS; the expected intensity in a time span of 300 years (10% exceedance probability in 300 years) is X EMS.     

Preliminary Assessment on Seismic Vulnerability of Masonry Churches in Central Chile

ABSTRACT

The 2010 Maule Chile earthquake (Mw 8.8) caused extensive structural damage to the built heritage. In particular, the poor seismic performance of a set of unreinforced masonry (URM) churches highlighted the need to implement protective and safety strategies in order to preserve these buildings which exhibit unique constructive and typological features, as a result of a combination of Chilean and European construction cultures.

The peculiarity of this heritage and the high seismic hazard of Chilean territory have motivated the present study which aims to apply systematic procedures to assess the seismic vulnerability of these buildings. This article is of archival nature and presents a complete database generated from the geometrical, constructive, and structural characteristics of a representative stock of 106 churches located in central Chile, with the goal of proposing fragility curves to be used in seismic risk assessment. Considering variables related with geometrical, architectonic, and stylistic features, as well as damage levels for the 2010 Maule earthquake, this church sample is classified into three homogenous groups: colonial, neo-classic, and neo-gothic. Moreover, a preliminary qualitative assessment of the seismic capacity of these structures is provided using a survey and analysis of geometric indices for each of the three selected groups.     

Seismic Fragility Evaluation of Lightly Reinforced Concrete Beam-Column Joints

Fragility functions play an essential role in evaluating the seismic vulnerability of structures. To establish the seismic fragility functions of lightly Reinforced Concrete (RC) beam-column joints, the Park-Ang Damage model has been amended to quantify the damage states and the modified Bouc-Wen-Baber-Noori model has been employed and implemented in ABAQUS to predict the structural hysteresis behavior. Following successful calibration of the numerical results of a RC test frame from literature, the proposed model has been utilized to assess the seismic fragility curves of low to mid-rise RC frames in Singapore for 30 scaled ground motions using incremental dynamic analysis approach.     

Earthquake Risk Scenarios in Urban Areas: A Review with Applications to the Ciutat Vella District in Barcelona,Spain

ABSTRACT

The vulnerability index and capacity spectrum-based methods used to assess the expected physical damage in dwellings are revisited, and their main advantages and shortcomings are analyzed and discussed. Then, a vulnerability index-based method is used to assess the expected damage in the oldest district of Barcelona, Spain. The risk analysis is performed for earthquake scenarios defined by macroseismic intensities of V, V-VI, VI, VI-VII, and VII to design seismic emergency plans. According to the Spanish Seismic Code, the basic peak ground acceleration for a 475-year return period is 0.04 g, which corresponds to an intensity of VI. Thus, the expected physical damage is quantified and its impact on population and other quantities, such as debris and economic cost, are studied. In spite of the low-to-moderate seismic hazard in Barcelona, the results show that the risk is high, due to the high exposure and vulnerability of the built environment.     

A Multidisciplinary Study on the Seismic Vulnerability of St. Agostino Church in Amatrice following the 2016 Seismic Sequence

ABSTRACT

The big earthquake of August 24, 2016 and subsequent major shocks severely damaged many historic villages in Central Italy and dramatically showed the intrinsic vulnerability of the diffused architectural heritage. The St. Agostino church is one of the collapsed historical buildings, being inside the epicentre village of Amatrice. During the long seismic earthquake swarm, progressively the church was damaged and monitored. This multidisciplinary study of the damage of the church includes correlations of all the data derived from three steps geomatics surveys (3D aerial and terrestrial models): the archival drawings and images documenting previous events distressing the building, the previous strengthening intervention, and finally the seismic site response analysis (from Amatrice’s accelerometric station). Through a back analysis carried out by a finite elements model, it was possible to understand the seismic vulnerability of this historical building, in relation to the previous interventions and damage events. The proposed methodology, based on the interdisciplinary data analysis, provides useful information for the next strengthening projects of damaged historical monument.     

METHODOLOGY FOR THE PROBABILISTIC ASSESSMENT OF q FACTORS. A DAMAGE INDEX APPROACH

The objective of the present work is to present a methodology for the identification of relevant limit states, namely ultimate limit states leading to structural collapse, and for the assessment of design q factors (or force reduction factors) for reinforced concrete structures under seismic loading. It follows a probabilistic approach based on damage indices. The utilised nonlinear models, as well as the damage indices, which are those proposed by Miner and by Park and Ang, are.described. The methodology of analysis is presented emphasising its probabilistic characteristics. Some parametric studies are carried out, including the analysis of one regular plane frame reinforced concrete structure, designed for three different ductility classes (those proposed by Eurocode 8) and assuming different q factors in design. Results show how the chosen damage indices can be used as parameters to characterise the structural response and how the proposed methodology can be used to assess the design q factors. It is also shown that, for moderate seismic input, the three ductility classes are essentially equivalent in terms of maximum damage indices, but that for higher seismic levels the differences are evident, justifying the use of different q factors.     

ESTIMATION OF NEAR-SOURCE GROUND MOTION AND SEISMIC BEHAVIOUR OF RC FRAMED STRUCTURES DAMAGED BY THE 1999 ATHENS EARTHQUAKE

On September 7, 1999 an earthquake with magnitude M _W =5.9 occurred close to the city of Athens in Greece. More than 80 buildings collapsed, about 150 deaths and hundreds of injuries were reported. Soon after the event a damage investigation was carried out by two of the authors in the most heavily struck areas. The most serious damages were observed in the northern suburbs of Athens, where reinforced concrete frames and masonry buildings represent the prevalent construction systems. The hysteretic energy demands imposed on RC buildings should have been rather severe considering the structural systems characteristics and the inadequate construction details. However, over-strengths, redundancy and especially the presence of infill walls, provided a significant increase of the seismic capacity and contributed to the survival of many buildings.

The objective of the present work is to reproduce and analyse the response of typical RC frames subjected to the 1999 Athens earthquake in areas where the observed damage was particularly severe but no recordings of the ground motion were available. After a general overview of the seismotectonic environment, seismological data, observed macro-seismic intensities, structural typologies and observed building behaviour, an attempt is made to identify representative excitations in the meizoseismal area. Specifically, the required accelerograms are obtained by modifying available records so as to reproduce a given global energy content and to be consistent with the observed damage. To study the seismic response of RC models, the obtained accelerograms are used to perform nonlinear dynamic analyses.     

A PROCEDURE FOR ESTIMATING INPUT ENERGY SPECTRA FOR SEISMIC DESIGN

In this paper, the damage potential of an earthquake ground motion is evaluated in terms of the total power of the acceleration of the ground motion. By assuming an appropriate spectral shape for the input energy spectrum, and using the well-known Parseval theorem for evaluating the total power of a random signal, the peak amplification factor for the equivalent input energy velocity spectrum can be determined. It is shown that the peak amplification factor for the input energy spectrum depends on the peak-ground-acceleration to peak-ground-velocity ratio and duration of the strong motion phase of the ground motion. Values for the equivalent input energy velocity amplification factor vary from about 2 to 10 for most of the recorded ground motions used in this study. Although a considerable scatter of data is observed in this study, the peak amplification factor predicted by the Fourier amplitude spectrum of the ground acceleration provides a fairly good estimate of the mean value of the peak input energy compared to that determined from inelastic dynamic time history analyses, particularly for systems with high damping and low lateral strength. The peak amplification factor derived in this paper provides a more consistent approach for estimation of seismic demand when compared to an earlier empirical expression used for the formulation of duration-dependent inelastic seismic design spectra, even though only a slight difference in the required lateral strength results from the use of the new formula.     

An Analytical Study on the Seismic Vulnerability of Masonry Buildings in India

Two analytical models for unreinforced masonry (URM) buildings are proposed with the aim to simulate their seismic response and to estimate corresponding vulnerability functions. The proposed models are implemented in SAP 2000 nonlinear software to obtain capacity curve parameters for representative Indian URM buildings, based on a field survey and statistical analysis. Vulnerability functions are estimated using the obtained capacity curves. Damage Probability Matrices (DPMs) are obtained using the approximate PGA-intensity correlation relationship as per Indian seismic building code and are compared with the commonly used intensity scales and empirical damage data observed after the 2001 Bhuj earthquake.     

ANALYTICAL MODELS FOR BRICK MASONRY INFILLED R/C FRAMES UNDER LATERAL LOADING

Proposed in this paper are two analytical models for predicting the inelastic response of unreinforced brick masonry infills in reinforced concrete frames subjected to mono-tonic and reversed cyclic loading. The first model is based on the traditional diagonal strut concept, while the second one is a simple isoparametric element with shear deformation only. All the essential characteristics of the hysteretic behaviour of the panel, including strength and stiffness degradation, pinching and slippage, are explicitly taken into account. The models are implemented in a general-purpose program for the inelastic time-history analysis of structures, and are used for studying the seismic behaviour of typical multistorey frames with various arrangements of infill panels, including structures with an open ground storey. The results of the analysis are in agreement with both experimentally observed behaviour and with experience regarding seismically damaged buildings.     

Simple Seismic Assessment of Traditional Unreinforced Masonry Buildings

A framework for quick seismic assessment and retrofit of traditional unreinforced masonry (URM) structures is presented. The proposed methods build on simple principles of structural dynamics and are used as an alternative to detailed time-history analysis, in recognition of the prevailing need for simple and practical methods, compatible with the low-budget and the limited level of knowledge regarding materials, internal force paths, connectivity and condition of older URM structures. An objective is to identify areas in the building that are particularly susceptible to damage and for guiding the types of the required global interventions to improve seismic response. Demand and supply are expressed in terms of relative drift ratios that quantify the intensity of out-of-plane differential translation and in-plane shear distortion of masonry walls. A characteristic traditional building type of timber-laced masonry is used as a model structure for illustration of concepts. The morphology and geometry of the building correspond to a statistical sample of the actual traditional unreinforced masonry buildings (TURM) found in historical centers of many towns in the greater region of Northern Greece. The methodology is particularly useful for setting retrofit priorities and management of the collective seismic risk of historical entities.     

A DAMAGE MODEL FOR THE ANALYSIS OF THE SEISMIC RESPONSE OF MONUMENTAL BUILDINGS

In this paper the Author proposes a damage model for the analysis of masonry plates and shells, which is based on an improvement of a previous constitutive model. The modifications introduced, connected to the head joint damage, allow us to study the influence of masonry texture on the damage modes once the mechanical characteristics of the elements constituting the masonry and the results of tests on simple assemblages are known. Having a nonlinear constitutive model is certainly one of the basic elements for understanding the damage mechanisms in masonry buildings. If, in fact, an elastic-linear constitutive model may be used under normal loading conditions, in critical situations it is necessary to model the damage and the dissipation mechanisms that occur between the elements, stone (brick) and mortar, in correlation with their characteristics and kind of masonry. To validate the model a comparison is made between the numerical and experimental results, in the case of tests available in the literature in masonry panels subjected to out-of plane loading and in a real structure through the observation of the damage in Umbria (Italy) surveyed after the 1997 earthquake.     

SEISMIC SOIL-STRUCTURE INTERACTION: BENEFICIAL OR DETRIMENTAL?

The role of soil-structure interaction (SSI) in the seismic response of structures is reex-plored using recorded motions and theoretical considerations. Firstly, the way current seismic provisions treat SSI effects is briefly discussed. The idealised design spectra of the codes along with the increased fundamental period and effective damping due to SSI lead invariably to reduced forces in the structure. Reality, however, often differs from this view. It is shown that, in certain seismic and soil environments, an increase in the fundamental natural period of a moderately flexible structure due to SSI may have a detrimental effect on the imposed seismic demand. Secondly, a widely used structural model for assessing SSI effects on inelastic bridge piers is examined. Using theoretical arguments and rigorous numerical analyses it is shown that indiscriminate use of ductility concepts and geometric relations may lead to erroneous conclusions in the assessment of seismic performance. Numerical examples are presented which highlight critical issues of the problem.     

SIMULATION OF THE CYCLIC BEHAVIOUR OF R/C RECTANGULAR HOLLOW SECTION BRIDGE PIERS VIA A DETAILED NUMERICAL MODEL

In the search for robust constitutive models suitable for reproducing the performance of bridge piers during a seismic event, this paper details the simulation of the cyclic responses of four rectangular hollow section R/C bridge piers. These four R/C bridge piers were built at scale 1/2.5 and tested experimentally. Both tall and short piers are considered, covering situations where bending or shear are of relevance. Furthermore, the four piers were reinforced according to rather different design strategies: (I) the first is a 30-year-old bridge designed without allowance to the seismic action, and (ii) the second is a bridge fulfilling the EC8 provisions. The detailed constitutive model that provides the numerical predictions includes two submodels: one with two scalar damage variables, reproducing the tensile and compressive degradations of concrete, and the other is based on the Giuffre-Menegotto-Pinto formulation, simulating the cyclic behaviour of the re-inforcement. The Damage Mechanics submodel is implemented at the Gauss points of the finite elements that discretize the concrete, whereas the steel submodel is implemented on the 2-noded truss elements adopted for the rebars. A comparison between the numerical and the experimental results is discussed in detail in this paper.