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.     

Crack Patterns Induced by Foundation Settlements: Integrated Analysis on a Renaissance Masonry Palace in Italy

This study presents some numerical results related to the analysis of the structural damage of a historic masonry building, Palazzo Gulinelli, in Ferrara, Italy. A detailed analysis of the inhomogeneities of the facade, historic documentation, and recent restoration interventions carried out in an adjacent building, suggest that the Palace underwent various modifications both on the structural configuration and on the borne loads. Such modifications might be the main cause of some differential settlements and of the consequent significant crack pattern on the load-bearing walls. Therefore, in the present paper the occurrence of a crack pattern on the facade is simulated by carrying out standard linear and non-linear finite element (FE) homogenized models; differential settlements are applied in order to reproduce the structural changes occurred over time. Previous experiences of the authors (for example, Acito and Milani in 2012 and Mallardo et al. in 2008), the current crack pattern of the building (of its facade in particular) and the monitoring data referring to some of them are the main references for the analysis carried out. The structural survey, the numerical results, and the data monitoring suggest two main conclusions: 1) a good correlation between numerical results and monitoring data is assessed, therefore the cracks can be reasonably related to past differential settlements; and 2) the cracks/damage that occurred as a consequence of differential foundation settlements reduce the ability of the facade to resist seismic actions.     

Experimental Characterization of Ancient Metal Tie-Rods in Historic Masonry Buildings

Metal tie-rods play a decisive role in the control of horizontal thrusts in historic masonry buildings. The main goal of the present study is to investigate the relationship between metallurgical and mechanical properties of original tie-rods in order to contribute to a wider study on ancient building stability and their restoration protocols. This article presents the results of an experimental test campaign carried out on 14 historic tie-rods (dating back from 16^th–19^th century) recovered from restoration works or building demolitions. Stress-strain mechanical tests showed that the elastic modulus of the material is comparable to that of modern structural steel, while the strength and the elongation capability are significantly lower, with a large scatter. Further analyses based on metallography allowed us to assess that this mechanical behavior depends on the heterogeneous nature of the material, which can eventually be compared to a composite with vitreous elongated particles in a ferritic or ferrito-pearlitic matrix. The origin of such metallurgical condition is related to the iron making based on direct smelting from ores.     

Discrete Element Modeling of Stone Masonry Walls With Varying Core Conditions: Prince of Wales Fort Case Study

The Prince of Wales Fort was constructed in the 18th century as a Vauban style stone masonry fortification where the Churchill River flows into Hudson’s Bay, across the river from Churchill, Manitoba, Canada. Since completion the fort has been exposed to harsh weather conditions, which have led to significant deterioration and deformations in the walls, with some cases of localized collapse. Recently, an increase in the rate of degradation has made preventative conservation an issue of interest. For this conservation to be possible, an understanding of the cause of failure of the walls is first required. Discrete element modeling (DEM) using the non-smooth contact dynamics (NSCD) method utilized in the Program LMGC90 has been used as a first step in understanding the failure mechanism of the wall system. The results of the modeling show that the rubble core of the walls can transition from stability to instability as the cohesion between the stones is altered. Grouting the core will alter the bond between stones, increasing the stability of the core, and is thus one possible conservation method.     

In-Plane Seismic Response Analyses of a Historical Brick Masonry Building Using Equivalent Frame and 3D FEM Modeling Approaches

ABSTRACT

This article aims at contributing to the seismic performance assessment of a historic brick masonry building by finding a strength reduction coefficient through the use of linear and nonlinear modeling approaches, using Finite Element Method and Equivalent Frame modeling. To reduce the uncertainties, ambient vibration tests (AVT) were implemented. Series of simulations was performed using nonlinear dynamic analyses and incremental dynamic analysis curves were compared with the pushover curves. Results indicate that the mass-proportional pushover curve meets the mean of results obtained from IDA and the strength reduction coefficient falls into the range given in EN 1998–1 for unreinforced masonry.     

In-Situ Destructive Testing of Ancient Strengthened Masonry Vaults

ABSTRCT

Developing suitable tools to assess the actual structural performance and designing and executing interventions to improve that performance is a key issue in the field of conservation and enhancement of architectural heritage. This article presents the results of five full-scale destructive tests performed on the Castello di San Pietro in Verona (North-East Italy), a building set on a hill above the city and going back to the 19th century under the Habsburg Empire. It evaluates the behavior of the barrel vaults of 5.6 m span, 1.1 m rise, and 27 cm thickness in the original building. Although experimental work is common in the relevant literature, the testing program described here was not performed on reconstructed vaults but on original elements, which can reveal their real behavior more clearly. Four strengthening solutions were also evaluated, in which organic and inorganic fibers were applied to both types of matrix.     

Dynamical Assessment of the Work Conditions of Reinforcement Tie-Rods in Historical Masonry Structures

Tie-rods are essential structural elements, which have been employed for centuries in masonry historical buildings, either during the construction or in successive strengthening interventions, with the aim of containing dangerous horizontal actions. The actual work conditions of these tie-rods, which are strongly influenced by their load history, are difficult to be quantified theoretically, and an effective method for their measure is of great importance in order to ensure the efficiency of these elements during the time and the stability of the entire building. Common measurements are often carried out adopting models based upon significant simplifications, like, for example, hinges at the extremities. These assumptions, rarely represent the real work conditions for anchorages. In this work, a non-destructive testing method is presented, based upon sophisticated dynamical models that can take into consideration many of the circumstances neglected by the simplified models. Four case studies are extensively described, trying to embrace the most common situations in term of peculiar features of the building, structural configuration, and load history. The discussion of the results yields the safety margin of the rod with respect to the material failure and provides important indications about the overall stability of the whole building.     

Simulation of Shake Table Tests on Out-of-Plane Masonry Buildings. Part (IV): Macro and Micro FEM Based Approaches

ABSTRACT

This article presents a study on the out-of-plane response of two masonry structures without box behavior tested in a shaking table. Two numerical approaches were defined for the evaluation, namely macro-modeling and simplified micro-modeling. As a first step of this study, static nonlinear analyses were performed for the macro models in order to assess the out-of-plane response of masonry structures due to incremental loading. For these analyses, mesh size and material model dependency was discussed. Subsequently, dynamic nonlinear analyses with time integration were carried out, aiming at evaluating the collapse mechanism and at comparing it to the experimental response. Finally, nonlinear static and dynamic analyses were also performed for the simplified micro models. It was observed that these numerical techniques correctly simulate the in-plane response. The collapse mechanism of the stone masonry model is in good agreement with the experimental response. However, there are some inconsistencies regarding the out-of-plane behavior of the brick masonry model, which required further validation.     

Simulation of Shake Table Tests on Out-of-Plane Masonry Buildings. Part (V): Discrete Element Approach

ABSTRACT

The analysis of the shaking table test of a 3-wall stone masonry structure performed with a discrete element model is presented. The numerical model, created with the code 3DEC, employed a rigid block representation and a Mohr-Coulomb joint model. Joint stiffness calibration to match the experimental natural frequencies is discussed, as well as the boundary conditions to simulate the shake table. Comparisons are made with the measured displacements at key locations, and the modes of deformation and fracture of the walls. The DEM model was able to reproduce important features of the shaking table tests. The experimental deformation and near collapse patterns were clearly identifiable in the numerical simulations, which produced displacements within the observed orders of magnitude, for the various levels of excitation.     

Salt Effects in Plastered and Unplastered Outdoors Brick Masonry: Quantitative Laser Monitoring of Surface Decay Evolution

In masonry materials, the superficial decay is a widespread problem. Aggressive environmental agents such as moisture and salts trigger the damage by propagating through the material capillary pores. Although several studies have been carried out on salt crystallization and their damaging effects, additional research effort is required to better investigate this phenomenon on real cases and real weathering conditions. To this purpose, testing and monitoring tools capable of following degradation process since the early beginning are necessary. Repeated visual inspections are commonly used to monitor the superficial decay, but this technique is subjective and thus not capable of providing any quantitative information. In this work, an experimental campaign, carried out in Bologna, Italy, is presented. A two-header brick wall, one main face unplastered and one plastered, was stored outdoors and exposed to weathering over two summers. Before the start of the second aging season, moisture and salt capillary rise was simulated by low-concentrated sodium chloride solution (0.1% -wt). The aim was to favor solution evaporation and salt crystallization and to provoke material damage. The degradation process was monitored based on a contactless, rapid and accurate image diagnostic technique. In particular, high-resolution laser scanning by triangulation technique was adopted. Three-dimensional data acquisition was repeated at the end of both seasons. The proposed procedure successfully extracted quantitative information approximately areas of material spalling and detachment even in the initial phases of decay.     

Methods and Challenges for the Seismic Assessment of Historic Masonry Structures

ABSTRACT

Despite the high vulnerability of historic structures to earthquakes, the approaches for evaluating seismic demand and capacity still appear inadequate and there is little consensus on the most appropriate assessment methods to use. To develop an improved knowledge on the seismic behavior of masonry structures and the reliability of analysis tools, two real-scale specimens were tested on a shake table, and several experts were invited to foresee failure mechanism and seismic capacity within a blind prediction test. Once unveiled, experimental results were simulated using multi-block dynamics, finite elements, or discrete elements. This article gathers the lessons learned and identifies issues requiring further attention. A combination of engineering judgment and numerical models may help to identify the collapse mechanism, which is as essential as it is challenging for the seismic assessment. To this purpose, discrete modeling approaches may lead to more reliable results than continuous ones. Even when the correct mechanism is identified, estimating the seismic capacity remains difficult, due to the complexity and randomness of the seismic response, and to the sensitivity of numerical tools to input variables. Simplified approaches based on rigid body dynamics, despite the considerable experience and engineering judgment required, provide as good results as do advanced simulations.     

A Comparative Study on the Compressive Strength of Bricks from Different Historical Periods

The aim of this article is to present the results of compressive strength tests for bricks from different historical periods. The studies were conducted on hand-molded and mechanically formed bricks. The bricks that were used for the studies came from historical structures from the center of the royal city of Crakow. Compressive strength was determined on rectangular prisms and on cylinders cut out from bricks in various directions—anisotropy and shape effects were then analyzed.

?The basic aim of the conducted studies was to estimate the possibility of carrying out the strength tests on relatively small samples and re-calculating these results on normalized brick strength determined according to EN772–1. Based on the tests results, a range of correlation coefficient values for cylinder samples with diameters of 30 mm and 50 mm was given. It was indicated that for the tested historical bricks characterized by significant material non-homogeneity within the element and sensitivity to damages while cutting out the samples, correlation coefficients are higher than for bricks used contemporarily.

?The results of these studies are presented alongside the findings from existing studies on the compressive strength of bricks.     

Analytical Investigations of Traditional Masonry Mortars from Ancient City Walls Built during Ming and Qing Dynasties in China

With the development of China’s economy, the protection and conservation of ancient buildings were put on the agenda. However, the current understandings on Chinese traditional mortars are limited and rarely reported in the literature. In this article, the authors investigate seven ancient city wall sites built during the Ming and Qing dynasties (1368–1841 AD) in situ, and subsequently the laboratory analysis were carried out on the collected mortar samples. The characterizations of mortar samples were performed using digital microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), simultaneous thermal analysis (TG-DSC), as well as wet chemical analysis. The analytical results show that pure lime mortar was widely used in construction during the Ming and Qing dynasties, and it was also a common practice adding sticky rice soup into slaked lime to form sticky-rice lime mortar during preparations. This organic-inorganic composite material could effectively improve mechanical strength of the lime mortar. Moreover, it was first found that the sticky-rice lime mortar sample from Kaifeng ancient city wall contained very fine quartz aggregates, with an approximate binder/aggregate ratio of 1:1. The appearance of this type of mortar probably indicates a great development of Chinese traditional mortars during the mid-19th century.     

Mineralogical and Mechanical Properties of Masonry and Mortars of the Lucknow Monuments Circa the 18th Century

The Lucknow monuments of the 18th century are large masonry structures built using thin burnt-clay bricks (Lakhauri) and lime-crushed brick aggregate (surkhi) mortars. Investigations were carried out to characterize the engineering properties of old masonry materials and new mortars being used for renovation work. Mechanical properties of reclaimed Lakhauri bricks were found comparable to good quality contemporary bricks of the region. Moreover, X-ray diffraction (XRD) and scanning electron microscopy–energy dispersive X-ray spectrometry (SEM-EDS) analyses indicated that mineralogical composition is not too different, except for few minerals. The lime-surkhi mortar used in old masonry work was found to be lime-rich with binder to aggregate ratio of approximately 1:2 to 3 by volume. The renovation mortar had poor hydraulic property as compared to old mortars indicated by thermal gravimetric analysis–differential thermal analysis (TGA-DTA) analyses. The compressive behavior of multi-wythe recreated Lakhauri masonry prisms was characterized with low compressive strength, low modulus, and significant deformability which result in lower stress demands imposed on the structural assemblages by various environmental forces.     

Stability of Slender Masonry Columns with Circular Cross-Section under Their Own Weight and Eccentric Vertical Load

This work concerns the stability of unreinforced masonry slender circular cross-sectional columns subjected to their own weight and eccentric vertical load. Cantilever columns are examined, considering that the material has infinitely linear elastic behavior in compression and has no tensile strength. For the analysis, an existing numerical model and solution procedure developed for the stability analysis of masonry elements with rectangular cross-section are utilized and adapted to the circular columns. For the instability of the columns, an appropriate criterion that relates the top lateral deflection to the intensity of the applied eccentric vertical load is employed. By considering a reference column, critical buckling load is obtained, behavior of the column interpreted and efficiency of the numerical model emphasized. Performing a nonlinear buckling analysis using a general purpose software on this reference column, obtained results are compared with those of the adapted procedure of the present study. Implementing parametric analyses on reference column, effects of the column slenderness, eccentricity of vertical load, elastic modulus, and self-weight on the buckling load are investigated. Presented calculation procedure provides a useful tool in order to calculate the critical loads or to check the stability of masonry circular columns.     

Methods and Approaches for Blind Test Predictions of Out-of-Plane Behavior of Masonry Walls: A Numerical Comparative Study

ABSTRACT

Earthquakes cause severe damage to masonry structures due to inertial forces acting in the normal direction to the plane of the walls. The out-of-plane behavior of masonry walls is complex and depends on several parameters, such as material and geometric properties of walls, connections between structural elements, the characteristics of the input motions, among others. Different analytical methods and advanced numerical modeling are usually used for evaluating the out-of-plane behavior of masonry structures. Furthermore, different types of structural analysis can be adopted for this complex behavior, such as limit analysis, pushover, or nonlinear dynamic analysis.

Aiming to evaluate the capabilities of different approaches to similar problems, blind predictions were made using different approaches. For this purpose, two idealized structures were tested on a shaking table and several experts on masonry structures were invited to present blind predictions on the response of the structures, aiming at evaluating the available tools for the out-of-plane assessment of masonry structures. This article presents the results of the blind test predictions and the comparison with the experimental results, namely in terms of formed collapsed mechanisms and control outputs (PGA or maximum displacements), taking into account the selected tools to perform the analysis.     

Classical Temples and Industrial Stores: Survey Analysis of Historic Unreinforced Masonry (URM) Precincts to Inform Urban Seismic Risk Mitigation

ABSTRACT

Oamaru, Winton, and Invercargill feature some of New Zealand’s most intact heritage precincts that are confronted by ongoing threats of seismic activity. The 2010/2011 Canterbury earthquake sequence and Canterbury Earthquakes Royal Commission of 2012, identified a nationwide trend through the proportion of deaths that occurred in public places as a result of the prevalent historic unreinforced masonry (URM) building stock. The reported study was undertaken to address urban safety and seismic risk mitigation through the lens of heritage conservation. The range of classically designed public buildings and industrial warehouses in the South Island of New Zealand were often produced by singular architectural practices, using locally sourced materials and construction techniques. It is vital to incorporate an examination of unique architectural qualities within urban seismic risk assessment and mitigation. Historic urban layout, architectural deployment of masonry, and extent of retrofits were recorded through onsite visual surveys via Geographical Information Systems and three-dimensional representation technologies. Extending the scope of information collected for engineering seismic risk assessment by focusing on the historical architectural context informs the selection of future mitigation measures. Oamaru, Winton, and Invercargill present intriguing case studies for multidisciplinary analysis, prior to testing urban-scale survey approaches within comparable historic centers across New Zealand.     

Paper 5: Historic Mortars from the Coudenberg Archaeological Site: Characterization and Source of Raw Materials

Abstract

The characterization of historic mortars by means of a concise methodology of material analyses can provide crucial information with regard to the origin of the raw materials and the ancient mortar technology. For the analysis of the historic mortars of the Coudenberg archaeological site, the methodology consists of optical and scanning electron microscopy, simultaneous thermal analysis, and an acidic treatment. These analyses were carried out on a total of seventeen samples lifted from various areas in the site, in function of the building chronology resulting from a historic built investigation. The type of binder and aggregate as well as their volumetric ratio were determined.

Both binder and aggregate present distinctive features, which made it possible to identify the probable geological provenance of the raw materials. The observations are verified with available historical records regarding the construction of the main banqueting hall — the Aula Magna — and the use of raw materials such as limestone and sand for the production of lime and construction purposes.     

Importance of Monitoring,Behavior Analysis,and Diagnostic Techniques for Preservation of Great Historical Structures

A synthetic overview is presented of the motivations, technological possibilities, and benefits of the practice of providing large structures with monitoring installation and interpretative activities. Starting from the large body of experience gained in the field of dam engineering, the gradual penetration of these techniques in the area of preservation of monumental building is surveyed. Particular attention is dedicated to the case of the Brunelleschi Cupola in the Florentine Cathedral of Santa Maria del Fiore. The more pressing needs for the next-future development of these studies and practices are then enunciated, with the auspice that the obstacle posed to their diffusion by the difficulty of collecting adequate financial funds may be overcome in the best interest of the conservation of a precious historical-cultural heritage.