Residential Masonry Buildings Research Articles

Prediction of damage intensity to masonry residential buildings with convolutional neural network and support vector machine

During their life cycle, buildings are subjected to damage that reduces their performance and can pose a significant threat to structural safety. This paper presents the results of research into the creation of a model for predicting damage intensity of buildings located in mining terrains. The basis for the research was a database of technical and mining impact data for 185 masonry residential buildings. The intensity of damage to buildings was negligible and ranged from 0 to 6%. The Convolutional Neural Network (CNN) methodology was used to create the model. The Support Vector Machine (SVM) methodology, which is commonly used for analysis of this type of issue, was used for comparisons. The resulting models were evaluated by comparing parameters such as accuracy, precision, recall, and F1 score. The comparisons revealed only minor differences between the models. Despite the small range of damage intensity, the models created were able to achieve prediction results of around 80%. The SVM model had better results for training set accuracy, while the CNN model achieved higher values for F1 score and average precision for the test set. The results obtained justify the adoption of the CNN methodology as effective in the context of predicting the damage intensity of masonry residential buildings located in mining terrains.

Issues related to typological fragility curves derivation starting from observed seismic damage

In this study typological fragility curves are proposed with a macro-seismic approach. To this scope, a stock of 56.338 residential masonry buildings struck by L’Aquila 2009 seismic sequence is analyzed, whose AeDES forms are archived within Da.D.O. platform, that is a web-gis database collecting the observed seismic damage data related to buildings surveyed after several Italian earthquakes.Moreover, issues significantly influencing the fragility curves derivation are in depth discussed. In particular, a criterion for the buildings stock completion adding undamaged and not surveyed buildings is proposed, based on the distributions known of the residential building typologies. Comparisons highlight that the database completion affects the resulting fragility curves, and in particular for low damage levels. Furthermore, it is shown how the fundamental parameters estimation, by using the Maximum Likelihood Estimation (MLE) method, is conspicuously influenced by the PGA intervals number (nint), that is an issue often ignored when fragility curves are derived. The numerical investigations show that, although a non-monotonic trend is observed, the fundamental parameters tend to converge to the asymptotic values as the nint of PGA increases, and that they are markedly dispersed when nint is low.

Seismic retrofit cost model for Italian masonry residential buildings to support territorial-scale risk analysis

Over the last 50 years, earthquakes forced the Italian Government to pay emergency, recovery and reconstruction costs amounting to 180 billion euros, i.e., about 3.6 billion euros per year. These figures underline the poor seismic resilience of Italy and therefore the need for sustainable risk mitigation plans at national level.Within this context, this study aims to provide a seismic retrofit cost model for Italian unreinforced masonry (URM) residential buildings, to support territorial-scale risk analysis. To this end, well-established intervention techniques, suitable for being analyzed on a large scale, were selected. These interventions include strengthening of masonry walls, stiffening and anchoring of floors, improving the wall system connection, and their possible combinations. First, for each of the selected interventions, the related cost items (obtained via a work-breakdown-structure procedure) were identified. Second, their unit cost was either retrieved from Italian price lists or estimated according to market analysis ad hoc conducted. Third, a quantity-survey-method approach was implemented to a set of 445 URM buildings to estimate the retrofit costs per square meter (€/m2) of investigated retrofit interventions. Lastly, based on the estimated cost of retrofitting of these buildings, parametric cost models were developed to inform seismic risk analyses at various territorial scales, depending on the available building information (i.e., exposure data).The cost models here developed and proposed can be used to support the design of cost-effective seismic mitigation measures, i.e., to identify retrofit solutions that are technically effective but also economically sustainable at large territorial scale.

Study of Rapid Evaluation Method for Structural Load‐Bearing Capacity of Typical Rural Masonry Residential Buildings in Shandong Province, China

Typical rural masonry residential buildings mainly include brick–wood and brick–concrete structures, and they occupy a significant proportion among individual buildings in Shandong Province, and their structural reliability directly affects the safety of life and property. Structural load‐bearing capacity can be used for quantitative judgment of structural reliability level. For evaluating the structural load‐bearing capacity of rural masonry residential buildings rapidly, factors affecting the structural bearing capacity and positions with weak structural bearing capacity are determined by field investigation and modeling analysis with software for structural calculation. The ratio of structural resistance to action effect is taken as the evaluation index of structural bearing capacity, and the quantitative relationships between this index and the masonry compressive strength, mortar strength, window–hole ratio, and the cantilever width are established through regression analysis. The accuracy and applicability are verified by Elman neural network model as well as comparison results between rapid evaluation formula and modeling analysis. The results show that the rapid evaluation model for structural load‐bearing capacity in this paper can be used to accurately describe the relationships between the ratio of structural resistance to action effect with affecting factors, and it can play a role in screening structural monomers with irregular load‐bearing capacity in group evaluation of structural bearing capacity.

Towards a multi-parametric fragility model for Italian masonry buildings based on the informative level

This study provides a multi-parametric fragility model for Italian masonry buildings, which varies based on available information about buildings characteristics, sources from data of varying accuracy level. Three increasing levels are considered: limited, extensive, and exhaustive. These levels correspond to different degree of knowledge about the building stock, ranging from detailed in situ inspections, where a comprehensive understanding of nearly all the building features is achievable, to the case where it must necessarily rely upon a limited data (census data). This multilevel classification is established based on the number of explanatory parameters employed in defining building taxonomies. The parameters considered in this study are derived from post-earthquake damage data collected after the 2009 L'Aquila earthquake. They have undergone a thorough review and a refinement process and have been supplemented with 2001 census data to overcome the critical issue of data completeness. In addition to providing information about the geometric and typological characteristics of residential masonry buildings, the same data source also yields insights into the extent of damage sustained by these buildings. This, in turn, enables the derivation of a Damage Probability Matrix (DPM), obtained as a function on ground motion intensity values evaluated from ShakeMap of the event. The outcomes of a nonparametric statistical test, applied on DPMs, are used to drive an agglomerative clustering procedure, to establishing a hierarchical ranking of the parameters in term of their discriminatory power. The absolute (number of cases where the null testing hypothesis is rejected) and the relative (examining the test’s strength) comparison of the outcomes, allows to identify the parameters with the greatest discriminatory power. These are the one that define the branches of the taxonomies under consideration. Conversely, the less influential parameters with regard to seismic vulnerability are eligible to be grouped together, allowing the definition of a more compact taxonomy. This approach yields distinct sets of fragility curves, contingent upon the information level gained for the specific building stock being investigated, ranging from census data to comprehensive in-situ surveys. A last focus on the impact of the enhancement in the level of knowledge on seismic vulnerability is also done.

Performance based probabilistic seismic risk assessment for urban heritage. An example in Pla del Remei Area (Valencia)

The assessment of the seismic behaviour of historic residential buildings and the estimation of their possible losses in the event of an earthquake, is a must for defining strategic mitigation plans to prevent irreplaceable heritage losses. In this study an integrated performance based probabilistic risk assessment methodology is developed. An archival study and a field survey allow to identify architectural and construction characteristics of heritage residential buildings in urban areas and determine realistic structural models. These are analysed by using a limit state approach, coded in the FaMIVE method, considering different construction hypotheses, to produce capacity curves which support the identification of a discrete number of typologies representative of the entire building stock in the area. Their fragility functions are then derived using the modified N2 method. Because of the difficulty in quantifying the expected probable losses in purely economic terms, given the heritage value of these assets, losses are computed in terms of damaged floor surface area and mean damage ratio. These have been obtained through the earthquake loss estimation platform SELENA, considering different possible seismic scenarios. The procedure is applied to masonry residential buildings in Pla del Remei area of Valencia, Spain, built between the end of the 19th Century and the end of the Spanish War (1939). This neighbourhood embodies the cultural values, construction techniques and historic legacy of a new and brief era of modernity, inspired by the new urban theories and architectural styles of Eclecticism and Modernism. Despite Valencia being located in an area of low to moderate seismicity, the results show that the maximum percentage of built damaged area ranges from 5.8 to 11.6% for 475 years return period, increasing to 33.59–51.59% for 975 years return period. The high level of resolution of the study allows mapping and identifying the structures at higher risk and is therefore a valuable tool to support sensitive and targeted retrofitting policies.

Experimental study on using steel wires via the NSM method to improve the behaviour of masonry panels

The use of masonry materials in load-bearing walls has a history of centuries. Many efforts have been made to overcome their poor structural strength; one such solution is the near-surface mounted method. In the present study, steel wires 2.5 mm in diameter were used as reinforcement in the near-surface mounted method to strengthen masonry walls. Compared to rival materials, steel wires enjoy such advantages as small dimensions, eliminating buckling damage, lower cost, and ease of installation. The objective of the study was to determine the feasibility of using wires in the near-surface mounted method and to identify the best wire arrangement. For the purposes of, eight masonry wall panels of 920 × 920 × 100 mm were constructed to investigate the effects of different steel wire arrangements on such panel properties as strength, load-bearing capacity, and wall pseudo-ductility. The results showed that steel wires placed along the wall in the diagonal direction had the best effects on improving the performance of the masonry wall panels. Experimental results confirmed the desirable effects of the steel wire in the near-surface mounted method. This is evidenced by a 21-fold increase in Load-bearing capacity, a 52-fold increase in energy dissipation, and a 17-time rise in shear modulus as a result of using the wires. The near-surface mounted method is an appropriate method to reduce damage to residential masonry buildings and to safeguard historical and cultural heritage monuments.

Effect of retrofit interventions on seismic fragility of Italian residential masonry buildings

In this paper, the vulnerability of ordinary unreinforced masonry (URM) buildings is analyzed, and the literature related to possible seismic retrofit interventions is reviewed in order to investigate their feasibility and effectiveness. These interventions are then simulated on a database of 445 buildings through Vulnus_4.0 software, that performs simplified mechanical analyses accounting for both global and local behavior of masonry buildings. The fragility of each building is assessed both in its as-built state and after the simulation of retrofit interventions. Fragility curves are then processed, and a fragility model for four building typologies is obtained for the as-built and the seismic retrofitted configurations. Lastly, mean damage maps are elaborated, and the performance of the proposed retrofit interventions is analyzed. The results of this work allow evaluating and comparing the improvement of seismic behavior brought by various retrofit interventions and could serve as a basis for further theoretical studies and for practical design in real cases.

Seismic Retrofitting of Mid-Rise Unreinforced Masonry Residential Buildings after the 2010 Kraljevo, Serbia Earthquake: A Case Study

There is a significant building stock of post-WWII low- and mid-rise unreinforced masonry (URM) buildings in Serbia and the region (former Yugoslavia). Numerous buildings of this typology collapsed due to the devastating 1963 Skopje, Yugoslavia earthquake, causing fatalities, injuries, and property losses, as well as experienced damage in a few recent earthquakes in the region, including the 2010 Kraljevo, Serbia earthquake (MW 5.5) and the 2020 Petrinja, Croatia earthquake (M 6.4). These buildings are three- to five-stories high, have clay brick masonry walls, and rigid floor slabs, usually with an RC ring beam at each floor level. This paper presents a case study of a URM building which was damaged due to the 2010 Kraljevo earthquake and subsequently retrofitted. A comparison of seismic analysis results, including the capacity/demand ratio and displacement/drift values, for the original and retrofitted building according to the seismic design and retrofit codes which were followed in Serbia as well as some of the neighboring countries for several decades and Eurocode 8 has been presented. The results of this study show that the selected retrofit solution that satisfied the Yugoslav seismic code requirements is not adequate according to the Eurocode 8, primarily due to significantly higher seismic demand.

Seismic Vulnerability Assessment of Masonry Residential Buildings in the Older Parts of Tehran through Fragility Curves and Basic RVS Scores

The present study aims to determine the Rapid Visual Screening (RVS) basic scores for four representative Unreinforced Masonry (URM) and their corresponding Confined Masonry (CM) buildings. Two types of analysis were carried out on the finite element models: modal and push-over analysis. It was observed that confining URM walls with horizontal and vertical RC ties leads to a significant improvement in both the ultimate strength and ductility ratio of URM buildings. The natural frequency and strength of the studied buildings were strongly influenced by the walls’ relative area. The push-over-based fragility curves indicate that there is an average of 100% increase in the spectral acceleration related to the 50% exceedance probability of the CP performance level of CM buildings compared to their corresponding URM buildings. Moreover, the average resulted RVS basic score of CM buildings was 45% higher compared to those of their corresponding URM buildings and their sensitivity to the higher seismicity of the region was lower, thus greatly reducing the vulnerability of masonry buildings.

Effectiveness of seismic mitigation strategies for the Italian masonry building heritage

The seismic events that struck Italy in the last decades have highlighted the high seismic vulnerability of the built heritage. It is therefore of utmost importance to plan and prioritize mitigation strategies that can effectively reduce the amount of economic losses and the number of casualties produced by earthquakes.This work focuses on the definition of vulnerability for Italian residential masonry buildings. Fragility curves are elaborated for a database of 445 buildings through the software Vulnus 4.0, both for the as-built configuration and different intervention solutions. These vulnerability models are then combined with hazard and exposure data within the IRMA platform (Italian Risk MAps) to elaborate seismic risk maps for Italy, which show the possible losses for different return periods and time windows. By comparing the results provided by IRMA for the as-built configuration and the retrofit cases, it is possible to quantify the effectiveness of different mitigation strategies in terms of vulnerability reduction.

Fragility curves derivation for masonry buildings damaged after 2009 L'Aquila earthquake accounting for the effect of construction age

The aim of this study is the analysis of seismic fragility of residential masonry buildings, with particular emphasis to the evolution of seismic behaviour over the years. To this purpose, a detailed and comprehensive taxonomy has been established, considering a restricted selection of building's features, avoiding the ineffective fragmentation of the database. The fragility assessment has been performed based on the data collected after the L'Aquila 2009 earthquake and made available by the Italian Department of Civil Protection through the online platform Da.D.O. (Database of Observed Damage). The database has undergone a refinement process to guarantee the completeness of the information, avoiding possible bias in the subsequent fitting procedure for fragility analysis. Thus, PGA (peak ground acceleration) from the ShakeMap has been used for ground motion characterization and 5 + 1 damage levels defined according to the European Macroseismic Scale have been considered for damage classification. Different regression models have been adopted to determine the parameters of lognormal fragility curves, measuring their goodness of fit with the observed damage probability matrices.Starting from the unconstrained model, further regression constraints (i.e., a common value for logarithmic standard deviation and the respect of the hierarchy of median PGA with the construction age) have been introduced, thus leading to the definition of the constrained model. The benefits in the introduction of further regression constraints are counterposed to the effectiveness of constrained curves to model observational data through the comparison of the goodness of fit between the unconstrained and constrained models.

A hybrid approach for the seismic vulnerability assessment of the modern residential masonry buildings

In this paper a hybrid approach for the seismic vulnerability assessment of the existing modern masonry buildings is developed. The procedure takes advantage of the standardized designs and technological features of the XX century masonry structures to define a hybrid framework constituted by two different phases: an urban scale one and one at the building level. The methodology is applied at the external outskirt of the city of Florence, where the residential stock is characterized by a significant number of masonry constructions. At the urban level a cognitive research based on archive research and data collection allowed the identification of the architectural and structural features of modern masonry buildings. Then, a selected case study representative of a wider class is chosen for a probabilistic procedure based on nonlinear static analysis and targeted at the derivation of fragility curves. The analytical results have been assumed to calibrate a simplified procedure available in literature and targeted at the definition of bilinear capacity curves. The calibration of the different coefficients was conducted in terms of generic outcomes, defining correlations within architectural elements and their seismic behavior (facades, side walls). The rapid methodology has been finally implemented at the urban scale, and the results of the work exhibit a relevant vulnerability of existing buildings. The simplified methodology overcomes the limits of the empirical methodologies at the urban scale constituting a valid tool for the rapid seismic vulnerability assessment at urban scales of the modern masonry structures of different contexts.

Development of expeditious methods for seismic assessment of pre‐code masonry buildings in Portugal

AbstractAlthough Portugal has not been hit by high‐magnitude earthquakes in recent years, its history is marked by tragic seismic events and it remains susceptible due to its geographical location. The Portuguese building stock is constituted approximately by 45% masonry residential buildings and most were built before the enforcement of the first seismic code in 1958. For several years, structural interventions in these buildings were allowed without the need to assess their seismic vulnerability. In 2019, a new law was approved to regulate the rehabilitation interventions to provide safety and comfort of existing buildings. The seismic assessment of existing buildings became mandatory and based on the procedures and requirements included in NP EN 1998–3: 2017 (Portuguese version of Eurocode 8 – part 3), which establishes the performance requirements and compliance criteria for existing buildings subjected to a certain level of seismic action. According to this normative requirements, analytical seismic vulnerability assessment and reliability‐based analyses were carried out on a large set of masonry buildings representative of the Portuguese housing stock, leading to the development of surrogate and expeditious method for seismic assessment in compliance with the reference method defined in the European standard. The method allows the seismic assessment of masonry buildings with rigid and flexible floors, without explicit numerical analyses, using only geometric parameters and the material properties. Compliance of results assessed by the proposed method and the corresponding values obtained by the code were carried out by confidence tests.

Effect of Retrofit Interventions on Seismic Fragility of Italian Residential Masonry Buildings

Effect of Retrofit Interventions on Seismic Fragility of Italian Residential Masonry Buildings

Analysis of Tram Traffic-Induced Vibration Influence on Earthquake Damaged Buildings

The Zagreb 2020 earthquake severely damaged the historic centre of the city. Most of the damage occurred on historic masonry residential buildings, many of which are situated very close to the tram track. Although traffic-induced vibrations generally do not affect surrounding buildings, they can be harmful to buildings damaged by a previous earthquake. Vibrations could contribute to the further propagation of existing cracks. The effect of vibrations depends on many factors, one of the most important being the distance between the track and the building. The vibrations are highest at the source, and the energy loss occurs due to transfer through the soil to the recipients. The impact of tram-induced vibrations on earthquake-damaged buildings in the city of Zagreb is investigated in this paper. The analysis is conducted on a tramway network scale to identify critical locations by performing continuous monitoring on the tramway network and risk analysis based on the distance of buildings from the track, vibration amplitude at source, and building damage. Further investigation is based on the level of buildings to evaluate the influence of vibrations on actual buildings damaged in the Zagreb earthquake. Based on detailed signal analysis, the vibration characterization is performed, and the influence on damaged masonry buildings is evaluated.

Bi‐directional collapse fragility assessment by DFEM of unreinforced masonry buildings with openings and different confinement configurations

AbstractUnreinforced masonry (URM) buildings that are characterized by brittle, heterogeneous, and anisotropic responses have complex nonlinear dynamic behavior and high vulnerability under seismic loading. While masonry confined by tie‐columns and lintel beams can achieve better ductility and stability, the wall openings induce stress concentration around the corners and diminish the strength. Furthermore, the interacting in‐plane and out‐of‐plane responses of masonry walls could significantly affect the post‐cracking behavior and increase the collapse risk. To attain reliable seismic design of confined masonry buildings with openings, the collapse fragility under bi‐directional seismic loading shall be addressed and thoroughly investigated in this study. Advanced discrete finite element models (DFEM) with coupled damage‐plasticity traction‐separation law, which can simulate complex nonlinear dynamic behavior such as disintegration and progressive collapse, were developed for the masonry structures and validated against experimental results. Four one‐storey residential masonry buildings: (1) unconfined (UCM), (2) confined by tie‐columns at four building corners (CM‐I), (3) confined by toothed tie‐columns (CM‐II), and (4) confined by toothed tie‐columns and lintel beams (CM‐III) were considered. A series of incremental dynamic analyses (IDA) with 15 bi‐directional ground motions and fragility analyses were performed to investigate the dynamic characteristics, base shear, hysteresis behavior, failure mechanism, collapse probability, and exceedance probability for different drift limits were studied in‐depth. CM‐II with toothed tie‐columns had the lowest collapse probability and fragility at different drift limit states. The introduction of lintel beams to CM‐III lead to an increase of the storey‐drift‐based fragility compared to CM‐II, as a result of the increased maximum base shear of CM‐III with higher post‐damage stiffness. The lintel beams also inflicted short‐column effects on the tie‐columns. Nevertheless, the lintel beams could delay the out‐of‐plane collapse of the masonry walls by shortening the effective wall arching length. In some cases, the CM‐III could achieve better performances than CM‐II even in terms of storey drifts. The response variations of CM‐III to the changing of the non‐intensity related ground motion parameters are also lower than CM‐II.

Intervention Strategies for the Seismic Improvement of Masonry Buildings Based on FME Validation: The Case of a Terraced Building Struck by the 2016 Central Italy Earthquake

Residential masonry buildings represent a large stock among highly vulnerable structures in medium–high seismic hazard areas, often built without any anti-seismic provisions. Their rehabilitation and/or strengthening according to optimised intervention strategies is topical and may contribute to revaluating zones characterized by depopulation phenomena. In this paper, a terraced building struck by the 2016 Central Italy earthquake is analysed through a frame by macro element (FME) model. The building is composed of six two-storey units made of stone and clay block masonry walls and semi-rigid diaphragms. The numerical model was calibrated based on the damage pattern caused by the earthquake and then used to carry out parametric analyses on the strengthened conditions by simulating both one unit and the entire terrace. The effects of interventions applied to either vertical or horizontal components, both singularly and in combination, were analysed in terms of nonlinear static analyses, and quantified by a performance factor, according to the upgraded seismic code in Italy. Kinematic analyses also completed the assessment of the building. Results compared the capacity of interventions in attaining the targets defined for improvement at both local and overall levels.

Simplified Seismic Assessment of Unreinforced Masonry Residential Buildings in the Balkans: The Case of Serbia

The paper presents a study on the existing low-rise unreinforced masonry (URM) buildings constructed in the period from 1945 to 1980 in Serbia and neighbouring countries in the Balkans. Buildings of this typology experienced damage in a few earthquakes in the region, including the 2010 Kraljevo, Serbia earthquake and the 2020 Petrinja, Croatia earthquake. The focus of the study is a seismic design approach for Simple masonry buildings according to Eurocode 8, Part 1, which is based on the minimum requirements for the total wall area relative to the floor plan area, which is referred to as Wall Index (WI) in this paper. Although the intention of Eurocode 8 is to use WI for design of new buildings, the authors believe that it could be also used for seismic assessment of existing masonry buildings in pre- and post-earthquake situations. A study on 23 URM buildings damaged in the 2010 Kraljevo, Serbia earthquake has been presented to examine a relationship between the WI and the extent of earthquake damage. Seismic evaluation of a typical 3-storey URM building damaged in the 2010 earthquake was performed according to the requirements of seismic design codes from the former Yugoslavia and Eurocode 8.

Numerical analysis of the influence of mining ground deformation on the structure of a masonry residential building

Numerical analysis of the influence of mining ground deformation on the structure of a masonry residential building