Two-storey Masonry Research Articles

Seismic Assessment and Proposal for Interventions of a Historical Masonry Building in Rhodes

The aim of this study is the seismic assessment of a historical two-storey masonry building, located in the city of Rhodes and the investigation of intervention ways to strengthen the building and improve the mechanical characteristics of its materials. The 3DR.PESSOS software was used for the simulation and analysis of the structure. For the evaluation of the seismic behaviour of the building, an elastic static analysis (lateral force analysis) was carried out based on the Greek Code for Structural Interventions of Masonry Structures. Elastic static analysis methods with global behaviour factor (q) or local ductility indices (m) were applied for performance levels B1 and B2. From the analyses and the code checks it was concluded that the building is vulnerable to in-plane and out-of-plane actions. For this reason, methods of intervention are being investigated to increase the diaphragm function of the building and to improve the mechanical characteristics of the masonry.

Analysis of two-storey masonry structure under blast loading

Analysis of two-storey masonry structure under blast loading

DETECT-AGING blind prediction contest: a benchmark for structural health monitoring of masonry buildings

The installation of monitoring systems on buildings allows analyzing variations in structural parameters over time, creating room for detection of damage. Structural Health Monitoring (SHM) systems have the potential to support pro-active risk management, where structural interventions are planned if specific thresholds related to target performance losses are achieved.DETECT-AGING is a research project of relevant national interest that was funded by the Italian Ministry of University and Research (MUR) through the PRIN 2017 programme. The project started in September 2019 and involves the universities of Bologna, Genova, Napoli Federico II, and Perugia. The main goal of the project is to develop a new analytical-instrumental approach aimed at the quantitative assessment of the effects of aging and material degradation on structural safety of cultural heritage, with special focus on masonry structures. Based on a combined use of structural models and health monitoring systems, indications and operational tools will be provided for the identification and quantification of structural damage, supporting the management of built cultural heritage. To this purpose, a two-storey masonry building, having a single room with a vault at the first floor and a timber roof, was built with the aim of being monitored and progressively and will be damaged during the project. It is equipped with a hybrid SHM system managed by the University of Perugia, which is based on both vibration and strain measurements. The present paper illustrates the main features of the case-study building and presents the results of the experimental program aimed at characterizing the mechanical properties of masonry the materials used. The final part of the paper presents a blind prediction contest based on prediction of modal features of the building in different damaged configurations.

Numerical issues on brittle shear failure of pier-wall continuous vertical joints in URM dutch buildings

Terraced houses built in the Netherland after 1980 are often characterized by the use of large units connected at corners by continuous thin layer mortar joints. Unlike the running bond pattern, usually modelled as a rigid connection, the vertical continuous connection may fail in shear and influence the global seismic capacity of the entire building. This work aims at investigating and comparing different numerical modelling approaches for simulating the vertical connections. Two different constitutive models are adopted to simulate the quasi-brittle nonlinear behaviour of the continuous joint, and their advantages and limitations are pointed out in terms of robustness and accuracy. The study considers both the component level in terms of U-shaped pier-wall configuration, and the full-scale structural level in terms of the global capacity for a two-storey masonry house assemblage, characterized by a running bond arrangement. The results of this work show that the shear failure involving the continuous joint usually reduces the strength capacity of the structure. Both the selection of constitutive models for the connection interface and masonry material are demonstrated to affect the results significantly. Decoupled direct traction-displacement relations for the interfaces appear to provide more robust results than coupled plasticity-based Coulomb friction laws. The selection of either a pre-fixed orthotropic smeared crack model for the masonry or a standard isotropic concrete-like rotating smeared crack formulation is demonstrated to strongly influence the activation of the different failure mechanisms and hence the response of the structure.

Seismic response control of low-rise unreinforced masonry building test model using low-cost and sustainable un-bonded scrap tyre isolator (U-STI)

Large stock of scrap tyres in waste disposal ground is a huge threat to the environment. In many civil engineering applications, potential of using scrap tyres have been explored in the last two decades. In this paper, effectiveness of Un-bonded Scrap Tyre Isolator (U-STI), as a seismic isolation system, has been evaluated by both experimental and numerical studies. Simple design approach of low-cost U-STI for seismic response control of the test model is outlined first. The mechanical properties of U-STI, under simultaneous action of horizontal cyclic displacement and vertical load, have been determined. Shake table testing of 1/5th scale two-storey masonry building supported on U-STIs has been carried out. Shake table testing confirmed that transmissibility of peak ground acceleration to the test model is reduced to a large extent and the peak floor accelerations are of the order of 12%–15% of the peak table accelerations, which establishes the effectiveness of the U-STI in controlling the seismic response of the test model. Results of the numerical analysis of the test model, using SAP 2000 v.19, have been validated by the experimental results. The U-STIs have been modelled using multi-linear pivot hysteretic plasticity model. Comparison of acceleration and displacement responses at various floor levels obtained from numerical analysis is done with that obtained from shake table tests. Results from the numerical tests are found to be in reasonably good agreement with those obtained from the experimental tests under the action of considered ground motions. It is concluded from the study that low-cost U-STIs are effective in reducing the seismic response of low-rise masonry building test models.

Masonry structures subjected to tsunami loads: Modeling issues and application to a case study

Tsunamis are among the most dangerous natural disasters for coastal areas experiencing tsunami hazard. One of the major concerns in the assessment of strategies for the risk mitigation is to estimate vulnerability of structures and infrastructures. However, reliable approaches for the evaluation of the structural capacity under tsunami loads are nowadays not always available for all the types of structures, especially masonry. On this aim, the paper deals with the modeling issues of 3D masonry structures subjected to tsunami loads and the effect on the structural behavior of different modeling approaches. First, a brief state of the art on the available studies is presented regarding the evaluation of tsunami forces on buildings and the studies carried out on the determination of structural capacity.Then, an advanced structural analysis software based on the Finite Element Method (FEM) is used to analyze the influence of parameters such as load type, masonry type and interaction properties type. Finally, an application on a typical two-storey masonry structure subjected to tsunami load according to the actual codes is presented and discussed, providing recommendations on the assumptions to be made for the definition of a reliable numerical model.The findings of the numerical simulations revealed that the structural response is strongly influenced by the modeling approach defined for the masonry walls in terms of interaction properties and the type of connection between orthogonal walls. Moreover, it was observed that, as for the case of seismic analysis, when local behavior governs the failure, lower structural capacity is obtained, while in the case of global behavior governing the failure, higher structural performances are provided.

Seismic behaviour of timber-laced stone masonry buildings before and after interventions: shaking table tests on a two-storey masonry model

Seismic behaviour of timber-laced stone masonry buildings before and after interventions: shaking table tests on a two-storey masonry model

Experimental Study on Seismic Failure Modes of Confined Masonry Structures with Different Enhancements

In this study, confined masonry specimens with regular arranged openings are tested in order to study the influence of different enhancements of the columns on seismic failure modes. In particular, five brick masonry walls and three half-scale two-storey masonry structures are tested under quasi-static loads. The experimental results show that increasing column ratio improves the seismic behavior of the wall specimens to some extent, but an excessive reinforcement ratio of the columns decreases the ductility. The global failure mode of the two-storey masonry structures is modified by inserting iron wires in the mortar bed joints, improving the structural collapse resistant capacity effectively.

Seismic behavior of three-leaf stone masonry buildings before and after interventions: Shaking table tests on a two-storey masonry model

The aim of this work is to reach a better understanding of the seismic behaviour of historic three-leaf stone masonry buildings with timber floors, before and after interventions. For this purpose, shaking table tests were performed on a building model (scale 1:2). Initially, the dynamic characteristics of the model were identified. Subsequently, biaxial earthquake tests were performed with the base acceleration increased step-wise until the occurrence of repairable damages. Afterwards, the masonry was strengthened by means of grouting and the diaphragm action of the floors was enhanced. Then, the strengthened model was re-tested. The comparison of the performance of the model under earthquake actions before and after strengthening shows that the selected intervention techniques significantly improved the seismic behaviour of the structure.

The importance of ambient and forced vibration measurements for the results of seismic performance assessment of buildings obtained by using a simplified non-linear procedure: case study of an old masonry building

The seismic performance assessment of existing masonry buildings involves many uncertainties, whose impact can be reduced to some extent by using non-destructive in-situ tests of such buildings, at least when destructive in-situ tests, which can provide more reliable results, cannot be performed. In this paper the extent of the potential beneficial effects achievable by calibration of a structural model of a building to its experimentally estimated vibration periods has been investigated. This was done by performing measurements of ambient and forced vibrations on an old two-storey masonry building, and by then assessing its seismic performance using a simplified nonlinear method. The results of numerical investigations revealed that the natural vibration periods of such buildings can be reproduced with sufficient accuracy, although it is possible that they will be overestimated or underestimated by analysts by up to around 40 %. This means that the accuracy of the prediction of the intermediate results of the seismic performance assessment of any particular building can be significantly increased by calibration of the structural model. Additionally, the beneficial effects of such calibration were observed even in the case of the final outcome of the nonlinear analysis, which is expressed through the near-collapse limit state capacity in terms of the peak ground acceleration.

Out-of-plane behaviour of existing stone masonry buildings: experimental evaluation

Masonry structures can be considered as the simplest type of structures concerning its assemblage but, at the same time, it is one of the most complex construction materials in terms of mechanical properties and correct behaviour assessment. In this context, the work herein presented aims at describing an experimental testing campaign recently carried out in order to characterize the out-of-plane behaviour of traditional masonry constructions. Taking advantage of the existence of a traditional two-storey masonry building abandoned after the 1998 Azores earthquake, several in-situ tests were defined and performed with the application of quasi-static cyclic loads at the building top level in the out-of-plane direction. In addition, the efficiency of retrofitting and/or strengthening techniques applied during the 1998 Azores reconstruction process was also experimentally evaluated. Finally, an overall discussion of these techniques is presented, resorting also to previous tests’ results carried out by the same authors, aiming at inferring and suggesting quantifications of strengthening techniques’ contributions for future interventions on existing buildings. For this purpose, simple analytical mechanical approaches were adopted in order to provide numerical estimates of strength that were found in good agreement with the experimental results.

Numerical Simulation of Damage of Low-Rise RC Frame Structures with Infilled Masonry Walls to Explosive Loads

Terrorist bombing attacks on civilian structures could cause catastrophic effect with loss of lives and properties. Recent published US DoD (United States Department of Defence) anti-terrorist and US DoD Explosive Safety Guidelines give safe stand-off distance for building structure protection. However, the definition of structural damage and structural types and configurations in those guidelines is vague. To have a clearer picture of structural damage, it is therefore very important to carry out further studies to define damage severity of various structures under different explosion scenarios. As blasting tests are not only very expensive, but also in many cases not possible owing to safety consideration, predictions of structural damage with reliable numerical means become very important. In this study, numerical analysis of structural response and damage to surface explosions is carried out. A one-storey and a two-storey masonry infilled RC (reinforced concrete) frame are used as examples. Nonlinear orthotropic material model is employed to model RC frames and a homogenized masonry material model is used for masonry infilled walls. Strain-rate effect on RC material properties is included in the model. The commercial software LSDYNA3D (Whirley and Englemann 1991) with user defined material model subroutines is used to perform the numerical calculations. Structural damage levels corresponding to the various stand-off distances are defined from the numerical results. The results are also compared with the stand-off distances recommended in the US DoD Anti-Terrorist and Explosive Safety Guidelines.

Dynamic response and damage analysis of masonry structures and masonry infilled RC frames to blast ground motion

This paper performs a 3-dimensional dynamic response and damage analysis of masonry and masonry infilled RC frame structures to blast induced ground excitations. A two-storey masonry structure and a two-storey masonry infilled RC frame as well as a six-storey RC frame filled with masonry wall are used as examples in the study. A previously developed 2-dimensional continuum material damage model including the orthotropic elastic properties, strength envelope and damage threshold of masonry, is extended to 3-dimensions and applied to masonry. Another 2-dimensional material damage model developed for reinforced concrete structures is also extended to 3-dimensions for modelling RC damage to high-frequency ground excitations. These material damage models are programmed into the commercial software Autodyn3D as its user subroutines to perform the analysis. Damage patterns of different structures under different ground excitations are simulated and discussed. The ductility ratios of the masonry structure and the inter-storey drift of the masonry infilled RC frames to blast excitations are also calculated. Numerical results indicate that under the same ground motion, the two-storey masonry structure suffers the most severe damage as compared to the two-storey masonry infilled RC frame. The six-storey RC frame filled with masonry wall experiences the least damage. It also shows that a structure under high frequency ground motions suffers brittle failure and its damage is governed by the force or stress rather than the inter-storey displacement or ductility. The present results further verify the conclusions drawn in the previous studies based on the 2-dimensional numerical model and scale model tests, namely, structural responses and damage to high-frequency blast ground motions are dominated by high vibration modes. Therefore displacement response-based criteria such as ductility ratios and inter-storey drifts as commonly used in earthquake engineering for assessing structural performances cannot be directly applied to structures under blast ground motions. The present numerical results are also compared with those obtained from the 2-dimensional analyses. Discussions on the adequacy of the code specified as well as the empirical allowable blast ground vibration limit to structures are also made.

Shaking table tests on 24 simple masonry buildings

The paper presents the results of a large experimental programme carried out on models, scaled 1:2, of two-storey masonry buildings. After suffering damage, the models were repaired and strengthened and tested again. A total of 24 buildings were subjected to 119 shaking-table tests, by ISMES (Italy) and LEE (Greece) facilities. The results allow to assess the efficiency of the various strengthening techniques employed and to describe the change of dynamic properties of the systems at the increase of damage. © 1998 John Wiley & Sons, Ltd.

Shaking table tests on 24 simple masonry buildings

The paper presents the results of a large experimental programme carried out on models, scaled 1:2, of two-storey masonry buildings. After suffering damage, the models were repaired and strengthened and tested again. A total of 24 buildings were subjected to 119 shaking-table tests, by ISMES (Italy) and LEE (Greece) facilities. The results allow to assess the efficiency of the various strengthening techniques employed and to describe the change of dynamic properties of the systems at the increase of damage. © 1998 John Wiley & Sons, Ltd.

A two-storey masonry wall under monotonic loading: a comparison between experimental and numerical results

A comparison between experimental and numerical results has been worked out for a brick masonry wall, which is a full scale test performed by the Operative Research Unity of the Department of Structural Mechanics of the University of Pavia (Italy); the research program has been funded by the Italian National Group for the Protection from Earthquakes. This test has been chosen because of the availability of material characteristics, crack pattern at collapse and ultimate load. The numerical simulation of the tested wall has been carried out via ANSYS code. The masonry wall has been discretized by means of an eight noded solid element and a finite element incremental analysis has been performed under in-plane monotonic loading in order to trace the crack growth and propagation, and to evaluate the ultimate load at failure. The masonry wall has been modelled by assuming the masonry material to be homogeneous and isotropic on the basis of average properties. A parametric investigation has been worked out in order to identify numerical data which allow the best fitting of experimental results.

A Two-storey Masonry Wall Under SeismicLoading: A Numerical Comparison Between SimpleAnd Strengthened Masonry

Aim of the proposed paper is to present a method for checking the efficiency of reinforcing interventions adopted in order to strengthen a two-storey masonry wall with openings, by means of numerical simulation. Seismic excitation has been represented by a displacement history used as input base motion for a test, and the masonry wall has been discretized via FEM. The dynamic analysis has been performed via ANSYS code; the masonry wall has been discretized by means of a eight noded solid element, which allows to simulate a linearly elastic-brittle behaviour of material either in tension and compression, and to trace the onset and growth of cracks (opening, closure, re-opening in the principal directions) in the check points. The failure condition is represented by a multi-mode surface. The masonry wall has ben modelled by assuming the masonry material to be homogeneous and isotropic on the basis of average properties. The seismic response of the structure under investigation has been evaluated in either cases of simple and strengthened wall, the strengthening being represented by horizontal and vertical pretcnsioned steel bars. Storey-drift and stress time-histories, and crack patterns at failure have been reported in order to evaluate the efficiency of the strengthening. Comparing time-histories and crack patterns allowed to find out the key parameters, namely tensile strength of masonry material, shear transfer coefficients across the crack face, pretension level of reinforcing bars. Furthermore, unsafely of single vertical reinforcement is exhibited. Transactions on the Built Environment vol 20, © 1996 WIT Press, www.witpress.com, ISSN 1743-3509