Comparative analysis on the seismic behaviour of unreinforced masonry buildings with flexible diaphragms

2014 ◽  
Vol 61 ◽  
pp. 195-208 ◽  
Author(s):  
Michele Betti ◽  
Luciano Galano ◽  
Andrea Vignoli
Keyword(s):  
Comparative Analysis ◽  
Unreinforced Masonry ◽  
Masonry Buildings ◽  
Seismic Behaviour ◽  
Flexible Diaphragms

scholarly journals Numerical Simulation of Unreinforced Masonry Buildings with Timber Diaphragms

Buildings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 205
Author(s):  
Igor Tomić ◽  
Francesco Vanin ◽  
Ivana Božulić ◽  
Katrin Beyer
Keyword(s):  
Failure Modes ◽  
Unreinforced Masonry ◽  
Masonry Walls ◽  
Masonry Buildings ◽  
Seismic Behaviour ◽  
Plane Failure ◽  
Friction Resistance ◽  
Flexible Diaphragms ◽  
Out Of Plane ◽  
Equivalent Frame

Though flexible diaphragms play a role in the seismic behaviour of unreinforced masonry buildings, the effect of the connections between floors and walls is rarely discussed or explicitly modelled when simulating the response of such buildings. These flexible diaphragms are most commonly timber floors made of planks and beams, which are supported on recesses in the masonry walls and can slide when the friction resistance is reached. Using equivalent frame models, we capture the effects of both the diaphragm stiffness and the finite strength of wall-to-diaphragm connections on the seismic behaviour of unreinforced masonry buildings. To do this, we use a newly developed macro-element able to simulate both in-plane and out-of-plane behaviour of the masonry walls and non-linear springs to simulate wall-to-wall and wall-to-diaphragm connections. As an unretrofitted case study, we model a building on a shake table, which developed large in-plane and out-of-plane displacements. We then simulate three retrofit interventions: Retrofitted diaphragms, connections, and diaphragms and connections. We show that strengthening the diaphragm alone is ineffective when the friction capacity of the wall-to-diaphragm connection is exceeded. This also means that modelling an unstrengthened wall-to-diaphragm connection as having infinite stiffness and strength leads to unrealistic box-type behaviour. This is particularly important if the equivalent frame model should capture both global in-plane and local out-of-plane failure modes.

scholarly journals Applicability of nonlinear static procedures for low-rise unreinforced masonry buildings with flexible diaphragms

2017 ◽  
Vol 137 ◽  
pp. 1-18 ◽  
Author(s):  
Yasuto Nakamura ◽  
Hossein Derakhshan ◽  
Michael C. Griffith ◽  
Guido Magenes ◽  
Abdul H. Sheikh
Keyword(s):  
Unreinforced Masonry ◽  
Masonry Buildings ◽  
Flexible Diaphragms ◽  
Nonlinear Static

scholarly journals Seismic analysis of in-plane loaded walls in unreinforced masonry buildings with flexible diaphragms

2014 ◽  
Vol 47 (4) ◽  
pp. 275-289
Author(s):  
Yasuto Nakamura ◽  
Hossein Derakhshan ◽  
Jason M. Ingham ◽  
Michael C. Griffith
Keyword(s):  
Seismic Analysis ◽  
Unreinforced Masonry ◽  
Mode Analysis ◽  
Analysis Approach ◽  
Masonry Buildings ◽  
Alternative Analysis ◽  
Response Modification Factor ◽  
Seismic Demands ◽  
Flexible Diaphragms ◽  
Modification Factor

It is well recognised that the dynamic response of unreinforced masonry buildings with flexible timber diaphragms typically contains multiple dominant modes associated with the excitations of the diaphragms and the in-plane walls. Existing linear analysis methods for this type of structure commonly account for the multi-mode behaviour by assuming the independent vibrations of the in-plane loaded walls (in-plane walls) and the diaphragms. Specifically, the in-plane walls are considered to be rigid and the unmodified ground motion is assumed to be transmitted up the walls to the diaphragm ends. While this assumption may be appropriate for many low-rise unreinforced masonry buildings, neglecting the dynamic interaction between the diaphragms and the in-plane walls can lead to unreliable predictions of seismic demands. An alternative analysis approach is proposed in this paper, based on the mode properties of a system in which (1) the mass ratios between the diaphragms and the in-plane wall are the same at all levels, and (2) the periods of the diaphragms are the same at all levels. It is proposed that under these conditions, two modes are typically sufficient to obtain the peak seismic demands of the in-plane walls in elastically responding low-rise regular buildings. The applicability of the two-mode analysis approach is assessed for more general diaphragm configurations by sensitivity analysis, and the limitations are identified. The two-mode approach is then used to derive a response modification factor, which may be used in conjunction with a linear static procedure in the seismic assessment of buildings with flexible diaphragms.

Seismic evaluation of unreinforced masonry buildings — a state-of-the-art report

1994 ◽  
Vol 21 (3) ◽  
pp. 512-539 ◽  
Author(s):  
Michel Bruneau
Keyword(s):  
State Of The Art ◽  
Unreinforced Masonry ◽  
Theoretical Background ◽  
Analytical Models ◽  
Specific Method ◽  
Masonry Buildings ◽  
Seismic Evaluation ◽  
Seismic Behaviour ◽  
Practical Applications ◽  
Research Activities

The potential vulnerability of old unreinforced masonry buildings, designed with little or no consideration for seismic-design requirements, is well documented. In regions without seismic retrofit ordinances prescribing a specific method to evaluate existing unreinforced masonry buildings, engineers have generally resorted to either conservative methods or various advanced analytical models. Although some approaches have received broader acceptance than others, there is still no consensus among practising engineers in North America. To provide perspective on the spectrum of strategies available and a clear overview of the state-of-the-art on this topic, this paper (i) presents the theoretical background and practical applications of a new procedure to evaluate unreinforced masonry bearing wall buildings, developed in California and recently integrated into the new Canadian Guidelines for the Seismic Evaluation of Existing Buildings, and (ii) summarizes the findings from other recent experimental and analytical research activities on the seismic behaviour of unreinforced masonry buildings, and from advances in their modelling. Key words: unreinforced masonry, masonry, earthquake, seismic response, state-of-the-art, evaluation, rehabilitation, analysis, models, buildings.

scholarly journals Fragility curves for Italian URM buildings based on a hybrid method

2021 ◽  
Author(s):  
A. Sandoli ◽  
G. P. Lignola ◽  
B. Calderoni ◽  
A. Prota
Keyword(s):  
Seismic Vulnerability ◽  
Fragility Curves ◽  
Limit State ◽  
Ultimate Limit State ◽  
Masonry Building ◽  
Masonry Buildings ◽  
Seismic Behaviour ◽  
Building Stock ◽  
Ground Acceleration ◽  
Damage Scenario

AbstractA hybrid seismic fragility model for territorial-scale seismic vulnerability assessment of masonry buildings is developed and presented in this paper. The method combines expert-judgment and mechanical approaches to derive typological fragility curves for Italian residential masonry building stock. The first classifies Italian masonry buildings in five different typological classes as function of age of construction, structural typology, and seismic behaviour and damaging of buildings observed following the most severe earthquakes occurred in Italy. The second, based on numerical analyses results conducted on building prototypes, provides all the parameters necessary for developing fragility functions. Peak-Ground Acceleration (PGA) at Ultimate Limit State attainable by each building’s class has been chosen as an Intensity Measure to represent fragility curves: three types of curve have been developed, each referred to mean, maximum and minimum value of PGAs defined for each building class. To represent the expected damage scenario for increasing earthquake intensities, a correlation between PGAs and Mercalli-Cancani-Sieber macroseismic intensity scale has been used and the corresponding fragility curves developed. Results show that the proposed building’s classes are representative of the Italian masonry building stock and that fragility curves are effective for predicting both seismic vulnerability and expected damage scenarios for seismic-prone areas. Finally, the fragility curves have been compared with empirical curves obtained through a macroseismic approach on Italian masonry buildings available in literature, underlining the differences between the methods.

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