Abstract

Seismic actions have been a great challenge for structures in the structural engineering community, and the need for further developments has been approved by catastrophic seismic events at each time. Reproducing the dynamic behavior of structures with an acceptable level of accuracy is a complex task due to uncertainties related to the geometrical, material and physical structural system, more particularly, in the case of existing historical masonry structures. The use of dynamic analysis is a better choice than the use of static or quasi-static approaches since it is a better representation of the dynamic response of a structure by taking account of its energy dissipation capacity. The scope of the present paper is focused on a seismic assessment of a historical masonry structure, Kütahya Kurşunlu Mosque located in Turkey, before and after it has been retrofitted. The historical mosque is located in a seismic prone zone where it is crucial to ensure seismic safety of structures and the local community. Based on the condition of the structure reported from the site inspections, a seismi retrofitting by using steel girder elements was implemented on the structural load-bearing walls. The effectiveness of the seismic retrofitting to the seismic response of the mosque was investigated by means of the finite element method. Three bi-directional nonlinear dynamic analyses were performed by using real ground motion records aiming at the validation of the nonlinear dynamic response of the numerical model in terms of damage patterns, and demonstration of the contribution of the seismic retrofitting by comparing the representative model with its retrofitted counterpart. The comparison has been carried out in terms of peak displacement and damage patterns. It is found that the contribution of the seismic retrofitting is considerable for the out-of-plane displacements of the load-bearing walls. Furthermore, a good correlation between existing damage and the numerical damage is achieved, and, therefore, the validation of the nonlinear response of the representative model is attained.

Abstract

Over the past few decades, the conservation and seismic assessment of historical buildings has gained great importance. In particular, the prediction of the dynamic response of masonry constructions plays a central role in retrofitting and conservation interventions. Finite element modelling has become the most common and accessible approach to study the behavior of complex masonry structures, however, the gap between numerical and experimental analysis may lead to erroneous results. This work describes the model updating procedure applied to the finite element model of San Giovanni’s church in Macerata, condemned in October 2016 after the Central Italy Earthquake. The laboratory of Proof and Research on Structures and Materials of Roma Tre University carried out an extensive in-situ testing campaign including geometric survey, video endoscopy, flat-jack test, sonic tomography and ambient vibrations test in order to investigate the state of the building. The work involved both numerical and experimental analysis: the results of the testing campaign were interpreted and correlated with an accurate finite element model developed with the software Midas Gen. Operational modal analysis was performed in order to extract the modal parameters of the building (modal frequencies, shape vectors and modal damping). Material characteristics and boundary conditions were updated according to the Douglas-Reid method. In the end, the final model was compared to the initial model to evaluate and discuss the process.

Abstract

The archaeological site of Pompeii is an extraordinary evidence of Roman architectural heritage which comprehends a large number of masonry constructions, buried after the Vesuvius eruption in 79 AD. They were discovered in the XVIII century when renewed cultural interest induced numerous archaeological excavations. In this scenario, the remains of the Roman aqueduct system, i.e. Castellum Aquae system [1], includes a series of approximately 6 m height masonry water towers (WTs). Among the fourteen surveyed, four free-standing towers (i.e. no. 1, 2, 3 and 4) have been investigated in 2015 by means of nondestructive techniques (sonic pulse velocity tests, ground penetrating radar (GPR), ambient vibration tests), aimed at gathering information on the constructive systems and the current conservation state, as well as data on the overall dynamic behaviour. According to the on-site inspections outcomes, 3D finite element models of the towers were constructed and calibrated on the results of operational modal analysis (OMA) [2]. The model updating procedure was able to describe and simulate the soil-structure interaction, introducing a Winkler elastic soil model, and to define the elastic parameters of masonry. This paper describes the seismic vulnerability assessment of the four WTs, considering both equilibrium capacity and material strength, performing analytical kinematic analyses and numerical finite element modelling. Aiming at improving the previous studies [3], equivalent modal parameters (i.e. natural frequencies and mode shapes) are used to calibrate analytical models and furtherly refine FE model updating. The numerical models were generated using DIANA software [4], implementing a nonlinear constitutive law for masonry material, i.e. total strain crack model. Afterwards, sensitivity analyses are performed to calibrate both the elastic properties of materials and the Winkler springs’ stiffness. Eventually, analytical kinematic approach and FE pushover analyses (with uniform and modal force distribution) are executed to assess the seismic vulnerability of the WTs, according to Italian code [5]. Results of the analyses are presented and discussed. The study was the occasion to compare the results of kinematic and numerical procedures applied to archaeological structures. The results report the FE approach as more conservative than kinematic model. Thus, the importance to adopt a combined global (numerical) and local (limit analysis) approach in the assessment of archaeological structures is stressed.