Structural assessment and seismic vulnerability of earthen historic structures. Application of sophisticated numerical and simple analytical models

Abstract

Adobe constructions account for a significant portion of the built heritage, associated with early building techniques, material accessibility and low-cost. Nonetheless, adobe buildings, due to their low mechanical properties and overturning resistance, are subject to early structural damage, such as cracking, separation of structural elements and, possibly, collapse in areas of high seismic hazard. The lack of maintenance and absence of adequate retrofitting techniques usually intensifies the loss of historic fabric. The current paper, aims at the structural assessment and seismic safety, in current conditions, of the Church of Kuño Tambo, a religious adobe structure of the 17 th century, in Cusco region, in Peru. The inspection and diagnosis involved sonic testing and damage mapping, while ambient vibration tests revealed the modal response of the structure. The assessment of seismic vulnerability, together with the necessity of retrofitting measures were verified through nonlinear static and pushover parametric analyses, complemented with a macro-block limit analysis and a performance based assessment, under local seismic criteria. A more realistic response from dynamically induced ground motions was performed, by a nonlinear time history analysis, according to the Eurocode 8 framework. Through an integrated approach, in situ inspection, testing, numerical and 2 analytical modelling are associated under the scope of reproducing the existing structural damage, the sequence of inelastic behavior and verification of the necessity of retrofitting measures. based approach. Short Title: Seismic vulnerability of earthen historic structures walls, out-of-plane mechanisms can involve smaller portions of the walls. The lateral resistance is related to the compressive strength of adobe masonry and to the effective compressive area of the cross-section, which counteracts the inertia destabilizing forces [Tomazevic 1999]. Thus, the compressed part of the rotation plane is often crushed under compression (toe crushing) ["OPCM 3431" 2005, "NTC" 2008]. Yet, in specific adobe historic structures, composed by walls of large width and low in height, the compressive strength is not much influencing the maximum load capacity, as shown in this work. Adobe structures have a compressive strength in the range 0.5-3 MPa, with the modulus of elasticity being usually lower than 1 GPa, thus experiencing high deformations and relatively brittle failures ["NIKER" 2010]. When box behavior is present, out-of-plane vertical cracks can still be formed, due to bending at the corners and in the middle of the walls. But, in-plane bending and mostly shear, cause horizontal, vertical and diagonal cracks. Damage mechanisms depend mainly on the geometry of the wall (height/width ratio), boundary conditions and additional vertical loading. The presence of discontinuities and openings are also influential, with shear cracks forming in the proximity of spandrel beams and at the corners of openings. In-plane damage can also be the result of interaction or...

Seismic Structural Assessment of the Christchurch Catholic Basilica, New Zealand

“…[60], [65]- [68]. Likewise, comparable failure patterns were also derived but, damage appears to be more localized in the pushover analysis and more spread in dynamic ones, see [65], [66], [68].…”

“…Focusing on the particular type of URM buildings with historical and cultural values, several works demonstrate that quasi-static approaches allow a good estimation of the lateral load capacity when compared with the results from a dynamic analysis, see e.g. [60], [65]- [68]. Likewise, comparable failure patterns were also derived but, damage appears to be more localized in the pushover analysis and more spread in dynamic ones, see [65], [66], [68].…”

Stochastic Vulnerability Assessment of Masonry Structures: Concepts, Modeling and Restoration Aspects

“…Additionally, the probabilistic nature of earthquakes, directly connected and influenced by a large number of parameters, must be taken into account. Due to the high uncertainty of the parameters influencing the behavior of masonry structures, the assessment of their vulnerability cannot be conducted in terms of a deterministic approach [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. To the contrary, a probabilistic approach would be more appropriate, in order to be applied in cases where the response of the structure is evaluated and compared with limit states, such as specific limit values of response directly interlinked with structural damages.…”

Evaluation of the Seismic Response of a Historical Earthen Structure Based on a Discrete Macro-Element Modelling Approach

“…Such behavior is related to low values of tensile and compressive strength, limited ductility, poor connection of orthogonal wall, lack of maintenance, and large inertial forces when subjected to seismic loading. In this sense, recent investigations have been conducted for the assessment of the seismic response of these type of structures by means of refined and sophisticated numerical models [9][10][11]. This papers presents the evaluation of an earthen historical construction by means of the adopted discrete macro-element modelling approach.…”