Advanced Materials Research Vols. 133-134

Abstract: This paper presents an investigation about the capabilities of simplified kinematic limit analysis for the safety evaluation and for the design of strengthening of masonry historical buildings. Limit analysis allows, with a reduced number of mechanical properties and for a given ultimate condition of the structure, affordable safety analysis and design of strengthening to the practitioners. Masonry buildings subjected to earthquake show in most cases local failure mechanisms rather than global failure mechanisms due to the lack of integrity of structure. For this reason, simplified kinematic limit analysis has been accepted as a method to design the strengthening of masonry buildings, according to the Italian Ordinance (O.P.C.M. 3431). To validate the applicability of this method, its results had been compared with those provided by three dimensional macro block limit analysis (Bustamante, 2003) for the Via Arizzi house. It is worth noting that results of simplified kinematic limit analysis provided similar results as those achieved by 3D macro block. Also this method was implemented to seismic safety assessment of Tekyeh Amir Chakhmagh in Iran based on the results obtained for the out of plane and in plane behaviour of walls. Tekyeh Amir Chakhmagh is an early 19th century tiled edifice that was built to serve as grand-stand for watching religious rites and also provided an imposing entrance to Amir Chakhmagh bazaar. This stunning three-story facade of the building is one of the most recognizable and unusual buildings in Iran.

Abstract: Given the particular difficulty in classifying and defining the characteristics of the structural systems of historical buildings, especially when they are part of complex historical constructions, the vulnerability study efforts becomes significantly more difficult than the study of regular modern structural systems. Furthermore, old buildings may have been altered repeatedly over time, may be founded on older buildings that got buried over and could be connected one to the others. This will cause dynamic interactions with other buildings or sub-structures during an earthquake. Therefore, the particular architectural and structural history of each structure adds uncertainties in the assessment of its seismic vulnerability. In this paper the dynamic response of CEDRAV building, part of the historical centre of Cerreto di Spoleto (Italy), is analyzed, by means of the data recorded by several temporary deployments of velocimeters. The complexity in assessing seismic behavior of the historical built environments is pointed out and so the dynamic interaction with adjacent buildings.

Abstract: The Pisco earthquake of August 15, 2007 resulted in 519 deaths and 1366 injured, with a total of 650,000 people affected and 80,000 dwellings damaged. Preliminary reports indicated that significant earthen sites were damaged. A few months after the earthquake a rapid assessment to better understand the failure of the affected sites was performed by a multidisciplinary team convened by the Getty Conservation Institute (GCI) in response to a request from the Instituto Nacional de Cultura del Perú (INC). This paper presents the highlights of that evaluation and its implications for the future design and retrofit of earthen buildings.

Abstract: Unreinforced stone masonry is common in heritage structures worldwide. Unfortunately, these structures are susceptible to failure or severe damage when subject to dynamic or seismic loading. Conservation of historic structures is a challenge as the heritage and cultural values need to be preserved while the advent of new seismic codes may require major strengthening to be implemented. The new seismic codes demand high seismic strength and ductility for such structures, whereas neither the strength nor the ductility of an existing stone masonry building can be quantified easily. The Parliament buildings of Canada fall into this category. Therefore, an extensive experimental program was carried out to investigate the dynamic and seismic behaviours of stone walls representative of Canada’s Parliament buildings. The walls were constructed of double stone wythes with the cavity between being filled with weak mortar, shards and small stones, constituting a rubble core of the walls. The experimental program included in-plane quasi-static, free vibration and high frequency loadings, together with out-of-plane shake table tests. The tests were aimed at investigating the integrity, strength, damping, stiffness degradation, and ductility of the walls. Different potential strengthening methods were assessed, methods that would minimize structural intervention and preserve the heritage values of the building. The methods involved different metallic anchors and traditional stone interlocking to tie the two outer wythes together. Fortunately, the stone walls exhibited satisfactory performance in all cases. In addition, the test results suggested that plain un-strengthened stone walls had strength and other characteristics similar to those of the rehabilitated walls, in the range of the imposed load scenarios.

Abstract: The limitation of intervention in historical buildings is one of the basic challenges for choosing a strengthening method. Base isolation is one of the best methods which can satisfy such limitations. Although there is a probability to reduce base shear and have negligible drift by base isolating, but it is very important to make sure that the integrity of superstructure reliably stands against the induced acceleration. Lack of integrity leads to local failure mechanisms rather than global failure mechanisms in masonry buildings. For this reason, simplified kinematic limit analysis has been selected as a method in earthquake safety assessment. This paper presents an investigation about the capabilities of simplified kinematic limit analysis as a complementary method, for the seismic safety evaluation of the superstructure of a base isolated masonry historical construction. This method has been applied on the “Naghareh Khaneh” edifice. The Naghareh Khaneh is a masonry historical building in Iran which was constructed around 400 years ago. The main body of this study focuses on the vulnerability assessment of the superstructure after using isolators on the base and the efficiency of simplified kinematic limit analysis will be discussed which shall be based on the results obtained from the out of plane and in plane behaviour of walls after installing isolators and dampers on the base of the Naghareh Khaneh structure.

Abstract: With the main objective of providing basic information for calibration of analytical models and procedures for determining seismic response of historic stone masonry buildings, a shaking table testing program was undertaken at the Institute of Engineering of UNAM. A typical colonial temple was chosen as a prototype. The model was built at a 1:8 geometric scale. Increasing levels of seismic intensities were applied to the table. Main features of the measured response are compared in this paper to those computed though a nonlinear, finite element model; for the latter, a constitutive law corresponding to plain concrete was adopted for reproducing cracking and crushing of the irregular stone masonry, which could be considered as a conglomerate with low anisotropy. From the results of the analytical models, it was found that response is strongly governed by damping coefficient and tensile strength of masonry. Measured damping coefficients were found to significantly exceed those commonly used for modern structures. Observed damage patterns as well as measured response could be reproduced with a reasonable accuracy by the analytical simulation, except for some local vibrations, as those at the top of the bell towers.

Abstract: The scope of this paper is to illustrate a strategy for assessing the seismic performance of medieval city walls with emphasis on the Byzantine Walls of the city of Thessaloniki. Despite the relatively simple structural system of such structures, their response under earthquake excitation in 3D space and in the time domain, has not yet been adequately studied primarily due to the lack of efficient numerical tools, the high computational cost associated and the uncertainty related to the spatial variation of material properties and seismic input motion characteristics. Nowadays, the advances in scientific knowledge and the increase in computational power, the ability to efficiently conduct sensitivity analyses and the deeper knowledge of earthquake engineering aspects, provides the opportunity for a more refined simulation and study; however, such approach still remains heavy enough and as such, unsuitable for all practical purposes. Along these lines, a comprehensive computational framework is established and presented herein that aims at quantifying the relative importance of the uncertainty associated with modeling parameters, structural and soil material properties, as well as the earthquake ground motion selection process and application assumptions, the latter refering to the consideration of different angles of incidence of the incoming seismic wavefield and the spatially variable nature of ground motion that excites asynchronously the particularly long historic structures. It is foressen that this detailed 3D dynamic analysis will assist in identifing the relative impact of earthquake characteristics and material properties, permit justified simplifications and facilitate the overall process undertaken by the authors to assess the seismic history of the city of Thessaloniki through a set of detailed back analyses of well-selected parts of the extended wall cirquit.

Abstract: In this paper, we purpose to assess the crack and deterioration level of composed stones in Angkor Monument, Cambodia, by an elastic wave test. The degree of deterioration and crack is generally examined by supersonic wave test, electromagnetic wave test and hardness test. However, the above general methods are difficult to be applied to the stones in Angkor Monument, because there are some problems such as damages on the surface relief and an accuracy of the test results which highly depend on the surface deterioration level. Therefore, in this paper, we suggest the method of an elastic wave test by slightly knocking on the stones. Then, we analyze the elastic wave’s profile, such as velocity, amplitude ratio and frequency etc. From the results, we examine about the relationship between the elastic wave profile and existence of crack or deterioration level of stone. The above examinations are applied to assess the structural safety of composed stones in Angkor Monument.

Abstract: The objective of this paper is to provide basic information on structural behavior of Korea traditional wooden frames under earthquake loading. One of prototype wooden frames for this study was chosen from a designated national treasure in Korea. A series of experimental work were prepared to investigate the behavior and hysteresis characteristics of traditional wooden frames under cyclic lateral loading. Three test specimens of a full scale were performed for cyclic hysteretic behaviors based on one static test specimen as a pilot test. The experimental observation showed stiffness degradations and slips after experiencing initial yield point and the first cycle at a new larger displacement due to inherent gaps in connections between columns and connection parts of beams and a gradual indentation of interfaces under pull and push. Addition of structural components such as an upper beam and clay-filled wall to the basic beam and columns increased the initial stiffness, strength and energy dissipation than those of basic frames. The behaviors of the wooden frames were simulated by DRAIN-2DX program for the dynamic analysis of an entire wooden frame system. Comparison between analysis models and the experimental behaviors showed that the behavior of wooden frames under consideration could be represented by a combination of link and truss elements. The maximum response of a wooden frame system under three earthquakes showed a safe behavior for a potential earthquake.

Abstract: The paper presents the experimental modal analysis recently carried out on the historic iron bridge at Paderno d’Adda (1889). The dynamic tests were performed in operational conditions (i.e. under traffic and wind-induced excitation) between June and October 2009 and different output-only identification techniques were used to extract the modal parameters from ambient vibration data. The described tests represent the first experimental investigation carried out on the global characteristics of the bridge, since the load reception tests of 1889 and 1892.