Carlos Cuadra

Earthquake risk to Inca's historical constructions in Machupicchu

The citadel of Machupicchu is probably the most famous Inca heritage site in Peru. Considering the seismically active region, this research is an attempt to perform a seismic risk analysis of the heritage structures at Machupicchu. A systematic approach is adopted for this purpose. Characteristic seismicity of the region, where these historical constructions are located, is discussed based on the seismic hazard analysis. Evaluation of the vulnerability of the structures under the prevalent earthquake hazard is another important aspect essential for risk analysis. As a first step to proper understanding of the seismic behavior of these heritage structures, typical elements of Inca construction are studied by simple analytical models to verify basic aspects of structural integrity. The possibility that peak ground acceleration corresponding to even relatively low hazard may produce instability in some structural components like gable walls was noted. In view of this preliminary result, attempt was made to identify the dynamic characteristics of typical buildings units from more detailed investigation. This forms part of the outcome from the field study program, which included microtremor measurement of free field as well as typical constructions, planned and undertaken by the authors. The results of the microtremor measurements are utilized to estimate the dynamic characteristics of the Inca stone structures. That is, the analytical results are compared with the measurements to calibrate the analytical model. Since microtremor measurements involve very small displacements, the characteristics of stones structures thus obtained correspond to elastic behavior applicable to small strain condition. Based on this scheme, an approach has been proposed to evaluate the seismic behavior and hence the seismic vulnerability of these structures. The procedure also permits identification of the probable mode of failure of the structures concerned.

Seismic vulnerability of historical adobe buildings in the coast of Peru

This paper attempts to describe the structural conditions of the historical adobe buildings that are located in the coast of Peru, which is a zone of high seismic activity. The seismicity of the zone is discussed through an earthquake hazard analysis and the importance of action towards the protection of heritage architecture is emphasized. It is noted that the state of general disrepair and the intrinsic weakness of the earthen constructions add to the seismic vulnerability of this kind of heritage architecture. Besides, the repair after actual damage or destruction from earthquakes, even when timely undertaken, may lead to alteration of the valuable originality of heritage structures, owing to the unavailability of materials or skill from the time of the original constructions. The need for initiatives towards preventive actions for protection from damages and prevention of collapse due to earthquake disasters appears quite evident.

Earthquake Resistance Of A Historical BrickBuilding In Akita Prefecture, Japan

During the Meiji period (by the end of the 19 th century) many brick masonry buildings were constructed in Japan. However, due to the lack of reinforcement, these structures collapsed during the great Kanto earthquake, which occurred in the year 1923. Since then, this type of structure is not used for buildings and only a few historical constructions remain from that era. In Akita Prefecture, in the northeastern part of Japan, some of these buildings have been declared as local culture heritages. One of them is located in Ani village and was constructed in 1879 to serve as the residence for a German engineer who was working for a local mining company. As an initial step to evaluate the seismic vulnerability of this historical building, dynamic characterization has been undertaken. For that purpose, measurements of the micro vibration of the building was planned and undertaken by the authors. For the analytical modeling, mechanical parameters were estimated from a series of laboratory tests on masonry brick units obtained from the stock that are conserved near the building under study. The results of the microtremor measurements are discussed in relation to the analytical procedure adopted to estimate the dynamic characteristics of this historical brick structure. The structure shows intricate modes of vibration that are reflected in the multiple peaks observed in the transfer functions of microtremor records. With the analytical simulation considering only the effect of the brick walls, the multiple predominant frequencies are obtained for a certain range. With this good agreement of the analytical procedure and the measurement results, the reliability of the employed methodology was verified.

Estimation of dynamic properties of traditional wooden structures using new bolt sensor

Dynamic properties of traditional wooden structures are estimated from forced vibration test performed on a prototype constructed for this purpose. The prototype corresponds to a framed wooden construction with traditional connections between columns and beams without nails and with wedges inserted into joints to fix them. To verify the applicability of a new type of piezoelectric bolt sensor the test series were performed using also commercial accelerometers and laser displacement transducer for comparison. The new bolt sensor is intended to be used for structural health monitoring of important and small structures like historical shrines or other small historical buildings. Bolt sensors were installed in selected frame joints and changes in the voltage signal were detected when the prototype is subjected to dynamic excitation. The response of the new sensor is comparable with that obtained by high precision commercial accelerometers and laser displacement transducer. In addition the dynamic response of the structure and the response of the bolt senor were verified analytically using finite element method. For analytical modeling semi-rigid joint is used where the moment rotation relationship is specified for each beam end. The research serves also to calibrate the analytical model by using experimental results obtained from forced vibration test.

Vibration Characteristics of an Old Steel Bridge

This paper describes the dynamics characteristics of an old steel truss bridge. The bridge, known as Yurikyo was constructed in the sixth year of the Showa era (1931) and become a symbol of Honjo city and of the Yuri region in Akita Prefecture, Japan. The bridge spans 175.6 m over the Koyoshi river been formed by three identical single trusses of 57.6 m. Due to aged and corrosion of steel elements, replacements of this old bridge by new reinforced concrete one was planned during the year 2005 and construction is planned to be started in 2009. In this research, the old steel bridge is investigated by means of micro vibration measurements, Fourier analysis and finite element method to estimate the dynamics properties of the bridge and to obtain the basic data that could be a reference for future structural monitoring of the new bridge.

Preliminary evaluation of the seismic vulnerability of the Inca's Coricancha temple complex in Cusco

Coricancha was probably the most important Inca temple complex dedicated primarily to Inti, the Sun god. At present, a small part of the Inca stonework is all that remains of the ancient complex. Most of the complex was demolished by Spaniard conquistadors in the 17 th century to make way for the construction of Catholic Church of Santo Domingo on this site, using part of the Inca construction as the foundation. This complex is a fine example of how Inca stonework had been incorporated into the structure of a colonial building. Major earthquakes have severely damaged the church, but the Inca stone walls, built out of huge, finely cut tightly-fitting blocks of stone, still stand as a testimony to Incas architectural skills and sophisticated stone masonry practice. In this complex, a series of microtremor measurements were carried out to estimate the dynamic characteristics of the structures and the ground. Measurements on buildings include the Incas masonry walls as well as the tower of the colonial church. Measurements to estimate the ground characteristics were performed in the inner yard and at the outer garden of the complex. In this paper, the results of the measurements and corresponding interpretations are discussed. It was found that the predominant period of vibration of the church tower is comparable to the predominant period of the ground, and therefore, the tower appears to be more vulnerable to earthquake occurrence because of the possible resonance phenomenon to be expected.

Avalanche and Falling Rock Measurement Using Piezoelectric Dynamics and Static Sensors

Under certain weather conditions, avalanches can occur because of snow cover on a steep slope. Such avalanches can reach snow fences that are arranged as countermeasures. Furthermore, traffic is completely blocked when fences collapse and snow falls on a road. Therefore, prediction of avalanche occurrence is important, but such predictions are considered difficult. To resolve this difficulty, this study assessed measurement of the danger degree by measuring the risk to the avalanche fence at the time of snowfall and falling rock according to changes in the load and the impact of voltage proportional to the avalanche barrier deformation. This measurement system has fixed sensors attached with mounting brackets to a dedicated avalanche prevention measurement fence. It measures the pressure and vibration measurement of the snowfall at the time of avalanche or rock fall occurrence at the main structure of the fence. Furthermore, this fence made of lumber from thinned timber is useful as a defensive barrier countermeasure against avalanches and falling rock. It is designed to withstand a snow load of 3–5 [t / m 2 ] during an avalanche.

DYNAMIC CHARACTERISTICS OF A BRIDGE ESTIMATED WITH NEW BOLT-TYPE SENSOR, AMBIENT VIBRATION MEASUREMENTS AND FINITE ELEMENT ANALYSIS

Applicability of new bolt-type piezoelectric bolt sensor to estimate dynamic properties of bridges is verified by comparing measurement results with those obtained from ambient vibration observations and from finite element method of analysis. For this study a bridge located at Yurihonjo city, Japan, was chosen as the target structure. The structure is a multiple-span type bridge with steel beams of variable sections and reinforced concrete slabs to support the asphalt carpet. The bridge consists of seven spans with a total length of 256 m. The experimental measurements using the new bolt-type sensor were performed only on the first span near the left abutment. However, ambient vibration measure ments and analysis were done for all spans. In general, responses were obtained appropriately using the new sensor and that results are comparable with those obtained from analysis and ambient vibration measurements.

Preliminary evaluation of piezoelectric sensors for the prediction of compression failure of brick masonry components

Applicability of a piezoelectric bolt-type sensor to detect or predict compression failure of masonry specimens is investigated in this paper. Originally, masonry specimens were constructed to investigate the influence of the type of bond on compression strength. Flemish bond style and English bond style were selected in the present study and 3 specimens for each bond style were constructed. Flemish bond style specimens show slightly lower strength in comparison to English bond style specimens. In 4 of these specimens, piezoelectric bolt-type sensors were installed and signal responses were observed at different stages of compression tests. It is believed that these responses correspond to different levels of cracking and the most important is the signal observed just before crushing since this response could be used for collapse prevention in case of actual structure.

Vulnerability of Machu Picchu citadel 100 years after its scientific discovery

In the year 2011, Peru celebrates 100 years since Hiram Bingham discovered the citadel of Machu Picchu. The Inca citadel of Machu Picchu has become the most famous historical site in Peru; the site was declared as world cultural heritage by UNESCO in 1983 and also as one of the New Seven Wonders of the World in 2007. All of its constructions are made of stone masonry, and during almost four centuries the citadel endured and survived under a thick rain forest, until it was discovered in 1911. This paper attempts to describe mainly the seismic vulnerability by observing the structural conditions of historical stone buildings which are located in the citadel. The Andean region of Peru corresponds to a zone of low seismic activity however, these low intensity earthquakes could produce damage in the stone constructions. Moreover, the present structural conditions of some buildings lead one to think that these constructions have been subjected to the action of past earthquakes or other geodynamic actions. The characteristics of failures are discussed in this paper, through field survey, micro vibration measurements and dynamic analysis. The field survey on damage consisted of a detailed observation and evaluation of a group of selected buildings. Also, micro vibration measurements were performed on the ground and on some buildings to estimate their dynamic characteristics.