The objective of this thesis consists of identifying and quantifying the influence of the mechanical properties of friction dampers on the seismicresponse of steel frames. A friction damper can be modeled as an elastic brace, characterized by its stiffness, in series with a Coulomb friction device, characterized by its activation force. Three realistic steel frames of 3, 6 and 9 stories were considered. In order to observe the influence of each of the aforementioned properties on the seismicresponse, the structures were equipped with braces of varying stiffness and with friction devices of varying activation forces. The seismicresponse was obtained through nonlinear time-history analysis using real seismic records as the ground motion input. Other relevant properties such as the number of sto- ries, the height-wise distribution of the properties and the characteristics of the seismic input were also analyzed. The study concludes that the reduction of the inter-story drift response of the 3-story structure is mainly controlled by the stiffness of the braces, whi- le that of the 6- and 9-story structures is roughly equally controlled by both the friction devices and the braces. It was also found that a uniform height-wise distribution of the activation force of the friction devices results in lower axial forces in the central columns and lower floor accelerations with respect to those obtained with a varying height-wise distribution. Finally, the study also concludes that neither the height-wise distribution of the brace stiffness nor the seismic source of the ground motion records are of significant relevance.
However, some analyzes show that the combination of isolators and dampers can increasing the seismicresponse in the superstructure, depending on the level of damping provided , other research shows that seismicresponse of the structure with isolators and additional dampers varies in function of the seismicity of each region . In Peru, the response in buildings with the combination of these devices has not been studied, nor has the way in which the seismicresponse of building varies according to different types of complementary viscous dampers that provide different levels of damping.
We studied the analytical and experimental seismicresponse of La Mision bridge, and estimated the site sub-surface characterization at the bridge neighborhood. We used the SAP 2000 program, v. 12, to model and characterize numerically the expected response of the bridge in terms of their vibration frequencies and maximum displacement. It was also generated the scenario of the bridge response upon strong motion. In both cases, ambient vibration measurements were used for the experimental studies. The stiffness matrix method was used for the analytical study (forward modeling) of wave propagation in layered media. By calculating the power spectra, we estimated experimental vibration frequencies, which was compared with the theoretical spectra using the PSA (at 0% of damping). The relevant characteristics of the results are next succinctly described:
Seventeen wood frame shear walls of different lengths (1200, 2400 and 3600 mm) and 2470 mm height were tested under cyclic and monotonic in-plane shear loads. The walls have five 2x6” end studs, strong hold-down anchorages and standard 11.1 mm structural OSB panels (1200 x 2400 mm) on both faces of the wall and with nails in the edge of the OSB sheets spaced at 50 or 100 mm. The main objectives of this research are to evaluate the seismicresponse of these shear walls and to assess how well current code expressions (Special Design Provisions for Wind and Seismic, SDPWS) fit with the measured behaviour of shear walls with sturdy end studs, to be used in mid-height timber buildings (up to 6 stories high). The results showed that while, cyclic loads considerably reduce the monotonic shear strength of walls, the ultimate displacement and stiffness were not influenced by cyclic loads. The stiffness calculated at 40% P peak was slightly larger in the
The author proposed a new seismicresponse control system using a block and tackle (hereinafter, referred to as a dynamic pulley damper system) developed especially for the high-rise buildings. The proposed system has a configuration where a damper is installed on the track of the cable-stayed wire, amplifying the amount of movement of the wire by using a movable pulley that increases the damping effect to reduce the vibration of a building. we apply this system to connect the core structure (parking tower) and the surrounding frame (housing part) of a high-rise building. This system aims to reduce the earthquake response of the building by the force of the damper attached to the core structure. To verify the effectiveness of this response control system, two types of shaking table tests were conducted; one is the large-scale shaking table test using a magnetic damper, an-other one is the small-scale shaking table test using a steel damper. The mathematical model of the dynamic pulley damper system to implement the frame analysis was developed and the results of simulation analysis are compared with the experiments.
The city of Mexicali in Baja California, Mexico, is exposed to high seismic hazard due to its location on the region of interaction between the Pacific and North-American Plates. Applying empirical methods, this study evaluates the seismicresponse of ground and the damage to critical structures in Mexicali. Two major earthquakes with high probability of occurrence in the next 50 years (Anderson & Bodin, 1987) were adopted to prepare seismic scenarios: a Mw=6.5 earthquake at the Imperial Fault, and a Mw=6.5 earthquake at the Cerro Prieto Fault. The results include: 1) Spatial distribution of ground peak acceleration, velocity, and response spectra, and isoseismal maps, calculated using empirical predictive equations, 2) Expected damage for a group of critical structures, calculated by applying vulnerability relations proposed by the ATC-13 (1985), and 3) Seismic safety factors for a sample of critical structures, estimated through a rapid visual screening method (FEMA- 154, 2002).
The site response analyzes provide an idea of the behavior of soils under seismic loads, involving a large number of variables that determine the non-linear behavior of the soil. Due to the complexity of these analyzes, in practice the effects of nonlinear soil behavior are incorporated as factors that modify the seismicresponse spectrum in rock (linear behavior). In this study, nonlinear site response analysis has been performed for 50 soil profiles in an attempt for covering a wide range of shear wave velocity profiles using the software DEEPSOIL V.7. For this purpose, 03 seismic records have been spectrally adjusted to uniform hazard spectrum of 475, 1000 and 2475 years of return period of a reference soil profile with Vs 30 of 760 m/s. Subsequently, a comparison
Several models exist to evaluate the seismicresponse of RC buildings, from simplified models using a single beam (e.g. Encina & de la Llera, 2013; Sep´ulveda, de la Llera, & Jacobsen, 2012) to complex FE models to asses super-tall buildings (Besjak, McElhatten, & Biswas, 2010; Lu, Lu, Zhang, & Ye, 2011). Recent technical documents provide guide- lines to create structural models for tall buildings, e.g., PEER/ATC-72 (ATC-72, 2010) and LATBSDC (LATBSDC, 2014), which focus on Performance-Based Seismic Design (PBSD) procedures. However, these guidelines provide limited prediction capability for building simulations and are a source of inherent epistemic uncertainty. Moreover, free- plan buildings are particularly sensitive to model uncertainty given their low structural redundancy. These modeling assumptions include aspects such as the in-plane and out- of-plane diaphragm stiffness considered for each floor slab, the soil-structure interaction effects (SSI) considered, and the fixity level of the structure to the ground. These effects and others can have a large influence in the seismicresponse. Moreover, some of these modeling assumptions are still today a matter of discussion in design offices.
In order to verify the procedure proposed, a model of a simple 2D elastic can- tilever beam (gure 5.8(a)) is subjected to the following excitation; (i) one accelero- gram obtained with constant damping and analyzed with modal dynamics (MRHA), considering the same damping; and (ii) one record with the same spectrum than the previous accelerogram, but obtained with Rayleigh damping and calculating with direct dynamics (DRHA). Figure 5.8(b) presents the drift of the top section in the cantilever, observing that the extreme response is nearly the same with both proce- dures, despite the time-history is dierent as it was expected. Extended validation analyses were conducted in other (more complex) structures, like the model rep- resenting only the `H'-shaped tower of a cable-stayed bridge, concluding that the records generated with variable damping are appropriate for direct dynamics, in order to compare the extreme seismicresponse with procedures in which the damp- ing is constant. However, it should be admitted that only the maximum response was considered here, and no attempt has been proposed to take into account the equivalence of the response history, which may be important if variables related to the energy balance in nonlinear analysis are of interest.
School buildings have been characterized in this article by structural typologies and are designed for a specific design code level which varies from pre-code (buildings without code design) to low code and high code; all these levels are related to the capacity standards for seismic strength. The retrofitting or strengthening alternatives considered herein are the following: a) unreinforced masonry buildings are replaced by new facilities of reinforced masonry; this alternative not only improves the seismic safety, but also upgrades the infrastructure. b) For the remaining structural typologies, low-code / high-code capacity spectra have been assumed for the current and retrofitted case, respectively. Additional modifications have been adopted in the ductility and seismic coefficient for these typologies according to the requirements of the Colombian building code NSR-10. The sources of the parameters of the capacity spectra are summarized in Table 3. The vulnerability curves (expected values) are shown in Figure 4(a) and Figure 4(b) for the current and retrofitted cases, respectively.
It is possible to observe that the values obtained for in situ period are below the maximum value marked by the codes so we can consider that the repaired and undamaged building has the necessary stiffness conditions. Moreover if the stiffness conditions are adequate does not imply that the building support the stresses coming from the seismic action. Due to this the building needs to be reinforced at those zones where these admissible tensions could be surpass, particu- larly on tensile stress.
Although the resolution of the profiles is not good enough along the continental slope, previous studies, which are also based on seismic exploration profiles, have shown that most of the Alpine deformation in the margin concentrates along that area. A set of N- vergent thrusts developed and they are responsible for the shortening, uplift and steepness of the slope (Gallastegui et al., 2002).
WED is a powerful method that can be used to increase the signal-to-noise ratio and the resolution of marine and land seismic data. In the terrestrial environment, it has been used to improve the static corrections on crustal (i.e., ) and high resolution (i.e., ) seismic data; recently, it was applied successfully to process S-wave data . In the marine environment, WED was used to process sparse ocean bottom seismometer (OBS) data for deep crustal prospecting . After WED, shots and OBSs were relocated at the same datum (sea level), allowing for processing with the use of commercial software, and improving the final result with respect to the conventional approach.
Abstract. This paper focuses on prediction and prevention of seismic risk through a system for decision making. Data Warehousing and OLAP operations are applied, together with, data mining tools like association rules, decision trees and clustering to predict aspects such as location, time of year and/or earthquake magnitude, among others. The results of the data mining and data warehouse application help to confirm uncertainty about problems behavior in decision making, related to the prevention of seismic hazards.
A nivel mundial se ha profundizado en las investigaciones de este concepto y en países como EEUU se ha desarrollado a tal punto de poder utilizar está tecnología de la información en los diferentes ámbitos de una emergencia, desde ayudar a adultos mayores en la motivación, usabilidad y sociabilidad hasta combatir emergencias provocadas por acciones terroristas. Estas y otras investigaciones han sido desarrolladas por miembros de la Universidad de Maryland, la que implementó un sitio web en su página principal que permite a diferentes niveles, ya sea, estudiantes, administrativos o seguridad pública, coordinarse y organizarse frente a diferentes emergencias (Community Response Grid (CRG) for a University Campus: Design Requeriments and Implications, 2008)
Classification trees: A set of conditions is organized in a hierarchical structure, so the final decision can be determined according to the conditions to be met from the path from root to some of its leaves. One of the great advantages of classification trees is that, choices from a given condition are mutually exclusive . In particular, J48 algorithm generates a classification tree from data taken by performing a recursive data partition. The tree was constructed using depth-first strategy . The classification trees were used to answer the question, can you determine the depth of a seismic event due to its magnitude?
with the scientific knowledge on the seismicity in eastern Colombia and the llanero foothills, determining patterns of seismicity distribution - temporary space to define the seism tectonic of the region and on the other stage with the report to the authorities and the community in general aspects seismological of earthquakes occurring in the complex work in the seismic risk mitigation. The information that this network will offer will be in the public domain and will contribute to the development of theseismological knowledge Colombian and the northwestern region of South America.Then generally, it concludes that the Academy at least in the case of Colombia has assumed the leadership of the development of seismological knowledge in Colombia since the beginning of the 20th century. Universities in particular with its centers of geophysical research and Civil Engineering programs, have contributed to the increase of Seismology in Colombia from historical, geophysical research and knowledge of Civil Engineering, to increase the understanding of the phenomenon in the country, and similarly have supported authorities in plans of management about seismic riskIn the same role and assuming leadership for the Llanero foothills seismic risk management and research, the University Corporation of Meta with its programme of Civil Engineering with the support of their teachers investigative work, has managed to lead in the last decade of the llanero foothills seismic theme and also helped with the investigation of the seismic hazard from other regions of the country such as the Colombian Caribbean platform and the Colombian West. References Chicagoan, g. (2009). Brief history of handling seismic and post-conflict
Seismic signals classification is important by itself in order to discover factual interactions between volcanic earthquakes and volcanic processes. In this paper, it is presented the application of Gaussian processes for seismic events classification registered at Nevado del Ruiz volcano. Feature extraction is accomplished using the coefficients of an autoregressive model, employed for the estimation of the power spectral density. The predictive distribution for classification is approximated using the Laplace method. Obtained performance is higher than the one obtained with an artificial neural network, the state of the art classifier for this kind of task.
Because of the convergence of different tectonic plates, Medellín is located in an active seismic region and as a result of this interaction the city has an intermediate hazard level with possible events associated to three main systems: the Romeral Fault System, Murindó Fault System and Benioff Intermediate Zone (Salgado et al. 2010; Pulido 2003). No destructive earthquakes have yet occurred in the vicinities of the city but historical records account for a quake in 7 September 1882, a shallow 5.2 magnitude earthquake in 12 November 1979 and also a shallow 7.1 magnitude event on 18 October 1992 that generated considerable damage in different parts of the city, specifically on facades and division walls (Ramírez 2004). The consideration of the local site-effects in Medellin is of the upmost importance due to the characteristics of some soft soil and clay deposits that may give some important amplification factors for the fundamental periods.
Abstract. The risk identification, assessment and reduction are indispensable steps on the way of the sustainable development of the countries. Risk assessment requires a multidisciplinary approach that takes into account not only the expected physical damage, the number and type of casualties or the economic losses, but also other social, organizational and institutional factors that contribute to risk. At urban level, for example, vulnerability should be related not only to the physical susceptibility of buildings and infrastructure, but also to the social fragility and the lack of resilience of the exposed community. The absence of institutional and community organization, weak preparedness for emergency response, political instability and lack of economic health, which are development problems, contribute to increasing of risk in a geographical area. This article presents and applies a methodology for evaluating risk in urban center using a holistic approach. A multidisciplinary estimation of risk to guide the decision making, that takes into account geophysical and structural aspects, and also social, economic, institutional variables, among others, is considered here as holistic approach, involving all the aspects and comprehensive. The paper includes four case studies, the cities of: Barcelona, Spain; Bogotá and Manizales, Colombia; and Metro- Manila, The Philippines.