Refinement of the seismicity of construction sites for high-rise buildings

The development of the construction of high-rise residential buildings requires a separate approach, depending on the engineering and geological conditions of the site for seismic microzoning. There are not only engineering sectors but also large premises that will serve as business offices and technical centers in the underground part of high-rise buildings. In this regard, the foundation of the building goes to great depth. The influence of soil conditions at the level of abutment of the buildings’ foundation can be determined with seismic microzoning. As a result, the task of clarifying the projected construction site in construction is currently relevant. It includes the refinement of the seismic intensity of the construction site during the construction of high-rise buildings, which are located in different multilayer soil types.

Estudio comparativo de análisis y diseño de estructuras aporticadas de hormigón armado, aplicando los espectros de la microzonificación sísmica del cantón Portoviejo y los espectros de la NEC-15

La ciudad de Portoviejo cuenta desde el 2017 con espectros de diseño específicos resultados del estudio de microzonificación sísmica del cantón. Esta investigación se origina por el escaso uso que se da a los espectros de diseño indicados en el estudio de microzonificación por parte de calculistas estructurales, quienes continúan usando los espectros que se indican en la Norma Ecuatoriana de la Construcción del 2015 para analizar y diseñar las estructuras, tanto de hormigón armado como de acero estructural. El objetivo de esta investigación es medir las variaciones de desplazamientos laterales y esfuerzos globales en estructuras aporticadas de hormigón armado mediante un análisis sísmico, empleando tanto los espectros de la norma ecuatoriana como los espectros de la microzonificación sísmica de Portoviejo. Se analizaron seis estructuras, tres de ellas regulares en planta y en elevación, las cuales eran de tres, cinco y ocho niveles de altura y otras tres estructuras irregulares de tres y dos niveles. Las estructuras fueron modeladas en Etabs, y se usó el análisis sísmico modal espectral en que se variaba el espectro de diseño. En cuanto a los espectros de la microzonificación se usaron los indicados para las microzonas M4 y M5 mientras que los espectros de la norma considerados corresponden a la zona sísmica VI en suelos tipo D y E consistentes con los tipos de suelo de las microzonas M4 y M5. Adicionalmente se evaluó la variación del área de aceros de refuerzo en elementos principales. De este esta investigación se puede concluir que: i) en las estructuras de dos, tres y cinco niveles, los desplazamientos se amplificaron al emplear los espectros de la microzonificación sísmica, la microzona 4 entrega el mayor valor. En la estructura de ocho niveles los espectros de la norma dan los mayores desplazamientos. ii) en la estructura de ocho niveles los mayores esfuerzos de corte y momento se presentaron al emplear los espectros de la norma ecuatoriana de la construcción. iii) al diseñar las estructuras los resultados no presentaron una variación significativa, se obtuvo una mínima diferencia en cuanto a los aceros de refuerzos longitudinales. iv) en la ciudad de Portoviejo, las estructuras construidas con frecuencia no superan los tres niveles y al ser diseñadas con los espectros de la norma se estaría subestimando la aceleración sísmica de diseño. Se recomienda el uso de los espectros de la microzonificación, que son resultado de un trabajo específico para las condiciones de la ciudad. Palabras claves: Microzonificación Sísmica, Espectros de Diseño, Análisis Sísmico, Diseño Sísmico. Abstract— The Portoviejo city has since 2017 with specific design spectrum results of the study of seismic microzoning in the canton. This research originates from the limited use given to the design spectrum indicated in the microzonation study by structural engineers, who continue to use the spectrum indicated in the 2015 Ecuadorian Construction Standard to analyze and design the structures, both reinforced concrete and structural steel. The objective of this investigation is to measure the variations of lateral displacements and global efforts in structures provided with reinforced concrete to be analyzed seismically using both the spectrum of the ecuadorian norms and the spectrum of the seismic microzoning of Portoviejo. Six structures were analyzed, three of them regular in plan and elevation, which were three, five and eight levels high and three other irregular structures of three and two levels. The structures were modeled in Etabs, and the spectral modal seismic analysis was used, varying the design spectrum. Regarding the microzonation spectrum, those indicated for microzones M4 and M5 were used, while the spectrum of the standard considered correspond to seismic zone VI in soils type D and E consistent with the soil types of microzones M4 and M5. Additionally, the variation of the area of reinforcement steels in main elements was evaluated. From this research it can be concluded that: i) in the structures of two, three and five levels, the displacements were amplified by using the spectrum of the seismic microzonation, the microzone 4 generated the highest value. In the eight-level structure the spectrum of the norm give the greatest displacements. ii) in the eight-level structure the greatest cutting and momentum efforts were presented when using the spectrum of the Ecuadorian construction standard. iii) when designing the structures, the results did not show a significant variation, a minimum difference was obtained regarding the longitudinal reinforcement steels. iv) in the city of Portoviejo, the structures built frequently do not exceed three levels and being designed with the spectrum of the standard would be underestimating the seismic acceleration of design. The use of microzonation spectra is recommended, which are the result of specific work for city conditions. Keywords: Seismic microzonation, Design spectrum, Seismic Analysis, Seismic Design.

“Análisis Estructural y propuesta de reforzamiento del edificio de Facultad de Ciencias Humanísticas de la Universidad Técnica de Manabí”

El Ecuador se ha caracterizado por ser un País de alto riesgo sísmico debido a que se encuentra ubicado en la zona denominada “Cinturón de fuego del Pacifico”, esta denominada así por ser la región más susceptible de experimentar los efectos de terremotos y erupciones volcánicas. Por esta razón los estudios de peligrosidad sísmica son imprescindibles para saber de la manera más precisa posible, los niveles de movimiento del terreno que deberá soportar una determinada estructura a partir de un sismo. En esta investigación se comienza con el análisis de los estudios de suelo ya realizados verificando el tipo de respuesta que tiene el suelo. De acuerdo al estudio de microzonificación sísmica se especifica las zonas donde y como se puede construir dependiendo del tipo del suelo que exista en cada sector, esto se encuentra especificado en la Norma Ecuatoriana de la Construcción NEC (2015). En cualquier análisis estructural que se realice se debe tomar en cuenta normativas y especificaciones que garanticen un comportamiento sismo-resistente de las estructuras. Para realizar el presente estudio se aplicarán las normas y recomendaciones especificadas por el Código Ecuatoriano de la Construcción, se realizará un análisis estructural del edificio, cuenta con una cimentación de zapata corrida en dos direcciones, funciona como aulas y oficinas, está caracterizado por ser regular, cuenta con 2 bloques estructurales los cuales posee 3 niveles cada uno, son de estructuras aporticada de concreto armado, el análisis sísmico se efectuó en el programa ETABS. Una vez realizado el análisis aplicando los métodos estáticos equivalente y dinámico modal espectral se obtuvo como resultado que las derivas de piso exceden a los límites establecidos por la Norma Ecuatoriana de la Construcción NEC (2015) en dos bloques estructurales, por lo que se planteó la propuesta de reforzamiento estructural aumentando la sección de columnas e implementando muros de corte. Palabras clave: Riesgo sísmico, microzonificación sísmica, fuerza cortante, deriva de piso, dinámico modal espectral. Abstract— Ecuador has been characterized by being a country of high seismic risk because it is located in the area called “Pacific Fireincturon”, which is called the region most susceptible to experiencing the effects of earthquakes and volcanic eruptions. For this reason, seismic hazard studies are essential to know in the most precise way possible the levels of movement of the terrain that a certain structure will have to withstand from a seism. In this investigation, analysis of soil studies already carried out by verifying the type of response of the soil. According to the seismic microzoning study, the areas where and how it can be built depending on the type of soil that exists in each sector, this is specified in the Ecuadorean Standard of Construction NEC (2015). Any structural analysis carried out must take into account regulations and specifications that ensure the same-resistant behaviour of the structures. To carry out this study, the norms and recommendations specified by the Ecuadorean Construction Code will be applied, a structural analysis of the building will be carried out, it has a foundation of strip footing in two directions, it functions as classrooms and offices, it is characterized by being regular, it has 2 structural blocks which have 3 levels each, they are of structures aporticated of reinforced concrete Once the analysis has been carried out using the static equivalent and dynamic spectral modal methods, it was obtained that the floor shifts exceed the limits set by the Ecuadorean Standard of Construction NEC (2015) in two structural blocks, so the proposal for structural reinforcement was proposed by increasing the column section and implementing cutting walls. Index Terms—Seismic risk, seismic microzoning, shear force, floor drift, spectral modal dynamic.

Seismic hazard assessment for the underwater gas pipeline route in the water area of the Nevelskoy Strait

The presence of seismic threat multiplies the environmental hazard, especially for oil and gas production and transport facilities in water areas. Currently, there are no normative maps of general seismic zoning of the water areas of the inland and marginal seas of Russia, especially since there are practically no maps of detailed seismic zoning and seismic microzoning of even individual parts of the water areas. Taking into account the fact that intensive development of offshore oil and gas fields and the Northern Sea Route has begun, the development of such maps becomes a very urgent scientific and practical task. The seismic hazard assessment for the submerged crossing was carried out in 2008. The initial seismic effects were calculated using a probabilistic seismic hazard analysis based on five models of seismic zones and three types of models of attenuation of peak and spectral accelerations. The results of the performed calculations, including deaggregation, have shown that the initial seismicity of the area of the gas pipeline crossing route through the Nevelskoy Strait for a return period of 1,000 years is lower than indicated on the OSR-2016-B map, where the eastern end of the crossing route through the strait is characterized by the initial seismicity equal to 9 points. The soil conditions (seismic microzoning) have been taken into account by three different methods: the seismic rigidity method, the calculation method, and the method considering the thickness of Quaternary deposits. The present studies show that seismic effects vary along the pipeline route from the mainland to Sakhalin Island from 8.4 to 8.9 on the MSK-64 scale for the recurrence period of seismic shaking T = 1,000 years and from 9.3 to 9.7 points for T = 5,000 years.

SEISMIC MICRO ZONING OF THE TERRITORY OF ALMATY ON A NEW METHODOLOGICAL BASIS

In connection with the reform of regulatory framework for construction sector of the Republic of Kazakhstan, the development of seismic zoning maps poses an urgent problem. The article presents a set of seismic microzoning maps of Almaty, developed on a new methodological basis for Kazakhstan, and provides explanatory materials on the development, understanding and use. Calculation of background seismic hazard was carried out in accordance with the basic provisions of Eurocode 8. Seismic microzoning included the implementation of two main tasks - the assessment of background seismicity and taking into account influence of soil conditions. Based on the analysis results, a set of maps have been arranged. When taking into account the influence of engineering and geological conditions, Russian and Kazakh works were used. The main maps ready for use in regulatory documents are provided. Analysis of capacities of the sediments of same age in different blocks made it possible to understand the dynamics of tectonic regime of the city territory. In the process of neotectonic activation, almost all previously existing tectonic disturbances were improved. In the contemporary relief of the urban area, most faults are not expressed.