Seismic analysis

[1] AnirudhGottala, Kintali Sai Nanda et al (2015)carried out comparative study of static and dynamic seismic analysis of a multistorey building. A multi-storied framed structure of (G+9)pattern is selected. Linear seismic analysis is done for the building by static method (Seismic Coefficient Method) and dynamic method (Response Spectrum Method) using STAAD-Pro as per the IS-1893-2002-Part-1. A comparison is done between the static and dynamic analysis, the results such as Bending moment, Nodal Displacements, Mode shapes are observed, compared and summarized for Beams, Columns and Structure as a whole during both the analysis.

The seismic analysis ought to be dispensed for the buildings that have lack of resistance to earthquake forces. Seismic analysis can take into account dynamic effects thence the precise analysis typically become complicated. However, for simple regular structures equivalent linear static analysis is sufficient one, this type of analysis is carried out for regular and low-rise buildings. Seismic analysis of multi-storey building will be carried out for the building as specified by the code IS 1893-2002 (part 1). Dynamic analysis carried out either by response spectrum method or time history analysis method. The different analysis procedures are:-

The paper presents an overview of Russian regulatory approaches to seismic design and seismic analysis of NPP Piping. The paper is focused on categorization and seismic analysis of nuclear power plant items (piping, equipment, supports, valves, but not building structures). The paper outlines the current seismic recommendations, corresponding methods with the examples of calculation models. The paper considers calculation results of the mechanisms of dynamic behavior and the problems of developing a rational and economical approaches to seismic design and seismic protection.

Abstract- Seismic Analysis is a part of structural analysis and it deals with the calculation of the response of a building structure to earthquakes. Retrofitting of an existing building is often considered to be more cost-effective than constructing a new building. It represents an opportunity to upgrade the overall performance, sustainability and efficiency of an existing building. Seismic retrofitting is mainly done to provide existing structures with more resistance to seismic activity due to earthquake. Most losses of lives in the earthquakes in developing countries have occurred due to collapse of buildings that are mostly non-engineered. However, not designed and constructed to meet the seismic requirements. In this study, the seismic analysis of reinforced concrete (RC) buildings with different types of bracing (Diagonal, V type, and inverted V type, X type) is studied. The bracing is provided for peripheral columns. A six-storey (G+5) building is situated at seismic zone III. The building models are analyze by equivalent static analysis as per IS 1893:2002 using Staad Pro V8i software. The main parameters consider in this paper to compare the seismic analysis of buildings are lateral displacement, storey drift, axial force, base shear. It is found that the X type of steel bracing significantly contributes to the structural stiffness and reduces the maximum interstorey drift of R.C.C building than other bracing system.

Here the Study is carried out for the behavior of G+14 Multistory Buildings, Floor height provided as 3m and also the properties are defined for the building structure. The model of the buildings is created in ETABs Software. The Seismic Zone considered is Zone IV and soil type is medium. The modeling of Building is done for the Indian seismic zone IV, IS 1893-2002 for the given structure, loading with the applied loads includes Live load, Earthquake Load and Dead load. Analysis is carried out by the Response spectrum analysis using ETABs software. The analysis is carried out to determine maximum storey displacement, storey drift and base shear. After analysis, results are obtained in the form of graphs which are in tern observed to form conclusion. 2.1 METHODS OF SEISMIC ANALYSIS

evolve. Traditional design methods have the objective of achieving life safety in a building by providing sufficient strength and ductility to resist total and/or partial collapse. In this proposed study G+14 Two Building With And Without Shear Wall model is generated & tested by the ETABS under the guideline of IS-875-Part3 & IS1893- 2002- Part1.And we find Base shear, Displacement, Seismic analysis , Storey drift, stiffness dynamic story shear is less than static story shear for all cases From all cases, it is concluded that lateral force obtained from response spectrum method is higher than those obtained by equivalent static lateral force method for story one up to five and the rest higher stories have less values.The maximum story displacement, overturning moment obtained from response spectrum method is lesser than those obtained by equivalent static lateral force method. The base shear, lateral force, story shear, maximum story displacement and overturning moment are increased.in both directions (i.e., X & Y) as the seismic zone goes from II to V for the same frame type building in both methods.

The results of Modal and Seismic analysis are tabulated. The seismic analysis is carried out through transient response with Rayleigh damping. Antisymmetric validation of steel frame is compared with existing and present values. The mode frequencies of the four composite frames are tabulated and compared. The peak acceleration response due to earthquake loading for different material is presented in figures 9, 10, 13, 14. The corresponding acceleration due to seismic loads under spectrum is shown in figures 10 and 12 through analysis, and the results of the four composites are compared in table 4. The stiffness ratio of steel is the highest in comparison with composites. The idea of introducing composite frames is to reduce the weight of the structure, which in turn reduces the damage during the earthquake.

Mahesh N. Patiletal.(2015) studies of seismic analysis of multi storied building. The effective design and the construction of earthquake resistant structures have much greater importance in all over the world. In this paper, the earthquake response of symmetric multi storied building is studied by manual calculation with the help of ETABS 9.7.1software. The method includes seismic coefficient method as recommended by IS1893:2002.The responses obtained by manual analysis as well as by soft computing are compared. From the data revealed by the manual as well as software analysis for the structures with seismic coefficient method conclusions are Calculation of seismic weight by both manual analysis as well as software analysis gives exactly same result .There is slight variation in the values of base shear in manual analysis as well as software analysis. And also there is a gradual increase in the value of lateral forces from bottom floor to top floor in both manual as well as software analysis.

Analysis of SGDHR system is done by multi support response spectra method and multi support time history method. Floor response spectra (FRS) corresponding to each elevation for 5% damping is extracted from the seismic analysis of nuclear island connected building. Modal combination rule used to combine various modes within a group is SRSS. This resulting solution for each individual group experiencing their respective excitations is combined through SRSS to get the response of entire system. Artificial spectrum compatible time histories are generated based on FRS. These time histories are used for the multi support time history analysis of the system. Central difference method corresponding to Newmark –β method with a time step of 0.0078 sec is used for the time history analysis of the integrated model. The FRS and the corresponding time histories are shown in Figure 2-7.

In fact, the response of each mode of the structure will be magnified under the seismic spectrum. If some frequency of the structure just corresponds to the peak of the seismic spectrum, namely, the frequency is very close to the natural frequency of the building, moreover, the participation factor and the effective mass of this mode are much larger than other modes, then the magnifying effect of the seismic spectrum on the response of this mode is remarkable, and the response of this mode will contribute most to the response of the whole structure, which is resonance phenomenon. So when doing the seismic analysis, if the response of the structure is very large, after the above reason is determined, not only can we determine which mode contribute most to the whole response of the structure, but can we adopt some measures to avoid that the natural frequency of the structure meets the peak of the seismic spectrum, such as changing the mass distribution of the structure and so on.

The Liquid storage tanks are a part of many industrial and nuclear installations. Safety of these tanks is a concern under seismic events. Tanks storing hazardous chemicals pose danger due to postulated failures. Seismic analysis of liquid containing tanks becomes complicated due to fluid-structure interaction and sloshing phenomenon leads to additional loads on the tank wall. Sloshing in some cases might damage the top roof. Deformation behavior of tanks vessel under seismic loads is of concern in predicting the damage modes. Liquid containing vessels subjected to accelerations find application like liquid carrying tanks subjected to acceleration that leads to sloshing phenomenon. Analysis becomes significant as the sloshing induces additional loads onto tank structure. Due to this tank will undergo severe deformation leading to damage. In present analysis, tank is analyzed for a given seismic accelerations signals by time history method. This analysis, a typical tank containing water is taken for studying the seismic effects. The tank is made of steel with varying thickness along the length. The tank has a roof, and girder MODAL ANALYSIS

Due to the loss of life and damage to surface and underground structures, stabilization of trenches in order to control and stabilize landslides is very important. In the current study, the effect of the implementation of the pile has been analyzed to increase the stability of the trench under the impact of the earthquake. Therefore, a trench with 45° angle which reinforced by the pile, was analyzed with variable parameters, including the diameter of the pile (D) that was with a 0.9m diameter and other pile with 1.5m diameter, the buried length of the pile (L) was 10m and 15m. The space between the piles (S) to each other was implemented by three sizes; 0.3m, 4.5m and 0.6m, and the implementation of the pile with five forms on the span of the trench was analyzed to study its different behavior under seismic conditions. The results showed that with increasing the diameter of the pile and the implementation of the pile, the horizontal displacement of the span of the trench reduces 25% to the normal state. In addition, with an increase in the length of the pile, the level of the subsidence is 24 to 30 percent lower than the normal state.

Seismic isolation also known as base isolation is one of the best earthquake resistant design concept in which a building is decoupled from the earthquake ground motion or seismic waves. In base isolation the base of the structure is isolated using isolators (normally bearing isolators) which help in decoupling (it should be notice that the structures are generally failed due to couple formation during seismic action). When a building is decoupled from ground motion it significantly reduces response in the structure which would have affected building if it is fixed base. Base isolation decouples the building from ground motion by decreasing the fundamental frequency when compared to fix based building. This concept of base isolation also makes to remaining building behave elastic during an earthquake. Base isolation concept is also useful in other infrastructures like bridges, nuclear power plants and liquid storage tanks etc.

Abstract— Buildings are subjected to different earthquake loading and behaves differently with diversification in the types of soil condition, such as dense soil, medium and soft soil. Different soil properties can affect seismic waves as they pass through a soil layer. When a structure is subjected to an earthquake excitation, it interacts with the foundation and soil, and thus changes the motion of the ground. It means that the movement of the whole ground structure system is influenced by type of soil as well as zone by the type of structure. As the seismic waves transfer from the ground which consist of alteration in soil properties and performs differently according to soil’s respective properties. Efficient lateral systems, decreases the lateral deformations caused by the seismic forces in the buildings. In this work, it is proposed to carry out an analytical study, on multistory buildings of 15 stories, was carried out accounting for different seismic zones and soil types. The suitability and efficiency of different lateral bracing systems that are commonly used and also that of concrete in fills are investigated. The different bracing systems viz., X-brace, V- brace, inverted V or Chevron brace, Outriggers and in fills, are introduced in the buildings through analytical models. These were analyzed in 45m height, using ETABS software, for the action of lateral forces employing linear static and linear dynamic methods as per IS 1893 (Part I): 2002. The results of the analyses, in terms of lateral deformations and Base shears, Displacement, Drift, storey shear were obtained for all the different conditions discussed above The suitability of the types of lateral system for the buildings is suggested based on the soil type in particular zone.

The three sources, suggest a retrofit scheme to make up for the deficiencies and demonstrate that the retrofitted structure will be able to safety resist the future earthquake forces expected during the lifetime of the structure Thus, the structural engineering community has developed a new generation of design and seismic procedures that incorporate performance based structures and is moving away from simplified linear elastic methods and towards a more non-linear technique.

Buildings with same types of the zonal condition and for the same category can be adopted. Regular and irregular buildings i.e. center position and corner position building can be adopted. It shows the behavior of different position of the buildings. Analysis of response such as storey displacement, storey shear, storey drifts and time period is carried out using the ETABS 2015.

Himalee Rahangdale , S.R.Satone [5]work on design and analysis of multi-storey building with effect of shear wall. The G+5 storey building is analysed for lateral loading and seismic loading by STAAD-Pro software. They studied with the help of four different models. Model one is bare frame, and other three models have shear wall at different location in building. From result they observed that different location of shear wall effect on axial load on the column. In absence of shear wall axial load and moments are maximum on column. Shear walls are one of the most effective building elements in resisting lateral forces during earthquake. By constructing shear walls damages due to effect of lateral forces due to earthquake and high winds can be minimized.Shear walls construction will provide larger stiffness to the buildings there by reducing the damage to structure and its contents.

The same mathematical models of the superstructure (3-D beam and 3-D plate finite elements) are used for two considered foundations - hard rock and soft layered soil[r]

An increasing number of structures to be isolated reflect the fact that base isolation system is gradually becoming accepted as a proven technology in earthquake hazard mitigation. Lead-plug bearings are made up of low-damping elastomers and lead cores with diameters between 15% to 33% of the bonded diameter of the bearing. By combining laminated-rubber bearings with a lead-plug insert, which provides hysteretic energy dissipation, the damping required for a successful seismic isolation system can be incorporated in a single compact component.

The methodology includes fixing the dimensions of components for the selected water tank and performing nonlinear dynamic analysis by: 1893- 2002 (Part 2) draft code. This work proposes to study Circular tanks of different zones with all type of soil condition. The analysis is carried out for tank with full tank and empty condition. Finite Element Model (FEM) is used to model the elevated water tank using ETAB software.