Non-linear soil structure interaction of shear wall system with super element
Shear wall is commonly employed as a principal element to resist lateral loads due to wind or earthquake forces. An accurate model for shear wall system needs to consider the effect of all components for analyses i.e. shear wall, foundation and subsoil. This investigation presents modeling of shear wall structure - foundation and soil system using the super element, finite and infinite elements after considering soil nonlinearity. A finite element program has been written based on the proposed physical and material model for the analysis of the system. The applicability of the proposed idealization has been shown by analyzing a shear wall structure under static loading. In order to explore the efficiency of using super elements, an attempt has also been made to model the shear wall building using fully conventional finite element discretization. Furthermore the paper investigates the necessity of including soil structure interaction in analyzing shear wall structures. The results obtained from the analysis of shear wall model considering five different types of soil for the soil media show that the influence of soil interaction is very significant in the displacement as well as stresses induced in shear wall. Furthermore this investigation highlighted the effect of considering nonlinearity of soil in total displacement and stresses in shear wall system.
Effect of soil-flexibility on dynamic behaviour of building frames on raft foundation
Abstract The overall lateral stiffness of any building decreases due to the compressibility of soil. This leads to a subsequent increase in the natural periods of the structural system. The seismic lateral response may change due to natural periods while seismic torsional response arising out of mass or stiffness eccentricity depends on the ratio of uncoupled torsional-to-lateral natural period of the building. Hence, the effect of soil–structure interaction on lateral natural period, seismic base shear and fundamental torsional-to-lateral period ratio of building frames resting on raft foundation needs a detailed investigation. Present study is a limited effort to accomplish these objectives. Influence of the variation of a number of parameters such as (a) different soil conditions, (b) number of stories, (c) number of bays, (d) the ratio of flexural stiffness of columns to that of beams and (e) ground excitation frequency is considered in the present study. Buildings are modelled by two parallel approaches, viz., (1) frame with brick in-fill having fixed supports and (2) frame with brick in-fill having supports accounting for soil-flexibility. The soil-flexibilities for various types of soil and foundation based on their properties, e.g., shear modulus, the Poisson ratio of the soil, and shape and size of the rafts are computed following the well-accepted literature. The lateral natural period, torsional-to-lateral natural period ratio and seismic base shear of a variety of building frames at fixed base condition are compared to the same considering soil-flexibility due to variation in different influencing factors. The trends observed are attempted to be interpreted physically. The curves and tables presenting the change in lateral natural period and torsional-to-lateral period ratio due to effect of soil-flexibility of various building frames seem to be useful for calculating base shear of low-rise buildings through a simple methodology. Such simple methodology may be useful in the design offices for its simplicity and accuracy.
Accurate measurements of output characteristics and detonations of motorbike high-speed racing engine and their optimization at actual atmospheric conditions and combusted mixture composition
Abstract At a motorbike high speed racing engine there is very important an output engine characteristics which depends significantly on a detonation combustion rate, atmospheric conditions and a combusted mixture composition. The combustion process has got a relevant influence on a wear degree of main engine parts or on their damage eventually. The detonation combustion rate is very important because this kind of burning can be not only destructive but a useful phenomenon, as well. If the process of detonation burning is kept on a certain level, it can help significantly to the next increasing of an engine power output. In this article there is described the measurements of output characteristics of a high-speed racing engine which were performed by means of a data-recording system and the detonation combustion was evaluated using a quantitative method. The actual values of atmospheric conditions and the mixture composition were added to the measured values. Then the obtained values are compared visually with a damage degree of an engine piston caused by the detonation burning. The result is a limit value expressed in a number of detonation units related to a run distance interval of the vehicle driven by the high-speed racing engine. In framework of this run distance interval there is the process of detonation burning profitable. As well as it increases an engine power output and together it is not destructive with regard to engine design parts.