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.
Experimental verification of basic analytical assumptions used in the analysis of structural wall buildings
The observed response of medium high-rise buildings during the latest earthquakes in the USA, Chile, Mexico and Japan have indicated that buildings with structural walls or dual systems of frames and walls behave considerably better during strong shaking. A series of strong motion and ambient vibration records have been obtained in a 22-stories high structural wall Chilean building. Dynamic properties and response characteristics are identified using parametric and nonparametric system identification techniques. A strong coupling of translational modes and very low damping values are observed during medium intensity seismic events and ambient excitations. Typical values for critical damping ratios are between 1 and 2%. Rocking is observed as an appreciable effect on the overall displacements of the structure. Torsional effects are not important in the observed seismic response but they become relatively important during low level ambient excitations. The basic response characteristics identified are compared with those of a three-dimensional model. The model was determined using typical consulting office assumptions. The agreement between model and experimental records is good for global dynamic parameters, and with further adjustment, seismic response can be modeled with a good degree of accuracy validating a series of modeling assumptions.
The interaction of plane frames with elastic foundation having normal and shear moduli of subgrade reactions
Abstract The interaction of plane frames with an elastic foundation, of the Winkler type, having normal and shear moduli of subgrade reactions was studied. An exact stiffness matrix for a beam element on an elastic foundation having only a normal modulus of subgrade reaction was modified to include the shear modulus of subgrade reaction of the foundation as well as the axial force in the beam. A computer program was written and used in two case studies. In the first case study the convergence of the modified element was tested: in the second it was employed to study the effect of the foundation normal and shear moduli of subgrade reactions on the bending moments in a selected plane frame. The results indicated that bending moments might be considerably affected according to the type of frame and loading.