Asian journal of civil engineering
Volume:5 Issue: 1, January & April 2004

This paper addresses the collapse process of wooden houses subject to earthquake ground motions and characteristics of its ground motion by employing DEM analysis. In order to evaluate the traditional characteristic of ground motion, Instantaneous Instrumental Seismic Intensity (hereafter, IISI), which was previously proposed as an index of seismic intensity, is used. This paper combines both of the IISI and collapse process of house and evaluates the ground motion characteristics based on the results of DEM calculation, which induces a time-sequence of collapse modes.

This paper describes the numerical tests for the nonlinear analysis of eight reinforcedconcrete (RC) deep beams. A stringer-panel model is presented for the nonlinear analysis of the deep beams. Cracked reinforced concrete is treated as an orthotropic material. Tomodel nonlinear material response, the constitutive relations currently utilized are those ofthe modified compression field theory. Stiffness matrices are defined for concrete andreinforcement, and element stiffness matrices are derived for stringer and panel elements. A solution algorithm is described. The ability of the stringer-panel model to assess ultimate load is evaluated by correlation studies with available experimental data. The computational efficiency, numerical stability, and potential application of the model are demonstrated through example analyses.

Recently developed nonlinear beam/columns elements based on large displacement theoryare easily accessible to the research community for the dynamic analysis of earthquakeexcited structures. It is of interest to assess whether the application of these elements isdesirable in engineering practice and research. This study is intended to provide quantitative knowledge on the importance of large displacement effects on the response of seismically excited structures. Generic frame models are utilized to represent SDOF and MDOF structures. Equivalent pulses are used to represent seismic input, since their effect on structural response is comparable to that of near fault ground motions. Large displacements of frame structures give rise to second-order amplification and thus, structure and member P-delta effects are addressed. The results demonstrate that the influence of large displacement formulations is of secondary importance for the response prediction of elasticplastic SDOF and MDOF frame structures. Keywords: large displacements; generic frame structures; pulse-type ground motion; nonlinear response; P-delta effect; seismic response

The vibration serviceability requirements for wooden floors in accordance with Eurocode-5(EC-5) as illustrated by Ohlsson [1] are rated using a combination of Value Analysis (VA)and the Checking Point Method (CPM) of the First-Order Reliability Procedure (FORP).The implied safety indices for the current requirements were first estimated andconsequently the associated potential losses were deduced for varying design inputsconsidered as random variables with practical probability distributions. The preliminaryresults indicate the direction for enhancing the effective use of timber in flooring systems to withstand human-induced vibrations safely and economically.

This paper presents a new method for optimization of dynamic response of structuressubjected to seismic excitation. This method is based on the concept of uniform distribution of deformation. In order to obtain the optimum distribution of structural properties, an iterative optimization procedure has been adopted. In this approach, the structural properties are modified so that inefficient material is gradually shifted from strong to weak areas of a structure. This process is continued until a state of uniform deformation is achieved. It is shown that in general for a MDOF structure there exists a specific pattern for distribution of structural properties that results in an optimum seismic performance. The application of the proposed method for optimum seismic design of different structural forms such as truss-like structures and shear-buildings is presented.

It has been generally accepted that the tensile strength and elastic modulus of concrete is proportional to the square-root of its compressive strength. This relationship, however, may not be applicable for high-performance concrete. The study presents data on strength and stiffness of concretes containing a laboratory produced metakaolin and commercial silica fume as cement replacement materials, with water-to-cementitious materials ratio of 0.27 to 0.33. Approximately 750 specimens were tested and compressive strength of up to 110 MPa at 90 days were reported. Analysis of the best-fit relationships for tensile-compressive strength and stiffness-compressive strength found that the square-root function recommended by most codes of practice is inadequate when applied to concretes of higher strength, particularly in the case for tensile strength prediction.