• Structural Engineering and Mechanics
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• v.72 no.5
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• pp.585-595
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• 2019

Foundations are a vital part of structures. Over time, the foundations can deteriorate due to unforeseen overloads and/or settlements, resulting in the appearance of cracks in the concrete. These cracks produce changes in the static and dynamic behavior of the affected foundation, which alter its load carrying capacity. In this work, non-destructive techniques of relative simplicity of application are presented for the detection, location, and quantification of damage, using numerical models, solved with the finite element method and Power Series. For this, two types of parameters are used: static (displacement and elastic curvature) and dynamics (natural frequencies). In the static analysis, the damage detection is done by means of a finite elements model representing a beam supported on an elastic foundation with a discrete crack that varies in length and location. With regard to dynamic analysis, the governing equations of the model are presented and a method based on Power Series is used to obtain the solution for a data set, which could be the Winkler coefficient, the location of the crack or the frequency. In order to validate the proposed methodologies, these techniques are applied to data obtained from laboratory tests.

• Structural Engineering and Mechanics
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• v.58 no.5
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• pp.905-929
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• 2016

This paper assesses efficiency of the continuum method as the idealized system of building structures. A modified Coupled Two-Beam (CTB) model equipped with classical and non-classical damping has been proposed and solved analytically. In this system, complementary (non-classical) damping models composed of bending and shear mechanisms have been defined. A spatial shear damping model which is non-homogeneously distributed has been adopted in the CTB formulation and used to equivalently model passive dampers, viscous and viscoelastic devices, embedded in building systems. The application of continuum-based models for the dynamic analysis of shear wall systems has been further discussed. A reference example has been numerically analyzed to evaluate the efficiency of the presented CTB, and the optimization problems of the shear damping have been finally ascertained using local and global performance indices. The results reveal the superior performance of non-classical damping models against the classical damping. They show that the critical position of the first modal rotation in the CTB is reliable as the optimum placement of the shear damping. The results also prove the good efficiency of such a continuum model, in addition to its simplicity, for the fast estimation of dynamic responses and damping optimization issues in building systems.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.2
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• pp.193-201
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• 2004

The aim of this study is focused on getting an almost exact solution which is the simplicity and exactness of an axisymmetrically loaded cylindrical shell. This method replaces the finite element method which is a very powerful tool for analysis of any kind of structure which has an arbitrary shape, but is still a numerical analysis. Instead, this study uses the method of distribution of end actions which is a kind of iteration technique to implement the leading matrix method. The distribution and carry-over factors of a cylinder are calculated by the theory of a differential equation of a beam on an elastic foundation. The results are satisfactory when this method is applied to a cylinder that is subjected to a concentrated load and hydrostatic pressure when compared with the BEF analogy separately.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.795-800
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• 2007

In the previous study, a simple but effective analysis procedure, named as an Improved Modal Pushover Analysis (IMPA) was proposed to estimates the seismic capacities of multi-span continuous bridge structures, on the basis of the modal pushover analysis which considers all the dynamic modes of a structure. Differently from other previous studies, IMPA maintains the simplicity of the capacity-demand curve method and also gives a better estimation of the maximum dynamic response of a structure. Nevertheless, its applicability has never been approved for multi-span continuous bridges with large differences in the length of their adjacent piers. This paper, accordingly, concentrates on a parametric study to verify the efficiency and limitation in application of IMPA through a correlation study between various analytical models including the Equivalent Single Degree Of Freedom (ESDOF) and Modal Pushover Analysis (MPA) usually used in the seismic design of structures. Based on the obtained numerical results, this paper introduces a practical guidance and/or limitation for using IMPA to predict the seismic response of a bridge effectively.

• Structural Engineering and Mechanics
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• v.35 no.4
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• pp.459-478
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• 2010

This paper contains detailed descriptions of a dynamic time-history modal analysis to calculate deflection, inter-storey drift and storey shear demand in single-storey and multi-storey buildings using an EXCEL spreadsheet. The developed spreadsheets can be used to obtain estimates of the dynamic response parameters with minimum input information, and is therefore ideal for supporting the conceptual design of tall building structures, or any other structures, in the early stages of the design process. No commercial packages, when customised, could compete with spreadsheets in terms of simplicity, portability, versatility and transparency. An innovative method for developing the stiffness matrix for the lateral load resistant elements in medium-rise and high-rise buildings is also introduced. The method involves minimal use of memory space and computational time, and yet allows for variations in the sectional properties of the lateral load resisting elements up the height of the building and the coupling of moment frames with structural walls by diaphragm action. Numerical examples are used throughout the paper to illustrate the development and use of the spreadsheet programs.

• Computers and Concrete
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• v.7 no.6
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• pp.483-496
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• 2010

This work deals with the determination of crack openings in 2D reinforced concrete structures using the Finite Element Method with a smeared rotating crack model or an embedded crack model. In the smeared crack model, the strong discontinuity associated with the crack is spread throughout the finite element. As is well known, the continuity of the displacement field assumed for these models is incompatible with the actual discontinuity. However, this type of model has been used extensively due to the relative computational simplicity it provides by treating cracks in a continuum framework, as well as the reportedly good predictions of reinforced concrete members' structural behavior. On the other hand, by enriching the displacement field within each finite element crossed by the crack path, the embedded crack model is able to describe the effects of actual discontinuities (cracks). This paper presents a comparative study of the abilities of these 2D models in predicting the mechanical behavior of reinforced concrete structures. Structural responses are compared with experimental results from the literature, including crack patterns, crack openings and rebar stresses predicted by both models.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2396-2406
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• 2021

The Pacific Earthquake Engineering Research (PEER) Center has been developing a performance-based earthquake engineering (PBEE) methodology, which is based on explicit determination of performance, e.g., monetary losses, in a probabilistic manner where uncertainties in earthquake ground motion, structural response, damage estimation, and losses are explicitly considered. To carry out the PEER PBEE procedure for a component of the nuclear power plant (NPP) such as the cable tray system, hazard curve and spectra were defined for two hazard levels of the ground motions, namely, operation basis earthquake, and safe shutdown earthquake. Accordingly, two sets of spectral compatible ground motions were selected for dynamic analysis of the cable tray system. In general, the PBEE analysis of the cable tray in NPP was introduced where the resulting floor motions from the time history analysis (THA) of the NPP structure should be used as the input motion to the cable tray. However, for simplicity, a finite element model of the cable tray was developed for THA under the effect of the selected ground motions. Based on the structural analysis results, fragility curves were generated in terms of specific engineering demand parameters. Loss analysis was performed considering monetary losses corresponding to the predefined damage states. Then, overall losses were evaluated for different damage groups using the PEER PBEE methodology.

• Structural Engineering and Mechanics
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• v.70 no.3
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• pp.289-301
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• 2019

Hysteretic energy is defined as energy dissipated through inelastic deformations during a ground motion by the system. It includes frequency content and duration of ground motion as two remarkable parameters, while these characteristics are not seen in displacement spectrum. Since maximum displacement individually cannot be the appropriate criterion for damage assessment, hysteretic energy has been evaluated in this research as a more comprehensive seismic demand parameter. An innovative methodology has been proposed to establish a new equivalent linear model to estimate hysteretic energy spectrum for bilinear SDOF models under two different sets of earthquake excitations. Error minimization has been defined in the space of equivalent linearization concept, which resulted in equivalent damping and equivalent period as representative parameters of the linear model. Nonlinear regression analysis was carried out for predicting these equivalent parameter as a function of ductility. The results also indicate differences between seismic demand characteristics of far-field and near-field ground motions, which are not identified by most of previous equations presented for predicting seismic energy. The main advantage of the proposed model is its independency on parameters related to earthquake and response characteristics, which has led to more efficiency as well as simplicity. The capability of providing a practical energy based seismic performance evaluation is another outstanding feature of the proposed model.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.3
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• pp.407-415
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• 2022

In this study, a square rounding sidewalk block frame was developed considering the simplicity of construction and the superiority of aesthetics. In addition, it is possible to prevent damage, deformation, and settlement of adjacent sidewalk blocks due to plastic deformation during car impact load of installed bollad. A non-linear structural analysis was performed through finite element analysis to examine the performance of a car crash to which this was applied. Structural safety was confirmed through car crash simulation according to the direction of impact, and it is estimated that the function can be restored by replacing some parts in case of damage due to impact.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.91-100
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• 2008

A technique strengthened to the reinforced concrete members using the external post- tensioned method offers the advantages in speed and simplicity of installation over other, established, strengthening techniques. But this technique has many unreasonable facts. This paper are analyzed an unreasonable facts of the previous external post-tension technique. The purpose of this paper proposed Bow system as the new technique strengthened to the reinforced concrete members. The Bow system which is better technique than the previous technique was introduced with the experimental/analytical data.