Hideki Idota

Response uncertainty and time‐variant reliability analysis for hysteretic MDF structures

Response uncertainty evaluation and dynamic reliability analysis corresponding to classical stochastic dynamic analysis are usually restricted to the uncertainties of the excitation. The inclusion of the parameter uncertainties contained in structural properties and excitation characteristics has become an increasingly important problem in many areas of dynamics. In the present paper, a point estimate procedure is proposed for the evaluation of stochastic response uncertainty, and a response surface approach procedure in standard normal space is proposed for analysis of time-variant reliability analysis for hysteretic MDF structures having parameter uncertainties. Using the proposed procedures, the response uncertainties and time-variant reliability can be easily obtained by several repetitions of stochastic response analysis under given parameters without conducting sensitivity analysis, which is considered to be one of the primary difficulties associated with conventional methods. In the time-variant reliability analysis, the failure probability can be readily obtained by improving the accuracy of the first-order reliability method using the empirical second-order reliability index. The random variables are divided into two groups, those with CDF and those without CDF. The latter are included via the high-order moment standardization technique. A numerical example of a 15F hysteretic MDF structure that takes into account uncertainties of four structural parameters and three excitation characteristics is performed, based on which the proposed procedures are investigated and the effects of parameter uncertainties are discussed. Copyright

Risk-Based Strategies for Upgrading Existing Nonconforming Wooden Houses and Risk Information for Promoting Upgrading

There is widespread awareness in seismic-prone countries about the necessity to upgrade the seismic performance of old buildings and wooden houses for disaster mitigation; however, upgrading occurs at a very slow pace. At present, Japan has approximately 11 million nonconforming old wooden houses, but most of them remain without upgrade because of the large expenditure that would be incurred by both house owners and the local government. An owner would need to spend approximately US

Upgrade Decision-Making for Earthquake-Vulnerable Wooden Houses Using Probabilistic Damage Index Functions

11,000 on average to upgrade his/her house such that it satisfies the current design requirements. In Aichi prefecture alone, upgrading would cost approximately US

Assessment of Redundant Steel Structural Systems Considering Effects of Member Strength Variability on the System

10 billion in total, which is approximately 40% of the annual budget. This study, therefore, investigates alternative strategies for upgrading existing nonconforming wooden houses more efficiently and cost-effectively. The seismic risks of wooden houses as a whole in Aichi prefecture are estimated, and then the effective target level for upgrading is discussed from the viewpoint of both economic loss and the number of fatalities. It is shown here that it is worthwhile from the viewpoint of life safety to consider a target upgrading level that is lower than the current design requirements. Although the analytical models discussed in this paper might be specific to Japan, the framework of the risk assessment is universal and the conclusions drawn from this analysis are applicable to other seismic-prone regions and countries.

DESIGN LIVE LOADS FOR ROOFTOP GARDENS BASED ON SURVEY RESULTS OF URBAN DETACHED HOUSES

AbstractThere is widespread awareness in seismic-prone countries of the necessity to improve the seismic performance of old buildings and houses for disaster mitigation. To support the decision mak...

Comparison of Probabilistically Evaluated COF with the Base Shear Distribution of IBC and Japanese Code

In the present study, the failure of basic redundant steel structural systems is investigated. By considering that each member of the system has brittle, semi-brittle, or perfectly plastic properties, the statistical behavior of perfectly brittle systems, semi-brittle systems, perfectly plastic and combination systems are evaluated, and the effects of the coefficient of variation (CoV) of members on the systems are investigated. Uncorrelated strengths with the same mean are considered for the system elements. By using the Monte Carlo simulation (MCS) method, maximum strength, yield strength and residual strength of the redundant steel structural systems are evaluated. The CoV of member strength is an essential parameter for statistical assessment of steel structural systems. In this study, the strength is defined random variable a selected normal distribution represents the random variable, for the member strength. The deformation capacity of the member is strongly depends to the characteristics of member strength, but the post failure factor has deterministic values, only for the combination system. The post failure factor is a random variable that represents the uncertainty, uniform distribution is selected to represents random variable, in combination system post failure factor.

A Three-Parameter Distribution Used for Structural Reliability Evaluation

The design live load for residence is often used for designing rooftops of residences, but the validity of using residence live load for rooftop gardens has not been confirmed. In the present study, new design value of live load for rooftop gardens are proposed based on the building survey results from 24 steel-framed houses in Tokyo area. The proposed design live load value will allow for the rational structural design of residences with rooftop gardens and also allow rational consideration of future changes to rooftop occupancy.

A STUDY ON ENERGY ABSORPTION CAPACITY OF STEEL FRAMES CONSIDERING UNCERTAINTY OF MEMBER DUCTILITY

Abstract In the earthquake resistant design concept, frame structures are usually designed with a column over design factor (COF) to ensure the preferable failure mode during earthquakes. Initially, in the present study, the failure modes of multistory ductile frame structures are investigated probabilistically by applying the first order reliability method (FORM). The base shear distribution of the International Building Code (IBC-2006), which adopted the seismic design provisions of ASCE 7-05, and the Ai distribution of the Building Standard Law of Japan are taken into account in this study. Based on the investigations, the target values of the COF that probabilistically ensure the preferable entire beam hinging failure mode prior to story collapse are evaluated and compared. The study has been conducted for different reliability levels and the corresponding COF values are presented in this paper.