Inyeol Paik

Design Life and Reliability-based Design Concept for Long-Span Cable-Supported Bridge

The basic design concepts for the limit state design code under development in Korea for the longspan cable-supported bridge are presented. Considering the importance of the structure, higher target reliability level and longer design life are defined compared to those of the ordinary bridges. In deciding the amount of safety increase, the construction cost and the consequence of structural failure are examined. Safety factors including the importance factor which is multiplied to the design strength of the structural member are calibrated through reliability analysis of the actual design examples. It is also shown that the nonlinear analysis of the cable-supported bridge yields higher reliability index of the main cable than that obtained by the linear analysis.

Estimation of Live Load Effect of Single Truck Through Probabilistic Analysis of Truck Traffic on Expressway

PURPOSES : This study estimated the load effect of a single heavy truck to develop a live load model for the design and assessment of bridges located on an expressway with a limited truck entry weight. METHODS : The statistical estimation methods for the live load effect acting on a bridge by a heavy vehicle are reviewed, and applications using the actual measurement data for trucks traveling on an expressway are presented. The weight estimation of a single vehicle and its effect on a bridge are fundamental elements in the construction of a live load model. Two statistical estimation methods for the application of extrapolation in a probabilistic study and an additional estimation method that adopts the extreme value theory are reviewed. RESULTS : The proposed methods are applied to the traffic data measured on an expressway. All of the estimation methods yield similar results using the data measured when the weight limit has been relatively well observed because of the rigid enforcement of the weight regulation. On the other hand, when the estimations are made using overweight traffic data, the resulting values differ with the estimation method. CONCLUSIONS : The estimation methods based on the extreme distribution theory and the modified procedure presented in this paper can yield reasonable values for the maximum weight of a single truck, which can be applied in both the design and evaluation of a bridge on an expressway.

Statistical Estimation of Specified Concrete Strength by Applying Non-Destructive Test Data

The aim of the paper is to introduce the statistical definition of the specified compressive strength of the concrete to be used for safety evaluation of the existing structure in domestic practice and to present the practical method to obtain the specified strength by utilizing the non-destructive test data as well as the limited number of core test data. The statistical definition of the specified compressive strength of concrete in the design codes is reviewed and the consistent formulations to statistically estimate the specified strength for assessment are described. In order to prevent estimating an unrealistically small value of the specified strength due to limited number of data, it is proposed that the information from the non-destructive test data is combined to that of the minimum core test data. The the sample mean, standard deviation and total number of concrete test are obtained from combined test data. The proposed procedures are applied to an example test data composed of the artificial numerical values and the actual evaluation data collected from the bridge assessment reports. The calculation results show that the proposed statistical estimation procedures yield reasonable values of the specified strength for assessment by applying the non-destructive test data in addition to the limited number of

Evaluation of Reliability Index of Governing Load Combination for Design of Cable Supported Bridge Members

Abstract In this paper the reliability analyses of the cable-supported bridge design code which is recently issued in Korea are performed and the results are presented. Governing load combinations for the member design and the statistical properties of the main members are introduced and the analysis is performed using an example cable-stayed bridge for which the design is performed following the load and resistance factors defined in the design code. The reliability analysis shows the target reliability index can be achieved by applying load and resistance factors and the application of the resistance modification factor can enhance the reliability level if the importance of the bridge needs to be increased. The sensitivity analysis reveals that decreasing uncertainty of the cable strength is critical for obtaining the target reliability index. The study results show that the design using the load and resistance factors of the code can achieve the target reliability indexes for the design of cable supported bridge.

Reliability Analysis of Pylon for Yi Sun-sin Bridge

This paper presents the reliability assessment of the pylon for a real suspension bridge in Korea using the advanced first-order second-moment method(AFOSM)[1]. The P-M interaction diagram (PMID)[2], presenting the strength of the pylon, is defined as a limit state function. Random variables include the load and strength parameters. Because the PMID is nonlinear with respect to the random variables, the iterative procedure is needed to solve the AFOSM . In this paper, double iteration loops based on the modified Newton-Raphson method [3], are adopted to estimate the most probable failure point(MPFP) and reliability index. The sensitivities of the PMID with respect to random variables are obtained by direct differentiation. Cubic spline interpolation [4] is utilized to construct the continuous and differentiable PMID.

Investigation of Design Loads and Load Combinations for Limit State Design of Long Span Cable-Supported Bridge

For the design of long span cable supported bridge (LSCSB), the reliability based limit state design manual is under development. Statistical and probabilistic definition of the design loads and the load factors in the load combination are examined in relation to the design period and the safety level. For the purpose of investigating the reliability level of the design load combinations in the ultimate limit state and the extreme event limit state, the definitions of the variable loads are reviewed in terms of the design period and exceedance probability. An example of cable-stayed bridge is presented to show the reliability indexes of design load combinations of earthquake load.