Title: Revised Statistical Resistance Models for R/C Structural Components

Author(s): Andrzej S. Nowak, Anna M. Rakoczy and Ewa K. Szeliga

Publication: Symposium Paper

Volume: 284

Issue:

Appears on pages(s): 1-16

Keywords: concrete, resistance factor, bias factor, coefficient of variation, cumulative distribution function, statistical parameters, material test data

DOI: 10.14359/51683801

Date: 3/1/2012

Abstract:
The objective of this study is to revise the resistance model for calibration of the ACI 318 Code, using the new material test data. The research focused on the development of statistical parameters of the load carrying capacity for reinforced concrete beams, slabs and columns. The considered materials include ordinary concrete and high strength concrete, both cast-in-place and plant-cast. Resistance is considered as a product of three random variables representing the uncertainty in material properties, dimensions and geometry (fabrication factor) and analytical model (professional factor). Material test data is presented in form of the cumulative distribution functions (CDF) plotted on the normal probability paper for an easier interpretation of the results. In addition, the statistical parameters are determined for a normal distribution that is fitted to the lower tail of the CDF. The most important parameters are the mean value, bias factor and the coefficient of variation. It was observed that the quality of materials and workmanship have been improved over the last 30 years and this is reflected in reduced coefficients of variation. The two other parameters, i.e. fabrication and professional factors, are also considered and summarized based on the available literature. The developed resistance models were obtained by Monte Carlo simulations. They can serve as a basis for the selection of resistance factors (strength reduction factors).