Reliability of beams designed in accordance with Brazilian codes

Abstract

This paper presents an investigation on the safety of structural elements submitted to pure bending, produced in reinforced concrete, in steel and steel-concrete composites, and designed according to Brazilian codes NBR8681:2003, NBR6118:2007 and NBR8800:2008. The study allows a comparison of the relative safety of beams produced with these materials and designed using these codes. Comparative studies between the performances of different materials are difficult to find in the published literature. The present study shows that reliability indexes for reinforced concrete beams are satisfactory; however, results for steel beams are below limit values established in international design standards. Reliability indexes found herein for steel-concrete composite beams are intermediate to concrete and steel beams.

The impact of the quality of materials on the differentiation of the reliability of a reinforced concrete beam

“…For example: including due to the variability in time: dead and variable, variability in space: free and non-free, the type of the impact on the structure: static, dynamic, and due to the reason for the uprising: caused by natural phenomena: snow, wind, caused by human activity (technological load ), whether subject to control and disasters. Analysis of the structural element / structure must take into account the influence of all loads that can have a significant impact on the structure [1,20].…”

“…PN-EN 1990 [1] defines the characteristic values of dead loads as 95% quantiles when the effects are unfavorable or when the effects are favorable. The probabilistic model for dead loads is usually a normal distribution [6,9,[11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”

“…The accepted variable load in the conducted analyses is the variable load in buildings, commonly represented by log-normal distributions [6,9,[11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Alternatively.…”

“…where: fm -medium strength of material; σ /  -standard deviation / material strength variation coefficient. The statistical model of compressive concrete strength was adopted on the basis of the models proposed in [6], [9], [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. The log-normal distribution was used to describe the distribution of the probability of concrete compressive strength.…”

“…For the description of the steel strength probability distribution, according to [6], [9], [11][12][13][14][15][16][17][18][19][20][21][22][23][24], log-normal distribution was also used. The coefficient of variation for tensile strength of steel was adopted in accordance with [6], [9], [11][12][13][14][15][16][17][18][19][20][21][22][23][24] at the level of 0.04.…”