Abstract
Abstract Nowadays it is known that it is important to study the safety of structures to avoid tragic accidents or economic losses. The most widely used method in the world to evaluate the safety of structures is structural reliability. The reliability index of prestressed precast beams of bridges designed using Brazilian standards (NBR6118 and NBR7188) is not known. This work evaluates the annual reliability indexes of a prestressed precast beam bridge at the serviceability limit state (SLS) projected using the Brazilian standard and compares it with results from the literature. The studied bridge has 33.5 meters of span, is simply supported, constituted by five precast concrete beams with U section. The reliability analysis was carried out using two methods for the four limit state equations: First Order Mean Value (FOMV) and First Order Reliability Method (FORM). Sensitivity analyzes were performed to consider both the relative contribution of these variables and the effect of their distributions on the annual reliability indexes for SLS. It was verified that the effect of load trains and the allowable stress significantly reduce the reliability index obtained for Brazilian standard. The service limit state equations are particularly sensitive to load trains, allowable stress and prestress losses, as well as their respective distributions.
Highlights
A bridge is a construction meant to establish the continuation of a path going over an obstacle and is an important component for transportation
The concentrated load “Q” in kN and distributed load “q” in kN/ m2 are the values of the vertical moving load applied at pavement level, equal to the characteristic values increased by the Vertical Impact Coefficients (VIC), the Number of Lanes (NoL) and of the Additional Impact (AI) coefficients, defined as follows
The bridge was considered to be in an environment with an 15°C annual average temperature and a 60% average relative humidity (RH)
Summary
A bridge is a construction meant to establish the continuation of a path going over an obstacle and is an important component for transportation. It is important to study the safety of these structures so that they can have a longer service life, without interruption, and at the lowest cost possible. In Brazil, use of reliability theory caused a significant change in the way structural elements, such as cantilever slabs and pillars, are designed. To help with the analysis of structural reliability, the concept of reliability index β was introduced. Some standards, such as the Eurocodes and the Load and Resistance Factor Design of the United States, specify a target reliability index value, according to the importance of the structure or structural element
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