PSI - Issue 5
Hołowaty J. et al. / Procedia Structural Integrity 5 (2017) 1043 – 1050 Hołowaty / Struc ural Integrity Procedia 00 ( 2017) 000 – 000
1044 2
Nomenclature A
annealed specimens
A 5
percentage elongation after fracture on a 5d gauge length
d f d
diameter of a round specimen
design strength
f yH f yL f uB FA f u
upper yield strength lower yield strength ultimate strength
ultimate strength according to Brinell hardness
shear-fracture appearance
H
height of the main carrying members (plate girder or truss)
HB
Brinell hardness
K energy required to break a specimen with a pendulum impact testing machine KV(T) impact energy in Joule (J) in a test at a temperature T with Charpy V notch specimen L span length of a bridge, gauge length l length of a specimen N normalized specimen S naturally-aged specimen T temperature (° C) T t transition temperature (DBTT) T 27J temperature at which a minimum energy KV will not be less than 27 J in a Charpy V-notch impact test T 50 % temperature at which fracture is 50 % cleavage and 50% ductile t plate thickness V V-notch (type of notch) Ed stress accompanying the reference temperature T Ed s partial factor for steel Riveted railway bridges are associated with historical railway lines and many of these bridges are still in operation despite their long lifespan. They have undergone repairs, modernization works, strengthening or even relocation due to war damage and renovations. They require assessment in order to estimate their current technical condition and load bearing capacity. The data collected over many years of bridge evaluations has resulted in the establishment of special codes in some countries as well as European recommendations [Kühn et al. (2008)]. The rules and approaches developed for old structures allow for more rational recognition and assessment. Many structures may remain in operation without the need for major strengthening or replacement. 2. Assessment of old bridges Different types of steels have been used in railway bridge construction. The material testing of steel in old bridge structures usually involves ascertaining the chemical content, taking hardness measurements, performing simple tensile tests and calculating weldability when required. On the basis of these results the grade of steel is established along with its current mechanical properties. The final assessment of the steel relies on whether the steel in post service conditions still fulfills the code and technical requirements. As a comparison level for changes in mechanical properties under operation, a simulation of the initial structure of the material was undertaken by normalized heating. Specimens were heated at a temperature of 930 °C for an hour and then were cooled in air in order to achieve the finest possible grain size in the steel. This is a factor which usually increases yield strength and lowers the transition temperature of the steel. 2.1. Investigation of steel properties
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