Optimising Surveys and Reliability Assessments of Historic Cast-Iron Columns

Abstract

Cast iron structures mostly date back to the second half of the 19th century. Material properties vary due to different composition and production techniques that have been used in different regions over decades. This is why it is of crucial importance to obtain case-specific information on properties of historic structures. Many historic metal structures do not fulfil requirements of present standards. Decisions about adequate construction interventions should be based on complex assessment of structural reliability. In this contribution, the material properties of an iron column are investigated and the key considerations for reliability assessment are presented. Three fundamental issues are addressed to optimise surveys and reliability assessments of cast iron columns: 1) an optimum number of material tests; 2) the selection between a finite element (FE) and analytical model; and 3) the target reliability level for a historic structure. It is shown that uncertainties due to limited test data, variability of material and geometrical properties, and resistance model uncertainty can be treated by a semi-probabilistic verification method. As a first approximation, five tensile tests might be considered as an optimum survey strategy. The application of FE models is more demanding than that of simplified analytical formulas, but it can better reflect structure-specific conditions and may increase structural resistance by about 15%. Optimum target reliability level for existing structures with a cultural heritage value could be lower than that for structural design and the assessment value of resistance may increase by about 20% for a reduced target level.

Measurement Uncertainty in Tests of Cast Irons

“…The obtained results are critically compared, considering also the results of previous studies. The contribution is an extended version of the previous study [19]. Fig.…”

“…1 Iron columns [19] Fig. 2 Damaged column used for specimens [19] Tensile Strength Six specimens were prepared for tensile strength tests in accordance with EN ISO 6892-1:2014 [23]. One specimen was removed from the sample due to large pores (Fig.…”

Heritage value assessment method – Application to historic steel bridgein prague

“…Fifteen per cent is thus the expected gain when the characteristic value of steel yield strength is estimated based on five DTs instead of a large number of NDTs. While similar observations are expected to apply for wrought irons [10], the use of tensile and compressive tests (DTs) is recommended for cast iron structures due to the inherent variability of their strength, the weaker relationship between the hardness of surface layers and tensile or compressive strength, and the overly conservative estimates of cast iron properties provided in normative documents [11,12].…”

Corrosion of historic grey cast irons: indicative rates , significance, and protection

“…Due to a limited scope of this contribution, a simplified analysis based on the commonly adopted semi-probabilistic approach -see EN 1990:2002 and ISO 2394:2015 for the basis of design and reliability analysis, respectively -is presented here. The design value of resistance, R d , takes into account resistance model uncertainty and variability of material strength and geometry [13,14]:…”

“…In the second example, a thin-walled short cast iron column supporting a roof of a historic arbour [4,14] is analysed (Ø = 114 mm, thickness of 12.5 mm, Ø in = 89 mm). In this case, the uncertainty in resistance slightly increases due to uncertainty in corrosion losses that is taken into account in reliability analysis.…”