DEMSA Protocol: Deterioration Effect Modelling for Structural Assessment of RC Buildings

Abstract

The effects of deterioration strongly impact the expected future service life and the structural performances of existing reinforced concrete structures. Currently, straightforward methodologies are required to include such effects in the assessment and renovation of the RC buildings’ heritage. A simplified protocol enabling the detection, evaluation, and modelling of corrosion effects is presented in this paper. The protocol provides the guidance for the design and management of the on-site diagnostic campaign, aimed at identifying a possible corrosion risk scenario. Then, equivalent damage parameters describing corrosion effects in the structural models can be calibrated. Structural performances over time can be assessed to predict the structural residual life, maintenance management criteria and timing, and major indications on the feasibility of the retrofit intervention, or the unavoidable need of demolition. The application of the proposed protocol to some case studies emphasises the effectiveness of the procedure for detecting possible activated corrosion processes and for supporting engineers in their decision-making process and choice of renovation strategy.

Toward the definition of equivalent damage parameters for the assessment of corroded RC structures

“…Therefore, from the designer point of view, the applicability of the available knowledge into the diagnosis and assessment process may be limited due to the lack of a shared simplified multidisciplinary approach dealing with all the sectorial fields involved in the problem. 6 A great effort is being made recently to integrate such knowledge in the current practice, involving both researchers and practitioner engineers. 4,5 In this context, the recently proposed DEMSA Protocol 6 (Deterioration Effect Modeling for Structural Assessment) provides a step-by-step procedure guiding the engineer from building inspection to structural evaluation and selection of the best renovation strategy by including corrosion effects.…”

“…6 A great effort is being made recently to integrate such knowledge in the current practice, involving both researchers and practitioner engineers. 4,5 In this context, the recently proposed DEMSA Protocol 6 (Deterioration Effect Modeling for Structural Assessment) provides a step-by-step procedure guiding the engineer from building inspection to structural evaluation and selection of the best renovation strategy by including corrosion effects. In the Protocol, validated aspects from the literature are collected, and new tools allowing interaction among the different levels of the assessment process are integrated.…”

“…F I G U R E 2 Definition of the equivalent damage parameters to be implemented: In blue the input data related to corrosion risk, in light blue the corrosion attack characteristics selected from the Scenarios, in dark blue the final equivalent damage parameters 6 Addressing concrete material properties, a reduced compressive strength is calculated for cracked concrete cover, dependent on the corrosion attack penetration, as proposed in Coronelli & Gambarova 19 through Equation 5, where k is a coefficient related to bar roughness and diameter (assumed as 0.1 for medium-ribbed bars); ε c0 is the strain associated with the maximum compressive stress f c (uncracked concrete) and ε 1 the average tensile strain in the cracked concrete (Equation 6). In this case, b 0 is the section width in the uncracked stage and b f the section width increased by corrosion cracking, approximated as in Equation 7, where n bars is the number of bars in the top layer (compression zone) and w cr the total crack width for a corrosion level p (penetration of the corrosion attack), which is evaluated by following Molina et al 20 as reported in Equation 8; υ rs is the ratio of volumetric expansion of the oxides with respect to the virgin material (assumed equal to 2) and u i,corr the opening of each corrosion crack.…”

“…The latter usually corresponds with T 0 unless environmental aggressiveness conditions may have changed during the structure life. 6 Then, the time necessary for the aggressive substances to reach bars (initiation time T i ) is calculated (Equation 2):…”

The LCT Challenge: Defining New Design Objectives to Increase the Sustainability of Building Retrofit Interventions

“…From an environmental point of view, renovation avoids all the impacts connected to the demolition of the existing building and to the construction of a new building, which requires greater emissions than renovation; on the other hand, it may be expected that, from a technological viewpoint, a new building requires fewer interventions of maintenance and repair with respect to an existing retrofitted building. In addition, some other issues should be considered in such a choice: economic issues, given that in some cases demolition may be more convenient, especially when deep renovation works are required; technical issues, considering that the structural capacity of existing buildings may be compromised by heavy structural decay [47]; and social issues, given that demolition of a building always requires relocation of its occupants, which is acknowledged as the first barrier to the renovation of buildings [48]. Advantages of renovation against reconstruction are also discussed in Hasik et al [49] and in Dunant et al [36], among others.…”