Life Cycle Vulnerability Assessment of Masonry Infilled Steel Frame Structures

In this study, the anticipated cost throughout a structure’s operational period has been estimated, following a life cycle model. A scenario has been defined in order to assess the structural performance of a mid-rise infilled steel frame over its expected lifetime. Since the characteristics of the index building play a critical role in estimating the losses, the one selected is designed and modelled based on common existing residential buildings. The life cycle cost of the index building has been estimated by considering progressive deterioration due to aging of the structure (e.g. corrosion, fatigue) and also cumulative damage caused by extreme sudden events (e.g. earthquake, hurricane, flood, blast, etc.). The adapted model is capable of considering the initial construction cost along with the cost of damage and failure consequences including death and injuries, as well as discounting cost over time. The performance of the index building at different life stages has been assessed by implementing incremental dynamic analysis (IDA). Using the obtained results, the exceedance probabilities required for the cost analysis are calculated by means of fragility curves for multiple damage limit states. Furthermore, the limit states’ exceedance frequencies are obtained by convolving fragilities with site a specific hazard curve. Having a good understanding of the structural behavior and its expected cost forecast can be beneficial as a decision making tool for planning and allocating financial resources in case of both pre- and post- disaster

A new approach to flood vulnerability assessment for historic buildings in England

The recent increase in frequency and severity of flooding in the UK has led to a shift in the perception of risk associated with flood hazards. This has extended to the conservation community, and the risks posed to historic structures that suffer from flooding are particularly concerning for those charged with preserving and maintaining such buildings. In order to fully appraise the risks in a manner appropriate to the complex issue of preservation, a new methodology is presented here that studies the nature of the vulnerability of such structures, and places it in the context of risk assessment, accounting for the vulnerable object and the subsequent exposure of that object to flood hazards. The testing of the methodology is carried out using three urban case studies and the results of the survey analysis provide guidance on the development of fragility curves for historic structures exposed to flooding. This occurs through appraisal of vulnerability indicators related to building form, structural and fabric integrity, and preservation of architectural and archaeological values. Key findings of the work include determining the applicability of these indicators to fragility analysis, and the determination of the relative vulnerability of the three case study sites

Moisture dynamics in the masonry fabric of historic buildings subjected to wind-driven rain and flooding

Current climatic projections show clearly that increasingly more extreme weather events are to be expected in the future. Historic buildings are considered to be the most vulnerable to this adverse climatic impact, via moisture induced deterioration and resulting strength decay in their construction materials. Therefore, the identification of these climatic effects is important to be able to develop suitable tools to mitigate them, both for individual buildings and on a regional scale. This paper presents the analysis of a comprehensive environmental monitoring of two historic buildings in Tewkesbury, Gloucestershire, UK, to provide thorough insight on their performances under environmental loading on a comparative basis. Firstly, the effect of wind-driven rain (WDR) and flooding is assessed by correlation with relative humidity (RH) measurements. The WDR measurements are then compared against values calculated using well established semi-empirical models and reasons behind the limited correlation are discussed. The dynamic hygrothermal response of two different historic fabrics is studied in greater detail by monitoring in-wall temperature and RH. The conclusions drawn from the analysis of the monitoring outputs are then further elaborated on by using hygrothermal characterization obtained by dynamic vapour sorption (DVS) testing of material samples extracted from the fabric of these buildings. The study concludes that the current environmental conditions pose a threat on the building envelopes unless routine maintenance is provided, and that monitoring methodology devised is clearly successful in quantifying the exposure of the two historic buildings to environmental conditions, onsetting deterioration phenomena in the envelop materials

Testing and design procedure for corner connections of masonry heritage buildings strengthened by metallic grouted anchors

Structural connections are crucial in determining the seismic behaviour of buildings; their importance is indeed acknowledged by current design codes, both in the case of new built and of heritage structures. Eurocode 8 in particular encourages the strengthening of connections of existing structures so as to ensure global response; yet, at the state of the art, clear prescriptions regarding the assessment of connections of heritage buildings and the design of appropriate strengthening systems are missing. Even the scientific literature seldom deals with the issue of connections, both in the unreinforced and strengthened set-up. As such, designers are left with the issue of experimentally characterise the capacity of connections, and of sourcing data and choosing suitable design procedures in order to comply with the requirements prescribed for retrofit interventions on historic buildings. In the attempt of tackling the lack of quantitative data, as well as of providing template for the experimental assessment and design of strengthening systems for connections, the authors carried out two sets of laboratory tests on masonry samples strengthened by metallic grouted anchors. Parameters significant to the performance of the connection are identified through experimental results and a design procedure is developed. The paper analyses in detail the response of a widely-applied strengthening technique, but also provides general guidance for dealing with the repair and strengthening of connections of heritage buildings

2015 Nepal earthquake: seismic performance and post-earthquake reconstruction of stone in mud mortar masonry buildings

This report is an outcome of the analysis of data and information related to the damage and post-earthquake reconstruction of residential buildings, collected during the field survey by the authors, in light of 2015 Nepal earthquake sequence

Displacement-based design procedure of grouted anchoring systems for the seismic upgrade of heritage buildings

A displacement-based design procedure is proposed to control the out-of-plane motion of masonry walls during seismic events by means of a Grouted Anchoring System (GAS) and a Dissipative Grouted Anchoring Systems (D-GAS). Combining the non-linear static capacity of walls in three different configurations (unstrengthened, strengthened with GAS or D-GAS) with the inelastic demand spectra gives the expected performance of the system, which is then compared to a set of damage thresholds corresponding to the progression from linear to nonlinear behaviour of the system. The design method is validated comparing the expected performance with the evolution of the wall’s rocking motion obtained by means of time-history analysis for a seismic acceleration adapted to the design spectrum used in the static analysis. The results highlight that the D-GAS provides the optimal design solution as it controls the amplitude and acceleration of the rocking motion while dissipating the seismic energy through friction. This allows for a reduced number of required anchors, thus a less invasive of the intervention, which is beneficial especially for applications to historical building with aesthetic value

Use of the Knowledge-Based System LOG-IDEAH to Assess Failure Modes of Masonry Buildings, Damaged by L'Aquila Earthquake in 2009

This article, first, discusses the decision-making process, typically used by trained engineers to assess failure modes of masonry buildings, and then, presents the rule-based model, required to build a knowledge-based system for post-earthquake damage assessment. The acquisition of the engineering knowledge and implementation of the rule-based model lead to the developments of the knowledge-based system LOG-IDEAH (Logic trees for Identification of Damage due to Earthquakes for Architectural Heritage), a web-based tool, which assesses failure modes of masonry buildings by interpreting both crack pattern and damage severity, recorded on site by visual inspection. Assuming that failure modes detected by trained engineers for a sample of buildings are the correct ones, these are used to validate the predictions made by LOG-IDEAH. Prediction robustness of the proposed system is carried out by computing Precision and Recall measures for failure modes, predicted for a set of buildings selected in the city center of L’Aquila (Italy), damaged by an earthquake in 2009. To provide an independent meaning of verification for LOG-IDEAH, random generations of outputs are created to obtain baselines of failure modes for the same case study. For the baseline output to be compatible and consistent with the observations on site, failure modes are randomly generated with the same probability of occurrence as observed for the building samples inspected in the city center of L’Aquila. The comparison between Precision and Recall measures, calculated on the output, provided by LOG-IDEAH and predicted by random generations, underlines that the proposed knowledge-based system has a high ability to predict failure modes of masonry buildings, and has the potential to support surveyors in post-earthquake assessments

Assessment of flood and wind driven rain impact on mechanical properties of historic brick masonry

As a result of increased rainfall and flooding the building fabric of historic structures in exposed areas are likely to be subject to higher and more sustained moisture content levels, along with experiencing an increased frequency and severity of wetting and drying cycles. This study aims to evaluate the impact of such cyclic wetting and drying on the mechanical behaviour of historic brick masonry. The reported results are obtained from a series of weathering and mechanical tests carried out on clay bricks and masonry specimens. The weathering test regime derives from analysis of observed weather data, combined with review of similar existing test protocols. Similarly, a modified mechanical test procedure is applied to simulate fatigue observed in the field. The results indicate that exposure to the weathering tests results in a reduction of masonry shear strength. This is discussed within the context of wider work carried out at a case study location, and highlights the value of designing a weathering regime that can more closely replicate the in-situ weathering processes. In this way the data collected in this experimental programme is shown to be suitable for use in contextual analysis of individual historic masonry case studies, with respect to climate change and the associated alteration of wetting regimes

Wind Driven Rain (WDR) Laboratory Tests on Cavity Wall Specimens treated with surface waterproofing products

Wind driven rain (WDR) is one of the most common sources of moisture risks affecting buildings in the UK. Water penetration can lead to defects such as ineffective insulation, damp inner walls and freeze-thaw damage, causing issues in both energy efficiency and wall integrity. Surface waterproofing products have shown great potential as a new method of improving the moisture condition in buildings. This paper is focused on real size cavity walls tested under WDR exposure to study the hygrothermal performance of surface waterproofing products. Test results show both acrylic-based liquid and silane/siloxane blend cream products were capable of lessening moisture enrichment of masonry cavity walls under cyclic WDR loading