120 research outputs found
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
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
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
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