Environmental Loading Of Heritage Structures Research Articles

Environmental loading of heritage structures.

This theme issue, featuring Environmental loading of heritage structures, provides a snapshot of current civil engineering approaches to assessing ageing structures under a variety of loads. The publication arose from a serendipitous sequence of interactions. Academics at the University of Plymouth were contacted by Trinity House in 2010 to investigate reported vibrations in their rock lighthouses when impacted by storm waves. A pilot study on the nearby Eddystone lighthouse captured structural response data from the catastrophic storms of 2013/2014 and paved the way for a more comprehensive project. The STORMLAMP project brought together expertise across various civil engineering disciplines, hydrodynamics, field-based structural monitoring and structural modelling, at the University of Plymouth, University of Exeter and UCL, respectively. It has investigated rock lighthouses across all three of the General Lighthouse Authorities of UK and Ireland (Trinity House, Irish Lights and the Northern Lighthouse Board). Field modal testing was undertaken at seven rock lighthouses right across this region to support the characterization of extreme impulsive breaking wave loads, and the identified modal properties have subsequently been used to validate structural models. These models have also required the best estimates of likely wave loads in order to predict maximum structural responses, provided by researchers in the team. The Special Issue features comprehensive investigations undertaken on the Wolf Rock lighthouse [1], located eight nautical miles from Land's End at the southwest tip of England, and one of the most exposed lighthouses in the British Isles (figure 1). Open in a separate window Figure 1. Locations of heritage structures described in this Special Issue (adapted from [2]). (Online version in colour.)

Stochastic subspace identification of modal parameters during ice-structure interaction.

Identifying the modal parameters of structures located in ice-infested waters may be challenging due to the interaction between the ice and structure. In this study, both simulated data from a state-of-the-art ice-structure interaction model and measured data of ice-structure interaction were both used in conjunction with a covariance-driven stochastic subspace identification method to identify the modal parameters and their corresponding variances. The variances can be used to assign confidence to the identified eigenfrequencies, and effectively eliminate the eigenfrequencies with large variances. This enables a comparison between the identified eigenfrequencies for different ice conditions. Simulated data were used to assess the accuracy of the identified modal parameters during ice-structure interactions, and they were further used to guide the choice of parameters for the subspace identification when applied to measured data. The measured data consisted of 150 recordings of ice actions against the Norströmsgrund lighthouse in the Northern Baltic Sea. The results were sorted into groups defined by the observed ice conditions and governing ice failure mechanisms during the ice-structure interaction. The identified eigenfrequencies varied within each individual group and between the groups. Based on identified modal parameters, we suggested which eigenmodes play an active role in the interaction processes at the ice-structure interface and discussed the possible sources of errors. This article is part of the theme issue 'Environmental loading of heritage structures'.

Historical review of lighthouse design under wind load: the Ile Vierge lighthouse.

The purpose of the study presented here is to describe the design method used by engineers in the nineteenth and early twentieth centuries to size lighthouse structures and to compare them with current European standards. The historical information presented here is derived from two sources in particular: the archives of the Ile Vierge lighthouse, which was built at the northern tip of Brittany between 1897 and 1902, and the scientific journals, books and courses available at that time. Firstly, the article describes the structure of the Ile Vierge lighthouse, which is the tallest stone lighthouse in Europe. The wind load acting on lighthouses and chimneys was formulated in France by L. Fresnel in 1825. Fresnel's work is compared to W. J. M. Rankine's theory used in the UK. The safety coefficients applied with respect to the stability of the towers in France and the UK in the nineteenth-century are compared. On the occasion of the construction of the Ile Vierge lighthouse, the masonry strength under wind loads led to a discussion among engineers of the French lighthouse authorities. They also worried about the risk of excessive oscillations of the towers, which could cause a dysfunction of the lamp. Thirdly, the standard wind action defined in Eurocode 1 is applied to the Ile Vierge lighthouse. Calculation results are given. A comparative analysis of the ancient and modern methods is presented. Overall, this historical research shows that the designers of lighthouses in the nineteenth-century had the same objectives as today: to build strong, durable structures in which deformations under loads are compatible with serviceability. This article is part of the theme issue 'Environmental loading of heritage structures'.

La Jument lighthouse: a real-scale laboratory for the study of giant waves and their loading on marine structures

This paper presents results from an experiment designed to improve the understanding of the relationship between extreme breaking waves and their mechanical loading on heritage offshore lighthouses. The experiment, conducted at La Jument, an iconic French offshore lighthouse, featured several records of wave, current and structure accelerations acquired during severe storm conditions, with individual waves as high as 24 m. Data analysis focuses on a storm event marked by a strong peak in the horizontal accelerations measured inside La Jument. Thanks to stereo-video wave measurements synchronized to the acceleration record we were able to identify and describe the breaking wave responsible for this intense loading. Our observations suggest that this giant wave (19 m high) had a crest elevation high enough to directly hit the lighthouse tower, above the substructure. This paper reveals the potential for conducting ambitious field experiments from offshore lighthouses in order to collect valuable storm waves and wave loading observations. This offers a possible second service life for these heritage structures as in situ laboratories dedicated to the study of the coastal hydrodynamics and its interaction with marine structures. This article is part of the theme issue 'Environmental loading of heritage structures'.

Wind loads on open truss structures: applications of blockage to historic transporter bridges.

The overall aim of this study is to compare and contrast the design of the two remaining working examples of early twentieth-century transporter bridges in the UK, namely, those at Newport and Middlesbrough. With the aid of modern finite-element analysis, the behaviour of the structures under loading is investigated, likely modes of failure determined and the efficiency of each structure evaluated. The important horizontal load component due to wind at the exposed locations of the bridges is examined using 'current blockage', ideas transferred from recent work on wave-current-structure interaction for space-frame structures in offshore engineering. This article is part of the theme issue 'Environmental loading of heritage structures'.

Seismic damage to ancient monuments in Chiang Saen (Northern Thailand): implication for historical earthquakes in Golden Triangle area

Over the last few decades, three moderate earthquakes (Mw greater than 6.0) occurred in and around the Golden Triangle area (including Myanmar, Thailand and Lao PDR) causing unprecedented damage and loss of lives in the epicentral region. In addition to the damage to modern structures, most heritage structures in Chiang Saen, a major city of the Lan Na kingdom (from the thirteenth to the eighteenth century), were also affected. This work is intended to present observed historical structure damage from recent earthquakes, which could provide evidence for the severity of historical earthquakes from the thirteenth to the eighteenth century. Based on historical records, geological evidence and observed damage to ancient monuments in this historic town, existing heritage stupas and temples constructed since the fourteenth century sustained only minor to moderate damage from these historical earthquakes. Considering the seismic vulnerability of these historical monuments, Chiang Saen might have never been subjected to severe ground shaking greater than MMI intensity VII, similar to the major earthquake in 460 A.D. along the Mae Chan fault, which was responsible for the large-scale liquefaction and inundation of ancient Yonok town. This information could be important for paleoseismological and historical earthquake research to constrain the recurrence interval of major active faults in this area. This article is part of the theme issue 'Environmental loading of heritage structures'.

Structural response of French offshore heritage lighthouses.

Offshore lighthouses are a remarkable historical heritage often over 100 years old. The management of their ageing is a challenge and requires a thorough understanding of their structural response under wave loading. With this aim in view, the dynamic response of the 'La Jument' lighthouse in the French Iroise Sea was characterized in situ, with accelerometers, under the action of a breaking wave, during a winter storm in January 2018. Detailed exploitation of the measurement data complemented by photographic documentation of the same wave event helped determine eigenfrequencies and damping coefficients of the structure as well as the likely orientation of the wave and the position of its crest with respect to the lighthouse tower. The results of these analyses were put into perspective with those of literature and more specifically from three-dimensional finite element modelling of the structural response of the lighthouse under the action effects of breaking waves. This article is part of the theme issue 'Environmental loading of heritage structures'.

A Bayesian model updating framework for robust seismic fragility analysis of non-isolated historic masonry towers.

Seismic assessment of existing masonry structures requires a numerical model able to both reproduce their nonlinear behaviour and account for the different sources of uncertainties; the latter have to be dealt with since the unavoidable lack of knowledge on the input parameters (material properties, geometry, boundary conditions, etc.) has a relevant effect on the reliability of the seismic response provided by the numerical approaches. The steadily increasing necessity of combining different sources of information/knowledge makes the Bayesian approach an appealing technique, not yet fully investigated for historic masonry constructions. In fact, while the Bayesian paradigm is currently employed to solve inverse problems in several sectors of the structural engineering domain, only a few studies pay attention to its effectiveness for parameter identification on historic masonry structures. This study combines a Bayesian framework with probabilistic structural analyses: starting from the Bayesian finite element model updating by using experimental data it provides the definition of robust seismic fragility curves for non-isolated masonry towers. A comparison between this method and the standard deterministic approach illustrates its benefits. This article is part of the theme issue 'Environmental loading of heritage structures'.

Wolf Rock lighthouse: past developments and future survivability under wave loading.

Lighthouses situated on exposed rocky outcrops warn mariners of the dangers that lurk beneath the waves. They were first constructed when approaches to wave loading and structural response were relatively unsophisticated, essentially learning from previous failures. Here, we chart the evolution of lighthouses on the Wolf Rock, situated between Land's End and the Isles of Scilly in the UK. The first empirical approaches are described, followed by design aspects of the present tower, informed by innovations developed on other rocky outcrops. We focus on a particular development associated with the automation of lighthouses: the helideck platform. The design concept is described and the structure then scrutinized for future survivability, using the latest structural modelling techniques of the entire lighthouse and helideck. Model validation data were obtained through a complex logistical field operation and experimental modal analysis. Extreme wave loading for the model required the identification of the 250-year return period wave using a Bayesian method with informative prior distributions, for two different scenarios (2017 and 2067). The structural models predict responses of the helideck to wave loading which is characterized by differential displacements of 0.093 m (2017) and 0.115 m (2067) with associated high tension forces and plastic strain.This article is part of the theme issue ‘Environmental loading of heritage structures’.

Documentation, structural health monitoring and numerical modelling for damage assessment of the Morris Island Lighthouse.

Heritage structures serve as invaluable records of cultural achievement that should be preserved for future generations. To ensure the successful preservation of these structures, there must be an affordable and effective way to conduct conservation. The objective of this work is to outline an efficient workflow for the structural analysis of preservation projects through a case study on the Morris Island Lighthouse in Charleston, South Carolina. Thorough documentation of the cultural significance and structural condition of the lighthouse was completed through archival research, photogrammetry and crack mapping. Structural Health Monitoring and Distinct Element Modelling were used to analyse past structural damage and the present condition. The behaviour of masonry and crack propagation was evaluated under gravity, wind, wave and seismic loading. The results of these analyses were summarized in a virtual tour and informational modelling environment, which allows the results to be accessed and associated with their physical location on the structure. The benefits and limitations of this process are discussed, and a standardized workflow for efficient structural analysis of cultural heritage is proposed. This article is part of the theme issue 'Environmental loading of heritage structures'.

Brick masonry industrial chimneys: assessment, evaluation and intervention.

Masonry chimneys were key elements of post-industrial factory buildings. Built on a large scale in Portugal from the nineteenth century, factory buildings have been in use until the beginning of the twentieth century, afterwards being progressively abandoned, transformed or demolished. During this degradation process, the industrial chimneys are often separated from other structures and become isolated elements, i.e. sculptures to the memory of the site's past activity. Moreover, although most of these industries and chimneys were located outside ordinary living areas, they are actually surrounded by dwellings or placed inside leisure areas. This new framework demands safety evaluations of the chimneys, which involve preliminary on-site surveys. This work shows the analysis of the geometric and material data from on-site surveys and dynamic identification procedures carried out on 10 industrial brick masonry chimneys. In particular, it establishes correlations between the chimneys geometrical and mechanical characteristics and proposes simple procedures to help designers to assess the safety conditions of these chimneys and evaluate eventual reinforcement needs. This article is part of the theme issue 'Environmental loading of heritage structures'.

Seismic retrofitting of Māori wharenui in Aotearoa New Zealand

The design of Māori wharenui (meeting houses), refined over the last 180 years, has given rise to a distinctive typology that demonstrates an understanding of tectonic-narrative expression. It is a visual codex designed to be read. Set within the context of pre-disaster readiness, this current study investigated the resilience of Māori buildings and communities through a dual interpretation of seismic, regulatory and historical frameworks. The literature on Māori building technologies scarcely addresses matters of resilience and there is currently no formalized methodology to guide wharenui seismic retrofit practice. Through a macro level analysis of recently completed retrofit projects, this current study identified issues present in current practice. The resulting research presented a pathway for the future development of an approach (to inform methodologies) and strategy (to build capability) founded on the recognition of wharenui as a new category of building within building regulations. It is also recommended that research continues to develop alternative engineered solutions, expert knowledge bases and best practice guidelines. This article is part of the theme issue 'Environmental loading of heritage structures'.

The Gap Rock Lighthouse: construction and typhoon damage.

This paper focuses on the Gap Rock lighthouse, a legendary maritime infrastructure built 130 years ago in the Chinese territory and an early example of joint venture among the Qing Dynasty, the British Empire and the Hong Kong Colonial Government over a course of two decades. Based on 4 years of cross-territorial archival and field research as well as in-depth interviews with descendants of two key stakeholders, the origin of this lasting legacy on the sea is traced, followed by a detailed account of its challenging processes of planning, design and construction, and of the considerable damage to the compound by a severe typhoon in 1893. A qualitative analysis of the key contributing factors of the damage was conducted by taking into consideration the Island's unique topography and the historical records of territorial weather reports. A re-construction of the typhoon impact on the Lighthouse is presented to explain the possible mistakes in its siting and design that eventually caused the severe damage. This serves as a reminder of the significance of a thorough geographical investigation for any infrastructure for all construction professionals in the face of climatic change. This article is part of the theme issue 'Environmental loading of heritage structures'.

High-resolution time-dependent probabilistic assessment of the hydraulic performance for historic coastal structures: application to Luarca Breakwater.

Historic coastal structures have played a key role in small- to medium-size ports, being the driving force for the local development of coastal communities. Because coastal managers require reliable risk-based analysis of the whole life cycle of these coastal structures, previous lifetimes should be studied. This is a differentiating factor with respect to the newly built breakwaters. For this reason, in this work, a methodology for assessing how the hydraulic performance of an expired lifetime has evolved over the years is presented. It is performed following a probabilistic approach due to the uncertainty related to both the involved variables (wave climate, geometrical and structural breakwater variables) and the hydraulic response of the structure. The first ones are characterized by reliable probability distribution functions. The second ones are characterized by reliable formulae for the analysis of the hydraulic response. However, their non-conventional designs located in shallow-water locations require site-dependent formulae. To overcome this problem, a novel methodology to apply CFD numerical models is presented. Finally, it is integrated in a high-resolution time-dependent probabilistic methodology which takes into account the stochastic behaviour of all the involved variables, coastal and structural processes with a good uncertainty level. This article is part of the theme issue 'Environmental loading of heritage structures'.