Historic Timber Research Articles

Selected Solutions for Rehabilitation of Wooden Structures: Some Portuguese Case Studies

Timber is one of the most used materials in the roofs and floors of monumental constructions in Portugal. The geometry is defined by elements that occupy a limited and well defined part of the tri-dimensional space, with a clear evidence of the hierarchy of the components. Timber elements are often visible, which allows easier conservation, identification of the wood species, characterization of details and evaluation of deterioration. Complex timber structures, such as those belonging to the roofs of large monuments, are often not easy to understand in a expedite way. As the coverings of monuments as cathedrals, public buildings, mansions or villas show very complicate features, not easy to be understood during the first inspection. This is not only due to the fact that the system is very elaborate and to the large number of members but also due to continuous changes and repair past works, mostly with additional stiffening or propping. The typical result of the history of the construction is the increase in the number and the heterogeneity of the members, together with a multiplicity of connections and diversity of supports. This means that the original must be distinguished from the additions and the replacements. This complexity makes the field of conservation of historical timber structures not only a challenge but a field much in need of modern research. The objective of this paper is to present some of the Portuguese experience in this field, showing how the rehabilitation solutions can be supported by the inspection techniques and by an extensive knowledge about the constituent material from which the structure was made, both from the mechanical point of view and from the physical point of view. A number of case studies will be presented to illustrate common conservation problems, and design problems as well as the possibilities and limitations of several solutions and to discuss the suitability of several intervention methods.

Learning from Case Studies: Timber Tower of Gospić Cathedral and Traditional Timber Church

The conservation of historical timber structures requires both the knowledge of structural behavior of complete building and behavior of any single element in structure. Because of a poor communication between the institutions involved in the conservation and restoration of buildings and institutions that urgently require renovation of structures, renovation of historic buildings is often performed inappropriately due to engineering and architectural approach. Buildings are frequently subjected to inappropriate interventions, replacements of structural elements, or even worse, they are demolished. First case study in this paper is Cathedral from Gospic city which was subjected to inappropriate reconstruction in 1990s. Second case study is small traditionally constructed timber chapel in village Lijevi Stefanki which represents a valuable monument of rural cultural heritage.

<i>In Situ</i> Compression Stress-Deformation Measurements along the Timber Depth Profile

The paper presents a novel concept and a prototype of a diagnostic tool for in-situ assessment of timber in existing structures and buildings. The device enables direct determination of conventional compressive strength and modulus of deformation in arbitrary depth along timber profile. The measurement of the stress-deformation relationship is performed in a prepared hole of a very small diameter by means of a special small size symmetrical loading jack. Testing and verification of the new device behaviour during loading of wood along the fibres has been carried out on fir which is the most frequent wood species in European buildings. The comparison of stress-strain diagrams acquired by means of the new device with those measured in compliance with the European standard for testing of wood shows a very good correlation including the determination of the compressive strength values. This semi-destructive method causes a very gentle damage and can be also used for the assessment of historic timber structures.

Selected Methods of Diagnosis of Historic Timber Structures – Principles and Possibilities of Assessment

The paper presents a survey of state-of-the-art nondestructive and semi-destructive diagnostic techniques of testing timber structures and examples of their application. Nondestructive testing is a field of study which covers: identifying the mechanical and physical properties of materials and structural components, detecting material defects and discontinuities, and measuring the geometric dimensions of objects without affecting their performance. The nondestructive and semi-destructive methods are described in a systematic manner and the relevant equipment, technology and applications are discussed. The paper focuses on acoustic methods, resistance drilling techniques and radiography, which are suitable for detecting internal defects, decay and cracks, determining the location and dimensions of degraded areas and assessing the mechanical properties of structural timber members. Much attention is devoted to the techniques that are used in practice and have shown significant promise for future development. The results of several drilling resistance tests carried out on historic timber structures are presented.

Structural Reliability of Spanish Softwoods. A New Answer for an Old Problem

A group of databases making a total of ca. 9.000 beams from coniferous trees from Spain, tested according EN 384 and visually graded according Spanish standards were analyzed. The main goal was to reach a detailed comprehension about the true state of nature of the three reference structural material properties (density, MOR and MOE), in the conditions it reaches the real market. Provided the existing beams (reasonably) came from the same populations, the use of reliability updating technics is a meaningful approach to the problem of conjecturing its resistant behavior. Distribution parameters for the target species have been proposed. Spanish softwood (with the exception of p. radiata) has proved to be extremely dense and quite stiff related to its resistance, compared with usual North American, Central or North European coniferous trees. Hence, the basic information of these last species should not be used when dealing with Spanish historical timbers, as it leads to rather uneconomical conjectures (as deformation and joints use to be design governing factors). Also therere significant differences related to the current Probabilistic Model Code suggestion on the topic (as the Code itself warns of).

Life History as a Predictor of Salamander Recovery Rate from Timber Harvest in Southern Appalachian Forests, U.S.A

Forest management often represents a balance between social, economic, and ecological objectives. In the eastern United States, numerous studies have established that terrestrial salamander populations initially decline in abundance following timber harvest, yet the large-scale and long-term consequences are relatively unknown. We used count data from terrestrial survey points to examine the relation between salamander abundance and historic timber harvest while accounting for imperfect detection of individuals. Overall, stream- and terrestrial-breeding salamanders appeared to differ by magnitude of population decline, rate of population recovery, and extent of recolonization from surrounding forest. Specifically, estimated abundance of both species groups was positively associated with stand age and recovery rates were predicted to increase over time for red-legged salamanders (Plethodon shermani) and decrease in stream-breeding species. Abundance of stream-breeding salamanders was predicted to reach a peak by 100 years after timber harvest, and the population growth rate of red-legged salamanders was predicted to undergo a significant increase 100 years after harvest. Estimated abundance of stream-breeding salamanders in young forest stands was also negatively associated with the distance to adjacent forest, a result that suggests immigration has a role in the recovery of these species. Our results indicate that salamander abundance in young forest stands may be only modestly lower than in more mature forest but that full recovery from timber harvest may take a substantial amount of time and that species life history may affect patterns of recovery. Historia de Vida como un Vaticinador de la Tasa de Recuperación de una Salamandra a la Colecta de Madera en los Bosques del Sur de los Apalaches, E.U.A.

Sorption properties of historic and recent pine wood

Restorers of historic timber structures often face the necessity of using recent timber to replace structural elements destroyed by fungi and insects. As a rule new wood is of the same species, approximately the same wood density and annual increment.The paper presents data on differences in the sorption/desorption processes in recent and historic Scots pine (Pinus sylvestris L.) wood. Data loggers Materialfox (Germany) were installed in the 18th–19th cc. monuments of the Kizhi museum (Republic of Karelia, Russia). Wood moisture was measured with a 4 h interval for 150 days.The data obtained proved the working hypothesis about differences in the sorption properties of historic and recent timber.High wood moisture content of historic timber treated with borax chemicals increases the risk of fungi development in the joints with new insertions. It also increases the risk of infestation by borers.Using recent timber for insertions in the historic timber structures should be limited. Special requirements to the recent wood to be used for restoration are to be set up. They should be protected from environmental impact, especially if the structure had previously been treated with chemicals.

Technology of Coupled Timber–Concrete Ceiling Using Bonded Shear Connectors

Abstract The article describes the specific technological process that has been examined in the reconstruction of the ceiling structure of a house on Sokolska Street in Ostrava. Following experimental testing in laboratories at the Faculty of Civil Engineering VSB - TU Ostrava the technology of bonded shear bars under static reinforcement of timber ceilings was first applied and successfully tested in construction practice. This paper deals with the possibilities of using coupled timber-concrete structures by means a glued coupling bar. The described process of static reinforcement is particularly suitable for reconstruction of historic timber ceilings and places where it is necessary to prevent damage to non-supporting structures (e.g. ceiling, plaster, stucco decorations, etc.). The method is also employed in those cases where it is necessary to allow traffic-flow in the rooms below the reconstructed ceiling.

Modeling of Historical Timber Roof Truss of Želiv Monastery

Historical timber roof trusses are illustration of carpentry skills of an old era. Complexity of created structures is problem even in nowadays full usage of computer aided design. Especially in area of modeling joints and interaction of structural elements are ambiguities and inaccurate interpretations. The above issue is illustrated on 300 years old timber roof truss in Želiv monastery. The structure is Queen post shape with main trusses and secondary trusses. Especially static modeling of main trusses is problematic and difficult with utilization of beam or truss elements. Complex static model shows stiffness properties of joints as well as resistance of the whole truss structure against to climate loads and loads from rehabilitation intervention like replacement of roofing.

Radial growth variations of black pine along an elevation gradient in the Cazorla Mountains (South of Spain) and their relevance for historical and environmental studies

In southern Spain, the Cazorla Mountains (500–2,100 m a.s.l.) have supplied construction timber from black pine (Pinus nigra Arn.) for buildings and ships since at least the Middle Ages. To establish the age and provenance of wooden cultural heritage originating from this area, well-replicated long-span chronologies are needed. Old-living trees occur at high elevations, whereas many historical timbers originated from lower altitudes; hence, crossdating possibilities were questionable. To assess the potential of this species for the development of a multi-millennia tree-ring data set with living trees and historical timbers for the western Mediterranean, we developed four ring-width chronologies along the circa 1,000 m altitudinal range of black pine in these mountains and examined crossdating patterns and climate–growth responses along with altitude and through time. Teleconnections with other Iberian and Mediterranean tree-ring data were also tested. A well-replicated chronology spanning AD 1331–2009 was obtained at the upper site, while lower elevations delivered shorter chronologies. Similarity among chronologies and responses to climate were dependent on elevation. Tree-ring width was negatively related to temperature in previous late summer and positively to February–March, whereas precipitation had an opposite effect; some negative influence of early summer temperature was also observed. However, growth responses were rather unstable throughout the twentieth century. These chronologies showed good tele- and heteroconnections with conifer chronologies from Iberia, northern Morocco and Turkey, evidencing the existence of a common macroclimatic signal, which also varied along with elevation. The relevance of these results for dendrohistorical studies is discussed.

Lateral Performance of Nail Connections from Century-Old Timber Floor Diaphragms

AbstractNail connections salvaged from the timber floor diaphragms of two ∼100 year old unreinforced masonry buildings were pseudostatically tested to determine their hysteretic behavior. The research objective was to establish expected load-slip characteristics of nail connections in historic timber diaphragms to facilitate improved seismic assessment accuracy. A summary of the testing procedure, test results, and performance characterization is presented. Nail connections constructed from Kauri (Agathis australis) timber and wire-drawn nails in the 1890s were found to have an average yield strength of 1.0 kN and an average maximum strength 1.4 kN. Nail connections constructed in 1914 from Rimu (Dacrydium cupressinum) timber and wire-drawn nails were found to have an average yield strength of 0.8 kN and an average maximum strength of 1.0 kN. Both connection types exhibited an average ultimate displacement capacity of approximately 11.4 mm.

Ultrasonic technique for evaluation of bio-defects in wood: Part 2 – In situ and in vitro analyses of old beams using ultrasonic and bending tests

Heads of 17 markedly bio-damaged fir beams, proposed for replacement in historical ceilings, were subjected to in situ and in vitro analyses. At in situ tests, average velocities of ultrasonic wave (UW) in transverse directions c⊥ (height and width) were significantly lower in parts 0·1–0·2 m off the ends (300–400 m s−1) than in those 0·5–1·0 m off the ends (700–1100 m s−1). Average velocities of UW in longitudinal direction ║ reached 1875–5598 m s−1. At in vitro tests, tight linear correlations between densities, dynamic MOEd (determined by ultrasonic), static MOE and MOR (determined by bending) were observed for 153 specimens prepared from the beams. In vitro parameters MOEd, MOE and MOR corresponded well with in situ ultrasonic parameter c⊥. Relations between in situ and in vitro results could help better evaluate bio-defects in historical timber structures.

Filling the Eastern European gap in millennium-long temperature reconstructions

Tree ring-based temperature reconstructions form the scientific backbone of the current global change debate. Although some European records extend into medieval times, high-resolution, long-term, regional-scale paleoclimatic evidence is missing for the eastern part of the continent. Here we compile 545 samples of living trees and historical timbers from the greater Tatra region to reconstruct interannual to centennial-long variations in Eastern European May-June temperature back to 1040 AD. Recent anthropogenic warming exceeds the range of past natural climate variability. Increased plague outbreaks and political conflicts, as well as decreased settlement activities, coincided with temperature depressions. The Black Death in the mid-14th century, the Thirty Years War in the early 17th century, and the French Invasion of Russia in the early 19th century all occurred during the coldest episodes of the last millennium. A comparison with summer temperature reconstructions from Scandinavia, the Alps, and the Pyrenees emphasizes the seasonal and spatial specificity of our results, questioning those large-scale reconstructions that simply average individual sites.

Reply to comment by Jackson and Martin on “Does timber harvest influence the dynamics of marine-derived nutrients in Southeast Alaska streams?” 1Original article by Levi et al. appears in Can. J. Fish. Aquat. Sci. 68(8): 1316–1329 and is available at http://www.nrcresearchpress.com/doi/full/10.1139/f2011-067. Comment by Jackson and Martin appears in Can. J. Fish. Aquat. Sci. 69: this issue, and is available at

The stated goal of Levi et al. (2011, Can. J. Fish. Aquat. Sci. 68: 1316–1329) was to determine the influence of geomorphic complexity on the dynamics of salmon-derived nutrients. We studied seven streams in Southeast Alaska with varying degrees of historical (mid-1900s) timber harvest and, as a result, differences in stream geomorphology. In a comment on our study, Jackson and Martin (2012, Can. J. Fish. Aquat. Sci. 69: this issue) suggest that the geomorphic complexity we ascribe to timber harvest may be due to natural variation in watershed characteristics and offer alternative hypotheses. We sought to reduce the natural variation among our study streams by using a stratified sampling design (i.e., selecting reaches classified as floodplain 4 or 5 by the USDA Forest Service), but acknowledge that, as with any ecological field study, alternative hypotheses may exist to explain observed patterns in ecological responses. We maintain that our study design was sufficiently robust (i.e., 300 m reaches studied in seven streams for 3 years, totaling 21 stream-years) to draw inferences about the influence of salmon on streamwater nutrients and, secondarily, the role of geomorphic variation in mediating nutrient dynamics. Our data also support our finding that the legacy of timber harvest altered nutrient dynamics in salmon-bearing streams via alterations to stream geomorphology that were quantifiable.

Timber-Framed Buildings and Structural Restoration of a Historic Timber Pavilion in Turkey

Timber buildings were widely constructed until reinforced concrete became popular due to availability of the material and workmanship in Turkey. The masters of the timber works presented different construction techniques, configurations, and styles. After the trend turned to reinforced concrete and steel, the timber construction techniques became obsolete and even the existing timber buildings suffered from the lack of interest, repair, and maintenance. As a result the historical building stock started to perish. Despite some appropriate restoration attempts for the timber structures, the limited number does not offer any confidence for the future of those structures. In this respect, this study aims to present the timber structural systems for buildings, to expose the current conditions of existing timber structures, and to concentrate on the structural restoration of an important historical timber structure in Turkey.

Investigation and Analysis on Seismic Damage of Historic Timber Structures Caused by Wenchuan Earthquake in Zhaohua Ancient City

According to the investigation on historic structures in Zhaohua Ancient City, there are a total of 210 historic structures in the city, of which the historic timber structures account for 93.8%, namely 197 in total. In this paper, damage degrees of the historic timber structures have been determined, although the timber structures had not considered seismic design when they were built, nearly 60% of the historic timber structures are of relatively minor damage. Besides, based on the analysis on seismic damage of the historic timber structures, the failure modes of the timber structures have been concluded, namely the tenon pullout or tenon break-off, the pillar break-off, the pedestal slip and the retaining wall damage.

Preservation of historic monuments in the “Kizhi” Open-Air Museum (Russian Federation)

Abstract The paper presents information about preservation of historic timber structures in the Kizhi open-air museum (Russian Federation). The approaches used by the restorers and conservators at the time of the museum establishment and existence are described. The system of biological control of timber structures used nowadays in the museum aims to prevent biodeterioration as a main factor decreasing the service life of wooden structures. The proposed monitoring system enables determination of the zones damaged by fungi and insects, assessment of the activity of a wide range of biological agents at initial stages, environmental control of biodeterioration. Introduction of the proposed monitoring system in the Kizhi museums proved its effectiveness. In combination with timely repair and elimination of the revealed defects, it increases the service life of historic timber structures while preserving their authenticity.

The tree-ring chronology of Scots pine (Pinus sylvestris L.) from the Nesvizh castle XVI–XIX cc. in central Belarus

This article presents for the first time Scots pine tree-ring chronology created from historical timber (XVII–XIX cc.) from central Belarus. The chronology includes 59 tree-ring series which were collected from the different wood structures in the Nesvizh castle. This samples show different stages of the castle renovations. The chronology presented in this paper embraces 222 years covering the period between 1608 and 1829.

Incorporating management history into forest growth modelling

Mechanistic modelling is an important tool for understanding the impacts of climate change and pollutants on forest growth. One of the common practical limitations of these models is a lack of specific information regarding management activities such as thinning or harvesting, which can have a very strong influence on the accuracy of results. The use of inventory data for model parameterization and calibration is also problematic, as inventories are designed to have large volumes of data amalgamated to give accurate mean results across large areas. The precision of single point estimates is often quite low.This study uses BIOME-BGC to model forest growth on 1133 sites of the Austrian National Forest Inventory, and develops a method to estimate timber removal patterns prior to the commencement of record keeping on the sites. Recognizing the poor precision of individual point estimates in the data, we do not seek to precisely calibrate the model to the data on each point. Rather, we assume that the point-wise inventory estimates will be normally distributed around the true values. We then model each site assuming no management interventions, and compare this with inventory results. Plotting the “error” between model results and NFI data shows a strong right-skew, reflecting the modelled lack of timber removals. A Box-Cox transformation of the error plot, centred on zero, would represent an unbiased model estimate of the data, thus we can determine the historic timber removals as the difference between the original error curve and its Box-Cox transformation. Calibrating the model with this information allow us to represent forest volume with greater accuracy than would otherwise be possible.

Damage Detection of Historic Timber Structure Based on Cross Correlation Function Amplitude Vectors

Cross Correlation Function Amplitude Vector(CorV) is a method of damage detection which is based on random vibration .In this paper, CorV is introduced in the damage detection of historic timber structure according to the characteristics of structure and damage.Meanwhile,the research has been done. CorV of structural damage before and after the change has been expressed that is based on Cross Correlation function amplitude Vector Criterion(CVAC) .Results show that there is a remarkable decrease of CVAC among the CorVs between damaged and intact structures.Damage locations can be determined through the relative change of CorVs which is before or after the damage of the structure . A basis can be provided for the damage of buildings and the ancient structure protection through this paper.