Historic Timber Structures Research Articles

Seismic Vulnerability Assessment and Strengthening of Heritage Timber Buildings: A Review

Recent studies highlight the potential impact of earthquakes on cultural heritage sites and monuments, which in turn yield significant adverse impacts on economies, politics, and societies. Several aspects such as building materials, structural responses, and restoration strategies must be considered in the conservation of heritage structures. Timber is an old organic construction material. Most of the historic timber structures were not designed to withstand seismic forces; therefore, the seismic vulnerability assessment of heritage timber structures in areas with high seismic hazard is essential for their conservation. For this purpose, different strategies for the numerical modeling of heritage timber buildings have been developed and validated against tests results. After performing seismic analysis using detailed analytical methods and predicting the susceptible structural components, strengthening techniques should be utilized to mitigate the risk level. To this aim, various methods using wooden components, composite material, steel components, SMA etc., have been utilized and tested and are reviewed in this study. There are still some gaps, such as full-scale numerical modeling of strengthened buildings and investigating the soil–structure interaction effects on the seismic behavior of buildings that should be investigated.

The effect of wind on historical timber towers analyzed by plastic limit analysis in the focus of a collapse

Climate change severely impacts the architectural heritage. Old buildings may have survived many large storms and heavy snows in the past, but extremes have increased recently. Meanwhile, the condition of historical structures gradually degrades even if they have had regular maintenance.Church towers are strongly affected: they are subject to increased wind compared to the other parts of the building. They are in a high location and gain less attention because of their out-of-the-way position.On 17th September 2017, a massive storm in the Banat region, Romania, caused several church towers to collapse: the towers of Toager, Remetea Mare, Donceni and Ghilad fell down to pieces that day. The collapse of the tower of Dumbrava was one of the buildings involved, this study aims to clarify whether the poor condition of the building, or the flaw of the original design was the main reason for the failure in this village.The structural analysis of such historical timber structures can be problematic as the weak joints of the structure limit the load-bearing capacitance in an exceptionally low level if the traditional elastic analysis is used. The present paper points out that the plastic limit analysis can give a more realistic breaking load level for the high order statically indeterminate carpenter roofs.

Book review

Book review

A Modelling Approach for the Assessment of Climate Change Impact on the Fungal Colonization of Historic Timber Structures

Climate change is anticipated to affect the degradation of the building materials in cultural heritage sites and buildings. For the aim of taking the necessary preventive measures, studies need to be carried out with the utmost possible precision regarding the building materials of each monument and the microclimate to which they are exposed. Within the present study, a methodology to investigate the mold risk of timber buildings is presented and applied in two historic constructions. The two case studies are located in Vestfold, Norway. Proper material properties are selected for the building elements by leveraging material properties from existing databases, measurements, and simulations of the hygrothermal performance of selected building components. Data from the REMO2015 driven by the global model MPI-ESM-LR are used in order to account for past, present, and future climate conditions. In addition, climate data from ERA5 reanalysis are used in order to assess the accuracy the MPI-ES-LR_REMO2015 model results. Whole building hygrothermal simulations are employed to calculate the temperature and the relative humidity on the timber surfaces. The transient hygrothermal condition and certain characteristics of the timber surfaces are used as inputs in the updated VTT mold model in order to predict the mold risk of certain building elements. Results show a significant increase of the mold risk of the untreated timber surfaces due to climate change. The treated surfaces have no mold risk at all. It is also observed that the most significant increase of the mold risk occurs in the north-oriented and the horizontal surfaces. It is underlined that the mold risk of the timber elements is overestimated by the MPI-ES-LR_REMO2015 model compared to ERA5 reanalysis. The importance of considering the surface temperature and humidity, and not the atmospheric temperature and humidity as boundary conditions in the mold growth model is also investigated and highlighted.

A Modelling Approach for the Assessment of Climate Change Impact on the Fungal Colonization of Historic Timber Structures

A Modelling Approach for the Assessment of Climate Change Impact on the Fungal Colonization of Historic Timber Structures

An analytical model for the loading capacity of splice-retrofitted slender timber columns

Retrofitting timber columns in traditional timber structures with a steel jacketed splice joint has advantages of aesthetic appearance and similar mechanic performance to the intact columns as compared to conventional simple splice columns. The axial compression behavior of such retrofitted splice columns has been studied experimentally in detail. However, there is still a lack of a calculation model for their axial compressive strength and general guideline for their design. The objective of this study is to establish a theoretical calculation model for this type of retrofitted splice columns. Firstly, a theoretical model for the axial compressive strength of splice columns retrofitted with a steel jacket is proposed considering the contact stresses at a splice joint and the relevant stability theory. Secondly, the buckling modes of splice columns and the actual stress distributions at the splice joints (i.e. the compressive stresses at the steel-timber and timber-timber interfaces) are thoroughly investigated. Finally, the theoretical model is validated by the experimental data and finite element analysis results with different splice parameters. Comparisons show that the theoretical calculations in terms of the bearing capacity and stability coefficient agree well with the experimental results. The proposed theoretical model is also shown to be suitable for predicting the axial compressive strength of a retrofitted splice column with the location of the splice from the column end ranging from 1/5 to 1/2 of the column length. The relative errors in the theoretical bearing capacities with respect to the finite element results are found to be less than that using the stability coefficient. From the analysis results, the length of the splice and the total length of the steel jacket are recommended to be in the range of 0.5~1.5 and 2~4.5 times of the column diameter, respectively. This proposed theoretical model can be applied in the retrofitting design of timber columns in historical timber structures, and it can also be applied in the development of new large-space timber structures where splice columns may be incorporated.

A Case Study from Istanbul’s Westernization Period: The Technical Documentation of Prinkipo Palace

ABSTRACT The deterioration and the consequent collapse of historic timber structures lead to a significant loss of knowledge transfer of local construction methods and building technics. In this article, based on a case study of an exceptional timber frame structure in Istanbul dating from the end of the 19th century, is an attempt to provide documentation on the structure and materials of the specific building. The main objective is to underline the general structural system and materials as a reference. The case study covers the traditional characteristics such as local timber framework techniques and features of the transition era in construction and materials, with industrialized and standardized construction members.

HBIM for storing life-cycle data regarding decay and damage in existing timber structures

The conservation and maintenance of the historical heritage is an issue of great importance, especially when dealing with elements that can easily suffer damage along the time, either to intrinsic materials properties or by exposure conditions, like often happen for timber structures. For the management and maintenance of historic timber structures, HBIM (Historic Building Information Modeling) is here presented as a fundamental tool. This work presents the application of a methodology that uses common HBIM software in combination with results obtained from non-destructive testing and geometric surveying, allowing it to perform modeling, analysis and storage of geometric data, levels of decay and lack of material of timber structures within a tridimensional space. Moreover, the proposed framework incorporates different time stages, thus allowing to make periodic comparisons along time, that substantiate a decision making process to take decisions about maintenance and intervention actions. In this work two case studies are used to validate this methodology and present its possible use. The case studies are: (i) the timber structure of the roof of the key tower of the Castle of Guimarães, and (ii) the timber structure of the ceiling and roof of the room of the Knight's Room in the Convent of Christ, Tomar, both Portuguese buildings listed as UNESCO World Heritage Sites.

Experimental and computational study on mechanical behaviour of carpentry corner log joints

This work concerns experimental and numerical research on carpentry joints used in historic wooden buildings in southeastern Poland and western Ukraine. These structures are mainly sacred buildings, and the types of corner log joints characteristic of this region are primarily saddle-notch and dovetail joints; thus, these two types of joints were analysed in this study.The modelling of historic timber structures is a complex issue, so the following steps are necessary to obtain accurate solutions: verification, validation and uncertainty quantification. The first and third steps were performed in a previous study, so the current research aimed to validate the numerical models and perform simulations of carpentry joints. Herein, the authors created finite element models of two types of joints and subsequently analysed the mechanical behaviour of these joints.Due to issues concerning model validation, the authors designed a testing stand for corner joints, which formed a part of a biaxial testing machine. The joints were subjected to horizontal loads (deformations), which may cause damage to the connection. Thus, special parts were designed for the stand, which made it possible to fix the joint and prevented eccentric forces that could possibly damage the machine during testing.The authors presented the differences and similarities in the behaviour of both types of joints, emphasizing the corresponding advantages and disadvantages. In addition, the authors determined which type of joint was the most susceptible to damage and what elements failed first.This paper also showed the complexity of modelling timber structures and the accuracy of the proposed numerical models for both types of joints through comparisons of the numerical and experimental results. This work primary addressed the problems in accurately reflecting material, load and boundary conditions in numerical modelling of tested carpentry corner log joints.

Moment-rotation relationship of mortise-through-tenon connections in historic timber structures

This paper investigates the moment-rotation relationship of historic timber structures. In particular, the embedded compressive mechanism of these connections subjected to cyclic loading was investigated and a simplified equation for predicting the moment-rotation relationship was derived. The analytical model was validated by using the results of three 1/3.2-scaled mortise-through-tenon connections, including one intact connection and two connections with a gap between the mortise and through-tenon, tested under quasi-static loading. Then, the so-validated model was used for extensive parametric analysis by changing different parameters, such as the gap between the mortise and through-tenon, friction coefficient and material properties of wood. It is shown that the friction coefficient and elastic modulus perpendicular to grain along the radial direction of wood had an influence on the moment-rotation relationship of the connections, especially for the initial stiffness and ultimate moment of the connections, and both of them increased with a larger friction coefficient and elastic modulus. However, with the increment of the gap between the mortise and through-tenon, the initial stiffness and ultimate moment decreased gradually.

Investigation on the behaviors of Tou–Kung sets in historic timber structures

To investigate the structural performance of Tou–Kung, two 1/3.52-scaled models of Tou–Kung were designed and tested subjected to vertical loading and quasi-static loading. Also, the finite element models of intact Tou–Kung and tilting Tou–Kung were established. Based on the validation of experimental results and finite element models, numerical simulation analysis of the models was carried out to study the influence of tilting angle on the behaviors of Tou–Kung. It is shown that the failure modes of the models were the compressive fracture of Da-Tou under vertical load, the shear failure of the dowel at Da-Tou, and the slipping between Da-Tou and Pingban-Fang subjected to lateral cyclic loads. The relationship of vertical load and vertical displacement was obtained and analyzed, and the vertical initial stiffness and bearing capacity of the models descended with the increase in tilting angle. The hysteretic loops of the tilting models subjected to cyclic loads are asymmetrical in positive and negative loading, and the asymmetrical degrees of the curves are much significant with a larger tilting angle of the models. With the increase in tilting angle, the lateral stiffness and ultimate load increased in positive loading, and both of them decreased in negative loading due to the tilting of the models. Also, the equivalent viscous damping coefficient of the models decreases with a larger tilting angle of Tou–Kung.

Finite Element Model Updating and Dynamic Analysis of a Restored Historical Timber Mosque Based on Ambient Vibration Tests

Abstract The use of timber as a construction material is based on much older dates than concrete and steel. Therefore, the preservation of historical timber structures such as bridges, monuments, towers, mosques, etc. is very important for cultural heritage. The perspective of preservation for this kind of structures has been developed and has gained more importance in the last two decades. However, there are some issues that need to be addressed. Timber is an anisotropic material and is not fire resistant. Also, moisture causes significant swelling. So, structural behavior should be carefully evaluated by experimental techniques before and after restoration and verified numerically using finite element models. This article presents a detailed study on the structural condition assessment of a restored historical timber mosque: its finite element analysis (FEA), ambient vibration tests, model updating to minimize the differences and reflect the current situation, and dynamic analyses before and after updating procedure. The Kuşluca historical timber mosque located in the Sürmene District of Trabzon, Turkey was selected as an application. The mosque was built in the early 20th century and includes two floors. Significant timber decorative elements are available in the entrance door, minbar, and mihrab. The restoration projects began in 2008, and the restored mosque was opened in 2011. Finite element modeling of the mosque was accomplished using SAP2000 software (Computers and Structures, Inc., Walnut Creek, California), considering the restoration project drawings. Modal analysis was performed using orthotropic material properties, considering literature review, to determine the initial dynamic characteristics. Nondestructive experimental measurements were conducted after construction to validate the numerical results using in situ testing. Ambient vibration-based system identification was employed using the Enhanced Frequency Domain Decomposition method in the frequency domain and Stochastic Subspace Identification method in the time domain. The first three natural frequencies were obtained between 5.160 Hz to 7.153 Hz and 3.960 Hz to 5.873 Hz numerically and experimentally, respectively. There is close agreement between mode shapes, but 30.0 % differences in natural frequencies. To minimize the differences, the finite element model of the timber mosque is updated using the manual model updating procedures, with a changing of material properties to reflect the real structural behavior. The maximum differences are reduced to below the acceptable limits as 5 %. To evaluate the structural behavior and determine the model updating effect, linear dynamic-time history analyses are performed, and displacements with internal forces are compared to each other.

Repair and Reinforcement of Historic Timber Structures with Stainless Steel—A Review

Recent trends in the use of stainless steel profiles for repair and reinforcement of historic timber structures, after degradation due to biotic and non-biotic attacks, are discussed in this paper. These structural challenges can vary from inadequate load carrying capacity to complexities involved with choice of repair materials and techniques. Given the recurring requirements of conservation authorities in terms of reversibility of interventions and compatibility between historic and new materials, an increase in the use of non-invasive reinforcement materials and reversible techniques was observed. Subsequently, engineers and researchers have increasingly employed stainless steel alloys in retrofitting historic timber structures. This paper therefore presents the state of the art in the use of stainless steel profiles in retrofitting timber structural elements within historic structures. It includes a review of the development of the retrofitting methods and existing experimental studies on the mechanical behavior of timber structures reinforced with stainless steel. Finally, it presents a number of case studies and draws conclusions on current trends and practices based on reported studies.

Historical timber as a sustainable material, Studies about Islamic architecture in Egypt

<p>Wood is an old – modern material, It was and still used in a wide range in a various purposes as construction, decoration and remains the most popular material all over the world, The research provides an overview of the role of timber as an important heritage element which forms the main characters and distinguishes features of many historical buildings in Islamic architecture and used widely in many applications, it had been played a great role in construction and structure of buildings, besides that it had been used in a beautiful purpose in different places whether indoors or outdoors use<strong> </strong>. The research presents the case studies of historical timber in different types of building in Islamic architecture which constructed from more than 1400 years ago, although the historical timber in old buildings exposed to many disasters and faced quite numbers of problems as a result of natural phenomena, man-made, humidity, and termites but it still stands proudly as a great sustain materials. The research shows how he use of timber in historical buildings as sources of inspiration and living evidence of ways of sustainable building practices the types of deterioration which appeared clearly an effect on the statue of historical timber, for that the research introduces some recommendations in the light of ICOMOS international charter “ <a href="http://www.icomos.org/en/home/179-articles-en-francais/ressources/charters-and-standards/163-principles-for-the-preservation-of-historic-timber-structures">Principles for the Preservation of Historic Timber Structures</a> 1999” that Emphasizes the necessity of taking a serious steps and clear strategy to save our heritage elements</p>

Structural assessment of a lapped scarf joint applied to historical timber constructions in central Europe

ABSTRACTThe article deals with assessment of suitable applications of all-wooden lapped scarf joints intended for use in retrofitting of existing historical timber structures in Central Europe. The first part of the article addresses the bearing capacity and stiffness of a lapped scarf joint. In the second part, four types of roof structures typical for the region were analyzed and potential application of the joints is discussed. The third part of the article describes the influence of the application of the lap joints on the force distribution of the repaired structure, since lower stiffness of one member induces forces elsewhere in the structure as it is transmitted by the other members to the rest of the structure. Extent and influence of the stiffness change on the force distribution is briefly discussed.

Evolution and rationalization of timber frame design in Istanbul in the second half of the nineteenth century

ABSTRACTUntil the mid-19th century, the traditional Istanbul house was a building constructed with a timber frame with adobe or brick infill (hımış). This timber frame construction technique evolved in the second half of the 19th century into a timber frame with closely placed thin vertical braces without infill. The causes behind this change are still unknown. This study traces the causes of change and the evolution pattern of Istanbul timber-frame construction through Ottoman building-cost estimates, cost journals and other written sources of the period. The Western influence on science and technology affected the newly emerging engineering discipline in Istanbul and caused the gradual change in timber-frame design. However, the rationalization of timber-frame design went hand in hand with the industrialization of the woodworking sector in the Western world, whereas in Istanbul the lack of steam-powered woodworking machines caused the extensive use of hand-sawn timber-frame elements. This violated the basic design principles of vertically braced timber frames and caused the construction of fragile frames in need of frequent maintenance. Only in the last decade of the 19th century did the industrialization of the woodworking sector lead to the full rationalization of timber-frame construction. Identifying the timber frame types of this transition period is of crucial importance while dating the historic timber structures and assessing their structural strengths and weaknesses.

Stiffness of scarf joints with dowels

Repairs to historical timber structures include connecting existing beams and new beams. Older ways of making the connection need to be used to ensure authenticity of the beam. In most cases, e.g. floor structures, the second limit state – serviceability – is of decisive importance. The new connection softens the beam and increases the displacement. The most widely-used joint is a scarf joint with two or more bolts or dowels. It is not clear whether greater obliquity of its cheeks is desirable, or the effect of different numbers of bolts on the stiffness of the beam. In Germany, a scarf joint with four bolts is recommended, but there is no validation for this from the structural perspective. The behaviour of joints with two bolts or with four bolts seems to be the same. In the process of repairing historically valuable timber structures, the most widely-used joint is with wooden dowels. One pin can be combined with two dowels, or two dowels with one pin. There is currently no relevant information available about the behaviour of the joint, although practical engineers require such information. A theoretical solution requires simplifications, and these are derived from experimental results. The force method (based on the elastic strain energy) is used for a theoretical solution for a statically indeterminate structure. The results of numerical analysis are very encouraging. The final changes in the stiffness of repaired beams in comparison with the original beams are in very good agreement with experimental results.

Experimental and numerical analysis of semi-destructive device for in situ assessment of wood properties in compression parallel to grain

A reconstruction of historical timber structures requires precise diagnostics of mechanical properties of particular structural members, which would subsequently underlie a reliable plan of the reconstruction. Mechanical properties of wood are determined most exactly using destructive techniques, but often they cannot be used in historical constructions. This calls for using nondestructive or semi-destructive techniques that are still reasonably exact, not too invasive and can be profitably used in situ. This work examines a new nondestructive diagnostic tool that enables to determine strength and stiffness parameters of wood parallel to the grain in situ. The function of the instrument was verified using standard compression tests parallel to the grain that correlated with the instrument well (r = 0.92). Complicated stress state in the drilled hole was examined by contact finite element analysis and revealed high contribution of longitudinal elastic moduli in force measurement (r = 0.96).

Structural health assessment of historical timber structures combining non-destructive techniques: The roof of Giotto's bell tower in Florence

Examining the timber structure supporting the roof of Giotto's bell tower in Florence, this paper discusses the combination of non-destructive (NDT), wave-based methods for the characterization of timber structural elements. In particular, it analyses the on-site applicability of selected wave-based techniques for the identification of decay, damage, defects, and moist areas in structural timber. The applied NDT techniques are IR termography, microwave reflectometry, time-of-flight tomography, and mapping by means of elastic waves. Experimental results are compared with data obtained by means of consolidated NDT techniques, such as the electric resistance method for moisture content estimation and the drill-resistance test for decay characterization. These can be considered non-destructive, although they are invasive. The wave-based NDT methods are found to be a value-added complement to routine methodologies for a holistic diagnosis of timber members. Normal practice based on visual inspection, decay detection through point measurements of drill resistance, and moisture content estimation through local readings of electric resistance, can be substantially improved through full-field, multi-sensor, multi-resolution imaging. Nevertheless, while the diverse NDT methods illustrated here can be useful for screening large areas in a completely non-invasive way, local measurements (i.e., the drill resistance and the electric resistance measurements) are still necessary.

Bearing Capacity of a Scarf Joint

The bearing capacity of a scarf joint depends on the length of the joint and the type of connection. It is possible to use circular bolts or squared dowels. Both connection tools used in the repairs of historic timber structures are made of wood according to the requirements of the heritage authority.