Traditional Timber Research Articles

Seismic performance of stone supported traditional timber frames with or without cap beams

Traditional timber frames in East Asia rest on stone bases, and are uncapped or capped with flat timber beams on their top. This study quantified the influence of the cap beam on the seismic performance of stone supported traditional timber frames. Four column foot and head joints were half-scale fabricated and reversed cyclically tested. Typical damage modes of the joints were identified. Methods were proposed to characterize the joints' rotational behavior. Finite element models of stone supported traditional timber frames with or without cap beams were developed. Lateral performance analysis was conducted on typical full-scale frames based on the developed models; fragility analysis was further performed to evaluate the full-scale frames' seismic performance. The tests indicated that the column foot joints were self-centering and had minor residual parallel to grain deformation. However, the column head joints were found with the embedment deformation at the cap beams, resulting to the pinching of their moment-rotation hysteretic curves. By use of existing hysteretic models in OpenSess whose parameters expressed by the theoretical maximum moment and elastic rotational stiffness, the joints’ rotational behavior was well captured. The numerical study indicated that the cap beam significantly increased the lateral performance and deformability of a frame. The elastic stiffness, lateral load-resisting capacity and cumulative energy dissipation of the frame increased by 77%, 81% and 42%, respectively. Fragility analysis indicated that the cap beam increased more than 33% and 23% of the PGAs corresponding to 50% probability exceedance under life safety drift limit and collapse prevention drift limit, respectively.

Experimental study on fire resistance of traditional timber mortise-tenon joints with damages

This paper presents the experimental results on the fire resistance of traditional timber mortise-tenon joints with looseness, decay and cracking in the jointing area. Static loading test and fire resistance tests were conducted on six full scale joint specimens. The development of the temperature, the charring depth and rate, and the degradation of the rotational stiffness of the joints with fire exposure time was quantified. It was found that the service damage can have significant influence on the fire resistance of the traditional timber mortise-tenon joints. The charring rate calculated from the beam and column cross-sections is close to the recommended value in design code for softwood. The displacement of the damaged joints with wood decay and cracking increased by 69% and 90%, respectively, with respect to that of the undamaged joint after 30 min of dire exposure. The rotational stiffness of a damaged joint after 30 min of fire exposure can drop down to 11.4% of the initial rotational stiffness of a sound joint at ambient temperature. The influence of the stiffness degradation of joints on the moment redistribution and fire endurance of neighbouring beams and columns is worth of further investigation.

Low energy characteristics and low carbon strategies for traditional timber framing in the full life cycle -The case studying on Tujia hanging foot in southwest Hubei

The issue of carbon emissions has attracted a great deal of attention in recent years, both at home and abroad. There are also more and more people engaged in related research. In the field of architecture, more people are starting to look at the whole life cycle of buildings to explore energy saving and emission reduction of buildings. It is not just about exploring how to reduce the energy consumption of a building during its use. This paper will analyze the advantages of traditional wooden buildings and modern buildings in terms of low carbon from five perspectives: material selection, transportation, construction, use, transportation and demolition, and summarize the related strategies from a whole life cycle analysis of buildings.

Experimental and Numerical Analyses on the Fire Resistance of Timber–Concrete Composite Boards Using an Innovative Form of Partial Protection

Compared with traditional timber boards, timber–concrete composite (TCC) boards demonstrate a higher rigidity and bearing capacity, improved vibration, and better behavior under seismic conditions. However, they become charred when exposed to fire due the combustibility of timber, and the fire safety of this material is considered essential. In this research, 60 min fire exposure tests and residual load-carrying capacity tests following fire exposure were carried out on three full-scale composite boards, two of which were covered with an innovative form of gypsum board protection. The effect of the innovative protection on the temperature field and fire resistance of the TCC boards was studied in detail. The test results indicate that the fire resistance of the TCC boards was effectively improved by using the innovative protection. If the coverage ratio is identical, a wider single gypsum board can demonstrate a slight increase in residual carrying capacity. Finite element models of TCC boards were established to investigate the temperature field during fire exposure and the residual load-carrying capacity of the TCC boards after fire exposure, demonstrating high applicability and accuracy. The conclusions in this paper can provide reference for fire design in engineering.

Comparison of Self-Tapping Screws and Bamboo Nails in Reinforcing the Zuo-Dou Connections in Traditional Oriental Timber Frames of Asia

This paper is focused on the retrofitting techniques of Zuo-Dou connections in Dieh-Dou timber frames in Far East Asia. The target is to develop appropriate techniques for the reinforcement and maintenance of the wooden cultural heritage. A series of full-scale tests are intended for the evaluation of the rotational and shear characteristics of the various retrofitting techniques for the Zuo-Dou joints. These retrofitting techniques are conceived by this study based on the principles of the conservation of cultural heritage. The reversible materials, invisible layouts, and structurally efficient schemes are taken into account to figure out the reinforcement strategies. Regarding the conservation targets, this study applies the self-tapping screw (STS) and the bamboo nail for reinforcement. Corresponding to the loading circumstances, moment- and shear-constraining schemes are developed. The STS and the bamboo nail are applied by means of moment- or shear-constraining strategies. Then, rotational and shear tests are carried out to estimate the structural efficiency of the conceived retrofitting techniques. With the appropriate schemes, the STS and the bamboo nail contribute to the enhancement of the structural performance of the Zuo-Dou connection. The STS in a moment-constraining profile can ameliorate the Zuo-Dou’s rotational behaviour. As far as post retrofitting and preventing reinforcing are concerned, the STS reveals considerable structural efficiency. The bamboo nail in a shear-constraining scheme can increase the shear capacity of the Zuo-Dou joint. Besides the quantitative outcomes, these retrofitting techniques exhibit ductility and enhance the deformation processes of the connections. With the alternative fasteners, the slump or vibration during the deformation becomes moderate and the severe damages, such as rocking or block shear failure, are alleviated. The techniques and associated materials used in this study exhibit compatibility and feasibility for constraining the rotation, deformation, and crack of the Zuo-Dou connection. These effects are helpful for retaining the joints’ structural behaviour and contribute to the conservation of traditional timber constructions.

Theoretical Model for the Analysis of Rotational Behavior of Penetrated Mortise-Tenon Joints in Traditional Timber Structures

ABSTRACT Penetrated mortise-tenon joints (PMJs) are typical wood-to-wood connections commonly used in traditional Chinese timber structures. They play a crucial role in the structural behavior of timber constructions. This study derived a method of theoretical estimation for the rotational behavior of PMJs, which is unique and more comprehensive in that it takes both movement of the rotation center and bending deformation of the tenon into consideration. In addition, it experimentally and numerically validated the theoretical model, and quantitatively analyzed the position changes of the rotation center and the effect of the bending deformation. On this base, simplified calculation formulas are proposed for the prediction of equivalent elastic stiffness and peak moment of PMJs, and then applied for the calculation of the lateral stiffness of timber frames. As a result, the predicted lateral stiffness shows good agreement with test results, demonstrating the validity of the estimation method derived and its applicability to the structural analysis. The results of this study show that the rotation center of the tenon is not stationary, and its moving range in the horizontal direction is much larger than that in the vertical direction. Another pattern found is that the bending deformation of the smaller tenon counteracts more than 20% of the compressive deformation caused by the rigid-body motion, and therefore must be considered when analyzing the rotational behavior of PMJs.

A Mechanical Model Used for the Multifactor Analysis of Through-Tenon Joints in Traditional Chinese Timber Structures

ABSTRACT The through-tenon joint is one of the most widely used joints in traditional Chinese timber structures. The moment-rotation relationship of the joints was established using geometric, physical, and equilibrium conditions as well as full consideration of various influencing factors. Furthermore, three types of joints with different tenon lengths were manufactured and tested under quasi-static tests. The damage features and the moment-rotation relationship curves of these joints were obtained and used to verify the proposed mechanical model. Additionally, we compared the proposed model to the existing mechanical models using the experimental results of 16 groups from other scholars and conducted parameter analyses through the model. The results showed that the lengths of the tenon had a remarkable influence on the mechanical properties of the joints. The proposed mechanical model agreed well with the experimental results. The moment-rotation relationship can be divided into the slip and elastic stages as well as the yield at one side, and yield at both sides. The comparisons to the existing models indicate that the proposed model in this paper has broader applicability and can be used as a reference for the protection and reinforcement of mortise-tenon joints used in traditional timber structures.

Inspection and structural assessment of traditional timber floors: a practical systematization

PurposeThis paper addresses the evaluation of traditional wooden floors, based on (1) visual strength grading (VSG) techniques adopted for ancient wooden structures; (2) a new approach to biological damage and (3) structural safety analysis. This assessment includes complex concepts. Therefore, the study presents a highly needed practical tool to help technicians make a preliminary assessment whereby many of the timber elements in our heritage can be saved from removal.Design/methodology/approachA simple and effective procedure was developed for each step. An inspection and diagnosis datasheet was drawn up, and the structural analysis presented by the Eurocodes was summarized. This methodology was then applied in a case study to demonstrate the complete procedure. During the assessment of this sort of structures, the drilling technique was a relevant method utilized as it provided essential and clear information about the beams' conservation.FindingsThe case study results indicate that 70% of the beams of the analysed structure exceed strict minimum performance criteria. This shows that other similar buildings can have their wooden elements saved from demolition, which is not the current regular refurbishment approach.Originality/valueThe current reality shows that the technicians' lack of capacity for a pragmatic assessment of the timber members’ structural capacity promotes their disinterest in them. To avoid that, this text presents a process for evaluating wooden floors using a simple and clear approach. This will prevent the demolition of wooden elements and instead encourage their preservation.

Numerical analysis of traditional Chinese timber structure: Simplified finite element model and composite elements of joints

Mortise-tenon (M-T) joint, column foot joint, and Dou-Gong joint play a key role in the seismic behavior and energy dissipation of traditional timber structures. To simplify the modeling process and predict accurately the hysteretic behaviors of traditional timber joints as well as the global seismic responses of traditional timber structures, three types of composite elements, which were composed of varying non-linear one-dimensional spring elements available in the ANSYS finite element (FE) software, were proposed to characterize the hysteretic performance of the M-T joint, the column foot joint, and the Dou-Gong joint, respectively. The beam element was used for simulating the timber components with large size and not easily damaged. The parameters of the composite elements were identified from the simplified hysteretic model or test hysteretic curve of each type of joint. The simplified FE models of the M-T joint, M-T jointed timber frame, column foot joint, and Dou-Gong joint were developed, and verified using the cyclic loading tests of joints, respectively. Based on the validated composite elements and simplified FE models of varying joints, the three-dimensional simplified bar system FE model of a 1/3.52-scaled palace-style ancient timber structures was established using the ANSYS, and also validated using the shaking table tests, in terms of its dynamic characteristics and responses. Good agreements between the model predictions and test results were observed. Additionally, parametric analyses were performed, while revealing and quantifying the effects of performance degradation for the M-T joint, column foot joint, and Dou-Gong joint on the dynamic responses to the structure. It is found that the damage to the Dou-Gong joint had little effect on the maximum story drift of column frame layer, however, the damage to the M-T joint and column foot joint would significantly increase the maximum story drift of column frame layer. When the damage degree of the M-T joint, Dou-Gong joint, and column foot joint in the structure was up to 60%, the maximum story drift ratios of column frame layer were close to 1/48, 1/50, and 1/39, respectively, the maximum story drift ratios of Dou-Gong layer were approximately 1/164, 1/98, and 1/125, respectively.

Experimental study on the compression behavior of long timber column strengthened with the novel hybrid fiber sheets

Long timber columns are widely used in traditional timber structures worldwide; however, many of them possess bearing capacity issues and have to be strengthened. The current study aims to develop the novel Hybrid fiber reinforced polymers (HFRP) sheets suitable for long timber columns. In the first stage, six HFRP sheets were designed, and the evaluation of these sheets was carried out by the tensile tests and the Scanning electron microscopy (SEM) tests. Secondly, for the compression test, two sets of 36 timber columns were designed utilizing six types of HFRP sheets. Finally, the effects of different sheet types and strengthening methods on the compressive performance of timber columns were investigated. The findings reveal that bidirectional HFRP sheets have excellent compressive performance for timber columns. In the case of using one-layer interval reinforcement, the bearing capacity can be increased by 22.27%, which is 12.15–17.81% higher than that of the unidirectional HFRP sheets. Compared with one-layer reinforcement, the two-layer reinforcement increased from 0.91% to 5.35%. The current study's findings are intended to provide an essential scientific foundation for the advancement of fiber-reinforced timber column technology and the preservation of the heritage of timber structures.

Construction Techniques and Detailing for Romanian Paiantă Houses: An Engineering Perspective

Traditional houses represent landmarks of local cultures all over the world. In seismically prone countries, the traditional timber frames with different types of infills have shown quite good earthquake resilience, an essential feature considering their large number, their simplicity and their reduced cost, owing to the use of local materials and workmanship. In fact, their seismic behavior fostered the interest in further scientific research, including that addressing engineering aspects. Because of their diversity in layout and detailing, noticeable even among houses in the same area, developing general methods to preserve and strengthen such buildings is still a difficult task. This paper presents an overview of the traditional building construction techniques in Romania, focusing on the structural configuration and detailing of the so-called paiantă houses. Largely used all over the country, these houses have shown that they can generally withstand earthquakes at least without collapsing and, most frequently, with minor or repairable damage. Their preservation is nowadays a major challenge, as they are being gradually either demolished and replaced, or retrofitted by using invasive techniques. Their cultural and heritage value is undeniable, and there are still many things to be learned from the past craftsmanship and re-valuated in the future. Three case studies of rural buildings located in different areas of the country were chosen among the most widespread paiantă versions, and comprehensive engineering assessments were conducted to identify their detailing and degradations. Based on the most common degradations, the conclusions drawn from this study can be used to substantiate further research aimed at selecting the most appropriate construction and strengthening techniques.

Ingenuity Incision in Traditional Malay Wood Carving Calligraphy Motif

Malay woodcarvings are an ornament that symbolizes the identity and creativity of the Malay community at the house or palace. The difference will be in the design complexity and the number of ornaments used to decorate the palaces. Motif is considered one of the primary elements behind the creation of woodcarving and is included visually in various arts and crafts categories. Thus, the purpose of this study was to present an analytical study to investigate the visual forms of calligraphy motifs on the ornamentation wood carving at Istana Tengku Long, Terengganu. The study utilized the qualitative methodology in collecting data besides the field study at the selected palace and in-depth interviews with related persons. The Fractal Dimension Analysis (FDA) was applied to measure the complexity of the intricacy of the calligraphy panel. The finding indicated that the Islamic belief in the daily activities and local culture has assimilated to produce such intricate calligraphy motifs in Istana Tengku Long. The combination was carved in two compositions together with relief which, non-relief forms and floral motifs were the types of motifs that dominated the woodcarving at Istana Tengku Long. The Quranic verse of the calligraphy motifs gives the implied meaning to the royalty status and socio-culture of the Malay during that period. The knowledge gained from the study presents the Malay royalty's belief that the verses would influence their daily life and the palace as a place of residence. This study will contribute to the understanding of cultural assimilation and its impact on the architectural component revolution, specifically the ornamentation of the building. Preserving the calligraphy motif with indigenous incision shows the sustainability of Malay craftsmanship in wood carving. It emphasizes the inheritance of the aesthetic ornamentation in the traditional timber palaces in Malaysia that potentially involved heritage tourism and education prospects.

Simplified structural analysis method for traditional timber buildings with cross frame

Simplified structural analysis method for traditional timber buildings with cross frame

Implications of Siesmic Detailing on the Fire Performance of Post-Tensioned Timber Frames

Post-Tensioned Timber (PTT) frames have significant advantages over traditional timber frame systems especially where a low damage design and fast construction are desired. New Zealand practitioners designing timber structures for fire are accustomed to applying ambient design methods to an element cross-section reduced by a char depth based on a duration of Standard Fire exposure following NZS 3603 or AS/NZS 1720.4. The behaviour of PTT frames in fire remains a concern because this approach does not account for the actual mechanics of PTT connection and frame response under natural fires that will occur in the structure. This paper examines the individual and interdependent response of PTT connection components (tendon, dissipater, fasteners, etc) to fire. It is shown that the ambient analysis tool for PTT connections, the Modified Monolithic Beam Analogy, cannot be applied to the fire case by only using char reduced cross-sections of timber elements. This approach of combining ambient methodologies with reduced cross-sections does not account for the specific connection detailing, which result in unique damage in fire that may govern the structural response. The responses of two seismically detailed PTT connections are predicted using this approach and compared to a first principles assessment of connection behaviour to demonstrate that failure will occur earlier than otherwise predicted. Numerical thermal analyses of these two connections also qualitatively corroborate the damage that occurs. This investigation establishes that additional studies are required to understand the complex behaviour of these connections when exposed to fire before a design methodology can be developed.

ANALYSIS OF ROCKING COLUMN BEHAVIOR CONSIDERING STRESS DISTRIBUTION OF COLUMN USING FIBER ELEMENTS

In this paper, a numerical model considering the embedment reaction of column foot by the beam-column finite element method was proposed for evaluating the restoring force characteristics of the rocking column in traditional timber structures. Wood compression tests in contact with stones were conducted to investigate the characteristics of the embedment reaction and initial deformation generated at the end of the wood, and these characteristics were considered in the column foot numerical model. The validity and applicability of the numerical model were verified by analyzing several static loading tests of the rocking column.

Robustness Analysis of Historical Timber Roofs: A Case Study of the Gaggiandre Shipyard at the Arsenale of Venice

In this work, a deterministic approach is adopted to analyze the robustness of the timber roof of the Gaggiandre shipyard at the Arsenale of Venice. The capacity of the traditional timber truss to withstand the design loads as a result of the damage in the strut-tie node is evaluated according to the alternative load path method. Two layouts of the trusses are analyzed and compared: before and after the Austrian retrofitting intervention, performed in the late 1800s. For both configurations, robustness analyses are carried out by using linear 2D numerical models that consider the effective rotational capacity of the structural nodes in relation to the construction methods of the timber joints. For the configuration subject to the 19th-century restoration, the 3D response of the roof is also analyzed to verify the additional contribution provided by the longitudinal bracing system to the activation of alternative load paths (bridge effect). The results obtained with the different analyses are thoroughly evaluated, providing an indication of the deterministic robustness index of the roofing system based on different assumptions. The outcomes of this work allow to draw some general considerations on the method that could be used for the robustness assessment of historical wood systems.

Experimental investigation of the behavior of traditional timber mortise-tenon T-joints under monotonic and cyclic loading

• Monotonic & cyclic tests on traditional cylindrical mortise-tenon timber T -joints. • Great displacement capacity but also severe pinching in hysteresis loops. • Significant difference in force capacity if tenon under shear or bending. • Behavior also influenced by inherent material variations, construction etc. Monotonic and cyclic tests on cylindrical mortise-tenon timber T-joints typical of Ottoman-period mansions in mainland Greece were carried out, aiming towards a better understanding of such connections and their influence on timber-framed wall seismic performance in numerical and experimental investigations. Configurations from the head and foot of posts were tested so that the tenon was under either combined bending and shear, or pure shear. The two types of loads led to significantly different hysteretic behavior, force and energy dissipation capacity of the examined joints. Joints with gap and under push–pull out load were also tested.

CONSERVATION OF TRADITIONAL HOUSES AND A CASE STUDY ON SAFETY EVALUATION BY USING LIMIT ANALYSIS

Most of the traditional houses in western Anatolia are a type of hımış (traditional timber frame) structure. Deterioration of these traditional houses is mostly due to their abandonment. Abandonment causes the structure’s load-bearing system vulnerable to environmental effects and ultimately weakens the structure against seismic loads. A case study is performed on the Orhaneli houses. Building-scale suggestions are proposed towards the conservation of these houses based on the performed analysis and documentation. The results of simplified limit analysis of 20 houses utilized in this study are presented and the need for finite element modeling of these structures with sophisticated connection detailing is underlined. It is observed that the majority of examined houses are resilient for the seismic events of 50% probability of exceedance in 50 years, however, they need to be retrofitted for the seismic events of 10% probability of exceedance in 50 years.

Wind effects on Chinese traditional timber buildings in complex terrain: The case of Baoguo Temple

Traditional timber buildings are one of the most precious types of architectural heritage. These heritage buildings suffer from various natural hazards every year, including wind storms, floods, and earthquakes. The existing studies on traditional timber buildings generally focus on seismic performance, while the wind-related studies are limited. Specifically, there is no previous research on the wind effects of the surrounding environment on historic timber buildings.Based on a case study of the 1000-year-old Baoguo Temple, this paper intends to (1) evaluate the extent to which the surrounding buildings of the main hall and the hilly terrain affect the wind environment in the temple with CFD simulation, (2) validate the CFD simulation and extract wind pressure data, and (3) calculate the structural responses of the main hall using FEM. The research proposed a methodology for evaluating the wind effects of surrounding buildings and the hilly terrain on ancient timber buildings with CFD simulation. Moreover, a numerical approach employing FEM analysis is put forward for predicting the structure response of ancient timber buildings to wind hazards, considering the actual structural deterioration. Resultsincluding wind pressures, wind speeds, and streamlines obtained from the CFD simulation, as well as vibration mode shapes, accelerations, and displacements calculated by FEM are presented. The CFD simulation result points out the significant influence of the upstream hill's elevation and surrounding structures on the wind environment. The FEM analysis presents the structural response of the building with inclined columns and various support stiffnesses using the obtained wind pressure as load input. In its current status, the main hall of the Baoguo temple would exceed the elastic deformation limit, and rectifying the column incline would effectively minimize wind-induced damage in case of hazards.

Effects of gaps on the seismic performance of traditional timber frames with straight mortise-tenon joint: Experimental tests, energy dissipation mechanism and hysteretic model

The gaps are very common in the mortise-tenon (M-T) joints of the column-frame layer for the existing ancient timber buildings, which severely threaten the whole stability and safety of the structures. To study the effects of gaps on the seismic performance of traditional timber frames with straight M-T joint. Three 1/3.2-scaled straight M-T jointed timber frames, including one intact timber frame as a contrast and two timber frames with different gaps, were fabricated using Pinus sylvestris logs, and subjected them to reversed cyclic loading tests in strict accordance with the international test standard ISO-16670. The failure modes, load-displacement hysteretic response, strength, initial elastic stiffness, ductility, and stiffness degradation of the specimens were analyzed. The energy dissipation mechanisms of the timber frames with different gaps were evaluated, based on the law of energy conservation. Results indicated that the strength, initial elastic stiffness, and hysteretic energy dissipation capacity of the timber frames with gaps decreased significantly with increasing damaged degree. The gap can weaken the ductility of the timber frame, however, the inter-story drift ratio of the timber frame with gap can reached 0.16, indicating good deformation capacity. The gap had little effect on the degradation degree of the residual stiffness of the timber frame under large displacement amplitude. When the damage degree was 10%, under large displacement amplitude, the hysteretic energy consumption, elastic strain energy, and gravitational potential energy of the timber frame approximately accounted for 54%, 16%, and 30% of the total input energy, respectively. Based on the experimental results, the empirical formulas related to key cyclic performance parameters, considering the gap effects, were established. Based on the empirical relationships of the key hysteretic parameters of the timber frame with gaps, an improved hysteretic model for a timber frame with a gap was proposed and also validated. Good agreement between the model predictions and experimental results was observed.