Duration of Load and Fatigue in Wood Structures: Progress Report of a Sub-Committee of the Committee on Timber Structures of the Structural Division

1957 ◽  
Vol 83 (5) ◽  
Author(s):  
Keyword(s):  
Progress Report ◽  
Timber Structures ◽  
Wood Structures ◽  
Duration Of Load

scholarly journals Comparison of reliability evaluation methods between China and Canada standards for wood structures featuring duration of load

2020 ◽  
Vol 66 (1) ◽  
Author(s):  
Qiongyao Wu ◽  
Shuang Niu ◽  
Enchun Zhu
Keyword(s):  
Reliability Analysis ◽  
Analysis Method ◽  
Safety Level ◽  
Wood Structures ◽  
Load Effect ◽  
Key Factor ◽  
Live Loads ◽  
High Level ◽  
Partial Factor ◽  
Duration Of Load

Abstract Duration of load (DOL) is a key factor in design of wood structures, which makes the reliability analysis of wood structures more complicated. The importance of DOL is widely recognized, yet the methods and models through which it is incorporated into design codes vary substantially by country/region. Few investigations of the effect of different model assumptions of DOL and other random variables on the results of reliability analysis of wood structures can be found. In this paper, comparisons are made on the reliability analysis methods that underlie the China and the Canada standards for design of wood structures. Main characteristics of these two methods, especially the way how DOL is treated are investigated. Reliability analysis was carried out with the two methods employing the same set of material properties and load parameters. The resulted relationships between reliability index β and resistance partial factor γR* (the β–γR* curves) for four load combinations are compared to study the safety level indicated by the two methods. The comparison shows that the damage accumulation model (Foschi–Yao model) in the Canada analysis method is highly dependent on the type and duration of load, resulting in more conservative design than the China analysis method in loading cases dominated by dead load, but less conservative design in cases of high level of live loads. The characteristics of the load effect term of the performance function are also found to make considerable difference in reliability levels between the two methods. This study aims to provide references for researchers and standard developers in the field of wood structures.

scholarly journals In-situ density estimation by four nondestructive techniques on Norway spruce from built-in wood structures

Holzforschung ◽  
2018 ◽  
Vol 72 (10) ◽  
pp. 871-879 ◽  
Author(s):  
Daniel F. Llana ◽  
Guillermo Íñiguez-González ◽  
Joaquín Montón ◽  
Francisco Arriaga
Keyword(s):  
Norway Spruce ◽  
Density Estimation ◽  
Penetration Resistance ◽  
Timber Structures ◽  
Engineering Structures ◽  
Wood Structures ◽  
Needle Penetration ◽  
Screw Withdrawal ◽  
The Relationship

AbstractNeedle penetration resistance (NPR), screw withdrawal resistance (SWR), core drilling (CD) and drilling chips extraction (DCE) are nondestructive and semi-destructive techniques used to estimate density in timber structures. In most of the previous studies, these techniques were tested in clear sawn timber and clear specimens. The goal of the present paper is to study the relationship between density and these techniques by means of five different devices in whole pieces of timber from built-in engineering structures, which are from 12 4.5-m long structural timber joists of Norway spruce from a 19thcentury building in Barcelona (Catalonia, Spain). Although determination coefficients (R2) for density estimation models were lower than those from clear timber, the results obtained confirmed that these four techniques are suitable forin-situdensity estimation of woods in buildings. The best results were obtained by CD (the bigger the bit, the higher the correlation), followed by DCE, and SWR. The worst correlation was found for NPR devices, but the results could be probably improved with more measurements.

scholarly journals Analysis of hygroscopic self-shaping wood at large scale for curved mass timber structures

2019 ◽  
Vol 5 (9) ◽  
pp. eaax1311 ◽  
Author(s):  
Philippe Grönquist ◽  
Dylan Wood ◽  
Mohammad M. Hassani ◽  
Falk K. Wittel ◽  
Achim Menges ◽  
...  
Keyword(s):  
Large Scale ◽  
Manufacturing Industry ◽  
Deformation Mechanisms ◽  
Timber Structures ◽  
Geometric Complexity ◽  
Wood Structures ◽  
Material Parameters ◽  
Industrial Manufacturing ◽  
Shape Prediction ◽  
Mass Timber

The growing timber manufacturing industry faces challenges due to increasing geometric complexity of architectural designs. Complex and structurally efficient curved geometries are nowadays easily designed but still involve intensive manufacturing and excessive machining. We propose an efficient form-giving mechanism for large-scale curved mass timber by using bilayered wood structures capable of self-shaping by moisture content changes. The challenge lies in the requirement of profound material knowledge for analysis and prediction of the deformation in function of setup and boundary conditions. Using time- and moisture-dependent mechanical simulations, we demonstrate the contributions of different wood-specific deformation mechanisms on the self-shaping of large-scale elements. Our results outline how to address problems such as shape prediction, sharp moisture gradients, and natural variability in material parameters in light of an efficient industrial manufacturing.

Reliability-based design of wood structures: background to CSA-086.1-M89

1993 ◽  
Vol 20 (3) ◽  
pp. 349-357 ◽  
Author(s):  
Ricardo O. Foschi ◽  
Bryan Folz ◽  
Felix Yao
Keyword(s):  
Calibration Procedure ◽  
Code Design ◽  
Limit States ◽  
Wood Structures ◽  
Design Procedures ◽  
Reliability Based Design ◽  
Working Stress ◽  
Adjustment Factors ◽  
Duration Of Load ◽  
The Impact

The limit states design version of the 1989 Canadian code for engineering design in wood (CSA-086.1-M89) is, for the most part, reliability-based. This paper discusses the methodology employed in the calibration procedure and the reliability levels adopted. Particular emphasis is given to the results obtained for duration of load and system (load sharing) strength adjustment factors, to serviceability limit states, and to the design of columns. Final comments address the impact of the new code in comparison to the traditional working stress design procedures. Key words: code, design, reliability, timber construction, wood.

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