Skip header and navigation

4 records – page 1 of 1.

Design of Post-Tensioned Timber Beams for Fire Resistance

https://research.thinkwood.com/en/permalink/catalogue4
Year of Publication
2012
Topic
Design and Systems
Fire
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Author
Buchanan, Andrew
Abu, Anthony
Carradine, David
Moss, Peter
Spellman, Phillip
Year of Publication
2012
Format
Conference Paper
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Topic
Design and Systems
Fire
Keywords
Full Scale
Furnace Tests
Post-Tensioned
Box Beams
Vertical Loads
Failure
Conference
International Conference on Structures in Fire
Research Status
Complete
Notes
June 6-8, 2012, Zurich, Switzerland
Summary
This paper describes a series of three full-scale furnace tests on post-tensioned LVL box beams loaded with vertical loads, and presents a proposed fire design method for post-tensioned timber members. The design method is adapted from the calculation methods given in Eurocode 5 and NZS:3603 which includes the effects of changing geometry and several failure mechanisms specific to post-tensioned timber. The design procedures include an estimation of the heating of the tendons within the timber cavities, and relaxation of post-tensioning forces. Additionally, comparisons of the designs and assumptions used in the proposed fire design method and the results of the full-scale furnace tests are made. The experimental investigation and development of a design method have shown several areas which need to be addressed. It is important to calculate shear stresses in the timber section, as shear is much more likely to govern compared to solid timber. The investigation has shown that whilst tensile failures are less likely to govern the fire design of post-tensioned timber members, due to the axial compression of the post-tensioning, tensile stresses must still be calculated due to the changing centroid of the members as the fire progresses. Research has also highlighted the importance of monitoring additional deflections and moments caused by the high level of axial loads.
Online Access
Free
Resource Link
Less detail

The Fire Performance of Timber Floors in Multi-Storey Buildings

https://research.thinkwood.com/en/permalink/catalogue234
Year of Publication
2013
Topic
Fire
Design and Systems
Material
LVL (Laminated Veneer Lumber)
Timber-Concrete Composite
Application
Floors
Author
O'Neill, James
Organization
University of Canterbury
Year of Publication
2013
Format
Thesis
Material
LVL (Laminated Veneer Lumber)
Timber-Concrete Composite
Application
Floors
Topic
Fire
Design and Systems
Keywords
Abaqus
Finite Element Model
Full Scale
Furnace Tests
Charring Rate
Dead Load
Live Load
Zero-Strength Layer
Research Status
Complete
Summary
This research investigated the fire performance of unprotected timber floors, focussing on composite joist floors, composite box floors and timber-concrete composite floors. The study of these floors was conducted using the finite element software ABAQUS using a thermo-stress analysis in three dimensions, and with experimental fire tests of floor assemblies. The major goal of this research was to develop a simplified design approach for timber floors, validated against the numerical and experimental work. Four furnace tests were conducted on unprotected timber floor systems in the full-scale furnace at the BRANZ facilities in New Zealand. A sequentially coupled thermal-stress analysis was conducted to determine the effects of a fire on floor assemblies under load. The thermal modelling predicted the charring damage of the floors tested in the experiments to within a few millimetres of precision, and the simplified assumptions made in relation to fire inputs, boundary conditions, mesh refinement and effective material parameters were accurate to the desired level of precision. A sensitivity study was conducted comparing different mesh sizes, time step sizes, material model approaches and software suites to determine any shortfalls which may be encountered in the analysis. It was found that a material model adopting a latent heat approach was the most adequate for modelling timber in fires using these effective values, and mesh sizes of up to 6 mm produced relatively precise results. The structural modelling predicted the displacement response and failure times of the floors to within 20% of the experimental data, and the simplified assumptions made in relation to fire inputs, boundary conditions, mesh refinement and effective material properties were once again accurate to the desired level of precision. A modification to the reduction in tension strength at elevated temperatures was proposed to better predict the observed behaviour. A sensitivity study concluded that the material model definition plays a vital role in the output of the modelling. Non-standard fire exposures were also modelled for completeness. A simplified design method to estimate the fire resistance of unprotected floor assemblies was also developed. The method uses a bi-linear charring rate the assumption of a zero strength layer in the timber. The method was compared to the experimental data from this research and others around the world. The results were also compared to other charring rate methodologies from around the world.
Online Access
Free
Resource Link
Less detail

Full-Scale Fire Tests of Post-Tensioned Timber Beams

https://research.thinkwood.com/en/permalink/catalogue257
Year of Publication
2012
Topic
Fire
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Author
Spellman, Phillip
Carradine, David
Abu, Anthony
Moss, Peter
Buchanan, Andrew
Year of Publication
2012
Format
Conference Paper
Material
LVL (Laminated Veneer Lumber)
Application
Beams
Topic
Fire
Keywords
Failure Mechanisms
Steel Anchorage
Full Scale
Furnace Tests
Post-Tensioned
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
July 15-19, 2012, Auckland, New Zealand
Summary
: This paper describes a series of full-scale furnace tests on loaded post tensioned LVL beams. Each beam was designed to exhibit a specific failure mechanism when exposed to the standard ISO834 fire. In addition to the beams a number of steel anchorage protection schemes were also investigated. These included wrapping the ends in kaowool, using intumescent paint, covering the anchorage with fire rated plasterboard and covering the anchorage with timber (LVL). The results of the full-scale tests cover temperature distributions through the timber members during the tests, the temperatures reached within the cavity and those of the tendons suspended within the cavity, the relaxation of the tendons during the test, the failure mechanisms experienced, and a summary of the anchorage protection details and their effectiveness. Recommendations for the design of both post-tensioned timber beams and associated anchorages are also provided.
Online Access
Free
Resource Link
Less detail

Solutions for Mid-Rise Wood Construction: Intermediate-Scale Furnace Tests with Encapsulation Materials

https://research.thinkwood.com/en/permalink/catalogue353
Year of Publication
2014
Topic
Fire
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Author
Berzins, Robert
Lafrance, Pier-Simon
Leroux, Patrice
Lougheed, Gary
Su, Joseph
Bénichou, Noureddine
Organization
National Research Council of Canada
Year of Publication
2014
Format
Report
Material
CLT (Cross-Laminated Timber)
Light Frame (Lumber+Panels)
Application
Wood Building Systems
Topic
Fire
Keywords
Encapsulation
Mid-Rise
Furnace Tests
Research Status
Complete
Summary
The acceptable solutions provided in the 2010 National Building Code (NBC) Division B [1] limits the use of combustible (wood) construction based on building height. For example, for Group C (Residential), Group D (Business and Personal Services) and Group E (Mercantile) occupancies, combustible construction can be used up to 4 storeys, and up to 2 storeys for Group A – Division 2 (Assembly) occupancies. In addition to the building height limitation, there are also building area limitations in the 2010 NBC for the use of combustible construction for these occupancies. For buildings that exceed the height and area requirements for combustible construction, the prescriptive requirements in the 2010 NBC require that noncombustible construction be used for the primary structural elements. Three materials were selected for investigation as encapsulation materials for combustible structural elements: Type X gypsum board (12.7 mm thick and 15.9 mm thick), cement board (12.7 mm thick) and gypsum-concrete (25 mm thick and 39 mm thick). This report documents the results of intermediate-scale furnace tests conducted to investigate the performance of the three encapsulation materials.
Online Access
Free
Resource Link
Less detail