{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "# Material characteristics\n", "\n", "This section contains tables with the material properties of the different timber strength classes. With the aid of a modification factor the characteristic values are adapted to the local environment and use.\n", "\n", "## Durability class\n", "\n", "The upper table below can be used to judge whether wood species belonging to a particular durability class (D1-D5) is sufficiently durable or needs extra protection. The durability class of different wood species is depicted in the lower table below. The higher the durability class, the less durable a wood species.\n", "\n", "| Use class | D1 | D2 | D3 | D4 | D5 |\n", "|----|----|----|----------|----|----|\n", "| 1 | O | O | O | O | O |\n", "| 2 | O | O | O |(O) |(O) |\n", "| 3 | O | O | (O) |(O)-(X)|(O)-(X) |\n", "| 4 | O |(O) | (X) | X | X |\n", "| 5 | O | X | (X) | X | X |\n", "\n", "O: Natural durability is sufficient \n", "(O): Natural durability in principle sufficient but some circumstances require wood treatment \n", "(O)-(X): Natural durability can be sufficient \n", "(X): Chemical treatment is advisable but for some applications the natural durability can suffice \n", "X: Chemical treatment is necessary\n", "\n", "| Species | Natural durability |\n", "|-------------------|---------------------|\n", "| Spruce | D4 |\n", "| Pine | D3-D4 |\n", "| Oak (European) | D2 |\n", "| Oak (American) | D4 |\n", "| Larch | D3-D4 |\n", "| Azobe | D2 |\n", "| Robinia | D1-D2 |\n", "| Western Red Cedar | D2-D3 |\n", "\n", "## Use class\n", "\n", "| Class | Description | Example |\n", "|-------|--------------------------------------------------------------------------------------------------------------|-------------------|\n", "| 1 | Situations in which the wood or wood-based product is inside a construction, not exposed to the weather and wetting. | roof beam |\n", "| 2 | Situations in which the wood or wood-based product is under cover and not exposed to the weather (particularly rain and driven rain) but where occasional, but not persistent, wetting can occur. | beam of open canopy |\n", "| 3 | Situations in which the wood or wood-based product is above ground and exposed to the weather (particularly rain) | external column |\n", "| 4 | A situation in which the wood or wood-based product is in direct contact with ground and/or fresh water | foundation pile |\n", "| 5 | A situation in which the wood or wood-based product is permanently or regularly submerged in salt water (i.e. sea water and brackish water) | sea lock gate |\n", "\n", "## Service classes\n", "\n", "| Service class | Environment | R.H. in construction* | Use class |\n", "|---------------|-------------------------|----------------------------|-----------|\n", "| 1 | Relative humidity exceeding 65% only a few weeks per year. Temperature 20°C, | 12% R.H. | 1 |\n", "| 2 | Relative humidity exceeding 85% only a few weeks per year. Temperature 20°C | 20% R.H. | 1 |\n", "| 2 | If the component is in a situation where it could be subjected to prolonged wetting by liquid water e.g. condensation | 20% R.H.| 2 |\n", "| 3 | Climatic conditions leading to higher moisture contents than in service class 2 | > 20% R.H. | 3 or higher if used externally |\n", "\n", "\n", "* The relative humidity of in the material given in this column holds for most softwoods\n", "\n", "## Load duration class\n", "Load duration class | Order of load duration | Example \n", "--------------------|------------------------------|------------------------\n", "Permanent | More than 10 years | Self weight \n", "Long-term | 6 months to 10 years | Storage \n", "Medium-term | 1 week to 6 months | Imposed floor load, snow\n", "Short-term | Less than 1 week | Snow, wind \n", "Instantaneous | - | Wind, accidental load \n", "\n", "## Modification factors $k_{mod}$\n", "\n", "| Material | Service class | Permanent | Long-term | Medium-term | Short-term | Instantaneous |\n", "|----------------------------|---------------|-----------|-----------|-------------|------------|---------------|\n", "| Solid Timber and Glued Laminated Timber | 1 | 0.60 | 0.70 | 0.80 | 0.90 | 1.10 |\n", "| Solid Timber and Glued Laminated Timber | 2 | 0.60 | 0.70 | 0.80 | 0.90 | 1.10 |\n", "| Solid Timber and Glued Laminated Timber | 3 | 0.50 | 0.55 | 0.65 | 0.70 | 0.90 |\n", "\n", "\n", "Note that the modification factor needs to be chosen according to the load duration of the whole load combination.\n", "\n", "## Creep factors $k_{def}$\n", "The creep factor is based on the service class.\n", "\n", "| Material | 1 | 2 | 3 |\n", "|----------------------------|-----|-----|-----|\n", "| Solid Timber and Glued Laminated Timber | 0.60 | 0.80 | 2.00 |\n", "\n", "\n", "## Material properties: solid timber\n", "\n", "## Material properties: glued laminated timber\n", "\n", "## Material properties: solid timber\n", "\n", "## Design values of material properties in ULS\n", "\n", "## Final deflection\n", "\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [] } ], "metadata": { "kernelspec": { "display_name": "Python 3", "language": "python", "name": "python3" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 3 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython3", "version": "3.8.0" }, "widgets": { "application/vnd.jupyter.widget-state+json": { "state": {}, "version_major": 2, "version_minor": 0 } } }, "nbformat": 4, "nbformat_minor": 4 }