Module 1: Introduction to Timber Engineering - Examples & Applications

Module 1: Introduction to Timber Engineering - Examples & Applications

Properties of Philippine Wood

Case Study 1: Grain Orientation in Columns

A residential contractor is installing a timber column to support a heavy roof load. They are provided with a square timber post. They can either install it so the load acts parallel to the grain (longitudinal axis) or perpendicular to the grain (radial/tangential axis). Evaluate the correct installation method based on the orthotropic properties of wood.

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Case Study 2: Hygroscopic Effects on Flooring

A high-end restaurant features solid Yakal wood flooring installed during the dry season. A few months later, during the peak of the monsoon season, the floorboards begin to cup, warp, and press tightly against each other, causing buckling. Explain the cause of this failure.

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Lumber Grading & Species Grouping

Case Study 1: Material Selection for a Bridge Deck

An engineer is designing a small timber bridge for light vehicular traffic in a rural area. The bridge deck will be directly exposed to rain, sunlight, and heavy abrasive loads. The available local timber species are Narra, Tanguile, and Almon. Select the most appropriate species group and justify the choice.

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Case Study 2: Framing for Interior Partitions

An architect is specifying the timber framing for non-load-bearing interior partition walls in an office building. The walls will be covered with drywall and are not exposed to moisture. Cost-effectiveness and ease of nailing are the primary concerns. Choose between Yakal (Group I) and Bagtikan (Group III/IV).

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NSCP Provisions & Adjustment Factors

Calculating Adjusted Allowable Bending Stress

Calculate the adjusted allowable bending stress (

F_b'

) for a Guijo (Group I) beam subjected to a combination of dead load and wind load.

The beam dimensions are

150 \text{ mm}

wide by

300 \text{ mm}

deep.

Assume standard dry service moisture conditions and normal temperatures. The beam is isolated and does not qualify as a repetitive member.

Given Parameters:

Reference Bending Stress ( $F_b$ ): $21.8 \text{ MPa}$
Size Factor ( $C_F$ ) for $300\text{mm}$ depth: $0.86$

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Adjusting for Extreme Environments

200\text{mm} \times 200\text{mm}

Yakal timber post (Group I) serves as an exposed structural support for a coastal deck. It is subject to continuous elevated temperatures averaging

40^\circ\text{C}

and high moisture levels (

MC \gt 19\%

). It carries primarily normal duration dead and live loads.

Given Parameters:

Reference Compression parallel to grain ( $F_c$ ): $16.5 \text{ MPa}$
Wet Service Factor ( $C_M$ ) for $F_c$ : $0.80$
Temperature Factor ( $C_t$ ) for $F_c$ at $T \gt 38^\circ\text{C}$ : $0.90$
Size Factor ( $C_F$ ) for $200\text{mm}$ post: $1.0$

Calculate the adjusted allowable compressive stress (

F_c'

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Advanced: Cumulative Adjustment Factors for Roof Framing

50 \text{ mm} \times 150 \text{ mm}

Apitong (Group II) rafter is used in a repetitive roof framing system spaced at

400 \text{ mm}

on center, covered with structural wood sheathing. The roof must support a combination of dead load and a seven-day roof live load (e.g., construction workers/materials). The roof is uninsulated and expected to experience sustained temperatures over

38^\circ\text{C}

due to direct tropical sunlight, but remains dry (

MC \lt 19\%

Given Parameters:

Reference Bending Stress ( $F_b$ ): $16.5 \text{ MPa}$
Load Duration Factor ( $C_D$ ) for Seven-day Roof Live Load: $1.25$
Temperature Factor ( $C_t$ ) for $F_b$ at $T \gt 38^\circ\text{C}$ : $0.80$
Size Factor ( $C_F$ ) for $150 \text{ mm}$ depth: $1.10$
Repetitive Member Factor ( $C_r$ ): $1.15$

Calculate the final adjusted allowable bending stress (

F_b'

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Advanced: Adjustment for Form Factor (Circular Section)

A circular timber pole (

D = 250 \text{ mm}

) made of Apitong (Group II) is used as a beam subjected to bending.

Given Parameters:

Reference Bending Stress ( $F_b$ ): $16.5 \text{ MPa}$
Form Factor ( $C_f$ ) for circular sections: $1.18$

Calculate the adjusted allowable bending stress (

F_b'

), assuming all other adjustment factors are

1.0

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Engineered Wood Products

Case Study 1: Long-Span Roof Structure

An architect is designing an indoor swimming pool facility requiring a clear, unobstructed roof span of 30 meters over the pool. Solid sawn timber is unavailable in such lengths and would likely suffer from severe natural defects at that scale. Select an appropriate Engineered Wood Product (EWP) for the main roof arches and justify the choice.

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Case Study 2: Mass Timber Multi-Story Building

A structural engineer is tasked with designing the floor system for a new 6-story "mass timber" office building. The floor needs to act as a rigid structural diaphragm, support significant live loads, and provide immediate a walkable surface during construction. Compare the use of traditional timber joists with Cross-Laminated Timber (CLT) panels.

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