Testing and Modeling In-Plane Behavior of Retrofitted Timber Diaphragms

Rizzi, Ermes; Giongo, Ivan; Ingham, Jason; Dizhur, Dmytro

doi:10.1061/(asce)st.1943-541x.0002473

Cited by 16 publications

(6 citation statements)

References 21 publications

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“…Because the main failure mode of the prototype involves the development of two plastic hinges in the fasteners, the impact of screw diameter is, as expected, very relevant, with a great in-plane strength and stiffness increase for larger diameters. For the same reason, the influence of plywood thickness is lower, but can lead to a variation in strength of 2%/mm of panel thickness for the investigated range, similarly to past findings on floors retrofitted with a single plywood overlay [13]. In this work, a plywood-based in-plane retrofitting for existing timber floors has been presented.…”

Section: Influence Of Diameter Of Screws and Plywood Thicknesssupporting

confidence: 77%

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Experimental and Numerical Assessment of an Improved Plywood-Based in-Plane Retrofitting Method for Timber Floors in Highly Seismic Areas

Mirra,

Gerardini

2023

Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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Wood-based retrofitting techniques for seismic upgrading and architectural conservation of existing buildings have found increasing application in the last decades. With reference to the in-plane seismic strengthening of existing timber floors, a particularly efficient solution consists of an overlay of plywood panels fastened to the sheathing. This technique allows a great improvement in strength, stiffness, and energy dissipation of the floors. Yet, when adopting this strengthening solution for existing floors in highly seismic regions, the target design loads could require large values of in-plane strength and stiffness for the retrofitted diaphragms, and this could cause their beneficial, dissipative potential to be reduced. Thus, in this work, a strengthening solution is presented, able to retrieve high strength and at the same time activate large energy dissipation in the floors. The proposed technique consists of the creation of two independent shear planes by means of two different superimposed overlays of plywood panels. Previously developed analytical and numerical models describing the inplane response of floors retrofitted with a single plywood overlay were adapted for the present case with two overlays, validating the results against an experimental test conducted on a sample representing a floor portion. Very good agreement was obtained between experimental and analytical as well as numerical results, thus the proposed approaches enable an efficient design process and an accurate simulation of the proposed retrofitting technique.

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Section: Influence Of Diameter Of Screws and Plywood Thicknesssupporting

confidence: 77%

“…In particular, the overlay of plywood panels on the existing sheathing has proved to be a valid and versatile strengthening method, as demonstrated by several investigations and applications in different contexts, e.g. in the United States [10], [12], New Zealand [9], [12], [13], the Netherlands [14], [23]- [27], and Italy [28], [29].…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Assessment of an Improved Plywood-Based in-Plane Retrofitting Method for Timber Floors in Highly Seismic Areas

Mirra,

Gerardini

2023

Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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“…These models were constructed assuming that the post‐peak stiffness is equal to the average gradient of the experimental data from 50 to 100 mm (or the maximum experimental datapoint of 67 mm for Test R1). This assumption was made for consistency with the related literature 11,27,28 and also due to the experimental stiffness remaining near constant in this region. The yield force was calculated using the equal energy principle and assuming an ultimate displacement of 100 mm for both experimental and idealised models.…”

Section: Force‐displacement Behaviourmentioning

confidence: 59%

“…As the improvements due to both the upgrade (R1) and the more extensive upgrade (R2) were similar, one may conclude that the enhancement due to plywood overlay less pronounced than that reported for plywood overlays on horizontal floors. 27,28 The reason for this difference is predominantly attributed to the discontinuity that existed at the ridge beam in the tested roofs.…”

Section: Backbone Curve Idealizationmentioning

confidence: 98%

Simulated seismic testing of two pitched roofs constructed using timber trusses extracted from vintage unreinforced masonry buildings

Derakhshan,

Ingham,

Griffith

et al. 2023

Earthq Engng Struct Dyn

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Two roof structures representing vintage unreinforced masonry (URM) building components were subjected to longitudinal pseudo‐static cyclic loading. The overall roof dimensions were 8.94 m (span) by 3.1 m (length), with each roof incorporating a pair of as‐built timber trusses that were retrieved from two demolished URM buildings. Both roofs were tested first with nailed connections representing original construction and then again with connections that included proprietary metal brackets and straps representing a remediation of the original construction. The loading was applied perpendicular to the trusses, hence parallel to the diaphragm purlins. Damage patterns and deformation profiles were used to interpret the mechanics governing the roof behaviour utilizing existing modelling techniques for timber floors. It was found that the roof behaviour was shear‐dominated, akin to the in‐plane response of timber floors. For the direction of applied loading, both roof stiffness and roof strength were governed by the strength of the connections between the trusses and the diaphragm purlin members and the purlin spacing. Consistent with these findings, a method was suggested to estimate the stiffness and strength of similar roof structures that may have different aspect ratios using the results from the tests. A comparison between the various test results showed that implementing upgrades that were focused on the connections significantly improved the roof stiffness and roof strength.

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“…Compared with natural wood, plywood generally has improved physical and mechanical properties. [ 1–4 ],[ 5–7 ] Plywood is a wood composite material that is classified as either coated or uncoated plywood. There are some problems with uncoated wood composites.…”

Section: Introductionmentioning

confidence: 99%

Multifunctional wood composites based on Camellia oleifera shell with harsh‐weather and self‐mildew resistance

et al. 2022

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Camellia oleifera shell is rich in lignin and tea saponin and other natural active substances, and it is used to directly prepare fuel and biochar, which are low‐value applications. Inspired by the tea oil fruit shell, a new type of wood‐based composite was designed, which was bonded between inner layers and coated on the surface with Camellia oleifera shell‐based phenolic resin through a one‐step manufacturing process. The acid catalyst type, reaction time, and substitution ratios (Camellia oleifera shell/phenol) were used to optimize the formulation and process of Camellia oleifera shell phenolic resin. The chemical structure, wet bonding strength, harsh‐weather resistance, thermal properties, and flame resistance of the composites (Camellia oleifera shell phenolic resin surface coated plywood [CSPCPs]) were evaluated. The results indicated that the CSPCPs showed better‐wet bonding strength and thermal properties and harsh‐weather resistance compared with the common uncoated plywood. CSPCP‐3 presented the maximum wet bonding strength of 1.63 MPa. The limiting oxygen indexes of the CSPCPs were all higher than that of common plywood. All CSPCPs displayed excellent acid rain corrosion resistance, with little mass loss under simulated acid rain conditions. Grayscale was used to compare the samples' color to assess their self‐mildew resistance. As the amount of shell increased, the mold resistance of CSPCPs increased. CSPCP‐3 showed excellent comprehensive performance and can be a multifunctional wood composite suitable for outdoor applications.

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Testing and Modeling In-Plane Behavior of Retrofitted Timber Diaphragms

Cited by 16 publications

References 21 publications

Experimental and Numerical Assessment of an Improved Plywood-Based in-Plane Retrofitting Method for Timber Floors in Highly Seismic Areas

Experimental and Numerical Assessment of an Improved Plywood-Based in-Plane Retrofitting Method for Timber Floors in Highly Seismic Areas

Simulated seismic testing of two pitched roofs constructed using timber trusses extracted from vintage unreinforced masonry buildings

Multifunctional wood composites based on Camellia oleifera shell with harsh‐weather and self‐mildew resistance

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