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Description - Panelized Timber Vaulted Floors

Why
- A floor system where timber and insulation works together as a structurally sound system through dry connections.
What
- Develop a hybrid timber system for medium to large spans (8-12 m) in offices and residential areas
Considerations
- Sketch first System must come first regarding ease of fabrication and assembly. Only then comes analysis -> Quatify section
- Infill Use infill to increase the weight and dampen vibrations e.g. CEM wood
- Dry Assembly Use dry connections without pouring liquid material into the other (no glue, not steel)
- Masonry logic Interconnect slab components by sides
- Joinery Timber connections works for thin plates e.g. 4 cm. Otherwise thicker plates such as CLT panels that vary from 4 to 32 cm in thickness can be connected using external connectors only: a) https://www.x-fix.at/
- Document models in compas_assembly2 https://brg-research.github.io/compas_assembly2/latest/examples.html
- Key Geometry Challenges Bottom surface must be flat, develop column or wall to slab connection, timber is linear, start from a single curvature vault
Quantify
- Material usage
- Fabrication an assembly time
- Acoustics, fire, vibrations
- Structural peformance (timber works better in tension than compression)
- Circularity

Division into boxes with infill

Types of In-Plane connectors

Screws (in differenct angles)
TS3 Glue https://www.ts3.biz/en/technologien/
Rothoblaas slot
Rothoblaas glued steel elements
Milling out timber that is not parallel to the main span direction
X-fix connectors + dowels + timber inserts
Stepped Milling of CLT with additional webs and screws
Timber inserts
Finger joints + metal bolts
Finger joints + screws

X-fix Connector

Hilti Panel Connector

Existing Systems

Existing Systems in Timber Construction
- System: Beam-to-Beam and Beam-to-Plate The most economical timber slab model is a beam-to-beam or beam-to-plate slab. Often, these slabs are hybrids made from timber and concrete. And often they do not have a flat surface on the bottom.
- System: Flat Bottom Surface is more expensive The cost and material usage increase, especially for mass timber and box-beams with a long span, when there is a need to have a flat surface instead of being interrupted with beams.
- System: Vaulted Slabs Vaulted slabs are less common due to the complexity of fabrication and the pragmatic need to have a flat surface. There are two main groups of timber vaulted systems: a) continuous vaults, and b) segmented vaults. All the found segmented vaults are either actual shells without a flat surface or theoretical visualized ideas.

History

Click to expand

* **Delorme Philibert**

* **Timber Vaults**

Literature

Click to expand

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Menardo Andrea

Spans of floors:
a) Starts from parking: 1.35, 2.7, 5.4, 8.1 m (most common: 5-8 m)
b) Daylight x < 6.5 m
c) Spans are decreasing nowadays
d) Longer spans leads to vibrations problems, more C02 emitions for bigger sections
e) Space of around 10 cm can be left for services

Commonly missing information about structural systems:
a) Geography - floor types depends on the region and companies are producing. Also distance to them.
b) Cost - it is almost impossible to find the cost of the systems
Material properties and the floor systems:
a) Floors have connections to enable shear and bending
b) Division is specific to each timber product e.g. CLT, LVL, Glulam
c) Not the same support condition

Suggestions:
a) Dome that is supported on all sides
b) Make an arch from Lignatur and compare
b.1) what is the longest span one can do with Lignatur in an arch with the same thickness
b.2) what is the minimum thickness of arch that can be done compareing with the same span of flat Lignature slab
c) Understand if it is worth to consider the linearity and bending
d) Does discretization in timber makes sense? The length in timber is advantage. Is it a grid or linear subdivision?
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Francesco Ranaudo

* Start by asking why not what.
* Timber infill is not the key points and it is a question if it makes sence to fill a slab with heavy material.
* The building systems are often comoposed from columns and beams and the slab is already a infill.
* Dimensions of floors systems depends on facade systems that vary in different countries, that defines the step size of a slab
* You should not start from the economical point of view and the comparative data, since it is very speculative and vary from today to tomorrow and information publicly and privately available rather start what the material can do, systems, natural gradient of material through section, environmental impact, timber has strong direction and linearity.
* Maybe it can be a mixture of timber and concrete, but the interface must be dry.
* Stay-in-place forwork
* Sound transfer requirements, Airborne x > 52 DB, Impact x < 53 DB for Crea tower project.
* Ribs in the slab does the main job, while the slab is just a infill as serves as a fire prtection and physical ceiling element.
* https://www.som.com/research/timber-tower-research/
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Prof. Pauli Jacqueline

* Lignum
* swiss timber association
* Atlas Books of the Detail
* BFH school
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Sun Qiming

* Offcuts from CLT productions by combining flat CLT panels in two layers and connecting them with rods or dowels.
* Open for collaborations. I gave her a few ideas to avoid steel connections, she had first in her mind. And maybe possible segmented arch prototypes, e.g. using inclined hard-wood dowels to have intermediate space between two plates similar to TStud products for beams. The way she would like to work is first through small scale prototypes e.g. some laser cutting tests. It feels for these kind of early works, it would be better for her to start from normal CNC cutting, but this is a bit a constraint to equipment.
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Hilti

* Developing a more reliable timber connections than X-Fix for in-plane and sheer forces for slabs. They might be an interesting option to work with too.
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Oxara

* Box blocks made out of timber, panels are casted separately and placed inside the box as a dry element.
* Do not mix wet material with timber.
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Reisach Dominik

* Offcuts from timber beams, then assembly into arches via hardwood keys
* PhD topic is different. Not interested in collaboration.
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Aryan Rezaei Rad

* use timber as structural frame and fill it with Oxara green concrete
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CONFERENCE PAPER The design and development of a demountable and reconfigurable segmented fan concrete shell flooring system. .

LIFE CYCLE ASSESSMENT The sustainability point here is that it is reconfigurable. But it is only that it is possible to demount pieces without cutting them.

OPTIMIZED STRUCTURAL FORM USING FAN VAULTS TOPOLOGYS Compression dominated to avoid opening of interfaces and hinge formation, and minimal shear forces along the surface of the interface to avoid slipping

JOURNAL PAPER Digital fabrication of ribbed concrete shells using automated robotic concrete spraying.

DESCRIPTION The 4.5 x 4.5 m structure (concrete layer 3-6 cm, largest segment 1.8 m x 1.8 m) is using a dual system where concrete panels and metal structure is positioned as far away from the concrete connection as possible.

ALTERNATIVE FROM TIMBER The bottom base can be made from CLT (there are thickness from 4, 6, 8, 12 to 32 cm) including the top part of the metal structural.

PRECISION the precisions of 3d printed joint might have less sufficient joint contact surface comparing to machined edges: Due to issues with tolerances of the timber frame resulting in approximately 10 mm deviations at each segment (amounting to an error of around 0.5%), the segments did not fit flush with each other. Manual modifications on each segment were performed once demoulded in order to allow them to fit together for assembly.

AESTHETICS OF FINISHING the bottom surface is not clean

ONLINE PUBLICATION: When low strength materials meet funicular structures: a sustainable clay floor structure solution for emerging contexts.

ONLINE PUBLICATION: Plywood on steroids: CBE experiments with building materials for a sustainable future.

ACOUSTICS mass timber has an acoustics problem. This can be addressed by topping timber with a concrete slab, which increases embodied carbon and makes reuse almost impossible. Otherwise it is possible to solve by geometry.

FORMWORK SIMPLIFICATION Simplification of the formwork for the fabrication of concrete shells. Historical solutions: a) Candela's hyperpoloids from straight timber pieces to create curved surfaces, b) Nervi precast elements which included ribs and corrugations, c) Neff and Bini used pneumatic formwork to inflate a flat concrete cast into the desired shape.

FORMWORK COST IN LABOUR The global rise in labour costs led to a decrease in the usafe of thin-shell concrete structures due to the high cost of manufacturing complex forwork and trowelling.

WEBSITE: Mass Timber - FastEpp.