http://www.logandtimberconnections.com/PDFs/CLT%20reinforced%20with%20self%20tapping%20screws.pdf
Cross Laminated Timber (CLT) – Reinforcements with
Self-Tapping Screws
Peter Mestek1, Stefan Winter2

ABSTRACT: This paper illustrates a research project about the calculation and design of Cross Laminated Timber(CLT) elements stressed by concentrated loads. Its focus lies on the shear design of CLT-elements next to punctual supports including reinforcements with self-tapping screws with continuous threads in areas of high shear stresses

Different influencing parameters on the distribution of shear forces next to a punctual support were evaluated by using comparative FEM-analyses. In the course of laboratory tests material-mechanical principles were determined to considerthe interaction of rolling shear stresses and compression perpendicular to the grain. In addition to FEM simulations several experimental tests were carried out to describe the load bearing behavior and the strengthening effect of CLT-elements reinforced by self-tapping screws. The investigations aim at developing a design concept including
the effects mentioned above.

System Solution ASSY Plus VG Fully Threaded Self Tapping Screws

Problem

A portal frame is defined as an assembled load-carrying system of posts and beams. When portal frames are not clamped but tilt mounted on the support leg, they are also able to transfer horizontal loads. Instead of a fixed support at the post base a rigid connection between pillars and beams is created. For this reason a rigid design of the frame corner is necessary. With the increasing relevance of engineered timber frame structures time and cost effective solutions for rigid timber connections between posts and beams are essential.

Current Solution

Currently rigid frame corners in timber structures can be achieved by:

• Post and beam connected by metal parts and nails/drift pins (high assembly effort on site)
• Post and beam connected by pre-glued single or double finger jointing at the shop (elaborate and bulky)
• Post and beam connected by steel parts, for tensile forces, and hardwood inserts for compressive forces.
• Post and beam connected by doweled haunch

 

The disadvantage of these solutions is that they consume too much time, money and effort upon assembling.

SWG solution

The SWG solution is a combination of wood and steel parts. Its essence is a system solution around the ASSY Plus full thread screw, containing of the ASSY Plus VG and tension-compression plates (ZD-plates). In addition to that conventional steel plates and steel bolts (M16) are used.

Technical benefits of the SWG system

• Combining wood and steel construction
• Simple pre-manufacturing
• high level of pre-manufacturing possible
• easy to assemble
• reduced on site construction time
• Optimized connection capacity through combination of tension and compression screws
• reverse loads are taken with ZD-Plate - tension and compression screws

 

The ability to transfer tension and compression forces is unique to the ZD-Plate system.

Commercial benefits of the SWG system

• value added for timber construction companies
• standard timber cross sections can be used
• Reduced number of fasteners when compared to common connection systems
• Time and cost reduction for assembly

Application examples

Timber frame constructions of all kinds

• Warehouses
• Workshops
• Sport centres
• Storage units
• Gym's
• Community halls   

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Reinforcing notched beam with ASSY Plus VG's

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Producing ASSY Structural Wood Screws/Self Tapping Wood Screws

Punching into raw shape

• cutting to length
• head pre-shaping
• final shaping with AW-drive and label

Pinching of the screw tip

• no cutting process
• ASSY Plus tip for wood screws
• Pias-tip for sheet metal drilling screws

Rolling on the thread

no cutting process when rolling on the thread

Hardening

The first and foremost used procedures in the production process of a screw are heat treatment processes for case hardening, tempering and annealing. The structure of the alloy is converted to ensure the required mechanical features.

 

Depending on the carbon content the screw is heated up to a certain temperature which is kept for an extended period of time. Thereby the microstructure is converted and an increase of hardness is achieved through a subsequent quenching in oil.

The now glass-hard (brittle) screw cannot be used in the field yet. In a second process called annealing it is heated up once more. During this process the high hardness decreases and the tenacity improves considerably.

Galvanizing

• Zinc coating for corrosion protection
• Layer thickness 5µ-12μ
• Example: blue cremated or yellow zinc coated

Wood-Concrete-Composite Slab

http://swg-produktion.web7.serverdienst.net/573.html?&L=3

A wood-concrete-composite is a connection between supporting timber beams and a concrete slab mounted on them. A rigid connection is achieved with shear connectors or screws which transfer shear forces between beams and slab. Wood-concrete-composite floors are utilized when large beam spacing’s or spans must be bridged and high pay loads must be carried after retrofitting the ceiling. This bonding is deemed to be the ideal solution for increasing the load-carrying capacity and stiffness of ceiling systems.