Photo: MGA via Minnpost.com

A 7 story hybrid timber building has been proposed for downtown Minneapolis. The project, named T3 is a projected 7 stories in height and offers a spacious 210,000 sqft of office space. Michael Green Architecture has designed the project and was chosen for their many previous successes including BC's Wood Innovation and Design Centre in Prince George. The T3 building represents a turning point in American construction where renewable materials play a major roll in the healthy development of our modern cities. These projects work to illustrate and tighten the relationship humanity has with our natural environment. Heavy timber panels and  glulam columns will be used to meet fire structural design requirements for this landmark project. 

The project is set to begin construction in late autumn of this year with a total budget of 65 million Euros. The building is a projected 24 stories high with an overall floor area of 19500m^2 being built on a 4000m^2 lot in Vienna. The current name of the project is "HoHo," how this name was derived is still unclear for the moment. Initial design releases indicate the project will be a hybrid timber-concrete system with 75% of the construction material being European wood fibre. The architect is Rüdiger Lainer + Partner ZT GmbH, paired with the engineer RWT + ZT.  A two year build time is anticipated for the project which is uncommonly long for modern timber construction. Possibly this time accounts for testing and approval processes which will become more clear as the office development moves forward. 

Edit: HoHo stands for Holzhochhause Wien. 

Images: ©OLN OFFICE LE NOMADE

The final development of V3 for the UBC Brock Commons tall wood project pushes the boundaries of timber construction into new and experimental realms. This third exploration ( see V1, and V2) uses a hex grid system combined with reciprocal framing. A system of this nature presents unique challenges in terms of assembly and connection optimization. Reciprocal framing makes use of distributed load paths which can allow for smaller dimensions of the material used. Depending on the final configuration this can result in overall material savings, but more commonly the usage of smaller sizes of materials (yet overall higher volume) which can also result in cost savings. 

A basic dimension of 6 m for the hexagon arm length, or hex radius was used to allow for appropriate room sizes and for the building to fit within the lot sizing allocations. These hex grid panels are broken up into six sections of 6 m equilateral triangles. A reciprocal framed floor breaks this grid down smaller to 3 m equilateral floor panels. This size of floor panel makes the units easy to move and allows for enhanced mass production. This also gives us the option for a variety of manufacturing techniques. The first technique allows massive adaptability, but takes more install time by installing each 3 m equilateral CLT panel individually onto the reciprocal frame. The second involves using the larger 6 m equilateral grid section (comprised of four, 3 m panels). The smaller 3 m CLT panels are prefabricated along with the reciprocal beam grid and services into a larger 6 m equilateral base panel. These large base panels placed on the reciprocal beam grid system are landed in a special six way steel connector which is attached to a glulam (or LVL/ parallam) column. As a third, and likely most cost-effective option floor panels can be produced in regular manufacturing widths and installed in 12 m lengths, reducing overall crane time and manufacturing re-work. 

Due to the nature of the grid, bracing is spread out between a 3 component plane. Depending on the direction of exterior forces they are dispersed as X/Y components into the hex-grid structure. Bracing is placed in key walls arranged within the hex grid. This supplies a unique architectural challenge, yet can still produce a beautiful quality of space. There are specific challenges around the elevator core and how to fit a square unit into a distinct geometric pattern. This would be an area of ongoing analysis. A concrete service core runs up through both towers, also providing stiffness to the structure. Specially attention needs to be paid to differential height changes with moisture content in the vertical members. Although this is minimized by only using end grain there are still tolerances to be implemented. 

One of the key advantages of the reciprocal framing used in this instance is its vibration mitigation effects. The triangular based grid changes the manner in which vibration propagates throughout the structure. This has profound effects on the sound and impact insulation of the floor system. This allows us to use thinner CLT or solid wood panels and reduce the amount of topping materials. 

The structure can be wrapped in a cable stay system for enhanced seismic performance. Along this line of thought we also explored the use of a reciprocal framed shell structure or grid-shell for the facade system. New commercial applications should come out soon in light of enhanced modelling capabilities, see Reciprocal Framing Made Easy (4mb pdf).

This third exploration into the UBC Brock Commons student housing project is highly experimental in nature, and provides new concepts for tall timber projects. These types of approaches further illustrate the adaptability of timber to create limitless possibilities in structural and architectural design. 

The development of V2 from the UBC Conceptual Massing, takes a different approach than the CLT based V1. V2 focuses on hybrid construction with timber and concrete as well as taking a balloon framing approach.  This allows the structure to take on a new form architecturally and reach new heights. V2 is 18 stories tall with a stepped terrace layout.

V2 is based on Glulam beams, columns and a central concrete core. Concrete composite timber panels are used as structural flooring members spanning just under 7m. This system allows for an open floor plan that is flexible to many architectural arrangements and works exceptionally well for office spaces. The building is broken into two centres of stiffness with special detailing measures. Additional bracing can be added with steel cross bracing or solid timber panels. This must be compared proportionally to the stiffness of concrete core(s) though. 

This system allows for a repetitive production producing results that are highly adaptable to a variety of design considerations. Modules based on columns run 3 stories tall, dictated by glulam production length. Each module contains:

CCT can be produced offsite or poured in larger slabs onsite. Production onsite will increase time, and bring moisture into the construction environment, but it will also add stiffness to the structure. 

V2 needs special attention between the elevator stiffness core and height variation in the rest of the building due to moisture changes. Vertical glulam columns with no cross grain minimize moisture swelling with regard to height, however there will still be specific solutions to mitigate this. A variety of construction approaches could be taken to a system like this for goal oriented efficiencies or multi-criteria optimization. 

Stay tuned for UBC Brock Commons V3 proposal! Things will only get more interesting. 

As explored in our previous post, UBC Conceptual Massing, we have been investigating the development of 3 different timber based construction systems to meet the volumetric requirements for the UBC Brock Commons project.  This simplistic model is based off of V1 in the early massing stage. The model is focused on linear loads and repetitive construction techniques. This system generates a monolithic block specifically designed for ease of construction. 11 stories of CLT hybrid construction are used to produce a robust structural system containing 400 mixed form student housing units.

Elevator and staircase core CLT panels run vertically as opposed to horizontally. The rest of the structure is erected sequentially floor by floor.
Each floor consists of:

• 45 CLT floor panels segmented with concrete composite sections. 
  
• 54 CLT wall & load bearing panels
  
• 24 Exterior wall panels 

A CLT system of this nature would need some adjustments to achieve heights of 16-18 stories. The concrete composite floor system aids in regards inter-story shrinkage and fire suppression tactics. 

This type of a design has numerous benefits from a construction point of view. The structure is cut into repetitive modules which can be prefabricated off site. Balloon framing is minimized to the elevator/staircase cores, which makes assembly by crane easier, while allowing for quicker installation times of individual panels. 

As we move on we will develop other concepts relating to our earlier massing concept (V2, V3) which will reach targets of 16-18 stories with different timber hybrid construction methodologies. 

*Check out V2 here!