18-story Hotel Gradienten designed to stand tall and firm despite thin prefabricated walls
Hotel Gradienten in Jönköping, Sweden, developed by Skanska Sweden is scheduled to be completed in the first quarter of 2021.
The hotel will feature 18 stories with 229 hotel rooms. Totaling circa 12,300 m2, the property will also offer conference space, a restaurant and 2 floors of underground parking with more than 110 parking spaces. The construction contract is worth nearly 38 million euros. Construction began in the first quarter of 2018, and Nordic Choice Hotels has signed a 20-year lease for the operation of the hotel after the building has been completed.
Due to the building’s height and thin prefabricated walls (200 mm and 250 mm), its structural design and construction involved many challenges. The height of the building causes tension and shearing forces on the foundation and between the wall units. Other challenges include complicated curved geometry in the hotel area, high forces from traffic, and earth pressure on the parking floors. These factors caused the need to design many non-standard parts and solutions, make many changes to the design, and to coordinate among the project parties. Another challenge was working with several factories at the same time. Steel structures were fabricated at Litana ir Ko’s factory and precast concrete units at several different suppliers.
The project requires 536 tons of steel, hundreds of reinforced precast units, including wall elements and hollow-core slabs, and more than 26,000 drawings in total, as well as many reports and specifications for material ordering and delivery to construction site or factories. More than 86,000 reinforcing bars and more than 1300 reinforcing meshes were designed in the model.
BIM helped design the building with no clashes or other failures
Litana ir Ko provided the design and construction of the load-bearing structures for the hotel project. Their scope of work included all structural calculations and the design, fabrication, delivery and assembly of the building components on site for both the underground parking and the hotel, excluding foundations. The company used Tekla Structures 2018i default environment. The Tekla model was also used on mobile devices during the project. Trimble Connect will be used with steel fabrication and construction.
All project parties except the facade designers worked in a 3D workspace. Exchanging models in IFC format was considered easy, and all issues were solved quickly. All design issues were solved in weekly online meetings between the project participants by sharing the model on screen.
In its role as the contractor, Litana ir Ko provided the QTO for estimation and sales and pour sequencing, reinforcing bar coordination, material QTO, field layout and progress and cost monitoring by using BIM. In the model, the company used many Peikko embeds and components, Halfen cast-in channels, some warehouse components and some custom components for 3rd party custom parts, such as couplers and lifting loops. In addition to QTOs, object data was taken from the model to production planning, material optimization, casting table planning, delivery planning and scheduling, for example. Custom reports with steel elements were uploaded to the company’s own file sharing system which automatically translated values from reports to weight values for the system. NC files for plasma cutting were exported to FastNest software and rebar meshes to the Unitechnik system on request of the factory.
The Tekla model was used for communication purposes in all phases of the project. Most reference models were imported in IFC format. The IFC files were used for design and detailing by all disciplines and uploaded at least once a week on the client’s server. These models served the project every week during online meetings to solve design and other issues. Some reference data was used in 2D DWG format. Software products used by other parties include Revit, MagiCad, AutoCAD, NavisWorks Manage, and ArchiCAD. Sofistik software was used for analysis and design. Some joints and reinforcement maps were detailed with Scia Engineer and some joints with Idea StatiCa. Column shoes and welding plates were created with Peikko Designer and specific bars or locations with Hilti Profis Anchor. Excel sheets were also in use for calculations.
Some standard details were imported to Tekla drawings from AutoCAD but the final design is fully detailed with Tekla Structures and all documentation except calculation reports is done in Tekla. According to Litana ir Ko, the benefits of using Tekla in the project include fast and accurate view of 3D reference models, reference model change detection, fast and easy updating of reference models and implementation of holes, openings, and parts in accordance with the reference models, and element conversion to Tekla objects from the reference models.
Subcontractor: Litana ir Ko, UAB
Structural design and detailing: Litana ir Ko, UAB
Steel fabrication: Litana ir Ko, UAB
Delivery of prefabricated elements: Litana ir Ko, UAB
General contractor: Skanska AB
Architectural design: Enter Arkitektur AB
Foundation and BIM coordination: Skanska Teknik AB
Electrical design and installation: Elajo Group
Sprinkler design and installation: Assemblin VS AB
Ventilation design and installation: Assemblin Ventilation AB
Fire protection systems: Deap AB
Facade design, fabrication and installation: UPB AS
Structural inspection: Jönköpings Kommun
Acoustic design: Soundcon AB