Precast elements ensure unrivaled quality standard
The Pure One office building was constructed at Oberneuland Office Park, in the German city of Bremen, for an architects’ and consultant civil engineers’ practice. It was built exclusively with precast elements, thus ensuring quick completion.
Cost and time savings were one of the major factors to be considered for project execution. When seeking a suitable contractor, the client, an architect and publicly appointed consultant engineer specializing in assessing damage to buildings, came across the website of B. Lütkenhaus GmbH, and thus the SySpro range of precast elements. Andree Sachmerda, owner of the architects’ and consultant engineers’ practice, intended to exclusively rely on precast elements for designing and completing the building because he wanted to also present it to his clients as a showcase project.
B. Lütkenhaus GmbH based in Dülmen, Germany, was contracted with producing the semi-precast elements, which include a combination of thermal wall units, fully precast components, stairs, double walls, and precast floors. The largest unit produced measured 7.91 × 3.46 m, was 43 cm thick, and weighed 8.83 metric tons.
Thermal walls and precast floors
The external walls of the building consist of SySpro thermal wall panels, which feature a double-shell design with an integrated 16 cm insulation on their insides. These units are composed of two factory-produced precast concrete panels that are connected to each other by thermal pins ensuring the specified spacing. The outer shell’s inside features a factory-attached insulation layer. The free space between the two shells was filled with cast-in-place concrete after final positioning of the panels. It forms the structural framework in combination with the inner shell. The exposed sides of the prefabricated inner and outer shells feature smooth concrete surfaces to create a distinct façade appearance on the outside and finished wall surfaces in the interiors.
The installed SySpro precast floor units are prefabricated slabs with a structural cast-in-place concrete infill. Precast concrete units are equipped with the rigid reinforcement (i.e. a lattice girder) needed to ensure appropriate stiffness during installation, as well as with the flexural reinforcement in the longitudinal and transverse directions required for both the installation phase and the final condition. Elements are designed to accommodate all block-outs, floor penetrations, junction boxes, drip edges, oblique sections, embedded parts etc. required at later stages of the construction process. Precast panels serve as formwork in the construction phase and fulfil a structural function across their entire cross-section after placement and hardening of the cast-in-place infill.
The scheduled construction time was shortened considerably thanks to the smart combination of precast elements. The building complies with currently applicable energy efficiency and soundproofing standards.
Industrial prefabrication saves time
Custom assembly plans were prepared for this project to support the quick, safe and reliable installation on-site. Prior to the installation process, B. Lütkenhaus GmbH prepared a 3D visualization of the entire building in order to highlight detailing points and transitions. At this stage, the graphical representations of the fully precast narrow window lintels with integrated block-outs for shades in conjunction with the thermal wall units proved to be particularly helpful and made it possible to optimize the design even further.
“The 3D-based detailed preliminary design exercise provides the opportunity to display and optimize all interfaces and transitions between the individual components,” explains Volker Steinhoff, Technical Director at B. Lütkenhaus GmbH. “The state-of-the-art software suite we’re using utilizes its integrated 3D visualization functionality to optimize the entire construction phase, including process planning, production, logistics, and assembly. We are thus able to put figures and quantities to the sophisticated process steps that are derived from the digital building model to inform the construction process and completion of the building. Also, this automated approach to designing walls and floors provides unrivaled cost efficiency.”
All precast elements were thus prefabricated and delivered to the job site just in time. Industrial prefabrication saves a huge amount of time – the wall units were produced and delivered in a sequence perfectly adjusted to actual construction progress, thus eliminating the need for complex, time-consuming formwork installation on the construction site. Managing Director Ulrich Lütkenhaus continues: “Exclusively relying on precast elements makes it possible to complete a single story exceedingly quickly. Also, individual elements can be produced to a high quality standard while saving costs at the same time. And we can also accommodate additional requests at short notice thanks to the flexible collaboration between the precast plant and the contractor.”
The Pure One office building was completed ahead of schedule owing to the smart combination of double wall panels and precast floors. The sophisticated design of the building also resulted in smooth, appealing concrete façades and architectural concrete surfaces in the interiors completed at a relatively low cost.