Building light and comfortable

Abstract

Limitations in the modern housing market supply and the high demand for city centre living space ask for a robust urban densification way of building. This results in the exploration of innovative vertical extension projects, such as the ’De Karel Doorman’ case in Rotterdam. However, demanding the construction method to be extreme light-weight revealed an unexpected normative serviceability phenomenon. The reducedmass did not dissipate enough vibrational energy induced by human activities such as walking, leading to an excessive and disturbing perception of vibrations. This caused nuisance for both the home situation where the motion takes place as for the neighbouring floor fields. The critical motion-related limit state has to be satisfied to create a comfortable living environment. This thesis aims to further develop the concept of light-weight steel and timber building structures focussing on vibration comfort. This is done by exploring structural measures that can steer the vibrational floor response for both the induced situation as for the transmittance to adjacent fields. Broadening research shows the general impact of the damping, natural frequency and modal mass. From this starting point, new practical building tools are developed to affect and control the path and magnitude of vibrations positively. General guidelines are provided that show the demands for a structural assembly to create suitable apartments. The proposed measures to steer the vibration comfort were researched using both the conventional handcalculation method from the SBR-guideline and by more accurate finite element analyses from SoViST and Autodesk Robot. The resulting OS-RMS90 values indicate the response velocity of the floor and have to meet the limit criteria proposed for the specific function of a building. For the light-weight residential building concept, these criteria were set to 0,8 [-] and 0,2 [-] for respectively the home and neighbouring situation. It was found that for light-weight building structures the implementation of a large amount of stiffness is inevitable in both the floor assembly as in the junction. The consequence of additionalmass and height can be balanced by using efficiently shaped profiles and smart placement of the joists. For the supporting beams, these demands encourage the use of rectangular hollow structural sections whereas for the floor assembly I-joists are recommended. Additional transverse stiffness stretches the clustering of natural frequencies for orthotropic plates but is most effective for two-way span floors. A smaller span will result in improved comfort levels but will complicate the structural assembly by introducing more elements and connections. Besides the overall performance enhancing measures, it was found that the limit criterion for neighbouring apartments is harder to achieve without additional interventions. Introducing more substantial obstacles for the vibrations to overcome along the path, will reflect the transmittance and hence steer the floor response towards improved comfort levels. The use of an alternating floor field can provide in this issue as it avoids the mode-coupling of natural frequencies from adjacent elements. One other recommendation is the differentiation of the home-separating and in-home junctions. This results in maintaining more vibration energy in the home situation and limits the nuisance caused from excitements in a neighbouring apartment. The as-built ’De Karel Doorman’ revealed the impact of additional stiff elements in the wall that substantially increase the bending and torsional stiffness in the junction. It was found that these elements mitigate the nuisance caused by footfalls to imperceptible values for adjacent floor fields. However, these elements do leave a mark on the flexibility of the floor plan. Light-weight building structures face new challenges and acknowledge the shift from strength-design to serviceability-design criteria. Regarding vertical extension projects, not just the building engineering aspects but also the practical implementation was found to contribute in the consideration for structural assembly measures.