The stiffening of modular timber buildings against lateral forces: Calculation of the horizontal displacement

Abstract

This thesis aims to analyze the bracing of timber multi-storey modular buildings against horizontal forces in general, primarily focusing on determining structural displacement. This report categorizes into three main research areas. The first part provides a broad illustration of the modular timber system. The second part summarizes the theoretical background related to horizontal forces and vibration. In addition, the theory section also covers methods for calculating structural displacement due to the forces. The third part includes two case studies where the displacement is estimated based on the on-site data by applying two chosen methods. The results were compared together, as well as with the recorded displacement data, to achieve an accurate way of determining horizontal displacement.

The first part of the research area explains how a modular timber building is designed and constructed. It explains the leading architectural and structural components of a module. It also illustrates how different types of structural loads act on the components. The various modules offer us an apartment layout and a building typology. The arrangement and installation of these modules are challenging, especially against horizontal forces, i.e., the wind load. Timber material specification, connection and interconnection types, and location of the shear walls can provide a proper bracing structure against the forces.

The second part centres on the theory and effect of the wind load, as seismic forces, are not common in Finland. The wind force instigates movement, vibration, and lateral displacement in high-and low-rise timber buildings. Stabilization and comfort are the most desired outcomes for such buildings. Shear walls are a well-known bracing method in the modular structure that stabilizes through diaphragm action along with the roof of a module. The bracing system must withstand the wind load, the vertical loads, and the additional horizontal loads acting on the buildings. Theoretically, the total displacement in the modular structure determines by the sum of various deformations contributed by the modules’ shear walls. Therefore, four deformation impacts include transitional, rotation, bending, and panel shear.

The final part examines determining the displacement more nearly. The simplest and cheapest way is the acceleration measurement, and then using the acceleration data to calculate the displacement of a structure. A direct approach would need complex instruments, more effort, and resources. The report illustrated two case studies where the acceleration measurements were recorded. The direct displacement data is also retrieved for the first case study as it was an elementary work project. In many works of literature, mathematically complex methods propose to convert acceleration into displacement data. However, double integration is more suitable for engineering calculations. In both case studies, the displacement data is determinable by double numerical and equation integration methods. The results were then compared to each other and with the recorded displacement. The calculations affirm that the double equation integration is more accurate than double numerical integration.