Vibrations induced by people walking is one of the most important issue in timber floor design. Low natural frequency and low mass require a careful analysis in order to prevent significant annoyance and to guarantee an acceptable human comfort. This paper is concerned with the assessment of vibration performance of a timber-concrete composite timber floor and a cross laminated timber floor used in two timber buildings under construction in Trento (Italy). Different approaches suggested by Standards and literature were employed: analytical methods, numerical analyses and laboratory tests. About analytical methods the uniformed distributed load deflection criterion (ULD), the Eurocode 5 criterion and some criterions from literature were compared, whereas the Vibration Dose Value (VDV) method, as suggested by ISO 10137, was used for the numerical models and the laboratory tests. The numerical analyses were carried out by means of a finite element modelling. The load due to footfall was simulated by static and dynamic vertical forces. The laboratory tests were characterized by thirty walking tests for each floor. Impact testing with modal hammer was also undertaken in order to investigate the dynamic properties of the specimens. All results are compared and discussed.
Hybrid structural systems assembled connecting steel elements and cross-laminated timber panels (CLT) can be a valid alternative to traditional systems in the construction of residential buildings. Such systems can combine the industrialized construction technology typical of steel systems with the advantages offered by CLT panels, namely lightness and geometric stability. Moreover, CLT panels are timber-based products, and wood is recognized as an eco-friendly and eco-compatible material. In hybrid structural systems, the seismic-resistant capacity of the structure can be achieved by ensuring an adequate transmission of actions among the resistant elements, namely plain timber panels (floor and wall) and steel frame elements (beams and columns). Specifically, the interaction between the steel frame and the wood panels shall ensure both horizontal and vertical bracing to floors and walls, respectively. The work presented hereafter concerns the study of the connections to be used among the individual building components of the horizontal elements, with the aim of developing an effective collaboration among the materials, maximizing the level of prefabrication and industrialization of the final components. In particular, the preliminary results of the experimental tests carried out on full-scale steel-to-timber floor specimens, loaded by in-plane actions, will be presented.
The present study proposes a new connection system for Cross Laminated Timber (CLT) structures in earthquake prone areas. The system is suitable for creating wall-floor-wall and wall-foundation connections, where each connection device can transfer both shear and tension forces, thus replacing the role of traditional “hold downs” and “angle brackets”, and eliminating possible uncertainty on the load paths and on the force-transfer mechanism. For design earthquakes intensity, the proposed system is designed to remain elastic without accessing the inelastic resources, avoiding in this way permanent deformations in both structural and non-structural elements. However, in case of unforeseen events of exceptional intensity, the system exhibits a pseudo-ductile behaviour, with significant deformation capacity. Furthermore, in the proposed system the vertical forces are directly transferred through the contact between wall panels, avoiding compressions orthogonal to the grain of the floor panels. In this research, the connection system was analysed via finite element modelling based on numerical strategies with different levels of refinements. Nonlinear analyses were performed in order to investigate the response of the connection to shear, tension and a combination of such forces. The numerical responses were compared with those of full-scale experimental tests performed on the proposed connection subjected to different kind of loading configuration. The results appear as promising, suggesting that the proposed connection system could represent a viable solution to build medium-rise seismic-resistant CLT structures, that minimise damage to structural and non-structural elements and the cost of repair.
International Association for Bridge and Structural Engineering Conference
September 23-25, 2015, Geneva, Switzerland
This paper deals with a contemporary integrated and sustainable construction technology for new residential buildings. Specifically, this research aims at developing innovative steel-timber hybrid structures which allow a rapid assembly of the individual prefabricated components, minimizing the construction times and limiting the costs of the work. The numerical analyses performed on a multi-storey building for social housing will be presented and discussed. The in-plane behaviour of the floors and shear walls will be analysed, considering in particular the types and arrangement of the different timber- and steel-timber joints. The connections to be used among the construction elements will be selected in order to develop a sufficient stiffness, ductility and bearing capacity according to the design criteria for seismic-resistant structures. These connections allow to enhance the on-site assembly operations, therefore working effectively also under harsh climatic conditions.
The outcome of an experimental campaign on the long-term behaviour of timber floors retrofitted with timber-to-timber composite methods is presented. Four diaphragm specimens, 5.2 m long (5 m span) were tested out-ofplane. Each specimen consisted of a solid wood-spruce joist strengthened with a crosslam panel. A layer of timber boards...
Structures and Architecture: Concepts, Applications and Challenges
Modern seismic design procedures are widely represented by the concept of Performance-Based Seismic Design (PBSD). Direct Displacement-Based Design (DDBD) procedure for PBSD of buildings is considered a very promising method which uses displacement as an input design parameter. The DDBD procedure first codified by Priestley requires an a priori estimate of the design displacement and the associated equivalent viscous damping of the structure, at design performance levels. In this paper, design parameters for the ultimate limit state have been developed for a common construction system for timber buildings. Such parameters are defined as a function of mechanical and geometrical connection configurations.