Feasibility of Tall Timber Buildings

Feasibility of Tall Timber Buildings

Timmer, S.G.C.

Nijsse, R. (mentor)
Ravenshorst, G.J.P. (mentor)
Terwel, K.C. (mentor)
Sandhaas, C. (mentor)
Vambersky, J.N.J.A. (mentor)

Civil Engineering and Geosciences

Design and Construction

Structural and Building Engineering

2011-10-21

Advantages of timber as a building material are: small dead weight, good thermal characteristics and in some cases low overall building cost. Nature has created large cantilever structures of 150 m high in the form of eucalyptus threes. History show furthermore manmade structures as timber radio towers of 190 m high and wooden religious structures of almost a 1000 years old, towering 67 m in the air. The most recent modern tall timber building is about 29 m high, contains nine storey’s is located in London, UK, and is called “the Murray Grove Tower”. What is discussed above leads to the question: “What is the height limit for tall timber buildings”. To answer this question, the objective of this thesis is twofold. The first objective of this thesis is to determine the influence factors on the height of timber buildings. The second objective is to create proof through analysis of a case study design of at least 100 m high within a determined set of boundary conditions. A preliminary study was conducted to realise the first objective. This preliminary study contained a problem analysis in which the influence factors were determined and a definition was found for tall timber buildings. The main influence factors are part of architectural requirements, structural issues, fire safety and building physics. The influence factors are quantified to achieve the highest potential. This deduction of influence factors resulted in a set of boundary conditions and proposed solutions. First a universal floor plan was designed as a starting point. A minimum wall-window ratio of 15% and a building slenderness of 1:4 were set as architectural boundary conditions. The material applied to the load bearing structure was chosen to consist of timber laminations of strength class D70 which has a positive effect on the structural and fire characteristics. The proposed stability system consists of a braced tube-in-tube structure. The investigated types of bracing are the Diagid geometry, simple diagonal bracing and a solid timber shear wall bracing. To realize a fire safe design, relevant objectives are satisfied though the choice of a fire concept, in combination with fire suppression measures, resulting in compartment burn out. In the second part of the thesis these proposed solutions are investigated. Four variants where created consisting of a set, corresponding to the geometry of the proposed types of bracing and associated joint solution. Three-dimensional models where created with finite element software of these variants. Of these models, parameters are modified in order to investigate: the influence of the joint stiffness; the building core stiffness; and the support stiffness on the global behavior. The investigation on the global behavior of the systems focused on the deflection at the top, the development of bending moments within members and the dynamical behavior. An optimisation of the cross sections of structural members was also conducted in order to investigate the competition of feasibility between variants. The fire behaviour of variants was determined for a combination of structural solutions, fire safety concepts and fire suppression measures. The deflection at the top of the timber building satisfied the limits of the building code for all variants. It was derived that the deflection at the top of the building is for 14% to 20% due to the joint stiffness, for 39% to 56% due to the stiffness of the cross laminated timber building core and for 16% to 23% influenced by the stiffness of the foundation of concrete bored piles. The results of the dynamical analysis is strongly dependant on the used method. The dynamic behavior of some combinations of structural system and calculation method, did not satisfy the requirement stated in the Dutch standard, NEN 6702. It was concluded that a tall timber building structure of 112 m high is possible on a fundamental level. Several structural systems can be applied in combination with an appropriate fire concept.

tall buildings
timber
wood
firesafety

http://resolver.tudelft.nl/uuid:5da007ef-1021-46be-98ab-13284dba0505

Student theses

master thesis

(c) 2011 Timmer, S.G.C.