1,721,165 research outputs found
Experimental and numerical analysis of in-plane compressed unprotected log-haus timber walls in fire conditions
No full textThe paper presents an experimental and Finite Element (FE) numerical analysis of the behavior of unprotected log-haus timber walls in fire conditions under in-plane compressive loads. The aim is to assess their overall structural performance and to provide possible design suggestions. In doing so, the main results derived from a full-scale experimental test of a log-haus specimen subjected to the standard fire curve and loaded in-plane in compression are first described. FE numerical simulations are then carried out, to further assess the test results and to perform - based on the rather close correlation between test and FE results - a parametric study on the examined structural system. The effects of several influencing parameters are then investigated, including the presence of an initial geometrical out-of-plane global curvature, the possible exposure to fire of orthogonal logs and carpentry joints acting as lateral outriggers for the main log-haus wall, and the compressive loading ratio acting in combination with the fire loading. The most significant effects of such influencing parameters are highlighted in terms of overall buckling resistance and failure mechanisms for the examined walls in fire conditions, providing evidence for the reduction of their actual load carrying capacity. In conclusion, aiming to derive useful design suggestions, a possible extension to log-haus systems of the “Reduced Cross-Section Method” (RCSM) currently in use for the verification of fire exposed timber members is proposed
Analysis of rigid and semi-rigid steel concrete composite joints under monotonic loading. Part I:finite element modelling and validation
No full textReliability-based overstrength factors of cross-laminated timber shear walls for seismic design
No full textThe ductile collapse mechanisms of structures should be less resistant than the brittle mechanisms to ensure a ductile seismic response: in this way, the ductile mechanisms activate before the brittle ones. This sort of chronological law of collapse is obtained in the design phase by providing a proper ”overstrength” to the brittle mechanisms. The realization of overstrength plays a crucial role in the design, and several studies endeavoured to estimate the best overstrength factors, defined as the ratio between the characteristic load-carrying capacity of the non-ductile element and the characteristic load-carrying capacity of the ductile element. In this paper, the conventional definition of overstrength is discussed and compared to a probabilistic definition based on reliability methods. The probabilistic definition of overstrength drives the assessment of the overstrength factors of Cross-Laminated Timber buildings using a sort of indirect approach. The Extended-Energy dependent generalized Bouc-Wen model is used to estimate the nonlinear seismic response of a set of Cross-Laminated Timber shear walls with different ductility. The results are compared with the existing formulations, attempting to draw correlations possibly useful in the design phase
Analysis of rigid and semi-rigid steel-concrete composite joints under monotonic loading. PartII:parametric study and comparison with the Eurocode 4 proposal
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On the rocking behavior of CLT wall assemblies
No full textIn the design of buildings in earthquake-prone areas, it is crucial to identify the dissipative regions, namely areas where energy will be dissipated to ensure the structural integrity during a seismic event. It is important to evaluate the number of dissipative elements, their location within the structure and, wherever possible, to assess their mutual interactions in order to foresee their behavior. In CLT structures, connections between adjacent panels in a wall can be designed either to ensure a monolithic behavior of the wall or to be flexible, leading to a coupled behavior of the wall. In the first case, the energy dissipation occurs only in the base connections (hold-downs and angle brackets), whilst in the second case also the panel-to-panel connections contribute to the energy dissipation. In this paper, a formula for the design of wall-to-floor and wall-to-wall connections is proposed. Giving the external loads (axial load and shear load on the wall), the geometry of the wall assembly and the characteristics of the connections involved, the proposed method allows the designer to evaluate the stiffness of the connections between adjacent panels in order to obtain a monolithic or a coupled behavior. This formula has been validated based on the results of experimental tests and numerical analyses. © WCTE 2018 Committee
Timber-to-timber and steel-to-timber screw connections: Derivation of the slip modulus via beam on elastic foundation model
No full textThe aim of this paper is to propose formulations for the slip modulus prediction of timber-to-timber connections (TTC) and steel-to-timber connections (STC) with inclined screws and possible interlayers. The beam on elastic foundation model, previously developed for timber-to-concrete connections, was extended to consider the flexibility of both media where the screw is inserted. Since a significant influence of the fastener diameter on the foundation modulus was observed in tests, an interpolating formula correlating the foundation modulus with timber density and the fastener diameter was derived. The exact solution of the timber-to-timber analytical model was found to agree well with experimental results for total and double thread screws. A parametric study was undertaken to prove that connections with inclined screws have significantly higher slip modulus and lower degradation of performance as the diameter decreases or the thickness of the intermediate layer increases compared to connections with screws perpendicular to the sliding plane. Furthermore, the slip modulus of inclined screws was found to be limited by the weakest timber layer. Closed form expressions for the prediction of the slip modulus were derived by interpolation for the most important cases of technical interest. These formulas can be proposed for the implementations in codes of practice such as the Eurocode 5, since simplified formulas of the slip modulus are currently missing for connections with inclined fasteners and interlayers
Numerical investigation of the in-plane seismic performance of timber log-haus walls with reinforced dovetails.
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