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This paper presents and assesses a new numerical framework for the nonlinear, inelastic analysis of two-dimensional (2D) vertical wood building systems that incorporate sheathed light-frame wood shear walls as seismic force-resisting system. The 2D building model is based on a sub-structuring approach that considers each floor diaphragm as a rigid body with three kinematic degrees-of-freedom (DOF). Each inter-storey shear wall assembly, including the floor diaphragms above and below, can then be simulated by a six-DOF sub-structure element with internal nonlinear DOF. The shear wall element takes into account deformations in the framing members, contact/ separation phenomena between framing members and diaphragms, anchoring equipment such as anchor bolts and hold-downs and all sheathing-to-framing connections. Corotational descriptions are used to solve for displacement fields that satisfy the equilibrium equations in the deformed configuration, accounting for geometric nonlinearity and P-Δ effects. To appraise the proposed numerical framework, the predictions of the numerical model are compared to experimental results from single and two-storey full-scale shear wall specimens. These examples demonstrate the capability of the numerical framework to simulate accurate load paths in the shear wall assemblies and successfully predict variations in strength, stiffness and energy dissipation characteristics of the seismic force-resisting system.
Cross Laminated Timber (CLT) structures are nowadays increasingly used worldwide and mostly in Europe where the system originated. However, in spite of this diffusion which led to the construction of a great number of multi-storey buildings all over Europe, still Eurocodes are almost completely missing provisions for CLT designers, especially regarding the seismic design. Nevertheless, Eurocode 8 requires in most cases, due to the regularity criteria being not fulfilled for most of the buildings, the use of the modal response spectrum analysis method, i.e. the linear dynamic analysis. This method requires the correct estimation of the lateral stiffness of the building in order to accurately calculate the design seismic forces in the building, which may be significantly underestimated or overestimated depending on the size of the building and the shape of the design spectrum. This can be done by modelling each connection with different methods that are often based on available test results, which are not easily accessible by a practicing engineer. This paper provides a design approach for dynamic linear modelling of CLT structures using SAP 2000. Equations are proposed based on available design codes and literature references, and used to design a 3-storey case study building. Further provisions for the seismic design of CLT buildings which are not included in Eurocode 8 are also given. Finally, the proposed design model is also compared with the results of the shaking table tests conducted in 2006 in Japan by CNR-IVALSA on a three-storey CLT building.
Carpentry joints, transmitting forces between timber members by direct contact and friction, were the key-elements of traditional timber construction. Often, such joints were reinforced with metal devices with the aim at avoiding disassembly under exceptional, but undefined and not quantified, loading conditions. Currently, interventions performed to improve carpentry joints are still largely based on empirical state-of-practice schemes, or on simplified assumptions on their behaviour, without explicit reference to seismic conditions. The elastic and post-elastic behaviour of the most widely adopted joints for monotonic and cyclic load has been the object of an extended research program. Results have permitted to define general criteria for the seismic improvement or strengthening of these connections.
This paper presents an experimental study aimed at collecting information on the response of knee connections to high amplitude fully-reversed rotational deformations, and compares the findings with seismic performance requirements in Eurocode 8. The connections investigated attached twinned outer glulam members to a single glulam member sandwiched between them using steel dowels. Attention is also directed at assessing whether the timber design provisions of Eurocode 5 can be used to estimate moment capacities and rotational stiffness of such knee connections.
This paper investigates the numerical modelling of the cyclic behaviour of light-frame timber structures for non-linear seismic analyses. Two models with different detail levels are used: in the first approach, called M1, every nail connecting the frame to the sheathing is schematized through two non-linear springs, acting on two perpendicular translational degrees of freedom in the plane of the wall, to represent the slip between the two timber parts; in the second approach, called M2, the entire wall is modelled using two equivalent diagonal springs, with mechanical properties derived either from experimental testing on the wall, or from detailed analysis conducted with the M1 approach. Due to its simplicity and limited computational burden, the M2 model is particularly convenient for analyses of entire buildings. The proposed models have been implemented in Abaqus via a purposely developed external user subroutine, and in SAP2000 using the multi-linear pivot hysteretic cycle available in the software library. The models are first validated on experimental tests carried out on screws and individual walls, and subsequently used for modelling an entire light-frame building for which the results of several shaking table tests are available in literature. The experimental-numerical comparison confirms the effectiveness of the models for light frame building and the possibility of use from practicing engineers via the SAP2000 or equivalent software package.
Ying-Xian timber pagoda is the existing oldest and highest wooden pagoda in China. Because of strong earthquake action and material aging, Ying-Xian timber pagoda is severely damaged and needs to be strengthened urgently. Aiming at the characteristics of complicated structural conformation and numerous damaged types of the pagoda, this paper discussed practical expression technology of computer simulation, determined the conformation character of layers-superposition and the modeling method of the pagoda based on the construction rule of traditional Chinese timber structures, and proposed the adjustment method to sectional area or elastic modulus of members according to the damage degree and position by the recognition research on damaged condition and stiffness variation of the pagoda. The finite element model of Ying-Xian timber pagoda was constructed and the dynamic behavior was analyzed by program ANSYS. The analysis results indicate that this FEA model is effective to describe the conformation character and damaged condition of the pagoda, and can be applied to seismic behavior study and security evaluation for the strengthening project of the pagoda.
The paper contains the scientific and technical considerations that accompanied the implementation of provisional safety measures for residential and monumental structures after the 2009 Abruzzo Earthquake. Emphasis is dedicated to the use of timber shoring, as most common strengthening technique.
The paper is available in Italian only.