Dynamic Characterization and Vibration Analysis of a Four-Story Mass Timber Building

Abstract

Mass timber construction has been gaining momentum in multi-story residential and commercial construction sectors in North America. As taller mass timber buildings are being planned and constructed, in-situ dynamic tests of this type of construction can be performed to further validate their design and use. As part of this larger effort, an in-situ dynamic characterization testing campaign based on ambient vibration measurements was conducted on a recently constructed four-story mass timber building located in Portland, Oregon. The building features cross-laminated timber (CLT) floors, a glued laminated timber (GLT) framing gravity system, and light-frame shear walls and steel HSS hold-downs that compose the lateral resisting system of the building. Ambient vibration acceleration testing data were collected using 18 accelerometers that were wired to a portable data acquisition system in two experimental setups. Approximately 2 h of bi-directional horizontal acceleration data were recorded. In this paper, two operational modal analysis methods are used for estimating the modal parameters (frequency, damping, and mode shapes) based on the data collected. In addition, a multi-stage linear Finite Element (FE) model updating procedure is presented for this building type and the FE estimates of frequencies and mode shapes are compared to estimates from the collected data. The calibrated FE model provides confidence to the operational modal results and presents a comprehensive modal characterization of the building. At ambient levels of excitation, the developed FE model suggests that stiffness of the non-structural elements, such as the exterior wall cladding, and glazing affects the modal response of the building considerably. Lessons learnt on this unique and first of a kind four-story structure constructed in the United States and implications for taller mass timber buildings are summarized and provide valuable insight for the design and assessment for this building type under future dynamic excitation events.

Model updating of seven-storey cross-laminated timber building designed on frequency-response-functions-based modal testing

“…The modal properties of TTBs are difficult to predict, however it is possible to learn about the as-built modal properties of the operational TTBs. Output-only ambient vibration testing (AVT) was performed for a limited number of tall CLT buildings (see, Aloisio, Pasca, Tomasi, & Fragiacomo, 2020;Mugabo, Barbosa, & Riggio, 2019;Reynolds, Casagrande, & Tomasi, 2016;Reynolds et al, 2015), where the fundamental vibration modes were identified and compared with FE results. The AVT methods are based on measured response due to unmeasured ambient excitation, which varies with time and produces estimates that vary from one data block to another.…”

On the reliability of the equivalent frame models: the case study of the permanently monitored Pizzoli’s town hall

“…The refinement of models' calibration in the elastic range was carried out acting: on the masonry stiffness properties (more specifically on the Young Modulus E and the Shear Modulus G), for both SWs; also on the stiffness of the diaphragms, in the case of 3Muri. It should be pointed out that other sources that can contribute to the increased frequencies measured in AVT results, such as the explicit modelling of structural and non-structural elements (Soti et al 2020) or the impact of the mass distribution and of non-structural elements (Mugabo et al 2019), were neglected. Actually, the role of the non-structural elements can be relevant particularly in structures less massive and less stiff than masonry buildings.…”

Acoustic Characteristics of Cross-Laminated Timber Systems

“…Although it has appeared on the market only recently, CLT (cross-laminated timber), also known by other trade names such as X-Lam or CrossLam, composite plywood, cross-laminated wood, BBS (Binder BrettSperrholz), or MM-BSP (Mayr-Melnhof-Brett Sperrholz Platten), has attracted considerable interest in the field of technological innovation and eco-sustainable construction materials [24,25]. CLT structures are becoming a reference model in Europe, especially in the field of multi-storey wooden constructions [26][27][28][29][30][31] and not only for residential use [32,33]. The use of the CLT is very adaptable and it allows constructing walls, floors, and roofs in various types of buildings: Multi-storey residential buildings, schools, auditoria, exhibition places, worship places, sports halls, theatres, and commercial buildings.…”