Seismic Design and Testing of Post-tensioned Timber Buildings With Dissipative Bracing Systems

Abstract

This paper describes a seismic design procedure for low-damage buildings composed by post-tensioned timber framed structures coupled with hysteretic dissipative bracing systems. The main goal of the design procedure is preventing or limiting earthquake-induced damage to the structural and non-structural elements. For this aim, a target design displacement is defined according to the desired performance level. Then, the corresponding design force, strength, and stiffness of the post-tensioning and of the dissipative braces are evaluated in order to size post-tensioned connections and dissipating devices. The results of shaking table testing performed at the University of Basilicata are also reported. A prototype model −2/3 scaled, three-dimensional, and three stories with a post-tensioned timber structure without and with V-inverted braces and U-shaped flexural steel dampers-has been extensively tested. During testing, the specimen was subjected to a set of seven earthquakes at different intensity levels of the peak ground acceleration. The effectiveness of the bracing system and the reliability of the proposed procedure are experimentally demonstrated. Non-linear dynamic analyses have been performed in order to simulate the experimental seismic response. The numerical model is based on a lumped plasticity approach, which combines the use of elastic elements with linear and rotational springs representing energy dissipating devices and plastic rotations of the connections. The numerical results accurately predict the non-linear behavior of the prototype model, obtaining a satisfactory matching with the target drift considered for design.

Experimental seismic response of a resilient 3-storey post-tensioned timber framed building with dissipative braces

“…It is interesting to note that for the BF configuration the values of the MIDs at all stories were comparable (this means an optimal activation of the dampers) and the mean value of MID was about 1.5% at 100% of PGA, coherently with experimental results of Pres-Lam structures with rocking walls at the DBE level (Newcombe et al 2010;Pei et al 2019). This result further proved the reliability and robustness of the design procedure (design drift 1.25%) meeting the criteria for regularity in elevation required by code for buildings categorised as regular in elevation (Ponzo et al 2019). The MCF profiles highlighted that the introduction of dissipative bracing systems was effective in reducing the columns shear respect to DF and F configurations.…”

“…The dimensions of the structural elements, post-tensioning and dissipative devices were designed according to the displacement-based design procedure proposed by Priestley et al (2007) and optimized for post-tensioned timber framed buildings with passive energy dissipation systems (Di Cesare et al 2019a;Ponzo et al 2019). The Modified Monolithic Beam Analogy (MMBA) procedure (Newcombe et al 2008) was used for dimensioning the post-tensioned beam-column and column foundation connections.…”

“…All experimental results showed a complete re-centering capability of post-tensioned walls, demonstrating the effectiveness of the system with dissipative dampers in minimizing the uplift forces on the floor with limited damages to the system. A few seismic tests on Pres-Lam building specimens have been performed in New Zealand (Newcombe et al 2010), United States (Pei et al 2019 and Italy (Di Cesare et al 2017;Ponzo et al 2019). Newcombe et al (2010) tested a 2/3-scale two-story LVL post-tensioned specimen by applying quasi-static loads.…”

“…In this study the resilient seismic performance of Pres-Lam buildings has been improved by coupling post-tensioned frame with dissipative bracing systems allowing a more flexible architectural configuration respect to heavy-timber gravity-framing systems combined with cross-laminated timber (CLT) walls or post-tensioned rocking walls. The dissipative bracing systems included dissipative devices able to dissipate large amounts of energy during a strong seismic event, significantly reducing the inter-storey drifts and regularizing also the structure (Ponzo et al 2019), due to the additional stiffness and damping provided to the structural system. In case of moderate earthquakes, the system remained elastic until the fixed yielding level of damper was reached.…”

DIBRAST: A Computer-Aided Seismic Design Procedure for Frame Structures Equipped With Hysteretic Devices

“…In addition, the authors proposed an analytical formulation of the behavior factor of braced structures as a result of a wide parametric analysis. Ponzo et al (2019) proposed a design approach for low-damage braced posttensioned timber frames providing the mechanical properties of both post-tensioned and the hysteretic dissipative brace systems at the target displacement to achieve a reference level of seismic intensity. Mazza (2019b) developed a displacement-based design procedure to size hysteretic damped braces according to a target performance level, accounting for the degrading cyclic response of r.c.…”