26 results for Palermo, A.

  • Quasi-static cyclic testing of two-thirds scale unbonded post-tensioned rocking dissipative timber walls

    Sarti, F.; Palermo, A.; Pampanin, S. (2016)

    Journal Articles
    University of Canterbury Library

    Post-tensioning low-damage technologies were first developed in the late 1990s as the main outcome of the U.S. PRESSS (PREcast Seismic Structural System) program coordinated by the University of California, San Diego and culminated with the pseudo-dynamic test of a large scale five-story test building. The extension of post-tensioned techniques to timber elements led to the development of new structural systems, referred to as Pres-Lam (Prestressed Laminated timber). Pres-Lam systems consist of timber structural frames or walls made of Laminated Veneer Lumber, Glue laminated timber (Glulam) or cross-laminated timber (CLT). Pres-Lam walls consist of a rocking timber element with unbonded post-tensioned tendons running through the length and attached to the foundation, which provides a centering force to the wall, while energy dissipation is supplied by either internal or external mild steel dissipaters. Previous tests carried out on post-tensioned timber walls focused on small scale (one-third) specimens with the main objective of evaluating the general response of the system. The main objective of the experimental program herein presented is the testing and estimating of the response of a series two-third scale post-tensioned walls, with alternative arrangements and combination of dissipaters and post-tensioning, focusing on the construction details adopted in real practice. The paper first presents a brief discussion on the seismic demand evaluation based on the Displacement-Based Design approach. The construction detailing of the steel dissipater connections, post-tensioning anchorage and shear keys are then presented. The main objectives of the experimental program were the investigation of the experimental behaviour of large scale post-tensioned timber walls, with particular focus on the system connection detailing and optimization of post-tensioning anchorage, fastening of the dissipation devices and shear keys. The program consisted of several quasi-static cyclic tests considering different steel dissipater configurations, different levels of post-tensioning initial stress and different dissipater options were considered: both internal and external mild steel tension-compression yield devices were used. The experimental results showed the performance of post-tensioned timber wall systems which provide high level of dissipation while showing negligible residual displacements and negligible damage to the wall element. The final part of the paper presents the experimental evaluation of the area-based hysteretic damping for the tested specimens and the results highlight the great influence of the connection detailing of the dissipaters.

    View record details
  • Comparison of Force-Based and Displacement-Based seismic design of dissipative post-tensioned rocking timber wall systems

    Sarti, F.; Palermo, A.; Pampanin, S. (2015)

    Conference Contributions - Published
    University of Canterbury Library

    Based on numerical studies performed by the authors, the paper presents to Force-Based (FBD) and Displacement-Based (DBD) seismic Design provisions for dissipative post-tensioned rocking timber wall (Pres-Lam) systems. At first, a discussion on the seismic design requirements of post-tensioned rocking timber wall systems is provided, including suggested material limit states to be considered in the design phase (Ultimate Limit State) also aimed to prevent collapse in case of more severe events. The required amendments to a Force-Based Design provision in accordance to NZS1170.5 are then discussed focussing on the development and significance of the inelastic spectrum scaling factor (kμ). Similarly, the key modifications to design equations required within a Displacement Based Design Provisions are proposed, based on extensive numerical analyses and focusing on the as the design inelastic displacement shape and the equivalent viscous damping. In the final part of the paper a multi-storey building is designed using both FBD and DBD and the two different approaches are discussed.

    View record details
  • Development and testing of an alternative dissipative post-tensioned rocking timber wall with boundary columns

    Sarti, F.; Palermo, A.; Pampanin, S. (2016)

    Journal Articles
    University of Canterbury Library

    The unbonded post-tensioned rocking and dissipative technology was first developed as the main outcome of the PRESSS (PREcast Seismic Structural Systems) Program in US. After the first developments and significant refinement, the technology was extended to steel and, more recently, timber structures. The timber version, referred to as Pres-Lam (Prestressed laminated) system can be either implemented for timber walls (single or coupled) or frames or combination of the above, with unbonded post-tensioning and supplemental dissipation devices. In unbonded post-tensioned dissipative wall systems a combination of re-centering capacity and energy dissipation leads to a “controlled rocking” mechanism which develops a gap opening at the wall base. This generates an uplift displacement which is transferred to the floor diaphragm. This vertical displacement incompatibility can represent a potential issue if the connection detailing between floor and lateral resisting system is not designed properly. The same issue can be mitigated by adopting an alternative configuration of the rocking/dissipative wall system, based on the use of a column-wall-column post-tensioned connection. This concept, originally proposed for precast concrete walls and referred to as PreWEC (Prestressed Wall with End Column), has been extended and adapted to post-tensioned timber structures and validated through experimental testing. The paper presents the design, detailing and experimental testing of a two-thirds scale wall specimen of this alternative configuration. Different wall configurations are considered in terms of post-tensioning initial force as well as dissipation devices layout. The experimental results confirm the excellent seismic performance of the system with the possibility to adopt multiple alternative configurations.

    View record details
  • Design Procedure and Behaviour of Advanced Flag-Shape (AFS) MDOF Systems

    Kam, W.Y.; Pampanin, S.; Palermo, A.; Carr, A. (2008)

    Conference Contributions - Published
    University of Canterbury Library

    Paper 38

    View record details
  • Dynamic Testing of Precast, Post-Tensioned Rocking Wall Systems with Alternative Dissipating Solutions

    Marriott, D.; Pampanin, S.; Bull, D.; Palermo, A. (2008)

    Conference Contributions - Published
    University of Canterbury Library

    During the past two decades, the focus has been on the need to provide communities with structures that undergo minimal damage after an earthquake event while still being cost competitive. This has led to the development of high performance seismic resisting systems, and advances in design methodologies, in order respect this demand efficiently. This paper presents the experimental response of four pre-cast, post-tensioned rocking wall systems tested on the shake-table at the University of Canterbury. The wall systems were designed as a retrofit solution for an existing frame building, but are equally applicable for use in new design. Design of the wall followed a performance-based retrofit strategy in which structural limit states appropriate to both the post-tensioned wall and the existing building were considered. Dissipation for each of the four post-tensioned walls was provided via externally mounted devices, located in parallel to post-tensioned tendons for re-centring. This allowed the dissipation devices to be easily replaced or inspected following a major earthquake. Each wall was installed with viscous fluid dampers, tension-compression yielding steel dampers, a combination of both or no devices at all – thus relying on contact damping alone. The effectiveness of both velocity and displacement dependant dissipation are investigated for protection against far-field and velocity-pulse ground motion characteristics. The experimental results validate the behaviour of ‘Advanced Flag-Shape’ rocking, dissipating solutions which have been recently proposed and numerically tested. Maximum displacements and material strains were well controlled and within acceptable bounds, and residual deformations were minimal due to the re-centring contribution from the post-tensioned tendons. Damage was confined to inelastic yielding (or fluid damping) of the external dampers.

    View record details
  • Shake-table testing of hybrid post-tensioned precast wall systems with alternative dissipating solutions

    Marriott, D.J.; Pampanin, S.; Palermo, A.; Bull, D. (2008)

    Conference Contributions - Other
    University of Canterbury Library

    It is fast becoming common practice for civil engineering infrastructure and building structures to be designed to achieve a set of performance objectives. To do so, consideration is now being given to systems capable of sustaining minimal damage after an earthquake while still being cost competitive. This has led to the development of high performance seismic resisting systems, followed by advances in design methodologies. The paper presents the experimental response of four pre-cast, post-tensioned rocking walls with high-performing dissipating solutions tested on the shake-table at the University of Canterbury. The wall systems were designed as a retrofit solution for an existing frame building however, can also be used for the design of new, high-performance structures. The use of externally mounted dampers allowed numerous dissipation schemes to be explored including mild-steel dampers (hysteretic dampers), viscous dampers, a combination of both or no dampers. The advantages of both velocity and displacement dependant dissipation was investigated for protection against strong ground motions with differing rupture characteristics i.e. far-field and near-field events. The experimental results are used to verify a proposed design procedure for post-tensioned rocking systems with supplementary hysteretic and viscous dissipation. The predicted response compared well with the measured shake-table response.

    View record details
  • Innovative seismic solutions for multi-storey LVL timber buildings

    Palermo, A.; Pampanin, S.; Fragiacomo, M.; Buchanan, A.H.; Deam, B.L. (2006)

    Conference Contributions - Published
    University of Canterbury Library

    Describes an extensive experimental program at the University of Canterbury, for the development of new structural systems and connections for multi-storey laminated veneer lumber (LVL) timber buildings in earthquake-prone areas. The proposed innovative ductile timber connections are conceptually similar to recent seismic solutions successfully developed for precast concrete multi- storey buildings. The paper gives an overview of the research program, and the results of quasi-static cyclic tests on frame subassemblies, including exterior beam-column joints and cantilever columns, as well as pseudo-dynamic tests on cantilever columns. The experimental results showed significant dissipation of hysteretic energy, good self-centering capacity and no appreciable damage of the structural elements, confirming the expected enhanced performance of the proposed structural systems.

    View record details
  • Code provisions for seismic design of multi-storey post-tensioned timber buildings

    Pampanin, S.; Palermo, A.; Buchanan, A.H.; Fragiacomo, M.; Deam, B.L. (2006)

    Conference Contributions - Published
    University of Canterbury Library

    Recent developments and successful preliminary experimental validations of innovative types of ductile connections for multi-storey seismic-resisting laminated veneer lumber (LVL) timber buildings have opened major opportunities for extensive use of structural timber in seismic regions. These particular solutions, named jointed ductile connections or hybrid systems are based on post-tensioning techniques to assemble structural LVL members for both frame and shear wall systems which are designed to exhibit controlled rocking deformations during seismic loading. These systems have been proposed and uccessfully tested using concepts developed for high-performance seismic-resisting precast concrete buildings, currently being approved in major seismic codes and design guidelines worldwide. The extremely satisfactory results of quasi-static cyclic and pseudodynamic experimental tests on exterior beam-column joint subassemblies, column-to foundation connections and shear wall systems have provided valuable confirmation of the high seismic performance of these LVL systems, as well as the reliability of the adopted design criteria and methodology. In this paper, after a brief introduction to the concept of post-tensioned seismic-resisting LVL structures and an overview of experimental results, particular focus will be given to seismic design aspects, within a performance-based design approach, as a sound basis for the preparation of seismic design code provisions.

    View record details
  • Efficiency of simplified alternative modelling approaches to predict the seismic response of precast concrete hybrid systems

    Palermo, A.; Pampanin, S.; Carr, A.J. (2005)

    Conference Contributions - Published
    University of Canterbury Library

    Two alternative simplified modelling approaches in representing the seismic behaviour of different jointed ductile precast/prestressed connections/systems is herein illustrated. Particular emphasis is given to the modelling of hybrid connections, developed in the PRESSS Program (PREcast Seismic Structural System) coordinated by the University of San Diego, for frame and wall systems. The efficiency and accuracy of the two alternative simplified approaches and analytical methods, one based on section analysis procedure and lumped plasticity models and the other one based on the use of multi-contact spring models, are herein critically discussed and compared through analytical validations of a beam-column subassembly and a wall specimen.

    View record details
  • Quasi-static cyclic tests on seismic-resistant beam-to-column and column-to-foundation subassemblies using Laminated Veneer Lumber (LVL)

    Palermo, A.; Pampanin, S.; Fragiacomo, M.; Buchanan, A.H.; Deam, B.L.; Pasticier, L. (2006)

    Conference Contributions - Published
    University of Canterbury Library

    This paper describes part of an extensive experimental programme in progress at the University of Canterbury to develop Laminated Veneer Lumber (LVL) structural systems and connections for multistorey timber buildings in earthquake-prone areas. The higher mechanical properties of LVL, when compared to sawn timber, in addition to its low mass, flexibility of design and rapidity of construction, create the potential for increased use of LVL in multi-storey buildings. The development of these innovative ductile connections in LVL, proposed here for frame systems, have been based on the successful implementation of jointed ductile connections for precast concrete systems, started in the early 1990s with the PRESSS Program at the University of California, San Diego, further developed in Italy and currently under further refinement at the University of Canterbury. This paper investigates the seismic behaviour of the so-called “hybrid” connection, characterised by the combination of unbonded post-tensioned tendons and either external or internal energy dissipaters passing through the critical contact surface between the structural elements. Experimental results on hybrid exterior beam-to-column and column-to-foundation subassemblies under cyclic quasi-static unidirectional loading are presented. The proposed innovative solutions exhibit a very satisfactory seismic performance characterised by an appreciable energy dissipation capacity (provided by the dissipaters) combined with self-centring properties (provided by the unbonded tendons) and negligible damage of the LVL structural elements.

    View record details
  • Uni and bi-directional quasi static tests on alternative hybrid precast beam column joint subassemblies

    Amaris, A.; Pampanin, S.; Palermo, A. (2006)

    Conference Contributions - Published
    University of Canterbury Library

    Recent developments on high performance seismic resisting precast concrete frame systems, based on the use of unbonded post-tensioned tendons with selfcentring capabilities in combination with additional sources of energy dissipation, are herein presented. Alternative arrangements for jointed ductile connections to accommodate different structural or architectural needs have been implemented and validated through quasi-static cyclic tests on a series of 2/3 scaled beam-column subassemblies under uni- or bi-directional loading regime. The satisfactory results confirmed the unique flexibility and potentiality of the proposed solutions for the development of the next generation of seismic resisting buildings.

    View record details
  • Experimental validation of high-performance hybrid bridge piers

    Marriott, D.; Boys, A.; Pampanin, S.; Palermo, A. (2006)

    Conference Contributions - Published
    University of Canterbury Library

    An appreciation of the crucial need for a high level of performance from reinforced concrete structures located in seismically active regions has been extensively recognised in the past decade. Appropriate performance-based criteria are essential in ensuring the desired behaviour of structures, especially when a low level of postearthquake damage is desired. “Hybrid” jointed ductile connections originally developed for either pre-cast concrete frames and wall systems have been shown to exhibit superior performance complemented with a reduced level of damage and negligible residual deformations of the structural systems. These innovative advanced systems, consisting of relatively simple construction methods (based on post-tensioning techniques), have been recently proposed to be adopted in bridge piers and systems as a viable and highly competitive alternative to traditional monolithic cast-in-place construction. The present work reports on the experimental validation into the performance of hybrid bridge pier systems in a cantilever configuration (pier to foundation connection). The response of a single hybrid solution, tested under a uni-directional quasi-static testing regime is compared against a monolithic benchmark. Analytical-experimental comparisons are also carried out to validate and further refine simplified procedures, previously presented in literature and available in code-design provisions, to predict the cyclic behaviour of jointed connections.

    View record details
  • Experimental investigations on LVL seismic resistant wall and frame subassemblies

    Palermo, A.; Pampanin, S.; Buchanan, A.H. (2006)

    Conference Contributions - Published
    University of Canterbury Library

    listed in oral section of abstracts book

    View record details
  • Seismic design of multi-storey buildings using laminated veneer lumber (LVL)

    Palermo, A.; Pampanin, S.; Buchanan, A.; Newcombe, M. (2005)

    Conference Contributions - Other
    University of Canterbury Library

    The recent development of laminated veneer lumber (LVL) as an alternative to solid timber or glue-laminated timber has greatly improved the viability of structural timber for the seismic design of certain types of buildings. The low mass, flexibility of design and rapidity of construction all create the potential for increased use of LVL timber in low-rise multi-storey buildings. Based on recent developments in the seismic design of precast concrete for multi-storey buildings, proposals are made for innovative types of jointed ductile connections in LVL timber buildings, based on post-tensioning techniques to assemble structural members for both frame and wall systems. This contribution gives an overview of an going comprehensive research project involving both numerical and experimental investigations. The extremely satisfactory preliminary results of quasi-static cyclic tests of exterior beam-column joint subassemblies are presented as a confirmation of the expected high seismic performance of the proposed solutions for LVL seismic resisting systems.

    View record details
  • Advanced Flag-Shaped Systems For High Seismic Performance

    Kam, W.Y.; Pampanin, S.; Palermo, A.; Carr, A. (2006)

    Conference Contributions - Published
    University of Canterbury Library

    listed in poster section of abstracts book

    View record details
  • Experimental Investigations On High-Performance Jointed Ductile Connections For Precast Frame Systems

    Pampanin, S.; Amaris, A.; Akguzel, U.; Palermo, A. (2006)

    Conference Contributions - Published
    University of Canterbury Library

    Recent developments on high performance seismic resisting precast concrete frame systems, based on the use of unbonded post-tensioned tendons with self-centring capabilities in combination, when required, with additional sources of energy dissipation, are herein presented. Alternative arrangements for jointed ductile connections to accommodate different structural or architectural needs have been implemented and validated through quasi-static cyclic tests on a series of exterior beam-column subassemblies under uni- or bi-directional loading regime. The results confirmed the unique flexibility and efficiency of these systems for the development of the next generation of seismic resisting structures, able to undergo high inelastic displacement with limited level of damage and negligible residual displacement when compared to traditional monolithic (cast-insitu) ductile solutions. In order to further emphasize the enhanced performance of these systems, a comparison with the experimental response and observed damage of 2-D and 3-D monolithic beam-column benchmark specimens designed according to the NZ3101:1995 seismic code provisions is carried out. The reliability and simplicity of recently implemented special code provisions for the design and analysis of jointed ductile systems is also confirmed by satisfactory results of analyticalexperimental comparison. In addition, the practical feasibility and efficiency of simple technical solutions to connect precast floor systems and lateral resisting frame systems, without incurring in damage due to displacement incompatibilities are experimentally demonstrated. The reliability of recently implemented special code provisions for the design and analysis of jointed ductile hybrid systems is also confirmed.

    View record details
  • Improving the Seismic Performance of Existing Reinforced Concrete Buildings using Advanced Rocking Wall Solutions

    Marriott, D.; Pampanin, S.; Bull, D.K.; Palermo, A. (2007)

    Conference Contributions - Published
    University of Canterbury Library

    Recent major earthquakes such as Northridge 1994 and Izmit Kocaeli 1999 highlighted the poor performance of existing buildings constructed prior to the early 1970’s. Low lateral seismic design coefficients and the adopted “working stress design” methodology (essentially an elastic design) lacked any inelastic design considerations, thus leading to inadequate detailing. Insufficient development lengths, lapping within potential plastic hinge regions, lack, or total absence of joint transverse reinforcement, and the use of plain round reinforcement and hooked end anchorages were common throughout the structure. The behaviour is generally dominated by brittle local failure mechanisms (e.g. joint or element shear failures) as well as possible soft-storey mechanisms at a global level. Amongst several possible retrofit interventions, a typical solution is to provide the structure with additional structural walls i.e. external buttressing or column in-fills. Extensive developments on precast, post-tensioned, dissipative systems have shown promise for the use of rocking wall systems to retrofit existing poorly detailed frame structures. In this contribution, the feasibility of such a retrofit intervention is investigated. A displacement-based retrofit procedure is developed and proposed, based on targeting pre-defined performance criteria, such as joint shear and/or column curvature deformation limits. A design example, using the proposed retrofit strategy on a prototype frame is presented. A brief overview on experimental work ongoing at the University of Canterbury investigating the dynamic response of advanced rocking walls for retrofit purposes will be provided.

    View record details
  • Advanced Flag-Shaped Systems for High Seismic Performance Including Near Fault Effects

    Kam, W.Y.; Pampanin, S.; Carr, A.J.; Palermo, A. (2007)

    Conference Contributions - Published
    University of Canterbury Library

    Experience with recent earthquakes near urban centers (Northridge 1994, Kobe 1995, Chi-Chi 1999) highlighted two major challenges in seismic engineering: the hazard and peculiarity of near-fault earthquakes, characterised by low number of cycles and high velocity pulses in its motion and the urgent need for performance-based design and retrofit approaches for buildings in near-fault urban centers such as Wellington City. Meanwhile, the development of high-performance seismic resistant hybrid systems or flag-shape systems, incorporating combination of re-centering elements and hysteretic energy dissipation, have shown to significantly reduce the expected level of damage when compared with traditional (i.e. monolithic) ductile systems. However, traditional hysteretic dissipation is considered inherently inadequate to counteract the near-fault effects. In this paper, the innovative concept of Advanced Flag-shape Systems (AFS) is proposed as an alternative solution for high-seismic performance system in near-fault regions. AFS combines alternative forms of energy dissipation (yielding, friction or viscous damping) in series and/or in parallel together with re-centering elements to achieve high seismic performance for both far-fault and near-fault motions. The concept of AFS is first briefly discussed qualitatively and then numerically investigated using SDOF models subjected to push-pull and time-history analyses under a suit of far field and near fault events. Finally, the enhanced performance of AFS systems is compared and discussed with monolithic solutions or more traditional Flag-shape systems.

    View record details
  • Implementation of advanced flag-shaped (AFS) systems for moment-resisting frame structures

    Kam, W.Y.; Pampanin, S.; Palermo, A.; Carr, A. (2008)

    Conference Contributions - Published
    University of Canterbury Library

    A second generation of self-centering/dissipating systems, referred to as Advanced Flag-Shape (AFS) systems, has been recently proposed by the authors, consisting of combination of alternative forms of energy dissipation (yielding, friction or viscous damping) in series and/or in parallel with re-centering elements to achieve high seismic performance for both far-fault and near-fault motions. In particular, the unique properties of a system combining friction dampers in series with viscous dampers, then combined in parallel with re-centering and hysteretic dissipation elements, was found to lead to an enhanced, predictable and controllable performance of single-degree-of -freedom (SDOF) systems. In this contribution, after a brief introduction on the concept of the AFS systems, the extension of the concept from SDOF to MDOF frames systems is discussed and numerically investigated. Two critical issues of extending AFS for SDOF systems to MDOF frame systems are briefly discussed: a) the excitation velocities up the structure b) the global frame damping capacity within DDBD design. With reference to a set of frame systems, initially designed for self-centering un-bonded post-tensioned precast concrete frames using Direct Displacement-Based Design (DDBD), the seismic performance of AFS frames in comparison to conventional frames is investigated by means of non-linear time-history analyses using a suite of far field and near-fault earthquake excitations, where three key global response parameters are examined.

    View record details
  • Parametric Investigation of Seismic Interaction Between Precast Concrete Cladding Systems and Moment Resisting Frames

    Baird, A.; Diafeira, R.; Palermo, A.; Pampanin, S. (2011)

    Conference Contributions - Published
    University of Canterbury Library

    This paper presents the results of a preliminary numerical investigation into the interaction between precast concrete cladding systems and moment resisting frames. Macro-scale models of cladding systems are implemented in existing lumped plasticity models for moment resisting frames. Different failure mechanisms and various configurations are considered in order to show the effect of the entire cladding system upon a structure’s seismic behavior. Several parameters are varied in order to establish their associated influence on the overall structural response. Results show that it is clearly more advantageous to have a failure mechanism governed by the connection than one governed by either the panel or the frame. An experimental program is now underway building on what has been learnt from the parametric investigation. The authors intend to continue the research to successively develop improved or innovative low-damage cladding-moment resisting frame systems. They also aim to produce simple design tools that provide easy inclusion of the seismic effects of cladding-frame interaction.

    View record details