99 results for University of Canterbury Library, Pampanin, S.

  • Experimental investigation of the seismic residual capacity of earthquake-damaged concrete buildings: Preliminary results

    Cuevas, Alberto; Malek, A; Pampanin, S.; Scott, A.; MacRae, G.; Marder, K.; Elwood, K.; Clifton, G. (2016)

    Conference Contributions - Other
    University of Canterbury Library

    This poster presents preliminary results of ongoing experimental campaigns at the Universities of Auckland and Canterbury, aiming at investigating the seismic residual capacity of damaged reinforced concrete plastic hinges, as well as the effectiveness of epoxy injection techniques for restoring their stiffness, energy dissipation, and deformation capacity characteristics. This work is part of wider research project which started in 2012 at the University of Canterbury entitled “Residual Capacity and Repairing Options for Reinforced Concrete Buildings”, funded by the Natural Hazards Research Platform (NHRP). This research project aims at gaining a better understanding and providing the main end-users and stakeholders (practitioner engineers, owners, local and government authorities, insurers, and regulatory agencies) with comprehensive evidence-based information and practical guidelines to assess the residual capacity of damaged reinforced concrete buildings, as well as to evaluate the feasibility of repairing and thus support their delicate decision-making process of repair vs. demolition or replacement.

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  • Seismic Performance of Existing New Zealand Shear Wall Structures

    Dashti, F.; Dhakal, R.P.; Pampanin, S. (2015)

    Conference Contributions - Other
    University of Canterbury Library

    Assessment of the structural performance of existing buildings requires a better understanding of seismic performance of the structural components designed according to different versions of design codes. This study provides a summary of the evolution of the reinforced concrete wall design provisions in New Zealand, and investigates their effect on seismic performance of structural walls. For this purpose, a typical rectangular wall is designed according to different versions of New Zealand concrete design standards, and a finite element approach is used for numerical simulation of the walls subject to cyclic loading. The modeling approach has been verified using experimental results of walls with different shear-span ratios which failed in different modes. Performance of the designed wall models is investigated in terms of failure pattern, drift capacity and displacement as well as curvature ductility. Seismic performance of the walls designed according to the previous versions of NZ design codes will provide a considerable contribution to better understanding of the wall capacity in seismic assessment of existing buildings.

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  • 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.

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  • Smart Semi-Active MR Damper to Control the Structural Response

    Hazaveh, N.K.; Chase, J.G.; Rodgers, G.W.; Pampanin, S. (2015)

    Journal Articles
    University of Canterbury Library

    One advanced means of protecting structures against earthquake ground motions is the use of semi-active devices to customise and limit structural response. Thus, the design, modelling and analysis of different semi-active control devices have received increasing research attention. This study presents a method to determine optimal control forces for magneto-rheological (MR) dampers, using three algorithms: a discrete wavelet transform (DWT), a linear quadratic regulator (LQR), and a clipped-optimal control algorithm. DWT is used to obtain the local energy distribution of the motivation over the frequency bands to modify conventional LQR. The clipped-optimal control algorithm is used to get the MR damper control force to approach the desired optimal force obtained from modified LQR. A Bouc-Wen phenomenological model is utilized to capture the observed nonlinear behaviour of MR dampers. Time history analysis for a single degree of freedom (SDOF) with periods of T= 0.2-5.0 sec is utilized to compare the impact of using classic and modified LQR in controlling the MR damper force under 20 design level earthquakes of the SAC (SEAOC-ATC-CUREE) project. Performance is assessed by comparing the maximum displacement (Sd), total base shear (Fb) and the controller energy. This study shows the proposed modified LQR is more effective at reducing displacement response than conventional LQR. The modified LQR method reduces the median value of uncontrolled Sd by approximately 40% to 88%, over all periods to 5.0 seconds. Moreover, the modified LQR uses about 45% less energy than conventional LQR. Overall, these results indicate the robustness of the proposed method to mitigate structural response and damage using MR devices.

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  • The history of design guidelines and details of reinforced concrete column in New Zealand

    Niroomandi, A.; Pampanin, S.; Dhakal, R.P. (2015)

    Conference Contributions - Published
    University of Canterbury Library

    Existing New Zealand (NZ) building stock contains a significant number of structures designed prior to 1995 with non-ductile reinforced concrete (RC) columns. Recent earthquakes and research show that columns with such details perform poorly when subjected to seismic demand, losing gravity load carrying capacity at drift levels lower than the expected one. Therefore, in order to have a better understanding of existing RC columns in NZ, the history of these elements is investigated in this paper. The evolution of RC column design guidelines in NZ standards since the 1970s is scrutinized. For this purpose, a number of RC columns from Christchurch buildings built prior to 1995 are assessed using the current code of practice.

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  • Control of Structural Response with a New Semi-Active Viscous Damping Device

    Khanmohammadi Hazaveh, N.; Pampanin, S.; Chase, J.G.; Rodgers, G.W. (2015)

    Conference Contributions - Published
    University of Canterbury Library

    Semi-active control devices can perform significantly better than passive devices, but also have the potential to achieve the performance approaching that of a fully active system. Semi-active devices offer significant promise for their ability to add supplemental damping and reduce seismic structural response in an easily controllable manner, and can be used in some modes to modify or reshape hysteretic structural response. However, many current semi-active devices are highly complex, limiting robustness, while those that can generate larger forces suffer from increased response lag time to do so. Thus, an ideal semi-active device would offer high forces, low complexity, and fast response. The semiactive viscous dampers could offer all these properties and could reduce not only the displacement response of a structure, but also the base shear. There are three semi-active viscous dampers, a 1-4, 1-3 and 2-4 device. In this study, a spectral analysis over periods of T= 0.2-5.0 sec under 20 design level earthquakes from the medium suite of the SAC project is used to compare three device control laws individually or in combination to sculpt structural hysteretic behaviour. Performance is assessed by evaluating reduction factors (RFs) compared to an uncontrolled structure for maximum displacement (Sd) and total base-shear (Fb), indicative of structural and foundation damage, respectively. Results show that combining the control laws to reshape the hysteresis loop can reduce the median value of both Sd and Fb by approximately 30% for periods less than 3.0 sec and 20% for periods more than 3.0. Thus, the results show that the proposed device and control laws have significant effect to reduction both structural response and base-shear. Overall, these results indicate the robustness of potentially very simple and robust semi-active viscous dampers to mitigate the risk of seismic damage to both the structure and foundation in a way that is economically suitable for either new designs or retrofit.

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  • Mitigating Structural Response using Semi-active Viscous Dampers to Reshape Structural Hysteresis

    Khanmohammadi Hazaveh, N.; Pampanin, S.; Chase, J.G.; Rodgers, G.W. (2015)

    Conference Contributions - Published
    University of Canterbury Library

    Semi-active devices offer significant promise for their ability to add supplemental damping and reduce seismic structural response in an easily controllable manner, and can be used in some modes to modify or reshape hysteretic structural response. However, many current semi-active devices are highly complex, limiting robustness, while those that can generate larger forces suffer from increased response lag time to do so. Thus, an ideal semi-active device would offer high forces, low complexity, and fast response. The semi-active viscous dampers could offer all these properties and could mitigate not only the displacement response of a structure, but also the base shear. This paper first outlines the structural performance when semi-active viscous dampers, with varying control laws are applied. A spectral analysis over periods of T= 0.2-5.0 sec under 20 design level earthquakes from the medium suite of the SAC project is used to compare three device control laws individually to sculpt the structural hysteretic behaviour. Performance is assessed by evaluating reduction factors (RFs) compared to an uncontrolled structure for maximum displacement (Sd) and total base-shear (Fb), indicative of structural and foundation damage, respectively. These results show that the reduction in terms of both displacement and base-shear demand is only available with the use of the 2-4 control law, which provides damping in the second and fourth quadrants. In the second part, a method to calculate the reduction factor of response for structures using 2-4 devices with different device damping coefficients is presented. Overall, these results indicate the robustness of potentially very simple and robust semi-active viscous dampers to mitigate the risk of seismic damage to both the structure and foundation in a way that is economically suitable for either new designs or retrofit.

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  • Semi-active viscous damper for seismic response control

    Khanmohammadi Hazaveh, N.; Pampanin, S.; Chase, J.G.; Rodgers, G.W.; Kordani, R. (2015)

    Conference Contributions - Published
    University of Canterbury Library

    - Semi-active devices offer significant promise for their ability to add supplemental damping and reduce seismic structural response in an easily controllable manner, and can be used in some modes to modify or reshape hysteretic structural response. However, many current semi-active devices are highly complex, limiting robustness, while those that can generate larger forces suffer from increased response lag time to do so. Thus, an ideal semi-active device would offer high forces, low complexity, and fast response. Semi-active viscous dampers could offer all these properties given the widespread high force use of viscous dampers in large vehicles and other applications. Such a simple, well-known device used semi-actively to reshape hysteresis could bring the real application of such devices far closer to a reality.To demonstrate the efficacy of the proposed devices, they are installed in a bi-linear elastic structure. Three earthquakes from the medium suite of the SAC project is used to compare two device control laws individually or in combination to sculpt structural hysteretic behavior.Performance is assessed by evaluating maximum displacement (Sd), total base-shear (Fb) and maximum acceleration (Sa) indicative of structural, foundation and content damage, respectively. Results show that, the reduction in terms of displacement, base-shear and acceleration demand is only available with the semi-active 2-4 control method.Overall, these results indicate the robustness of potentially very simple and robust semi-active viscous dampers to mitigate the risk of seismic damage to both the structure and foundation in a way that is economically suitable for either new designs or retrofit. .

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  • 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.

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  • Experimental evaluation of the in-plane stiffness of timber diaphragms

    Brignola, A.; Podestà, S.; Pampanin, S. (2012)

    Journal Articles
    University of Canterbury Library

    The seismic response of unreinforced masonry (URM) buildings, in both their as-built or retrofitted configuration, is strongly dependent on the characteristics of wooden floors and, in particular, on their in-plane stiffness and on the quality of wall-to-floor connections. As part of the development of alternative performance-based retrofit strategies for URM buildings, experimental research has been carried out by the authors at the University of Canterbury, in order to distinguish the different elements contributing to the whole diaphragm's stiffness. The results have been compared to the ones predicted through the use of international guidelines in order to highlight shortcomings and qualities and to propose a simplified formulation for the evaluation of the stiffness properties.

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  • Reality-check and renewed challenges in earthquake engineering: Implementing low-damage structural systems - from theory to practice

    Pampanin, S. (2012)

    Journal Articles
    University of Canterbury Library

    Earthquake Engineering is facing an extraordinarily challenging era, the ultimate target being set at increasingly higher levels by the demanding expectations of our modern society. The renewed challenge is to be able to provide low-cost, thus more widely affordable, high-seismic-performance structures capable of sustaining a design level earthquake with limited or negligible damage, minimum disruption of business (downtime) or, in more general terms, controllable socio-economical losses. The Canterbury earthquakes sequence in 2010-2011 has represented a tough reality check, confirming the current mismatch between societal expectations over the reality of seismic performance of modern buildings. In general, albeit with some unfortunate exceptions, modern multi-storey buildings performed as expected from a technical point of view, in particular when considering the intensity of the shaking (higher than new code design) they were subjected to. As per capacity design principles, plastic hinges formed in discrete regions, allowing the buildings to sway and stand and people to evacuate. Nevertheless, in many cases, these buildings were deemed too expensive to be repaired and were consequently demolished. Targeting life-safety is arguably not enough for our modern society, at least when dealing with new building construction. A paradigm shift towards damage-control design philosophy and technologies is urgently required. This paper and the associated presentation will discuss motivations, issues and, more importantly, cost-effective engineering solutions to design buildings capable of sustaining low-level of damage and thus limited business interruption after a design level earthquake. Focus will be given to the extensive research and developments in jointed ductile connections based upon controlled rocking & dissipating mechanisms for either reinforced concrete and, more recently, laminated timber structures. An overview of recent on-site applications of such systems, featuring some of the latest technical solutions developed in the laboratory and including proposals for the rebuild of Christchurch, will be provided as successful examples of practical implementation of performance-based seismic design theory and technology.

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  • Seismic Performance of Reinforced Concrete Buildings in the 22 February Christchurch (Lyttleton) Earthquake

    Kam, W.Y.; Pampanin, S.; Elwood, K. (2011)

    Journal Articles
    University of Canterbury Library

    Six months after the 4 September 2010 Mw 7.1 Darfield (Canterbury) earthquake, a Mw 6.2 Christchurch (Lyttelton) aftershock struck Christchurch on the 22 February 2011. This earthquake was centred approximately 10km south-east of the Christchurch CBD at a shallow depth of 5km, resulting in intense seismic shaking within the Christchurch central business district (CBD). Unlike the 4 Sept earthquake when limited-to-moderate damage was observed in engineered reinforced concrete (RC) buildings [35], in the 22 February event a high number of RC Buildings in the Christchurch CBD (16.2 % out of 833) were severely damaged. There were 182 fatalities, 135 of which were the unfortunate consequences of the complete collapse of two mid-rise RC buildings. This paper describes immediate observations of damage to RC buildings in the 22 February 2011 Christchurch earthquake. Some preliminary lessons are highlighted and discussed in light of the observed performance of the RC building stock. Damage statistics and typical damage patterns are presented for various configurations and lateral resisting systems. Data was collated predominantly from first-hand post-earthquake reconnaissance observations by the authors, complemented with detailed assessment of the structural drawings of critical buildings and the observed behaviour. Overall, the 22 February 2011 Mw 6.2 Christchurch earthquake was a particularly severe test for both modern seismically-designed and existing non-ductile RC buildings. The sequence of earthquakes since the 4 Sept 2010, particularly the 22 Feb event has confirmed old lessons and brought to life new critical ones, highlighting some urgent action required to remedy structural deficiencies in both existing and “modern” buildings. Given the major social and economic impact of the earthquakes to a country with strong seismic engineering tradition, no doubt some aspects of the seismic design will be improved based on the lessons from Christchurch. The bar needs to and can be raised, starting with a strong endorsement of new damage-resisting, whilst cost-efficient, technologies as well as the strict enforcement, including financial incentives, of active policies for the seismic retrofit of existing buildings at a national scale.

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  • 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.

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  • 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

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  • Effects of SSI on the Seismic Response of Older Structures Before & After Retrofit

    Arefi, J.M.; Pampanin, S.; Cubrinovski, M. (2009)

    Conference Contributions - Published
    University of Canterbury Library

    Comprehensive experimental and analytical studies have been conducted to understand the behaviour of frame buildings constructed before the introduction of modern design codes. This usually has been done assuming a fixed-base structure while ignoring the flexibility of soil. The interaction between the super-structure and sub-structure (SSI) is investigated by modelling the soil as simple as possible to capture the overall response of the system. As new analytical hysteresis rules and more advanced tools of analysis have been developed in recent years, and as part of a more comprehensive investigation on the response of older structures before and after retrofit, focus will be herein given on the response of SDOF systems representing a broad range of existing, newly designed and, retrofitted structures, while allowing for flexibility of the soil-foundation system. The results of this study suggest that the compliance of simply modelled soil for typical building structures have in average beneficial effects in terms of structural demand especially in the case where as a consequence of implementing a retrofit strategy, the stiffness of the structure might increase. On the other hand, the governing component of these effects, i.e. rocking of foundation, can result on average in higher absolute displacement of floors.

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  • Design and Construction of Prestressed Timber Buildings for Seismic Areas

    Smith, T.; Pampanin, S.; Fragiacomo, M.; Buchanan, A. (2008)

    Conference Contributions - Published
    University of Canterbury Library

    This paper describes the structural design of low-rise multi-storey timber buildings using a new and exciting structural system. This system, originally developed for use with pre-cast concrete, combines un-bonded post-tensioning and additional energy dissipaters, providing a recentering capability after the earthquake, while great reducing the structural damage. This new structural system can be used in multi-storey buildings, with large structural timber members made from laminated veneer lumber (LVL) or glulam timber, with lateral loads resisted by prestressed timber frames or walls, separately or in combination. A case study of a six storey timber office building in a moderate seismic area is analysed and a virtual design development of many construction and connnection details for rapid construction. Total building cost is compared to equivalent steel and reinforced concrete options.

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  • Seismic Behaviour of Prestressed Timber Columns under Bi-directional Loading

    Iqbal, A.; Pampanin, S.; Buchanan, A. (2008)

    Conference Contributions - Published
    University of Canterbury Library

    Structural members made of laminated veneer lumber (LVL) in combination with unbonded posttensioning have recently been proposed, which makes it possible to design moment-resisting frames with longer spans for multi-storey timber buildings. Moreover, prefabricated and prestressed timber buildings can be designed to have enhanced re-centering and energy dissipation characteristics for seismic resistance. The post-tensioning provides re-centering capacity while energy is dissipated through the addition of special dissipating devices. As part of a research program on timber structures, experimental and analytical studies have been performed to investigate response of prestressed LVL columns under bi-directional seismic loading. The results show excellent seismic performance, characterized by negligible damage of the structural members and small residual deformations, even under the combined effect of loading in two directions. Energy is dissipated mostly through yielding of external mild steel axial dissipators connecting the column and the foundation, which can be easily removed and replaced after an earthquake. Since post-tensioning can be economically performed on site, the system can be easily implemented in multi-storey timber buildings.

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  • Feasibility and Detailing of Post-tensioned Timber Buildings for Seismic Areas

    Smith, T.; Pampanin, S.; Buchanan, A.; Fragiacomo, M. (2008)

    Conference Contributions - Published
    University of Canterbury Library

    Paper 53

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  • Experimental Investigation on a Hybrid Jointed Precast Frame with Non-tearing Floor Connections

    Amaris, A.; Pampanin, S.; Bull, D.; Carr, A. (2008)

    Conference Contributions - Published
    University of Canterbury Library

    Paper 26

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  • Experimental Study of Prestressed Timber Columns under Bi-directional Seismic Loading

    Iqbal, A.; Pampanin, S.; Buchanan, A.H. (2008)

    Conference Contributions - Published
    University of Canterbury Library

    Paper 31

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