Recycling of damaged RC frames: Replacing crumbled concrete and installing steel haunches below/above the beam at connections

Ahmad, Naveed; Arifullah,; Ilyas, Babar; Hussain, Sida

doi:10.5459/bnzsee.54.4.282-298

Cited by 2 publications

(3 citation statements)

References 19 publications

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“…In addition to this editorial, this issue includes four other technical articles [38][39][40][41]. Among them, the first two relate to non-structural elements (NSEs); i,e, secondary components that do not contribute to the building strength.…”

Section: Articles In This Issue Of Nzsee Bulletinmentioning

confidence: 99%

“…The third paper by Ahmad et al [40] presents an experimental and numerical validation of using steel haunches to repair critically damaged and RC frames. The paper also proposes a code-based procedure for seismic analysis and preliminary design of steel haunches for strengthening of seismically deficient RC frames.…”

Section: Articles In This Issue Of Nzsee Bulletinmentioning

confidence: 99%

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Hybrid posttensioned rocking (HPR) frame buildings: Low-damage vs low-loss paradox

Dhakal

2021

BNZSEE

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The 2010-11 Canterbury Earthquake Sequence inflicted seismic losses worth more than $40B, which is about 25% of the GDP of New Zealand (as per 2011 data). More than 80% of these losses were insured, which comprised of more than $10B covered by the Earthquake Commission (a New Zealand crown entity providing insurance to residential property owners) and more than $22B (comprising of roughly equal split between domestic and commercial claims) by private insurers [1]. The scale of financial impact has been perceived to be disproportionately large given the building regulatory regime in New Zealand is relatively stringent and the earthquakes and aftershocks were of moderate magnitude. As it is well known that some of the major faults spread in the Wellington region and the subduction boundary passing through the centre of New Zealand can generate much bigger earthquakes (upwards of magnitude 8), people are left pondering whether New Zealand is able to cope with the financial impact of larger earthquakes. This fearful realisation gradually led to people being dissatisfied with merely life-safe buildings and demanding more resilient buildings that meet the objectives of performance based design; i.e. suffer less damage, incur less loss, and can remain functional after earthquakes. In light of the extensive building damage resulting in high financial loss in recent earthquakes, practicing engineers and researchers in New Zealand have been advocating for revising the current design approach to improve performance of new structures and infrastructure in future earthquakes [2-5]. As a result, large proportion of buildings constructed in the last decade (including those built to replace earthquake-damaged buildings) have shied away from the traditional damage-friendly ductile structural systems and instead adopted one of the new and emerging structural systems claimed to be “low-damage”. In many cases, the adopted structural systems are not covered by existing design standards and are approved as alternate solutions through expert peer review. The “low-damage” attribute of most structural systems has been validated by component (or sub-assembly) level experimental tests, but their interactions with other building components and implications of their use in buildings have not been rigorously scrutinised. Hence, the rushed adoption of some of these systems in buildings can surprise the engineering community in future earthquakes with mismatch between the expected and real performances of the buildings; akin to what New Zealand engineering fraternity is currently going through due to realisation of poor seismic performance of precast hollow-core flooring system that has been widely used in New Zealand buildings without rigorous scrutiny. One such “low-damage” structural system is precast post-tensioned rocking frames with supplemental energy dissipaters. This paper summarises the development of this structural system, critically reviews the literature reporting the seismic performance of this system, and qualitatively evaluates system-level implications of its use in buildings. This paper is intended to better inform engineers of the likely seismic performance of buildings with this structural system so that they can optimise its benefits by giving due consideration to its effect on other building components.

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Section: Articles In This Issue Of Nzsee Bulletinmentioning

confidence: 99%

Section: Articles In This Issue Of Nzsee Bulletinmentioning

confidence: 99%

Hybrid posttensioned rocking (HPR) frame buildings: Low-damage vs low-loss paradox

Dhakal

2021

BNZSEE

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“…The recent damaging earthquakes have raised concerns among designers regarding the economically viable repair or demolition and reconstruction of earthquake-damaged reinforced concrete frames. Research is needed to determine whether strengthening existing RC frames with haunches that have weaker beamcolumn joints can improve seismic performance [7][8][9][10][11][12][13][14][26][27][28][29][30][31][32][33][34]. It may also be useful in restoring and potentially strengthening the seismic resistance of seismically damaged RC frames with weaker beamcolumn joints.…”

Section: Introductionmentioning

confidence: 99%

In-Plane Quasi-Static Cyclic Testing of Rc Frames Retrofitted With Rigid/Dissipating Steel Haunches

Ilyas,

Jan,

Khedher

et al. 2024

Preprint

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This research assessed the reliability of haunch retrofitting technique for seismic upgrade of critically damaged frames. Two 1:3 reduced scale two-story RC frames were taken under considered, which were tested previously till the near collapse state. The haunches are employed to strengthen the joint shear strength of the badly damaged joints, which are indicative of old, non-seismic, or defective joints. Damaged concrete was replaced with new high-strength concrete, and haunch-retrofitting technique was adopted to strengthen beam-column connections, in order to avoid shear hinging at joints under lateral loads. The retrofitted frames were tested through quasi-static cyclic loads in a displacement-control condition for multiple-levels of roof drifts. In order to assess the following seismic response factors: stiffness, strength, ductility, and response modification factors—lateral force-displacement capacity curves were created and examined. Hysteretic responses of tested models were analyzed to quantify hysteretic damping. The seismic performance assessment of the retrofitted frames was conducted utilizing a code-based static force approach in multiple seismic zones. The rigid haunches contributed to the over strength factor while the dissipating haunch has major contribution in energy dissipation of the retrofitted frames.

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Recycling of damaged RC frames: Replacing crumbled concrete and installing steel haunches below/above the beam at connections

Cited by 2 publications

References 19 publications

Hybrid posttensioned rocking (HPR) frame buildings: Low-damage vs low-loss paradox

Hybrid posttensioned rocking (HPR) frame buildings: Low-damage vs low-loss paradox

In-Plane Quasi-Static Cyclic Testing of Rc Frames Retrofitted With Rigid/Dissipating Steel Haunches

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