@article {bnh-7961, title = {Generalized Loading Protocols for Experimentally Simulating Multidirectional Earthquake Actions on Building Columns in Regions of Low-to-Moderate Seismicity }, journal = {Journal of Structural Engineering}, volume = {147}, year = {2021}, month = {04/2021}, abstract = {

This study aimed to quantitatively develop realistic quasi-static loading protocols for simulating bidirectional cyclic actions and axial load variation on building columns in a way that is representative of an actual response during earthquake ground excitation. A case-study building was subjected to a suite of 15 ground motions that were scaled to design basis earthquake (DBE) and maximum considered earthquake (MCE) levels of a typical region of low-to-moderate seismicity. The results showed that the displacement path of a building column under earthquake actions is generally in the form of elliptical loops of various orientations due to the phase difference in the sinusoidal displacements in the two orthogonal axes of the column. Accordingly, this work proposes a bidirectional lateral loading protocol that simplifies and generalizes the displacement path of the column in the form of elliptical loops of four different orientations. Similarly, the patterns of axial load variation in columns were also studied in detail, which led to the development of separate axial load variation protocols for external and internal columns of a building, which can be applied in tandem with the bidirectional lateral loading protocol. The paper concludes with a brief overview of the results of two reinforced concrete (RC) column specimens, which were experimentally tested using the proposed bidirectional loading protocol.

}, keywords = {earthquakes, engineering, reinforced concrete structures}, doi = {https://doi.org/10.1061/(ASCE)ST.1943-541X.0003056}, url = {https://ascelibrary.org/doi/abs/10.1061/\%28ASCE\%29ST.1943-541X.0003056}, author = {Saim Raza and Hing-Ho Tsang and Scott Menegon and John Wilson} } @article {bnh-7017, title = {Axial Load Variation of Columns in Symmetrical RC Buildings Subject to Bidirectional Lateral Actions in Regions of Low to Moderate Seismicity}, journal = {Journal of Earthquake Engineering}, year = {2020}, month = {06/2020}, pages = {1-29}, abstract = {

Columns in building frame systems are subjected to the combined action of bidirectional horizontal loading and axial load variation during an earthquake. Whilst the behaviour of RC columns under unidirectional and bidirectional lateral loading with constant axial load is understood well, the behaviour under bidirectional lateral loading with axial load variation is rarely studied, especially for limited ductile RC columns prevalent in regions of low to moderate seismicity. This paper begins with a numerical study that aims to obtain the generalised patterns and range of axial load variation in RC building columns. To this end, a case study building is subjected to a suite of 15 ground motions, representative of low to moderate seismic regions, in OpenSees. This is followed by an experimental study in which limited ductile high-strength RC columns are tested under bidirectional lateral loading and two different axial load variation protocols, namely synchronous and nonsynchronous variable axial loading protocols. The results of the numerical study demonstrated that axial load variation of the columns in an RC building is primarily dependent on the response spectral acceleration corresponding to the fundamental period of the structure in the two orthogonal horizontal directions and/or the vertical direction. The results of the experimental testing showed that nonsynchronous axial loading (compared to constant and synchronous axial loading) results in the lowest collapse drift capacity and energy dissipation of the RC columns.

}, keywords = {Axial load variation, bidirectional loading, drift capacity, earthquake, RC columns}, doi = {https://doi.org/10.1080/13632469.2020.1772151}, url = {https://www.tandfonline.com/doi/abs/10.1080/13632469.2020.1772151?journalCode=ueqe20}, author = {Saim Raza and Scott Menegon and Hing-Ho Tsang and John Wilson} } @mastersthesis {bnh-8097, title = {Collapse behaviour of limited ductile high-strength RC columns under multidirectional earthquake actions}, volume = {Doctor of Philosophy}, year = {2020}, school = {Swinburne University of Technology}, address = {Melbourne}, abstract = {

Raza (2020) employed experimental, numerical and empirical methods to develop a fundamental understanding of the collapse behaviour of limited ductile high-strength reinforced concrete columns, designed as per Australian concrete standard, under multidirectional earthquake loading. The adequacy of the requirements of the concrete design standard in Australia was assessed and adequate design recommendations were proposed to ensure collapse prevention of such columns in a major earthquake event. The research outcomes are expected to have important implications for the earthquake safety of building stocks in Australia and globally.

}, keywords = {actions, Behaviour, Collapse, ductile, earthquake, high-strength RC columns, limited, multidirectional}, doi = {http://hdl.handle.net/1959.3/456529}, url = {https://researchbank.swinburne.edu.au/items/10dd9ce0-2aa2-4a20-b78b-dd5695225dbe/1/}, author = {Saim Raza} } @article {bnh-6050, title = {Strengthening and repair of reinforced concrete columns by jacketing: state-of-the-art review}, journal = {Sustainability}, volume = {11}, year = {2019}, month = {06/2019}, pages = {3208}, abstract = {

Sustainability necessitates the protection of infrastructure from any kind of deterioration over the life cycle of the asset. Deterioration in the capacity of reinforced concrete (RC) infrastructure (e.g., bridges, buildings, etc.) may result from localised damage sustained during extreme loading scenarios, such as earthquakes, hurricanes or tsunamis. In addition, factors such as the corrosion of rebars or ageing may also deteriorate or degrade the capacity of an RC column, thereby necessitating immediate strengthening to either extend or ensure its design life is not limited. The aim of this paper is to provide a state-of-the-art review of various strengthening and repair methods for RC columns proposed by different researchers in the last two decades. The scope of this review paper is limited to jacketing techniques for strengthening and/or repairing both normal- and high-strength RC columns. The paper also identifies potential research gaps and outlines the future direction of research into the strengthening and repair of RC columns.

}, keywords = {Infrastructure, Multi-hazard, sustainability}, doi = {https://doi.org/10.3390/su11113208}, url = {https://www.mdpi.com/2071-1050/11/11/3208}, author = {Saim Raza and Muhammad Khan and Scott Menegon and Hing-Ho Tsang and John Wilson} } @article {bnh-5160, title = {Unified models for post-peak failure drifts of normal- and high-strength RC columns}, journal = {Magazine of Concrete Research}, volume = {70}, year = {2018}, month = {11/2018}, pages = {1101}, chapter = {1081}, abstract = {

Displacement-based design of reinforced-concrete (RC) columns requires reliable estimation of the drift capacity beyond the elastic range. Although many post-peak drift models exist for normal-strength RC (NSRC) columns, very limited work has been done in this area on high-strength RC (HSRC) columns. This paper evaluates the capability of existing drift models to predict post-peak drift capacity of both NSRC and HSRC columns. A comparative study is conducted using a comprehensive database of 190 RC columns (79 HSRC and 111 NSRC) from past experimental studies. The results of the comparative study indicate that most of the existing drift models overestimate post-peak drift capacity of HSRC columns, primarily because the influence of concrete strength has been ignored. This paper also proposes a unified set of empirical drift models that have a unique ability to predict post-peak drift capacity of lightly to moderately reinforced NSRC as well as HSRC columns. The new models can serve as tools for structural design engineers to estimate drift capacity of RC columns at an early design stage. Moreover, the models can assess the drift performance of RC columns in existing buildings and hence can also aid in decision-making regarding the need for retrofitting.

}, doi = {https://doi.org/10.1680/jmacr.17.00375}, url = {https://www.icevirtuallibrary.com/doi/10.1680/jmacr.17.00375}, author = {Saim Raza and Hing-Ho Tsang and John Wilson} }