Muhammad Tariq Chaudhary | Al-Imam University (original) (raw)

Papers by Muhammad Tariq Chaudhary

Bridges constitute a vital link in a transportation system and their functionality after an earth... more Bridges constitute a vital link in a transportation system and their functionality after an earthquake is critical in reducing disruption to social and economic activities of the society. Bridges supported on pile foundations are commonly used in many earthquake-prone regions. In order to properly design or investigate the performance of such structures, it is imperative that the effect of soil-foundation-structure interaction be properly taken into account. This study focused on the influence of soil and seismic ground motion variability on the dynamic impedance of pile-group foundations typically used for medium-span (about 30 m) urban viaduct bridges. Soil profiles corresponding to various AASHTO soil classes were selected from actual data of such bridges and / or from the literature. The selected soil profiles were subjected to 1-D wave propagation analysis to determine effective values of soil shear modulus and damping ratio for a suite of properly selected actual seismic ground motions varying in PGA from 0.01g to 0.64g, and having variable velocity and frequency content. The effective values of the soil parameters were then employed to determine the dynamic impedance of pile groups in horizontal, vertical and rocking modes in various soil profiles. Pile diameter was kept constant for bridges in various soil profiles while pile length and number of piles were changed based on AASHTO design requirements for various soil profiles and earthquake ground motions. Conclusions were drawn regarding variability in effective soil shear modulus, soil damping, shear wave velocity and pile group impedance for various soil profiles and ground motions and its implications for design and evaluation of pile-supported bridges. It was found that even though the effective soil parameters underwent drastic variation with increasing PGA, the pile group impedance was not affected much in properly designed pile foundations due to the corresponding increase in pile length or increase in a number of piles or both when subjected to increasing PGA or founded in weaker soil profiles.

The tremendous loss of life that resulted in the aftermath of recent earthquakes in developing co... more The tremendous loss of life that resulted in the aftermath of recent earthquakes in developing countries is mostly due to the collapse of non-engineered and semi-engineered building structures. Such structures are used as houses, schools, primary healthcare centers and government offices. These building are classified structurally into two categories viz. non-engineered and semi-engineered. Non-engineered structures include: adobe, unreinforced masonry (URM) and wood buildings. Semi-engineered buildings are mostly low-rise (up to 3 story) light concrete frame structures or masonry bearing walls with reinforced concrete slab. This paper presents an overview of the typical damage observed in non-engineered structures and their most likely causes in the past earthquakes with specific emphasis on the performance of such structures in the 2005 Kashmir earthquake. It is demonstrated that seismic performance of these structures can be improved from life-safety viewpoint by adopting simple ...

Lecture Notes in Civil Engineering, 2017

Dynamic impedance of pile groups is dependent on soil parameters, i.e. soil unit weight (q s), Po... more Dynamic impedance of pile groups is dependent on soil parameters, i.e. soil unit weight (q s), Poisson's ratio (m), shear modulus (G s), shear wave velocity (V s) and damping ratio (b s). The last three soil parameters (G s , V s & b s) strongly depend on the strain level caused by propagating seismic waves. Near surface (30 m depth) values of soil design parameters (G s , V s & b s) are normally used in design and these are influenced by variation in soil properties like plasticity index (PI), over consolidation ratio (OCR), effective stress (r'), depth of soil strata over bedrock (H) and impedance contrast ratio (ICR) between the strata and the bedrock. The aim of this study was to investigate the sensitivity of dynamic pile-group impedance to variation in soil design parameters (G s , V s & b s) caused by variation in soil properties for a typical bridge that was founded in site classes C and D according to the AASHTO Code and were subjected to a suite of actual earthquake ground motions.

Latin American Journal of Solids and Structures, 2020

Modal parameters, determined through forced vibration testing, ambient vibrations or seismic exci... more Modal parameters, determined through forced vibration testing, ambient vibrations or seismic excitations, are central to the structural health monitoring process for bridges. These parameters are used to obtain highfidelity numerical models through FEM model updating by fine-tuning mass, stiffness and boundary conditions and matching the numerical and observed modal parameters. This study investigated sensitivity of modal parameters to changes in boundary conditions (soil-structure interaction effect) and pier column inelasticity (stiffness effect) through more than 450 non-linear dynamic time-history analysis of an ordinary multi-span bridge. The bridge system was founded on shallow foundations in five rock profiles and on pile foundations in five soil profiles and was subjected to 21 seismic ground motions of varying intensity (0.036 to 0.61g). Modal frequencies showed sensitivity to the SSI and pier column inelasticity effects for low and higher levels of seismic excitations respectively. Mode shapes, on the contrary, were insensitive to SSI as well as pier column inelasticity for all levels of seismic excitations.

Bulletin of the New Zealand Society for Earthquake Engineering, 2018

Seismic site amplification factors and seismic design spectra for bridges are influenced by site ... more Seismic site amplification factors and seismic design spectra for bridges are influenced by site conditions that include geotechnical properties of soil strata as well as the geological setting. All modern seismic design codes recognize this fact and assign design spectral shapes based on site conditions or specify a 2-parameter model with site amplification factors as a function of site class, seismic intensity and vibration period (short and long). Design codes made a number of assumptions related to the site conditions while specifying the values of short (Fa) and long period (Fv) site amplification factors. Making these assumptions was necessary due to vast variation in site properties and limited availability of actual strong motion records on all site conditions and seismic setting in a region. This paper conducted a sensitivity analysis for site amplification factors for site classes C and D in the AASHTO bridge design code by performing a 1-D site response analysis in which ...

Canadian Journal of Civil Engineering, 2013

Structural engineers are key players in architectural or civil infrastructure projects. However, ... more Structural engineers are key players in architectural or civil infrastructure projects. However, their contribution seems to be limited in sustainability rating systems. This review analysed the credits available in the Leadership in Energy and Environmental Design green building rating systems related to the structural aspects. It concluded that the points related to the structural aspects are proportional to the cost of structural elements in a building. Embodied and total energy requirements of typical buildings were examined and it was determined ...

Australian Journal of Structural Engineering, 2013

This paper examines role of structural engineers in design of green buildings by analysing credit... more This paper examines role of structural engineers in design of green buildings by analysing credits available for the structural aspects of buildings in the four rating systems (LEED, BREEAM, Estidama and Green Star). It was concluded that the points related to the structural credits are roughly proportional to the cost of structural elements in buildings. However, participation of structural engineers in the sustainability efforts is disproportionally low based on the percentage of structural engineers holding LEED Accredited Professionals (LEED AP) designation. Embodied and total energy requirements of typical buildings were examined and it was concluded that embodied energy in the structural components has a share ranging from 2% for traditional buildings to 25% for net-zero buildings. Finally, the sustainability aspects related to structural design that are currently ignored in the rating systems were identifi ed and discussed. Such aspects include: baseline material usage, structural robustness and resilience to disasters, structural adaptability and reuse, structural durability and longevity. It was emphasised that a structure can be sustainable, in true spirit of the terminology, without achieving signifi cant points in the rating systems as long it satisfi es the guiding principle of reducing burden on natural resources and the environment.

Sustainability

Many cities of the world suffer from air pollution because of poor planning and design and heavy ... more Many cities of the world suffer from air pollution because of poor planning and design and heavy traffic in rapidly expanding urban environments. These conditions are exacerbated due to the Urban Heat Island (UHI) effect. While there have been studies linking the built environment and air pollution with health, they have ignored the aggravating role of UHI. The past urban planning literature in this field has also ignored the science of materials, vehicles and air pollution, and technological solutions for reducing cumulative health impacts of air pollution and UHI. Air Pollution, built environment and human health are complex discussion factors that involve several different fields. The built environment is linked with human health through opportunities of physical activity and air quality. Recent planning literature focuses on creating compact and walkable urban areas dotted with green infrastructure to promote physical activity and to reduce vehicle emission-related air pollution...

KSCE Journal of Civil Engineering, 2016

Australian Journal of Structural Engineering, 2016

International Journal of Built Environment and Sustainability, 2015

Engineering Structures, Aug 1, 2001

Identification of system parameters with the help of records made on a base-isolated bridge durin... more Identification of system parameters with the help of records made on a base-isolated bridge during earthquakes, provides an excellent opportunity to study the performance of various components of such a bridge system under these loading conditions. This study utilizes a two-stage system identification methodology for identifying the modal and structural parameters of base-isolated Yama-agé bridge in Japan from multiple set of recorded seismic acceleration data. By comparing the identified and physical parameters, performance of the base-isolation system is evaluated and the effect of soil-structure interaction on the overall performance of the bridge is examined. 

Journal of Bridge Engineering, Apr 15, 2004

Identification of system parameters by recorded accelerographs on base-isolated bridges during ea... more Identification of system parameters by recorded accelerographs on base-isolated bridges during earthquakes provides an opportunity to investigate the performance of such bridges. Stiffness degradation in reinforced concrete piers of four multispan continuous base-isolated bridges in Japan during eighteen earthquakes is examined by using system identification results and theoretical loaddisplacement curves of reinforced concrete piers. Soil-structure interaction ͑SSI͒ effect identified in these bridges is found to be independent of free field acceleration and weakly dependent on dynamic soil properties. This apparent contradiction with the popular belief of strong SSI in weaker soil prompted to consider the fact that with increasing seismic intensity, similar degradation in pier stiffness also takes place and it is the ratio of pier and foundation stiffness (k c /k h ) which should be examined to determine the influence of SSI. A relatively strong relationship between these variables supports the hypothesis that SSI is more strongly related to the stiffness ratio of pier and foundation than dynamic soil properties.

Proceedings of SPIE - The International Society for Optical Engineering

Base-isolation is a relatively new technology to improve seismic performance of cMI structures by... more Base-isolation is a relatively new technology to improve seismic performance of cMI structures by reducing natural frequency and increase damping using typically bearing made of rubber, and has recently been applied to construction and retrofitting of bridges. However, performance of base-isolated bridges during severe earthquakes has not yet been confirmed quantitatively. The purpose of this paper is to investigate its actual seismic behavior and performance of base-isolated bridge. The seismic performance of base-isolated bridge is verified by quantitatively showing the uncertainties associated with both measurement and modeling.

Journal of Bridge Engineering, 2004

Soil Dynamics and Earthquake Engineering, 2001

Identification of system parameters with the help of records made on base-isolated bridge during ... more Identification of system parameters with the help of records made on base-isolated bridge during earthquakes provides an excellent opportunity to study the performance of the various components of such bridge systems. Using a two-stage system identification methodology for non-classically damped systems, modal and structural parameters of four base-isolated bridges are reliably identified using acceleration data recorded during 18 earthquakes. Physical

Engineering Structures, 2001

Cyclic test of the columns is of practical relevance to the performance of compression members du... more Cyclic test of the columns is of practical relevance to the performance of compression members during an earthquake loading. The strength, ductility and energy absorption capabilities of reinforced concrete (RC) columns subjected to cyclic loading have been estimated by many researchers. These characteristics are not normally inherent in plain concrete but can be achieved by effectively confining columns through transverse reinforcement. An extensive experimental program, in which performance of four RC columns detailed according to provisions of ACI-318-08 was studied in contrast with that of four columns confined by a new proposed technique. This paper presents performance of columns reinforced by standard detailing and cast with 25 and 32 MPa concrete. The experimentally achieved load-displacement hysteresis and backbone curves of two columns are presented. The two approaches which work in conjunction with Response 2000 have been suggested to draw analytical back bone curves of RC columns. The experimental and analytical backbone curves are found in good agreement. This investigation gives a detail insight of the response of RC columns subjected to cyclic loads during their service life. The suggested analytical procedures will be available to the engineers involved in design to appraise the capacity of RC columns.