Ehsan AhmadiBirmingham City University | BCU · Faculty of Technology, Engineering and the Environment
Ehsan Ahmadi
B.Sc., M.Sc., Ph.D. in Structural Engineering
About
51
Publications
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555
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Citations since 2017
Introduction
Additional affiliations
January 2018 - October 2018
November 2014 - July 2018
November 2011 - July 2014
Education
November 2009 - December 2011
November 2005 - November 2009
Publications
Publications (51)
This paper reviews structural health monitoring (SHM) techniques of bridge structures based on machine learning (ML) algorithms. Regular inspections or using non-destructive testing are still the common damage detection methods; they are susceptible to subjectivity, human error, and prolonged duration. With emerging technologies such as artificial...
Large sympathetic, resonance-like, structural behaviour to earthquake excitations with analogous frequency content often plays a critical role in determining its maximum seismic response. Earthquake excitation typically contains a broad spectrum of non-stationary frequency content, wave packets, which are difficult to observe from the recorded time...
Application of precast post-tensioned segmental (PPS) bridge piers has increased in recent years in accelerated bridge construction (ABC). In order to increase the use of PPS piers in high seismicity regions, this work investigates the nonlinear behaviour of a segmental bridge pier with unbonded post-tensioned superelastic Shape Memory Alloy (SMA)...
Damage detection of bridge structures plays a crucial role in in-time maintenance of such structures, which subsequently prevents further propagation of the damage, and likely collapse of the structure. Currently, the application of machine learning algorithms are growing in smart damage detection of structures. This work focuses on application of...
A large part of Iranian railway bridge asset comprises masonry arch bridges, which have been in service for over 70 years. Seismic assessment of such structures is of great importance, particularly for high-seismic regions. Hence, this study assesses the seismic performance of Veresk masonry arch bridge, the longest masonry arch bridge of Iranian r...
![SMA parameters used in this study [11].](profile/Mohammad-Kashani-7/publication/362231191/figure/tbl1/AS:1181659500150788@1658740987396/SMA-parameters-used-in-this-study-11_Q320.jpg)
In recent years, accelerated bridge construction (ABC) has led to substantial application of precast posttensioned segmental (PPS) bridge piers in bridge construction. However, PPS piers are not to be used in high-seismicity regions due to their low-energy dissipating capacity. To address this deficiency, this paper examines a segmental bridge pier...
The use of precast post-tensioned segmental (PPS) piers is growing in bridge industry, particularly in Accelerated Bridge Construction (ABC). The PPS piers provides durable, low-maintenance and demountable accelerated bridge construction technique that could be resilient to natural hazards. To expand their application in seismic regions, it is esse...
Damage detection is of great importance in reducing maintenance cost and preventing collapse of structures. Despite existing damage detection methods, the current literature lacks a comprehensive method, which: (i) is applicable to complex structures with large degrees of freedom, (ii) captures even low-level damages, and (iii) gives reasonable acc...
Precast post-tensioned segmental (PPS) bridge piers mitigate global and local damages of bridge structures through natural hinges (joints between their segments) and rocking motion of their segments. The application of the PPS piers is currently growing in Accelerated Bridge Construction (ABC) where the segments are manufactured offsite with higher...
The application of precast post-tensioned segmental (PPS) bridge piers is growing in order to reduce global damages through rocking motion of the segments when subject to lateral excitations. However, local damages still exist in form of concrete spalling and crushing at the compression zones when one segment rocks on top of the underlying segment....
The interaction between structures and walking humans is an important factor in vibration serviceability assessment of slender, lightweight, and low-damping structures. When on bridges humans form a human-structure system and interact with the structural vibration. The conventional vertical moving force (MF) model neglects human-structure interacti...
The ultra-high-speed (UHS) Hyperloop is the next-generation mode of passen-ger/freight transportation, and is composed of a tube or a system of tubes through which a pod travels free of friction. The entire system must be supported by piers (multi-span viaducts), where the tubes act as the bridge deck. The UHS moving Hyperloops can exert large dyna...
Application of post-tensioned segmental columns are increasing in accelerated bridge construction, where rocking motion of the segments results in lateral displacement of the column and the post-tensioning tendon provides self-centering capacity of the system. Analytical solution of such system is very complex as the equations of rocking motion are...
Precast post-tensioned segmental (PPS) columns lower vulnerability of bridges because of natural hinges and rocking motion of the segments. The use of the PPS columns in bridge construction is increasing as high-quality segments are constructed offsite, and are rapidly put together onsite. Hence, the seismic performance assessment of the PPS column...
Suitable numerical models of masonry structures are very important in their response evaluation under various loading events. Masonry is a heterogeneous material, made of mortar and masonry units, and joined together by interfaces. Constitutive models of mortar joints and masonry-mortar interfaces play a crucial role in achieving high-fidelity nume...
The next generation of ultra-high-speed (UHS) trains, known as Hyperloop and TransPod, are aerospace type vehicles designed to carry passengers. The UHS employs a vehicle capsule within a protected vacuum tube deck, supported by reinforced concrete piers (i.e. multi-span viaduct). The tube environment allows multiple UHS vehicles to run in parallel...
Accelerated Bridge Construction (ABC) philosophy has resulted in extensive developments of precast post-tensioned segmental (PPS) bridge piers in the bridge construction. Currently, there is a significant paucity in the literature on nonlinear mechanics and dynamics of PPS piers. Hence, this wok numerically investigates the nonlinear static and dyn...
Human activities and occupancy can induce excessive structural vibrations. Human-structure interaction (HSI) can significantly affect responses. However, this phenomenon is not accounted for in many design guidelines due to lack of experimental studies. Concurrently, there is increasing application of lightweight high-strength materials such as gla...
This research explores potential application of entangled wire materials as intermediate layers between segments of pre-tensioned segmental bridge columns. An ensemble of free-decay vibration tests was conducted on small-scale columns with various configurations of intermediate layers. Wooden blocks were used for segments and the entire system was...
The rocking mechanism has been widely recognized as a beneficial technique to reduce structural damage arising from lateral excitations particularly earthquake loading, and hence, segmental pre-tensioned bridge piers have been recently emerged due to their self-centring property accompanied by accelerated construction of such structures. Hence, thi...
![Figure 1. The biologically-inspired bridge pier concept [33].](profile/Mohammad-Kashani-7/publication/330934911/figure/fig1/AS:723714144477187@1549558306795/The-biologically-inspired-bridge-pier-concept-33_Q320.jpg)
This work focuses on entangled wire materials as an option for use between segments of a novel self-centring bridge pier inspired from the human spine mechanism to increase energy dissipation capability of the pier in rocking. A comprehensive set of free-decay vibration tests was conducted on small-scale columns with and without entangled wire mate...
The rocking mechanism has been widely recognized as a beneficial technique to reduce structural damage arising from lateral excitations particularly earthquake loading, and hence, segmental pre-tensioned bridge piers have been recently emerged due to their self-centring property accompanied by accelerated construction of such structures. Hence, thi...
This research explores potential application of entangled wire materials as intermediate layers between segments of pre-tensioned segmental bridge columns. An ensemble of free-decay vibration tests was conducted on small-scale columns with various configurations of intermediate layers. Wooden blocks were used for segments and the entire system was...
Cumulative damage effects Structural energy distribution Kinematic and inertial interactions A B S T R A C T Repeated cyclic loading is well-known to have detrimental effects on inelastic response of structures. Distribution of structural energy and quantification of cumulative damage effects are very important components in performance-based seism...
As a key stage of performance-based seismic design of structures, strength-ductility-period relationship is used to determine either inelastic strength or ductility ratio of the structure with a specific fundamental vibration period. On the other hand, period, strength, and ductility demands of structures are significantly affected by inertial and...
Lightweight structures are sensitive to dynamic force generated by human walking and consequently can exhibit excessive vibration responses. The imparted forces, known as ground reaction forces (GRFs), are a key input in the vibration serviceability assessment of footbridges. Most GRF measurements have been conducted on rigid surfaces such as instr...
In lightweight structures, there is increasing evidence of the existence of interaction between pedestrians and structures, now commonly termed pedestrian-structure interaction. The presence of a walker can alter the dynamic characteristics of the human-structure system compared with those inherent to the empty structure. Conversely, the response o...
In seismic design codes and documents, the period and damping ratio of a linear fixed–base single degree-of-freedom (SDOF) system are tuned to return the dynamic response of a given nonlinear fixed–base SDOF structure through a so-called equivalent linearization method. The period and damping ratio of the equivalent linear system are referred to as...
To predict the vibration response of footbridges, many codes of practice use a deterministic moving force (MF) model. This approach may not be well suited for the design of slender, lightweight, low-damping, and low-frequency footbridges because it ignores the pedestrian interaction with the vibrating footbridge. On the other hand, a spring-mass-da...
p>Pultruded glass fibre reinforced polymer (GFRP) is a strong, light, and durable material that is very well suited to modular structural forms. The replacement of aged and deteriorated small footbridges is an ideal use for such structures. However, GFRP has low stiffness; this and the typical low mass of GFRP structures, mean that they can be susc...
In this paper, human–structure interaction system models for vibration in the vertical direction are considered. This work assembles various moving load models from the literature and proposes extension of the single pedestrian to a crowd of pedestrians for the FE formulation for crowd–structure interaction systems. The walking pedestrian vertical...
Human presence can change the dynamic characteristics of human-structure interaction systems, i.e. particularly their damping and frequency. In many design codes, the pedestrian is regarded as a moving force (MF) while a more complete model, referred to as moving spring-mass-damper (MSMD) has received attention recently. Unlike the MF model, the MS...
The effects of input parameters of pulse-like ground motions on the response of soil–structure systems are investigated through employing an ensemble of 64 ground motions. The soil and superstructure are idealised as a semi-infinite cone and a non-linear multiple-degrees-of-freedom shear building, respectively. The results confirm that the location...
The effects of input parameters of pulse-like ground motions on the response of soil–structure systems are investigated through employing an ensemble of 64 ground motions. The soil and superstructure are idealised as a semi-infinite cone and a non-linear multiple-degrees-of-freedom shear building, respectively. The results confirm that the location...
Consequences of near-fault ground motions to strength reduction factors of flexible-base multi-story structures are addressed by employing synthetic pulses. For this purpose, three non-dimensional parameters are adopted as the key parameters of interacting systems: (1) non-dimensional frequency as the structure-to-soil stiffness ratio, (2) aspect r...
A parametric study is devoted to investigating the dynamic instability of soil-structure systems under far-fault earthquakes. The superstructure and soil are simulated as a bilinear single-degree-of-freedom (SDOF) oscillator and based on the cone model concept, respectively. The results show that soil flexibility makes the system dynamically more u...
In this study, the role of soil material damping in the engineering demand parameters (EDPs) of soil-structure systems is investigated. For this purpose, a superstructure is modeled as a two-dimensional nonlinear multi-story shear building. The soil beneath the foundation is simulated based on the concept of the cone model. The effects of various p...
In lightweight structural systems there is increasing evidence that the presence of humans influences the dynamics characteristics of the system. In the past, most effort on determining the footfall-induced vertical force to the walking surface has been conducted using rigid or non-flexible surfaces such as treadmills. However, should the walking s...
This study is devoted to investigate the effects of inertial soil–structure interaction (SSI) on the constant-strength inelastic displacement ratios of elastoplastic single-degree-of-freedom systems using a suit of 91 pulse-like ground motions. The soil beneath the foundation is simulated based on the cone model. A local minimum for the inelastic d...
In this paper, a comprehensive study is carried out to examine the possibility of dynamic instability produced in soil-structure systems using an ensemble of 50 pulse-like records. A number of structural models with various vibration periods varying from 0.1 to 2 s are used in this study. The superstructure is simulated as a non-linear SDOF oscilla...
This study is devoted to estimate higher-mode effects for multi-story structures with considering soil-structure interaction subjected to decomposed parts of near-fault ground motions. The soil beneath the super-structure is simulated based on the Cone model concept. Two-dimensional structural models of 5, 15, and 25-story shear buildings are ideal...
This paper is devoted to investigate the effects of near-fault ground motions on the seismic responses of nonlinear MDOF structures considering soil-structure interaction (SSI). Attempts are made to take into account the effects of different frequency-content components of near-fault records including pulse-type (PT) and high-frequency (HF) compone...
This study is devoted to estimate higher-mode effects for multi-story structures with considering
soil-structure interaction subjected to decomposed parts of near-fault ground motions. The soil beneath the
super-structure is simulated based on the Cone model concept. Two-dimensional structural models of 5, 15,
and 25-story shear buildings are ideal...
In this study, attempts are made to investigate the effects of inertial soil–structure interaction (SSI) on damping coefficients subjected to pulse-like near-fault ground motions. To this end, a suit of 91 pulse-like near-fault ground motions is adopted. The soil and superstructure are idealized employing cone model and single-degree-of-freedom (SD...
a b s t r a c t In this paper, effects of Soil-Structure Interaction (SSI) on Inelastic Displacement Ratios (IDRs) of super-structure are addressed. Four non-dimensional parameters are employed as the crucial parameters which affect the IDRs of soil-structure systems: (1) non-dimensional frequency as the structure-to-soil stiffness ratio; (2) aspec...
This paper attempts to investigate the effects of different components of near-fault ground motions on the response of soil-structure systems. The structure and soil are simulated as a nonlinear SDOF oscillator and a semi-infinite cone. The results show that high-frequency effects are more significant for short-period structures. As structural duct...
In this paper, the effects of pulse period associated with near-field ground motions on the seismic demands of soil–MDOF structure systems are investigated by using mathematical pulse models. Three non-dimensional parameters are employed as the crucial parameters, which govern the responses of soil–structure systems: (1) non-dimensional frequency a...
In this paper, attempts have been made to address the strength reduction factors of soil-MDOF structure system under idealized pulses. The soil beneath the super-structure is simulated based on the concept of Cone model and the super-structure is modeled as a nonlinear 15-story shear building. Three non-dimensional parameters are employed as the cr...
Evaluation of the target displacement by means of the simplified nonlinear static procedures (NSPs), known as the Coefficient Method, is presented in FEMA 356 and FEMA 440 documents. In this method, C 1 is defined as modification factor to obtain the expected maximum displacement of an inelastic SDOF oscillator from displacement of the correspondin...
Questions
Question (1)
Hi everyone,
I am trying to implement a new material model in OpenSees. When I successfully create the .dll file, and run an example, it gives me this error: WARNING: could not create uniaxial material ....
When I create the .dll file for the ElasticPP example presented in the opensees tutorial for adding new material, I still get the same error. I reckon it might be the version of opensees I am using or I am missing a file. If you have recently implemented a new material in Opensees and it works nicely, Is that possible for you to send me a working example of the ElasticPP example including all required files and folders (Opensees.exe, Developer, and etc) which can allow me to check if I am missing any file?
Projects
Projects (3)
We are calling for full papers for a special issue on Resilience-Based Design for Next-Generation Bridge Design and Construction dedicated to the broad topics of Accelerated, Automated, and Robotic
Bridge Construction. This issue follows the University of Southampton (UoS) Workshop on the same topics. The workshop will be held at the UoS in the UK on 15-16 July 2020, and is supported by the UK Engineering and Physical Sciences Research Council (EPSRC) [grant number EP/R039178/1]: SPINE: Resilience-Based Design of Biologically Inspired Columns for Next-Generation Accelerated Bridge Construction.
The main focus of this special issue will be on recent advances in the design, fabrication, construction, inspection, and accelerated bridge construction. This issue is expected to become an international forum for researchers and engineers in the field and will summarise recently developed scientific results. Potential topics include, but are not limited to:
• Accelerated bridge construction (ABC)
• Sustainability and resilience-based design and construction of bridges
• Application of composite and smart materials in bridge construction
• Robotic bridge repair and construction
• Robotic/autonomous inspection including NDT methods
• Off-site manufacturing
• Nonlinear dynamics and seismic performance of ABC bridges
• Application of ABC bridges for High-Speed and Ultra-High-Speed Trains
Guest Editors:
-----------------------
Dr Mohammad Mehdi Kashani, School of Engineering, University of Southampton, United Kingdom, Email: Mehdi.Kashani@soton.ac.uk
Prof Saiid Saiidi, Department of Civil & Environmental Engineering, University of Nevada, Reno, United States, Email: saiidi@unr.edu
Prof Marc O. Eberhard, Department of Civil & Environmental Engineering, University of Washington, United States, Email: eberhard@uw.edu
Further information is available at the following link:
https://www.journals.elsevier.com/structures/call-for-papers/special-issue-on-resilience-based-design-for-next-generation
A resilience-based design approach plays an important role in the design of new bridges and other structures. The structural elements of bridges are often directly exposed to the environment without any protection. Even though life-cycle and sustainability criteria have been incorporated in new design guidelines, there is still no design and construction technique that can fully address the future demands of a resilient and sustainable transport infrastructure.
The aim of this research is to produce innovative and transformative engineering solutions for a durable, low-maintenance, low-cost, and demountable accelerated bridge construction technique, which is resilient to environmental threats, and natural hazards. The solutions will include a completely new resilience-based bridge design approach and biologically inspired composite columns for next-generation accelerated bridge construction.
Towards this goal, this research will construct an innovative composite bridge column, which is inspired by the mechanics of the human spine. In the human spine, intervertebral discs provide flexibility, dissipate energy from the movements of the human body, and absorb and transmit forces without damaging the vertebrae bones. The proposed spinal bridge column will be constructed using precast composite segments (the 'vertebrae'). A new smart composite material will be developed and used in between of these solid composite segments (the 'intervertebral discs'). This will keep the vertebrae from rubbing against each other, transfer the shear forces through friction, absorb the impact due to the rocking of vertebrae, and provide mechanical damping under dynamic loading. Finally, the vertebrae and intervertebral discs will be tied together using an unbonded composite post-tensioning tendon (the 'longitudinal ligament'), to provide self-centring mechanism in the column when subjected to lateral force.
In this 24 moths research, the underlying science of the new spinal column will be investigated through experimental testing and numerical modelling. During the entire duration of the project a series of review meetings, short visits to academics as well as industry partners, and an international workshop will be organised. This interaction is deemed vital for the co-development of new concepts, the transfer of know-how and the resilient and sustainable accelerated bridge construction.
