Mehdi Ahmadizadeh

Sharif University of Technology | SHARIF · Department of Civil Engineering

A fully implicit iterative integration procedure is presented for local and geographically distributed hybrid simulation of the seismic response of complex structural systems with distributed nonlinear behavior. The purpose of this procedure is to seamlessly incorporate experimental elements in simulations using existing fully implicit integration...

Stone masonry construction is still a common practice in remote mountainous areas of many developing countries. Field investigations have shown that the traditional construction practices do not usually provide adequate seismic resistance for such buildings. This study was carried out to investigate and improve the construction of single-story ston...

It is generally accepted that active control systems provide better structural performance when compared to their passive counterparts. On the other hand, the design of active control systems based on linear control theory is highly dependent on the structural properties. For this reason, their performance is expected to be affected more severely b...

An effective iterative method is proposed for three-dimensional large-displacement analysis of structures consisting of slack cables as the primary load-bearing system. This approach takes advantage of substructuring technique that is specially tailored to address the analysis and form-finding problem of slack cables subjected to arbitrary loads, a...

To reduce both displacement and absolute acceleration response of structures subjected to seismic excitations, novel and improved passive structural control design methods tend to modify the stiffness and strength of structures in addition to supplementing their energy dissipation capacity. In this study, a practical and streamlined methodology has...

A strategy is developed for design of passive control systems for structures experiencing inelastic deformations during earthquake loading. Besides the addition of passive energy dissipation devices, the proposed method suggests the required changes to the stiffness and strength of the structure, to reduce the absolute acceleration and relative def...

This study aims at development of a reliable and versatile technique for large deformation analysis of slack cable structures subjected to dynamic loading. Ordinary numerical analysis methods are usually unable to handle these structures due to their singularities arising from large deformations and rotations following any alteration of the applied...

A practical procedure is developed for design of passive control systems using viscous fluid dampers for nonlinear structures. The design methodology takes advantage of modification of both damping, strength and stiffness properties of the structure to achieve the desired relative displacement and absolute acceleration response. For this purpose, a...

Hybrid simulation is a powerful test method for evaluating the seismic performance of structural systems. This method makes it feasible that only critical components of a structure be experimentally tested. This paper presents a newly proposed integration algorithm for seismic hybrid simulation which is aimed to extend its capabilities to a wide ra...

Buckling-restrained braces (BRBs) are known to improve the energy dissipation properties of structures by preventing the bracing elements from buckling in compression. As a result, structures equipped with BRBs exhibit better performance mainly in terms of maximum responses. On the other hand, the bilinear behaviour and usually low post-yield stiff...

Hybrid simulation is a powerful test method for evaluating the seismic performance of structural systems.This method makes it feasible that only critical components of structure be tested experimentally while the rest of the structure is numerically modeled. This paper presents a newly proposed integration algorithm for seismic hybrid simulation wh...

SUMMARY A methodology is developed for the design of optimum viscous fluid passive energy dissipation systems using pole assignment active control algorithm. In this method, the procedure to assign the new structural poles is slightly modified such that the resulting structural properties (i.e., the optimum locations of system poles) can be achieve...

An effective method is developed for design of passive viscous fluid dampers for structural control, considering the flexibility of braces used for installation of dampers. In the first step of this method, a suitable damping ratio is determined based on the optimization results of single-degree-of-freedom systems with various natural periods and b...

https://onlinelibrary.wiley.com/doi/abs/10.1002/stc.1991

: A methodology is developed for designing optimum passive energy dissipation systems using active control algorithms. A combination of stiffness reduction and increase of damping is utilized to reduce both acceleration and displacement response. In this method, first an active control system is designed using pole assignment control algorithm. Her...

: Slack cable structures exhibit large displacements and rotations in response to the applied loads before reaching an equilibrium state. Consequently, following any alteration of the applied loads, the structure is essentially unstable and ordinary numerical analysis methods break down due to singularities. In this paper, an effective iterative me...

An all-inclusive web resource has been developed that links the study of earthquakes and engineering design to middle grades' (students of ages 10–15) science, mathematics, and technology. It was created to help students understand how earthquakes affect humans and how engineered solutions can mitigate damage. One key component of the website is an...

In this paper, a methodology has been proposed for design of passive energy dissipation systems through active control theory. The passive control system is designed to achieve a structural response as close to that of active control system. It may be needed to reduce the stiffness of the original structure at some locations to reduce the accelerat...

A fully implicit iterative integration procedure is developed for local and geographically distributed hybrid simulation of the seismic response of complex structural systems with distributed nonlinear behavior. The purpose of this procedure is to allow experimental elements in simulations using existing fully implicit integration algorithms design...

Hybrid simulation is an effective structural test technique combining the numerical simulation of substructures with predictable behavior, and experimental testing of complex components that are difficult to model. Consequently, hybrid simulation is prone to both numerical and experimental errors. In this paper, the dominant sources of numerical an...

A fully implicit iterative integration procedure is presented for hybrid simulation of the seismic response of structural systems. The advantage of this approach is that experimental elements can be introduced into a simulation using fully implicit integration algorithms designed for pure numerical simulations. The procedure utilizes the tangent st...

Improved numerical integration procedures are essential for the extension of hybrid numerical and experimental simulation to large and complex structural systems. While implicit integration algorithms are widely used in pure numerical simulations for their superior stability and accuracy, their direct application to hybrid simulation has been parti...

Hybrid simulation is an effective structural test technique that takes advantage of numerical simulation of substructures with well-identified behavior, and experimental testing of complex and nonlinear components. As a result of combining numerical and experimental simulations, hybrid simulation is prone to both numerical and experimental errors....

Two novel implementation methods of implicit integration procedures for hybrid simulation are presented. The first solves the equation of motion using a fully implicit iterative formulation. The experimental restoring force for each iterative displacement is estimated from curve-fitting of recent force-displacement measurements, avoiding physical i...

Hybrid simulation is an effective structural test technique that takes advantage of numerical simulation of substructures with well-identified behavior, and experimental testing of complex and nonlinear components. As a result of combining numerical and experimental simulations, hybrid simulation is prone to both numerical and experimental errors....

Compensation of delay and dynamic response of servo-hydraulic actuators is critical for stability and accuracy of hybrid experimental and numerical simulations of seismic response of structures. In this study, current procedures for compensation of actuator delay are examined and improved procedures are proposed to minimize experimental errors. The...

Explicit integration procedures have been widely adapted and applied to hybrid simulations of the seismic response of structures due to their simplicity. However, these procedures are only conditionally stable and have limited recent applications of hybrid simulations to simple structural models with few degrees of freedom. A novel integration proc...

In this paper, the capabilities of passive control of structures using hydraulic fluid dampers are compared to those of semi-active control. It is demonstrated that, in most cases, the performance achieved by a properly designed passive control system can be comparable to that of semi-active systems that use the state-of-the-art control algorithms....

Explicit integration procedures have been widely adapted and applied to hybrid simulations of the seismic response of structures due to their simplicity. However, these procedures are conditionally stable and require small time steps for stiff systems, or systems involving high-frequency modes. In this study, a combined implicit or explicit integra...

In this study, the effects of important ground motion parameters and site conditions on linear and nonlinear, pseudo-acceleration and input energy response spectra are evaluated. These parameters include magnitude, epicentral distance of recording station, strong motion duration, soil conditions, damping and ductility. A total of 620 Iran's earthqu...

In this paper, the capabilities of passive control of structures using hydraulic fluid dampers are compared to those of semi-active control. It is demonstrated that, in most cases, the performance achieved by a properly designed passive control system can be comparable to that of semi-active systems that use the state-of-the-art control algorithms....

Compensation of delay and dynamic response of servo-hydraulic actuator is critical to the stability and accuracy of hybrid experimental and numerical simulations of the seismic response of structures. In this study, current procedures for compensation of actuator delay are examined and improved procedures are proposed. The proposed procedures need...

In this paper, the December 26, 2003, earthquake in the historical city of Bam is studied. The seismological aspects are considered and the earthquake source is introduced. The strong ground motion is studied and its spectra are compared to the design spectra of UBC-97 and the Iranian seismic code, as well as previous earthquakes in Iran. Finally,...

Two novel implementation methods of implicit integration procedures for hybrid simulation are presented. The first solves the equation of motion using a fully implicit iterative formulation. The experimental restoring force for each iterative displacement is estimated from curve-fitting of recent force-displacement measurements, avoiding physical i...

A fully implicit iterative integration procedure is developed for local and geographically distributed hybrid simulation of the seismic response of complex structural systems with distributed nonlinear behavior. The purpose of this procedure is to allow experimental elements in simulations using existing fully implicit integration algorithms design...