Sharif Digital Repository

This study aims to develop the Consistent Fish-Bone (CFB) simplified model for efficient estimation of Engineering Demand Parameters (EDPs) in irregular steel Moment Resisting Frames (steel-MRFs). To achieve this goal, some modifications based on the energy consistent approach have been applied to the Improved Fish-Bone (IFB) simplified model previously presented for reinforced concrete MRFs. These modifications include: 1) adding truss elements to the IFB model to consider the effect of flexural deformations and determining their areas by balancing the overturning moment and the strain energy due to the axial deformation of columns in the original steel-MRF with the overturning moment and... 

This research investigates a rotary disk with variable cross-section and incompressible hyperelastic material with functionally graded properties in large hyperelastic deformations. For this purpose, a power relation has been used to express the changes in cross-section and properties of hyperelastic material. So that (m) represents the changes in cross-section and (n) represents the manner of changes in material properties. The constants used for hyperelastic material have been obtained from experimental data. The obtained equations have been solved for different m, n, and (angular velocity) values, and the values of radial stresses, tangential stresses, and elongation have been compared.... 

Natural Gas Distribution Networks (NGDNs) are complex infrastructure systems that play an essential role in ensuring the welfare and prosperity of many communities by serving their residential, commercial, industrial, and transportation sectors. Earthquakes can damage the critical components of NGDNs and disrupt their services. The disruption of NGDN services can lead to significant economic and social losses. These losses can be mitigated by adopting appropriate resilience enhancement measures. This study puts forward a probabilistic framework to quantify the seismic resilience of NGDNs. This framework comprises multiple interconnected probabilistic models that work in harmony to... 

In this study, a nonlinear absorber that works with a negative stiffness is introduced to control vibration and its effect on reducing earthquake damage is investigated. Negative stiffness increases structural softness and damping. Also, due to its inherent nonlinear nature, negative stiffness can cause internal resonance and transfer vibration energy from a directly excited vibrating mode to a higher frequency mode. Using these features can be effective in reducing vibration. First, to investigate the dynamic behavior in conditions without internal resonance and with 1:3 internal resonance, the proposed absorber is added to a nonlinear main system and when the system is under external... 

This paper presents a novel computer vision-based methodology for assessment of the seismic damage in reinforced concrete moment frames using visual characteristics of surface damage following an earthquake. An extensive collected database comprising 974 images associated with 256 cyclic-loaded damaged beam-column joints, providing a set of cracking and crushing progression with increasing the evolution of damage level, is collected and used for the development and validation of the methodology. Employing image processing techniques, the characteristics of the surface damage, including the cracking length and crushing areas, are measured and used in a scenario-based assessment for the... 

The seismic responses of steel water tanks are unconventional given their complex dynamic behavior and the sources of nonlinearity. Therefore, providing a reliable, finite-element model is instrumental in better understanding their dynamic behavior and improving the design conditions. This paper aims to evaluate the seismic performance of steel water tanks using shaking table tests and provide a finite-element reference model for simulating real-size, semi-anchored water tanks by conducting a series of large-scale tests in the Shaking Table Lab of the Sharif University of Technology (SUT). Since scaling the tank requires a difficult process involving changing the liquid density, this paper... 

This article proposes a novel index along with a user-friendly platform for resilience evaluation of the urban water distribution networks (WDN). WDN is of great importance in preserving the safety and sustainability of communities and cities. Resilience of a given system results in its sustainability. In recent years, many studies have focused on resilient urban WDN. However, these studies did not provide a comprehensive evaluation index and platform that could simultaneously consider hydraulic analysis, resilience parameters, and significant uncertainties. In this study, a novel resilience index was defined, and a user-friendly and practical platform (REWAT) was developed to calculate the... 

Distribution systems are one of the most important infrastructures of each country which are exposed to numerous damages through unexpected events. The development of distributed energy resources (DERs) is one of the solutions which can bring several benefits to the operation and planning of distribution systems in both normal and event situations. This paper proposes a new multi-objective planning model for optimal siting and sizing of DERs in distribution systems to minimize the total planning costs including operation and active power loss costs, as the normal operation objective, and to minimize the expected prioritized load shedding exposed to an earthquake incident, as the resilience... 

One of the acceptable assumptions in engineering practice is vertical propagation of earthquake waves. When the source of earthquake is located very deep in the ground, this assumption is valid, but for sources located in shallow ground, it loses its viability. In this study, linear seismic analysis of a system of concrete dam-massed foundation-reservoir is performed under inclined earthquake excitation. Both P- and SV-type earthquakes are considered for the purpose of the seismic analysis. To consider the effects of inhomogeneous waves for the case of SV wave propagation, post-critical angles are also considered in the analysis. To investigate the effects of earthquake frequency content on... 

Torsion is one of the most important causes of building collapse during earthquakes. Sometimes, despite the symmetric form of the building, infill walls disturb the symmetry of the lateral resisting system. The purpose of this research is to investigate the effect of urban layout on developing torsion caused by infill walls. For this purpose, a typological study was conducted based on the conditions of perimeter walls on 364 buildings and then 9 cases were selected. The dimensions of the selected buildings are constant and the conditions of the perimeter walls including facades with openings and cantilevered facades are variable. The selected buildings with 60 different layouts of infill... 

In this paper, the numerical studies on the semi-elliptical crack behavior in different locations of welded zones in the supporting structure of a spherical pressure vessel under an earthquake are presented. The cracks in the welded zones of supporting structures under earthquake effects may jeopardize the safety of spherical pressure vessels and result in catastrophic failure. A detailed finite element sub-modeling technique is carried out to compute the mixed-mode stress intensity factors along the crack front. Furthermore, crack behavior with different aspect ratios a/c: 0.25, 0.5, and 0.75 at the weld and the heat-affected zone of the supporting structure is evaluated. The... 

The efficient planning of search and rescue (SAR) operations is highly impactful in the disaster response phase, which offers a limited time window with a declining chance for saving trapped people. The present paper introduces a new robust decision support framework for planning SAR resource deployment in post-disaster districts. A two-stage decomposition approach is applied to formulate the problem as iterative interrelated stages of mixed-integer programming (MIP) models. The first stage presents a robust multi-period allocation model for maximizing fair and effective demand coverage in the affected districts during the entire planning horizon. It takes into account the time-sensitiveness... 

Irregular buildings constitute a large portion of the modern urban structures. Based on experiences of past earthquakes, irregular configuration of buildings or asymmetrical distribution of structural properties trigger an increase in seismic demand, intensifying the vulnerability of the structure. In this work, the effects of splitting in levels, classified as vertical irregularity, on the seismic behaviour of some 3D steel structures are studied. Studied models consisted of five-, ten- and fifteen-storey 3D steel special moment-resisting frames, split just in one direction, with six different plans. Equivalent static method together with a special pattern for distributing the base shear,... 

This paper develops the seismic damage models of brick masonry veneer attached to the masonry infill without metal ties and assesses the life cycle cost of veneers subjected to earthquake excitation. Even though anchoring veneers to the backup wall has been prescribed in recent building codes, most of the existing brick veneers in seismic prone areas around the world lack the anchoring details. Besides, the damage and consequence models of masonry façades have not been presented in the FEMA-P58 database restricting detailed performance evaluation of buildings with unanchored masonry veneers. This study develops detailed finite element models to simulate various failure modes of the masonry... 

In this paper, the effects of rocking and fixed base prestressed columns and conventional reinforced concrete columns on the response of frames are investigated. Also, the influence of some selected rocking base prestressed columns on the response of the concrete frame was studied. Three types of a concrete frame with conventional Reinforced Concrete columns, rocking, and fixed base prestressed columns were modeled using the finite element method in Opensees software. The details of the simulation of the rocking and fixed base columns in Opensees are described precisely. The results obtained from the models were compared with those of the literature to evaluate the validity of the results.... 

This study proposes predictive equations for estimating the peak-experienced drift ratio of unreinforced masonry walls based on the visual characteristic of the damages. In this regard, a comprehensive database comprised of 190 images associated with 30 unreinforced masonry walls at different drift ratios between 0.0 and 1.1 percent is collected, and the visual features of the progressive damages are extracted. Various image processing filters are implemented to the images to quantify the cracking length and crushing areas. The filters are capable of distinguishing different crack patterns, such as joint cracking and block cracking. In the following, four scenarios are introduced based on... 

Recent earthquakes clarified that existing a soft/weak-story in a building could completely invert the failure mechanisms of the structure. Several studies were implemented to evaluate the potential risk subjected to the buildings under the earthquake hazard. However, these researchers discarded the effect of soft/weak-story on the demand parameters of their models. This paper presents a rapid demand estimation framework for generic buildings considering the effect of soft/weak-story. In this regard, the simplified model developed according to the HAZUS approach is rectified to apply the effect of soft/weak-story on the structural behavior of the generic buildings. Artificial neural networks... 

The performance of several regression methods is investigated to estimate the distribution of engineering demand parameters conditioned on intensity measures (EDP|IM) for small record sets. In particular, the performance of the multivariate ordinary least squares (OLS), a simultaneous mean-variance regression (MVR) done by a penalized weighted least-square loss function, and a mean-covariance/variance regression based on expectation maximization method (EM) are assessed. The efficiency of the introduced methods is compared with FEMA-P58 methodology. Performance assessment of EM and MVR methods shows that the overall increase in efficiency is about 25–45% for maximum inter-story drift ratios,... 

Seismic performance of postmainshock buildings considering seismic mainshock-aftershock sequences are studied. The case studies correspond to three SAC steel MRF buildings of three, nine and twenty stories. The 2-D models are able to capture important properties of deterioration of strength and stiffness. Endurance time method is used to predict the response of structures in different hazard levels. Results are compared with those from of nonlinear incremental dynamic analysis. Maximum dynamic seismic responses of structures are captured during synthetic mainshock-aftershock seismic sequences which are produced by endurance time method. Interactional-conceptual curves for different seismic... 

This research attempts to propose a new simulating model capable of generating synthetic stochastic earthquake scenario including both seismological, and acceleration signal properties. The Iranian plateau is selected as a mainland for developing the model due to the existence of high-quality earthquake databases. This model is composed of two sub-models. The first one generates random seismic event scenarios including mainshocks and aftershocks. The second one procreates 3-dimensional synthetic stochastic accelerograms for each of the previously simulated events. This scenario-based predictive model offers a powerful tool to the risk modelers interested in lifetime seismic risk assessment...