Sharif Digital Repository

The present study deals with the development of development of fragility curves for confined masonry buildings with the emphasis on masonry school buildings by means of numerical simulation. In doing so and based on the results of several previously-performed tests in Iran, simple analytical models for confined masonry walls capable of predicting various failure modes and also simulating different behavioral characteristics of these walls in the form of cyclic force-displacement curves were presented. In order to endure the ability of the proposed analytical models in simulation of seismic response of existing confined masonry buildings, a static-cyclic in-situ test on a real typical... 

Adobe buildings on one hand are very heavy and hence generate great amounts of inertia loads during earthquakes. Their response is also amplified in the high-frequency earthquake waves due to great stiffness. On the other hand, these structures proved vulnerable during past earthquakes because of low strength and ductility. Considering the fact that there are too many structures of this kind throughout the country and a majority of their residents are the poor, seismic retrofitting of these building should be taken as a priority rather than reconstruction. It is obvious that the proposed retrofitting technique should be simple, feasible and economical, as well. Among possible retrofitting... 

Today, with improvements in industries such as the sensitive equipment’ industries and the optics industries which need great precision for their optimum performance, the need for a vibration-free environment is felt more than ever. The main objective in this thesis is the effective reduction of the effects of ambient vibrations on points on an optical concrete table using active control. In this research, other than separating the table with the passive method, the reduction of vibrations with active control and the LQR algorithm is investigated. In order to study the dynamic characteristics of the table and to observe the active control process better and more carefully, finite element... 

This study aimed to develop a method for locating damages in the early stages of damage expansion in plate components of the structure using a one-dimensional discrete wavelet function. Continuous monitoring of the health of structures to preserve and repair them to protect the lives and property of individuals and national capitals and to lower the direct and indirect economic costs imposed on society is vital and inevitable for society's decision-makers. Because the damage to the structure caused by earthquakes occurring during the lifetime of the structure, exhaustion of structural components, improper implementation of the structure at the time of construction, and other events that... 

Reinforced concrete buildings with open ground storey are vulnerable to accumulate of large lateral displacement at the ground story. This is due to drastic reduction in the relative stiffness of the ground story compared to the upper stories, a phenomenon known as soft storey effect. Furthermore inevitable Existence of Opening in masonry infill and increasing it’s area reduces both the lateral strength and stiffness of the fully infilled RC frames so when percentage of the central opening is very high, the behaviour of the infilled frame approaches the bare frame. It is a perception about open ground storey buildings that openings in the upper stories infilled frame offset the soft storey... 

Due to structural and nonstructural damage after the occurrence of Northridge 1994 and Kobe 1995 earthquakes, Seismic design basics was modified and philosophy of performance based design was suggested. In this novel solution, Predefined limitations are considered. Performance criteria were usually related to displacement or other correlated factors such as hinge plastic rotation. All the mentioned limitations are related to different damage states.Most of the codes and articles use following assumptions for assessing structural performance: 1) considering first vibrational mode for structural response to any seismic excitation regardless of seismic input acceleration records or structural... 

This research focuses on probabilistic damage detection in the finite element model by using an application of Bayes' inference rule. Density and elastic modulus are sources of uncertainties in structures, therefore the probabilistic method is chosen instead of deterministic. According to the test's data, the distribution of density and elastic modulus have been updated. Then through Bayes' rule the probability of each damage state updates by modal data. Damage states are defined through a coefficient between 0-1 by multiplying to the inertia of elements of the structure. After each observation, the posterior probabilities are updated and this process happens through the multiplication of... 

The main purpose of this research is to evaluate the impact of mainshock and aftershocks on the response and fragility of power transmission towers and to provide an approach to assess the risk of transmission lines under mainshock-aftershock sequence. The transmission line studied in this research has 27 self-supported 400 kV transmission towers. The reason for choosing this line is the proximity of the line to the active faults of Tehran like Mosha and North-Tehran, as well as the service of the line to a large residential and industrial area, which, in case of damage by an earthquake, will cause considerable direct and indirect loss to the society. In the three-dimensional models... 

Adobe structures are considered as masonry structures which are out of scope of 2800 Iranian code. Due to this code, since these structures are made of weak materials, they do not have a considerable resistance to earthquakes. Since these structures can be found all around Iran; therefore, seismic study of walls as an important component of these structures, is, indeed, necessary. During this study, cyclic tests on three types of adobe walls, without opening, with window-opening, and with door-and-window-opening with a scale of 2:3 were done to study their in-plane behavior and also their failure modes. Based on our observations, in these walls, because of small ratio of height to length,... 

In the ongoing research project on tall buildings, the study of wind-induced demands is categorized as: along-wind and crosswind responses. These demands are caused by different mechanisms. Moving along the wind-induced is due to the effects of turbulence impact while the perpendicular component is related to the effects of windstorm. Along-wind response may be of special importance with respect to the comfort criteria. The loading condition on skyscrapers may differ from low-rise buildings due to the number of stories, on structures due to the high number of stories, and the importance of dynamic effects of current loading (wind). On the other hand the effect of wind load on tall structures... 

Tall buildings with lightweight and low damping are vulnerable under wind load. The wind loads stimulate tall buildings in the alongwind and acrosswind direction so the wind loads should be considered in addition to the earthquake loads. Wind tunnel testing is one of the empirical testing that used to study the behavior of tall buildings under wind load besides the simulation of turbulence components of the wind field is one of the issues that have been studied by researchers. In this research we have simulated two models of tall building with different side ratio and we have surveyed wind and earthquake loads in the different loading conditions. The models have been analysis in both time... 

Seismic isolation is a method for seismic-resistant design of structures against earthquake and is one of the important control of structures technologies. Codification and publishing of codes for design of seismic isolation takes place widely since 1980s and this codification has undergone extensive evolutions during its developing process. In this project initially the developing process and fundamentals of codifying regulations of seismic design have been investigated and then the developing process of codifying regulations of seismic isolation in current important international codes like ASCE7-05, Eurocode 8, and Japanese code has also been considered. After considering these two... 

Crack detection is a critical task in monitoring and inspection of civil engineering structures. This study proposes a deep-learning-based model for automatic crack detection on the concrete surface. The proposed model is an encoder-decoder model which uses EfficientNetB7, the state-of-the-art convolutional neural network, as encoder and the U Net’s expansion path as decoder. To minimize the training time and maximizing the accuracy, we use transfer learning in our approach. We train our model with a novel training strategy on images from an open-source dataset and achieve 96.44% F1-score for unseen test data. To compare the performance of the proposed method, we evaluate our model on CFD... 

In some activities, an almost free of any vibration environment is needed. Semi conductor production process and microelectronic microscopes are two examples in which a quiet environment is essential. The goal of this thesis is to attenuate ambient vibrations effectively and to prepare a suitable environment for two microelectronic microscopes. The designed system must be practical, economical and capable of being made in a short time interval. Considering mentioned properties a steel table with bolt connections supported on 4 air springs was built. To investigate dynamic properties, modal analysis was performed with the aid of finite element packages and experiments. To extract oscillations... 

Earthquake motions are among random excitation loads. For that we used random vibration approach to estimate response of multi-degree of freedom base isolated structures under ground excitation. Some models including linear model ,nonlinear Bouc-Wen and BBW models are studied for modeling the superstructure .Several base isolation models including the laminated rubber bearing, high damping laminated rubber bearing ,resilient-friction base isolator with or without sliding upper plate and the Electricity de France system, are studied . El Centro 1940 and Mexico City 1985 earthquake which preserve the nonstationary evolutions of amplitude and frequency content of ground accelerations... 

Nowadays, base isolation technique is widely used in the old and new structures, so it is necessary to assess the seismic performance of base-isolated buildings probabilistically, it is also essential to assess their performance during near-source versus far-field earthquakes.
Developing the fragility curves is useful probabilistic method for the seismic assessment of structures. These curves define the probability of exceedance of different damage states for a given level of seismic intensity parameter. Former investigations has been done to assess the seismic behavior of base isolation systems consider base isolated highway bridge piers.
In this thesis fragility curves are derived... 

Investigation of the dynamic characteristics of an existing structure system based on field tests is of practical significance, since it can be employed in the field of examining construction quality, validating or improving analytical finite element structural models, or conducting damage assessment. The main purpose of this study is to investigate the dynamic characteristics of dams using the seismic response data. Whereas, in the process of frequency domain identification of dam properties, frequency response function (FRF) plays the most important role, evaluating the corresponding parameters with better accuracy has always been desirable. Therefore, a comparison was made between some... 

This thesis contains experimental studies on mechanical properties of adobe and mud material and investigating seismic performance of a conventional adobe house using shake table tests. Mechanical properties of adobe and mud material were studied experimentally based on ASTM and BS standard tests. These experiments were designed to evaluate compressive strength of adobe sun-dried blocks and mud mortar cubes. Besides, shear behavior and tensile bond strength of adobe assemblages were under consideration and shear tests were done on adobe panels. As next part of the research, several shaking table tests were conducted on a dome-roof adobe house as a conventional representative of arch-roof... 

Statistical studies indicate the fact that in Iran, like many other developing countries, a significant percentage of buildings are made of traditional materials and most of them are adobe buildings especially in rural areas. Furthermore, geological data indicates that Iran is located in alps-Himalayas seismic zone and exposed by destructive earthquakes and adobe buildings suffer the most damages comparing with other type of the structures. According to these explanations, this research deals with adobe buildings behavior and provides solutions for reinforcing them and improving the seismic response of these buildings. These studies include numerical modeling with finite elements methods by... 

This thesis is concerned with the performance of heavy equipments like electric substation transformers and bushings under earthquake loading. It begins with the description of the transformers, attached bushings, and some typical examples of substation failures in earthquake loading. This is followed by the field test and development of numerical models of transformer and two different types of seismic isolations, Natural rubber bearings (NRB) and high damping rubber bearings (HDRB) and in order to find the appropriate isolator, responses of fixed base and isolated transformers are compared. Important observations were made on the seismic responses of the transformer and its bushing....