Pounding between adjacent buildings is a detrimental issue for buildings in cities because they are closely located while vibrating out of phase due to different dynamic properties (mainly different mass and/or height) during Earthquake excitation. This paper presents a numerical study on the pounding between the adjacent buildings with different masses during Earthquake excitation. The buildings modeled via lumped mass procedure are connected by linear vico-elastic contact force model during pounding. Seismic responses of the buildings due to Earthquake acceleration are obtained for different building configurations and the results are discussed and compared. Pounding effect is amplified for the lighter building while pounding effect is negligible for the heavier building.

In this paper the control algorithm for controlled civil structures subjected to Earthquake excitation isthoroughly investigated. The structural control consists of monitoring and analyzing the incomingexcitation signal and the response of structure, applying the control algorithm for the calculation of therequired control action, and, finally, implementing this action to the structure. The objective of this work isthe control of structures by means of the pole placement algorithm, in order to improve their responseagainst Earthquake actions. The pole placement or pole assignment algorithm is a well-known, classicalcontrol algorithm that estimates the feedback matrix so that the system will have poles (eigenvalues) thatare pre-decided by the designer. Successful application of the algorithm requires judicious placement of theclosed-loop eigenvalues from the part of the designer. The pole placement algorithm was widely applied tocontrol mechanical systems. In this paper, a modification in the mathematical background of the algorithmin order to be suitable for civil fixed structures is primarily presented. The proposed approach isdemonstrated by numerical simulations for the control of both single and multi-degree of freedom systemssubjected to seismic actions. Numerical results have shown that the control algorithm is efficient inreducing the response of building structures, with small amount of required control forces.

Worldwide networks of seismic recording instruments mostly record only translational ground motion in two or three orthogonal directions. Rotational component of Earthquake is not commonly recorded. Several theories are available to estimate a torsional component from recorded translational components of ground motion. In this paper detailed investigations are made to study the relative performance of some available methods. This paper suggests practical approach for obtaining true SH component from two recorded horizontal components of ground excitation. This new approach will help to obtain optimum torsional time histories from translational time histories.

An effective method for the damage diagnosis of structures under seismic excitation via discrete wavelet transform is proposed in this paper. The proposed method is based on the detection of abrupt changes in seismic vibration responses by the analysis of displacement or velocity responses using wavelet analysis. Also, a wavelet-based method is presented for denoising of displacement and velocity responses for the damage detection problem. The performance of the proposed method for de-noising and damage detection has been investigated using a benchmark problem provided by the IASC-ASCE Task Group on Structural Health Monitoring and a simulated shear wall model. The obtained results indicate that the proposed method can be provided useful information for the damage occurrence using the seismic response of structures.

In this article at first the wavelet theory is described that if s advantages are informations about the location of frequencies content in the time domain, determining noises and denoising them from raw dataor process, knowing about distributaries of energy of signal at time-frequency space,... which can be used for fast computation and relatively exact analysis of structures. In following for a SDOF system of vibrationa relationship between input wavelet coefficient and output (response) wavelet coefficient is provided. So with input wavelet coefficient before exact analysis the response or excited modes of vibration of MDOF systems can be determinate and by facilities of wavelet transform, the response of system with denoising that cause lower memory occupation or how energy of process is distributed around specific scales, fast computation can be done. At the end, for demonstration of the true and accuracy of this method some examples are solved. It is nicely recommend that this method can be provided and adapted for MDOF system of vibration.

Seismic pounding occurs as a result of lateral vibration and insufficient separation distance between two adjacent structures during Earthquake excitation. This research aims to evaluate the stochastic behavior of adjacent structures with equal heights under Earthquake-induced pounding. For this purpose, many stochastic analyses through comprehensive numerical simulations are carried out. About 4. 65 million time-history analyses were carried out over the considered models within OpenSees software framework. Various separation distances effects are also studied. The response of considered structures is obtained by means of Hertzdamp contact element. The models have been excited using 25 Earthquake records with different peak ground accelerations. The probability of collision between neighboring structures has been evaluated. An efficient combination of analytical and simulation techniques is used for the calculation of the separation distance under the assumptions of non-linear elasto-plastic behavior for the structures. The results obtained through Monte Carlo simulations show that use of the current provision’ s rule may significantly overestimate or underestimate the required separation distance, depending on the natural vibration periods of adjacent buildings. Moreover, based on the results, a formula is developed for stochastic assessment of required separation distance.

Structural damage identification can be considered as the main step in Structural Health Monitoring (SHM). There are many different methods which use structural dynamic responses for damage prognosis. Although some of them are concentrated on solving an inverse problem for damage identification, others suggest a direct procedure for defect detection. Despite the good performance of these methods in damage identification, researchers are attempting to find efficient and simple methods for damage identification with high level of accuracy. This paper presents a reference-free method for structural damage identification under Earthquake excitation. Damages are defined by some changes in the special instants during an Earthquake occurrence, and structural time history responses are used as an input signal for discrete wavelet analysis. Finally the “detail coefficients” are inspected for determination of the damage characteristics including the appearance, the time sequence, and the location of damage(s). Although the peak values in the detail coefficients can show the existence and time sequence of damage, these peak values must be inspected for determining the damage location and finding the maximum value. As a result, the element associated with a signal which has the maximum peak value, can be considered as the damaged element. Applicability of the presented method is demonstrated by studying three numerical examples. The first is devoted to damage identification in a four-story shear frame. It is assumed that all of the stories are equipped by sensors for recording structural responses. Three different damage scenarios with single and multiple damage cases are studied under two samples of Earthquake records, namely El-Centro (1940), and Northridge (1994) Earthquakes. In addition, the effects of using different wavelet mother functions and different input signals, such as displacement and velocity responses, are investigated in this research. Obtained results emphasize on the applicability of the presented method in damage identification. In the second example, a simple concrete beam is considered with ten elements for simulating two different damage scenarios. In this case, applicability of the method is inspected by considering only the transitional degrees of freedom (DOF) as the equipped DOFs by sensors. This can be interpreted as using limited number of sensors. In addition, the displacement time histories are used for damage identification. In order to reach a clear strategy in damage localization, two rules are proposed for judging about elements’ health. The rules are based on seeking maximum values of the wavelet coefficients in the damaged instants. Obtained results show the reliable performance of the presented method in finding time sequence of damage occurrence and damage location. In the third example, applicability of the presented method is investigated in the presence of complex damage models by defining bilinear stiffness reduction. Although the damage can cause some reduction in the effective stiffness of damaged structures of this case, the reduction is different in positive and negative displacements. Two different damage scenarios are simulated on a single DOF structure under different excitations, namely Earthquake excitations and generated White Noise excitation. Obtained results reveal the robustness of the presented method in damage prognosis in the presence of complex damage models.

In the present paper, the improved sliding mode control algorithm are presented. This strategy is based on the combination of sliding mode control and Bang-Bang control theory. The Bang-Bang theory can switch abruptly between the on and off situation, this property can improve the performance of sliding mode control strategy. Also, three thresholds used to decrease the time of using the control system and optimizing the responses of structure.

Arch bridges have been commonly used in high-seismicity regions of the world, as a result of which notable damage has been documented in several arch bridges during past Earthquakes. Certain aspects of seismic behavior of arch bridges are different from those in typical slab-on-girder bridges, including the significance of axial loads, sizable differences between in-plane and out-of-plane stiffness, and the use of piers with different heights. However, limited previous studies have addressed the seismic behavior of concrete arch bridges. In the present study, the effects of Earthquake incidence angle and asynchronous support excitation on reinforced concrete arch bridges are investigated. Nonlinear 3-D models of four existing reinforced concrete deck-type arch bridges in Iran were developed. The bridges had arch spans of 23, 35, 45 and 50 meters and were subjected to nonlinear time history analyses using seven acceleration records. The incidence angle was changed in 15 degrees increment between 0 and 90 degrees. Moreover, the effect of asynchronous support excitation was investigated by means of introducing a time delay between excitation input for different supports. The relative displacement (drift) of the piers, the curvature ductility demands within the piers, the curvature ductility demand at different locations of the arch, and the displacement of the deck at the abutments (unseating) were used as damage indicators. The results showed that unseating of the bridge deck from abutments and pier drifts were the most and the least sensitive damage parameter to the change in incidence angle, respectively. The axial force at the end points of the arch was found to change significantly during Earthquake, with a maximum of 40 percent in case of 90-degree incidence angle. The effect of asynchronous support excitations was relatively small, with a maximum increase of 10 percent in damage indicators and 5 percent in the axial forces and bending moments.