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This paper proposed a swift multi-objective optimization algorithm for the performance-based design of steel moment-resisting frame (MRF) buildings considering life-cycle cost (LCC). Two components of the life-cycle cost, including the initial construction cost and the lifetime seismic damage cost of the building, are considered as two separate objectives of the optimization problem and are minimized simultaneously using the proposed algorithm. The proposed algorithm called Multi-objective Uniform Damage Optimization (MUDO) is an adaptive method that utilizes the concept of uniform damage (deformation) theory. MUDO leads to design alternatives for the building that are optimal (minimum) for both mentioned objectives. These alternatives, called Pareto optimal designs, allow decision-makers to choose the optimal investment option according to the project goals and by the trade-off between optimization objectives. The proposed algorithm is used to optimize three steel MRF buildings with 3, 6, and 9 stories. The lifetime seismic damage cost is calculated by assessing seismic losses at several ground motion intensities and using a probabilistic approach presented in HAZUS. A Monte Carlo analysis is used in this research to account for inherent uncertainties in structural response. The results demonstrate that MUDO can find competitive Pareto optimal designs in a much shorter time compared to a well-known metaheuristic algorithm called non-dominated sorting genetic algorithm II (NSGA-II).

Concrete bridge piers are vulnerable to strong ground motions because of inducing significant residual drifts, which reduce the seismic resilience of bridges. A broad range of mitigation techniques is presented in the literature to reduce the vulnerability of bridge piers located in high seismic zones. Hybrid reinforced concrete piers are the most popular techniques to improve the seismic resilience of highway bridges. In addition, posttensioned segmental bridge piers are proposed as an alternative to expedite the construction procedure and also meliorate the performance of bridges in terms of residual deformations. However, very limited studies investigated the seismic performance of a whole bridge, especially for the purpose of comparing seismic resilience of the bridge columns. In this paper, a comparative study is implemented to explore the seismic vulnerability of a bridge reinforced with a hybrid configuration (i.e. combination of shape memory alloys (SMA) and normal-strength bars, and combination of high-strength and normal-strength bars) as compared to a reference conventional pier, which fully reinforced by normal-strength rebars. Moreover, a posttensioned segmental pier is considered to evaluate the strength and self-centering ability of this pier as compared to the monolithic ones. To do so, a 2D bridge model is developed in OpenSees simulation platform. Fragility curves are developed to assess the seismic vulnerability of the bridge model constructed with different piers. In this regard, a suite of 20 near-fault earthquake motions are applied to the bridge through Incremental Dynamic Analysis (IDA). Each of these records is scaled to 15 Peak Ground Accelerations (PGAs) ranging from 0.1 g to 1.5 g . The fragility curves reveal the chance of failure for each bridge model and aid in determining the impact of each pier on the seismic vulnerability of the bridge.

Investigating the economic consequences of the natural hazards on the infrastructures is a crucial task in any risk-based decision-making process. Life-cycle cost (LCC) analysis is an important too...

It is so important to consider the passive defense problem in any places there have been attacks by varies kinds of military threats and terrorists. It is certain that social security is related to overcoming on these perils and protection from country. Vital facilities are one of examples that should be protected. Vital facilities include roads, bridges, transmission lines, and telecom and media network. With attention to the intense dependent to export and transmit of oil and gas and with consideration of this point that many places are full of gas and oil resource, the protection of these lines is very important. In recent years, occurrence of varies kinds of terrorist accidents in relation to important structures in all the world causes that the explosion loads have special attention. Explosion can generate much damage with vibration in vast soil media. Thus, it is important to predict the dynamic impact load and its treatment response. With attention to regardable development of numerical methods in recent decades, it is possible to investigate the explosion effects on surface and underground structures. In this research, the newest applied method modeling of the explosion phenomenon has been investigated and comprehensive information has been earned. In this investigation, problem of explosion wave’s propagation effects on buried pipes simulated by ABAQUS/CAE 6.10-1 was studied based on the finite element method. Surface explosion effects on gas buried pipe lines and their dynamic response have been investigated depending on properties and their characteristics. The variation of buried pipe depth effects and variation effects in soil properties around pipe in different cases has been considered, and the results are here. The results showed that in buried pipes under surface explosions, displacements, major stresses, and strains decrease in clay, dense, and loose sands with increase of buried depth. These results obtain that because of increase of closuring of pipes in soil when internal friction angle increases for a kind of soil, the stress on pipe rim will decrease also. It was also observed that the pipe performance in clay and loose sands is better than that in compacted sand, respectively.

Dams are essential infrastructures as they provide a range of economic, environmental, and social benefits to the local populations. Damage in the body of these structures may lead to an irreparable disaster. This paper presents a cost-effective vibration-based framework to identify the dynamic properties and damage of the dams. To this end, four commonly occurred damage scenarios, including (1) damage in the neck of the dam, (2) damage in the toe of the structure, (3) simultaneous damage in the neck and the toe of the dam, and (4) damage in the lifting joints of the dam, are considered. The proposed method is based on processing the acceleration response of a gravity dam under ambient excitations. First, the random decrement technique (RDT) is applied to determine the free-vibration of the structure using the structural response. Then, a combined method based on Hilbert–Huang Transform (HHT) and Wavelet Transform (WT) is presented to obtain the dynamic properties of the structure. Next, the cubic-spline technique is used to make the mode shapes differentiable. Finally, Continuous Wavelet Transform (CWT) is applied to the residual values of mode shape curvatures between intact and damaged structures to estimate the damage location. In order to evaluate the efficiency of the proposed method in field condition, 10% noise is added to the structural response. Results show promising accuracy in estimating the location of damage even when the structure is subjected to simultaneous damage in different locations.

Several studies on steel plate shear wall systems have shown that the seismic demand on the vertical boundary elements is extremely large for typical buildings. To overcome this problem, an enhanced approach is introduced in this paper. It involves utilizing not only a modular steel shear panel, but also contains column-independent boundary element which eventually facilitates retrofitting of the existing building. First, a four-story building was designed based on pushover analysis, followed by more accurate finite element analysis to refine the section design parameters. Next, a full scale single-story modular steel shear panel welded to the steel boundary elements was constructed and tested under cyclic load protocol to simulate the hysteresis behavior under severe excitations. The test results show a high initial stiffness, excellent ductility, and significant energy dissipation capacity. Observed failure modes were discussed.

As a destructive phenomenon in most parts of the world, earthquake has threatened the safety of structures and the lives of its inhabitants and is considered as the main problem in the seismic vulnerability of buildings. Steel shear walls are regarded as one of the newest structural systems resistant to lateral load in steel structures. The present study aimed to investigate the impact of effective parameters on cyclic behavior by numerically modeling a steel shear wall and comparing it with laboratory results. The results indicated the significant contribution of the thickness of steel shear sheet so that when the thickness changes to 25%, the final response of the structure increased by approximately 20% and decreased by 15%.

This paper investigates the effects of various demand parameters involved in the optimal performance-based design of steel moment frame buildings. These parameters include the peak values of story drift ratio, floor velocity, floor acceleration, and residual drift ratio. The performance-based design is performed to minimize two conflicting objectives, including the initial construction cost and the expected annual repair cost of the building under the design constraints. FEMA P-58 is utilized as a comprehensive and popular methodology for seismic risk assessment and building loss estimation in this paper. It evaluates the building performance in a probabilistic manner in terms of several metrics such as repair cost, repair time, carbon emissions, embodied energy, injuries, and fatalities. The Monte Carlo analysis is used to consider various uncertainties affecting seismic performance. A set of three steel moment-resisting frame (MRF) buildings representative of low-to mid-rise frames are selected as a case study in this research. The results of this study indicate that the story drift ratio has a major role in the performance-based optimal design of steel MRFs. Accordingly, despite increasing the two parameters of floor acceleration and floor velocity due to increasing the initial cost of structural moment frames, the annual repair cost of the building decreases when the story drift ratio decreases.

The equivalent statistical methods, spectral analysis, and time history analysis are usually offered in the steel structure design regulations. Among these methods, the third one is more accurate; however, it requires more time to align the accelerometers due to a large number of analyses. In the endurance time (ET) method, incremental acceleration functions gradually and uniformly increases over time while their linear and nonlinear response spectra are proportional to the mean of the real seismic spectrum. These functions are used as input functions to analyze the nonlinear time history of structures, and the performance of structures is evaluated based on the maximum length of time they can meet specified performance goals. A three-story steel bending frame with (slotted web) SW and (web unslotted flange) WUF connection is examined through the performance time method in performance-based design. This article aimed at evaluating the seismic performance of these connections in the bending frame through endurance time analysis to predict the structural response in the probabilistic evaluation of the seismic performance of the structures. It is found that the endurance time analysis is justified with the seismic performance of the connections with low computational cost and proper accuracy. The results of comparing both SW and WUF connections indicated that the SW connection prevents the connection welding area from being failed due to transferring the plastic joint into the beam and in an area away from the column face and causes less damage compared to the WUF connection.

Segmental precast post-tensioned bridge piers are one of the latest options for accelerated bridge construction. However, their application in seismic zones is limited due to the low energy dissipation observed in such piers and a lack of research. This paper reports on the construction and testing of a half-scale model pier equipped with an innovative external energy dissipation device. A combination of lead and steel plates were used in the segment joints to improve energy dissipation. The hysteresis behaviour, dissipated energy, effective stiffness and equivalent viscous damping for several consecutive cycles of loading were obtained. Furthermore, the hysteresis behaviour of the pier was modelled using numerical methods. The energy dissipation device was found to increase the energy dissipation capability of the pier by up to 30% at high drifts (more than 3%) while reducing damage criteria and residual displacement at the end of the test.

In this paper, a new algorithm is proposed to multi-objective optimum seismic design of steel moment frames. This algorithm is based on the uniform damage (also known as uniform deformation) theory and so-called multi-objective uniform damage optimization (MUDO). MUDO is a swift algorithm formulated according to a bi-objective approach. Structural weight and maximum interstory drift ratio (IDR) are treated as two conflicting objectives representing economy and safety measures, respectively, and they are minimized simultaneously subject to a set of design constraints. To achieve the optimal Pareto front , MUDO tries to create a uniform distribution of story drifts in the structure and bring it to a target value that gradually varies from the low (minimum damage) to high (maximum damage). In this way, the algorithm obtains a set of optimal solutions in terms of structural weight at different damage levels, which is the Pareto front. To demonstrate the efficiency and robustness of the proposed algorithm, its results for 3-, 6- and 9-story steel moment frames are compared with those of two well-known multi-objective optimization algorithms, NSGA-II and MOPSO. Results indicate that MUDO can achieve better optimal solutions set in a much less computational time than the other two methods.

Braces are one of the retrofitting systems of structure under earthquake loading. Buckling restrained braces (BRBs) are one of the very efficient braces for lateral loads. One of the key needs for a desirable and acceptable behavior of bucklingrestraining brace members under intensive loading is that it prevents total buckling until the bracing member tolerates enough plastic deformation and ductility. This paper presents the results of a set of analysis by finite element method on buckling restrained braces in which the filler materials within the restraining member have been removed. These braces contain core as the conventional BRBs, but they have a different buckling restrained system. The purpose of this analysis is conducting a parametric study on various empty spaces between core and restraining member, the effect of friction between core and restraining member and applying initial deformation to brace system to investigate the global buckling behavior of these braces. The results of analysis indicate that the flexural stiffness of restraining member, regardless of the amount of empty space, can influence the global buckling behavior of brace significantly.

The use of superelastic shape memory alloys (SMAs) as reinforcements in concrete structures is gradually gaining interest among researchers. Because of different mechanical properties of SMAs compared to the regular steel bars, the use of SMAs as reinforcement in the concrete may change the response of structures under seismic loads. In this study, the effect of SMAs as reinforcement in concrete structures is analytically investigated for 3-, 6- and 8-story reinforced concrete (RC) buildings. For each concrete building, three different reinforcement details are considered: (1) steel reinforcement (Steel) only, (2) SMA bar used in the plastic hinge region of the beams and steel bar in other regions (Steel-SMA), and (3), beams fully reinforced with SMA bar (SMA) and steel bar in other regions. For each case, columns are reinforced with steel bar. Incremental Dynamic Analyses (IDA) are performed using ten different ground motion records to determine the seismic performance of Steel, Steel-SMA and SMA RC buildings. Then fragility curves for each type of RC building by using IDA results for IO, LS and CP performance levels are calculated. Results obtained from the analyses indicate that 3-story frames have approximately the same spectral acceleration corresponding with failure of frames, but in the cases of 6 and 8-story frames, the spectral acceleration is higher in frames equipped with steel reinforcements. Furthermore, the probability of fragility in all frames increases by the building height for all performance levels. Finally, economic evaluation of the three systems are compared.

Steel systems composed of Reinforced Concrete column to Steel beam connection (RCS) have been raised as a structural system in the past few years. The optimized combination of steel-concrete structural elements has the advantages of both systems. Through beam and through column connections are two main categories in RCS systems. This study includes finite-element analyses of mentioned connection to investigate the seismic performance of RCS connections. The finite element model using ABAQUS software has been verified with experimental results of a through beam type connection tested in Taiwan in 2005. According to verified finite element model a parametric study has been carried out on five RCS frames with different types of lateral restraint system. The main objective of this study is to investigate the forming of plastic hinges, distribution of stresses, ductility and stiffness of these models. The results of current research showed good performance of composite systems including concrete column-steel beam in combination with steel shear wall and bracing system, are very desirable. The results show that the linear stiffness of models with X bracing and steel shear wall increase remarkably and their ultimate strength increase about three times rather than other RCS frames.

This article presents a vibration-based technique for damage detection in the cylindrical equipment. First, a damage index based on the residual frequency responses is defined. This technique uses the principal component analysis for data reduction by eliminating the components that have the minimum contribution to the damage index. Then, the principal components are fed into neural networks to identify the changes in the damage pattern. Furthermore, the efficiency of this technique in the field condition is investigated by adding different noise levels to the output data. This study aims at proposing a cost-effective damage detection model using only one sensor. Therefore, the optimal location of the sensor is also discussed. A case study of capacitive voltage transformer is used for validation of finite element models. The neural networks are trained using numerical data and tested with experimental one. Several parametric analyses are performed to investigate the sensitivity of the model.

Pile-supported wharves, as one of the main components in marine harbor systems, are subjected to multiple hazards such as earthquakes and corrosion during their lifetime. In this paper, the corrosion initiation time due to chloride ion diffusion (using both the deterministic and probabilistic approaches), temperature and humidity variations are calculated for various steel materials in the typical pile-supported wharf of port Los Angeles. Various deterioration sources such as reduction in the ultimate strength and strain of prestressed strands and concrete compressive strength are simulated. The updating limit state functions are identified by nonlinear static analysis. Finally, the time-dependent fragility curves are developed using incremental dynamic analysis. Results show that corrosion considerably reduces the seismic performance due to both structural strength and ductility over the life cycle of the wharf. It also causes brittle fracture, a sudden and complete failure of the corroded piles towards the end of the structure’s life cycle. Finally, a set of analytical models is proposed to estimate the median of the aging fragility functions with a nearly constant dispersion.

An improved direct displacement design procedure is proposed for frictional damping based structural systems. The system is composed of beams and columns which are connected by simple connections and bracing members equipped with frictional dampers. It is shown that under the seismic loading no material yielding occurs in the structure, no component replacement is needed and the repair operation only involves re-centering of the dampers. Using the proposed design procedure, the slippage loads of the dampers are chosen such that the target displacement is satisfied. This method is used to design several structures with different heights. Non-linear transient analysis is performed to evaluate the applicability of the proposed methodology. Results show that all the case studies satisfy the intended performance objectives.

The progressive collapse phenomenon in structures has been interested by civil engineers and the building standards organizations. This is particularly true for the tall and special buildings ever since local collapse of the Ronan Point tower in UK in 1968. When initial or secondary defects of main load carrying elements, overloads or unpredicted loads occur in the structure, a local collapse may be arise that could be distributed through entire structure and cause global collapse. One is not able to prevent the reason of failure as well as the prevention of propagation of the collapse. Also, one is not able to predict the start point of collapse. Therefore we should generalize design guides to whole or the part of structure based on the risk analysis and use of load carrying elements removal scenario. There are some new guides and criteria for elements and connections to be designed to resist progressive collapse. In this paper, codes and recommendations by various researchers are presented, classified and compared for steel structures. Two current design methods are described in this paper and some retrofitting methods are summarized. Finally a steel building with special moment resistant frame is analyzed as a case study based on two standards guidelines. This includes consideration of codes recommendations. It is shown that progressive collapse potential of the building depends on the removal scenario selection and type of analysis. Different results are obtained based on two guidelines.

This study presents a technique to identify the vibration characteristics in power transmission towers and to detect the potential structural damages. This method is based on the curvature of the mode shapes coupled with a continuous wavelet transform. The elaborated numerical method is based on signal processing of the output that resulted from ambient vibration. This technique benefits from a limited number of sensors, which makes it a cost-effective approach compared to others. The optimal spatial location for these sensors is obtained by the minimization of the non-diagonal entries in the modal assurance criterion (MAC) matrix. The Hilbert–Huang transform was also used to identify the dynamic anatomy of the structure. In order to simulate the realistic condition of the measured structural response in the field condition, a 10% noise is added to the response of the numerical model. Four damage scenarios were considered, and the potential damages were identified using wavelet transform on the difference of mode shapes curvature in the intact and damaged towers. Results show a promising accuracy considering the small number of applied sensors. This study proposes a low-cost and feasible technique for structural health monitoring.

This work evaluates the stability of the Boostan earth dam by investigating its long-term performance and interpreting the measured data. To measure the dam response, several sensitive locations are instrumented. This process includes measuring various quantities such as pore water pressure, water level, and internal stress ratios using inspection devices such as ordinary and Casagrande piezometers, and total pressure cells. The recorded data shows that the pore pressure is in good agreement with the initial (stable) design condition. The installed piezometers show that the drainage is efficient, and the water table in the body is adequate. The instrument also shows a reasonable horizontal stress in the dam body. Overall, the condition of the case study dam is assessed to be normal. The results of this case report can be used as a guide in similar dams for instrumented health monitoring.

This article aims to identify the dynamic characteristics (natural frequency in particular) of existing buildings by experimental methods, and then, to compare the results with those reflected by several code provisions and numerical analyses. To this end, ambient vibration tests were carried out on 40 existing concrete and steel buildings in order to obtain the natural frequency of such buildings. The results were then investigated as compared with those arising from several codes and standards, and also with those obtained from numerical analyses. It can be shown in this study that the test results are significantly different from those calculated based on the codes and standards. Moreover, the effect of in-fill walls on the fundamental natural frequency of such buildings is shown. The findings of this research can be used for model calibration and revision of the existing legislations.

In this paper, the concept of a semi active frictional damper called Adjustable Frictional Damper (AFD) is introduced. The clamping force of such damper is secured by hydraulic pressure, which not only reduces the manufacturing costs but also makes it possible to control the seismic response of the structure by changing the clamping force of the dampers. The hysteretic behavior of AFD is studied by experimental means as well as by numerical model. Experimental process involves tests with various hydraulic pressures (which cause various frictional forces) at nearly static loading as well as dynamic loading with various frequencies. The results show that the proposed damper has significant energy absorption by stable hysteretic loops, which can be used for enhancement of the performance of structures subjected to earthquake loads with various intensities. Force–displacement characteristics of AFD such as slippage load, dissipated energy, effective stiffness and equivalent viscous damping for consecutive cycles of loading is calculated. The system is qualified based on the requirements for displacement-dependent devices according to ASCE/SEI 41-06 specification. Furthermore, the hysteretic behavior of AFD is studied by numerical method and a close agreement between the experimental and numerical results is observed.

Structural frames with masonry infill panels make up a significant portion of the buildings constructed in earthquake-prone areas prior to the developing of the seismic design standards. In this paper, the effects of masonry panels on the vibration response of an infilled steel-frame building are investigated. Various ambient and steady state forced vibration tests are carried out to realize the dynamic characteristics of the system. 3D finite element models of the building with and without infill panels are provided based on marcomodeling theorem. A set of analytical approximate formulas are also derived to estimate the vibrational period. The natural frequencies of the building are computed using numerical, analytical, and experimental methods. The results show that neglecting the effect of infill panels leads to considerable error. Moreover, it is shown that there is good agreement among the results obtained by the three methods considering the effect of infill panels.

New approximate formulas are proposed to determine the natural frequencies of structures considering the effects of panel zone flexibility and soil-structure interaction. Several structures with various earthquake resisting systems are idealized as prismatic cantilever flexural-shear beams. Floor masses are considered as lumped masses at each story level and masses of columns are evenly distributed along the cantilever beam. Soil-structure interaction is considered as axial and rotational springs, whose potential energy are formulated and incorporated into overall potential energy of the structure. Subsequently, natural frequency equations are derived on the basis of energy conservation principle. The effect of axial forces on natural frequency is also considered in the proposed formulas. Using the method presented in this study, natural frequencies are computed using a simplified method with no complex numerical modeling. The proposed formulas are verified via experimental and numerical methods. Close agreement between the results from these three approaches are observed. Furthermore, the effects of panel zone flexibility, continuity plates and doubler plates on the natural frequencies of buildings are investigated.

Comparative studies on seismic performance for various types of steel moment resisting frames subjected to near field and far field earthquakes are performed through Incremental dynamic analysis (IDA) method in this study. Near field earthquake has a pulse like effects on the structures. It imports immediate force in very short duration to buildings. Therefore, destructive effects of surge energy are not negligible. Four intensity indices are used, namely, peak acceleration (PGA), spectral acceleration at the structure’s first-mode period (Sa(T1, 5%)), spectral acceleration at the structure’s nth effective-mode period (Sa(Tn, 5%)) and the Spectral velocity at the structure’s first-mode period (Sv(T1, 5%)). Numerical results illustrate that the intensity measure parameters related to ground velocity and the higher mode-related parameters present better correlation with the seismic responses of near source ground motion for given systems. The higher mode-related parameters are more suitable for tall systems subjected to near field earthquakes. Moreover, the chosen parameters Sa(Tn, 5%) and Sv(T1, 5%) of near-fault impulsive ground motions enhance the performance of intensity measure of corresponding conventional parameters, i.e. Sa(T1, 5%). A comparison for the special and intermediate steel moment resisting frames is made as regard to performance using IDA method. A more efficient performance is observed for the special moment resisting frames compare to intermediate ones.

The design of structures to withstand seismic loading is primarily governed by horizontal ground motion, and the effects of vertical ground motion have long been deemed unimportant or secondary. However, an emerging body of evidence suggests that vertical ground motions have great destructive potential, especially for certain site conditions.Using nonlinear dynamic analyses, the seismic performance of frames is evaluated by simultaneously applying the horizontal and vertical components of earthquake motion. Three special moment frames are subjected to 15 recorded near-field earthquake motions and the results of the analyses are used for performance evaluations, based on FEMA 350 guideline. It is found that, within the elastic range of response, considering the vertical component of ground motion, does not alter the dynamic structural response significantly, however, some tangible differences emerge in nonlinear range of response once the horizontal component of ground motion is accompanied by the vertical component.