Scientia Iranica
Volume:29 Issue: 6, Nov-Dec 2022

In this paper, for the first time, the combination of these two concepts is used for the earthquake acceleration wave. For this purpose, eight earthquakes from four different locations in the world have been selected. Initially, each earthquake is filtered up to 5 stages using a discrete wavelet transform. Due to the close approximation of the frequency content of the wave to the original earthquake, the approximate wave is used for subsequent calculations. In the next stage, the spectrum of Fourier and the diagram of five of the frequency of dominant of the earthquake are plotted. Also, using the continuous wavelet transform, the time-frequency curves of the main earthquakes and the time-frequency curves of the wave obtained from the discrete wavelet transform are investigated. The goal is to find the best stage of a discrete wavelet filter based on frequency content to reduce computations to over 80%. In the next step, the study examines the time of the strong ground motion, the structure response of single degree of freedom, and the dynamical response of the timing of the structure of a degree of freedom. By examining the above parameters, the best-performing wavelet transformation step is inferred.

Vibration data analysis is an applicable approach to Structural Health Monitoring (SHM) using statistical pattern recognition. The objective of the paper is to identify the location of damage by a new feature extraction technique and propose some feature analysis tools as statistical distance measures. The proposed algorithm of feature extraction relies on a combination of the well-known Principal Component Analysis (PCA) and a convolution strategy. After extracting the features from raw vibration signals of undamaged and damaged conditions, those are applied to the proposed feature analysis approaches called the coefficient of variation, Fisher criterion, Fano factor formulated by using the features extracted from the PCA-convolution algorithm. To localize damage, the sensor location with the distance value exceeded from a threshold limit is identified as the damaged area. The main innovations of this research are to present a new hybrid technique of feature extraction suitable for SHM applications and four effective statistical measures for feature analysis and damage identification. The performance and reliability of the proposed methods are verified by a four-story building model and a benchmark beam. Results demonstrate that the approaches presented here can influentially identify the location of damage by using the features extracted from the proposed PCA.

Nowadays, construction activities and projects are becoming much more challenging and complex to handle. Being involve with different stakeholders is a difficult task and information and communication technology (ICT) has been addressed as a solution. Afterwards, there was a major shift in ICT usage for construction projects and furthermore, Building Information Modeling (BIM) has been found its position among the experts as a Computer Aided Design (CAD) paradigm. By inspiration from modality of BIM, there can be an adoption to other sub-branch of construction industry such as infrastructure domain. Since BIM has proven benefits in buildings, infrastructure projects might gain similar advantages through proper implementation. This new dimension can be called Infrastructure Building Information Modeling (I-BIM). The main aim of conducting this research is to identify and prove the existing lack of using BIM for infrastructure projects. In order to fulfill this gap, questionnaire survey designed and respondents were mostly located at United States of America and Turkey. As a finding, authors clarify the preponderance and impediment components in the path of I-BIM utilization and discuss five main categories with total number of 26 variables. Furthermore data mining among selected countries has been done for all variables with comprehensive discussion.

In present study, the dynamic analysis of concrete arch dam-reservoir systems is formulated by FE-(FE-TE) approach. In this technique, dam and reservoir are discretized by solid and fluid finite elements. Moreover, the GN high-order condition imposed at the reservoir truncation boundary. This task is formulated by employing a truncation element at that boundary. It is emphasized that reservoir far-field is excluded from the discretized model. The formulation is initially explained in details. Subsequently, the response of idealized Morrow Point arch dam-reservoir system is obtained for two fully reflective and absorptive reservoir bottom/sidewalls conditions for all three types of excitations. Different Orders of GN condition are considered and convergence process is evaluated. Furthermore, the results are compared against exact solutions which are based on rigorous FE-(FE-HE) approach. It is shown that the technique converges prior to beginning of instability problems which is known to exist for high orders in GN condition. It must be emphasized that although time harmonic analysis is considered in the present study, the main part of formulation is explained in the context of time domain. Therefore, the approach can easily be extended for transient type of analysis.

Loop connection for precast RC structural components using U-bars is advocated by researchers on the grounds of simple mechanism and strength. However, the system is difficult to materialize on-site, in the lieu of which U-bars may be replaced with steel wire ropes, which offer a more suitable system with regards to convenience during the installation process. However, literature lacks on design requirements and methodology for loop connection. Thus, a theoretical study was undertaken to formulate the design methodology for loop connection formed using steel wire ropes. The behaviour of loop connection is governed by tension and shear, influenced by characteristics of wire ropes, grout and vertical transverse bar. A design example is illustrated for loop connection between precast wall-column, whose validation is demonstrated through numerical analysis and performance compared with monolithic system and U-bar connection. The advantages of the research relates to the systematic design approach considering all the influencing parameters of steel wire loop connection for precast components. It is expected that the proposed design methodology will be useful to practising engineers for designing the loop connection for precast components.

Granular soil liquefaction, due to developed pore water pressure during undrained cyclic shear of saturated soils, is regarded as a common phenomenon under earthquakes loading. This phenomenon results in the huge damage to infrastructures. Various reinforcement materials have been successfully implemented with particular attention to use waste materials to satisfy design specifications and also reducing the adverse environmental effects. This paper investigates the possibility of using waste plastic fibers as a reinforcement material to mitigate liquefaction potential and pore pressure generation of reinforced sand under cyclic loading. For this purpose, 42 stress-controlled cyclic triaxial tests were conducted on Babolsar sand, reinforced by polyethylene terephthalate (PET) and polypropylene (PP) fibers with fiber contents of 0.25%, 0.5% and 1%, under confining pressures of 50, 100 and 200 kPa, and with cyclic stress ratios (CSR) of 0.2 and 0.35. Results revealed that the addition of these waste plastic fibers could significantly increase the liquefaction resistance of Babolsar sand, and also, with an increase in the waste content, the number of cycles leading to liquefaction increased. Adding wastes decreased the pore water pressure generation, and this effect was more pronounced with an increase in the waste content.

The success of embedded chaos in metaheuristic algorithms is mainly due to providing good balance between exploration and exploitation for metaheuristics. Comparison of optimization results with algorithms in standard mode and embedded of chaos shows a significant improvement in quality of the metaheuristic algorithms, thus reducing the weight of truss structures. Four chaos metaheuristic algorithms with logistic, Tenet and Gaussian maps are considered to improve the results. Despite truss optimization is severely nonlinear and non-convex, and often has several local optimizations, the use of different scenarios chaos allows the local optimizations to be escaped and global optimization to be achieved.

Thin walled cylindrical shells are being widely used as silos, liquid tanks, marine structures, and industrial chemical plants. In such applications, the shells are mostly exposed to liquids. When shells filled with low-pH-liquids, corrosion occurs at the surface. Corroded material loss, causes the thickness of the shells to decrease, and it reduces the buckling capacity of shells. The purpose of this study is to investigate the effects of corrosion on the buckling capacity of thin walled cylindrical shells subjected to uniform external pressure. The model shells were half or full filled with 5% and 10% HCl (Hydrochloric Acid) solutions for corrosion. To tolerate the negative effects of corrosion, the cylinders were coated with varying sizes of CFRP sheet. Totally 12 models were investigated throughout this research, with the dimensions of 800x400x0.45 mm (with and without CFRP). The perfect non-corroded models were used to compare the behavior of all the models. Results show that corrosion causes a significant decrease on the buckling capacity of thin walled cylindrical shells. Acid ratio, filling rate and surface area coated with CFRP fabrics affects the buckling capacity of cylinders. Coating the cylinders with one layer of CFRP resulted with tolerating the buckling capacity loss.

The present study investigates the blast effect on hoop stresses and displacements created on the wall of over-ground cylindrical reinforced concrete water storage tanks and the effect of blast waves, fluid surface motion, and the surface tension of water due to water-structure interaction using ABAQUS software. Three tanks with heights of 4, 6, and 8 m and a fixed radius of 3 m were used for simulation, each of which was filled with 0, 25, 50, 75, and 100% water from the depth of the tank. The results revealed that the above parameters affect the tank structure’s dynamic response so that the surface tension of water is higher in tanks with 50% water filling. Also, increasing the water filling percentage, the hardness of the tank increased and decreased the tank wall displacement by 31.25% for a filled tank compared to an empty tank. Water filling also reduced the sensitivity of tanks to instability. The results showed that the tank wall’s hoop stresses were affected by blast waves from the outside and water tension from the inside, so that the water tension in the tank caused an approximate 20 MPa increase in the hoop stresses on the wall.

Long-span structures like bridges experience different movements at the supports because of the wave-passage, incoherence, and site-response effects. In this study, spatially varying ground motions were used to evaluate the seismic vulnerability of different RC bridges. To gain the goal, three prototypes of Caltrans reinforced concrete curve bridges with different column heights and various radii were selected and used for the numerical study. The spatially correlated ground motions were generated by the conditional simulation method and then converted to corresponding displacements time histories to perform non-uniform excitations. The structures were analyzed under generated series and the fragility curves were developed based on the defined limit states. Furthermore, soil-structure interactions and different soil conditions were included in evaluating the non-linear behavior of the bridges. The results show that the damage exceedance probability increased under non-uniform excitations and it is more obvious for long-span bridges. Also, it is found that the effect of soil-structure interactions on the probability of failure of short-span bridges is negligible but for long-span bridges, the effect is significant. Moreover, it is obvious that for long-span structures situated on soft deposits, a combination of spatially varying ground motions in conjunction with soil-structure inter-actions remarkably increases the responses.

Freeze-thaw (F-T) cycles cause substantial detriment to geotechnical structures, especially roads, every year. Recently, researchers have increasingly used nanomaterials to improve soil resilience. This study evaluated the effect of soil stabilization by cement and nanocement on resistance changes subjected to F-Tcycles.For this purpose, clayey soil was combined with 1, 2, 3, and 4% stabilizers based on dry unit weight. Atterberg limits and standard compaction tests were performed on the prepared mixtures. The results showedthat increasing the stabilizers enhanced the optimum moisture content, liqid limit, and plastic limitwhile decreasingthe maximum dry density and plastic limit. Then, the cylindrical specimens of the pure and stabilized soilswere prepared and curedwithin 42 days. Finally, unconfined compressive strength(UCS) tests were conducted on the samples after applying zero, three, six, and nineF-T cycles. UCSin the stabilized soil increased to a value about12 times thatin the pure soil. The UCSvalue was reduced on average to 49%inthe pure soil specimens by applying nine F-T cycles, whichfurther decreased on averageto 36% and 31%after adding cement and nanocement, respectively. However, the lowest UCS value was observed in the stabilized soil specimens, reaching 26% and 19%in 42 daysafter applying nineF-T cyclesand adding 4% cement and nanocement, respectively.

Soil-structure interaction analysis is one of the most challenging problems in the field of structural engineering. In this paper, two aspects less discussed in the literature, namely: (ⅰ) the effect of considering all three components of near-field earthquake excitations instead of just one horizontal component, and (ⅱ) elimination of the part of inter-story drifts caused by the foundation rocking, have been investigated. Theoretical aspects of both phenomena have been considered, and useful considerations have been proposed. To provide a more comprehensive description of the suggested modifications, the seismic behavior of a 15-story steel moment-resisting frame building subjected to four near-field earthquake excitations has been studied. To that end, 3D nonlinear time-history analysis was conducted using ABAQUS finite element software. The structure is supported by a shallow raft foundation on soft-clayey soil. The results indicate that the two mentioned points are of prime importance and should be considered in the soil-structure interaction analysis due to near-field excitations to evaluate the seismic structural responses more accurately.

Air pollution, as a major urban problem in metropolises, has harmful impacts on societies in many aspects. According to the worn-out fleet of diesel buses and fossil fuel dependencies in Tehran, alternative fuels have become more popular in sustainable public transportation. Although battery electric buses (BEBs) provide many benefits, their purchase price and required infrastructure are the main challenges for decision-makers. This paper provides a systematic approach to examine the environmental, traffic and economic efficiency of overnight-charging electric buses (OCEBs) in Tehran, Iran. Environmental analysis shows that Carbon Oxide and Nitrogen Oxide will reduce to zero, and eliminate dependence on fossil fuels. The payback period predicted to be 7 years. Due to the better acceleration of OCEBs, the travel time, delay and stop time reduce about 4%, 10.67%, and 5.15% on average, respectively which leads to a better experience of passengers and an increase in public transportation utility that cause more people attract to OCEBs. The present results indicate the feasibility of OCEBs implementation as a sustainable transportation mode and can be useful in decision-making of policymakers and planning for future public transport system.

This paper investigates the seismic performance of Intermediate Moment-Resisting Steel Frame structures considering the effects of height and soil-structure interaction. For this purpose, three 3D structures of 3, 6 and 9-story were designed using CSI ETABS software in accordance with ASCE7-16. Then the 2D frames of the structures were simulated by OpenSEES software and to account for the nonlinearity of the material, the plastic hinge elements were used. The 2D frames were analyzed using IDA method subjected to 22 far-field ground motion records of FEMA-P695. Finally, the fragility curves of the structures were developed. The results showed that consideration of soil-structure interaction leads to lower spectral acceleration as height increases, meaning that higher-rising structures have record-induced Sa (T1,5%) closer to Sa (Design), and with decreasing height the difference tends to increase. Exceedance probability decreases with the increase of structure’s height and soil-structure interaction consideration adapts to lower exceedance probability. Also, the investigated Intermediate Moment-Resisting Steel Frame structural models designed according to ASCE7-16 consideration showed to have acceptable seismic performance against far-field records indicating that their exceedance probability in terms of the LS and CP performance level respectively are less than 0.45 and 0.03.

This paper presents a new hybrid algorithm generated by combining advantageous features of the Imperialist Competitive Algorithm (ICA) and Biogeography Based Optimization (BBO) to create an effective search technique. Although the ICA performs fairly well in the exploration phase, it is less effective in the exploitation stage. In addition, its convergence speed is problematic in some instances. Meanwhile, the BBO method's migration operator strongly emphasizes local search to focus on promising solutions and finds the optimum solution more precisely. The combination of these two algorithms leads to a robust hybrid algorithm that has both exploratory and exploitative functionalities. The proposed hybrid algorithm is named Migration-Based Imperialist Competitive Algorithm (MBICA). To validate its performance, MBICA is used to optimize a variety of benchmark truss structures. Compared to some other methods, this algorithm converges to better or at least identical solutions by reducing the number of structural analyses. Finally, the results of the standard BBO, ICA, and other recently developed metaheuristic optimization methods are compared with the results of this study.