Journal of Rehabilitation in Civil Engineering
Volume:8 Issue: 1, Winter 2020

The existence of torsion, as well as consideration of the Soil-Structure Interaction (SSI), increase the natural periods of the structure resulting from a subsequent decrease in the seismic demand of the system. This paper summarizes the probabilistic assessment for evaluation of collapse fragility curves in concrete moment resisting structure with different mass center eccentricities. A 12-story, 3-D, moment resisting concrete structure with fixed-base and considering SSI, both types of one- and two-way eccentricities is employed to estimate the collapse fragility curve by the IM-based approach. According to the obtained results, increasing the torsion due to shifting the mass centers decreases the median of the collapse fragility curve. In addition, it was observed that the SSI consideration for soil type D with shear wave velocity of 180m/s to 360m/s leads to reduction of the median of collapse capacity by  in the presence of torsion effect due to one- and two-way mass center eccentricities in range of 0-20% of the building's plan dimensions respectively. In other words, the fixed-base assumption overestimates the median of collapse capacity and leads to unsafe design. Moreover, shifting the mass centers of all the stories up to 20% of the building's plan dimensions, with or without the consideration of the SSI, decreases the median of collapse capacities and increases the seismic vulnerability of the building. Accordingly, the fixed-base assumption can be underestimated the dispersion range of the collapse fragility curve. The result shows that the mentioned differences cannot be neglected.

The worldwide use of precast concrete frames leads to an increase in the need for the investigation of efficient precast connections, particularly in the seismic regions. The current paper provides a numerical and experimental study on a dry precast connection. Experiments were conducted to validate the finite element method in the laboratory of the University of Science and Culture. To verify the validity of the result, the outcomes of the non-linear analysis of cross-shaped models were compared with the experimental results in terms of failure mode, ductility, lateral load-bearing capacity, and energy dissipation. The finite element non-linear analyses of the models represented an acceptable compatibility with experimental results. A parametric study has been carried out to survey the effect of the couplers and grout compressive strength on semi-dry connection behavior. Eventually, the response modification factors were determined for the case studies to demonstrate the seismic behavior in design forces. Statistical analysis of the numerical results demonstrates a 6 % increase for response modification factors of the specimens with the closest distance of couples to the column face in relation to those with the couplers farthest away from the column face. Eventually, it can be concluded that the specimens with a shorter coupler distance from the external face of the column and with a higher grout compressive strength lead to the appropriate results.

The chloride corrosion of reinforcing steel in reinforced concrete (RC) structures is a significant reason for premature deterioration and failure of RC structures in aggressive environments such as the Persian Gulf region. This is one of the most important sources of engineering and economic problems in developed countries. So, modeling chloride permeation and investigating different methods for the repair and maintenance of RC structures exposed to corrosive environments are very important for optimizing the service life and life cycle cost of these structures. In this research, a finite element model is applied to assess the time-dependent capacity of corroded RC structures using nonlinear analysis; this includes the impact of corrosion on inelastic buckling and low-cycle fatigue degradation of reinforcements. In this analysis, the influence of shotcrete repair after the initial cracking of concrete cover as a rehabilitation method on the performance of a corroded square RC column due to chloride-induced corrosion is investigated.

In the present study using the wavelet theory (WT) and later the nonlinear spectrum response of the acceleration (NSRA) resulted in estimating a strong earthquake record for the structure to a degree of freedom. WT was used in order to estimate the acceleration of earthquake mapping with equal sampling method (WTESM). Therefore, at first, the acceleration recorded in an earthquake using WTESM was studied in 5 levels. And then for calculating the strong ground parameters (SGP) and the NSRA of the structure the filtered wave was used instead of using the main earthquake record (MER). The wavelet stages result in a more lenient filtered wave and it is better for calculating SGP and NSR because the noise is filtered. The method suggested for a large number of earthquakes was used and the results are detailed in the case of Kermanshah earthquake. Results show that in case of using WTESM, SGP error estimation would be less than 2% and the calculation error for NSRA would be less than 11%.

One of the most important factors in determining the depth of foundations in structures adjacent to the water flow is the scouring phenomenon; the scouring is a phenomenon caused by the interactions between water flow and erodible bed materials, which causes the removal of sediments where hydraulic structures are located, including bridge piers. Every year, a great number of bridges are damaged due to local scoring of their piers and foundations. In this paper, the geotechnical study of Malahide viaduct failure due to scouring was carried out using Plaxis 2D software. For this purpose, the Malahide viaduct, which was damaged in 2009 due to bed scouring of one of its piers, was selected and the necessary simulations were carried out based on the bridge specifications, and the conditions of the bridge underlying bed was investigated. Simulations results showed that the cause of scouring in the bed of collapsed pier was the high shear strains of the bed, bed shear strength parameters (i.e. angle of internal friction and cohesion) reduction and as a result, reducing the bed resistance to the scouring. It was also found that by using the micropile group below the foundation of bridge pier as a solution to reduce the scouring effect, the bed maximum scour depth is significantly reduced compared to the shallow foundations without micropiles; Also, by using the micropile group, the shallow foundation thickness can be reduced, provided that after foundation thickness reduction and micropiles application, the structure safety factor remains in the stable range.

In this study, Adaptive Neuro-Fuzzy Inference System (ANFIS) and Monte Carlo simulation are utilized for reliability analysis of structures. The drawback of Monte Carlo Simulation is the amount of computational efforts. ANFIS is capable of approximating structural response for calculating probability of failure, letting the computation burden at much lower cost. In fact, ANFIS derives adaptively an explicit approximation of the implicit limit state functions. For this purpose, a quasi-sensitivity analysis based on ANFIS was developed for determination of dominant design variables, led to the approximation of the structural failure probability. Preparation of ANFIS however, was preceded using a relaxation based method developed by which the optimum number of training samples and epochs was obtained. That was introduced to more efficiently reduce the computational time of ANFIS training. The proposed methodology was considered using some illustrative examples.

Pavement surface texture and its skid resistance are two key safety parameters of highways, which both are influenced by pavement characteristics. This research is done on a newly constructed asphalt pavement (Qom-Garmsar freeway) in Iran. The goal is investigating the relation between skid resistance and pavement texture in order to asphalt content changes in Hot Mix Asphalt. Mean Texture Depth (MTD) and British Pendulum Number (BPN) are being used to quantify pavement texture and skid resistance, respectively. The results show that the asphalt content has a significant effect on MTD and consequently, BPN in loaded pavements, as well as non-loaded pavements. The result showed that the lowest BPN value obtained, when the asphalt content is about the optimum value. Moreover, it is demonstrated that using asphalt contents less and more than the optimum value, results in BPN improvement. Asphalt content increasing, around optimum value, leads to MTD decrease. The results also show that by increasing the MTD, the BPN decreases to 75 (in MTD value of 0.62 mm) and then increases.

Adding steel braces to reinforced concrete frames is a common way for seismic rehabilitation of these structures. Due to ease of installation and the possibility of creating openings in the braced bays, this method of rehabilitation has been more preferred than using shear walls. In this paper, three experimental specimens including a reinforced concrete frame, a reinforced concrete frame with concentric bracing and a reinforced concrete frame with eccentric bracing are constructed and their cyclic behavior investigated and compared with each other. Results show that the ultimate loads of the both concrete frames with concentric and eccentric braces are about 2.11 and 1.9 times more than that of reinforced concrete frame, respectively. Ductility of rehabilitated frame by eccentric bracing is more than that of reinforced concrete frame and rehabilitated frame by concentric bracing too. Moreover, the absorbed energy of the rehabilitated frames with eccentric and concentric bracing is about 1.98 and 1.63 times more than that of concrete frame.

In this paper, a computationally simple approach for damage localization and quantification in beam-like structures is proposed. This method is based on using modal flexibility curvature (MFC) and particle swarm optimization (PSO) algorithm. Analytical studies in the literature have shown that changes in the modal flexibility curvature can be considered as a sensitive and suitable criterion for identifying damage in the beam-like structures. Modal flexibility curvature can be calculated utilizing central difference approximation, based on entries of the modal flexibility matrix. The PSO algorithm, as a powerful optimization tool, is used to minimize the error function which is formulated as an error function between the measured modal flexibility curvatures of the damaged structure and those calculated from the analytical structure. To demonstrate the efficiency of the method, two beam-like structures under different damage scenarios are studied. In addition, the robustness of presented method is investigated when only the first several modal data are available. It is observed that the proposed approach is able to localize and quantify various damage cases only by a few lower vibrational modes and also, it is low-sensitive to measurement noise.

Deterioration models are important and essential part of any Pavement Management System (PMS). These models are used to predict future pavement situation based on existence condition, parameters causing deterioration and implications of various maintenance and rehabilitation policies on pavement. The majority of these models are based on roughness which is one of the most important indices in pavement evaluation. High correlation between International Roughness Index (IRI) and user comfort led to modeling pavement deterioration based on IRI during PMS history. On the other hand, in recent years Artificial Neural Network (ANN) which is a valuable tool of soft computing is used in pavement modeling, widely. This study assessed the development of an ANN pavement deterioration model based on IRI using Back-Propagation Neural Networks (BPNN) technique. The Long-Term Pavement Performance (LTPP) data was extracted from two General Pavement Study (GPS) sections including GPS-1 and GPS-2. After training and testing the developed model, results were compared with a polynomial regression model. Results showed that predicted IRI values with developed ANN model have a good correlation with measured values rather than the polynomial regression model for both GPS-1 and GPS-2 sections.

In this paper, the effect of asphalt overlays, which were reinforced with geogrid, modified by sasobit and combination of them on rehabilitation of reflective cracking, is studied. The laboratory tests were conducted under dynamic loading in bending mode to investigate reflective cracking retardation compared to reference samples. The results illustrated that in a certain range of variables, temperature variations and sasobit percentages are the most effective parameters on fatigue life and other responses. Another effective variable was the type of interlayer in asphalt slabs. Furthermore, it has been found that the combination of samples (modified by sasobit ,reinforced with geogrid and a 3cm sand asphalt layer) (1SP.G.SA & 2SP.G.SA) had a better performance such as improving fatigue life and reducing crack propagation in all loading and temperature conditions compared to the reference samples. Based on the image processing results, the process and shape of crack growth vary greatly at different temperatures. Generally, at low temperatures (20 °C) and frequencies the cracks grow from bottom to top and the width of them get smaller. However, with increasing the temperature and loading frequency, the top down cracks are also observed, which is due to the reduced resistance of the asphalt resulting from the reduction of adhesion and the fastening between the aggregate and bitumen.

As a result of environmental and accidental actions, damage occurs in structures. The early detection of any defect can be achieved by regular inspection and condition assessment. In this way, the safety and reliability of structures can be increased. This paper is devoted to propose a new and effective method for detecting, locating, and quantifying beam-like structures. This method is based on Rayleigh-Ritz approach and requires a few numbers of natural frequencies and mode shapes associated with the undamaged and damaged states of the structure. The great advantage of the proposed approach against the other methods is that it considers all kinds of boundary and damping effects. To detect damage using the penalty method, this article considers lumped rotational and translational springs for determining the boundary conditions. Result will show that the proposed method is an effective and reliable tool for damage detection, localization, and quantification in the beam-like structures with different boundary conditions even when the modal data are contaminated by noise.