Journal of Rehabilitation in Civil Engineering
Volume:9 Issue: 4, Autumn 2021

The compacting and mixing processes involving hot mix asphalt during asphalt production can lead to air pollution as a result of a high volatile organic compound. An alternative solution that can reduce greenhouse gas emissions is by using warm mix asphalt (WMA). A proper application of additives to the WMA can improve the asphalt mixture's strength, durability, and workability. In this study, a 60/70 grade asphalt binder was added with 5% of crumb rubber (CR) and three different WMA additives at the recommended dosages, namely Sasobit, Cecabase, and Rediset. The wet method was used to blend the additives with virgin asphalt binders. The mixing and compacting temperatures were set at 135°C and 125°C, respectively, to mix the asphalt mixture. Mechanical performance tests were performed to evaluate the impact of WAM additives with CR on asphalt mixture. Based on the results, all the modified asphalt mixtures showed a better mechanical performance than the virgin asphalt mixture in terms of indirect tensile strength, moisture resistance, permanent deformation, and stiffness. Among all the WMA additives, Sasobit with CR showed the most significant impact on the asphalt mixture's performance.

Historical sites and remnant monuments from different eras in Iran are the main reasons of tourist attraction. One of the factors that endanger existence of these monuments is earthquakes and it is well known that Iran is located on the Alpide seismicbelt and earthquakes are inevitable. Understanding the structural behavior as well as possible weaknesses and then seismic strengthening under the earthquake are the ways of mitigating hazard in architectural heritage. Minaret of Tarikhanehmosque which is one of the oldest minarets and most precious historical monuments in Islamic world was built between 130 and 170 AH (750-760 AD). In the present study, this minaret is first modeled via ABAQUS finite element software considering geometric details and different seismic analysis such as pushover, modal and nonlinear time history analysis is conducted under the different earthquake frequency contents. After realizing the current state and weaknesses of the minaret, seismic strengthening is done via three different methods including FRP sheets, Ferro-cement (welded wire mesh with micro-concrete/mortar), and fiber reinforced cementitious matrix (FRCM) material. Finally, results of these three strengthening methods were evaluated and the most appropriate method was selected. According to the results, it was observed that Ferro-cement strengthening method is the most effective one among the proposed methods; so that, in comparison to the FRCM strengthening method, this method is effective by up to 100 %.

The purpose of this study is to obtain one of the important dynamical properties, namely natural frequency (ω) for a number of tall buildings with tube and tapered tube systems. Furthermore, it presents an approximate method to analyze the free vibration of tall buildings by tube, tube-in-tube, bundled tube, and tapered tube structures. The method we have proposed would enable us to compute the natural frequency of tubular vertical and tapered tall buildings by the help of computer programming. The models were analyzed by finite element and analytical methods. The results indicate that the investigated analytical method correctly calculates the natural frequency and is in decent accord with the finite element results and has better compatibility with tapered structures without angle with higher altitude. The resulting computational error is very low. Also, this analytical method has the least error for tube systems and the highest error is for tube-in-tube systems.

In this study, the distribution of correlation coefficients between maximum interstory drift ratio (MIDR) of multistorey building structures and ground motion characteristics intensity measures (IMs) is evaluated and compared.  For this purpose, a continuum beam model is used to estimate the MIDR of multistory building structure including higher mode effects. The MIDRs are computed for building structures with three different lateral resisting systems (structural walls, moment-resisting frames, and their combination) and fundamental periods that ranges from 0.05 to 10s. Nine different ground motion parameters of pulse-like ground motions including PGD, PGA, PGV, Ic, CAV, Ia, SMV, ESD, SMA are selected as ground motion characteristics IMs. The effects of the type of lateral resisting system and the acceleration pulse on the distribution of correlation coefficients are also considered in the study. Based on the assessment results, MIDRs in mid and long-period buildings show a high correlation to PGV, SED and SMV, while a low correlation occurs with respect to PGA and SMA. Also, type of lateral resisting system causes changes in the correlation coefficients and results showed that long-period shear wall structure gives lower coefficients with respect to other structural systems.

This study evaluates geocell reinforced slope behavior under seismic loading using calibrated hypoplastic soil constitutive model. The constitutive soil model used in this simulation was calibrated for poorly graded dense sand by conducting a series of triaxial and odometer tests. A three dimensional analysis is carried out to simulate geocells and this soil model using the finite element software PLAXIS3D. To investigate the geocell seismic behavior, the lateral displacement, induced tensile force in geocell, slope stability and frequency content effect have been assessed. Furthermore, a comparison has been made among hypoplastic, Hardening soil with small strain and Mohr-Coulomb model. The obtained results indicated that the volumetric plastic strain and inter granular strain consideration by hypoplastic model had a significant effect on the lateral displacement of the reinforced and unreinforced slope. Using the geocell layers leaded to decrease the plastic points. This behavior caused to decrease the estimated results difference when performing three constitutive models as soil failure criterion. Also, the tensile force showed hypoplastic model was not sensitive to the earthquake reversible force. In addition, it was found that the geocells lost their effect when the PGA increased and the slope was apt to fail.

The application of Digital Image Processing (DIP) and computer vision is increasing in civil engineering branches nowadays. By implementing DIP methods, analyzation, and detection of intended objects and elements on the images will be done. So, these methods can be used for automatic inspection and decreasing manpower's direct controls on structures and infrastructures. This paper will study the application of DIP such as health monitoring and damage detection in structures. After reviewing various researches in this field, a classification including five classes was done. These classes including 1-identification and evaluation of the crack, 2-identification and evaluation of defects in steel structures, 3-identification and evaluation of other imperfections and defects, 4-deflection, deformation, and vibration assessment, and 5-identification of texture, dimensions, elements, and components. The researches also are classified based on various aspects such as the implemented methods, specification of images, the performance of the method, and so on. Finally, after investigating the shortage of researches, the future suggestion for researchers was made.

Since the beginning of the 21st century, the rapid development of road infrastructure has facilitated enhanced mobility and accessibility that has caused environmental degradation due to the continuous extraction of natural aggregates. To address this increasing problem, recycled aggregates and Reclaimed Asphalt Pavement (RAP) materials have been utilized in road construction worldwide. The studies related to various emulsified asphalt contents on permanent deformation and other parameters are limited. This study examined the performance characteristics of cold recycled emulsified asphalt bases with RAP materials in different proportions, i.e., 25%, 50%, and 75%, and evaluated in terms of the indirect tensile strength, tensile strength ratio, density, water loss, and permanent deformation at lower and higher emulsified asphalt contents than optimum. The results demonstrated that the total residual binder content influences the permanent deformation characteristics of cold mixes. There was no significant variation in the durability and strength with the RAP at the optimum emulsified asphalt content. But, the emulsified asphalt contents other than optimum influence the strength, density, and permanent deformation. The logarithmic and power-law models are best suited to predict the first-stage permanent deformation of cold mixes.

In this paper, shear and flexural behavior of structural steel beams strengthened by high modulus carbon fiber reinforced polymer (CFRP) laminates are presented. Totally, 18 steel specimens including 6 un-strengthened beams as control specimens and 12 strengthened steel beams with simple supports were tested under 3-point bending test set-up. All specimens were strengthened using the bonded system. Influence of different parameters including length of steel beams, section size of specimens, number of CFRP laminates, and location of CFRP laminates were studied. Based on anticipated failure modes, the bonded laminates were implemented on the surface of tension flange, compression flange, and web of beams. Three failure modes of flexural, shear, and lateral-torsional buckling failures were observed in the tested beams. The main goal of these experiments was to evaluate the enhancement in load capacity, beam ductility, and initial stiffness. The results showed that the yield load, ultimate load capacity, and energy absorption of strengthened steel beams improved up to 15, 29 and 28 percent, respectively. Finally, in order to predict test results and compare the actual and predicted valves, analytical and numerical studies were carried out.