Journal of Rehabilitation in Civil Engineering
Volume:12 Issue: 2, Spring 2024

The assessment of two circular reinforced concrete (RC) silos built in the 1970’s decade is presented. The methodology implemented is described, including the data collection, testing, analysis requirements, structural model, evaluation results, and retrofitting design. The RC silos were designed in the 1970’s decade with very low seismic demand and insufficient engineering details. The evaluation of this special type of existing structure has reported stability and strength severe issues that need to be improved.The national and international codes, as well as guidelines, were consulted to define the most appropriate seismic demand, the gravitational, and eventual loads. Moreover, the load combinations criteria, the evaluation and diagnostic requirements, the structural design criteria, and some adequate retrofitting techniques.The main retrofit strategy was oriented to improve the stability of the silos against overturning, reducing the normal stresses on the ground, and strengthening the RC walls subjected to the axial and bending combined effects due to the current requirements. The retrofit design implemented was able to respond to the described issues by an extension of the foundation and RC jacketing of the silo walls.A rational approach to evaluating and retrofitting this type of non-conventional RC structure was developed. In addition, a cost assessment based on a comparison of concrete and steel reinforcement volume between the existing silo and the strengthening components is presented.

This paper focused on confining effects of externally bonded composites with polymer and grout matrices equipped with steel fibers, respectively named steel reinforced polymer (SRP) and steel reinforced grout (SRG) composites, as novel and effective methods of strengthening structures. To achieve this goal, an experimental database including 13 and 10 concrete columns with square cross-sections respectively confined by SRP and SRG composites was compiled from a recent empirical study. Moreover, after a comprehensive review and conducting a trial and error process of 45 existing models for estimating the relative compressive strength of confined concrete columns, six models for the SRP-confined concrete columns and six models for SRG-confined concrete columns with square cross-sections were selected and their performance was evaluated by comparing the Pearson correlation coefficient (R) and the mean absolute percentage error (MAPE) criteria. The results illustrated that for the SRP-confined concrete columns with square cross-sections, the selected model from the CNR-DT200 standard with respectively R and MAPE values of 0.7671 and 7.39% outperformed other selected SRP models. On the other hand. for the SRG-confined concrete columns with square cross-sections, the selected model from the research work of Isleem et al. with respectively R and MAPE values of 0.4405 and 18.45% surpassed the other selected SRP models. As most of the proposed models to estimate the relative compressive strength of confined concrete columns were suggested for the fiber-reinforced polymer (FRP) composites rather than the textile-reinforced mortar (TRM) composites, the overall comparison showed that all the selected SRP models outperformed the selected SRG models.

Several strong earthquakes hit Lombok Island in 2018. The earthquake that occurred in sequence caused damage to many buildings and even destroyed housing for residents. This residential sector suffered enormous damage and losses in Mataram City, the province's capital. The reconstruction and rehabilitation process was carried out in 2 phases, and the last Phase was completed in April 2021. A total of 14140 houses received assistance funds for repair and rebuilding in the first Phase, while the number of houses receiving repair funds in the second Phase was 1339. Compared to the initial data in the Reconstruction and Rehabilitation Action Plan, the number of major damaged houses decreased by 43.66% to 1350 houses. However, the number of medium and minor damaged houses increased to 30.75% and 10.83%, respectively, to 3631 and 9159 houses. Through the implementation of the housing reconstruction and rehabilitation in Mataram City, it can be concluded that either the funding or the process was under the central government's guidance. Meanwhile, the local government was an aid to ensure the effective implementation of reconstruction. The relationship between the central and local governments was conducive to running the process effectively and according to the timeline. The local government allows the community to choose the type of earthquake-resistance house for rebuilding. Of the various types of more earthquake-resistant houses, the people preferred the reinforced concrete panel type housing because the construction is faster, so they can live in it immediately.

In seismic areas, steel structures are considered one of the best choices due to the inherent properties of materials such as integrity and ductility. Recent research to simplify the repair of earthquake-resistant steel structures after severe earthquakes has focused on designing structures that have localized plastic damage at the desired locations, which dissipates earthquake energy and easily replace after severe earthquakes. It is replaceable, so that the normal life of the residents can be immediately restored with low repair costs. However, repairing and regenerating damaged organs is a challenging and time-consuming process. In this study, the proposed fuse element consists of a number of steel sheets that connect the link beam to out-of-link beam through a complete joint connection, in the form of groove and tongue by pin. When cyclic loads (compressive and tensile) are applied to the eccentric frame, the fuse causes the concentration of force in the beam by showing shear behavior and thus dissipates the force of the earthquake. The results of the numerical studies conducted on the integrated three-dimensional finite element model of the eccentric frame equipped with a fuse show that the damage was limited to the fuse section, and no other structural components were damaged. Also, this system has shown similar hysteresis behavior in tension and pressure, and the coefficient of behavior of this system is higher than conventional eccentric frames, which indicates better performance and ductility of this system. On the other hand, since the damage is concentrated on a relatively small element, and the connection of this member to the frame is fully jointed, so after a large earthquake, with a small cost, it is easy to replace the damaged fuse and the building will be usable.

Ordinary concrete production is highly energy intensive and caused to greenhouse gas emission responsible for global warming. Geopolymer mixtures are the eco-friendly alternative for to protect the CO2 emission in concrete industry. In this study, the post-fire behavior of fiber reinforced geopolymer concrete (FRGPC) was investigated based on molarity changing approach. To do so, supplementary cementitious materials such as fly ash, metakaolin and zeolite are used to provide binary and ternary FRGPC mixtures. For this aim, FRGPC exposed to elevated temperature at the 200, 500, 800 °C. In addition, three molarity (12, 14, 16) of solution is studied for better strength performance. The result of this study presented that the ratio of the post-fire residual strength of the sample of Z10MK20 increased by 8.1% at 200 °C, 14.1% at 500 °C, and decreased by 5.2% at 800 °C. The 28-day sample resistance, with 20% replacement of metakaolin, was measured at 45.8 MPa after adding fibers (2% constant volume of 1-3% polypropylene fibers). Also, with increasing the molarity of FRGPC mixtures from 12 to 16, the heat resistance behavior in FRGPC had an increase about 6%. Increasing the volume of polypropylene (PP) fibers up to 3% by volume did not have much effect on the heat resistance behavior of FRGPC. Beside, post-fire strength of FRGPC was predicted using artificial neural network (ANN) and support vector machines (SVM) with the integration of water cycle algorithm (WCA). Based on the coefficient of determination obtained in the training and testing stages, ANN-WCA model had an acceptable performance in predicting the post-fire residual strength of FRGPC. Additionally, the sensitivity analysis manifested that the molarity of the FRGPC mixtures and the exposed temperature had the greatest effect and PP fibers had the least effect on post-fire residual strength of FRGPC.

The use of wrapping geosystems such as soilbags as reinforcement has been increasingly studied. Soilbag columns may be utilized as an alternative method for improving the weak soil under the footing. An analytical approach was developed to predict the stress-strain response of the soilbags under compression. Using three-dimensional numerical modeling, the validity of the relationships was investigated and then developed for the soilbag columns supporting the footing loads. Compared to numerical results, it was found that for the stiffer wrapping materials, the analytical approach overestimates the bearing stress of the soilbag columns. However, the estimation of the bearing stress of soilbag columns matches well with the numerical results for high values of backfill friction angles. The results from the analyses were used to develop the design guidelines for the design of soilbag columns for the given settlement. Design charts propose a preliminary selection for the tensile stiffness of wrapping geosystems.

The present study includes experimental and numerical investigations of the behavior and the load carrying capacity of RC two-hinged beams with radius corner arch at the bottom face subjected to static loading conditions. The experimental program included four specimens with the same volume of concrete and amount of steel reinforcement but, with a different span of the arch (1180 mm, 900 mm, 740 mm, and 600 mm). The goals were to evaluate the effect of a span of the arch and to find the optimum ratio of the arch length to beam span for the maximum load capacity as well as to validate the numerical results taken from the finite element model. From the results of this work, it was found that the best load carrying capacity for the beam with a radius corner arch is when the arch length/beam span ratio is equal (0.62). Also, the FEM result seems efficient and gives good accuracy through comparison with the experimental results.

The flexural and shear behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) reinforced with different ratios of glass-fiber-reinforced polymer (GFRP) and conventional steel rebars is experimentally studied in this paper. For this purpose, three beams with dimensions of 250×300×1650 mm were reinforced with GFRP rebars in three different ratios (0.64%, 1.05%, and 1.45%) and hooked-end (H) steel fibers by 2% volumetric ratio. Similar procedure was carried for beams reinforced with conventional rebars. Additionally, Nonlinear regression analyses were also carried out to simulate the flexural load-deflection behavior of the beams. Results showed that the role of hooked-end fibers in compensating for the brittle nature of GFRP rebars was insignificant. Besides, increase of the longitudinal reinforcement ratio changed the failure mode from flexural to shear failure in specimens with GFRP rebars. Finally, nonlinear regression models were proposed that successfully capture the load-deflection behavior of the test specimens with coefficient of correlation (R^2) very close to unity.

Asphalt pavement is used in road construction with the aim of withstanding loads and heavy traffic. Increasing axial loads and heavy vehicle traffic lead to failures, including rutting, thermal cracking, and fatigue cracking. These are the three most frequently observed distresses, especially in high-temperature regions that affect flexible pavement performance. Various studies over the years have investigated the causes of Hot mix asphalt failure and proposed a number of solutions to such failure problems. For upgrading the properties of asphalt mixtures against rutting, the asphalt bituminous exploited in the asphalt mixture was modified by employing Powdered Activated Carbon in this investigation. To apply the aging phenomenon, the specimens of control asphalt concrete and the specimens modified with Powdered Activated Carbon were held in the oven for 5 days at a temperature of 85 ℃. Bending beam rheometer (BBR) and dynamic shear rheometer (DSR) tests were performed on the specimens. The results revealed that the specimens containing Powdered Activated Carbon exhibited better performance against rutting. By adding 5% Powdered Activated Carbon, the high operating temperature of pure asphalt binder in the aged state has reached from 58 °C to 82 °C.