Sharif Digital Repository

Soils are usually weak in tension therefore different materials such as geosynthetics are used to address this inadequacy. Worldwide annual consumption of geosynthetics is close to 1000 million m2, and the value of these materials is probably close to US$1500 million. Since the total cost of the construction is at least four or five times the cost of the geosynthetic itself, the impact of these materials on civil engineering construction is very large indeed. Nevertheless, there are several significant problems associated with geosynthetics, such as creep, low modulus of elasticity, and susceptibility to aggressive environment. Carbon fiber reinforced polymer (CFRP) was introduced over two... 

Rammed earth (RE) structures are widely used for more sustainable and environment-friendly buildings. Due to lack of design standards, the engineering decisions often rely on rule-of-thumb method which may lead to quite conservative or unsafe designs. In this study, load and resistance parameters were treated as random variables in reliability analysis. The reliability index and failure probability of RE structures were evaluated using First-Order-Reliability-Method (FORM) and then compared with Second-Order-Reliability-Method (SORM) and Monte Carlo Sampling method. The analysis was performed based on the different a) load combinations, b) wall geometry, c) material type (unstabilized or... 

Polymer concrete (PC) has been widely used for quick repairing of concrete pavement and structures in recent years. This paper studies the mechanical behavior of the rubberized polymer concrete. Crumb and chipped rubber were used to replace fine and coarse aggregates in PC, respectively. A complete series of destructive tests including impact test, compression and splitting tensile tests and non-destructive methods including ultrasonic test, digital signal processing, electrical conductivity, and microstructure analysis was performed to demonstrate the various potential applications of the rubberized PC. X-ray diffraction (XRD) also provided information regarding the chemical composition and... 

Sliding friction between a pavement and tire is an important concern in traffic safety. The British pendulum test has been used worldwide to evaluate friction characteristics of pavement surfaces. However, because of considerable differences in apparatus, procedures, and operation, significant variability can occur for evaluations of British pendulum number (BPN). In this investigation, a direct shear test (DST) device is modified and proposed to determine the sliding friction coefficient between tire and pavement surface under dry and wet conditions. Dissipated energy values obtained from DST were compared with evaluations of BPN, and a high correlation was obtained. Tests were done using... 

Nowadays, the growth of energy consumption in buildings is an important topic. Rammed earth (RE) structures have attracted the attention of engineers and contractors in recent years due to their advantages such as sustainability, availability and low embodied energy content. These advantages result in less energy consumption in the life cycle of the RE structures. However, there is a lack of research on the mixture composition of RE materials containing admixtures. This research introduced integrated analytic network process (ANP) and genetic algorithm (GA) methodology to select the optimum mixture of RE material containing cement, expanded polystyrene(EPS), and phase change materials(PCM)... 

Ribbed bracing system (RBS) is an innovative structural system designed to eliminate the buckling of braces and enhance the behavior of structures under seismic loads. In this study, a collaborative performance of 2 RBS devices bracing a frame was assessed numerically and experimentally. In the numerical phase, the collaboration of ribbed braces at various stages of reversal loading was elaborated mathematically and was used for representing the system using finite element modeling. In the next phase, the numerically observed behavior was validated experimentally by conducting cyclic quasistatic tests of the proposed configurations. Two alternative RBS configurations—called completely closed... 

This article evaluates the seismic performance of structures equipped with a ribbed bracing system (RBS). RBS uses ribbed faces that freely slide under compression, however, interlock under tensile forces. Two RBS mechanisms; Completely-closed RBS (CC-RBS) and Improved-centering RBS (IC-RBS), were proposed and successfully tested for eliminating compressive buckling of braces. CC-RBS and IC-RBS provide high energy dissipation capacity and small residual story drifts, respectively. Here, these mechanisms were employed for design and modeling of three structures with varying heights. The models were then subjected to incremental dynamic analysis (IDA), and their seismic performance was... 

This research investigated the long-term environmental effects on the bond at the interface between fiber-reinforced polymer (FRP) and a masonry brick. Seven types of FRP fabrics were used and placed on the masonry brick using the wet lay-up technique. Unidirectional and bidirectional fibers made of aramid, carbon, and glass and also combination of these fabrics were used. A total of 525 specimens were exposed to five chemical solutions with pH values of 2.5, 7, 10, 12.5 and substitution sea water for 1, 3, 6, 9 and 12 months. A chamber was also used to simulate the ultraviolent (UV) radiation on the specimens. A series of single-lap shear tests were performed on these specimens to determine... 

Concrete is widely used for many practices in Civil Engineering. Therefore, an understanding of its behavior helps engineers and researchers to perform more accurate and cost-effective analyses and designs. In this respect, several models have been proposed to predict the behaviors of concrete most of which are satisfactorily accurate. However, by increasing the accuracy of the models, their computational cost increases, too. In this study, a model with the least computational cost is proposed to predict the behaviors of various concretes and confinement conditions. This model does not require any experimental tests to determine its parameters. It was proved to be able to predict the... 

In this study, a new plasticity-based constitutive model is proposed for the behavior of soil-structure interfaces under monotonic and cyclic loadings. The features of the interface including the strain-softening behavior, phase transformation, steady-state, and dilatancy behavior were described by the proposed model with satisfactory accuracy. The proposed model does not require additional concepts such as damage or disturbance, and the model parameters can be obtained easily using straight-forward analyses of the results obtained from constant normal stress tests. Moreover, the results of the proposed model showed its capability in predicting the experimental results obtained from various... 

The advantages of fiber reinforced polymer (FRP), such as high specific strength, resistance against corrosion and formability, have made it a more acceptable alternative to conventional materials regarding repairing and retrofitting of structures. Although investigations in recent years have proved the concern of civil engineers about the environmental effects on the bond between FRP and concrete or masonry (especially moisture and temperature), only few researches have been reported on FRP-wood interfaces. This research investigated the effect of five different environments on the bond at the interface between FRP and wood. A series of pull-out tests were performed on 375 wood specimens... 

Impact loading leads to micro-crack formation that can compromise the performance of the concrete. The purpose of this paper is to evaluate plain concrete and fiber-reinforced concrete specimens using ultrasound methods under impact loading. These specimens were prepared and subjected to impact loading. Ultrasound tests were performed at different stages of impact loading on each specimen. The loading continued until cracks on the surface of the specimens were observed. Investigations were performed for both plain concrete and fiber-reinforced concrete to establish a correlation between ultrasound response characteristics, and the damage caused by impact loading due to the energy of blows... 

The permeability of roller-compacted concrete (RCC) substantially affects its functionality and safety. This study investigates the effect of mix design parameters on the performance of RCC. For this purpose, approximately 500 laboratory specimens were prepared and tested. A formula and an artificial neural network (ANN) were proposed to predict the permeability coefficient of RCC by considering the main parameters, which were then verified independently using new specimens. Furthermore, the experimental data were analyzed by the Taguchi method and analysis of variance (ANOVA) to evaluate the level of parameter contribution. Based on the results, the permeability coefficient was highly... 

Usage of masonry system in many regions of the world like the Eastern Mediterranean, the Middle East, India, and China is still significantly high, despite their highly energy and intensive emission. Most of the failures in this system are caused by low ductility of cement mortars. This type of failure could be seen in masonry structures in areas in east Iran after Kermanshah earthquake in 2017. The present study investigates the shear bond characteristics of structures constructed by masonry using green materials. “Taftan” natural pozzolan and two types of rice husk ash (RHA) were used in mix design of used mortars as green materials. In this investigation, a modified direct shear test... 

Buckling-restrained braces (BRBs) have been spread widely, especially in high seismic hazard zones due to their excellent energy absorption capacity. BRBs are composed of a main load-carrying steel core restrained with other elements mostly made of concrete and steel casing to preserve it from buckling. Although BRBs provide excellent cyclic behavior, a problem is with their heaviness, which leads to difficulties such as installation and transportation. This study presents a numerical and experimental investigation on a BRB with a new proposed restraining system composed of concrete panels confined with partially carbon fiber reinforced polymer (CFRP) strips to reduce the weight of the... 

Many concrete structures such as bridges, offshore structures, and pavements are under cyclic loads when they are exposed to different environmental conditions during their lifespan. The durability and fatigue performance of these structures are significant issues that should be considered. Therefore, this study investigated the long-term environmental effects on Polymer Concrete (PC) and Ordinary Cement Concrete (OCC) subjected to cyclic fatigue loading under four different environmental conditions (freshwater, seawater, acidic and alkaline) for six months. Concrete specimens are tested under high cyclic loading with the frequency of 6 Hz and low cyclic loading with a frequency of 1 Hz.... 

Polymer concrete is well-known for quick repairing of concrete structures and pavement. However, there are relatively few studies on the durability of epoxy polymer concrete (EPC). This study aims to investigate the long-term environmental effects on the mechanical properties of EPC. Therefore, EPC and ordinary cement concrete (OCC) specimens were prepared and exposed to four chemical solutions with pH values of 2.5, 7, 12.5 and artificial seawater in intervals of 1, 3, 6, 9 and 12 months. Epoxy resin (10 and 12% by weight) and Portland cement were used as binder phase in EPC and OCC specimens, respectively. Scanning electron microscopy (SEM) was additionally applied to investigate the... 

Rammed earth (RE) is an eco-friendly building material and has been capturing special attention among researchers. Many of the recently studied RE additives are extremely resource- and energy-consuming. On the other hand, the usage of fly ash (FA), which is a sustainable replacement for cement, has been scarcely investigated in RE construction. In this paper, an experimental investigation was performed on the physical and mechanical properties of RE materials stabilized with the combination of cement and alkali-activated FA. This scrutiny consists of density measurements, pulse velocity tests, unconfined compression tests, and direct shear tests. Additionally, the carbon dioxide emission and... 

This study explores the effect of Guar gum as an eco-friendly additive on concrete mechanical characteristics. In the first stage, the slump and relative humidity tests were carried out for the fresh mortar, and tensile and compressive strengths were then determined for fifteen different mixture designs with two different curing times. Further, an exponential correlation was obtained between the ultrasonic pulse velocity and the compression test results. Additionally, scanning electron microscope (SEM) was employed to assess the bond between aggregates and Guar gum. At last, the Taguchi method and ANOVA were utilized to conduct the optimum states of the mechanical characteristics of the... 

The interface behavior of rock and concrete and between layers of concrete highly affects the performance of concrete dam structures. In this investigation, a modified direct shear test was implemented in the laboratory to evaluate the interface behavior between (1) rock and conventional vibrated concrete (CVC), (2) rock and roller compacted concrete (RCC), (3) CVC and RCC and (4) two layers of RCC. Series of in situ shear tests were also performed between rock and concrete. The friction angle and cohesion for all tested interface were determined and analyzed. The effect of uniaxial compressive strength (UCS) of concrete on the interface behavior was determined. Additionally, the effect of...