Mahdi Arezoumandi

An experimental study on flexural strength of reinforced concrete beams with 100% recycled concrete aggregate

Abstract The following paper presents the results of an experimental investigation of the flexural strength of full-scale reinforced concrete beams constructed with both 100% recycled concrete aggregate (RCA) as well as conventional concrete (CC). This experimental program consisted of eight beams (four for each concrete type). The test parameters for this study include longitudinal reinforcement ratio and concrete type. The beams were tested under a simply supported four-point loading condition. The experimental cracking, yielding, and ultimate moment of the beams were compared with the ACI 318-11 and Eurocode 2-05 provisions and the modified compression field theory (MCFT) method. Furthermore, the experimental flexural strengths of the beams were compared with both flexural test databases of CC and RCA specimens. Results of this study show that the RCA beams have comparable ultimate flexural strength and approximately 13% higher deflection corresponding to the ultimate flexural strength of the CC beams.

An experimental study on shear strength of reinforced concrete beams with 100% recycled concrete aggregate

An experimental investigation was conducted to study the shear strength of full-scale beams constructed with 100% recycled concrete aggregate (RCA) as well as conventional concrete (CC). This experimental program consisted of 12 beams (six for each concrete type). The test parameters for this study include longitudinal reinforcement ratio and concrete type. The experimental shear strengths of the beams were compared with the shear provisions of both U.S. and international design codes (U.S., Australia, Canada, Europe, and Japan) as well as a shear database of CC specimens. The shear strengths of the beams were also evaluated based on different fracture mechanics approaches and the modified compression field theory (MCFT) method. Furthermore, statistical data analyses (both parametric and non-parametric) were performed to evaluate whether or not there was any statistically significant difference between the shear strength of the recycled aggregate concrete (RAC) and CC beams. Results of these statistical tests show that the 100% RCA beams possess approximately 12% lower shear strength compared with the CC beams. 2013 Elsevier Ltd. All rights reserved.

Estimation of Travel Time Reliability for Freeways Using Mean and Standard Deviation of Travel Time

Abstract Variable speed limit (VSL) signs are in use across Interstate 255/270 (I-270/I-255) in St. Louis County, Missouri, varying the speed limit in real time during peak periods to reduce congestion. This paper evaluates the effects of the VSL system on travel time distribution and travel time reliability. Several distributions, including gamma, largest extreme value, log-logistic, log-normal, and Weibull, were fitted to the 24-hour travel time data to determine which provides the best fit for post-VSL conditions. Log-normal distribution provided the best. This paper also proposes a new method to estimate the 95th percentile of travel time, one of the most important factors for travel time reliability, using the mean and standard deviation of travel time. Parametric and nonparametric statistical tests were performed to validate this method using 36 field data sets from four congested segments of I-270/I-255.

Shear Behavior of High-Volume Fly Ash Concrete versus Conventional Concrete

AbstractThe production of portland cement—the key ingredient in concrete-generates a significant amount of carbon dioxide. However, due to its incredible versatility, availability, and relatively low cost, concrete is the most consumed manufactured material on the planet. One method of reducing concrete’s contribution to greenhouse gas emissions is the use of fly ash to replace a significant amount of the cement. An experimental investigation was conducted to study the shear strength of full-scale beams constructed with both high-volume fly ash concrete (HVFAC)—concrete with at least 50% of the cement replaced with fly ash—and conventional concrete (CC). This experimental program consisted of 16 beams (12 without shear reinforcing and four with shear reinforcing in the form of stirrups). Additionally, three different longitudinal-reinforcement ratios were evaluated within the test matrix. The beams were tested under a simply supported four-point loading condition. The experimental shear strengths of the b...

Effect of Recycled Concrete Aggregate Replacement Level on the Shear Strength of Reinforced Concrete Beams

An experimental investigation was conducted to study the mechanical properties and shear strength of full-scale beams constructed with recycled concrete aggregate (RCA). This study included two RCA mixtures and one conventional concrete (CC) mixture. The two RCA mixtures are different in the amount of RCA replacement, with one mixture replacing 50% of the virgin aggregate with RCA (RAC50) and the other replacing 100% (RAC100). This experimental program consisted of 18 beams with three different longitudinal reinforcement ratios. The experimental shear strengths of the beams were compared with the shear provisions of both U.S. and international design codes. Furthermore, the shear strengths of the beams were evaluated based on fracture mechanics approaches, Modified Compression Field Theory (MCFT), and a shear database of CC specimens. In addition, statistical data analyses were performed to evaluate whether there is any statistically significant difference between the shear strength of the recycled-aggregate concrete (RAC) and CC beams. Results of this study show that the RAC100 has 11% lower shear strength, on average, compared with the RAC50 and CC beams; however, the RAC50 and CC beams showed similar shear resistance. The decrease in basic mechanical properties (splitting tensile strength, flexural strength, and fracture energy) for the RAC parallels the decrease in full-scale shear behavior and can be used as a predictor in mixtures containing recycled concrete as aggregate.

Hybrid Jacketing for Rapid Repair of Seismically Damaged Reinforced Concrete Columns

This study proposes hybrid jacketing for rapid repair of seismically damaged concrete columns for bridge safety. The hybrid jacketing for a reinforced concrete (RC) column is composed of a thin cold-formed steel sheet wrapped around the column and its outside prestressing strands. Although the prestressing strands can prevent buckling of the confining steel sheet, the steel sheet can in turn prevent the prestressing strands from cutting into the concrete. The hybrid jacketing concept was validated with testing of a large-scale RC column with lap splice deficiency typical of pre-1970 bridge constructions in the Central United States. Results from the original and repaired columns were compared for hysteresis loops, strength, stiffness, ductility, and energy dissipation. The hybrid jacketing proved to be effective in restoring structural behavior of the damaged column to prevent bridge collapse. Such a cost-effective solution can be implemented at bridge sites in hours. Design equations to establish the lateral force–displacement relationship of the tested column to design the hybrid jacket are derived in detail.

Shear Behavior of High-Volume Fly Ash Concrete versus Conventional Concrete: Experimental Study

AbstractThe production of portland cement—the key ingredient in concrete—generates a significant amount of carbon dioxide. However, due to its incredible versatility, availability, and relatively low cost, concrete is the most consumed synthetic material on the planet. One method of reducing concrete’s contribution to greenhouse-gas emissions is the use of fly ash to replace a significant amount of the cement. This paper compares two experimental studies that were conducted to investigate the shear strength of full-scale beams constructed with both high-volume fly ash concrete (HVFAC)—concrete with at least 50% of the cement replaced with fly ash—and conventional concrete (CC). The primary difference between the two studies involved the amount of cementitious material, with one mix having a relatively high-total cementitious content [502  kg/m3 (850  lb/yd3)] and the other mix having a relatively low-total cementitious content [337  kg/m3 (570  lb/yd3)]. Both HVFAC mixes used a 70% mass replacement of por...

Shear Strength of Chemically Based Self-Consolidating Concrete Beams: Fracture Mechanics Approach versus Modified Compression Field Theory

AbstractAn experimental investigation was conducted to study the shear strength of full-scale beams constructed with both chemically based self-consolidating concrete (SCC) and conventional concrete (CC). This experimental program consisted of 12 beams without stirrups with three different longitudinal reinforcement ratios. The beams were tested under a simply supported four-point loading condition. The experimental shear strengths of the beams were compared with the shear provisions of both U.S. and international design codes. Furthermore, the shear strengths of the beams were evaluated based on fracture mechanics approaches, modified compression field theory (MCFT), and a shear database of CC specimens. Results of this study show that the SCC possesses comparable shear strength to the CC.

Flexural Behavior of High-Volume Fly Ash Concrete Beams: Experimental Study

An experimental investigation was conducted to study both mechanical properties and the flexural strength of full-scale reinforced concrete beams constructed with both high-volume fly ash concrete—concrete with 70% of the cement replaced with fly ash—and conventional concrete (CC). The beams were tested under a simply supported four-point loading condition. The experimental cracking, yielding, and ultimate moments as well as deflection on ultimate load of the beams were compared with both the ACI 318-11 and Eurocode 2-05 provisions. Furthermore, the experimental flexural strengths of the beams were compared with both the modified compression field theory method and a flexural test database of CC specimens. Results of this study showed that the high-volume fly ash concrete beams had comparable flexural strength compared with the CC beams.

Effect of High-Volume Fly Ash on Shear Strength of Concrete Beams

Every year concrete production exceeds 6.5 billion tons worldwide, nearly 1 ton for every man, woman, and child on the planet. In fact, concrete is used 10 times more than any other building material in the world, primarily because of its incredible versatility, availability, and relatively low cost. Unfortunately, the production of portland cement—the key ingredient in concrete—generates approximately a pound of carbon dioxide for every pound of cement produced. One method of reducing concretes carbon footprint is to replace a significant amount of the cement with fly ash, a by-product of coal-burning thermal power stations. This paper presents the results of an investigation of the shear strength of full-scale reinforced concrete beams constructed with both high-volume fly ash concrete (concrete with at least 50% of the cement replaced with fly ash) and conventional concrete. A test matrix of 16 beams included 12 beams without shear reinforcing and four with shear reinforcing in the form of stirrups; e...