Jeffery S. Volz

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.

Testing and Evaluation of Polyurethane-Based GFRP Sandwich Bridge Deck Panels with Polyurethane Foam Core

AbstractThis paper presents the evaluation of an innovative low-cost small-scale prototype deck panel under monotonic and fatigue bending. This new system introduces a trapezoidal-shaped polyurethane foam core with a thermoset polyurethane resin that has a longer pot life to facilitate the infusion process. The proposed panel exhibited a higher structural performance in terms of flexural stiffness, strength, and shear stiffness. The panels consist of two glass fiber–reinforced polymer (GFRP) facings with webs of bidirectional E-glass–woven fabric that are separated by a trapezoidal-shaped low-density polyurethane foam. The GFRP panels were manufactured using a one-step vacuum-assisted resin transfer molding process. The specimens studied were constructed in the Composite Manufacturing Laboratory in the Mechanical and Aerospace Engineering Department at Missouri University of Science and Technology. Small-scale prototype deck panels were tested both statically and dynamically in four-point bending to inves...

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.

EVALUATION OF AERODYNAMIC AND SEISMIC COUPLING FOR WIND TURBINES USING FINITE ELEMENT APPROACH

The behavior of a wind turbine consists of complex interactions between different components and subsystems. As more large scale wind turbines are constructed in seismically active regions, earthquake excitation makes an even more challenging problem when calculating extreme loads. Turbine specific simulation codes that directly include simulation of aerodynamics and seismic loading often include considerable simplifications to the turbine model that might cause unrealistic scenarios when designing such structures. Turbine related simulation codes are also often unfamiliar for civil engineers. For these reasons, it is desirable to come up with an approach that can handle a more realistic model that can simulate coupling between the influenced loads involved. In this work, the emphasis is put on the response of the tower of a large scale wind turbine subjected to aerodynamic and seismic loading. To capture the inclusive behavior of the structure, finite element analysis was used that consisted of shell elements for the tower, and beam elements for the blades. Various interactions were also used to model the rotation of the rotor during the operation of turbine under wind loading. Results of this approach were compared with previous findings using a selection of ground motions and turbulent wind fields. It is shown that for the turbine operational condition, the presented approach agrees well with the previously verified design codes. The outcome of this approach will provide a better understanding of more detailed structural aspects of wind turbines such as nonlinear behavior and failure criteria that might be considered necessary for a more comprehensive design.

High-Volume Fly Ash Concrete for Sustainable Construction

With worldwide production of fly ash approaching 800 million tonnes annually, increasing the amount of fly ash used in concrete will remove more material from the solid waste stream and reduce the amount ending up in landfills. However, most specifications limit the amount of cement replacement with fly ash to less than 25 or 30%. Concrete with fly ash replacement levels of at least 50% – referred to as high-volume fly ash (HVFA) concrete – offers a potential green solution. The following study investigated the structural performance of HVFA concrete compared to conventional portland-cement concrete. Specifically, the research examined both the bond strength of reinforcing steel in HVFA concrete as well as the shear behavior of HVFA reinforced concrete. The results indicate that HVFA concrete performs as well or better than conventional portland-cement concrete.

Modeling and Analysis of GFRP Bridge Deck Panels Filled with Polyurethane Foam

This paper presents finite-element analyses and analytical models of innovative, small-scale, prototype deck panels examined under monotonic bending. The deck panels consisted of two glass fiber–reinforced polymer (GFRP) facesheets separated by webs formed from E-glass–woven fabric placed around trapezoidal-shaped, low-density, polyurethane foam segments. The proposed panel exhibited a higher structural performance in terms of flexural stiffness, strength, and shear stiffness than those of conventional sandwich panels. Analytical models were used to predict critical facesheet wrinkling in the sandwich panel. Furthermore, a three-dimensional model using simulation software was developed for analysis of the proposed panel system under monotonic four-point loading. The finite-element results in terms of strength, stiffness, and deflection were found to be in good agreement with those from the experimental results. A parametric study was also conducted to further evaluate the effects of the stiffness of the top facesheet fiber layers, the mass density of the polyurethane foam, the existence of web layers, and the introduction of an overlay above the top facesheet. A flexural beam theory approach was used to predict the flexural strength of the sandwich panel.

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.