No abstract

Bonding between reinforcement and concrete play an important parameter in the behavior and strength of reinforced concrete. Many parameters influence the bond between reinforcement and concrete such as concrete cover depth, concrete conditions, overall thickness of the structural element and curing. In the present study, a total of sixty specimens as cube with four different percentages of polypropylene fiber (0, 0.5,1 and 1.5) % is used to evaluate the bond strength and stress-slip relationship. The compressive strength of concrete, rebar diameter, concrete cover, and embedded length of reinforcement are taken into account as variables. The test results show that the ultimate bond strength increases with increasing each of the compressive strength of concrete, concrete cover, polypropylene fiber content and decreasing the nominal diameter of the reinforcing bar. The best percentage that gave the maximum failure load, is 1.5% of polypropylene fiber.

Abstract. In this study, nonlinear three-dimensional finite element analysis has been used to conduct a numerical investigation of the effect of applied impact load on the foundation based on sandy soil using the finite element method by ANSYS (Version 11) computer program. The 8-node brick elements are used to model the concrete of foundation and the soil under the foundation which are denoted by Solid 65 for concrete and Solid 45 for the soil while the interface is modeled by using three-dimensional surface-to-surface (Target 170 and Contact 174) contact elements connected with concrete and soil. As a case study, a square concrete foundation with dimensions of 3×3×0.3 m placed on the foundation soil 15 m deep and 9 m away from the edge of plate is subjected to impact load. A parametric study is carried out to investigate the effect of several parameters including: foundation thickness, load eccentricity and amplitude of impact load. It was concluded that the load eccentricity increases the displacement and decreases the stress at the foundation center. This is attributed to non-uniformly distributed stresses on the loaded area, where the loads are concentrated locally within the loaded area. The presence of damping leads to a considerable decrease in the foundation displacements and stresses. The increase in the damping ratio reduces the vertical displacement of the foundation at the same time at all damping ratios.

Reactive powder concrete (RPC) possesses superior structural and mechanical characteristics. Despite these excellent properties, the main drawback of RPC is that it is a very costly material. This study included an experimental program for studying the flexural behavior of hybrid beams containing RPC together with self-compacting concrete (SCC) in the same section. Five specimens with dimensions of 100 x 150 x 1000 mm were investigated. The first crack load, ultimate load, maximum deflection, load-deflection response, and crack pattern were investigated. The experimental program included testing five reinforced concrete beams with four-point loading. The specimens were cast as follows: full depth of self-compacting concrete; full depth of reactive powder concrete; half of the section depth of RPC (tension zone); quarter of the section depth of RPC (tension zone); and half of the section depth of RPC (compression zone). The experimental results of the hybrid beams showed that using RPC in the tension zone of the beam significantly improved the performance of the hybrid beams when compared with the SCC beam. The improvement rate increased with the RPC layer thickness in the tension zone. Using RPC in the compression zone together with SCC did not produce a significant improvement in the performance of the hybrid beams.

Dynamic analysis for reinforced concrete precast piles with (300x300 mm) in dimension and length (12 m) with different types of loading was carried out. The common precast pile in Iraq was adopted in this study. Finite element analysis by ANSYS software was adopted and dynamic loading was applied to check out the strength and performance of pile. The frequency range adopted is based on the low, medium and high frequency. The analysis consisted of single pile (without surrounding soil) and pile embedded in soil as nonlinear material (soil) analysis to evaluate the vertical and horizontal displacements at the location of applied load. According to the analysis of single pile without soil and when the model of pile embedded in the soil indicated that the soilstructure interaction represented the worst case that is mean the simulation of the pile must take into account the effects of soil on the behavior and performance of the precast pile. The applied static loading on the pile model and checking the results of pile strength capacity showed that the applied load equal to the value calculated as per ACI 543R-2000 suggested equation. Based on the finite elements analysis results in case of friction between the contact surface of soil and pile increased the strength capacity of the pile due to the forces developed along the pile so that these forces add to the bearing resistance of the pile. The displacements in case of low and medium frequency are tenth time more in case of soil-structure interaction as compared with the analysis results of single pile alone. It was concluded that the presence of friction between the contact surface of soil and pile increased the strength capacity of the pile due to the forces developed along the pile so that these forces add to the bearing resistance of the pile.