Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : reinforced concrete


An Experimental Study on the Shear Strength of High-performance Reinforced Concrete Deep Beams without Stirrups

Sinan Abdulhkaleq Yaseen

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2123-2139

High-performance fiber-reinforced concrete is a new class of concrete that has been developed in recent decades. It exhibits enhanced properties such as high compressive strength and improved tensile strength. Three types of concrete with different compressive strengths, namely, normal-strength concrete, high-strength concrete, and high-performance concrete, were used in this study. The experimental program included casting and testing sixteen reinforced concrete deep beams without stirrups to study the shear strength and behavior of these beams under two-point loading. The variables considered were the compressive strength of concrete (f′c ) (40–120 MPa), shear span-to-depth ratio (1, 1.5, 2, 2.5, and 3), and the ratio of the amount of flexural steel bar ratio (1.35%, 2.40%, 3.76%, and 6.108%). Experimental results showed that increasing concrete compressive strength and flexural steel bar ratio increased ultimate shear capacity. By contrast, increasing shear span-to-depth ratio and span-to-depth ratio reduced ultimate shear capacity. Based on the test results of this investigation (16 beams) and those of available literature (233 deep beams), an equation that considered the parameters affecting shear stress (f′c, l/d, a/d, andw) was proposed using SPSS software. The proposed equation was compared with predictions made by the American Concrete Institute (ACI) and the works of other researchers, including that of Zsutty and Aziz. The ACI predictions were conservative and the proposed equation had a lower coefficient of variation.

Direct Shear Behavior of Carbon Fiber Reinforced Self- Compacting Concrete

Kaiss F. Sarsam; Tareq S. Al-Attar; Ghzwan Ghanim Jumah

Engineering and Technology Journal, 2014, Volume 32, Issue 10, Pages 2491-2513

This paperrepresents an experimental and statistical investigation for the behavior of connectionpoints produced by using self-compacting concrete and subjected to direct shear. The investigation also includes the effect of carbon fiber inclusion as reinforcement on self-compacting concrete (SCC) behavior in direct shear.
This study gives results of sixteen push-off or direct shear specimens in four groups. Variations include volume fraction for carbon fiber (V_f= 0.00, 0.50, 0.75 and 1.00) % for every percentage change in the steel reinforcement. The steel reinforcement parameter ρ_vf f_y values are (0.00, 2.66, 5.33 and 7.99) MPa(where ρ_vf varies from 0.00 to 0.0173 and f_y=585.7MPa) . The main material properties studied include compressive strength, splitting tensile strength and modulus of rupture. Measurements of deformations were made throughout testing of shear specimens.
The dimension of the shear plane in the push-off specimenswas 170x185 mm. The shear reinforcement was normal to the shear plane. Specimens were cast by using SCC which is a type of high performance concreteand reinforced with carbon fiber.
This work aims to investigate the direct shear behavior of SCC with or without carbon fiber at constant water to cementitious materials ratio of 0.3 by weight. It is found that using carbon fiber increased the direct shear strength. However, carbon fiber alone (without reinforcement) leads to brittle failure. In contrast, adding rebars leads to higher strain and more ductile behavior-increased shear capacity is obtained when higher steel quantity is used. The aim of adding carbon fibers was the increase of the horizontal strain (displacement). It was found that the optimum percentage of volume fraction was 0.75 % for fresh and hardened concrete.
In addition, the effects of carbon fiber on compressive strength of SCC lead to a drop in compressive strength (f_c^') compared with reference specimens. This drop in f_c^' was 2.39, 8.38 and 13.58% for V_f=0.50, 0.75 and 1.00%, respectively. In contrast, the splitting tensile strength increased by 3.34, 31.2 and 18.2 as compared with the cylinder strength without carbon fibers atV_f equal to0.50, 0.75 and 1.00% respectively. The modulus of rupture increased by [11.9, 21.99 and 13.83%] as compared with SCC without carbon fibers at〖 V〗_f equal to 0.50, 0.75 and 1.00% respectively.
Based on push-off tests results for this work and those available in the literature, two statisticalmodels have been established using regression analysis. Four variables f_c^',f_ct,ρ_vf f_y and V_f, were included in these models. Both models showed good representation according to their coefficients of variation (COV)values. Verification of the models were done by using 273 observations from literature and the present work.

Investigation of the Behavior for Reinforced Concrete Beam Using Non-Linear Three-Dimensional Finite Elements Model

Israa Kh. AL-Shimmari; Nagham T.Hamad; Waleed A Waryosh

Engineering and Technology Journal, 2011, Volume 29, Issue 10, Pages 1870-1885

This study presents theoretical investigation that reinforced concrete and composite construction might be suitably combined to give a new structural material: composite reinforced concrete. To study theoretically the composite beam, nonlinear three-dimensional finite elements have been used to analyze the tested beam.
The 8-node brick elements in (ANSYS) are used to represent the concrete, the steel bars are modeled as discrete axial members connected with concrete elements at shared nodes assuming perfect bond between the concrete and the steel. The results obtained by finite element solution showed good agreement with experimental results.

Evaluation of Elastic Deflections and Bending Moments for Orthotropically Reinforced Concrete Rectangular slabs Supported on Three Edges Only

Hisham M. AL-Hassani; Husain M. Husain; Aama; a Ali Ahmad

Engineering and Technology Journal, 2009, Volume 27, Issue 7, Pages 1247-1259

This paper deals with the evaluation of the elastic deflections and bending moments
for orthotropically reinforced concrete rectangular slabs supported on three variously
restrained edges with the fourth edge free and subjected to uniformly distributed load.
Six cases are considered for such slabs to cover all possible restraining conditions at the
three supported edges. Based on the finite difference approach, equations are derived to
calculate the maximum values of the positive and negative bending moments as well as
the maximum deflection in any of these six slab cases caused by the applied uniform
load.

Experimental Tests on Orthotropically RC Rectangular Slabs Having Various Restrained Edges and Subjected to Uniform Load

Husain M. Husain; Hisham M.AL-Hassani; Sarmad S. Abdul-Qader AL-Badri

Engineering and Technology Journal, 2009, Volume 27, Issue 5, Pages 913-929

In this research, nine orthotropically reinforced concrete (RC) rectangular slabs
having various boundary restraints at the edges are tested under uniformly distributed
load. The main aim of these tests is to show that when some or all edges of a slab are
restrained against rotation and horizontal translation the ultimate load carrying capacity
of the slab will be enhanced greatly above that suggested by the simple Johansen ,s yield
line theory(1). For this purpose, a specially designed rig is constructed and used for
providing slabs with various boundary restraints along their edges.
The results of tests, which are presented in the form of load-deflection curves plotted
non-dimensionally, show that for restrained slabs the enhancement in load above
Johansen ,s load ranges between 50% and 100% depending on the number and positions
of the slab restrained edges. These results are also used to examine the accuracy of a
recently submitted elastic-plastic theoretical model(2).

Design charts for channel shaped reinforced concrete short columns subjected to axial compressive load and uniaxial bending

Asma; a A. Ahmad; Sarmad S. Abdul-Qader AL-Badri

Engineering and Technology Journal, 2009, Volume 27, Issue 4, Pages 809-820

Eight design charts are presented for reinforced concrete short C-columns subjected to
axial compressive load plus uniaxial bending. For design these charts can be used for
determining the required column dimensions and amount of steel, while for analysis
these charts can be used for estimating the loaded column capacity.
Four examples are given to explain the use of design charts for both design and
analysis, two of which are design examples while the other two are analysis. It has been
shown by these examples that the new proposed charts are very simple to use in
structural applications.

Flexural Rigidity of Slender RC Columns

Sabeh Z. Al-Sarraf; Ihsan A. S. Al-Shaarbaf; Bassman R. Al-Bakri; Kaiss F. Sarsam

Engineering and Technology Journal, 2009, Volume 27, Issue 1, Pages 96-115

166320 hypothetical reinforced concrete (RC) columns, each with a different
combination of variables, were used to investigate the major variables that affect the
flexural rigidity (EI) of slender RC columns. Using linear regression analysis, new EI
expression was statistically developed for 131 slender RC columns. These columns were
experimentally tested and available in the literature. This proposed EI expression were
introduced into the ACI 318M-05 Code column design procedure to make comparisons
between 150 column experimental data with theoretical estimates of the nominal
strength using theoretical other methods. These estimates include, in addition to the proposed
EI expression, other calculations from the literature.