Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Reinforced concrete

Influence of Minimum Tension Steel Reinforcement on the Behavior of Singly Reinforced Concrete Beams in Flexure

Ali A. Abdulsada; Raid I. Khalel; Kaiss F. Sarsam

Engineering and Technology Journal, 2020, Volume 38, Issue 7, Pages 1034-1046
DOI: 10.30684/etj.v38i7A.902

The requirements of minimum flexural reinforcement in the last decades have been a reason for controversy. The structural behavior of beams in bending is the best way of investigating and evaluating the minimum reinforcement in flexure. For this purpose, twelve singly reinforced concrete beams with a rectangular cross-section of (125 mm) width by (250 mm) height and (1800 mm) length were cast and tested under two-point loads up to failure. These beams were divided into three groups with different compressive strengths (25, 50, and 80 MPa). Each group consists of four beams with different amounts of tension steel reinforcement approximately equal to (0% Asmin, 50% Asmin, 100% Asmin and 150% Asmin), two bar diameters (Ø6 mm and Ø8 mm) were used as the longitudinal tension reinforcement with different yield and ultimate strengths, the minimum amount of reinforcement required is calculated based on ACI 318M-2014 code. The results show that for the reinforced concrete beams, the flexural reinforcement in NSC beams increases the first cracking load and the increment increased with an increasing amount of reinforcement, while for HSC beams the increasing in first cracking load are very little when the quantity of reinforcement less than the minimum flexural reinforcement and increased with the increasing amount above the minimum flexural reinforcement. The equation of ACI 318M-14 code gives adequate minimum flexural reinforcement for NSC and overestimate value for HSC up to (83 MPa), A new formula is proposed for HSC rectangular beams up to (90 MPa) concrete compressive strength by reducing the equation of ACI 318M-14 code for minimum flexural reinforcement by a factor depending on concrete compressive strength.

Durability Characteristics of Concrete and Reinforcing Bars Exposed to Harsh Environments

Sanaa Abdul Hadi Hafad; Farah Hamed Rashed

Engineering and Technology Journal, 2014, Volume 32, Issue 5, Pages 921-937

Saline pollution attack is an important factor that leads to the deterioration of the concrete, especially in industrial plants. In spite of research address the sustainability of concrete and particularly steel rebar submeserged in it steel rebar is the most important causal factors the deterioration in the reinforced concrete the main aim of this research is study the effect of additives added to reduce superior degree water and two types of mineral additives that include silica fumes and steel fiber, as well as the combined effect of these additives on the properties of concrete. The experimental work of this measure include concrete specimens have been partially submerged in a solution of chlorides and sulfates in concentrations similar to those found in aggressive conditions. The properties of concrete specimens were evaluated through the properties investigated included ultrasonic plus velocity, compressive strength electrochemical potential for various types of mixes. Concrete mixed with 10% of silica shown development all properties of concrete, while these properties deceases values of mix reference coated with natural rubber (RFCNR) and steel fiber coated with natural rubber (STFCNR). The result coated specimens has shown resistance to corrosion greater than specimens without coated when immersion in salt solution. Thus group (RFCNR )shown more develops in all properties as compared with all other mixture immersed in salt solution for 180 days at odds with group ( SF-SP) which had development in all properties as compared with the reference mixture at 180 days of immersion in salt solution .

Mechanical Properties and Dynamic Response of Lightweight Reinforced Concrete Beam

AzizI brahimAbdulla; a A. Ali; Alya; Ahmed Adnan Ghanee

Engineering and Technology Journal, 2012, Volume 30, Issue 2, Pages 293-311

The study is conducted to perform two goals: The first geal is to produce a
lightweight concrete using major components which are locally available with
some standard admixtures.Many mixtures are prepared using many ratios of
superplasticizer (SP) and silica fume (SF) admixtures to yield a lightweight
aggregate concrete, the effects of using different ratios of these admixtures on unit
weight, compressive strength and flexural strength are studied individually and
accumulatively. The secondis to study the dynamic specifications of normal and
lightweight reinforced concrete beams.
The results showed that the increasing in dosage of superplasticizer (SP) for
(LWAC) increases the density of (LWAC), and the increasing in dosage of silica
fume (SF) decreases the density of (LWAC). The experimental impact tests for
R.C. beams shows that the lightweight R.C. beams have a better response under
impact loading with respect to the maximum dynamic deflection (2.955mm for
normal weight beam and 1.58mm for lightweight beam). Also,Impact force
transferred to supports reactions of lightweight beams is smaller within 45% than
the impact force transferred to reaction of normal weight concrete under the same
impact load, and the time to reach 90% damping equal to 1.223 sec and 1.6 sec for
lightweight and normalweight R.C. beams respectively. Also, the reinforced
concrete beams are tested under repeated impact load up to failure. The tests
showed that the no. of blows to cause first crack for lightweight concrete beams
more than twice of this for normalweight concrete beams.