Flexural Behavior of Cracked RC Beams Retrofitted with Strain Hardening Cementitious Composites

Ali Basha,Sabry Fayed,Galal Elsamak 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.6

In the present research, the efficiency and the effectiveness of different Ultra High Performance Strain Hardening Cementitious Composites (UHP-SHCC) schemes for flexure retrofitting of a cracked RC beams were investigated experimentally, numerically and analytically. The experimental program consisted of six RC beams. The control specimen was loaded until failure. The middle third part of the control specimen was replaced with UHP-SHCC, then, it was loaded again until failure. The other five beams were loaded until 52% of the failure load of the control beam, then they were retrofitted with a layer of UHP-SHCC casted at tension side. The main parameters were thickness and the reinforcement ratio of UHP-SHCC layer with two different lengths of UHP-SHCC layer. The test results showed that using UHP-SHCC layer is a highly effective technique to increase the flexural capacity and the ductility of RC beams. As the reinforcement ratio of the layer increased, the flexural capacity increased. The flexural capacity of the beams with a layer length of 75% beam span was less than the capacity of the beams having a layer length equal to the beam span. Analytical and numerical results agreed with the experimental results.

Flexural strengthening of RC one way solid slab with Strain Hardening Cementitious Composites (SHCC)

Basha, Ali,Fayed, Sabry,Mansour, Walid Techno-Press 2020 Advances in concrete construction Vol.9 No.5

The main aim of the current research is to investigate the flexural behavior of the reinforced concrete (RC) slabs strengthened with strain hardening cementitious composites (SHCC) experimentally and numerically. Seven RC slabs were prepared and tested under four-points loading test. One un-strengthened slab considered as control specimen while six RC slabs were strengthened with reinforced SHCC layers. The SHCC layers had different reinforcement ratios and different thicknesses. The results showed that the proposed strengthening techniques significantly increased the ultimate failure load and the ductility index up to 25% and 22%, respectively, compared to the control RC slab. Moreover, a three dimensional (3D) finite element model was proposed to analyze the strengthened RC slabs. It was found that the results of the proposed numerical model well agreed with the experimental responses. The validated numerical model used to study many parameters of the SHCC layer such as the reinforcement ratios and the different thicknesses. In addition, steel connectors were suggested to adjoin the concrete/SHCC interface to enhance the flexural performance of the strengthened RC slabs. It was noticed that using the SHCC layer with thickness over 40 mm changed the failure mode from the concrete cover separation to the SHCC layer debonding. Also, the steel connectors prevented the debonding failure pattern and enhanced both the ultimate failure load and the ductility index. Furthermore, a theoretical equation was proposed to predict the ultimate load of the tested RC slabs. The theoretical and experimental ultimate loads are seen to be in fairly good agreement.

Post Buckling Behavior of Slender Piles Partially Embedded in Sand Soil under Axial Load

Ali Mohammed Basha 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.3

Pile instability due to buckling is considered to be one of the most important causes of superstructures failures especially in bridges and wind turbines. The mechanism of load-transfer of partially embedded piles in sand subjected to axial load to surrounded soil and the corresponding deformation are important aspects of pile design. In the present research, an experimental model was developed to measure the lateral displacement of piles subjected to axial loads. The experimental results indicated that the post buckling load of partially embedded pile was enhanced up to five times of the buckling load of free case. Two proposed formulas based on the laboratory experiments were induced to determine post buckling load of the partially embedded pile. The predicted buckling capacity of piles was compared to the experimental buckling load, which showed a good agreement.

Variation of the Hydraulic Conductivity and the Mechanical Characteristics of Plastic Concrete with Time

Ali Basha,Walid Mansour 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.4

Sand-bentonite-cement are commonly used as cut-off walls to isolate polluted soils or in ground improvement technologies and as retaining structures as secant pile wall. In this research, a laboratory program consisted from 105 sample were prepared and tested between different tests, such as hydraulic conductivity, porosity, and compressive strength to monitor the mechanical behavior of sand-bentonite-cement at different ages. Based on the experimental relationships between hydraulic conductivity coefficient and samples age; there were reduction due to added bentonite to mixture reach about 35.0% at 7 days. Moreover, the average reduction in the compressive strength of plastic concrete samples with bentonite was lower by average range about 51.0% than the compressive strength of plastic concrete samples without bentonite at 7 days. In this study, proposed formulas were derived to estimate the splitting tensile strength based on the compressive strength and the hydraulic conductivity in terms of the bentonite/cement ratio and testing age. The predicted values showed well agreement with the experimental records for samples of sand-bentonite-cement mixtures where the standard deviation and coefficient of variation were 0.02, and 0.94%, respectively.

Experimental Study on Effect of Recycled Reinforced Concrete Waste on Mechanical Properties and Structural behaviour of the Sandy Soil

Ali Basha,Fatma khalifa,Sabry Fayed 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.6

In recent years, constructing natural aggregates as a base layer for the roads has increased. Natural resources will run out as long as human consumption of them continues. Recycled concrete aggregate (RC) has thus emerged as a substitute material for the building of road base layers. Additionally, RC can be utilized to create interior city highways. The base layer for roads must have sufficient strength to support the working load on the pavement surface without damage deforming. As a result, the focus of this paper is on enhancing the structural performance of sandy soil reinforced with various RC percentages. The three key factors are relative soil density (Dr = 83 and 97%), recycled concrete aggregate reinforcing levels (RC = 0,5,10,15,20,25,30,40,50 and 100%), and reinforcement layer thickness (Rd = 0.0B, 0.5B, B, and 2B where B is the footing model width). Numerous laboratory experiments were conducted in order to examine the impact of important parameters on the properties of the mixtures. The plate bearing tests were carried out using a footing model (250 × 250 mm) inside a tank (1500 × 1500x1000 mm) to ascertain the stress–strain response, bearing capacity ratio (BCR), ultimate bearing capacity, and modulus of elasticity of the tested mixtures. It is clear that raising the RC has no effect on the diameters of the grains. It was found that as RC increased, the mixture's bulk density increased but specific gravity decreased. Maximum dry density rose as RC rose, whereas water content fell. It was noted that BCR unquestionably increased as RC increased for all RC levels and all values of settlement ratios. The appropriate reinforcing layer thickness is suggested to be no more than 2B. As the RC concentration in the sand and Rd increased, the difference between two pressure-settlement curves of densities 83% and 97% significantly decreased. Furthermore, when RC reaches 50%, two curves are roughly comparable. At RC = 50%, it is advised that the relative density of 83% is sufficient to produce the same behavior as the relative density of 97%. It was found that as RC and Rd grew, the tested mixtures' ultimate bearing capacity and elasticity modulus increased as well. A novel proposed formulas are developed to compute bearing capacity ratio, ultimate bearing capacity, and elasticity modulus of the tested mixtures taking into account the influence of RC, reinforcement layer depth, settlement ratio, and the relative density, and its results agree with the experimental results.

Experimental and numerical analysis of the punching behavior of RC isolated footings

Walid Mansour,Sabry Fayed,Ali Basha 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.5

In the current study, punching behavior of Reinforced concrete (RC) isolated footings was experimentally and numerically investigated. The experimental program consisted of four half-scale RC isolated footing specimens. The test matrix was proposed to show effect of footing area, reinforcement mesh ratio, adding internal longitudinal reinforcement bars and stirrups on the punching response of RC isolated footings. Footings area varied from 1200x1200 mm2 to 1500x1500 mm2 while the mesh reinforcement ratio was in the range from 0.36 to 0.45%. On the other hand, a 3D non-linear finite element model was constructed using ABAQUS/standard program and verified against the experimental program. The numerical results agreed well with the experimental records. The validated numerical model was used to study effect of concrete compressive strength; longitudinal reinforcement bars ratio and stirrups concentration along one or two directions on the ultimate load, deflection, stiffness and failure patterns of RC isolated footings. Results concluded that adding longitudinal reinforcement bars did not significantly affect the punching response of RC isolated footings even high steel ratios were used. On the contrary, as the stirrups ratio increased, the ultimate load of RC isolated footings increased. Footing with stirrups ratio of 1.5% had ultimate load equal to 1331 kN, 19.6% higher than the bare footing. Moreover, adding stirrups along two directions with lower ratio (0.5 and 0.7%) significantly enhanced the ultimate load of RC isolated footings compared to their counterparts with higher stirrups ratio (1.0 and 1.5%).

Automatic Monitoring of Water Pollution from Sentinal-2 Satellite Imagery: A Case Study of Mediterranean Coast, Egypt

Magda Farhan,Mahmoud Salah,Ali M. Basha,Ahmed Kahlil,Omnia Fathy 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.8

Water is the most important source among the natural sources on the earth's surface for the health of marine and near-shore ecosystems. Assessing water pollution in coastal areas is an essential process for sustainable development. El Gharbia coast, Egypt is one of the most important coasts of Egypt. The main objective of this work is to predict the future changes of water pollution in this coast using Sentinel-2 satellite imagery of three consequent times. First, three Sentinel-2 satellite imagery of consequent dates were acquired and processed for further classification process. The maximum likelihood classification algorithm was then used to prepare the base maps for: time 1, time 2 and time 3, with ten major classes (pollutants). The classified images of time 1 and time 2 were then used to predict the time 3 water pollution map using a Markov Chain Model. After that, the final predicted water pollution map for time 3 was validated with the classified one of the same time. Finally, and compared with the water pollution map of time 3, the future ratios of all types of pollutants have been predicted. The results showed that the proposed model can simulate water pollution changes with reliable results. Based on the simulated water pollution map and by 2030, the ratios of all pollutants will increase. Accordingly, El Gharbia coast and surrounding activities can be saved from more pollution in the future.