Ashraf Amer Mohammed Resheed Hiswa

This research investigates the complex interplay between stress impact, concrete shrinkage, and its implications on crack development. Utilizing theoretical and computational methods, the study analyzes the detrimental effects of structural cracks caused by stress variations. A distinctive behavior of long-term shrinkage concerning stress levels was observed. It was found that, positive stress enhances the mean Young’s modulus, while negative stress reduces modulus under negative stress conditions, heightened susceptibility to crack propagation under negative stress and improved resistance under positive stress. Temperature’s uniform impact on long-term shrinkage is demonstrated, highlighting differences among various cement classes

Abstract: This paper presents a work to validate formulae for maximum stress and deflection in glass panels by physical testing. The formulae were generated from finite element modelling using ANSYS. The physical testing revealed that unless the glass panel is restrained in position at the support points, membrane action is not developed and greater stresses and deflections are developed than predicted. Designer’s should therefore take a pessimistic view of support conditions and ignore the benefits of membrane action. Further physical testing is suggested, so that better representations of real glass panel support systems can be investigated.

ABSTRACT The rising need for utilizing alternative construction materials has promoted use timber as a construction material. Composite elements from available timber and other strengthening materials can be produced in order to find elements have strength similar to those of bigger size. Six timber beams have been strengthened with two steel channels and then tested. A finite element method was undertaken besides experimental tests as investigation methods. This study is conducted to investigate the bending behavior of composite timber-steel beams and also to enrich the research field regarding the investigation of such beams. According to the experimental tests, it was evident that both of the timber cracks and steel channels bond arrangement have strongly affected specimens’ behavior. The increases in the bond between the two channels have increased the load carrying capacity and the ductility for the specimens. Finite element method has showed a good tool in investigating the composite timber-steel beams behavior.

The influence of utilizing waste concrete aggregates on the flexural behavior of external reinforced concrete beams has been studied. Seven mixtures were prepared for this investigation where the concrete mixtures had different waste concrete percentages and admixtures. Also, seven beams were modeled by Ansys program and the properties of the seven mixtures have been used in the models to study their effects. It was found that using waste concrete aggregates has decreased the load bearing capacity and concrete ductility. It was found that the beam bearing capacity was decreased by 10.7% when using only waste concrete. Using admixtures have enhanced the concrete properties where the load capacity of beams has been increased by 39% when using silica fume and superplasticizer and the load capacity has increased by 44.6% when multi-admixtures have been used. Besides, it was found that using additives has enhanced the beam ductility significantly.

Prying force formation at bolts is considered as an important problem in steel connection design. It affects the connection bearing capacity, ductility and serviceability negatively by increasing stresses induced inside connections. In the present work, behavior of steel connection under prying force is studied. A connection of steel beam-column has been modeled using software Revit program. Tension load is applied increasingly and the connection displacement has been measured until failure. Finite element simulation of steel angles under the effect of tension load and prying force has been studied. It is found that the connection has three phases of bearing behavior. Plastic hinge formation noticed increased with prying force presence.

As a non-destructive technique for concrete compressive strength assessment for existing concrete structures, Ultrasonic Pulse Velocity (UPV) test method has been widely used. Since the UPV affected by many factors, it is not easy to accurately assess the concrete compressive strength. Effect of some factors which are coarse aggregate grading type, slump, the water-cement ratio (w/c), sand volume ratio, coarse aggregate volume ratio, testing age, concrete density, and pressure of steam curing, were analyzed on the relationship between ultrasonic pulse velocity and concrete strength. 436 records of data, extracted from published research work, were used to build seven supervised machine learning regression models which are; Artificial Neural Network (ANN), Support Vector Machine (SVM), Chi-squared Automatic Interaction Detector (CHAID) decision tree, Classification and Regression Trees (CART) decision tree, non-linear regression, linear regression, and stepwise linear regression models. Also, the independent variable importance for each predictor was analyzed and for each model. With an adequate tuning of parameters, ANN models have produced the highest accuracy in prediction, followed in sequent with SVM, CHAID, CART, non-linear regression. Linear and stepwise linear regression models have present low values of predictive accuracy. w/c was observed to be the highest importance factor in prediction of concrete strength, and the forecasting of the concrete strength was efficient when using w/c and UPV only as predictors in any of the used predictive models.