Optimum Design of RC Beams Strengthened with Externally Bonded FRP Using Pattern Search Noor Mohammed Sheet, Baraa J.M. AL-Eliwi, Rabi M. Najem Tikrit Journal of Engineering Sciences, 2025 This paper discusses the efficiency of using the Pattern Search (PS) tool to optimize the design of RC beams strengthened with externally bonded (EB) fiber-reinforced polymer (FRP) materials. The study considers shear strengthening (three-sided or two-sided configurations), flexure strengthening, and coupled shear-flexure strengthening. The design process involved an objective function that represents the cost function of the optimum solution and design variables that define the optimum dimensions of the beam and FRP material, such as beam width, effective beam depth, FRP strip thickness, FRP strips spacing, and FRP strip width, according to the design constraints of the ACI 440-2R-17 code. To achieve the goal of this paper, different examples were conducted under shear, flexure, and coupled shear-flexure strengthening. In each case, the PS technique resulted in more compact designs with a faster convergence rate, reducing costs compared to the original dimensions of the design variables. In this context, an extensive parametric study was conducted to determine the ability to redesign the FRP material dimensions compared to previously published data. The results showed that the pattern search technique could save costs in designing RC beams strengthened with externally bonded FRP under similar loading conditions.
Structural Importance Factor Effect on Reliability-Based Design of Steel Frame System Units: Dependent and Independent Failure Baraa J. M. Al-Eliwi, Rabi M. Najem, James H. Haido, Sevar Dilkhaz Salahaddin Civil and Environmental Engineering, 2025 The structural importance factor is essential in the reliability-based design of structural systems, affecting both dependent and independent failure modes. This factor is crucial for ensuring that the design meets the necessary safety and performance standards by considering uncertainties in material properties, load effects, and other relevant conditions. It adjusts the design parameters to achieve a target reliability level, which is vital for both individual components and the entire system. In this study, a reliability analysis of a frame system unit, represented by its main components, was conducted to determine the effect of the importance factor for each element on the overall survivor function of the frame, considering both dependent and independent failure. Fault trees and reliability block diagrams represented the structure function, and the importance factor was determined using Birnbaum’s concept, which was employed for evaluating the structure-function for the two cases. For independent failure, a comparison of the main objective function of the steel frame optimally designed units was performed with and without the importance factor effect, while for dependent failure, the β factor method was used to show the difference in the survivor function of the whole steel frame unit with and without using the importance factors of each component. The designed results show that including the importance factor in the analysis played a significant role in the resulting bolts diameter (10%) and shows a lesser effect in the case of beam and column, given that the type and degree of failure severity of the whole system as a unit are more closely linked to the design of these elements than other structural members. The use of the importance factor in this study revealed the significance of each structural member and the most important considerations taken into account when designing it, such as the strength reduction factor and the impact of its failure type on the failure of the entire system.
Evaluation of mechanical properties of high-strength concrete with sustainable materials Ahmed A Mohammed Ali, Roua Suhail Zidan, Baraa J M Al-Eliwi Iop Conference Series Materials Science and Engineering, 2020 This research deals with green concrete which is defined as environmental-friendly material that contains the waste material, and its production does not cause environmental pollution. Also, it has high performance and life sustainability. In this investigation, the effect of the curing period on the properties of green concrete made with different percentages of fly ash and recycled coarse aggregate has been studied. Nine mixtures with varying percentages of replacement of fly ash (25% and 50%) and recycled coarse aggregate (RCA) (25% and 50%) were prepared. In addition to the control mixture with 100% ordinary Portland cement and 100% normal coarse aggregate to compare the results. The standard concrete cylinders (150 x 300 mm) and cubes (150 x150 x150 mm) were prepared and tested at different ages (7, 14, 28, and 60 days) to get the compressive strength, splitting strength, and modulus of elasticity. The results showed that no noticeable effect on the cementing efficiency of fly ash if its replacement ratio has no more than 50% of cement, as well as, recycled coarse aggregate has no significant effect on concrete strengths when the replacement ratio of natural aggregate less than 50%.
Performance of lightweight aggregate and self-compacted concrete-filled steel tube columns B. J. AL-Eliwi, T. Ekmekyapar, Radhwan H. Faraj, M. T. Gögüs, Ahmed A. M. AL-Shaar Steel and Composite Structures, 2017 The aim of this paper is to investigate the performance of Lightweight Aggregate Concrete Filled Steel Tube (LWCFST) columns experimentally and compare to the behavior of Self-Compacted Concrete Filled Steel Tube (SCCFST) columns under axial loading. Four different L/D ratios and three D/t ratios were used in the experimental program to delve into the compression behaviours. Compressive strength of the LWC and SCC are 33.47 MPa and 39.71 MPa, respectively. Compressive loading versus end shortening curves and the failure mode of sixteen specimens were compared and discussed. The design specification formulations of AIJ 2001, AISC 360-16, and EC4 were also assessed against test results to underline the performance of specification methods in predicting the compression capacity of LWCFST and SCCFST columns. Based on the behaviour of the SCCFST columns, LWCFST columns exhibited different performances, especially in ductility and failure mode. The nature of the utilized lightweight aggregate led to local buckling mode to be dominant in LWCFST columns, even the long LWCFST specimens suffered from this behaviour. While with the SCCFST specimens the global buckling governed the failure mode of long specimens without any loss in capacity. Considering a wide range of column geometries (short, medium and long columns), this paper extends the current knowledge in composite construction by examining the potential of two promising and innovative structural concrete types in CFST applications.
