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In this paper, statistical analyses and a parametric study are presented for reinforced concrete beams strengthened in flexure using FRP composites. Five variables are considered in this study; namely, the FRP axial stiffness, concrete strength, steel reinforcement ratio, beam depth, and beam span. We aim to develop statistics-based design equations to predict the debonding load, the flexural capacity of the beam cross-section, the maximum deflection at the debonding load, the ductility index, and the debonding strain level in the FRP laminate. Simplifying these statistical models is then carried out to develop robust design equations. These equations hold an advantage over those available in most code specifications because they account for the effect of interactions between various variables on the predicted quantities. The statistical analyses are primarily based on the response surface methodology (RSM) technique. The proposed models are thus referred to as the RSM models. Proposed design equations are then developed by simplifying the RSM models using Monte Carlo simulations and nonlinear regression analysis. Of the five responses considered in the RSM analysis, only the debonding strain level in FRP laminates is considered in the design equations. The data required for the statistical analysis were obtained from finite element models for beams having different combinations of variables. The statistical analyses are followed by a parametric study to investigate the effect of the above five variables and their interactions on the debonding load and the corresponding debonding strain level in the FRP laminate. This involves comparisons in terms of the debonding strain between the predictions of the proposed equation and those of the ACI, fib, Chinese specifications, and Australian standards.

This paper reports on the results of an investigation carried out to examine the ability of fine glass to be used in the concrete industry. The pozzolanicity of the glass powder (GP) hydration with and without calcium hydroxide (CH) (lime) is assessed using different methods. A comprehensive experimental programme is carried out to investigate the chemical and physical properties of the hydrated activated GP with CH, as a cement hydration product, on the microstructural level. The experimental work focuses on the degree of hydration, pH and the alkalinity nature of the pore solution to evaluate the performance of the GP when it reacts with the CH. A flame emission spectroscopy test was used to quantify the alkali release from the GP as well as determining the rate of alkali release with time. It was found that the GP releases a small fraction of sodium ions into the solution. Test results showed that the finely ground GPs exhibited very high pozzolanic activity. It was observed that the GP–lime pastes show high non-evaporable water content. Moreover, the best performance of the GP reactivity can be obtained in the range of 10·5 < pH < 11·5 depending on the CH/GP ratio. According to the scanning electron microscope analysis, the gel product of the GP hydration precipitates on the surface of the large particle of the GP, at which the very small micro particles and the outer layer of the large GP particles react with CH.

In the case of heavily reinforced concrete structural members, bundled bars are required rather than spaced bars. The use of spliced bundled bars is necessary when available bar lengths are limited. No design recommendations regarding the use of bundled or spliced bundled FRP bars are available. The results of four-point flexural testing of nine concrete beams reinforced with spliced bundled CFRP bars are presented herein. The effects of the type of bundle and splice length on the bond strength of bundled CFRP bars are investigated. Based on the experimental results, a procedure for determining the critical splice length of FRP bars is presented and the corresponding values of bond stresses can be predicted. Moreover, the ultimate strength analysis method is used to predict the maximum stress in spliced bundled CFRP bars. Finally, comparisons with the existing recommendations regarding the use of bundled steel bars and the recommended modifications for bundled CFRP bars are presented.

Fabric-reinforced cementitous matrix (FRCM) composites are usually applied on the concrete surface for the purpose of strengthening reinforced concrete structures. However, the efficiency of FRCM strengthening is notably affected by the bond between the FRCM system and concrete substrate. In view of that, the current paper presents the results of a preliminary experimental study carried out to investigate the bond characteristics between FRCM composites and concrete. Six number of specimens, each consisted of a 150-mm concrete cube with a double-shear connection to an FRCM system, were subjected to direct-shear loading test. The parameters investigated include (a) FRCM material (carbon, polyparaphenylene benzobisoxazole (PBO), and glass); and (b) Bond length (75 mm or 100 mm). The FRCM systems typically included a single layer of fabric with the associated mortar, and the bond width was uniformly taken as 100 mm. The test results revealed that the bond capacity is enhanced with an increase in the FRCM bonded length. The PBO-FRCM showed the highest bond capacity between FRCM composite and concrete substrate among the three systems. The modes of failure observed in carbon-, PBO-, and glass-FRCM bond tests are fabric delamination, FRCM mortar/concrete debonding, and fabric rapture, respectively. The PBOand glass-FRCM bond tests thus exhibited a more brittle behavior at failure than that of the carbon-FRCM counterpart.

The authors would like to acknowledge the fund received by the NPRP grant # NPRP 9-110-2-052 from Qatar National Research Fund (a member of Qatar Foundation). The findings of this study are solely the responsibility of the authors

SYMBOLIC MATRIX STRUCTURAL ANALYSIS OF TRUSSES: STATIC AND DYNAMIC APPLICATIONS - 10th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering - 15-18 June 2025, Rhodes Island, Greece

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Six concrete mixes with different proportions of various pozzolanic materials were investigated for the development of high-strength non-autoclaved aerated concrete (NAAC). Fly ash and slag were used as partial cement replacements in order to perform comparative studies on the effects of fly ash and slag on NAAC. Aluminium powder was used as an expanding agent to produce gas in the mixes. The compressive strength of each mix after 7 and 28 d of curing was determined. The microstructure of the pozzolanic cellular concrete was also investigated using scanning electron microscopy. The influence of the pozzolanic materials on the microstructural and macrostructural characteristics of the cellular concrete was assessed. A cement-based concrete mix, with pozzolanic materials as partial replacements of cement and sand, was thus developed for lightweight cellular concrete with a 28 d compressive strength exceeding 17 MPa. The developed foam concrete with relatively high strength is ideal for several structural and non-structural applications.

This study presents experimental and analytical investigations on the axial capacity of 12 heat-damaged glass fiber-reinforced polymer reinforced concrete columns. The columns were prepared with dimensions of 200×200×1000 mm and 3 replacement ratios of seawater for concrete mixing and curing (0%, 50%, and 100%). At the age of 3 months, the columns were subjected to an elevated temperature of 500 oC for 30, 60, and 90 minutes and subsequently cooled and tested. The experimental results demonstrated that the compressive strength of concrete increased by 35% and 45% at seawater replacement ratios of 50% and 100%, respectively. In addition, seawater-concrete mixes exhibited a lower rate of strength development compared to the reference mix. Moreover, 100% seawater concrete columns reported an increase of 28% in the cracking and ultimate loads. However, columns at seawater replacement ratios of 0%, 50%, and 100% exhibited a drop of 27%, 53%, and 50% in the cracking load after being exposed to 500 oC for 90 minutes. Additionally, the columns exposed to elevated temperatures showed a reduction of 5% to 20% in the ultimate load. Furthermore, the analytical models of ACI 440.11-22 and CAN/CSA-S806-12 significantly underestimated the axial capacity of all columns. The most accurate prediction for the columns' axial capacity was associated with the analytical model of Mohamed et al. with mean, standard deviation, and coefficient of variance of experimental-to-predicted ratios of 1.17, 0.12, and 9.98%, respectively.

ABSTRACT This study investigates the effectiveness of steel‐reinforced grout (SRG) for strengthening continuous reinforced concrete (RC) beams. A more sustainable alternative to conventional cementitious mortars, geopolymer mortar was employed in SRG‐strengthened RC beams while maintaining structural efficiency. An extensive experimental program involving 15 two‐span continuous RC beam specimens was conducted. The experimental parameters considered include the overall SRG stiffness (by varying the number of fabric layers and fabric density), the span coverage ratio, and the locations of strengthening. Additionally, the performance of steel fabrics in SRG was compared with other types of fabrics, including carbon, glass, and polyparaphenylene benzobisoxazole (PBO) fabrics. The results revealed that strengthening significantly enhanced the flexural capacity of the beams, with improvements ranging from 24% to 81%. Steel fabrics in SRG outperformed all other fabric types in terms of load‐carrying capacity. Low‐density SRG demonstrated superior bonding with the concrete substrate, leading to enhanced strengthening effects compared to high‐density SRG. Several failure modes were observed, including steel yielding, concrete cover separation, fabric rupture and slippage, and SRG debonding. A theoretical model based on SRG effective strain was utilized to predict the maximum load capacity of the strengthened beams.