Thermal analysis of GFRP-reinforced continuous concrete decks subjected to top fire

Citation: Hawileh, R. A., & Rasheed, H. A. (2017). Thermal analysis of GFRP-reinforced continuous concrete decks subjected to top fire. International Journal of Advanced Structural Engineering. https://doi.org/10.1007/s40091-017-0168-7This paper presents a numerical study that investigates the behavior of continuous concrete decks doubly reinforced with top and bottom glass fiber reinforced polymer (GFRP) bars subjected to top surface fire. A finite element (FE) model is developed and a detailed transient thermal analysis is performed on a continuous concrete bridge deck under the effect of various fire curves. A parametric study is performed to examine the top cover thickness and the critical fire exposure curve needed to fully degrade the top GFRP bars while achieving certain fire ratings for the deck considered. Accordingly, design tables are prepared for each fire curve to guide the engineer to properly size the top concrete cover and maintain the temperature in the GFRP bars below critical design values in order to control the full top GFRP degradation. It is notable to indicate that degradation of top GFRP bars do not pose a collapse hazard but rather a serviceability concern since cracks in the negative moment region widen resulting in simply supported spans

Combined Transverse Steel-External FRP Confinement Model for Rectangular Reinforced Concrete Columns

Citation: Al-Rahmani, A., & Rasheed, H. (2016). Combined Transverse Steel-External FRP Confinement Model for Rectangular Reinforced Concrete Columns. Fibers, 4(1), 25. doi:10.3390/fib4010008Recently, the need to increase the strength of reinforced concrete members has become a subject that civil engineers are interested in tackling. Of the many proposed solutions, fiber-reinforced polymer (FRP) materials have attracted attention due to their superior properties, such as high strength-to-weight ratio, high energy absorption and excellent corrosion resistance. FRP wrapping of concrete columns is done to enhance the ultimate strength due to the confinement effect, which is normally induced by steel ties. The existence of the two confinement systems changes the nature of the problem, thus necessitating specialized nonlinear analysis to obtain the column's ultimate capacity. Existing research focused on a single confinement system. Furthermore, very limited research on rectangular sections was found in the literature. In this work, a model to estimate the combined behavior of the two systems in rectangular columns is proposed. The calculation of the effective lateral pressure is based on the Lam and Teng model and the Mander model for FRP wraps and steel ties, respectively. The model then generates stress-strain diagrams for both the concrete core and the cover. The model was developed for the analysis in extreme load events, where all possible contributions to the column's ultimate capacity should be accounted for without any margin of safety. The model was validated against experiments, and the results obtained showed good agreement with almost all of the available experimental data

Partial Confinement Utilization for Rectangular Concrete Columns Subjected to Biaxial Bending and Axial Compression

Citation: Abd El Fattah, A. M., Rasheed, H. A., & Al-Rahmani, A. H. (2017). Partial Confinement Utilization for Rectangular Concrete Columns Subjected to Biaxial Bending and Axial Compression. International Journal of Concrete Structures and Materials, 11(1), 135-149. doi:10.1007/s40069-016-0178-zThe prediction of the actual ultimate capacity of confined concrete columns requires partial confinement utilization under eccentric loading. This is attributed to the reduction in compression zone compared to columns under pure axial compression. Modern codes and standards are introducing the need to perform extreme event analysis under static loads. There has been a number of studies that focused on the analysis and testing of concentric columns. On the other hand, the augmentation of compressive strength due to partial confinement has not been treated before. The higher eccentricity causes smaller confined concrete region in compression yielding smaller increase in strength of concrete. Accordingly, the ultimate eccentric confined strength is gradually reduced from the fully confined value f(cc) (at zero eccentricity) to the unconfined value f(c)(1) (at infinite eccentricity) as a function of the ratio of compression area to total area of each eccentricity. This approach is used to implement an adaptive Mander model for analyzing eccentrically loaded columns. Generalization of the 3D moment of area approach is implemented based on proportional loading, fiber model and the secant stiffness approach, in an incremental-iterative numerical procedure to achieve the equilibrium path of P-epsilon and M-phi response up to failure. This numerical analysis is adapted to assess the confining effect in rectangular columns confined with conventional lateral steel. This analysis is validated against experimental data found in the literature showing good correlation to the partial confinement model while rendering the full confinement treatment unsafe

Buckling of Nonprismatic Column on Varying Elastic Foundation with Arbitrary Boundary Conditions

Citation: Ahmad A. Ghadban, Ahmed H. Al-Rahmani, Hayder A. Rasheed, and Mohammed T. Albahttiti, “Buckling of Nonprismatic Column on Varying Elastic Foundation with Arbitrary Boundary Conditions,” Mathematical Problems in Engineering, vol. 2017, Article ID 5976098, 14 pages, 2017. doi:10.1155/2017/5976098Buckling of nonprismatic single columns with arbitrary boundary conditions resting on a nonuniform elastic foundation may be considered as the most generalized treatment of the subject. The buckling differential equation for such columns is extremely difficult to solve analytically. Thus, the authors propose a numerical approach by discretizing the column into a finite number of segments. Each segment has constants  (modulus of elasticity),  (moment of inertia), and  (subgrade stiffness). Next, an exact analytical solution is derived for each prismatic segment resting on uniform elastic foundation. These segments are then assembled in a matrix from which the critical buckling load is obtained. The derived formulation accounts for different end boundary conditions. Validation is performed by benchmarking the present results against analytical solutions found in the literature, showing excellent agreement. After validation, more examples are solved to illustrate the power and flexibility of the proposed method. Overall, the proposed method provides reasonable results, and the examples solved demonstrate the versatility of the developed approach and some of its many possible applications

Shear strengthening of reinforced concrete beams using externally-bonded aluminum alloy plates: An experimental study

Citation: Jamal A. Abdalla, Adi S. Abu-Obeidah, Rami A. Hawileh, Hayder A. Rasheed, Shear strengthening of reinforced concrete beams using externally-bonded aluminum alloy plates: An experimental study, Construction and Building Materials, Volume 128, 15 December 2016, Pages 24-37 http://dx.doi.org/10.1016/j.conbuildmat.2016.10.071Recently developed high strength aluminum alloys (AA) have desirable characteristics that make them attractive as externally bonded strengthening materials. This paper investigates the potential of using AA plates for shear strengthening of reinforced concrete (RC) beams. Five shear deficient RC beams were externally strengthened using AA plates with different orientations. It is observed that the shear capacity of the strengthened beams has increased in the range of 24%–89% compared to the un-strengthened beam. Shear capacity of the strengthened beams was also predicted using the ACI440, FIB14, TR55 and SMCFT design guidelines with the later one giving the most accurate predictions

Moment-curvature based modelling of FRP-strengthened RC members anchored with FRP anchors

Debonding of externally bonded fibre-reinforced polymer (FRP) composites in FRP-concrete bonded interfaces occurs in generally a brittle manner and at a level of strain well below the strain capacity and deformability of the bonded interface. The proof of concept has been demonstrated in experimental studies over the years although there is much less development of modelling methods by comparison that address the full-range of response from initial loading to eventual interface and anchorage failure. This paper presents the details of a closed-form analytical model that enables the complete load-deflection response of FRP flexurally-strengthened RC members that contain anchorage devices to be generated. The method relies upon establishing predefined moment-curvature expressions corresponding to key stages of the member behaviour

Full-range load-deflection response of FRP-strengthened RC flexural members anchored with FRP anchors

The flexural resistance of reinforced concrete (RC) members such as beams and slabs can be enhanced by bonding fibre-reinforced polymer (FRP) composite plates to their tension face. The effectiveness of the strengthening can be compromised though by premature debonding failure of the FRP which can occur at strains significantly lower than the strain capacity of the FRP. Anchorage of the FRP strengthening can, however, increase its usable strain. A convenient means with which to represent the structural behaviour of such a strengthened and anchored member then is via its load-deflection response. The task of how to model this response therefore arises. The authors, as well as other research groups, have derived closed-form solutions which describe the complete load-deflection response of FRP-strengthened RC flexural members of which pre-defined moment-curvature relationships are observed. This paper reports an extension to such existing theory in order to incorporate the anchorage effect. The theory is finally calibrated with test results of FRP-strengthened RC slabs which have been anchored with FRP anchors. The paper sets a framework for future work centred on quantification of the FRP anchor effect

Moment-curvature based modelling of FRP-strengthened RC members anchored with FRP anchors

Debonding of externally bonded fibre-reinforced polymer (FRP) composites in FRP-concrete bonded interfaces occurs in generally a brittle manner and at a level of strain well below the strain capacity and deformability of the bonded interface. The proof of concept has been demonstrated in experimental studies over the years although there is much less development of modelling methods by comparison that address the full-range of response from initial loading to eventual interface and anchorage failure. This paper presents the details of a closed-form analytical model that enables the complete load-deflection response of FRP flexurally-strengthened RC members that contain anchorage devices to be generated. The method relies upon establishing predefined moment-curvature expressions corresponding to key stages of the member behaviour