Papers by Riadh al-Mahaidi
Bridge Maintenance, Safety, Management and Life Extension, 2014
Journal of Physics: Conference Series, 2021
The most evident properties of LWAC by which it is differentiated from normal weight concrete are... more The most evident properties of LWAC by which it is differentiated from normal weight concrete are its lower density and better insulating potential. The aim of this study is to examine the combined effect of lightweight coarse aggregate and steel fibers on concrete’s mechanical properties. In this study, three different types of coarse aggregate (normal weight, crushed clay brick and Attapulgite) with different percentages of steel fiber (0%, 0.5%, and 1%) were used. The results show that replacing normal weight concrete with lightweight concrete leads to a decrease in unit weight, compressive strength, splitting-tensile strength and modulus of elasticity, while water absorption increases. With the increase of steel fiber ratios in the mixtures, the mechanical properties of lightweight concrete improve significantly compared with the control sample with no fiber. When 1% steel fiber is used, the splitting-tensile strength increases by about 115.6% and 55.7% and compressive strength ...
Insights and Innovations in Structural Engineering, Mechanics and Computation, 2016
In this paper, two methods of FRP applications were carried out to study the fatigue life perform... more In this paper, two methods of FRP applications were carried out to study the fatigue life performance of CFRP laminates bonded to RC concrete block, by mean of investigating the influence of bond behavior application under cyclic loadings.
Maintenance, Safety, Risk, Management and Life-Cycle Performance of Bridges, 2018
Tubular Structures XVI, 2017
CFRPs are widely used in the automobile industry and civil engineering applications. However, the... more CFRPs are widely used in the automobile industry and civil engineering applications. However, the structural behaviour of CFRP-wrapped steel hollow sections under axial impact loading is not yet fully understood. This paper evaluates the effect of impact mass on the axial impact behaviour of CFRP-wrapped steel hollow square sections. FE models were developed using LS-DYNA explicit finite element code and validated using existing experimental data. The axial impact behaviour of the tubes was evaluated by studying the responses to peak impact force, axial deflection and energy absorption. Appropriate results are presented and the trends discussed.
Construction and Building Materials, 2018
h i g h l i g h t s Two large-scale RC slabs representing an interior slab-column connection were... more h i g h l i g h t s Two large-scale RC slabs representing an interior slab-column connection were tested. Steel bolts increased the load capacity of the slab by 15.4%. Strengthening technique change the punching shear failure to flexural failure. Numerical results showed good correlations with the experimental results.
Engineering Structures, 2018
This paper presents an application of prestressed carbon fiber-reinforced polymer (CFRP) plates f... more This paper presents an application of prestressed carbon fiber-reinforced polymer (CFRP) plates for the strengthening of metallic girders of a roadway bridge in Melbourne, Australia. The study also describes the application of a wireless sensor network (WSN) system for long-term structural monitoring of the retrofitted bridge girders. A flat prestressed unbonded retrofit (FPUR) system was developed to apply prestressed CFRP plates to the steel girders of the Diamond Creek Bridge (122 years old), which is subjected to daily passenger and heavy vehicles. The first section explains the results of sets of static and fatigue tests performed in the laboratory to examine the efficiency of the proposed FPUR system prior to its installation on the bridge. The second section presents details of different aspects of the CFRP strengthening of the bridge girders, fatigue design criteria, and layouts for short-and long-term monitoring. For the short-term measurements, the bridge was loaded with a 42.5-ton semi-trailer before and after strengthening. The CFRP plates were prestressed up to approximately 980 MPa (≈38% of the CFRP ultimate tensile strength), which resulted in about 50% reduction in the maximum tensile stress in the bridge girders. The third section discusses the development, installation, and preliminary results of the WSN system used to monitor the pre-stress level in the CFRP plates. The results of the short-and long-term measurements in this study show that the FPUR system is very effective for flexural and fatigue strengthening of bridge girders. Finally, a set of recommendations for long-term structural monitoring is provided. (I) concerns related to the long-term performance of CFRP-to-steel bonded joints under special environmental conditions (e.g.,
Composite Structures, 2019
The effectiveness of using FRP materials to strengthen existing concrete structures is hampered b... more The effectiveness of using FRP materials to strengthen existing concrete structures is hampered by the weak bond properties between the FRP and the concrete. Further, very few studies are available on the fatigue performance of FRP-strengthened reinforced concrete beams in bridges. Investigation of the fatigue performance of FRP bonded to concrete is important due to the fact that bridges are subjected to very high levels of cyclic loading throughout their lifetime. This paper focuses on a numerical and experimental investigation of the fatigue life of FRP laminates bonded to concrete. FRP-to-concrete joints were subjected to cyclic loading at various stress ratios and the number of cycles prior to failure was used to generate S-N curves which relate the stress ratio to the number of cycles. Further, numerical simulations using the finite element method were performed using a concrete material model capable of sustaining fatigue damage. The finite element results were found to be in good agreement with the experimental data and were used to provide further insights into the mechanisms of fatigue damage. Both the experimental and numerical results showed that no fatigue degradation occurred when the maximum stress ratio was less than 75% of the ultimate static capacity.
Composite Structures, 2017
Evaluation of bond properties of degraded CFRP-strengthened double strap joints. Composite Struct... more Evaluation of bond properties of degraded CFRP-strengthened double strap joints. Composite Structures, 173, pp. 144-155.
Journal of Reinforced Plastics and Composites, 2015
The strength models for fibre reinforced polymer wrapped columns available in the research litera... more The strength models for fibre reinforced polymer wrapped columns available in the research literature were developed at ambient temperatures. To date, no experimental or analytical data have been available on the behaviour of large-scale reinforced concrete circular columns loaded during heating and cooling and subsequently wrapped with carbon fibre reinforced polymer fabrics. This paper deals with the development of new design-oriented strength models to predict the compressive strength of unheated and heat-damaged reinforced concrete columns confined with carbon fibre reinforced polymer. In this paper, 18 Ø 204 mm × 750 mm identical reinforced concrete columns were fabricated and tested, of which 12 were subjected to elevated temperatures under stress and then subsequently confined with carbon fibre reinforced polymer sheets after air cooling. The variables considered in these tests included the level of heat exposure and the number of carbon fibre reinforced polymer sheet layers....
The official regional conference of the International Institute for FRP in Construction (IIFC) fo... more The official regional conference of the International Institute for FRP in Construction (IIFC) for the Asia-Pacific Region, 12-14 December 2007, Hong Kong, China.Organised by The University of Hong Kong and IIFC Working Groups on 'Bond Behaviour of FRP in Structures', 'FRP-Strengthened Metallic Structures' and 'FRP Bridge Decks
Journal of Composites for Construction
Journal of Composites for Construction, 2013
ABSTRACT The anchorage of fiber-reinforced polymer (FRP) composites when applied to reinforced co... more ABSTRACT The anchorage of fiber-reinforced polymer (FRP) composites when applied to reinforced concrete (RC) structures as externally bonded reinforcement is an effective means to achieve higher levels of fiber utilization prior to premature debonding failure. Commonly documented anchorage methods for FRP-to-concrete applications demonstrating encouraging results include FRP U-jackets, FRP anchors (also known as spike anchors, among other names), patch anchors (utilizing unidirectional and bidirectional fabrics), nailed metal plates (also known as hybrid bonding), near-surface mounted rods, mechanical fastening, concrete embedment, and mechanical substrate strengthening. Anchorages applied to F'RP systems have been verified through experimental testing and numerical modeling to increase the ductility, deformability, and strength of the member and also prevent, delay, or shift the critical mode of FRP debonding failure. Although the benefits of anchorage solutions have now been widely acknowledged by researchers, further studies are required in order to establish reliable design formulations to negate the requirement for ongoing laboratory verification by industry. The present paper is a state-of-the-art review of experimental studies conducted in the area of FRP anchorage systems applied to FRP-strengthened RC flexural members. Available experimental data are compiled and catalogued and an anchorage efficiency factor for each anchorage type under investigation is assigned in order to quantify the anchor's efficiency. Finally, current shortcomings in knowledge are identified, in addition to areas needing further investigation. DOT: 10.1061/(ASCE)CC.1943-5614.0000276. (C) 2013 American Society of Civil Engineers.
Engineering Structures, 2020
Abstract Reinforced concrete (RC) slabs can be strengthened using fiber reinforced polymers (FRPs... more Abstract Reinforced concrete (RC) slabs can be strengthened using fiber reinforced polymers (FRPs) to enhance their flexural and shear resistance. However, premature debonding of the FRP material limits the level of strengthening achievable and represents an under-utilization of the FRP material. As a result, a variety of anchorage systems have been explored by researchers in an attempt to prevent or delay this type of failure. This paper presents a new FRP patch anchorage system which can be used to mitigate the commonly-observed failure mode of intermediate crack-induced (IC) debonding. This is the first experimental application where patch anchors are investigated in flexurally-strengthened RC slabs. Seven slabs 2700 mm × 400 mm × 150 mm in size were tested. Of these, two were unstrengthened, three were strengthened with 100 mm wide × 1.4 mm thick FRP sheet and two were strengthened in the same manner and anchored with four patch anchors. The use of patch anchors showed significant enhancement of both the strength and ductility of RC slabs compared with unanchored specimens.
Thin-Walled Structures, 2018
Steel hollow sections used in structures such as bridges, buildings and space structures involve ... more Steel hollow sections used in structures such as bridges, buildings and space structures involve different strengthening techniques according to their structural purpose and shape of the structural member. One such technique is external bonding of CFRP sheets to steel tubes. The performance of CFRP strengthening for steel structures has been proven under static loading while limited studies have been conducted on their behaviour under impact loading. In this study, a comprehensive numerical investigation is carried out to evaluate the response of CFRP strengthened steel tubes under dynamic axial impact loading. Impact force, axial deformation impact velocities are studied. The results of the numerical investigations are validated by experimental results. Based on the developed finite element (FE) model several output parameters are discussed. The results show that CFRP wrapping is an effective strengthening technique to increase the axial dynamic load bearing capacity by increasing the stiffness of the steel tube.
Composites Part B: Engineering, 2018
In this study, a novel retrofitting system is developed to strengthen existing metallic I-girders... more In this study, a novel retrofitting system is developed to strengthen existing metallic I-girders using prestressed unbonded carbon fiber reinforced polymer (CFRP) plates. The system relies on a pair of mechanical clamps. Each clamp holds two CFRP plates (each having cross-sectional dimensions of 50 × 1.4 mm) and anchors their prestressing forces to a metallic I-girder via friction. A finite element (FE) model was established to optimize the design of the required mechanical components, and a set of pull-off tests was performed to evaluate the capacity of the optimized system. The proposed flat prestressed unbonded retrofit (FPUR) system was then applied on a 6.4-m-long steel I-beam, and the excellent performance of the system, in terms of stress reduction in the beam bottom flange, was confirmed based on the results of a set of static four-point bending tests. Moreover, a fatigue fourpoint bending test was conducted on the steel I-beam, strengthened using the proposed FPUR system with a prestressing level of 53% (i.e., approximately 1120 MPa prestress in the CFRPs). Experimental results of the high-cycle fatigue test confirmed the excellent fatigue performance of the proposed FPUR system, as no prestress loss was observed after 20 million fatigue cycles. An analytical model is proposed to accurately predict the stress state in an I-girder strengthened with the proposed FPUR system, while design recommendations are provided concerning the practical use of the system. Relying on the laboratory experimental test results, the proposed FPUR system was used to strengthen the metallic cross-girders of a 121-year-old bridge in Australia.
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Papers by Riadh al-Mahaidi