Debonding failure analysis of prestressed FRP strengthened RC beams

Hoque, Nusrat,Jumaat, Mohd Z. Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.4

Fiber Reinforced Polymer (FRP), which has a high strength to weight ratio, are now regularly used for strengthening of deficient reinforced concrete (RC) structures. While various researches have been conducted on FRP strengthening, an area that still requires attention is predicting the debonding failure load of prestressed FRP strengthened RC beams. Application of prestressing increases the capacity and reduces the premature failure of the beams largely, though not entirely. Few analytical methods are available to predict the failure loads under flexure failure. With this paucity, this research proposes a method for predicting debonding failure induced by intermediate crack (IC) for prestressed FRP-strengthened beams. The method consists of a numerical study on beams retrofitted with prestressed FRP in the tension side of the beam. The method applies modified Branson moment-curvature analysis together with the global energy balance approach in combination with fracture mechanics criteria to predict failure load for complicated IC-induced failure. The numerically simulated results were compared with published experimental data and the average of theoretical to experimental debonding failure load is found to be 0.93 with a standard deviation of 0.09.

Comparison of shear lag in structural steel building with framed tube and braced tube

Mazinani, Iman,Jumaat, Mohd Zamin,Ismail, Z.,Chao, Ong Zhi Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.3

Under lateral loads Framed Tube (FT) system exhibits reduction of cantilever efficiency due to the effect of shear lag. Braced Tube (BT) represents a valuable solution to overcome shear lag problems by stiffening the exterior frame with diagonal braced members. This study investigates the effect of shear lag on BT and FT under wind load. Shear lag and top-level displacement results are compared with previous findings by researchers on FT and BT systems. The investigation of the effect of various configurations in BT on the reduction the shear lag is another objective of this study. The efficiency of each structure is evaluated using the linear response spectrum analysis to obtain shear lag. STADD Pro software is used to run the dynamic analysis of the models. Results show there is relatively less shear lag in all the BT configurations compared to the FT structural system. Moreover, the comparison of the obtained result with those derived by previous studies shows that shear lag is not proportional to lateral displacement. With respect to results, optimum BT configuration in term of lower shear lag caused by lateral loads is presented.

Load-deflection analysis prediction of CFRP strengthened RC slab using RNN

Razavi, S.V.,Jumaat, Mohad Zamin,El-Shafie, Ahmed H.,Ronagh, Hamid Reza Techno-Press 2015 Advances in concrete construction Vol.3 No.2

In this paper, the load-deflection analysis of the Carbon Fiber Reinforced Polymer (CFRP) strengthened Reinforced Concrete (RC) slab using Recurrent Neural Network (RNN) is investigated. Six reinforced concrete slabs having dimension $1800{\times}400{\times}120mm$ with similar steel bar of 2T10 and strengthened using different length and width of CFRP were tested and compared with similar samples without CFRP. The experimental load-deflection results were normalized and then uploaded in MATLAB software. Loading, CFRP length and width were as neurons in input layer and mid-span deflection was as neuron in output layer. The network was generated using feed-forward network and a internal nonlinear condition space model to memorize the input data while training process. From 122 load-deflection data, 111 data utilized for network generation and 11 data for the network testing. The results of model on the testing stage showed that the generated RNN predicted the load-deflection analysis of the slabs in acceptable technique with a correlation of determination of 0.99. The ratio between predicted deflection by RNN and experimental output was in the range of 0.99 to 1.11.

Side-NSM composite technique for flexural strengthening of RC beams

Akter Hosen,Mohd Zamin Jumaat,A. B. M. Saiful Islam,Abdus Salam,Kim Hung Mo 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.20 No.4

Reinforced concrete (RC) infrastructures often require strengthening due to error in design, degradation of materials properties after prolong utilization and increases load carrying capacity persuaded by new use of the structures. For this purpose, a newly proposed Side Near Surface Mounted (SNSM) composite technique was used for flexural strengthening of RC beam specimens. Analytical and non-linear finite element modeling (FEM) using ABAQUS were performed to predict the flexural performance of RC specimens strengthened with S-NSM using steel bars as a strengthening reinforcement. RC beams with various SNSM reinforcement ratios were tested for flexural performance using four-point bending under monotonic loading condition. Results showed significantly increase the yield and ultimate strengths up to 140% and 144% respectively and improved failure modes. The flexural response, such as failure load, mode of failure, yield load, ultimate load, deflection, strain, cracks characteristic and ductility of the beams were compared with those predicted results. The strengthened RC beam specimens showed good agreement of predicted flexural behavior with the experimental outcomes.

Experimental Investigation on Fatigue Behavior of Wide-Flange Steel I-Beams Strengthened Using Diff erent CFRP End Cutting Shapes

Mohamed Kamruzzaman,MohdZamin Jumaat,N.H. Ramli Sulong,Kambiz Narmashiri,Khaled Ghaedi,Md. Akter Hosen 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.3

In recent decades, the application of carbon fi bre-reinforced polymer (CFRP) composites for strengthening structural elements has become an effi cient option to meet the increased cyclic loads, or repair due to fatigue cracking. The premature failure due to end-debonding is a key limitation to achieve high fatigue performance of strengthened steel beams with externally bonded CFRP plates. The objective of this study is to explore the reinforcing techniques using the CFRP in-plane end cutting shapes and the triangular spew fi llet of adhesive at the tips of the plate to care for fatigue damaged of wide-fl ange steel I-beams due to end-debonding. Four in-plane CFRP end cutting shapes were chosen, namely: rectangular, semi-elliptical, semi-circular and trapezoidal. The application of the trapezoidal end shape was found to be the best confi guration for delaying the end-debonding failure mode and high fatigue life compared to the other CFRP in-plane end cutting shapes. Applying the triangular spew fi llets of adhesive signifi cantly increased the end-debonding and steel beam fracture initiation life of the strengthened beams.

Debonding failure analysis of prestressed FRP strengthened RC beams

Nusrat Hoque,Mohd Z. Jumaat 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.4

Fiber Reinforced Polymer (FRP), which has a high strength to weight ratio, are now regularly used for strengthening of deficient reinforced concrete (RC) structures. While various researches have been conducted on FRP strengthening, an area that still requires attention is predicting the debonding failure load of prestressed FRP strengthened RC beams. Application of prestressing increases the capacity and reduces the premature failure of the beams largely, though not entirely. Few analytical methods are available to predict the failure loads under flexure failure. With this paucity, this research proposes a method for predicting debonding failure induced by intermediate crack (IC) for prestressed FRP-strengthened beams. The method consists of a numerical study on beams retrofitted with prestressed FRP in the tension side of the beam. The method applies modified Branson moment-curvature analysis together with the global energy balance approach in combination with fracture mechanics criteria to predict failure load for complicated IC-induced failure. The numerically simulated results were compared with published experimental data and the average of theoretical to experimental debonding failure load is found to be 0.93 with a standard deviation of 0.09.

Comparison of shear lag in structural steel building with framed tube and braced tube

Iman Mazinani,Mohd Zamin Jumaat,Z. Ismail,Ong Zhi Chao 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.3

Under lateral loads Framed Tube (FT) system exhibits reduction of cantilever efficiency due to the effect of shear lag. Braced Tube (BT) represents a valuable solution to overcome shear lag problems by stiffening the exterior frame with diagonal braced members. This study investigates the effect of shear lag on BT and FT under wind load. Shear lag and top-level displacement results are compared with previous findings by researchers on FT and BT systems. The investigation of the effect of various configurations in BT on the reduction the shear lag is another objective of this study. The efficiency of each structure is evaluated using the linear response spectrum analysis to obtain shear lag. STADD Pro software is used to run the dynamic analysis of the models. Results show there is relatively less shear lag in all the BT configurations compared to the FT structural system. Moreover, the comparison of the obtained result with those derived by previous studies shows that shear lag is not proportional to lateral displacement. With respect to results, optimum BT configuration in term of lower shear lag caused by lateral loads is presented.

Effect of High-cyclic Loads on Dynamic Response of Reinforced Concrete Slabs

Adiza Jamadin,Zainah Ibrahim,Mohd Zamin Jumaat,Ezahtul Shahreen Ab Wahab 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.3

Bridge reinforced concrete deck slabs are often subjected to various cyclic loadings—making regular checks for fatigue damage necessary. Several experiments on reinforced concrete structures were conducted to evaluate its mechanical fatigue behaviour. Nevertheless, adequate experimental investigations on its dynamic properties are still needed. This paper reports on the test performed on three identical reinforced concrete slabs, with different cyclic load number and after the cycles, the load was increased up to the static failure. Modal testing was performed after each step of loading to assess their dynamic performance using modal parameters (natural frequencies, mode shapes and damping ratios). Finite element model was used to predict the natural frequency of the reinforced concrete slabs and their reliability was checked through model updating. The results showed the intensity of fatigued structures causes significant changes to the modal parameters and structural loading capacity. The study explores how fatigued structure can be assessed from dynamic performance, and also can be quantified through its structural stiffness, ultimately offering a better way of using non-destructive modal testing in identifying its structural health as compared to conventional testing techniques.

Potential side-NSM strengthening approach to enhance the flexural performance of RC beams: Experimental, numerical and analytical investigations

Md. Akter Hosen,Mohd Zamin Jumaat,A.B.M. Saiful Islam,Khalid Ahmed Al Kaaf,Mahaad Issa Shammas,Ibrahim Y. Hakeem,Mohammad Momeen Ul Islam 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.85 No.2

The performance of reinforced concrete (RC) beam specimens strengthened using a newly proposed Side Near Surface Mounted (S-NSM) technology was investigated experimentally in this work. In addition, analytical and nonlinear finite element (FE) modeling was exploited to forecast the performance of RC members reinforced with S-NSM utilizing steel bars. Five (one control and four strengthened) RC beams were evaluated for flexural performance under static loading conditions employing four-point bending loads. Experimental variables comprise different S-NSM reinforcement ratios. The constitutive models were applied for simulating the non-linear material characteristics of used concrete, major, and strengthening reinforcements. The failure load and mode, yield and ultimate strengths, deflection, strain, cracking behavior as well as ductility of the beams were evaluated and discussed. To cope with the flexural behavior of the tested beams, a 3D non-linear FE model was simulated. In parametric investigations, the influence of S-NSM reinforcement, the efficacy of the S-NSM procedure, and the structural response ductility are examined. The experimental, numerical, and analytical outcomes show good agreement. The results revealed a significant increase in yield and ultimate strengths as well as improved failure modes.

Palm oil industry’s bi-products as coarse aggregate in structural lightweight concrete

Md. Nazmul Huda,Mohd Zamin Jumaat,A. B. M. Saiful Islam,Kh Mahfuz ud Darain,M. Obaydullah,Md. Akter Hosen 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.5

Recent trend is to use the lightweight concrete in the construction industry because it has several advantages over normal weight concrete. The Lightweight concrete can be produced from the industrial waste materials. In South East Asian region, researchers are very keen to use the waste materials such as oil palm shell (OPS) and palm oil clinker (POC) from the palm oil producing industries. Extensive research has been done on lightweight concrete using OPS or POC over the last three decades. In this paper the aggregate properties of OPS and POC are plotted in conjunction with mechanical and structural behavior of OPS concrete (OPSC) and POC concrete (POCC). Recent investigation on the use of crushed OPS shows that OPSC can be produced to medium and high strength concrete. The density of OPSC and POCC is around 20-25% lower than normal weight concrete. Generally, mechanical properties of OPSC and POCC are comparable with other types of lightweight aggregate concrete. It can be concluded from the previous study that OPSC and POCC have the noteworthy potential as a structural lightweight concrete.