Thermal Resistance of Insulated Precast Concrete Sandwich Panels

Sani Mohammed Bida,Farah Nora Aznieta Abdul Aziz,Mohd Saleh Jaafar,Farzad Hejazi,Nabilah Abu Bakar 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.6

Many nations are already working toward full implementation of energy efficiency in buildings known as Green Building. In line with this perspective, this paper aims to develop a thermally efficient precast concrete sandwich panels (PCSP) for structural applications. Therefore, an experimental investigation was carried out to determine the thermal resistance of the proposed PCSP using Hotbox method and the results were validated using finite element method (FEM) in COMSOL Multiphysics Software. The PCSP were designed with staggered shear connectors to avoid thermal bridges between the successive layers. The staggered connectors are spaced at 200 mm, 300 mm and 400 mm on each concrete layer, while the control panel is designed with 200 mm direct shear connection. In the experimental test, four (4) panels of 500 mm × 500 mm and 150 mm thick were subjected to Hotbox Test to determine the thermal resistance. The result shows that thermal resistance of the PCSP with staggered shear connection increases with increase in spacing. The PCSP with 400 mm staggered shear connectors indicates the best thermal efficiency with a thermal resistance (R value) of 2.48 m²K/W. The thermal performance was verified by FEA which shows less than 5% error coupled with a precise prediction of surface temperature gradient. This indicates that, with conventional materials, thermal path approach can be used to develop a precast concrete building with better thermal resistant properties. Hopefully, stakeholders in the green building industry would find this proposed PCSP as an alternative energy efficient load bearing panel towards sustainable and greener buildings.

Evaluation of Rubberized Fibre Mortar Exposed to Elevated Temperature using Destructive and Non-Destructive Testing

H. Mahir Mahmod,A. A. Farah Nora Aznieta,Sarah Jabbar Gatea 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.4

The mechanical properties of concrete containing crumb rubber (CR) as a replacement for fine aggregate have been studied by many researchers. The consequence of these studies indicates that when CR is used as a substitute for fine aggregates in concrete, the properties in the fresh and hardened states are affected. Although the compressive strength of rubberised concrete decreased as the percentage of CR increased, rubberised concrete had better thermal resistivity. Therefore, this paper presents the results of research on the evaluation of conventional compressive strength ( fcu) and non-destructive testing (NDT) at high temperatures for lightweight mortar made with CR and oil palm fruit fibre (OPFF). Sixteen mortar mixtures with 0-30% CR and 1-1.5% OPFF as a replacement ratio by weight of aggregate and cement were tested. All samples were subjected to elevated temperatures (ETs) of 200°C, 400°C and 600°C. The results show that both compressive strength and NDT decreased for all samples, especially samples containing 30% CR and exposed to 600°C. Despite this fact, the compressive strength of more than 97% of the samples fell within the range of moderate to structural lightweight concrete.

Energy absorption of reinforced concrete deep beams strengthened with CFRP sheet

Mohammad Panjehpour,Abang Abdullah Abang Ali,Farah Nora Aznieta 국제구조공학회 2014 Steel and Composite Structures, An International J Vol.16 No.5

The function of carbon fibre reinforced polymer (CFRP) reinforcement in increasing the ductility of reinforced concrete (RC) deep beam is important in such shear-sensitive RC member. This paper aims to investigate the effect of CFRP-strengthening on the energy absorption of RC deep beams. Six ordinary RC deep beams and six CFRP-strengthened RC deep beams with shear span to the effective depth ratio of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00 were tested till failure in this research. An empirical relationship was established to obtain the energy absorption of CFRP-strengthened RC deep beams. The shear span to the effective depth ratio and growth of energy absorption of CFRP-strengthened deep beam were the significant factors to establish this relationship.

The Synergistic Effects of Different Types of Hybridized Synthetic Fibers on Concrete Post-Crack Residual Strength

S. M. Iqbal S. Zainal,Farzad Hejazi,Farah Nora Aznieta Abd. Aziz,Mohd Saleh Jaafar 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.1

The use of fibers in cement composites has been shown to improve the mechanical properties of concrete through the fiber-bridging effect, which implies the fiber’s crack-resisting property. Additionally, the combination of two or more different fibers in the concrete mixture yielded better strength than the individual fibers due to its more versatile applications. Therefore, this study was conducted to investigate the combination of multiple synthetic fibers to improve the concrete residual strength and evaluate the hybridization synergistic effect. Ferro macro-sized fiber (FF) as the primary load-bearing fiber and four different secondary synthetic microfibers comprising Ultra-Net (UN), Super-Net (SN), Econo-Net (EN), and Nylo-Mono (NM) were utilized to develop a total of 16 hybrid fiber reinforced concrete (HyFRC) combinations and the performance were compared against their single-fiber counterpart. The tensile strength, bonding power, physical form, length, and volume fraction of the fibers were measured under the ASTM C1399 test standard in order to calculate the average residual strength (ARS) of concrete in the post-cracking region as well as to assess the synergistic effect of the fiber combination. The results recorded positive fiber synergy for all specimens tested. In addition, the Ferro-Nylo, Ferro-Super, Ferro-Econo, and Ferro-Ultra hybrids improved the ARS compared to the controlled specimens by 20.41, 10.2, 7.48, and 6.12%, respectively.

Development of Finite Element Analysis for Intermediate Length Coupling Beams Considering Bond‑Slip Interface

Abu Bakar Nabilah,Chan Ghee Koh,Abd. Karim Izian,Farah Nora Aznieta Abd. Aziz 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.5

Finite element analysis is performed on four reinforced concrete coupling beams of intermediate length using 2-D plane stress elements, under monotonic load up to failure. The model is verified using the results from (Nabilah and Koh in KSCE J Civil Eng 21:2807–2813, 2017). The bond-slip interface for the longitudinal reinforcement is modeled in the finite element, as it is found that it better predicts the load-deformation behavior compared to perfect bond. The comparison between finite element analysis and the experiment found that the model is able to predict the overall behavior of the structure, especially the maximum load capacity. The maximum deformation and the shear deformation from the finite element analysis are found to be underestimated, due to the inability of the model to predict shear deformation accurately. Flexural deformation (due to flexure and slip) is found to be well predicted, as the bond-slip behavior is modeled in the analysis. Generally, the shear deformation and slip are found to be significant in the intermediate length coupling beam and should not be ignored in the analysis. Finally, the effective stiffness prediction using finite element analysis is found to be overestimated and should be determined instead using existing equations.

Effective compressive strength of strut in CFRP-strengthened reinforced concrete deep beams following ACI 318-11

Mohammad Panjehpour,Abang Abdullah Abang Ali,Yen Lei Voo,Farah Nora Aznieta 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.13 No.1

Strut-and-tie model (STM) has been recommended by many codes and standards as a rationalmodel for discontinuity regions in structural members. STM has been adopted in ACI building code foranalysis of reinforced concrete (RC) deep beams since 2002. However, STM recommended by ACI 318-11is only applicable for analysis of ordinary RC deep beams. This paper aims to develop the STM for CFRPstrengthened RC deep beams through the strut effectiveness factor recommended by ACI 318-11. Two setsof RC deep beams were cast and tested in this research. Each set consisted of six simply-supportedspecimens loaded in four-point bending. The first set had no CFRP strengthening while the second wasstrengthened by means of CFRP sheets using two-side wet lay-up system. Each set consisted of six RC deepbeams with shear span to effective depth ratio of 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00.The value of struteffectiveness factor recommended by ACI 318-11 is modified using a proposed empirical relationship in thisresearch. The empirical relationship is established based on shear span to effective depth ratio.