Shear strengthening of pre-cracked and non pre cracked reinforced concrete continuous beams using bi directional CFRP strips

Shear failure of a reinforced concrete beam is catastrophic where it occurs suddenly and without any warning. The use of FRP sheet as a strengthening and repairing material is an effective method to enhance the shear capacity of the beam. Extensive researches have been conducted on the shear strengthening of reinforced concrete simply supported beams using FRP composites. However, strengthening continuous beams in shear have received very little attention among the researchers although most of the existing structures are in the form of continuous condition. Furthermore, there are restraints to add shear reinforcement to the existing reinforced concrete beams when beams are part of the floor-beam system. In the design guideline by ACI 440 Committee mentioned that the existing theoretical model have not been confirmed to be use for strengthening in negative moment region which existed in continuous beam. Therefore, in order to address the problem, a study on shear strengthening of reinforced concrete continuous beam using CFRP strips was conducted. An experimental work on 14 full-scale reinforced concrete continuous beams with a size of 150x350x5800mm was carried out. Simulation using finite element software ATENA v4 and theoretical analysis was also conducted. The variables involved a number of CFRP strips layers (one and two layers), wrapping schemes (four sides and three sides), orientation of CFRP strips (0/90 and 45/135 degree) and shear span to effective depth ratio, av/d (2.5 and 3.5). The type of FRP used was bi-directional CFRP strips. Two beams were un-strengthened and treated as the control specimens whilst the other 12 beam were wrapped with CFRP strips. From the experimental results, all beams failed in shear as expected. Beams wrapped with CFRP strips recorded shear capacity enhancement of around 10.12% to 53.74% compared to the control specimens. Beam wrapped with two layers of CFRP strips at four sides of the beam recorded the highest shear enhancement. Simulation study also showed similar behaviour in terms of shear capacity and crack patterns. Three existing theoretical models; ACI 440, Khalifa and Nanni and fib models were adopted for theoretical comparison of shear capacity contributed by CFRP, Vf while for shear capacity contributed by concrete, Vc and stirrups, Vs, the equation from ACI 318-08, BS8110 and EC2 was adopted. The ACI 440 model had shown the closer value with the experimental results and a modified ACI 440 model was proposed on the effective strain limit and bond-reduction coefficient

Reinforced Concrete Beams with Opening Strengthened using CFRP Sheets

This study explores the behavior of reinforced concrete beam with opening strengthened using CFRP sheets. The beams were deficient in bending and under-reinforced in order for the beams to fail in bending. Load-deflection behavior and strain profile were observed besides the crack pattern and modes of failure. A total of five (5) beams were casted and tested. One (1) beam was treated as control specimen, two (2) beams were reinforced concrete beams with square and circular opening respectively while the other two (2) beams were reinforced concrete beams with square and circular opening strengthened using CFRP sheets. For the strengthened beams, they were wrapped at three sides (U-wrap) of the beams with CFRP sheets. From the experimental results, it is observed that all beams fail in bending as expected. Beam with circular opening (un-strengthened) recorded the lowest ultimate load with 25.7 kN, a decreased for about 6.4% compared to control specimen. On the other hand, beams with circular opening strengthened using CFRP sheets recorded the highest ultimate load of 30.7 kN, which is an increased for about 11.9% compared to control specimen. The conclusion that can be drawn from this study is CFRP sheets can be used to increase the ultimate load of beam with the presence of opening

Flexural strength of concrete prism strengthened using CFRP with modified mortar

Reinforced concrete (RC) is a good durable material that commonly used in construction compared to others. However, reinforced concrete structures may be damaged and are suffering from various deteriorations because of overloading and an inadequacy of design which may be attributed to cracks, spalling, large deflection, and more. Hence, it is essential to find repair and strengthening techniques of deteriorated concrete structures not only suitable in terms of the economy, but also to use them for their intended service life

Study on Shear Strengthening of RC Continuous Beams with Different CFRP Wrapping Schemes

This paper presents the results of an experimental investigation for enhancing the shearcapacity of reinforced concrete (RC) continuous beams using different CFRP wrappingschemes. A total of five concrete beams were tested and various sheet configurations andlayouts were studied to determine their effects on ultimate shear strength and shear capacity ofthe beams. One beam was kept as control beams, while other beams were strengthened withexternally bonded CFRP strips with four or three sides bonding and one or two layers ofCFRP strips. From the test results, it was found that all schemes were found to be effective inenhancing the shear strength of RC beams. It was observed that the strength increases with thenumber of sheet layers and four sides wrap provided the most effective strengthening for RCcontinuous beam. Beam strengthened using this scheme showed 54% increase in shearcapacity as compared to the control beam. Two prediction models available in literature wereused for computing the contribution of CFRP strips and compared with the experimentalresults

Fresh Properties and Compressive Strength of 3D Printing Concrete Containing GGBS as Partial Cement Replacement

3D printed concrete is a particular mix of concrete that has been specially prepared to flow easily through the printing nozzle. The foundations of 3D printed concrete constructions are stacked, with each layer put on top of a preceding layer of pumped concrete. Despite its potential, the construction industry has been confronted with several material issues. The cement replacement in the concrete has also been intensively studied, but in 3D printed concrete, this matter has not been seen clearly. It still cannot be seen whether the cement replacement produces a good result for the 3D printed concrete. This research investigated the fresh characteristics and compressive strength of 3D printed concrete using GGBS as a partial cement replacement in the mixture. In addition, the optimal proportion of GGBS as a partial cement replacement in 3D printed concrete is also evaluated. In this study, the fresh properties of 3D printing were examined by a flow table test, a buildability test, and an extrudability test, while compression strength was assessed for the mechanical properties. The percentage of GGBS used will vary from 20% to 50% with a 10% increment by weight of cement, and the water-cement ratio was fixed at 0.5. The cube specimen for the compression test was 50 mm x 50 mm x 50 mm and was cured for 7 and 28 days. The findings show that the flowability of this 3D printed concrete increased as the percentage of GGBS increased. All of the specimens also passed the buildability and extrudability tests. The compressive strength of this 3D printed also increased as the percentage increased, but it decreased back at 50% GGBS replacement. Overall, this experiment shows that 40% GGBS replacement is the optimum proportion as cement replacement in 3D printed concrete as it shows the highest compressive strength, which is 57.3 MPa

Shear Capacity of Reinforced Concrete Beam with an Opening Retrofit Using Steel Fiber and Metakaolin

This study presents the experimental work of reinforced concrete beam with opening at shear zone and added with steel fibre and metakaolin to increase the shear capacity of the beam. A total of five (5) beams were casted and tested under four-point bending test. One beam served as the control specimen, two beams were beams with one and two opening respectively while the other two beams were beams with added steel fibre and metakaolin. The type of steel fibre used was a hooked-end steel fibers with the dimensions of 0.9mm in diameter, 60mm in length, and 0.5% of steel fiber was added by volume of beam, and 5% of metakaolin by volume of beam were used. From the experimental results, it was found that the two beams with added steel fibre and metakaolin shows an increase in shear capacity compared with the beams with opening without the steel fibre and metakaolin. The highest shear force recorded was 79.11 kN (beams with added steel fibre and metakaolin) which shows an increase for about 54.3 % compared with the same beam with opening without added steel fibre and metakaolin

Fresh Properties and Flexural Strength of 3D Printing Concrete Containing GGBS with Varies in Water-Cement Ratio

In the recent years of construction industry, the need of 3D printing technologies start to booming throughout the global and significant progress has been achieved in the development of large scale of 3D printing industry. The use of 3D concrete printing to produce structural components and buildings is extremely feasible. Freeform of building is allowed in 3D concrete printing without the necessity of high cost of formwork, which has big advantage over traditional method of pouring concrete into formwork. The aim to conduct this study is to investigate the flexural strength of 3D Printing Concrete contain Ground Granulated Blast Furnace- Slag (GGBS) with varies in water-cement ratio and its fresh properties. The percentage of GGBS that used to replace the Portland cement in this study is 30% because GGBS has various benefit compare to traditional cement. The main goal of this experiment is to determine the amount of water required for cement contained with GGBS as partial cement replacement which will benefit to the largescale 3D printing technology. The water-cement ratio varied from 0.4-0.6 with 0.05 increment. The findings of this study shown that the fresh properties of the mixture increased with the increment of water-cement ratio while the hardened properties, flexural strength decreased with the increment of water-cement ratio

Modified Epoxy for Fibre Reinforced Polymer Strengthening of Concrete Structures

Fibre-Reinforced Polymer (FRP) is a preferable material for repairing concrete structure due to excellent material properties and effective installation cost over the long-term maintenance of structures. The successful application of FRP strengthening system very much depends on the bond between the concrete substrate and the FRP material using epoxy adhesive. Epoxy acts as a bridge to transfer stress from the concrete to the FRP material. The use of wet lay-up technique to apply FRP onto concrete structure requires epoxy to undergo a curing process normally referred to as cold curing. This paper intends to give a review of the problems with cold-cured epoxy and its effect on structural performance. Cured epoxy is characterised as brittle; therefore, modifications of epoxy are required to toughen the epoxy to suit the purpose of repairing a concrete structure. The methodological approaches from previous studies on modified epoxy were collected and reviewed in this paper. This review also offers some important insights regarding the use of sustainable materials, as well as recommendations for new epoxy in the future. &nbsp

Strength Properties of Untreated Coal Bottom Ash as Cement Replacement

Coal Bottom Ash (CBA) is a mineral by-product of thermal power plants obtained from the combustion of coal. In many countries, CBA wastes are identified as hazardous materials. The utilization of CBA can help in alleviating environmental problems; thus, this research was carried out to explore the possibility of its use as cement replacement in concrete manufacturing. Presently, In Malaysia, research that concerns about the use of CBA as cement replacement is very limited. Therefore, this study was aimed to investigate the properties of CBA as cement replacement and to identify the optimum percentage of untreated CBA as cement replacement. The CBA used in this study were taken from the Tanjung Bin power plant. In this research, the amount of CBA in the concrete mixture varied from 20% to 40% to replace cement. The properties of concrete containing CBA as cement replacement was examined through slump test, sieve analysis, concrete compressive strength test and splitting tensile strength test. The compressive strength test and splitting tensile strength test were performed at 7 and 28 days of curing time. Based on this research, it can be concluded that the optimum percentage of CBA as cement replacement is 25% for a curing time of both 7 and 28 days with the concrete compression strength of 45.2 MPa and 54.6 MPa, respectively. Besides, the optimum percentage for tensile strength is also at 25% CBA for a curing period of both 7 and 28 days with the tensile strength of 2.91 MPa and 3.28 MPa, respectively.

Cooling panel wall system with difference types of cooling mediums

Global warming has caused worldwide average surface temperature to rise about 0.74oC during the past 100 years, which is partly aggravated by air-conditioning that releases chlorofluorocarbons (CFCs) and forming a vicious cycle. This paper proposes a cooling house system that can promote thermal comfort in buildings without air-conditioning. The cooling panel wall forms a part of an Integrated Building System (IBS), and is essentially made of tubes filled with either water or glycerin as the coolant. Target strength for the panel wall was designed based on the Malaysian Standard (MS) while the building ventilation system followed the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) standard. The results are reported based on indoor and outdoor temperature difference together with relative humidity to identify the best performing house model and also coolant. The outcome of this research is expected to add value to heritage house design concepts with a better promotion of air flow and circulation in the building, without over-usage of natural resources and higher building cost to achieve the same objective