Effectiveness Of Repair Method Using Hybrid Fiber Reinforced Polymer Fabric On Concrete-Filled Double Skin Steel Tubular Columns Exposed To Fire

Concrete-filled double skin steel tubular (CFDST) column is becoming more popular nowadays due to its superior performance compared to conventional composite column and concrete-filled steel tubular (CFST) column. However, the use of this type of column is still limited to outdoor construction such as bridge piers and transmission tower where fire is not a main concern. Moreover, existing research studies on CFDST column only focused on fire performance and limited research studies can be found on residual strength of the CFDST column. Residual strength can be used to determine the most suitable repair method needed in order to retrofit the column. Therefore, this study aims to study the effect of different parameter towards residual strength of CFDST column. Among discussed parameter is thickness of outer steel tube ( ) and fire exposure time. In addition, this study is also aim to determine the effectiveness of repair method using Single and Hybrid fiber reinforced polymer (FRP) of fire-damaged CFDST columns. CFDST columns were heated in accordance of ASTM E119-11: Standard Test Methods for Fire Tests of Building Construction and Materials until the temperature reached 600°C. Afterwards, the temperature was kept constant for two different durations, i.e., 60 minutes and 90 minutes. The specimen was then left to cool down to room temperature inside the furnace before it was taken out and repaired by Single and Hybrid FRP. The specimens were categorized into the following three groups: (1) unheated or control specimens, (2) heated and unrepaired and (3) heated and repaired. All specimens were subjected to axial compression loading until failure. The first and second category specimens failed by local outward buckling of outer steel tube, crushing of concrete and local buckling of inner steel tube; whereas, specimens in third category failed by rupture of FRP followed by similar local buckling and concrete crushing as those observed in first and second category specimens. Ultimate strength, secant stiffness and Ductility Index (DI) decreased as temperature of the specimen increased. The lost in secant stiffness of thinner CFDST specimens exposed to 60 minutes of fire exposure time is similar to thicker CFDST specimens exposed to 90 minutes of fire exposure time regardless of its diameter. In addition, CFDST specimens exposed to 90 minutes of fire exposure time were more ductile than control specimen. RSI and secant stiffness increased with the increased in fire exposure time. Interestingly, the highest RSI achieved is only 22% which means the specimens were still able to carry more than 70% of its initial load after being exposed to 90 minutes of fire exposure time with only 3 mm thickness of outer steel tube. Repairing the fire-damaged CFDST columns with Single and Hybrid FRP are proven to improve ultimate compressive strength significantly. The increment in ultimate compressive strength is more pronounced in specimen with Hybrid FRP and thinner outer steel tube. The secant stiffness and Ductility Index (DI) of repaired specimens were however not able to be restored to those of control specimen

Strength and Quality Assessment of Recycled Aggregate and Crumb Rubber Concrete Using the Ultra Pulse Velocity Method

This study focuses on the strength and quality of concrete incorporated with recycled aggregate and crumb rubber through the compressive strength test and the Ultra Pulse Velocity (UPV) test. RA was used to replace coarse aggregate while CR was used to replace fine aggregate in concrete production. A total of 36 specimens consisting of cubes (100 mm 100 mm 100 mm) with partial replacements of 50% RA and 0, 1, 2, 3, 4, and 5% CR were prepared, subjected to water curing for 7 and 28 days and tested in terms of compressive strength and quality using the compressive strength test and the UPV method. The UPV test and the compressive strength test were conducted at day 7 and day 28. The results show that the compressive strength of concrete decreased slightly with the increase of rubber content. Additionally, the quality of concrete slightly decreased as the percentage of rubber content increased. Finally, the optimum percentages for partial replacement of concrete suggested based on the results are 3% CR and 50% RA as this concrete mix achieved the highest velocity in the UPV test and the highest compressive strength compared to the control mix

Proceedings of the Sustainable Concrete Materials and Structures in Construction 2020

Seminar on Sustainable Concrete Materials and Structures in Concrete Construction 2020 was held virtually for the first time on 24 August 2020. This event was organized by the Faculty of Civil Engineering and Built Environment (FKAAB), Universiti Tun Hussein Onn Malaysia (UTHM) in collaboration with Concrete Society of Malaysia (CSM) and Civil Engineering and Built Environment Postgraduate Society, FKAAB (CiBPS). The theme of this seminar is Toward Sustainable Green Concrete. This seminar marks the first collaboration between these three organizations

Thermal Conductivity of Crumb Rubber as Partial Sand Replacement and Recycled Aggregates as Partial Coarse Aggregate Replacement in Concrete

Disposal of waste tire rubber has become a major environmental issue worldwide and is increasing day by day, especially in Malaysia where carbon emission is among the highest in the world. Therefore, recycled waste materials are being used as construction materials in order to create new innovative products that are able to mitigate environmental pollution, reduce the cost of construction and improve the properties of concrete. This study discusses the utilisation of crumb rubber and recycled aggregates in concrete construction and the objective of this study is to determine the thermal conductivity of crumb rubber and compare the optimum strength of concrete materials. 12 cube samples measuring 200 200 100 mm containing different percentages of crumb rubber (0, 1, 2, 3, 4, and 5%) as fine aggregate substitute and 50% of recycled aggregates as coarse aggregate substitute were produced. The concrete grade used for these specimens is grade 35. The curing process was conducted on the samples to achieve the standard strength of concrete in 7 and 28 days. Therefore, the real strength of concrete was measured after the curing process. A slump test was conducted to determine the properties of crumb rubber. In addition, the samples were examined using the guarded hot box method to obtain the optimum percentage of crumb rubber as partial sand replacement in concrete for thermal conductivity. The results show that thermal conductivity (k-value) decreased slightly with the increase in crumb rubber content. However, the quality of concrete also slightly increased as the percentage of crumb rubber content increased. Lastly, based on the results, 5% of crumb rubber and 50% of recycled aggregates were suggested as the optimum percentages to be used in concrete as it achieved the lowest thermal conductivity compared to conventional concrete

Effects of Recycled Aggregate Resin (RAR) in Concrete Material

This paper discussed the recycled aggregates produced from construction and demolition waste and their utilization in concrete construction. Along with a brief overview of the engineering properties of recycled aggregates, the paper also summarizes the effect and use of recycled aggregates on the properties of fresh and hardened concrete. The recycled aggregates were treated with epoxy resin to reduce the water absorptions with different percentages of resin such as 0%, 25%, 50%, 75%, and 100%. Epoxy resin is widely used in recent years owing to the enhancing of mechanical and durability of the concrete. This research also showed, recycled aggregate concrete are close proximity to normal concrete in terms of split tensile strength, compression strength and wet density. The low usage of resin was obtained good strength concrete compared to high percentage contained treated aggregates due to low bonding between material

Identifying the Crack Nature Using b-Value Acoustic Emission Signal Analysis

Concrete is an important constituent of structures. The strength performance of the concrete decrease due to several factors. Concrete suffers from deterioration at a later stage. Early and constant identification of concrete deterioration is necessary. Nowadays, non-destructive testing (NDT) is widely used especially on continuous real-time monitoring system with minimum labor involvement. It could also be used to discriminate the different types of damage occurring in reinforced concrete (RC) beam and real structure. In this research was monitored by using Acoustic Emission testing and it have several analysis such as RA-value, b-value, intensity signal analysis and historical index. To determine the acoustic emission signals for concrete structures and cracking identification this research using b-value analysis. b-value signals analysis contain useful information about damage mechanisms. A high b-value arises due to a large number of small AE hits, it representing new crack formation and slow crack growth, whereas a low b-value indicates faster or unstable crack growth accompanied by relatively high amplitude AE in large number. Reinforced concrete beams measuring of size 150 mm 250 mm 1500 mm were used during the acoustic emission test. A four-point load test was carried out on specimens until cracking occurred. The signals generated from the equipment were used for the analysis process, and the values are compared to define and summarise type of cracking and cracking processes

Laminated Veneer Lumber (LVL) sengon: an innovative sustainable building material in Indonesia

Laminated Veneer Lumber (LVL) is recently available in Indonesian markets. The veneers are majority from Sengon wood (Paraserianthes falcataria), which is a fast-growing timber species native to Indonesia. Their use in practice is limited to non-structural components since Sengon wood species has low engineering properties and less resistance to termite attacks. The LVL production introduced few years ago has significantly improved both mechanical properties and durability as well as has expanded its utilization into various structural components. This remarkable improvement has made LVL Sengon wood as an innovative sustainable building materials in Indonesia. This paper summarized a series of authors’ work conducted since couple years ago to initiate the utilization of LVL Sengon in structural components such as shear walls and floor systems as parts of a project to develop its design standard. In addition, creep behavior of this LVL is also highlihgted here as this phenomenon is essential for designers and engineers to anticipate their designs within their service life. In particular, the test results showed that addition of diagonal members increased both racking resistance and equivalent viscous damping ratio of the developed LVL shear walls. And the LVL floor model which is composed of built-up box joists and plywood sheathing remained liniear-elastic under bearing load up to 18.75 kN/2

Effectiveness of repair method using hybrid fiber reinforced polymer fabric on concrete-filled double skin steel tubular columns exposed to fire

Concrete-filled double skin steel tubular (CFDST) columns were often used in outdoor construction where fire is not a main concern. Therefore, this series of research deals with behaviour of CFDST columns after fire exposure, residual strength and method of repairing fire-damaged columns. This particular paper focused on the effectiveness of Hybrid Fiber Reinforced Polymer (FRP) repairing method. Total of 42 specimens were casted and 36 of the specimens were exposed to ASTM E-119 until the temperature of 600˚C. After that, the temperature was kept constant for 60 and 90 minutes. Out of 36 specimens that were exposed to fire, 24 of the specimens were repaired with FRP using hand lay-up method. All of the specimens (control, heated unrepaired and heated repaired) were subjected to concentric axial loading. It was found that by using Hybrid FRP, the ultimate strength at failure of repaired specimens greatly increased when compared to fire-damaged specimens to the extent of exceeding the control specimens. In addition, FRP is also effectively confined thinner outer steel tube than thicker outer steel tube. However, the effectiveness of Hybrid FRP repair method depends on several factor such as thickness of outer steel tube and maximum exposure time

Theoretical and actual bearing capacity of driven piles using model piles in sand

In general, increasing of penetration rate may result in an increased of pile capacity. Occasionally, there were differences between theoretical and actual bearing capacity of the piles. Rate of penetration of pile influenced the pile bearing capacity. The bearing capacity of model pile increased as the rate of loading increased based on pile driving formula. Therefore, the study was conducted to determine the bearing capacity of model piles with different penetration forces based on theoretical method and experimented analysis. Five circular hollow section model piles using pipe pile were used to penetrate into cohesionless soil with different penetration force respectively. The loading for ultimate bearing capacity using theoretical calculation was approximately about 0.163kN. However, referring to the limitation of a laboratory setup, the maximum loading was 0.12kN. Several trials had been initiated but when it reached 0.14kN, the setup was unstable and dangerous to be continued. Therefore, the ultimate bearing capacity derived by the pile load test results were based on a pile moved up to 10% of its tip diameter criteria. In the future, both theoretical and actual calculation must be made to avoid any confusion and detect mistakes in near futur

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.