Behaviour of Precast Concrete Beam-to-Column Connection with SHS Hidden Corbel Subjected to Monotonic Load

Beam-to-column connection is the most critical part of a precast concrete (PC) that governs the integrity of the entire structure, hence its characteristics need to be determined for safe applications in the construction industry. Therefore, this study developed a beam-to-column connection with square hollow section (SHS) hidden corbel. A full-scale test was conducted on eleven T-subframe specimens with various configurations used to investigate the behaviour of the connection under an incremental static load. It was further evaluated using the beam-line method to determine the moment-rotation response and the mechanical properties. Furthermore, this research analyzed the parametric response, the load resisting mechanism, and the feasibility of the connection for PC structures. Due to extensive usage of steel elements, the PC connection gave a higher ultimate strength than the reinforced concrete (RC). Its moment resistance was largely contributed by the hidden corbel embedded in the beam and column, increasing with the column and beam's embedded length. The grout infill prevented the lateral deformation of the hidden corbel and hence strengthened the connection. Due to the low bending resistance of the steel endplate, the PC connection possessed a low stiffness, which led to a larger rotation deformation than the RC connection, and a low design strength. This could be overcome by modifying the shape of the endplate for a higher second moment of inertia in resisting bending. The PC connection was classified as semi-rigid and partial-strength, and only specimen PC-3 was considered feasible for PC structures

Behaviour of Reinforced Concrete Beams With Circular Transverse Openings Under Static Loads

Transverse opening in a reinforced concrete beam allows the crossing of mechanical and electrical services through the beam. However, it affects the strength of a beam. Understanding its structural behaviour is crucial to ensure a safe design of the beam. For that, an experimental study was carried out on reinforced concrete beams with circular transverse openings. The four-point load test was conducted to study the effects of the size and the position of the opening on the beam performance under the shear and flexural loads. In addition, three reinforcing methods for the opening were tested. The beams were evaluated in terms of the load-displacement responses, mechanical properties, deflections, and failure modes. The opening with the diameter not exceeding 0.25 times beam height affected about 20% of beam strength (without reinforcements at the opening). The diagonal bar reinforcing method effectively restored the beam strength for the opening size not exceeding 1/3 of beam height. The equation model proposed conservatively predicted the ultimate capacity of the beam with a transverse opening

Utilization of Oil Palm Empty Fruit Bunch in Cement Bricks

Oil palm empty fruit bunch (EFB) is a biomass waste abundantly produced by the oil palm industry in Malaysia. To minimize the environmental impacts, it needs to be properly disposed of or being rapidly consumed as a raw material of another industry. This study investigated the feasibility of substituting EFB in cement bricks, which is in high demand by the construction industry. A total of 120 specimens having the cement-to-sand (c/s) ratios of 1:2.5 and 1:3 were produced in the laboratory. EFB fibre was used to replace 10% to 25% of sand in the mix by volume. The specimens were tested for the compressive strength, density and water absorption after 28 days of casting. For the mix of 1:2.5 c/s ratio, 25% EFB content reduced 22% of density, decreased 59% of compressive strength and increased 43% of water absorption capacity of normal cement brick. This was mainly attributed to the porous cellular structure of EFB fibre that created a large volume of voids in the mix. Based on the feasibility evaluation, EFB fibre can only replace up to 15% and 10% of sand in the mixes of 1:2.5 and 1:3 c/s ratios respectively

The Development of Finite Element Model to Investigate the Structural Performance of Reinforced Concrete Hollow Beams

The self-weight of a reinforced concrete beam contributes to the permanent loads of a structure. This can be reduced by creating a longitudinal void along the beam so that it will not affect the performance of the beam. In addition, this process can reduce the amount of building cost. Therefore, a finite element model was developed in this study with the aid of a computer program, Ansys, to investigate the behavior of the hollow beam. The model was tested for reliability by comparing the predicted results with those obtained from the experiment in terms of the load-displacement responses, mechanical properties, and parametric responses. The result showed that the reliability of the model was questionable. The main cause of the non-reliability was the inaccurate prediction of the beam deflection by the model. The poor prediction of beam deflection led to significant variations of relevant mechanical properties including stiffness, deflection, and ductility. For beam deflection, only 1/3 of the specimens were correctly predicted with a reliability of 36% while the strength properties were discovered to have higher values as observed in the yield and the ultimate strengths with 73% and 64% respectively. However, both the model and experimental results showed the hollow beam was relatively effective when the diameter of the longitudinal void was 1/3 times the beam width and placed at the neutral axis. For the evaluation to improve the reliability, some revision including the properties of the materials, boundary conditions of the beam support, bonding conditions between different materials, and meshing shape and size suppose to be applied to the model.

LEARNING ABOUT CONCRETE-FILLED TUBE USING CHATGPT

ChatGPT is an artificial intelligence that can understand context and respond appropriately. It could be used for research on a topic. However, ChatGPT does not always provide accurate information. Its performance has not been tested in engineering fields. In this study, ChatGPT was consulted about concrete-filled tubes (CFT), which is a structural element primarily subjected to axial load. Fifty-eight questions were posted to ChatGPT. ChatGPT’s responses (370 sentences) were evaluated. ChatGPT generated plagiarism-free statements, with only a 12% Turnitin similarity index. 78.6% of ChatGPT’s sentences were long and complex. Thus, Hemingway Editor gave them a Grade 14 for poor readability. The information given by ChatGPT can be classified as correct, erroneous, contradictory, and unverified. ChatGPT could be used as a research tool, but with limitations. It can explain the basic concepts of CFT but also provide inaccurate and contradictory information. A researcher needs to be cautious while using ChatGPT in research. ChatGPT could be used to test some hypotheses or theories. However, the quality of the output is dependent on the user’s critical inputs and an in-depth conversation with ChatGPT

CONCRETE-FILLED TUBULAR COLUMN MADE OF VARIOUS TYPES OF MATERIAL

Concrete-filled tubes (CFT) are gaining popularity due to their excellent performance under compression. Various materials have been used to produce CFTs. Their behaviour varied significantly due to the properties of the materials. In this study, numerous articles related to CFT were reviewed. The effects of carbon steel, stainless steel, fibre-reinforced polymers (FRP), plastic materials, and various kinds of concrete on CFT were observed. The fundamental principles governing the behaviour of CFT were then determined. The confinement effect of the tube was the key to the outstanding performance of CFT. CFT performed well when the tube had high compressive strength, elastic modulus, tensile strength, ultimate strain, and corrosion resistance. The concrete with high compressive strength and ultimate strain, as well as low elastic modulus and shrinkage, experienced greater strength enhancement under confinement. Nevertheless, confinement effectiveness was greatly affected by the slenderness ratio. Short CFT subjected primarily to axial loads was preferred

Experimental Study on the Flexural Behavior of Reinforced Polystyrene Blocks in Concrete Beams

A new type of lightweight beam system was recently proposed by embedding polystyrene in beams to improve structural efficiency. This removes the non-performing concrete in the neutral axis and tension region to provide a comparable strength as a solid beam. There are, however, limited studies conducted to investigate the structural behavior of such beams. Therefore, this research presents an experimental investigation to assess the effect of polystyrene shapes in the beams. This involved testing a solid beam and five lightweight beams under flexural load using a four-point load test. The inclusion of polystyrene was estimated to have reduced the self-weight of beams by 8.6% to 11.8% when compared with the solid beam. The results also showed the ellipse polystyrene with a width of 70 mm and height of 50 mm produced the highest effective strength to weight ratio (sw) of 1.12 and performed 12% better than the solid beam. Moreover, the lightweight beams have more weight reduced than the strength, and those with ellipse polystyrene were found to have performed better than circular ones based on first crack load, ultimate load, and effective strength to weight ratio (sw). The beams with ellipse polystyrene allowed better stress distribution and this gave them a higher strength than sphere shape. For industry application, the polystyrene content is recommended to be greater than 10% while the effective strength to weight ratio (sw) of the beam is greater than 1. The successful reduction of the weight without affecting the structural performance has the ability to help in reducing construction costs

Properties of Cement Brick with Partial Replacement of Sand and Cement with Oil Palm Empty Fruit Bunches and Silica Fume

Oil palm empty fruit bunches (EFB) and silica fume (SF) are the by-products of the oil palm plantation and the ferroalloy smelting industries, respectively. Improper disposal of these materials leads to negative implication to the environment. This study was carried out to investigate the potential application of EFB and SF in cement bricks. EFB fibre and SF replaced up to 25% of sand and cement in the mix, respectively, in several groups of specimens that distinguished the normal, EFB-, SF- and EFB-SF-cement bricks. The specimens were tested for the compressive strength, density and water absorption property. The results reveal that SF, at an optimum amount of 10% cement replacement, increased 10% of the strength of the cement brick. EFB fibre reduced the strength and density but increased water absorption property of the cement brick. For application in the construction industry, SF and EFB fibre contents should be kept within 10% and 20% respectively

Experimental Study of RC Hollow Beams with Embedded PVC Pipes

This study investigated the behaviour of reinforced concrete (RC) hollow beams under incremental static loads. Polyvinyl Chloride (PVC) pipes were used to create longitudinal voids in hollow beams. The parameters studied included the size (25 mm, 50 mm and 75 mm diameter) and location (39 mm and 139 mm from beam soffit) of the PVC pipes in the beam. Nine specimens were tested under the four-point load test setup. The loads were progressively increased until the specimens failed. The specimens were analysed based on the failure modes, load-displacement responses and mechanical properties. The hollow beams gave a 2% to 36% lower strength than the solid beams. In terms of the strength per unit concrete, the hollow beams were less efficient than the solid beams. The efficiency ratio of hollow beams ranged from 0.67 to 1.0. For that, none of the proposed hollow beams was recommended

Community-acquired Methicillin-resistant Staphylococcus aureus in Children, Taiwan

Highly virulent community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) with Panton-Valentine leukocidin (PVL) is common worldwide. Using antimicrobial drug susceptibility testing, staphylococcal cassette chromosome mec typing, exotoxin profiling, and pulsed-field gel electrophoresis typing, we provide evidence that supports the relationship between nasal strains of PVL-positive MRSA and community-acquired disease