Effect of randomly dispersed short fibers on the flexural resistance factor of concrete beams reinforced with GFRP bars

Purpose The purpose of this paper is to investigate the potential design advantage in terms of resistance factors for normal weight concrete beams containing moderate-dose randomly dispersed short fibers and reinforced with glass fiber reinforced polymer (GFRP) bars.Design/methodology/approach An analytical model based on the current code specifications is used to calculate the moment capacity of over-reinforced sections. The vast majority of the considered beams are over-reinforced, compression-controlled. The data of the fiber-reinforced concrete (FRC) reinforced with GFRP bars are collected from three published research studies which are based on experimentally tested results. Three different types of short fibers with four volume fractions are considered. Probabilistic model is established to conduct reliability-based calibration using Monte-Carlo Simulation. Limit state function, relevant load and resistance random variables are identified, and adequate statistical parameters are selected. Target reliability index consistent with the one used to develop current design code specifications is used.Findings Reliability analysis and calibration process are carried out with the intention of estimating the flexural resistance factors for FRC beams reinforced with GFRP bars.Originality/value The predicted flexural resistance factors ranged from 0.72 to 0.95, giving the resistance factors the potential to be increased above the currently specified value of 0.65 for compression-controlled members reinforced with FRP bars.

STUDY ON THE PROPERTIES OF POLYURETHANE-CEMENT COMPOSITE (PUC)

In order to study the properties of polyurethane cement composite (PUC) material, this paper has carried out the tests of compressive resistance, flexural resistance, axial tension, bonding and acid and alkali corrosion resistance of the material. The average compressive strength of the material is 59.3 MPa, the average flexural strength is 41.5 MPa, and the average axial tensile strength is 31.0 MPa. The bonding strength between the material and concrete in axial tension is 3.56 MPa, and that between the material and concrete in bending is 3.16 MPa. The failure interface of the two bond tests is not on the bond surface, indicating that the polyurethane cement composite (PUC) material has good bonding property. The chemical corrosion resistance test of polyurethane cement material showed no visible change on the surface of the material, indicating good chemical corrosion resistance.

Flexural Resistance Analysis on Hot Asphalt Mixtures with Wire Mesh Placement Modeling as Reinforcement

Flexural resistance is the ability of a specimen to withstand force in two pedestals with vertical axis until it is broken. Flexible pavement is a type of pavement which is very dependent with pavement course underneath. The dependency of flexible pavement in both base course and subgrade makes this pavement difficult to apply in unstable soil. Using wire mesh course as reinforcement is considerably able to raise the flexural resistance. This study is aimed to analyze flexural resistance value in hot mix by using wire mesh course as reinforcement. The study is conducted by applying experimental method with designing four types of wire mesh laying models in hot mix using three points flexural test equipment. Based on the study result, it is found that hot mix with wire mesh laying 30 mm from specimen surface is the best model type with 291,85 KN flexural resistance value with 8 mm of deflection depth. In this laying, it can be concluded that wire mesh course can raise up the flexural resistance up to 35,41% compared to the hot mix without wire mesh course.

Environmentally Clean Ceramics Manufacturing With Application of Hazardous Car Production Mud and Galvanic Process Glass Waste

It was developed new ceramics composites with hazardous car production mud (CPM) and galvanic process glass waste with high content of heavy metals. They were applied as valuable components of red ceramics sintered at 700°, 750°, 800°, 850°, 900°, and 950°C to provide flexural resistance of up to 17.6 MPa, water absorption at 950°C 6.53 -10.45%, linear shrinkage – 5.24-6.29%, density 2.7 – 3.2 g/cm³, and dilatation coefficient 5.3 -13.8%. Structure formation studies by the XRD, SEM, EDS, and LAMMA methods demonstrated the synthesis of amorphous glassy material with small inclusion of mullite Al6Si2O13. Car production mud and galvanic process glass waste play the role of the intensifiers of the ceramics’ structures formation processes. The ceramics' leaching and solubility tests by the atomic absorption spectroscopy method showed strong chemical bond of heavy metals of the hazardous raw materials in insoluble structures. According to Brazilian standards, they can be used to produce tiles, bricks, blocks, and similar materials with high environmental eficiency.

Flexural Strength of an Indirect Composite Modified with Single-Wall Carbon Nanotubes

Objectives The low resistance to fracture has limited the use of indirect composite resins for dental restorations, particularly in regions that are exposed to strong occlusal forces. To overcome this issue, different types of reinforcement for composites have been proposed, one of which is carbon nanotubes (CNTs). The aim of this study was to evaluate the flexural resistance of one commercial indirect composite resin (Sinfony, 3M/ESPE) after incorporation of single-wall carbon nanotubes (SWCNTs; Sigma–Aldrich, Inc., St. Louis, Missouri, United States) with or without the silanization form. Materials and Methods Specimens of composite resin were fabricated in a Teflon mold. The composite resin was prepared according to the manufacturer’s instructions (n = 10 for each group), with SWCNTs in three concentrations. Statistical Analysis The SWCNTs and SWCNT/SiO2-ATES specimens were evaluated by transmission electron microscopy, and a flexural test was conducted according to the ISO 4049/2009. Flexural strength data in MPa were submitted to one-way ANOVA following Tukey (p < 0.05). Results The SWCNTs did not improve the flexural strength of indirect composite resin when compared with the control, independent of the concentration added (p > 0.05). However, when SWCNTs and SWCNTs/SiO2-ATES were compared, the SWCNTs/SiO2-ATES showed higher values than the three concentrations of SWCNTs (p < 0.05). Conclusion The silanization process improves the SWCNTs strength proprieties, but the modification of chemical bonding between SWCNT and SWCNT/SiO2-ATES modified resins, in different concentrations, did not improve the composite resin flexural strength.

EXPERIMENTAL ANALYSIS OF BEAM-TO-COLUMN JOINTS 1 EQUIPPED WITH SPRAYED ALUMINIUM FRICTION DAMPERS

In this paper, the results of an experimental analysis regarding beam-to-column joints equipped with friction dampers is presented. Even though the overall concept is not new, the connection structural detail and the friction pad material are different from previous proposals. In particular, the beam is connected to the column with a classical fixed T-stub fastening the upper flange and a friction damper located at the beam lower flange. The friction damper is composed of a stack of steel plates conceived to assure symmetrical friction. The friction pads are made of steel plates coated with thermally sprayed aluminium. The friction damper is designed in order to slide for a force level equal to or lower than the ratio between the nominal flexural resistance of the connected beam and the lever arm, i.e. the distance between the top T-stub and the friction damper. In this way, it is possible to obtain connections able to dissipate the seismic input energy almost without any damage to the steel elements, provided that all the joint components are designed with sufficient over-strength with respect to the actions corresponding to the friction damper sliding force. In this paper, such approach is validated reporting the results of an experimental campaign.

Recyclability Process of Gypsum Reinforced with Hemp Fabrics: Impact and Flexural Behaviour

Gypsum is an ancient material, still widely used and suitable for many applications in the constructions due to its low cost, availability, lightweight, good thermal and sound isolating behaviour, fire resistance and low energy consumption. One of the most established application is its use as building walls and as pointed out in authors previous research works, it can be very useful and interesting to reinforce the gypsum with vegetable fibres like hemp. This aspect is in line with the current world situation where every industrial company needs to decrease the materials waste, increase recyclability and use more eco-friendly materials. Therefore, this work aims at designing, manufacturing, and testing of both commercial and recycled gypsum specimens reinforced with hemp fabrics, in order to improve impact and flexural resistance of traditional gypsum boards. The recycling process was carefully studied to detect the best grinding time, temperature and time of the heat treatment required to allow the reutilization of gypsum powders. Three point bending and impact tests at different energy levels were carried out in order to understand how the presence of the hemp fabrics within the gypsum matrix and how the recycling process affect the mechanical response of reinforced gypsum.