The effect of loss of ignition, specific gravity, fineness, specific surface area and soluble fly ash to compressive strength of geopolymer paste were studied. Six fly ashes from two different sources and different time of collection were evaluated. Sodium hydroxide and sodium silicate were used as alkali activator. Concentration of sodium hydroxide and mass ratio of sodium hydroxide to sodium silicate were fixed 14M and one respectively. The result indicated that the improvement in compressive strength of geopolymer paste was more influenced by fineness, specific surface area and soluble content of fly ash. Soluble content of fly ash greatly affected the compressive strength of geopolymer paste compare to the compressive strength of cement paste with 20% fly ash replacement.
A low-cost digital image correlation system is used to visualize the formation and propagation of concrete cracking in a reinforced concrete beam. The system employed comprises an ordinary digital camera, a remote image recording controller (a smartphone) and a freely-available, open-source image correlation software package Ncorr. In this paper, the application of this system is demonstrated to obtain a comprehensive time-lapse of longitudinal strain fields developing before and after the onset of shear cracking, thus allowing one to appreciate the mechanisms of shear failure in the beam fully. It is shown that the longitudinal strain fields obtained from the DIC system are in a good agreement with hand-drawn crack maps and that obtained from nonlinear finite element analysis.
Three reinforced concrete beams, one with no shear reinforcement and two others with shear reinforcement ratios of 0.4% and 1.1%, were tested to investigate the influence of stirrup spacing on the mode of failure, overall strength and ductility. The results show that the beam reinforced with closely-spaced shear reinforcement failed in a ductile manner, whereas the other two beams with large stirrup spacing and no stirrup exhibited only a small measure of ductility and failed in a brittle manner. The importance of the provisions of maximum spacing is highlighted to ensure adequate anchorage for the stirrups and prevent a premature shear failure to occur. The application of a non-contact monitoring system employing the open source digital image correlation software Ncorr, an ordinary digital camera and a smartphone is demonstrated to provide a visualization of the cracking process throughout the load history.
Chloride ingress is one of the major causes of durability problems in reinforced concrete structures. This research focused to investigate the chloride penetration process through the concrete subjected to wetting and drying cycle. This research used 150 x 150 mm normal concrete prism sample with a 40 mm concrete cover. Three wetting and drying configurations used in this study to investigate the effect of wetting and drying period to the chloride penetration. The result indicated that the chloride concentration and penetration depth were highly influenced by the duration of wetting and drying. Based on the experimental result, concrete exposed to 5 hours drying and 3 hours wetting has the highest chloride concentration compared with the sample exposed to other wetting and drying configuration.
External confining devices are often used to enhance the strength and ductility of reinforced concrete columns. Among the available external confining devices, steel tube is one of the most widely used in construction. However, steel tube has some drawbacks such as local buckling which needs to be considered when estimating the axial load carrying capacity of the concrete-filled-steel-tube (CFST) column. To tackle this problem in design, Eurocode 4 provided guidelines to estimate the effective yield strength of the steel tube material. To study the behavior of CFST column, in this paper, a non-linear analysis using a fiber-based approach was conducted. The use of the fiber-based approach allows the engineers to predict not only the axial load carrying capacity but also the complete load-deformation curve of the CFST columns for a known confining pressure. In the proposed fiber-based approach, an inverse analysis is used to estimate the constant confining pressure similar to design-oriented models. This paper also presents comparisons between the fiber-based approach model with the experimental results and the 3D non-linear finite element analysis.
Abstract This paper is aimed to review the current researches on Cold-formed steel (CFS) structures, particularly for screw connections, welded connections, bolted connections and adhesive connections. Connection presents as a major parameter of the important elements for CFS framing system in order to attain its structural stability. The performance of different CFS connections is well-discussed in order to capture the behaviour of each type of connection. Based on the review assessment, the results highlighted that all types of connections except adhesive connections have shown the proper behaviour that can trigger the change of any design codes. Otherwise, adhesive connection is given several advantages that leads a novelty in the construction technology. Hence it still has some gaps of knowledge that are needed to be filled with comprehensive future researches.Keywords cold-formed steel, connection, screw, welded, bolted, adhesive Abstrak Makalah ini bertujuan untuk mengkaji ulang penelitian terkini mengenai struktur baja berbentuk dingin (CFS), terutama untuk sambungan sekrup, sambungan las, sambungan yang dilipat dan sambungan perekat. Sambungan merupakan parameter utama elemen penting sistem pembingkaian CFS untuk mencapai stabilitas strukturalnya. Kinerja koneksi CFS yang berbeda dibahas dengan baik untuk menangkap perilaku setiap jenis koneksi. Berdasarkan penilaian review, hasilnya menyoroti bahwa semua jenis koneksi kecuali koneksi perekat telah menunjukkan perilaku yang tepat yang dapat memicu perubahan kode desain apapun. Jika tidak, koneksi perekat diberi beberapa keunggulan yang mengarah pada kebaruan dalam teknologi konstruksi. Oleh karena itu masih ada beberapa celah pengetahuan yang perlu diisi dengan penelitian masa depan yang komprehensif.Kata Kunci baja tahan dingin, sambungan, sekrup, dilas, dilipat, perekat
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.