Current Issue : January - March Volume : 2015 Issue Number : 1 Articles : 6 Articles
The analysis and design of a multiple residential building, seismically protected by a base isolation system incorporating double\nfriction pendulum sliders as protective devices, are presented in the paper.The building, situated in the suburban area of Florence,\nis composed of four independent reinforced concrete framed structures,mutually separated by three thermal expansion joints. The\nplan is L-shaped, with dimensions of about 75min the longitudinal direction and about 30malong the longest side of the transversal\ndirection.These characteristics identify the structure as the largest example of a base-isolated ââ?¬Å?artificial groundââ?¬Â ever built in Italy.\nThe base isolation solution guarantees lower costs, a much greater performance, and a finer architectural look, as compared to a\nconventional fixed-base anti seismic design. The characteristics of the building and the isolators, the mechanical properties and the\nexperimental characterization campaign and preliminary sizing carried out on the latter, and the nonlinear time-history design\nand performance assessment analyses developed on the base isolated building are reported in this paper, along with details about\nthe installation of the isolators and the plants and highlights of the construction works....
All construction professionals such as civil, mechanical, and electrical engineers, quantity surveyors, and architects have important\nroles in the construction process. Among these, architects are frequently appointed as a project manager (PM). The role of a\nPM will drive the success of the projects implementation. Therefore, the capability of an architect as a PM (ArPM) is critical in\nreducing challenges encountered. Accordingly, the identification of these challenges is an important task in selecting an appropriate\nArPM. The aim of this study is to identify the most critical challenges faced by an ArPM for construction projects. The data were\ncollected through questionnaires and interviews with architects and professionals in the Malaysian construction industry. Because\nof the fuzziness and uncertainty of subjective responses, Fuzzy Set Ttheory is applied to identify critical challenges. A total of 65\nquestionnaires were distributed and 36 questionnaires were returned.The results revealed that the critical challenges faced by an\nArPM are ââ?¬Å?poor planning,ââ?¬Â ââ?¬Å?unfamiliar technology,ââ?¬Â ââ?¬Å?unfamiliarity with green buildings and materials,ââ?¬Â ââ?¬Å?inappropriate scheduling,ââ?¬Â\nand ââ?¬Å?poor workmanship.ââ?¬Â All critical challenges were then categorized into six main groups including technical, managerial,\npersonal skills, contractual, psychological, and financial....
Ultrahigh performance concrete (UHPC) realized distinctly high mechanical, impermeability, and durability characteristics\nby reducing the size and content of capillary pore, refining the microstructure of cement hydrates, and effectively using\nfiber reinforcement. The dense and fine microstructure of UHPC favor its potential to effectively disperse and interact with\nnanomaterials, which could complement the reinforcing action of fibers in UHPC. An optimization experimental program\nwas implemented in order to identify the optimum combination of steel fiber and relatively low-cost carbon nanofiber in\nUHPC. The optimum volume fractions of steel fiber and carbon nanofiber identified for balanced improvement of flexural\nstrength, ductility, energy sorption capacity, impact, and abrasion resistance of UHPC were 1.1% and 0.04%, respectively. Desired\ncomplementary/synergistic actions of nanofibers and steel fibers in UHPC were detected, which were attributed to their reinforcing\neffects at different scales, and the potential benefits of nanofibers to interfacial bonding and pull-out behavior of fibers in UHPC.\nModification techniques which enhanced the hydrophilicity and bonding potential of nanofibers to cement hydrates benefited their\nreinforcement efficiency in UHPC....
External posttensioning or unbonded prestressing was found to be a powerful tool for retrofitting and for increasing the life\nextension of existing structures. Since the 1950s, this technique of reinforcement was applied with success to bridge structures\nin many countries, and was found to provide an efficient and economic solution for a wide range of bridge types and conditions.\nUnbonded prestressing is defined as a system in which the post-tensioning tendons or bars are located outside the concrete crosssection\nand the prestressing forces are transmitted to the girder through the end anchorages, deviators, or saddles. In response to\nthe demand for a faster and more efficient transportation system, there was a steady increase in the weight and volume of traffic\nthroughout the world. Besides increases in legal vehicle loads, the overloading of vehicles is a common problem and it must also\nbe considered when designing or assessing bridges. As a result, many bridges are now required to carry loads significantly greater\nthan their original design loads; and their deck results still deteriorated by cracking of concrete, corrosion of rebars, snapping of\ntendons, and so forth. In the following, a case study about a railway bridge retrofitted by external posttensioning technique will be\nillustrated....
This research explains the results of an investigation carried out to understand the influence of a microwave incinerated rice husk\nash (MIRHA) powder on foamed concrete (FC) hydration. The experimental work was designed using the Taguchi approach. This\nmethod was selected to have a target for the optimum working conditions of the parameter that affects some physical properties\nof concrete mixtures. The loss on ignition (LOI) method was used to establish the nonevaporable water (????????) content at all selected\nages of hydration. It was observed that the MIRHA powder showed lower nonevaporable water contents than the normal FC,\nindicating that MIRHA powder facilitated enhancement in FC hydration. The optimum FC properties were achieved at 10%\nMIRHA composition as proven from the highest compressive strength. This level corresponds to the highest values in change\nin nonevaporable water and degree of hydration....
Regular dredging is necessary for the development of coastal regions and the maintenance of shipping channels. The dredging\nprocess dislodges sediments from the seabed, and the removed materials, termed dredged marine soils, are generally considered a\ngeowaste for dumping. However, disposal of the dredged soils offshores can lead to severe and irreversible impact on the marine\necosystem, while disposal on land often incurs exorbitant costs with no guarantee of zero-contamination. It is therefore desirable\nto reuse the material, and one option is solidification with another industrial waste, that is, steel slag. This paper describes the\nexploratory work of admixing dredged marine soil with activated steel slag for improvement of the mechanical properties. An\noptimumactivation concentration ofNaOHwas introduced to the soil-slag mixture for uniformblending. Specimenswere prepared\nat different mix ratios then left to cure for up to 4 weeks. The unconfined compressive strength test was conducted to monitor the\nchanges in strength at predetermined intervals. It was found that the strength does not necessarily increase with higher steel slag\ncontent, indicating an optimum slag content required for the maximum solidification effect to take place. Also, regardless of the slag\ncontent, longer curing time produces greater strength gain. In conclusion, steel slag addition to dredged sediments can effectively\nstrengthen the originally weak soil structure by both the ââ?¬Å?cementationââ?¬Â and ââ?¬Å?fillerââ?¬Â effects, though the combined effects were not\ndistinguished in the present study....
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