ASIAN JOURNAL OF CIVIL ENGINEERING (BUILDING AND HOUSING)
Year:2011 | Volume:12 | Issue:5|Papers Count:8

This study addresses the application of polypropylene (PP) nonwoven layers for strengthening cement composite by investigating its flexural performance. Nonwoven layers produced by two different bonding techniques (needle-punching and calendaring) were used to reinforce cement sheets. The effect of some parameters related to layers on cement reinforcement was considered in this study. In addition, the application of short fibers (PP and acrylic) on cement/nonwoven composites was experienced. It was found that the cement composite made of thinner layers exhibits greater load-bearing capacity, because of the better penetration of the cement paste to nonwoven layers. The cement matrixes reinforced by nonwoven layers showed better flexural performance and strain-hardening behavior compared to short fibers reinforced cement composites.

Utilization of industrial soil waste or secondary materials has encouraged in construction field for the production of cement and concrete because it contribute to reducing the consumption of natural resources. Copper slag is one of the materials that is considered as a waste which could have a promising future in construction Industry as partial or full substitute of either cement or aggregates. Many researchers have already found it possible to use copper slag as a concrete aggregate. But not much research has been carried out in India concerning durability and corrosion studies of copper slag admixed concrete. This paper presents the results of an experimental study on various corrosion and durability tests on concrete containing copper slag as partial replacement of sand and cement. For this research work, M20 grade concrete was used and tests were conducted for various proportions of copper slag replacement with sand of 0 to 60%, cement of 0 to 20% in concrete. The obtained results were compared with those of control concrete made with ordinary Portland cement and sand.

This article provides a comparison process on how to calculate seismic forces by the static analysis method stated both in the international Building Code (IBC) 2003 and in the Iranian Seismic Code (IS 2800-05). The seismic coefficient for the equivalent lateral force is specified by the following factors: fundamental period, importance factor, spectral response acceleration, and building response modification factor. In this article the above-mentioned parameters are obtained through the IBC 2003 and are compared against those covered in the IS 2800-05. Studies and comparison of factors would lead to significant differences in the results obtained using the two codes. In order to clarify the problem, design base shear of a building with combined system (special moment steel frames + eccentric bracings) in four different soil types and vertical distribution of base shear at story level is obtained, in accordance with both codes; and the results are compared with diagrams and tables. The results prove the need to review the IS 2800-05 and develop more appropriate relations towards achieving economic and functional objectives.

The purpose of this experimental investigation is to study the behavior of short columns produced from High Performance Concrete (HPC). In this investigation HPC was manufactured by usual ingredients such as cement, fine aggregate, coarse aggregate, water and mineral admixtures such as Silica Fume (SF) and Fly ash at various replacement levels and the Super Plasticizer used was CERAPLAST-300. The water binder ratio (w/b) adopted is 0.30. The concrete used in this investigation was proportioned to target a mean strength of 60 MPa. Specimens such as cubes, cylinders and prism beams were cast and tested for various mixes viz. Seven mixes M1 to M7 are cast with 0%, 5%, 7.5% and 10% replacement of SF and another set of specimens with 0%, 5%, 7.5% and 10% replacement of SF along with 10% constant replacement of Fly ash to study the mechanical properties such as compressive strength, split tensile strength and flexural strength at different ages of concrete such as 3, 7, 28, 56 and 90 days. The result shows that the optimum replacement of silica fume is 7.5%. If 10% of Fly ash is added the optimum replacement of silica fume is 5%. Totally 7 columns were cast for mixes M1 to M7. The column specimens were tested in 1000kN loading frame at 28 days. From this, Load-Mid height deflection (P-D) curves were drawn and compared. The same failed columns were rehabilitated with GFRP sheets with one or two layers and again tested in 1000 kN loading frame. The results were then compared with the initial results.

This paper presents probabilistic diagrams for assessing liquefaction resistance of Firoozkooh clean sand and sand-silt mixtures with silt content up to 60% based on laboratory shear wave velocity results. In the work described herein, at first cyclic triaxial and resonant column tests were conducted on specimens with different densities. Then, laboratory results are compared to liquefaction criteria derived from seismic field measurements by Andrus and Stokoe-2000. At last, a data base consisting of laboratory shear wave velocity measurements is analyzed with probabilistic 3a method. The laboratory results indicated that using the existing field-based correlations will over estimate the cyclic resistance of the Firoozkooh sand-silt mixtures when silt content is 60%. Also, analyses based on 3a method showed that probability curve PL=0.32 agree with deterministic curves in Fc£5%and Fc=20% fines content. With increasing fines content up to 60%, probability curve PL=0.99 agree with field measurements by Andrus and Stokoe-2000.

In this paper, semi-active response control of tall buildings equipped with magnetorheological dampers is studied. Clipped-optimal control algorithm based on linear quadratic regulator (LQR) is employed for semi-active controller design. Bouc-Wen phenomenological model is utilized to investigate the nonlinear behavior of the MR dampers. The performance of the resulting control system is compared to the uncontrolled structure for a benchmark building through simulation, and the efficiency of using MR dampers is evaluated.

Euler-Bernoulli beam model based non-local elasticity theory is developed for the static and buckling analysis of cantilever carbon nanotubes (CNTs). The size effect is taken into consideration using the Eringen’s non-local elasticity theory. The derivation of governing equation of bending and buckling from the shear and moment resultants of the beam and stress-strain relationship of the one-dimensional non-local elasticity model is presented. Buckling and deflection values of CNTs are obtained and presented in graphical form. Numerical results are presented to show the small-scale effect on bending of CNTs.

During this year, 150 earthquakes with magnitude greater than 4 occurred in Iran. In addition; more than 331 accelerograms were recorded by the accelerographs of the Iran Strong Motion Network, operated by the Building and Housing Research Center. Among these, the Qeshm Island earthquake of 10th Sep. 2008, with Mw6.1 was the greatest one. The main shock of this earthquake triggered 11 accelerographs. Its maximum PGA was about 597 Cm/s/s that were registered by Tomban Station. The strong motion and seismological data of important accelerograms are listed in the appendix table.