Current Issue : April - June Volume : 2013 Issue Number : 2 Articles : 7 Articles
There is significant concern in the engineering community regarding the safety and effectiveness of fiber-reinforced\r\npolymer (FRP) strengthening of RC structures because of the potential for brittle debonding failures. In this paper, previous\r\nresearch programs conducted by other researchers were reviewed in terms of the debonding failure of FRP laminates externally\r\nattached to concrete. This review article also discusses the influences on bond strength and failure modes as well as the existing\r\nexperimental research and developed equations. Based on the review, several important conclusions were re-emphasized, including\r\nthe finding that the bond transfer strength is proportional to the concrete compressive strength; that there is a certain bond\r\ndevelopment length that has to be exceeded; and that thinner adhesive layers in fact lower the chances of a concrete-adhesive\r\ninterface failure. It is also found that there exist uncertainty and inaccuracy in the available models when compared with the\r\nexperimental data and inconsistency among the models. This demonstrates the need for continuing research and compilation of\r\ndata on the topic of FRP�s bond strength....
This paper focuses on the finite element (FE) response sensitivity and reliability analyses considering smooth constitutive\r\nmaterial models. A reinforced concrete frame is modeled for FE sensitivity analysis followed by direct differentiation\r\nmethod under both static and dynamic load cases. Later, the reliability analysis is performed to predict the seismic behavior of the\r\nframe. Displacement sensitivity discontinuities are observed along the pseudo-time axis using non-smooth concrete and reinforcing\r\nsteel model under quasi-static loading. However, the smooth materials show continuity in response sensitivity at elastic to\r\nplastic transition points. The normalized sensitivity results are also used to measure the relative importance of the material\r\nparameters on the structural responses. In FE reliability analysis, the influence of smoothness behavior of reinforcing steel is\r\ncarefully noticed. More efficient and reasonable reliability estimation can be achieved by using smooth material model compare\r\nwith bilinear material constitutive model....
This paper presents the differences in growth of time-dependent strain values in reinforced cement concrete (RCC) and\r\npre-stressed concrete (PSC) flexural members through experiment. It was observed that at any particular age, the time-dependent\r\nstrain values were less in RCC beams than in PSC beams of identical size and grade of concrete. Variables considered in the study\r\nwere percentage area of reinforcement, span of members for RCC beams and eccentricity of applied pre-stress force for PSC\r\nbeams. In RCC beams the time-dependent strain values increases with reduction in percentage area of reinforcement and in PSC\r\nbeams eccentricity directly influences the growth of time-dependent strain. With increase in age, a non-uniform strain develops\r\nacross the depth of beams which influence the growth of concave curvature in RCC beams and convex curvature in PSC beams.\r\nThe experimentally obtained strain values were compared with predicted strain values of similar size and grade of plane concrete\r\n(PC) beam using ACI 318 Model Code and found more than RCC beams but less than PSC beams....
Increasing maximum use of sustainable materials in construction has lead to use of a variety of aggregate replacement materials in concrete. The scarcity of natural gravel and crushed stone aggregates has made it to utilize alternative materials for use in cement concrete. There are good quantities of waste materials available like fly ash, concrete waste, silica fumes, marble scum, industrial waste, agricultural waste, red soils etc. Use of many of this waste has become common in producing various products like fly ash concrete, jute boards etc. One of such waste material is recycled aggregates produced throughout the world in the form of crushed construction and demolished waste. The goal of this study was to show that the use of recycle aggregate in concrete is technically feasible. In this paper there for an attempt has been made to use recycle aggregate to replace course aggregate and finding are given. This research there for deals with studying the performance of concrete by replacing natural aggregates with recycle aggregates....
Rapid urbanization in India is creating a shortage of houses. Using artificial aggregates for quality concrete is innovative step to overcome this problem. Number of investigations carried out in the past has shown usefulness of artificial aggregates in construction. There are huge quantities of waste materials available like fly ash, concrete waste, silica fumes, marble scum, industrial waste, agricultural waste, red soils etc. Use of many of this waste has become common in producing various products like fly ash concrete, jute boards. One of such waste material is plastic produced in huge quantity throughout the world in the form of plastic carry bags, bottles and other plastic scrap etc. In this paper therefore an attempt has been made to use plastic granules to replace coarse aggregates and the findings are given. This research therefore deals with studying the performance of concrete by replacing natural aggregate with plastic granules....
An experimental study was carried out to evaluate fresh properties of a moderately high-strength (high-flowing) selfcompacting\r\nconcrete (SCC) and to investigate shear behavior and performance of deep beams made with SCC. Fresh and hardened\r\nproperties of normal concrete (NC) and SCC were evaluated. The workability and compacting ability were observed based on\r\ncasting time and number of surface cavities, respectively. Four-point loading tests on four deep beams (two made with SCC and\r\ntwo with NC) were then conducted to investigate their shear behavior and performance. Shear behavior and performance of beams\r\nhaving two different web reinforcements in shear were systematically investigated in terms of crack pattern, failure mode, and\r\nloadââ?¬â??deflection response. It was found from the tests that the SCC specimen having a normal shear reinforcement condition\r\nexhibited a slightly higher load carrying capacity than the corresponding NC specimen, while the SCC specimen having congested\r\nshear reinforcement condition showed a similar load carrying capacity to the corresponding NC specimen. In addition, a comparative\r\nstudy between the present experimental results and theoretical results in accordance with ACI 318 (Building Code\r\nRequirements for Reinforced Concrete (ACI 318-89) and Commentary-ACI 318R-89, 1999), Hsuââ?¬â??Mauââ?¬â?¢s explicit method (Hsu,\r\nCem Concr Compos 20:419ââ?¬â??435, 1998; Mau and Hsu, Struct J Am Concr Inst 86:516ââ?¬â??523, 1989) and strut-and-tie model\r\nsuggested by Uribe and Alcocer (2002) based on ACI 318 Appendix A (2008) was carried out to assess the applicability of the\r\naforementioned methods to predict the shear strength of SCC specimens....
The research presented in this paper analytically examines the fire performance of flat plate buildings. The modeling\r\nparameters for the mechanical and thermal properties of materials are calibrated from relevant test data to minimize the uncertainties\r\ninvolved in analysis. The calibrated models are then adopted to perform a nonlinear finite element simulation on a flat plate\r\nbuilding subjected to fire. The analysis examines the characteristics of slab deflection, in-plane deformation, membrane force,\r\nbending moment redistribution, and slab rotational deformation near the supporting columns. The numerical simulation enables the\r\nunderstanding of structural performance of flat plate under elevated temperature and, more importantly, identifies the high risk of\r\npunching failure at slab-column connections that may trigger large-scale failure in flat plate structures....
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