Asian journal of civil engineering
Volume:7 Issue: 3, June 2006

Flexural stiffness of a single load-induced crack is determined. Modal analysis is performedon the beam prior and after each load stage. Mode shapes are extracted and eigenvectorsused to determine the mode shape equations. Global flexural stiffness is derived by utilizingthe regressed variable λ and the local flexural stiffness is derived by applying the centeredfinite- divided-difference formula on the regressed data. The global stiffness decreases with increasing severity of the crack. Results compared with values computed using the loaddeflection plot showed similar trends. The algorithm may be used as a technique for detecting crack damage in reinforced concrete.

In this paper, an attempt is made to find out sustainable use of fly ash generated fromBarapukoria Power Plant. This is used as an admixture with Shah Special Cement in 5%,10% and 15% proportion. Laboratory test for different parameters such as compressivestrength, workability, flexural strength, splitting tensile strength of such mixtures are carried out to find out optimum content. The results show almost no sacrifice for the strength of cement due to mixture of fly ash with a proportion of 10%.

This paper presents a comparison study of Russian and Nigerian standards and codes ofpractice on wind load estimation for tall buildings. Despite the similarity of the philosophyon which the codes were developed some sizable scatter exist among the wind loadingestimation by the codes under similar wind flow conditions and location. Hence the paperseeks to present this scatter as regards static behaviour of a 10-storey building. It is to benoted that the scatter in the predicted wind load arises primarily from the variations in wind field factors and their values recommended in both codes.

This experimental work is a contribution to the improvement of the properties of theconcretes by mechanical activation (fineness) of two types of cements (C.E.M II)manufactured in various cement factories (cements with various mineral additions: slag and tuff). The physical properties of cements (C.E.M II) activated mechanically at anhydrous state and the state hydrated (specific weight, consistency of the cement pastes, setting times and shrinkage) thus the characteristics of the concretes made at their bases, such as the mechanical behavior (compressive strength for the concrete) are studied. According to the experimental results obtained, it comes that the increase of the specific surface and the chemical composition of cements to the mineral additions are the principal responsibles to the improvement of the latent reactivity of mineral additions and the increase of the mechanical strengths of the concretes.

Shear strengthening is required when an RC beam is found deficient in shear, or when itsshear capacity falls below its flexural capacity after flexural strengthening. A recenttechnique for the shear strengthening of RC beams is to provide additional FRP webreinforcement, commonly in the form of bonded external FRP strips/sheets. Over the lastfew years, several experimental studies have been conducted on this new strengtheningtechnique, which has established its effectiveness. While experimental methods ofinvestigation are extremely useful in obtaining information about the composite behaviourof FRP and reinforced concrete, the use of numerical models such as the one presented inthis paper helps in developing a good understanding of the behaviour at lower costs. In the study presented in this paper, ANSYS finite element program is used to examine theresponse of beams strengthened in shear by FRPs. The FE model is calibrated against testresults performed at the University of Kentucky. Once validated, the model is used toexamine the influence of fibre orientation, compressive strength of concrete, area of tensile and compressive reinforcements, and amount and distance between stirrups on the strength and ductility of FRP strengthened beam.

Cement concrete continues to be the pre-eminent construction materials for use in any type of civil engineering structure. Performance of these structures in terms of their strength and stability has withstood the test of time but the life span of the structures has become a matter of concern. This is on account of the environment becoming chemically ever more aggressive. The atmosphere is found increasingly laden with higher percentages of Sulfur Dioxide, Carbon Dioxide and Chlorides. Oxides of Sulfur are injurious to concrete while Chlorides are harmful to the reinforcing steel. As a consequence of these, the life-span of the reinforced concrete structures have got compromised significantly from its original estimated life of about ninety years. The role of Sulphate ions in causing deterioration of concrete has been investigated intensively. Based on the literature available, the present paper discusses this aspect with particular attention to the use of blended cement in recent times with the influences of the parameters related to the Sulphate resistance of cement concrete and mortar.

The curiosity to understand the behavior of confined concrete columns has led researchers to carry out extensive experimental work over the years. Numerous empirical confinement models have been reported in the literature for the prediction of stress-strain response of the columns behavior under concentric loading, though, nothing significant has been said about the numerical modeling of the problems wherein the nonlinear response of confined concrete columns may be reasonably predicted. In the present study, material models for both concrete and steel have been formulated and nonlinear finite element analysis of threedimensional confined concrete models has been carried out. The analysis included the provisions for cover spalling. A couple of examples have been presented for the validation of the numerical methodology proposed in this work. A parametric study has also been carried out to find out the effect of different parameters like concrete strength, reinforcement configuration, spacing of lateral ties and type of cross-section on the response of the confined concrete columns. The parametric study revealed some very important observations regarding the behavior of confined concrete columns.

Longitudinal shear strength is considered as a major constraint in the design of compositeslab and it can be assessed by expensive and time consuming experimental techniques. The objective of the present work is to provide a numerical tool to minimize hurdles in thedesign process and to reduce the dependency on expensive and time-consumingexperiments. In this article, Artificial Neural Networks model has been developed forfinding the m and k values for determination of the horizontal shear resistance. It isdemonstrated that, with proper training of the neural network using the ratio of pitch length to width of top flange and depth of profile as input values, the proposed neural network model can generate the values of m and k quite accurately. Inherently the Artificial Neural Network is computationally efficient tool and hence the developed Artificial Neural Network will be very useful in optimization procedures of the composite slab.

This paper uses Artificial Neural Network (ANN) models to compute structural response ofa structural system by training the model for a particular earthquake. Here, the earthquakes in India viz. at Chamoli and Uttarkashi ground motion data have been considered for the analysis. The neural network is first trained here for a single real earthquake data on a single degree of freedom structural system. The trained ANN architecture is then used to simulate earthquakes by feeding various intensities as well as other earthquake data and it is found that the predicted responses given by ANN model are good for practical purposes. If the ANN is trained by a part of the ground motion data then it can also identify the responses of the structural system well for the total period. The safety of the structural systems may be predicted in case of future earthquakes without having to wait for the earthquake to occur for the lessons.

Iran Strong Motion Network (ISMN) that runs under the authority of Building and HousingResearch Center (BHRC) of Iran started its activity since 1973. At the date of this study this network consisted of more than 1049 digital (SSA-2) and 61 analog (SMA-1)accelerographs. The recorded earthquake accelerograms are downloaded, controlled,processed, and then added to the accelerograph comprehensive data bank, which is quiteuseful for scientists and engineers. Herein the recorded accelerograms and causalearthquakes are briefly explained and more detailed information is presented in Table 1 and also available on (http://www.bhrc.ac.ir).