Asian journal of civil engineering
Volume:16 Issue: 1, Feb 2015

This paper presents an experimental study on the properties and the durability of selfcompacting concrete (SCC) containing alginate in variety values with artificial stone resin, micro and nano silica. The values of 0.5 and 1% alginate, 10% micro silica, 0.5% nano silica and 0.5% artificial stone resin are used. Artificial stone resin is used as the super plasticizer. Properties of hardened SCC such as compressive, split tensile, flexural strength and water absorption are assessed and represented graphically. Eventually, based on comparisons and interpretations, conclusions are drawn.

Seismic vulnerability assessment for steel X-braced and chevron-braced RC frames has been performed via development of analytical fragility curves. Several parameters including the height of the frame, the P-Δ effect, the fraction of base shear for which the bracing system has been designed and type of bracing system have been investigated. Definition of damage states based on the descriptions as provided by HAZUS which gives the limit states and the associated inter-storey drift limits for RC buildings has been used. The results of fragility curves show that strengthening the concrete frames by internal steel bracing can reduce the probability of damage and this reduction is higher when chevron bracing system is used.

Dynamic response of a structure is a remarkable characteristic which can be optimized (controlled) by imposing constraints on natural frequencies. But it is mentionable that size and shape optimization of trusses with multiple frequency constraints is a very non-linear and non-convex problem that may be converged to local optima when using meta heuristic algorithms. To concur this problem, researchers have developed hybrid meta-heuristic algorithms. In this paper recently introduced dolphin echolocation algorithm is applied for optimum design of truss structures with frequency constraints. Four numerical examples are considered to demonstrate the efficiency of the algorithm in comparison to hybrid metaheuristic algorithms.

In the present study two popular approaches for the seismic fragility evaluation of RC buildings are considered. First approach is based on series of time history analysis and a power law representing probabilistic seismic demand model. Second approach is based on Incremental Dynamics Analysis to determine the median collapse intensity measure. The two methods are formulated with different assumptions and methodologies for evaluations. The fragility curves and reliability indices are developed for a typical four storeyed frame by both the approaches and a comparison study is performed. The both methods yield almost the same results at same total dispersions.

This paper explores the flexural behaviour of carbon fiber reinforced polymer (CFRP) retrofitted reinforced concrete (RC) beams. For flexural strengthening of RC beams, a total of sixteen beams were cast and tested over an effective span of 3000 mm up to failureunder static monotonic and compression cyclic loads. The beams were designed as underreinforced concrete beams. Twelve beams were retrofitted with bonded CFRP fabrics in one layer, two layers and three layers which are parallel to beam axis at the bottom under virgin condition and tested until failure; the remaining four beams were used as control specimens. Static and cyclic responses of all the beams were evaluated in terms of strength, stiffness, ductility ratio, energy absorption capacity factor, compositeness between CFRP fabrics and concrete, and the associated failure modes. The theoretical moment-curvature relationship and the load-displacement response of the retrofitted beams and control beams were predicted by using FEA software ANSYS. Comparison has been made between the numerical (ANSYS) and the experimental results. The results show that the retrofitted beams exhibit increased flexural strength, enhanced flexural stiffness, and composite action until failure.

Frequency domain procedure of the scaled boundary method (SBM) for analyzing unbounded mediums has been modified recently using the hybrid spectral element (SE) approach and lumped coefficient matrices. In this paper, the modified method is extended to analyze 2D non-homogenous unbounded domains. In the modified frequency domain approach, elasticity modulus and mass density of unbounded domains can be considered as power functions in the radial direction. Accuracy and efficiency of the presented method is evaluated by some benchmark examples and it is shown that the modified method leads to correct answers.

One of the ways to confront the problem of debonding failure of externally-bonded carbon fiber reinforced polymers (CFRP), used for strengthening of steel members, is to provide a proper and practical bonding detail. If the high stress-concentration zones of the bonded strip such as curtailment points of CFRP or member discontinuities are suitably detailed or reinforced, then bonding resistance will be improved. This paper describes experimentally the methods which successfully prevent the premature debonding failure of externally-laminated steel members. The double-lap shear test set up has been chosen as a frame work to compare the results. Therefore bond zones includes shear stresses and peel stresses. The mechanical clamps in different arrangements were examined as a bondenhancement detail. Also, the effect of the length of the CFRP laminate was investigated along with different types of end mechanical anchorage. Finally, a simple and efficient bonding enhancement method has been proposed, in the form of overlapping the critical debonding zones using steel plates. The test results show that both the overlapping and clamping methods considerably increase the bonding resistance, but the former method is preferable because of its simplicity for installation and because in this case further increase of strength is obtained.

This paper presents an experimental study of the influence of the viscosity modifying agent and the different mineral additions (limestone filler, natural pozzolana and slag) on the rheological properties (fluidity, deformability and stability) and compressive strength of self-compacting concrete (SCC). The workability of fresh SCC was measured using slump test, L-Box and sieve stability test. The compressive strength was determined on samples (160×320 mm) at the ages of 28 days. The results have allowed us to develop a range of SCC that can fill the formwork heavily armed without vibrations and have of the compressive strengths acceptable. The incorporation of superplasticizer (SP) increases the fluidity and deformability but reduces slightly the stability and compressive strength. For cons, adding a viscosity modifying agent (VA) is quite contrary. Loss of fluidity and deformability caused by adding a VA can be recovered by adding a SP without affecting the stability and compressive strength. However, high dosages of VA, the effect of SP is limited, or in other words, it is mainly related to dosage used of VA. The use of a dosage (VA = 0.03%) is sufficient to assure the best properties and with this dosage, SCC require reasonable quantities of SP.

This paper describes the results of an experimental investigation carried out to determine the fracture properties of geopolymer concrete. Geopolymer concrete of grade M30 was developed and the results were compared with that of conventional concrete of the same grade. A total number of 18 notched prisms of size 150mmx150mmx500mm with varying notch depth were prepared and subjected to bending test. Load deflection and load CMOD (crack mouth opening displacement) characteristics of each prism were observed. Based on this, the fracture parameters such as fracture energy and stress intensity factor were determined. The test results showed that geopolymer concrete exhibited enhanced performance compared to conventional concrete of the same grade. The results of experimental investigation have also been compared with those obtained by FEM analysis, and the comparison was found to be satisfactory.