Asian journal of civil engineering
Volume:12 Issue: 2, Apr 2011

This paper develops a reliability-based computational methodology for modeling nonstationary random critical earthquake loads on structures using the site response spectra.The power spectral density function and the envelope parameters of the ground acceleration are taken to be unknown and are computed such that the structural reliability index is minimized subjected to constraints reflecting known knowledge on the site seismicity.Specifically, bounds on the total energy, zero-crossing rate and entropy rate of theearthquake signal and positivity requirements are considered. These constraints are derived from the site response spectra. The formulation combines methods of structural reliability analysis, response surface fitting, FORM and nonlinear programming. Numericalillustrations on reliability-based critical earthquake inputs for elastic and inelastic framestructures are presented.

An improved heuristic particle swarm ant colony optimization (HPSACO) is presented tosolve engineering optimization problems. This new algorithm follows the HPSACO levels;however some modifications are performed in global and local searching levels to improveits performance. Here, the properties of the big bang–big crunch algorithm are added to PSO and ACO in global and local searching levels, respectively and these changes improveprecision of the solutions and the reliability of the algorithm. Benchmark engineeringoptimization problems are used to illustrate the reliability of the proposed algorithm.

The behaviour of deep beams is different from that of shallow beams in which the bending stress distribution is linear across the depth and the shear failure is ductile. This paper addresses the flexure and shear behaviour of polypropylene fibre reinforced fly ash concrete (PFRFAC) deep beams. The shear span to depth ratio of the beams used in theseinvestigations was maintained as 2.0. The variables of study include the Characteristicstrength of concrete, fck (15.0 MPa, 20.0 MPa, and 25.0 MPa) and polypropylene fibre(Recron 3s) content (0%, 0.5% and 1%). The polypropylene fibre and 20% of Fly ash ascement replacement are incorporated in all the concrete mix proportions considered in thisstudy. The test results indicate that compressive strength of concrete increases with theincreasing percentage of fibre. There has been a significant increase in flexural and shearstrengths of PFRFAC, in all the mix proportions, as fibre content increased from 0% to 1.0%. However, the ultimate failure was observed to be gradual in all the beams.

This paper deals with an atypical class of reinforced concrete beams, whose reinforcementis a steel truss structures. This typology of beams is quite unknown within the engineeringcommunity. Moreover they have been used for three decades in Italy, principally forindustrial or special structures. Differently from traditional reinforced concrete beams, thesteel trusses can bear their own weight and the weight of slabs and fluid concrete withoutany provisional support during a first «dry» assembly stage; after that, when concrete develop its own mechanical characteristics, they can collaborate with the cast in place concrete. Nowadays, interest for this technology is growing up in Italy, mainly because of some advantages it provides with respect to the traditional reinforced concrete beams. Nonetheless, neither in the current Italian nor in the European codes there are specificregulation for this class of reinforced beams. In order to achieve this goal, the main aim ofthis work is to illustrate possible mechanical models and verification principles to be used indesigning these particular reinforced concrete beams when subject to static loads. Finally some practical design examples, done by using a specifically developed computercode, are presented to illustrate complete design procedures.

The objective of present investigation is to develop stress – block parameters for the design of reinforced recycled aggregate concrete members. To arrive at the objectives, acomprehensive experimental programme was undertaken. The influence of replacementratio, (Rr) the ratio of recycled coarse aggregate to total coarse aggregate (Rr = RCA/TCA) on properties of recycled aggregate concrete was studied. The scope of the investigation programme is defined to generate stress strain test data of concrete, viz; M15, M20, M25, M30, and M35 and five replacement ratios, viz; 0, 0.5, 0.75, 0.85, and 1.0 were considered.A total of 150 cylinder specimens’ and 48 RC beam specimens were cast for the stressstrain characteristics and flexural design of hardened concrete and design parameters are developed for recycled aggregate concrete.

The purpose of this study is to study the application of electrodeposition method indecreasing carbonation and chloride penetration of cracked reinforced concrete. Reinforced concrete specimens with the dimension of 10 x 10 x 37 cm are used. The specimens are loaded to cracking by third point loading and then are immersed in a salt solution. Three electrolytic solutions, namely, MgCl2, MgSO4 and ZnSO4 at 0.1, 0.2 and 0.5 mol/L concentrations are used. Direct current potential of 6V is applied between the reinforcing steel and an external electrode to force deposition. It is found that electrodeposition method can be used to decrease the carbonation and chloride penetration of cracked reinforced concrete.

Performance enhancement of non-engineered infra-structural systems in rural areas withlocally available materials has become necessary in current day technology, mainly tocounter unanticipated loads like Earthquake. In many smaller towns and villages in southern parts of India, materials result in the form of fibers and granular materials as waste. This paper is aimed to characterize the structure related properties of concrete composite with locally available rice husk fibers, for achieving reasonable energy absorbing capacity.Experimental investigations were performed to find the mechanical, shear, impact andflexural properties of concrete with and without rice husk composites. Microstructure of asreceived and reacted rice husk fibers with concrete for two years are also studied fordurability considerations.

This paper inscribed in the setting of the research onto concrete material conducted the team within engineering of the materials of the laboratory materials and durability of theconstructions, in the context of the conception of the self compacting concrete to basis of the local materials. The concept of the self compacting concrete that is born of a need of economy and quality increased for the constructions of reinforced concrete. The present document treats the deferred behaviour (creep and shrinkage of the self compacting concretes); for this phenomenon, we elaborated an experimental program therefore. For a better approach, the study was comparative: the tests have been made in parallel, in the time, on a concrete at low strength and concrete at medium strength with a compressive strength to 28 days of 20 and 40 MPa respectively. It has been put in evidence a kinetics of creep of the SCC of low strength similar to the one of the SCC of medium strength, whereas this kinetics is notoriously different from the one of the VC.The gotten results are comparable to those gotten in the literature.This study brings a lighting on the deformations deferred of these new concretes andshould help towards term, to the setting up of rules of formulation of the self compactingconcretes.Finally some of the results gotten are used in the goal to propose an optimization of themixtures according to criterias of justified choices

Natural vibration sources are multiple. Those due to the explosions of mine can bedangerous. During the fracture a considerable energy propagated in the form of seismicwaves generating a series of vibratory movements on the ground surface witch aretransmitted to the constructions trough the foundations. The aim of this paper is to study the effects of the vibrations due to the shootings of mine of the quarriers Socar and Altro companies located at Mechta Bouzitoune on neighbouring constructions of the city Elwième, 50 residences at Héliopolis, in the east of Algeria, which are characterized by the appearance of the cracks in the masonry walls on all the height of the buildings. It resides in the determination of the acceptable explosive load, particulate speed threshold, the radius of safety and the level of the vibrations on the level of constructions for compared with the principal standards and international recommendations.

The dynamic stability is studied for thin-walled structural elements with variable stiffnesssubjected to periodically alternating axial force in this paper. Here, the variation stiffnessmeans that it changes with periodically alternating axial force as for nonlinear geometrystiffness matrix of thin-walled member. Damping is considered and the governing equations are expressed in terms of a system of two second-order differential equations of the Mathieu type, with periodic coefficients. MATLAB package is used to determine the stability boundary. Numerical example is presented for the dynamic stability boundary of a simply supported beam with I-shaped cross section. Comparison is made with finite element analysis. Considered damping, some conclusions are drawn out: Excited zone of thin-walled member is continuous, the dynamic instability is highly dominant in the first region while the second and third instability regions are of much less practical importance; The larger the ratio of damp, the less the dynamic instability region; The larger the ratio of damp, the more time dependent components of the load wanted, absorption of damping is commonly of no effect to prevent parametrically excited vibration from dynamic instability; Parametrically excited vibration considering damping is much more different from damped forced vibration in nature.

The fracture of High Performance Concrete (HPC) occurs in a very explosive manner without previously exhibiting any cracking pattern as a warning. By using special fibre cocktails, (combinations of steel and polypropylene fibres) the explosive failure behaviour of High Performance Concrete (HPC) may be avoided. With the variation of cocktail composition different seismic performance of the material could be adjusted. An experimental programme has been carried out to compare the behaviour of high performance concrete and cocktail fibre reinforced high performance concrete beam column joint under reversed cyclic loading. HPC mix has been designed to obtain a concrete grade of M 60. The mix was designed based on modified ACI 211 method suggested by Shetty [1]. Five numbers of exterior beam-column joints modeled to one fourth of a prototype of a building [2], designed according to Bureau of Indian Standards were cast and tested under reversed cyclic loading. The first specimen was made with high strength concrete and designed as per IS 456:2000 [3] and reinforcedaccordingly without considering the seismic requirement. The second specimen was madewith high strength concrete,designed as per 1893 (Part I) 2002 [4] and reinforcements in the beam-column joint portion was detailed according to IS 13920-1993 [5], for seismicrequirements. The remaining three specimens were similar to the first one but variouscombinations of cocktail fibre concrete in the joint region (constant % (1.5) of steel fibre and 0 to 0.4 % of polypropylene fibre) were used. The cocktail fibre combinations of 1.5% of steel fibre and 0.2% of polypropylene fibre have best performance considering the strength, energy dissipation capacity, and ductility factor. Results indicate that the addition of polypropylene fibre to the steel fibre is optimum for a percentage of 0.2, which have more energy absorbing capacity, less joint rotation, more shear strength, more curvature ductility factor and less reinforcement strain.