Asian journal of civil engineering
Volume:17 Issue: 5, Aug 2016

The present investigation is mainly focused on finding the mechanical properties of geopolymer concrete (GPC) mixes with different fine aggregate blending. Sand and granite slurry (GS) are blended in different proportions (100:0, 80:20, 60:40 and 40:60). Coarse aggregates of size 20 mm and 10 mm are blended in 60:40 proportions by percentage of weight of total coarse aggregate. Fly ash (class F) and ground granulated blast furnace slag (GGBS) were used at 50:50 ratio as geopolymer binders. Combination of sodium hydroxide (8M) and sodium silicate solution was used as an alkaline activator. Compressive strength, splitting tensile strength (STS) and flexural strength (FS) were studied after 7, 28 and 90 days of curing at ambient room temperature. From the results, it is revealed that the mechanical properties were increased till fine aggregate blending of 60:40 and decreasing trend has been observed at 40:60 fine aggregate blending. It is concluded that optimum fine aggregate blending was 60:40. The measured STS and FS of all mixes were compared with ACI 363R, CEB-FIP and ACI 318R predicted equations.

The damage of structures due to earthquake is the cause of loss of life and property and hence it is necessary to study the vulnerability characteristics of structures subjected to such seismic excitations. In this paper a brief review of seismic performance evaluation of a G+10 Reinforced Cement Concrete (RCC) frame by Capacity Spectrum Method (CSM) is presented as per IS: 1893 (Part 1):2002.Further the vulnerability assessment of different RCC frames and the applicability of HAZUS drift ratio based damage state thresholds for building designed as per IS 456: 2000 code are also studied. Fragility curves were developed for frames with setbacks on different storeys indifferent bays for frames with and without infill walls. Infill is provided by “Diagonal Strut Method” and their damage probabilities are compared. Study of performance of shear wall placed in least stiffness direction as a remedial measure for setback frames was also carried out. It was concluded from this study that setback frames are more vulnerable compared to regular frames, however setback frames with provision of infill are found to perform as regular RC frames.

The degradation of concrete due to various hygro-chemo-mechanical actions is inevitable for the structures particularly built to store water. Therefore, it is essential to determine the material properties of dam like structures due to ageing in order to predict the behavior of such structures after certain age. The degraded material properties are calculated by introducing isotropic degradation index. The predicted material properties are used to study the behavior of aged dam-reservoir coupled system. Both the dam and infinite reservoir are modeled by finite elements. Displacement and pressure are considered as nodal variable for dam and reservoir respectively. The effect dynamic interaction between dam and reservoir are calculated in a coupled manner. The parametric study reveals that the responses of damreservoir system are unexpectedly large at an age when system frequency matches with the exciting frequency. The outcomes of the present study indicate the importance of the consideration ageing effect of concrete exposed to water for the safe design of dam throughout its life time.

An experimental investigation was carried to measure the compressive strength Cs (MPa) and the carbonation depth of the concrete by the height of capillary initial imbibition using the capillary absorption test. The results obtained, the good estimate of the compressive strength Cs (MPa) and the carbonation depth Cd (mm) of only be deduced by determining the height of capillary initial imbibition of concretes Zi (mm) for one hour. Therefore, the height of capillary initial imbibition of concretes Zi (mm) is a true indicator of the durability.

In the present paper, seismic performance-based optimization of steel frames is implemented using a number of advanced meta-heuristic algorithms. The optimization process is implemented by two newly developed meta-heuristics, dolphin echolocation optimization (DEO) and enhanced colliding bodies optimization (ECBO). In the present study, a slight modification is achieved on the ECBO to improve its convergence rate and therefore it is named here as ECBO-II. Furthermore, the results of DEO, ECBO and ECBO-II are compared with those of particle swarm optimization (PSO). Evaluating the structural responses by nonlinear time-history analysis during the optimization process is very time consuming. In order to reduce the computational rigor, radial basis function (RBF) neural network is utilized to predict the necessary structural time-history responses during the optimization process. Two numerical examples are presented to illustrate the efficiency of the meta-heuristics for tackling the seismic performance-based optimization problems.

This article discusses on the behavior of unwrapped and GFRP (Glass fiber reinforced polymer) wrapped hollow circular steel tubes under axial and eccentric compression (25 mm and 50mm). Finite element analyses through ANSYS were carried out on similar specimens. Comparisons of results proved that GFRP jacketing is an effective method for arresting elephant foot buckling in hollow steel tubes under both loading conditions. It also enhanced the stiffness, ultimate load and ductility of unwrapped tubes. More than two number of GFRP layers showed unfavorable inward buckling of tubes. Effective confinement was achieved by restricting the number of wrapped layers to two.

In this paper, based on the studies made on thirty single degree of freedom systems for four mass ratios and eight different depths of soil stratum, for site-specific scenario earthquake, depth of soil stratum above rock has been identified as an important parameter which influences the response reduction of building with TMD. A methodology has been proposed for arriving at the properties of TMD for design of multi-storey building, for site-specific earthquake including the effect of depth of soil stratum. The methodology has been demonstrated for six storey reinforced concrete(RC) and fifteen storey steel building assumed to be located at Delhi for a site-specific scenario earthquake of moment magnitude 8.5 from central seismic gap of Himalayan region for eight different depths of soil stratum above rock. From the studies made for the two shear type buildings, the mass ratio of 0.05 for six storey RC building and mass ratio of 0.005 for the fifteen storey steel building are found to be suitable. The methodology proposed can be adopted for design of TMD for nonshear type buildings also for regions where information on scenario earthquake, depth of soil stratum and relevant geotechnical information are available.

During severe seismic excitations, a large amount of kinetic energy is fed into a structure. In this investigation, seismic response of steel structures utilizing Cylindrical Frictional Dampers (CFD) is studied. CFD is an innovative frictional damper which comprises two principal elements, the shaft and the hollow cylinder. These two elements are assembled such that one is shrink-fitted inside the other. If the damper’s axial force overcomes the static friction load, the shaft inside the cylinder will move and results in considerable mechanical energy absorption. To assess the efficacy of CFD, various steel frames are constructed and analyzed using OpenSees software. Nonlinear time history analyses and Incremental Dynamic Analysis (IDA) are applied to the frames and clear distinction has been drawn between the frames comprising CFD and the counterparts without CFD to emphasize the effectiveness of CFD in altering seismic responses. The results show that CFD extremely improves the seismic response of the structure.

This experimental study investigates the effect of using binary natural fine aggregates (dune sand and crushed sand) on mortar. This method is utilized to modify the particle size distribution of various sands used in mortar. For this investigation, two sands were used: a dune sand (DS) and crushed sand (CS) at different proportions in mortar. The effect of the quality and grain size distribution of natural fine aggregates (DS ad CS) on the physical properties of binary sand confected (apparent or bulk density, absolute or gravity density, porosity, fineness modulus, particle size distribution and water absorption). The properties of fresh and hardened mortar were also analysed. The results obtained showed that the mechanical strength of mortar depends on the nature and particle size distribution of sand studied. This study shows the potential of this method to make mortar with binary sand (dune and crushed fine aggregates) in order to improve the physical properties of sand. The increase in the quantity of mixing water generated by addition of quarry waste was modified by the addition of a superplasticizer or water reducing admixture (Medaflow 30) what led to the improvement of the physical and mechanical properties of the mortar. The inclusion of crushed sand (CS) at replacement levels of 40 % to 50% resulted in a increase in the mechanical strength of the mortar. However, the improved performance was observed when quarry waste as fine aggregate was used in presence of chemical admixture (1% of Medaflow 30).

In this paper the recently developed method, Grey Wolf Optimizer, is employed for design of castellated beams. These types of open-web beams have found widespread use, primarily in buildings, because of great savings in materials and construction costs. Hence, the minimum cost is taken as the design objective function and the Grey Wolf Optimizer method is utilized for obtaining the solution of the design problem. A number of design examples are selected from literature to demonstrate the efficiency of the utilized algorithm. The results demonstrate that the Grey Wolf Optimizer algorithm is a potential alternative optimization algorithm to solve castellated beam problems.