Asian journal of civil engineering
Volume:15 Issue: 2, Apr 2014

The performance of buildings subjected to earthquake loads has shown that asymmetric structures are caused more extensive damages in comparison with symmetric structures. Hence, the seismic performance of asymmetric structures should be assessed due to future random earthquakes. Reliability-based seismic assessment as one of the tools in performance-based earthquake engineering has been introduced to quantify the seismic reliability for existing structures due to future random earthquakes. This paper deals with the reliability-based seismic assessment of asymmetric multi-storey buildings with RC shear walls with consideration of the angle of ground motion incidence. To implement this purpose, in the first stage, the multi-component incremental dynamic analysis (MIDA) is used for the assessment of asymmetric 6 and 9-storey buildings with RC walls. The MIDA as an efficient procedure can estimate the seismic capacity of a structural system with randomness on incident angle. In the second stage, the mean annual frequency exceeding of a specified level of structural demand is calculated to predict the reliability of these structures. The results show that the effects of earthquake incident angle should be considered in the assessment of the assessment of asymmetric multi-storey building.

Ductility and energy absorption capacity are the main requirement of earth quake resistant structures. Concrete can be modified to perform in a more ductile form by the addition of randomly distributed discrete fibres in the concrete matrix. This study presents the structural behaviour of hybrid fibre reinforced concrete column made with the combination of steel and glass fibres under axial loading. The various parameters like load carrying capacity, ductility, energy absorption capacity and toughness index of hybrid fibre reinforced concrete column are compared with that of conventional reinforced concrete column and steel fibre reinforced concrete column. It has been observed from the experimental investigation that the behaviour of HFRC column is relatively better than conventional reinforced concrete column and steel fibre reinforced concrete column in all respects.

In this article, an improvement is proposed for bat algorithm and it is utilized for size optimization of skeletal structures consisting of truss and frame structures. Various optimization problems are implemented to demonstrate the ability of the enhanced bat algorithm. These numerical examples are along with different constraints and loading conditions such as stress, displacement and frequency constraints, static and time history dynamic loadings. Furthermore, these optimization problems are in two form of discrete and continuous. Results show the suitability and efficiency of the present algorithm for optimal design of skeletal structures.

The efficiency of the Newton-Raphson iteration method for solving nonlinear equations has made it popular, although the time required to achieve convergence inspires aspirations to find a more efficient alternative. In the current study a hybrid iterative algorithm is employed for solving nonlinear problems. To that effect, an alternative to the Newton- Raphson method, and related classical methods in numerical computing based on a Homotopy Perturbation Method (HPM) is introduced. In perturbation methods, perturbation quantities are used to replace a nonlinear problem by a number of manageable linear subproblems. Then, an approximate solution is reached by summing up the results of these subproblems. In this paper three global methods belonging to this family are discussed and then it is shown how to combine a global method with Newton-Raphson method into a hybrid algorithm as a possible way to reduce computational cost. Several well-known and difficult applications are considered for testing the performance of the new approach. The results reveal that using 2nd HPM coupled with two-point method requires less time to achieve convergence and reduces the total number of iterations.

Experiments on circular steel tubes filled with steel fibre reinforced concrete (SFRC) and normal concrete have been performed to investigate the contribution of steel fibres to the load bearing capacity of short composite columns. The main variables considered in the test study are diameter to thickness ratio of the steel tube and the percentage of steel fibres added to the in-filled concrete. All the specimens were tested under axial compression until failure state realization. Extensive strain and deformation measurements were taken at compression and tension zones and the results show that 1.00% SFRC in-filled steel columns exhibit enhanced ultimate load carrying capacity, stiffness and ductility coefficient. Also a nonlinear finite element model was developed to study the load carrying mechanism of CFTs using the Finite Element software version ABAQUS. This model was validated using the experimental load–deformation curves and the corresponding modes of collapse. A comparison of the observed load carrying capacity and flexural stiffness with various codal recommendations has been carried out to check the applicability of the expressions recommended by the various codes of practice. Of all the codes compared, Eurocode 4 showed the least variation and is found to be more viable to predict the strength of normal as well as SFRC in-filled steel tubes under axial compression.

This paper presents on an experimental study of confined high-strength concrete columns tested under axial compression. The main objective of the research is to know the performance of spirals and hoops with medium strength (400 MPa < fy < 600 MPa) in their contribution on the behaviour of confined high-strength concrete columns. The parameters of the study were concrete strengths, confining steel characteristics i.e: type of confinement (spirals and hoops), yield strength, spacing and volumetric ratio. From the experimental results it was found that the strength enhancement and ductility of confined concrete will decrease with if both of concrete strength and spacing of spirals or hoops increase, and the strain in the test also showed that the release of a cover of concrete core occurs prematurely. Other results shows that satisfactory of circular hoops as confinement steel behaved as good as the spiral reinforcement. The spiral reinforcement provision adopted in the Indonesian Concrete Standard 2002 (SNI 03-2847-2002) is quite reliable when applied in the design of confining steel with medium strength of high-strength concrete columns, therefore it is proposed that the upper limit provision of yield strength of confining steel warrant to be modified.

In order to illustrate the effect of damping on the response of a base-isolated building, a large investigation is made. It consists in a parametric study which takes into account the progressive variation of the damping ratio (10% to 30%) under different nature of seismic excitations (near and far field). A time history analysis is used to determine a response of the structure represented in this case by terms of relative displacements and inter-stories drift at various levels of the building, additionally a strong deviation of energy capacity by the LRB (Lead Rubber Bearing) system will be recorded, therefore the results show that the efficiency of the isolator increases with the assumed damping ratio, provided that this latter is less or equal to 20%. Beyond this value, the isolator becomes less convenient.

Creating a comfortable environment is one of the most important parameters to be considered when designing buildings. Human comfort condition is investigated by many researchers from different points of view. In this paper, the effect of changes in floor-toceiling height on comfort condition in a certain indoor thermal condition is investigated. Changes in net height have been discussed in details from thermal, energy, economical, architectural, safety and other related perspectives in previous studies and Results are published in organized forms or as standards. However, what emphasized in this research is people’s feeling of comfort. The investigation carried out in a laboratory with adjustable ceiling height designed for the test. People's opinion on comfort satisfactory is collected and results are presented. It is possible to take advantage of the findings to suggest the optimum height for common urban residential units in Iran.

During January–December 2011 more than 311 records were recovered from permanent Iran strong motion stations operated by the Road, Housing and Urban Development Research Center. Accelerograms were recovered from ISMN triggered by 199 earthquakes in the magnitude 2.0 to 7.2 ranges. Peak ground acceleration was recorded in Baba Monir station about 299 cm/s2 on March 5th, 2011 earthquake.

Prestressing steel has been popular in the recent past, due to the developments in the field of anti-corrosive coatings. The literature substantiates the application of technique of prestressing to steel structures both in safety and economy point of view. However, for all design calculations, the maximum allowable span for a given load carrying capacity is based on maximum deflection which is calculated by principle of superposition (considering the effect of prestress and total load individually). This paper proposes a method of arriving at expression for deflection of simply supported, prestressed homogenous steel I-beams calculated by considering the combined effect of prestressing and total load. A straight tendon configuration with an eccentric prestressing force is considered for study.