ASIAN JOURNAL OF CIVIL ENGINEERING (BUILDING AND HOUSING)
Year:2010 | Volume:11 | Issue:3|Papers Count:8

A discrete version of the Charged System Search algorithm (CSS) is developed to optimize truss structures with discrete variables. The discrete CSS algorithm, similar to its original version, is based on some laws from electrostatics and the Newtonian mechanics. Each agent in Ute CSS is considered as a charged sphere having a uniform volume charge density which can affect an electric force to the other ones. However, contrary to the original CSS, for the discrete CSS, the affected forces can be attractive or repulsive. In addition, a new approach is presented to handle the constraints, which is called the fly to boundary method. Some design examples are tested using the new method and the results are compared to those of other meta-heuristic algorithms to demonstrate the effectiveness of the present method.

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 seism city. Specifically, bounds on the total energy, zero-crossing rate and entropy rate of the earthquake 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. Numerical illustrations on reliability-based critical earthquake inputs for elastic and inelastic frame structures are presented.

In response spectrum method of seismic analysis of irregular and complex structures, the response contributions of modes up to rigid frequency are considered for the analysis and the effect of truncated high frequency modes are taken into account using suitable "missing mass" correction methods. In this paper, an alternate method using a cut-off frequency less than rigid frequency for the truncation of modes is proposed. The proposed method is validated with the help of numerical examples by evaluating the response of structures for EI Centro (1940) and Fruili (1976) earthquake ground motions.

Presented herein is a new technique and a low cost method to estimate the ratio of air voids in hardened concrete within 30 minutes using available flatbed scanner, black inkjet, personal computer and image treatment software This test method includes contrast enhancement steps ensuring black ink (air voids) in gray concrete (aggregate and paste), image acquisition and computer analysis of scanned image. It is applied on specimens of normal concrete (NSC), high strength concrete (HSC) and high strength concrete with Polypropylene fibers. Results obtained are compared with the peer values of wet concrete ratios of air voids. As compared with other ASTM procedures, it is concluded that this method may have superiority over other methods due to its simplicity, low cost, less time and no need of skilled technicians. It is recommended to be used for hardened concrete as well as rock specimens.

For preliminary design including the proportioning of the structure, the variation of wind force on a structure with variation of site parameters and structural parameters should be known. The present study is an effort to achieve the same, primarily based on Indian wind code. The proposed draft of the Indian wind code is also included in the scope of the study. Comparisons of the wind forces obtained by Indian Standard and that by American Standard are also presented for some representative cases to gaze the relative level of protection attributed by Indian wind codes. The study also includes an exhaustive comparison of the wind forces obtained by Force coefficient based static analysis and Gust factor based dynamic analysis interpreting where which method should be used for better protection. The general observations and simple guidelines emerged from the study may prove useful for choosing the appropriate method by design engineers, depending on the requirement of safety, economy and availability of time. The large number of case studies presented in the paper in the form of the variations curves may be used for preliminary design and cross checking the results and hence, may prove useful in the design offices.

This paper describes the application of the Profiled Steel Sheet Dry Board (PSSDB) system as a structural component in an innovative lightweight composite structural roofing panel system. The composite panel system consists of profiled steel sheet attached to the dry board' via mechanical self drilling and self tapping screws. Newly introduced materials for the profiled steel sheet and dry board have been proposed as components of the PSSDB system in this study. In this case, the normal position of the PSSDB system has been reversed. The dry board plays an important role in enhancing the stiffness and strength of the roofing system as well as providing a flat surface which conveniently forms the ceiling inside the room in a building. The behaviour of the PSSDB roofing system in the reversed position was investigated. In addition, the effect timber strips introduced along the side edge of the roof panels was studied. From the test results, it was found that the use of Ajiya Clip-lock 660 profiled steel sheet together with 9 mm Primaflex dry board for the roof panel system was acceptable. The stiffness value of the panel system in the reversed position is almost identical to the one in the normal position. It was also found that the application of the timber strips could increase the stiffness of the composite panel by 35.8% compared to the panel without timber strips. The results from the tests also found that the load after failure of the panel with timber strips decreases gradually compared to the panel without timber strips. It can be concluded that the timber strips play an important role in stiffening the roof panel system. Some interesting applications of the system in real buildings are also highlighted in this paper.

In the present work, an attempt is made to investigate shear strength and ductility of fiber reinforced concrete beams by using hooked steel fibers. All the test beam specimens were 100mm in width, 150mm in depth and 1200mm in length and the primary variables of the investigation were percentage of fibers (0.5 to 5 %), percentage longitudinal tension steel (0.8 to 3.22 %) and cube compressive strength of concrete (in the range of 34 to 41 MPa), with a view to cover a wide spectrum of concrete strength in shear. The shear span-to-depth ratio (a / d ratio) was kept constant at 3.20. This has resulted into casting and testing of twenty SFRC beam specimens. All the beam specimens were tested under four-point loading (2-active, 2-passive) test set-up and the failure load, crack pattern and deflections were recorded concisely and precisely. The experimental results clarify the enormous influence of hooked mild steel fibers on shear strength of concrete. At low fiber volume fraction, the influence of fibers is negligible and is significant with the increase in the fiber volume fraction. The concrete beam specimens exhibited substantial increase in their ultimate load as well as in the load at first cracks, enhanced deformation characteristics at all stages of loading up to failure.In general, the significant improvement in various strengths is observed with the inclusion of steel fibers in the plain concrete. However, maximum gain in strength of concrete is found to depend up on the amount of fibre content.

The present work aims to study the seismic performance of exterior beam column joint with non-conventional reinforcement detailing. Four joint sub assemblages were tested under reverse cyclic loading applied at beam end. The specimens were sorted into two groups based on the joint reinforcement detailing. The first group (Group A) comprises of two joint assemblages having joint detailing as per construction code of practice in India (IS 456:2000) with two axial load cases. The second group (Group B) comprises of two specimens having additional cross bracing reinforcements for the joints detailed as per IS 456:2000 with similar axial load cases that in first group. The experimental investigations are validated with the analytical studies carried out by fmite element models using ANSYS. The experimental results and analytical study indicate that additional cross bracing reinforcements improves the seismic performance.