Asian journal of civil engineering
Volume:7 Issue: 5, October 2006

An investigation was carried out to assess the subsurface suitability of the River Nzoiafloodplain in Budalangi Division of western Kenya for supporting shallow foundationstructures. An analysis of the conditions in the area during flood seasons was conductedusing soil mass characterisation, geotechnical testing, slope stability analyses, terrainevaluation and analysis of ground conditions in buildings in the area. The analyses revealthat significant slope failure occurs when the percentage of water exceeds 50% in slopes cut at angles greater that 24°. The suitability of the ground for supporting shallow foundation structures has been established from the results of fieldwork and from laboratory studies.

The strut-and-tie method can be used for the design of Disturbed regions (D-regions) ofstructures where the basic assumption of flexure theory, namely plane sections remainingplane before and after bending, does not hold true. Such regions occur near staticaldiscontinuities arising from concentrated forces or reactions and near geometricdiscontinuities, such as abrupt changes in cross section etc. The strut-and-tie method ofdesign is based on the assumption that the D-regions in concrete structures can be analysed and designed using hypothetical pin-jointed trusses consisting of struts and ties interconnected at nodes. Continuous deep beams occur as transfer girders in multi-storey frames, as pile caps and as foundation wall structures etc. The usual design practice for continuous deep beams has been to employ empirical equations, which are invariably based on simple span deep beam tests. Given the unique behavioural pattern of continuous deep beams, this practice is unrealiable. Since continuous deep beams contain significant extents of D-regions and they exhibit a marked truss or tied arch action, the strut-and-tie method offers a rational basis for the analysis and design of such beams. The mechanics and behavior of continuous deep beams are briefly discussed from which a strut-and-tie model for such a beam is developed. A complete example on the analysis and design of a continuous deep beam using the strut-and-tie method is presented. The design has been carried out using the recommendations of the ACI Code 318-02.

The aim of the present paper is to review a novel modular constructional element for thebuilding and construction industries that was patented by Coventry University. Modularelements have been used in the past in the construction of structures in order to speedconstruction and cut on time and cost. The modular element, the subject of this study,comprises hexagonal elements made of steel or other appropriate material, assembledtogether to form a constructional assembly of honeycomb form secured by fixings thatclamp together the sides of adjacent elements. Concrete, or other appropriate material, isdisposed within the elements providing a composite type of action. Reinforcement is alsopresent in the form of bars or tubes, providing extra strength to the assembled element. The novel type of modular construction has potential applications in the building, construction, substructure and highways sectors. It could be used as a permanent or temporary structure for roofs and walls. It may also be used for concrete pavements, tunnelling, and retaining wall structures.

In this paper, the development of a mesh reduction Dynamic Finite Element (DFE)technique for the coupled extension-torsion vibration analysis of braided/twisted wire ropes and cables is presented. The weighted residual method together with frequency-dependant trigonometric shape functions, are exploited to derive the frequency-dependent element DFE matrices. Assembling the element matrices generates the global stiffness matrix that leads to the eigenvalue problem of the system. The natural frequencies and modes of vibration of the structure are then evaluated by solving the resulting non-linear eigenproblem. The free vibration analyses based on DFE are consequently carried out for a variety of cable configurations. The comparison between the DFE, exact and FEM results and those available in literature validated the proposed DFE and confirmed its practical applicability and superiority, when compared to conventional FEM.

Mass isolation is a method of structural vibration control against environmental loads suchas strong earthquakes. Buildings with local isolation systems are a practical method of massisolation. These buildings can be non-proportionally damped systems. Available methodsfor dynamic analysis of these buildings are complex and time-consuming. In this paper, theconcept and efficiency of these buildings at seismic response reduction is examined. Asimple method for their dynamic analysis is introduced. Proof of the accuracy of the method is also presented.

In this second part of a two-paper, presents a comparison study of Russian and Nigerianstandards and codes of practice on wind load estimation on tall building with reference to its dynamic behaviour. Under the same conditions of wind flow, dynamic analysis of thebuilding is carried out using numerical method and the differences in the drifts andaccelerations estimated for both codes are identified to be related to wind field factors and values recommended by both codes. The result of the dynamic analysis indicates thatNigerian code of practice is more conservative than the Russian.

The present paper attempts to develop a new analytical integration to evaluate the element stiffness matrix for the finite elements with irregular shapes. Most of the finite elements developed by Sabir are based on the strain rather than displacement approach. They are characterized by a regular form and appropriate coordinates with the form of the element. Together, they tend to decrease the elements utilization domain. Hence, for reasons of importance and particularity of these elements (higher order shape functions expressed in terms of independent strains); it is necessary to introduce irregular forms, which require a special integration technique, and a specific classification in programming level for different geometric forms. To overcome this geometrical inconvenience; the paper presents a new integration solution routine. This will help to know how the elements will behave when they have irregular form, and to extend their applications domain for the curved structures no matter what the geometrical shape of the element might be.

Iran Strong Motion Network (ISMN) started its activities in 1973 and running by Buildingand Housing Research Center (BHRC) since 1981. At the date of this study ISMN consist of more than 1103 digital (SSA-2) and 52 analog (SMA-1) accelerographs. The accelerograms of different earthquake, are downloaded, controlled, processed, and then added to the comprehensive data bank, which is very useful for scientists and engineers. In this catalog the most important earthquakes are briefly described. More information is presented in Table 1 and also available on the web page of BHRC (http://www.bhrc.ac.ir).