سال:1386 | دوره: | شماره: |تعداد مقالات:8

It is a general practice to provide a flat or sloping slab called canopy at the entrance door of the building at the ground level wherever space permits. This may be cantilever type slab or supported one. While designing various structural elements and cladding units of buildings for wind loads, values of wind pressure coefficients are obtained from relevant code of practice where in the values are available for buildings with plane cladding only. Very limited information is available regarding wind pressure on canopies in codes of practice on wind loads including Indian Standard Code of Practice. Present paper enumerates the available codal information with respect to wind loads on buildings with attached canopies. It also describes in brief the latest research work done in this area.

This paper presents a procedure for finding the analytical Moment Curvature behaviour of statically determinate reinforced concrete beams, taking into consideration, the confinement offered by shear reinforcement to concrete in compression zone. Six selected confinement models reported in literature in the last decade are used as a stress block for confined concrete for generating the complete analytical Moment Curvature behaviour. The Moment Curvature behaviour obtained using the selected confinement models are compared with experimental results. In general it is observed that the results obtained from the selected models were close to the experimental values. However, it is observed that the analytical values obtained using Mendis and Cusson model are closer to the experimental results when compared to that obtained using the other models.

BS 8110-1997, ACI 318-2000 and IS 456-2000 Codes provide methods for calculating the short-term deflection, deflection due to Creep effects and Shrinkage effects for beams and oneway slabs. Though the codes are giving the provision for two-way slabs, as span to depth ratio for deflection control, much variation exists among them. Deflection calculation with creep and shrinkage effects is not included for two way slabs. Hence an attempt is made in this paper, to determine the total deflection including creep and shrinkage effects by suitably modifying the available formula for beams as per Equivalent frame method. A programme is developed in MATLAB to determine the exact deflection for two-way beamless slabs including short-term effects, Creep effects and Shrinkage effects. A numerical example is solved for flat plates by varying the parameters such as total thickness, characteristic compressive strength of concrete, clear cover of reinforcement, creep coefficient and the disparities among BS 8110-1997, ACI 318-2000, and IS 456-2000 are highlighted.

Structural control against earthquakes is becoming increasingly important. The linearquadratic optimal control algorithm is proposed here to design active control system for buildings against earthquake excitations. Full-state feedback system has been adopted. Active Tuned Mass Damper is used as the control mechanism. The efficiency of the designed system has been verified against El-Centro earthquake. Active control gives 35% more reduction in vibration of the structure than passive control. Mass of the damper has appreciable effects on response parameters than its stiffness. A flexible damper proves to be more effective, but at the cost of actuating forces required. Performance of system is found to be optimum, when mass-damper is tuned to fundamental frequency of the structure. Stability of the structure is also enhanced by Active Control system. A SDOF building is presented to illustrate the study.

The behavior of coupled shear walls is governed by coupling beams. This paper presents a simple technique for the purpose of design to determine an appropriate level of yield moment capacity for the coupling beams. This technique is checked against nonlinear static pushover analysis performed using DRAIN-3DX for the usual case of symmetric coupled shear walls with different types of coupling beams. The assumption of pinned base in the shear walls with steel coupling beams yields results which agree closely with those of DRAIN-3DX. For the case of fixed base shear walls, the design technique is expected to be conservative.

Under destructive earthquakes, a medical sector should play a crucial role for taking care of injured people. Hospital building should also maintain their function. By the way, since a hospital has a system like a city, composing of buildings and many lifeline systems, seismic reliability of the hospital is not determined only by building but by lifeline facilities including inside and outside the hospital. Present paper proposes a seismic risk assessment method for hospital lifeline as a part of the Seismic Risk Management method. The assessment method is to evaluate availability of hospital systems, considering damage probability of building and lifeline facilities, and the loss related to pipeline damage. The proposed method is applied to ten hospitals in Osaka, and its applicability is discussed.

On 26 December 2003 at 1:57 GMT, the historical city of Bam, located in the south-eastern region of Kerman province in Iran, was shaken by a relatively strong and destructive earthquake. The earthquake located at 29.0 oN and 58.26oW had a Mb of 6.3 by Geophysics Institute of the University of Tehran and an Ms of 6.5 estimated by the U.S. Geological Survey (USGS). The main shock killed nearly 35000 people, left more than 50000 homeless, and destroyed virtually all buildings in the region. Based on the reconnaissance visit by the authors, most common types of damaged buildings in the earthquake-affected area were non-engineered adobe, un-reinforced masonry houses and steel buildings. Most houses in the epicentral area were of adobe construction, made of sun dried clay brick walls, and heavy domestic roofs or vaults with clay or mud mortar. This earthquake clearly demonstrated that combination of relatively rigid load-bearing external brick walls and flexible internal steel columns, existing similarly in most other regions of the country, is quite hazardous. Also use of steel beams and columns in buildings without observing proper seismic proisions showed no improvement over non-engineered buildings. Unlike Some researchers who claimed that the performance of reinforced concrete structures in the area was satisfactory, probably due to the fact that the number of the reinforced concrete structures in the stricken area was for less than the other type of structures, authors believe that it was not so better than others. In this paper after summarizing the seismological and engineering field investigations of the devastating earthquake, the performance of the existing structures during the earthquake is discussed.

Nonlinear static methods are simplified procedures in which the problem of evaluating the maximum expected response of a MDOF system for a specified level of earthquake motion is replaced by response evaluation of its equivalent SDOF system. The common features of these procedures are the use of pushover analysis to characterize the structural system. In pushover analysis both the force distribution and the target displacement are based on the assumptions that the response is controlled by the fundamental mode and that the mode shape remains unchanged after the structure yields. Therefore, the invariant force distributions does not account for the change of load patterns caused by the plastic hinge formation and changes in the stiffness of different structural elements. That could have some effects in the outcome of the method depending on different structural parameters. This paper introduces an adaptive pushover analysis method to improve the accuracy of the currently used pushover analysis in predicting the seismic-induced dynamic demands of the structures. Comparison of the common pushover analyses, adaptive pushover analyses and time-history analyses performed for a number of multiple-bay, short and high-rise steel structures, demonstrates the efficiency of the proposed method.