This paper outlines the common observed failure patterns in the buildings of Nepal after M W 7.8 Gorkha (Nepal) earthquake. Several types of damage patterns were observed for reinforced concrete buildings, as well as for unreinforced masonry and adobe houses during the reconnaissance survey performed immediately after the earthquake of 25 April 2015. Several field visits in the affected districts were conducted and associated failure/damage patterns have been identified and analyzed. This paper also covers damage patterns in non-engineered buildings, middle and high-rise buildings, commercial complexes, administrative buildings, schools and other critical facilities from Kathmandu valley as well as other affected districts. The construction and structural deficiencies are identified as the major causes of failure, however local soil amplification, foundation problems, liquefaction associated damages and local settlement related damages are also significantly observed during this earthquake and reported in the present paper. In the end, the lessons learned from the field survey are resumed in order to give some guidelines for future construction practices.
Background: Disasters like earthquakes and flood cause enormous loss of lives and property in Nepal frequently. However, during such events particular types of houses are found to be more resilient than common types of housing stocks. This paper outlines the disaster resilient vernacular housing technologies in two of the physiographic regions of Nepal. The vernacular houses are analyzed in terms of their performance and shortcomings during earthquake and flood disasters and found to be technologically resilient in many aspects of impending disasters in Nepal distributed within the physiographic regions. Using the comparative case study approach, field visits and non-structured interviews with local people, the resilient features in terms of construction technology of vernacular houses are identified in this study and the preliminary findings are highlighted as observed during the field visits without numerical modeling and analysis. The seismic performance of Rajbanshi, Gurung and Magar houses in Nepal during 1934Nepal during , 1988Nepal during and 2015 earthquakes is presented in order to justify the performance of these particular housing stocks. Results: The vernacular construction technology in Terai is found to be technologically resilient in terms of floods and earthquakes, and earthquake resistant technologies are identified in the dwellings of the western mid-hill of Nepal. The traditional Rajbanshi houses in eastern Nepal are found to be resilient in terms of earthquake and flood disasters and the Gurung and Magar houses in western mid hills are found to be resilient in terms of earthquake disaster. The statistical distribution of housing stocks is presented and survival scenario is discussed with regard to specific building features. Apart from this, the field reconnaissance after Gorkha earthquake in western Nepal shows better performance of buildings with identified features in comparison to common housing stocks in neighborhoods.
This paper presents a novel way of strengthening thin-walled steel cylindrical shells against buckling during axial compression in which a small amount of fiber-reinforced polymer (FRP) composite, coated from both sides can increase the buckling strength effectively. The effects of the reinforcement and the angle of fiber orientation as well as initial geometric imperfections on the buckling load-carrying capacity have been made clear through the three kinds of analytical procedures; the conventional linear eigen value buckling analysis, the reduced stiffness (RS) buckling analysis and the fully nonlinear numerical experiments. These multiple treatments suggest obtaining valuable information for the design of FRP-based hybrid structural elements and discusses influence of FRP to increase the load-carrying capacity of the thin-walled metallic structures having complex buckling collapse behavior. This paper also discusses how the angle of fiber orientation affects on the buckling strength and the associated buckling modes of the thin-walled shells.
In this paper, the strengthening of thin-walled metallic shells with the application of CFRP (carbon fibre reinforced polymer) has been investigated. To lower down the downside of the lower stiffness exhibited by CFRP shells and to diminish the major problem associated with steel shells, a new composite sandwich structure has been introduced in this paper and effect of CFRP reinforcements under axial compression has been studied through three kinds of analytical procedures; the linear Eigen value problem, the modified RS (reduced stiffness) analysis and the fully nonlinear numerical experiment. With these multiple treatments it has been suggested that recently developed modified RS analysis which effectively compute the lower bounds provides the significant information to evaluate the buckling capacity of reinforced shells that display the unstable behaviour and imperfection-sensitivity than the general RS Analysis. This paper also illustrates the application of the methodology to cases of axial loaded shells with the varying thickness of veneers of CFRP.
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