Overview on the Nonlinear Static Procedures and Performance-Based Approach on Modern Unreinforced Masonry Buildings with Structural Irregularity

Performance-based design plays a significant role in the structural and earthquake engineering community to ensure both safety and economic feasibility. Its application to masonry building design/assessment is limited and requires straightforward rules considering the characteristics of masonry behavior. Nonlinear static procedures mainly cover regular frame system structures, and their application to both regular and irregular masonry buildings require further investigation. The present paper addresses two major issues: (i) the definition of irregularity in masonry buildings, and (ii) the applicability of classical nonlinear static procedures to irregular masonry buildings. It is observed that the irregularity definition is not comprehensive and has different descriptions among the seismic codes as well as among researchers, particularly in the case of masonry buildings. The lack of global language may result in the misuse of the procedures, while adjustments may be essential due to irregularity effects. Therefore, irregularity indices given by different codes and research studies are discussed. Furthermore, an overview of nonlinear static procedures implemented within the framework of the performance-based approach and improvements proposed for its application in masonry buildings is presented.

Study on The Effect of Soft Story on Infill RC Frames Under Seismic Effect

Construction practice of reinforced concrete (RC) frames infilled with unreinforced masonry is quite common now-days in urban cities in Nepal and elsewhere. Previous study shows the lateral load transfer mechanism is different than that of bare frames in infill buildings. Because of the unavoidable circumstances like elimination of central columns, elimination of infill wall in basement for parking purpose and reducing the size of frame members etc. may cause the particular story to be soft.In this study the infill RC frames with stiffness irregularity has been analysed with linear time history method using Gorkha-2015 earthquake as ground motion using structural analysis and design software (ETABS 2000 V.16). In total 8-numbers of 6-story RC infilled frames were analysed introducing the soft story in each story level respectively from basement to top. Regular frame was designed as per IS 1893:2002 load combination considering torsional effect. After analyse of bare frame, regular frame and irregular frames the global and story level seismic demand parameters were studied comparatively. Base/Story shear, Story displacement, inter-story drift and fundamental time period were the parameters compared taking regular frame as reference case.Results showed that, there is significant effect of location of irregularity on the seismic demand. The global and story level seismic demand is higher when the irregularity is introduced in bottom part of the buildings and further it showed that the lateral strength of RC frames get highly enhanced due to introductions of infill in analytical models.Kathmandu University Journal of Science, Engineering and TechnologyVol. 13, No. 2, 2017, page:79-91

STUDI PENGARUH REDISTRIBUSI MOMEN TERHADAP DAKTALITAS STRUKTUR

The combined effect of gravity loads and seismic forces often results inframe moment patterns that do not allow efficient design of beam andcolumn members. Even in the seismic dominated regular frame, wheregravity load moments are approximately 30% of seismic moments, theresulting combination of gravity and seismic moments results in themaximum negative beam moment being about 2.5 times the maximumpositive moment. In line with load increasing, plastic hinges may occur atother locations along the span and may trigger structure collapse but this is only possible when redistribution moment occurs. The structure analysis used is SAP 2000 Version 10.01 and analysis of non-linear staticpushover using Drain 2DX for evaluation and plastic hinge mechanism.Redistribution moment analysis produces an average moment reduction of30%. This result is later analysed with DRAIN 2DX to calculate non-linearstatic pushover analysis both before and after redistribution moment. Afterthe analysis, it is found that the structure ductility is 2.42 beforeredistribution moment and 3.58 after redistribution moment. The resultproves that this method can be used as an alternative design forreinforced concrete frame.

Compactifications from generators and relations

We show that any compactification of a regular frame can be realised as a frame which is freely generated on a suitable meet semilattice subject to certain relations, and we provide familiar examples of compactifications which can be regarded as such frames.

Strong 0-dimensionality in Pointfree Topology

Classically, a Tychonoff space is called strongly 0-dimensional if its Stone-Cech compactification is 0-dimensional, and given the familiar relationship between spaces and frames it is then natural to call a completely regular frame strongly 0-dimensional if its compact completely regular coreflection is 0-dimensional (meaning: is generated by its complemented elements). Indeed, it is then seen immediately that a Tychonoff space is strongly 0-dimensional iff the frame of its open sets is strongly 0-dimensional in the present sense. This talk will provide an account of various aspects of this notion.

Prediction of fundamental period of regular frame buildings

The most important structural parameter in the estimation of the seismic demand on a building is the natural period of the building’s fundamental/first mode of vibration. There are several existing empirical, analytical, and experimental methods which can be used to estimate the fundamental period of a building. The empirical equations prescribed in the building codes are simple, but they do not consider actual building properties, and are very approximate. On the other hand, analytical methods like Eigenvalue analysis and Rayleigh method are able to consider most of the structural parameters that are known to affect the period of a building. Nevertheless, the analytical methods require considerable effort and expertise; often requiring structural analysis software’s to estimate the fundamental period of a building. In this paper, a generic method is developed to estimate the fundamental period of regular frame buildings and a simple yet reliable equation is proposed. The equation is derived using the basic concept of MacLeod’s method for estimation of roof/top deflection of a frame building, which is modified to more accurately predict the lateral stiffness of moment resisting frames under triangular lateral force distribution typically used in seismic design and analysis of frame buildings. To verify the reliability and versatility of the developed equation, the fundamental periods predicted are compared with the periods obtained from Eigenvalue analysis for a large number of low to medium rise RC frame buildings. The fundamental period predicted using the proposed equation is also verified using the period obtained using the Rayleigh method and measured in experimental tests. Since the proposed equation was found to closely predict the fundamental period, the results are used to study the limitations of the empirical equations prescribed in building codes. The applicability of the proposed equation to predict the fundamental period of low to medium rise frame buildings with minor irregularity is also investigated, and it was found that the proposed equation can be used for slightly irregular frame buildings without inducing any additional error. The proposed equation is simple enough to be implemented into building design codes and can be readily used by practicing engineers in design of new buildings as well as assessment of existing buildings.

Localic remote points revisited

We consider remote points in general extensions of frames, with an emphasis on perfect extensions. For a strict extension ?XL ? L determined by a set X of filters in L, we show that if there is an ultrafilter in X then the extension has a remote point. In particular, if a completely regular frame L has a maximal completely regular filter which is an ultrafilter, then ?L ? L has a remote point, where ?L is the Stone-C?ch compactification of L. We prove that in certain extensions associated with radical ideals and l-ideals of reduced f-rings, remote points induced by algebraic data are exactly non-essential prime ideals or non-essential irreducible l-ideals. Concerning coproducts, we show that if M1 ? L1 and M2 ? L2 are extensions of T1-frames, then each of these extensions has a remote point if the extensionM1?M2?L1?L2 has a remote point.