A comparison of IBC with 1997 UBC for modal response spectrum analysis in standard-occupancy buildings

This paper presents a comparison of the seismic forces generated from a Modal Response Spectrum Analysis （MRSA） by applying the provisions of two building codes, the 1997 Uniform Building Code （UBC） and the 2000-2009 International Building Code （IBC）, to the most common ordinary residential buildings of standard occupancy. Considering IBC as the state of the art benchmark code, the primary concern is the safety of buildings designed using the UBC as compared to those designed using the IBC. A sample of four buildings with different layouts and heights was used for this comparison. Each of these buildings was assumed to be located at four different geographical sample locations arbitrarily selected to represent various earthquake zones on a seismic map of the USA, and was subjected to code-compliant response spectrum analyses for all sample locations and for five different soil types at each location. Response spectrum analysis was performed using the ETABS software package. For all the cases investigated, the UBC was found to be significantly more conservative than the IBC. The UBC design response spectra have higher spectral accelerations, and as a result, the response spectrum analysis provided a much higher base shear and moment in the structural members as compared to the IBC. The conclusion is that ordinary office and residential buildings designed using UBC 1997 are considered to be overdesigned, and therefore they are quite safe even according to the IBC provisions.

Energy and Buildings

In 2011,the Danish government published an energy strategy for Denmark where one of the main targets are that Denmark should be a fossil-free society by 2050.Calculations show,that in order to reach this goal it is necessary to reduce the energy consumption of the existing building stock by 50 % on average.Since a 50 % reduction is obviously not possible for all buildings,those that can should aim for a so-called “deep energy renovation”,i.e.reducing the energy consumption to a level corresponding to that of new buildings or even more.This paper describes two case studies where multi-story apartment buildings have undergone deep energy renovation.“Traneparken” where the expected energy use after renovation aimed at a level corresponding to that of a new building according to the Danish Building Regulations from 2015.“Sems Have” where the aim was to go even further and meet the requirements expected for new buildings in 2020,i.e.corresponding to the Danish “nearly zero energy”-definition according to the EPBD.The paper reports on calculations and measurements of energy savings,the economy of the projects and looks at the added benefits or co-benefits that residents,housing association and society in general have achieved in addition to significant energy savings.

Optimum lateral extent of soil domain for dynamic SSI analysis of RC framed buildings on pile foundations

This article describes a novel approach for deciding optimal horizontal extent of soil domain to be used for finite element based numerical dynamic soil structure interaction(SSI)studies.SSI model for a 12 storied building frame,supported on pile foundation-soil system,is developed in the finite element based software framework,OpenSEES.Three different structure-foundation configurations are analyzed under different ground motion characteristics.Lateral extent of soil domain,along with the soil properties,were varied exhaustively for a particular structural configuration.Based on the reduction in the variation of acceleration response at different locations in the SSI system(quantified by normalized root mean square error,NRMSE),the optimum lateral extent of the soil domain is prescribed for various structural widths,soil types and peak ground acceleration levels of ground motion.Compared to the past studies,error estimation analysis shows that the relationships prescribed in the present study are credible and more inclusive of the various factors that influence SSI.These relationships can be readily applied for deciding upon the lateral extent of the soil domain for conducting precise SSI analysis with reduced computational time.