Leaderboard

I accidentally came across these useful case studies, which, I would like to share. You can use them if you are working on a commercial or residential building retrofitting project. These case studies provide insight about seismic retrofitting and also on analytical methods, that are used for building assessment. I would also like to give due credit to people who are involved in these studies. All these studies were performed under a US-Pakistani Joint Cooperation Project. The details for the project are. 6-Storey Mixed Use Building in Karachi.pdf 10-Storey Office Building in Karachi.pdf RS-4 Storey Academic Building in Karachi.pdf Five Storey Residential Apartment.docx

I have observed few issues while getting the design results of reinforced concrete members from ETABS (v 9.7.4). I wanted to share this issues with you and get your input and observation on it. ETABS always considers the minimum eccentricity for selecting the design moment of columns irrespective of the probable behavior of the column, whether short or long column. See section 10.10.6.5 and its commentary of ACI 318-08 which deals with minimum eccentricity of long columns. You should always check the design moments that ETABS uses for columns if you want to bring down the cost of construction. If your model has lateral loads, ETABS will give you design moments in column irrespective of its status as braced or un-braced as per ACI 318 criteria. You should investigate if the storey under consideration is braced, or un-braced (10.10.5.2), and decide appropriate design moments of columns. ETABS has a tendency to select a time period of the building that is considerably less than the value obtained by the approximate method, Method A, of the section 1630.2.2 of UBC 97. To quote the FEMA 451 document: ''Because this formula is based on lower bound regression analysis of measured building response in California, it will generally result in periods that are lower (hence, more conservative for use in predicting base shear) than those computed from a more rigorous mathematical model". So, there is no need to use the value of time period that is lot less than Ta. One should always check the time period used by the software; ETABS can overestimate the seismic force by more than 2 times. Method A gives lower T and higher V, so FEMA 451 has advised not to use the value of time period less than this value even if rigorous analysis gives a lower value. I have seen the results where Etabs have use the value of time period less than Ta; in-fact as low as 0.5Ta, which can increase the base shear two times.

Here is an update: 3-Storey Library Building In Karachi.pdf Four Storey Office Building In Muzaffarabad.pdf Stone Masonry School In Abbottabad.pdf Storey Mixed Use Building In Karachi.pdf 6-Storey Mixed Use Building in Karachi.pdf And finally a step by step method on how to create and analyse your model. A_Practical_Guide_to_Nonlinear_Static_An.pdf The attachments are conclusive in manner that they provide extensive informaiton about modelling infills. For further information related to subject topic, please also visit: http://framedinfill.org/ Thanks.

Here are my 2 cents:- 1. It depends upon whether the design code, you are following for your project, permits the use of brick masonry struts for the seismic resistance in general, and also in Zone 3 or otherwise. Following links discuss how some of the design codes account for the use of brick masonry infills for seismic resistance:- a. Brick Masonry Infills in Seismic Design of RC Framed Buildings_Part 1.pdf b. Brick Masonry Infills in Seismic Design of RC Framed Buildings_Part 2.pdf 2. Discussion at the following links, might help you understand how you can model brick masonry infills in a structural software. like ETABS or SAP2000: a. Modelling of brick masonry in ETABS with reference to Indian Standard Code (1) http://www.sefindia.org/forum/viewtopic.php?t=15975 (2) http://www.sefindia.org/forum/viewtopic.php?t=9922&postdays=0&postorder=asc&start=0 b. Modelling of brick masonry in SAP2000 with reference to FEMA 273 https://www.researchgate.net/post/How_can_I_model_masonry_infill_in_sap_2000_as_an_equivalent_strut HTH Regards.

Read the section 14.4 of ACI 318-11 for axial capacity of the RCC wall. There should be some option of displaying axial forces in shell members in SAP.

this book also useful NED research paper https://www.academia.edu/8983144/A_Practical_Guide_to_Nonlinear_Static_Analysis_of_Reinforced_Concrete_Buildings_with_Masonry_Infill_Walls