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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.

THIS paper is good for joints but there is no mention of time duration between pouring of successive concrete especially in massive concrete.

Refer to "ACI 224.3R-95 Joints in Concrete Construction", Chapter 7 at the following link, for your required information:- http://xa.yimg.com/kq/groups/2173108/199513267/name/2243r_95.pdf Regards.

Even though the structure is not indented to be supported as mentioned in topic of the thread, Truss can be supported as cantilever by exhibiting classical truss action (tension and compression members). Answering your question Tension in top chord, compression in bottom and moment arm between them at any cross-section will resist bending moment at that section. Shear at any cross-section will be resisted by tension and compression in web members. The moment at the support will be resisted by the reaction-couple at the support.

The statement shows your observation.What is your question?