Reliability of ASCE 41-13 equations to predict nonlinear behavior of URM In-plane walls     

Thursday November 15, 2015
List of task to be completed by December 20, 2015
Tasks to complete first case study
Tasks Subtasks deadlines
NSP in SAP2000, Yi et al. Experiment Create model with only frames
define Plastic Hinges in the model
Apply plastic hinges to the model
Apply SDL to the model
Verify weight of the building
Define loading protocol
Create displacement load cases
Run NL Gravity analysis, verify
Apply protocol to roof and floor
Run Loading protocol
Compare to experiment
Write up Report Nov 29,2015

Model used to estimate axial loads in piers is based on 150928_M4.sdb.
name of the model=160107_M1.sdb
Pier 8, rocking and shear is consistent with MAEW-111124-1.xmcd. 

What is rocking in URM walls? Is this rocking similar to Rocking as in Rigid Body Rocking? or is more like a flexural deformation capacity of the pier, similar to what happens in a RC column?. why do we have to use Moment curvature analysis to obtain the rotational capacity of the pier? Isnt more like a discrete-event, followed by toe-crushing?
Saturday January 9th, 2016
Shall we just include the controlling hinge in the model? or shall we include all possible failure modes?
Perhaps for linear analysis it does not really matter, but for nonlinear analysis it could....
we should double check both cases and conclude on this matter.

Model 160109_M1.sdb is the refined element model used to obtain the axial forces happening at the bottom of each pier. Groups were assigned and created and sections cut were defined using those group definitions. 

Model 160109_M2.sdb is the equivalent model which needs to be updated so that the levels of axial forces in the piers are similar to those found in the previous model. One interesting finding is that the cross sections still have 12 inches as width, which is wrong. All sections in Wall 1 should have width=8 in or less.

What if we obtain the axial forces from the model without plastic hinges? Check Model 160109_M3.sdb ====> The previous model was correct!. It is that I was measuring the axial force in the wrong location.  so now we go back to work with 160109_M2.sdb.

Sunday, January 10, 2016

We are running the first cyclic model using 160109_M2.sdb. the models produces conservative estimates of the base shear force vs displacement at the roof behavior. the actual force capacity is about 55kips, but this model produces 29 Kips. which is 55% of the max capacity only. This explains why I was trying to make the bottom part of the building a bit stronger the first time I conducted the analysis. The model needs more axial load so that the capacity gets increased at the bottom. Check 160110_F-D_plots.xlsx. On the positive side, the models exhibits strength degradation, in good agreement to the experiment.

Shall we run the model using the weight from the flanges and increase the initial axial load to estimate the cyclic behavior? not sure if we got enough time....remember we still need to run the other walls, run the linear procedure using only equations, maybe run Chapter 15 analysis?.

Lets run the model using only the controlling Plastic hinge in each pier, which means we have to eliminate the rocking hinges and sliding hinges from certain walls. Use model 160110_M1. sdb.
Check 160110_F-D_plots.xlsx. It is basically the same!!!! so the influence of removing the additional hinges is negligible. Does this mean that the model can only fail in this way?  Or the failure mode will change given a different loading pattern, dynamic loading? I guess it depends of the relationship between rocking and sliding capacity. 

Lets implement the nonlinear model using shell elements in SAP2000., then we will compare LSP, using EFM, shell elements, NSP, using EFM, and Shell elements.
Use Model 160110_M2.sdb with shell elements.