CONCLUSIONS AND FUTURE WORK
8.3 Recommendations for Future Research
Results of this research suggest that computational simulation of progressive collapse, even including nonlinear dynamic analysis, is relatively simple to perform through available finite-element computer programs such as SAP2000. Also, experimental evidence is useful to verify the computational models and analyses. Based on the observations and analysis results, the followings are recommended to extend this research.
(1) One of most important results from this research was the experimental data compared relatively well with the analysis results of SAP2000. The strain data obtained from each field-testing showed that 3-D model was more accurate than 2-D model.
However, more experimental data would be required to validate computational analysis for the progressive collapse, and better simulate the actual behavior of structural members. For example, the experimental deflection data is needed in this research to validate vertical displacement values calculated from SAP2000. For the measurement of vertical displacements in the field, linear potentiometers can be used by measuring the change in the distances between their two ends (i.e., joints to the ground), as described in previous research (Sasani and Sagiroglu, 2008). A laser scanning device and a high
resolution line-scan camera could be also used to measure global and local deformations in the building.
Installation of additional strain gauges in the upper floors would be useful to monitor changes in strains of columns and beams as the building floor gets higher. In this research, higher DCR values and larger deformations in the top story were observed from SAP2000 analysis. Strain data measured at each floor level would be very valuable to determine the alternate load path caused by the loss of load-bearing columns.
(2) This research only considered the removal of exterior frame columns to evaluate progressive collapse potential. Even though the minimum requirement in the GSA (2003) and DoD (2005) guidelines was removal of exterior members, interior columns were also required to be considered for the removal of columns, especially, in underground parking area and uncontrolled public ground floor areas. Since interior frames have approximately twice gravity loads than exterior frames, the loss of interior columns enables the buildings more vulnerable to progressive collapse. For example, Yagob (2007) observed that the moderately ductile building was susceptible to progressive collapse when an interior column at the first story was removed, while no progressive collapse was expected when an exterior or corner column was removed.
Therefore, it would be important to assess the potential of progressive collapse when interior frame columns of the building were removed. Both field tests and SAP2000 analysis could be performed to investigate the structure response resulted from the loss of interior columns.
investigate vulnerability of the buildings to progressive collapse. It would be interesting to evaluate the progressive collapse potential of other buildings with different structural systems and configurations, such as concrete-frame structures and atypical structural configurations. The experimental and computational assessments on progressive collapse potential of various buildings would enable making more specific conclusions for a wide range of building structures.
(4) There are four types of analysis methods that may be used in the assessment of the potential for progressive collapse: linear static analysis, linear dynamic analysis, nonlinear static analysis, and nonlinear dynamic analysis. In this research, linear static and nonlinear dynamic analyses were conducted using SAP2000 computer program. It would be interesting to examine nonlinear static and linear dynamic analyses, and compare the analysis results. The effect of nonlinearity or the dynamic effect on the progressive collapse analysis could be examined by comparing the results from the four different analyses. It is also expected that this comparison can prove the most accurate and suitable method to analyze the progressive collapse vulnerability of the buildings.
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