Axial load-displacement responses

The experimentally-measured lateral load vs. top displacement response for column specimens 2S10M (subjected to an axial load level corresponding to 10 % of its axial load capacity) is compared with the analytical model prediction in Fig. 20.8. The comparison indicates that the model provides reasonably accurate load-displacement response predictions. Overall, a good level of agreement is achieved between the test data and model results in terms of column lateral load... 

For the noncooled specimen NC, during the pre-fire mechanical loading, a linear-elastic load-axial displacement response was observed until the maximum load of 145 kN was achieved. The lateral deflection at this load at midheight remained small 1.4 mm toward the fire side. When fire exposure started (attime t = 0), lateral deflection toward the fire side started to increase owing to the thermal expansion of the inner fire-exposed face sheet and reached a maximum of 8.1 mm after 20 min, see Figure 7.8. From this point on, lateral deflections started to decrease owing to... 

The load-axial displacement responses for aU the specimens are shown in Figure 8.11. Comparing the slopes of the linear responses (below 1000 kN), the fire-exposed specimens exhibited almost the same stiffness reduction to 75% as... 

Figure 8.11 Load-axial displacement responses [14]. (With permission from ASCE.)...

The load-axial displacement curves for aU temperatures are summarized in Figure 5.11. The specimens exhibiting tensile failure mode (up to 100°C) showed an almost linear behavior until failure (only 16% loss of secant stiffness on average), while those exhibiting shear failure (above 140°C) showed a highly nonlinear response and a less steeply descending branch, similarly as observed for the shear experiments, see Figure 5.6. 

The load-axial displacement curves are shown in Figure 5.14. The linear response until failure was similar for all temperatures. Only strength and stiffness decreased with temperature. Figure 5.15 shows the continuous decrease of nominal compressive strength with increasing temperature (calculated from Eq. (5.18)) up to 180 °C, where stabilization at only 9.2% of the initial value was reached (see Table 5.2). 

Typical load-lateral deformation responses at midheight are shown in Figure 7.33 for temperatures up to 180 °C [22], At 220 °C, deformations were less than 0.5 mm and therefore below the photographic measurement accuracy. The curves exhibit similar pre- and post-buckling shapes and temperature-dependence as shown in Figure 7.32 for the axial displacements. 

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