Civil Engineering Reference
In-Depth Information
The end column analysis results are shown in Fig. 8.37. The horizontal end
column movements are shown as nearly a mirror image of the retaining wall
movements presented in Fig. 8.35. This indicates minimal restraining effect of the
soil retained behind the structure during the temperature cycles. The bending
moment diagrams show that the maximum magnitude of flexural stresses occur
during the last expansion cycle, albeit only slightly larger than their counterparts
found during the contraction cycles.
8.4 Conclusions
The effects of large temperature changes on the displacement of, and stresses
developed in RFERS, and the lateral earth pressure developed in the retained the
soil mass were investigated. Two-dimensional plane strain finite element analysis
of single-story rigidly framed earth retaining structures of varying number of bays,
bay lengths, and member stiffness were performed using the commercial finite
element analysis software Plaxis. The analysis of single-story single-bay rigid
frames indicates that the lateral earth pressure developed behind RFERS due to
temperature variations is larger when the lateral stiffness of the RFERS is larger.
For frames with similar stiffness, the expansion length also plays an important
role. The lateral earth pressure found during the expansion cycle of multi-bay
frames are substantially larger than those of the single-bay frames, and smaller
during the contraction cycle for the same frame. Similarly, RFERS undergo larger
displacements, particularly at the free end when the lateral stiffness decreases, and
develop higher stresses, when the frames lateral stiffness and length increase.
Furthermore, the rigid frames are shown to move into the original plane of the
retained soil mass during expansion, unlike the less stiff RFERS analyzed.
For relatively stiff RFERS, the lateral earth pressure developed in the backfill
soil during the various expansion cycles are much larger compared with the
contraction cycles and the initial backfill stage. The pressure distribution in some
cases is nearly an inverted triangle with the maximum pressure occurring near the
top of the structure.
The magnitudes of the maximum shear force and bending moment are
substantially affected by thermal cycles, particularly for stiffer frames.
Additionally, walls assume a variety of curved shapes due to temperature. These
results indicate that a reinforced concrete wall designed for the flexural stresses
produced from the application of the backfill soil will be inadequately reinforced
to resist the stresses produced during the expansion cycles.
A large number of parametric studies for 3, 6, 15 bay frame structures for
φ
=
30° is also included in Appendix A as well as analyses for
= 40° in order to aid
with identifying the effect of thermal soil structure interaction on structures, which
might be of interest to the reader.
φ
