Experiment Study On Working Properties Of Slab-and-beam Foundation

With the development of economic and people’s concerns on the utilization of underground space, foundation of high-rise buildings has changed from box foundation to raft foundation gradually. Slab-and-beam foundation is one kind of raft foundation, and it is widely used in multi-story buildings, high-rise buildings and their skirt buildings.In order to reveal the characters of the slab-and-beam foundation, according to model test in the laboratory, this paper has done some research, which contains two groups of multi-column and single-column models with the same plate thickness but different beam height, sitting on the natural ground. The multi-column model includes a double-column and a triple-column specimens, the grid plate of which has the same thickness to span ratio.1/12, and the beam of which also has the same height to span ratio,1/6. The single-column model includes4specimens, the grid plate of which has the same thickness to span ratio,1/12, but the height to span ratio of beam are different, followed by1/10、1/8、1/6、1/4.The deformation, contact pressure and failure behavior of each specimens were been measured. Through the analyzing of experimental data, the deformation feature and contact pressure distribution law of slab-and-beam foundation under different foundation stiffness conditions have been obtained, and this paper receives some significative conclusion:1. Load transfer order of slab-and-beam foundation is that the column load passes around from the ribbed beam first, then transfers to the grid plate.2. Ribbed beam has the capability of adjusting deformation and contact pressure under column, beam and grid plate to be uniform distribution, but this capability is limited。3. When the height to span ratio of beam is greater than1/6, and the thickness to span ratio of grid plate is less than1/6, at the characteristic value of subsoil bearing capacity, contact pressure, under the column, beam and grid plate, is approximately1.2times, equal to and80%of average load, respectively.4. It is also found in the test that the failure behavior of slab-and-beam foundation is punching failure under the column. By the crack location and its development process, we conclude that the punching body is an approximate circular truncated cone.5In addition, this paper also gives some advice in the aspect of deformation control and structural measures in the design of slab-and-beam foundation.