Presented in this paper are results of an experimental investigation on the rivet flexibility and load transmission in a riveted lap joint representative for the aircraft fuselage. The test specimens consisted of two aluminium alloy Alclad sheets joined with 3 rows of rivets. Two different squeeze forces were applied to install the rivets. Rivet flexibility measurements have been performed under constant amplitude fatigue loading using several methods including two original optical techniques developed by the present authors. The axial tractions in the sheets required to determine the rivet flexibility have been derived from strain gauge measurements. In order to eliminate the effect of secondary bending the strain gauges have been bonded at the same locations on the outside and faying surface of the sheet. The experiments enabled an evaluation of the usefulness of various techniques to determine the rivet flexibility. It was observed that, although the measured flexibility was identical for both end rivet rows, the load transfer through either of these rows was different. Previous experimental results by the present authors suggest that behind the non-symmetrical load transfer distribution through the joint are large differences between the rivet hole expansion in the sheet adjacent to the driven rivet head and the sheet under the manufactured head [1]. It has been concluded that commonly used computation procedures according to which the load transfer is only related to the rivet flexibility may lead to erroneous results.

The mechanical properties of soil in soft soil area are poor, and the settlement of the underlying layer in the composite foundation accounts for a large proportion of the total settlement. At present, most of the research focuses on the settlement of the reinforced area, and the research on the settlement of the underlying layer is of great significance for the settlement of soft soil composite foundation. The differences in load transfer modes of soil and pile are analyzed, and based on the Boussinesq solution and Mindlin solution, a calculation method for the stress and settlement of the underlying layer in flexible and rigid pile composite foundation is proposed. The relative displacement of soil and pile in flexible pile composite foundation is small, and the negative friction can be ignored, but the influence of effective pile length should be considered. The relative displacement of soil and pile in rigid pile composite foundation is large, so the negative friction should be considered. Part of soil top stress is transmitted to the pile via negative friction, and then the pile axial force is transmitted back to the soil via positive friction. In addition to effective pile length, the change of stress transfer path caused by negative friction should also be considered in settlement calculation.

A theoretical formula for large-diameter rock-socket depth is developed to support pail embedding in a large bridge pile foundation project. There is a horizontal additional stress concentration at the place where the soil around the rock-socketed pile meets the soil layer under the horizontal load. When the rock-socketed tip stress and bending moment of the pile are relatively small, the pile shows favourable embedment effect and the pile foundation can be considered safe. The function curve of soil resistance around the pile under the action of horizontal force was obtained by finite element analysis. The force characteristics reveal the depth of the largediameter rock-socketed pile under the horizontal load. As the rock-socketed pile rotates under the action of horizontal force, the rock mass resistance around the pile changes according to the cosine. The distribution of pileside soil resistance is proportional to the displacement and distributed according to the sine. A comprehensive correction coefficient of pile shaft resistance beta is introduced to deduce the theoretical formula of the depth r h of the large-diameter rock-socketed pile embedded in the bedrock. It is verified through both experiments and numerical analysis.