Laboratory and numerical based analysis of floating sand columns in clayey soil

The inclusion of sand columns results in enhancing the bearing capacity of clayey soil, increase the rate of consolidation, presentation of liquefaction in loose sandy soils and provide lateral resistance against the horizontal movement. This research aims at investigating the effects of floating columns in clayey soil with silty deposits by developing small scale laboratory models. The effects of sand columns on soils of different shear strengths, slenderness ratio (L/D) of columns were investigated. Group effect was also investigated by varying spacing between the columns. Experimental results were compared with the numerical analysis results. A 15-noded triangular mesh was generated using a finite element tool PLAXIS 2D. Finite element analysis was performed using Mohr’s Coulomb’s criterion considering undrained analysis for soft clayey soil and drained analysis for sand columns. It was concluded that the sand columns can significantly increase the ultimate loading capacity of soft soils. Results show that critical length for floating column ranges from 4 to 5.5 times the diameter of the column, beyond which bulging occurs and loading capacity decreased. The effect of group was also investigated and observed that with high spacing between the sand columns, the group efficiency decreased. The axial capacity of sand columns decreases while increasing spacing between the columns.

Parametric Study on the Response of Composite Single Piles to Lateral Load by Numerical Simulation (FDM)

This paper entails a detailed numerical and parametric study on the lateral behavior of piles in foundation designs. Single-piles are one of the major components of a foundation as they act as the primary component in the transmission of the weights above the structure into the ground for stability to be attained. For this reason, a detailed study on the influence generated on the p-y curves is mandatory to create a numerically valid model for use in the process of foundation design without much ado. Modeling procedure under consideration employs the use of the finite difference method (FMD) embedded in FLAC2D. FDM is used to implement a solution to the coded input for example soil and pile element parameters. The model validation process done in this paper involves the variation of some of the critical parameters such as the variation on the type of soil in the area under consideration. Next, modification of the elastic modulus of the given soil as a check on the cohesiveness, change on the loading velocity at the top of the pile, a variation of the pile material stiffness and the difference of the pile eccentricity. The results obtained from the p-y curves generated from the parameters undergo sifting through for any effects on the ultimate loading capacity of the pile to the allowed design loading limits upon full structural installation. This variation is necessary for the approval of the validity of the model in engineering design. The parametric study from this study shows that the structure is of functional strength and a tolerable factor of safety.

Impact and Post-Impact Performance of Sandwich Wall Boards with GFRP Face Sheets and a Web-Foam Core: The Effects of Impact Location

In recent years, load-bearing exterior sandwich wall boards have been adopted in civil engineering. The exterior walls of structures are often exposed to low velocity impacts such as stones, tools, and windborne debris, etc. The ultimate loading capacity, deformation, and ductility of sandwich walls are weakened by impact loads. In this study, the sandwich wall boards consisted of glass fiber reinforced plastic (GFRP) face sheets and a web-foam core. The core of wall boards was not the isotropic material. There was no doubt that the mechanical performance was seriously influenced by the impact locations. Therefore, it is necessary to carry out an investigation on the impact and post-impact performance of exterior wall boards. A comprehensive testing program was conducted to evaluate the effects of impact locations and impact energies on the maximum contact load, deflection, and contact time. Meanwhile, the compression after impact (CAI) performance of wall boards were also studied. The results indicated that the impact location significantly affects the performance of wall boards. Compared with an un-damaged wall board, the residual ultimate loading capacity of damaged wall boards reduced seriously, which were not larger than 50% of the designed ultimate loading capacity.

Reinforcement of Underground Excavation with Expansion Shell Rock Bolt Equipped with Deformable Component

The basic type of rock mass reinforcement method for both preparatory and operational workings in underground metal ore mines, both in Poland and in different countries across the world, is the expansion shell or adhesive-bonded rock bolt. The article discusses results of static loading test of the expansion shell rock bolts equipped with originally developed deformable component. This component consists of two profiled rock bolt washers, two disk springs, and three guide bars. The disk spring and disk washer material differs in stiffness. The construction materials ensure that at first the springs under loading are partially compressed, and then the rock bolt washer is plastically deformed. The rock bolts tested were installed in blocks simulating a rock mass with rock compressive strength of 80 MPa. The rock bolt was loaded statically until its ultimate loading capacity was exceeded. The study presents the results obtained under laboratory conditions in the test rig allowing testing of the rock bolts at their natural size, as used in underground metal ore mines. The stress-strain/displacement characteristics of the expansion shell rock bolt with the deformable component were determined experimentally. The relationships between the geometric parameters and specific strains or displacements of the bolt rod were described, and the percentage contribution of those values in total displacements, resulting from the deformation of rock bolt support components (washer, thread) and the expansion shell head displacements, were estimated. The stiffness of the yielded and stiff bolts was empirically determined, including stiffness parameters of every individual part (deformable component, steel rod). There were two phases of displacement observed during the static tension of the rock bolt which differed in their intensity.

Structural Response of Timber-Concrete Composite Beams Predicted by Finite Element Models and Manual Calculations

This paper presents the structural response of timber-concrete composite (TCC) beams predicted by finite element models (i.e. continuum-based and 1D frame) and manual calculations. Details of constitutive laws adopted for modelling timber and concrete are provided and application of the Hashin damage model in conjunction with continuum-based FE for capturing failure of timber under bi-axial stress state is discussed. A simplified strategy for modelling the TCC connection is proposed in which the connection is modelled by a nonlinear spring and the full load-slip behaviour of each TCC connection is expressed with a formula that can be directly implemented in the general purpose FE codes and used for nonlinear analysis of TCC beams. The developed FE models are verified by examples taken from the literature. Furthermore, the load-displacement response and ultimate loading capacity of the TCC beams are determined according to Eurocode 5 method and compared with FE model predictions.

Analysis of Ultimate Loading Capacity of Inner Concave Cable-Arch Structure with Different Arch Rise-Span Ratio

Parametric analysis of ultimate loading capacity is performed by the finite element method considering the dual non-linear effects for inner concave cable-arch structure with different arch rise-span ratio. The results show that for the inner concave cable-arch structure with other given conditions, the failure loads of the steel arch and the cable increase with the increase arch rise-span ratio, but the increasing ratios are different. The failure modes of inner concave cable-arch structure may be divided into three types: the steel arch failure, the overall failure and the cable failure. According to the considered parameters range in this paper, the steel arch failure mode may occur when the arch rise-span ratio is less than 0.3; the overall failure mode may occur when the arch rise-span ratio is between 0.3 to 0.35; and the cable failure mode may occur when the arch rise-span ratio is greater than 0.35. This provides some useful references for rational design of such structures.