Study on dynamic response of cushion layer-reinforced concrete slab under rockfall impact based on smoothed particle hydrodynamics and finite-element method coupling

Duncan J.M., Chang C.

A simple, practical procedure for representing the nonlinear, stress-dependent, inelastic stress-strain behavior of soils was developed. The values of the required parameters employed in the stress-strain relationship may be derived from the results of standard triaxial tests on plane strain compression tests involving primary loading, unloading, and reloading. Comparisons of calculated and measured strains in specimens of dense and loose silica sand showed that the relationship was capable of accurately representing the behavior of this sand under complex triaxial loading conditions, and analyses of the behavior of footings on sand and clay showed that finite element stress analyses conducted using this relationship were in good agreement with empirical observations and applicable theories.

Matsimbe J.

Abstract With increasing awareness of geotechnical risks in civil and mining structures, taking advantage of smartphone technology to study rocky slopes can play a key role in the development of safe and economical structures for human welfare. In Malawi, there is a research gap on application of portable devices to collect geotechnical data. Geological engineers still use the unsafe tedious handmapping technique to collect geotechnical data. A road cut that experiences frequent rockfall is used as a case study to investigate if there is a role for smartphones in geotechnics by comparing set statistics of data clusters collected through photogrammetry, smartphone and clar inclinometer. Besides low cost, smartphone’ data capture speed is faster than clar inclinometer. Stereographic and kinematic analysis shows that the 75° dipping road cut is predominantly prone to wedge failure with minor planar failure. For slope stability, Q-slope suggests a new slope angle of 60–66°. An acceptable tolerance limit or error between handmapping and remote data capture systems should be less than ±15°. Set analysis on 111 comparable data points gave a maximum pole vector difference of 10.5°, with the minimum having a difference of 4.8°. For dip, the standard deviations vary from 4.9 to 9.5°, while their mean values vary from −2 to 2.75°. For dip directions, the standard deviations vary from 3.2 to 4.3°, while their mean values vary from −6 to 0.75°. Therefore, android smartphones have a role in geotechnics due to their allowable orientation errors, which show less variance in measured dip/dip direction.

Lu D., Liang J., Du X., Ma C., Gao Z.

A novel three-dimensional (3D) fractional plastic flow rule that is not limited by the coordinate basis of the differentiable function is proposed based on the fractional derivative and the covariant transformation. By introducing the 3D fractional plastic flow rule into the characteristic stress space, a 3D fractional elastoplastic model for soil is established for the first time. Only five material parameters with clear physical significance are required in the proposed model. The capability of the model in capturing the strength and deformation behaviour of soils under true 3D stress conditions is verified by comparing model predictions with test results.

Yan P., Zhang J., Fang Q., Zhang Y.

A spherical falling rock is usually assumed in the design of reinforced concrete (RC) sheds. Little attentions have been paid to the effects of falling rock’s shape on impact force and structural response theoretically, numerically and experimentally. This paper aims to reveal the influence of falling rock’s shape on the impact effect of RC slabs. Firstly, ellipsoidal models are established to simulate falling rocks approximately, and sphericity is employed as the representative index of falling rock’s shape. A numerical analysis approach is then presented to simulate RC slabs under falling rock impact, which is validated by the test data. Finally, the impact forces and the dynamic responses of RC slabs are analyzed and discussed, focusing on the effects of falling rock’s shape and impact angle. It is demonstrated that sphericity and impact angle have significant effects on the impact force and dynamic response of RC slabs. The assumption of spherical falling rocks leads to unsafe of RC slabs in some rockfall impact scenarios.

Sun Y., Xiao Y.

This paper presents a fractional order plasticity model by using the concept of fractional order plastic flow. The flow direction is obtained by performing fractional order derivative of the plastic potential function with respect to loading stress. Unlike the classical model, the obtained flow direction changes with the changing fractional order, which makes the model capable for modelling various kinds of plastic flow patterns of different granular soils without changing the details of the potential function. The flexible ability of the proposed model is further validated by simulating multiple series of experimental results of different granular soils subjected to drained and undrained triaxial compressions.

Chuzel-Marmot Y., Ortiz R., Combescure A.

This paper is mainly dedicated to the presentation of a general method to couple standard finite elements with SPH methods for fast transient analysis. The method is based on hand shake formulation and developed for fast transient. This type of gluing permits to use SPH only in the region of interest. The SPH methods is often CPU time consuming, hence this coupling strategy is interesting provided one knows in advance where the critical zone is. The method is applied to the prediction of perforation of available reinforced concrete slabs experiments. A concrete damage model adapted to high strain rate is also described.

Bhatti A.Q., Khatoon S., Mehmood A., Dastgir A., Kishi N.

In this paper, a falling-weight impact test using full scale arch type reinforced concrete (RC) structures was conducted to verify a proposed impact response analysis method. The applicability of the numerical analysis method was confirmed by comparison with the experimental results. The validity of the current impact resistant design procedure to the performance based design procedure was investigated using the proposed numerical analysis method. From this study, it is confirmed that by applying the current impact resistant design procedure, a performance based impact resistant design with a sufficient safety margin may be obtained for the full scale arch type RC structures.

Roscoe K.H., Schofield A.N., Thurairajah A.

Synopsis The consequences of the assumption that soil is an isotropic, elasto-plastic, continuous medium are examined. A new energy equation is proposed, well supported by experimental evidence, from which a stress-strain relationship is developed for virgin and lightly overconsolidated clays. An alternative stress-strain relationship is derived from the “normality condition” specified in the theory of plasticity, and this is shown to be identical to that proposed by Roscoe and Poorooshasb (1963). These two relationships are then combined to give, in terms of only four fundamental soil constants, a unique stress-strain relationship, simple equations for a new state boundary surface and a unique yield locus or plastic potential. The shape of these surfaces necessitates a complete revision of currently accepted pictures of the mechanism of virgin consolidation and entails the possibility of the occurrence of shear distortion under isotropic stress. The concept is supported by experimental evidence obtained from creep tests. Finally it is suggested that if the theory is accepted then soil testing procedures may be greatly simplified, and that new methods may be applied to solve earth pressure problems. Les conséquences de l'hypothèse selon laquelle le sol est un milieu isotrope, de plasticité élastique et continu sont examinées. On propose une nouvelle équation d'énergie d'après laquelle on développe un rapport entre les contraintes et la déformation pour des argiles surconsolidées vierges et légères. On déduit un rapport alternatif entre les contraintes et la déformation d'après la “condition de normalité” spécifiée dans la théorie de plasticité et on montre qu'il est identique à celui proposé par Roscoe et Poorooshasb (1963). Ces deux rapports sont alors réunis pour donner, avec seulement quatre constantes de sol fondamentales, un rapport unique entre les contraintes et la déformation et des équations simples pour une nouvelle surface-limite de l'état existant et aussi un potentiel unique pour le lieu géométrique de limite élastique ou la plasticité. La forme de ces surfaces exige une révision complète des points de vue acceptés couramment sur le mécanisme de consolidation vierge et entraîne la possibilité de déformation par cisaillement sous des contraintes isotropes. Cette conception est supportée par l'évidence expérimentale obtenue des essais de fluage. Enfin on suggère que si la théorie est acceptée les méthodes à suivre pour les essais de sols seraient grandement simplifiées, et de nouvelles méthodes pourraient être appliquées pour résoudre les problèmes de pression terrestre.

Dafalias Y.F.

The mathematical foundation of the general bounding surface constitutive formulation in plasticity is presented. Along these lines the concept of hypoplasticity is formally introduced, and it is shown that a particular class of hypoplastic formulations arises naturally from certain bounding surface models, with the distinguishing feature being the dependence of the elastoplastic moduli and/or the plastic strain rate direction on the stress rate direction. The general analytical perspective allows the better understanding and improvement of existing bounding surface plasticity and hypoplasticity models, which are briefly discussed, and suggests the proper way to construct new ones for future applications.

Zineddin M., Krauthammer T.

Reinforced concrete slabs are among the most common structural elements. In spite of the large number of slabs designed and built, the effect of their details on their behavior under impact loads are not always appreciated or properly taken into account. This experimental study was aimed at understanding the dynamic behavior of structural concrete slabs under impact loading to improve the state of the art of protective design. This study investigated the effects of different types of slab reinforcements and the applied impact loads on the dynamic response and behavior of reinforced concrete slabs. Three different types of 90×1524×3353 mm (3−1/2″×5′×11′) slabs were tested, as follows: First; using two 152×152 mm (6″×6″) meshes of welded steel wires located under 25 mm (1″) of concrete cover on both faces of the slab; second, with one 152×152 mm (6″×6″) mesh of No. 3 steel bars located at the middle of the slab thickness ; and third, with two 152×152 mm (6″×6″) meshes of No. 3 steel bars located under 25 mm (1″) of concrete cover on both faces of the slab. The drop heights of the impact weight were 152, 305, and 610 mm (6″, 12″, and 24″), respectively.

Haberler-Weber M., Huber M., Wunderlich T., Kandler C.

In 1999, a rockfall occurred at the Eiblschrofen, near Schwaz (Tyrol, Austria). Immediately after this event, a monitoring system consisting of GPS, geodetic and geotechnical sensors was installed in this area. The data of this different group of sensors are now for the first time analysed together within a hybrid assessment tool. This tool shall imitate the knowledge and decision making process of a human expert looking at different data. Therefore a fuzzy-based approach is chosen to implement the assessment tool. The paper describes the situation at the Eiblschrofen area, the monitoring system as well as the first implementation steps for the fuzzy-based assessment tool.

Pichler, Β., Hellmich, C., Mang, H.A.

Mougin J., Perrotin P., Mommessin M., Tonnelo J., Agbossou A.

This paper concerns the protective structures against rock fall. We propose a new concept of rock-shed protection. The proposed rock-shed protection is made of reinforced concrete slabs held up by specially designed supports that act as a type of expendable fuse to absorb high rock-fall energy especially when shock occurs on the side of the slab. Thus, by a simple change of damaged supports and local restoration of concrete in the impact area, the structure can continue to be used. We present also an experimental method to characterize and analyze shock absorption effected by this type of reinforced concrete slab. The analyzed slab is a 1/3 scale reproduction of an actual structure.

Johnson G.R., Stryk R.A.

This paper presents a description of an algorithm to automatically convert 3D distorted elements into meshless particles during dynamic deformation. It also includes an improved (invariant) particle algorithm that allows for a more accurate treatment of boundaries and interfaces. These new 3D algorithms have been incorporated into an explicit Lagrangian code that includes both elements and particles. They provide for increased capability and accuracy for Lagrangian computations involving severe distortions. Several 3D examples are included to demonstrate the new technique.

Liu G.R., Liu M.B.

Lin Z., Wang Y., Fu Z., Zhong D., Du X., Zhang J.

Jin L., Wang Z., Jiao P., Zhou P., Wu T.

The failure pattern of recycled aggregate concrete (RAC) under uniaxial loading directly relates to its mesoscopic structure. However, the macroscopic physical experiments are no longer sufficient to investigate its failure mechanism further. In this paper, the mechanical behavior of RAC during uniaxial compression is investigated using mesoscopic numerical analysis. In order to fully consider the effects of the randomness of the shape and location of the recycled coarse aggregate (RA) and the mesoscopic structure on the compression performance of RAC, a two-dimensional multi-phase random convex polygonal aggregate model of RAC was established by a self-compiled program. The numerical simulation of uniaxial compression of RAC was realized by combining it with the concrete damage plasticity model, and the validity of the numerical model was verified by comparing it with the experimental data and the three-dimensional random spherical aggregate model. The influence of the end restraint effect and mesoscopic structure on the compression performance of RAC was further investigated. The main findings include: 1) the RAC without end restraint exhibits a crack development pattern similar to splitting failure, whereas with increasing end restraint the RAC exhibits an ideal conical axial compression failure pattern; 2) the shape of RA has a significant effect on the displacement, damage evolution and failure pattern of RAC, and the simulation results of the two-dimensional convex polygonal aggregate model are closer to the actual situation; 3) among the mesoscopic phases caused by the RA, the old adhesive mortar has the most obvious effect on the compression performance of the RAC.