Development of a new connection for precast concrete walls subjected to cyclic loading

The Industrialized Building System （IBS） was recently introduced to minimize the time and cost of project construction. Accordingly, ensuring the integration of the connection of precast components in IBS structures is an important factor that ensures stability of buildings subjected to dynamic loads from earthquakes, vehicles, and machineries. However, structural engineers still lack knowledge on the proper connection and detailed joints o fiBS structure construction. Therefore, this study proposes a special precast concrete wall-to-wall connection system for dynamic loads that resists multidirectional imposed loads and reduces vibration effects （PI2014701723）. This system is designed to connect two adjacent precast wall panels by using two steel U-shaped channels （i.e., male and female joints）. During casting, each joint is adapted for incorporation into a respective wall panel after considering the following conditions： one side of the steel channel opens into the thickness face of the panel; a U-shaped rubber is implemented between the two channels to dissipate the vibration effect; and bolts and nuts are used to create an extension between the two U-shaped male and female steel channels. The developed finite element model of the precast wall is subjected to cyclic loads to evaluate the performance of the proposed connection during an imposed dynamic load. Connection performance is then compared with conventional connections based on the energy dissipation, stress, deformation, and concrete damage in the plastic range. The proposed precast connection is capable of exceeding the energy absorption of precast walls subjected to dynamic load, thereby improving its resistance behavior in all principal directions.

Damage modeling of ballistic penetration and impact behavior of concrete panel under low and high velocities

This work presents a numerical simulation of ballistic penetration and high velocity impact behavior of plain and reinforced concrete panels.This paper is divided into two parts.The first part consists of numerical modeling of reinforced concrete panel penetrated with a spherical projectile using concrete damage plasticity(CDP)model,while the second part focuses on the comparison of CDP model and Johnson-Holmquist-2(JH-2)damage model and their ability to describe the behavior of concrete panel under impact loads.The first and second concrete panels have dimensions of 1500 mm1500 mm150 mm and 675 mm675 mm200 mm,respectively,and are meshed using 8-node hexahedron solid elements.The impact object used in the first part is a spherical projectile of 150 mm diameter,while in the second part steel projectile of a length of 152 mm is modeled as rigid element.Failure and scabbing characteristics are studied in the first part.In the second part,the comparison results are presented as damage contours,kinetic energy of projectile and internal energy of the concrete.The results revealed a severe fracture of the panel and high kinetic energy of the projectile using CDP model comparing to the JH-2 model.In addition,the internal energy of concrete using CDP model was found to be less comparing to the JH-2 model.

Deformation coordination analysis of CC-RCC combined dam structures under dynamic loads

A combined dam structure using different concrete materials offers many practical benefits.There are several real-world cases where largevolume heterogeneous concrete materials have been used together.From the engineering design standpoint,it is crucial to understand the deformation coordination characteristics and mechanical properties of large-volume heterogeneous concrete,which affect dam safety and stability.In this study,a large dam facility was selected for a case study,and various design schemes of the combined dam structure were developed by changing the configurations of material zoning and material types for a given dam shape.Elastoplastic analysis of the damfoundation-reservoir system for six schemes was carried out under dynamic conditions,in which the concrete damaged plasticity(CDP)model,the Lagrangian finite element formulation,and a surface-to-surface contact model were utilized.To evaluate the mechanical properties of zoning interfaces and coordination characteristics,the vertical distribution of the first principal stress at the longitudinal joint was used as the critical index of deformation coordination control,and the overall deformation and damage characteristics of the dam were also investigated.Through a comparative study of the design schemes,an optimal scheme of the combined dam structure was identified:large-volume roller-compacted concrete(RCC)is recommended for the dam body upstream of the longitudinal joint,and high-volume fly ash conventional concrete(CC)for the dam body downstream of the longitudinal joint.This study provides engineers with a reference basis for combined dam structure design.

基于塑性模型法的钢筋混凝土靠泊码头损伤检测（英文）

A conventional method of damage modeling by a reduction in stiffness is insufficient to model the complex non-linear damage characteristics of concrete material accurately.In this research,the concrete damage plasticity constitutive model is used to develop the numerical model of a deck beam on a berthing jetty in the Abaqus finite element package.The model constitutes a solid section of 3D hexahedral brick elements for concrete material embedded with 2D quadrilateral surface elements as reinforcements.The model was validated against experimental results of a beam of comparable dimensions in a cited literature.The validated beam model is then used in a three-point load test configuration to demonstrate its applicability for preliminary numerical evaluation of damage detection strategy in marine concrete structural health monitoring.The natural frequency was identified to detect the presence of damage and mode shape curvature was found sensitive to the location of damage.

Numerical modelling of reinforced concrete flexural members strengthened using textile reinforced mortars

Externally bonded(EB)and near-surface mounted(NSM)bonding are two widely adopted and researched strengthening methods for reinforced-concrete structures.EB composite substrates are easy to reach and repair using appropriate surface treatments,whereas NSM techniques can be easily applied to the soffit and concrete member sides.The EB bonded fiber-reinforced polymer(FRP)technique has a significant drawback:combustibility,which calls for external protective agents,and textile reinforced mortar(TRM),a class of EB composites that is noncombustible and provides a similar functionality to any EB FRP-strengthened substrate.This study employs a finite element analysis technique to investigate the failing failure of carbon textile reinforced mortar(CTRM)-strengthened reinforced concrete beams.The principal objective of this numerical study was to develop a finite element model and validate a set of experimental data in existing literature.A set of seven beams was modelled and calibrated to obtain concrete damage plasticity(CDP)parameters.The predicted results,which were in the form of load versus deflection,load versus rebar strain,tensile damage,and compressive damage patterns,were in good agreement with the experimental data.Moreover,a parametric study was conducted to verify the applicability of the numerical model and study various influencing factors such as the concrete strength,internal reinforcement,textile roving spacing,and externally-applied load span.The ultimate load and deflection of the predicted finite element results had a coefficient of variation(COV)of 6.02%and 5.7%,respectively.A strain-based numerical comparison with known methods was then conducted to investigate the debonding mechanism.The developed finite element model can be applied and tailored further to explore similar TRM-strengthened beams undergoing debonding,and the preventive measures can be sought to avoid premature debonding.

YIELD CRITERION IN PLASTIC-DAMAGE MODELS FOR CONCRETE

A class of plastic-damage models for concrete require an unambiguous definition of cohesion in the yield criteria. For this reason, the Lubliner yield criterion has been adopted by many investigators and the commercial FE program Abaqus. As is well known, this criterion has achieved great success especially in plane stress states. In this paper, we are trying to extend it to triaxial compression stress states. First, a major limitation of the Lubliner criterion is analyzed. Then, a revised version of the Lubliner criterion is proposed, which shows appropriate properties over a wide range of stress states often encountered in engineering structures, and the predicted failure envelopes fit well with experimental data. For the concrete damaged plasticity model in Abaqus, a calibration strategy is suggested for uniformly confined concrete.

Nonlinear numerical simulation of punching shear behavior of reinforced concrete flat slabs with shear-heads

This paper examines the structural response of reinforced concrete flat slabs,provided with flillyembedded shear-heads,through detailed three-dimensional nonlinear numerical simulations and parametric assessments using concrete damage plasticity models.Validations of the adopted nonlinear finite element procedures are carried out against experimental results from three test series.After gaining confidence in the ability of the numerical models to predict closely the full inelastic response and failure modes,numerical investigations are carried out in order to examine the influence of key material and geometric parameters.The results of these numerical assessments enable the identification of three modes of failure as a function of the interaction between the shear-head and surrounding concrete.Based on the findings,coupled with results from previous studies,analytical models are proposed for predicting the rotational response as well as the ultimate strength of such slab systems.Practical recommendations are also provided for the design of shear-heads in RC slabs,including the embedment length and section size.The analytical expressions proposed in this paper,based on a wide-ranging parametric assessment,are shown to offer a more reliable design approach in comparison with existing methods for all types of shear-heads,and are suitable for direct practical application.

Analysis on damage causes of built-in corridor in core rock-fill dam on thick overburden:A case study

The stress state of the built-in corridor in core rock-fill dam on thick overburden is extremely complex,which may produce cracking and damage.The purpose of this paper was to investigate the effect of thick overburden on the stress and deformation of the built-in corridor in a rock-fill dam,and ascertain the damage causes of the corridor.The rationality of the analysis method for corridor with similar structure is another focus.The approach is based on finiteelement method and the calculation result accuracy is verified by the field monitoring data.The improved analysis method for corridors with similar structure is proposed by comparing various corridor load calculation methods and concrete constitutive models.Results demonstrate that the damage causes of the corridor are the deformability difference between the overburden and concrete and the special structural form.And the calculation model considering dam construction process,contact between concrete and surrounding soil,and concrete damage plasticity can reasonably reflect the mechanical behavior of the corridor.The research conclusions may have a reference significance for the analysis of tunnels similar to built-in corridors.