• Computers and Concrete
• /
• 제18권2호
• /
• pp.165-178
• /
• 2016

The present work is concerned with a numerical investigation of the behaviour of reinforced-concrete beams with non-bonded flexural tension reinforcement. The numerically-established behaviour of such beams with and without transverse reinforcement is compared with its counterpart of similar beams with bonded reinforcement. From the comparison, it is found that the development of bond anywhere within the shear span inevitably leads to inclined cracking which is the cause of 'shear' failure. On the other hand, the lack of bond within the shear span of the beams is found, not only to prevent cracking within the shear span, but, also, to lead to a flexural type of failure preceded by the formation of horizontal splitting of concrete in the compressive zone. It is also found that delaying the extension of horizontal splitting through the provision of transverse reinforcement in the beam mid span can lead to flexural failure after yielding of the tension reinforcement. Yielding of the tension reinforcement before the horizontal splitting of the compressive zone may also be achieved by reducing the amount of the latter reinforcement.

• Computers and Concrete
• /
• 제18권2호
• /
• pp.155-163
• /
• 2016

This paper, proposes 20 models for predicting compressive strength of recycled aggregate concrete (RAC) containing silica fume by using gene expression programming (GEP). To construct the models, experimental data of 228 specimens produced from 61 different mixtures were collected from the literature. 80% of data sets were used in the training phase and the remained 20% in testing phase. Input variables were arranged in a format of seven input parameters including age of the specimen, cement content, water content, natural aggregates content, recycled aggregates content, silica fume content and amount of superplasticizer. The training and testing showed the models have good conformity with experimental results for predicting the compressive strength of recycled aggregate concrete containing silica fume.

• Computers and Concrete
• /
• 제7권2호
• /
• pp.145-158
• /
• 2010

In this work the implementation of a production-level port of the Microplane constitutive model for concrete into the EPIC code is described. The port follows guidelines outlined in the Material Model Module (MMM) standard used in EPIC to insure a seamless interface with the existing code. Certain features of the model were not implemented using the MMM interface due to compatibility reasons; for example, a separate module was developed to initialize, store and update internal state variables. Objective strain and deformation measures for use in the material model were also implemented into the code. Example calculations were performed and illustrate the veracity of this new implementation.

• Computers and Concrete
• /
• 제7권2호
• /
• pp.87-102
• /
• 2010

This paper discusses new capabilities developed for the Virtual Penetration Laboratory (VPL) software package to address the challenges of determining Penetration Resistance (PR) equations for concrete materials. Specifically, the paper introduces a three-invariant concrete constitutive model recently developed by the authors. The Advanced Fundamental Concrete (AFC) model was developed to provide a fast-running predictive model to simulate the behavior of concrete and other high-strength geologic materials. The Continuous Evolutionary Algorithms (CEA) automatic fitting algorithms used to fit the new model are discussed, and then examples are presented to demonstrate the effectiveness of the new AFC model. Finally, the AFC model in conjunction with the VPL software package is used to develop a PR equation for a concrete material.

• Computers and Concrete
• /
• 제7권2호
• /
• pp.169-190
• /
• 2010

The focus of this research effort was characterization of the flexural and tensile properties of a specific ultra-high-strength, fiber-reinforced concrete material. The material exhibited a mean unconfined compressive strength of approximately 140 MPa and was reinforced with short, randomly distributed alkali resistant glass fibers. As a part of the study, coupled experimental, analytical and numerical investigations were performed. Flexural and direct tension tests were first conducted to experimentally characterize material behavior. Following experimentation, a micromechanically-based analytical model was utilized to calculate the material's tensile failure response, which was compared to the experimental results. Lastly, to investigate the relationship between the tensile failure and flexural response, a numerical analysis of the flexural experiments was performed utilizing the experimentally developed tensile failure function. Results of the experimental, analytical and numerical investigations are presented herein.

• Computers and Concrete
• /
• 제24권2호
• /
• pp.117-123
• /
• 2019

Optimization is an important subject which is widely used in engineering problems. In this paper, an analytical method is developed for optimum design of reinforced concrete beams considering both flexural and shear effects. A closed-form formulation is derived for optimal height and rebar of beams. The total material cost of steel and concrete is considered as the objective function which is minimized during the optimization process. The ultimate flexural and shear capacities of the beam are considered as the main constraints. The ultimate limit state is considered for deriving the relations for flexural capacity of the beam. The design requirements are considered according to the item 9 of the Iranian National Building. Analytical formulas and some curves are proposed to be used for optimum design of RC beams. The proposed method can be used to perform the optimization of RC beams without the need of any prior knowledge in optimization. Also, the results of the studied numerical example show that the proposed method results in a better design comparing with the other methods.

• Computers and Concrete
• /
• 제23권2호
• /
• pp.107-119
• /
• 2019

In-service reinforced concrete structures are simultaneously subjected to a combination of multi-deterioration environmental actions and mechanical loads. The combination of two or more deteriorative actions in environments can potentially accelerate the degradation and aging of concrete materials and structures. This paper reviews the coupling and synergistic mechanisms among various deteriorative driving forces (e.g. chloride salts- and carbonation-induced reinforcement corrosion, cyclic freeze-thaw action, alkali-silica reaction, and sulfate attack). In addition, the effects of mechanical loads on detrimental environmental factors are discussed, focusing on the transport properties and damage evolution in concrete. Recommendations for advancing current testing methods and predictive modeling on assessing the long-term durability of concrete with consideration of the coupling effects are provided.

• Computers and Concrete
• /
• 제23권2호
• /
• pp.121-131
• /
• 2019

Due to the heterogeneity nature of the concrete, it is difficult to simulate the hyperdynamic behaviour and crack trajectory of concrete material when subjected to explosion loads. In this paper, a 3D nonlinear numerical study was conducted to simulate the hyperdynamic behaviour of concrete under various loading conditions using Riedel-Hiermaier-Thoma (RHT) model. Detailed calibration was conducted to identify the optimal parameters for the RHT model on the material level. For the component level, the calibrated RHT parameters were used to simulate the failure behaviour of plain concrete (PC) slab under free air blast load. The response was compared with an available experimental result. The results show the proposed numerical model can accurately simulate the crack trajectory and the failure mode of the PC slab under free air blast load.

• Computers and Concrete
• /
• 제27권2호
• /
• pp.143-152
• /
• 2021

Large dams are a part of the infrastructure of any society, and a huge amount of resources are consumed to build them. Among the various types of dams, the optimum design of concrete gravity dams requires special attention because these types of dams require a huge amount of concrete for their construction. On the other hand, concrete gravity dams are among the structures whose design, regarding the acting forces, geometric parameters, and resistance and stability criteria, has some complexities. In the present study, an optimization methodology is proposed based on Sequential Quadratic Programming (SQP), and a computer program is developed to perform optimization of concrete gravity dams. The optimum results for 45 concrete gravity dams are studied and regression analyses are performed to obtain some explicit formulas for optimization of the gravity dams. The optimization of concrete gravity dams can be provided easily using the developed formulas, without the need to perform any more optimization process.

• Computers and Concrete
• /
• 제30권2호
• /
• pp.113-126
• /
• 2022

Reinforced concrete bearing walls (RCBWs) are one of the most applicable structural systems. Therefore, vulnerability analysis and rehabilitation of the RCBW system are of great importance. In the present study, in order to the more precise investigation of the performance of this structural resistant system, pushover and nonlinear time history analyses based on several assumptions drawing upon experimental research were performed on several models with different stories. To validate the nonlinear analysis method, the analytical and experimental results are compared. Vulnerability evaluation was carried out on two seismic hazard levels and three performance levels. Eventually, the need for seismic rehabilitation with the basic safety objective (BSO) was investigated. The obtained results showed that the studied structures satisfied the BSO of the seismic rehabilitation guidelines. Consequently, according to the results of analyses and the desired performance, this structural system, despite its high structural weight and rigid connections and low flexibility, has integrated performance, and it can be a good option for earthquake-resistant constructions.