•A novel simulation method for massive concrete structures with cracks is proposed.•Refined simulation model with irregular cracks is established based on the method.•The method reduces meshing ...difficulty in complex 3D models with cross-scale cracks.•Crack propagation during dam construction and under an earthquake is examined.
The irregular cross-scale cracks in massive concrete structures threat the safety. Due to huge difference in scale between structures and cracks, the stability of the irregular cross-scale cracks (millimeter level) cannot be accurately analyzed in the massive concrete structures (hundred-meter level). The imprecision of the mesh model is incompatible with existing advanced cracking methods. To address the problem, this paper presents a novel numerical simulation method for irregular cross-scale cracks in massive concrete structures with node projection strategy. The elements that the crack passes through are identified on the original mesh model without cracks, and the numerical simulation model with irregular cracks is generated by projecting the corresponding nodes of elements that the crack passes through onto the crack point cloud. The primary advantage of this method is that it does not require modifying the original element types or meshing the geometric model with cracks. To verify the present method, the three-point bending beams of concrete with regular cracks and irregular cracks are examined with experiment and numerical simulation. It demonstrates that the shape characteristics of an irregular crack can result in distinct tension damage patterns compared to a regular crack. In addition, the crack propagation during dam construction and earthquake loading is investigated to demonstrate the applicability of the present method for simulating crack propagation in massive concrete structures.
•Steel slag reduces more hydration temperature rise than fly ash.•Temperature match curing does not promote the early strength of HVSS concrete so much.•The effect of temperature match curing on the ...permeability of HVSS concrete is small.
Massive concrete structures tend to have high cracking risk due to early temperature rise. High-volume mineral admixture concrete, which has low hydration heat, is suitable for massive concrete structures. In this paper, the properties of high-volume fly ash (HVFA) concrete and high-volume steel slag (HVSS) concrete were compared under two different curing conditions (standard curing condition and temperature match curing condition). The results show that the promoting effect of temperature match curing on the early strength of HVFA concrete is more obvious than that on HVSS concrete. Temperature match curing has negative effect on the late strength and elastic modulus of HVSS concrete. The promotion of temperature match curing to the elastic modulus development is not so obvious as that to the strength development. Temperature match curing can significantly decrease the chloride permeability of HVFA concrete, but its influence on the chloride permeability of HVSS concrete is inconspicuous. Though the adiabatic temperature rise of HVSS concrete is lower than that of HVFA concrete, which is beneficial to its application to the massive concrete structures, its strength especially the splitting tensile strength and resistance to chloride ion penetration need to be improved.
•The temperature field caused by hydration heat in a pier model was measured.•Finite element model of hydration heat in the tested pier model was established.•The rested data and FEA results were ...compared.•Influence of thermal parameters on the thermal behaviors of mass concrete was studied.•Pipe cooling method was found to be an effective method to reduce the hydration heat.
Thermal cracks are the main concerns when temperatures increase in mass concrete structures. It is important to explore the temperature rise rules and to find effective methods to control the hydration heat of mass concrete structures. In this study, based on a 1:5 scaled segmental model test of an arch bridge, the temperature field and temperature time histories for the core concrete of the massive pier caused by the hydration heat were measured. The finite element method (FEM) was also used to simulate the hydration temperature field through commercial FEM software. The tested temperature time history curves showed that the temperature of the concrete increases rapidly but decreases slowly. The maximum temperature at the center of the concrete reached 86.6 °C, and the maximum temperature difference from the center to the surface reached 30.6 °C, which may lead to concrete cracks. It was also found that the calculated temperature contours and temperature time history curves agreed well with the tested ones, which verified the accuracy of the FE model. Finally, the verified FE model was used to perform parametric analysis to explore the effects of thermal parameters on thermal behaviors, and an effective heat control method, i.e., the pipe cooling method with cold water, was proposed. Thermal stress analysis was also conducted and results showed that the pipe cooling method is an effective way to reduce both the hydration temperature and thermal stress.
Concrete with high content of admixture is effective in reducing the stress-strength ratio because of the low heat generation associated with the hydration reaction. However, concrete with high ...content of admixture is out of the scope of general stress-strength ratio estimation formulas. Therefore, the authors conducted an analytical study and developed a stress-strength ratio estimation formulas for concrete with high content of admixture. Case studies using this estimation formula showed that the estimated values can be evaluated safer than the analytical values, and that concrete with high content of admixture is more applicable to massive concrete.
Synchrotron accelerator facilities such as the NSLS II require extreme stability, both transient (short-term) and quasi-static (long-term) to achieve the desired resolution performance. Consequently, ...even μm-level movements, particularly differential movements between locations in the concrete structure supporting the accelerator electron beam lattice (storage ring) or high sensitivity experiments (experimental floor) will lead to serious degradation of its performance. Differential settlement in the overall structure or structural movement exceeding anticipated levels will inevitably degrade the performance and will require intervention. Presented in this paper are the design philosophy of the NSLS II ring structure favoring a monolithic ring, the observed cracking behavior of the young NSLS II concrete following casting and in combination with extreme ambient temperature fluctuation, the results of a non-linear, high-fidelity numerical analysis used to emulate the observed cracking and establish the driving mechanism, the numerical analysis-based identification of the crack-arresting solution and finally the implementation of the remediation solution and the long-term performance of the adopted engineering solution. The multi-stage process revealed that computational methods such as non-linear finite element methods have the potential of providing engineering guidance even when complex structures and in combination with non-linear materials, such as steel reinforcement and concrete are involved.
Traditionally, temperature control for massive concrete structures during the construction phase is based on experience instead of using advanced methods such as predictive control method. In this ...paper, a predictive control method with a hybrid data-based artificial neural network (ANN) model is proposed. The main parameters of the numerical model are identified based on the data measured from the site. Since the limitation of the measured data, a rich dataset is generated by the numerical model with the identified parameters. Finally, a hybrid data-based ANN model for predicting the temperature indicator of massive concrete is developed. A case study in which the temperature control of concrete in a real bridge anchorage foundation construction in Southwestern China is conducted. Results show that the maximum temperature of concrete can be controlled around the target temperature by the proposed method. The average temperature decline rate decreases from 0.19 °C/h to 0.14 °C/h in the period of 120 h (i.e., from 60 h to 180 h after the concrete pouring) at a sudden decrease of 8 °C in environmental temperature, thereby enabling a significant reduction in the risk of concrete cracking.
•The cement blended with GCS can effectively reduce the hydration heat.•Utilizing GCS to replace cement can improve the workability while reducing the yield stress.•The concrete sample containing GCS ...can reduce the adiabatic temperature rise.•The GCS has great potential as an SCM for massive concrete in the saline-soil environment.
The present study aimed to utilize granulated copper slag (GCS) as a mineral admixture for massive concrete in the saline-soil environment, then analyze the feasibility through the experiment. A contrastive analysis was conducted on the hydration heat in paste mixtures with a partial replacement of Ordinary Portland cement (OPC) by GCS and FA at different temperatures (25 °C and 50 °C). Results showed that the properties of cement blended with GCS were similar to that of FA, which can effectively reduce the hydration heat. The GCS influence on the fluidity, rheological performance, compressive strength, and chloride permeability of concrete was investigated. Results showed that utilizing GCS to replace cement can improve workability while reducing the yield stress, plastic viscosity, mechanical strength, and chloride permeability of concrete. By adjusting the w/b ratio and the GCS amount, three groups of concrete samples (C-0.40, G35-0.35, G40-0.32) with similar workability, compressive strength, and chloride permeability were selected for adiabatic temperature rise testing. A detailed analysis was conducted on the compressive strength, splitting tensile strength, chloride ion permeability, and sulfate attack resistance of concrete under the temperature match curing (TMC) condition. Results showed that the concrete sample containing GCS can reduce the adiabatic temperature rise, while slightly increasing the compressive strength, splitting tensile strength, chloride permeability, and sulfate attack resistance. The present study provided a theoretical basis for the application of GCS to the massive concrete.
These recommendations have been prepared by the corresponding working group within RILEM TC 287-CCS “Early-age and long-term crack width analysis in RC structures”, following work by the previously ...ceased RILEM TC 254-CMS “Thermal cracking of massive concrete structures”. This recommendations document is developed in complementarity to the state-of-the-art report of RILEM TC 254-CMS and aims to provide expert advice and suggestions to engineers and scientists interested in modelling the thermo-chemo-mechanical behaviour of massive concrete structures since concrete casting. Recommendations regarding geometrical characteristics and complexities, concrete properties and appropriate material models, boundary conditions and loads, and numerical model peculiarities with relevance to the simulation of the thermo-chemo-mechanical behaviour of massive concrete structures are given herein. The recommendations have been reviewed and approved by all members of the TC 287-CCS.
This study presents a probability-based surface deterioration evaluation framework to evaluate the cracking damage of bridge pylons subjected to repetitive thermal stresses caused by daily ...temperature variations. First, a temperature prediction model for massive concrete bridge members was utilized, incorporating the effects of convection and radiation. Subsequently, the thermal loads applied to the bridge pylon were computed using the finite element (FE) method. A modified linear elastic fracture mechanics (LEFM) crack model combined with random field theory for predicting crack propagation in concrete was employed. A probability-based surface damage grade method for a bridge pylon was proposed. Moreover, the deterioration state evaluation was updated by incorporating Bayesian inference, which involved using in situ inspection results (i.e. spatial distribution associated with surface crack lengths). The methodology was implemented using an illustrative example that considers a bridge pylon. The results provide useful information for aiding decision-making strategies concerning the maintenance and repair of massive concrete bridge components.
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