Papers by Keyword: Concrete Structure

Abstract: The main structure of wind tunnel is special-shaped thin-walled structure. During the design and construction phase, its static strength, static stiffness and dynamic characteristics have to be taken into account. The author explains the meshing method of the main structure of wind tunnel in which finite element computing model is established through ABAQUS according to model simplification principle and analysis of stress, deformation and modality is done on this wind tunnel model. Analysis results show that the main structure of this wind tunnel caters for requirements of static strength and static stiffness in which overall stiffness distributes reasonably, modal frequency presents good distribution and condition permits to do further optimization on part of components. Straight section wall of wind tunnel affords the most pressures while dip angle section amplifies or reduces according to cross section of downwind section. Amplification section is suction-based and wall of amplification section is pressure-based. This analysis result would provide references for tension analysis of roof surface.

Abstract: Carbonation of the concrete is a process influencing acceleration of the aging of concrete during the time, at reinforced concrete structures it is usually accompanied with corrosion of the reinforcement and disturbances of the covering layer of the concrete. Its consequence is decrease of the static reliability of the reinforced concrete building structures. Carbonation of the construction from common concrete and lightened concrete causes just in the CR damage worth billions of Czech Crowns every year. The paper refers about seriousness of the current technical state of reinforced concrete structures and influence of the most important factors on the course of their degradation caused by carbonation and specifies principles for designing new reinforced concrete constructions.

Abstract: The safety of concrete structure can be evaluated by manual survey through the visible crack shown on structural surface, but the manual survey is costly and time-consuming. To improve this, a novel image-based crack length measurement is proposed. The method starts with getting time varying crack images by proposed inspection system. Then retrieve crack skeleton from crack images by pre-processing, and construct crack skeleton of tree structure. After getting crack trunk by pruning small edges from crack skeleton, the length of crack is figure out. This method can measure crack length automatically, which will make contribution to enhance the stability, durability and safety of concrete structure. The validity and accuracy of the proposed method was tested by an experiment using images of a real concrete surface.

Abstract: An improved nonlocal peridynamic model was proposed to analyze the progressive failure and crack propagation in concrete structures. Integration-typed equations of motion rather than partial differential equations are utilized so that the cracks will propagate naturally as a consequence of simulation. The anisotropy of concrete and the short-range repulsion between material points were incorporated into the pericynamic constitutive model for concrete, and the damage of material was defined locally at the level of pairwise bond. Its validity was established through qualitative and quantitative comparisons against finite element analysis and experimental observations.

Abstract: The factors affecting durability of concrete structures is described in This paper .It is pointed out here that is the concept of durability in prefabricated concrete structure , the influencing factors and failure mechanism in cold regions. It is proposed which are the methods and corresponding measures to enhance the durability of concrete structures.

Abstract: Paper deals with the applicability of impedance spectroscopy method to testing of cement-based composites prepared from a mix of type CEM I cement and siliceous sand, as well as by substituting 25 % of sand with shredded automobile tires and by adding acrylic polymer binder (10 % w/w of the polymer mass to cement mass). The monitoring of structural changes in the thermal stress is very important, for example for determining the reliability of the whole structure. Samples were intentionally degraded by high-temperature (in a temperature range from 25 °C to 400 °C). The primary monitored magnitudes were electrical capacitance C, the relative permittivity ε_r and components of electric impedance |Z|. Based on the Debye theory of dielectric the models were created, their applications and received parameters measured dielectric material is characterized and discussed the uniqueness of determining the values of model parameters. Development of electrical parameters and permittivity at each temperature areas reliably show thus structural changes and thus the structural reliability.

Abstract: This paper deals with the application of the method of impedance spectroscopy to testing of cement-based composites prepared from a mix of cement mortar and quartz sand, which were intentionally degraded by high-temperature treatment (in the temperatures range from 25 °C to 400 °C). The monitoring of structural changes in the thermal stress is very important, for example for determining the reliability of the whole structure. Based on the Debye theory of dielectric the models were created, their applications and received parameters measured dielectric material is characterized and discussed the uniqueness of determining the values of model parameters. Development of electrical parameters and permittivity at each temperature areas reliably show these structural changes and thus the structural reliability.

Abstract: An experimental structure from high performance concrete was created within the scope of long-term research and development program of the Department of Concrete and Masonry Structures, Faculty of Civil Engineering, CTU in Prague that is focused on advanced cementitious composites. The intention was to build a structure of so called “CyclePoint” (resting place for bikers) interesting from architectural point of view and made from non-traditional, high durability material. Transfer of high performance concrete composition designed in the laboratory to the mixing plant construction company was accomplished. This required series of confirmation material tests. The technology of casting high performance concrete into the formwork of thin-walled precast elements was optimized. The use of engineered mix of fibres enabled the authors to design structures without main rebar reinforcement. The design was carried out using finite element based software and verified by loading experiments executed on structural elements in full-scale.

Abstract: Concrete structure is widely used in civil engineering. Concrete cracking, a common and frequently occurring disease, is one of the main factors that cause impaired concrete structure durability. This paper analyzes the generation process and features of non-longitudinal concrete cracking. With on-site investigation of selected buildings in Ningbo, the paper discusses the main existing non-longitudinal cracks and their impact on the durability of concrete structure.

Abstract: A method for monitoring the crack damage of concrete structure based on piezoceramics transducers was introduced in the paper. The PZT patches were packaged as smart aggregates which buried into concrete structures in pair. One is as actuator to transmit monitoring signals, and the other is as sensor to receive the monitoring signals. Sine sweep frequency wave was used as monitoring signal type, and its energy value was used as damage identification parameter. At last, a test was conducted to prove the effectiveness of monitoring method. The crack damage of a reinforced concrete beam under the load was monitored during the whole test process. The develop trend of damage identification parameter could reflect the develop trend of damage. The method proposed in the paper is feasible for crack damage monitoring of concrete structure.