Effect of encased concrete on section temperature gradient of corrugated steel web box girder

Thirty-two temperature sensors, a solar radiation sensor, wind speed, and direction sensor were installed on the bridge for the field monitoring of structural temperature, solar radiation, and wind. The frequency was set at 60 min for 211 days. Empirical equations were used to predict the maximum vertical and lateral temperature gradients, and the daily maximum and minimum mean temperatures of the corrugated steel web box girder. The results showed that the temperature gradient of the corrugated steel web box girder was closely related to the temperature gradient of air. The vertical maximum temperature gradient occurred at 4 pm. The height of the box girder had a significant effect on the accuracy of the predicted vertical maximum temperature gradient. Compared with the section without encased concrete, the maximum temperature gradient of the encased concrete section was reduced by 10.48%. Encased concrete showed minimal effect on both the vertical and lateral temperature gradient of the top plate part, however, the effect on the vertical temperature gradient of the haunch reduced by 17.19%. The maximum temperature gradient of corrugated steel with a composite encased concrete section was 4.12°C, which was less than that of the section without encased concrete at 5.06°C. The encased concrete had a significant effect on the maximum temperature gradient of corrugated steel web with a 26.99% deviation.

A Review on Strengthening and Repair of RC Column by Jacketing

The research aims to investigated the efficiency of repairs of the damaged concrete column using the concrete jacketing. Strengthen what's more, restoration by the reinforce concrete jacketing of the column is assessed, consider of the diverse useful aspect anchor and slab cross of the add longitudinal reinforced, interface surface readiness separating of widow stirrup transitory shoring of the structural and the addition of news to the concrete. Late research the topic and the main recommendation to accomplish great RC jacketing are introduced. Also, factors such as corrosions of the rebar or aging may be deteriorated or then again corrupt to the limit of the reinforce concrete section, thereby necessary prompt strength to either extends or ensured it designs life isn't constrained’s. As in the instances of RC basic, segments are exposed to the garbs and ceaseless stacking with the increments in the no. of story and may prompt the incomplete relinquishment or plane aggregates disappointment of the sections. RC segments even before its help period is over immediately consideration is required in and the harmed piece of fortified cement is fixed by Greek and Latin made strengthened cement jacketing. The range of observation of these papers is limited to jacketing techniques for making strength warm feeling, desire fixing both typical and high strengths RC sections. The paper moreover takes to be the same possible unused quality operation of making observations openings, nothing in between, and outlines the future direction of operation of making observations into the making stronger and put right of RC columns.

Temperature Distributions inside Concrete Sections of Renewable Energy Storage Pile Foundations

A new pile foundation system is being developed for renewable energy storage through a multi-disciplinary research project. This system utilizes the compressed air technology to store renewable energy inside the reinforced concrete pile foundation configured with hollowed sections. The compressed air can result in high air pressure to which the structural response of the pile foundation subjected has been studied. However, the temperature in the pile foundation can be affected by the compressed air if sufficient cooling is not provided. The temperature change can generate thermal stresses and affect the structural safety of the pile foundation. As a first step to investigate this thermal effect, this paper studies temperature distributions inside the concrete section for the pile foundation through non-steady state heat transfer analyses. Several parameters were considered in the study, including thermal conductivities of the concrete, specific heat capacities of the concrete, and dimensions of the pile foundation. It has been found that the temperature distribution along the concrete section varies significantly during a daily energy storage cycle as well as subsequent cycles due to the cumulative effect of residual temperatures at the end of each cycle. The temperature distribution is largely affected by the thermal conductivity of the concrete and the geometry of the pile foundation. The obtained temperature distribution can be used for investigation of the thermal stress inside the foundation and surrounding soil.

ADHESION OF COMPONENTS OF COMPOSITE STEEL AND CONCRETE CROSS SECTION IN ANALYSIS OF BEAMS WITH CONCRETE ENCASED SECTIONS

A brief overview of the issues of aggregate work of components of the composite steel and concrete section is made. It is presented various options for the layout of the cross-section of beams used in the practice of design. A review of the design of the regulatory documents regarding the issues of adhesion of cross-section el­ements is performed. The characteristic of experimental models is given. The features of destruction of models are shown. The reasons of the destruction are analyzed. The case of the loss of the bearing capacity of the ele­ment due to relaxation (loss) of adhesion at the steel - concrete interaction boundary is considered. Various shear surfaces of the concrete section are given. Calculations of the bearing capacity of the composite steel - concrete beams for each computational surface were performed, the obtained results were evaluated. Conclusions have been made on the question of ensuring aggregate work in case of composite steel - concrete beams with a fully encased steel core.

Design Aspects of Proposed Alternative Solutions for Tertiary Irrigation Canal

This study presents a five alternative systems for the protection of old lined mesqas. The main causes of damages were identified and the hydraulic calculations for mesqas were carried out. The suggested technical alternatives for old lined mesqas were; 1- U-shape reinforced concrete section under the ground level; 2- U-shape reinforced concrete section above the ground level; 3- Reinforced concrete pipe mesqa; 4- Fiber reinforced concrete lined mesqa; and 5- Grouted stone pitched lined mesqa. The design aspects of these five alternatives were analyzed and deliberated. The most promising alternative for protecting old lined mesqas is fiber reinforced concrete lining. Also, the grouted stone pitched lined mesqas economically recommended.

A simplified estimation approach for service life of steel bar within concrete

Evaluating corrosion of steel bars within concrete cross section was the major task for durability of reinforced concrete structures. Although plenty of steel bars with various boundary condition caused huge computation load in numerical simulation, most of them were in different geometric locations while their other configuration was similar, such as temperature, moisture, and concrete composition. In this article, shape-based estimation approach was introduced for simplifying assessment of durability of concrete structures regarding numerical simulation. Based on the same penetration condition and diffusing media, the similarity of geometric configuration was the primary consideration of shape-based estimation and a mathematic model regarding the length of involving outline within a circular region with given radius was proposed. The crossbeam of an aged reinforced concrete arch bridge in coastal area was assessed, based on which shape-based estimation was proved to be applicable by comparing with finite element analysis. An evaluating tools called Weighed Corrosion Index in terms of corrosion degree of rebar in the whole concrete section was proposed and discussed in the application on degradation of concrete members. Moreover, for the purpose of modeling and post-processing, designed rebar within concrete section might not be exactly occupied by the nodes of meshed section and thus, content of aggressive agent cannot be directly obtained. An approach for identifying of rebar position and interpolating the content at rebar position was introduced.

ON THE REDUCTION OF PRESTRESSING FORCE NEAR SUPPORTS IN PARTIALLY PRESTRESSED CONCRETE FLEXURAL MEMBERS

Straight tendons in pretensioned members can cause high-tensile stresses in the concrete extreme fibers at end sections because of the absence of the bending stresses due to self-weight and superimposed loads and the dominance of the moment due to prestressing force alone. Accordingly, the concrete tensile stresses at the ends of a member prestressed with straight tendons may limit the service load capacity of the member. It is therefore important to establish limiting zone in the concrete section within which the prestressing force can be applied without causing tension in the extreme concrete fibers. Two practical methods are available to reduce the stresses at the end sections due to the prestressing force. The first method based on changing the eccentricity of some tendons by raising them towards the end zone. The second method is based on bond prevention by encasing some of the tendons in plastic sheathing, effectively moving the point of application of prestressing force inward toward midspan for part of tendons. The present study focuses on a proposed third method to reduce the effect of the prestressing force near end supports by using straight strands with limited initial prestressing value in compression zone. New equations were suggested for the cracking moment and the prestressing force which consider the prestressed tendons in compression zone.