SummaryThe structural performance of bridge structures is temporal and is mainly controlled by the types of the applied loads. To continuously observe the structural performance of bridges, structural health monitoring sensors that include among many temperature sensors are used. The impact of nonuniform temperature distributions in bridge girders due to the environment thermal loads has been recognized by former researchers and bridge design codes. To evaluate these and other effects on the structural behavior of bridge structures, many field and experimental structural health monitoring studies were carried out. However, more researches are required to investigate the temperature distributions in other girder configurations. This work is directed to investigate the impact of air temperature and solar radiation on temperature gradient distributions in concrete-encased composite girders. For this purpose, an experimental concrete-encased steel girder segment was instrumented with thermocouples and other sensors. The experimental data recording continued for 6 months during the hot and cold seasons. Furthermore, a thermal finite element (FE) parametric study was conducted to investigate the effect of the girder size. The test results showed that the vertical and lateral temperature gradient distributions and the variation of the temperature gradients with time are controlled by the amount and location of the received solar radiations. The FE analysis showed that the daily temperature variations are higher in smaller girders, whereas the temperature gradients are smaller than in larger girders. Moreover, the FE results showed that the thickness of the girder's concrete members has an important impact on temperature gradients and temperature distributions.

The mud is considered as one of the oldest construction materials in Iraq and is still used in the country regions for farmer’s houses or animal shelters. In Iraq, there are different types of mud constructions, including adobe, unfired bricks and cob. The presented study has focused on unfired clay brick where the clay is the main material. To ensure that the clay is pure and clean, it was excavated from the depth of 2 m below the natural ground level. Different types of unfired clay bricks produced by adding different materials to the clay to improve its properties and especially large deformation due to shrinkage. The added materials are classified into three concepts, the first additives are the natural fibers (straw, sawdust, and rice husk) and they are used to improve the tensile strength of brick and reduce the cracking due to shrinkage. The second additives included added the fine and coarse sand as a stabilizer to reduce the volumetric changes. The third additives are adding cement to increase the adhesive and cohesion of the mud matrix. The measurements included compressive strength of brick, mortar, and masonry and the flexural strength of bricks alone. The behaviour of unfired masonry prisms was also compared to the traditionally fired clay brick prisms. The results indicate that higher compressive strength of bricks was got for the mix that included clay, coarse sand and straw. The maximum flexural strength of bricks was got for the mix that included clay and sawdust, while for unfired masonry prism the higher compressive strength was obtained with a mix that included clay, coarse sand and straw. Finally, a proposed formula to obtain the compressive strength of unfired brick masonry from the compressive strength of brick and mortar is presented.

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Based on experimental records from a composite beam with a steel section and topping concrete flange, a finite element thermal analysis model was conducted and verified. The experimental beam was provided with 14 embedded and surface temperature sensors inside the concrete flange and on the steel section. The temperature records from the experimental beam were collected for two winter months. The finite element thermal model was conducted to simulate the thermal response of composite beams under the influence of open-field thermal conditions. The model solves for the conduction of heat in concrete and steel considering the different boundary conditions that include; solar radiation, reflected radiation, temperature of air and the speed of the ambient air. To verify the introduced thermal model, the predicted temperatures at the 14 thermocouples were compared with the experimental ones along the 24 hours of three days with different weather conditions. The comparisons showed that for the three days, the model could capture the temperature-time behavior accurately for all thermocouples with moderately low average absolute errors of 0.4 to 2.0 °C. Another notice was that the maximum errors in the steel section were higher than in concrete.

This article presents experimental results from a concrete-steel composite girder. The girder is composed of an I-shape steel beam that is topped by a reinforced concrete slab. The girder was constructed in an open environment so that it is freely subjected to the variation of the atmospheric thermal loads. These loads include the solar radiation, temperature of the surrounding air and speed of the wind. Therefore, a weather station that includes sensors to measure the three aforementioned thermal loads was installed beside the girder. The girder was instrumented with thermocouples that were either embedded in the concrete slab or attached to the steel beam. The thermocouples were distributed across the slab thickness, along its width and along the vertical centerline of the composite girder. The aim of this research is to provide experimental measurements that facilitate better understanding of temperature gradient distributions in composite bridge girders in winter. The test records were continued for approximately two months during the cold season. The test results showed that the negative vertical temperature gradient was higher than the corresponding positive one due to the low intensity of solar radiation. Similarly, the lateral positive temperature gradient along the width of the concrete slab was higher than the vertical positive temperature gradient due to the low altitude of solar radiations.