No abstract

Unlike other road materials, aeolian sand has some compaction characteristics that are key factors in construction qualities of highway in the desert. In order to study the characteristics, a series of laboratory and field tests were performed, including sieve analysis, standard modified compaction, vibrating compaction and field test. By analyzing the sieve analysis test data, it was found that the gradation of aeolian sand was bad, with fine grains whose diameters mostly ranged from 0.25 mm to 0.074 mm. Then, from the laboratory compaction test results, a compaction curve similar to the horizontallywritten letter S was obtained. That was quite different from the other kinds of road materials. There were two peak values in the curve with the increase of water content, which was the special characteristic of aeolian sand: to be well compacted whether it was dry or wet. Also, according to laboratory vibrating test results, the best vibrating frequency range was proposed. It was from 45 Hz to 50 Hz. Moreover, some field compaction tests were carried out. On the construction site of the highway, the aeolian sand subgrade was compacted in the condition of natural water content with optimizing construction machines. Its compaction degree reached 96%, meeting the current specifications. At last, comparative studies were carried through with electron microscope. It was shown that the microstructure of compacted dry aeolian sand is much denser than that of the natural one in the field test.

No abstract

An improper configuration of masonry infill walls in RC frame may lead to short column effect on the columns, which is harmful to the seismic behavior of the structure. In this study, a bare frame and two single-story, single-bay RC frames, partially infilled with masonry, were tested under cyclic loading. The failure mechanism and seismic performance of these partially infilled RC frames (with an infill height of 600 mm) with different types of connections were analysed. Based on the experiment, nonlinear finite element simulation and analysis were conducted to study the effects of the infill walls and connections. The results show that both mechanical performance and failure mode are affected by the infill height, the type of connection between the frame and the infill, and the ratio of shear bearing capacity of the frame column to that of the infill. For the masonry-infilled frame with rigid connection, the higher the infill wall is, the lower the shear bearing capacity ratio will be. Thus, the effect of the lateral constraint of the infill wall on the column increases, and the shear span ratio of the free segment of the column decreases, resulting in the short column effect. Based on the analysis results, a value of 2.0 is suggested for the critical shear bearing capacity ratio of the frame column to the infill wall. If the shear bearing capacity ratio is less than 2.0 and the shear span ratio of the column free segment is not more than 2.0, the short column effect will occur. For the infilled frame with flexible connection, both the lateral constraint from the wall to the column and the wall-frame interaction decrease; this reduces or prevents the short column effect. The conclusion can present guidance for the design and construction of masonry-infilled RC frame structure.

The development of the smart geosynthetics in recent years has shown tremendous potential with regard to its capability to strengthen geotechnical structures and, meanwhile, evaluate the local strains/stresses. This paper introduced the application of a distributed monitoring system to monitor a laboratory model slope reinforced with smart geogrids, in which the coherent optical frequency domain reflectometry technology (C-OFDR) was used to continuously monitor the geogrid deformations under different surcharge loadings. It showed that the measured results using C-OFDR technology were generally consistent to those from the fiber Bragg grating (FBG) sensors; however, C-OFDR has other significant advantages over the FBG technology. Empirical relationships between the geogrid characteristic strain measured by the C-OFDR sensors and the factor of safety calculated by the conventional limit equilibrium method were established, making it possible to use the geogrid characteristic strain to monitor the slope stability. This study proved the effectiveness of the distributed C-OFDR sensing technology in monitoring the geogrid-reinforced slope stability in the laboratory scale, a critical stepping stone to extend this technology to the field.

No abstract

No abstract

Multi-bolt shear connectors (MBSCs), arranging bolts as a group in several rows, can be applied in prefabricated steel–concrete composite beams or bridges (SCCBs) to reduce the construction time and meet the requirements of sustainable development. The mechanical behavior of bolt shear connectors has been broadly investigated in recent years, but they were mainly focused on the normal arrangement. The shear performance of MBSCs is not consistent with that of the same number of single bolts. In this study, a three-dimensional (3D) finite element model (FEM) was developed to investigate the multiple bolts effect and its mechanical performance. Material non-linearities and the interactions among all components were included in the FEM. The accuracy and reliability of the proposed FEM were initially verified against the available push-out test results. The validated FEM further studied the load–slip relationship, shear capacity, and shear stiffness of the MBSCs. A parametric study was carried out to determine the effect of the bolt spacing, bolt row numbers, the concrete strength, and the bolt diameter on the shear performance of MBSCs. Based on the extensive parametric analyses, design recommendations considering the multiple bolts effect for predicting the shear resistance per bolt in multi-bolt connectors were proposed and verified.