Preliminary study of internal impact on metal silo for granular solids under seismic loading

Silo is an economical design for storing large quantities of granular solids or fluids. A smaller silo structure is often built with a cylindrical steel shell and several local brackets. For such a structure installed in seismic zone, it has to resist to external excitation and internal impact from media. Since buckling is one of the main failure type of silo, researches focus often on the Finite Element Analysis (FEA) of an empty steel container under earthquake. The dynamic behavior of internal granular solids under seismic loading is close to liquid flow, and the impact force of the internal media on silo wall is related to its dynamic liquid pressure. That is, the silo-granular solid system is a complex structure-granular media interaction system. In this study, the Discrete Element Analysis (DEA) was used to evaluate the influence of internal granular solids on the shell wall of silo structure. After systematic verifications, it has been shown that the DEA is feasible on research for more detailed simulations of silo with granular solids under seismic loading

Performance analysis of Reinforced Polymer Cement Mortars "RPCMs" used for repairing concrete structures

Concrete structures operating under different environmental conditions are subject to the action of aggressive gaseous and liquid media, which leads to their degradation and even collapse. Even well-designed buildings, after time, can have problems to fulfil appropriate requirements concerning their further service life. In such case, the structures need renovation. Fiber reinforced mortars based on cement modified with different types of polymers are commonly used materials for renovating concrete structures. The materials are called “Reinforced PCMs” or “RPCMs”. According to current standards, repair materials should fulfil requirements concerning their high adhesion to mineral substrate, minimum tensile strength, compatibility with repaired concrete and low shrinkage. The aim of the work was to compare the performance of three reinforced PCMs based on various polymers. The following features were tested: adherence to concrete substrate, shrinkage and flexural strength. Moreover, Scanning Electron Microscopy was used to observe the interfacial transition zones among the old concrete, a bonding slurry and repair material

Bending tests to estimate the axial force in steel bridge members

This work compares two nondestructive static methods used for the axial load assessment in prismatic steel bridge members. Examples include the struts and ties or the tension chords and diagonal braces of truss bridges. The first method requires knowledge of the member’s flexural rigidity under investigation, whereas the second requires knowledge of the corresponding Euler buckling load. In both procedures, short-term flexural displacements must be measured at the given cross sections along the member under examination and subjected to an additional transverse load. The proposed methods were verified by numerical and laboratory tests on beams of a small-scale space truss bridge prototype made from aluminum alloy and rigid connections. In general, if the higher second-order effects are induced during testing and the corresponding total displacements are accurately measured, it would be easy to obtain tensile and compressive force estimations

Review on prestress loss evaluation in concrete beams

In the last few decades, prestressing techniques have been used to build very important structures, infrastructures, and bridges. Since the serviceability and the safety of prestressed concrete members rely on the effective state of prestressing, development of tools and dynamic procedures capable of estimating the effective prestress loss have been widely carried on. Amongst other techniques, static identification using second-order deflections has proved to be an accurate and reliable method to evaluate prestress loss. This paper represents a review of some important research works on prestress loss evaluation in concrete beams presented in the literature. Comments and recommendations will be made at proper places, while concluding remarks including future research directions will be presented at the end of the paper

An investigation into the dynamic and static response of an uncracked prestressed concrete bridge member in Taiwan

The influence of prestress force on the fundamental frequency and static deflection shape of an uncracked Prestressed Concrete (PC) bridge beam made in Taiwan was examined in this work. In literature, due to the conflicts among existing theories, the models for properly considering the dynamic and static response of these members is not straightforward. A set of experiments were conducted for a total period of approximately 2.5 months on a PC beam prototype composed of a high strength concrete made in Taiwan, subsequently and closely to the 28 days of concrete age. In specific, the simply supported PC specimen was short term subjected to free transverse vibration and three-point bending tests during its early-age. Subsequently, the experimental data were compared with a solution that represents the dynamics of PC girders as a combination of two substructures interconnected, i.e., a compressed Euler–Bernoulli beam and a tensioned parabolic cable. It was established that the fundamental frequency of uncracked PC bridge beams in Taiwan is sensitive to the variation of their initial elastic modulus in the early-age based on Model B4-TW. Moreover, the small variation in experimental frequency with time makes doubtful its use in inverse problem identifications. By contrast, the relationship between prestress force and static deflection shape is properly described by the magnification factor formula of the “compression-softening” theory by assuming the variation of the chord concrete elastic modulus with time. The obtained results are proper information for developing the patent of a nondestructive method for prestress loss prediction in PCI bridge beams in Taiwan based on static deflection measurements

Influence of prestressing on the behavior of uncracked concrete beams with a parabolic bonded tendon

The influence of prestress force on the fundamental frequency and static deflection shape of uncracked Prestressed Concrete (PC) beams with a parabolic bonded tendon was examined in this paper. Due to the conflicts among existing theories, the analytical solutions for properly considering the dynamic and static behavior of these members is not straightforw ard. A series of experiments were conducted for a total period of approximately 2.5 months on a PC beam made with high strength concrete, subsequently and closely to the 28 days of age of concrete. Specifically, the simply supported PC member was short term subjected to free transverse vibration and three point bending tests during its early age. Subsequently, the experimental data were compared with a model that describes the dynamic behavior of PC girders as a combination of two substructures interconnected, i.e., a compressed Euler Bernoulli beam and a tensioned parabolic cable. It was established that the fundamental frequency of uncracked PC beams with a parabolic bonded tendon is sensitive to the variation of the initial elastic modulus of concrete in the early age curing. Furthermore, the small variation in experimental frequency with time makes doubtful its use in inverse problem identifications. Conversely, the relationship between prestress force and static deflection shape is well described by the magnification factor formula of the “compression softening ” theory by assuming the variation of the chord elastic modulus of concrete with time

Prestress force prediction in concrete bridge beams with a parabolic tendon using compression-softening theory

The deflected shape of a post–tensioned concrete beam with a parabolic tendon, subjected to an additional vertical load, was short-term measured in several laboratory experiments. The “compression–softening” theory was applied in this study. Currently, due to the conflicts among existing theories, the analytical solution for properly considering the structural behavior of these prestressed members is not clear. Thus, more ways had been tried to make the analytical displacements more similar to the experimental displacements. Furthermore, according to the “compression-softening” theory, Song’s formula (2000) was applied on the concrete beam with a parabolic tendon. Finally, after all these modifications, it has been possible to predict the flexural displacements for the concrete beam with a parabolic tendon

Axial load identification of a slender pre-stressed concrete beam

The paper brings out the axial load identification of a slender pre-stressed concrete beam by applying a concentrated load and measuring the flexural displacements in different points of the beam span under investigation, by using optical and dial gauge sensors system. The Simplified Formula and the Tullini’s formula [Tullini, 2013] are the non-destructive methods for the axial load identification which can be found in the paper. A 3D Frame and a 3D Bridge prototype were used to verify the accuracy of the two non-destructive procedures

Health monitoring on a repaired earthquake damaged bridge by optic fiber differential settlement sensors

This paper is about the design and application of optical-fiber differential settlement measurement (DSM) sensor for bridges. By using the law of connected vessels, bouncy principle, forces equilibrium condition, and the photo elasticity of Fiber Bragg Grating (FBG), the DSM sensor is easily manufactured and sensitive to the level change. Besides the design principle, this study illustrates the application of the DSM sensors on underpass bridges. From the field case, it is shown that the proposed DSM sensors are stable and precise to monitor the behavior of multiple-span underpass bridges. In this paper, to share the optical fiber DSM field-experience is the aim of this study. Based on the field experience, enhancement design for the DSM sensor will be discussed for the future application