Structural and Thermal Performance of a Novel Form of Cladding Panel: the I-beam Beetle Elytron Plate

To develop a nonbearing prefabricated straw sandwich concrete wallboard (I-beam beetle elytron plate: IBEPsc), the effect of certain structural parameters (e.g., panel thickness T, number of I-cores N and core height h) on the mechanical and thermal insulation performance was investigated by using the finite element method. The results are as follows: 1) The bearing capacity of the IBEPsc is controlled by the maximum principal tensile stress; the optimal structural parameters of the IBEPsc for a self-insulated wall with a large safety margin are presented. 2) The consideration of strips vs. whole plates and the selected upper bearing constraint type have little influence on the mechanical properties. In practical applications, the strips and whole plates can be reasonably selected according to engineering needs, and these components can be connected with the main structure by conventional mortar. 3) According to a qualitative analysis and comparison with common I-shaped thermal insulation walls, the IBEPsc requires the least material and weight while ensuring a sufficient safety margin in terms of mechanical and thermal insulation performance. Hence, biomimic techniques can play a key role in breaking through the limitations of traditional structures. This paper can help direct the application of beetle elytron plates in prefabricated wallboards.

Numerical Study on Failure Mechanisms of Shaft Wall Consisting of Steel Plate and Concrete under the Effects of Explosion

To enhance the antidynamic and static load resistance of reinforced concrete structures, the measure of covering steel plates on the inner surface of concrete structures arises, which has been rapidly developed and applied in civil engineering and other fields and has achieved a good performance. A new shaft wall structure consisting of steel plate reinforced concrete has been widely used in shaft of deep mining. In order to investigate the stability and obtain the optimum structure parameters of the new shaft structure, the numerical software of LS-DYNA was used to analyze the influences of different factors, including the explosive payload, steel plate thickness, concrete strength grade, and the included joint angle between two plates, on the stability of steel plate reinforced concrete structures. After the verification of the accuracy of numerical simulation results, 23 simulation schemes were proposed and numerically calculated. For all the tests, the principal tensile stress and particle vibration velocity were, respectively, chosen as the failure criteria to evaluate the impacts of those four factors. The results indicate that a quadratic function can be well used to describe the relationships between each factor and both the principal tensile stress and particle vibration velocity. Based on the results, the optimum structure parameters were finally determined, which are suggested as 250 kg, 15 mm, C85, and 40° for the explosive payload, steel plate thickness, concrete strength grade, and joint angle, respectively. The research results can provide a certain theoretical basis and design guidance for solving the problem of water leakage of single-layer shaft wall structures.

Concrete Protective Layer Cracking Caused by Non-Uniform Corrosion of Reinforcements

The volume expansion of reinforcement corrosion products resulting from the corrosion of steel reinforcement embedded into concrete causes the concrete’s protective layer to crack or spall, reducing the durability of the concrete structure. Thus, it is necessary to analyze concrete cracking caused by reinforcement corrosion. This study focused on the occurrence of non-uniform reinforcement corrosion in a natural environment. The characteristics of the rust layer were used to deduce the unequal radial displacement distribution function of concrete around both angular and non-angular bars. Additionally, the relationship between the corrosion ratio and the radial displacement of the concrete around the bar was established quantitatively. Concrete cracking due to the non-uniform corrosion of reinforcements was simulated using steel bars embedded in concrete that were of uneven displacement because of rust expansion. The distribution of the principal tensile stress around the bar was examined. A formula for calculating the critical radial displacement at the point when cracking began was obtained and used to predict the corrosion ratio of the concrete cover. The determined analytical corrosion ratio agreed well with the test result. The effect factor analysis based on the finite element method indicated that increasing the concrete strength and concrete cover thickness delays concrete cracking and that the adjacent rebar causes the stress superposition phenomenon.

Strengthening of seismically deficient exterior beam-column connections using embedded steel bars

Several techniques for improving performance of reinforced concrete (RC) beam-column (BC) connections have been developed in last two decades, but these techniques have been criticized for being labourintensive and susceptible to premature de-bonding. To overcome these shortcomings, a novel technique utilising embedded steel bars has been developed in this study for strengthening seismically deficient RC BC connections. This technique involves drilling holes within the joint core. After the drilled holes are cleaned, they are partially filled with epoxy. Finally, steel bars are inserted in the epoxy-filled holes. Two exterior BC connections were constructed and loaded under displacement-controlled cyclic loading. The first specimen was a control specimen designed in accordance with the pre-1970s building codes to represent BC connections requiring strengthening. The second specimen was strengthened with eight 8 mm steel bars embedded within the concrete core in the joint area and epoxied to maintain the bond between the concrete and the steel bars. The strengthened specimen had superior performance compared to that of the control specimen in terms of joint shear stress, normalised principal tensile stress demand and stiffness degradation. The results show that shear stress of the joint was enhanced by about 8% whereas the enhancement in the principal tensile stress demand was 24% compared to that of the control specimen. The results showed that the proposed technique is capable in upgrading the seismic performance of seismically deficient RC BC connections.

Analysis on stress state of box-girder web under prestressing effect

In order to study the effect of prestressed box girder webs stresss state, determining the stress distribution within a web, research and analysis of vertical prestressed box girder, curved beam prestressed sensitivity under the web. Establishing the finite element model of the box girder web vertical prestressing effect is analyzed, results show that the principal tensile stress of the web is sensitive to the vertical prestress, applying the vertical prestress can effectively reduce the principal tensile stress of the web; with the decrease of the effective vertical prestress, the neutral axis above the principal compressive stress decreases rapidly, while below the neutral axis decreases relatively slow; Under the same vertical preloading stress level, the roots of cross section of the compressive stress of web reserves than L / 4 section of the web. Calculation and analysis of curved beam under bending point, different bending angles and bending radius of principal stress effect on the web, Results show that the set of curved beam web when the curved beam bending stress concentration easily, appear the main tensile stress; Increase the bending radius can effectively reduce beam cross-section of web principal tensile stress, along with the rising of the next corner, principal tensile stress peak value increases gradually, thus setting bending beam, should try to reduce the bending angle.

Fatigue Evaluation of Trough Splice Joints in Orthotropic Steel Decks

Fatigue tests for full-scale orthotropic steel decks were conducted to evaluate and validate the fatigue performance of welded and bolted splice joints of longitudinal ribs. The test results indicated that the fatigue properties of two splice joints met the design requirements. The bolted splice joints whose principal tensile stress was largely lower than welded splice joints under the same loading conditions appeared to have superior fatigue resistance to the welded one. No fatigue cracks were detected among all the specimens and the principal tensile stress of measuring points had few changes during the whole fatigue tests. Systematic analysis of test data showed that bolted splice joints appeared to be more reasonable for improving the fatigue performance of longitudinal ribs.

Analysis on Stress State of Box-Girder Web under Prestressing

In order to study the stress of box-girder web under prestressing, and confirming the internal stress distribution of the web, analyzing of vertical prestressed box girder, curved beam prestressed sensitivity under the webs. Establishing finite element model of the box-girder webs vertical prestressing effect is analyzed, results show that the principal tensile stress of the web is sensitive to the vertical prestress, applying the vertical prestress can effectively reduce the principal tensile stress of the web; with the decrease of the effective vertical prestress, the neutral axis above the principal compressive stress decreases rapidly, while below the neutral axis decreases relatively slow; Under the same vertical preloading stress level, the roots of cross section of the compressive stress of web reserves than L/4 section of the web.

Analysis of the Arrangement of Prestressed Steel in Web of Continuous Concrete Box-Girder Bridges

Concrete continuous box- girder bridges have a large proportion in small span and long span bridges, and it has very broad prospects for development. Along with the large-scale construction of this kind of bridge, various problems have also emerged, especially the damage of RC beam’s diagonal section in bridge girder deflection. It always appears the inclined cracks in webs which cause by principal tensile stress, so it will be the potential damage to the whole bridge. However, the existence of the vertical prestress, will make the principal tensile stress of box girder in greatly reduced. So as to make cracking resistance performance of diagonal section is better than the ordinary reinforced concrete bridge. For an engineering example, this paper puts forward several different vertical prestressed steel arrangements. Based on different decorate a form of vertical pretressd bridge girder under stress numerical simulation, it is concluded that bridge’s web principal tensile stress distribution and its variation law, and then optimize the vertical reinforcing steel arrangement, improve the overall safety of bridge structure. It can provide the reference in the process of construction when we face the similar problems in the future.

Seismic Affection Analysis of Weir Dam Based on 3-D FEM

The vibrant-type-disintegration method is applied to calculate structure seismic action of a weir dam. Based on calculation and analysis of the weir dam, special attention is paid to the stress state of key parts. The results show that the displacement and stress of weir dam are affected by earthquake excitation direction. Since large principal tensile stress appears in the joint of girder and pier, and the zone of principal tensile stress is large because of the thrust of radial gate and steep changes of geometry shape, we should pay special attention when calculating anti-seismic checking and reinforcement arrangement.

Seismic Behavior Analysis of Spillway Weir Section Based on ANSYS

The response spectrum method was applied to calculate the seismic behavior analysis of a spillway weir gate. Based on the analysis of the structure performance, special attentions were paid to the stress state of the key parts on the surface and root of the pier. The results showed that the displacement and stress of the whole structure were related to the direction of earthquake excitation; large principal tensile stress and principal tensile stress area appeared in steep change points of geometry shape, special attention should be paid when calculating anti-seismic checking and reinforcement arrangement; the displacement and stress of the weir section met the standard requirements.