Experimental study on spalling risk of concrete with 115~120MPa subject to ISO834 Fire

[EN] High strength concrete encased columns are being developed for erecting high-rise buildings as their higher load bearing capacity and smaller cross section size than normal concrete encased column. At ambient temperature, high strength concrete is always mixed with steel fibers to improve its ductility to match the material properties of high strength steel while constructing concrete encased columns. However, for high strength concrete at elevated temperature, spalling usually can be observed due to different thermal properties of various materials mixed such as siliceous aggregate, cement, silica fume, grit and moisture. Most of previous studies present that pore vapor compression induces high strength concrete spalling and propylene fiber can prevent it from spalling. The aim of the present experimental study is to discover the minimum propylene fiber ratio to prevent spalling of 115~120MPa concrete with aggregate and steel fiber. The experimental study carried out on 17 specimens with different water-binder ratio, steel fiber ratio and monofilament propylene fiber ratio exposed to ISO834 fire. The test results that 0.15% by volume of propylene fibers can prevent 115/120MPa high strength concrete with aggregate from spalling. It is worth noting that propylene fiber mixture ratio of 0.15% is lower than that of EN 1992-1-2 proposed up to 0.22%. Lower propylene fiber mixture ratio has been soak to improve the workability of 115~120MPa high strength concrete with steel fibers.The authors gratefully acknowledge the financial support of the International Structural Fire Research Laboratory (ISFRL) in Nanjing Tech University, China.Du, Y.; Zhu, Y.; Liew, R. (2018). Experimental study on spalling risk of concrete with 115~120MPa subject to ISO834 Fire. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 857-861. https://doi.org/10.4995/ASCCS2018.2018.7024OCS85786

Steel Concrete Composite Systems for Modular Construction of High-rise Buildings

[EN] Modular construction has gained popularity and attention particularly in low-rise building lately due to its numerous advantages: faster construction speed, better quality control, reduction in work force and construction waste, etc. This innovative technology promotes off-site manufacturing of modular units and on-site assembly, improving the construction efficiency and productivity. However, modular construction is not commonly used in high-rise buildings because of the joints’ flexibility as well as manufacturing and construction tolerance, which have significant impact on the overall stability of the building. This paper highlights the existing challenges of modular construction of high-rise buildings and provide several options to address these challenges. Firstly, the weight of a module is constrained by the transportation and lifting crane capacities. For this reason, lightweight concrete is introduced together with structural steel section to form lightweight steel-concrete composite system to reduce the weight of the module without compromising the strength and stiffness. Secondly, to speed up the site assembly of modular units, special joints are developed to resist the forces due to gravity and horizontal loads. Fast and easy joining techniques with acceptable tolerance control are essential to ensure the structural integrity and stability of the building. Finally, the innovation for productivity can be maximized by implementing automation technologies in the manufacturing and construction of the modular units.The authors would like to acknowledge the financial support by the National Research Foundation (NRF) and SembCorp-NUS Corp Lab under project grant R-261-513-009-281.Liew, R.; Dai, Z.; Chau, YS. (2018). Steel Concrete Composite Systems for Modular Construction of High-rise Buildings. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 59-65. https://doi.org/10.4995/ASCCS2018.2018.7220OCS596

Strength of concrete-filled steel box columns with local buckling effects

The key aspects and features of a nonlinear fiber element analysis method for predicting the strength and behavior of concrete-filled steel box columns with local buckling effects are discussed. The methods is quite useful in predicting the ultimate strengths and behavior of concrete slabs and can also be employed in the advanced analysis of composite frames

Robustness of Prefabricated Prefinished Volumetric Construction (PPVC) High-rise Building

[EN] Due to the safety awareness arisen from natural and human-caused disasters, robustness design of building is increasingly important to ensure the stability of the building and to prevent progressive collapse. For this reason, the robustness design of innovative construction technologies such as modular construction may be essential due to its relative novel structural form and numerous joints among modules. Particularly in Singapore, Prefabricated Prefinished Volumetric Construction (PPVC) has been highly promoted in residential and commercial buildings, hostels and hospitals to boost the construction productivity and quality as well as to reduce the reliance on foreign workforce. PPVC offers high quality and efficiency because most of the finishes and mechanical and electrical services are manufactured and installed together with the modules in factory, before sending for on-site assembly. To maximize the productivity of PPVC, modular design standardization and repetition can be improved by going for high-rise. Nonetheless, there are limited studies on the robustness of PPVC high-rise building and its behavior under progressive collapse remains uncertain. Therefore, this paper investigates the robustness of steel PPVC high-rise building under column removal scenarios by conducting non-linear numerical analysis. The effects of joint design and diaphragm action between modules are studied to ensure continuity of horizontal and vertical tying. This paper provides insight on the behaviour and alternative path for load transfer under column removal scenario for future design guideline of robustness PPVC building.The authors would like to acknowledge the financial support by the National Research Foundation (NRF) and SembCorp-NUS Corp Lab under project grant R-261-513-009-281Chua, YS.; Liew, JYR.; Pang, SD. (2018). Robustness of Prefabricated Prefinished Volumetric Construction (PPVC) High-rise Building. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 913-919. https://doi.org/10.4995/ASCCS2018.2018.6955OCS91391

Buckling Resistance of Axially Restrained Chord Members of Grid Structure at Elevated Temperatures

This paper investigates the behavior of large span grid structure exposed to a localized fire. The localized fire may generate hot smoke and thus induce non-uniform temperature distribution in the grid structure. The thermal expansion of the heated members tend to be axially restrained by the adjacent cold members thus inducing additional forces on the critical members of the grid structure. The buckling resistance of axially restrained member at elevated temperature may be obtained based on second order analysis of member with initial lateral imperfection by considering force equilibrium at deformed geometry and cross section resistance being reached. The critical temperature of the member is reached when the axial force reaches its buckling resistance. It is found that the critical temperature of members with initial lateral imperfection was higher than that without such imperfection for chord members with large slenderness ratio and high axial restraint

Dense and accurate motion and strain estimation in high resolution speckle images using an image-adaptive approach

Digital image processing methods represent a viable and well acknowledged alternative to strain gauges and interferometric techniques for determining full-field displacements and strains in materials under stress. This paper presents an image adaptive technique for dense motion and strain estimation using high-resolution speckle images that show the analyzed material in its original and deformed states. The algorithm starts by dividing the speckle image showing the original state into irregular cells taking into consideration both spatial and gradient image information present. Subsequently the Newton-Raphson digital image correlation technique is applied to calculate the corresponding motion for each cell. Adaptive spatial regularization in the form of the Geman-McClure robust spatial estimator is employed to increase the spatial consistency of the motion components of a cell with respect to the components of neighbouring cells. To obtain the final strain information, local least-squares fitting using a linear displacement model is performed on the horizontal and vertical displacement fields. To evaluate the presented image partitioning and strain estimation techniques two numerical and two real experiments are employed. The numerical experiments simulate the deformation of a specimen with constant strain across the surface as well as small rigid-body rotations present while real experiments consist specimens that undergo uniaxial stress. The results indicate very good accuracy of the recovered strains as well as better rotation insensitivity compared to classical techniques

Simulation of impulsive loading on column using inflatable airbag technique

The purpose of this study was to simulate impulsive loading on columns by an innovative lab-based experimental technique that utilises inflatable airbags. Mild and stainless steel hollow sectioin columns with effective lengths of 955mm and under simply supported condition were used in this study

Stability of cenospheres in lightweight cement composites in terms of alkali-silica reaction

10.1016/j.cemconres.2012.02.010Cement and Concrete Research425721-72

Polygenic Sex Determination System in Zebrafish

Contains fulltext : 94011.pdf (publisher's version ) (Open Access

Behavior of steel-concrete-steel sandwich structures with lightweight cement composite and novel shear connectors

10.1016/j.compstruct.2012.05.023Composite Structures94123500-350