Plenary lectures


Prof. Guochang Li, Dean of the Faculty of Civil Engineering at Shenyang Jianzhu University,
Invited Lecture: Working mechanisms and design method of HCFHSST columns

Abstract of the presentation:  The utilisation of high-strength materials in concrete-filled steel tubular members represents an efficacious methodology for enhancing the ultimate bearing capacity of the member while concomitantly reducing cross-sectional dimensions and dead weight, which exhibits considerable promise for prospective applications. However, the extant codes do not adequately address the use of high-strength materials. It is therefore essential to conduct a comprehensive investigation into the working mechanism and loading performance of high-strength concrete-filled square high-strength steel tubular (HCFHSST) members, followed by a further revision of the design codes and an expansion the application scope these codes. In this study, an experimental investigation was conducted to analyse the damage modes of the HCFHSST members. A total of 146 HCFHSST specimens were tested, and the buckling development mechanism of the steel tube under different loads was determined. On this basis, a refined numerical model was established. The application scope of the conversion equation between yield strength and tensile strength of high-strength steel was modified, and a constitutive relationship for composite materials in HCFHSST members was formulated. Furthermore, the deformation evolution law, strain development law, balance point motion law, and steel-concrete contact pressure of the members were analysed throughout the entire loading process, thereby revealing the working mechanism and stress performance of HCFHSST members. Finally, the bearing capacity calculation equations and the simplified bearing capacity calculation formula for various basic members have been established, thereby satisfying the criteria for reliable indexes for ductility failure structural members as outlined in GB 50068-2018.


Prof. Borko BULAJIĆ, Faculty of Technical Sciences at the University of Novi Sad, Serbia,
Invited Lecture: Eurocode 8 and design response spectra: historical background, contemporary approaches, and prospects for the future

Abstract of the presentation:  In common seismic design applications, response spectra are a common means of specifying seismic action. According to Eurocode 8, every country may adopt its own elastic response spectrum form after defining it in the National Annex. Since such country-specific spectra should, if possible, be derived through analysis of the strong motion data recorded in the same seismo-tectonic region, the strong motion records currently available for the North-Western Balkan region are examined for several strong-motion recording sites. The results show that the shallow and deep geology conditions have a significant influence on the severity of surface strong ground motion. Moreover, it is demonstrated that the parameter that modifies the spectral amplitudes in relation to viscous damping is also dependent on the deep and shallow geology, and that it alters with vibration periods in a way that is comparable to the amplitudes of the pseudo-velocity spectra. Therefore, this parameter is neither independent of vibration periods nor amenable to being averaged over a large range of vibration periods. Lastly, it is shown that the uniform hazard spectra should be used directly to define the Eurocode 8 spectra, instead of scaling the spectra by just two spectral amplitudes (as has been recently proposed for the upcoming version of Eurocode 8) or scaling the normalized spectra by the peak acceleration values (which is the method still used).


Prof. Baoxin Qi,  School of Civil Engineering, Shenyang Jianzhu University, Liaoning Shenyang, China
Invited Lecture: Study on the Dynamic Compressive Mechanical Properties of PVA-basalt Fiber Concrete after Freeze-Thaw Circulation

Abstract of the presentation:  In order to study the static and dynamic mechanical properties of polyvinyl alcohol (PVA)-basalt fiber concrete after freeze-thaw damage under appropriate mixing ratios, as well as the enhancement mechanism of mixed fibers on the freeze-resistant properties of concrete, the quasi-static compression test and separated Hopkinson compression bar (SHPB) test were carried out for the PVA-basalt fiber concrete and ordinary C35 concrete treated with freezing and thawing cycles, respectively, for a controlled investigation. The degradation of mass loss rate and compressive strength of PVA-basalt fiber concrete under freeze-thaw cycle was investigated by quasi-static compressive test and separated Hopkinson compression bar (SHPB) test, to analyze the degradation of mass loss rate and compressive strength of PVA-basalt fiber concrete under freeze-thaw cycle, and to introduce "freeze-thaw degradation function C(n)" and dynamic increase factor (DIF), to establish a dynamic equation of compressive strength for the concrete by considering the double factors of strain rate effect and freeze-thaw damage. The results show that PVA-basalt fiber can well limit the freeze-thaw damage of concrete and the development of internal microcracks, the quality loss rate of PVA-basalt fiber concrete is 0.22% at 100 times of freezing and thawing, and only a slight spalling of the surface cement mortar and aggregate and a small amount of fiber exposure occurred; the static-dynamic mechanical test data were processed and analysed, and it was found that the mixed fiber of PVA-basalt has a significant influence on the Concrete compressive mechanical properties after freezing and thawing damage has a significant improvement, slowing down the decay rate of static and dynamic compressive strength; PVA-basalt fiber concrete after freezing and thawing still has a significant strain rate effect, the use of dynamic compressive strength formula obtained from the theoretical value and the experimental value of the good degree of agreement, which verifies the reliability of the calculation model, the formula to a certain extent for the preliminary estimation of PVA-basalt fiber concrete in any freezing and thawing damage. To a certain extent, this formula provides a convenient means to preliminarily predict the dynamic compressive strength of PVA-basalt fiber reinforced concrete under freeze and thaw damage at high strain rate.


Prof. Ercan IŞIK,  Civil Engineering Department in Bitlis Eren University, Türkiye
Invited Lecture:  Effects of the 2023 Destructive Türkiye Earthquakes on R/C Structures in Kahramanmaraş
Abstract of the presentation:  Two independent and very destructive earthquakes occurred with epicentres of Pazarcık (Mw=7.7) and Elbistan (Mw=7.6) with an interval of 9 hours in same day. Kahramanmaraş suffered major structural destruction and thousands of casualties, which was the epicentres of the February 6, 2023 Earthquakes, which was the disaster of the century for Türkiye. A large part of the province is located directly on the Eastern Anatolian Fault Zone, which is one of the main tectonic elements of Türkiye, has very high seismic risk. Various levels of destruction and damage have occurred in reinforced concrete (R/C) structures, which are the dominant urban building stock in Kahramanmaraş province and districts. The main earthquakes and the subsequent aftershocks were negatively affected the damage level in R/C buildings with low earthquake performance. The structural damages in R/C structures in Kahramanmaraş and districts as a result of field observations were evaluated within the scope of civil-earthquake engineering within the scope of this study. Incomplete or non-existent application of earthquake resistant building design principles during the design and construction phase, inadequate R/C and structural irregularities have been determined as the main causes of damages. In this study, the effects of transverse reinforcement’s space were also tried to be revealed by performing structural analyses for a sample R/C structure.

Assoc. Prof. Zihao Zhao,  School of Civil Engineering, Shenyang Jianzhu University, Liaoning Shenyang, China
Invited Lecture:  Ultimate horizontal soil resistance of multi-pile foundations in clay considering the strain softening effect.
Abstract of the presentation: Multi-pile foundation is an important foundation form for offshore wind turbines in water depths of 40-100m due to its advantages of high lateral stiffness and strong ability of anti-overturning. However, the mechanism of pile-soil interaction and the analysis method of soil resistance of multi-pile foundation under horizontal loads still lag behind the requirement of engineering application. Therefore, this talk has introduced researches on the horizontal loading problems of multi-pile foundations in soft clay in the following two aspects: (1) Based on the upper bound theory of limit analysis, different types of horizontal failure mechanisms considering the weakening on the interface were constructed, and the theoretical upper bound solutions for the ultimate soil resistance of the multi-pile foundation were obtained via the optimized calculations. (2) By utilizing the ABAQUS vumat subroutine, the constitutive model considering the strain softening feature of soft clay was embedded into the finite element analysis model of a multi-pile foundation. The effects of soil parameters, interface parameters, and size of foundation model on the horizontal soil resistance distribution and soil resistance of the multi-pile foundation were systematically discussed. It was found that the strain softening feature of the soil around the pile have a significant impact on the soil resistance of the foundation. When considering the weakening of the soil strength, the soil resistance factor of the multi-pile foundation will decrease by about 1/3; The relationship between the soil strain rate parameter and the ultimate soil resistance shows a linear positive correlation; The soil sensitivity parameters have a more significant impact on the horizontal soil resistance and ultimate soil resistance of the foundation than the cumulative plastic strain parameters of the soil.

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