Thermal structure of continental subduction zone: high temperature caused by the removal of the preceding oceanic slab

The thermal structure of the continental subduction zone can be deduced from high-pressure and ultra-high-pressure rock samples or numerical simulation.However,petrological data indicate that the temperature of subducted continental plates is generally higher than that derived from numerical simulation.In this paper,a two-dimensional kinematic model is used to study the thermal structure of continental subduction zones,with or without a preceding oceanic slab.The results show that the removal of the preceding oceanic slab can effectively increase the slab surface temperature of the continental subduction zone in the early stage of subduction.This can sufficiently explain the difference between the cold thermal structure obtained from previous modeling results and the hot thermal structure obtained from rock sample data.

Experimental study of human-induced effects on floor slab of an ancient Tibetan structure

With the opening of ancient Tibetan structures to visitors worldwide, human load has become the principal live load on these structures. This project studies the properties of the floor structure of an ancient Tibetan building and its behavior under human-induced load effects. Tests were conducted with static and dynamic crowd load, including stepping and jogging by people at a fixed position. The tests show that the floor structure does not behave as a continuous slab. It takes the load from local areas with minimal load transference properties. The acceleration response shows significant peaks when the footstep frequency is close to the natural frequency of the s~＇ucture, but the human jogging excitation frequency does not have any obvious effect on the structural response. The elastic modulus of the Agatu material is estimated to be close to zero from the measured natural frequency of the slab. The Agatu material is concluded to be a discrete compacted material with insignificant contribution to the structural rigidity of the floor slab.

Effect of cooling structure on thermal behavior of copper plates of slab continuous casting mold

A three-dimensional finite-element model of slab continuous casting mold was conducted to clarify the effect of cooling structure on thermal behavior of copper plates. The results show that temperature distribution of hot surface is mainly governed by cooling structure and heat-transfer conditions. For hot surface centricity, maximum surface temperature promotions are 30 ℃and 15 ℃ with thickness increments of copper plates of 5 mm and nickel layers of 1 ram, respectively. The surface temperature without nickel layers is depressed by 10 ℃ when the depth increment of water slots is 2 mm and that with nickel layers adjacent to and away from mold outlet is depressed by 7℃ and 5 ℃, respectively. The specific trend of temperature distribution of transverse sections of copper plates is nearly free of cooling structure, but temperature is changed and its law is similar to the corresponding surface temperature.

Study Segregation of Alloying Elements in Continuous Casting Slab with Valence Electron Structure

By calculating the electron structures of the phases that phosphor, sulfur and alloying elements dissolving inγ-Fe, the reason why alloying elements can bring centerline segregation in continuous casting slab (CCS) with nA, the number of electrons on the strongest covalent bonds, and the structure formation factor S were investigated, and an electron structural criterion to control and to eliminate the centerline segregation was advanced. Basing on this, the electron structures of a part of rare earth phosphides and sulfides are calculated, the physical mechanism that rare earth elements can control the segregation of phosphor and sulfur is analyzed, and the criterion is well verified.

Study of Suitability of Out-of-Codes Tall Slab-Column and Shearwall Structure

The purpose of this paper is to discuss the suitability of out-of-codes tall slab-column and shearwall structure and to popularize the structure in seismic region.In the research,flat-plate floor was used in slab-column and shearwall structure in the practical engineering,the key parameters of slab-column and shearwall structure and frame-shearwall structure such as deflection,punching shear behavior,story drift and capability curve were worked out by static plastic analysis,elastic-plastic time history analysis and pushover analysis,then the suitability of out-of-codes tall slab-column and shearwall structure was evaluated.The results show that the out-of-codes tall slab-column and shearwall structure studies could satisfy the require of deflection and punching shear behavior,the story drift under 7 degree expected rare earthquake waves could satisfy the limit value in the codes and the seismic design spectrum was crossed by the capability curve of the structure and the structure could not collapse.The conclusion is that slab-column and shearwall structure with reasonable design built in Ⅱ soil site of intensity 7 seismic fortification zone can be designed higher than the limit height in the codes.

Effects of edge beams on mechanic behavior under lateral load in reinforced concrete hollow slab-column structure

In order to get the formulae for calculating the equivalent frame width coefficient of reinforced concrete hollow slab-column structures with edge beam,the finite element structural program was used in the elastic analysis of reinforced concrete hollow slab-column structure with different dimensions to study internal relationship between effective beam width and the frame dimensions.In addition,the formulas for calculating the increasing coefficient of edge beam were also obtained.

Exploring the Synergy: Experimental and Theoretical Investigation of Steel and Glass Fiber Reinforced Polymer (GFRP) Reinforced Slab Incorporating Alccofine and M-Sand

Introduction: This study investigates the Experimental and Theoretical Investigation of Steel and Glass Fiber Reinforced Polymer (GFRP) Reinforced Slab Incorporating Alccofine and M-sand. Objective: Specific objectives include evaluating the mechanical properties and structural behaviour of steel and GFRP-reinforced one-way slabs and comparing experimental and theoretical predictions. Methods: Four different mix proportions were arrived at, comprising both conventional concrete and Alccofine-based concrete. In each formulation, a combination of normal river sand and M-sand was utilized. Results: Concrete with Alccofine exhibits superior mechanical properties, while M-sand incorporation minimally affects strength but reduces reliance on natural sand. GFRP-reinforced slabs display distinct brittle behaviour with significant deflections post-cracking, contrasting steel-reinforced slabs’ gradual, ductile failure. Discrepancies between experimental data and design recommendations underscore the need for guideline refinement. Conclusion: Alccofine and M-sand enhance concrete properties, but reinforcement type significantly influences slab behaviour. GFRP-reinforced slabs, though exhibiting lower values than steel, offer advantages in harsh environments, warranting further optimization.

Comparative Study between Waffle and Solid Slab Systems in Terms of Economy and Seismic Performance of a Typical 14-Story RC Building

In order to maximize the return of investments and at the same time improve the quality in the construction industry of midrise buildings, it is very important to derive an optimal solution to the building structural system, which would facilitate faster and easier construction activities with minimal quantity of construction material, while maintaining the satisfactory level of building safety and performance. This paper makes a comparative study between a ＂solid＂ and a ＂waffle＂ slab system. A typical 14-story RC building structure is selected as an example for this study purpose. The first part of this study is focused in deriving an optimal solution for a solid and waffle slab system which are later on considered as constituents of all stories of the 14-story building. In the second part, it is elaborated the effect of both slab systems over the 14-story building model. This study aims to emphasize the advantages of mid-rise buildings constituted of waffle slab system over the buildings characterized with solid types of slabs, in terms of economy, structural safety and performance.

Hydrodynamic Conditions in Front of a Vertical Wall with an Overhanging Horizontal Cantilever Slab

Transforming wave heights from offshore to the shoreline is the first step of any coastal engineering work. Wave breaking is analyzed to understand hydrodynamic conditions. For vertical breakwaters and sea walls, wave reflection is an important process that affects the determination of the wave height. Many of the design formulas presented in the literature depend on empirical studies based on the structures tested. In this study, the hydrodynamic conditions in front of a vertical wall with an overhanging horizontal cantilever slab with a foreshore slope of 1/20 are determined experimentally under regular wave conditions to assess the applicability of the formulas of Goda(2000) for predicting the nearshore wave height and breaker index equation(Goda, 2010). The selection of wave measurements used to determine the design wave height, the reflection coefficients, and wave breaking is also analyzed, and the reflection equations are derived from the dataset covering different breaker types. Small-scale tests show that the incident wave height is a good representative of the design wave height and that the values predicted by Goda are in good agreement with actual measurements. However, the predicted Hmax values are overestimated. In addition, the inception of the wave breaking point is postponed because of the reflection and/or turbulence left over from preceding waves, which is an effect of the vertical wall. At higher water levels, the effect of the vertical wall on the inception point becomes more significant.

NONLINEAR ANALYSIS OF REINFORCED CONCRETE RECTANGULAR SLABS USING FINITE ELEMENT METHOD

The nonlinear analysis of reinforced concrete rectangular slabs undermonotonic transverse loads is performed by finite element method.The layered rectangu-lar element with 4 nodes and 20 degrees of freedom is developed,in whichbending-stretching coupling effect is taken into account.An orthotropic equivalentuniaxial stress-strain constitutive model of concrete is used.A program is worked out andused to calculate two reinforced concrete slabs.The results of calculation are in goodconformity with the corresponding test results.In addition,the influence of tension stif-fening effect of cracked concrete on the results of calculation is discussed.

Analysis of vibration reduction characteristics and applicability of steel-spring floating-slab track

A coupled dynamics computation model for metro vehicles, along with a steel-spring floating-slab track, is developed based on the theory of vehicle-track coupled dynamics. Using the developed model, the influences of the thickness, length and mass of floating-slab, spring rate and its arrangement space, running speed, etc. on the time and frequency domain characteristics of steel-spring fulcrum force are analyzed. The applicability of steel-spring floatingslab track is discussed through two integrated example cases of metro and buildings possessing distinct natural vibra- tion characteristics. It is concluded that, it is quite significant, in the optimization modular design of the parameters of steel-spring floating-slab track, to take the matching relationship of both the amplitude-frequency characteristics of steel-spring fulcrum force and natural vibration characteristics of integrated structures into comprehensive consideration. In this way the expensive steel-spring floating-slab track can be economically and efficiently utilized according to the site condition, and at the same time, the economic losses and bad social impact resulted from the resonance during usage of steel-spring floating-slab track can be avoided.

Study on the Distribution Law of Horizontal Seismic Forces between Slab-Column and Shear Wall

In slab column-shear wall structures,both the whole structure′s seismic behavior and failure mode are greatly influenced by the distribution of horizontal seismic forces between slab-column and shear wall.In this paper,a pushover analysis of topical slab column-shear wall structure was carried out,the seismic shear force that the slab-column and shear wall should undertake was worked out,the influences of plastic internal force redistribution and structure stiffness characteristic value on horizontal seismic distribution were studied and the calculation formula was given.The analysis results showed that with the yield of the shear walls,the story shear force was undertaken by slab-columns correspondingly increased while with the decrease of characteristic value of stiffness of a structure,and the horizontal seismic force was undertaken by slab-columns correspondingly decreased.According to the code,the design of horizontal force distribution may be cause insecurity problems,so it is necessary to give the distribution law of horizontal seismic forces in slab-column shear wall structures as the supplement to the corresponding regulation of the Code.

Structural Optimization of Concrete Slab Frame Bridges Considering Investment Cost

The present study investigates computer-antomated design and structural optimization of concrete slab frame bridges considering investment cost based on a complete 3D model. Thus, a computer code with several modules has been developed to produce parametric models of slab frame bridges. Design loads and load combinations are based on the Eurocode design standard and the Swedish design standard for bridges. The necessary reinforcement diagrams to satisfy the ultimate and serviceability limit states, including fatigue checks for the whole bridge, are calculated according to the aforementioned standards. Optimization techniques based on the genetic algorithm and the pattern search method are applied. A case study is presented to highlight the efficiency of the applied optimization algorithms. This methodology has been applied in the design process for the time-effective, material-efficient, and optimal design of concrete slab frame bridges.

Behavior of Cantilever Slabs in a Blast Environment

Behavior of structural elements under blast loading is different from that under usual loading conditions that are considered in conventional structural deigns. Cantilever slabs are more vulnerable than most other elements under blast loads because of their shape. Understanding the blast behavior of cantilever slabs is useful in strengthening them against blast loads. In this paper, blast loading design envelopes for cantilever slabs are proposed using which, the blast behavior of conventional cantilever slabs can be identified. The paper describes the theories behind these envelopes and the way they can be applied to improve conventional designs. These envelopes have been prepared using numerical techniques. The theories used are accepted, verified and validated theories. The paper shows the possibility of converting a conventional cantilever slab design into impulsive regime design with minor adjustments to the structural design. It points out the importance of increasing slab thickness and controlling steel/concrete ratio for strengthening conventional cantilever slab designs and the requirement of reinforcement at top and bottom fibers.

Environmental Impact Optimization of Reinforced Concrete Slab Frame Bridges

The main objective of this research is to integrate environmental impact optimization in the structural design of reinforced concrete slab frame bridges in order to determine the most environment-friendly design. The case study bridge used in this work was also investigated in a previous paper focusing on the optimization of the investment cost, while the present study focuses on environmental impact optimization and comparing the results of both these studies. Optimization technique based on the pattern search method was implemented. Moreover, a comprehensive LCA （life cycle assessment） methodology of ReCiPe and two monetary weighting systems were used to convert environmental impacts into monetary costs. The analysis showed that both monetary weighting systems led to the same results. Furthermore, optimization based on environmental impact generated models with thinner construction elements yet of a higher concrete class, while cost optimization by considering extra constructability factors provided thicker sections and easier to construct. This dissimilarity in the results highlights the importance of combining environmental impact （and its associated environmental cost） and investment cost to find more material-efficient, economical, sustainable and time-effective bridge solutions.

Structural Glass Fiber Reinforced Concrete for Slabs on Ground

This paper aims to contribute to the classification and specification of glass fiber reinforced concrete (GFRC) and to deal with the question if structural glass fiber reinforced concrete as a special kind of glass fiber reinforced concrete is suited for use in load-bearing members. Despite excellent material properties, the use of glass fibers in a concrete matrix is carried out so far only in non- structural elements or as a modification for the prevention of shrinkage cracks. The aim of re- search at the University of Applied Sciences in Leipzig is the use of alkali-resistant macro glass fibers as concrete reinforcement in structural elements as an alternative to steel fiber reinforcement. Slabs on ground, as an example for structural members, provide a sensible application for the new material because they can be casted as load bearing and non-load bearing and are mostly made of steel fiber reinforced concrete. In the future, structural glass fiber reinforced concrete shall provide a simple and visually appealing alternative to conventional steel bar or steel fiber reinforced concrete. The glass fibers can also be used in combination with conventional reinforcing bars or mat reinforcements. Initial investigations have announced some potential.

随州公共活动中心结构设计

随州公共活动中心是体型复杂的多馆合一式综合性城市公共建筑,具有平面单向超长、质量分布明显不对称、大跨度、大悬挑、顶板大开洞等特点。在对该结构体系进行了重难点分析的基础上,采用现浇预应力钢筋混凝土框架+屈曲约束支撑的减震结构体系,利用屈曲约束支撑解决平面单向超长造成的扭转,同时使结构形成多道抗震防线;大跨度楼盖采用预应力密肋楼盖控制结构高度;针对顶板大开洞的嵌固端问题提出了具体的加强措施。提出了针对该类结构的BRB布置及减震参数设计,通过有限元数值仿真分析论证了BRB的减震效果。针对超限情况提出了抗震性能目标及抗震措施。

双向受力的开槽混凝土叠合板力学性能试验研究

为了解决双向受力的叠合板拼缝处外伸的胡子筋容易与其他部件产生冲突从而影响施工的问题,采用了一种双向受力的开槽混凝土叠合板,在板件拼缝位置预留槽口,并在槽口处放置附加钢筋进行预制板之间的连接,共设置了3个试件对其力学性能进行试验研究.试验结果表明,双向受力的开槽混凝土叠合板与现浇混凝土板的承载力、刚度比分别达到0.99和1.08,延性系数达到9.59,且二者破坏形态一致,增加槽口数量对试件弹性刚度、开裂荷载、极限承载力的影响有限,但是可以提升叠合板的延性.双向受力的开槽混凝土叠合板可以实现拼缝处的有效传力,具有与现浇混凝土板一致的力学性能,在应用于实际工程时,可以提高施工效率、降低钢筋用量、提升经济效益,具有广阔的应用前景.

跨地裂缝三孔斜交箱涵结构受力性能和变形规律研究

以西安站改扩建项目为工程背景,完成足尺三孔斜交箱涵结构受力性能数值模拟研究,分析荷载与地裂缝协同作用下结构的受力过程与可能破坏形态,开展缩尺比例为1∶15的三孔斜交箱涵缩尺模型静载试验,与有限元结果进行对比分析,明确变形缝斜交和板墙开洞等复杂条件下箱涵结构的裂缝发展、位移变形和应力分布规律,验证了数值分析的可行性,并提出设计建议。结果表明:足尺数值模型与缩尺试验模型的应力路径和裂缝分布吻合较好;最不利工况下,箱涵顶板混凝土开裂部位较多,纵向挠度变形较小;斜交变形缝处,钝角较锐角处更易产生应力集中现象,各部位易出现应力集中的顺序依次为跨中、钝角、锐角和板墙隅角;采用平行于变形缝的斜向布筋方式可降低因钢筋截断而产生的应力集中,优化传力路径;建议在顶板洞口横向位置处增设暗梁,洞角布置斜向钢筋,降低洞口周围的局部集中应力。

全装配式钢结构楼板动力性能及舒适度有限元分析

针对全装配式楼板刚度偏低、舒适度不足的问题,优化设计一种已有的新型全装配式钢结构楼板;基于承载力和自振频率对该楼板的承重结构进行选型,并建立考虑构造体的全装配式钢结构楼板精细化有限元模型,采用有限元方法分析该楼板的动力性能,研究全装配式钢结构楼板特型波纹板厚度、高度和楼板跨度对楼板自振频率及加速度响应的影响。结果表明:优选的全装配式钢结构楼板特型波纹板具有较大承载力并可以满足楼板自振频率要求;增大全装配式钢结构楼板特型波纹板厚度、高度,减小楼板跨度,可以增大楼板的自振频率,减小峰值加速度,有效改善楼板的舒适度;全装配式钢结构楼板特型波纹板厚度宜选为1.5 mm,并得到常用全装配式钢结构楼板特型波纹板高度的适用楼板跨度范围。