Slab Structure Research Articles

Efficient Thermo-Optic Switching and Modulating in Nonlocal Metasurfaces.

High-Q optical resonances in nonlocal metasurfaces, benefiting from significantly enhanced light/matter interactions, feature strong responses even under a weak external stimulus. In this work, we leverage the high-Q resonances of quasi-guided modes (QGMs) supported by a photonic crystal slab (PCS) structure to achieve efficient optical switching/modulation. The QGMs with an experimentally measured Q-factor of ∼2200 are realized by shifting every second column of air holes in a rectangular lattice within a silicon slab. At a weak illumination intensity of less than 4.0 W/cm2 from a 532 nm continuous-wave pump laser, the QGM resonance around 1550 nm experiences a pronounced spectral shift, with modulation depth exceeding 55%. This is attributed to the thermo-optic response caused by photothermal heating of the metasurface triggered by the absorption of the pump laser in silicon, which is further verified by the electrical heating approach. Our reported results showcase a simple yet effective way of tailoring light propagation in nonlocal metasurfaces.

The persisting conundrum of mantle viscosity inferred from mantle convection and glacial isostatic adjustment processes

Mantle viscosity exerts important controls on the long-term (i.e., >106 years) dynamics of the mantle and lithosphere and the short-term (i.e., 10 to 104 years) crustal motion induced by loading forces including ice melting, sea-level changes, and earthquakes. However, mantle viscosity structures inferred from modeling observations associated with mantle dynamic and loading processes may differ significantly and remain a hotly debated topic over recent decades. In this study, we investigate the effects of mantle viscosity structures on observations of the geoid, mantle structures, and present-day crustal motions and time-varying gravity by considering five representative mantle viscosity structures in models of mantle convection and glacial isostatic adjustment (GIA). These five viscosity models fall into two categories: 1) two viscosity models derived from modeling the geoid in mantle convection models with ∼100 times more viscous lower mantle than the upper mantle, and 2) the other three with less viscosity increase from the upper to lower mantles that are derived from modeling the late Pleistocene and Holocene relative sea level changes and other observations in GIA models. Our convection models use the plate motion history for the last 130 Myrs as the surface boundary conditions and depth- and temperature-dependent viscosity to predict the present-day convective mantle structure of subducted slabs and the intermediate wavelength (degrees 4–12) geoid. Our GIA models using different ice history models (e.g., ICE-6 G and ANU) compute the GIA-induced present-day crustal motions and time-varying gravity. Our calculations demonstrate that while the viscosity models with a higher viscosity in the lower mantle (∼2 × 1022 Pa.s) reproduce the degrees 4–12 geoid and seismic slab structures, they significantly over-predict the geodetic (i.e., GPS and GRACE) observations of crustal motions and time varying gravity. Our calculations also show that while two viscosity models derived from fitting the RSL data with averaged mantle viscosity of ∼1021 Pa.s for the top 1200 km of the mantle reproduce well the geodetic observations independent of ice models, they fail to explain the geoid and seismic slab structures. Therefore, our study highlights the persisting conundrum of mantle viscosity structures derived from different observations. We also discuss a number of possible ways including transient, stress-dependent and 3-D viscosity to resolve this important issue in Geodynamics.

Formation of the primary structure of cast slabs from aluminum alloys during their twin-roll casting

Formation of the primary structure of cast slabs from aluminum alloys during their twin-roll casting

Experimental investigation on the shear performance of hybrid structures comprising textile reinforced concrete stay-in-place formwork and reinforced concrete

Recently, the application of textile-reinforced concrete (TRC) in thin-walled precast structures has gained significant attention. Among these innovations, the combination of TRC and reinforced concrete (RC) has emerged as an effective method for creating hybrid structural systems. This paper presents the experimental results analyzing the shear behavior of a hybrid deck slab structure consisting of TRC stay-in-place (SiP) formwork and RC components. Shear performance was evaluated using 3-point bending tests on four large-scale specimens with aspect ratios (a/d) varying from 1.6 to 2.3. The average load carried by the TRC SiP formwork prior to failure—due to textile reinforcement rupture—was approximately 26.3 kN, with compressive strains at the top edge ranging from 2.8 to 3.4 ‰, just below the concrete's ultimate strain. The findings demonstrate the versatility of TRC SiP-formwork, highlighting its adaptable cross-section and substantial load-bearing capabilities, making it particularly suitable for composite bridge deck applications. The specimens experienced both shear compression and diagonal shear failures. Moreover, the TRC SiP-formwork effectively mitigated transverse cracking at the interface, enhancing bond strength and improving overall structural performance

Design of a Six-Story Teaching Building: A Comprehensive Approach to Safety and Structural Efficiency

This paper describes teaching building design. The project, designed for the teaching building, prioritizes safety in its main structure, a reinforced concrete frame with six floors above ground. The story heights are 4.2m, 3.9m, 3.9m, 3.9m, 3.9m and 3.9m, respectively, and the building's total height is 27.6m. The construction site category is classified as type II, and the first group's seismic fortification intensity is 7 degrees. The process includes architectural design, structural design, and PKPM checking calculation. Architectural design mainly consists of a general description. The plan, elevation, section, and draft of the corresponding building are drawn according to the relevant information and requirements provided by the design task book. Structural design mainly includes load statistics, calculation of internal force and displacement of the frame, a combination of internal force, and calculation of staircase, slab roof, floor slab and frame structure. The calculation of displacement, internal force, and reinforcement of the whole frame structure is carried. Out using PKPM. In the course of architectural design, safety is a paramount consideration, in line with the principles of safety, applicability, beauty, economy, and energy-saving requirements, referring to national standards and relevant materials, and strictly following the requirements of relevant architectural design standards, the design of each link is not only a comprehensive scientific consideration of its own but also a related discussion with teachers, as detailed in the construction plan. The frame structure is adopted,in this structural type. It mainly includes structure layout and calculation sketch determination, load calculation, internal force calculation, internal force combination, main beam section design, and reinforcement calculation, frame column section design and reinforcement calculation, secondary beam section design and reinforcement calculation, floor and roof design, staircase design etc. Among them, the D-value method is used to calculate the internal force of the structure under horizontal load, and the distribution method is used to calculate the internal force of the structure under vertical load (dead load and live load).

Modeling Subduction With Extremely Fast Trench Retreat

AbstractThe Tonga‐Kermadec subduction zone exhibits the fastest observed trench retreat and convergence near its northern end. However, a paradox exists: despite the rapid trench retreat, the Tonga slab maintains a relatively steep dip angle above 400 km depth. The slab turns flat around 400 km, then steepening again until encountering a stagnant segment near 670 km. Despite its significance for understanding slab dynamics, no existing numerical model has successfully demonstrated how such a distinct slab morphology can be generated under the fast convergence. Here we run subduction models that successfully reproduce the slab geometries while incorporating the observed subduction rate. We use a hybrid velocity boundary condition, imposing velocities on the arc and subducting plate while allowing the overriding plate to respond freely. This approach is crucial for achieving a good match between the modeled and observed Tonga slab. The results explain how the detailed slab structure is highly sensitive to physical parameters including the seafloor age and the mantle viscosity. Notably, a nonlinear rheology, where dislocation creep reduces upper mantle viscosity under strong mantle flow, is essential. The weakened upper mantle allows for a faster slab sinking rate, which explains the large dip angle. Our findings highlight the utilizing rheological parameters that lead to extreme viscosity variations within numerical models to achieve an accurate representation of complex subduction systems like the Tonga‐Kermadec zone. Our study opens new avenues for further study of ocean‐ocean subduction systems, advancing our understanding of their role in shaping regional and global tectonics.

Identification of crack width behavior of one-way reinforced concrete slab structure at different steel reinforcement area

An evaluation study of crack limit states based on design codes and prior research is presented in this publication. Its main goal is to connect research findings to common design codes. Researchers continue to face a difficult dilemma when it comes to reinforced concrete structure fractures, particularly in one-way slab constructions where there is still significant damage and corrosion in the reinforcement because of cracks. Practitioners will find it easier to construct these structures and solve the slab durability issue if the proper formula is discovered. One can overcome reinforced concrete. A method for estimating the maximum fracture width formula in one-way reinforced concrete slabs with varying steel areas is suggested based on this research. Slabs use a variety of steel areas, including 1000 mm2, 1200 mm2, and 1400 mm2.The test specimens are the same length of 2 meters and have a slab width of 0.6 meters with steel reinforcement. Findings from a literature review of research codes and prediction formulas from earlier studies, namely wmax(prop)=1.5*10-2fsAs-0.4, indicate that the maximum crack width is not significantly influenced by steel area (As). Overall, the findings from the two methods used in this analysis match the suggested formula and the observed experimental testing. This data indicates that the maximum fracture width has been greatly lowered by increasing the steel Area (As) of the reinforced concrete slab, leading to the determination of the experimental formula, As a result, a unique approximation formula has been developed to assess the impact of steel area parameters for pure slabs on the maximum crack width formula for one-way reinforced concrete slabs. This crack width formula is only applicable to one-way slabs in practice.

Along-strike forearc and subducted upper slab structure beneath north Chile: Slow slip implications

We evaluate the lateral variation of the lithospheric structure beneath the forearc of the North Chile subduction zone along strike, extending from Iquique to Valparaiso, to understand a possible seismic structure that hosts deep slow earthquakes by comparing the deep slow slip areas around 60 km depth, using receiver function and inversion method. Relative differences are investigated in seismic velocities around the plate interface, especially underlying the mantle wedge, the upper part of the subducted oceanic crust, and the oceanic mantle along the subduction strike. We estimate and compare the thickness and velocity of subducted oceanic crust, slab top, subducted oceanic Moho, continental Moho, and wedge mantle velocity beneath the seismic stations. The oceanic crustal thickness range from ∼5 to 10 km respectively, and the oceanic Moho depth is ∼40 km–∼90 km. It was observed that the disparities in velocities were more pronounced near the south of the Iquique zone (18°S-25°S), with high subducting oceanic crust velocities. These discrepancies in velocities could be regarded as the presence of fluids from subducted ridges and seamounts, which might alter seismicity in the area, including slow slip.

Symmetry-protected bound states in the continuum on an integrated photonic platform

Abstract Bound states in the continuum (BICs) have attracted much attention in the field of nanophotonics owing to their ability to trap photons without loss. Recently, a low-refractive-index (RI) waveguide loaded on a high-RI slab structure was demonstrated to support BICs. However, strict control of structural parameters is required due to the accidental nature of those BICs. Here, we propose a novel structure consisting of two low-RI vertically coupled waveguides loaded on a high-RI slab. This structure supports symmetry-protected BICs (SP-BICs), which do not require strict control of the geometric parameters. Such SP-BICs can also possess an infinitely high quality factor in resonant structures, which can be harnessed for ultranarrow-bandwidth spatial and spectral filters. Our work opens a new way of harnessing BICs on an integrated photonic platform for realizing nanophotonic circuits and devices.

Topological Rainbow Trapping of Plate‐Mode Waves Based on 1D Gradual Phononic Crystal Slabs

In this article, the concept of topological rainbow is introduced into the plate‐mode waves system of 1D phononic crystal slabs, achieving adjustable topological elastic rainbow trapping by employing gradient‐tuned Su–Schrieffer–Heeger (SSH) structures. First, based on the classical SSH model, a phononic crystal slab composed of steel and aluminum is set up, and the band structure of plate‐mode waves is studied using the finite‐element method. Band inversion can be induced by changing the height of the steel in the unit cell, leading to topological phase transitions. Then, phononic crystals with different topological properties are connected to form a phononic crystal slab, realizing topological interface states. Furthermore, a sandwich‐like ultrathin structure is constructed to couple the adjacent two topological interface states. Finally, a 1D alternating SSH structure of phononic crystal slab is designed under gradient structural parameters, and based on eigenfrequency and full‐wave simulation, adjustable topological rainbow trapping based on coupled interface states is achieved. The designed device can trap wide frequencies exceeding 15 kHz, providing more possibilities for the design of elastic‐energy‐harvesting devices.

Barriers to Introduce Mass Timber in Construction in Ecuador - Exploratory Study

In recent years, there has been a great interest in the use of mass timber in the construction industry. Thanks to configurations such as laminated timber (GLT and CLT), it has been possible to build high-rise buildings with its entire structure (beams, columns, slabs, and walls) made of wood. As technology improves, the gap between the use of reinforced concrete, steel, and wood will be reduced, and within a few years, wooden buildings may be as common as their concrete and steel counterparts. In Ecuador, the use of wood in construction is quite limited, with its most common use being with guadua cane (guadua angustifolia) and hardwoods for two-story houses. Mass timber could change this perception and be introduced as an alternative to concrete and steel. As its implementation is relatively new in the world, there is an opportunity to develop and exploit the potential of a new industry in the country. However, despite the potential of this material, its introduction may not have the expected impact, and this can occur due to a wide range of factors. This study developed a questionnaire using existing literature on mass timber in relation to: raw material production, manufacturing process, construction process, maintenance, cultural context, and environmental impact. With this, 10 interviews were conducted with professionals related to the construction industry. The responses were transcribed, analyzed, and coded to identify the perceived barriers for the introduction of this construction system in Ecuador. Finally, the article proposes ways to deepen academic research as well as the professional use of this material.

Blast-resistance characteristics and design of steel wire reinforced ultra-high performance concrete slabs

Steel wire reinforced ultra-high performance concrete (SWRUHPC) offers exceptional resistance to impacts and blast, making it a promising construction material for infrastructure with blast-resistance demands. However, limited research has been conducted on the blast-resistance characteristics and design of SWRUHPC elements under blast loading, particularly in considering multiple influencing parameters and levels. Therefore, this study employed finite element simulation methods to investigate the influence of scaled distance (Z), reinforcement ratio (ρ) and slab thickness (D) as well as slab length (L) on the failure mode and maximum deflection of SWRUHPC slabs. Range analysis and variance analysis methods were used to quantitively analyze the effects of various factors on the blast resistance performance, culminating in the proposal of a design formula for SWRUHPC slabs. The results demonstrated that SWRUHPC exhibits superior blast resistance compared to ordinary concrete, effectively reducing the occurrence of concrete spalling and splashing, thus enhancing overall structural resilience in blast scenarios. Among the four factors analyzed, their influence on maximum deflection follows this order: D > Z > ρ > L. Notably, the maximum deflection decreases by 82 % when the slab thickness increases from 40 mm to 90 mm. Additionally, the established design formula for SWRUHPC slabs under different scaled distances shows good agreement with the numerical simulation results, offering valuable design guidelines for SWRUHPC slabs in protective engineering structures.

Progressive Collapse and Post Impact Damage Assessment in a Regular Beam-Slab Building & Flat-Slab Building on the Intermediate Floor

Progressive collapse, where a localized member failure causes widespread structural collapse, has become a critical concern nowadays, due to its potential to cause significant financial losses and loss of human life. Triggers include natural disasters like earthquakes and floods, as well as accidents, attacks and explosions. Reinforced concrete flat slab structures, which are eminent for their architectural flexibility and have larger spans, are particularly susceptible to disproportionate collapse, due to the lack of floor beams, which can redistribute loads after a column failure, unlike moment frame buildings. This research examines how multi-story reinforced concrete flat slab buildings behave, under prescribed gravity load combinations, compared to conventional framed buildings. The effects of removing columns at specified locations from an intermediate floor of the multistorey building are also examined. However, this investigation covers both the column removal approaches to check a possibility of disproportionate collapse which are; static removal and dynamic instantaneous removal. Furthermore, the research also assesses the efficacy of perimeter beams, in minimising the risk of gradual collapse in flat slab structures, by scrutinising their ability to reduce joint displacement, chord rotation, and demand capacity ratio. ETABS v18 was used to analyze all the 18 models. The findings revealed that buildings are more prone to progressive collapse when corner columns are removed, as opposed to edge and interior columns, due to higher Demand-Capacity Ratios (DCR) and joint displacement. In comparison to dynamic analysis, the static evaluation exhibited greater DCR values and vertical joint displacement. Furthermore, since they have a more efficient load redistribution mechanism, traditional framed structures performed better than flat slab models. The simulations additionally indicated that, adding edge perimeter beams, substantially lowered the possibility of progressive collapse in flat slab structures. Moreover, the tested flat slab building models, with and without perimeter beams showed no indications of progressive collapse, when specified columns were removed from the intermediate floors, since the DCR values of the crucial columns stayed within the permissible range of 2.0. In conclusion, structures built in compliance with IS 1893:2016 code and designed to withstand seismic loads demonstrate stronger resistance against significant damage, brought about by column failures.

Present day mantle structure from global mantle convection models since the Cretaceous

SUMMARY Using forward mantle convection models starting at 140 Ma, and assimilating plate reconstructions as surface velocity boundary condition, we predict present-day mantle structure and compare them with tomography models, using geoid as an additional constraint. We explore a wide model parameter space, such as different values of Clapeyron slope and density change across 660 km, density and viscosity of the thermochemical piles at the core–mantle boundary (CMB), internal heat generation rate, and model initiation age. We also investigate the effects of different strengths of a weak layer below 660 km and weaker asthenosphere and slabs. Our results suggest that slab structures at different subduction zones are sensitive to the viscosity of the asthenosphere, strength of slabs, values of Clapeyron slope and the density and viscosity of the thermochemical piles, while different internal heat generation rates do not affect the slab structures. We find that with a moderately weak asthenosphere ($10^{20}$ Pa·s) and strong slabs, the predicted slab structures are consistent with the tomography models, and the observed geoid is also matched well. Moreover, our models successfully reproduce the degree-2 structure of the lower mantle beneath Africa and the Pacific, also known as Large Low Shear Velocity provinces (LLSVPs). A moderate Clapeyron slope of −2.5 MPa K−1 at 660 km aids in slab stagnation while higher values result in massive slab accumulation at that depth, ultimately leading to slab avalanches. We also find that the convective patterns in the thermal and thermochemical cases with slightly denser LLSVPs are similar, although the geoid amplitudes are lower for the latter. However, with more dense LLSVPs, the slabs cannot perturb them and no plumes are generated. Plumes arise as thermal instabilities from the edges of the LLSVPs, when cold and viscous slabs perturb them. While our predicted plume locations are consistent with the observed hotspot locations, matching the plume structures in tomography models is difficult. These plumes are essential in fitting the finer features of the observed geoid. In longer-duration models, more voluminous subducted material reaches the CMB, which tends to erode the LLSVPs significantly, and yields a poor fit to the observed geoid. Our results suggest that with the presence of a thin, moderately weak layer below 660 km, a slightly dense LLSVP, and Clapeyron slope of −2.5 MPa K−1, the velocity anomalies in seismic tomography and the long-wavelength geoid can be matched well. One of the limitations of our models is that the assimilated plate motion history may be too short to overcome arbitrary initial conditions effects. Also, assimilated true plate velocities in our models may not represent the true convective vigour of the Earth.

RESEARCH OF THE STRESS-STRAIN STATE OF PRECAST REINFORCED CONCRETE HOLLOW CORE SLABS UNDER THE ACTION OF A CONCENTRATED AND UNIFORMLY DISTRIBUTED LOAD

The scientific work is devoted to a comprehensive study of the stress-strain state of prefabricated hollow-core floor slabs, establishing the nature of deformation, as well as determining the characteristics of crack resistance, deformability and load-bearing capacity experimentally under short-term loads. The experimental data obtained were confirmed by theoretical calculations. The scientific novelty of the experiments carried out within the framework of the presented work lies in the improvement of the principles of direct design of floor slabs from commercially produced beam slabs, the possibility of determining the stress-strain behavior of a slab structure using the formed ends. The method of monitoring the stressed behavior of a slab structure was also further developed. For the first time, the results of full-scale experimental studies of the stress-strain behavior of a prefabricated slab, carried out using the hydraulic loading method, have been obtained, and the features of the deformation of a slab embedded in the wall of a multi-story building have been experimentally established. The article provides recommendations for the practical use of the research results obtained, and also develops technical specifications for the production of concrete slabs during design and construction. The developed proposals were used in the construction of residential buildings in Kharkiv. When using the recommended grade of concrete C25/30 (instead of the actual grade C20/25 tested), the rigidity of the slab increases and its deflections will be smaller. Based on the data obtained from the experimental testing of the slabs, a generally positive test result should be stated. During further serial production of slabs, periodic testing of batches of slabs should be carried out in accordance with DSTU B V.2.6-53:2008. In this case, the slabs are accepted according to the indicators of strength, rigidity, crack resistance, fire resistance limits, frost resistance limits, as well as water resistance of slabs intended for use in aggressive environments. Keywords: concentrated load, testing, concrete, calculation, deflection, transverse force.

Seismic Performance Evaluation of Steel Braces in Enhancing the Lateral Load Resistance of RCC Flat Slab Structures

This research paper conducts a comprehensive investigation into the seismic performance of reinforced concrete flat slab structures, employing different configurations of steel bracing systems. The seismic behavior of flat slab buildings with 5, 7, and 9 stories is scrutinized through Equivalent Lateral Force (ELF) analysis and Response Spectrum Analysis (RSA). The study delves into the efficacy of various bracing configurations, encompassing X-bracing, eccentric bracing, and knee bracing, in augmenting the lateral load resistance of these structures. Additionally, the research evaluates the influence of bracing systems on crucial structural response parameters such as displacement, drift ratio, base shear, and fundamental natural period. Keywords: steel bracing, seismic performance, flat slab structures, comparative study

An Experimental Study on Compressive Properties of Composite Fiber Geopolymer Concrete

Background: The production process of Portland cement (OPC) consumes energy and releases carbon dioxide, which affects the environment. It has been found that geopolymer cementing material is a better substitute for it. The strength effect of fiber on geopolymer materials is the basis of the application of fiber geopolymer concrete in structural beams, slabs, and other components. Methods: Geopolymer concrete was prepared with fly ash, slag, and water glass as the main raw materials, and the effects of fiber type, quality, and blending method on the compressive properties and elastic modulus of geopolymer concrete were compared to explore the working mechanism of fiber-reinforced geopolymer concrete. Results: Through experimental research, the results showed that in 0.2% flocculent lignin fibers, when the mass ratio of carbon fibers was increased, the strength of the geopolymer concrete decreased. Due to the increased mass ratio of wavy steel fibers, comprising 0.2% flocculent lignin fibers, the strength enhancement effect was not apparent. Moreover, with regard to enhancing the modulus of elasticity of geopolymer concrete, blending fibers exerted the most significant effect. The fiber was added to geopolymer concrete to form a three-dimensional supporting frame system. When cracks occurred under the action of force, the development of cracks was limited due to the fibers, and the bonding slip delayed the propagation of cracks. The composite fiber could make full use of the advantages of each material and improve the strength of geopolymer concrete. Conclusion: The compressive properties of geopolymer concrete could be enhanced by blending single-fiber or mix-fibers, and the effect of mix-fibers was more optimal than that of others. The above research results provide a theoretical reference for the design of geopolymer concrete and a theoretical basis for the application of fiber geopolymer concrete in structural beams, slabs, and other components.

Band gap tuning and wave separator design in 3d composite slab structures based on periodic thermal fields

In the thesis, we investigate a two-dimensional period slab composite structure composed of steel/epoxy and adhered with a series of heat films. Various types of periodic thermal fields are introduced into the structure by loading diverse powers of heat on the heat films. Leveraging the thermal sensitivity of epoxy, these introduced thermal fields facilitate changes and tuning in the band structures of the composite slab. Therefore, a thermal–mechanical coupling model based on finite element method via commercial software is established to obtain the dispersion curves and transmission spectrums of the period structure. The numerical prediction of band gaps indicates that band structures of composite slabs can be effectively tuned by thermal fields. Furthermore, intelligent waveguides and wave separators are designed by thermal fields with line-type or L-type of thermal defects. The results also exhibit an interesting phenomenon that in-plane wave and out-of-plane wave can be decoupled when T-type of thermal defects with proper heat flux are employed. The results of this research may lay theoretical foundation and provide a novel routine for the designing of intelligent acoustic devices such as waveguides and wave separators.

Multi-criteria decision making for timber constructions: analysis of ceiling types using utility analysis

Abstract Purpose: Timber constructions are gaining prominence in global decarbonization efforts for climate goals. While addressing greenhouse gas emissions is crucial, building planning must consider multiple factors. Methods: This study compares three timber construction methods for office ceilings—solid wood, linear-shaped, and composite timber-concrete—to conventional reinforced concrete. Fourteen timber alternatives are analyzed based on thirteen criteria, covering environmental and construction aspects of resource use, climate protection, building physics, and structural considerations. The utility analysis, a multi-criteria decision-making method, ranks the alternatives while considering all criteria simultaneously. Sensitivity analyses with different criteria weightings examine the robustness of the rankings. Results: A ribbed slab structure with a wet screed is recommended for office ceilings, prioritizing vibration behavior and environmental aspects. Solid wood and linear-shaped ceilings outperform composite timber-concrete or reinforced concrete in building physics and structural aspects. Dry-screed alternatives are not presently recommended due to vibration and economic reasons. Conclusions: This study shows that the utility analysis supports the decision-making in the wooden building parts’ design and planning process. Since the ranking of alternatives depends on the set criteria and their weighting, the seemingly objective decision is based on subjective evaluations. Thus, sensitivity analyses with different weightings are essential, and transparent decision-making documentation is crucial.

Seismic and vibration control of segmented isolation layer in underground structure-diaphragm wall system

In this paper, a seismic and vibration reduction measure of subway station is developed by setting a segmented isolation layer between the sidewall of structure and the diaphragm wall. The segmented isolation layer consists of a rigid layer and a flexible layer. The rigid layer is installed at the joint section between the structural sidewall and slab, and the flexible layer is installed at the remaining sections. A diaphragm wall-segmented isolation layer-subway station structure system is constructed. Seismic and vibration control performance of the diaphragm wall-segmented isolation layer-subway station structure system is evaluated by the detailed numerical analysis. Firstly, a three-dimensional nonlinear time-history analysis is carried out to study the seismic response of the station structure by considering the effect of different earthquake motions and stiffness of segmented isolation layer. Subsequently, the vibration response of site under training loading is also studied by considering the influence of different train velocities and stiffness of the segmented isolation layer. Numerical results demonstrate that the diaphragm wall-segmented isolation layer-subway station structure system can not only effectively reduce the lateral deformation of station structure, but also reduce the tensile damage of the roof slab. On the other hand, the developed reduction measure can also significantly reduce the vertical peak displacements of site under training loading.