Structural Engineering Challenges Research Articles

Coprecipitation Strategy for Halide-Based Solid-State Electrolytes and Atmospheric-Dependent In Situ Analysis.

In the continuous pursuit of an energy-efficient alternative to the energy-intensive mechanochemical process, we developed a coprecipitation strategy for synthesizing halide-based solid-state electrolytes that warrant both structural control and commercial scalability. In this study, we propose a new coprecipitation approach to synthesized Li3InCl6, exhibiting both structural and electrochemical performance stability, with a high ionic conductivity of 1.42 × 10-3 S cm-1, comparable to that of traditionally prepared counterparts. Through the in situ synchrotron X-ray diffraction technique, we unveil the stability mechanisms and rapid chemical reactions of Li3InCl6 under dry Ar, dry O2, and high-humidity atmosphere, which were not previously reported. Furthermore, the fast reversibility capability of moisture-exposed Li3InCl6 was tracked under vacuum, revealing the optimal recovery conditions at low temperatures (150-200 °C). This work addresses the critical challenges in structural engineering and sustainable mass production and provides insights into chemical reactions under real-world conditions.

Estimating nonlinear wind-induced response of roof cable nets by aeroelastic experiments and ML modeling

The paper examines the structural engineering challenges related to the assessment of the wind-induced vertical displacements of lightweight, hyperbolic-paraboloid cable-supported membrane roofs. Analysis and comparisons are conducted using three distinct methods for calculating the roof vertical, out-of-plane displacements. Finite element method (FEM) analysis is employed using: (i) estimated static nodal forces obtained from wind pressure coefficients determined by aerodynamic wind tunnel tests on a rigid building model, and (ii) loads found from wind pressure coefficients, estimated through machine learning (ML) methods, and (iii) measured roof response found from aeroelastic wind tunnel tests on a flexible model. The study examines three different roof geometries (square, rectangular and circular) and two distinct membrane curvatures for each geometry. Furthermore, wind directionality (three mean-wind incidence angles) and Reynolds number effects (seven mean wind velocities) are studied. Comparisons show that the non-linear FEM analysis, based on estimated static wind loads, underestimates the roof displacements at the roof center, compared to the direct measurements on the aeroelastic model. The main contribution of the study consists of a novel application of ML models, and Artificial Neural Networks (ANNs) in particular, which are employed to correct roof displacement estimations, found by simplified aerodynamic test pressure measurements on rigid roof models. The goal is to better describe the complex fluid-structure interaction of the roof membranes, which can only be achieved by direct aeroelastic tests that are difficult to design and execute. Finally, the study demonstrates that ANNs can be used not only for the preliminary design of the full-scale structure but also for construction of wind tunnel scale models.

Application and Assessment of an Experiential Deformation Approach as a Didactive Tool of Truss Structures in Architectural Engineering

Experiential learning methods are advantageous for students as they motivate them to comprehend structural concepts without complex calculations, enhancing their inherent understanding of static principles. This research introduces a novel, cost-effective haptic didactic tool to enhance the approach to teaching trusses to students in a School of Architecture. The primary goal is to address challenges associated with the complexities of teaching structural systems within the context of architectural education. The proposed approach is related to the most critical issue, which is the state in which the individual elements are under applied load, compression, or tension. The approach explores the deformation of the truss elements and establishes a connection between their visible deformation and the stress they develop under various loads. As a didactic tool, this approach offers an alternative perspective to help students understand truss function under various loads. Also, an assessment procedure of learning outcomes and satisfaction indices has been structured to validate the impact on students on the proposed educational procedure. The findings underscore the significant educational efficiency of the proposed procedure as a sustainable way to connect the structural engineering challenges arising during design courses and creative skills in architecture engineering.

Unboxing machine learning models for concrete strength prediction using XAI

Concrete is a cost-effective construction material widely used in various building infrastructure projects. High-performance concrete, characterized by strength and durability, is crucial for structures that must withstand heavy loads and extreme weather conditions. Accurate prediction of concrete strength under different mixtures and loading conditions is essential for optimizing performance, reducing costs, and enhancing safety. Recent advancements in machine learning offer solutions to challenges in structural engineering, including concrete strength prediction. This paper evaluated the performance of eight popular machine learning models, encompassing regression methods such as Linear, Ridge, and LASSO, as well as tree-based models like Decision Trees, Random Forests, XGBoost, SVM, and ANN. The assessment was conducted using a standard dataset comprising 1030 concrete samples. Our experimental results demonstrated that ensemble learning techniques, notably XGBoost, outperformed other algorithms with an R-Square (R2) of 0.91 and a Root Mean Squared Error (RMSE) of 4.37. Additionally, we employed the SHAP (SHapley Additive exPlanations) technique to analyze the XGBoost model, providing civil engineers with insights to make informed decisions regarding concrete mix design and construction practices.

Comparison of risk-based robustness indices in progressive collapse analysis of building structures

A current challenge in Structural Engineering is the identification of a robustness index for the design of structures subject to low-probability high-consequence load events. Robustness indices proposed in the literature have not been subject to comprehensive scrutiny. Few comparisons presented so far have been limited to simple academic examples involving idealized systems, which cannot suggest robustness values for practical design. In this paper a comprehensive evaluation of two risk-based robustness indices is presented, addressing progressive collapse of regular frame structures subject to damage by abnormal loads. Herein frames of different aspect ratios are considered, subject to local damage of different size, in hazard-independent and hazard-dependent (blast loading) scenarios. System damage states include plastic bending failure of beams, as well as local and global column crushing. Moreover, robustness indices are compared for structures conventionally designed, for structures strengthened following the codified Alternate Path Method (APM), and for structures resulting from risk-based optimization, for different hazard probability levels. Results suggest that the robustness index of Baker, Schubert and Faber performs better when comparing conventional to APM-strengthened codified designs. The Praxedes, Yuan and He robustness index is less sensitive but appears to be more appropriate to describe structures resulting from risk-based optimization.

Seismic control of vertically and horizontally irregular steel high-rise buildings by tuned mass dampers including SSI

The architectural requirements imposed on the structural design of buildings sometimes necessitate vertical and horizontal irregularities with their possibly dangerous effects when these structures are subjected to earthquakes. One of the greatest challenges in structural engineering is the design of a steel high-rise building (HRB) with vertical and horizontal irregularities. In this research, two irregular steel high-rise buildings (HRBs) were seismically analyzed as 3D models considering soil–structure interaction (SSI) and tuned mass damper (TMD) systems were used to mitigate their seismic response under different earthquakes. The two studied HRBs were a vertically irregular (step-pyramid-shaped) steel HRB, and a both vertically and horizontally irregular (L-shaped in-plan, stadium-shaped) steel HRB. The SSI provides the actual response of the tall buildings subjected to earthquake, and mitigation schemes using TMDs were suggested with arrangements of the TMDs on the top plan and along the elevation of the steel high-rise buildings to achieve seismic control of these structures. The present study has shown that the best efficiency in the mitigation of the effect of earthquakes on vertically and horizontally irregular steel high-rise buildings is obtained by implementing TMDs at the corners of the HRB plan on the top of the HRB and also at different floor levels along the upper half-height of the HRB.

Retrofitting Reinforced Concrete One–Way Damaged Slabs Exposed to High Temperature

Exposure of reinforced concrete buildings to an accidental fire may result in cracking and loss in the bearing capacity of their major components, columns, beams, and slabs. It is a challenge for structural engineers to develop efficient retrofitting techniques that enable RC slabs to restore their structural integrity, after being exposed to intense fires for a long period of time. Experimentalinvestigation was carried out on twenty one slab specimens made of self compacting concrete, eighteen of them are retrofitted with CFRP sheets after burning and loading till failure while three of them (which represent control specimens) are retrofitted with CFRP sheet after loading till failure without burning. All slabs had been tested in a simply supported span and subjected to two-point loading. The main variables were the effect of different temperature levels (300ºC, 500ºC and 700ºC),different concrete compressive strength (20MPa, 30MPa and 40MPa) and cooling rate (gradually and sudden cooling conditions) on the behavior of retrofitted one way slabs .The structural response of each slab specimen was investigated in terms of load-deflection behavior, ultimate load carryingcapacity and mode of failure. The experimental results, generally, indicate that slabs retrofitted using CFRP sheets restored flexural strength values nearly equal to or lower than those of the reference slabs, the retrofitted slabs exhibited larger deflection than the control slabs at ultimate loads. Retrofitted control slabs after loading regained about 93.95% to 97.92% of their original load capacity(before retrofitting) while the other slabs regained from 42.% to 84% of the load capacity of the original control specimens. Most of the tested slabs failed by concrete crushing at mid span and partial debonding of certain retrofitting systems was also observed for a few cases

Case Study: Roof Truss Structure With Large Cut Out and Elliptic Glazing Surface

The article presents the technical solutions implemented during the design of the roof trusses and the elliptic skylight structure (Figure. 1) for the extension of the "Shopping City Sibiu" commercial centre in Romania. The area of the roof structure was approximately 1600 sqm (29x56 m). In the central region of the roof, a 27 m long and 10 m wide elliptic skylight was placed. The challenges of the project arouse from the relatively large span of the structure, being supported only on 13 non-symmetrically placed perimeter concrete columns. Thus, the structure had to be designed in such a way, that it would support the extra 20 tones coming from the skylight structure, while also bring inside the natural light unobstructed by any main structural elements. The relatively large deformations between the supporting points of the skylight under variable loads (especially snow loads) can also have adverse effects on the glazing surface during operational phase. Due to this, also the serviceability limit state checks had an important role in the engineering calculations. The structural configuration steps with performed analyses on the partial structural models and on the complex 3D model were especially useful for the identification of the sensitive zones, helping to create the surface shape and develop adequate structural details. The paper summarizes the structural engineering challenges during the design and execution process.

Modal testing and finite element model updating of full-scale hybrid timber-concrete building

Serviceability of tall timber and hybrid timber buildings under wind-induced vibrations has become their leading design criterion. Accurate finite element models for predicting their modal properties are crucial for designing buildings that satisfy the current serviceability criteria. It is a challenge for structural engineers to decide what to include in the structural modelling. This is because elements that are typically considered non-structural (partition walls, plasterboards, screed, façade, etc.) have been shown to act structurally and can significantly influence the modal properties of timber buildings.This paper discusses the importance of including certain entities in finite element models of timber and hybrid timber buildings. A case study of a 5-storey hybrid timber-concrete building with masonry cladding is presented. Full-scale in-situ dynamic tests were performed on the building, using forced vibration testing with a shaker. Frequency-response-function-based modal identification resulted in 3 modes of vibration, identifying natural frequencies, mode shapes and damping ratios. A detailed finite element model was developed that estimated the measured natural frequencies with an error of slightly more than 11%.With an extensive sensitivity analysis was found that modelling of the foundation, the effect of the adjacent abutting building in contact, and the masonry cladding was needed. After model updating, it was found that the shear stiffness of CLT walls was initially underestimated, concluding that non-structural elements such as plasterboards and partition walls might influence the dynamic properties of this hybrid timber-concrete building.

Assessment of lime stabilization of black cotton soil for roads construction projects

The design foundation (i.e., pavements) on black cotton soil has always been a difficult task for the engineers as the structure resting on black cotton soil cracks without any warning. This research evaluates the effect of lime (anhydrous sodium sulphate) on engineering properties of black cotton soil which are considered highly problematic to civil engineering works. Black cotton soil brings about significant geotechnical and structural engineering challenges to property and infrastructure development around the world. The objective of the study is to investigate the use of lime-stabilized black cotton soil as subbase material in flexible pavements. Black cotton soil procured from the local area in Gaborone, Botswana, tested for suitability as subbase material, turned out to be unsuitable as it resulted in very less CBR value (4.8%). The black cotton soil-lime mix was checked for consistency limits, compaction, CBR for different proportions of lime (i.e., 0, 5, 10 and 15%). It was observed that the plasticity index of the soil shows a substantial decrease upon addition of the lime whereas CBR values show a marked increase with unsoaked CBR. The addition of 5%, 10% and 15% of lime produced some desirable soil properties. It can be concluded lime could be one of the best alternative stabilizer materials for highly expansive clayey.

Adaptive Chaotic Marine Predators Hill Climbing Algorithm for Large-Scale Design Optimizations

Meta-heuristic algorithms have been effectively employed to tackle a wide range of optimisation issues, including structural engineering challenges. The optimisation of the shape and size of large-scale truss structures is difficult due to the nonlinear interplay between the cross-sectional and nodal coordinate pressures of structures. Recently, it was demonstrated that the newly proposed Marine Predator Algorithm (MPA) performs very well on mathematical challenges. The MPA is a meta-heuristic that simulates the essential hunting habits of natural marine predators. However, this algorithm has some disadvantages, such as becoming locked in locally optimal solutions and not exhibiting a high level of exploratory behaviour. This paper proposes two hybrid marine predator algorithms, Nonlinear Marine Predator (HNMPA) and Nonlinear-Chaotic Marine Predator Algorithm (HNCMPA), as improved variations of the marine predator algorithm paired with a hill-climbing (HC) technique for truss optimisation on form and size. The major advantage of these techniques are that they seek to overcome the MPA’s disadvantages by using nonlinear values and prolonging the exploration phase with chaotic values; also, the HC algorithm has been used to avoid locally optimum solutions. In terms of truss optimisation performance, the proposed algorithm is compared to fourteen well-known meta-heuristics, including the Dragonfly Algorithm (DA), Henry Gas Solubility optimisation (HGSO), Arithmetic optimisation Algorithm (AOA), Generalized Normal Distribution Optimisation (GNDO), Salp Swarm Algorithm (SSA), Marine Predators Algorithm (MPA), Neural Network Algorithm (NNA), Water Cycle Algorithm (WCA), Artificial Gorilla Troops Optimiser (GTO), Gray Wolf Optimiser (GWO), Moth Flame Optimiser (MFO), Multi-Verse Optimiser (MVO), Equilibrium Optimiser (EO), and Cheetah Optimiser (CO). Furthermore, seven algorithms were chosen to test HNCMPA performance on benchmark optimisation sets, including MPA, MVO, PSO, MFO, SSA, GWO, and WOA. The results of the experiment demonstrate that the optimisation techniques put forth surpass previously established meta-heuristics in the field of optimisation, encompassing both traditional and CEC problems, by a margin of over 95% in terms of attaining a superior ultimate solution. Additionally, with regards to solving truss optimisation difficulties as a large-scale real-world engineering challenge, the outcomes indicate a performance boost of over 65% in obtaining significantly better solutions for problems involving 260-bar and 314-bar; conversely, in the case of 340-bar issues, the improvement rate is slightly lower at almost 25%.

On the DInSAR technique for the structural monitoring of modern existing bridges

The setting up of efficient strategies for safety assessments and maintenance of modern existing bridges is a crucial research challenge in structural engineering. In Italy, this topic has recently been addressed in guidelines issued by the Ministry of Infrastructures and Transport in 2020. The guidelines outline procedures and tools for safety assessments and maintenance interventions: a mandatory step is the analysis of original documents (concerning the design, the construction process and the maintenance interventions) in order to acquire robust knowledge of the structure. As noted in recent works in the literature, non-invasive structural monitoring approaches play a crucial role in the safety assessment of existing bridges. One such approach is multi-temporal differential synthetic aperture radar interferometry (DInSAR). This paper presents a cross-disciplinary process for the structural monitoring of modern existing bridges, based on integration of DInSAR measurements, exploiting Cosmo-SkyMed measurements collected during the period 2011–2019, and accurate knowledge of the structures derived from analysis of original documents conserved in historical archives. The procedure is applied to two reinforced concrete Gerber bridges in Rome, designed in the 1930s.

Secondary silane grafting on aramid fibers improves the interfacial bonding performance in textile composite materials

To improve the chemical and physical surface features of aramid fibers and the bonding quality at the interface, carbon nanotubes, dopamine and silane coupling reagent KH560 were used to modify the surface of aramid fibers. The fiber surface was characterized by FTIR, XPS, SEM and AFM. The single-fiber specific strength, surface roughness, wettability and interfacial shear strength of the modified fiber were quantified. Finally, the uniaxial tensile behaviour of the textile composite laminate with the modified fibers was tested. The experimental results show that: after the grafting of silane coupling reagent as a second modification step, the amount of oxygen-containing groups on the surface of aramid fibers, and the surface roughness, and the ability to impregnate resin are further improved. The single-fiber specific strength, the interfacial shear strength by fiber pull-out tests, and the tensile strength of the laminate are increased by 21.62%, 73.57%, and 51.60%, respectively. This work demonstrates a general surface modification strategy working for diverse types of fibers, synthetic or natural. The present findings help to develop a broad range of high-performance textile composites to address long-term challenges in structural engineering.

Deformation of unsaturated collapsible soils under suction control

Abstract Collapsible soils present significant geotechnical and structural engineering challenges worldwide. They can be found in arid or semi-arid regions and are directly affected by the multi-step wetting procedure due to the reduction of soil suction. The main objectives of this paper are to investigate the volume change behaviour, collapse mechanism and deformation characteristics under the control of suction and net vertical stress. In this study, three types of collapsible soils were investigated such as natural soils of sandy gypseous, silty loess, and artificial soil of gypsum–sand mixture. A series of constant net stress-suction control (wetting and drying) tests using a combination of axis-translation and vapor equilibrium techniques were deployed to cover a wide range of applied suction. The test results show that large volume change and collapse deformation occur upon a stepwise suction decrease. On the other hand, shrinkage behaviour resulting from increases in imposed suction is observed during the drying path. The collapse deformation depends on the stress path and is a function of net normal stress, suction, dry density, and degree of saturation. The water content and the degree of saturation dramatically increase as the applied suction decreases from the initial high to zero values at the drying path.

Improving the punching shear and shear capacity of reinforced concrete elements with a new post-installed retrofitting system

Finding appropriate strengthening solutions for existing reinforced concrete (RC) elements is always a challenge for structural engineers. Additional load capacity may be needed as the change of type of occupancy and more restrictive design standards require higher load levels or different detailing of reinforcement. This paper introduces a post-installed retrofitting system consisting of an adhesive and a concrete screw anchor that can be used to improve either the pure shear capacity or the punching shear capacity of a RC beam or slab. This post-installed retrofitting system acts as shear reinforcement that can be installed with relatively minimal disruption as it is only installed at the soffit of the RC element being strengthened. The system was tested for its suitability and the results were approved by the German Construction Authority with a National Technical Approval. Published parameters are used for the standard methods of detailing shear and punching shear of a RC element according to EN1992-1 and EN1992-2. Calculations and tests have shown that with the use of this post-installed retrofitting system, the shear strength of existing concrete elements can increase by up to 100% and consequently increase the lifetime of a structure. This paper also discusses the test methods employed, the test results, and sample projects that made use of the said system. Another important finding is the substantial savings in project cost attributed to the installation methodology that comes with the system.

Review on Seismic Analysis of Multistoried Building in Hilly Region

Abstract: Due to sloping land and high seismically active zones, designing and construction of multistory buildings in hilly regions is always a challenge for structural engineers. This review paper focuses to establish a review study on the Possible Types of building frame configuration in the hilly region and he behavior of Such building frames under seismic loading conditions, and (3) The recent research and developments to make such frames less vulnerable to earthquakes. This paper concludes that the dynamics characteristics of such buildings are significantly different in both horizontal and vertical directions, resulting in the center of mass and center of stiffness having eccentricity at point of action and not vertically aligned for different floors. When such frames are subjected to lateral loads, due to eccentricity it generates torsion in the frame. Most of the studies agree that the buildings resting on slanting ground have higher displacement and base shear compared to buildings resting on plain ground and the shorter column attracts more forces and undergoes damage when subjected to earthquake. Keywords: Building frame configuration, Seismic behavior, Dynamic characteristics, Response spectrum analysis, time history analysis.

Seismic Response of Large span slab in Horizontal Setback Building

Abstract: The demand for multi-storey buildings is increasing day by day. Residential plus commercial building is mainly used for wide span needs. Wide span required for Flat slab, Waffle slab and ribbed slab stands An excellent option for architects when larger openings in a building need to be covered with as few columns as possible. The use of different types of plates is developing as a new trend and is becoming a major challenge for structural engineers. Therefore, it is necessary to study about its structural behavior. The project is carried out under earthquake zone III under the earthquake analysis of G+9 storey building. For this study, four different types of large span slab structure are modelled in C-shape (Horizontal Setback Building) having 10-stories i.e. G+9 storied buildings with 3.50 meters height for each story is modelled and analysed. The plan area of all four buildings is same i.e. 2859 square meters (49.50 m x 82.50 m) each. These buildings were designed in compliance with the Indian Code of Practices for earthquake resistant design of buildings. Base of the building were fixed. The square sections are used for structural elements. The height of the buildings is considered constant throughout the structure. The buildings are modelled using ETABSvr.2016. Keywords: large span slab, ETABSvr.2016, Horizontal Setback Building, Flat slab, Waffle slab and ribbed slab

Seismic Response of Large span slab in Horizontal Setback Building: A Review

Abstract: The demand of multistory Building is increases day by day. The residential plus commercial building predominantly used for the need of large span. The large span is needed for Flat slab, Waffle slabs & ribbed slab stands as an excellent option for architects when larger spans in a building has to be covered with the least possible number of columns. The use of different types slabs are evolving as a new trend and are becoming a big challenge for structural engineers. Therefore it is necessary to study about its structural behavior. The paper is review the behavior of different types slab for large span type of building. Final aim to gets the suitable type of slab for large span for effective manner. It is found that very less work is taken setback building with large span, it is required to analysis on the setback building with large span. Keywords: Flat slab, Waffle slabs, ribbed slab, multistory Building, large span.

Seismic risk assessment of a steel building supported on helical pile groups

Designing structures to be the least vulnerable within earthquake-prone areas is a serious challenge for structural engineers. One common and useful tool that structural engineers use to predict the vulnerability of a structure during an earthquake is a fragility curve. However, most structural fragility curves do not take into consideration the contribution of pile foundation systems in the structural vulnerability. Therefore, this study aims to modify existing fragility curves of a six-story fixed-base steel frame hospital building with buckling-restrained braces, to incorporate the effect of helical pile group behavior on the fragility of the structure. To that end, a finite element model of the investigated structure was modified with results from a full-scale shake table test performed on two groups of helical piles embedded in dense sand supporting a superstructure. The primary results show that fixed-base design may not be conservative for all conditions and soil–foundation interaction should be considered when creating fragility curves, especially for a stiff structure on soft soils where a high-intensity earthquake is anticipated.

Comparison of different finite element model updates based on experimental onsite testing: the case study of San Giovanni in Macerata

Understanding the behavior of historic structures that have undergone structural changes, restorations, and damage over time is still a significant challenge for structural engineers, particularly in those countries subject to high seismic risk, such as Italy. The study of built heritage for its prevention and conservation is an active research topic, due to the numerous uncertainties present in historic structures. Finite element modelling has become the most common and accessible method to study the behavior of complex masonry structures, however, the gap between numerical and experimental analysis may lead to erroneous results. Model updating techniques can reduce the discrepancy between the behavior of the numerical models and the testing results. The goal of this work is to illustrate a methodology to integrate the information derived from local, global, and geotechnical investigations into the finite element model of the masonry historical church of San Giovanni in Macerata, considering the Douglas–Reid model updating method. The PRiSMa laboratory of Roma Tre University carried out local investigations such as sonic tomography, video endoscopy and double flat jack tests, along with five ambient vibration tests that were processed through the operational modal analysis to extrapolate the dynamic properties of the building (modal frequency, modal shape vector and modal damping). The combined use of global, local and geotechnical information implemented in the methodology effectively reduced the uncertainties of the model and led the refinement and validation of the most relevant structural parameters.