Advances in Modern Structural Engineering: From Materials to Building Structures

1. Introduction

Driven by the development of engineering technology, the “dual carbon” goal, and the construction of urban resilience, modern structural engineering is undergoing comprehensive innovation. On the one hand, integrating new materials (recycled aggregate concrete, UHPC, smart fibers, etc.) and industrialized building technologies (both modular and prefabricated) promotes the transformation of the industry towards high efficiency and environmental protection. On the other hand, the safety of engineering structures in disaster scenarios—such as earthquakes, explosions, and frozen soil—imposes higher requirements for structural performance. Meanwhile, pressures such as labor shortages and carbon emission control force the industry to abandon traditional construction models and shift towards standardization and intelligent development. From large-scale structures above ground to underground stations, and from over-height buildings in cities to light-steel residential buildings in rural areas, structural engineering application scenarios continue to expand. There is an urgent need to integrate multi-dimensional research such as material innovation, structural optimization, and disaster prevention to solve the technical bottlenecks in practice.

Current research has covered core directions such as the application of new materials, industrialized structural systems, disaster prevention, and intelligent monitoring. In the field of materials, the physical properties of recycled aggregate concrete, fiber-reinforced concrete, and coral sand have been explored [1,2,3]. In terms of structural forms, industrialized technologies such as modular and prefabricated concrete structures and light-steel composite frames have demonstrated high-efficiency and low-carbon advantages [4,5]; they have been applied in scenarios such as bridges, residential buildings, and subway stations [6]. In terms of disaster prevention and monitoring, technologies such as seismic vulnerability analysis, fiber grating sensing monitoring, and image-recognition intelligent detection are seeing increased promotion [7], and relevant specifications for anti-progressive collapse and anti-explosion design are also gradually being improved [8,9].

However, there are still significant deficiencies in the research: Firstly, in-depth material studies are lacking. For example, the scope of SRPRAC performance research is limited [10,11], the mechanism of the synergistic effect of steel-fiber self-compacting high-strength concrete’s key parameters is unclear, and there is a lack of quantitative modeling of the coupling effect of recycled aggregate particle size and content [12,13]. Secondly, research on structural systems is fragmented. Modular buildings lack a life-cycle perspective, prefabricated joints have problems such as reinforcement congestion and uneven quality [14,15], and new connection methods (welding, bolting, prestressing) each have their own downsides. Thirdly, research on special scenarios is weak. There are disputes about the mechanical properties of mortar–masonry stones under cold conditions and the dynamic interaction between soil, piles, and over-height structures [16,17]. Furthermore, there is a lack of anti-impact performance evaluation for steel frames with anti-channel steel joints. Fourthly, the pathways to technical implementation are insufficient. For some innovative technologies (such as the combined shear–slot connection and recycled aggregate system), a mature application plan has not yet been formed, and traditional detection methods’ problems of low efficiency and strong subjectivity have not been completely solved.

This Special Issue focuses on the core theme of “Advances in Modern Structural Engineering: From Materials to Building Structures” and includes the latest research results in the fields of material innovation, structural system optimization, disaster prevention, and intelligent monitoring.

2. Overview of the Published Articles

A total of nineteen articles have been published, presenting key progress in, for example, application breakthroughs for new materials (such as UHPC and recycled aggregate concrete), life-cycle optimization of industrialized structures (modular and prefabricated), and structural design innovation in special scenarios (seismic-resistant, anti-explosion, and cold regions).

Guo developed a random distribution program for steel-recycled polyethylene terephthalate hybrid fiber recycled concrete (SRPRAC) (Contribution 1), examining the compressive failure mode and influence of different factors. Results indicate that the failure was mainly distributed within the specimen, forming a distinct X-shaped damage zone. Increasing fiber content reduced the equivalent plastic strain area above the compressive failure threshold, though the effect diminished beyond 1% total fiber volume. The mesoscopic model effectively captured SRPRAC’s stress–strain damage behavior under compression.

Liu developed a novel recycled aggregate (RA) equivalence parameter (λeq), considering the influence of RA content and size on the mechanical properties of concrete (Contribution 2). Empirical equations were developed using linear regression to describe the test results and predict the impact of RA content and size. The results showed that the measured mechanical properties and regression equations provided a reference and basis for engineering applications.

The effects of water–binder ratio and mortar and steel fiber content on the workability and mechanical properties of high-performance concrete were also studied by Liu (Contribution 3), and the mechanical properties were evaluated according to compressive and flexural strengths. The results show that when the compressive strength of self-compacting high-strength concrete with steel fiber is 90 MPa, the optimum mix ratio is a water–binder ratio of 0.22, sand ratio of 46%, and steel fiber content of 0.3%. This provides insights into the potential for the large-scale and high-value utilization of steel fibers and the development of cost-effective ways to reduce the carbon footprint of self-compacting concrete production.

To solve the durability degradation problem of traditional rubble masonry in cold regions, Dong studied polypropylene fiber–mortar–masonry blocks with different fiber contents (Contribution 4). Using acoustic emission and digital image technology, the author conducts a series of tests on a scaled-down polypropylene fiber–mortar–masonry structure. The results show that when the dosage of PPF is 0.9–1.1 kg/m³, the conte is optimal, and under the same number of freeze–thaw cycles, the strength of the specimens without fiber addition decreases more rapidly than those with.

The initial rotational stiffness and ultimate moment of fully bolted connections in panelized steel modular structures were investigated by Wang, who combined finite element analysis via ABAQUS with experimental tests (Contribution 5). The effects of the column wall thickness in the core zone, internal diaphragm configurations, angle steel thickness, and stiffener layouts on the joint stiffness and ultimate strength were evaluated, leading to practical optimization suggestions, which offer a theoretical foundation for engineering applications of panelized steel modular structural joints.

A new self-locking unlockable modular building with an inter-module connection is introduced by Liu, and its seismic performance investigated (Contribution 6). This new connection can achieve fast connection and unlocking during construction through exceptional design. Taking the Tianjin Binhai Apartment project as the background, five- and six-story structural models, using traditional rigid connections and new connections, respectively, were established. Reaction spectrum analysis was carried out, and it was suggested that the new connections can be applied in buildings up to six stories high.

A P-DFMA (Platform Design for Manufacture and Assembly) building product platform architecture for modular apartments is proposed by Wang (Contribution 7). Verified via the case of the modular dormitory building project at Tianjin Chengjian University, the results show that, compared with the traditional prefabricated construction mode, the P-DFMA platform mode achieves a cost saving rate of 54.8% in project design, production, and cross-link collaboration.

A new type of prefabricated concrete beam–column node is proposed by Cui (Contribution 8) to address the problems of steel bar congestion, installation and construction difficulties, as well as the difficulty in ensuring node quality in existing concrete beam–column nodes. The node structure and design method are provided, and scaled model tests are conducted to analyze the stress distribution and bearing capacity of the node’s core area under low-cycle reciprocating loads. The research results will be beneficial for the design and engineering application of new prefabricated concrete beam–column joints and will further promote the application of prefabricated concrete buildings.

Liu proposed a new type of modular steel structure emergency repair pier joint that facilitates rapid assembly and connection between modular units (Contribution 9). The author employed the finite element method to analyze bending performance under lateral displacement loads both perpendicular and parallel to the joint-opening direction. Furthermore, a simplified component method-based calculation model for the joint is proposed.

Bian developed a new prefabricated floor system (Contribution 10) featuring prefabricated slabs made from recycled concrete, connected via reinforced shear pocket joints. This study investigated the shear performance of this new type of floor joint, examining the effects of various parameters such as joint configuration, stud diameter, and both recycled concrete and grout strengths. Their research revealed stud–shear as the floor joint failure mode under different design parameters, and optimal reserved hole diameter proved beneficial for enhancing joint shear performance, with a diameter of 40 mm showing superior performance.

Liu proposed a novel diaphragm wall–beam joint (Contribution 11) based on post-poured ultra-high-performance concrete (UHPC) and non-contact lap-spliced steel bars. A full-scale experiment was conducted on the diaphragm wall–beam joints, and the failure modes, bearing capacity, overall stiffness, crack resistance performance, and force transmission mechanism of the new joint type were investigated. The results show that, compared with traditional cast-in-place concrete joints, the cracking and yield moments of the proposed UHPC joint increased by 8.7% and 5.4%, respectively.

Yang investigated a novel steel grid shear wall (SGSW) structure with lightweight and discrete lateral-resistance members (Contribution 12), focusing on its structural behavior in lateral resistance. The formulas for SGSW lateral-resistant capacity and initial stiffness were derived through the static equilibrium method. Then, the influence laws of the span–height ratio, steel member spacing and section size of the steel members on the SGSW lateral-resistant performance were determined via parametric analysis. The accuracy of the calculation formula was validated, showing high accuracy and reliability, with the error between the formula’s calculation and simulation results not exceeding 8%.

The structural health monitoring and stress prediction of large-span steel roof structures in airport terminals was investigated by Cui (Contribution 13), focusing on the impact of temperature variations and developing an advanced hybrid prediction model. A comprehensive monitoring system was designed and implemented to track key structural responses, including stress, displacement, and temperature, revealing significant correlations between thermal effects and structural behavior. The findings highlight the importance of temperature effects on structural integrity and offer practical insights for large-span steel structure health monitoring in complex environments.

Xue proposed a recognition model for identifying member shapes in images of cuplok scaffolds (Contribution 14). Combined with an energy method-based judgment criterion, the scaffold system’s safety state was evaluated, ultimately forming an image recognition-based technique for detecting cuplok scaffold safety performance. Experimental studies on a reduced-scale model demonstrated that the proposed method achieved an accuracy and efficiency of 80% in both recognition and judgment.

A prefabricated reinforced concrete column–steel girder (RCS) hybrid frame structure using column–column connections was investigated by Wang (Contribution 15). The seismic susceptibility and key influencing factors were systematically evaluated by establishing an analytical model and employing the incremental dynamic analysis (IDA) method. A typical three-span, six-story prefabricated RCS hybrid frame structure is designed and numerically modeled, showing good agreement with the test data.

Liang developed a refined 3D finite element model of a 52-storey soil–pile–structure system in ABAQUS, analyzing the seismic performance and damage characteristics of high-rise frame–core–tube structures on soft soil and explicitly incorporating dynamic soil–pile–structure interactions (SSIs) (Contribution 16). Key findings demonstrate that SSIs significantly alter structural response; they amplify lateral displacements and inter-story drift ratios throughout the structure, particularly at the top level, highlighting the necessity of including dynamic SSIs in seismic analysis for high-rises on soft soil.

Wu developed a three-dimensional finite element model of an underground station (Contribution 17), using LS-DYNA to evaluate the blast resistance performance of underground station structures under ground-level nuclear explosion air shock waves. The blast mitigation effects of phononic crystals are primarily analyzed and the influence of parameters such as spatial arrangement, buried depth, and material properties of phononic crystals on blast resistance is systematically examined. Key findings offer insights for designing phononic crystal-based blast protection in underground station structures.

An overall three-dimensional finite-element model of a utility tunnel–soil–pipeline is established in Abaqus by Wang (Contribution 18). The author applied overpressure loads to the inner wall of the gas chamber in the utility tunnel, calculated and analyzed the dynamic response laws of the utility tunnel and the pipeline, and proposed anti-explosion protection measures such as reinforcing the gas chamber, using energy-absorbing materials around the utility tunnel, and setting up hollow piles between the utility tunnel and pipelines.

Wang investigated the impact resistance of steel-framed subassemblies with extended reverse channel connections under the impact of falling debris (Contribution 19), conducting drop-hammer impact tests to obtain baseline data. With a focus on impact resistance, a validated finite element model using ANSYS/LS-DYNA was employed for the parametric analyses. The author’s useful findings offer critical technical support for optimizing steel structure designs to resist falling debris impact and enhance overall structural robustness.

3. Conclusions and Outlook

The field of modern structural engineering—from material research and development to structural system innovation—has always been a research hotspot in academic and engineering spheres. The research results collected in this Special Issue report on key progress in this area, such as application breakthroughs for new materials (e.g., UHPC, recycled aggregate concrete), the full-life-cycle optimization of industrialized structures (modular, prefabricated), and structural design innovation in special scenarios (seismic resistance, explosion resistance, cold regions). The above-mentioned achievements combine theoretical foresight and engineering practicality, providing important references for researchers and engineering technicians engaged in the fields of new material research, development and application; industrialized structural system construction; and engineering disaster prevention.