Ultra-high performance concrete(UHPC) waffle panels have the advantages of light weight, high stiffness and load-bearing capacity, and have good application prospects in projects such as large-span bridge decks and building roofs. Four UHPC waffle panels model with a 1∶2 scale were designed and completed for static loading tests, with a focus on exploring the crack resistance, stiffness, load-bearing capacity, and mechanical characters of the UHPC waffle panels under four point and four edge support boundary conditions, and different transverse rib spacing. A fine finite element model was established using ABAQUS to further study the influence of design parameters such as the reinforcement ratio, distribution of longitudinal and transverse ribs, top plane thickness and rib height on the mechanical performance of UHPC waffle panels, and to propose optimization design suggestions. The test results show that the UHPC waffle panels do not crack under the designed wheel load during the four point loading stage. During the single point loading stage, the four point supported waffle panels undergo bending failure, mainly bearing longitudinal force. The four edge supported waffle panel undergoes punching failure with a significant increase in stiffness and load-bearing capacity. Properly increasing the transverse rib spacing and reducing the number of transverse ribs can make the bidirectional stress state of the UHPC waffle panels more obvious and the material utilization rate higher. The diameter of the tensile reinforcement at the bottom of the longitudinal and transverse ribs and the top plane thickness are the main factors affecting the stiffness and load-bearing capacity of the UHPC waffle panels. Based on the research results, a combination of 3 longitudinal ribs and 3 to 5 transverse ribs is recommended for UHPC waffle panels with a span of 5 to 6 meters, and the top plane thickness does not exceed 100 mm.

Through static tests on 12 ultra-high performance concrete (UHPC) corbels, this study investigates the influence of key parameters, such as shear span-to-depth ratio, steel fiber volume ratio, and stirrup reinforcement ratio, on the shear behavior of corbels. The results indicate that, compared to high performance concrete corbels without steel fibers, UHPC corbels exhibit a significant increase in cracking load, accompanied by a transition in failure mode from shear failure to flexural failure. Reducing the shear span-to-depth ratio and increasing the stirrup reinforcement ratio enhance the shear carrying capacity of the corbels. Collected experimental data of UHPC corbels were used to evaluate the applicability of shear capacity calculation formulas for corbels in the specifications GB 50010—2010 ‘Code for design of concrete structures’ and JGJ/T 465—2019 ‘Standard for design of steel fiber reinforced concrete structures’, as well as the theoretical models. It is observed that the existing models tend to be conservative, resulting in underestimated predictions of UHPC corbel capacity. Based on this assessment, an improved strut-and-tie model suitable for predicting the shear capacity of UHPC corbels was proposed. The model’s average ratio of computed results to the experimental results collected in this study is 1.15, with a coefficient of variation of 0.07. The improved model demonstrates better accuracy and consistency compared to existing computational models, serving as a reference for UHPC corbel design.

To enhance the loadbearing capacity and durability of tunnel segments, a structural reinforcement method that is corrosionresistant and easy to construct was proposed.  Based on optimizing the working performance and mechanical properties of sprayed ECC, CFRP grid-reinforced sprayed ECC (CFRP-ECC) composite was used to strengthen the tunnel segment in this paper. Considering parameters such as reinforcing materials, thickness of ECC and CFRP grid, static loading tests were conducted on the simply supported CFRP-ECC composite reinforced tunnel segments to investigate their mechanical behavior. The test results indicate that the cracking bending moment of segment strengthening with ECC and CFRP-ECC increased by 26.67% and 13.33%, respectively, compared with the unreinforced segment. The proposed strategy effectively inhibits the generation of cracks. Both the ultimate bearing capacity and ductility of the segment are improved by strengthening with 20mm thickness of ECC, whose ductility increased by 44.6% compare to unreinforced segment. The ultimate bearing capacity of the segment reinforced with CFRP fabric is slightly lower than that of the unreinforced segment, but its ductility is increased by 195%. In addition, the analytical model established by ABAQUS could effectively analyze the mechanical properties and failure modes of segments. The contact between ECC and concrete established through the cohesive model can effectively simulate the interfacial bond slip performance.

To repair cracks at the arc-shape cutouts of the diaphragm in steel bridges, reinforcement methods of bonding CFRP sheets, SMA/CFRP composite patches, and Fe-SMA plates were proposed based on the traditional crack-stop hole method. The fatigue tests were conducted on eight cracked diaphragm specimens with different repair methods. The results show that bonding CFRP sheets, SMA/CFRP composite patches, and Fe-SMA plates can effectively improve the stiffness of the cracked region and introduce precompression by activating SMA, thereby reducing the stress concentration, delaying the crack initiation and propagation, thus significantly improving the fatigue life. The fatigue life of diaphragms repaired by CFRP sheets and SMA/CFRP composite patches are 2.59 and 5.10 times that of the diaphragm repaired solely by crack-stop holes，respectively. Moreover, the diaphragm repaired by Fe-SMA plates exhibits a remarkable enhancement, where the resulting fatigue life is 12.68 times that of the diaphragm repaired using crack-stop holes. Furthermore, the feasibility and effectiveness of Fe-SMA plates covering crack-stop holes method were verified through actual repair applications of cracked diaphragm cutouts in the Sutong Bridge and other kilometer-level steel bridges.

Modular structures have the advantages of high construction efficiency, high standardization, labor saving, low carbon emission, environmental protection, safety and reliability compared with traditional structural forms, which show great development potential in the context of new building industrialization. With the development of economy and society, modular structures have been gradually used in multi-story and high-rise buildings in recent years, which face more challenges in terms of bearing performance and construction technology. In order to promote the research and application of multi-story and high-rise modular structures, research progress of modular units, modular structural systems, structural mechanical properties and design requirements and modular construction technologies was summarized. The classification of modular units was reviewed, and the advantages, disadvantages and application scope of different types of modular units were compared. Multi-story and high-rise modular structural systems and their engineering applications were introduced. The research on the mechanical properties of modular structures under various types of loads and related design standards were sorted out. The existing modular construction technologies were summarized, and the various aspects of modular construction are discussed in detail according to the construction sequence. At present, there are still deficiencies in connections, structural system analysis, application of high-performance materials, standard specifications, installation equipment and integrated design, which require systematic studies that take into account the whole construction process and synergies among various disciplines to build a technology system for multi-story and high-rise modular structures.

Material-structure integrated design is to consider the material performance in structural design and to originate the material design from the requirements of the structure, forming a multi-scale design from materials to structures, which is a research focus in concrete constructions in recent years. The design of concrete materials and structures based on data and artificial intelligence algorithms subverts the traditional paradigm of relying on experience and requiring repeated trials, improving effeiciency in material design and structural innovation. This study reviewed the current research on the intelligent design of concrete materials and integrated design of material and structure. The research scope and key issues of data-driven properties prediction and design at the material level was summarized first. The strategies and effects of crack resistance material-structure integrated design considering complex interactions of temperature, humidity and constraint was discussed. The method for durability design and the improving measures using chloride diffusion as an example were described. The method of high-performance design using ultra-high performance concrete as an example was also explained. Finally, the framework for future data-driven material-structure integrated design as well as a comprehensive research concept including material production, design, preparation and structural application were proposed. The further studies should focus on database construction, knowledge-informed machine learning algorithms and multi-scale correlation.

To enhance the seismic performance of steel frame structures, prestressed self-centring hybrid connections (SCHC) equipped with SMA were introduced into self-centring hybrid steel frames (SCHF). A simplified numerical model to simulate the hysteretic behaviour of the SCHC was developed based on the physical test data. Validated modelling techniques were employed to develop codified frame structures, considering the fracture behaviour of prestressed cables and SMA bolts. The seismic performance of the SCHF was assessed via static pushover analyses, nonlinear dynamic analyses and fragility analyses. The results indicated that the SCHF exhibited trilinear flag-shaped hysteretic features and excellent self-centring performance. Compared to the self-centring steel frames (SCF) equipped with prestressed cables only, the SCHF exhibited better collapse resistance performance and self-centring performance. The collapse margin ratio of the SCHF was increased by 50%, and the maximum damage margin ratio was increased by 55%. Nonlinear spectral analyses were conducted based on the equivalent single-degree-of-freedom systems, confirming the introduction of the complementary mechanism composed of prestressed cables and SMA bolts can effectively reduce the inelastic seismic demand, which revealed the seismic mechanism of the SCHF from the perspective of material-structure integration.

This paper presents a study on the relationship between material-structure and seismic performance for glued laminated timber frame-shear wall structures. Six six-story prototype glued laminated timber frame-shear wall structures were designed with different construction types of CLT shear walls. The finite element models of the prototype structures were established in OpenSees. Modal analyses and incremental dynamic analyses were conducted. The fundamental periods, base shear, maximum inter-story drifts, and peak floor accelerations of these prototype structures were obtained and compared. The fragility of the connections within CLT shear walls and glulam frames was also evaluated. The results show that, compared to frame-shear wall structures with platform-type CLT shear walls, those with balloon-type CLT shear walls have smaller inter-story drifts, while their acceleration-sensitive nonstructural components and CLT connections are more prone to damage. For the connections in balloon-type CLT shear walls, the probabilities of exceeding severe damage and collapse exceed 70% and 40%, respectively, during eight-degree strong earthquakes. The connection damage of glulam frames remained low during seismic events. Their probabilities of exceeding minor damage were lower than 25% during eight-degree strong earthquakes.

To study the in-plane mechanical behavior of the half steel ultra-high performance concrete composite plate (HSUHPC), twelve HSUHPC panels are designed and tested by a self-developed planar bi-directional multi-functional element tester in this paper. The test program includes three uniaxial tensile tests, three biaxial tensile tests, and six cyclic shear tests. The results show that the steel plates, bars, and UHPC can realize compatibility of deformation at the elastic and initial cracking stages and they can sustain the load together at all loading stages. Effective stress redistribution can be developed between the steel bars and UHPC. Due to the high residual tensile strength and significant strain hardening properties, the UHPC is capable of providing at least 50% of tensile and shear capacity. The reinforcement ratio and steel ratio both have an influence on the bearing capacity of the HSUHPC plate. The biaxial tensile condition has little influence on the bearing capacity of the HSUHPC plate, of which the capacity is close to that of the HSUHPC plate under uniaxial tensile condition. Based on the test data and methods in the codes, formulas for calculating the tensile and shear capacities are proposed for the HSUHPC element.The deviation between the calculation results of the formula and the test results is within 10%,which proves that the high accuracy of the proposed formula.

When using FRP-steel composite panels instead of pure steel plates are used as shear wall panels in steel frame-steel plate shear walls, the tensile field effect is enhanced. However, the ductility of the structure is reduced, due to the limited tensile strain of the fibers. To address this issue, filling PET foam between the FRP and inner steel plate was proposed to improve the ductility and out-of-plane bending stiffness of the shear panel. Quasi-static test studies on two 1/3 scale shear wall specimens with hinged rigid frame were completed to investigate the effects of FRP corrugated panels and PET foam on the seismic performance, where the wall panels were made of pure steel plates and form-infilled CFRP-steel composite panels, The study demonstrated that filling PET foam between CFRP and steel plates effectively reduces the strain of CFRP in the limit state, thereby enhancing the ductility of the wall panels. Additionally, the use of CFRP-steel composite panels increases the initial stiffness, peak load, and accumulative energy dissipation by 32.11%, 36.39%, and 105.93%, respectively, compared to a pure steel plate shear wall. The theoretical analysis on the tensile and shear bearing capacities of CFRP-steel composite panels was conducted. Furthermore, a structural restoring force model was proposed and its accuracy was verified through comparison with test results. The maximum errors of the initial stiffness and the bearing capacity within the drift of 2% are 6.0% and 5.8%, respectively. The stress and deformation modes of each component were studied through finite element simulation. The stress of CFRP in the shear wall was concentrated in the bolt area, and local failure occurred near the washer plate. To avoid local failure of CFRP and improve its stress level, full-length washer plates and a fiber ply scheme of ±45° are recommended.

To investigate the tensile properties and piezoresistive response of carbon-glass hybrid fiber grid reinforced cementitious matrix (C-GFRCM), 12 sets of C-GFRCM plates were subjected to uniaxial tensile tests. The influence of mortar type, prestress level, adhesive, and the arrangement of glass fiber sheet on their tensile properties and fiber utilization rate was analyzed. The changes in electrical resistance of carbon fiber bundles during the tensile process of C-GFRCM plates and the response mechanism of specimen stress state, as well as the law of resistance response and crack occurrence position, were studied. The results showed that prestressed C-GFRCM plates mostly exhibited a single crack failure mode, while epoxy resin adhesive C-GFRCM plates mostly experienced fiber pullout failure, and C-GFRCM plates with geopolymer adhesive saw fiber slip and pullout failure. The prestressing process mainly enhances the cracking load of C-GFRCM plates, and the higher the prestress level, the more significant the enhancement effect, with a maximum increase of 267%. Dispersion pasting of glass fiber cloth using epoxy resin adhesive can significantly enhance the ultimate load of C-GFRCM plates, with a maximum increase of 320%. During the tensile process, the piezoresistive response of C-GFRCM plates exhibited three stages: in the elastic stage, the resistance showed no significant change; in the crack development stage, the resistance began to increase and fluctuate at the crack initiation point; in the crack enlargement and failure stage, the resistance at the main crack increased significantly. The resistance response can accurately characterize the stress state of C-GFRCM plates and determine the occurrence position of cracks. The sensitivity of resistance  of C-GFRCM plates to stress state varies changes with different design parameters.