Infilled Frames Research Articles (Page 1)

This study experimentally and numerically examines the structural and seismic performance of recycled solid-brick masonry infills and load-bearing walls constructed from demolition materials. Solid bricks recovered from demolished structures were reused as infill in reinforced concrete (RC) frames and as standalone walls. Five full-scale panels, bare, 50% infilled, and 100% infilled frames, were tested under diagonal compression in accordance with ASTM E519-17, simulating in-plane seismic loading. Results showed that fully infilled frames exhibited a 149% increase in diagonal shear strength but a 40% reduction in ductility relative to the bare frame, indicating a trade-off between stiffness and deformation capacity. Finite element simulations using the Concrete Damaged Plasticity (CDP) model reproduced the experimental load–displacement curves with close agreement (within 6–8% in peak load) and captured the main failure patterns. Reusing cleaned demolition bricks reduces the demand for new fired bricks and helps divert construction waste from landfill, contributing to sustainable and circular construction. The findings confirm the potential of recycled masonry for low-carbon and seismic-resilient construction, provided that ductility limitations are appropriately addressed in design.

Impact of prefabricated constructional columns on the seismic performance of infill wall frames with half-wall openings

Multi-story buildings in seismic regions are susceptible to earthquake-induced damage; however, the direct correlation between observed damage patterns and underlying failure mechanisms remains insufficiently understood. The Ms6.8 Luding earthquake, which struck Luding County, Sichuan Province, China, in September 2022, offers a unique opportunity to investigate this relationship, as it affected a concentrated area with diverse building types and preserved a wide range of damage states. This study leverages the distinctive conditions of the Luding earthquake to elucidate the influence of wall element distribution on structural failure modes under seismic loading. To elucidate the underlying mechanisms, three representative buildings were analyzed using a one-dimensional numerical model. The simulations yielded shear force distributions, shear ratios, and displacement ratios across structural components, enabling a detailed assessment of failure modes. The results indicate that torsion-dominated structures are susceptible to premature failure of low-stiffness components due to excessive displacement, whereas high-stiffness components generally remain intact owing to their ductility. In contrast, translation-dominated structures fail when high-stiffness components fracture at small displacements, resulting in global collapse without substantial ductility or load-bearing contribution from other elements. Structures that remained undamaged exhibited a relatively uniform stiffness distribution, enabling them to resist seismic forces primarily through overall capacity rather than ductility. The numerical results closely reproduced the observed damage patterns, thus validating the proposed mechanisms for the three structural categories. These findings contribute to a deeper understanding of seismic damage processes and provide a basis for enhancing seismic design and retrofitting strategies for both new and existing structures.

Reinforced concrete (RC) frames infilled with brick masonry are widely used in construction due to their improved lateral resistance. However, their behavior under lateral loading is complex due to the interaction between the frame and the infill. Modifying the interface materials has shown potential in improving the overall performance under lateral loads. However, the influence of interface material type and thickness on structural response needs further exploration. Limited research exists on the effect of interface materials and their thicknesses on the non-linear behavior of infilled frames, particularly when using flexible materials. This study evaluates the static lateral performance of Y-joint with brick masonry infill using three interface materials—cement mortar, bitumen, and rubber—across varying thicknesses. The interaction is analyzed for displacement, stress concentration, and failure load in ABAQUS. Rubber interfaces increase displacement by 80–90% compared to cement mortar and bitumen interface, while bitumen interfaces show negligible variation in stiffness across different thicknesses. Rubber interface with 20 mm thickness reduces stress concentration by 34.3% compared to 5, 10, and 15 mm. Cement mortar presents bonding issues at increased thicknesses for 20 mm thick model, with maximum debonding of 58.9% was found. These findings demonstrate that selecting appropriate interface materials and thicknesses can significantly enhance structural resilience. ANN-based approaches can efficiently identify optimal configurations, reducing dependence on computational simulations. The regression (R) value among the training, testing and validation for all cases reaches above 0.9 for stress distribution, stiffness, and contact area.

Out-of-plane mechanical behavior and theoretical analysis of concealed column timber frame infill wall

ABSTRACT To improve the seismic performance of infilled wall-reinforced concrete (RC) frame structures, a novel type of masonry and connectors has been developed, forming a flexible infilled mortise-tenon masonry-RC frame (IMTM-RCF). The design objective is to enhance wall integrity and eliminate the adverse effects of wall-frame interaction. Two bays of 1/3 scaled frame specimens, including the IMTM-RCF and bare frame, were designed and fabricated. Low-cycle loading tests demonstrated that the integration of the IMTM system not only mitigated damage progression in the frame structure but also reduced seismic-induced damage in reinforced concrete (RC) frames under extreme earthquake loading conditions, compared to the bare frame. A separated refined finite element analysis model was proposed, which accurately depicted the force and damage conditions of the IMTM-RCF. A systematic investigation was conducted to evaluate the effects of wall frame constraint stiffness on damage progression and load-bearing capacity in IMTM-RCF systems. It was revealed that the structural load-bearing capacity could be effectively enhanced by appropriately increasing the constraint stiffness while ensuring that the damage remained within an acceptable range. Finally, the equation derivation for the structure’s initial stiffness was completed by the equivalent constrained infilled mortise-tenon masonry model, and the accuracy of the equation was verified.

For the past few decades, during each disastrous earthquake, severe damage and poor seismic performance of masonry infilled RC frames, including many newly designed ones, have been reported extensively. Inherent problems related to analysis and design methods for tight-fit infilled frame structures have not yet been solved and are recognized as being far from satisfactory in terms of completeness and reliability. The primary objective of this research was to propose and test an innovative method that can effectively mitigate undesirable interaction damage to masonry infilled RC frame structures. This proposed technical solution consists of connection of the infill panel to the bounding columns with steel reinforcement connections deployed in mortar layers and anchored to the columns. This is practical, cheap and easy to implement without any specific technology, which is especially important for developing countries. A three story, two bay RC building model with the proposed connection implemented on the infill walls was designed and tested on the shake table at IZIIS in Skopje, N. Macedonia. The test results and design guidelines/recommendations from the proposed research are also expected to benefit the infrastructural development in other countries threatened by earthquakes, preferably in the Balkan and the Mediterranean region.

ABSTRACT This paper presents an experimental and numerical investigation of the seismic performance of Autoclave aerated Lightweight Concrete (ALC) panel-filled reinforced concrete framed structure. For this, a full-scale experimental test was conducted on a two-storey reinforced concrete (RC) framed building infilled with ALC panels subjected to lateral quasi-static cyclic loading. The performance of ALC panels on in-plane and out-of-plane walls was in focus to study, especially the structural behaviour of panel walls with and without opening. Furthermore, a numerical model with minute details was presented, and the contribution of ALC panels to the stiffness of the building was assessed. The presented numerical model predicts good agreement with experimental results. In-plane wall panels experienced more damage compared to panels on the out-of-plane wall. Moreover, damage initiation and propagation in ALC panels near the opening were critical. The ALC panel infill frame showed more promising seismic performance.

Exploring the effect of various types of interface materials on the structural behavior of infill frame: a numerical study

Ceramsite aerated concrete blocks (CACB) are widely used in reinforced concrete frame infill walls due to their green, energy-saving, waste utilization, and thermal insulation characteristics. Investigations into building projects in areas with low seismic intensity and frequent typhoons have found that the cracking of CACB infill walls is severe, which hinders the use of this material. This article was dedicated to studying the reasons and development process of cracks in CACB infill walls, and proposing solutions. First, a 13 story framework building was analyzed using PKPM software to study the inter-story drift ratio under local reference wind pressure and gust wind pressure. Then, three full-scale models were made for quasi-static tests under horizontal loads to study the correlation between inter-story drift ratio and infill wall cracking. Experimental studies have shown that the inter-story drift ratio was 1/2149 and 1/2347 for infill wall frames with and without windows, respectively, when CACB infill walls cracked. Comparing PKPM analysis and experimental results, it could be seen that when the building was subjected to local reference wind pressure, the inter-story drift ratio was 1/2433, which was smaller than the cracking inter-story drift ratio. When subjected to the wind pressure corresponding to the gust wind, the structural deformation was much greater than the cracking inter-story drift ratio. Therefore, it could be concluded that the main reason for diagonal cracks in CACB infill walls was the unreasonable use of reference wind pressure in current design. To avoid the diagonal cracks, gust wind pressure should be used as the horizontal load instead of reference wind pressure in design. Simultaneously to improve both structural construction measures and material crack resistance to avoid cracking of CACB infill walls.

Numerical analysis of innovative layered infilled RC frames with rice husk-magnesium oxysulfate cement (RMOC) masonry

Machine learning-based seismic fragility curves of regular infilled RC frames

Block infills are usually regarded as non-loadbearing components in buildings, and are frequently neglected in the analysis and design of building structures. The main objective of this study is to perform static nonlinear analysis of hollow concrete block (HCB) infilled reinforced concrete buildings (RC) subjected to a seismic excitation. For this study, three different buildings were selected as case studies: a seven-story, an eleven-story, and a sixteen-story building, each with a standard floor plan. Bare RC frame buildings were analyzed and designed on ETABS based on Ethiopian Buildings Code Standards (ES EN: 2015). While numerical modeling and static pushover analysis of the designed building model cases were computed using SeismoStruct. The masonry panel model was employed to reproduce the behaviour of the full-scale infilled frame model using diagonal compression struts. The results from the pushover analysis were used to determine the fundamental vibration period and generate the capacity curves. It was observed that the presence of infills had a highly significant impact, causing a considerable increase in base shear until the infills began to crack. Additionally, the infills played a major role in reducing the fundamental vibration period of the structures. A seismic base shear of 5,150kN was found at significant damage performance levels with the corresponding roof displacements of 300, 420, and 600mm for seven-story, eleven-story and sixteen-story building models respectively. While their respective on set cracks of infills were observed at 17mm, 20mm and 24mm roof displacement. Therefore, for relatively high-rise buildings, the contribution of infills in terms of stiffness and energy dissipation becomes more important, as their impact on base shear and fundamental period is both substantial and significant.

ABSTRACTSeveral earthquake events revealed the severity of damage in reinforced concrete (RC) building structure mainly from the irregular placement of masonry infill and negligence of code compliant detailing provisions in structural components on building response. This study aims to evaluate the detrimental effects of nonuniform placement of infill panels in building structures constructed in regions susceptible to high seismic risk. Therefore, a finite element model (FEM) model of an older infilled frame RC building employed herein with various combinations of infill placement along with noncompliant detailing in structural components including bond‐slip effects in plastic region of frame components and the short column effects from frame infill interaction. Results are presented in terms of modal periods and confirm that the period obtained from theoretical or empirical models reported in literature provides a good estimate. Furthermore, the interstory drift ratio (IDR) at ultimate limit states obtained from nonlinear static and dynamic analyses depict the poor performance of in‐plan irregular configurations compared with the counterpart. Moreover, in irregular configurations, the roof displacement calculated from N2 and Extended N2 methods miscalculate the roof displacement obtained from nonlinear dynamic analysis and the difference in results increases from serviceability to ultimate limit states.

Open Ground Storey (OGS) structures are particularly vulnerable to seismic failures due to their inherent soft storey behaviour, which reduces lateral stiffness and significantly increases shear forces in the ground floor columns. This study aims to analyze the shear forces in columns of three-dimensional (3D) OGS Reinforced Concrete (RC) frames subjected to seismic loads, focusing on the effectiveness of two Lateral Load-Resisting Systems (LLRS): the use of stiff columns at the ground floor and the implementation of shear walls in various configurations. The seismic performance of these systems is compared with conventional OGS configurations and bare frames, considering the impact of infilled frames. The results of the study reveal that infilled frames significantly reduce the shear force in columns, with a reduction of up to 70% compared to bare frames. However, the shear force in ground floor columns of OGS frames is increased by about 78% compared to fully infilled frames due to the reduction in stiffness. The inclusion of shear walls in OGS frames effectively reduces this increased shear force. The ratio of ground-floor to first-floor shear forces for the OGS model ranges from 6.25 to 8.60, which can be reduced to 0.52 to 5.74 with the provision of various types of shear walls. Furthermore, the study finds that shear forces in peripheral and corner columns of OGS frames are about 10% higher compared to inner peripheral and core columns. It also highlights that increasing the ground floor height by 1 meter induces approximately 25% higher shear forces in ground floor columns. These findings underscore the importance of optimizing shear wall placement and other structural configurations to enhance the seismic resilience of OGS buildings.

The existence of diverse modeling approaches for masonry-infilled frames causes uncertainty among practicing engineers when seeking a definitive model for their design practice. This paper presents a practical and simple approach to modeling the masonry-infilled frames. The proposed approach models the plasticity in the beams and columns of the reinforced concrete (RC) frames using flexural plastic hinges while modeling the masonry panel as a nonlinear equivalent strut. The implementation of the hinge is based on discretizing the frame cross-section into fibers and utilizing a popular formula to estimate the plastic hinge length specific to masonry-infilled frames. Furthermore, the implemented equivalent strut model employs a trilinear force–displacement backbone curve. The efficiency of this approach was evaluated against the experimental results of four different tested infilled RC frames available in the literature. A conventional approach based on a typical explicit plastic hinge was included for comparison. Unlike the conventional approach, the numerical results obtained from the presented approach better matched the experimental results. Subsequently, the presented approach was utilized to investigate the effect of the aspect ratio of clay masonry infill panels on the behavior of RC frames. The investigation revealed that the panels with larger aspect ratios provided a larger contribution to the ultimate lateral load, despite experiencing lower ultimate axial stresses compared to panels with smaller aspect ratios. However, increasing the thickness of the masonry infill with a small aspect ratio appeared to improve its effectiveness in resisting the lateral force.

Although the influence of infill masonry on horizontal load structure behavior is well-documented, current standards and regulations have yet to fully incorporate or explicitly define the load-bearing capacity of this complex system. Canadian and American standards present more comprehensive and specific methodologies for calculating the load-bearing capacity of infill masonry and frame systems. In contrast, European standards tend to focus on offering general guidelines for the design of these systems without delving into the detailed calculation procedures. However, extensive data and experimental studies on this topic are available in the literature. The primary aim of this paper was to compile a database of experiments involving frames with different types of infill masonry. Subsequently, the empirical results obtained through the application of analytical expressions from various standards are compared to the experimental data included in the compiled database. The obtained load-bearing values were compared to different standards and work conducted by various researchers found in the literature in order to assess their reliability. Based on the obtained results, important conclusions were drawn, specifically to the most accurate equivalent diagonal model used and the analytical expressions to be used in the assessment of the masonry-infilled steel frame behavior. The equivalent diagonal model, utilized in all analytical expressions, can provide highly accurate estimations of load-bearing capacities that closely align with the experimental results. Regardless of the type of infill element, the analytical expressions consistently overestimated the load-bearing capacity. In the presence of longitudinal force, analytical expressions tend to be conservative, providing significantly lower load-bearing values compared with experimental results, which ensures a safety margin. The database can be utilized to develop numerical models, which can subsequently serve as the foundation for probabilistic methods used in conducting reliability assessments.

Infill frame structures are utilized to provide lateral stability in areas with high seismic activity, particularly where masonry remains a practical choice due to cost and tradition. They also help reduce bending moments in the frame, thereby lowering the risk of collapse. Seismic analysis has been conducted using the "Equivalent Static Analysis Method" on various reinforced concrete frame models, including a bare frame without infill, infilled frames at the interior only, exterior only, both interior and exterior, and infill between the interior and exterior. All models were modeled and analyzed using ETABS software. Infilled frames are preferred over open-storey frames in seismic regions because the presence of infill walls significantly influences the seismic behavior of the structure, enhancing its strength and stiffness. In contrast, open-storey frame structures tend to experience much greater storey drift than upper levels, increasing the risk of collapse during a strong earthquake.

In the composite walls stiffness system of reinforced concrete walls with composite boundary members, boundary members resist most of the moment due to seismic loading. In contrast, the reinforced concrete (RC) wall provides shear resistance. The SRCW system comprises partially restrained steel frames with reinforced concrete infill walls. The steel columns and beams act as boundary members to resist gravity loads and most of the overturning moment due to seismic loading, while the reinforced concrete (RC) infill wall acts as shear-resisting web. The RC infills increase the lateral stiffness dramatically compared to a bare steel frame, thus avoiding excessive drift and reducing the seismic demands on the steel frames. In that way, why not use just steel shear frames instead of partially restrained steel frames with reinforced concrete infill walls? This paper presents a numerical study of the behavior of a composite structural system consisting of steel shear frames with reinforced concrete infill walls (SFRCW). The composite interaction is achieved using welded bolts as shear connectors along the steel frame–infill interfaces. Welded bolts were used as shear connectors because they are frequently used in Colombia due to their ease of installation. The SFRCW system may be particularly appropriate for low-to-moderate-height structures. In addition, the steel shear frame will support gravity loads at the construction stage, allowing progress in height. The system can also be used to strengthen existing steel buildings. The relatively light steel frame constructed using shear connections maximizes the system's economy.This study compared the behavior of the SFRCW with columns acting in their weak and strong axes and with different numbers of shear connectors. It also compared the behavior of the bare steel moment frame, bare steel shear frame, and reinforced concrete wall. The numerical models show interesting results.

Study on failure mechanism and seismic performance of RC Frame-Infilled walls structures reinforced by CFRP