Influence Of Infill Walls Research Articles

Collapse performance of post-tensioned steel frames considering influence of infill walls

The aim of this paper is to study the effect of infill walls on load resisting behaviors of post-tensioned (PT) steel frames against collapse. Three planar PT steel frames are simulated using finite element (FE) method, one of which has no infill wall while the other two are installed with infill walls. The applied loads, lateral displacements, failure patterns, stress developments in infill walls, resisting mechanisms, as well as re-centering capabilities of three PT steel frames are studied and the role that infill walls play is discussed. Parametric analyses are conducted to investigate influences of magnitude of PT forces and critical material properties. Results indicate that infill walls work as compressive struts, significantly increasing initial stiffness, resistance and story drifts of PT steel frames, and play as energy dissipation devices during the collapse process. The existence of opening makes the stiffness distributed discontinuously throughout infill walls, greatly changing the failure pattern and increasing story drifts of PT frames. The resistances of infilled PT steel frames increase with increasing PT forces, bed joints strength and masonry unit strength in the initial stage. A design scheme is also developed to precisely predict the collapse resistance of infilled PT steel frame structures.

Influence of Infill Walls on Resilience Index of RC Schools Using the BIM Analysis and FEMA P-58 Methodology

Influence of Infill Walls on Resilience Index of RC Schools Using the BIM Analysis and FEMA P-58 Methodology

Seismic performance of mid-rise reinforced concrete buildings in Izmir Bayrakli after the 2020 Samos earthquake

On October 30th 2020, offshores of Samos Island, Greece was hit by a shallow earthquake of Mw = 6.9 moment magnitude. Located 76 km away from the earthquake’s epicenter, the mid-rise reinforced concrete (RC) building stock of the densely populated Izmir Bayrakli district experienced the most severe structural damage. Although the horizontal peak ground acceleration recorded at the site (PGA = 0.11 g) was well below design values recommended by the past and the present Turkish seismic codes, many buildings suffered heavy damage and 12 buildings collapsed, resulting in a death toll of 117. This paper aims to identify the seismic performance of mid-rise infilled RC frame buildings in Bayrakli by investigating the ground motion recordings, local soil conditions, characteristics of the building stock and the observed damages. The structural performance of 140 RC buildings between 7 and 12 stories that have exhibited poor performance during the earthquake was inspected in detail based on the field surveys conducted right after the earthquake. A database was created documenting the number of stories, major seismic deficiencies, date of construction, geographic coordinates, damage state of structural members and masonry infill walls of the inspected buildings. The localization of structural damage could be partially attributed to the amplified long-distance seismic waves for 0.5–1.5 s periods range due to local soil conditions and basin effects. Seismic vulnerabilities, structural deficiencies and construction quality of the buildings played a significant role in the experienced damage intensity. The influence of infill walls on the seismic performance of RC frame buildings is also clearly observed for code-compliant as well as aseismic buildings.

Performance of structures in İzmir after the Samos island earthquake.

The October 30, 2020 Earthquake caused unexpectedly significant damage in İzmir considering its distance to the city. This paper evaluates the recorded ground motions, summarizes the performance of structures affected from the earthquake with emphasis on the reasons of damage. A detailed damage assessment was carried out by the Earthquake Engineering Research Center of Middle East Technical University to compile data on the damage of RC and masonry buildings. It was observed that majority of the damage was concentrated in the Bayraklı district due to its peculiar soil properties where many 7–10 story mid-rise RC buildings suffered heavy damage and collapse. The level of amplified ground motions combined with deficiencies of apparently non-code compliant buildings exacerbated the damage. The main reasons of damage were mainly attributed to the presence of soft stories, lack of proper detailing, poor construction quality, presence of heavy overhangs, and hence significant lack of code-compliance in essence. The influence of infill walls on seismic performance of deficient and inadequate buildings was clearly seen in this earthquake. This paper also discusses seismic code requirements in effect and their influence on the observed building performance. The recorded ground motions were compared with the code spectra to evaluate the performance of the buildings. The code response spectra were found to be well above the recorded ground motion spectra at the sites where significant damage was observed.

Influence of infill walls on modal expansion of distribution of effective earthquake forces in RC frame structures

It is quite apparent that engineering concerns related to the influence of masonry infills on seismic behavior of reinforced concrete (RC) structures is likely to remain relevant in the long term, as infill walls maintain their functionalities in construction practice. Within this framework, the present paper mainly deals with the issue in terms of modal expansion of effective earthquake forces and the resultant modal responses. An adequate determination of spatial distribution of effective earthquake forces over the height of the building is highly essential for both seismic analysis and design. The possible influence of infill walls is investigated by means of modal analyses of two-, three-, and four-bay RC frames with a number of stories ranging from 3 to 8. Both uniformly and non-uniformly infilled frames are considered in numerical analyses, where infill walls are simulated by adopting the model of equivalent compression strut. Consequently, spatial distribution of effective earthquake forces, modal static base shear force response of frames, modal responses of story shears from external excitation vector and lateral floor displacements are obtained. It is found that, infill walls and their arrangement over the height of the frame structure affect the spatial distribution of modal inertia forces, as well as the considered response quantities. Moreover, the amount of influence varies in stories, but is not very dependent to bay number of frames.

Non-linear analysis of RC masonry-infilled frames using the SLaMA method: part 1\u2014mechanical interpretation of the infill/frame interaction and formulation of the procedure

The simple lateral mechanism analysis (SLaMA) is an analytical method to assess the force–displacement capacity curve of Reinforced Concrete (RC) structures composed of frames, cantilever walls or dual wall/frame systems. The current version of the method was proposed in the 2017 New Zealand guidelines for the seismic assessment (NZSEE in New Zealand Society for Earthquake Engineering, the seismic assessment of existing buildings—technical guidelines for engineering assessments, Wellington, 2017). Regarding frame structures, the possible influence of infill walls is currently considered locally with checks on the RC members. However, it is universally known that infills have a major effect on the global capacity curve of the frame. In this paper, a comprehensive SLaMA method for infilled frames is proposed, which allows considering the influence of the infills on the global force–displacement curve without any numerical algorithm. The extended SLaMA method is herein formalised and it is validated in a companion paper (part 2) through an extensive parametric analysis. The extended SLaMA is based on the possibility to separately calculate the base shear contributions of the frame and the infills, in turn based on global equilibrium considerations. Such considerations also allow defining a novel procedure to post-process the results of pushover or time-history analyses where infills are modelled as diagonal struts, or to interpret experimental tests. This allows, within a single numerical analysis, to decouple the frame and infills contributions to the base-shear capacity. The decoupling procedure is herein demonstrated for an ideal two-storey, one-bay masonry-infilled frame with different infills configurations.

Research on the influence of infill walls on seismic performance of masonry buildings with bottom frame-shear walls

Research on the influence of infill walls on seismic performance of masonry buildings with bottom frame-shear walls

Nonlinear Simulation Analysis on Loaded-Bearing Performance of Multistory Infilled R.C. Frame Structure with Openings Under Horizontal Force

The influence of infill walls on the mechanical property of RC frame structures is distinct, the rational lateral stiffness of infilled frame structures and the design method of filler wall which are considered in resistance urgently need to be discussed. A group of single-span single-story infilled frame models (three) are nonlinear simulation analyzed by using ANSYS program, and verify the results of ANSYS by comparing with their experimental results. Then, establish a group of single-span three-stories infilled frame models (seven) with different opening sizes and different opening locations to simulate and analyze the lateral performance of multistory infilled frame structure with openings. And the following conclusions are drawn: the frame beam is in the unfavorable condition of “short beam sheared” with the existence of the openings in up and down stories; the lower the location of story is, the bigger the lateral stiffness of infilled frame is, and the quicker the degradation speed of stiffness is and so on.

Experimental Response of Reinforced Concrete Frames With AAC Masonry Infill Walls to In-plane Cyclic Loading

The paper presents an experimental investigation to assess some aspects of the influence of non-structural masonry infill walls on seismic resistance of RC frames. Low cycle horizontal loading of nine half-scale specimens, employing autoclave-cured aerated concrete (AAC) blocks as infill, is designed to test the influence of four parameters. The main effects indicated by the results are: The overall influence of the masonry infill walls, as compared with frames without infill walls, is some 200% increase in the yield load (the capacity) and close to 60% decrease in ductility. While the influence of the aspect ratio (height/width) on capacity appears to be small, narrow panels (high aspect ratio) have substantially higher ductility. The influence of the infill wall's construction method is a mild increase in capacity and a slight reduction in ductility of integral wall (built before frame casting) as compared to non-integral wall (built following frame casting) construction. Vertical prestress of the masonry wall panel has a large positive effect on both, capacity and ductility of integral infill panels. While the method of prestress applied does not represent adequately the effect of gravity loads, it could serve as a potential method for seismic upgrade. Openings in masonry infill walls produce capacity and ductility values that are intermediate between those of the frame with full infill wall and the frame without infill.

Experimental study on infilled frames strengthened by profiled steel sheet bracing

The purpose of this study is to investigate the seismic performance of reinforced concrete (RC) frames strengthened by profiled steel sheet bracing which takes the influence of infill walls into consideration. One-bay, two-story, 1/3 scale two specimens shared same feature of dimensions, one specimen consists only beams and columns; the other one is reinforced by profiled steel sheet bracing with infill walls. Hysteretic curves, envelope curves, stiffness degradation curves and energy dissipation capacities are presented based on test data. Test results indicate that the ultimate load of strengthened specimen has been improved by 225%. The stiffness of reinforced by profiled steel sheet bracing has been increased by 108%. This demonstrates that infill walls and profiled steel sheet bracing enhanced the strength and stiffness distinctly. Energy dissipation has an obvious increase after 12 cycles. This shows that the reinforced specimen is able to bear the lateral load effectively and absorb lots of seismic energy.

Analysis of Masonry Infill in a Multi-Storied Building

In many literatures, studies show that infill’s modify the behavior of framed structures under lateral loads; the contribution of panels is generally neglected in common structural analyses. The structural effect of brick infill is generally not considered in the design of columns as well as other structural components of RC frame structures. The brick walls have significant in-plane stiffness contributing to the stiffness of the frame against lateral load. The lateral deflection is reduced significantly in the infilled frame compared to the deflection of the frame without infill. It is observed that frames with infill produce much smaller deflections as compared to frames without infill. The results reflect the significance of infill in increasing the strength, stiffness and frequency, of the entire system depending on the position and amount of infilling. Lower infilling is noted to provide more stiffness for the system as compared with upper locations. A number of non-linear static (pushover) analyses were performed on proper structural models of the building, considering both bare framed structure and the infilled one, in order to appraise the influence of infill walls on the failure mechanisms. In particular, a sensitivity analysis was performed by assigning different Partial Safety Factors (PSF) to the mechanical parameters of infill walls, in order to investigate their effect on the overall structural response of the building.

Implementation and Verification of a Masonry Infill Model Considering the Out-Of-Plane Behaviour

The response of reinforced concrete buildings to earthquake loads can be substantially affected by the influence of infill walls. Also the out-of-plane failure of the infill can cause heavy casualties. In this article, an improved numerical model for the simulation of the in-plane and out-of-plane behaviour of masonry infill is proposed. First, the proposed model is presented. This is an upgrading equivalent strut model composed of two beam-column type elements, with a node at the mid-span assigned a mass in the in-plane and the out-of-plane direction to account for the inertial forces in both directions. Second, the main results of the calibration analyses obtained with two experiments are presented and discussed.

Equivalent lateral force method for buildings with setback: adequacy in elastic range

Static torsional provisions employing equivalent lateral force method (ELF) require that the earthquake-induced lateral force at each story be applied at a distance equal to design eccentricity (<TEX>$e_d$</TEX>) from a reference resistance centre of the corresponding story. Such code torsional provisions, albeit not explicitly stated, are generally believed to be applicable to the regularly asymmetric buildings. Examined herein is the applicability of such code-torsional provisions to buildings with set-back using rigid as well as flexible diaphragm model. Response of a number of set-back systems computed through ELF with static torsional provisions is compared to that by response spectrum based procedure. Influence of infill wall with a range of opening is also investigated. Results of comprehensive parametric studies suggest that the ELF may, with rational engineering judgment, be used for practical purposes taking some care of the surroundings of the setback for stiff systems in particular.

Simplified Macro-Model for Infill Masonry Panels

In structural analyses, masonry infill walls are commonly considered to be non structural elements. However, the response of reinforced concrete buildings to earthquake loads can be substantially affected by the influence of infill walls. In this article, an improved numerical model for the simulation of the behavior of masonry infill walls subjected to earthquake loads is proposed and analyzed. First, the proposed model is presented. This is an upgrading of the equivalent bi-diagonal compression strut model, commonly used for the nonlinear behavior of infill masonry panels subjected to cyclic loads. Second, the main results of the calibration analyses obtained with two series of experimental tests are presented and discussed: one on a single frame with one story and one bay tested at the LNEC Laboratory; and the second, on a full-scale four story and three-bay frame tested at the ELSA laboratory.

Influence of infill walls on building frames: An example from the May 12, 1971 earthquake in Turkey

Abstract The Burdur earthquake of May 12, 1971, although only of moderate-sized magnitude, was responsible for much loss of life and property damage. The presence of full-height and/or partial-height infill walls in some reinforced concrete-framed structures completely altered the behavior of the frame elements. Damage to a four-story, reinforced concrete school building is described, as a typical example of this kind of failure.