FEA Modelling of Externally-Strengthened Concrete Beam with CFRP Plates Under Flexural Test

This study concentrates on FEA modelling of concrete beam strengthened with externally bonded CFRP lates under bending by using Traction Separation Law (TSL) as constitutive law to require maximum cohesive stress and fracture energy values. The FEA models were developed following experimental work reported by Al-Rousan et al. and Ding et al. Combination of two numerical techniques were adopted, i.e., Extended Finite Element Method (XFEM) and Cohesive Zone Method (CZM) assigned within cracked beam region and adhesive layer respectively. The consistence of FEA beam deformations to capture debonding failure as seen during experimental observations and load-displacement was evaluated accordingly. Additionally, combination of XFEM-CZM techniques provides good strength predictions with experimental dataset. It is clearly shown that the failure mode exhibited are determined by testing method, CFRP width and CFRP length. CFRP sheets provides a significant contribution to concrete ductility, which is noticeable in longest CFRP sheet. All testing series were examined, the discrepancies of less than 25% were found. Note that current approach used calibrated fracture energy values from similar concrete grade and CFRP plates, however better prediction can be produced if fracture energy values were independently determined from experimental set-up. &nbsp

FEA Modelling of Externally-Strengthened Concrete Beam with CFRP Plates Under Flexural Test

This study concentrates on FEA modelling of concrete beam strengthened with externally bonded CFRP lates under bending by using Traction Separation Law (TSL) as constitutive law to require maximum cohesive stress and fracture energy values. The FEA models were developed following experimental work reported by Al-Rousan et al. and Ding et al. Combination of two numerical techniques were adopted, i.e., Extended Finite Element Method (XFEM) and Cohesive Zone Method (CZM) assigned within cracked beam region and adhesive layer respectively. The consistence of FEA beam deformations to capture debonding failure as seen during experimental observations and load-displacement was evaluated accordingly. Additionally, combination of XFEM-CZM techniques provides good strength predictions with experimental dataset. It is clearly shown that the failure mode exhibited are determined by testing method, CFRP width and CFRP length. CFRP sheets provides a significant contribution to concrete ductility, which is noticeable in longest CFRP sheet. All testing series were examined, the discrepancies of less than 25% were found. Note that current approach used calibrated fracture energy values from similar concrete grade and CFRP plates, however better prediction can be produced if fracture energy values were independently determined from experimental set-up. &nbsp

Vulnerability Assessment of Building Frames Subjected to Progressive Collapse Caused by Earthquake

Progressive collapse is an initial local failure of the structural component and leading to the additional collapse of the building frames. This study investigated the vulnerability of four- and six-storey moment resisting concrete frame (MRCF) buildings subjected to progressive collapse. The four- and six-storey MRCF buildings were designed based on British Standard (BS) and Eurocode (EC). The differences between these two codes were investigated. Nonlinear static analysis, which is also known as pushover analysis (POA), and nonlinear dynamic analysis or incremental dynamic analysis (IDA), were performed for each model to obtain capacity curve and explore vulnerability measures. IDA was conducted using a sample of ground motion from an earthquake that occurred in Ranau, Sabah in 2015. The four-storey building was more vulnerable than the six-storey building

Progressive Collapse Analysis of Steel Frame Structure

The importance of studying the behavior of the progressive collapse of steel frame buildings has been demonstrated by the loss of almost 3000 people in the World Trade Center (WTC) September 11th attack. Numerous studies have established that the alternate load path method (ALPM) of analysis can be used to study the robustness of a structure in order to prevent the collapse from occurring. The method utilises an event-independent approach, where the actual load arising from the complicated triggering event is not considered. The method proposes the removal of one or more load bearing elements of a structure, such as a column, thuscausing the structure to be susceptible to dynamic effects. However, the current ALPM practice of using a single removal time in representing different extreme events only provides a limited assessment of the overall structural robustness. Furthermore, the location of the column to be removed also requires careful consideration, since different removal locations will initiate different responses from the structure.This study proposes two approaches in the effort to further enhance the utilisation of the alternate load path method. Firstly, the study proposes the use of a removal time variation during the column removal process to obtain a more comprehensive view of the structural resistance to progressive collapse. In addition to the removal time, different modelling approaches are used by considering different elements - beam elements and shell elements. These are herein extensively investigated. Secondly, a systematic algorithm was developed using MATLAB and the SAP 2000 finite element software version 15, for selecting the location of columns to be removed so as to determine which removal location would cause the most distress to the structure. The selection of the column location is based on newly proposed damage assessment criteria developed in this work, which are independent of the column grid spacing and consequently their use is more general and suitable for all types of buildings.The finite element method was used as an investigative tool. The general finite element package SAP 2000 version 15 and ABAQUS/standard version 6.10 have been chosen to carry out the detailed column removal analyses. The effect of varying the removal time and the modelling approach in a column removal analysis was first investigated on a small scale structure, namely, a two bay steel frame structure using a nonlinear dynamic implicit analysis. In order to evaluate the effectiveness of the proposed algorithm, the analysis was than extended to more detailed structures encompassing two types of 3-dimensional ten storey steel frame finite element models, namely a moment resisting frame and a braced frame.The results from both the preliminary and the primary models clearly demonstrate that the faster column removal time causes larger dynamic effects in terms of vertical displacement and energy manifestation in all the numerical models. A clear implication of these results is that an accurate and comprehensive assessment of structural robustness using ALPM necessitates the use of a removal time range, not just a single removal time. With regards to the modelling approaches, modelling the beam element without a proper offset i.e. based upon the centreline to centreline geometry of the beam element model may overestimate the actual stiffness of the structure. For the location of the column to be removed, the proposed algorithm has successfully determined the worst column locations that cause the maximum response to the two primary models. The proposed algorithm has the potential to be a very useful enhancement to the current ALPM procedure. It can be concluded after a detailed investigation of the results presented in this study, that it is crucial to carefully and systematically select the position of columns for removal, whichwould result in the most significant response in the structure, and then to investigate the structural response under various removal times for those columns

Utilizing XFEM model to predict the flexural strength of woven fabric Kenaf FRP plate strengthened on plain concrete beam

The evolution of advancing computing technology has encouraged the use of finite element analysis to require constitutive models, mostly adopted extensive experimental datasets. Never¬theless, fewer material properties are required within the bilinear traction-separation relationship incorporated with the XFEM technique and require fewer computation efforts due to the energetic approach simulation. This study used ABAQUS CAE 2021 to predict the flexural strength of plain concrete beams strengthened with Kenaf Fibre Reinforced Polymer (KFRP) plates under a four-point bending test, later validated with experimental datasets. The varying parameters, including woven fabric architectures, lengths, widths, and plate thickness, were considered. The results demonstrated that the consistency proposed modelling technique in this study well-captured failure modes and crack development as experimental observations. All models demonstrated an increase in peak load, and a comparison of load-deflection profiles was made between the numerical FEA modelling with the experimental works. The peak load discrepancies between the numerical outputs and the experimental datasets were found to be less than 12% in all testing series. Despite promising findings, stress analysis on peel and shear stresses associated with failure modes exhibited was performed. It was found that KFRP ruptures occurred due to peel stress peak at plate mid-span, while shear mode failure demonstrates concentrated peel stress (to lesser extent shear stress) at KFRP edge tip. Hence, a more unified approach is promoted to require only two material properties (preferably independently measured values). This approach enables a designer to choose the optimum FRPs size using the current modelling tool, substan¬tially reducing laborious and expensive experimental setup

Utilizing XFEM model to predict the flexural strength of woven fabric Kenaf FRP plate strengthened on plain concrete beam

The evolution of advancing computing technology has encouraged the use of finite element analysis to require constitutive models, mostly adopted extensive experimental datasets. Nevertheless, fewer material properties are required within the bilinear traction-separation relationship incorporated with the XFEM technique and require fewer computation efforts due to the energetic approach simulation. This study used ABAQUS CAE 2021 to predict the flexural strength of plain concrete beams strengthened with Kenaf Fibre Reinforced Polymer (KFRP) plates under a four-point bending test, later validated with experimental datasets. The varying parameters, including woven fabric architectures, lengths, widths, and plate thickness, were considered. The results demonstrated that the consistency proposed modelling technique in this study well-captured failure modes and crack development as experimental observations. All models demonstrated an increase in peak load, and a comparison of load-deflection profiles was made between the numerical FEA modelling with the experimental works. The peak load discrepancies between the numerical outputs and the experimental datasets were found to be less than 12% in all testing series. Despite promising findings, stress analysis on peel and shear stresses associated with failure modes exhibited was performed. It was found that KFRP ruptures occurred due to peel stress peak at plate mid-span, while shear mode failure demonstrates concentrated peel stress (to lesser extent shear stress) at KFRP edge tip. Hence, a more unified approach is promoted to require only two material properties (preferably independently measured values). This approach enables a designer to choose the optimum FRPs size using the current modelling tool, substantially reducing laborious and expensive experimental setup

Progressive Collapse Assessment: A review of the current energy-based Alternate Load Path (ALP) method

The Alternate Load Path (ALP) is a useful method that has generated a considerable recent research interest for the assessment of progressive collapse. The outcome of the ALP analysis can be assessed either using the force-based approach or the energy-based approach. The Unified Facilities Criteria (UFC- 4- 023-03) of progressive collapse guideline - have outlined that the force-based approach can either be analysed using static or dynamic analysis. The force-based approach using static analysis is preferable as it does not require a high level of skill and experience to operate the software plus no effort is required in scrutinising the validity of the analysis results output. However, utilising the static approach will eliminate the inertial effect in capturing the actual dynamic response of the collapsed structure. In recent years, the development of the energy-based progressive collapse assessment is attracting widespread interest from researchers in the field; as the approach can produce a similar structural response with the force-based dynamic analysis by only using static analysis. Most of the current energy-based progressive collapse assessments are developed following the requirements which are given in the progressive collapse guidelines provided by the Unified Facilities Criteria. However, little attention is given to the development of the energy-based approach using the Eurocode standards as a base guideline. This article highlights the merits of utilising the energy-based approach against the force-based approach for a collapsed structure and explains the collapse mechanism of a steel frame in the perspective of the energy concept. The state of the art of energy-based progressive collapse assessment for a structural steel frame is reviewed. The comprehensive review will include insights on the development of the energy-based method, assumptions, limitations, acceptance criterion and its applicability with the European standards. Finally, potential research gaps are discussed herein

Progressive Collapse Assessment: A review of the current energy-based Alternate Load Path (ALP) method

The Alternate Load Path (ALP) is a useful method that has generated a considerable recent research interest for the assessment of progressive collapse. The outcome of the ALP analysis can be assessed either using the force-based approach or the energy-based approach. The Unified Facilities Criteria (UFC- 4- 023-03) of progressive collapse guideline - have outlined that the force-based approach can either be analysed using static or dynamic analysis. The force-based approach using static analysis is preferable as it does not require a high level of skill and experience to operate the software plus no effort is required in scrutinising the validity of the analysis results output. However, utilising the static approach will eliminate the inertial effect in capturing the actual dynamic response of the collapsed structure. In recent years, the development of the energy-based progressive collapse assessment is attracting widespread interest from researchers in the field; as the approach can produce a similar structural response with the force-based dynamic analysis by only using static analysis. Most of the current energy-based progressive collapse assessments are developed following the requirements which are given in the progressive collapse guidelines provided by the Unified Facilities Criteria. However, little attention is given to the development of the energy-based approach using the Eurocode standards as a base guideline. This article highlights the merits of utilising the energy-based approach against the force-based approach for a collapsed structure and explains the collapse mechanism of a steel frame in the perspective of the energy concept. The state of the art of energy-based progressive collapse assessment for a structural steel frame is reviewed. The comprehensive review will include insights on the development of the energy-based method, assumptions, limitations, acceptance criterion and its applicability with the European standards. Finally, potential research gaps are discussed herein

Vulnerability Assessment of Building Frames Subjected to Progressive Collapse Caused by Earthquake

Progressive collapse is an initial local failure of the structural component and leading to the additional collapse of the building frames. This study investigated the vulnerability of four- and six-storey moment resisting concrete frame (MRCF) buildings subjected to progressive collapse. The four- and six-storey MRCF buildings were designed based on British Standard (BS) and Eurocode (EC). The differences between these two codes were investigated. Nonlinear static analysis, which is also known as pushover analysis (POA), and nonlinear dynamic analysis or incremental dynamic analysis (IDA), were performed for each model to obtain capacity curve and explore vulnerability measures. IDA was conducted using a sample of ground motion from an earthquake that occurred in Ranau, Sabah in 2015. The four-storey building was more vulnerable than the six-storey building

Evacuation egress in high rise building: Review of the current design evacuation solution

In the aftermath of the September 11th attack, design of tall buildings particularly in the aspect of safety systems and structural robustness, arguably the most crucial issues that is deliberated till to date. Concerning the safety systems specifically on evacuation egress, many novels and innovative evacuation solutions for high rise buildings that have been researched and put forward, for instances Platform Rescue Systems (PRS), Controlled Descent Devices (CDD) and Escape Chutes. Still, the practicability of the existing proposed egress systems to be implemented in the real-life situation and its compliance with the tall building design legislation remain unknown. For developing countries such as Malaysia and United Arab Emirates, tall buildings play a role as an iconic landmark. While countries like China and Hong Kong, tall building is needed due to the scarcity of land and high populations. As more than one hundred tall structure exists in the world, and will be increasing by 2020; therefore, it is urgently needed that existing engineering practices in designing tall building to be reviewed with respect to evacuation egress. The main objective of this paper is to create awareness among developers, consultants and contractors that proper evacuation egress in tall building design and development is a must. This paper provides a comprehensive review of the existing engineering practices on tall building evacuation planning systems and design. Furthermore, the effectiveness of the currently proposed systems and its consideration amongst structural and safety engineers are also reported