Large Web Openings Research Articles

Numerical Study on the Impact Response of Steel Beams with Large Web Openings: Investigating Key Parameters

Numerical Study on the Impact Response of Steel Beams with Large Web Openings: Investigating Key Parameters

GFRP continuous RC beams having web openings and externally strengthened with CFRP composites

With the enormous development of modern buildings, it is highly required to accommodate web openings in continuous reinforced concrete (RC) beams for passing utility service equipment. A wide range of studies had been conducted with regard to this subject. wtCurrent study examined numerically the major effect of the large rectangular web openings in (GFRP) reinforced concrete continuous beams under concentrated loads. Moreover, it investigated the effects of different CFRP strengthening schemes that would retrieve the ultimate capacity of the solid beam. Based on that, the main parameters that had been utilized here are the opening size, opening location and the strengthening scheme. Results showed that openings reduced the ultimate load capacity of the beams and increased the overall deflections. Furthermore, using CFRP sheets to strengthen continuous RC beams including opening retrieved (70%) of the ultimate capacity of continuous RC solid beams especially beams with openings near the external support or midspan. Likewise, using CFRP composites retrieved (48%) of the ultimate capacity of continuous RC solid beams with openings near the interior support. Furthermore, the optimum location for constructing web openings was near the external supports, which was subjected to the lowest values of shear forces and sagging moments and leaded to accommodate greater ultimate loads (85.18 kN) than other beams of other openings location.

Ultimate Load Behaviour of Castellated Beams with Stiffened Octagonal Openings

ctagonal castellated beam is fabricated by adding spacer plates between the web joints of the hexagonal castellated beam to further increase the beam depth. The resulted deep beam is advantageous to enhance the shear carrying capacity and moment resistance. However, large web openings are prone to Vierendeel mechanism in the deformation that lowers the overall beam performance due to formation of plastic hinges. The present paper is concerned with non-linear analysis to predict the ultimate load behaviour of octagonal castellated beams. Finite element models were developed by using a commercial programme LUSAS. The numerical models were first validated against the experimental results reported by other researchers. This study aims to propose the ideal configuration of web opening stiffeners and evaluate the effectiveness of the additional stiffening material for different beam span lengths. Provision of ring stiffeners is effective in short span beams in respect of resistance to Vierendeel failure. The stiffeners have increased the ultimate load to the extent of 73% in which the strength restoration is considerably near to the capacity of its parent universal beam. In long span beams, however, the stiffeners can only improve the performance up to 26.61% with larger additional steel materialthan that of shorter span. In all cases, the stiffener thickness is found to be the governing factor to restoring the loss of shear strength due to large web openings. The number of stiffeners contributes no appreciable variation of ultimate load particularly in long span beams where bending is prominent

Bearing capacity of headed studs under combined tension and shear loading in composite beams with large web openings

AbstractThe use of steel‐concrete composite structures with a high installation grade is becoming increasingly popular in building and industrial construction. To reduce construction height building services are routed through web openings in the girders. However, these openings represent local points of interference where, in the case of composite girders, parts of the acting shear forces are transferred from the web of the steel profile into the concrete slab. This results in additional, local stresses in the remaining steel girder and in the concrete chord, which must be considered in the design of the floor girders and shear connectors. Web openings in composite girders are not addressed in the current European design standard for steel‐concrete composite construction (EC 4). Only with the introduction of the second generation of Eurocodes in the coming years this case will be normatively regulated. During the preparation of the standard further questions about the load‐bearing behaviour arose, as the existing design approaches usually only consider a selection of possible failure scenarios or neglect essential verification steps. A joint research project between the University of Kaiserslautern‐Landau and RWTH Aachen University aims to develop a suitable design concept for composite girders with web openings. Model and beam tests accompanied by numerical simulations will provide further information on the complex local and global load‐bearing behaviour of the composite girders.This paper presents the results of experimental investigations and numerical simulations on the influence of large web openings on the global load‐bearing behaviour of the shear connectors in the composite joint. Based on 60 pull‐out tests and numerical simulations, the load‐bearing behavior of head bolt anchors under combined shear and tensile loading was researched and evaluated.

Investigation on shear buckling of steel welded I‐section beams with reinforced web openings

AbstractPlate girders with I‐section frequently require large web openings to accommodate ducts and pipes in buildings and bridges. It is known that the critical load equivalent to an unperforated plate can be achieved by an appropriate reinforcement of the web opening. The majority of the investigations on thin‐walled webs with web opening under shear loading has been focused on web slendernesses ranging between 200 to 360. Three tests on plate girders with a web slenderness of 416 are presented that contain web openings. The effect of an all‐around reinforcement (hollow section) of the web opening is studied in three‐point bending tests. The tests are calculated with finite elements accounting for imperfections that had been measured before testing. A parametric study is performed to evaluate different types of reinforcements for high web slendernesses.

Transient response and performance of prestressed concrete deep T-beams with large web openings under impact loading

Abstract This study reports testing results of the transient response of T-shape concrete deep beams with large openings due to impact loading. Seven concrete deep beams with openings including two ordinary reinforced, four partially prestressed, and one solid ordinary reinforced as a reference beam were fabricated and tested. The effects of prestressing strand position and the intensity of the impact force were investigated. Two values for the opening’s depth relative to the beam cross-section dimensions were inspected under the effect of an impacting mass repeatedly dropped from different heights. The study revealed that the beam’s transient deflection was increased by about 50% with greater amplitudes for response oscillations due to impact loading as the impact force increased twice. The results showed that the transient strains in the reinforcement and concrete increased when increasing the opening depth with higher amplitudes for the response oscillations, whereas it had a minimal effect on the beam’s transient deflection. The reinforcement and concrete strain results indicated a higher damping for the strains as the prestressing strands were introduced. Comparison with solid deep beam response showed remarkable increase in the beam deflection and strains with greater amplitudes for response oscillations when large openings were introduced in the web.

Numerical Study on Upgrade of Steel I-Beams and Columns with Rectangular Web Openings

This study investigated numerically the effect of small and large rectangular web openings in unstrengthened and strengthened steel I-beams and columns. With the use of a numerical model, 25 simply supported steel I-beams were subjected to a four-point bending test. In addition, 25 steel I-columns were tested numerically under axial compressive load. All steel I-beams and columns were compared with solid reference specimens without web openings (control specimen), where all specimens have the same 400 mm depth and 177 mm width steel section dimensions. Twelve of the 25 steel I-beams and columns with openings were strengthened with steel plates, and all had different web openings that were symmetrically located near the support areas. The performance of all steel I-beams and columns was compared before and after a strengthening procedure. The selected opening depths ranged from 40 to 280 mm. Aspect ratios of opening length to opening depth of 1.0, 2.0, and 3.0 were chosen. ABAQUS software was used to perform numerical analysis on I-sections (beams and columns) that were either unstrengthened or strengthened. All specimens were analyzed in terms of their load-displacement characteristics and failure modes. Finite element analysis showed that those beams and columns with small web openings have a slight decrease in strength and stiffness, which is considered to be within acceptable limits unlike solid steel beams and columns (control specimen). I-section beams and columns that have been strengthened have significant effects on increasing the load-displacement characteristics.

Behavior of Reinforced Concrete Deep Beams with Openings under Vertical Loads Using Strut and Tie Model

This research aims to study the effects of the size and location of openings on deep beams. The analysis of deep beams with openings presents a rather complex problem for engineers, as there are currently no guidelines within the design codes for this problem. Using the strut and tie model is a feasible solution, but also gives some uncertainties due to the various models that can be used. This paper proposes using a strut and tie model for the deep beams with openings where reinforcement is laid out in the form of embedded struts and ties. The study is divided into an experimental and a numerical part. The experimental study was conducted on eight reinforced concrete deep beams under vertical loads. Seven of the beams had web openings of different sizes and locations, while the eighth specimen was a reference beam without any openings. The beams had the same concrete dimensions with the size of the openings in the web taken as 150 150 mm and 300 300 mm, and the location of the opening in the horizontal direction was varied between 0.11 to 0.4 the span. The experimental results were analyzed in terms of cracking pattern, mode of failure, and load-deflection behavior and then compared to numerical analysis conducted using a finite element program. A parametric study followed to investigate the influence of reinforcement arrangement and reinforcement around the openings on the behavior of deep beams. The results showed that large web openings that directly interrupted the compression strut had the most reduction in beam capacity and that the location of the opening did not significantly affect the strength of the beam in the case of small openings. Doi: 10.28991/CEJ-SP2021-07-011 Full Text: PDF

A Semi-Empirical Equation based on the Strut-and-Tie Model for the Shear Strength Prediction of Deep Beams with Multiple Large Web Openings

The behavior and shear strength of full-scale (T-section) reinforced concrete deep beams, designed according to the strut-and-tie approach of ACI Code-19 specifications, with various large web openings were investigated in this paper. A total of 7 deep beam specimens with identical shear span-to-depth ratios have been tested under mid-span concentrated load applied monotonically until beam failure. The main variables studied were the effects of width and depth of the web openings on deep beam performance. Experimental data results were calibrated with the strut-and-tie approach, adopted by ACI 318-19 code for the design of deep beams. The provided strut-and-tie design model in ACI 318-19 code provision was assessed and found to be unsatisfactory for deep beams with large web openings. A simplified empirical equation to estimate the shear strength for deep T-beams with large web openings based on the strut-and-tie model was proposed and verified with numerical analysis. The numerical study considered three-dimensional finite element models, in ABAQUS software, that have been developed to simulate and predict the performance of deep beams. The results of numerical simulations were in good agreement and exhibited close correlation with the experimental data. The test results showed that the enlargement in the size of web openings substantially reduces the elements' shear capacity. The experiments revealed that increasing the width of the openings has more effect than the depth at reducing the load-carrying capacity.

Buckling and ultimate load prediction models for perforated steel beams using machine learning algorithms

Large web openings introduce complex structural behaviors and additional failure modes of steel cellular beams, which must be considered in the design using laborious calculations (e.g., exercising SCI P355). This paper presents seven machine learning (ML) models, including decision tree (DT), random forest (RF), k-nearest neighbor (KNN), gradient boosting regressor (GBR), extreme gradient boosting (XGBoost), light gradient boosting machine (LightGBM), and gradient boosting with categorical features support (CatBoost), for predicting the elastic buckling and ultimate loads of steel cellular beams. Large datasets of finite element (FE) simulation results, validated against experimental data, were used to develop the models. The ML models were fine-tuned via an extensive hyperparameter search to obtain their best performance. The elastic buckling and ultimate loads predicted by the optimized ML models demonstrated excellent agreement with the numerical data. The accuracy of the ultimate load predictions by the ML models exceeded the accuracy provided by the existing design provisions for steel cellular beams published in SCI P355 and AISC Design Guide 31. The relative feature importance and feature dependence of the models were evaluated and discussed in the paper. An interactive Python-based notebook and a user-friendly web application for predicting the elastic buckling and ultimate loads of steel cellular beams using the developed optimized ML models were created and made publicly available. The web application deployed to the cloud allows for making predictions in any web browser on any device, including mobile. The source code of the application available on GitHub allows running the application locally and independently from the cloud service.

Prestressing Effects on Full Scale Deep Beams with Large Web Openings¨: An Experimental and Numerical Study

Most studies on deep beams have been made with reinforced concrete deep beams, only a few studies investigate the response of prestressed deep beams, while, to the best of our knowledge, there is not a study that investigates the response of full scale (T-section) prestressed deep beams with large web openings. An experimental and numerical study was conducted in order to investigate the shear strength of ordinary reinforced and partially prestressed full scale (T-section) deep beams that contain large web openings in order to investigate the prestressing existence effects on the deep beam responses and to better understand the effects of prestressing locations and opening depth to beam depth ratio on the deep beam performance and behavior. A total of seven deep beam specimens with identical shear span-to-depth ratio, compressive strength of concrete, and amount of horizontal and vertical web reinforcement ratios have been tested under mid-span concentrated load applied monotonically until failure. The main variables studied were the effects of depth of the web openings and the prestressing location on deep beam performance. The test results showed that the enlargement in the size of web openings substantially reduces the element’s shear capacities while prestressing strands location above the web openings has more effect at increasing the element’s shear capacities. The numerical study considered three-dimensional finite element models that have been developed in Abaqus software to simulate and predict the performance of prestressed deep beams. The results of numerical simulations were in good agreement with the experimental ones.

Numerical investigation on flexural behavior of RC beams with large web opening externally strengthened with CFRP laminates under cyclic load: Three-point bending test

In the current paper, the effect of carbon fiber reinforced polymer (CFRP) laminates on the flexural strength of reinforced concrete beam (RCB) with the web opening in the flexural zone was investigated using a numerical method. The main aim of the current work is to model the reinforced concrete beam strengthen by two shape of CFRP laminates (2layer and U-shape), to observe the influences of CFRP on the flexural strength of the beam. To this end, cyclic loading was applied to investigate the flexural behaviour of the Twelve RC beams under the cyclic loading. All beams kept the same dimensions length, breadth, and depth (2400 × 300 × 200) mm were modeled in the finite elements adopted by ABAQUS software. Steel bars have been used for both flexural strengthening and stirrups. A Three-point bending tests were performed using cyclic loading. Furthermore, the effect of web openings with different sizes (Side length of 40, 60, 75% of the breadth) on the flexural behavior of RC beams was investigated in detail. The flexural strength, local analysis, and ductility of the base beam and CFRP reinforced beam were analyzed. The results of the simulations revealed that the CFRP laminates enhanced the strength of the base beam significantly.

Shear transfer mechanism of perforated web connection for concrete encased steel structures

The size of the steel section in concrete encased steel (CES) structure of bridge engineering is much larger than that of the building construction, accompanied by great shear demands at the steel–concrete interface. To enhance the interfacial shear performance, perforated web connection (PWC), which perforates the web of steel section with perforating rebars passing through the web openings, is proposed in this research for bridge application. Push-out tests and refined numerical analysis were performed on CES specimens with PWC, aiming to evaluate its effectiveness and to reveal the shear transfer mechanism. The effect of various parameters on the shear resistance was also investigated through a parametric study using the validated modeling method. Eventually, an Artificial Neural Network (ANN) was developed to predict the ultimate shear resistance of PWC. The results indicate that the interfacial shear-slip response especially the post-peak behavior is significantly improved by PWC with perforating rebars, which transforms the failure manner from brittle to ductile. The failure process of the PWC with perforating rebars experiences the loss of bonding, activation of perforating rebars, as well as shear failure of perforating rebars and concrete dowels. The parametric analysis shows that the PWC with large web openings exhibits great ultimate shear resistance and sensitivity to the variation in other parameters owing to good compatibility between the natural bond and reinforced concrete dowels. The well trained ANN model is a powerful tool for efficiently predicting the ultimate shear resistance of such connection.

ENHANCING OF FLEXURAL STRENGTH OF WEB OPENING REINFORCED GEOPOLYMER BEAMS BY USING FRP STRIPS

This study is devoted to inspect the flexural behavior of Geopolymer reinforced concrete beams with “large” web transverse opening and strengthened by three kinds of Fiber Reinforced Polymer materials. The implemented experimental program comprised casting eight beams under static and “one stage” repeated load, two of these are normal concrete beams and the others are Geopolymer beams. These beams are divided into two groups, the first comprised four beams of solid and beams “with transvers web opening” under static load for normal and Geopolymer concrete beams. The second group are of four Geopolymer beams that one of them is “un strengthened and having transvers web opening” while the others are also have transvers web opening but strengthened by different kinds of Fiber Reinforced Polymer materials sheets that installed vertically aligned and accompanied with the 90mm diameter large circular web opening. The strengthening materials included are Carbon Fiber Reinforced Polymer, Glass fiber Reinforced Polymer and Hybrid (one layer of Glass + one layer of Carbon) reinforced polymer sheets. The results showed that for the ultimate load capacity was decreased by 9.96% for holed normal concrete beam if compared with solid normal concrete solid beam while such capacity was decreased 2.25% and 11.89% for solid and holed Geopolymer beams respectively. In addition to that, the maximum load capacity is also decreased by 8.16%, 10.20% and 12.25% for Glass, Carbon and Hybrid fiber reinforced polymer strengthened beams if compared with reference beams “holed un strengthened beam” subjected to cyclic load.

Experimental study of various stiffened openings

AbstractOpenings in the web of steel beams have a growing use in steel and composite structures. However, in some cases, the presence of large web openings reduces significantly the beam strength, especially in areas of high shear or when a local force is being applied at the location of an opening. As a consequence, steel manufacturers often need to weld stiffeners to reinforce the openings. The actual European design rules do not provide design guidelines for those stiffeners. However, previous design codes, such as the ENV version of the Eurocode, propose some limitations. An example of limitation is to not consider the stiffener additional section in the bending strength of the opening member in the case of a single sided stiffening configuration. However, it could be observed that this kind of limitation can be very conservative. Thus, two experimental test campaigns have been led in order evaluate the behavior of openings with stiffeners. Different stiffening configurations have been tested and evaluated regarding the opening member deflection, strain distribution and strength. The first campaign consists of testing a beam with a rectangular opening in three points bending. Those tests allow the observation of the Vierendeel mechanism and its reinforcement provided by various stiffening configurations. The second test campaign is dedicated to the study of openings loaded directly on the upper member. Those tests allow the comparison of the mechanical behavior between various opening shapes and stiffening configurations under local load.

Numerical and analytical study of intermediate web‐post buckling

AbstractIn the case of two adjacent large web openings, the beam may fail by the plastification or the buckling of the intermediate web part known as the web‐post failure. Various analytical approaches have been developed to define the failure load of the intermediate web‐post which can be a key point in the design of beams with web openings. The authors led numerical studies on rectangular openings. Those studies allowed to observe that in a majority of cases, the web‐post reaches a total plastic strength. Furthermore, it allowed to observe that the loss of the web‐post did not lead to the beam failure. The beams generally failed by the formation of a Vierendeel mechanism of an enlarged or elongated opening. As a consequence, the authors propose an alternative approach for the definition of the web‐post buckling strength, considering the web‐post failure load based on lateral buckling failure and on the additional strength provided by the formation of a plastic mechanism.

Reinforcement schemes for cold-formed steel joists with a large web opening in the flexural zone: an experimental investigation

The objective of this investigation was to develop an economical and an efficient reinforcement scheme for large web openings in cold-formed steel (CFS) joists in flexural zones that would restore the original moment resistance of the section. This investigation considered commonly used floor joists in North American CFS construction. Tests on joists webs with no openings and with large circular and square openings located at the mid-depth revealed that large openings can reduce the flexural strength by 23%. A reinforcement scheme was established consisting of the screw fastening of bridging channels [38.1 mm × 12.7 mm (1.5″ × 0.5″)] with the same thickness as the receiving joist, along the compression and the tensile edges of the opening, using a screw spacing of 31.75 mm. Three identical tests utilizing the proposed reinforcement scheme restored the corresponding flexural strengths of the CFS section under consideration, and the failure locations were outside the reinforced opening regions.

Design concept of reinforced concrete beams with large web openings

This paper presents numerical investigations in studying large web openings. Based on the previous guidelines, the web openings in reinforced concrete beams are being investigated. The simple verification design procedure is followed by ACI-318. In general, web openings have to consider a certain position so that each chord sides imply a sufficient area to expand the ultimate compression in flexure and give the appropriate reinforcement. In this case, two openings are placed nearly to one-half from support on each side. The analysis follows the recommended procedure for elastic bending moments and shear forces while the deflections are evaluated both in the short and long-term periods. It is found that the beam with a large web opening meets the required standard in all aspects, but it is indicative of having a large moment.

Strength compensation of deep beams with large web openings using carbon fiber–reinforced polymer sheets

This article presents the results of an experimental investigation of using carbon fiber–reinforced polymer sheets to enhance the behavior of reinforced concrete deep beams with large web openings in shear spans. A set of 18 specimens were fabricated and tested up to a failure to evaluate the structural performance in terms of cracking, deformation, and load-carrying capacity. All tested specimens were with 1500-mm length, 500-mm cross-sectional deep, and 150-mm wide. Parameters that studied were opening size, opening location, and the strengthening factor. Two deep beams were implemented as control specimens without opening and without strengthening. Eight deep beams were fabricated with openings but without strengthening, while the other eight deep beams were with openings in shear spans and with carbon fiber–reinforced polymer sheet strengthening around opening zones. The opening size was adopted to be 200 × 200 mm dimensions in eight deep beams, while it was considered to be 230 × 230 mm dimensions in the other eight specimens. In eight specimens the opening was located at the center of the shear span, while in the other eight beams the opening was attached to the interior edge of the shear span. Carbon fiber–reinforced polymer sheets were installed around openings to compensate for the cutout area of concrete. Results gained from the experimental test showed that the creation of openings in shear spans affect the load-carrying capacity, where the reduction of the failure load for specimens with the opening but without strengthening may attain 66% compared to deep beams without openings. On the other hand, the strengthening by carbon fiber–reinforced polymer sheets for beams with openings increased the failure load by 20%–47% compared with the identical deep beam without strengthening. A significant contribution of carbon fiber–reinforced polymer sheets in restricting the deformability of deep beams was observed.

Seismic behaviour of RWS moment connections to deep columns with European sections

The design of reduced web section (RWS) connections is becoming more often, while the research is focusing on both areas: (a) the performance of beams with large web opening areas near the supports, and (b) the seismic behaviours of steel beam-to-column connections of different types when subjected to cyclic loads. The beam web opening is used as a mechanism to counterbalance the low inelastic capacity of the welds and to shift the stresses from the welding and shear panel zones to the weak beam section in line with the concept of “weak beam-strong column” often employed for the seismic-resistant design of Moment Resisting Frames (MRFs). However, limited data yet exists on the design and seismic behaviour of such connections and those are only for UKB and UKC section profiles. This paper presents an extensive FE study of the seismic performance of fully welded RWS moment connections to deep columns. The effect of using different beam spans is also investigated together with the effect of web opening size and position (web opening at different shear-moment interactions). European HE and IPE profiles are employed for this study in an effort to introduce RWS connections in Eurocode 8, and understand potential variations in design when using European sections as previously reported in RBS connections. Finally, a step-by-step design procedure is presented based on AISC 358 (AISC 358[3]).