Presence Of Web Openings Research Articles

Restoration of load capacity and stiffness of continuous steel–concrete composite beams having web openings using externally applied FRP strips

AbstractThe aim of this study is to explore the applicability of externally bonded fiber‐reinforced polymer (FRP) composites to enhance the structural performance of steel–concrete composite beams with web openings in terms of load capacity and stiffness. In order to achieve this aim, the ABAQUS software was used to create a three‐dimensional (3D) non‐linear finite element model (FEM) to simulate the behavior of FRP‐strengthened continuous composite beams with web openings exposed to monotonic loadings. After ascertaining the accuracy of the proposed model's results in successfully predicting failure patterns and load capacities of the experimentally tested specimens available in the literature, the suggested model was used to create a parametric study. The parametric study focused on the impacts of the opening location, opening shapes, and opening area on the failure pattern, load carrying capacity, and stiffness of continuous steel–concrete composite beams. Additionally, strengthening the web openings using different configurations and lengths of FRP strips with and without bolts was investigated. Results showed that the presence of web openings in location 2 exhibited the lowest load capacity of all investigated beams (20.80%–42.50% lower than the control composite beam). Moreover, the continuous composite beams with a circular opening were the best case and gave a higher failure load as compared to the rectangular opening at all locations. Additionally, all the simulated FRP‐strengthened composite beams in the third group demonstrated significant values of load capacities and stiffness among all the analyzed specimens.

Enhancing the Shear Capacity of RC Beams with Web Openings in Shear Zones Using Pre-Stressed Fe-SMA Bars: Numerical Study

Openings in the shear span can significantly affect the structural behavior of reinforced concrete (RC) beams, particularly in terms of shear capacity and crack propagation. This paper aims to investigate the feasibility of strengthening the web opening in the shear zone of RC beams by using iron-based shape memory alloy (Fe-SMA) bars, providing valuable insights for structural engineers and researchers. Numerical analysis with ABAQUS/CAE 2020 software was employed in the current study. The research was divided into six groups of beams with web openings of different lengths (150, 300, and 450 mm), prestressing levels (0%, 30%, and 60%), and reinforcement diameters (14, 18, and 22 mm) of Fe-SMA bars. The results show that the presence of web openings can cause a significant reduction in the cracking and ultimate loads of the beams, with reductions ranging from 11% to 50% and 36% to 48%, respectively. However, by adding pre-stressed Fe-SMA bars around small web openings (100 × 150 mm), the shear capacity of the beam is restored, and the beam exhibits behavior similar to solid beams. Additionally, activating the Fe-SMA bars by 30% and 60% resulted in almost similar cracking loads but improved load-carrying capacity of the beam with small openings by 12% and 9%, respectively, compared to the solid beam. The technique proposed for enhancing shear strength is most effective for beams with small (100 × 150 mm) and medium (100 × 300 mm) web openings as it can restore both the beam’s shear strength and stiffness. However, for beams with larger web openings (100 × 450 mm), the use of activated Fe-SMA beams can recover almost 90% of the solid beam’s shear capacity. Furthermore, reinforcing small openings with Fe-SMA bars of different diameters enhances beam shear capacity and stiffness, while for larger openings, higher Fe-SMA reinforcement ratios could potentially restore the beam’s full strength and stiffness. This study emphasizes the importance of strengthening web openings in RC beams, particularly in shear zones, and provides significant insights into how to strengthen beams with web openings, thereby contributing to developing safer structures. However, further laboratory experiments are recommended to validate, complement and extend the findings of this numerical study.

Shear performance and design rules for welded stainless steel I-shaped members with web openings

The use of stainless steel I-shaped members as primary load-bearing members has become increasingly popular, particularly in acidic environments, owing to their corrosion resistance and other advantages. Openings on the web are often introduced for ease of installation. The presence of web openings can reduce the shear resistance and produce high stresses around the openings, limiting their application. However, no previous study has investigated the shear resistance and design rules of such welded stainless steel I-shaped members with web openings. This work presents a detailed numerical analysis to examine the shear performance of perforated stainless steel members. Finite element (FE) models considering material nonlinearity and initial geometric imperfections were developed and verified using corresponding test data presented by the authors and many researchers. A parametric study including 434 FE models was undertaken to analyse the influence of web openings on the shear resistance of such members. The results suggested that for members with a hole diameter–web height ratio of 0.7, web openings can reduce the shear resistance by 61.4% on average, when compared to unperforated members. The generated numerical results were used to evaluate the current design recommendations given in the Eurocode (EN 1993-1-4+A1) (2015), American standard (ANSI/AISC 370-21) (2021), and those design rules proposed by Chen et al. (2018), although they were designed only for unperforated members. The comparisons demonstrated that the current design guidelines provided non-conservative predictions for calculating the shear resistance of perforated members. New design formulas were proposed using the strength reduction factor. A reliability analysis was undertaken, which indicated that the new design formulas were reliable for predicting the shear resistance of such members.

Shear Resistance of Fibrous Reinforced Concrete Deep Beams with Opening – A Critical Review

Reinforced concrete deep beams are more prone to shear failure. Thus, it is important to study the shear behavior for structural reinforcements. The presence of web openings in reinforced concrete deep beams is frequently required to provide accessibility such as doors and windows or to accommodate essential services such as ventilating and air conditioning ducts that affect the shear resistance. This research highlights the limited research on the shear resistance of fibrous reinforced concrete deep beams containing openings worldwide and illustrates their influence on shear behavior. This review has shown that the ultimate and the first cracking loads increase, increasing steel fiber content to a certain limit. End hooked steel fiber with 1.5% gave the highest shear resistance and ultimate load capacity compared with other types of steel fiber. Moreover, the stiffness of reinforced concrete deep beams increased with increasing fiber content from 0 to 1.5%. In addition, the effect of web openings on the shear strength of deep beams at the ultimate and cracking loads depends on the degree of interruption of the natural load path joining the loading.

Shear behaviour of ultra-high performance concrete beams with openings

An experimental investigation of the shear behaviour of Ultra-high performance concrete (UHPC) beams with web openings was conducted. Eight UHPC beams were experimentally cast and subjected to a four-point bending test. One beam, which was considered the control specimen, had no web openings, whereas the seven other beams contained openings. The studied parameters were steel fibre content, opening position, opening shape and reinforcement schemes around the web openings. Shear behaviour was evaluated on the basis of cracking patterns, load-deflection behaviour, ductility, initial stiffness, toughness and strain. Experimental results showed that increasing the volume fraction of steel fibres enhanced the shear strength, stiffness, toughness, ductility and strain in steel reinforcements. The presence of web openings in the shear region led to a decrease in the shear strength by 33.7%. The ultimate load of UHPC beams with openings has been evidently improved using reinforcement around the openings. An analytical verification was proposed to evaluate the experimental test results of UHPC beam by using design codes, different prediction equations and the empirical equation proposed herein. The proposed empirical equation showed an excellent agreement with available experimental data.

EFFECTS OF WEB OPENINGS ON SHEAR BEHAVIOUR OF NORMAL AND INTERNALLY STRENGTHENED CONCRETE BEAMS

Web openings in reinforced concrete (RC) beams are provided to pass utility pipes and ducts through them. This causes high stresses (with local cracking) around the transverse web openings, which may lead to reduction in ultimate strength and stiffness of RC beams. Internal strengthening with shear reinforcement can increase ultimate strength of the beam with web openings. This paper presents an experimental study which was conducted to investigate load carrying capacity, mid-span deflection and failure modes of beams with web openings. A total of eighteen RC beams were included in the testing programme, which were tested under two-point loading. The beams contained both pre-planned and post-planned web openings. Experimental results showed that ultimate load of the beams decreased from forty-two to sixty-seven percent due to the presence of web openings in the shear zones. Shear strength of the beams with pre-planned web openings increased by thirty-six percent and one-hundred two percent as compared to the reference beam due to the increase of shear reinforcement by one-hundred twenty-two percent and three-hundred three percent, respectively. Similarly, increase in shear capacity up to six percent and fourteen percent was found for the beams with post-planned web openings due to the aforementioned increase in the area of shear reinforcement, respectively. The ultimate load carrying capacity was also compared with the theoretical models. Internal strengthening and pre planned opening were found effective for providing web openings in the beams.

An experimental approach for strengthening of RC deep beams with web openings using GFRP fabrics and gas actuated fasteners

In this paper, the influences of externally bonded (EB) glass fibre reinforced polymer (GFRP) fabrics and gas actuated fasteners (GAF) on the strengthening of reinforced concrete (RC) deep beams with circular/square web openings of different sizes are investigated experimentally with respect to shear strength, failure mode, load-deflection and stiffness. A total of 19 deep beams having 120 × 420 × 1000 mm size are prepared and tested under two-point loading. One solid deep beam is left un-strengthened, which is considered as the control beam. Out of 18 beams with web openings, six beams, i.e. one beam for each opening size are kept un-strengthened. Other six counterpart beams are strengthened with U-wrapped EB-GFRP fabrics throughout the beam length. In order to improve the bond strength between GFRP fabric sheets and concrete surface, the remaining six counterpart beams are strengthened using both EB-GFRP fabrics and GAF at shear spans only. Test results demonstrate that the presence of web openings in deep beams significantly reduces the shear strength of the beams up to 72% with respect to the solid beam. The beams with web openings strengthened using both the EB-GFRP fabric and GAF are seen to be effective in enhancing the shear strength up to 64% with respect to the counterpart un-strengthened deep beams. Finally, the theoretical shear strength results obtained from the theoretical models available in the previous works are compared with the experimental results for the verification of their accuracy.

A detailed investigation on thermal behaviour of slim floor beams with web openings at elevated temperatures

Purpose In recent times, the use of steel sections with web openings has become common as slim floor beams because they offer a reduction in weight of the steelwork, accommodate services within the floor depth and provide the composite action. The composite action in these beams is achieved either through the concrete dowels or through concrete plugs. Though these web openings offer several benefits in slim floor beams, they induce the material discontinuity in the steel web, which may affect their shear capacity and/or thermal behaviour. The purpose of this study is to investigate the thermal behaviour of slim floor beams with web openings in fire. Design/methodology/approach This research presents findings from experimental and analytical investigations conducted to study the thermal behaviour of slim floor beams with web openings in fire. For this purpose, an experimental investigation was conducted, which shows that the presence of web openings has a major influence on temperature development across the steel section as well as along the span of these beams. The behaviour of the tested slim floor beam is validated using finite element modelling. The validated finite element model is then used to conduct a sensitivity study to analyse the influence of different opening spacings, sizes and shapes on the thermal performance of slim floor beams in fire. Findings Test results show that the presence of web openings has a major influence on temperature development across the steel section as well as along the span of these beams. Temperatures on the web below the openings are found to be higher as compared to those recorded on the adjacent solid steel web. It is also observed that temperatures on the steel web above the openings are lesser than those on the adjacent solid steel web. Parametric studies conducted using the verified analytical modelling methods show that different opening spacings, sizes and shapes have a variable impact on the thermal behaviour of slim floor beams in fire. Closely spaced and larger opening sizes were found to have a more severe influence on their thermal behaviour in fire as compared to widely spaced and smaller openings. It was also found that the behaviour of these beams is influenced by the shape of the openings with rectangular openings resulting in more severe thermal distributions as compared to circular openings. Originality/value The findings from this research study are highly valuable as they contribute to the existing knowledge database. There is a lack of experimental and analytical investigation on performance of slim floor beams with web openings at elevated temperatures. The results and conclusions from this study will help in developing innovative designs for slim floor beams and will help in reducing the fire related risk associated with structures comprising of slim floor beams with web openings.

Energy Absorption Capacity Of Layered Lightweight Reinforced Concrete Beams With Openings In Web

This research presents the flexural behavior on reinforced concrete beam with transverse web opening constructed from layered concrete. The layered concrete combining normal concrete and lightweight aggregate concrete (LWC) are depended in present study. In the experimental program, 13 models of normal and layered reinforced concrete beams are tested under the effect of four-point loads. All beams had the same overall geometrical dimensions and main longitudinal top and bottom with internal diagonal reinforcement provided around the openings. One of the beam specimen is tested as control beam and the other specimens are divided into three groups [G1, G2, and G3] to study the effects of the following variables: effect of presence of web openings, layered system, lightweight aggregate (partially volumetric replacement of normal aggregate by thermostone) on the ultimate load, cracking load, cracking pattern and energy absorption capacity. The existing of an opening in beam specimens reduced the flexural capacity of beams with a percentage depending on the size of opening and opening number. The test data obtained from the adopted layered technique of (NEW) and (LWC) have shown that for beams constructed from two layered concrete (LWC with thermostone in the web and bottom flange of I-beam section) ultimate load is decreased about (9.3%-48.8%). It has also, the beams constructed from three-layered of concrete (LWC with thermostone in the web of I-beam section), their ultimate load is decreased about (25.6%-58.1%). On the other hand, magnitude increased of energy absorption capacity are achieved by the decreased opening size, introducing the full size opening of dimension (100×1000) mm reduces the energy absorption capacity of the RC I-section beams at least 80% compared to solid beam while the beam with opening size (100×100) mm decrease up to 16%. In the case of the layered concrete beams specimen, the real influence of lightweight concrete (LWC) type in the layered reinforced concrete is observed significantly after increasing the length of opening more than 100 mm.

Shear behaviour and design of Lipped Channel Beams with non-circular web openings

Cold-formed steel Lipped Channel Beams (LCB) with web openings are commonly used as floor joists and bearers in building structures. Their shear behaviour is influenced by the presence of web openings and the shear capacities are considerably reduced. However, the shear behaviour and capacity of LCBs with non-circular web openings (square, rectangular and elliptical web openings) has not been investigated adequately. Hence a detailed numerical study was conducted to investigate the shear behaviour and capacity of LCBs with non-circular web openings. Finite element models of simply supported LCBs under a mid-span load with aspect ratios of 1.0 and 1.5 were developed and validated by using the available shear test results. They were then used in a detailed parametric study to investigate the effects of various influential parameters. Numerical results showed that the current shear design equations in cold-formed steel structures design standards are conservative or unsafe. New shear design equations were therefore proposed for the accurate prediction of the shear capacity of LCBs with non-circular web openings. This paper presents the details of finite element modelling of LCBs with unreinforced non-circular web openings and the development of new shear design rules. The proposed shear design equations in this paper can be considered for inclusion in the future versions of cold-formed steel design standards. Suitable design equations were also developed under the direct strength method.

EFFECT OF WEB OPENING ON THE AXIAL LOAD CAPACITY OF STEEL COLUMNS WITH COLD FORMED THIN WALLED SECTION (CFS)

In this paper, an experimental study has been presented to investigate the effects of web opening on the behavior and failure of steel columns with cold formed thin walled sections (CFS) subjected to axial compressive load. Twenty small scale steel columns with cold formed box and channel sections and a total length of 500 mm have been considered in the experimental tests. Ten of the tested steel columns specimens have a box section with dimensions of (100×100×2) mm (height × width× thickness), and the other ten columns specimens have a channel sections with dimensions of (100×50×2) mm (height × width× thickness). To investigate the effect of the number and the shape of web opening on the axial compressive strength of steel columns, each ten columns with same cross section shape was divided into three groups of three columns in addition to the reference column which has no web openings. All groups of columns have same opening area which is located at the web of the section, but each group has a different opening shape (square, rectangular, and circular shapes), and each steel column within each group has different numbers of opening distributed along column length (one, two, and three openings). Each steel column specimens was subjected to an increasing static load up to column failure which indicated by the reloading of the test machine. The study has shown that for most of the tested columns, increasing the numbers of web openings results in decreasing the column axial strength compared to the reference steel column. The maximum percentage of the reduction in the columns axial compressive strength caused by the presence of web opening was found to be about 30% and 45% of the reference columns strength for columns with box and channel shape sections, respectively. It has also been found that the reduction in the axial compressive strength of the column specimens caused by the presence of web openings is lower for the circular shape openings compared to that for rectangular and/or square shape web openings.

Behaviour of composite frames with castellated steel beams at elevated temperatures

The behaviour of composite frames with castellated steel beams at elevated temperatures is investigated, and the results obtained were compared with the companion results of simply supported composite castellated steel beams. Overall, it is aimed to investigate the effect of axial and rotational restraining of the steel beam via rigid connections with protected steel columns at elevated temperatures. A previously reported finite element model for the analysis of composite beams in fire was extended to perform the nonlinear analyses of composite frames at elevated temperatures. The finite element model has accounted for the frame geometries and boundary conditions, nonlinear material properties of steel, concrete, profiled steel sheeting, longitudinal and lateral reinforcement bars as well as shear connection behaviour at ambient and elevated temperatures. The thermal properties at the steel beam top flange/profiled steel sheeting and profiled steel sheeting/concrete elements interfaces were considered in the thermal heat transfer analysis that allowed the temperatures to be accurately predicted in the composite slab during fire exposure. The comparison of composite frames and composite beams behaviour has shown that if the columns were sufficiently protected and the connection maintained its rigidity during fire exposure, such that it can restrain the composite beam thermal expansions, this would result in considerable reduction in fire resistances of the composite frames compared with that of simply supported composite beams. This is attributed to the premature failure at elevated temperatures due to local buckling at the bottom flange of the steel beams in the frame connections. Furthermore, the variables that influence the fire resistance and behaviour of the composite frames comprising different load ratios during fire, different fire curves, presence of web openings and different steel grades were investigated by parametric studies. It is shown that the strength of steel and the fire scenarios have a considerable effect on the time–displacement behaviour and fire resistances of the composite frames.

Nonlinear analysis of composite castellated beams with profiled steel sheeting exposed to different fire conditions

This paper discusses the nonlinear analysis and design of unprotected composite castellated and noncastellated steel beams with profiled steel sheeting at elevated temperatures. The nonlinear material properties of steel, concrete, profiled steel sheeting, longitudinal and lateral reinforcement bars as well as shear connection behaviour at ambient and elevated temperatures were considered in the finite element models. The thermal properties at the steel section/profiled steel sheeting and profiled steel sheeting/concrete element interfaces were considered in the thermal heat transfer analysis that allowed the temperatures to be accurately predicted in the composite slab during fire exposure. It has been shown that the finite element models can efficiently predict the thermal and thermal–structural behaviour of the composite beams at elevated temperatures during the heating and cooling phases of fire. Furthermore, the variables that influence the fire resistance and behaviour of the composite beams comprising different load ratios during fire, different fire curves, presence of web openings and different steel grades were investigated in parametric studies. It is shown that the fire resistances of the unprotected simply supported composite castellated and noncastellated steel beams could be below 30min when heated using the standard fire curve. It is also shown that the strength of steel beam has a considerable effect on the behaviour and failure modes of the composite beams, which could change the failure mode of the composite beams in fire. The fire resistances of the castellated and noncastellated composite beams obtained from the finite element analyses were compared with the design values obtained from the Eurocode 4 for composite beams at elevated temperatures. It is shown that the EC4 is conservative for most of the unprotected composite castellated and noncastellated steel beams, except for some composite beams heated using the standard fire curve under load ratios of 0.4 and 0.5.

Improved shear design rules for lipped channel beams with web openings

Cold-formed steel Lipped Channel Beams (LCB) with web openings are commonly used as floor joists and bearers in building structures. The shear behaviour of these LCBs with web openings is complicated and their shear capacities are considerably reduced by the presence of web openings. However, limited research has been undertaken on the shear behaviour and strength of LCBs with web openings. Hence a detailed numerical study was undertaken to investigate the shear behaviour and strength of LCBs with unreinforced circular web openings. Finite element models of simply supported LCBs under a mid-span load with aspect ratios of 1.0 and 1.5 were developed and validated by comparing their results with test results. They were then used in a detailed parametric study to investigate the effects of various influential parameters. Experimental and numerical results showed that the current design rules in cold-formed steel structures design codes are very conservative. Improved design equations were therefore proposed for the shear strength of LCBs with web openings based on both experimental and numerical results. This paper presents the details of finite element modelling of LCBs with unreinforced circular web openings, validation of finite element models, and the development of improved shear design rules. The proposed shear design rules in this paper can be considered for inclusion in the future versions of cold-formed steel design codes.

AN APPROXIMATE METHOD FOR THE ULTIMATE SHEAR STRENGTH OF HORIZONTALLY CURVED COMPOSITE PLATE GIRDERS

The paper is concerned with the ultimate load capacity of horizontally curved composite plate girders. An approximate method to predict the ultimate shear strength of the girders is presented. The proposed method accounts for the tension field action in web panels, composite action between steel plate girder and reinforced concrete slab with full interaction and presence of web openings. The accuracy of the method is assessed by comparing the predicted values of ultimate shear strength with the corresponding results obtained by using the nonlinear finite element analyses through a computer package LUSAS. The comparisons show that the proposed method is capable of predicting the ultimate shear strength with an acceptable accuracy. Presence of web openings of different proportions and their effects on ultimate strength of the girders are examined. Girders with trapezoidally corrugated webs are also considered in the study.

Experimental studies of the shear behaviour and strength of lipped channel beams with web openings

Cold-formed steel members are increasingly used as primary structural elements in the building industries around the world due to the availability of thin and high strength steels and advanced cold-forming technologies. Cold-formed lipped channel beams (LCB) are commonly used as flexural members such as floor joists and bearers. However, their shear capacities are determined based on conservative design rules. Current practice in flooring systems is to include openings in the web element of floor joists or bearers so that building services can be located within them. Shear behaviour of LCBs with web openings is more complicated while their shear strengths are considerably reduced by the presence of web openings. However, limited research has been undertaken on the shear behaviour and strength of LCBs with web openings. Hence a detailed experimental study involving 40 shear tests was undertaken to investigate the shear behaviour and strength of LCBs with web openings. Simply supported test specimens of LCBs with aspect ratios of 1.0 and 1.5 were loaded at mid-span until failure. This paper presents the details of this experimental study and the results of their shear capacities and behavioural characteristics. Experimental results showed that the current design rules in cold-formed steel structures design codes are very conservative for the shear design of LCBs with web openings. Improved design equations have been proposed for the shear strength of LCBs with web openings based on the experimental results from this study.

Tests of Fibrous and Nonfibrous Reinforced Concrete Continuous Deep Beams with Web Openings

Test results of twenty four two-span reinforced concrete deep beams, with or without web openings and with or without steel fibers are reported. All test specimens had the same cross-section, main longitudinal top and bottom reinforcement, and web reinforcement. The main parameters considered were the shear span-to-total beam depth ratio (a/h), position of the web openings, and the amount of steel fibers. Test results indicated that the presence of web openings within exterior or interior shear spans had great effects on the beam capacity and its behavior, with the diagonal cracking between loads and supports being dominant. In these beams, the crack patterns revealed the fact that the contribution of the top reinforcement was not significant. However, the top reinforcement showed better contribution in solid beams and beams with openings within midspan region especially when the shear span-to-depth ratio was increased. The crack patterns were less affected by the addition of steel fibers, however, an increase in the ultimate load capacity was obtained. The amount of increase in the ultimate load was about 10% in solid beams and beams having openings within midspan region, while the amount of increase was dependent on the shear span/depth ratio and location of the openings in the other beams. Also the fibrous beams showed better degree of serviceability requirements.

Effect of Beam Length and Braced Length on Moment-Rotation Behavior of Castellated Beams

The presence of web openings in castellated beams introduces different modes of failure at the perforated sections such as excessive stresses in tee-sections, excessive stresses in mid-depth of the web post, web-post buckling, developing plastic Vierendeel mechanism. This paper presents nonlinear behavior of castellated beams under moment gradient loading and investigates the effect of beam length and braced length on moment-rotation behavior and ductility of this type of beams. Accuracy of finite element models of plain-webbed beams is evaluated comparing moment-rotation behavior and failure mode of other researchers’ numerical models and cleared a satisfactory accuracy. Rotational capacity of castellated beams, derived from numerical modeling, is compared with corresponding I-shaped plain-webbed steel beams and it is cleared that for the short beams, web openings reduce energy absorbance and plastic moment capacity of the beams more than long ones.

Shear Behaviour and Strength of LiteSteel Beams with Web Openings

The LiteSteel Beam (LSB) is a new cold-formed steel hollow flange channel beam recently developed in Australia. It is commonly used as a floor joist or bearer in buildings. Current practice in flooring systems is to include openings in the web element of floor joists or bearers so that building services can be located within them. Shear behaviour of LSBs with web openings is more complicated while their shear strengths are considerably reduced by the presence of web openings. However, no research has been undertaken on the shear behaviour and strength of LSBs with web openings. Therefore a detailed experimental study involving 26 shear tests was undertaken on simply supported LSB test specimens with web openings and an aspect ratio of 1.5. This paper presents the details of this experimental study and the results of their shear capacities and behavioural characteristics. Experimental results showed that the current design rules in cold-formed steel structures design codes are very conservative for the shear design of LSBs with web openings. Improved design equations have been proposed for the shear strength of LSBs with web openings based on the experimental results from this study.

Standardized Design of Double Tees With Large Web Openings

This paper is the second of two papers dealing with research conducted at the University of Nebraska on the design of double tees with large web openings. The earlier paper dealt with experimental and theoretical studies as well as initial design recommendations. This phase of the project aims to further maximize and standardize opening sizes and locations. It also aims to simplify the additional design steps required to account for the presence of web openings. The results of the study show that a significant number of large openings can be incorporated into the webs of double tees without reducing the structural capacity of the member if two main conditions are met: (1) No openings are placed within a distance equal to the strand development length from the member end, and (2) additional vertical stirrups, as detailed in this paper, are provided at the edges of the openings.