Current Design Specifications Research Articles

Structural Performance and Reasonable Cross-Ratio of Cross-Cable Multi-Tower Cable-Stayed Bridges

The Queensferry Crossing in the UK is the first multi-tower cable-stayed bridge in the world to use mid-span cross-stayed cables to improve structural rigidity. To study the structural performance and economy of cross-cable multi-tower cable-stayed bridges, a total of 11 finite element models were established using two cross-cable setting methods. By changing the number of crossed cables in the mid-span, the variation laws of structural deformation and internal force are obtained. The cross-cable efficiency based on structural stiffness and the cross-cable economy based on the consumption of cables used in the entire bridge are quantitatively analyzed, and it is considered that there is a reasonable cross-ratio of cross-cables. Combined with the current design specification and the empirical data of the actual bridge, the limits of the double indicators were determined, and a scheme comparison chart was formed. The results show that under the action of unbalanced load, the cross cable can greatly reduce deformation and balance the internal force of the structure. The optimal solution is to form a mid-span cable crossing by adjusting the cable spacing, and the reasonable range of cross-ratio is 15%~35%. If the structural stiffness is improved by adding additional cross cables, the cross-ratio should be controlled within 16% to ensure structural economy. This provides a reference for the design and research of cross-cable multi-tower cable-stayed bridges in the future.

Recommendation in Government Hospital Buildings in Context of Means of Escape based on Other Countries Cases

The guidelines on hospital safety been developed with a target to increase the safety of a hospital structurally and functionally and decrease the risks to human’s life. The current government hospitals are mostly been built before these guidelines been developed. There are many factors that put hospitals and health facilities at high risk which includes buildings, their location, design specification and patient. For this paper, researcher’s aim is to focus on the current design specification on other countries cases and compare it with the selected government hospitals. In this paper, literature study been done thoroughly on the hospitals and cases which is caused by a poor design. Hospital may differ in area of a small hospital with a less beds and no emergency facilities or city hospital with emergency facilities including extra care, diagnostics service and hundreds of beds. Therefore, designers need to understand how each hospital operates. The latest case in our country in March 2018 is the one that occurred at Hospital Kuala Lumpur. The accident occurred at the forensic department which is caused by short circuit at its store. The fire spread very quick and destroy a portion of the forensic department. The latest incident which occurs in Hospital Sultanah Aminah (HSA) on 28th June 2020. The fire involves the oxygen panel, call bell, vacuum and switch at the bed number five. There is one more case which occurred on 26 October 2016 at Hospital Sultanah Aminah (HSA).

Observing Planet-driven Dust Spirals with ALMA

Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations of thermal emission from the dust component of protoplanetary disks have revealed an abundance of substructures that may be interpreted as evidence for embedded planets, but planet-driven spiral arms—perhaps one of the most compelling lines of evidence—have proven comparatively elusive. In this work, we test the capabilities of ALMA to detect the planet-driven spiral signal in continuum emission. Carrying out hydrodynamic simulations and radiative transfer calculations, we present synthetic Band 7 continuum images for a wide range of disk and observing conditions. We show that thermal mass planets at tens of astronomical units typically drive spirals detectable within a few hours of integration time, and the detectable planet mass may be as low as ∼Neptune mass (0.3 M th). The grains probed by ALMA form spirals morphologically identical to the underlying gas spiral. The temperature of the dust spiral is crucial in determining its contrast, and spirals are easier to detect in disks with an adiabatic equation of state and longer cooling times. Resolving the spiral is not necessary for its detection; with the help of residual maps, the optimal beam size is a few times the spiral width at a constant noise level. Finally, we show how the presence of gaps and rings can impair our ability to recognize colocated spirals. Our work demonstrates the planet-finding potential of the current design specification of ALMA, and suggests that observing capability is not the bottleneck in searching for spirals induced by thermal mass planets.

Numerical Investigation of the Flexure Behavior of Reinforced Concrete Spandrel Beams with Distributed Tension Reinforcement

When the flange of a reinforced concrete spandrel beam is in tension, current design codes and specifications enable a portion of the bonded flexure tension reinforcement to be distributed over an effective flange width. The flexural behavior of the RC L-shaped spandrel beam when reinforcement is laterally displaced in the tension flange is investigated experimentally and numerically in this work. Numerical analysis utilizing the finite element method is performed on discretized flanged beam models validated using experimentally verified L-shaped beam specimens to achieve study objectives. A parametric study was carried out to evaluate the influence of various factors on the beam’s flexure behavior. Results showed that as the percentage of the reinforcement distributed has increased over a greater width of the flange, a considerable drop in beam flexure strength was observed with excessive deflection. According to the study, not more than 33% of the web tension reinforcement might be distributed over an effective flange width less than ln/10, including the web region, as recommended by the ACI318-14.

High-cycle fatigue tests of pretensioned concrete beams

Pretensioned concrete beams are widely used as bridge girders for simply supported bridges. Understanding the fatigue behavior of such beams is very important for design and construction to prevent fatigue failure. The fatigue behavior of pretensioned concrete beams is mainly influenced by the fatigue of the prestressing strands. The evaluation of previous test results from the literature indicated a reduced fatigue life in the long-life region compared with current design methods and specifications. Therefore, nine additional high-cycle fatigue tests were conducted on pretensioned concrete beams with strand stress ranges of about 100 MPa (14.5 ksi). The test results confirmed that current design methods and specifications overestimate the fatigue life of embedded strands in pretensioned concrete beams.

Extension and application of the TRANSURANUS code to the normal operating conditions of the MYRRHA reactor

This work deals with the performance analysis of the MYRRHA hottest fuel pin in normal operating conditions, employing the TRANSURANUS fuel performance code, with the aim of assessing the current design specifications considering conservative design limits. To allow the proper simulation of the MYRRHA pin behaviour, TRANSURANUS is extended with novel correlations for the creep and void swelling response of the specific cladding material (DIN 1.4970). The analysis of the best-estimate reference scenario is complemented by a sensitivity analysis on models describing fuel and cladding phenomena and properties, determining those which most affect the pin performance results and identifying the worst-case scenarios. The simulation outcomes point out the high level of safety related to the MYRRHA fuel pin performance in normal operating conditions, which keeps far from any design or critical limit, even in the most challenging (worst-case) scenarios.

The impact of variability and combined loads on fuses in braced frames

In lateral force resisting systems, fuses enable expedient repair while ensuring ductile system response. A bracing system is explored herein, in which hollow rectangular sections (RHS) and double channel sections (UPN) are used as the energy dissipating mechanism. Analyzed members have the same Eurocode section class (1st) and elastic section modulus. Loading on these fuses is a combination of bending moment, axial and shear loads (M−N−V). An analytical model is developed based on the Huber-Mises criterion to analytically describe the interaction between (M−N−V). The accuracy of the analytical model is benchmarked by a comparison with results of an experimental campaign and obtained through a finite element numerical model. The paper continues with a sensitivity analysis of the ultimate moment to the variation in axial and shear force. The analytical model is then adopted to assess how the fuse response is affected by the randomness in the design parameters (the geometrical features and mechanical properties). The impact of statistical variation in design parameters is elucidated through a Monte Carlo simulation. Variability in member geometric features was determined from current design specifications, while variability in steel mechanical properties was determined via experimental testing. The work concludes with an analysis and discussion of the Monte Carlo simulation with recommendations for designers and fabricators to encourage higher quality control in manufacturing. Variability in steel yield strength was found to have the most significant impact on the brace structural response, and must be tightly controlled for to produce accurate designs.

Equivalent imperfections for the out-of-plane stability design of steel beams by second-order inelastic analysis

In current structural design specifications, such as EN 1993-1-1 for steel and EN 1993-1-4 for stainless steel, the stability of members is typically assessed through the use of buckling curves, which consider the influence of initial geometric imperfections and residual stresses. An alternative, more direct, approach is to perform either an elastic or inelastic second-order analysis of the member or structure with imperfections. For modelling convenience, so-called ‘equivalent’ imperfections are typically utilised, which consider the combined influence of both geometric imperfections and residual stresses. Equivalent imperfections for the design of columns and beams by second-order elastic analysis, also referred to as geometrically nonlinear analysis with imperfection (GNIA), are provided in the current design specifications. For columns, equivalent imperfections for design by second-order inelastic analysis, also referred to as geometrically and materially nonlinear analysis with imperfections (GMNIA), were recently developed, but for beams that are susceptible to lateral-torsional buckling (LTB), there are currently no appropriate provisions. The aim of this study is therefore to develop equivalent imperfections for use in out-of-plane stability design of steel and stainless steel members by GMNIA. The proposals are calibrated against the results of benchmark finite element (FE) simulations performed on a large number of steel and stainless steel members with geometric imperfections and residual stresses subjected to major axis bending. Two proposals for equivalent imperfection amplitudes are developed: (1) e0,mod, for use with eigenmode-affine imperfections and (2) e0,bow, for use with sinusoidal bow imperfections. The latter is applied solely in the lateral direction and as a summation of a half-sine wave and a full-sine wave. Relative to the traditional Eurocode design calculations, employing the proposed LTB imperfections in GMNIA provides generally more accurate member resistance predictions, while remaining safe-sided relative to the benchmark FE results. The reliability of the design provisions is demonstrated through statistical analysis, where it is shown that partial safety factors of 1.0 for steel and 1.1 for stainless steel can be safely adopted.

Investigation of concrete box girder positive temperature gradient patterns considering different climatic regions

Due to the inevitable exposure of bridges to complex ambient environment, the effects of temperature variation on the structure itself should be considered. Accurate evaluation of the cross-sectional temperature distribution is a significant concern in the bridge design phase. Temperature gradient patterns have been provided by current bridges codes with the consideration of the thermal effects on the structures. However, the current codes are insufficient to describe the temperature gradients of different climatic regions in China. This paper aims to develop a more efficient positive temperature gradient pattern considering different climatic regions within a 100-year return period. Long-term numerical simulations of two-year continuous thermal actions regarding seven different regions have been conducted to investigate the thermal effects on concrete box girders. Then, the comparison of the simulated results and current bridge design specifications illustrates the deficiencies of the current specifications. Furthermore, a 2-step method with curve fitting and extreme values analysis (EVA) has been utilized to determine the temperature gradient patterns. The curve fitting shows that the temperature gradient patterns of different regions can be described by a piecewise function with parabola. And, EVA shows that all the temperature gradients fit well with the Weilbull distribution. The representative values of different regions have also been obtained through the EVA. Finally, a positive temperature gradient pattern with the consideration of both the locations and design period has been proposed in this paper. The proposed temperature gradient pattern shows a better applicability in different regions comparing with the current Chinese codes. It hopes that the present study could contribute to further application of bridge temperature gradients and the investigation of other infrastructural areas in respect of the temperature gradients.

Shear bearing capacity of Self-drilling screw group connections of CFS sheets

Self-drilling screws are commonly used as connectors in cold-formed steel (CFS) buildings as they can be drilled easily through thin sheet steels, allowing on-site assembly. The screw connections in the project all appear in the form of screw group connections. Studies have shown that the shear bearing capacity of a screw group connection of CFS sheets is not simply the shear bearing capacity of a single screw connection multiplied by the number of screws. But instead, there is a reduction effect of the screw group connection, called the Group Effect. However, there is no design provision for the shear bearing capacity of the screw group connection in the current design specifications, AISI S100-16w/S1-18, AS/NZS-4600:2018, EN1993-1–3, and GB50018-2002. Based on the authors' and other researchers' tests collected by authors, this paper verifies and analyzes the four existing design equations for the connection strength of the screw group connections that consider the Group Effect. The results show that the four current design equations cannot cover the test data that list in the paper because the existing four design equations all have their respective scopes and limitations, such as the screw spacing and the strength of steel sheetings, etc. For that, the paper proposed a new design equation that can calculate the nominal shear capacity of self-drilling screw group connections, including high-strength steel such as G550 CFS sheets and extensive screw spacing connections. The authors' new test of twelve screw group connections and the other 237 tests verified the new equation. The unsafe rate for the new design equation is 4.42% among the 249 connections test, and the new design equation has high reliability and broader application scope.

Mechanical behaviour and design of concrete-filled K and KK CHS connections

The mechanical behaviour of concrete-filled K and KK circle hollow section (CHS) connections are assessed experimentally and numerically in this paper. Three large-scale concrete-filled K and KK connections were tested. The experimental stress concentration factor (SCF) values of the KK connection were compared with the predictions calculated using the current design specifications. The finite element (FE) models were developed and validated against the current and previous test results. Based on the developed models, the parametric study was conducted to study the influence of the two pairs of K-braces and the axial compressive force of the chord on the punching shear stress distribution and ultimate strength. The applicability of the design specifications intended for the design of pure steel CHS connections and the previously proposed design equation for concrete-filled T and Y CHS connections to the concrete-filled K- and KK-type connections were evaluated. Both experimental and numerical results demonstrated that the concrete-filled CHS connection failed at punching shear fracture on the chord-wall near the weld toe. The interaction between two K-pairs should be considered in the strength design, and the level of the chord compressive load should be controlled to avoid the occurrence of the combined failure mode. The proposed design methods for K and KK connections can predict the punching shear strength of concrete-filled K and KK connections with reasonable accuracy.

Experimental study on the properties of modern blue clay brick for Kaifeng People's Conference Hall

This article presents building assessment research comprising on-site inspections, indoor scientific tests, and material performance studies on the wall blue clay bricks in the Kaifeng People’s Conference Hall, objectively developing an enhanced scientific understanding to renovate modern buildings. Using X-ray diffraction (XRD), scanning electron microscopy (SEM), alongside a parametric study of density, moisture content, water absorption, void ratio, frosting, compressive strength, and softening coefficient in assessing the material health of the blue clay bricks and it’s non-key parts, in developing “appropriate and compatible renovation” to repair contemporaneous buildings. The composition, pore characteristics, weathering degree, and mechanical properties of the blue clay brick samples were analyzed. These parameters showed that blue clay brick fired at less than 1000 °C; the main mineral composition as quartz, followed by albite, mica, and anorthite. Its density was 1.573 g/cm3, less than the 1.70 g/cm3 of ordinary clay brick. According to the standards, the water absorption was greater than that of regular sintered bricks by more than 18% and was slightly frosted. Compressive strength being less than MU10 did not meet the current design specifications for masonry. Its softening coefficient was between 0.70 and 0.85, but its water resistance was relatively good. The research results provide an essential reference for judging the health and longevity of modern buildings to achieve scientific guidelines for practical protection.

A Proposal for a Simple Method for Determining the Concrete Slab Width of Composite Beam-to-Column Joints

Extensive brittle failures in the weld zone of the beam bottom flange in composite joints of SMRFs were observed during the Northridge earthquake and the Kobe earthquake. One of the main reasons is the large tensile strain demand generated at the beam bottom flange zone under positive bending. The key to accurately understanding the mechanical properties of composite joints is the effective width of the slab. However, researchers have no consensus on the flange slab’s effective width for composite joints, even with the simplest solid concrete slab. Therefore, the best way to design the composite joint specimen is by following the current design specifications. However, each specification implements different ideas and approaches for specifying an effective slab width. This paper presents comparisons of the effective flange width provisions in China, the United States, Australia/New Zealand, and the European Union. The characteristics of each provision are briefly described and summarized. Numerical comparisons for positive and negative moment regions of continuous spans follow. Based on the commonalities and main differences among all these provisions, we propose a recommended equation for calculating the effective width of a solid concrete slab, reflecting the specification differences. The reliability of the recommended equation was verified with ABAQUS software analysis. The recommended equation can meet the fast and secure design requirements for composite joints in tests with concrete slabs.

Behaviour of duplex stainless steel bolted connections

This study deals with the behaviour of duplex stainless steel bolted connections. The aim of the study is to respond to the question if the current stainless steel design specifications are able to predict the behaviour of such connections. Firstly, the net cross-section capacity of duplex stainless steel plates subjected to tensile loading are presented. They were conducted to obtain the stress–strain curves and tensile fracture behaviour used to support the finite element (FE) fracture simulations. Secondly, nonlinear FE models are developed for duplex stainless steel bolted connections subjected to tensile loading. The FE models are validated against experimental data in terms of load–displacement curves, failure modes and ultimate loads. Then, a numerical parametric study that consists of 133 duplex stainless steel grade EN 1.4162 bolted connection specimens is carried out. The failure modes of bolted connections are carefully examined, including combined tear out and bearing, bearing and net section, looking at the influence of parameters such as end distance, edge distance and spacing between the bolts in the connections. The results are compared to the design rules prescribed in the current stainless steel design specifications. Generally, it is found that the Australian/New Zealand (AS/NZS), American (SEI/ASCE) Specification and European codes conservatively predict the ultimate strengths of the bolted connections, whereas the strengths predicted by the AS/NZS and SEI/ASCE specifications are overall more accurate and less scattered.

Wall-diaphragm interactions in seismic response of single-story building systems

The objective of this paper is to investigate the seismic time history response of single-story buildings with a wide range of wall and roof diaphragm periods and ductility. Current design specifications, e.g., ASCE 7-16, are transitioning from accounting for inelasticity in only the vertical lateral force resisting systems, i.e., the walls, to including inelasticity in the horizontal lateral force resisting system, i.e., the roof diaphragm. It is not clear if the wall and roof inelasticity can be considered independently, nor if they can utilize their own seismic response modification coefficients. More fundamentally, the basic manner in which stiffness, mass, and ductility of the wall and roof interact is not fully understood. Here, a single-story building is approximated with a reduced order mass-spring model and parameters are varied so that a wide range of wall periods, diaphragm periods, and wall and diaphragm inelasticity are explored. The model is imposed to vibration analyses, elastic time history analyses, and inelastic time history analyses. The results show clear regimes where the wall and diaphragms interact, and those where the response is largely independent. When inelasticity occurs the ductility demands can be significant for the building component, wall or diaphragm, that initiates the yielding, and greater than traditionally expected. The model results are compared to current and proposed provisions for predicting force and ductility demands and conclusions are drawn with respect to the accuracy of available methods.

Failure Modes Of Cold Formed Steel Angle Sections

Tension members consisting of single and double angles, single channels and similar sections are frequently used for lateral bracing and as truss elements. Such members normally have eccentric connections which results in bending of tension member. It is often permitted, by current design specifications, to neglect this eccentricity in the design of the member. The present study is focus on mode of failure on cold formed steel angle. This analysis carries single angles and double angles sections of 2mm under plain (without Lipped) and with Lipped conditions subjected to tension. Analyses were carried out for thirty-six numbers of angle sections under condition such as double angle were connected same side to gusset plate and connected to opposite side. Figure shows connection failure and mode of failure. Local buckling, global buckling, tearing failure, net section failure, and block shear failure.

Buckling behaviour of Q460GJ welded H-section columns subjected to minor axis under axial compression

To study the overall buckling behavior of Q460GJ steel columns around the minor principal axis under axial compression, experimental investigations were carried out on 8 pin-ended H-section steel columns. The main parameter of the specimens is slenderness λ, ranging from 36 to 86. Besides, material properties, initial geometrical imperfections and residual stresses of the specimens were measured. During the loading process, horizontal displacements at the mid-span of the specimens and the strain development were monitored. All the specimens failed with overall buckling and the bearing capacity was obtained. Moreover, a finite element model that considered initial geometric imperfections and residual stress was established and verified, and numerical studies were followed. The buckling factor φ - nondimensional slenderness λn relationship is compared with that in current design specifications. The curve “c” in the Chinese standard GB50017-2017 and curve “c” in Eurocode 3 are recommended to evaluate the overall buckling resistance of 460GJ welded H-section columns under axial compression conservatively.

Development of models for facing tensile forces of soil nail walls using statistical approaches

ABSTRACT The facing is a key component for the design of soil nail walls. However, current design specifications of soil nail walls in China do not specify methods for estimation of facing tensile forces, which has posed challenges for engineers to produce consistent, safe, and cost-effective facing designs. This study first constructs the facing tensile force as the product of the maximum nail load and a facing factor. Then a database containing 91 measured facing tensile force data collected from the literature is developed and used to calibrate the facing factor matching six maximum nail load models that are commonly adopted in China, namely, the simplified incremental calculation models based on the Rankine and Coulomb earth pressure theories, the China Academy of Building Research model, and the China Association for Engineering Construction Standardization model. Based on the developed database, the accuracies of the six proposed models for facing tensile forces are demonstrated to be unbiased on average and the dispersions in the prediction accuracy are ranked from low to medium. Furthermore, the influences of three wall working conditions on prediction accuracy of the developed models are investigated and shown to be practically insignificant. Last, the model biases are characterised as lognormal random variables.

Reliability-based design approach for high-rise buildings subject to earthquakes and strong winds

Current design specifications often deal with seismic and wind events in isolation, which may underestimate the failure probability. In this paper, a reliability-based approach is presented to compute the load modification factor for designing high-rise buildings in regions prone to earthquake and strong wind events. The paper illustrates the proposed procedure from the construction of hazard models to load modification calculations, which is implemented in a 42-story steel frame-reinforced concrete (RC) core tube building located in the Dali region, southwest of China. The uncertainties associated with hazard models, material properties, input loads, demand models and structural capacity are considered to improve the accuracy of failure probability estimations. The effects of individual and concurrent earthquakes and strong winds are accounted for in the reliability-based design method. Then, the load modification factor is determined by comparing the calculated failure probability with the rational target value. Finally, a suggested combined factor will be used to modify the value of the design wind load in the limit state function. More work is needed before load modification can be applied in practice. However, this study offers a practical and extensible approach to improve the future calibration of load combination criteria for designing high-performance structures against various hazards.

Tests of cold-formed steel built-up sections with web holes subjected to web crippling

This paper presents an experimental study on web crippling behaviour of cold-formed steel built-up Isections with circular web holes. The built-up sections were formed by connecting two identical unlipped channels with self-tapping screws. The web hole was located at mid-height of the web and directly beneath the bearing plates. Web crippling tests were conducted on 6 built-up sections without web holes and 19 built-up sections with perforated web under End-Two-Flange and Interior-Two-Flange loading conditions. The web crippling strengths, failure modes and load-displacement curves were reported. The experimental ultimate strengths for specimens without web holes were compared to the nominal strengths predicted from North American Specification, Australian/New Zealand Standard and European Code for cold-formed steel structures. It should be mentioned that the existing international design codes do not have explicit design formula to predict the web crippling strength of cold-formed steel built-up sections with perforated web. Therefore, the test strengths of specimens with perforated web were compared with the strengths derived from the design equations proposed in the literature. It is shown that the design strengths predicted from current design specifications are either conservative or unconservative for the specimens without web holes, while the design equations in the literature are generally unconservative for the specimens with perforated web.