Live Load Research Articles

Comparative CO2 emissions of concrete and timber slabs with equivalent structural performance

Comparing the environmental impacts of building materials at the building level can be biased because a building design is optimized for a primary structural material. To achieve objective comparisons, this study compares the environmental impact of reinforced concrete (RC), cross-laminated timber (CLT), and timber-concrete composite (TCC) at the component level with equivalent structural performance. A slab was selected as the target structure member because its design does not consider lateral forces. Equivalent structural performance was defined as the minimum quantity of slab materials for comparable span and live load conditions. The functional unit for this study was defined as a 1 m2 slab. The system boundary covered the cradle-to-gate perspective, including raw material extraction, transportation, and manufacturing. The structural design method and material design values followed the Korean building code and standards. Environmental product declaration data developed in Korea were used to evaluate the carbon footprint. The CLT emitted 75 % less carbon dioxide, the primary greenhouse gases responsible for anthropogenic climate change, compared with RC regardless of conditions, while the TCC emitted 65 % less CO2, and its environmental impact improved as the span lengthened. The results also indicated that timber slabs are thinner than concrete slabs and can be structurally rational.

Modelos probabilísticos para a ação de utilização em edifícios: análise crítica, comparação com normas brasileiras de projeto, e calibração dos fatores parciais de segurança

abstract: Nowadays, structural “limit state” design is made using characteristic or nominal values of actions, partial safety factors and load combination factors. The actual loading that a structure will be subjected to throughout its life is not known at the design phase. Yet, probabilistic models of such loadings are useful for the rational determination of partial safety factors and load combination factors. The probabilistic model leading to nominal live loads of NBR 6120:2019 (Design Loads for Structures) has never been openly discussed. Herein a simple probabilistic model describing spatial and temporal variabilities of live loads in buildings is presented and discussed. The model is built as a sum of two stochastic processes representing the sustained and intermittent parts of the live load. Model parameters are the ones recommended by the Joint Committee on Structural Safety (JCSS), based on extensive surveys done in several countries. By way of Monte Carlo simulations, sample values of live load actions are obtained for buildings of different occupancy types. These values are compared with those recommended by international standards, and those recommended in NBR 6120:2019 and NBR 8681:2003 (Actions and Safety of Structures). The corresponding statistics for the fifty-year extreme and arbitrary point-in-time distributions of live loads are presented; these statistics are very relevant for reliability analyses and for reliability-based code calibration. The stochastic live load model is also employed in a reliability-based calibration to obtain partial safety factors and load combination factors to be used in Brazilian design codes, for ultimate and serviceability limit state verifications.

Influência da resistência do concreto na distribuição do momento fletor em pontes curvas alargadas

abstract: The study proposes to analyze the distribution of bending moment due to live load in curved bridges that have undergone a process of widening, considering the influence of concrete’s strength variation. The results show that the bending moment redistribution is more significant the higher the stiffness in the widenings. In addition, the redistribution induced by the variation of stiffness depends on the live load positioning but, generally, it results in the migration of bending moments to the stiffer regions, relieving the original girders. The curvature did not significantly alter the response induced by the stiffening of the widened segments. Also, the divergences found between the MEF and the V-load Method results for models with uniform and variable stiffness were similar. Finally, the Modification Factors (MF) proved to be more sensitive to the influence of curvature than to the concrete strength in the widenings.

Extrapolation of Load Histories Based on MCMC and POT

Load spectrum is essential for fatigue life analysis, strength and durability tests of vehicles and components, but the whole life load cannot be acquired by measurement. To extrapolate a short measured load history to a longer time period, a method was presented in this paper based on Markov Chain Monte Carlo (MCMC) in conjunction with the Peak Over Threshold (POT) method. Firstly, we extend the load by MCMC to increase the randomness of load and the number of extreme samples; then fit a generalized Pareto distribution (GPD) using POT method to extrapolate the extreme values. Methods of threshold selection in POT were also presented briefly in this paper. Rain flow curves of the original, the MCMC extended and the extended extrapolated signal comparison verified the effectiveness of this method.

Análise de confiabilidade de pórticos em concreto armado sujeitos a recalques pós-construção

Abstract Most papers in the literature address reliability analysis of isolated elements, like beams and columns. However, symmetry and regularity are often exploited in the construction of regular RC frames, resulting in the same or similar designs for all columns of a floor or all beams of a building. This leads to significant differences in member reliability, due to different axial load to bending moment ratios, in different parts of the structure. Moreover, load effects increase, and symmetry is lost under individual support settlements. In this scenario, reliability analyses are performed, for an intact 4-floors and 3-spans RC frame; and considering different settlement conditions. Monte Carlo simulation is performed, considering uncertainties in dead and live loading, and steel and concrete strengths. The results show that a settlement of 10 mm, corresponding to an angular distortion of 1/500, reduced the average reliability of the frame by only 14%, just the same, it reduced the reliability index of several cross-sections of the beams to up to 2.40, value lower than that recommended in the Model Code 2010. It is concluded that the methodology used in this work presents an important tool for the analysis of events not foreseen in the design, supporting the decision making about the need for intervention in the structures.

Investigating UHPC in deck bulb-tee girder connections, part 1: Analytical investigation

Precast concrete deck bulb-tee girder systems offer an excellent choice for prestressed concrete bridges with spans of 100 ft (30.48 m) or more. These girders are placed side by side in the field and connected using longitudinal joints. The wide top flange of the girders acts as a deck, eliminating the need for a cast-in-place concrete deck and providing a solution for accelerated bridge construction. However, the longitudinal joints between the girders often crack under service loads, allowing for water and deicing chemicals to enter the system and cause corrosion. An analytical study with ultra-high-performance concrete (UHPC) longitudinal joints was performed to investigate the joint performance when subjected to thermal and live loads. A continuity diaphragm with UHPC in the top flange was also investigated for negative moment over pier. Results of the investigation suggest that the use of UHPC can improve the performance of the connections. The high bond strength of the UHPC reduces the connection length and allows for simpler reinforcement details.

Seismic response evaluation of waffle slab with and without bracing system using time history analysis

In the analysis and design of structures, seismic ground motion is a significant factor. Seismic criteria consideration is necessary for serviceability and feasibility of existing as well as new structures. Time History analysis is the one in which base is subjected to a specific ground motion and dynamic response of structure is analysed at each increment of time. The bracing system increases the structure’s resistance to lateral loads by transferring load from the frame to the braces. This study uses the ETABS software to do a time history analysis on a G+4 RCC building with a waffle slab and an X-type bracing system. For designing purposes, the IS 456-2000 code is thought about. According to IS 875-part 1, live loads are measured, and IS 1893-2016 earthquake analysis is carried out. For this structure, a number of factors are analysed, including storey drift, base shear, storey stiffness, and storey displacement, among others.

Thermal Analysis of Reinforced Beam-Column Joint

In concrete structures, temperature changes can cause strains of the same order of magnitude as live and dead loads in some circumstances. When thermal expansion or contraction is controlled, thermal stresses are induced. This report discusses the performance of reinforced joints under thermal loading conditions. Here we analysed the variance in stress and deflection when the temperature increases. The joints are modelled in ETABS and imported into ANSYS for further thermal analysis. The aim is to evaluate the RC beam-column joints at high temperatures in transient response. The results discuss how RC joints respond to temperature variations. The deformations with temperature variation are examined at high-temperature conditions.

Shape optimization of hanging structure using the concept of Biomimics

In the field of construction industry there has been a lot of newly adopted technology, one among that is hanging structures. Hanging structures can help reduce a lot of space as there are no direct columns supporting the sub structure and super structure. The usage of construction materials can be reduced thus making it economical compared to conventional buildings. The structural stability of hanging buildings depends on its shape and size. This idea led to incorporating the concept of bio mimics for optimizing the efficient shape of hanging structure from weaver bird’s nest. Bio mimics is the concept of emulating and iterating any naturally existing organism or element, it is the process of mimicking either the shape or mechanism of any naturally existing element. The weaver bird’s nest is lightweight in nature and also structurally stable against gravity and wind load. Two conventional hanging structure of Rectangle and Octagonal shape were selected for this study. The material adopted for numerical investigation using finite element software Abaqus v 6.14 is ferrocement because of its lightweight nature. The structure is hanged with the help of a connection wire which is hooked into it and a beam column that is fixed at bottom. The models are analyzed under the application of gravity, wind, live load for a fixed penetration length and by varying the diameter of the connection wire. Also, the hanging structure bio-mimicked from the shape of weaver bird’s nest is modeled and analyzed by applying same loading and boundary condition. The structural stability of conventional hanging structure is then compared to that of bio-mimicked hanging structure in terms of stress and deformation. From the results it is observed that bio-mimicked hanging structure is more stable compared to that conventional hanging structure.

The impact of plan irregularity on multistory building response: A pushover analysis

Structural irregularity often stems from a combination of plan and elevation irregularities, as perfect regularity is seldom achieved in real structures. Defining structural irregularities is challenging due to their varying nature. While scientific literature tends to separate plan and elevation irregularities, there's a need to understand the behavior of real structures that possess plan irregularities. This paper investigates the impact of plan irregularities on multi-story building responses through pushover analysis. The study aims to evaluate various parameters such as capacity curves, performance levels, story drifts, and displacements for irregular building models compared to regular ones. Four and eight-story buildings are designed according to Indian standards, and nonlinear static analysis is conducted using a plastic hinge model. Plastic hinges are assigned at possible failure locations, and pushover analysis is performed. Eccentricity is incorporated by shifting the position of live loads and adjusting column dimensions on both sides of the axis of symmetry at eccentricity values of 10%, 20%, 30%, and 40%. Displacement-controlled pushover analysis is conducted, and pushover curves are obtained in the X direction. The performance of building models is compared with a regular reference frame. Capacity curves, performance points, and story response plots are analyzed using ETABS 9.7.0. The results indicate a reduction in base shear capacity with increasing irregularity, with eccentricity showing a greater effect than soft story irregularity. Irregularity also influences the height-wise variation of story drifts differently.

Rail Structure Interaction Analysis for Providing CWR on Un-Ballasted Multi-Span Open Web Steel Girder Bridge

Rail structure interaction (RSI) requires thorough study to understand the force transfer mechanism between the track and bridge components due to train vertical live loads, braking/traction loads and thermal loads accordingly. RSI analysis gives us an outline of the axial stress in rail, support reactions transferred to the bridge components and the relative displacement caused between the track and bridge. This paper investigates rail structure interaction analysis of unballasted multi-span steel through girder railway bridge carrying dedicated freight corridor (DFC) of 32.5t axle load. For this purpose, RSI analysis is performed as per the guidelines given in UIC774-3R [7] Code of Practice (International Union of Railways) for two different multi-span bridge with a span configuration of 7x63m and 6x48m respectively and the axial stress in rail, relative displacement between rail and bridge and support reactions transferred to the bridge components are calculated based on the span and stiffnesses of the bridges. From the analysis results, it shall be concluded whether to explore the possibility of providing a provision of continuous welded rail (CWR) on the bridge or to adopt switch expansion joints (SEJ) or other expansion devices accordingly.

Experimental study of reinforced concrete piles wrapped with fibre reinforced polymer under vertical load

This research mainly focuses on the nature of Fiber-Reinforced Polymers (FRP) wrapped piles for the axial compression load. Normally, the degradation of Reinforced Cement Concrete (RCC) structures occurred due to corrosion, inadequate quality materials, aging, live load increments, fatigue, damages and deterioration, and so forth. RCC pile foundations are commonly affected by the above reasons. So, these structures can be strengthened with suitable methods such as jacketing, stitching, overlaying, sealing, grouting, coating, Near Surface Mounted (NSM) systems, FRP wrapping, repairing, and blanketing. FRP wrapping is well suited for strengthening pile structures because of its easy application, and this method is done without using heavy tools and skilled labor. Due to its being non-metallic, FRP reinforcing has desirable properties such as high resistance to chemicals as well as heat, flexibility, large tensile strength, permeability, and also no oxidation. Thus, FRP wrapping was selected as the chosen approach for this ongoing research. In this study, we apply an axial compression load as well as a skin friction condition to a pile member that has been modified to assess its performance and behavior.

Orthotropic plates with dynamic vertical seismic load modeled as multi line

Calculation plate floor concrete, using a static load which is a gravity load consisting of a live load and a dead load, with various of boundary conditions, floor slabs are orthotropic plate, and rarely account for dynamic loads due to vertical seismic loads, with other boundary conditions, such as Clamped, simply supported, ES (Elastic Support), ER (Elastic Restraint), and ESR (Elastic Support and Restraint). Analytical solution based on the Modified Bolotin Method to analyze floor slab under Vertical Peak Ground Acceleration (PGAv), the natural frequency solution based on auxiliary Levy’s type problems. Dynamic vertical seismic loads using multiline, first line at 0 < t < 0.5 is linear equation, second line at 0.05 < t < 0.15 is quadratic equation, third line 0.15 > t < 0.6 is sextic equation, last line, t > 0.6 is linear equation, vertical seismic load with two conditions far fault and near fault, multi-line equation are depending on (PGAv/g). A numerical example is given, for various boundary conditions, and far fault, translational stiffness (kx, ky) and rotational stiffness (cx ,cy), from the results of plate calculations due to dynamic vertical seismic loads with 5 types of edge support, ES (elastic support) is the best result.

"Reliability Analysis of Axially Compressed Steel Columns "

"In the past, the evaluation of the strength and safety of compressed steel columns has primarily relied on deterministic concepts. However, these concepts fail to account for the significant variability observed in buckling strength test results. This study aims to address this limitation by adopting a probabilistic approach to assess the buckling strength of steel columns; following the Indian standard specification IS 800-2007. In this investigation, the statistically variable nature of the material properties is considered by treating them as random variables and assuming a normal distribution. By incorporating this variability, a more comprehensive evaluation of the buckling strength can be achieved. The buckling strength of the steel column is computed using Merchant Rankine's formula, which takes into account deductive uncertainty. This formula considers various factors such as the slenderness ratio, live load to dead load ratio, and other relevant parameters to estimate the buckling strength of the column. Furthermore, the reliability of axially loaded columns is assessed using the First Order Second Moment (FOSM) technique. The effects of the slenderness ratio and the live load-to-dead load ratio on the reliability of the columns are specifically investigated and discussed. Overall, this study contributes to a more comprehensive understanding of the buckling strength of steel columns, incorporating statistical variability and providing insights into the reliability assessment of such structural elements."

Wind and Seismic Analysis of Pre-Engineered Building

Abstract: With the development of science and technology in the field of structural engineering, it is possible to adopt preengineered buildings in both industrial and residential construction sectors. For important buildings it is more suitable to use pre engineered building as these are more safe and take less time in construction in comparison of RCC structures. In this paper, pre-engineered steel structure will be design and analyzed for wind and seismic analysis with different parameters using software Staadprov8i and analyzed with different loads on building i.e. dead load, live load, wind load, seismic load and load combinations on structure. The main objective of this work is to understand the concepts of PEB and find the least possible weight of structure and various displacement or significance of forces in each direction which will help the structure to be safe and stable. The pre-engineered construction concept involves pre-engineering and quality construction systems which will help to minimize the use of cost and time.

Planning Earthquake-Resistant Upper Building Structures With Moment Grabbing Frame System In The Mardhika Park Apartment Building 20 Floors Tambun – Bekasi

Indonesia is an area with a high level of vulnerability to earthquake disasters, where this earthquake has caused a lot of losses and damage to building structures. Therefore, to reduce the risk due to the earthquake, it is necessary to plan earthquake-resistant building structures. The structural planning of building construction is needed to get the most effective and efficient dimensions and configuration of the structure. Collapsed buildings that are not strong enough to withstand lateral loads caused by the earthquake have resulted in significant loss of property and even lives. The purpose of writing this thesis is to design an earthquake-resistant Mardhika Park Apartment Building with a moment-resisting frame system (SRPM) which is planned in accordance with SNI 1726:2019 Earthquake (Earthquake Resistance Planning Procedures for Building and Non-Building Structures), SNI 2847 for Reinforced Concrete: 2019 (Requirements for structural concrete for buildings and their explanations), and the loading in accordance with SNI 1727:2020 for (Minimum Loads for Design of Buildings and Other Structures). The structural design of the Mardhika Park Apartment Building includes the design of this superstructure which includes columns, beams, and floor plates. Then the loads that are reviewed for structural element planning are dead, live, and earthquake loads. To assist in calculating the structure is also used Software "SAP2000 " to facilitate the calculation of the structure.

Towards predicting dynamic reliability of bridge spans

In conditions of increasing impact of temporary live load, a premature wear of bridge superstructures occurs, operational strength and durability decrease. The paper discusses the dynamic reliability of the load-bearing elements of superstructures within the frame of ensuring the structure safety during operation, with regard to defects and overloads. Reliability is considered within the framework of random events and processes based on the possible superstructure exit beyond its serviceability based on the statistical dynamic properties. The par ametric and structural reliability is considered. Based on the mathematical statistics and random numbers theories, the dynamic reliability theory is characterized by the quality deployed in time. The effect of load variation for a long time is considered. The possibility is predicted for changing resources and structure failure. The dynamic reliability conditions are approximated based on the Gauss and Weibull distribution curves. Mathematical expressions are given to the structure indestructibility. The superstructure failure is considered with respect to possible overload using the principle of accidental release.

Numerical Study On Response Of Exterior Beam-Column Joint Under Cyclic Loading

In Present scenario, recent earthquakes have illustrated the severity of existing reinforced concrete (RC) beam-column joints to lateral loading. The sub-assemblage of Beam-Column are severe portion in reinforced concrete moment resisting frame as the high shear forces and larger moments getting attracted towards the joint. The Philosophy of Exterior beam-column joint are to observe its behaviour and has a significant role on the response of the reinforced concrete structure. This study includes numerical study on Exterior reinforced beam column joint with adequate shear reinforcement at joint as per IS: 13920-2016 and without shear reinforcement at joint as per IS: 456-2000. The seismic performance of G+5 RC Building of Zone III analyzed using SAP2000 and output of maximum shear force and bending moments are obtained, and one of the exterior beam-column joints at an intermediate storey is designed and satisfied for strong column and weak beam concept. The earthquake analysis of RC building of Zone III are carried out by incorporating all the modifications as per IS 1893:2002(Part-I) for Seismic loading, the loading is followed as per IS: 875 for dead and live loads and design as per code IS 13920:2016 and IS456:2000. Full scaled specimens were Numerically modelled in ANSYS 19.0 for constant axial load on column top and cyclic loading on beam end of each specimen, detailed as per IS 456:2000 and the other as per IS 13920:2016, were tested and response are obtained. This study outlined that model of IS13920:2016 performs more effective in controlling the seismic responses compared with model of IS456:2000. Further, there is significant reduction in Shear stress and observed improved ductility by providing adequate shear reinforcement in joint core of beam-column sub-assemblage.

Effect of Curve Angle on Single Cell Box-Girder Bridge

The behaviour of curved box-girder bridge is quite different from the straight one as it is experienced by the additional torsional moments. The analysis and design of such box-girder bridges are quite complicated when the curve angle is varied. The effect of curve angle on the forces and deflection in the girders, inner and outer, of a simply supported single cell reinforced concrete curved box-girder bridge is investigated in this study. A Finite element based software, CSiBridge v.20, was used for the analysis. A convergence study was performed on the proposed model to select the optimum mesh size and the results obtained are validated with the published literature. The variation of absolute values of forces and deflection along both the girders, under dead load (DL) and IRC (Indian Road Congress) live load (LL), is observed and the equations are proposed for their prediction in terms of non-dimensional parameters, using the statistical approach. The present results may be helpful to the designers in the analysis and design of curved single cell reinforced concrete box-girder bridges.

Finite Element Analysis of Bridge Deck Using MATLAB

Bridges are the most common types of structures generally adopted when there is a obstacle in the path such as water body, valley, road etc without closing the way underneath. Moving live load is one of the critical loading for which bridge superstructure need to be analysed by developing model as realistic as possible. Even though various conventional methods are present for the analysis of bridge superstructure but finite element analysis gives us more realistic behavior of structure. The objective of the thesis is to develop a finite element model of T-beam slab bridge ,bridge pier and pier footing and analyse to study behavior of bridge superstructure for moving live load as per Indian road congress standards given in IRC:6-2017 and IRC: 112-2011 and the dead load of the structure. In my work, bridge deck is modelled as Mindlin-Reissner plate element which is two dimensional plate in which shear deformations effect is considered whereas longitudinal girders ,cross girders and diaphragms are modelled using Euler-Bernoulli’s grid element which are a one dimensional element . A MATLAB code is developed to model T-beam slab composite action in which beam elements is modelled in plane of plate element so that the nodes of beams are coincide to the nodes of the plate by doing such center of gravity of the beam coincides with the plate element ignoring offset present between them. Moving live load analysis is performed using step by step method in which load moves in longitudinal as well as transverse direction giving the worst case for maximum bending moments, shear forces and deflections. Then Moving live load analysis for 2 lane T-beam bridge is carried out for IRC Class 70R wheeled vehicle and compare the result by modeled in sap2000,2016 of same dimension and the effect of the number of cross girders in the deck span on bending moments, shear forces and deflections of longitudinal girders is presented.