Wall Bracing Research Articles

RELATIVE STUDY OF SEISMIC ANALYSIS BETWEEN FLAT SLAB AND GRID SLAB OF RCC STRUCTURES WITH DIFFERENT MASONRY INFILLS IN TWO DIFFERENT ZONES

Recently there has been a considerable increase in the number of tall buildings, both residential and commercial, and modern trend is towards taller structures, Flat slab is most widely used systems in reinforced concrete construction in offices, residential and industrial buildings in many parts of the world. The flat plate system, in which columns directly support floor slabs without beams. To improve the performance of building having flat slabs under seismic loading, provision of flat slab with drop is proposed. The object of the present work is to compare the behaviour of multi-storey buildings having flat slabs with drops with that of conventional beam column framing so called grid slab system under linear dynamic analysis (Response spectrum analysis) with different masonry infills i.e. shear wall and concrete bracing in two different zones i.e. zone III and zone IV with medium soil type conditions. Software ETABS is used for this purpose. The parameters study are Time Period, Base shear, Displacements and Story Drift. And it is found that the structure with infills shows better performance in comparison with structures without infills. In addition to this the structure with shear wall reduced max displacement and storey drift and time period of different types of structures in both the zone in comparison with structure with concrete bracing.

Finite Element Modeling and Mechanical Behavior of Masonry-Infilled RC Frame

During the analysis of reinforced concrete structures, the infill wall is usually simplified as a diagonal inclined strut to facilitate finite element modeling calculations. However, the actual seismic damage and single frame-filled wall pushover experimental results show that when the earthquake shear force is huge, the top of the infill wall and the beam–column connections are usually, thus the path of the force transfer will be changed. Based on this actual failure phenomenon, a new calculation model which has different contact position between the equivalent bracing walls and the frame columns is generated. Thus, the force analysis is given based on this model, the formulae for calculating the equivalent width of bracing walls, the shear bearing capacity of the wall-filled frame, and the infill wall’s actual participation in the stiffness. A finite element simulation method by ABAQUS is used to determine an empirical formula for calculating the reasonable contact position between the equivalent bracing walls and the frame columns. The verification results show that the finite element model presented in this paper is more reasonable, and the stiffness and shear resistance of infill wall should not be neglected. The calculation formula of stiffness of infill wall presented in this paper is coincided with seismic code. But the calculation formula of shear resistance of infill wall presented in seismic code is higher than the actual value, so it is suggested that calculation formula presented in this paper should be accepted.

Stress concentration factors of negative large eccentricity tubular N-joints under axial compressive loading in vertical brace

Negative large eccentricity tubular N-joints sometimes are used in welded trusses and offshore structures under fatigue loading. It is imperative that researches should be done on fatigue behavior of negative large eccentricity tubular N-joints under fatigue loading, though static behavior of negative large eccentricity tubular N-joints has been researched. The stress concentration factors (SCFs) are the main parameters in the fatigue behavior analysis of negative large eccentricity tubular N-joints. Four negative large eccentricity tubular N-joints specimens were separately tested for calibration and verification of finite element analysis models by considering axial compression in vertical brace case. All experimental joints were simply hinge supported at one end of chord and inclined brace end. Elastic gradient strain distributions along the intersection of joints were measured. Strain concentration factors (SNCFs) at hot spots including saddle and crown points were computed taking advantage of an extrapolation approach. As eccentricity decreased, the position of maximum SCF moved from the saddle point to the crown point at the inclined brace and vertical brace intersection near the vertical brace or the inclined brace. The maximum SCF at the chord and inclined brace intersection near the chord or the inclined brace occurred on the crown point. For the FE analysis, solid elements and certain mesh size were used to model the N-joints. Effects of brace diameter to chord diameter ratio (β), chord diameter to thickness of chord ratio (2γ), brace wall thickness to chord wall thickness ratio (τ) and eccentricity ratio (ε) on the SCFs distribution of the negative large eccentricity tubular N-joints were numerically investigated. SCF linearly increased with the increase of eccentricity ratio at the inclined brace and vertical brace intersection near inclined brace and at chord and inclined brace intersection near inclined brace. The effect of eccentricity ratio on SCF equations of small eccentricity tubular N-joints was not considered in current code. A series of parametric equations considering eccentricity ratio were proposed for calculating the SCFs of negative large eccentricity tubular N-joints based on 256 joints FEA models calculation result.

On the equivalent simple models of braced steel shear panels

Through the combination of two types of seismic resisting systems including braced frames and steel shear walls, braced steel shear panel systems can be formed. This new lateral load-resisting system solves some of the defects of current special steel shear walls, such as imposing significant loads on boundary elements along with gravity load effects. Analysis and design of this new structural system underline the importance of having simple and precise finite-element models. To this aim, this paper presents two types of equivalent braced frames termed ‘overall equivalent brace’ and ‘equivalent mid-brace’. The equations of brace area, material strength and strain-hardening ratio are obtained in two states of considering both braces or regardless of compressive brace. Next, non-linear lateral displacement, yield and ultimate values of base shear of one-storey and three-storey equivalent models are compared with the results of strip models. The findings show that the proposed models can obtain acceptable results by considering both braces only with equivalent area along with material strength.

Inelastic behavior of cold-formed braced walls under monotonic and cyclic loading

The ever-increasing need for housing generated the search for new and innovative building methods to increase speed and efficiency and enhance quality. One method is the use of light thin steel profiles as load-bearing elements having different solutions for interior and exterior cladding. Due to the increase in CFS construction in low-rise residential structures in the modern construction industry, there is an increased demand for performance inelastic analysis of CFS walls. In this study, the nonlinear behavior of cold-formed steel frames with various bracing arrangements including cross, chevron and k-shape straps was evaluated under cyclic and monotonic loading and using nonlinear finite element analysis methods. In total, 68 frames with different bracing arrangements and different ratios of dimensions were studied. Also, seismic parameters including resistance reduction factor, ductility and force reduction factor due to ductility were evaluated for all samples. On the other hand, the seismic response modification factor was calculated for these systems. It was concluded that the highest response modification factor would be obtained for walls with bilateral cross bracing systems with a value of 3.14. In all samples, on increasing the distance of straps from each other, shear strength increased and shear strength of the wall with bilateral bracing system was 60 % greater than that with lateral bracing system.

A Simplified Approach for Estimation of Braced Wall Deflection During Excavation in Soft Clay

The construction of braced excavations in urban areas requires control of surrounding ground movements since excessive ground movements damage adjacent properties. Reasonably good amount of work on numerical analysis and field studies on the estimation of ground surface settlement adjacent to excavation have been reported in the literature. However, theoretical studies or mathematical modeling have not been well addressed in the literature. This paper presents a simplified design approach for estimation of wall deflection where diaphragm wall is assumed as continuous beam. Earth pressure in the backfill side is taken as load, exerted on the beam and strut load along with earth pressure in cut side represents support of the beam. Peck’s earth pressure diagram for braced wall is used for load calculation while Terzaghi’s equation is considered to derive coefficient of modulus of subgrade reaction. Applicability of the proposed approach has been verified by comparing the estimated values of wall deflection with the measured values of three different case studies.

Parameters Affecting the Elasto-Plastic Behavior of Outrigger Braced Walls to Earthquakes

Parameters Affecting the Elasto-Plastic Behavior of Outrigger Braced Walls to Earthquakes

Performance Evaluation of Midply and Standard Corner Joints of Wood Portal Frames

AbstractExperimental results to determine the moment-resisting capacity of wood portal frame corner joints are presented in this paper. Two types of corner joints (standard and MIDPLY) were tested with different configurations. An L-shaped corner joint including a narrow braced wall segment and header was used as a test specimen. A total of 37 corner joints were tested. Test results showed that the installation of metal strap or the adding of exterior oriented strand board (OSB) sheathing, while using high-density wood product (LVL, LSL) as header increased the moment-resisting capacity of corner joints. Furthermore, the MIDPLY corner joint had higher moment capacity than the standard corner joint. The moment-carrying capacity of corner joints could be further increased by applying fiber-reinforced polymer (FRP) on top of exterior OSB sheathing. A detailed finite element (FE) model of a corner joint is presented. The FE model predictions correlated well with the experimental results.

Seismic Performance Research of Viscous Dampers under Different Arrangement

This paper introduces a variety of viscous damper installation form, including brace, herringbone and cantilever wall installation. By an example, install the bracing form, herringbone installation form and type cantilever wall installation condition are compared, And to calculate the results of its damping effect has carried on the comparative study, The superiority of the cantilever wall type layout pattern is obtained.

Field testing of stiffened deep cement mixing piles under lateral cyclic loading

Construction of seaside and underground wall bracing often uses stiffened deep cement mixed columns (SDCM). This research investigates methods used to improve the level of bearing capacity of these SDCM when subjected to cyclic lateral loading via various types of stiffer cores. Eight piles, two deep cement mixed piles and six stiffened deep cement mixing piles with three different types of cores, H shape cross section prestressed concrete, steel pipe, and H-beam steel, were embedded though soft clay into medium-hard clay on site in Thailand. Cyclic horizontal loading was gradually applied until pile failure and the hysteresis loops of lateral load vs. lateral deformation were recorded. The lateral carrying capacities of the SDCM piles with an H-beam steel core increased by 3–4 times that of the DCM piles. This field research clearly shows that using H-beam steel as a stiffer core for SDCM piles is the best method to improve its lateral carrying capacity, ductility and energy dissipation capacity.

Performance Evaluation of Portal Frame System in Low-Rise Light-Frame Wood Structures

AbstractIn this paper, results are presented from a testing program focused on evaluating the performance of portal frame systems. A total of nine full-scale portal frame assemblies with six different configurations were tested under monotonic and reversed cyclic loading. The portal frames were 3.66 m in length and 2.44 m in height, with a 406-mm wall segment at each end of the portal frame. From the experimental results, it was observed that the corner joint between the header and narrow braced wall segment governs the lateral load-carrying capacity and ultimate displacement of the portal frame. Installation of metal straps considerably increased the lateral load-carrying capacity of the portal frame assemblies. Straps placed directly on the lumber framing showed increased resistance compared to those installed on the oriented strand board. Portal frames with hold-downs had a greater lateral load-carrying capacity those without hold-downs. A comparison was made between portal frames and conventional brac...

Welder-optimized CJP-equivalency welds for tubular connections

This paper will present the experimental and numerical investigation on the fatigue crack failure at the root of the enhanced partial joint penetration welds in the circular hollow section X-joint specimens subjected to constant-amplitude brace in-plane bending actions. The enhanced partial joint penetration welds, which include a portion of the brace wall as the inherent “back-plate” for the welds, reduce the workmanship requirement on the welding procedure and improve the quality control of the welded joint. This study compares the fatigue crack developments observed at both the weld toe and the weld root in three large-scale X-joint specimens with different post-weld surface treatments. Root cracking does not take place in as-welded tubular X-joint specimens, of which the fatigue life depends on the weld toe failure. In specimens with post-weld grinding treatments to enhance fatigue resistance of the material near the weld toe, however, the finite-length root face triggers the initiation and propagation of fatigue cracks with an applied number of cycles more than that required to initiate a toe crack in the same tubular X-joint. Ultimate strength testing of specimens with large fatigue cracks, and post-test sectioning, reveals that fatigue failure weld-toe fatigue cracks remain more critical than the root cracks.

Comparative Analysis of Traditional Braced Wall System and Retaining Wall System with Pre-Stressed Wale and Square Pipe Struts

H shape steel strut, which is the most commonly used material in traditional braced wall system (TBWS), has some disadvantage such as narrow strut spacing and cost ineffectiveness. Therefore, a newly retaining wall system with pre-stressed (PS) wale and square pipe struts is developed for widening strut spacing and saving construction costs. In this study, three cases, which are changed from TBWS with H shape steel strut to retaining wall system with PS wale and square pipe struts, are compared construction costs and constructability. This results reveal that construction costs is decreased by 46.9% on average and constructability is improved by decreasing the amount of material and widening the strut spacing.

Comparative Analysis of a 15 Story Flat Plate Building with and Without Shear Wall and Diagonal Bracing Under Wind and Seismic Loads

A flat plate is a reinforced concrete slab supported directly by concrete columns without the use of beams, column flares or drop panels. Flat plate system has been adopted in many buildings constructed recently taking advantage of the reduced floor height to meet the economical and architectural demands. However, In Multistoried structures the flat plate floor system has week resistance to lateral loads like wind and earthquake hence this paper is concerned to increase lateral stiffness of flat plate structure and to minimize the displacement of the structure under lateral loading. This paper is also concerned about column axial load and to review our structure with special features like shear walls & diagonal bracing. In present work, a 15 storied flat plate garments building have been modeled using software package STAAD Pro for earthquake zone II in Bangladesh .This model is considered in most vulnerable situation where we took wind speed as 260 kmph and Earthquake load has been taken as per Bangladesh National Building Code(BNBC)

Earth pressures in trench rescue shoring systems

A three-dimensional parametric finite element analysis of the earth pressures on a shoring system used in trench rescue or as a shallow trench bracing was performed. Field monitoring of the deformation of an instrumented, full-scale braced wall section was also undertaken in two shallow trenches, one where the soil was mostly granular in nature and one where the soil was clayey, in order to gauge the effect of soil type on the shoring system performance. The study showed that the most significant effect on earth pressures was the strut loading. It was found that the magnitude and distribution of the soil pressure on shallow trench bracing was significantly different from that determined by the currently accepted one used for braced deep excavations. A method for calculating earth pressures on shallow trench bracing was developed that determines the earth pressures as a function of strut loading. It can be used to determine the maximum strut loading that can be used without causing a passive failure of the soil.

SEISMIC STRENGTHENING FOR BRACED FRAME STRUCTURE OF EXISTING WOODEN HOUSES USING ULTRAVIOLETRAYED-HARDENING FRP

The purpose of this study is to develop the new seismic strengthening method of existing wooden houses. In this study, the fiber reinforced plastics (FRP) are used as the reinforcement material. This FRP hardens by irradiating the ultraviolet ray. In this study, we develop a good workability seismic strengthening method for existing wooden houses by using this FRP sheet. As a result, we were able to develop the new reinforcement design for the braced frame structural wall of the element ultimate strength (the wall ultimate strength factor) as over 4.0(kN/m) which was target value in this study.

Forensic Engineering Analysis Of Responsibility For Failure Of Temporary Wall Bracing

A Concrete Sub-Contractor Was Injured When A Tall Standing Wood Stud-Framed Wall Fell During A Strong Wind Storm. The Accident Happened On A Friday Afternoon As Concrete Workers Waited For The Opportunity To Finish A Morning Concrete Pour For A New Restaurant That Was Under Construction. Realizing That The Wind Was Going To Topple The Interior Wall On The Newly Placed Concrete, Efforts Were Made To Keep The Wall From Falling. The Wall Could Not Be Steadied And It Fell, Allegedly Injuring A Concrete Worker. The Framing Sub-Contractor Had Used Typical 2x6 Lumber To Make Temporary Braces To Steady The Walls Plumb And True As The Framing And Standing Of Walls Progressed Toward The Completion Of The Roof Structure. To Avoid Damage To An Exposed Decorative Concrete Surface In The Dining Area, The Main Interior Wall Was Braced To The Kitchen Side Where The Concrete Sub-Contractor Was Placing Concrete That Day. The Framing Sub-Contractor Was Named As A Defendant In The Lawsuit That Followed. The Attorney For The Framing Sub-Contractor Secured The Services Of The Fe On Behalf Of The Framing Sub-Contractor. Depositions Revealed That Bracing For The Standing Stud-Framed Interior Wall Was Not In Place At The Time Of The Accident. This Paper Pieces Together The Sequence Of Events And Reviews The Roles And Contractual Responsibilities Of Both The General Contractor And The Sub-Contractor As Related To Project Scheduling, Project Management, Jobsite Coordination, And Overall Jobsite Safety. Acceleration Of The Project Schedule And Coordination Issues With Overlapping Jobsite Activities Were Identified As Contributing Factors Preceding The Collapse Of The Wall. The Case Was Settled Out-Of-Court For Nuisance Value One (1) Day Before Trial Was Scheduled To Begin.

Observations of the performance of earth buildings following the February 2011 Christchurch earthquake

A reconnaissance survey of earth walled buildings in the Christchurch area was carried out following the February 2011 Christchurch Earthquake. Twenty six earth buildings were inspected during the survey including historic earth buildings and recent reinforced earth buildings. Some of these buildings had previously been inspected following the September 2010 Darfield Earthquake.
 The February 2011 Earthquake caused comparable patterns of damage to earth buildings as the September 2010 Darfield earthquake except for unreinforced pressed brick buildings which performed particularly badly. Reinforced earth buildings constructed since the 1990’s performed well during the February 2011 earthquake provided the overall wall bracing was adequate and detailing of the reinforcement and connections were generally in accordance with the NZ Earth Building Standards. Some older unreinforced rammed earth buildings constructed between 1950 and 1980, all of which had reinforced concrete foundations and bond beams, performed relatively well with only minor cracking. Unreinforced cob and adobe buildings in the area of strong shaking suffered significant damage and will require reconstruction or repair of the walls and strengthening of the upper floor or ceiling diaphragms. The performance of six houses are discussed as case studies that cover the range of buildings observed.

Seismic performance of post and beam timber buildings I: model development and verification

This paper presents a structural model called “PB3D” to perform nonlinear time history analyses of post and beam timber buildings under seismic loads. The model treats the three-dimensional structure as an assembly of roof/floor diaphragms and wall subsystems. The roof/floor diaphragms are modeled by beam elements and diagonal brace elements in order to take into account the in-plane stiffness. The wall system consists of vertical beam elements, for wall posts, as well as nonlinear shear springs to consider the contribution of diagonal wall bracing members or sheathing panels. The hysteretic characteristics of the shear springs are represented by a simplified, mechanics-based model named a “pseudo-nail”. Standard finite element procedure is used to construct the system’s equation of motion, which is solved by Newmark’s integration. The model was verified against shake test results of a three-story post and beam building subjected to strong ground motions scaled to the 1995 Kobe earthquake. Model predictions agreed very well with the test results in terms of base shear forces and inter-story drift responses. This model provides a robust and efficient tool to study the seismic behavior of post and beam timber buildings.

Observations of the performance of earth buildings following the September 2010 Darfield earthquake

A reconnaissance survey of earth walled buildings in the Canterbury area was carried out in mid October 2010 following the Darfield Earthquake. Fifteen earth walled buildings were inspected during the survey including historic earthbuildings and recently constructed reinforced earthbuildings.
 Reinforced earth houses constructed since the 1990s performed well provided the overall wall bracing was adequate and detailing of the reinforcement and connections was generally in accordance with the NZ Earth Building Standards. Several unreinforced earth buildings constructed before 1930 (or reconstructed historic buildings) suffered significant structural damage and will require reconstruction or substantial repair. Unreinforced rammed earth buildings, and reinforced cinva ram brick buildings, constructed between 1930 and 1990 with reinforced concrete foundations and bond beams and adequate overall wall bracing generally performed moderately well given the level of shaking they experienced.
 Minor cracking was observed in all but one of modern houses, performance was good where reinforcement and construction complied with the New Zealand Standards. Where buildings did not comply the damage could have been prevented by following the Standards.