This study describes observations on the earthquake performance of unreinforced masonry buildings from a reconnaissance mission following the 2023 Kahramanmaraş earthquake sequence. The area affected by the earthquakes is home to a remarkably diverse masonry building stock, which is introduced first. Specific attention is given to the stone and timber-laced unreinforced masonry constructions, which are the most common typologies. Then, an overview of the dominant collapse mechanisms in wall structures is presented, with a view to highlighting key features that affected the seismic performance. It is observed that buildings with negligible or minor damage indicated good quality construction, where connection detailing enabled box behavior during the earthquake sequence. In contrast, lack of proper connections among load-bearing walls, internal disaggregation of masonry due to poor construction quality, poor timber connections and the use of incompatible strengthening interventions prevented box behaviour and led to partial or complete collapses. Observations of building features that improve seismic performance (e.g., through stones, timber beams, tie rods, ring beams) are highlighted.
TMS 402-22 provides an equation for determining the cracked moment of inertia of a reinforced masonry wall under out-of-plane loading. TMS 402-22 states that the equation is valid for a fully grouted wall or a partially grouted wall with the neutral axis in the face shell. Other implicit assumptions that are not stated in TMS 402- 22 are that the tension reinforcement has yielded, there is only one layer of tension reinforcement, and the axial load can be replaced by equivalent reinforcement at the mid-depth of the section, with the area of the reinforcement being the factored axial load divided by the yield stress. This paper provides equations for the cracked moment of inertia when these assumptions are not met. Tips for design are also provided.
As part of a larger project jointly sponsored by the National Concrete Masonry Association (NCMA) Foundation, Canadian Concrete Masonry Producers Association (CCMPA), Canada Masonry Design Centre (CMDC) and Canadian Standards Association (CSA), a team of engineers and researchers from U.S. and Canada worked together to examine the key differences and similarities between the design provisions for reinforced masonry walls subject to out-of-plane (OOP) and axial loads. The scope was limited to the strength design provisions of TMS 402-16 and the limit state design provisions of CSA S304-14 masonry design standards. Several parametric studies were conducted to quantify the comparisons, as well as to identify possible limitations within each code. These studies explored factors that directly impact the calculation of combined flexural and axial capacity, wall stiffness, second-order moments, and shear capacity of the masonry walls subjected to OOP loading. Parameters considered include the compressive strength of the masonry assembly, wall geometry, as well as the size, strength and spacing of the steel reinforcement. In general, it was found that the Canadian provisions are more conservative than those in the U.S. The paper also provides a list of areas of further research or code revisions that should be considered in the future. It is the team’s goal to propose improvements to both codes as a result of this work.
This work is one of the four companion papers associated with the Canada/US (CANUS) collaborative project: Harmonization of Canadian and American Masonry Structures Design Standards. This particular paper specifically delves into a comparison of the design and detailing provisions for masonry beams in the U.S. and Canada. The scope of the investigation covers the similarities and divergences between the two design standards (CSA S304-14 and TMS 402-16), through first a comparative discussion of the provisions followed by parametric studies that illustrate the differences quantitatively. Several areas of further investigation are identified as a result of this work, which if addressed, may improve and harmonize the two standards and practices. For instance, the 𝜒 factor utilized in C SA S 304-14 amplifies the divergence such that most masonry beam designs that have been safely constructed in the U.S. are not possible in Canada. In contrast, TMS 402-16 does not have clear guidance on deflection limits or intermediate reinforcement for regular beams; and a reconsideration for modulus of rupture values may be warranted, as the code-provided values are based on historic wallette tests instead of beams.
A large stone barn built in 1820s in the Valley Forge historic national park in Pennsylvania used some of the early historic lime mortars in the US masonry construction during the time when natural cement was just produced in the US and about to gain its momentum for next 70 years, and Portland cement, though formulated in Europe, didn’t enter the US market for at least 50 years. A brown original fist-size bedding mortar fragment was examined, which showed many interesting microstructures of a clay-mixed historic lime mortar. The fragment was examined by a plethora of analytical techniques encompassing optical and scanning electron microscopy and microanalysis, acid digestion, chemical (gravimetric) analysis, XRD, XRF, thermal studies (TGA, DSC, DTG), FTIR, and ion chromatography. Such a comprehensive investigation provided detailed information about the mortar type, composition, and grain size distribution of masonry sand, original non-hydraulic dolomitic lime plus clay-based binder compositions and resultant microstructure of paste, origin of lime lumps, along with evidence of any distress and alterations from two centuries of exposures to a moist outdoor environment. Based on all these studies, the overall condition, extent of deterioration/alterations, and sand and binder proportions of the original mortar were assessed by reverse engineering, from which a suitable replacement mortar was recommended for long-term restoration.
